Nattapon Mahavik, Takehiko Satomura, Shoichi Shige, Bounteum Sysouphanthavong, Souvanny Phonevilay, Masaru Wakabayashi, Somchai Baimoung

Released: March 21, 2014

Rainfall pattern over the middle of Indochina Peninsula during 2009–2010 summer monsoon

Nattapon Mahavik1), Takehiko Satomura1), Shoichi Shige1), Bounteum Sysouphanthavong2), Souvanny Phonevilay2), Masaru Wakabayashi3), Somchai Baimoung4)

1) Graduate School of Science, Kyoto University
2) Department of Meteorology and Hydrology, Laos
3) Japan International Cooperation Agency (JICA), Laos
4) Ministry of Information and Communication Technology, Thailand

Rainfall patterns during summer monsoon in 2009 and 2010 over the middle of the Indochina Peninsula (ICP) are investigated using calibrated daily accumulated radar rainfall (CDARR). Empirical orthogonal function (EOF) analysis applied to CDARR shows that the first three modes explain 40% of the total rainfall variance. The pattern of the first EOF mode is only positive over the radar observation area with a large value near the foot of the Annam range in the eastern region of the radar site. The second EOF mode is a dipole pattern that has positive and negative regions in the eastern and western regions of the radar observation area, respectively. The third EOF mode also shows a dipole pattern with positive and negative areas in the southern and northern regions of the observation area, respectively. Composite analysis results suggest that the first EOF mode is possibly produced by a difference in positive vorticity, in which the difference in the southerly wind component likely causes orographic rainfall in the eastern region of the radar site. In addition, the second and third EOF modes are possibly produced by differences in westerly and southwesterly wind components, respectively.

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