First,based on routine meteorological data,the synoptic characteristics of a heavy warm-sector rainfall that occurred on June 13,2008 in the Pearl River Delta were analyzed.Second,a mesoscale numerical model,Weather R...First,based on routine meteorological data,the synoptic characteristics of a heavy warm-sector rainfall that occurred on June 13,2008 in the Pearl River Delta were analyzed.Second,a mesoscale numerical model,Weather Research and Forecasting(WRFV2.2),was used to simulate the heavy rainfall. Diagnostic analyses were done of moist potential vorticity(MPV)for its horizontal components(MPV2) and vertical components(MPV1)based on the simulation results of WRFV2.2 to identify the mechanism of the rainfall development.The results showed that the heavy rainfall occurred when there were high MPV1 in the upper levels and low MPV1 and high MPV2 in the lower levels.Disturbances of high MPV1 in the upper levels came from the southwest or northwest,those of low MPV1 in the lower levels came from the southwest,and those of high MPV2 came from the south.Disturbances of low MPV1 at low levels were the direct cause of convective instability.Enhanced vertical shear of meridional wind led to increased MPV2 at lower levels,strengthened baroclinicity,and active warm and wet flows.These distributions of MPV helped to trigger the release of unstable energy and produce warm-sector heavy rainfall.As it integrates the evolution of dynamic and thermal fields,MPV is able to reveal the development of this heavy rainfall effectively.展开更多
In the light of the theory on moist potential vorticity (MPV) investigation was undertaken of the 700 hPa vertical (horizontal) component MP1 (MPV2) for the heavy rain event occurring in July 5–6, 1991. Results show ...In the light of the theory on moist potential vorticity (MPV) investigation was undertaken of the 700 hPa vertical (horizontal) component MP1 (MPV2) for the heavy rain event occurring in July 5–6, 1991. Results show that the distribution features of the two components were closely related to the development of a mesoscale cyclone as a rainstorm-causing weather system in the lower troposphere in such a way that the ambient atmosphere of which MPV1 > 0 and MPV2 < 0 with |MPV1| ≥ |MPV2| favored the genesis of conditional symmetric instability (CSI) and that, as indicated by calculations, a CSI sector was really existent in the lower troposphere during the heavy rain happening and contributed greatly to its development.展开更多
Moist potential vorticity (MPV) and its generation may be important in the development of mesoscale structures such as rainbands within cyclones. In an adiabatic and frictionless flow, MPV generation is possible if th...Moist potential vorticity (MPV) and its generation may be important in the development of mesoscale structures such as rainbands within cyclones. In an adiabatic and frictionless flow, MPV generation is possible if the flow is three-dimensional and the air is unsaturated. Moist potential vorticity can be generated through the combined effects of gradients in the potential temperature and moisture fields. The diagnosis of MPV generation in an extratropical cyclone was performed with the ECMWF objectively analyzed fields for a system that developed during February 1992. It was found that at various stages during the development of the cyclone, negative MPV was generated: at the north end of the cold front; along the occluded front and the cold front; and in the region of the warm core. This pattern of negative MPV generation is in excellent agreement with the predictions of previous theoretical and numerical studies. After the cyclone ceased to deepen, the region of negative MPV generated in the cyclone was horizontally advected into a saturated area. The area of negative MPV generated both along the occluded front in this case study and in the region of the bent-back warm front in a numerical simulation showed a mesoscale structure with a width of about 200-500 km. It was found that the intrusion of moist or dry air into baroclinic zones was important for MPV generation. In addition, baroclinicity increase (adjacent to the area of condensation) in the regions of high moisture gradients led to significant MPV production.展开更多
