Balmaseda M. A., D. L. T. Anderson, and M. K. Davey, 1994: ENSO prediction using a dynamical ocean model coupled to statistical atmospheres. Tellus A, 46( 4), 497- 511.10.1034/j.1600-0870.1994.00012.xad425656b8c02ba4213874692a4d12f6http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1034%2Fj.1600-0870.1994.00012.x%2Fabstracthttp://onlinelibrary.wiley.com/doi/10.1034/j.1600-0870.1994.00012.x/abstractABSTRACT The predictability of El Niño/Southern Oscillation (ENSO) events is addressed by means of statistical and dynamical schemes. The statistical schemes are based on principal oscillation pattern (POP) analysis of various observed and model ocean fields: these statistical predictions establish a lower limit for the predictability of such a system. For the dynamical predictions, an ocean model of intermediate complexity is coupled to several statistical surface wind stress models. In these coupled models, the atmospheric anomalies are a linear response to the oceanic fields: several combination of fields are considered, such as SST and heat content. The spatial features of predictability are discussed. Predictions seem to be better in the central Pacific. In the western and eastern Pacific, the predictability skill scores are poorer, possibly due to deficiencies in the ocean thermodynamics and in the coupling. The model predictions exhibit a pronounced seasonal dependence, with spring and summer being less predictable. Best results are obtained with seasonally-dependent predictors. |
Barnett T. P., N. Graham, S. Pazan, W. White, M. Latif, and M. Flügel, 1993: ENSO and ENSO-related predictability. Part I: Prediction of equatorial Pacific sea surface temperature with a hybrid coupled ocean-atmosphere model. J.Climate, 6, 1545- 1566.1781993cee300d90520c022f595b54aehttp%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1993JCli....6.1545B/s?wd=paperuri%3A%28c9f3a1fc1ad9cef06c70754055e8e948%29&filter=sc_long_sign&tn=SE_xueshusource_2kduw22v&sc_vurl=http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1993JCli....6.1545B&ie=utf-8&sc_us=13200152207448981875 |
Bjerknes J., 1969: Atmospheric teleconnections from the equatorial Pacific. Mon. Wea. Rev., 97, 163- 172.10.1175/1520-0493(1969)097<0163:ATFTEP>2.3.CO;29f0298dd45e510c14c05703bfaea0d37http%3A%2F%2Fwww.rand.org%2Fpubs%2Fpapers%2FP3882.htmlhttp://www.rand.org/pubs/papers/P3882.htmlAbstract The “high index” response of the northeast Pacific westerlies to big positive anomalies of equatorial sea temperature, observed in the winter of 1957–58, has been found to repeat during the major equatorial sea temperature maxima in the winters of 1963–64 and 1965–66. The 1963 positive temperature anomaly started early enough to exert the analogous effect on the atmosphere of the south Indian Ocean during its winter season. The maxima of the sea temperature in the eastern and central equatorial Pacific occur as a result of anomalous weakening of the trade winds of the Southern Hemisphere with inherent weakening of the equatorial upwelling. These anomalies are shown to be closely tied to the “Southern Oscillation” of Sir Gilbert Walker. |
Cane M. A., S. E. Zebiak, and S. C. Dolan, 1986: Experimental forecasts of El Niño. Nature, 321( 6073), 827- 832. |
Chen D., S. E .Zebiak , A. J. Busalacchi , and Cane M.A., 1995: An improved procedure for El Niño forecasting: Implications for predictability. Science, 269, 1699- 1702.f0c8e6c1-a7a5-42ca-a30d-b9e4b80bf729f10992904d7c885966104328d9c51383http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F245343887_An_improved_procedure_for_El_Nino_forecastingrefpaperuri:(20ab5bab11cc11dc54936082b810ee79)http://www.researchgate.net/publication/245343887_An_improved_procedure_for_El_Nino_forecasting |
Derber J., A. Rosati, 1989: A global oceanic data assimilation system. J. Phys. Oceanogr., 19( 9), 1333- 1347.10.1175/1520-0485(1989)019<1333:AGODAS>2.0.CO;2ce029d0611dc3e5ccbc82bd90cc1a156http%3A%2F%2Fci.nii.ac.jp%2Fnaid%2F80004766911http://ci.nii.ac.jp/naid/80004766911Not Available |
Dommenget D., D. Stammer, 2004: Assessing ENSO simulations and predictions using adjoint ocean state estimation. J.Climate, 17( 22), 4301- 4315.10.1175/3211.18523642a3793eb91fd550539508fe52bhttp%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2004JCli...17.4301Dhttp://adsabs.harvard.edu/abs/2004JCli...17.4301DSimulations and seasonal forecasts of tropical Pacific SST and subsurface fields that are based on the global Consortium for Estimating the Circulation and Climate of the Ocean (ECCO) ocean-state estimation procedure are investigated. As compared to similar results from a traditional ENSO simulation and forecast procedure, the hindcast of the constrained ocean state is significantly closer to observed surface and subsurface conditions. The skill of the 12-month lead SST forecast in the equatorial Pacific is comparable in both approaches. The optimization appears to have better skill in the SST anomaly correlations, suggesting that the initial ocean conditions and forcing corrections calculated by the ocean-state estimation do have a positive impact on the predictive skill. However, the optimized forecast skill is currently limited by the low quality of the statistical atmosphere. Progress is expected from optimizing a coupled model over a longer time interval with the coupling statistics being part of the control vector. |
Evensen G., 1994: Sequential data assimilation with a nonlinear quasi-geostrophic model using Monte Carlo methods to forecast error statistics. J. Geophys. Res., 99, 10 143- 10 162.10.1029/94JC00572ef8053eecb8d37c88057c7928546f3a5http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F94JC00572%2Fcitedbyhttp://onlinelibrary.wiley.com/doi/10.1029/94JC00572/citedbyCiteSeerX - Document Details (Isaac Councill, Lee Giles, Pradeep Teregowda): . A new sequential data assimilation method is discussed. It is based on forecasting the error statistics using Monte Carlo methods, a better alternative than solving the traditional and computationally extremely demanding approximate error covariance equation used in the extended Kalman filter. The unbounded error growth found in the extended Kalman filter, which is caused by an overly simplified closure in the error covariance equation, is completely eliminated. Open boundaries can be handled as long as the ocean model is well posed. Well-known numerical instabilities associated with the error covariance equation are avoided because storage and evolution of the error covariance matrix itself are not needed. The results are also better than what is provided by the extended Kalman filter since there is no closure problem and the quality of the forecast error statistics therefore improves. The method should be feasible also for more sophisticated primitive equation models. The computati... |
Galanti E., E. Tziperman, M. Harrison, A. Rosati, and Z. Sirkes, 2003: A study of ENSO prediction using a hybrid coupled model and the adjoint method for data assimilation. Mon. Wea. Rev., 131( 11), 2748- 2764.10.1175/1520-0493(2003)131<2748:ASOEPU>2.0.CO;29d8bcf9d-0573-49cd-b642-da998fc4dd6dccebf642d91bd910019a2920cf3664c2http%3A%2F%2Fconnection.ebscohost.com%2Fc%2Farticles%2F11280262%2Fstudy-enso-prediction-using-hybrid-coupled-model-adjoint-method-data-assimilationrefpaperuri:(8a2aadab711a909de65725230d4dc3c2)http://connection.ebscohost.com/c/articles/11280262/study-enso-prediction-using-hybrid-coupled-model-adjoint-method-data-assimilationAn experimental ENSO prediction system is presented, based on an ocean general circulation model (GCM) coupled to a statistical atmosphere and the adjoint method of 4D variational data assimilation. The adjoint method is used to initialize the coupled model, and predictions are performed for the period 1980-99. The coupled model is also initialized using two simpler assimilation techniques: forcing the ocean model with observed sea surface temperature and surface fluxes, and a 3D variational data assimilation (3DVAR) method, similar to that used by the National Centers for Environmental Prediction (NCEP) for operational ENSO prediction. The prediction skill of the coupled model initialized by the three assimilation methods is then analyzed and compared. The effect of the assimilation period used in the adjoint method is studied by using 3-, 6-, and 9-month assimilation periods. Finally, the possibility of assimilating only the anomalies with respect to observed climatology in order to circumvent systematic model biases is examined. It is found that the adjoint method does seem to have the potential for improving over simpler assimilation schemes. The improved skill is mainly at prediction intervals of more than 6 months, where the coupled model dynamics start to influence the model solution. At shorter prediction time intervals, the initialization using the forced ocean model or the 3DVAR may result in a better prediction skill. The assimilation of anomalies did not have a substantial effect on the prediction skill of the coupled model. This seems to indicate that in this model the climatology bias, which is compensated for by the anomaly assimilation, is less significant for the predictive skill than the bias in the model variability, which cannot be eliminated using the anomaly assimilation. Changing the optimization period from 6 to 3 to 9 months showed that the period of 6 months seems to be a near-optimal choice for this model. |
