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variational data assimilation USING WAVELET BACKGROUND ERROR COVARIANCE: INITIALIZATION OF TYPHOON KAEMI (2006)

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Journal of Tropical Meteorology 2010年第4期16卷 333-340页

作者：张卫民曹小群肖庆农宋君强朱小谦王舒畅 College of Computer National University of Defense Technology Collage of Marine Science University of South Florida

Background error covariance plays an important role in any variational data assimilation system, because it determines how information from observations is spread in model space and between different model variables. In this paper, the use of orthogonal wavelets in representation of background error covariance over a limited area is studied. Based on the WRF model and its 3D-VAR system, an algorithm using orthogonal wavelets to model background error covariance is developed. Because each wavelet function contains information on both position and scale, using a diagonal correlation matrix in wavelet space gives the possibility to represent some anisotropic and inhomogeneous characteristics of background error covariance. The experiments show that local correlation functions are better modeled than spectral methods. The formulation of wavelet background error covariance is tested with the typhoon Kaemi (2006). The results of experiments indicate that the subsequent forecasts of typhoon Kaemi’s track and intensity are significantly improved by the new method.

关键词： variational data assimilation background error covariance orthogonal wavelet typhoon

GENERALIZED variational data assimilation METHOD AND NUMERICAL EXPERIMENT FOR NON-DIFFERENTIAL SYSTEM

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Applied Mathematics and Mechanics(English Edition) 2004年第10期25卷 1160-1165页

作者：黄思训杜华栋韩威 P.O.Box 003 Nanjing 211101 P.R.China

The generalized variational data assimilation for non-differential dynamical systems is *** is no tangent linear model for non-differential systems and thus the general adjoint model can not be derived in the traditional *** weak form of the original system was introduced, and then the generalized adjoint model was derived. The generalized variational data assimilation methods were developed for non-differential low dimensional system and non-differential high dimensional system with global and local observations. Furthermore, ideas in inverse problems are introduced to 4DVAR (Four-dimensional variational) of non-differential partial differential system with local observations.

关键词： variational data assimilation non-differential system adjoint method

Parallel Computing of a variational data assimilation Model for GPS/MET Observation Using the Ray-Tracing Method

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Advances in Atmospheric Sciences 2004年第2期21卷 220-226页

作者：张昕刘月巍王斌季仲贞 Key Laboratory of Pure and Applied Mathematics Center for Computational Science and EngineeringSchool of Mathematical Sciences Peking University Beijing 100871 National Meteorological Center Beijing 100081 National Meteorological Center Beijing 100081 State Key Laboratory of Numerical Modeling for Atmospherics Sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029

The Spectral Statistical Interpolation (SSI) analysis system of NCEP is used to assimilate meteorological data from the Global Positioning Satellite System (GPS/MET) refraction angles with the variational technique. Verified by radiosonde, including GPS/MET observations into the analysis makes an overall improvement to the analysis variables of temperature, winds, and water vapor. However, the variational model with the ray-tracing method is quite expensive for numerical weather prediction and climate research. For example, about 4 000 GPS/MET refraction angles need to be assimilated to produce an ideal global analysis. Just one iteration of minimization will take more than 24 hours CPU time on the NCEP's Cray C90 computer. Although efforts have been taken to reduce the computational cost, it is still prohibitive for operational data assimilation. In this paper, a parallel version of the three-dimensional variational data assimilation model of GPS/MET occultation measurement suitable for massive parallel processors architectures is developed. The divide-and-conquer strategy is used to achieve parallelism and is implemented by message passing. The authors present the principles for the code's design and examine the performance on the state-of-the-art parallel computers in China. The results show that this parallel model scales favorably as the number of processors is increased. With the Memory-IO technique implemented by the author, the wall clock time per iteration used for assimilating 1420 refraction angles is reduced from 45 s to 12 s using 1420 processors. This suggests that the new parallelized code has the potential to be useful in numerical weather prediction (NWP) and climate studies.

关键词： parallel computing variational data assimilation GPS/MET

Storm surge model based on variational data assimilation method

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Water Science and Engineering 2010年第2期3卷 166-173页

作者： Shi-li HUANG Jian XU De-guan WANG Dong-yan LU College of Water Conservancy and Hydropower Engineering Hohai University Nanjing 210098 P. R. China Shanghai Water Authority Shanghai 200232 P. R. China Shanghai Water Planning and Design Research Institute Shanghai 200232 P. R. China College of Environmental Science and Engineering Hohai University Nanjing 210098 P. R. China

By combining computation and observation information, the variational data assimilation method has the ability to eliminate errors caused by the uncertainty of parameters in practical forecasting. It was applied to a storm surge model based on unstructured grids with high spatial resolution meant for improving the forecasting accuracy of the storm surge. By controlling the wind stress drag coefficient, the variation-based model was developed and validated through data assimilation tests in an actual storm surge induced by a typhoon. In the data assimilation tests, the model accurately identified the wind stress drag coefficient and obtained results close to the true state. Then, the actual storm surge induced by Typhoon 0515 was forecast by the developed model, and the results demonstrate its efficiency in practical application.

