doi:10.1007/s00376-015-4202-z

Bao J.-W., S. G. Gopalakrishnan, S. A. Michelson, F. D. Marks, and M. T. Montgomery, 2012: Impact of physics representations in the HWRFX on simulated hurricane structure and pressure-wind relationships. Mon. Wea. Rev., 140, 3278- 3299.

Beljaars A. C. M., P. Viterbo, 1998: Role of the boundary layer in a numerical weather prediction model. Clear and Cloudy Boundary Layers, A. A. M. Holtslag, and P. G. Duynkerke, Eds., Royal Netherlands Academy of Arts and Sciences, Amsterdam, 287- 304.f2b22d51-a29b-489a-aecd-c6adcba2c0cf/s?wd=paperuri%3A%28996da912208f796063774e7bfcc2da79%29&filter=sc_long_sign&sc_ks_para=q%3DThe%20role%20of%20the%20boundary%20layer%20in%20a%20Numerical%20Weather%20Prediction%20model&tn=SE_baiduxueshu_c1gjeupa&ie=utf-8

Bell M. M., M. T. Montgomery, and K. A. Emanuel, 2012: Air-sea enthalpy and momentum exchange at major hurricane wind speeds observed during CBLAST. J. Atmos. Sci., 69, 3197- 3222.10.1175/JAS-D-11-0276.1

0ddc6ad9-8481-4a41-8a05-e5d5ac81b73c

b6ed799e78f30abc6518ab41df96947d

http://www.researchgate.net/publication/258659563_Air-Sea_Enthalpy_and_Momentum_Exchange_at_Major_Hurricane_Wind_Speeds_Observed_during_CBLAST

http://www.researchgate.net/publication/258659563_Air-Sea_Enthalpy_and_Momentum_Exchange_at_Major_Hurricane_Wind_Speeds_Observed_during_CBLASTQuantifying air--sea exchanges of enthalpy and momentum is important for understanding and skillfully predicting tropical cyclone intensity, but the magnitude of the corresponding wind speed--dependent bulk exchange coefficients is largely unknown at major hurricane wind speeds greater than 50 m s-1. Since direct turbulent flux measurements in these conditions are extremely difficult, the momentum and enthalpy fluxes were deduced via absolute angular momentum and total energy budgets. An error analysis of the methodology was performed to quantify and mitigate potentially significant uncertainties resulting from unresolved budget terms and observational errors. An analysis of six missions from the 2003 Coupled Boundary Layers Air--Sea Transfer (CBLAST) field program in major hurricanes Fabian and Isabel was conducted using a new variational technique. The analysis indicates a near-surface mean drag coefficient CD of 2.4 X 10-3 with a 46% standard deviation and a mean enthalpy coefficient CK of 1.0 X 10-3 with a 40% standard deviation for wind speeds between 52 and 72 m s-1. These are the first known estimates of CK and the ratio of enthalpy to drag coefficient CK/CD in major hurricanes. The results suggest that there is no significant change in the magnitude of the bulk exchange coefficients estimated at minimal hurricane wind speeds, and that the ratio CK/CD does not significantly increase for wind speeds greater than 50 m s-1.

Black, P. G., Coauthors, 2007: Air-sea exchange in hurricanes: Synthesis of observations from the coupled boundary layer air-sea transfer experiment. Bull. Amer. Meteor. Soc., 88, 357- 374.10.1175/BAMS-88-3-357

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http://www.researchgate.net/publication/215877065_Air--sea_exchange_in_hurricanes_Synthesis_of_observations_from_the_coupled_boundary_layer_air--sea_transfer_experiment?ev=auth_pub

http://www.researchgate.net/publication/215877065_Air--sea_exchange_in_hurricanes_Synthesis_of_observations_from_the_coupled_boundary_layer_air--sea_transfer_experiment?ev=auth_pubAbstract The Coupled Boundary Layer Air–Sea Transfer (CBLAST) field program, conducted from 2002 to 2004, has provided a wealth of new air–sea interaction observations in hurricanes. The wind speed range for which turbulent momentum and moisture exchange coefficients have been derived based upon direct f lux measurements has been extended by 30% and 60%, respectively, from airborne observations in Hurricanes Fabian and Isabel in 2003. The drag coefficient ( C D ) values derived from CBLAST momentum flux measurements show C D becoming invariant with wind speed near a 23 m s 611 threshold rather than a hurricane-force threshold near 33 m s 611 . Values above 23 m s 611 are lower than previous open-ocean measurements. The Dalton number estimates ( C E ) derived from CBLAST moisture flux measurements are shown to be invariant with wind speeds up to 30 m s 611 , which is in approximate agreement with previous measurements at lower winds. These observations imply a C E / C D ratio of approximately 0.7, suggesting that additional energy sources are necessary for hurricanes to achieve their maximum potential intensity. One such additional mechanism for augmented moisture flux in the boundary layer might be “roll vortex” or linear coherent features, observed by CBLAST 2002 measurements to have wavelengths of 0.9–1.2 km. Linear features of the same wavelength range were observed in nearly concurrent RADARSAT Synthetic Aperture Radar (SAR) imagery. As a complement to the aircraft measurement program, arrays of drifting buoys and subsurface floats were successfully deployed ahead of Hurricanes Fabian (2003) and Frances (2004) [16 (6) and 38 (14) drifters (floats), respectively, in the two storms]. An unprecedented set of observations was obtained, providing a four-dimensional view of the ocean response to a hurricane for the first time ever. Two types of surface drifters and three types of floats provided observations of surface and sub-surface oceanic currents, temperature, salinity, gas exchange, bubble concentrations, and surface wave spectra to a depth of 200 m on a continuous basis before, during, and after storm passage, as well as surface atmospheric observations of wind speed (via acoustic hydrophone) and direction, rain rate, and pressure. Float observations in Frances (2004) indicated a deepening of the mixed layer from 40 to 120 m in approximately 8 h, with a corresponding decrease in SST in the right-rear quadrant of 3.2°C in 11 h, roughly one-third of an inertial period. Strong inertial currents with a peak amplitude of 1.5 m s 611 were observed. Vertical structure showed that the critical Richardson number was reached sporadically during the mixed-layer deepening event, suggesting shear-induced mixing as a prominent mechanism during storm passage. Peak significant waves of 11 m were observed from the floats to complement the aircraft-measured directional wave spectra.

Braun S. A., W.-K. Tao, 2000: Sensitivity of high-resolution simulations of hurricane Bob (1991) to planetary boundary layer parameterizations. Mon. Wea. Rev., 128, 3941- 3961.10.1175/1520-0493(2000)1292.0.CO;2

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http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F242581818_Sensitivity_of_High-Resolution_Simulations_of_Hurricane_Bob_%281991%29_to_Planetary_Boundary_Layer_Parameterizations

refpaperuri:(1fd0fedfedfbec6a59e20bb8309a370c)

http://www.researchgate.net/publication/242581818_Sensitivity_of_High-Resolution_Simulations_of_Hurricane_Bob_(1991)_to_Planetary_Boundary_Layer_ParameterizationsPresents information on a study which described the sensitivity of high-resolution simulations of Hurricane Bob to planetary boundary layer parameterizations. Role of surface fluxes of sensible and latent heat in the development and maintenance of tropical cyclones; Physics options for the coarse-grid simulation; Coarse-grid results; Conclusions.

Bryan G. H., 2012: Effects of surface exchange coefficients and turbulence length scales on the intensity and structure of numerically simulated Hurricanes. Mon. Wea. Rev., 140, 1125- 1143.10.1175/MWR-D-11-00231.1

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http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F258683536_Effects_of_Surface_Exchange_Coefficients_and_Turbulence_Length_Scales_on_the_Intensity_and_Structure_of_Numerically_Simulated_Hurricanes

refpaperuri:(ad83f7215cd6186c94cfe99bf579cc92)

http://www.researchgate.net/publication/258683536_Effects_of_Surface_Exchange_Coefficients_and_Turbulence_Length_Scales_on_the_Intensity_and_Structure_of_Numerically_Simulated_HurricanesAbstract Using numerical simulations, this study examines the sensitivity of hurricane intensity and structure to changes in the surface exchange coefficients and to changes in the length scales of a turbulence parameterization. Compared to other recent articles on the topic, this study uses higher vertical resolution, more values for the turbulence length scales, a different initial environment (including higher sea surface temperature), a broader specification of surface exchange coefficients, a more realistic microphysics scheme, and a set of three-dimensional simulations. The primary conclusions from a recent study by Bryan and Rotunno are all upheld: maximum intensity is strongly affected by the horizontal turbulence length scale l h but not by the vertical turbulence length scale l υ , and the ratio of surface exchange coefficients for enthalpy and momentum, C k / C d , has less effect on maximum wind speed than suggested by an often-cited theoretical model. The model output is further evaluated against various metrics of hurricane intensity and structure from recent observational studies, including maximum wind speed, minimum pressure, surface wind–pressure relationships, height of maximum wind, and surface inflow angle. The model settings l h ≈ 1000 m, l υ ≈ 50 m, and C k / C d ≈ 0.5 produce the most reasonable match to the observational studies. This article also reconciles a recent controversy about the likely value of C k / C d in high wind speeds by noting that simulations in a study by Emanuel used relatively large horizontal diffusion and low sea surface temperature. The model in this study can produce category 5 hurricanes with C k / C d as low as 0.25.

Carlson T. N., F. E. Boland, 1978: Analysis of urban-rural canopy using a surface heat flux/temperature model. J. Appl. Meteor., 17, 998- 1013.10.1175/1520-0450(1978)0172.0.CO;2

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http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F234451527_Analysis_of_Urban-Rural_Canopy_Using_a_Surface_Heat_FluxTemperature_Model

refpaperuri:(d91957d2135cb3202c8890b13904426c)

http://www.researchgate.net/publication/234451527_Analysis_of_Urban-Rural_Canopy_Using_a_Surface_Heat_FluxTemperature_ModelAbstract A one-dimensional numerical model, capable of simulating surface temperature and heat flux, is described in terms of the effective atmospheric and terrain variables. The two model parameters which are most responsible for the formation of important temperature variations in the horizontal over the urban-rural complex are the thermal inertia (thermal property) and moisture availability, the former being most responsible for shaping the nighttime temperature pattern while the latter has a greater effect during the day. The controlling substrate variables are not easily determinable by direct measurement over a surface consisting of an inhomogeneous agglomerate of elements. We present one method whereby surface temperature, a more readily obtainable quantity, can be used in conjunction with the surface model to determine by numerical or graphical inversion of the latter the effective values of moisture availability and thermal inertia and thereby provide a quantitative framework for analysis of a rough surface and for an evaluation of the surface energy budget.

