INTERACTION OF LARGE-SCALE ATMOSPHERIC CONDITION AND LOCAL CIRCULATION WHICH AFFECTS CAMBODIAN POST-MONSOON RAINFALLS

Abstract

Characteristics of the post-monsoon rainfalls in Cambodia are examined through the combined use of NCEP-FNL global reanalysis data and the in-situ raingauge and AWS data. In the western Cambodia, rainfall still occurs during one month after the withdrawal of the Asian summer monsoon. About 30~40% of which was revealed to be brought by the redistribution of water vapor over Cambodia by the local atmospheric circulation. This rainfall occurs only under the period when there exists enough precipitable water. Decrease of precipitable water in China at late November reduces water vapor over Cambodia, resulting in disappearance of the locally-produced rainfall after this period. In addition, even when enough precipitable water exists, if the nighttime land-breeze at the southwest of the lake or the northeast winter monsoon is too weak, it doesn’t rain. Too strong winter monsoon is also unfavorable for local rainfall.