doi:10.1007/s00376-016-5061-y

Alexand ru, A., R. De Elia, R. Laprise, L. Separovic, S. Biner, 2009: Sensitivity study of regional climate model simulations to large-scale nudging parameters. Mon. Wea. Rev., 137, 1666- 1686.10.1175/2008MWR2620.1

5aec42c9aca1df392636f580e168f5c2

http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2009MWRv..137.1666A

http://adsabs.harvard.edu/abs/2009MWRv..137.1666AAbstract Previous studies with nested regional climate models (RCMs) have shown that large-scale spectral nudging (SN) seems to be a powerful method to correct RCMs’ weaknesses such as internal variability, intermittent divergence in phase space (IDPS), and simulated climate dependence on domain size and geometry. Despite its initial success, SN is not yet in widespread use because of disagreement regarding the main premises—the unconfirmed advantages of removing freedom from RCMs’ large scales—and lingering doubts regarding its potentially negative side effects. This research addresses the latter issue. Five experiments have been carried out with the Canadian RCM (CRCM) over North America. Each experiment, performed under a given SN configuration, consists of four ensembles of simulations integrated on four different domain sizes for a summer season. In each experiment, the effects of SN on internal variability, time means, extremes, and power spectra are discussed. As anticipated from previous investigations, the present study confirms that internal variability, as well as simulated-climate dependence on domain size, decreases with increased SN strength. Our results further indicate a noticeable reduction of precipitation extremes as well as low-level vorticity amplitude in almost all length scales, as a side effect of SN; these effects are mostly perceived when SN is the most intense. Overall results indicate that the use of a weak to mild SN may constitute a reasonable compromise between the risk of decoupling of the RCM internal solution from the lateral boundary conditions (when using large domains without SN) and an excessive control of the large scales (with strong SN).

Camargo S. J., A. H. Sobel, 2004: Formation of tropical storms in an atmospheric general circulation model. Tellus A, 56, 56- 67.

Camargo S. J., H. L. Li, and L. Q. Sun, 2007: Feasibility study for downscaling seasonal tropical cyclone activity using the NCEP regional spectral model. Int. J. Climatol., 27, 311- 325.10.1002/joc.1400

b936385c5697a80712b7460eee6bcab0

http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1002%2Fjoc.1400%2Ffull

http://onlinelibrary.wiley.com/doi/10.1002/joc.1400/fullAbstract The potential use of the National Centers for Environmental Prediction (NCEP) Regional Spectral Model (RSM) for downscaling seasonal tropical cyclone (TC) activity was analyzed here. The NCEP RSM with horizontal resolution of 50 km, was used to downscale the ECHAM4.5 Atmospheric General Circulation Model (AGCM) simulations forced with observed sea surface temperature (SST) over the western North Pacific. An ensemble of ten runs for June-ovember 1994 and 1998 was studied. The representation of the TCs is much improved compared to the low-resolution forcing AGCM, but the TCs are not as intense as observed ones, as the RSM horizontal resolution is not sufficiently high. The large-scale fields of the RSM are examined and compared to both the AGCM and the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis. The large-scale fields of RSM characteristics are in general similar to those of the reanalysis. Various properties of the TCs in the RSM are also examined such as first positions, tracks, accumulated cyclone energy (ACE) and duration. While the RSM does not reproduce the higher number of TCs in 1994 than in 1998, other measures of TC activity (ACE, number of cyclone days) in the RSM are higher in 1994 than in 1998. Copyright 2006 Royal Meteorological Society.

Castro C. L., R. A. Pielke Sr., and G. Leoncini, 2005: Dynamical downscaling: Assessment of value retained and added using the regional atmospheric modeling system (RAMS). J. Geophys. Res., 110,D05108, doi: 10.1029/2004JD004721.10.1029/2004JD004721

582fe4a4fa9dbc346db366005eca1d1a

http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F2004JD004721%2Fcitedby

http://onlinelibrary.wiley.com/doi/10.1029/2004JD004721/citedbyThe value restored and added by dynamical downscaling is quantitatively evaluated by considering the spectral behavior of the Regional Atmospheric Modeling System (RAMS) in relation to its domain size and grid spacing. A regional climate model (RCM) simulation is compared with NCEP Reanalysis data regridded to the RAMS grid at each model analysis time for a set of six basic experiments. At large scales, RAMS underestimates atmospheric variability as determined by the column integrated kinetic energy and integrated moisture flux convergence. As the grid spacing increases or domain size increases, the underestimation of atmospheric variability at large scales worsens. The model simulated evolution of the kinetic energy relative to the reanalysis regridded kinetic energy exhibits a decrease with time, which is more pronounced with larger grid spacing. Additional follow-on experiments confirm that the surface boundary forcing is the dominant factor in generating atmospheric variability for small-scale features and that it exerts greater control on the RCM solution as the influence of lateral boundary conditions diminish. The sensitivity to surface forcing is also influenced by the model parameterizations, as demonstrated by using a different convection scheme. For the particular case considered, dynamical downscaling with RAMS in RCM mode does not retain value of the large scale which exists in the larger global reanalysis. The utility of the RCM, or value added, is to resolve the smaller-scale features which have a greater dependence on the surface boundary. This conclusion regarding RAMS is expected to be true for other RCMs as well.