Charnock H., 1955: Wind stress on a water surface. Quart. J. Roy. Meteor. Soc., 81, 639- 640.10.1002/qj.49708034514

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http://onlinelibrary.wiley.com/doi/10.1002/qj.49708135027/full

http://onlinelibrary.wiley.com/doi/10.1002/qj.49708135027/fullABSTRACT Values for the shear stress τ0 of the wind on a water surface, found in seven later experiments, are compared with the data of Francis (1951). Four sets of the new data show that the stress coefficient C = τ0/09u2 is not constant, but that it increases somewhat with windspeed u (09 = air density). Three sets merely show a large experimental scatter of C, and do not support any consistent law of drag. A theory is also discussed that τ0 is mainly caused by the drag of the small ripples, and not by the drag of the big waves.

Chen S. H., W.-Y. Sun, 2002: A one-dimensional time dependent cloud model. J. Meteor. Soc.Japan, 80( 2), 99- 118.10.2151/jmsj.80.99

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http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F228377988_A_one-dimensional_time_dependent_cloud_model

refpaperuri:(fb0bd712e71185e18f0ac5e1435a2166)

http://www.researchgate.net/publication/228377988_A_one-dimensional_time_dependent_cloud_modelA one-dimensional prognostic cloud model has been developed for possible use in a Cumulus Parameterization Scheme (CPS). In this model, the nonhydrostatic pressure, entrainment, cloud microphysics, lateral eddy mixing and vertical eddy mixing are included, and their effects are discussed. The inclusion of the nonhydrostatic pressure can (1) weaken vertical velocities, (2) help the cloud develop sooner, (3) help maintain a longer mature stage, (4) produce a stronger overshooting cooling, and (5) approximately double the precipitation amount. The pressure perturbation consists of buoyancy pressure and dynamic pressure, and the simulation results show that both of them are important. We have compared our simulation results with those from Ogura and Takahashi's one-dimensional cloud model, and those from the three-dimensional Weather Research and Forecast (WRF) model. Our model, including detailed cloud microphysics, generates stronger maximum vertical velocity than Ogura and Takahashi's results. Furthermore, the results illustrate that this one-dimensional model is capable of reproducing the major features of a convective cloud that are produced by the three-dimensional model when there is no ambient wind shear.

Chien F.-C., H.-C. Kuo, 2011: On the extreme rainfall of Typhoon Morakot (2009). J. Geophys. Res., 116,D05104, doi: 10.1029/2010JD015092.10.1029/2010JD015092

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http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F2010JD015092%2Fcitedby

refpaperuri:(57e6d6c7d7577336221aa423a27b1c24)

http://onlinelibrary.wiley.com/doi/10.1029/2010JD015092/citedby[1] Typhoon Morakot (2009), a devastating tropical cyclone (TC) that made landfall in Taiwan from 7 to 9 August 2009, produced the highest recorded rainfall in southern Taiwan in the past 50 years. This study examines the factors that contributed to the heavy rainfall. It is found that the amount of rainfall in Taiwan was nearly proportional to the reciprocal of TC translation speed rather than the TC intensity. Morakot's landfall on Taiwan occurred concurrently with the cyclonic phase of the intraseasonal oscillation, which enhanced the background southwesterly monsoonal flow. The extreme rainfall was caused by the very slow movement of Morakot both in the landfall and in the postlandfall periods and the continuous formation of mesoscale convection with the moisture supply from the southwesterly flow. A composite study of 19 TCs with similar track to Morakot shows that the uniquely slow translation speed of Morakot was closely related to the northwestward-extending Pacific subtropical high (PSH) and the broad low-pressure systems (associated with Typhoon Etau and Typhoon Goni) surrounding Morakot. Specifically, it was caused by the weakening steering flow at high levels that primarily resulted from the weakening PSH, an approaching short-wave trough, and the northwestward-tilting Etau. After TC landfall, the circulation of Goni merged with the southwesterly flow, resulting in a moisture conveyer belt that transported moisture-laden air toward the east-northeast. Significant mesoscale convection occurred on a long-lived east-west-oriented convergence line and on the mountain slope in southern Taiwan. This convective line was associated with large low-level moisture flux convergence caused by the northwesterly circulation of Morakot and the southwesterly flow. It is thus suggested that the long duration of Typhoon Morakot in the Taiwan area, the interaction of southwest monsoon and typhoon circulation, the mesoscale convection, and the presence of terrain are the key factors in generating the tremendous rainfall.

Davis C., Coauthors, 2008: Prediction of landfalling hurricanes with the advanced hurricane WRF model. Mon. Wea. Rev., 136, 1990- 2005.10.1175/2007MWR2085.1

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http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F253593423_Prediction_of_Landfalling_Hurricanes_with_the_Advanced_Hurricane_WRF_Model

refpaperuri:(cba6c11de7a1102cd1a0ca0cf867e52a)

http://www.researchgate.net/publication/253593423_Prediction_of_Landfalling_Hurricanes_with_the_Advanced_Hurricane_WRF_ModelABSTRACT Real-time forecasts of five landfalling Atlantic hurricanes during 2005 using the Advanced Research Weather Research and Forecasting (WRF) (ARW) Model at grid spacings of 12 and 4 km revealed performance generally competitive with, and occasionally superior to, other operational forecasts for storm position and intensity. Recurring errors include 1) excessive intensification prior to landfall, 2) insufficient momentum exchange with the surface, and 3) inability to capture rapid intensification when observed. To address these errors several augmentations of the basic community model have been designed and tested as part of what is termed the Advanced Hurricane WRF (AHW) model. Based on sensitivity simulations of Katrina, the inner-core structure, particularly the size of the eye, was found to be sensitive to model resolution and surface momentum exchange. The forecast of rapid intensification and the structure of convective bands in Katrina were not significantly improved until the grid spacing approached 1 km. Coupling the atmospheric model to a columnar, mixed layer ocean model eliminated much of the erroneous intensification of Katrina prior to landfall noted in the real-time forecast.

DeCosmo J., K. B. Katsaros, S. D. Smith, R. J. Anderson, W. A. Oost, K. Bumke, and H. Chadwick, 1996: Air-sea exchange of water vapor and sensible heat: The Humidity Exchange over the Sea (HEXOS) results. J. Geophys. Res., 101, 12 001- 12 016.10.1029/95JC03796

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http://onlinelibrary.wiley.com/doi/10.1029/95JC03796/abstract

http://onlinelibrary.wiley.com/doi/10.1029/95JC03796/abstractSurface layer fluxes of sensible heat and water vapor were measured from a fixed platform in the North Sea during the Humidity Exchange over the Sea (HEXOS) Main Experiment (HEXMAX). Eddy wind stress and other relevant atmospheric and oceanic parameters were measured simultaneously and are used to interpret the heat and water vapor flux results. One of the main goals of the HEXOS program was to find accurate empirical heat and water vapor flux parameterization formulas for high wind conditions over the sea. It had been postulated that breaking waves and sea spray, which dominate the air-sea interface at high wind speeds, would significantly affect the air-sea heat and water vapor exchange for wind speeds above 15 m/s. Water vapor flux has been measured at wind speeds up to 18 m/s, sufficient to test these predictions, and sensible heat flux was measured at wind speeds up to 23 m/s. Within experimental error, the HEXMAX data do not show significant variation of the flux exchange coefficients with wind speed, indicating that modification of the models is needed. Roughness lengths for heat and water vapor derived from these direct flux measurements are slightly lower in value but closely parallel the decreasing trend with increasing wind speed predicted by the surface renewal model of Liu et al. [1979], created for lower wind speed regimes, which does not include effects of wave breaking. This suggests that either wave breaking does not significantly affect the surface layer fluxes for the wind speed range in the HEXMAX data, or that a compensating negative feedback process is at work in the lower atmosphere. The implication of the feedback hypothesis is that the moisture gained in the lower atmosphere from evaporation of sea spray over rough seas may be largely offset by decreased vapor flux from the air-sea interface.

Donelan M. A., B. K. Haus, N. Reul, W. J. Plant, M. Stiassnie, H. C. Graber, O. B. Brown, and E. S. Saltzman, 2004: On the limiting aerodynamic roughness of the ocean in very strong wind. Geophys. Res. Lett., 31,L18306, doi: 10.1029/2004GL 019460.

Drennan W. M., J. A. Zhang, J. R. French, C. McCormick, and P. G. Black, 2007: Turbulent fluxes in the hurricane boundary layer. Part II: Latent heat flux. J. Atmos. Sci., 64, 1103- 1115.10.1175/JAS3889.1

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http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F228449591_Turbulent_fluxes_in_the_hurricane_boundary_layer._Part_II_Latent_heat_flux

refpaperuri:(0c983f7b9d04ab2dde8398c347c02d8d)

http://www.researchgate.net/publication/228449591_Turbulent_fluxes_in_the_hurricane_boundary_layer._Part_II_Latent_heat_fluxAbstract As part of the recent ONR-sponsored Coupled Boundary Layer Air–Sea Transfer (CBLAST) Departmental Research Initiative, an aircraft was instrumented to carry out direct turbulent flux measurements in the high wind boundary layer of a hurricane. During the 2003 field season flux measurements were made during Hurricanes Fabian and Isabel. Here the first direct measurements of latent heat fluxes measured in the hurricane boundary layer are reported. The previous wind speed range for humidity fluxes and Dalton numbers has been extended by over 50%. Up to 30 m s 611 , the highest 10-m winds measured, the Dalton number is not significantly different from the Humidity Exchange over the Sea (HEXOS) result, with no evidence of an increase with wind speed.

