Decreasing Trend in Rainfall over Indochina during the Late Summer Monsoon : Impact of Tropical Cyclones

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概要

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• We examined the decreasing trend in rainfall during the late summer monsoon season (September) in Thailand from 1951 to 2000 and associated changes in tropical cyclone (TC) activity. Thailand receives significant rainfall from May to October and experiences two rainy peaks in late May to early June and in September. A previous study reported a decreasing trend in September rainfall in Thailand and, based on a regional climate model, suggested that the trend was associated with local deforestation. However, the long-term trend may also be affected by changes in large-scale circulation. Thus, the purpose of this study was to investigate changes in large-scale circulation associated with the decreasing rainfall trend. Westward-propagating TCs from the South China Sea and the western North Pacific brought most of the rainfall over Thailand in September. TCs include tropical depressions, tropical storms, severe tropical storms, typhoons, and residual lows. 70% of the rainfall amount in September was estimated to be associated with TCs. The 50-year time-series of September rainfall over Thailand showed a significant decreasing trend. TC activity defined by 700-hPa relative vorticity, showed a weakening trend over the Indochina Peninsula. TC tracks also suggested the weakening of TC activity over this area. The long-term trend in rainfall during the late summer monsoon season was closely associated with changes in TC activity over the Indochina Peninsula; these changes were likely caused by changes in the major course of TCs. Concurrent with the changes in TC tracks, there was a change in the TC steering current around the Philippines archipelago and Taiwan. This led to the TC activity over the Indochina Peninsula being inactive, probably resulting in the long-term decrease in rainfall over Thailand.

• 社団法人日本気象学会の論文
• 2008-06-25

著者

• Yasunari Tetsuzo

  Frontier Research Center For Global Change:hydrospheric Atmospheric Research Center Nagoya Universit

• Yasunari Tetsuzo

  Frontier Research Center For Global Change (frcgc):japan Agency For Marine-earth Science And Technol

• TAKAHASHI Hiroshi

  Frontier Research Center for Global Change (FRCGC)

• Takahashi Hiroshi

  Frontier Research Center For Global Change (frcgc):japan Agency For Marine-earth Science And Technology (jamstec)

関連論文

• Assessment of the Diurnal Cycle of Precipitation over the Maritime Continent Simulated by a 20km Mesh GCM Using TRMM PR Data(5. Application to NWP Models,Precipitation Measurements from Space)
• Decreasing Trend in Rainfall over Indochina during the Late Summer Monsoon : Impact of Tropical Cyclones
• Climatology and Trends in Summer Precipitation Characteristics in Mongolia for the Period 1960-98(NOTES AND CORRESPONDENCE)
• Trends in Precipitation Amounts and the Number of Rainy Days and Heavy Rainfall Events during Summer in China from 1961 to 2000

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