The moist potential vorticity (MPV) equation is derived from complete atmospheric equations including the effect of mass forcing, with which the theory of Up-sliding Slantwise Vorticity Development, (USVD) is proposed...The moist potential vorticity (MPV) equation is derived from complete atmospheric equations including the effect of mass forcing, with which the theory of Up-sliding Slantwise Vorticity Development, (USVD) is proposed based on the theory of Slantwise Vorticity Development (SVD). When an air parcel slides up along a slantwise isentropic surface, its vertical component of relative vorticity will develop, and the steeper the isentropic surface is, the more violent the development will he. From the definition of MPV and the MPV equation produced here in, a complete vorticity equation is then put forward with mass forcing, which explicitly includes the effects of both internal forcings, such as variations of stability, baroclinicity, and vertical shear of horizontal wind, arid external forcings, such as diabatic heating, friction, and mass forcing. When isentropic surfaces are flat, the complete vorticity equation matches its traditional counterpart. The physical interpretations of some of the items which are included in the complete- vorticity equation but not in the traditional one are studied with a simplified model of the Changjiang-Huaihe Meiyu front. A 60-h simulation is then performed to reproduce a torrential rain event in the Changjiang-Huaihe region and the output of the model is studied qualitatively based on the theory of USVD. The result shows that the conditions of the theory of USVD are easily satisfied immediately in front of mesoscale rainstorms in the downwind direction, that is, the theory of USVD is important to the development and movement of these kinds of systems.展开更多
By using PSU/NCAR MM5 mesoscale model,a 60-h simulation is performed to reproduce a frontal cyclogenesis over the Western Atlantic Ocean during March 13- 15 1992.The model reproduces well the genesis,track and intensi...By using PSU/NCAR MM5 mesoscale model,a 60-h simulation is performed to reproduce a frontal cyclogenesis over the Western Atlantic Ocean during March 13- 15 1992.The model reproduces well the genesis,track and intensity of the cyclone,its associated thermal structure as well as its surface circulation.The major cyclone (M) deepens 45 hPa in the 60-h simulation and 12 hPa in 6 hours from 36 h to 42 h (model time) and 27 hPa in 24 hours from 36 h to 60 h (model time).Cross-section and isentropic analysis tell us that the cyclogenesis is in very close relation with slantwise isentropic surfaces;the cyclone is always superposed on the core of neutral convective stability with nearly vertical isentropic surfaces,which coincides with what the theory of Slantwise Vorticity Development (SVD) says.Beginning with the theory of SVD,the development and propagation of the oceanic frontal cyclone are studied by using high-resolution model output in the context of slantwise isentropic surfaces.The results show that the frontal cyclone deepens rapidly by the interaction with the large-scale environment after occurring over the ocean with weak static stability;and the theory of SVD can well interpret the development and propagation closely related with slantwise isentropic surfaces,The downstream slantwise up- sliding movement along canting isentropic surfaces makes vorticities develop (USVD) under favorable condition (C_D<0,where CD is SVD index),and results in the moving and development of the cyclone.展开更多
基金supported by the Chinese Academy of Sciences Program of Well-Known 0verseas Chinese Scholars under Dr.Samuel Shen and the Innovation Project of the Chinese Academy of Sciences under Grant No.KZCX3-SW-213by the National Natural Science foundation of China under Grant Nos.40023001 and 40135020.
文摘The moist potential vorticity (MPV) equation is derived from complete atmospheric equations including the effect of mass forcing, with which the theory of Up-sliding Slantwise Vorticity Development, (USVD) is proposed based on the theory of Slantwise Vorticity Development (SVD). When an air parcel slides up along a slantwise isentropic surface, its vertical component of relative vorticity will develop, and the steeper the isentropic surface is, the more violent the development will he. From the definition of MPV and the MPV equation produced here in, a complete vorticity equation is then put forward with mass forcing, which explicitly includes the effects of both internal forcings, such as variations of stability, baroclinicity, and vertical shear of horizontal wind, arid external forcings, such as diabatic heating, friction, and mass forcing. When isentropic surfaces are flat, the complete vorticity equation matches its traditional counterpart. The physical interpretations of some of the items which are included in the complete- vorticity equation but not in the traditional one are studied with a simplified model of the Changjiang-Huaihe Meiyu front. A 60-h simulation is then performed to reproduce a torrential rain event in the Changjiang-Huaihe region and the output of the model is studied qualitatively based on the theory of USVD. The result shows that the conditions of the theory of USVD are easily satisfied immediately in front of mesoscale rainstorms in the downwind direction, that is, the theory of USVD is important to the development and movement of these kinds of systems.
基金the Innovation Project of Chinese Academy of Sciences under Grant No.KZCX3-SW-213"Outstanding Overseas Chinese Scholars"project of the Chinese Academy of Sciences under Grant No.2002-1-2the National Key Program for Developing Basic Sciences(G1998040900-part 1)
文摘By using PSU/NCAR MM5 mesoscale model,a 60-h simulation is performed to reproduce a frontal cyclogenesis over the Western Atlantic Ocean during March 13- 15 1992.The model reproduces well the genesis,track and intensity of the cyclone,its associated thermal structure as well as its surface circulation.The major cyclone (M) deepens 45 hPa in the 60-h simulation and 12 hPa in 6 hours from 36 h to 42 h (model time) and 27 hPa in 24 hours from 36 h to 60 h (model time).Cross-section and isentropic analysis tell us that the cyclogenesis is in very close relation with slantwise isentropic surfaces;the cyclone is always superposed on the core of neutral convective stability with nearly vertical isentropic surfaces,which coincides with what the theory of Slantwise Vorticity Development (SVD) says.Beginning with the theory of SVD,the development and propagation of the oceanic frontal cyclone are studied by using high-resolution model output in the context of slantwise isentropic surfaces.The results show that the frontal cyclone deepens rapidly by the interaction with the large-scale environment after occurring over the ocean with weak static stability;and the theory of SVD can well interpret the development and propagation closely related with slantwise isentropic surfaces,The downstream slantwise up- sliding movement along canting isentropic surfaces makes vorticities develop (USVD) under favorable condition (C_D<0,where CD is SVD index),and results in the moving and development of the cyclone.