MODIS和NOAA衛星資料反演之大氣溫濕度剖線在夏季午後對流前兆分析之應用

Prediction of the Summer Afternoon Convection Onset with MODIS and NOAA

莊耀中(Yao-Chung Chuang)

指導教授 ： 劉振榮 ； 陳哲俊

國立中央大學/地球科學學院/太空科學研究所/碩士(2006年)

摘要

台灣地區在夏季期間常有劇烈午後熱對流的發生，伴隨而來的雷雨往往造成航空和民生方面的困擾。由於午後熱對流發展迅速且常生成於台灣四周海域，且傳統的觀測資料容易受到空間和時間的限制，因此衛星觀測資料之運用更顯得重要。本研究主要目的即在於利用TERRA及AQUA之MODIS（Moderate Resolution Imaging Spectro- radiometer）和NOAA（National Oceanic and Atmospheric Adminis- tration）衛星資料反演大氣溫濕垂直剖線將以應用於夏季午後熱對流發生之前兆分析。
　　併用MODIS和NOAA衛星資料時，首先要了解二組衛星資料是否具有一致性。本研究利用2003年1～10月衛星資料建立統計迴歸式以修正二組衛星資料間的差異，再用2002年9～12月衛星資料做為驗證。結果顯示溫度剖線的均方根誤差在1.5～2 ℃，露點剖線的均方根誤差在2～3 ℃，顯示這二組衛星資料具有一致性。再利用大氣溫濕垂直剖線估算大氣穩定指數K指數（K Index，KI）、總指數（Total Totals Index，TTI）和水氣含量等大氣熱力參數，並由地面測站資料計算輻散場代表以大氣動力參數，即可對夏季午後對流的發展進行分析。
　　本研究選取2003年6～9月的對流個案以建立各參數（大氣穩定指數、水氣含量和輻散場）門檻值，並選取2004和2005年6~9月對流個案做為驗證。結果顯示同時考慮此三項參數時，其2004與2005年整體準確率分別為76 %與74 %，隱含此方法有實用的價值。

關鍵字

對流 ； 大氣穩定度 ； 輻散場

並列摘要

Intense convections often occur in Taiwan during the sizzling summer afternoon. The ensuing afternoon thunderstorms may cause damages, or disrupt aviation operations. As the afternoon convection develops rapidly around the Taiwan region, the data observed by traditional methods are easily limited, both spatially and temporally. Thus, the utilization of satellite observational data is becoming ever increasingly important. The major purpose of this research is to apply a method in retrieving the temperature and dew point profiles from the MODIS and NOAA satellite data, where they can be applied in the analysis of summer afternoon convection.

In the employment of the MODIS and NOAA satellite data, it is important to understand whether or not the two types of data are consistent with each other. Thus, by using data from the two satellites between January and October of 2003, a regression equation is performed, to remove the consistencies between them. Another group of data from the two satellites (between September and December of 2002) was employed for verification. Results showed that the root mean square error of the retrieved temperature and dew point profiles was approximately 1.5～2 oC and 2～3 oC, respectively.

The retrieved temperature and dew point profiles were employed to estimate the atmospheric stability index or K index (KI), the total index or Total Totals Index (TTI), the water vapor content, along with other atmospheric thermal parameters. In addition, ground station data was used to calculate the divergence field in delineating the atmospheric dynamic parameters. Through these two approaches, it is hoped that the usual occurrence of convection development during the summer afternoon can be accurately analyzed.

This research chose convection cases that occurred between June to September of 2003 to set up the threshold value of three important parameters----Atmospheric stability index, Water vapor content and Divergence field . Convection cases recorded between June to September of 2004 and 2005, were then employed for verification. By considering all three parameters, the results showed that the prediction accuracy for actual convection activity during 2004 and 2005 reached 76% and 74 %, respectively; demonstrating the practical applications in this method.

並列關鍵字

convection ； atmospheric stability ； NOAA ； MODIS

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