南海夏季风建立的模式诊断研究

A Study of the Onset of the Summer Monsoon over the South China Sea

应用全球谱模式 (T42L9)对 1 986年和 1 987年个例进行了一系列有、无凝结潜热加热和地表感热以及地形作用的单因子敏感性数值预报试验 ,对预报模式输出的大气凝结潜热量和地面感热通量的时空变化特征进行了诊断分析。个例敏感性试验结果表明 ,大气凝结潜热对南海地区西南风的建立极为重要。诊断分析结果指出 ,在南海夏季风建立前 ,中南半岛地区是强大的凝结潜热加热区 ,远比印度半岛地区强。地形和中南半岛凝结潜热的共同作用可能是导致南海夏季风早于印度夏季风建立的重要原因。 1 987年 5月份在中南半岛地区的凝结潜热量比 1 986年明显偏低 ,直到 5月底 6月初才明显上升 ,这可能是该年南海夏季风建立晚的一个原因 ,中南半岛地区凝结潜热的变化可能是影响季风建立早晚的重要因子之一。

The sensitive numerical experiments with and without the topography effect and t he condensation latent heat for two cases are performed by using the global spec tral model (T42L9). Two cases are on 8 May 1986 and 3 June 1987, respectively. F urthermore the characteristics of temporal and spatial variation of the condensa tion latent heat (CLH) and the surface sensible heat flux (SSHF) predicted by nu merical model are analyzed. The results of various sensitive numerical forecast experiments show that the condensation latent heat plays most important role in the establishment of westerly wind at 850 hPa over the South China Sea (SCS). Th rough analyses of the CLH and the SSHF, following results are indicated. Before onset of summer monsoon over the SCS, the maximum center of the CLH is located i n the Indo-China Peninsula, and the CLH over the Indo-China Peninsula is far s tronger than that over the India Peninsula. It can be suggested that the effects of the strong condensation latent heat over the Indo-China Peninsula and the e ffects of the topography are both very important physical mechanisms leading to the earlier onset of the SCS summer monsoon than the Indian summer monsoon. The results also show that the interannual variability of the CLH is obvious .The CL H over the Indo-China Peninsula in May 1987 is weaker than that in May 1986, wh ich is one of physical reasons resulting in the later onset of the SCS summer mo nsoon in 1987.It can be indicated that the interannual variability of the CLH ov er the Indo-China Peninsula is an important factor for the earlier (later) onse t of the SCS summer monsoon