Cha D.-H., D.-K. Lee, 2009: Reduction of systematic errors in regional climate simulations of the summer monsoon over East Asia and the western North Pacific by applying the spectral nudging technique. J. Geophys. Res., 114,D14108, doi: 10.1029/2008JD011176.10.1029/2008JD011176

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http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F2008JD011176%2Fpdf

refpaperuri:(c8af5626d7962418a686dad4345a6ed4)

http://onlinelibrary.wiley.com/doi/10.1029/2008JD011176/pdfIn this study, the systematic errors in regional climate simulation of 28-year summer monsoon over East Asia and the western North Pacific (WNP) and the impact of the spectral nudging technique (SNT) on the reduction of the systematic errors are investigated. The experiment in which the SNT is not applied (the CLT run) has large systematic errors in seasonal mean climatology such as overestimated precipitation, weakened subtropical high, and enhanced low-level southwesterly over the subtropical WNP, while in the experiment using the SNT (the SP run) considerably smaller systematic errors are resulted. In the CTL run, the systematic error of simulated precipitation over the ocean increases significantly after mid-June, since the CTL run cannot reproduce the principal intraseasonal variation of summer monsoon precipitation. The SP run can appropriately capture the spatial distribution as well as temporal variation of the principal empirical orthogonal function mode, and therefore, the systematic error over the ocean does not increase after mid-June. The systematic error of simulated precipitation over the subtropical WNP in the CTL run results from the unreasonable positive feedback between precipitation and surface latent heat flux induced by the warm sea surface temperature anomaly. Since the SNT plays a role in decreasing the positive feedback by improving monsoon circulations, the SP run can considerably reduce the systematic errors of simulated precipitation as well as atmospheric fields over the subtropical WNP region.

Cha D.-H., C.-S. Jin, D.-K. Lee, and Y.-H. Kuo, 2011: Impact of intermittent spectral nudging on regional climate simulation using Weather Research and Forecasting Model. J. Geophys. Res., 116,D10103, doi: 10.1029/2010JD015069.10.1029/2010JD015069

e524653b222ba387ac156804ebec842c

http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F2010JD015069%2Ffull

http://onlinelibrary.wiley.com/doi/10.1029/2010JD015069/fullThis study examines simulated typhoon sensitivities to spectral nudging (SN) to investigate the effects on values added by regional climate models, which are not properly resolved by low-resolution global models. SN is suitably modified to mitigate its negative effects while maintaining the positive effects, and the effects of the modified SN are investigated through seasonal simulations. In the sensitivity experiments to nudging intervals of SN, the tracks of simulated typhoons are improved as the SN effect increases; however, the intensities of the simulated typhoons decrease due to the suppression of the typhoon developing process by SN. To avoid such suppression, SN is applied at intermittent intervals only when the deviation between the large-scale driving forcing and the model solution is large. In seasonal simulations, intermittent SN is applied for only 7% of the total time steps; however, this results in not only maintaining the large-scale features of monsoon circulation and precipitation corresponding to observations but also improving the intensification of mesoscale features by reducing the suppression.

Chen F., J. Dudhia, 2001: Coupling and advanced land-surface/hydrology model with the Penn State/NCAR MM5 modeling system. Part I: Model description and implementation. Mon. Wea. Rev., 129, 569- 585.609cbe5b-5261-4d8f-a70c-f188da93725a

5315527203b9a4a6186814b1238287d5

http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2001MWRv..129..569C

refpaperuri:(df73c9d7813d4fcabd37c76ee3598fc7)

/s?wd=paperuri%3A%28df73c9d7813d4fcabd37c76ee3598fc7%29&filter=sc_long_sign&tn=SE_xueshusource_2kduw22v&sc_vurl=http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2001MWRv..129..569C&ie=utf-8

Craig G. C., S. L. Gray, 1996: CISK or WISHE as the mechanism for tropical cyclone intensification. J. Atmos. Sci., 53, 3528- 3540.10.1175/1520-0469(1996)053<3528:COWATM>2.0.CO;2

3c1fc5bbc63979911a07c314283d3095

http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1996JAtS...53.3528C

http://adsabs.harvard.edu/abs/1996JAtS...53.3528CABSTRACT Examination of conditional instability of the second kind (CISK) and wind-induced surface heat exchange (WISHE), two proposed mechanisms for tropical cyclone and polar low intensification, suggests that the sensitivity of the intensification rate of these disturbances to surface properties, such as surface friction and moisture supply, will be different for the two mechanisms. These sensitivities were examined by perturbing the surface characteristics in a numerical model with explicit convection. The intensification rate was found to have a strong positive dependence on the heat and moisture transfer coefficients, while remaining largely insensitive to the frictional drag coefficient. CISK does not predict the observed dependence of vortex intensification rate on the heat and moisture transfer coefficients, nor the insensitivity to the frictional drag coefficient since it anticipates that intensification rate is controlled by frictional convergence in the boundary layer. Since neither conditional instability nor boundary moisture content showed any significant sensitivity to the transfer coefficients, this is true of CISK using both the convective closures of Ooyama and of Charney and Eliassen. In comparison, the WISHE intensification mechanism does predict the observed increase in intensification rate with heat and moisture transfer coefficients, while not anticipating a direct influence from surface friction.

