Abstract
In the inland of the Indochina Peninsula, i.e., in Cambodia, it is known that it rains even after the withdrawal of the Asian Summer Monsoon. The four requirements for the initiation of this rainfall have been proposed in the previous studies: (i) the existence of the very hot surface of Tonle Sap Lake, (ii) intrusion of cooler airmass from the southwest of the lake, (iii) strong nocturnal northeasterly, and (iv) abundant precipitable water in the atmosphere. In this study, the behavior and the mechanism of the third component was studied. It was shown that the mountain-valley circulation caused by the Annam Range strengthened the northeasterly during night at the inland (west side of the mountain) and it appeared as if northeasterly monsoon got stronger during night. Since this wind is a key to initiate the post-monsoon rainfall, it is notable that this wind is reproduced well by the GCM in the NCEP-FNL reanalysis model. This information could be used for the rainfall prediction in the further study.