Dudhia J., 1989: Numerical study of convection observed during the winter monsoon experiment using a mesoscale two dimensional model. J. Atmos. Sci., 46, 3077- 3107.10.1175/1520-0469(1989)0462.0.CO;2

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34a0f338a8622d0aee3c3811d44d3450

http%3A%2F%2Fci.nii.ac.jp%2Fnaid%2F10013124897

refpaperuri:(76536b43084d2ca4dd6ac23f1a23d059)

http://ci.nii.ac.jp/naid/10013124897Abstract A two-dimensional version of the Pennsylvania State University mesoscale model has been applied to Winter Monsoon Experiment data in order to simulate the diurnally occurring convection observed over the South China Sea. The domain includes a representation of part of Borneo as well as the sea so that the model can simulate the initiation of convection. Also included in the model are parameterizations of mesoscale ice phase and moisture processes and longwave and shortwave radiation with a diurnal cycle. This allows use of the model to test the relative importance of various heating mechanisms to the stratiform cloud deck, which typically occupies several hundred kilometers of the domain. Frank and Cohen's cumulus parameterization scheme is employed to represent vital unresolved vertical transports in the convective area. The major conclusions are: Ice phase processes are important in determining the level of maximum large-scale heating and vertical motion because there is a strong anvil component. The heating is initiated by a thermodynamic adjustment that takes place after the air leaves the updrafts and is associated with the difference between water and ice saturation. Melting and evaporation contribute to a 1ocalized mesoscale subsidence in a 50 km region to the rear of the moving convective area. The cooling associated with this almost cancels the cumulus heating in the lower to midtroposphere. Radiative heating was found to be the main ascent-forcing influence at high levels occupied by the widespread cirrus outflow. Additionally, radiative clear-air cooling helped the convection by continuously destabilizing the troposphere and countering the warming effect of convective updrafts. The overall structure and development of the system were well simulated, particularly the growth near the coast, and the propagation and decay in the cooler boundary layer further off-shore, but the rainfall may have been underestimated because of the two-dimensional assumptions of the model.

Dudhia, J., Coauthors, 2008: Prediction of Atlantic tropical cyclones with the Advanced Hurricane WRF (AHW) model. 28th Conf. on Hurricanes and Tropical Meteorology, Orlando, Florida, Preprint 18A. 2.cedcce8a-c9a9-4adb-b090-2b951b4a86d2/s?wd=paperuri%3A%28386dbb5c7ae7877cea0627e95a157023%29&filter=sc_long_sign&sc_ks_para=q%3DPREDICTION%20OF%20ATLANTIC%20TROPICAL%20CYCLONES%20WITH%20THE%20ADVANCED%20HURRICANE%20WRF%20%28AHW%29%20MODEL&tn=SE_baiduxueshu_c1gjeupa&ie=utf-8

Emanuel K. A., 1986: An air-sea interaction theory for tropical cyclones. Part I: Steady-state maintenance. J. Atmos. Sci., 43, 585- 605.10.1175/1520-0469(1986)0432.0.CO;2

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504439cc64b4832397ce434098772cbd

http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F215877085_An_air-sea_interaction_theory_for_tropical_cyclones._Part_I_Steady-state_maintenance

refpaperuri:(830a418b534890b226fee3a12303fa60)

http://www.researchgate.net/publication/215877085_An_air-sea_interaction_theory_for_tropical_cyclones._Part_I_Steady-state_maintenanceAbstract Observations and numerical simulators of tropical cyclones show that evaporation from the sea surface is essential to the development of reasonably intense storms. On the other hand, the CISK hypothesis, in the form originally advanced by Charney and Eliassen, holds that initial development results from the organized release of preexisting conditional instability. In this series of papers, we explore the relative importance of ambient conditional instability and air-sea latent and sensible heat transfer in both the development and maintenance of tropical cyclones using highly idealized models. In particular, we advance the hypothesis that the intensification and maintenance of tropical cyclones depend exclusively on self-induced heat transfer from the ocean. In this sense, these storms may be regarded as resulting from a finite amplitude air-sea interaction instability rather than from a linear instability involving ambient potential buoyancy. In the present paper, we attempt to show that reasonably intense cyclones may be maintained in a steady state without conditional instability of ambient air. In Part II we will demonstrate that weak but finite-amplitude axisymmetric disturbances may intensify in a conditionally neutral environment.

Emanuel K. A., 1995: Sensitivity of tropical cyclones to surface exchange coefficients and a revised steady-state model incorporating eye dynamics. J. Atmos. Sci., 52, 3969- 3976.10.1175/1520-0469(1995)0522.0.CO;2

26e5e6af-531d-4509-8a13-ed111ff2d09a

9ce2c9bb8eda1ddf38eebf370b607942

http://www.researchgate.net/publication/215877087_Sensitivity_of_tropical_cyclones_to_surface_exchange_coefficients_and_a_revised_steady-state_model_incorporating_eye_dynamics

http://www.researchgate.net/publication/215877087_Sensitivity_of_tropical_cyclones_to_surface_exchange_coefficients_and_a_revised_steady-state_model_incorporating_eye_dynamicsAbstract Numerical and theoretical models of tropical cyclones indicate that the maximum wind speed in mature storms is sensitive to the ratio of the enthalpy and momentum surface exchange coefficients and that the spinup time of tropical cyclones varies inversely with the magnitude of these coefficients. At the same time, the Carnot cycle model developed by the author predicts that the central pressure of mature cyclones is independent of the magnitude of the exchange coefficients. The author presents numerical simulations that prove this last prediction false and suggest that the reason for this failure is the neglect of eye dynamics in the steady-state theory. On this basis, the existing theory is modified to account for eye dynamics, and the predictions of the revised theory are compared to the results of numerical simulations. Both the revised theory and the numerical modeling results, when compared to observations, suggest that the ratio of enthalpy to momentum exchange coefficients in real hurricanes lies in the range 0.75-1.5, contradicting published speculations about the behavior of this ratio at high surface wind speed.

French J. R., W. M. Drennan, J. A. Zhang, and P. G. Black, 2007: Turbulent fluxes in the hurricane boundary layer. Part I: Momentum flux. J. Atmos. Sci., 64, 1089- 1102.10.1175/JAS3887.1

5d1f8c93-7f4c-4078-9b87-ff918a64a82e

baebbb88d10020b62bdc09f20b0d8d97

http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F240686670_Turbulent_Fluxes_in_the_Hurricane_Boundary_Layer._Part_I_Momentum_Flux

refpaperuri:(d9606d69e69040d8a8c6c3f787db99da)

http://www.researchgate.net/publication/240686670_Turbulent_Fluxes_in_the_Hurricane_Boundary_Layer._Part_I_Momentum_FluxAbstract An important outcome from the ONR-sponsored Coupled Boundary Layer Air–Sea Transfer (CBLAST) Hurricane Program is the first-ever direct measurements of momentum flux from within hurricane boundary layers. In 2003, a specially instrumented NOAA P3 aircraft obtained measurements suitable for computing surface wind stress and ultimately estimating drag coefficients in regions with surface wind between 18 and 30 m s 611 . Analyses of data are presented from 48 flux legs flown within 400 m of the surface in two storms. Results suggest a roll-off in the drag coefficient at higher wind speeds, in qualitative agreement with laboratory and modeling studies and inferences of drag coefficients using a log-profile method. However, the amount of roll-off and the wind speed at which the roll-off occurs remains uncertain, underscoring the need for additional measurements.

Garratt J. R., 1992: The Atmospheric Boundary Layer. Cambridge University Press,316 pp.

Geernaert G. L., K. L. Davidson, S. E. Larsen, and T. Mikkelsen, 1988: Wind stress measurements during the Tower Ocean Wave and Radar Dependence Experiment. J. Geophys. Res., 93, 13 913- 13 923.10.1029/JC093iC11p13913

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http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2FJC093iC11p13913%2Ffull

refpaperuri:(704ec49bde76404ed958669227e0cdb0)

http://onlinelibrary.wiley.com/doi/10.1029/JC093iC11p13913/fullDuring the Tower Ocean Wave and Radar Dependence Experiment (TOWARD), near-continuous measurements of the wind drag were conducted using the dissipation technique. An intercomparison between these measurements and direct stress magnitudes using a sonic anemometer was performed over 3 days of the experiment. The results indicated that the dissipation technique compared well to the directly determined values when conditions were steady and neutral; otherwise, the dissipation method performed poorly. When neutrally stratified data were used, the drag coefficient exhibited a systematic dependence on both surface tension and wave age.

Green B. W., F. Q. Zhang, 2013: Impacts of air-sea flux parameterizations on the intensity and structure of tropical cyclones. Mon. Wea. Rev., 141, 2308- 2324.10.1175/MWR-D-12-00274.1

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http://www.researchgate.net/publication/277449791_Impacts_of_AirSea_Flux_Parameterizations_on_the_Intensity_and_Structure_of_Tropical_Cyclones?ev=auth_pub

http://www.researchgate.net/publication/277449791_Impacts_of_AirSea_Flux_Parameterizations_on_the_Intensity_and_Structure_of_Tropical_Cyclones?ev=auth_pubFluxes of momentum and moist enthalpy across the air-sea interface are believed to be one of the most important factors in determining tropical cyclone intensity. Because these surface fluxes cannot be directly resolved by numerical weather prediction models, their impacts on tropical cyclones must be accounted for through subgrid-scale parameterizations. There are several air-sea surface flux parameterization schemes available in the Weather Research and Forecasting (WRF) Model; these schemes differ from one another in their formulations of the wind speed-dependent exchange coefficients of momentum, sensible heat, and moisture (latent heat). The effects of surface fluxes on the intensity and structure of tropical cyclones are examined through convection-permitting WRF simulations of Hurricane Katrina (2005). It is found that the intensity (and, to a lesser extent, structure) of the simulated storms is sensitive to the choice of surface flux parameterization scheme. In agreement with recent studies, the drag coefficient CD is found to affect the pressure-wind relationship (between minimum sea level pressure and maximum 10-m wind speed) and to change the radius of maximum near-surface winds of the tropical cyclone. Fluxes of sensible and latent heat (i.e., moist enthalpy) affect intensity but do not significantly change the pressure-wind relationship. Additionally, when low-level winds are strong, the contribution of dissipative heating to calculations of sensible heat flux is not negligible. Expanding the sensitivity tests to several dozen cases from the 2008 to 2011 Atlantic hurricane seasons demonstrates the robustness of these findings.