关键词： storm surge variational data assimilation synthetic data unstructured grid

Application of Nonlinear Balance Scheme in Three-Dimensional variational data assimilation

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Acta meteorologica Sinica 2006年第4期20卷 413-425页

作者：庄照荣薛纪善朱宗申李兴良 Chinese Academy of Meteorological Sciences National Meteorological Center

The dynamical constrains in three-dimensional variational data assimilation are discussed when considering the impact of stream divergence and convergence on the pressure and wind fields. For the analysis of severe tropical cyclone, frontal structures, and other rapidly changing structures, the geostrophic balance and linear balance cannot properly represent the relationship between wind and pressure fields. However, the nonlinear balance incremental equation takes into account the information of flow-dependent background, and makes response to the flow-dependent background covariance in the 3D-Var system. Results indicate that the application of the nonlinear balance equation to 3D-Var system improves the quality of severe tropical cyclone assimilation system, which has some positive effects on intensity prediction of tropical cyclones.

关键词： variational data assimilation nonlinear balance equation background covariance

variational data assimilation of Land Surface Model with MODIS data

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Variational Data Assimilation of Land Surface Model with MOD...

A temporal sliding procedure for ocean wave variational data assimilation and its application

2010 International Conference on Remote Sensing (ICRS 2010)

作者： Chunlei Meng Department of Urban Ecological Meteorology Institute of Urban Meteorology CMA Beijing China

A variational data assimilation algorithm for assimilating land surface temperature （LST） in the Common Land Model （CoLM） is *** leaf area index （LAI） and land cover classification retrieved from MODIS are also assimilated in the *** analysis results from CoLM with the LST assimilation algorithm are well compared with MODIS and field observations at YUCHENG site within the research *** results indicate that the surface temperature assimilation method is efficient and effective when only one time observational LST data for each day is available.

关键词： variational data assimilation land surface model land surface temperature MODIS

来源： cnki会议评论

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Chinese Journal of Oceanology and Limnology 2006年第1期24卷 35-41页

作者：杨永增赵伟滕涌 First Institute of Oceanography

For sequential performance of wave variational data assimilation, we proposed a temporal sliding method in which the temporal overlap is considered. The advantage of this method is that the initial wave spectrum of the optimization process is modified by the observations in latter and former times. This temporal sliding procedure is important for marginal region, such as the China seas, where the duration of assimilation effectiveness is 2-3 days. Experiments were performed in the whole course of Cyclone 9403 （Russ）. Around the cyclone center, the maximum value of wave elements did not change much by assimilation, because the extreme value was determined by wind energy input that was not yet optimized. In the area outside the cyclone center, this modification is evident especially for wind wave growth.

关键词： ocean wave variational data assimilation temporal sliding procedure

On the 4D variational data assimilation with Constraint Conditions

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Advances in Atmospheric Sciences 2001年第6期18卷 1131-1145页

作者：朱克云 Chengdu University of Information Technology Chengdu

An investigation is carried out on the problem involved in 4D variational data assimilation (VDA) with constraint conditions based on a finite-element shallow-water equation model. In the investigation, the adjoint technology, penalty method and augmented Lagrangian method are used in constraint optimization field to minimize the defined constraint objective functions. The results of the numerical experiments show that the optimal solutions are obtained if the functions reach the minima. VDA with constraint conditions controlling the growth of gravity oscillations is efficient to eliminate perturbation and produces optimal initial field. It seems that this method can also be applied to the problem in numerical weather prediction. Key words variational data assimilation - Constraint conditions - Penalty methods - finite-element model This research is supported by National Natural Science Foundation of China (Grant No. 49575269) and by National Key Basic Research on the Formation Mechanism and Prediction Theory of Severe Synoptic Disasters (Grant No. G1998040910).

关键词： variational data assimilation Constraint conditions Penalty methods finite-element model

Initialization and Simulation of a Typhoon Using 4-Dimensional variational data assimilation——Research on Typhoon Herb (1996)

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Advances in Atmospheric Sciences 2003年第4期20卷 612-622页

作者：张晓艳王斌季仲贞肖庆农张昕 LASG Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029 Mesoscale and Microscale Meterorology National Center for Atmospheric ResearchBoulderColoradoUSA

The MM5 and its four dimensional variational data assimilation (4D-Var) system are used in this paper. Based on the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data, the authors generate an optimal initial condition for a typhoon by using the bogus data assimilation (BDA) scheme. BDA is able to recover many of the structural features of typhoons including a warm-core vertex, the correct center position, and the strong circulation. As a result of BDA using a bogus surface low, dramatic improvement is achieved in the 72 h prediction of typhoon Herb. Through several cases, the initialization by BDA effectively generates the harmonious inner structure of the typhoon, but which is lacking in the original analysis field. Therefore the intensity forecast is improved greatly. Some improvements are made in the track forecast, but more work still needs to be done.

关键词： variational data assimilation bogus scheme BDA Typhoon Herb numerical simulation