Climatological Characteristics of the Intraseasonal Variation of Precipitation over the Indochina Peninsula

Abstract

With the use of daily rain gauge data observed at 210 stations in the Indochina Peninsula (ICP) for the 26 yr from 1978 to 2003, this paper describes climatological characteristics of 2 types of intraseasonal variations (ISVs): the 30?60-day variation (30?60DV) and the 10?20-day variation (10?20DV). The authors find that these characteristics are quite different from place to place in the ICP. During the rainy season, variance of the 30?60DV is generally larger in coastal regions than over inland regions and it has two local maxima: one found in the coastal region of Myanmar (CMY) and the other in the southern Laos and central Vietnam region (SLCV). Wavelet analysis reveals that the 30?60DV in the CMY is active throughout the rainy season (May?October) and exhibits the maximum activity in May?June. In addition, its typical time scale shifts from 40 days in the early half of the rainy season to 50 days in the latter half. Cross-correlation analysis reveals that its signal propagates northward. On the other hand, the 30?60DV in the SLCV is active only during July?October, and its signal propagates northwestward. The largest variance of the 10?20DV is found in the coastal regions of northern and central Vietnam (CNCV), while the variance in other coastal regions is generally smaller than that in inland regions. In contrast to the 30?60DV, the 10?20DV activity varies significantly over the course of the rainy season. The 10?20DV in the inland regions is active in May and September and inactive in July, while that in the CNCV is active during August?November. The 10?20DV exhibits high spatial coherence over most of the ICP, and its signal propagates west-northwestward. Relationship of the ISV in the ICP with synoptic-scale ISV structures is also discussed.