The effects of precipitation on the moist potential vorticity substance(MPVS) are investigated by analyzing the MPVS with precipitation mass forcing and its impermeability in daily 1°× 1° data of the Na...The effects of precipitation on the moist potential vorticity substance(MPVS) are investigated by analyzing the MPVS with precipitation mass forcing and its impermeability in daily 1°× 1° data of the National Centers for Environmental Prediction/National Center for Atmospheric Research(NCEP/NCAR) over the Yangtze River Basin from 21 June to 2 July 1999. The results show that the positive MPVS anomalies appear mainly along the Mei-yu front, where the maximum MPVS collocates with the maximum surface rainfall. Rain case diagnoses indicate that the MPVS anomaly may be used as a dynamical signal to detect the location and shift of the rain band when its impermeability is considered.展开更多
Due to the importance of the mass forcing induced by precipitation and condensation in moist processes, the La- grangian continuity equation without a source/sink term utilized to prove the Ertel-Rossby invariant （ER...Due to the importance of the mass forcing induced by precipitation and condensation in moist processes, the La- grangian continuity equation without a source/sink term utilized to prove the Ertel-Rossby invariant （ERI） and its con- servation property is re-derived considering the mass forcing. By introducing moist enthalpy and moisture entropy, the baroclinic ERI could be adapted to moist flow. After another look at the moist ERI, it is deployed as the dot product be- tween the generalized velocity and the generalized vorticity in moist flow, which constitutes a kind of generalized helicity. Thus, the baroclinic ERI is further extended to the moist case. Moreover, the derived moist ERI forumla remains formally consistent with the dry version, no matter whether mass forcing is present. By using the Weber transformation and the Lagrangian continuity equation with a source/sink effect, the conservation property of the baroclinic ERI in moist flow is revisited. The presence or absence of mass forcing in the Lagrangian continuity equation determines whether or not the baroclinic ERI in moist flow is materially conserved. In other words, it would be qualified as a quasi-invariant but only being dependent on the circumstances. By another look at the moist baroclinic ERI, it is surely a neat formalism with a simple physical explanation, and the usefulness of its anomaly in diagnosing atmospheric flow is demonstrated by case study.展开更多
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
The impacts of cloud-induced mass forcing on the development of the moist potential vorticity (MPV) anomaly associated with torrential rains are investigated by using NCEP/NCAR 1? × 1? data. The MPV ten...The impacts of cloud-induced mass forcing on the development of the moist potential vorticity (MPV) anomaly associated with torrential rains are investigated by using NCEP/NCAR 1? × 1? data. The MPV tendency equation with the cloud-induced mass forcing is derived, and applied to the torrential rain event over the Changjiang River-Huaihe River Valleys during 26–30 June 1999. The result shows that positive anomalies are located mainly between 850 hPa and 500 hPa, while the maximum MPV, maximum positive tendency of the MPV, and maximum surface rainfall are nearly collocated. The cloud-induced mass forcing contributes to the positive tendency of the moist potential vorticity anomaly. The results indicate that the MPV may be used to track the propagation of rain systems for operational applications.展开更多
基金the National Basic Research Program of China (Grant No.2014CB441402)；the National Natural Science Foundation of China (Grant Nos.41275065, 41475054, and 41075044).
文摘The effects of precipitation on the moist potential vorticity substance(MPVS) are investigated by analyzing the MPVS with precipitation mass forcing and its impermeability in daily 1°× 1° data of the National Centers for Environmental Prediction/National Center for Atmospheric Research(NCEP/NCAR) over the Yangtze River Basin from 21 June to 2 July 1999. The results show that the positive MPVS anomalies appear mainly along the Mei-yu front, where the maximum MPVS collocates with the maximum surface rainfall. Rain case diagnoses indicate that the MPVS anomaly may be used as a dynamical signal to detect the location and shift of the rain band when its impermeability is considered.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.41375054,41575064,and 91437215)the Opening Foundation of the State Key Laboratory of Severe Weather,Chinese Academy of Meteorological Sciences(Grant Nos.2015LASW-B01 and 2015LASW-A02)
文摘Due to the importance of the mass forcing induced by precipitation and condensation in moist processes, the La- grangian continuity equation without a source/sink term utilized to prove the Ertel-Rossby invariant （ERI） and its con- servation property is re-derived considering the mass forcing. By introducing moist enthalpy and moisture entropy, the baroclinic ERI could be adapted to moist flow. After another look at the moist ERI, it is deployed as the dot product be- tween the generalized velocity and the generalized vorticity in moist flow, which constitutes a kind of generalized helicity. Thus, the baroclinic ERI is further extended to the moist case. Moreover, the derived moist ERI forumla remains formally consistent with the dry version, no matter whether mass forcing is present. By using the Weber transformation and the Lagrangian continuity equation with a source/sink effect, the conservation property of the baroclinic ERI in moist flow is revisited. The presence or absence of mass forcing in the Lagrangian continuity equation determines whether or not the baroclinic ERI in moist flow is materially conserved. In other words, it would be qualified as a quasi-invariant but only being dependent on the circumstances. By another look at the moist baroclinic ERI, it is surely a neat formalism with a simple physical explanation, and the usefulness of its anomaly in diagnosing atmospheric flow is demonstrated by case study.
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by the National Natural Science Foundation of China under Grant Nos.40405007 , 40275015 the OlympicProject under Grant No.KACX1-02 partially sup-ported by the"Outstanding Overseas Chinese Scholars"Project of the Chinese Academy of Sciences under Grant No.2002-1-2.
文摘The impacts of cloud-induced mass forcing on the development of the moist potential vorticity (MPV) anomaly associated with torrential rains are investigated by using NCEP/NCAR 1? × 1? data. The MPV tendency equation with the cloud-induced mass forcing is derived, and applied to the torrential rain event over the Changjiang River-Huaihe River Valleys during 26–30 June 1999. The result shows that positive anomalies are located mainly between 850 hPa and 500 hPa, while the maximum MPV, maximum positive tendency of the MPV, and maximum surface rainfall are nearly collocated. The cloud-induced mass forcing contributes to the positive tendency of the moist potential vorticity anomaly. The results indicate that the MPV may be used to track the propagation of rain systems for operational applications.
