卫星水汽图像和位势涡度场在一次变性台风暴雨过程中的解译应用

Application of satellite water vapor imagery and potential vorticity analysis on a neutercane-related torrential rain

利用FY-2E卫星水汽图像、常规气象观测资料和ERA-Interim再分析资料,将高层动力场和水汽图像结合,对山东半岛一次台风和冷空气相关的大暴雨过程进行了解译分析。结果表明:台风北上过程中,槽后冷空气入侵台风环流,涡旋云系与斜压叶状云相结合,低层出现锋生。在卫星水汽图像上,台风的非对称结构表现为涡旋北侧加强的湿上升运动和南侧入侵的干闯入,具有高位涡特征的水汽暗区是活跃的动力干带。高空急流带位于短波槽前叶状云向极一侧边界附近的湿上升区一侧,急流的增强与水汽图像上明暗边界的锐化有关,暴雨区位于动力干带前方的湿上升区和高空急流入口区的右侧。强降水发生时,动力干带引起的高层位涡扰动造成正涡度柱的强烈下伸,与台风主体环流的正涡度柱在暴雨区上空形成相互贯通的涡旋系统。位涡异常区前侧的上升运动与台风环流本身的上升运动叠加,有利于加强对流层暖湿气流的抬升。卫星水汽图像体现了高层天气尺度动力强迫的特征,指示重要动力过程的发展。将卫星水汽图像和高层位涡场结合进行解译,有助于从水汽图像上判别高空动力特征的演变,为台风暴雨监测提供参考信息。

Using the water vapor imagery, conventional meteorological observations and ERA-Interim reanalysis data, a torrential rain event related to typhoon and the cold air in Shandong Peninsula was studied by analyzing the water vapor imagery and dynamical fields. Results reveal that as the typhoon moving northward, the cold air of the westerly trough intrudes the typhoon circulation,the vortex cloud system combines with the baroclinic leaf-shaped cloud, and it results in a frontogenesis at lower level. The water vapor imagery shows that the asymmetric structure of typhoon is characterized by a moist ascent in the north and dry intrusion in the south of the vortex system. The dark areas with high potential vorticity in the water vapor imagery indicate the active dynamic dry bands. The axis of maximum winds is near the poleward side of the leaf boundary and along the moist side. The strengthening of the upper-level jet is associated with the sharpening of the dark/light boundary. The heavy rain area lies in rear of the jet on the right and moist ascent area ahead of the dynamic dry band. During the heavy rain process, the disturbance of upper-level PV （Positive Vorticity） caused by the dynamic dry bands results in the stretching downward of cyclonic vorticity. The column of cyclonic vorticity associated with the dynamic dry band couples with the positive vorticity column of typhoon and forms a vortex system over the area of torrential rain. The combination of ascending motion ahead of the PV anomaly and ascending motion of the typhoon circulation could have been a fa- vorable factor to the strengthening of the moist ascending motion in the troposphere. The water vapor imagery reflects the synoptic scale forcing in the upper-level and indicates the development of important dynamical processes. A joint interpretation of water vapor imagery and upper-level potential vorticity fields can potentially provide dynamical insight into the imagery interpretation, thus provide valuable information for operational monitoring of neu- tercane-related torrential rain.