Prediction of the Summer Afternoon Convection Onset with MODIS and NOAA

• Main Authors: Yao-Chung Chuang, 莊耀中
• Other Authors: Gin-Rong Liu
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/9j5v24

碩士 === 國立中央大學 === 太空科學研究所 === 94 === 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.