Hall J. D., M. Xue, L. K. Ran, L. M. Leslie, 2013: High-resolution modeling of Typhoon Morakot (2009): Vortex Rossby waves and their role in extreme precipitation over Taiwan. J. Atmos. Sci., 70, 163- 186.10.1175/JAS-D-11-0338.1

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http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F258794807_High-Resolution_Modeling_of_Typhoon_Morakot_%282009%29_Vortex_Rossby_Waves_and_Their_Role_in_Extreme_Precipitation_over_Taiwan

refpaperuri:(7b32a105c98d6f5107db1ffe6962cd3a)

http://www.researchgate.net/publication/258794807_High-Resolution_Modeling_of_Typhoon_Morakot_(2009)_Vortex_Rossby_Waves_and_Their_Role_in_Extreme_Precipitation_over_TaiwanAbstract A high-resolution nonhydrostatic numerical model, the Advanced Regional Prediction System (ARPS), was used to simulate Typhoon Morakot (2009) as it made landfall over Taiwan, producing record rainfall totals. In particular, the mesoscale structure of the typhoon was investigated, emphasizing its associated deep convection, the development of inner rainbands near the center, and the resultant intense rainfall over western Taiwan. Simulations at 15- and 3-km grid spacing revealed that, following the decay of the initial inner eyewall, a new, much larger eyewall developed as the typhoon made landfall over Taiwan. Relatively large-amplitude wave structures developed in the outer eyewall and are identified as vortex Rossby waves (VRWs), based on the wave characteristics and their similarity to VRWs identified in previous studies. Moderate to strong vertical shear over the typhoon system produced a persistent wavenumber-1 (WN1) asymmetric structure during the landfall period, with upward motion and deep convection in the downshear and downshear-left sides, consistent with earlier studies. This strong asymmetry masks the effects of WN1 VRWs. WN2 and WN3 VRWs apparently are associated with the development of deep convective bands in Morakot southwestern quadrant. This occurs as the waves move cyclonically into the downshear side of the cyclone. Although the typhoon track and topographic enhancement contribute most to the record-breaking rainfall totals, the location of the convective bands, and their interaction with the mountainous terrain of Taiwan, also affect the rainfall distribution. Quantitatively, the 3-km ARPS rainfall forecasts are superior to those obtained from coarser-resolution models.

Haus B. K., D. Jeong, M. A. Donelan, J. A. Zhang, and I. Savelyev, 2010: Relative rates of sea-air heat transfer and frictional drag in very high winds. Geophys. Res. Lett. 37,L07802, doi: 10.1029/2009GL042206.10.1029/2009GL042206

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http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F2009GL042206%2Fpdf

refpaperuri:(87434d6e78a3294213503f22996ffc6b)

http://onlinelibrary.wiley.com/doi/10.1029/2009GL042206/pdfABSTRACT Hurricanes are fueled by evaporation and convection from the ocean and they lose energy through the frictional drag of the atmosphere on the ocean surface. The relative rates of these processes have been thought to provide a limit on the maximum potential hurricane intensity. Here we report laboratory observations of these transfers for scaled winds equivalent to a strong Category 1 hurricane (38 ms-1). We show that the transfer coefficient ratio holds closely to a level of &tilde;0.5 even in the highest observed winds, where previous studies have suggested there is a distinct regime change at the air-sea interface. This value is well below the expected threshold value for intense hurricanes of 0.75. Recent three-dimensional model studies also find that the coefficient ratio can be much lower than 0.75, which suggests that other factors such as eyewall and/or vortex dynamics are responsible for the formation of very strong hurricanes.

Hong S. Y., Y. Noh, and J. Dudhia, 2006: A new vertical diffusion package with an explicit treatment of entrainment processes. Mon. Wea. Rev., 134( 9), 2318- 2341.10.1175/MWR3199.1

79f98ee85a3853a6bfee0ec84e90c901

http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F252170327_A_New_Vertical_Diffusion_Package_with_an_Explicit_Treatment_of_Entrainment_Processes

http://www.researchgate.net/publication/252170327_A_New_Vertical_Diffusion_Package_with_an_Explicit_Treatment_of_Entrainment_ProcessesAbstract This paper proposes a revised vertical diffusion package with a nonlocal turbulent mixing coefficient in the planetary boundary layer (PBL). Based on the study of Noh et al. and accumulated results of the behavior of the Hong and Pan algorithm, a revised vertical diffusion algorithm that is suitable for weather forecasting and climate prediction models is developed. The major ingredient of the revision is the inclusion of an explicit treatment of entrainment processes at the top of the PBL. The new diffusion package is called the Yonsei University PBL (YSU PBL). In a one-dimensional offline test framework, the revised scheme is found to improve several features compared with the Hong and Pan implementation. The YSU PBL increases boundary layer mixing in the thermally induced free convection regime and decreases it in the mechanically induced forced convection regime, which alleviates the well-known problems in the Medium-Range Forecast (MRF) PBL. Excessive mixing in the mixed layer in the presence of strong winds is resolved. Overly rapid growth of the PBL in the case of the Hong and Pan is also rectified. The scheme has been successfully implemented in the Weather Research and Forecast model producing a more realistic structure of the PBL and its development. In a case study of a frontal tornado outbreak, it is found that some systematic biases of the large-scale features such as an afternoon cold bias at 850 hPa in the MRF PBL are resolved. Consequently, the new scheme does a better job in reproducing the convective inhibition. Because the convective inhibition is accurately predicted, widespread light precipitation ahead of a front, in the case of the MRF PBL, is reduced. In the frontal region, the YSU PBL scheme improves some characteristics, such as a double line of intense convection. This is because the boundary layer from the YSU PBL scheme remains less diluted by entrainment leaving more fuel for severe convection when the front triggers it.

Hosomi T., 2005: Implementation of targeted moisture diffusion for the JMA Regional Spectral Model (RSM). CAS/JSC WGNE Research Activities in Atmospheric and Oceanic Modelling/WMO. , 35, 7- 8.be97e683-2551-40e0-ba83-715691c7ba22

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http%3A%2F%2Fwww.wcrp-climate.org%2FWGNE%2FBlueBook%2F2005%2Findividual-articles%2F05_Hosomi_Takuya_jma_rsm_tmd.pdf

refpaperuri:(57fdf69fb5e1028815598792aae2e250)

http://www.wcrp-climate.org/WGNE/BlueBook/2005/individual-articles/05_Hosomi_Takuya_jma_rsm_tmd.pdfJapan Meteorological Agency operates the Regional Spectral Model (RSM) twice a day. It covers East Asia and makes a forecast up to 51 hours. A forecast of the JMA Global Spectral Model (GSM) is used for a lateral boundary condition. An initial condition is analyzed by a

Huang H.-L., M.-J. Yang, and C.-H. Sui, 2014: Water budget and precipitation efficiency of Typhoon Morakot (2009). J. Atmos. Sci., 71, 112- 129.10.1175/JAS-D-13-053.1

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http%3A%2F%2Fonlinelibrary.wiley.com%2Fresolve%2Freference%2FXREF%3Fid%3D10.1175%2FJAS-D-13-053.1

refpaperuri:(b5e7f05aa58f3e42145f90e79a9ca277)

http://onlinelibrary.wiley.com/resolve/reference/XREF?id=10.1175/JAS-D-13-053.1Abstract In this study, the Weather Research and Forecasting model, version 3.2, with the finest grid size of 1 km is used to explicitly simulate Typhoon Morakot (2009), which dumped rainfall of more than 2600 mm in 3 days on Taiwan. The model reasonably reproduced the track, the organization, the sizes of the eye and eyewall, and the characteristics of major convective cells in outer rainbands. The horizontal rainfall distribution and local rainfall maximum in the southwestern portion of the Central Mountain Range (CMR) are captured. The simulated rain rate and precipitation efficiency (PE) over the CMR are highly correlated. In the absence of terrain forcing, the simulated TC’s track is farther north and rainfall distribution is mainly determined by rainbands. The calculated rain rate and PE over the CMR during landfall are about 50% and 15%–20% less than those of the full-terrain control run, respectively. By following major convective cells that propagate eastward from the Taiwan Strait to the CMR, it is found that the PE and the processes of vapor condensation and raindrop evaporation are strongly influenced by orographic lifting; the PEs are 60%–75% over ocean and more than 95% over the CMR, respectively. The secondary increase of PE results from the increase of ice-phase deposition ratio when the liquid-phase condensation becomes small as the air on the lee side subsides and moves downstream. This nearly perfect PE over the CMR causes tremendous rainfall in southwestern Taiwan, triggering enormous landslides and severe flooding.

JMA, 2007: Outline of the operational numerical weather prediction at the Japan Meteorological Agency. Appendix to WMO Numerical Weather Prediction Progress Report, Japan Meteorological Agency, Tokyo, 194 pp./s?wd=paperuri%3A%28788531031b89ca05cba38bad7aa316f1%29&filter=sc_long_sign&sc_ks_para=q%3DOutline%20of%20operational%20numerical%20weather%20prediction%20at%20Japan%20Meteorological%20Agency&tn=SE_baiduxueshu_c1gjeupa&ie=utf-8

Large W. G., S. Pond, 1981: Open ocean momentum flux measurements in moderate to strong winds. J. Phys. Oceanogr., 11, 324- 336.49189dde-3478-4641-bcc6-5ced3167d6d3

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refpaperuri:(173ee46bbe9c0801121bf36602f46a6e)

http://www.bioone.org/servlet/linkout?suffix=i1551-5036-24-sp3-159-Large1&dbid=16&doi=10.2112%2F06-0795.1&key=10.1175%2F1520-0485(1981)011%3C0324%3AOOMFMI%3E2.0.CO%3B2

Li X., J. Ming, Y. Wang, K. Zhao, and M. Xue, 2013: Assimilation of T-TREC-retrieved wind data with WRF 3DVAR for the short-term forecasting of typhoon Meranti (2010) near landfall. J. Geophys. Res., 118, 10 361- 10 375.10.1002/jgrd.50815

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http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1002%2Fjgrd.50815%2Fabstract%3Bjsessionid%3D1661830CC2477FB16C828F39AE713ECF.f04t03

refpaperuri:(3539ed405e6e232a9a6bac2bf87961e1)

http://d.wanfangdata.com.cn/Conference_WFHYXW561532.aspx?f=datatangABSTRACT extended Tracking Radar Echo by Correlation (TREC) technique, called T-TREC technique, has been developed recently to retrieve horizontal circulations within tropical cyclones (TCs) from single Doppler radar reflectivity (Z) and radial velocity (Vr, when available) data. This study explores, for the first time, the assimilation of T-TREC-retrieved winds for a landfalling typhoon, Meranti (2010), into a convection-resolving model, the WRF (Weather Research and Forecasting). The T-TREC winds or the original Vr data from a single coastal Doppler radar are assimilated at the single time using the WRF three-dimensional variational (3DVAR), at 8, 6, 4, and 2 h before the landfall of typhoon Meranti. In general, assimilating T-TREC winds results in better structure and intensity analysis of Meranti than directly assimilating Vr data. The subsequent forecasts for the track, intensity, structure and precipitation are also better, although the differences becomes smaller as the Vr data coverage improves when the typhoon gets closer to the radar. The ability of the T-TREC retrieval in capturing more accurate and complete vortex circulations in the inner-core region of TC is believed to be the primary reason for its superior performance over direct assimilation of Vr data; for the latter, the data coverage is much smaller when the TC is far away and the cross-beam wind component is difficult to analyze accurately with 3DVAR method.

