我国南方MCC的涡度、水汽和热量收支平衡

The Vorticity, Heat, Moisture Budget Evolution of MCC over South China

采用合成分析方法 ,将我国南方中尺度对流复合体的生命史划分为 7个子阶段 ,详细探讨MCC演变过程中的涡度、水汽和热量收支平衡演变特征 ,着重分析了中小尺度系统在MCC过程中的作用。结果表明 :( 1)在MCC过程中 ,中γ尺度和中 β尺度系统活动是引起涡度不平衡的重要原因。( 2 )在MCC初始阶段有中小尺度对流系统消耗MCC的水汽、热量而积极活动 ,造成MCC的视热汇、视水汽汇。成熟阶段的源区域表明有中小尺度系统的活动造成MCC的视热源、视水汽源 ,这是MCC具有长生命史的原因。MCC后期 ,中小尺度对流系统活动造成的视水汽汇和视热汇 ,与有利的大尺度天气条件的逐渐消亡 ,使MCC渐渐消失。 ( 3 )MCC的形成和启动受大尺度环境场的控制 ;一旦MCC开始活动 ,对流层低层、中层的中尺度对流系统活动对MCC的发展与持续过程有十分重要的作用 ;在MCC前期 ,中小尺度对流活动消耗MCC的总能量而启动 ;在成熟阶段中小尺度对流活动释放总能量造成了MCC的长生命史 ;MCC后期 ,大形势发生改变 (如位势不稳定度的变化等 ) ,积云对流活动和(或 )中尺度对流活动的作用与大尺度形势趋势一致 ,致使MCC消亡。 ( 4 )在MCC前期 ,潜热释放是主要加热因子 ;而后对流垂直输送水汽和热量的作用比对流凝结加热的作用大。

Using the technique of composite analysis, the MCC life\|cycle of meso\|α\|scale convective complexes occurred over South China is divided into seven sub\|periods, then the MCC vorticity, heat, moisture budget evolution are revealed in detail and the role of meso\|scale and cumulus convection are stressed. The results are as follows: (1) It is an important factor that meso\|scale and cumulus convective activity over the MCC life\|cycle for vorticity residual term. (2) In the initial stages of the MCC life\|cycle, meso\|scale cumulus convection are active due to dissipating heat and water vapor and resulting in the apparent heat sink and the apparent moisture sink. In the mature stages, the meso\|scale systems and cumulus convection are active due to the apparent heat source and the apparent moisture source which is the cause of MCC long life\|cycle. In the later MCC life\|cycle, due to the apparent heat sink and apparent moisture sink from the meso\|scale systems and cumulus convection activities unfavorable large scale weather conditions, MCC is dissipating slowly. (3) Synoptic features control MCC genesis and growth, but once after MCC formed, the cumulus convection and mesoscale updrafts/downdrafts in the lower\| and middle\| troposphere have important role in MCC process. In the mature stages, the meso\|scale systems and cumulus convection release heat and lead to MCC long\|life. In the late stages of MCC, the large\|scale weather condition is changed and also the meso\|scale systems and cumulus convection elements are changed also, so the MCC is dissipating. (4) In the pre\|MCC, the latent heat release is main heating factor. And after that time, the convective vertical transfer water vapor and heat is more important than the latent heat does.