Dee D.P., Coruthors, 2011: The ERA-Interim reanalysis: Configuration and performance of the data assimilation system. Quart. J. Roy. Meteor. Soc., 137, 553- 597.10.1002/qj.828

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http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1002%2Fqj.828%2Fpdf

refpaperuri:(d4649bb38c91f047e85ec096d8587b99)

http://med.wanfangdata.com.cn/Paper/Detail/PeriodicalPaper_PM20383825ABSTRACT ERA-Interim is the latest global atmospheric reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ECMWF). The ERA-Interim project was conducted in part to prepare for a new atmospheric reanalysis to replace ERA-40, which will extend back to the early part of the twentieth century. This article describes the forecast model, data assimilation method, and input datasets used to produce ERA-Interim, and discusses the performance of the system. Special emphasis is placed on various difficulties encountered in the production of ERA-40, including the representation of the hydrological cycle, the quality of the stratospheric circulation, and the consistency in time of the reanalysed fields. We provide evidence for substantial improvements in each of these aspects. We also identify areas where further work is needed and describe opportunities and objectives for future reanalysis projects at ECMWF. Copyright 2011 Royal Meteorological Society

Dudhia J., 1989: Numerical study of convection observed during the winter monsoon experiment using a mesoscale two-dimensional model. Atmos. Sci., 46, 3077- 3107.34a0f338a8622d0aee3c3811d44d3450

http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1989JAtS...46.3077D

/s?wd=paperuri%3A%2876536b43084d2ca4dd6ac23f1a23d059%29&filter=sc_long_sign&tn=SE_xueshusource_2kduw22v&sc_vurl=http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1989JAtS...46.3077D&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- 604.10.1175/1520-0469(1986)0432.0.CO;2

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c083923be7feefcc5f7f0953e0b912ae

http://www.researchgate.net/publication/215877085_An_air-sea_interaction_theory_for_tropical_cyclones._Part_I_Steady-state_maintenance

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., J. D. Neelin, and C. S. Bretherton, 1994: On large-scale circulations in convecting atmospheres. Quart. J. Roy. Meteor. Soc., 120, 1111- 1144.10.1002/qj.49712051902

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http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1002%2Fqj.49712051902%2Fpdf

refpaperuri:(a3bc334e89c7fc4dfe1e82680b40a7b8)

http://onlinelibrary.wiley.com/doi/10.1002/qj.49712051902/pdfNot Available

Feser F., H. von Storch, 2008: A dynamical downscaling case study for typhoons in Southeast Asia using a regional climate model. Mon. Wea. Rev., 136, 1806- 1815.10.1175/2007MWR2207.1

90171c25257141b9d0811001d6cd6bcc

http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2008MWRv..136.1806F

http://adsabs.harvard.edu/abs/2008MWRv..136.1806FABSTRACT Abstract This study explores the possibility to reconstruct the weather of SE Asia for the last decades using an atmospheric regional climate model, the Climate version of the Lokal Model (CLM). For this purpose global National Centers for Environmental Prediction - National Center for Atmospheric Research (NCEP-NCAR) reanalyses data were dy- namically downscaled,to 50 km,and in a double-nesting approach to 16.5 km,grid distance. To prevent the regional model from deviating to a great extent from the reanalyses for spacious weather phenomena, a spectral nudging technique was used which serves as a constraint exclusively for the large spatial scales of the regional simulation. The performance,of this technique in dealing with SE Asian typhoons is now ex- amined. First case studies indicate that tropical storms which are described by the reanalyses are correctly identied and tracked; considerably deeper core pressure and higher wind speeds are simulated compared,to the driving reanalyses. When the re- gional atmospheric model is run without spectral nudging, signicant intra-ensemble variability occurs; also additional, non-observed typhoons form. Several sensitivity experiments were performed concerning varied grid distances, different initial starting dates of the simulations and changed spectral nudging parameters. 2

Haarsma R. J., J. F. B. Mitchell, and C. A. Senior, 1993: Tropical disturbances in a GCM. Climate Dyn., 8, 247- 257.10.1007/BF00198619

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eb212795a6e5bc20babea7ebd848a50e

http%3A%2F%2Flink.springer.com%2Farticle%2F10.1007%2FBF00198619

refpaperuri:(effa53e290305bf4a1ed3825460b27bc)

http://link.springer.com/article/10.1007/BF00198619ABSTRACT We have analyzed the tropical disturbances in a 11-layer atmospheric general circulation model (GCM) on a 2.5 3.75 horizontal grid coupled to a 50 m-mixed layer ocean. Due to the coarse resolution, the GCM is unable to resolve adequately tropical cyclones. The tropical disturbances simulated by the GCM are much weaker and have a much larger horizontal extent. However, they still display much of the essential physics of tropical cyclones, including low-level convergence of mass and moisture, upper tropospheric outflow and a warm core. For most ocean basins the spatial and temporal distribution of the simulated tropical disturbances compares well with the observed tropical cyclones. On doubling the CO2 concentration, the number of simulated tropical disturbances increases by about 50%. There is a relative increase in the number of more intense tropical disturbances, whose maximum windspeed increases by about 20%. This agrees with the theoretical estimate of Emanuel. However, because the low-resolution of the GCM severely restricts their maximum possible intensity, simulated changes in tropical disturbance intensity should be interpreted cautiously.

Harr P. A., R. L. Elsberry, 1995: Large-scale circulation variability over the tropical western North Pacific. Part I: Spatial patterns and tropical cyclone characteristics. Mon. Wea. Rev., 123, 1225- 1246.

Hong S.-Y., J. Dudhia, and S.-H. Chen, 2004: A revised approach to ice microphysical processer for the bulk parameterization of clouds and precipitation. Mon. Wea. Rev., 132, 103- 120.

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, 2318- 2341.10.1175/MWR3199.1

79f98ee85a3853a6bfee0ec84e90c901

http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2006MWRv..134.2318H

http://adsabs.harvard.edu/abs/2006MWRv..134.2318HAbstract 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.