Lin Y.-L., R. D. Farley, and H. D. Orville, 1983: Bulk parameterization of the snow field in a cloud model. J. Climate Appl. Meteor., 22( 6), 1065- 1092.

Liu Y. B., D.-L. Zhang, and M. K. Yau, 1999: A multiscale numerical study of Hurricane Andrew (1992). Part II: Kinematics and inner-core structures. Mon. Wea. Rev., 127, 2597- 2616.10.1175/1520-0493(1999)127<2597:AMNSOH>2.0.CO;2

b0c4d84d-39fe-4658-8e91-1c9eaa6f653d

92854b578b2d9d4412d2ef6605d09b62

http%3A%2F%2Fci.nii.ac.jp%2Fnaid%2F80010744120

refpaperuri:(e8dba250839fb18f58d52270a289bf35)

http://ci.nii.ac.jp/naid/80010744120ABSTRACT Despite considerable research, understanding of the temporal evolution of the inner-core structures of hurricanes is very limited owing to the lack of continuous high-resolution observational data of a storm. In this study, the results of a 72-h explicit simulation of Hurricane Andrew (1992) with a grid size of 6 km are examined to explore the inner-core axisymmetric and asymmetric structures of the storm during its rapid deepening stage. Based on the simulation, a conceptual model of the axisymmetric structures of the storm is proposed. Most of the proposed structures confirm previous observations. The main ingredients include a main inflow (outflow) in the boundary layer (upper troposphere) with little radial flow in between, a divergent slantwise ascent in the eyewall, a penetrative dry downdraft at the inner edge of the eyewall, and a general weak subsiding motion in the eye with typical warming/drying above an inversion located near an altitude of about 2--3 km. The storm ...

Malkus J. S., H. Riehl, 1960: On the dynamics and energy transformations in steady-state hurricanes. Tellus, 12, 1- 20.10.1111/j.2153-3490.1960.tb01279.x

e59be9d0-ced8-4e17-afc1-d10e89ace9b8

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http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1111%2Fj.2153-3490.1960.tb01279.x%2Fpdf

refpaperuri:(1cc9aa1428cb77949faa3143473cc3ec)

http://onlinelibrary.wiley.com/doi/10.1111/j.2153-3490.1960.tb01279.x/pdfFinally, rainfall, efficiency of work done by the storm, and kinetic energy budgets are examined in an attempt to understand the difference between the hurricane—a rare phenomenon—and the common sub-hurricane tropical storm.

Ming J., Y. Q. Ni, and X. Y. Shen, 2009: The dynamical characteristics and wave structure of typhoon Rananim (2004). Adv. Atmos. Sci.,26, 523-542, doi: 10.1007/s00376-009-0523-0.

Ming J., J. J. Song, B. J. Chen, and K. F. Wang, 2012: Boundary layer structure in typhoon Saomai (2006): Understanding the effects of exchange coefficient. J. Trop. Meteor., 18( 3), 195- 206.10.3969/j.issn.1006-8775.2012.02.009

41ff03a3-df92-42f6-b45f-9aa75fb1b889

80284d44fda421528b56279957e6498d

http://www.cnki.com.cn/Article/CJFDTotal-RQXB201202011.htm

http://www.cnki.com.cn/Article/CJFDTotal-RQXB201202011.htmRecent studies have shown that surface fluxes and exchange coefficients are particularly important to models attempting to simulate the evolution and maintenance of hurricanes or typhoons.By using an advanced research version of the Weather Research and Forecasting(ARW)modeling system,this work aims to study the impact of modified exchange coefficient on the intensity and structures of typhoon Saomai(2006)over the western North Pacific.Numerical experiments with the modified and unmodified exchange coefficients are used to investigate the intensity and structure of the storm,especially the structures of the boundary layer within the storm.Results show that,compared to the unmodified experiment,the simulated typhoon in the modified experiment has a bigger deepening rate after 30-h and is the same as the observation in the last 12-h.The roughness is leveled off when wind speed is greater than 30 m/s.The momentum exchange coefficient(CD)and enthalpy exchange coefficient(CK)are leveled off too,and CD is decreased more than CK when wind speed is greater than 30 m/s.More sensible heat flux and less latent heat flux are produced.In the lower level,the modified experiment has slightly stronger outflow,stronger vertical gradient of equivalent potential temperature and substantially higher maximum tangential winds than the unmodified experiment has.The modified experiment generates larger wind speed and water vapor tendencies and transports more air of high equivalent potential temperature to the eyewall in the boundary layer.It induces more and strong convection in the eyewall,thereby leading to a stronger storm.

Mlawer E. J., S. J. Taubman, P. D. Brown, M. J. Iacono, and S. A. Clough, 1997: Radiative transfer for inhomogeneous atmosphere: RRTM, a validated correlated-k model for the longwave. J. Geophys. Res., 102, 16 663- 16 682.10.1029/97JD00237

2e06658e-dcf6-4eb8-a12a-08b5972b271f

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http://onlinelibrary.wiley.com/doi/10.1029/97JD00237/pdf

http://onlinelibrary.wiley.com/doi/10.1029/97JD00237/pdfABSTRACT A rapid and accurate radiative transfer model (RRTM) for climate applications been developed and the results extensively evaluated. The current version of RRTM calculates fluxes and cooling rates for the longwave spectral region (10-3000 cm-1) for an arbitrary clear atmosphere. The molecular species treated in the model are water vapor, carbon dioxide, ozone, methane, nitrous oxide, and the common halocarbons. The radiative transfer in RRTM is performed using the correlated-k method: the k distributions are attained directly from the LBLRTM line-by-line model, which connects the absorption coefficients used by RRTM to high-resolution radiance validations done with observations. Refined methods have been developed for treating bands containing gases with overlapping absorption, for the determination of values of the Planck function appropriate for use in the correlated-k approach, and for the inclusion of minor absorbing species in a band. The flux and cooling rate results of RRTM are linked to measurement through the use of LBLRTM, which has been substantially validated with observations. Validations of RRTM using LBLRTM have been performed for the midlatitude summer, tropical, midlatitude winter, subarctic winter, and four atmospheres from the Spectral Radiance Experiment campaign. On the basis of these validations the longwave accuracy of RRTM for any atmosphere is as follows: 0.6 W m-2 (relative to LBLRTM) for net flux in each band at all altitudes, with a total (10-3000 cm-1) error of less than 1.0 W m-2 at any altitudes; 0.07 K d-1 for total cooling rate error in the troposphere and lower stratosphere, and 0.75 K d-1 in the upper stratosphere and above. Other comparisons have been performed on RRTM using LBLRTM to gauge its sensitivity to changes in the abundance of specific species, including the halocarbons and carbon dioxide. The radiative forcing due to doubling the concentration of carbon dioxide is attained with an accuracy of 0.24 W m-2, an error of less than 5%. The speed of execution of RRTM compares favorably with that of other rapid radiation models, indicating that the model is suitable for use in general circulation models.

Montgomery M. T., R. K. Smith, and S. V. Nguyen, 2010: Sensitivity of tropical-cyclone models to the surface drag coefficient . Quart. J. Roy. Meteor. Soc.,136, 1945-1953, doi: 10.1002/qj.702.10.1002/qj.702

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http://onlinelibrary.wiley.com/doi/10.1002/qj.702/pdf

http://onlinelibrary.wiley.com/doi/10.1002/qj.702/pdfThe contribution of M. T. Montgomery to this article was prepared as part of his official duties as a United States Federal Government employee.

Noh Y., W. G. Cheon, S. Y. Hong, and S. Raasch, 2003: Improvement of the K-profile model for the planetary boundary layer based on large eddy simulation data. Bound.Layer Meteor., 107( 3), 401- 427.10.1023/A:1022146015946

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http%3A%2F%2Flink.springer.com%2Farticle%2F10.1023%2FA%3A1022146015946

refpaperuri:(18193937665365080c4f347114f8bfc9)

http://link.springer.com/article/10.1023/A:1022146015946Modifications of the widely used K-profile model of the planetary boundary layer (PBL), reported by Troen and Mahrt (TM) in 1986, are proposed and their effects examined by comparison with large eddy simulation (LES) data. The modifications involve three parts. First, the heat flux from the entrainment at the inversion layer is incorporated into the heat and momentum profiles, and it is used to predict the growth of the PBL directly. Second, profiles of the velocity scale and the Prandtl number in the PBL are proposed, in contrast to the constant values used in the TM model. Finally, non-local mixing of momentum was included. The results from the new PBL model and the original TM model are compared with LES data. The TM model was found to give too high PBL heights in the PBL with strong shear, and too low heights for the convection-dominated PBL, which causes unrealistic heat flux profiles. The new PBL model improves the predictability of the PBL height and produces profiles that are more realistic. Moreover, the new PBL model produces more realistic profiles of potential temperature and velocity. We also investigated how each of these three modifications affects the results, and found that explicit representation of the entrainment rate is the most critical.

Nolan D. S., J. A. Zhang, and D. P. Stern, 2009: Evaluation of planetary boundary layer parameterizations in tropical cyclones by comparison of in situ data and high-resolution simulations of Hurricane Isabel (2003). Part I: Initialization, maximum winds, and the outer-core boundary layer structure. Mon. Wea. Rev., 137, 3651- 3674.

Ooyama K., 1969: Numerical simulation of the life cycle of tropical cyclones. J. Atmos. Sci., 26, 3- 40.10.1175/1520-0469(1969)026<0003:NSOTLC>2.0.CO;2

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http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F215877167_Numerical_simulation_of_the_life_cycle_of_tropical_cyclones

refpaperuri:(59c5752acdb9443cdac53f609537932d)

http://www.researchgate.net/publication/215877167_Numerical_simulation_of_the_life_cycle_of_tropical_cyclonesAbstract The tropical cyclone is a solitary creature of the tropical oceans accompanied by violent rotating winds and torrential rain. Observational studies and diagnostic analyses leave little doubt that the energy required for driving the vortex comes from the latent heat of condensation released by tall convective clouds around the center, and that the frictionally induced inflow in the vortex plays a major role in supporting the continued activity of convective clouds. This dual character with respect to important scales of motion poses a great difficulty in investigating the dynamics of tropical cyclones as time-dependent phenomena. However, in order to understand the large-scale aspects of tropical cyclones, one may formulate the role of convective clouds in terms of cyclone-scale variables with only implicit consideration of the dynamics of individual clouds. The present study is an attempt to understand the basic mechanism of tropical cyclones by constructing a numerical-dynamical model on such a basis. The model assumes that the large-scale hydrodynamical aspects of a tropical cyclone may be represented by an axisymmetric, quasi-balanced vortex in a stably stratified incompressible fluid, while the effects of moist convection may be formulated through the first law of thermodynamics applied to an implicit model of penetrative convective clouds. The airea exchange of angular momentum as well as latent and sensible heat is explicitly calculated in the model with the use of conventional approximations. Results of numerical integration show that the model is capable of simulating the typical life cycle of tropical cyclones, including the mature hurricane stage, with a remarkable degree of reality. The response of the model cyclone to changes in such parameters as the sea surface temperature, the coefficient of airea energy exchange, and the initial conditions is tested in a number of numerical experiments to show quite plausible results. A detailed diagnosis of the energy budget of the simulated tropical cyclone is also carried out. The rate of total rainfall, the production and dissipation of kinetic energy, and other energetic characteristics of the computed cyclone compare very well with available estimates for observed tropical cyclones. Because of the restrictive assumption of axisymmetry and other weak approximations, the model is not realistic enough to predict behavior of individual tropical cyclones in nature. The limitation of the present model in this regard is also discussed.