利用新疆自动站逐小时雨量资料和NCEP（1°×1°）再分析资料,从锋生作用和湿位涡特征出发,对2013年5月26～29日发生在南疆西部罕见暴雨的成因进行诊断分析。结果表明：（1）此次暴雨过程是中亚低涡影响造成的,高空西南急...利用新疆自动站逐小时雨量资料和NCEP（1°×1°）再分析资料,从锋生作用和湿位涡特征出发,对2013年5月26～29日发生在南疆西部罕见暴雨的成因进行诊断分析。结果表明：（1）此次暴雨过程是中亚低涡影响造成的,高空西南急流、低层偏东急流的耦合有利于次级环流的形成,对上升运动发展和水汽辐合抬升有重要作用;（2）降水出现在能量锋区上,暴雨中心位于等θse线密集且陡立的区域;（3）锋生函数与降水有很好的对应关系,锋生的强度和伸展高度与降水的强度及持续时间有非常明显的相关性;（4）暴雨发生在700 h Pa湿位涡零线附近等值线密集区,湿位涡＂上＋下-＂配置以及高湿位涡的下滑有利于对流发展和降水加强。展开更多
基金Open Foundation of the Key Laboratory on Ocean-Atmospheric Chemistry and Global Change from State Oceanological Administration(GCMAC0809)Natural Science Foundation of China(40775068)Development Planning for Key Foundamental Research of China(2010CB428504))
文摘First,based on routine meteorological data,the synoptic characteristics of a heavy warm-sector rainfall that occurred on June 13,2008 in the Pearl River Delta were analyzed.Second,a mesoscale numerical model,Weather Research and Forecasting(WRFV2.2),was used to simulate the heavy rainfall. Diagnostic analyses were done of moist potential vorticity(MPV)for its horizontal components(MPV2) and vertical components(MPV1)based on the simulation results of WRFV2.2 to identify the mechanism of the rainfall development.The results showed that the heavy rainfall occurred when there were high MPV1 in the upper levels and low MPV1 and high MPV2 in the lower levels.Disturbances of high MPV1 in the upper levels came from the southwest or northwest,those of low MPV1 in the lower levels came from the southwest,and those of high MPV2 came from the south.Disturbances of low MPV1 at low levels were the direct cause of convective instability.Enhanced vertical shear of meridional wind led to increased MPV2 at lower levels,strengthened baroclinicity,and active warm and wet flows.These distributions of MPV helped to trigger the release of unstable energy and produce warm-sector heavy rainfall.As it integrates the evolution of dynamic and thermal fields,MPV is able to reveal the development of this heavy rainfall effectively.
文摘In the light of the theory on moist potential vorticity (MPV) investigation was undertaken of the 700 hPa vertical (horizontal) component MP1 (MPV2) for the heavy rain event occurring in July 5–6, 1991. Results show that the distribution features of the two components were closely related to the development of a mesoscale cyclone as a rainstorm-causing weather system in the lower troposphere in such a way that the ambient atmosphere of which MPV1 > 0 and MPV2 < 0 with |MPV1| ≥ |MPV2| favored the genesis of conditional symmetric instability (CSI) and that, as indicated by calculations, a CSI sector was really existent in the lower troposphere during the heavy rain happening and contributed greatly to its development.
文摘Moist potential vorticity (MPV) and its generation may be important in the development of mesoscale structures such as rainbands within cyclones. In an adiabatic and frictionless flow, MPV generation is possible if the flow is three-dimensional and the air is unsaturated. Moist potential vorticity can be generated through the combined effects of gradients in the potential temperature and moisture fields. The diagnosis of MPV generation in an extratropical cyclone was performed with the ECMWF objectively analyzed fields for a system that developed during February 1992. It was found that at various stages during the development of the cyclone, negative MPV was generated: at the north end of the cold front; along the occluded front and the cold front; and in the region of the warm core. This pattern of negative MPV generation is in excellent agreement with the predictions of previous theoretical and numerical studies. After the cyclone ceased to deepen, the region of negative MPV generated in the cyclone was horizontally advected into a saturated area. The area of negative MPV generated both along the occluded front in this case study and in the region of the bent-back warm front in a numerical simulation showed a mesoscale structure with a width of about 200-500 km. It was found that the intrusion of moist or dry air into baroclinic zones was important for MPV generation. In addition, baroclinicity increase (adjacent to the area of condensation) in the regions of high moisture gradients led to significant MPV production.
文摘利用新疆自动站逐小时雨量资料和NCEP（1°×1°）再分析资料,从锋生作用和湿位涡特征出发,对2013年5月26～29日发生在南疆西部罕见暴雨的成因进行诊断分析。结果表明：（1）此次暴雨过程是中亚低涡影响造成的,高空西南急流、低层偏东急流的耦合有利于次级环流的形成,对上升运动发展和水汽辐合抬升有重要作用;（2）降水出现在能量锋区上,暴雨中心位于等θse线密集且陡立的区域;（3）锋生函数与降水有很好的对应关系,锋生的强度和伸展高度与降水的强度及持续时间有非常明显的相关性;（4）暴雨发生在700 h Pa湿位涡零线附近等值线密集区,湿位涡＂上＋下-＂配置以及高湿位涡的下滑有利于对流发展和降水加强。