Han G. J., W. Li, Z. J. He, K. X. Liu, and J. R. Ma, 2006: Assimilated tidal results of tide gauge and TOPEX/POSEIDON data over the China seas using a variational adjoint approach with a nonlinear numerical model. Adv. Atmos. Sci.,23, 449-460, doi: 10.1007/s00376-006-0449-8.10.1007/s00376-006-0449-8869cea61dc14065bc241deda79959e53http%3A%2F%2Fwww.cnki.com.cn%2FArticle%2FCJFDTotal-DQJZ200603012.htmhttp://d.wanfangdata.com.cn/Periodical_dqkxjz-e200603012.aspxIn order to obtain an accurate tide description in the China Seas, the 2-dimensional nonlinear numerical Princeton Ocean Model (POM) is employed to incorporate in situ tidal measurements both from tide gauges and TOPEX/POSEIDON (T/P) derived datasets by means of the variational adjoint approach in such a way that unknown internal model parameters, bottom topography, friction coefficients and open boundary conditions, for example, are adjusted during the process. The numerical model is used as a forward model. After the along-track T/P data are processed, two classical methods, i.e. harmonic and response analysis, are implemented to estimate the tide from such datasets with a domain covering the model area extending from 0 to 41N in latitude and from 99E to 142E in longitude. And the results of these two methods are compared and interpreted. The numerical simulation is performed for 16 major constituents. In the data assimilation experiments, three types of unknown parameters (water depth, bottom friction and tidal open boundary conditions in the model equations) are chosen as control variables. Among the various types of data assimilation experiments, the calibration of water depth brings the most promising results. By comparing the results with selected tide gauge data, the average absolute errors are decreased from 7.9 cm to 6.8 cm for amplitude and from 13.0 to 9.0 for phase with respect to the semidiurnal tide M2 constituent, which is the largest tidal constituent in the model area. After the data assimilation experiment is performed, the comparison between model results and tide gauge observation for water levels shows that the RMS errors decrease by 9 cm for a total of 14 stations, mostly selected along the coast of Mainland China, when a one-month period is considered, and the correlation coefficients improve for most tidal stations among these stations. |
Han G. J., X. R. Wu, S. Q. Zhang, Z. Y. Liu, I. M. Navon, and W. Li, 2015: A study of coupling parameter estimation implemented by 4D-Var and EnKF with a simple coupled system. Advances in Meteorology ,2015, doi:10.1155/2015/530764.101fe06ebd928cd1dd194033abaa3400http%3A%2F%2Fdownloads.hindawi.com%2Fjournals%2Famete%2Faip%2F530764.pdfhttp://downloads.hindawi.com/journals/amete/aip/530764.pdf |
Houtekamer P. L., H. L. Mitchell, 1998: Data assimilation using an ensemble Kalman filter technique. Mon. Wea. Rev., 126( 3), 796- 811.d3f8c1aa877d5eac5d73e53c0fdac200http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1998mwrv..126..796h/s?wd=paperuri%3A%28a746c15529ef81420dfd1d8ebc7aecc8%29&filter=sc_long_sign&tn=SE_xueshusource_2kduw22v&sc_vurl=http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1998mwrv..126..796h&ie=utf-8&sc_us=8718907562637087200 |
Kalnay E., 2003: Atmospheric Modeling,Data Assimilation and Predictability. Cambridge University Press, 342pp.10.1198/tech.2005.s32617d7fbb1594d0cade45315e4ab692760http%3A%2F%2Famstat.tandfonline.com%2Fdoi%2Fabs%2F10.1198%2Ftech.2005.s326%3FjournalCode%3Dutch20http://amstat.tandfonline.com/doi/abs/10.1198/tech.2005.s326?journalCode=utch20Atmospheric modeling, data assimilation and predictability Eugenia Kalnay Cambridge University Press, 2003 : hbk : pbk |
Keenlyside N., R. Kleeman, 2002: Annual cycle of equatorial zonal currents in the Pacific. J. Geophys. Res., 107( C8), 8- 1.10.1029/2000JC0007112aab7aa7e1ba6d8ebb183276b198bf4ahttp%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F2000JC000711%2Fabstracthttp://onlinelibrary.wiley.com/doi/10.1029/2000JC000711/abstractObservational (Tropical Atmosphere-Ocean array) data on the annual cycle of upper ocean zonal currents on the equator are analyzed using a simple dynamical ocean model in order to investigate underlying dynamics. The model, by treating linear and nonlinear terms semi-independently, allows a separation of various linear and nonlinear effects. The model focuses on linear dynamics of low-order baroclinic modes. By realistically simulating the vertical structure of annual cycle, the model shows that linear dynamics determines the vertical and meridional structure of the annual cycle. Nonlinearity is weak and only important in the undercurrent, where it provides a simple mechanism for the annual cycle: mean meridional advection of the annual cycle north of the equator onto the equator, with the boreal springtime surge in the undercurrent being a direct result of a surge centered at 2N. Model results show that annual variations in zonal currents are out of phase across the equator, surging in the corresponding spring. This behavior is a response to trade wind variations, which are also equatorially antisymmetric, and is generated by the second meridional mode Rossby wave. |
Keenlyside N., M. Latif, M. Botzet, J. Jungclaus, and U. Schulzweida, 2005: A coupled method for initializing El Niño Southern Oscillation forecasts using sea surface temperature. Tellus A, 57( 3), 340- 356.10.1111/j.1600-0870.2005.00107.x37496007-66d9-492d-a03b-06354e5d86533e30b3eff5293d5d3daaeb1ee9b760b6http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1111%2Fj.1600-0870.2005.00107.x%2Ffullrefpaperuri:(007affb0aa8d24f5bb59c1f7fe1610d6)http://onlinelibrary.wiley.com/doi/10.1111/j.1600-0870.2005.00107.x/fullABSTRACT Top of page ABSTRACT 1.68Introduction 2.68Model description and experimental design 3.68Coupled ENSO variability 4.68Assimilation scheme 5.68Ensemble member generation 6.68Hindcast results 7.68Discussion and conclusions 8.68Acknowledgments References A simple method for initializing coupled general circulation models (CGCMs) using only sea surface temperature (SST) data is comprehensively tested in an extended set of ensemble hindcasts with the Max-Planck-Institute (MPI) climate model, MPI-OM/ECHAM5. In the scheme, initial conditions for both atmosphere and ocean are generated by running the coupled model with SST nudged strongly to observations. Air–sea interaction provides the mechanism through which SST influences the subsurface. Comparison with observations indicates that the scheme is performing well in the tropical Pacific. Results from a 500-yr control run show that the model's El Ni09o Southern Oscillation (ENSO) variability is quite realistic, in terms of strength, structure and period. The hindcasts performed were six months long, initiated four times per year, consisted of nine ensemble members, and covered the period 1969–2001. The ensemble was generated by only varying atmospheric initial conditions, which were sampled from the initialization run to capture intraseasonal variability. At six-month lead, the model is able to capture all the major ENSO extremes of the period. However, because of poor sampling of ocean initial conditions and model deficiencies, the ensemble-mean anomaly correlation skill for Ni09o3 SST is only 0.6 at six-month lead. None the less, the results presented here demonstrate the potential of such a simple scheme, and provide a simple method by which SST information may be better used in more complex initialization schemes. |
Kirtman B. P., S. E. Zebiak, 1997: ENSO simulation and prediction with a hybrid coupled model. Mon. Wea. Rev., 125( 10), 2620- 2641.10.1175/1520-0493(1997)125<2620:ESAPWA>2.0.CO;29ede8d553e559520af01c7256d92eb6bhttp%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1997MWRv..125.2620Khttp://adsabs.harvard.edu/abs/1997MWRv..125.2620KNot Available |
