Based on the Lagrangian change equation of vertical vorticity deduced from the equation of three-dimensional Ertel potential vorticity （PVe）, the development and movement of vortex are investigated from the view of ...Based on the Lagrangian change equation of vertical vorticity deduced from the equation of three-dimensional Ertel potential vorticity （PVe）, the development and movement of vortex are investigated from the view of potential vorticity and diabatic heating （PV Q）. It is demonstrated that the asymmetric dis-tribution in the vortex of the non-uniform diabatic heating in both vertical and horizontal can lead to the vortex＇s development and movement. The theoretical results are used to analyze the development and move-ment of a Tibetan Plateau （TP） vortex （TPV）, which appeared over the TP, then slid down and moved eastward in late July 2008, resulting in heavy rainfall in Sichuan Province and along the middle and lower reaches of the Yangtze River. The relative contributions to the vertical vorticity development of the TPV are decomposed into three parts： the diabatic heating, the change in horizontal component of PVe （defined as PV2）, and the change in static stability θz. The results show that in most cases, diabatic heating plays a leading role, followed by the change in PV2, while the change of θz usually has a negative impact in a stable atmosphere when the atmosphere becomes more stable, and has a positive contribution when the atmosphere approaches neutral stratification. The intensification of the TPV from 0600 to 1200 UTC 22 July 2008 is mainly due to the diabatic heating associated with the precipitation on the eastern side of the TPV when it uplifted on the up-slope of the northeastern edge of the Sichuan basin. The vertical gradient of diabatic heating makes positive （negative） PVe generation below （above） the maximum of diabatic heating; the positive PVe generation not only intensifies the low-level vortex but also enhances the vertical extent of the vortex as it uplifts. The change in PVe due to the horizontal gradient of diabatic heating depends on the vertical shear of horizontal wind that passes through the center of diabatic heating. The horizontal gradient of diabatic heating makes positive （negative） PVe generation on the right （left） side of the vertical shear of horizontal wind. The positive PVe generation on the right side of the vertical shear of horizontal wind not only intensifies the local vertical vorticity but also affects direction of movement of the TPV. These diagnostic results are in good agreement with the theoretic results developed from the PV-Q view.展开更多
The development of vertical vorticity under adiabatic condition is investigated by virtue of the view of potential vorticity and potential temperature （PV-θ） and from a Lagrangian perspective. A new concept of gene...The development of vertical vorticity under adiabatic condition is investigated by virtue of the view of potential vorticity and potential temperature （PV-θ） and from a Lagrangian perspective. A new concept of generalized slantwise vorticity development （GSVD） is introduced for adiabatic condition. The GSVD is a coordinate independent framework of vorticity development （VD）, which includes slantwise vorticity development （SVD） when a particle is sliding down the concave slope or up the convex slope of a sharply tilting isentropic surface under stable or unstable condition. The SVD is a special VD for studying the severe weather systems with rapid development of vertical vorticity. In addition, the GSVD clarifies VD and SVD. The criteria for VD and SVD demonstrate that the demand for SVD is much more restricted than the demand for VD. When an air parcel is moving down the concave slope or up the convex slope Of a sharply tilting isentropic surface in a stable stratified atmosphere with its stability decreasing, or in an unstable atmosphere with its stability increasing, i.e., its stability θz approaches zero, its vertical vorticity can develop rapidly if its CD is decreasing. The theoretical results are employed to analyze a Tibetan Plateau （TP） vortex （TPV）, which appeared over the TP, then slid down and moved eastward in late July 2008, resulting in heavy rainfall in Sichuan Province and along the middle and lower reaches of the Yangtze River. The change of PV2 contributed to the intensification of the TPV from 0000 to 0600 UTC 22 July 2008 when it slid upward on the upslope of the northeastern edge of the Sichuan basin, since the changes in both horizontal vorticity ~？~ and baroclinity Os have positive effects on the development of vertical vorticity. At 0600 UTC 22 July 2008, the criterion for SVD at 300 K isentropic surface is satisfied, meaning that SVD occurred and contributed significantly to the development of vertical vorticity. The appearance of the stronger signals concerning the VD and SVD surrounding the vortex indicates that the GSVD concept can serve as a useful tool for diagnosing the development of weather systems.展开更多
