LAUSR

Summer precipitation in Thailand is a major resource for water and agriculture. Understanding the decadal variations of summer precipitation is useful for water resource management planning for long-term periods. This study investigates decadal changes in summer precipitation in Thailand. An evident increase in summer precipitation was found after the mid-1990s, and the possible causes have been discussed. An analysis of precipitation from observational stations revealed a significant shift in 1994; an increase in summer precipitation can be observed over most of Thailand after 1994. Inspections of the atmospheric circulation revealed cyclonic anomalies over the Indochina Peninsula in the lower troposphere, facilitating enhanced moisture transport towards Thailand. Meanwhile, the anomalous local Hadley circulation over eastern Thailand demonstrated stronger ascending motion after 1994, facilitating enhanced precipitation. The abovementioned changes in the atmospheric circulation and summer precipitation are closely related to the decadal changes in the sea surface temperature over the Atlantic Multidecadal Oscillation.