夏季青藏高原不同类型切变线的动力、热力特征分析

Studies on Dynamic and Thermal Characteristics of Different Shear Lines over Tibetan Plateau in Summer

利用1979-2009年NCEP 2.5°×2.5°月平均资料及2000年以来的1.0°×1.0°每日4次再分析资料,诊断分析了高原切变线的平均动力和热力特征、不同行星尺度环流背景下的横切变线特征和高原竖切变线特征。结果表明,多年平均的500hPa横切变线处于高原上相对暖湿区中,辐合上升运动与正涡度带吻合;不同行星尺度环流背景下的横切变线,其风场分布有较大差异,温度场特征也明显不同;合成的平均竖切变位于狭窄、浅薄的辐合与正涡度带上,切变线上上升运动特征与湿特征非常明显。

Using the monthly average data with 2.5°×2.5° resolutions and four-time data of a day with 1.0°×1.0° provided by NCEP,the diagnosis analyses of average dynamic and thermal characteristics of Plateau shear line,transversal shear line characteristic under certain planetary circulation conditions as well as perpendicular shear line characteristic have been done when Plateau shear lines have been divided into transversal and perpendicular shear line.The results show that transversal shear line averaged for many years is usually in comparative warmer and wetter zone.Convergence ascending and positive vorticity are identical.For transversal shear line under certain planetary circulation conditions,there are great differences of distribution of wind and temperature fields.Synthesized perpendicular shear line is usually in narrow flimsy area of convergence and positive vorticity.The characteristics of moving up and wet of shear line are very obvious.Some significative results have been obtained which reveal the character of Plateau shear lines,which are available to knowing plateau weather system and forecasting them better.