中央氣象局LAPS/MM5系統在短時（0-12小時）定量降雨預報之應用－梵高(Vamco,2003)颱風個案研究

Short-Range Precipitation Forecasts Associated with Tropical Storm Vamco (2003) Using the LAPS/MM5 System

簡國基(Guo-Ji Jian) ； 鄧仁星(Jen-Hsin Teng)

《大氣科學》 33卷1期 (2005/03) Pp. 77-101

摘要

本文使用中央氣象局LAPS (Local Analysis and Prediction System)非絕熱資料同化系統，即時整合五分山、七股、墾丁、花蓮都卜勒雷達徑向風場與回波資料、GOES-9衛星資料及其他傳統觀測資料，建立高解析度（9公里）非絕熱平衡初始場，熱啟動MM5模式，進行梵高(Vamco, 2003)颱風個案之短時定量降水預報研究。
校驗預報結果顯示，LAPS熱啟動MM5(LAPS/MM5)系統可降低模式驅動(spin-up)雲、雨的時間，有效在模式積分初期（預報0-6小時）掌握梵高颱風雨帶之移動、午後對流胞雲系之發展與消散；其預報準確度明顯優於不含LAPS雲分析的冷啟動實驗。進一步比較兩組預報實驗可知，經由LAPS雲分析引進都卜勒雷達資料及衛星資料，可在模式初始場中分析出較接近真實的大氣雲系分布，並透過LAPS平衡模組，架構三維非絕熱平衡初始場；此非絕熱同化過程，正是本文中熱啟動預報優於冷啟動預報的重要關鍵，換言之，將都卜勒雷達資料及衛星資料同化入模式初始場，對增進短時（0-12小時）定量降水預報有很大助益。
侵台颱風的定量降水預報，是中央氣象局所致力發展的重點課題之一；本研究已初步證實，就增進颱風短時定量降水預報而言，LAPS熱啟動MM5系統深具潛力。因此，未來將持續加強LAPS/MM5的分析、同化與預報功能，提升中央氣象局的颱風定量降水預報能力。

關鍵字

熱啟動 ； 颱風定量降水預報 ； LAPS/MM5

並列摘要

A high-resolution (9-km) diabatic data assimilation system-Local Analysis and Prediction System (LAPS) has been developed and used to initialize the real-time fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model (MM5) at the Central Weather Bureau in Taiwan. During 2003, the more extensive network of four high quality Doppler radars and the access to satellite data from the Geostationary Operational Environmental Satellite (GOES-9) provided an excellent opportunity for advancing the short-range precipitation forecasts near the Taiwan area. The parallel forecasts of Tropical Storm Vamco (2003) are performed, both with and without the inclusion of LAPS cloud analysis scheme. Except for the inclusion of the LAPS cloud field, the model integrations are identical in all other respects.
Forecast results demonstrate that using LAPS to diabatically initialize MM5 leads to an improved prediction of tropical cyclones in terms of storm's cloud pattern and movement of rainbands in the early portion of model prediction. During the first 6-h of the forecast, the heavy rainfall prediction associated with Vamco was improved when the LAPS cloud analysis scheme was included. The assimilation of data from Doppler radars and GOES-9 satellite played an important role in the improvement of storm hydrometeorological features in the model initial condition and thus had a beneficial impact on reducing the model spin-up time. However, further studies are needed to clarify the reasons for the high bias in simulating the rainfall amounts.
This paper represents a major step toward building a short-range mesoscale modeling system that predicts more realistic storm structures and rainfall distribution over the Taiwan area in real time. The overall results suggest that the impact of LAPS/MM5 system can be significant for short-range, high spatial-resolution, rainfall prediction associated with a tropical cyclone, especially for the heavy rainfall occurring during the early hours of the model integration.

並列關鍵字

QPF ； Short-range forecasts ； Diabatic data assimilation ； LAPS