基金Supported by the National Basic Research and Development(973)Program of China(2012CB417203 and 2010CB950403)National Natural Science Foundation of China(40875034 and 40925015)
文摘Based on the Lagrangian change equation of vertical vorticity deduced from the equation of three-dimensional Ertel potential vorticity （PVe）, the development and movement of vortex are investigated from the view of potential vorticity and diabatic heating （PV Q）. It is demonstrated that the asymmetric dis-tribution in the vortex of the non-uniform diabatic heating in both vertical and horizontal can lead to the vortex＇s development and movement. The theoretical results are used to analyze the development and move-ment of a Tibetan Plateau （TP） vortex （TPV）, which appeared over the TP, then slid down and moved eastward in late July 2008, resulting in heavy rainfall in Sichuan Province and along the middle and lower reaches of the Yangtze River. The relative contributions to the vertical vorticity development of the TPV are decomposed into three parts： the diabatic heating, the change in horizontal component of PVe （defined as PV2）, and the change in static stability θz. The results show that in most cases, diabatic heating plays a leading role, followed by the change in PV2, while the change of θz usually has a negative impact in a stable atmosphere when the atmosphere becomes more stable, and has a positive contribution when the atmosphere approaches neutral stratification. The intensification of the TPV from 0600 to 1200 UTC 22 July 2008 is mainly due to the diabatic heating associated with the precipitation on the eastern side of the TPV when it uplifted on the up-slope of the northeastern edge of the Sichuan basin. The vertical gradient of diabatic heating makes positive （negative） PVe generation below （above） the maximum of diabatic heating; the positive PVe generation not only intensifies the low-level vortex but also enhances the vertical extent of the vortex as it uplifts. The change in PVe due to the horizontal gradient of diabatic heating depends on the vertical shear of horizontal wind that passes through the center of diabatic heating. The horizontal gradient of diabatic heating makes positive （negative） PVe generation on the right （left） side of the vertical shear of horizontal wind. The positive PVe generation on the right side of the vertical shear of horizontal wind not only intensifies the local vertical vorticity but also affects direction of movement of the TPV. These diagnostic results are in good agreement with the theoretic results developed from the PV-Q view.
基金Supported by the National Basic Research and Development(973)Program of China(2012CB417203 and 2010CB950403)National Natural Science Foundation of China(40875034 and 40925015)
文摘The development of vertical vorticity under adiabatic condition is investigated by virtue of the view of potential vorticity and potential temperature （PV-θ） and from a Lagrangian perspective. A new concept of generalized slantwise vorticity development （GSVD） is introduced for adiabatic condition. The GSVD is a coordinate independent framework of vorticity development （VD）, which includes slantwise vorticity development （SVD） when a particle is sliding down the concave slope or up the convex slope of a sharply tilting isentropic surface under stable or unstable condition. The SVD is a special VD for studying the severe weather systems with rapid development of vertical vorticity. In addition, the GSVD clarifies VD and SVD. The criteria for VD and SVD demonstrate that the demand for SVD is much more restricted than the demand for VD. When an air parcel is moving down the concave slope or up the convex slope Of a sharply tilting isentropic surface in a stable stratified atmosphere with its stability decreasing, or in an unstable atmosphere with its stability increasing, i.e., its stability θz approaches zero, its vertical vorticity can develop rapidly if its CD is decreasing. The theoretical results are employed to analyze a Tibetan Plateau （TP） vortex （TPV）, which appeared over the TP, then slid down and moved eastward in late July 2008, resulting in heavy rainfall in Sichuan Province and along the middle and lower reaches of the Yangtze River. The change of PV2 contributed to the intensification of the TPV from 0000 to 0600 UTC 22 July 2008 when it slid upward on the upslope of the northeastern edge of the Sichuan basin, since the changes in both horizontal vorticity ~？~ and baroclinity Os have positive effects on the development of vertical vorticity. At 0600 UTC 22 July 2008, the criterion for SVD at 300 K isentropic surface is satisfied, meaning that SVD occurred and contributed significantly to the development of vertical vorticity. The appearance of the stronger signals concerning the VD and SVD surrounding the vortex indicates that the GSVD concept can serve as a useful tool for diagnosing the development of weather systems.
