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Scientific design and preliminary results of three-dimensional variational data assimilation system of GRAPES
JiShan Xue,ShiYu Zhuang,GuoFu Zhu,Hua Zhang,ZhiQuan Liu,Yan Liu,ZhaoRong Zhuang
Chinese Science Bulletin , 2008, DOI: 10.1007/s11434-008-0416-0
Abstract: The scientific design and preliminary results of the data assimilation component of the Global-Regional Prediction and Assimilation System (GRAPES) recently developed in China Meteorological Administration (CMA) are presented in this paper. This is a three-dimensional variational (3DVar) assimilation system set up on global and regional grid meshes favorable for direct assimilation of the space-based remote sensing data and matching the frame work of the prediction model GRAPES. The state variables are assumed to decompose balanced and unbalanced components. By introducing a simple transformation from the state variables to the control variables with a recursive or spectral filter, the convergence rate of iteration for minimization of the cost function in 3DVar is greatly accelerated. The definition of dynamical balance depends on the characteristic scale of the circulation considered. The ratio of the balanced to the unbalanced parts is controlled by the prescribed statistics of background errors. Idealized trials produce the same results as the analytic solution. The results of real data case studies show the capability of the system to improve analysis compared to the traditional schemes. Finally, further development of the system is discussed.
Direct assimilation of satellite radiance data in GRAPES variational assimilation system
GuoFu Zhu,JiShan Xue,Hua Zhang,ZhiQuan Liu,ShiYu Zhuang,LiPing Huang,PeiMing Dong
Chinese Science Bulletin , 2008, DOI: 10.1007/s11434-008-0419-x
Abstract: Variational method is capable of dealing with observations that have a complicated nonlinear relation with model variables representative of the atmospheric state, and so make it possible to directly assimilate such measured variables as satellite radiance, which have a nonlinear relation with the model variables. Assimilation of any type of observations requires a corresponding observation operator, which establishes a specific mapping from the space of the model state to the space of observation. This paper presents in detail how the direct assimilation of real satellite radiance data is implemented in the GRAPES-3DVar analysis system. It focuses on all the components of the observation operator for direct assimilation of real satellite radiance data, including a spatial interpolation operator that transforms variables from model grid points to observation locations, a physical transformation from model variables to observed elements with different choices of model variables, and a data quality control. Assimilation experiments, using satellite radiances such as NOAA17 AMSU-A and AMSU-B (Advanced Microwave Sounding Unit), are carried out with two different schemes. The results from these experiments can be physically understood and clearly reflect a rational effect of direct assimilation of satellite radiance data in GRAPES-3DVar analysis system.
Application of Direct Assimilation of ATOVS Microwave Radiances to Typhoon Track Prediction
ZHANG Hu,XUE Jishan,ZHU Guofu,ZHUANG Shiyu,WU Xuebao,ZHANG Fengying,
ZHANG Hu
,XUE Jishan,ZHU Guofu,ZHUANG Shiyu,WU Xuebao,ZHANG Fengying

大气科学进展 , 2004,
Abstract: In order to solve the difficult problem of typhoon track prediction due to the sparsity of conventional data over the tropical ocean, in this paper, the No. 0205 typhoon Rammasun of 4-6 July 2002 is studied and an experiment of the typhoon track prediction is made with the direct use of the Advanced TIROS-N Operational Vertical Sounder (ATOVS) microwave radiance data in three-dimensional variational data assimilation. The prediction result shows that the experiment with the ATOVS microwave radiance data can not only successfully predict the observed fact that typhoon Rammasun moves northward and turns right, but can also simulate the action of the fast movement of the typhoon, which cannot be simulated with only conventional radiosonde data. The skill of the typhoon track prediction with the ATOVS microwave radiance data is much better than that without the ATOVS data. The typhoon track prediction of the former scheme is consistent in time and in location with the observation. The direct assimilation of ATOVS microwave radiance data is an available way to solve the problem of the sparse observation data over the tropical ocean, and has great potential in being applied to typhoon track prediction.
Assimilation analysis of Rammasun typhoon structure over Northwest Pacific using satellite data
Hua Zhang,Jifan Chou,Chongjian Qiu
Chinese Science Bulletin , 2004, DOI: 10.1007/BF02900323
Abstract: The kinetic and thermodynamic structure of typhoon Rammasun (No. 0205) over the Northwest Pacific has been analyzed, using NOAA-16 polar orbiting Advanced Microwave Sounding Unit (AMSU) data collected on 2 July, 2002. The three-dimensional variational (3DVAR) assimilation technology is used to assimilate the satellite observation. The results show that the characteristics of the 3D typhoon structure can be more reasonably described from the assimilated data. The warm-cored structure of the typhoon is enhanced in the analyzed field, which corresponds to strong typhoon. The typhoon cyclonic circulation in the middle and lower layers is apparently strengthened, and the strong anticyclonic circulation appears at the top of the typhoon. The water vapor and its supply in the typhoon are enhanced. The microwave assimilation data may be used to supply the lack of the conventional observation data over the tropical ocean.
Assimilation analysis of Rammasun typhoon structure over Northwest Pacific using satellite data
ZHANG Hua,
ZHANGHua
,CHOUJifan,QIUChongjian