Kain J. S., J. M. Fritsch, 1990: A one-dimensional entraining/detraining plume model and its application in convective parameterization. J. Atmos. Sci., 47, 2748- 2802.10.1175/1520-0469(1990)047<2784:AODEPM>2.0.CO;2

f72637dabe45fcd81632ab46eaa0ab0b

http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1990JAtS...47.2784K

http://adsabs.harvard.edu/abs/1990JAtS...47.2784KCiteSeerX - Scientific documents that cite the following paper: A one dimensional entraining/detraining plume model and its application to convective parameterization

Kain J. S., J. M. Fritsch, 1993: Convective parameterization for mesoscale models: The Kain-Fritsch scheme. The Representation of Cumulus Convection in Numerical Models, K. A. Emanuel and D. J. Raymond, Eds., Amer. Meteor. Soc., 246 pp.

Knutson T. R., J. J. Sirutis, S. T. Garner, I. M. Held, and R. E. Tuleya, 2007: Simulation of the recent multidecadal increase of Atlantic hurricane activity using an 18-km-grid regional model. Bull. Amer. Meteor. Soc., 88, 1549- 1565.276418903e60fe9d8f3aa98898af945e

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http://icesjms.oxfordjournals.org/external-ref?access_num=10.1175/BAMS-88-10-1549&link_type=DOI

Lee C.-S., K. K. W. Cheung, J. S. N. Hui, and R. L. Elsberry, 2008: Mesoscale features associated with tropical cyclone formations in the western North Pacific. Mon. Wea. Rev., 136, 2006- 2022.10.1175/2007MWR2267.1

f291a8796294ddddb1d68dee81d3444b

http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2008MWRv..136.2006L

http://adsabs.harvard.edu/abs/2008MWRv..136.2006LThe mesoscale features of 124 tropical cyclone formations in the western North Pacific Ocean during 1999092004 are investigated through large-scale analyses, satellite infrared brightness temperature (TB), and Quick Scatterometer (QuikSCAT) oceanic wind data. Based on low-level wind flow and surge direction, the formation cases are classified into six synoptic patterns: easterly wave (EW), northeasterly flow (NE), coexistence of northeasterly and southwesterly flow (NE09W), southwesterly flow (SW), monsoon confluence (MC), and monsoon shear (MS). Then the general convection characteristics and mesoscale convective system (MCS) activities associated with these formation cases are studied under this classification scheme. Convection processes in the EW cases are distinguished from the monsoon-related formations in that the convection is less deep and closer to the formation center. Five characteristic temporal evolutions of the deep convection are identified: (i) single convection event, (ii) two convection events, (iii) three convection events, (iv) gradual decrease in TB, and (v) fluctuating TB, or a slight increase in TB before formation. Although no dominant temporal evolution differentiates cases in the six synoptic patterns, evolutions ii and iii seem to be the common routes taken by the monsoon-related formations. The overall percentage of cases with MCS activity at multiple times is 63%, and in 35% of cases more than one MCS coexisted. Most of the MC and MS cases develop multiple MCSs that lead to several episodes of deep convection. These two patterns have the highest percentage of coexisting MCSs such that potential interaction between these systems may play a role in the formation process. The MCSs in the monsoon-related formations are distributed around the center, except in the NE09W cases in which clustering of MCSs is found about 10009-200 km east of the center during the 12 h before formation. On average only one MCS occurs during an EW formation, whereas the mean value is around two for the other monsoon-related patterns. Both the mean lifetime and time of first appearance of MCS in EW are much shorter than those developed in other synoptic patterns, which indicates that the overall formation evolution in the EW case is faster. Moreover, this MCS is most likely to be found within 100 km east of the center 12 h before formation. The implications of these results to internal mechanisms of tropical cyclone formation are discussed in light of other recent mesoscale studies.

Lee D. K., D. H. Cha, and H. S. Kang, 2004: Regional climate simulation of the 1998 summer flood over East Asia. J. Meteor. Soc.Japan, 82, 1735- 1753.10.2151/jmsj.82.1735

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http%3A%2F%2Fci.nii.ac.jp%2Fnaid%2F130004788491%2F

http://ci.nii.ac.jp/naid/130004788491/In this study, the severe flood case over East Asia during the 1998 summer was simulated using a regional climate model (SNURCM) with 60 km horizontal resolution (EX60), and the model performance in reproducing the extreme climate events was evaluated. An experiment with higher horizontal resolution of 20 km (EX20) was also performed in order to assess the impact of increased resolution on precipitation simulation of the severe flood.The model reproduced the severe precipitation events occurring in central China in June. In EX60, the temporal and spatial variations of the abnormal Meiyu monsoon fronts, which were well observed were also simulated reasonably except in southern China. The area-averaged daily precipitation and surface air temperatures were underestimated, but their temporal evolutions were in good agreement with observation. In the higher resolution experiment (EX20), simulated downward solar radiation, latent heat flux and convective rain were increased in the major severe rain area over the Yangtze River Basin. The increased precipitation in EX20, which was attributed mainly to the increase of convective rain, resulted in the enhanced precipitation intensity, but only slightly affected total precipitation amounts. The improvement in the higher horizontal resolution simulation appeared in precipitation resulting, in particular, from increased convective activity due to increased latent heat flux at the surface. Nevertheless, the model had significant precipitation bias in some areas with disagreement between the simulated precipitation patterns and distribution, and the observations. The model also had surface air temperature bias resulting from cold biases of the land surface model. With horizontal resolution increased to 20 km, the convective and non-convective precipitation was increased for the late afternoon and early evening time, increasing the total precipitation slightly.

