本計畫考量ROCSAT-3/COSMIC衛星計畫科學研究目標，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，俾以改善區域天氣預報的準確度。目前已發展建置完成區域性的WRF/MM5 3DVAR預報系統，可以納入GPS掩星觀測折射率資料，進行同化模擬。目前折射率同化係模式局地折射率之同化，但經反演所得之觀測折射率為非局地折射率，因此為提高觀測資訊之可利用度，同化對象須對應為非局地折射率，方法為可將模式局地折射率沿射線路徑積分（稱為溢相值），再經反演得非局地折射率，即可進行同化。此法之向前算子已證實更為精確，但尚未進行同化評估，就COSMIC所提供之大量GPS掩星觀測而言，此快速而有效之同化方法亟須完成。基此，除沿續過去研究工作，本計畫提出今年（94年度）規劃工作目標： 1. 探討WRF/MM5 3DVAR同化模式使用CHAMP及ROCSAT-3/COSMIC（發射後）GPS觀測資料對區域天氣預報的影響。 2.與NCAR/MMM合作發展區域模式WRF GPS同化模組（折射率的local operator及溢相值的non-local operator），並進行比較實驗。 3.進行中大PC cluster後時模擬重要災害天氣及預報作業實驗。 2006年（95年度）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 WRF/MM5 3DVAR implemented in NCU is capable of assimilating GPS refractivity data in fulfill with the requirement of operation efficiency. The current refractivity operator is for assimilation of model local refractivity and is not representative of the retrieved non-local refractivity from occultations. To increase accuracy, the assimilation can be modified to target on the integrated refractivity along the raytrace (namely, the excess phase) which can be converted into the non-local refractivity. This more accurate and effective assimilation method thus should be developed, considering the missions of Taiwan ROCSAT-3/COSMIC with plentiful data on the improvement of regional weather forecast. Hence, the main goals of this project in this year (2005) are: 1.Conduct WRF/MM5 3DVAR assimilation simulations with CHAMP and ROCSAT-3/COSMIC observation data and assess the impact of the GPS data on regional weather prediction. 2.Continue to develop and evaluate GPS assimilation methods (local refractivity operator and non-local excess-phase operator) for regional model WRF. 3.Conduct the hindcast operation experiments for severe weathers using the NCU PC cluster. For the fifth year (2006), details of the plan will be provided later, but will be focused on the operation experiment to probe the impact of GPS data from CWB/TACC on regional weather forecast. 研究期間：9401 ~ 9412