Powell M. D., P. J. Vickery, and T. A. Reinhold, 2003: Reduced drag coefficient for high wind speeds in tropical cyclones. Nature, 422, 279- 283.10.1038/nature01481

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http%3A%2F%2Fmed.wanfangdata.com.cn%2FPaper%2FDetail%2FPeriodicalPaper_PM12646913

refpaperuri:(9f794ceb92e784a337ee22f4fed807a6)

http://med.wanfangdata.com.cn/Paper/Detail/PeriodicalPaper_PM12646913The transfer of momentum between the atmosphere and the ocean is described in terms of the variation of wind speed with height and a drag coefficient that increases with sea surface roughness and wind speed. But direct measurements have only been available for weak winds; momentum transfer under extreme wind conditions has therefore been extrapolated from these field measurements. Global Positioning System sondes have been used since 1997 to measure the profiles of the strong winds in the marine boundary layer associated with tropical cyclones. Here we present an analysis of these data, which show a logarithmic increase in mean wind speed with height in the lowest 200 m, maximum wind speed at 500 m and a gradual weakening up to a height of 3 km. By determining surface stress, roughness length and neutral stability drag coefficient, we find that surface momentum flux levels off as the wind speeds increase above hurricane force. This behaviour is contrary to surface flux parameterizations that are currently used in a variety of modelling applications, including hurricane risk assessment and prediction of storm motion, intensity, waves and storm surges.

Rosenthal S. L., 1971: The response of a tropical cyclone model to variations in boundary layer parameters, initial conditions, lateral boundary conditions and domain size. Mon. Wea. Rev., 99, 767- 777.10.1175/JCLI-3293.1

4184c72d-5ff7-4cde-8f33-1fa985e26c7c

ac5e8a56e6565a1c40fc3f604a2a8dbf

http://www.researchgate.net/publication/249611701_Estimating_the_Uncertainty_in_a_Regional_Climate_Model_Related_to_Initial_and_Lateral_Boundary_Conditions?ev=auth_pub

http://www.researchgate.net/publication/249611701_Estimating_the_Uncertainty_in_a_Regional_Climate_Model_Related_to_Initial_and_Lateral_Boundary_Conditions?ev=auth_pubThere is a growing demand for regional-scale climate predictions and assessments. Quantifying the impacts of uncertainty in initial conditions and lateral boundary forcing data on regional model simulations can potentially add value to the usefulness of regional climate modeling. Results from a regional model depend on the realism of the driving data from either global model outputs or global analyses; therefore, any biases in the driving data will be carried through to the regional model. This study used four popular global analyses and achieved 16 driving datasets by using different interpolation procedures. The spread of the 16 datasets represents a possible range of driving data based on analyses to the regional model. This spread is smaller than typically associated with global climate model realizations of the Arctic climate. Three groups of 16 realizations were conducted using the fifth-generation Pennsylvania State University ational Center for Atmospheric Research (PSU CAR) Mesoscale Model (MM5) in an Arctic domain, varying both initial and lateral boundary conditions, varying lateral boundary forcing only, and varying initial conditions only. The response of monthly mean atmospheric states to the variations in initial and lateral driving data was investigated. Uncertainty in the regional model is induced by the interaction between biases from different sources. Because of the nonlinearity of the problem, contributions from initial and lateral boundary conditions are not additive. For monthly mean atmospheric states, biases in lateral boundary conditions generally contribute more to the overall uncertainty than biases in the initial conditions. The impact of initial condition variations decreases with the simulation length while the impact of variations in lateral boundary forcing shows no clear trend. This suggests that the representativeness of the lateral boundary forcing plays a critical role in long-term regional climate modeling. The extent of impact of the driving data uncertainties on regional climate modeling is variable dependent. For some sensitive variables (e.g., precipitation, boundary layer height), even the interior of the model may be significantly affected.

Rotunno R., K. A. Emanuel, 1987: An air-sea interaction theory for tropical cyclones. Part II: Evolutionary study using a nonhydrostatic axisymmetric numerical model. J. Atmos. Sci., 44, 542- 561.10.1175/1520-0469(1987)044<0542:AAITFT>2.0.CO;2

10f56979-7771-4e79-9655-57c861f7428f

c30f99c2c09dabed521896d960950cbe

http://www.researchgate.net/publication/215877180_An_AirSea_interaction_theory_for_tropical_cyclones._Part_II_Evolutionary_study_using_a_nonhydrostatic_axisymmetric_numerical_model

http://www.researchgate.net/publication/215877180_An_AirSea_interaction_theory_for_tropical_cyclones._Part_II_Evolutionary_study_using_a_nonhydrostatic_axisymmetric_numerical_modelAbstract In Part I of this study an analytical model for a steady-state tropical cyclone is constructed on the assumption that boundary-layer air parcels are conditionally neutral to displacements along the angular momentum surfaces of the hurricane vortex. The reversible thermodynamics implied by this assumption allows the mature storm to be thought of as a simple Carnot engine, acquiring heat at the high-temperature ocean surface and losing heat near the low-temperature tropopause. Although the oceanic heat source is universally recognized as the sine qua non for the mature hurricane, there is also wide acceptance of conditional instability of the second kind (CISK) (which makes no specific reference to surface heat fluxes) as the formative mechanism. This ambivalence is seen in that all numerical-simulation studies find it essential to have transfer from the ocean surface yet all start from a conditionally unstable atmosphere. The hypothesis put forward in Part I, based on the steady-state theory, is that the truly important thermodynamic interaction, even in the developing star , is between vortex and ocean (as distinct from vortex and convection sustained by preexisting conditional instability as in the CISK theory) with cumulus convection rapidly redistributing heat acquired at the oceanic source upward and outward to the upper tropospheric sink. On this view, it is not the organization of convection that is needed per se, but the organization of surface heat flux. We have constructed a time-dependent nonhydrostatic axisymmetric numerical model with convection explicitly accounted for to examine this idea. The numerical experiments show that as a result of a finite-amplitude air-sea interaction instability a hurricane-like vortex may indeed amplify in an atmosphere which is neutral to cumulus convection and attain an intensity and structure which are in excellent agreement with the theoretical predictions of Part I. We examine in detail the model's heat budget which confirms the crucial importance of boundary-layer processes in controlling the structure and evolution of the vortex. We also confirm the conjecture made in Part I that, within a large-scale limit, the horizontal size of the mature tropical cyclone is determined by that of the initial disturbance.

Schwartz C. S., Z. Q. Liu, Y. S. Chen, and X. Y. Huang, 2012: Impact of assimilating microwave radiances with a limited-area ensemble data assimilation system on forecasts of Typhoon Morakot. Wea.Forecasting, 27, 424- 437.10.1175/WAF-D-11-00033.1

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http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F258724584_Impact_of_Assimilating_Microwave_Radiances_with_a_Limited-Area_Ensemble_Data_Assimilation_System_on_Forecasts_of_Typhoon_Morakot

refpaperuri:(dad552e05a0dd72a5b1b8e2983c56ded)

http://www.researchgate.net/publication/258724584_Impact_of_Assimilating_Microwave_Radiances_with_a_Limited-Area_Ensemble_Data_Assimilation_System_on_Forecasts_of_Typhoon_MorakotTwo parallel experiments were designed to evaluate whether assimilating microwave radiances with a cyclic, limited-area ensemble adjustment Kalman filter (EAKF) could improve track, intensity, and precipitation forecasts of Typhoon Morakot (2009). The experiments were configured identically, except that one assimilated microwave radiances and the other did not. Both experiments produced EAKF analyses every 6 h between 1800 UTC 3 August and 1200 UTC 9 August 2009, and the mean analyses initialized 72-h Weather Research and Forecasting model forecasts. Examination of individual forecasts and average error statistics revealed that assimilating microwave radiances ultimately resulted in better intensity forecasts compared to when radiances were withheld. However, radiance assimilation did not substantially impact track forecasts, and the impact on precipitation forecasts was mixed. Overall, net positive results suggest that assimilating microwave radiances with a limited-area EAKF system is beneficial for tropical cyclone prediction, but additional studies are needed.

Skamarock W.C., Coauthors, 2008: Description of the advanced research WRF version 3, Rep. NCAR/TN-475++STR, Natl. Cent. for Atmos. Res., Boulder, Colo., 113 pp.

