“81.8”持续暴雨期中-α尺度低涡发展的涡度变率及其热源  

THE VORTICITY CHANGE-RATE AND ITS HEAT SOURCE FOR DEVELOPMENT OF MESO-α SCALE VORTEX DURING A PERSISTENT HEAVY RAIN OF 14-22 AUGUST 1981

作　　者：程麟生[1] 

机构地区：[1]兰州大学大气科学系

出　　处：《高原气象》1991年第4期337-350,共14页Plateau Meteorology

摘　　要：1981年8月14日至22日(“81.8”)发生在陕、甘、川毗邻区的一次持续暴雨过程,与伴有切变线的低涡持续发展直接关联。涡度变率诊断揭示,涡度正变率中心初生于青藏高原东侧低空,其后出现了高、低空涡度正变率中心的迭加和耦合以及在垂直方向的贯通过程。涡度正变率中心的这种垂直结构及其演变,与切变线低涡生成和发展的正涡度中心垂直结构及其演变基本一致。在贡献于涡度变率的因子中,非线性相互作用涡度变率的相对数值最大;由于地形强迫的时间平均涡度变率只对切变线低涡的生成和维持是重要的;扰动涡度变率在切变线低涡强烈发展时才有值得注意的贡献。中尺度热量和水汽收支诊断揭示,视热源Q_1和水汽汇Q_2垂直积分的高值区同切变线低涡发展区及暴雨区大体一致;Q_1和Q_2的时空平均垂直廓线表明,Q_1的最大加热区间在570至400 hPa,而Q_2的最大区间在650至550 hPa;由于感热和潜热对流涡动通量辐合的加热,约等于凝结释放潜热量的一半。During the period of 14-22 August 1981, a persistent heavy rain event occurred over the adjacent region of the Shaanxi-Gansu-Sichuan Province. This heavy rain event was directly related to a persistent development of a meso-α scale vortex with shear line. Diagnoses of the vorticity change-rate reveal rhat the positive vorticity change-rate center originated over the lower levels of the Qinghai-Xizang Plateau lee side, and then a process of the superposition and coupling and vertically joining-up of the vorticity change-rate centers over upper-and lower-levels was occurred. The vertical structure and evolution of the positive vorticity change-rate centers are basically consistent with the vertical structure and evolution of the positive vorticity centers of the formation and development of the shear line-vortex. In the factors of contributing to the vorticity change-rate, the relative numeric of the nonlinear interactive vorticity change-rate is the most component; the time-mean vorticity change-rate owing to topographic forcing is important only for the formation and maintenance of the shear line-vortex; the contribution of the perturbation vorticity change-rate is worth notice only when the shear line-vortex is under an intensive development. Diagnoses of the mesoscale heat and moisture budgets reveal that the vertical integrated high value regions of the apparent heat source Q1 and apparent moisture sink Q2 are basically consistent with regions of developing shear line-vortex and heavy rain. The vertical profiles of temporal-and spatial-averaged Q1 and Q2 indicate that the maximum heating interval of the Q1 appears between 570 hPa and 400 hPa, while the maximum interval of the Q2 appears between 650 hPa and 550 hPa. The heating due to convective eddy flux convergence of the sensible and latent heat is about half the amount of latent heat due to condensation.

关 键 词：暴雨 尺中度 低涡 涡度 变率 热源 

分 类 号：P433[天文地球—大气科学及气象学]