Miguez-Macho G., G. L. Stenchicov, and A. Robock, 2004: Spectral nudging to eliminate the effects of domain position and geometry in regional climate model simulations. J. Geophys. Res., 109,D13104, doi: 10.1029/2003JD004495.10.1029/2003JD004495

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refpaperuri:(280faa1a0702af0d63167ea4af0f2a6e)

http://onlinelibrary.wiley.com/doi/10.1029/2003JD004495/fullIt is well known that regional climate simulations are sensitive to the size and position of the domain chosen for calculations. Here we study the physical mechanisms of this sensitivity. We conducted simulations with the Regional Atmospheric Modeling System (RAMS) for June 2000 over North America at 50 km horizontal resolution using a 7500 km 脳 5400 km grid and NCEP/NCAR reanalysis as boundary conditions. The position of the domain was displaced in several directions, always maintaining the U.S. in the interior, out of the buffer zone along the lateral boundaries. Circulation biases developed a large scale structure, organized by the Rocky Mountains, resulting from a systematic shifting of the synoptic wave trains that crossed the domain. The distortion of the large-scale circulation was produced by interaction of the modeled flow with the lateral boundaries of the nested domain and varied when the position of the grid was altered. This changed the large-scale environment among the different simulations and translated into diverse conditions for the development of the mesoscale processes that produce most of precipitation for the Great Plains in the summer season. As a consequence, precipitation results varied, sometimes greatly, among the experiments with the different grid positions. To eliminate the dependence of results on the position of the domain, we used spectral nudging of waves longer than 2500 km above the boundary layer. Moisture was not nudged at any level. This constrained the synoptic scales to follow reanalysis while allowing the model to develop the small-scale dynamics responsible for the rainfall. Nudging of the large scales successfully eliminated the variation of precipitation results when the grid was moved. We suggest that this technique is necessary for all downscaling studies with regional models with domain sizes of a few thousand kilometers and larger embedded in global models.

Miguez-Macho G., G. L. Stenchicov, and A. Robock, 2005: Regional climate simulations over North America: Interaction of local processes with improved large-scale flow. J.Climate, 18, 1227- 1246.10.1175/JCLI3369.1

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http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2005JCli...18.1227M

http://adsabs.harvard.edu/abs/2005JCli...18.1227MThe reasons for biases in regional climate simulations were investigated in an attempt to discern whether they arise from deficiencies in the model parameterizations or are due to dynamical problems. Using the Regional Atmospheric Modeling System (RAMS) forced by the National Centers for Environmental Predictionational Center for Atmospheric Research reanalysis, the detailed climate over North America at 50-km resolution for June 2000 was simulated. First, the RAMS equations were modified to make them applicable to a large region, and its turbulence parameterization was corrected. The initial simulations showed large biases in the location of precipitation patterns and surface air temperatures. By implementing higher-resolution soil data, soil moisture and soil temperature initialization, and corrections to the Kainritch convective scheme, the temperature biases and precipitation amount errors could be removed, but the precipitation location errors remained. The precipitation location biases could only be improved by implementing spectral nudging of the large-scale (wavelength of 2500 km) dynamics in RAMS. This corrected for circulation errors produced by interactions and reflection of the internal domain dynamics with the lateral boundaries where the model was forced by the reanalysis.

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( D14), 16 663- 16 682.10.1029/97JD00237

33ca9d21-1574-4293-8d4b-e7ef17cddd90

f4120d12c2c63e7bc01d0dead8c1827e

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.

Monin A. S., A. M. Obukhov, 1954: Basic laws of turbulent mixing in the surface layer of the atmosphere. Contributions of the Geophysical Institute of the Slovak Academy of Sciences, 24( 151), 163- 187.a974d11a-5d54-42c4-9002-55f83c738198

0358899783b9440f5606ef017d767657

http%3A%2F%2Fwww.mcnaughty.com%2Fkeith%2Fpapers%2FMonin_and_Obukhov_1954.pdf

refpaperuri:(a7e98612e58d9286ed759ef48cca2951)

http://www2.mmm.ucar.edu/wrf/users/phys_refs/SURFACE_LAYER/eta_part1.pdf

Nguyen K. C., K. J. E. Walsh, 2001: Interannual, decadal and transient greenhouse simulation of tropical cyclone-like vortices in a regional climate model of the South Pacific. J.Climate, 14, 3043- 3054.10.1175/1520-0442(2001)014<3043:IDATGS>2.0.CO;2

d1d04c52-4d92-4117-a81b-fd81143af1a2

bffdfd48d900e804f20f8d159bc22ecc

http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2001JCli...14.3043N

refpaperuri:(e28b24dfc1e06c3d00debce1b07730d4)

http://adsabs.harvard.edu/abs/2001JCli...14.3043NPurpose This study aims to determine the effect of human mesenchymal stem cell (hMSC) labeling with the fluorescent dye DiD and the iron oxide nanoparticle ferucarbotran on chondrogenesis. Procedures hMSCs were labeled with DiD alone or with DiD and ferucarbotran (DiD/ferucarbotran). hMSCs underwent confocal microscopy, optical imaging (OI), and magnetic resonance (MR) imaging. Chondrogenesis was induced by transforming growth factor-b and confirmed by histopathology and glycosaminoglycan (GAG) production. Data of labeled and unlabeled hMSCs were compared with a t test. Results Cellular uptake of DiD and ferucarbotran was confirmed with confocal microscopy. DiD labeling caused a significant fluorescence on OI, and ferucarbotran labeling caused a significant T2* effect on MR images. Compared to nonlabeled controls, progenies of labeled MSCs exhibited similar chondrocyte morphology after chondrogenic differentiation, but the labeled cells demonstrated significantly reduced GAG production ( p <0.05). Conclusion DiD and DiD/ferucarbotran labeling of hMSC does not interfere with cell viability or morphologic differentiation into chondrocytes, but labeled cells exhibit significantly less GAG production compared to unlabeled cells.

