干侵入强度指数的表征及其物理意义  

Dry Intrusion Index and Its Physical Interpretation

作　　者：姚秀萍[1,2,3] 彭广[4] 于玉斌[3] 

机构地区：[1]中国气象局武汉暴雨研究所,湖北武汉430074 [2]中国气象科学研究院灾害天气国家重点实验室,北京100081 [3]中国气象局培训中心,北京100081 [4]河南省气象局,河南郑州450003

出　　处：《高原气象》2009年第3期507-515,共9页Plateau Meteorology

基　　金：武汉暴雨开放基金项目(IHR2005K04);中国气象科学研究院灾害天气国家重点实验室开放课题(2008LASW-B06);国家自然科学基金项目(40875030)共同资助

摘　　要：综合考虑干侵入的特征、机制和效应,定义了干侵入强度指数(DII)以表征干侵入的强度,并从一个个例进一步揭示干侵入强度指数的物理意义。结果表明,DII是干侵入强度较好的定量描述指标,它与水平温度平流、位涡、假相当位温相关,正的DII表明存在干侵入过程,随着DII的增大,干侵入效应增强,此时可能高位涡异常越强、湿球位温越低、冷平流效应越强;345K等熵面上DII>1PVU/s的正值区与水汽图像暗区较为一致,DII在三维结构上表现为高层波状下传的特征,在任一特定的等熵面上,低涡西北方向的中高纬度地区是DII正值区的源地;DII体现了水平温度平流效应,低涡降水区西侧为冷平流,东侧为暖平流,冷暖平流一直贯穿于对流层整层,冷平流在西北气流引导下沿等熵面下滑,在冷暖平流交汇处出现降水,随着水平温度平流梯度的增大,对应的降水增强。在实际天气预报业务工作中,DII可用以界定干侵入区域、过程以及强度,具有一定实际业务应用价值。Based on the characteristics, mechanisms and impacts of the dry intrusion, a dry intrusion index （DII） is defined to characterize the dry intrusion intensity and its physical interpretation is explored by a case study as well. It is found that DII is related to the horizontal temperature advection, the potential vorticity and pseudo-equivalent potential temperature. The positive DII indicates that there exists the dry intrusion process. And the greater the positive DII is, the stronger the dry intrusion exists. Thus, this situation maybe correspond to stronger potential vorticity anomaly, the lower wet-bulb temperature or stronger cold horizontal temperature advection. There exists a good agreement between the positive DII area at the 345K isentropic surface and the dry intrusion illustrated by ＂dark zone＂ from the water vapor cloud images. The three dimension structure of DII is characterized by a wave disturbance from the upper troposphere to the lower one. The positive DII area originates from the mid-high latitude to the northwest of the low vortex on a certain isentropic surface. DII contains the horizontal temperature advection effect. The cold temperature advection locates to the west of the low vortex while the warm temperature advection locates to the east of the low vortex. The cold temperature advection led by the northwesterlies descends a- long the isentropic surface. The formation and enhancement of the heavy rainfall situates the area of the maximum gradient of the horizontal temperature advection while the cold temperature advection meets with the warm temperature advection. DII can be used to identify the area, the process and the intensity of the dry intrusion in the field of weather forecast operation which processes the application value in practically.

关 键 词：干侵入指数 物理意义 定量分析 冷平流效应 

分 类 号：P458.121.1[天文地球—大气科学及气象学]