Smith R. K., M. T. Montgomery, and N. Van Sang, 2009: Tropical cyclone spin-up revisited. Quart. J. Roy. Meteor. Soc., 135, 1321- 1335.10.1002/qj.428

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http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1002%2Fqj.428%2Fpdf

refpaperuri:(c63b2f02173a285d0f4388d307750245)

http://onlinelibrary.wiley.com/doi/10.1002/qj.428/pdfWe present numerical experiments to investigate axisymmetric interpretations of tropical cyclone spin-up in a three-dimensional model. Two mechanisms are identified for the spin-up of the mean tangential circulation. The first involves the convergence of absolute angular momentum above the boundary layer and is a mechanism to spin up the outer circulation, i.e. to increase the vortex size. The second involves the convergence of absolute angular momentum within the boundary layer and is a mechanism to spin up the inner core. It is associated with the development of supergradient wind speeds in the boundary layer. The existence of these two mechanisms provides a plausible physical explanation for certain long-standing observations of typhoons by Weatherford and Gray, which indicate that inner-core changes in the azimuthal-mean tangential wind speed often occur independently from those in the outer core. The unbalanced dynamics in the inner-core region are important in determining the maximum radial and tangential flow speeds that can be attained, and therefore important in determining the azimuthal-mean intensity of the vortex. We illustrate the importance of unbalanced flow in the boundary layer with a simple thought experiment. The analyses and interpretations presented are novel and support a recent hypothesis of the boundary layer in the inner-core region. Copyright 2009 Royal Meteorological Society

Smith S. D., 1980: Wind stress and heat flux over the ocean in gale force winds. J. Phys. Oceanogr., 10, 709- 726.10.1175/1520-0485(1980)0102.0.CO;2

efe69891-86b0-4f7c-b320-1687d39f7662

bafbb26d39d4cec11b371c48279d2260

http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F253496629_Wind_Stress_and_Heat_Flux_over_the_Ocean_in_Gale_Force_Winds

refpaperuri:(5b03b7ee69347df35f9970d87b7a3e40)

http://www.researchgate.net/publication/253496629_Wind_Stress_and_Heat_Flux_over_the_Ocean_in_Gale_Force_WindsAbstract An offshore stable platform has been instrumented with wind turbulence, temperature and wave height sensors. Data from this platform have been analyzed by the eddy correlation method to obtain wind stress and heat flux at wind speeds from 6 to 22 m s 1 in a deep-water wave regime, significantly extending the range of available measurements. The sea surface drag coefficient increases gradually with increasing wind speed. Sensible heat fluxes have been observed over a much wider range than previously available. Heat flux coefficients are higher in unstable than stable conditions, but are not seen to increase with increasing wind speed.

Stern D. P., D. S. Nolan, 2012: On the height of the warm core in tropical cyclones. J. Atmos. Sci., 69, 1657- 1680.10.1175/JAS-D-11-010.1

12848616-b05d-414d-9441-0cfefcec045c

ae7322f25d3fc14ff7f0e8af8db9fd35

http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F258659553_On_the_Height_of_the_Warm_Core_in_Tropical_Cyclones

refpaperuri:(2d62463265c6688e00f342ba0deb0e79)

http://www.researchgate.net/publication/258659553_On_the_Height_of_the_Warm_Core_in_Tropical_CyclonesAbstract The warm-core structure of tropical cyclones is examined in idealized simulations using the Weather Research and Forecasting (WRF) Model. The maximum perturbation temperature in a control simulation occurs in the midtroposphere (5–6 km), in contrast to the upper-tropospheric (>10 km) warm core that is widely believed to be typical. This conventional view is reassessed and found to be largely based on three case studies, and it is argued that the “typical” warm-core structure is actually not well known. In the control simulation, the height of the warm core is nearly constant over a wide range of intensities. From additional simulations in which either the size of the initial vortex or the microphysics parameterization is varied, it is shown that the warm core is generally found at 4–8 km. A secondary maximum often develops near 13–14 km but is almost always weaker than the primary warm core. It is demonstrated that microwave remote sensing instruments are of insufficient resolution to detect this midlevel warm core, and the conclusions of some studies that have utilized these instruments may not be reliable. Using simple arguments based on thermal wind balance, it is shown that the height of the warm core is not necessarily related to either the height where the vertical shear of the tangential winds is maximized or the height where the radial temperature gradient is maximized. In particular, changes in the height of the warm core need not imply changes in either the intensity of the storm or in the manner in which the winds in the eyewall decay with height.

Stull R. B., 1988: An Introduction to Boundary Layer Meteorology. Kluwer Academic,666 pp.10.1007/978-94-009-3027-8

ac92f54cac6d8f5af55b7961e5a03734

http%3A%2F%2Flink.springer.com%2F10.1007%2F978-94-009-3027-8

http://link.springer.com/10.1007/978-94-009-3027-8Part of the excitement in boundary-layer meteorology is the challenge associated with turbulent flow - one of the unsolved problems in classical physics. An additional attraction of the filed is the rich diversity of topics and research methods that are collected under the umbrella-term of boundary-layer meteorology. The flavor of the challenges and the excitement associated with the study of the atmospheric boundary layer are captured in this textbook. Fundamental concepts and mathematics are presented prior to their use, physical interpretations of the terms in equations are given, sample data are shown, examples are solved, and exercises are included.The work should also be considered as a major reference and as a review of the literature, since it includes tables of parameterizatlons, procedures, filed experiments, useful constants, and graphs of various phenomena under a variety of conditions. It is assumed that the work will be used at the beginning graduate level for students with an undergraduate background in meteorology, but the author envisions, and has catered for, a heterogeneity in the background and experience of his readers.

Wang C.-C., H.-C. Kuo, Y. H. Chen, H.-L. Huang, C.-H. Chung, and K. Tsuboki, 2012: Effects of asymmetric latent heating on typhoon movement crossing Taiwan: The case of Morakot (2009) with extreme rainfall. J. Atmos. Sci., 69, 3172- 3196.10.1175/JAS-D-11-0346.1

e47d7693-e512-48b1-bba6-f530639b8cd1

e5d2c37e7cf5bf1aa3df0ef2923b59dc

http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F258659562_Effects_of_Asymmetric_Latent_Heating_on_Typhoon_Movement_Crossing_Taiwan_The_Case_of_Morakot_%282009%29_with_Extreme_Rainfall

refpaperuri:(712e465dd86acb386eaa1256c0abf7d8)

http://www.researchgate.net/publication/258659562_Effects_of_Asymmetric_Latent_Heating_on_Typhoon_Movement_Crossing_Taiwan_The_Case_of_Morakot_(2009)_with_Extreme_RainfallAbstract Typhoon Morakot struck Taiwan during 6–9 August 2009, and it produced the highest rainfall (approaching 3000 mm) and caused the worst damage in the past 50 yr. Typhoon–monsoon flow interactions with mesoscale convection, the water vapor supply by the monsoon flow, and the slow moving speed of the storm are the main reasons for the record-breaking precipitation. Analysis of the typhoon track reveals that the steering flow, although indeed slow, still exceeded the typhoon moving speed by approximately 5 km h 611 (1 km h 611 = 0.28 m s 611 ) during the postlandfall period on 8 August, when the rainfall was the heaviest. The Cloud-Resolving Storm Simulator (CReSS) is used to study the dynamics of the slow storm motion toward the north-northwest upon leaving Taiwan. The control simulations with 3-km grid size compare favorably with the observations, including the track, slow speed, asymmetric precipitation pattern, mesoscale convection, and rainfall distribution over Taiwan. Sensitivity tests with reduced moisture content reveal that not only did the model rainfall decrease but also the typhoon translation speed increased. Specifically, the simulations consistently show a discernible impact on storm motion by as much as 50%, as the storms with full moisture move slower (~5 km h 611 ), while those with limited moisture (≤25%) move faster (~10 km h 611 ). Thus, in addition to a weak steering flow, the prolonged asymmetric precipitation in Typhoon Morakot also contributed to its very slow motion upon leaving Taiwan, and both lengthened the heavy-rainfall period and increased the total rainfall amount. The implications of a realistic representation of cloud microphysics from the standpoint of tropical cyclone track forecasts are also briefly discussed.

Wang C.-C., H.-C. Kuo, T.-C. Yeh, C.-H. Chung, Y. H. Chen, S.-Y. Huang, Y. W. Wang, and C.-H. Liu, 2013: High-resolution quantitative precipitation forecasts and simulations by the Cloud-Resolving Storm Simulator (CReSS) for Typhoon Morakot (2009). J. Hydrol., 506, 26- 41.10.1016/j.jhydrol.2013.02.018

8c8816ba-b3bf-4fda-a1fc-223ba182f0cd

7d58d39655d9d86897d76fa8c355f5ac

http%3A%2F%2Fwww.sciencedirect.com%2Fscience%2Farticle%2Fpii%2FS0022169413001303

refpaperuri:(b6d4425fdbe9c3e1dbc453ffaf84e981)

http://www.sciencedirect.com/science/article/pii/S0022169413001303Typhoon Morakot (2009) struck Taiwan during 7–9 August 2009, and brought extreme rainfall up to 285502mm and the worst damages in the past 5002years. The operational models showed deficiency and serious under-prediction in rainfall amount at real time. This study demonstrates that the Cloud-Resolving Storm Simulator (CReSS), a state-of-the-art, high-resolution model, at a grid size of 302km and starting as early as 0000 UTC 4 August, can successfully simulate and reproduce the event with high accuracy, including the distribution and timing of heavy rainfall in Taiwan. In the simulation starting at 0000 UTC 6 August, for example, the threat scores for 24-h rainfall for 8 August (with extreme amounts >145002mm) reach 0.8–0.4 even at thresholds of 100–50002mm. This result is only possible due to small track error and the phase-locking mechanism of the Taiwan topography to heavy rainfall.Furthermore, real-time forecast and hindcast integrations of the CReSS model show that high-quality quantitative precipitation forecasts (QPFs) with peak total amount 67–80% of the true value are also obtained from initial conditions at 0000 UTC 6 August, which is about 202days prior to the beginning of the heaviest rainfall in southern Taiwan. In these integrations, typhoon track errors in the global model forecasts used as boundary conditions are the major error source that prevent more ideal QPF results before and at 1200 UTC 5 August. When properly configured, it is believed that other similar cloud-resolving models can achieve comparable performance. Thus, the importance of and potential benefits from deterministic high-resolution forecasts is stressed, which may give an extended lead-time when the track error is small. With potentially longer time window for emergency action just prior to extreme rainfall events when it matters the most, such forecasts may ultimately lead to reduced losses in lives and properties.

Xie B. G., F. Q. Zhang, 2012: Impacts of typhoon track and island topography on the heavy rainfalls in Taiwan associated with Morakot (2009). Mon. Wea. Rev., 140, 3379- 3394.10.1175/MWR-D-11-00240.1

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http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F258683550_Impacts_of_Typhoon_Track_and_Island_Topography_on_the_Heavy_Rainfalls_in_Taiwan_Associated_with_Morakot_%282009%29

refpaperuri:(1fbff4dc801f3c9b6029654a7f753056)

http://www.researchgate.net/publication/258683550_Impacts_of_Typhoon_Track_and_Island_Topography_on_the_Heavy_Rainfalls_in_Taiwan_Associated_with_Morakot_(2009)Cloud-resolving ensemble simulations and sensitivity experiments utilizing the Weather Research and Forecasting model (WRF) are performed to investigate the dynamics and predictability of the record-breaking rainfall and flooding event in Taiwan induced by Typhoon Morakot (2009). It is found that a good rainfall forecast foremost requires a good track forecast during Morakot's landfall. Given a good track forecast, interaction of the typhoon circulation with complex topography in southern Taiwan plays a dominant role in producing the observed heavy rainfalls. The terrain slope, strength of the horizontal winds, and mid-lower-tropospheric moisture content in the southwesterly upslope flow are the primary factors that determine the rainfall location and intensity, as elucidated by the idealized one-dimensional precipitation-rate forecast model. The typhoon circulation and the southwesterly monsoon flow transport abundant moisture into southern Taiwan, which produces the heavy rainfall through interactions with the complex high terrain in the area. In the meantime, as part of the south China monsoon, the southwesterly flow may be substantially enhanced by the typhoon circulation.

