This paper focuses on deforestation impact on regional precipitation over Indochina, especially in Thailand. Analysis of observed precipitation in Thailand shows a significant decrease in precipitation only in September. Precipitation amounts at many meteorological stations in September have decreased approximately 100mm/month over the past three or four decades. Numerical experiments with a regional climate model are carried out for August and September. Results of the experiments also show a decrease in precipitation over the deforested area in September, but not in August. As the strong monsoon westerlies over Indochina disappear in September although it is typically the month of maximum precipitation, it is inferred that local deforestation impact may appear significantly only in September due to the absence of the strong external forcing. Preliminary analysis of stable isotopes in precipitation in Thailand indicates the importance of evaporation from land surface in September and October. These all suggest that local recycling of precipitation could be important for regional climate in a specific period of a year.
