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湿位涡和倾斜涡度发展   总被引:266,自引:22,他引:266  
从完整的原始方程出发,在导出精确形式的湿位涡方程的基础上,证得绝热无摩擦的饱和湿空气具有湿位涡守恒的特性。并由此去研究湿斜压过程中涡旋垂直涡度的发展。结果表明,在湿等熵坐标中,涡旋的发展与对流稳定度的减少,等熵面上的辐合和潜热的释放有关。由于等熵位涡分析的应用受等熵面倾斜的限制,又进而发展了Z坐标及P坐标中的倾斜涡度发展理论。指出无论是湿对称不稳定或对流不稳定大气,还是湿对称稳定或对流稳定大气,除对流稳定度的影响外,风的垂直切变的增加或水平湿斜压的增加均能因湿等熵面的倾斜而引起垂直涡度的增长。湿等熵面的倾斜越大,这种由干湿斜压性加强所引起的涡旋发展更激烈。在梅雨锋附近及其南侧暖湿区的北端,湿等熵面十分陡立,是涡旋发展及暴雨发生的重要地区。对1991年6月12—15日江淮流域暴雨过程的湿位涡分析表明,湿位涡分析,尤其是等压面上湿位涡量MPV1和MPV2的分析不仅在中高纬有效,在低纬度及低对流层也十分有效,是暴雨诊断和预报的有力工具。  相似文献   
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An accurate form of the moist potential vorticity(MPV)equation was deduced from a completeset of primitive equations.It was shown that motion in a saturated atmosphere without diabatic heat-ing and friction conserves moist potential vorticity.This property was then used to investigate the de-velopment of vertical vorticity in moist baroclinic processes.Results show that in the framework ofmoist isentropic coordinate,vorticity development can result from reduction of convective stability,orconvergence,or latent heat release at isentropic surfaces.However,the application of the usual analy-sis of moist isentropic potential vorticity is limited due to the declination of moist isentropic surfaces.and a theory of development based on z-coordinate and p-coordinate was then proposed.According tothis theory,whether the atmosphere is moist-symmetrically stable or unstable,or convective stable orunstable,the reduction of convective stability,the increase of the vertical shear of horizontal wind ormoist baroclinity may result in the increase of vertical vorticity,so long as the moist isentropic surfaceis slantwise.The larger the declination of the moist isentropic surface,the more vigorous the develop-ment of vertical vorticity.In a region with a monsoon front to the north and the warm and moist airto the south,or by the north of the front,the moist isentropes are very steep.The is the region mostfavorable for development of vorticities and formation of torrential rain.For a case of persistent torrential rain occurring in the middle and lower reaches of theChangjiang and Huaihe Rivers in June 11-15,1991,moist potential vorticity analysis,especially theisobaric analysis of its vertical and horizontal components,i.e.MPV1 and MPV2,respectively,iseffective for identifying synoptic systems not only in middle and high latitudes,but also in low lati-tudes and in the lower troposphere.It can serve as a powerful tool for the diagnosis and prediction oftorrential rain.  相似文献   
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