Title page for 986201003


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Student Number 986201003
Author Min-Chao Kuo(郭閔超)
Author's Email Address No Public.
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Department Graduate Institute of Atmospheric Physics
Year 2010
Semester 2
Degree Master
Type of Document Master's Thesis
Language zh-TW.Big5 Chinese
Title Improving short-range QPF in Taiwan by VDRAS and WRF using data from multiple weather radars.
Date of Defense 2011-06-10
Page Count 82
Keyword
  • 4DVAR
  • Quantitative Precipitation Forecast
  • VDRAS
  • WRF
  • Abstract In this research, the Variational Doppler Radar Analysis System (VDRAS) is used to assimilate radar data. The VDRAS has the capability to conduct forecast, but only over flat surface. Thus, it is attempted to merge the VDRAS analysis field with WRF, so that one can use the latter to resolve the terrain. In this study, we will use RCCG, RCKT, RCHL and S-POL radars to perform a series of assimilation experiments with different strategies.
    A real case of a shallow surface front occurred from 0500UTC to 0900UTC on 02 June 2008 during Southwest Monsoon Experiment IOP4 is selected. Experimental results reveal that assimilating more radar data leads to a better performance of the rainfall forecast. It is also shown that assimilating radar data is better than using WRF alone. Further improvements can be achieved when WRF is merged with VDRAS analysis field twice. By assimilating radar data on 0500~0600UTC, when convective system is still over the ocean, results in a more accurate forecast of the rainfall than performing the radar data assimilation on 0700~0800UTC, when convective system already reaches the complex terrain. This difference can be explained in the following. Since a large portion of the convection system is over the terrain on 0700UTC~0800UTC, therefore even with radar data assimilation, the VDRAS is not able to capture the major features of the convective structure due to its inability to resolve the complex terrain.
      The above-mentioned experimental results can be used as a guideline for applying VDRAS in Taiwan or other places with similar geographic environment and observational limitations.
    Table of Content 中文摘要-------------------------------------i
    英文摘要-------------------------------------ii
    目錄-----------------------------------------iii
    圖表說明-------------------------------------v
    一、前言
    1-1 研究動機---------------------------------1
    1-2 文獻回顧---------------------------------2
    1-3 研究目的---------------------------------3
    二、都卜勒雷達變分分析系統
    2-1 四維變分---------------------------------4
    2-2 雲模式-----------------------------------6
    2-3 中尺度背景場-----------------------------8
    2-4 雷達資料的品質控管-----------------------9
    三、個案介紹
    3-1 2008年西南氣流實驗-----------------------10
    3-2 資料來源---------------------------------11
    3-3 個案特徵---------------------------------11
    四、驗證方法
    4-1 降水預報以及觀測-------------------------13
    4-2 定量降水預報驗證公式---------------------14
      4-2-1公正預兆得分(ETS)-------------------14
      4-2-2偏離係數(Bias)----------------------15
      4-2-3 空間相關係數(SCC)------------------15
    4-3 風場驗證---------------------------------16
    五、模式設定及實驗設計
    5-1 VDRAS模式設定及其實驗設計----------------18
    5-2 WRF模式原理及其設定----------------------19
    5-3 VDRAS結合WRF方法-------------------------20
    5-4 VDRAS結合WRF的預報實驗設計---------------22
    六、實驗結果與討論
    6-1 VDRAS同化結果分析------------------------24
    6-2 預報結果分析-----------------------------24
      6-2-1 0600UTC~0900UTC預報結果------------24
      6-2-2 同化與未同化SPOL雷達的差異---------26
      6-2-3 不同時段同化對預報的差異-----------27
      6-2-4 以結合兩次檢視結合一次的可用性-----29
    七、總結與未來展望
    7-1 總結-------------------------------------30
    7-2 未來展望---------------------------------31
    參考文獻-------------------------------------33
    附表-----------------------------------------37
    附圖-----------------------------------------39
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    Advisor
  • Yu-Chieng Liou(廖宇慶)
  • Tai-Chi Chen Wang(陳台琦)
  • Files
  • 986201003.pdf
  • approve immediately
    Date of Submission 2011-07-06

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