Kleeman R., A. M. Moore, and N. R. Smith, 1995: Assimilation of subsurface thermal data into a simple ocean model for the initialization of an intermediate tropical coupled ocean-atmosphere forecast model. Mon. Wea. Rev., 123, 3103- 3114.10.1175/1520-0493(1995)123<3103:AOSTDI>2.0.CO;20aa5ba3a190add777b13bf5ca1b116b6http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1995MWRv..123.3103Khttp://adsabs.harvard.edu/abs/1995MWRv..123.3103KTo promote SE maturation, the influence of different media components on different developmental stages was quantitatively evaluated. Advanced maturation was achieved with a sequence of culture media (prematuration medium and maturation medium) that contained various carbohydrates, organic nitrogen compounds and plant growth regulators. Application of lactose, BA, L-glutamine and casein hydrolysate in the prematuration medium enhanced the total number of SEs and promoted advanced differentiation. The highest number of late torpedo stage SEs was observed on maturation medium supplemented with 200 mM lactose and 29 mM sucrose. Lactose and sorbitol favoured SE maturation up to the early cotyledonary stage. With application of PEG and high ABA concentrations (20–40 μM), only early torpedo stages were formed. The number of late torpedo stage SEs was significantly higher on hormone free media or with lower ABA concentrations (0–5 μM). Formation of early and late cotyledonary SEs was significantly enhanced by adding BA in the maturation medium: neither Zeatin nor 2iP were effective. In addition, low sucrose concentrations in the proliferation medium (29 mM compared to 58 mM) also favoured the formation of cotyledonary SE in the maturation medium. |
Klinker E., F. Rabier, G. Kelly, and J. F. Mahfouf, 2000: The ECMWF operational implementation of four-dimensional variational assimilation. III: experimental results and diagnostics with operational configuration. Quart. J. Roy. Meteor. Soc., 126, 1191- 1215.22fcd695-6783-4f22-ab52-0fd5f3f9fd48edada6689a6b7221fc7494b0b5e16b89http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F243768012_The_ECMWF_operational_implementation_of_four-dimen-sional_variational_assimilationrefpaperuri:(73cc689b18456ab212110050cfda519f)http://www.researchgate.net/publication/243768012_The_ECMWF_operational_implementation_of_four-dimen-sional_variational_assimilation |
Kumar A., H. Wang, Y. Xue, and W. Q. Wang, 2014: How much of monthly subsurface temperature variability in the equatorial Pacific can be recovered by the specification of sea surface temperatures?. J.Climate, 27, 1559- 1577.10.1175/JCLI-D-13-00258.1a1d4f0a2adcc695b6f1e75cc41c05ecehttp%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2014JCli...27.1559Khttp://adsabs.harvard.edu/abs/2014JCli...27.1559KNot Available |
Liu D. C., J. Nocedal, 1989: On the limited memory BFGS method for large scale optimization. Mathematical Programming, 45, 503- 528.10.1007/BF01589116a6518ad8ffc1ffc13a02a159fead6af3http%3A%2F%2Flink.springer.com%2F10.1007%2FBF01589116http://link.springer.com/10.1007/BF01589116On the limited memory BFGS method for large scale optimization LIU D. C. Math. Program. B 45, 503-528, 1989 |
McCreary J. P., 1981: A linear stratified ocean model of the equatorial undercurrent. Philos. Trans. Roy. Soc.London, 298, 603- 635.10.1098/rsta.1981.0002b66aa9fd7e3c7fc9e041372902540081http%3A%2F%2Fwww.jstor.org%2Fstable%2F36691http://www.jstor.org/stable/36691A linear stratified ocean model is used to study the wind-driven response of the equatorial ocean. The model is an extension of the Lighthill (1969) model that allows the diffusion of heat and momentum into the deeper ocean, and so can develop non-trivial steady solutions. To retain the ability to expand solutions into sums of vertical normal modes, mixing coefficients must be inversely proportional to the square of the background Vaisala frequency. The model is also similar to the earlier homogeneous ocean model of Stommel (1960). He extended Ekman dynamics to the equator by allowing his model to generate a barotropic pressure field. The present model differs in that the presence of stratification allows the generation of a baroclinic pressure field as well. The most important result of this paper is that linear theory can produce a realistic equatorial current structure. The model Undercurrent has a reasonable width and depth scale. There is westward flow both above and below the Undercurrent. The meridional circulation conforms to the 'classical' picture suggested by Cromwell (1953). Unlike the Stommel solution, the response here is less sensitive to variations of parameters. Ocean boundaries are not necessary for the existence of the Undercurrent but are necessary for the existence of the deeper Equatorial Intermediate Current. The radiation of equatorially trapped Rossby and Kelvin waves is essential to the development of a realistic Undercurrent. Because the system supports the existence of these waves, low-order vertical modes can very nearly adjust to Sverdrup balance (defined below), which in a bounded ocean and for winds without curl is a state of rest. As a result, higher-order vertical modes are much more visible in the total solution. This property accounts for the surface trapping and narrow width scale of the equatorial currents. The high-order modes tend to be in Yoshida balance (defined below) and generate the characteristic meridional circulation pattern associated with equatorial Ekman pumping. |
McCreary J. P., Jr., 1983: A model of tropical ocean-atmosphere interaction. Mon. Wea. Rev., 111( 2), 370- 387.10.1175/1520-0493(1983)111<0370:AMOTOA>2.0.CO;2d2a0c5bdf3b0fcd33a1875395d28fa10http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1983MWRv..111..370Mhttp://adsabs.harvard.edu/abs/1983MWRv..111..370MA model is used to study ocean-atmosphere interaction in the tropics. The model ocean consists of the single baroclinic mode of a two-layer ocean. Thermodynamics in the upper layer is highly parameterized. If the interface is sufficiently shallow (deep), sea surface temperature is cool (warm). The model atmosphere consists of two wind states that interact with the ocean according to the ideas of Bjerknes. When the eastern ocean is cool, the trade winds expand equatorward in the central Pacific, simulating an enhanced Walker circulation (WC). When the eastern ocean is warm, the trade winds expand eastward, simulating an enhanced Walker circulation (WC) there. For reasonable choices of parameters, the model oscillates at all time scales associated with the Southern Oscillation. |
Mu M., W.-S. Duan, D. Chen, and W. D. Yu.2015: Target observations for improving initialization of high-impact ocean-atmospheric environmental events forecasting. National Science Review, 2, 226- 236.10.1093/nsr/nwv0217bc9d266fbd90a28233b34be5aca941bhttp%3A%2F%2Fwww.cnki.com.cn%2FArticle%2FCJFDTotal-NASR201502019.htmhttp://www.cnki.com.cn/Article/CJFDTotal-NASR201502019.htmIn this paper, we emphasize the importance of accurate initial conditions in predicting high-impact ocean-atmospheric environmental events, such as El Nin?o-Southern Oscillation(ENSO), Indian Ocean Dipole(IOD), tropical cyclone(TC), and Kuroshio large meander(KLM), by reviewing recent progresses toward target observations for improving the initialization of these events forecasting. Since ield observations are costly and will never be dense enough to fully cover the vast space of these events, it is necessary to develop methodologies that guide the design of eicient and efective observation strategy. Of particular interest is a method called conditional non-linear optimal perturbation(CNOP), which has been shown to be very useful in determining the sensitive areas for target observations applicable to the predictions of ENSO, IOD, TC, and KLM. Further studies are needed to understand the predictability of these events under the inluence of climate change, and to explore the possibility of implementing ield programs of target observations. hese studies are challenging but are crucially important for improving our forecast skill of the high-impact ocean-atmospheric environmental events, and thus for disaster prevention,climate change mitigation, and sustainable socio-economic development. |
