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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/66747

    Title: 利用雷達觀測直接反演氣象變數進行資料同化以改進短期定量降水預報-2008 SoWMEX IOP8 個案分析;Direct retrieval of meteorological variables using weather radar for assimilation
    Authors: 廖浩彥;Liu,Hou-in
    Contributors: 大氣物理研究所
    Keywords: 熱動力反演;水氣調整;Thermodynamic retrieval;water vapor adjustment
    Date: 2014-12-16
    Issue Date: 2015-03-16 15:09:00 (UTC+8)
    Publisher: 國立中央大學
    Abstract: 雷達觀測具有高時空解析度的優點,常使用於劇烈天氣的監控與觀測。本研究是延續及改善前人的工作,選取2008西南氣流實驗計畫(SoWMEX)的IOP8個案,利用多都卜勒雷達觀測資料,改善模式當時的初始場,增進模式降水定量預報之能力。此方法主要包含三大部分:(1)多都卜勒風場合成、(2)熱動力反演、(3)水氣調整。然而前人的實驗存在一些問題:(1)同化後模式初始場壓力與反演的壓力場有很大差異,顯示壓力場並沒有被完整地同化到模式中;(2)模式預報時邊界會出現錯誤回波;(3)定量降水預報的高估及位置偏差。
    ;An important advantage of radar observations is their high temporal and spatial resolution data, which are suitable for heavy weather surveillance. The purpose of this study is to improve previous studies, which are to improve the initial field and hence the quantitative precipitation forecast (QPF) of the numerial model by using multiple-Doppler radar observation data. The assimilation technique includes three components: multiple-Doppler radar wind synthesis, thermodynamic retrieval and moisture adjustment. A case during IOP8, Southwest Monsoon Experiment (SoWMEX)2008 is selected in this study. Some problems have not solves in previous studies: such as the pressure field has not been fully assimilated into the model, the boundary of forecast field produces wrong reflectivity, and overestimate of the rainfall.
    In this study we replace the method of the retrieval pressure embedding the model, and use a newly designed moisture adjustment method. The results show improvement in reflectivity structure and the accuracy precipitation of forecast. In the microphysics schemes test, WSM6 is a reasonable choice.
    In assimilation test, the model QPF can be significantly improved after assimilating the radar data. In with or without sounding test, it is feasible to use the model outputs to replace the role played by a sounding for estimating the unknown constant at each altitude.
    In second assimilation study, it can improve the retrieval atmospheric state variables, convection position and QPF in first assimilation. None of the fraction show which strategy is better. These two experiments produce comparable forecast, the model QPF may be more effective when the second DA is postponed until two hours.
    Appears in Collections:[大氣物理研究所 ] 博碩士論文

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