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
Considering the non-uniform saturation of the real atmosphere,a diagnostic study of a torrential rain event is performed from the perspective of the anomaly of the generalized moist potential vorticity（GMPV） after i...Considering the non-uniform saturation of the real atmosphere,a diagnostic study of a torrential rain event is performed from the perspective of the anomaly of the generalized moist potential vorticity（GMPV） after introducing the generalized potential temperature into the thermodynamic frame of the real atmosphere. The results show that the anomaly appeared at mid-lower levels of the troposphere when the torrential rain happened.Analysis of the magnitudes and locations of maximum values of the tendency of the GMPV indicates that the anomaly of the GMPV was closely related to the occurrence of torrential rain. Therefore,the GMPV could be used to forecast and diagnose the occurrence of torrential rain in operational application.展开更多
The circulation, hygrothermal property and moisture transport character of typical hot and humid weather were analyzed in Beijing areas from July 30 to August 4, 2002. It was pointed out that, under the control of sub...The circulation, hygrothermal property and moisture transport character of typical hot and humid weather were analyzed in Beijing areas from July 30 to August 4, 2002. It was pointed out that, under the control of subtropical anticyclone which stretches to the west and north, downdraft suppresses the lifting of lower-troposphere moisture, which makes moisture keep in the lower troposphere. That is the direct reason causing hot and humid weather. Considering the non-uniformity saturated character in real atmosphere, generalized moist potential vorticity (GMPV) equation is derived by the introduction of generalized moist potential temperature concept. The analysis of GMPV shows that negative GMPV anomaly occurs in the lower troposphere. It has indicative sense to hot and humid weather. Thus, the GMPV anomaly can be utilized to identify this kind of weather and to make a short-term prediction.展开更多
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.
基金Supported by the Wuhan Institute of Heavy Rain(IHR2006K01)the China Meteorological Administration Special Research Project(GYHY200706020)
文摘Considering the non-uniform saturation of the real atmosphere,a diagnostic study of a torrential rain event is performed from the perspective of the anomaly of the generalized moist potential vorticity（GMPV） after introducing the generalized potential temperature into the thermodynamic frame of the real atmosphere. The results show that the anomaly appeared at mid-lower levels of the troposphere when the torrential rain happened.Analysis of the magnitudes and locations of maximum values of the tendency of the GMPV indicates that the anomaly of the GMPV was closely related to the occurrence of torrential rain. Therefore,the GMPV could be used to forecast and diagnose the occurrence of torrential rain in operational application.
基金This work was supported by the National Key Basic Research and Development Project of China(Grant No.TG1999045700)International Key Cooperation Sciences and Technology Project(Grant No.2004DFA06100)+1 种基金the Olympic Project of Chinese Academy Sciceces(Grant No.KACX1-02)projects of the National Natural Science Foundation of China(Grant Nos.40505009 and 40405007).
文摘The circulation, hygrothermal property and moisture transport character of typical hot and humid weather were analyzed in Beijing areas from July 30 to August 4, 2002. It was pointed out that, under the control of subtropical anticyclone which stretches to the west and north, downdraft suppresses the lifting of lower-troposphere moisture, which makes moisture keep in the lower troposphere. That is the direct reason causing hot and humid weather. Considering the non-uniformity saturated character in real atmosphere, generalized moist potential vorticity (GMPV) equation is derived by the introduction of generalized moist potential temperature concept. The analysis of GMPV shows that negative GMPV anomaly occurs in the lower troposphere. It has indicative sense to hot and humid weather. Thus, the GMPV anomaly can be utilized to identify this kind of weather and to make a short-term prediction.