Navon I. M., X. Zou, J. Derber, and J. Sela, 1992: Variational data assimilation with an adiabatic version of the NMC spectral model. Mon. Wea. Rev., 120, 1433- 1446.5e5f2109318126c6b6d30ab7b81fb2e5http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1992MWRv..120.1433N/s?wd=paperuri%3A%2852a87aab4fca961e5f08157ebd70f5a3%29&filter=sc_long_sign&tn=SE_xueshusource_2kduw22v&sc_vurl=http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1992MWRv..120.1433N&ie=utf-8&sc_us=17387289179188643444 |
Neelin J. D., 1990: A hybrid coupled general circulation model for El Niño studies. J. Atmos. Sci., 47( 5), 674- 693.10.1175/1520-0469(1990)047<0674:AHCGCM>2.0.CO;2460c3954-c2a0-4c94-8e02-6ad56e1cb1282f169ccbea16f7a23ccb9243f3eba3f0http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1990JAtS...47..674Nrefpaperuri:(315bac627d2201962ce3b3ba72cbf97e)http://adsabs.harvard.edu/abs/1990JAtS...47..674NA model is developed for tropical air-sea interaction studies, which is intermediate in complexity between the large coupled general circulation models (coupled GCMs) coming into use and the simple two-level models with which pioneering El Niño-Southern Oscillation studies were carried out. The model consists of a stripped-down tropical Pacific ocean GCM, coupled to an atmospheric model which is sufficiently simple that steady state solutions may be found for low level flow and surface stress, given oceanic boundary conditions. This hybrid coupling of an ocean GCM to a steady atmospheric model permits examination of the nature of interannual coupled oscillations in the absence of atmospheric noise. Tests of the atmospheric model against an atmospheric GCM simulation of El Niño anomalies are presented, and the ocean model climatology is examined under several different conditions. Experiments with the coupled model exhibit a variety of behaviors within a realistic parameter range. These indicate a partial bifurcation diagram in which the coupled system undergoes a Hopf bifurcation from a stable climatology, giving rise to sustained El Niño-period oscillations. The amplitude, period and eastward extent of these oscillations increase with the strength of coupling and the El Niño-period oscillation itself becomes unstable to a higher frequency coupled mode which coexists with it and may affect predictability. The difference between these flow regimes may be relevant to results found by other investigators in coupled GCM experiments. |
Peng S. Q., L. Xie, 2006: Effect of determining initial conditions by four-dimensional variational data assimilation on storm surge forecasting. Ocean Modelling, 14( 1), 1- 18.10.1016/j.ocemod.2006.03.0054f53a8ca-3ac1-405c-a2e7-7a52990bdaa0217fab128de6cfdfb647c8f60454c843http%3A%2F%2Fwww.sciencedirect.com%2Fscience%2Farticle%2Fpii%2FS1463500306000382refpaperuri:(5611df0f4273c0ce8a122baea3eb203a)http://www.sciencedirect.com/science/article/pii/S1463500306000382A tangent linear model and an adjoint model of the three-dimensional, time-dependent, nonlinear Princeton Ocean Model (POM) are developed to construct a four-dimensional variational data assimilation (4D-Var) algorithm for coastal ocean prediction. To verify and evaluate the performance of this 4D-Var method, a suite of numerical experiments are conducted for a storm surge case using model-generated "pseudo-observations". The pseudo-observations are generated by a nested-grid high-resolution numerical model which is coupled to an inundation/drying scheme that is not included in the original POM. The 4D-Var algorithm based on POM is tested thoroughly for both code accuracy and the potential application in storm surge forecasting. The assimilation cycles lead to effective convergence between the forecasts and the "observations". Assimilating water level alone or together with surface currents both lead to significant improvements in storm surge forecasts within and several hours beyond the data assimilation window. It is worth noting that, assimilating water level alone produces improvements in storm surge forecasts that are comparable to those by assimilating both water level and surface currents, suggesting that optimizations of water level and surface currents are linked through the 4D-Var assimilation cycles. However, it is also worth noting that, the benefit resulting from the reduction of initial error in water level and/or surface currents through data assimilation decreases rapidly in time outside the assimilation window. This suggests that determining initial conditions of water level and/or surface currents via data assimilation is only effective within and a few hours beyond the assimilation window for storm surge forecasting. Thus, alternative data assimilation approaches are needed to improve the accuracy and lead time in operational storm surge forecasting. |
Philand er, S. G. H., R. C. Pacanowski, N. C. Lau, M. J. Nath, 1992: Simulation of ENSO with a global atmospheric GCM coupled to a high-resolution tropical Pacific Ocean GCM. J.Climate, 5( 4), 308- 329.0a5a47b5-5055-4b19-8dab-fe4bbd9000af1e77c53b77a55ca4ff760a46f302f7b8http%3A%2F%2Fadsabs.harvard.edu%2Fcgi-bin%2Fnph-data_query%3Fbibcode%3D1992JCli....5..308P%26db_key%3DPHY%26link_type%3DABSTRACT%26high%3D04030refpaperuri:(6e22e6cd45045a7ea502d0e5f4a40d3d)/s?wd=paperuri%3A%286e22e6cd45045a7ea502d0e5f4a40d3d%29&filter=sc_long_sign&tn=SE_xueshusource_2kduw22v&sc_vurl=http%3A%2F%2Fadsabs.harvard.edu%2Fcgi-bin%2Fnph-data_query%3Fbibcode%3D1992JCli....5..308P%26db_key%3DPHY%26link_type%3DABSTRACT%26high%3D04030&ie=utf-8&sc_us=18190680938444575723 |
Reynolds R. W., N. A. Rayner, T. M. Smith, D. C. Stokes, and W. Wang, 2002: An improved in situ and satellite SST analysis for climate. J.Climate, 15( 13), 1609- 1625.1ecd9ceedf9ede6f75f40eecf88c95f5http%3A%2F%2Fwww.bioone.org%2Fservlet%2Flinkout%3Fsuffix%3Dbibr36%26dbid%3D16%26doi%3D10.1080%252F19425120.2012.675985%26key%3D10.1175%252F1520-0442%282002%290152.0.CO%253B2/s?wd=paperuri%3A%28ba996f056a7c404ef100fd71ca28ec61%29&filter=sc_long_sign&tn=SE_xueshusource_2kduw22v&sc_vurl=http%3A%2F%2Fwww.bioone.org%2Fservlet%2Flinkout%3Fsuffix%3Dbibr36%26dbid%3D16%26doi%3D10.1080%252F19425120.2012.675985%26key%3D10.1175%252F1520-0442%282002%290152.0.CO%253B2&ie=utf-8&sc_us=8005906790852054181 |
Rosati A., K. Miyakoda, and R. Gudgel, 1997: The impact of ocean initial conditions on ENSO forecasting with a coupled model, Mon. Wea. Rev., 125( 5), 754- 772.d74e234c-134d-4ea4-b7bd-230b25a6d61c10195e773ddacdd8d5379678e869ee0chttp%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1997MWRv..125..754Rrefpaperuri:(7f466904c11d40f13ef77520610868c1)/s?wd=paperuri%3A%287f466904c11d40f13ef77520610868c1%29&filter=sc_long_sign&tn=SE_xueshusource_2kduw22v&sc_vurl=http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1997MWRv..125..754R&ie=utf-8&sc_us=114775675340534505 |
Sugiura N., T. Awaji, S. Masuda, T. Mochizuki, T. Toyoda, T. Miyama, H. Igarashi, and Y. Ishikawa, 2008: Development of a four-dimensional variational coupled data assimilation system for enhanced analysis and prediction of seasonal to interannual climate variations. J. Geophys. Res., 113( C10), C10017.10.1029/2008JC004741a1d777f84ec09b95feb692fcf26878dfhttp%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F2008JC004741%2Ffullhttp://onlinelibrary.wiley.com/doi/10.1029/2008JC004741/full[1] A four-dimensional variational (4D-VAR) data assimilation system using a coupled ocean-atmosphere global model has been successfully developed with the aim of better defining the dynamical states of the global climate on seasonal to interannual scales. The application of this system to state estimations of climate processes during the 1996–1998 period shows, in particular, that the representations of structures associated with several key events in the tropical Pacific and Indian Ocean sector (such as the El Ni09o, the Indian Ocean dipole, and the Asian summer monsoon) are significantly improved. This fact suggests that our 4D-VAR coupled data assimilation (CDA) approach has the potential to correct the initial location of the model climate attractor on the basis of observational data. In addition, the coupling parameters that control the air-sea exchange fluxes of mass, momentum, and heat become well adjusted. Such an initialization using the 4D-VAR CDA approach allows us to make a roughly 1.5-year lead time prediction of the 1997–1998 El Ni09o event. These results demonstrate that our 4D-VAR CDA system has the ability to enhance forecast potential for seasonal to interannual phenomena. |