Oncley S. P., J. Dudhia, 1995: Evaluation of surface fluxes from MM5 using observations. Mon. Wea. Rev., 123, 3344- 3357.10.1175/1520-0493(1995)123<3344:EOSFFM>2.0.CO;2

5fb96c45d352e09e18a1fc583e125f2f

http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1995MWRv..123.3344O

http://adsabs.harvard.edu/abs/1995MWRv..123.3344ONot Available

Oouchi K., J. Yoshimura, H. Yoshimura, R. Mizuta, S. Kusunoki, and A. Noda, 2006: Tropical cyclone climatology in a global-warming climate as simulated in a 20 km-mesh global atmospheric model: Frequency and wind intensity analyses. J. Meteor. Soc.Japan, 84, 259- 276.10.2151/jmsj.84.259

ada5f2a7-47d8-4cf0-a75f-84bf2990b116

e0b889273e26220d7df948adacca4270

http%3A%2F%2Fci.nii.ac.jp%2Fnaid%2F110004720656

refpaperuri:(e61fd8a4503040fc75577adbee8b84e9)

http://ci.nii.ac.jp/naid/110004720656Possible changes in the tropical cyclones in a future, greenhouse-warmed climate are investigated using a 20km-mesh, high-resolution, global atmospheric model of MRI/JMA, with the analyses focused on the evaluation of the frequency and wind intensity. Two types of 10-year climate experiments are conducted. One is a present-day climate experiment, and the other is a greenhouse-warmed climate experiment, with a forcing of higher sea surface temperature and increased greenhouse-gas concentration. A comparison of the experiments suggests that the tropical cyclone frequency in the warm-climate experiment is globally reduced by about 30% (but increased in the North Atlantic) compared to the present-day-climate experiment. Furthermore, the number of intense tropical cyclones increases. The maximum surface wind speed for the most intense tropical cyclone generally increases under the greenhouse-warmed condition (by 7.3 ms^<-1> in the Northern Hemisphere and by 3.3 ms^<-1> in the Southern Hemisphere). On average, these findings suggest the possibility of higher risks of more devastating tropical cyclones across the globe in a future

Qian J.-H., A. Seth, and S. Zebiak, 2003: Reinitialized versus continuous simulations for regional climate downscaling. Mon. Wea. Rev., 131, 2857- 2874.10.1175/1520-0493(2003)131<2857:RVCSFR>2.0.CO;2

73e0e245d42dac2ee3eac6c26697397e

http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2003MWRv..131.2857Q

http://adsabs.harvard.edu/abs/2003MWRv..131.2857QThe methodology for dynamical climate downscaling is studied using the second-generation regional climate model (RegCM2). The question addressed is, in order to simulate high-resolution details as accurately as possible, what strategy should be taken: continuous long-term integration in climate prediction mode or consecutive short-term integrations in weather forcasting mode? To investigate this problem, the model was run for 5 months in three different ways: 1) a 5-month continuous simulation, 2) monthly reinitialized simulations, and 3) 10-day reinitialized simulations. Compared to the observed precipitation, the 10-day reinitialized simulation results in the smallest error, while the continuous run shows larger error. Analysis shows that the long-term continuous simulation is contaminated by the systematic errors associated with the steep Andes Mountains and the uncertainties in the moisture processes in the planetary boundary layer near the coast. The method of 10-day reinitialization effectively mitigates the problem of systematic errors and makes a difference in the subtle precipitation processes in the regional climate model, therefore improving the accuracy in dynamic downscaling.

Rinke A. and K. Dethloff, 2000: On the sensitivity of a regional Arctic climate model to initial and boundary conditions. Clim. Res., 14( 2), 101- 113.10.3354/cr014101

9de707c938d7609e2b3b6c93056d583c

http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F250221393_On_the_sensitivity_of_a_regional_Arctic_climate_model_to_initial_and_boundary_conditions

http://www.researchgate.net/publication/250221393_On_the_sensitivity_of_a_regional_Arctic_climate_model_to_initial_and_boundary_conditionsThe sensitivity of Arctic atmospheric simulations to initial and boundary conditions was investigated with the high horizontal resolution regional climate model HIRHAM driven by observational data analyses at the lateral and lower boundaries. Investigation of the constraint of the synoptic-scale flow in the specific circumpolar Arctic domain showed that even though the same domain size as in mid-latitude RCM (regional climate model) simulations was used, a weaker constraint of the synoptic scales and a smaller predictability were obtained. A simple spectral analysis showed that only scales with wavelengths longer than 1000 km contribute to the higher root-mean-square difference. Due to the weaker lateral boundary control a pronounced sensitivity of the Arctic simulations to uncertainties in initial conditions was found. The changes in the monthly mean atmospheric structures due to internal processes were of the same order as those due to inaccurate physical parameterizations. Sensitivity experiments concerning changed sea ice thickness showed a substantial impact of the lower boundary conditions on the monthly mean atmospheric structures up to the middle troposphere.

