高原切变线形态演变过程中的个例研究：结构特征

Case Study on Shape Evolution of Plateau Shear Line:Structural Characteristics

利用逐6 h 1°×1°的NCEP/NCAR FNL资料、中国气象局地面降水实况数据和青藏高原低涡切变线年鉴图集资料,分析了2010年7月16 17日S1019高原切变线由竖切变线转变为横切变线的形态演变过程中动力、热力结构特征及其演变。结果显示,在动力结构特征方面:在其生成发展期,高层200 h Pa受南亚高压控制,中低层相对涡度大值区在范围和强度上均出现迅速发展特征,垂直方向上呈现"干湿相间、冷暖相间"的斜压结构特征。在其减弱消亡期,高层200 h Pa南亚高压有所减弱,中低层相对涡度大值区发生断裂,大值区主体随西风槽和西南涡逐渐移出高原地区。在热力结构特征方面:在其生成发展期,高层300 h Pa附近呈明显的"暖心"和"湿心"结构特征,伴随着降水的发生发展,视热源Q_1和视水汽汇Q_2在垂直方向上均加强,Q_1的大值中心从400 h Pa抬升至300 h Pa,Q_2的大值中心从300 h Pa下降至600 h Pa。在其减弱消亡期,高层总体偏湿偏冷,当降水趋于结束,视热源Q_1和视水汽汇Q_2均迅速减弱。

Using NCEP/NCAR 1°×1°FNL datasets, the CMA surface precipitation data and Qinghai-Tibetan Plateau and shear line year books, the dimensional structure characteristics and their causes of the plateau shear line S1019 were diagnosed which occurred on July 16- 17, 2010. The results show, in its generative development period, there exist strong divergence area near the South Asia high ridge, and low level relative vorticity has developed rapidly in the aspect of scope and intensity. Overall, it shows a baroclinic vertical structural configuration. It appears a ＂warm and wet core＂ structure near the height of 300 hPa, the apparent heat source QI and apparent moisture sink Q2 both strengthening in the vertical direction, the Q1 maximum value center lifted from 400 hPa up to 300 hPa while the positive extreme value of Q2 decreased from 300 hPa to 600 hPa. In the decaying period, the divergence area decreased significantly near the top of 100 hPa along South Asia high ridge, it mainly appears wet and cold in the upper troposphere, and intensity, the southwest vortex gradually moves the low level relative vorticity value decreases in the scope out of the Qinghai-Tibetan Plateau area, the lower level completely controlled by the cold and wet air. When the precipitation tends to end, both the apparent heat source Q1 and apparent moisture sink Q2 reduce quickly.