Tang Y. M., W. W. Hsieh, 2001: Coupling neural networks to incomplete dynamical systems via variational data assimilation. Mon. Wea. Rev., 129( 4), 818- 834.10.1175/1520-0493(2001)1292.0.CO;2e98d16f2f292c7b5681c58fa87b557a1http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2001MWRv..129..818Thttp://adsabs.harvard.edu/abs/2001MWRv..129..818TInvestigates how a neural network model can be coupled to a dynamical model via variational assimilation. Development of a hybrid neural-dynamical Lorenz model; Results from simple hybrid model experiments; Determination of neural network parameters via variational assimilation. |
Tang Y. M., J. Amband an, and D. K. Chen, 2014: Nonlinear measurement function in the ensemble Kalman filter. Adv Atmos. Sci.,31(3), 551-558, doi: 10.1007/s00376-013-3117-9.10.1007/s00376-013-3117-9085f062099febbd343b493200c768080http%3A%2F%2Fwww.cqvip.com%2FQK%2F84334X%2F201403%2F49301875.htmlhttp://d.wanfangdata.com.cn/Periodical_dqkxjz-e201403006.aspxOn the above basis, we present two modified Kalman gain algorithms. Compared to the current Kalman gain algorithm, the modified ones remove the above assumptions, thereby leading to smaller estimated errors. This outcome was confirmed experimentally, in which we used the simple Lorenz 3-component model as the test-bed. It was found that in such a simple nonlinear dynamical system, the modified Kalman gain can perform better than the current one. However, the application of the modified schemes to realistic models involving nonlinear measurement functions needs to be further investigated. |
Wang B., X. L. Zou, and J. Zhu, 2000: Data assimilation and its applications. Proceedings of the National Academy of Sciences of the United States of America, 97( 21), 11 143- 11 144.10.1073/pnas.97.21.1114311027322a6601f9cb5cae987731f38f5aab9d1c6http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpubmed%2F11027322http://med.wanfangdata.com.cn/Paper/Detail/PeriodicalPaper_PM11027322In data assimilation, one prepares the grid data as the best possible estimate of the true initial state of a considered system by merging various measurements irregularly distributed in space and time, with a prior knowledge of the state given by a numerical model. Because it may improve forecasting or modeling and increase physical understanding of considered systems, data assimilation now plays a very important role in studies of atmospheric and oceanic problems. Here, three examples are presented to illustrate the use of new types of observations and the ability of improving forecasting or modeling. |
Weaver A. T., J. Vialard, and D. L. T. Anderson, 2003: Three and four dimensional variational assimilation with a general circulation model of the tropical Pacific Ocean: Part I: formulation, internal diagnostics, and consistency checks. Mon. Wea. Rev., 131, 1360- 1378.c1278724-f065-4da4-bc67-9d596729cbcce5725c23b5e641faaf8ae5f1f50688bdhttp%3A%2F%2Fmy.safaribooksonline.com%2Fbook%2Fbiotechnology%2F9781598298444%2Fbasic-concepts%2Fconsistency_checksrefpaperuri:(db79805794ab8e00a9982413e2a3d1c0)/s?wd=paperuri%3A%28db79805794ab8e00a9982413e2a3d1c0%29&filter=sc_long_sign&tn=SE_xueshusource_2kduw22v&sc_vurl=http%3A%2F%2Fmy.safaribooksonline.com%2Fbook%2Fbiotechnology%2F9781598298444%2Fbasic-concepts%2Fconsistency_checks&ie=utf-8&sc_us=7918370634512938217 |
Wu X. R., S. Q. Zhang, Z. Y. Liu, A. Rosati, T. L. Delworth, and Y. Liu, 2012: Impact of geographic-dependent parameter optimization on climate estimation and prediction: Simulation with an intermediate coupled model. Mon. Wea. Rev., 140( 12), 3956- 3971.10.1175/MWR-D-11-00298.1e60529c9db41d4d2e2804f6c0d5c80c5http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2012MWRv..140.3956Whttp://adsabs.harvard.edu/abs/2012MWRv..140.3956WNot Available |
Wu X. R., W. Li, G. J. Han, S. Q. Zhang, and X. D. Wang, 2014: A compensatory approach of the fixed localization in EnKF. Mon. Wea. Rev. , 142, 3713- 3733.10.1007/BF00323184ea368eec1ae38624e7e06685fdf2b620http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F273205738_A_Compensatory_Approach_of_the_Fixed_Localization_in_EnKFhttp://www.researchgate.net/publication/273205738_A_Compensatory_Approach_of_the_Fixed_Localization_in_EnKFNot Available |
Wu X. R., G. J. Han, S. Q. Zhang, and Z. Y. Liu, 2016: A study of the impact of parameter optimization on ENSO predictability with an intermediate coupled model. Climate Dyn. ,46, 711-727, doi:10.1007/s00382-015-2608-z.10.1007/s00382-015-2608-z0bbc07b0ef94b83f7a4d2e3f2a4bdccehttp%3A%2F%2Flink.springer.com%2F10.1007%2Fs00382-015-2608-zhttp://link.springer.com/10.1007/s00382-015-2608-zModel error is a major obstacle for enhancing the forecast skill of El Ni09o-Southern Oscillation (ENSO). Among three kinds of model error sources—dynamical core misfitting, physical scheme approximati |
Wyrtki K., 1975: El Niño-the dynamic response of the equatorial Pacific Ocean to atmospheric forcing. J. Phys. Oceanogr., 5( 4), 572- 584.c9899457-0dbd-421c-aae4-bccf5c62346df566ceef6c3c171977672c3b2f2e549dhttp%3A%2F%2Fci.nii.ac.jp%2Fnaid%2F10013127141%2Frefpaperuri:(435f5e0c9edbaff14bfe2e016ff4babe)http://ci.nii.ac.jp/naid/10013127141/El Nino-The dynamic response of the equatorial Pacific Ocean to atmospheric forcing. WYRTKI K. J. Phys. Oceanogr 5, 572-584, 1975 |
Zebiak S. E., M. A. Cane, 1987: A model El Niño-Southern oscillation. Mon. Wea. Rev., 115, 2262- 2278.10.1038/302295a0fbff0f50-8c26-4685-a6ef-b4f44b04cc05c65dd6c79eaaa702eee2a149cb0bddbbhttp%3A%2F%2Fwww.researchgate.net%2Fpublication%2F244948692_1987_A_model_El-Nino-Southern_Oscillationrefpaperuri:(02aa79a86a12d930aec389c613c4f943)http://www.researchgate.net/publication/244948692_1987_A_model_El-Nino-Southern_OscillationAt intervals that vary from 2 to 10 yr sea-surface temperatures and rainfall are unusually high and the tradewinds are unusually weak over the tropical Pacific Ocean. These Southern Oscillation El Niño events which devastate the ecology of the coastal zones of Ecuador and Peru, which affect the global atmospheric circulation and which can contribute to severe winters over northern America, often develop in a remarkably predictable manner. But the event which began in 1982 has not followed this pattern. |
Zhang R. H., C. Gao, 2015: Role of subsurface entrainment temperature (Te) in the onset of El Niño events,as represented in an intermediate coupled model. Climate Dyn., 1-19, doi: 10.1007/s00382-015-2655-5.10.1007/s00382-015-2655-5e37a52da624d4c240e1c735b1d05e68ehttp%3A%2F%2Flink.springer.com%2Farticle%2F10.1007%2Fs00382-015-2655-5http://link.springer.com/article/10.1007/s00382-015-2655-5An improved intermediate coupled model (ICM) is described for use in ENSO-related modeling in the tropical Pacific, with ten baroclinic modes included in the vertical and horizonatally varying stratification taken into account. One crucial component of the model is the way in which the subsurface entrainment temperature in the surface mixed layer (T e ) is explicitly used to determine the sea surface temperature (SST) variability. An optimized procedure is developed to depict T e using inverse modeling from an SST anomaly equation and its empirical relationship with the sea surface pressure variability. The coupled system realistically produces interannual variability associated with ENSO cycles, with a dominant 4-year oscillation. The onset and development of El Ni09o events from this ICM are examined in view of the well-known delayed oscillator paradigm; an example is given for the evolution of La Ni09a conditions in model year 2 to El Ni09o conditions in year 4. Right after a La Ni09a event (e.g., in year 2), there is a clear signature of reflections at the western boundary in early year 2, with related equatorial signals propagating eastward along the equator into the eastern basin in middle year 2. However, these reflected signals on the equator do not directly lead to an onset of an El Ni09o event at that time. Instead, approximately 1-year delay, a major El Ni09o event is seen to develop in the following year (late year 3), at a time when there is no reflected signal explicitly from the western boundary, indicating that the origin of the El Ni09o event cannot be directly ascribed to the reflection processes. Instead, Kelvin waves in the ocean that actually triggers the El Ni09o event in early year 3 are generated by interior wind anomalies near the date line that are associated with the first appearance of warm SST anomalies off the equator. Persisted T e anomalies off the equator in the western tropical Pacific initiate the warm SST anomaly near the date line along the North Equatorial Countercurrent region, which induces wind anomalies and an ocean–atmosphere coupling, leading to the El Ni09o event in year 4. The relevance of these ICM-based results to other onset mechanisms of El Ni09o and observations is also discussed. |