Skamarock W. C., J. B. Klemp, J. Dudhia, D. O. Gill, D. M. Barker, W. Wang, and J. G. Powers, 2005: A description of the Advanced Research WRF Version 2. NCAR Tech. Note TN-468+STR.10.5065/D68S4MVH

6e1e8ed5238484bf7e6021f9957054e6

http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F244955031_A_Description_of_the_Advanced_Research_WRF_Version_2

http://www.researchgate.net/publication/244955031_A_Description_of_the_Advanced_Research_WRF_Version_2The development of the Weather Research and Forecasting (WRF) modeling system is a multiagency effort intended to provide a next-generation mesoscale forecast model and data assimilation system that will advance both the understanding and prediction of mesoscale weather and accelerate the transfer of research advances into operations. The model is being developed as a collaborative effort ort among the NCAR Mesoscale and Microscale Meteorology (MMM) Division, the National Oceanic and Atmospheric Administration's (NOAA) National Centers for Environmental Prediction (NCEP) and Forecast System Laboratory (FSL), the Department of Defense's Air Force Weather Agency (AFWA) and Naval Research Laboratory (NRL), the Center for Analysis and Prediction of Storms (CAPS) at the University of Oklahoma, and the Federal Aviation Administration (FAA), along with the participation of a number of university scientists. The WRF model is designed to be a flexible, state-of-the-art, portable code that is an efficient in a massively parallel computing environment. A modular single-source code is maintained that can be configured for both research and operations. It offers numerous physics options, thus tapping into the experience of the broad modeling community. Advanced data assimilation systems are being developed and tested in tandem with the model. WRF is maintained and supported as a community model to facilitate wide use, particularly for research and teaching, in the university community. It is suitable for use in a broad spectrum of applications across scales ranging from meters to thousands of kilometers. Such applications include research and operational numerical weather prediction (NWP), data assimilation and parameterized-physics research, downscaling climate simulations, driving air quality models, atmosphere-ocean coupling, and idealized simulations (e.g boundary-layer eddies, convection, baroclinic waves).*WEATHER FORECASTING

Tsutsui J. I., A. Kasahara, 1996: Simulated tropical cyclones using the national center for atmospheric research community climate model. J. Geophys. Res., 101, 15 013- 15 032.10.1029/95JD03774

dd6c0d3fcbb62047301128af4c71963b

http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F95JD03774%2Fabstract

http://onlinelibrary.wiley.com/doi/10.1029/95JD03774/abstractThe possibility of simulating tropical cyclones (TCs) using the National Center for Atmospheric Research community climate model (CCM2) is explored. Daily outputs from two long-term simulation runs using the standard T42 resolution CCM2 are examined to identify simulated tropical cyclones (STCs) using a search scheme that selects qualified STCs resembling observed TCs. The two simulation cases are a 20-year run driven by climatological sea surface temperatures (SSTs) and a 10-year run, corresponding to the decade from 1979 to 1988, with the same model configuration except for the use of observed SSTs. A composite technique is adopted to reveal the horizontal and vertical structures of well-developed STCs, and a comparison with those of observed TCs is presented. Then, the climatologies of STCs from the two simulation cases are discussed in terms of their genesis, movements, and seasonal and interannual variations through the comparisons with observed TC statistics. Despite obvious shortcomings of the standard CCM2, such as a coarse horizontal resolution, the structure and climatology of STCs identified in both climate runs are in reasonably good agreement with those of observed TCs. The annual STC frequency shows a better agreement with the observed SST run than the climatological SST run, while many other aspects of STCs in the two climate runs are comparable.

Tulich S. N., G. N. Kiladis, and A. Suzuki-Parker, 2011: Convectively coupled Kelvin and easterly waves in a regional climate simulation of the tropics. Climate Dyn.,36, 185-203, doi: 10.1007/s00382-009-0697-2.10.1007/s00382-009-0697-2

f7b953fd123ef715b80b31f8c37705fe

http%3A%2F%2Flink.springer.com%2F10.1007%2Fs00382-009-0697-2

http://link.springer.com/10.1007/s00382-009-0697-2This study evaluates the performance of a regional climate model in simulating two types of synoptic tropical weather disturbances: convectively-coupled Kelvin and easterly waves. Interest in these two wave modes stems from their potential predictability out to several weeks in advance, as well as a strong observed linkage between easterly waves and tropical cyclogenesis. The model is a recent version of the weather research and forecast (WRF) system with 36-km horizontal grid spacing and convection parameterized using a scheme that accounts for key convective triggering and inhibition processes. The domain spans the entire tropical belt between 45°S and 45°N with periodic boundary conditions in the east–west direction, and conditions at the meridional/lower boundaries specified based on observations. The simulation covers 6years from 2000 to 2005, which is long enough to establish a statistical depiction of the waves through space-time spectral filtering of rainfall data, together with simple lagged-linear regression. Results show that both the horizontal phase speeds and three-dimensional structures of the waves are qualitatively well captured by the model in comparison to observations. However, significant biases in wave activity are seen, with generally overactive easterly waves and underactive Kelvin waves. Evidence is presented to suggest that these biases in wave activity (which are also correlated with biases in time–mean rainfall, as well as biases in the model’s tropical cyclone climatology) stem in part from convection in the model coupling too strongly to rotational circulation anomalies. Nevertheless, the model is seen to do a reasonable job at capturing the genesis of tropical cyclones from easterly waves, with evidence for both wave accumulation and critical layer processes being importantly involved.

von Storch, H.H. Langerberg, F. Feser, 2000: A spectral nudging technique for dynamical downscaling purposes. Mon. Wea. Rev., 128, 3664- 3673.dc262947082f6a5c59355dfe00dfdf50

http%3A%2F%2Fwww.bioone.org%2Fservlet%2Flinkout%3Fsuffix%3Di1551-5036-27-5-890-VonStorch1%26dbid%3D16%26doi%3D10.2112%252FJCOASTRES-D-10-00055.1%26key%3D10.1175%252F1520-0493%282000%291282.0.CO%253B2

