[A-CG32] Land-Atmosphere interactions and Asian monsoon precipitation (LAMos)

[ACG32-03] Long-term Trends and Interannual Variability in Precipitation over Vietnam during 1984 – 2016

*Hoa Thi Thanh Pham¹ (1.Department of Geography, Tokyo Metropolitan University)

Keywords:rainfall trend, wind trend, water vapor trend, Vietnam

The precipitation variability in Vietnam is unique because different types of precipitation are dominant during the boreal summer and winter. During the late summer, tropical disturbances are associated with the precipitation variation in Vietnam. On the other hand, cold or northerly surges of the winter Asian monsoon play an important role during winter. Thus, long-term variations in precipitation should be investigated with consideration of the seasonal march, including sub-seasonal timescale. This study investigated the long-term variations in precipitation over Vietnam for the period from 1984 to 2016, focusing on the wintertime (from October to March). To understand the long-term changes associated with climatological precipitation characteristics, we analyzed the long-term changes on a monthly basis. The result showed that despite the seasonal changes of atmospheric factors, regional characteristics of precipitation varied largely. In October and February, the decreasing trend was witnessed across most of the country while in November, December, and January, precipitation generally increased. The significantly clear-cut discrepancy along 15°-17°N latitude at the mid-winter declared the opposite rainfall trends over the north and the south of Vietnam. The weakening of northeasterly surges potentially reduced moisture transport, which caused the loss of precipitation over Vietnam during the winter monsoon.