Zhang R. H., S. E. Zebiak, R. Kleeman, and N. Keenlyside, 2003: A new intermediate coupled model for El Niño simulation and prediction. Geophys. Res. Lett.,30(19), doi:10.1029/2003 GL018010, 19. |
Zhang R. H., R. Kleeman, S. E. Zebiak, N. Keenlyside, and S. Raynaud, 2005a: An empirical parameterization of subsurface entrainment temperature for improved SST anomaly simulations in an intermediate ocean model. J.Climate, 18, 350- 371.10.1175/JCLI-3271.11a96302493af47d3b03534dc4da31a4fhttp%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2005JCli...18..350Zhttp://adsabs.harvard.edu/abs/2005JCli...18..350Z An empirical model for the temperature of subsurface water entrained into the ocean mixed layer (T-e) is presented and evaluated to improve sea Surface temperature anomaly (SSTA) simulations in an intermediate ocean model (IOM) of the tropical Pacific. An inverse modeling approach is adopted to estimate T-e from an SSTA equation using observed SST and simulated Upper-ocean currents. A relationship between T-e and sea surface height (SSH) anomalies is then obtained by utilizing a singular value decomposition (SVD) of their covariance. This empirical scheme is able to better parameterize T-e anomalies than other local schemes and quite realistically depicts interannual variability of T-e, including a nonlocal phase lag relation of T-e variations relative to SSH anomalies over the central equatorial Pacific. An improved T-e parameterization naturally leads to better depiction of the subsurface effect on SST variability by the mean upwelling of subsurface temperature anomalies. As a result, SSTA simulations are significantly improved in the equatorial Pacific a comparison with other schemes indicates that systematic errors of the simulated SSTAs are significantly small-apparently due to the optimized empirical T-e parameterization. Cross validation and comparisons with other model simulations are made to illustrate the robustness and effectiveness of the scheme. In particular it is demonstrated that the empirical T-e model constructed from one historical period can be successfully used to improve SSTA simulations in another. |
Zhang R. H., S. E. Zebiak, R. Kleeman, and N. Keenlyside, 2005b: Retrospective El Niño forecasts using an improved intermediate coupled model. Mon. Wea. Rev., 133, 2777- 2802.10.1175/MWR3000.1d7e01395-11cf-4052-9d08-8d6ef0786c74c56515f86939e580924fd4743b4cc8fchttp%3A%2F%2Fwww.researchgate.net%2Fpublication%2F242443365_Retrospective_El_Nio_Forecasts_Using_an_Improved_Intermediate_Coupled_Modelrefpaperuri:(d31ce0f823315f5ab6f96a7ab6efe803)http://www.researchgate.net/publication/242443365_Retrospective_El_Nio_Forecasts_Using_an_Improved_Intermediate_Coupled_ModelAbstract A new intermediate coupled model (ICM) is presented and employed to make retrospective predictions of tropical Pacific sea surface temperature (SST) anomalies. The ocean dynamics is an extension of the McCreary baroclinic modal model to include varying stratification and certain nonlinear effects. A standard configuration is chosen with 10 baroclinic modes plus two surface layers, which are governed by Ekman dynamics and simulate the combined effects of the higher baroclinic modes from 11 to 30. A nonlinear correction associated with vertical advection of zonal momentum is incorporated and applied (diagnostically) only within the two surface layers, forced by the linear part through nonlinear advection terms. As a result of these improvements, the model realistically simulates the mean equatorial circulation and its variability. The ocean thermodynamics include an SST anomaly model with an empirical parameterization for the temperature of subsurface water entrained into the mixed layer ( T e ), which is optimally calculated in terms of sea surface height (SSH) anomalies using an empirical orthogonal function (EOF) analysis technique from historical data. The ocean model is then coupled to a statistical atmospheric model that estimates wind stress ( ) anomalies based on a singular value decomposition (SVD) analysis between SST anomalies observed and anomalies simulated from ECHAM4.5 (24-member ensemble mean). The coupled system exhibits realistic interannual variability associated with El Niño, including a predominant standing pattern of SST anomalies along the equator and coherent phase relationships among different atmosphere-搊cean anomaly fields with a dominant 3-yr oscillation period. Twelve-month hindcasts/forecasts are made during the period 1963-2002, starting each month. Only observed SST anomalies are used to initialize the coupled predictions. As compared to other prediction systems, this coupled model has relatively small systematic errors in the predicted SST anomalies, and its SST prediction skill is apparently competitive with that of most advanced coupled systems incorporating sophisticated ocean data assimilation. One striking feature is that the model skill surpasses that of persistence at all lead times over the central equatorial Pacific. Prediction skill is strongly dependent on the season, with the correlations attaining a minimum in spring and a maximum in fall. Cross-validation experiments are performed to examine the sensitivity of the prediction skill to the data periods selected for training the empirical T e model. It is demonstrated that the artificial skill introduced by using a dependently constructed T e model is not significant. Independent forecasts are made for the period 1997-2002 when no dependent data are included in constructing the two empirical models ( T e and ). The coupled model has reasonable success in predicting transition to warm phase and to cold phase in the spring of 1997 and 1998, respectively. Potential problems and further improvements are discussed with the new intermediate prediction system. |
Zhang R. H., A. J. Busalacchi, and D. G. DeWitt, 2008: The roles of atmospheric stochastic forcing (SF) and oceanic entrainment temperature (Te) in decadal modulation of ENSO. J.Climate, 21, 674- 704.10.1175/2007JCLI1665.1d1946e4e-ceb5-41ef-84b7-a1bc6e177ace783fd267ae7027dd4a7b6bb9b9c59466http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F241204450_The_Roles_of_Atmospheric_Stochastic_Forcing_%28SF%29_and_Oceanic_Entrainment_Temperature_%28Te%29_in_Decadal_Modulation_of_ENSO%3Fev%3Dauth_pubrefpaperuri:(8be4a6c0b0b8608c3cdc672ed004e8a0)http://www.researchgate.net/publication/241204450_The_Roles_of_Atmospheric_Stochastic_Forcing_(SF)_and_Oceanic_Entrainment_Temperature_(Te)_in_Decadal_Modulation_of_ENSO?ev=auth_pubThe El Ni01±o09恪癝outhern Oscillation (ENSO) has been observed to exhibit decadal changes in its properties; the cause and implication of such changes are strongly debated. Here the authors examine the influences of two particular attributors of the ocean09恪癮tmospheric system. The roles of stochastic forcing (SF) in the atmosphere and decadal changes in the temperature of subsurface water entrained into the mixed layer (Te) in modulating ENSO are compared to one another using coupled ocean09恪癮tmosphere models of the tropical Pacific climate system. Two types of coupled models are used. One is an intermediate coupled model (ICM) and another is a hybrid coupled model (HCM), both of which consist of the same intermediate ocean model (IOM) with an empirical parameterization for Te, constructed via singular value decomposition (SVD) analysis of the IOM simulated historical data. The differences in the ICM and HCM are in the atmospheric component: the one in the ICM is an empirical feedback model for wind stress (0367), and that in the HCM is an atmospheric general circulation model (AGCM; ECHAM4.5). The deterministic component of atmospheric 0367 variability, representing its signal response (0367Sig) to an external SST forcing, is constructed statistically by an SVD analysis from a 24-member ensemble mean of the ECHAM4.5 AGCM simulations forced by observed SST; the SF component (0367SF) is explicitly estimated from the ECHAM4.5 AGCM ensemble and HCM simulations. Different SF representations are specified in the atmosphere: the SF effect can be either absent or present explicitly in the ICM, or implicitly in the HCM where the ECHAM4.5 AGCM is used as a source for SF. Decadal changes in the ocean thermal structure observed in the late 1970s are incorporated into the coupled systems through the Te parameterizations for the two subperiods before (196309恪79) and after (198009恪96) the climate shift (T6309恪79e and T8009恪96e), respectively. The ICM and HCM simulations well reproduce interannual variability associated with El Ni01±o in the tropical Pacific. Model sensitivity experiments are performed using these two types of coupled models with different realizations of SF in the atmosphere and specifications of decadal Te changes in the ocean. It is demonstrated that the properties of ENSO are modulated differently by these two factors. The decadal Te changes in the ocean can be responsible for a systematic shift in the phase propagation of ENSO, while the SF in the atmosphere can contribute to the amplitude and period modulation in a random way. The relevance to the observed decadal ENSO variability in the late 1970s is discussed. |