科学通报(英文版) , 2004,
Abstract: The kinetic and thermodynamic structure of typhoon Rammasun (No. 0205) over the Northwest Pacific has been analyzed, using NOAA-16 polar orbiting Advanced Microwave Sounding Unit (AMSU) data collected on 2 July, 2002. The three-dimensional variational (3DVAR) assimila-tion technology is used to assimilate the satellite observation. The results show that the characteristics of the 3D typhoon structure can be more reasonably described from the assimi-lated data. The warm-cored structure of the typhoon is en-hanced in the analyzed field, which corresponds to strong typhoon. The typhoon cyclonic circulation in the middle and lower layers is apparently strengthened, and the strong anti-cyclonic circulation appears at the top of the typhoon. The water vapor and its supply in the typhoon are enhanced. The microwave assimilation data may be used to supply the lack of the conventional observation data over the tropical ocean.
Assimilation and Simulation of Typhoon Rusa (2002) Using the WRF System
Assimilation and Simulation of Typhoon Rusa (2002) Using the WRF System

GU Jianfeng,Qingnong XIAO,Ying-Hwa KUO,Dale M BARKER,XUE Jishan,MA Xiaoxing,
GU Jianfeng
,Qingnong XIAO,Ying-Hwa KUO,Dale M. BARKER,XUE Jishan,MA Xiaoxing

大气科学进展 , 2005,
Abstract: Using the recently developed Weather Research and Forecasting (WRF) 3DVAR and the WRF model, numerical experiments are conducted for the initialization and simulation of typhoon Rusa (2002).The observational data used in the WRF 3DVAR are conventional Global Telecommunications System (GTS) data and Korean Automatic Weather Station (AWS) surface observations. The Background Error Statistics (BES) via the National Meteorological Center (NMC) method has two different resolutions, that is, a 210-km horizontal grid space from the NCEP global model and a 10-kn horizontal resolution from Korean operational forecasts. To improve the performance of the WRF simulation initialized from the WRF 3DVAR analyses, the scale-lengths used in the horizontal background error covariances via recursive filter are tuned in terms of the WRF 3DVAR control variables, streamfunction, velocity potential, unbalanced pressure and specific humidity. The experiments with respect to different background error statistics and different observational data indicate that the subsequent 24-h the WRF model forecasts of typhoon Rusa's track and precipitation are significantly impacted upon the initial fields. Assimilation of the AWS data with the tuned background error statistics obtains improved predictions of the typhoon track and its precipitation.
Typhoon 9707 observations with the MU radar and L-band boundary layer radar  [PDF]
M. Teshiba,H. Hashiguchi,S. Fukao,Y. Shibagaki
Annales Geophysicae (ANGEO) , 2003,
Abstract: Typhoon 9707 (Opal) was observed with the VHF-band Middle and Upper atmosphere (MU) radar, an L-band boundary layer radar (BLR), and a vertical-pointing C-band meteorological radar at the Shigaraki MU Observatory in Shiga prefecture, Japan on 20 June 1997. The typhoon center passed about 80 km southeast from the radar site. Mesoscale precipitating clouds developed due to warm-moist airmass transport from the typhoon, and passed over the MU radar site with easterly or southeasterly winds. We primarily present the wind behaviour including the vertical component which a conventional meteorological Doppler radar cannot directly observe, and discuss the relationship between the wind behaviour of the typhoon and the precipitating system. To investigate the dynamic structure of the typhoon, the observed wind was divided into radial and tangential wind components under the assumption that the typhoon had an axi-symmetric structure. Altitude range of outflow ascended from 1–3 km to 2–10 km with increasing distance (within 80–260 km range) from the typhoon center, and in-flow was observed above and below the outflow. Outflow and inflow were associated with updraft and downdraft, respectively. In the tangential wind, the maximum speed of counterclockwise winds was confirmed at 1–2 km altitudes. Based on the vertical velocity and the reflectivity obtained with the MU radar and the C-band meteorological radar, respectively, precipitating clouds, accompanied by the wind behaviour of the typhoon, were classified into stratiform and convective precipitating clouds. In the stratiform precipitating clouds, a vertical shear of radial wind and the maximum speed of counterclockwise wind were observed. There was a strong reflectivity layer called a ‘bright band’ around the 4.2 km altitude. We confirmed strong updrafts and down-drafts below and above it, respectively, and the existence of a relatively dry layer around the bright band level from radiosonde soundings. In the convective precipitating clouds, the regions of strong and weak reflectivities were well associated with those of updraft and downdraft, respectively. Key words. Meteorology and atmospheric dynamics (mesoscale meteorology; precipitation) Radio science (remote sensing)
The Effect of Three-Dimensional Variational Data Assimilation of QuikSCAT Data on the Numerical Simulation of Typhoon Track and Intensity
ZENG Zhihu,DUAN Yihong,LIANG Xudong,MA Leiming,Johnny Chung-leung CHAN,
ZENG Zhihu
,DUAN Yihong,LIANG Xudong,MA Leiming,Johnny Chung-leung CHAN