Zhang D. L., Y. B. Liu, and M. K. Yau, 2001: A multiscale numerical study of Hurricane Andrew (1992). Part IV: Unbalanced flows. Mon. Wea. Rev., 129, 92- 107.10.1175/1520-0493(2001)1292.0.CO;2

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http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F260906221_A_Multiscale_Numerical_Study_of_Hurricane_Andrew_%281992%29._Part_IV_Unbalanced_Flows

refpaperuri:(46700c8852a9433b026cea44b3c26785)

http://www.researchgate.net/publication/260906221_A_Multiscale_Numerical_Study_of_Hurricane_Andrew_(1992)._Part_IV_Unbalanced_FlowsAbstract Despite considerable progress in understanding the hurricane vortex using balanced models, the validity of gradient wind balance in the eyewall remains controversial in observational studies. In this paper, the structure and development of unbalanced forces and flows in hurricanes are examined, through the analyses of the radial momentum and absolute angular momentum (AAM) budgets, using a high-resolution (i.e., x = 6 km), fully explicit simulation of Hurricane Andrew (1992). It is found from the radial momentum budgets that supergradient flows and accelerations, even after temporal and azimuthal averaging, are well organized from the bottom of the eye center to the upper outflow layer in the eyewall. The agradient accelerations are on average twice greater than the local Coriolis force, and caused mainly by the excess of the centrifugal force over the pressure gradient force. It is shown by the AAM budgets that supergradient flows could occur not only in the inflow region as a result of the inward AAM transport, but also in the outflow region through the upward transport of AAM. The eyewall is dominated by radial outflow in which the upward transport of AAM overcompensates the spindown effect of the outflow during the deepening stage. The intense upper outflow layer is generated as a consequence of the continuous outward acceleration of airflows in the eyewall updrafts. In spite of the pronounced agradient tendencies, results presented here suggest that the azimuthally averaged tangential winds above the boundary layer satisfy the gradient wind balance within an error of 10%. The analyses of instantaneous fields show pronounced asymmetries and well-organized wavenumber-2 structures of the agradient flows and forces in the form of azimuthally propagating vortex ossby waves in the eyewall. These waves propagate cyclonically downstream with a speed half the tangential winds near the top of the boundary layer and vertically upward. Agradient flows/forces and AAM transport in the eye are also discussed.

Zhang D. L., H. Chen, 2012: Importance of the upper-level warm core in the rapid intensification of a tropical cyclone. Geophys. Res. Lett., 39,L02806, doi: 10.1029/2011GL 050578.10.1029/2011GL050578

a88e92d6-924f-4194-99dc-640cfd3b6923

89354b7a46f7e2a84e1a79d871543b3e

http://onlinelibrary.wiley.com/doi/10.1029/2011GL050578/full

http://onlinelibrary.wiley.com/doi/10.1029/2011GL050578/fullABSTRACT In this study, the rapid intensification (RI) of tropical cyclone is examined using a 72-h cloud-permitting prediction of Hurricane Wilma (2005) with a record-breaking intensity of 882 hPa. Results show the formation of an upper-level warm core from the descending air of stratospheric origin in the eye, which coincides with the onset of RI; it reaches the peak amplitude of more than 18 C from its initial conditions at the time of peak intensity. The descending air is associated with the detrainment of convective bursts in the eyewall, and it appears as (perturbation) cyclonic radial inflows above the upper outflow layer and causes the subsidence warming below. We hypothesize that the upper divergent outflow layer favors the generation of a warm core by protecting it from ventilation by environmental flows. Use of the hydrostatic equation shows that the warm core of stratospheric origin contributes more than twice as much as the lower-level warm column to the pressure change at the peak intensity of Wilma. Results suggest that more attention be paid to the magnitude of storm-relative flows and vertical wind shear in the upper troposphere, rather than just vertical shear in the typical 850-200 hPa layer, in order to reasonably predict the RI of tropical cyclones.

Zhang F. Q., Y. H. Weng, Y.-H. Kuo, J. S. Whitaker, and B. G. Xie, 2010: Predicting Typhoon Morakot's catastrophic rainfall with a convection-permitting mesoscale ensemble system. Wea.Forecasting, 25, 1816- 1825.10.1175/2010WAF2222414.1

8a37c8fb-e0c6-4974-9e5b-a99bd1e8ab2f

640e11a61dcb1f4573b809e5a92d0237

http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F241301420_Predicting_Typhoon_Morakot%27s_Catastrophic_Rainfall_with_a_Convection-Permitting_Mesoscale_Ensemble_System

refpaperuri:(472ef020d7f056e61ee7c17b56252c1b)

http://www.researchgate.net/publication/241301420_Predicting_Typhoon_Morakot's_Catastrophic_Rainfall_with_a_Convection-Permitting_Mesoscale_Ensemble_SystemThis study examines the prediction and predictability of the recent catastrophic rainfall and flooding event over Taiwan induced by Typhoon Morakot (2009) with a state-of-the-art numerical weather prediction model. A high-resolution convection-permitting mesoscale ensemble, initialized with analysis and flow-dependent perturbations obtained from a real-time global ensemble data assimilation system, is found to be able to predict this record-breaking rainfall event, producing probability forecasts potentially valuable to the emergency management decision makers and the general public. Since all the advanced modeling and data assimilation techniques used here are readily available for real-time operational implementation provided sufficient computing resources are made available, this study demonstrates the potential and need of using ensemble-based analysis and forecasting, along with enhanced computing, in predicting extreme weather events like Typhoon Morakot at operational centers.

Zhang J. A., P. G. Black, J. R. French, and W. M. Drennan, 2008: First direct measurements of enthalpy flux in the hurricane boundary layer: the CBLAST results. Geophys. Res. Lett., 35(14), L14813, doi:10.1029/2008GL034374.10.1029/2008GL034374

3b27a3ab-a15f-4b2e-9d6f-c75f443e575f

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http://onlinelibrary.wiley.com/doi/10.1029/2008GL034374/citedby

http://onlinelibrary.wiley.com/doi/10.1029/2008GL034374/citedbyABSTRACT Hurricanes extract energy from the warm ocean through enthalpy fluxes. As part of the Coupled Boundary Layer Air-Sea Transfer (CBLAST) experiment, flights were conducted to measure turbulent fluxes in the high-wind boundary layer of hurricanes. Here we present the first field observations of sensible heat and enthalpy flux for 10m wind speeds to 30 ms-1. The analyses indicate no statistically significant dependence of these bulk exchange coefficients on wind speed. As a measure of hurricane development potential, we compute the mean ratio of the exchange coefficient for enthalpy to that for momentum and find it to be significantly below the lowest threshold estimated by previous investigators. This suggests that the enthalpy flux required for hurricane development may come from sources other than turbulent fluxes, such as lateral fluxes from the vortex warm core, or sea spray. Alternatively, it demands a re-evaluation of the theoretical models used to derive the threshold.

Zhang J. A., R. F. Rogers, D. S. Nolan, and F. D. Marks, 2011: On the characteristic height scales of the hurricane boundary layer. Mon. Wea. Rev., 139, 2523- 2535.10.1175/MWR-D-10-05017.1

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db0385e39e35a45d026e3b856b13cd60

http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F259852999_On_the_Characteristic_Height_Scales_of_the_Hurricane_Boundary_Layer

refpaperuri:(5bd9ab6649365d4db9056cfe08b2de9e)

http://www.researchgate.net/publication/259852999_On_the_Characteristic_Height_Scales_of_the_Hurricane_Boundary_LayerAbstract In this study, data from 794 GPS dropsondes deployed by research aircraft in 13 hurricanes are analyzed to study the characteristic height scales of the hurricane boundary layer. The height scales are defined in a variety of ways: the height of the maximum total wind speed, the inflow layer depth, and the mixed layer depth. The height of the maximum wind speed and the inflow layer depth are referred to as the dynamical boundary layer heights, while the mixed layer depth is referred to as the thermodynamical boundary layer height. The data analyses show that there is a clear separation of the thermodynamical and dynamical boundary layer heights. Consistent with previous studies on the boundary layer structure in individual storms, the dynamical boundary layer height is found to decrease with decreasing radius to the storm center. The thermodynamic boundary layer height, which is much shallower than the dynamical boundary layer height, is also found to decrease with decreasing radius to the storm center. The results also suggest that using the traditional critical Richardson number method to determine the boundary layer height may not accurately reproduce the height scale of the hurricane boundary layer. These different height scales reveal the complexity of the hurricane boundary layer structure that should be captured in hurricane model simulations.

Zhang J. A., S. Gopalakrishnan, F. D. Marks, R. F. Rogers, and V. Tallapragada, 2012: A developmental framework for improving hurricane model physical parameterizations using aircraft observations. Trop. Cycl. Res. Rev.,1(5), 419-429, doi: 10.6057/2012TCRR04.01.10.6057/2012tcrr04.01

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http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F255729562_A_Developmental_Framework_for_Improving_Hurricane_Model_Physical_Parameterizations_Using_Aircraft_Observations

refpaperuri:(2d2ffcb7fc3e32a9ee61e42e0fa96c42)

http://www.researchgate.net/publication/255729562_A_Developmental_Framework_for_Improving_Hurricane_Model_Physical_Parameterizations_Using_Aircraft_ObservationsABSTRACT As part of NOAA650200s Hurricane Forecast Improvement Program (HFIP), this paper addresses the important role of aircraft observations in hurricane model physics validation and improvement. A model developmental framework for improving the physical parameterizations using quality-controlled and post- processed aircraft observations is presented, with steps that include model diagnostics, physics development, physics implementation and further evaluation. Model deficiencies are first identified through model diagnostics by comparing the simulated axisymmetric multi-scale structures to observational composites. New physical parameterizations are developed in parallel based on in-situ observational data from specially designed hurricane field programs. The new physics package is then implemented in the model, which is followed by further evaluation. The developmental framework presented here is found to be successful in improving the surface layer and boundary layer parameterization schemes in the operational Hurricane Weather Research and Forecast (HWRF) model. Observations for improving physics packages other than boundary layer scheme are also discussed.