1998年夏季HUBEX/GAME期间热量和水汽收支

摘要

使用1998年夏季高分辨率的GAME再分析资料,通过计算热量和水汽收支,分析了江准梅雨的热力和动力特征.梅雨期间,江准整个地区为强热源及水汽汇控制,並伴有强上升运动.热量和水汽收支计算表明,非绝热加热主要是降水产生的凝结潜热释放,地面感热和蒸发耗热均较小.江准梅雨降水是对流云和层状云共同产生的混合性降水.子波分析显示,热源、水汽汇和垂直运动有相似的时间变化和多尺度特征.江准梅雨期间,周期约为6天的天气尺度扰动以及周期约为2天和12小时的中尺度扰动同时发展,使江淮地区产生暴雨,並引起了热源、水汽汇和上升运动的最大值,对此中尺度扰动起了主要作用.%By using the high-resolution GAME reanalysis data, the heat and moisture budgets during the period of HUBEX/GAME in the summer of 1998 are calculated for exploring the thermodynamic features of Meiyu over the Changjiang-Huaihe (CH) valley. During the CH Meiyu period, an intensive vertically-integrated heat source and moisture sink are predominant over the heavy rainfall area of the CH valley, accompanied by strong upward motion at 500 hPa. The heat and moisture budgets show that the main diabatic heating component is condensation latent heat released by rainfall. As residual terms, the evaporation and sensible heating are relatively small. Based on the vertical distribution of the heat source and moisture sink, the nature of the rainfall is mixed, in which the convective rainfall is dominant with a considerable percentage of continuous stratiform rainfall. There are similar time evolutions of the main physical parameters(〈Q1〉,〈Q2〉,and vertical motion ω at 500 hPa).The time variations of〈Q1〉and〈Q2〉are in phase with those of -ω500, and have their main peaks within the CH Meiyu period. This shows the influence of the heat source on the dynamic structure of the atmosphere. The wavelet analyses of those time series display similar multiple timescale characteristics. During the CH Meiyu period, both the synoptic scale(～6 days) and mesoscale (～2 days and ～12 hours) increase obviously and cause heavy rainfall as well as the appearances of the maxima of the main physical parameters. Among them, the mesoscale systems are the main factors.