本計畫考量NSPO科研目標，配合氣象團隊整合計畫總體研究規劃，從基礎理論及實際應用層面探討變分同化模式系統，導入GPS掩星觀測資料於中尺度數值模式，俾以改善天氣預報的準確度。目前中大已發展建置完成區域性的MM5 3DVAR即時預報系統，可以納入GPS掩星觀測折射率資料進行同化模擬。使用3DVAR可以同化數值預報模式沒有直接預報或計算的觀測變數如GPS上游資料，偏折角(bending angle) ，或大氣折射率(refractivity)。 本計畫從ROCSAT-3/COSMIC衛星計畫研發與應用角度，提出分年規劃工作目標： 第一年（2002）完成在學術單位（如中大）MM5 3DVAR預報系統的建置，發展GPS掩星觀測折射率（refractivity）同化模組，了解GPS上游資料同化技術及其對颱風模擬效果。著手評估即時（real-time）或後時預報（hindcast）模擬建置。 第二年（2003）了解同化作業模式其程式、計算機速度、同化效果及未來可能的改善空間，同時探討區域模式GPS掩星觀測偏折角（bending angle）同化方法及評估其可行性。同時使用CHAMP及SAC-C觀測資料，於中大進行MM5 3DVAR同化模式模擬及PC cluster後時預報模擬平台測試。 第三年（93年度）進行同化模式的預報實驗，使用CHAMP及SAC-C觀測資料MM5 3DVAR同化模式，針對重要天氣（颱風、梅雨、寒潮等）進行模擬及預報。與NCAR/MMM及UCAR/COSMIC合作發展區域模式利用straightline or curved-line ray-tracing同化偏折角模組。使用MM5或WRF模式及其完成3DVAR ray-tracing同化模擬災害天氣。規劃PC cluster後時模擬及預報作業實驗，並針對選擇個案與工作站同化模式模擬比較。 第四年（2005）探討MM5 3DVAR及4DVAR同化模式使用ROCSAT-3/COSMIC （發射後）GPS觀測資料對台灣區域天氣預報的影響，並嘗試應用全球資料於WRF短期區域氣候模擬與分析。使用NCAR/MMM合作發展區域模式（MM5 或 WRF）偏折角同化及折射率同化模組並進行比較實驗。進行中大PC cluster後時模擬及預報作業實驗。 第五年（2006）其詳細規劃於後續執行進度期間再進一步擬定，但將著重於PC cluster後時預報實驗及客觀評估CWB/TACC的GPS資料對區域天氣預報之影響。 The goals of this project aim at the cooperation of research direction under the Integrated Research Project and the implementation of 3DVAR data assimilation for inclusion of the GPS occultation observations to improve regional weather forecast. The MM5 3DVAR implemented in NCU is capable of assimilating GPS refractivity data in fulfill with the requirement of operation efficiency. Considering missions of Taiwan ROCSAT-3/COSMIC on the improvement of regional weather forecast, the main goals of this project in each year are: First year (2002): Conduct MM5 3DVAR assimilation using CHAMP and SAC-C refractivity data and setup the PC cluster platform at a hindcast mode. Second year (2003): Conduct MM5 3DVAR/4DVAR assimilation simulations using CHAMP and SAC-C refractivity data, evaluate feasibility of ray-tracing assimilation of bending angle for regional models and perform some assimilation tests on the PC cluster. Third year (2004): Perform case simulations using the MM5 and/or WRF 3DVAR assimilation model with the GPS refractivity data. On collaboration with NCAR, develop and test bending angle assimilation modules using the straightline or curved-line ray-tracing method for regional models (MM5 or WRF). Conduct the operation experiment tests in the PC cluster and compare the assimilation simulations with the workstation results for some selected cases. The fourth year (2005): Conduct MM5 3DVAR/4DVAR assimilation simulations with ROCSAT-3/COSMIC observation data and assess the impact of the GPS data on regional weather prediction. Continue to test and evaluate ray-tracing methods for regional models (MM5 or WRF). Conduct the hindcast operation experiment in the NCU PC cluster. The fifth year (2006): Details will be determined later, but will be focused on the hindcast operation experiment and the objective assessments of CWB/TACC GPS data impact on regional weather forecast. 研究期間：9301 ~ 9312