Zhang R. H., F. Zheng, J. Zhu, and Z. G. Wang, 2013: A successful real-time forecast of the 2010-11 La Niña event. Sci. Rep., 3,1108, doi: 10.1038/srep01108.10.1038/srep0110823346365e49859a1-e895-4f7b-90b5-1d2e90766fe7c2be70db9eed1eb05a7cafcc13853e40http%3A%2F%2Flabs.europepmc.org%2Fabstract%2FPMC%2FPMC3552287refpaperuri:(2824948dabf5f33f50859bbc916a124d)http://labs.europepmc.org/abstract/PMC/PMC3552287ABSTRACT During 2010-11, a La Niña condition prevailed in the tropical Pacific. An intermediate coupled model (ICM) is used to demonstrate a real-time forecast of sea surface temperature (SST) evolution during the event. One of the ICM's unique features is an empirical parameterization of the temperature of subsurface water entrained into the mixed layer (T(e)). This model provided a good prediction, particularly of the "double dip" evolution of SST in 2011 that followed the La Niña event peak in October 2010. Thermocline feedback, explicitly represented by the relationship between T(e) and sea level in the ICM, is a crucial factor affecting the second cooling in 2011. Large negative T(e) anomalies were observed to persist in the central equatorial domain during 2010-11, inducing a cold SST anomaly to the east during July-August 2011 and leading to the development of a La Niña condition thereafter. |
Zhang R. H., C. Gao, X. B. Kang, H. Zhi, Z. G. Wang, and L. C. Feng, 2015: ENSO modulations due to interannual variability of freshwater forcing and ocean biology-induced heating in the tropical Pacific. Sci. Rep., 5,18506, doi: 10.1038/srep18506.10.1038/srep18506aa3f00b5e001cf336c6533289fd037dchttp%3A%2F%2Feuropepmc.org%2Farticles%2FPMC4683514%2Fhttp://europepmc.org/articles/PMC4683514/Recent studies have identified clear climate feedbacks associated with interannual variations in freshwater forcing (FWF) and ocean biology-induced heating (OBH) in the tropical Pacific. The interrelationships among the related anomaly fields are analyzed using hybrid coupled model (HCM) simulations to illustrate their combined roles in modulating the El Niño-Southern Oscillation (ENSO). The HCM-based supporting experiments are performed to isolate the related feedbacks, with interannually varying FWF and OBH being represented individually or collectively, which allows their effects to be examined in a clear way. It is demonstrated that the interannual freshwater forcing enhances ENSO variability and slightly prolongs the simulated ENSO period, while the interannual OBH reduces ENSO variability and slightly shortens the ENSO period, with their feedback effects tending to counteract each other. |
Zhang S., X. Zou, and J. E. Ahlquist, 2001: Examination of numerical results from tangent linear and adjoint of discontinuous nonlinear models. Mon. Wea. Rev., 129( 11), 2791- 2804.e87e3e83516cc49bbdcaf06283cdb8abhttp%3A%2F%2Fadsabs.harvard.edu%2Fcgi-bin%2Fnph-data_query%3Fbibcode%3D2001MWRv..129.2791Z%26db_key%3DPHY%26link_type%3DABSTRACT/s?wd=paperuri%3A%28b3ee69db961290912f9d787a4266667e%29&filter=sc_long_sign&tn=SE_xueshusource_2kduw22v&sc_vurl=http%3A%2F%2Fadsabs.harvard.edu%2Fcgi-bin%2Fnph-data_query%3Fbibcode%3D2001MWRv..129.2791Z%26db_key%3DPHY%26link_type%3DABSTRACT&ie=utf-8&sc_us=1812729966643523739 |
Zhang S., M. J. Harrison, A. T. Wittenberg, A. Rosati, J. L. Anderson, and V. Balaji, 2005c: Initialization of an ENSO forecast system using a parallelized ensemble filter. Mon. Wea. Rev., 133( 11), 3176- 3201.10.1175/MWR3024.1a9816a2e-275b-43b1-be61-d9750ecb72cb676d6bd510b545ed4583758b6f9219achttp%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2005MWRv..133.3176Zrefpaperuri:(656e75ebeaef2434aa84d777646ce1d1)http://adsabs.harvard.edu/abs/2005MWRv..133.3176ZNot Available |
Zhang S., M. J. Harrison, A. Rosati, and A. Wittenberg, 2007: System design and evaluation of coupled ensemble data assimilation for global oceanic climate studies. Mon. Wea. Rev., 135( 10), 3541- 3564.23f1211717e3690331b5400ab00e1685http%3A%2F%2Ficesjms.oxfordjournals.org%2Fexternal-ref%3Faccess_num%3D10.1175%2FMWR3466.1%26link_type%3DDOIhttp://icesjms.oxfordjournals.org/external-ref?access_num=10.1175/MWR3466.1&link_type=DOI |
Zhang S., Y. S. Chang, X. Yang, and A. Rosati, 2014: Balanced and coherent climate estimation by combining data with a biased coupled model. J.Climate, 27( 3), 1302- 1314.10.1175/JCLI-D-13-00260.1d54561989da58886ff753ffa5f4cb751http%3A%2F%2Fonlinelibrary.wiley.com%2Fresolve%2Freference%2FXREF%3Fid%3D10.1175%2FJCLI-D-13-00260.1http://onlinelibrary.wiley.com/resolve/reference/XREF?id=10.1175/JCLI-D-13-00260.1Abstract Given a biased coupled model and the atmospheric and oceanic observing system, maintaining a balanced and coherent climate estimation is of critical importance for producing accurate climate analysis and prediction initialization. However, because of limitations of the observing system (e.g., most of the oceanic measurements are only available for the upper ocean), directly evaluating climate estimation with real observations is difficult. With two coupled models that are biased with respect to each other, a biased twin experiment is designed to simulate the problem. To do that, the atmospheric and oceanic observations drawn from one model based on the modern climate observing system are assimilated into the other. The model that produces observations serves as the truth and the degree by which an assimilation recovers the truth steadily and coherently is an assessment of the impact of the data constraint scheme on climate estimation. Given the assimilation model bias of warmer atmosphere and colder ocean, where the atmospheric-only (oceanic only) data constraint produces an overcooling (overwarming) ocean through the atmosphere-搊cean interaction, the constraints with both atmospheric and oceanic data create a balanced and coherent ocean estimate as the observational model. Moreover, the consistent atmosphere-搊cean constraint produces the most accurate estimate for North Atlantic Deep Water (NADW), whereas NADW is too strong (weak) if the system is only constrained by atmospheric (oceanic) data. These twin experiment results provide insights that consistent data constraints of multiple components are very important when a coupled model is combined with the climate observing system for climate estimation and prediction initialization. |
Zhang X. F., S. Q. Zhang, Z. Y. Liu, X. R. Wu, and G. J. Han, 2015a: Parameter optimization in an intermediate coupled climate model with biased physics. J.Climate, 28( 3), 1227- 1247.6126e262-008a-4520-a8c4-f965ee992fde416fd8107351a205a2a3e1de44f26062http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2015jcli...28.1227z/s?wd=paperuri%3A%28d3be56f5b29ef06073f40fea96eb4198%29&filter=sc_long_sign&tn=SE_xueshusource_2kduw22v&sc_vurl=http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2015jcli...28.1227z&ie=utf-8&sc_us=9433316375189316790 |
Zhang X. F., G. J. Han, D. Li, X. R. Wu, W. Li, and P. C. Chu, 2015b: Variational estimation of wave-affected parameters in a two-equation turbulence model. J. Atmos. Oceanic Technol., 32( 3), 528- 546.10.1175/JTECH-D-14-00087.111ea80ba-f077-4cf5-9483-fb19664f43cef993fb0aa7b05a8437b0ab168cdc150ehttp%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2015JAtOT..32..528Zhttp://adsabs.harvard.edu/abs/2015JAtOT..32..528ZNot Available |
