Correlation between Heat Flux over the Indian Ocean and Rainfalls in Coastal Thailand by Using the MM5 Numerical Model

Abstract

Correlation between heat flux over the Indian Ocean and rainfalls in coastal Thailand by using the Pennsylvania State University/National Center for Atmospheric Research mesoscale model: MM5 is the method to study monsoon onset in Thailand. The study areas are over the Indian Ocean from Latitude 30°S to 30°N and Longitude 40°E to 120°E. The used data were during May to October since the years 1996 to 2000, and also covered the years where El Niño and La Niña were present. When the heat flux over the Southeast Indian Ocean was increased about100 w/m2, this persisted for approximately five consecutive days before the average onset date of the 15th May in Thailand. Once the recorded increase in heat flux of five days had passed, it was then observed that after a period of eleven days this caused the onset of rainfalls at nine Thai meteorological stations. From the observations recorded the results showed a correlation between the development of heat flux and rainfalls. During the normal years (1996, 1999 and 2000) the correlation of the heat flux with the rainfalls data at the twelve primary meteorological stations in Thailand were computed by linear regression analysis and the best of these resulted in coefficient of determination(R2)= 0.782. The results (correlation between heat flux which obtained from MM5 model and amounts of rainfalls from weather observation stations) of this study is possible to be utilize by the Thai Meteorological Department to predict the onset day of southwest monsoon rainfall, mainly for agricultural activities more accurately procedure.