大气科学进展 , 2005,
Abstract: In this paper, the three-dimensional variational data assimilation scheme (3DVAR) in the mesoscale model version 5 (MM5) of the US Pennsylvania State University/National Center for Atmospheric Research is used to study the effect of assimilating the sea-wind data from QuikSCAT on the prediction of typhoon track and intensity. The case of Typhoon Dujuan (2003) is first tested and the results show appreciable improvements. Twelve other cases in 2003 are then evaluated. The assimilation of the QuikSCAT data produces significant impacts on the structure of Dujuan in terms of the horizontal and vertical winds, sealevel pressure and temperature at the initial time. With the assimilation, the 24-h (48-h) track prediction of 11 (10) out of the 12 typhoons is improved. The 24-h (48-h) prediction of typhoon intensity is also improved in 10 (9) of the 12 cases. These experiments therefore demonstrate that assimilation of the QuikSCAT sea-wind data can increase the accuracy of typhoon track and intensity predictions through modification of the initial fields associated with the typhoon.
Reconstruct the Mesoscale Information of Typhoon with BDA Method Combined with AMSU-A Data Assimilation Method  [PDF]
Yunfeng Wang,Haiyang Zhang,Bin Wang,Yueqi Han,Xiaoping Cheng
Advances in Meteorology , 2010, DOI: 10.1155/2010/346516
Abstract: This paper conducts the assimilating experiments and simulating experiments on typhoon “Aere” (No. 0418), by use of bogus data assimilation (BDA) method combined with advanced microwave sounding unit-A (AMSU-A) data assimilation method in the fifth-generation National Center for Atmospheric Research (NCAR)/Penn State Mesoscale Model Version-3 (MM5V3), the Radiative Transfer for TIROS-N Operational Vertical Sounder Version-7 (RTTOV) model, and their adjoint models. The Bogus data constructed with BDA technique are mainly located at sea level, while the peak energy contribution levels of the sounder channels selected in AMSU-A data assimilation technique are mainly located at upper troposphere. The two types of data can reconstruct the meso-scale information and improve the typhoon initial fields under the model dynamic forcing effect, respectively from the low level and the upper level of atmosphere during the assimilating process. Numerical results show that with four-dimensional variational data assimilation (4DVAR) technique the circulation of initial fields is improved, the “warm core” of typhoon is enhanced, the “cloud water” phenomenon that occurs in the optimal initial fields and the numerical model is changed into “warm start” from “cold start”. 1. Introduction Typhoon is one of the most frequent disasters affecting human beings. With the development of numerical forecasting techniques, numerical forecasting of typhoon has entered an operational stage. However, the prediction accuracy is far from meeting the requirements of disaster prevention and reduction. If the track and intensity of typhoon can be accurately forecasted, necessary preparedness can be performed beforehand and serious economic loss can be much reduced. Due to severe deficiency of conventional observation data over sea, the results of objective analysis can not precisely describe the thermal structure and circulation characteristics of initial typhoon, especially its mesoscale structure, which is one of the main reasons for serious errors in typhoon numerical forecasting. Therefore, how to provide more rational initial values is an urgent task. Since 1990s, an initializing method of artificial typhoon mode is introduced into typhoon forecasting research [1–3]. With this method, an ideal bogus typhoon mode with 3-dimensional circulation structure and thermal structure is constructed according to the observation data, and then it is implanted into the initial typhoon analysis fields to construct new initial typhoon optimal fields. This method is now widely applied in Typhoon
Numerical Simulation of a Landfall Typhoon Using a Bogus Data Assimilation Scheme
LU Bing,WANG Bin,ZHAO Ying,
LU Bing
,WANG Bin,ZHAO Ying

大气和海洋科学快报 , 2011,
Abstract: A typhoon bogus data assimilation scheme (BDA) using dimension-reduced projection four-dimensional variational data assimilation (DRP-4-DVar), called DRP-BDA for short, is built in the Advanced Regional Eta Model (AREM). As an adjoint-free approach, DRPBDA saves time, and only several minutes are taken for the full BDA process. To evaluate its performance, the DRP-BDA is applied to a case study on a landfall typhoon, Fengshen (2008), from the Northwestern Pacific Ocean to Guangdong province, in which the bogus sea level pressure (SLP) is assimilated as a kind of observation. The results show that a more realistic typhoon with correct center position, stronger warm core vortex, and more reasonable wind fields is reproduced in the analyzed initial condition through the new approach. Compared with the control run (CTRL) initialized with NCEP Final (FNL) Global Tropospheric Analyses, the DRP-BDA leads to an evidently positive impact on typhoon track forecasting and a small positive impact on typhoon intensity forecasting. Furthermore, the forecast landfall time conforms to the observed landfall time, and the forecast track error at the 36th hour is 32 km, which is much less than that of the CTRL (450 km).
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