An accurate form of the moist potential vorticity(MPV)equation was deduced from a complete set of primitive equations.It was shown that motion in a saturated atmosphere without diabatic heat- ing and friction conserve...An accurate form of the moist potential vorticity(MPV)equation was deduced from a complete set 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 of moist isentropic coordinate,vorticity development can result from reduction of convective stability,or convergence,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 to this theory,whether the atmosphere is moist-symmetrically stable or unstable,or convective stable or unstable,the reduction of convective stability,the increase of the vertical shear of horizontal wind or moist baroclinity may result in the increase of vertical vorticity,so long as the moist isentropic surface is 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 air to the south,or by the north of the front,the moist isentropes are very steep.The is the region most favorable for development of vorticities and formation of torrential rain. For a case of persistent torrential rain occurring in the middle and lower reaches of the Changjiang and Huaihe Rivers in June 11-15,1991,moist potential vorticity analysis,especially the isobaric analysis of its vertical and horizontal components,i.e.MPV1 and MPV2,respectively,is effective 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 of torrential rain.展开更多
基金This study was supported by the Key Program No.49635170 and Program No.49575265 of the National Natural Science Foundation of China.
文摘An accurate form of the moist potential vorticity(MPV)equation was deduced from a complete set 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 of moist isentropic coordinate,vorticity development can result from reduction of convective stability,or convergence,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 to this theory,whether the atmosphere is moist-symmetrically stable or unstable,or convective stable or unstable,the reduction of convective stability,the increase of the vertical shear of horizontal wind or moist baroclinity may result in the increase of vertical vorticity,so long as the moist isentropic surface is 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 air to the south,or by the north of the front,the moist isentropes are very steep.The is the region most favorable for development of vorticities and formation of torrential rain. For a case of persistent torrential rain occurring in the middle and lower reaches of the Changjiang and Huaihe Rivers in June 11-15,1991,moist potential vorticity analysis,especially the isobaric analysis of its vertical and horizontal components,i.e.MPV1 and MPV2,respectively,is effective 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 of torrential rain.