/s?wd=paperuri%3A%286036df97503a3416e1cf414420b62e18%29&filter=sc_long_sign&tn=SE_xueshusource_2kduw22v&sc_vurl=http%3A%2F%2Fwww.bioone.org%2Fservlet%2Flinkout%3Fsuffix%3Di1551-5036-27-5-890-VonStorch1%26dbid%3D16%26doi%3D10.2112%252FJCOASTRES-D-10-00055.1%26key%3D10.1175%252F1520-0493%282000%291282.0.CO%253B2&ie=utf-8

Walsh K. J. E., K.-C. Nguyen, and J. L. McGregor, 2004: Fine-resolution regional climate model simulations of the impact of climate change on tropical cyclones near Australia. Climate Dyn., 22, 47- 56.10.1111/j.2042-7158.1973.tb10612.x

66fe5adc8fae5eeacb8217952f63650c

http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fbrmpmturdqvxh3vv%2F

http://www.springerlink.com/content/brmpmturdqvxh3vv/Not Available

Wang H., Y. Q. Wang, and H. M. Xu, 2013: Improving simulation of a tropical cyclone using dynamical initialization and large-scale spectral nudging: A case study of Typhoon Megi (2010). Acta Meteorologica Sinica,27(4), 455-475, doi: 10.1007/s13351-013-0418-y.10.1007/s13351-013-0418-y

2e5b2c6a-2445-4373-8069-612ab1dcaa52

b4794d541bc743b7ce6a56059decfb75

http%3A%2F%2Flink.springer.com%2F10.1007%2Fs13351-013-0418-y

refpaperuri:(38052d847591beb3fd58cee42abcf1e5)

http://d.wanfangdata.com.cn/Periodical_qxxb-e201304001.aspxIn this study, an approach combining dynamical initialization and large-scale spectral nudging is proposed to achieve improved numerical simulations of tropical cyclones (TCs), including track, structure, intensity, and their changes, based on the Advanced Weather Research and Forecasting (ARW-WRF) model. The effectiveness of the approach has been demonstrated with a case study of Typhoon Megi (2010). The ARW-WRF model with the proposed approach realistically reproduced many aspects of Typhoon Megi in a 7-day-long simulation. In particular, the model simulated quite well not only the storm track and intensity changes but also the structure changes before, during, and after its landfall over the Luzon Island in the northern Philippines, as well as after it reentered the ocean over the South China Sea (SCS). The results from several sensitivity experiments demonstrate that the proposed approach is quite effective and ideal for achieving realistic simulations of real TCs, and thus is useful for understanding the TC inner-core dynamics, and structure and intensity changes.

Weng H., A. Sumi, Y. N. Takayabu, M. Kimoto, and C. Li, 2004: Interannual-interdecadal variation in large-scale atmospheric circulation and extremely wet and dry summers in China/Japan during 1951-2000 part I: spatial patterns. J. Meteor. Soc.Japan, 82, 775- 788.

Wu G. X., N. C. Lau, 1992: A GCM simulation of the relationship between tropical storm formation and ENSO. Mon. Wea. Rev., 120, 958- 977.52843019-32dc-484d-b39b-1823990e6b93

df73aebe9800dbf1f3862e6c396824c3

http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1992mwrv..120..958w

refpaperuri:(c157d8af0f7d48b77eb24c1b8f8f5bc8)

/s?wd=paperuri%3A%28c157d8af0f7d48b77eb24c1b8f8f5bc8%29&filter=sc_long_sign&tn=SE_xueshusource_2kduw22v&sc_vurl=http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1992mwrv..120..958w&ie=utf-8

Yesubabu V., C. V. Srinivas, S. S. V. S. Ramakrishna, and K. B. R. R. Hari Prasad, 2014: Impact of period and timescale of FDDA analysis nudging on the numerical simulation of tropical cyclones in the Bay of Bengal. Natural Hazards, 74, 2109- 2128.10.1007/s11069-014-1293-2

786f1751c914f99dc435353478e778b6

http%3A%2F%2Flink.springer.com%2F10.1007%2Fs11069-014-1293-2

http://link.springer.com/10.1007/s11069-014-1293-2ABSTRACT In this study, the impact of four-dimensional data assimilation (FDDA) analysis nudging is examined on the prediction of tropical cyclones (TC) in the Bay of Bengal to determine the optimum period and timescale of nudging. Six TCs (SIDR: November 13–16, 2007; NARGIS: April 29–May 02, 2008; NISHA: November 25–28, 2008; AILA: May 23–26, 2009; LAILA: May 18–21, 2010; JAL: November 04–07, 2010) were simulated with a doubly nested Weather Research and Forecasting (WRF) model with a horizontal resolution of 9 km in the inner domain. In the control run for each cyclone, the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) analysis and forecasts at 0.5 resolution are used for initial and boundary conditions. In the FDDA experiments available surface, upper air observations obtained from NCEP Atmospheric Data Project (ADP) data sets were used for assimilation after merging with the first guess through objective analysis procedure. Analysis nudging experiments with different nudging periods (6, 12, 18, and 24 h) indicated a period of 18 or 24 h of nudging during the pre-forecast stage provides maximum impact on simulations in terms of minimum track and intensity forecasts. To determine the optimum timescale of nudging, two cyclone cases (NARGIS: April 28–May 02, 2008; NISHA: November 25–28, 2008) were simulated varying the inverse timescales as 1.0e-4 to 5.0e-4 s-1 in steps of 1.0e-4 s-1. A positive impact of assimilation is found on the simulated characteristics with a nudging coefficient of either 3.0e-4 or 4.0e-4 s-1 which corresponds to a timescale of about 1 h for nudging dynamic (u,v) and thermodynamical (t,q) fields.