Zheng F., J. Zhu, R. H. Zhang, and G. Q. Zhou, 2006: Ensemble hindcasts of SST anomalies in the tropical Pacific using an intermediate coupled model. Geophys. Res. Lett., 33( 19), L19604.10.1029/2006GL026994a643ac8e307005ceb7e558583fe8a59dhttp%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F2006GL026994%2Fabstracthttp://onlinelibrary.wiley.com/doi/10.1029/2006GL026994/abstract Ensemble hindcasts of sea surface temperature (SST) anomalies in the tropical Pacific are studied using an intermediate coupled model (ICM), in which an ensemble Kalman filter (EnKF) data assimilation system is implemented to provide the initial ensemble. A linear, first-order Markov stochastic model is adopted to represent model errors. Parameters in the stochastic model are estimated by comparing observation-minus-forecast values over 30 years. Twelve-month, 120 ensemble hindcasts are performed over the period 1995-2004, each with 100 ensemble members. This ensemble technique provides a simple method of extending the standard ICM forecasts to the probabilistic domain. The results show that the prediction skill of the ensemble mean is better than that of one single deterministic forecast using the same ICM. For the probabilistic perspective, those ensemble forecasts have their ensembles following observed SST anomaly variations well. |
Zheng F., J. Zhu, H. Wang, and R. H. Zhang, 2009: Ensemble hindcasts of ENSO events over the past 120 years using a large number of ensembles. Adv. Atmos. Sci.,26, 359-372, doi: 10.1007/s00376-009-0359-7.10.1007/s00376-009-0359-746b4cb1872e3da23cf3785e06025ff11http%3A%2F%2Fwww.cnki.com.cn%2FArticle%2FCJFDTotal-DQJZ200902020.htmhttp://d.wanfangdata.com.cn/Periodical_dqkxjz-e200902020.aspxBased on an intermediate coupled model (ICM), a probabilistic ensemble prediction system (EPS) has been developed. The ensemble Kalman filter (EnKF) data assimilation approach is used for generating the initial ensemble conditions, and a linear, first-order Markov-Chain SST anomaly error model is embedded into the EPS to provide model-error perturbations. In this study, we perform ENSO retrospective forecasts over the 120 year period 1886--2005 using the EPS with 100 ensemble members and with initial conditions obtained by only assimilating historic SST anomaly observations. By examining the retrospective ensemble forecasts and available observations, the verification results show that the skill of the ensemble mean of the EPS is greater than that of a single deterministic forecast using the same ICM, with a distinct improvement of both the correlation and root mean square (RMS) error between the ensemble-mean hindcast and the deterministic scheme over the 12-month prediction period. The RMS error of the ensemble mean is almost 0.2oC smaller than that of the deterministic forecast at a lead time of 12 months. The probabilistic skill of the EPS is also high with the predicted ensemble following the SST observations well, and the areas under the relative operating characteristic (ROC) curves for three different ENSO states (warm events, cold events, and neutral events) are all above 0.55 out to 12 months lead time. However, both deterministic and probabilistic prediction skills of the EPS show an interdecadal variation. For the deterministic skill, there is high skill in the late 19th century and in the middle-late 20th century (which includes some artificial skill due to the model training period), and low skill during the period from 1906 to 1961. For probabilistic skill, for the three different ENSO states, there is still a similar interdecadal variation of ENSO probabilistic predictability during the period 1886--2005. There is high skill in the late 19th century from 1886 to 1905, and a decline to a minimum of skill around 1910--50s, beyond which skill rebounds and increases with time until the 2000s. |
Zhu J., G. Q. Zhou, C. X. Yan, W. W. Fu, and X. B. You, 2006: A three-dimensional variational ocean data assimilation system: scheme and preliminary results. Science in China Series D: Earth Sciences, 49( 11), 1212- 1222.10.1007/s11430-006-1212-97b0e0f30e237011aca3c68bec7409f6bhttp%3A%2F%2Flink.springer.com%2F10.1007%2Fs11430-006-1212-9http://d.wanfangdata.com.cn/Periodical_zgkx-ed200611009.aspxA new 3DVAR-based Ocean Variational Analysis System (OVALS) is developed. OVALS is capable of assimilating in situ sea water temperature and salinity observations and satellite altimetry data. As a component of OVALS, a new variational scheme is proposed to assimilate the sea surface height data. This scheme considers both the vertical correlation of background errors and the nonlinear temperature-salinity relationship which is derived from the generalization of the linear balance constraints to the nonlinear in the 3DVAR. By this scheme, the model temperature and salinity fields are directly adjusted from the altimetry data. Additionally, OVALS can assimilate the temperature and salinity profiles from the ARGO floats which have been implemented in recent years and some temperature and salinity data such as from expendable bathythermograph, moored ocean buoys, etc. A 21-year assimilation experiment is carried out by using OVALS and the Tropical Pacific circulation model. The results show that the assimilation system may effectively improve the estimations of temperature and salinity by assimilating all kinds of observations. Moreover, the root mean square errors of temperature and salinity in the upper depth less than 420 m reach 0.63 and 0.34 psu. |
Zhu J. S., A. Kumar, H. Wang, and B. H. Huang, 2015: Sea surface temperature predictions in NCEP CFSv2 using a simple ocean initialization scheme. Mon. Wea. Rev., 143, 3176- 3191.10.1175/MWR-D-14-00297.1529a13e523e8d440aae9ab8f94e555d4http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2015MWRv..143.3176Zhttp://adsabs.harvard.edu/abs/2015MWRv..143.3176ZAbstract In contrast to operational climate predictions based on sophisticated ocean data assimilation schemes at the National Centers for Environmental Predictions (NCEP), this study applied a simple ocean initialization scheme to the NCEP latest seasonal prediction model - Climate Forecast System version 2 (CFSv2). In the scheme, sea surface temperature (SST) was the only observed information applied to derive ocean initial states. The physical basis for the method is that, through air-sea coupling, SST is capable of reproducing some observed features of ocean evolutions by forcing the atmospheric winds. SST predictions based on the scheme are compared against hindcasts from the National (lately North American) Multimodel Ensemble (NMME) project. It was found that due to substantial biases in the tropical eastern Pacific in the ocean initial conditions produced by SST assimilation, ENSO SST predictions were not as good as those with sophisticated initialization schemes, e.g., hindcasts in the NMME project. However, in other basins, SST predictions based on simple ocean initialization procedure were not worse (sometimes even better) than those with sophisticated initialization schemes. These comparisons indicate that it was helpful that subsurface ocean information be assimilated to improve the tropical Pacific SST predictions, while SST-based ocean assimilation was an effective way to enhance SST prediction capability in other ocean basins. By examining multimodel ensembles with the simple scheme-based hindcasts either included or excluded in NMME, it is also suggested that including the hindcast would generally benefit multimodel ensemble forecasts. In addition, possible ways to further improve ENSO SST predictions with the simple initialization scheme are also discussed. |
Zou X., I. M. Navon, M. Berger, K. H. Phua, T. Schlick, and F. X. Le Dimet, 1993: Numerical experience with limited-memory quasi-Newton and truncated Newton methods. SIAM Journal on Optimization, 3( 3), 582- 608.10.1137/080302992559443b519a5b0c2c34b5f0e64b270http%3A%2F%2Fwww.ams.org%2Fmathscinet-getitem%3Fmr%3D1230158http://www.ams.org/mathscinet-getitem?mr=1230158Computational experience with several limited-memory quasi-Newton and truncated Newton methods for unconstrained nonlinear optimization is described. Comparative tests were conducted on a well-known test library [J. J. Moré, B. S. Gaxbow, and K. E. Hillstrom, ACM Trans. Math. Software, 7 (1981), pp. 17–41], on several synthetic problems allowing control of the clustering of eigenvalues in the Hessian spectrum, and on some large-scale problems in oceanography and meteorology. The results indicate that among the tested limited-memory quasi-Newton methods, the L-BFGS method [D. C. Liu and J. Nocedal, Math. Programming, 45 (1989), pp. 503–528] has the best overall performance for the problems examined. The numerical performance of two truncated Newton methods, differing in the inner-loop solution for the search vector, is competitive with that of L-BFGS. ©1993 Society for Industrial and Applied Mathematics |