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Assimilation of Doppler Radar Data with an Ensemble Square Root Filter

Author: ChenJie
Tutor: ZuoJinZhong
School: Nanjing University of Information Engineering
Course: Meteorology
Keywords: Collection of square root filter Storm -scale Doppler Radar Data
CLC: P413
Type: Master's thesis
Year: 2011
Downloads: 57
Quote: 1
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Abstract

Doppler radar data assimilation is an important way to improve the quality of storm-scale numerical weather prediction. Advanced data assimilation method requires accurate dynamic field, thermodynamic and microphysical field from radar radial velocity and reflectivity factor analysis. Compared with the four-dimensional variational method, the ensemble Kalman filter assimilation method due to its background error covariance flow dependent nature, and does not require complex adjoint model provides another option for the development of data assimilation. The main purpose of this paper is the development of a storm mesoscale model ensemble Kalman filter assimilation system, so that it can direct assimilation of Doppler radar data of the new generation, to provide a more accurate initial field for storm-scale numerical weather prediction. After comparative tests, the main research work and the main conclusions are as follows: (1) In this paper, the of WRF-EnSRF assimilation for storm-scale data assimilation system independent build assimilation of Doppler radar data, to test its in Meiyu rainstorm, and once strong The process of assimilation of convective weather performance. The results show that the assimilation system are two examples demonstrate the effective assimilation capacity the assimilation analysis field after 60 minutes and 30 minutes to the field of the analysis of the initial collection do ensemble forecasting results are relatively close to the actual observations. This paper examines the initial disturbance when the audience disturbance with convection zone disturbance, and disturbance of the ambient wind field or not assimilation effect. The test results show that the local disturbance of the convection zone relative to the audience disturbance did not improve the assimilation effect; Meiyu front rainstorm for large scale disturbances environmental wind field assimilation better. In order to investigate the performance of the analysis of the field in the precipitation forecast, heavy rain in the two cases to analyze the field for the initial value of the 6-hour precipitation forecast the assimilation ensemble prediction and the deterministic forecast results than without assimilation control test results are accurate. (2) on the basis of the above research, this paper the assimilation of the WRF-EnSRF system the actual Doppler radar data, the the test collection square root filtering in strong convection, including three different structure types of squall lines and supercell storms and multi-cell storm weather process of assimilation effects, and the effects of different intensity bit mild water vapor disturbances the Forecast field collection of discrete degrees, as well as assimilation effect the initial field add disturbance. The results show the three examples of the assimilation system demonstrated effective assimilation capacity each case results are more reasonable. The disturbance intensity forecast field collection dispersion and assimilation effects on the thermal field is more sensitive and appropriate analysis of the effect of increased bit mild disturbance strength of the water vapor in the initial disturbance conducive to improve the collection of discrete and improve the radial velocity.

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