关于虚温订正CAPE求算方法的讨论  

Discussion About the Method of CAPE Calculation with Virtual Temperature Correction

作　　者：章丽娜[1] 朱禾[1] 周小刚[1] 

机构地区：[1]中国气象局气象干部培训学院,北京100081

出　　处：《气象》2016年第8期1007-1012,共6页Meteorological Monthly

基　　金：国家自然科学基金项目(41475042);中国气象局预报员专项(CMAYBY2015-096);南京信息工程大学气象灾害教育部重点实验室开放课题基金(KLME1311)共同资助

摘　　要：对流有效位能(CAPE)是强对流天气分析和预报中的重要参数,准确的CAPE计算应该采用虚温订正。目前MICAPS和GRADS两种常用软件计算经过虚温订正的CAPE时,积分起点采用的都是订正前的自由对流高度(LFC),即LFC是气块温度与环境温度之差由负值转为正值的转折点的高度。本文理论分析表明,虚温订正后环境的层结曲线和气块的状态曲线都将发生变化。作为求算虚温订正CAPE时的积分起点、环境虚温和气块虚温曲线的交点——LFC也有相应变化,且虚温订正后LFC通常是降低的。虚温订正后的LFC若仍采用订正前的高度,显然与LFC的定义相悖。实际分析示例表明,LFC变化对CAPE数值大小的贡献或许是不明显的,但是它在图形上的表示更加合理,物理意义更加清晰。Convective available potential energy（CAPE） is an important parameter in severe weather analysis and forecasting.The virtual temperature correction should be used in accurate CAPE calculation.MICAPS and GRADS both choose previous values of level of free convection（LFC） as the integral starting points in CAPE calculation when using virtual temperature corrections.LFC is defined as the altitude in the atmosphere where the temperature difference between air parcel and the environment turns from negative to positive.Using the same altitude of LFC in CAPE calculation with virtual temperature correction,is obviously contrary to the definition of LFC.Theoretical analysis in this paper indicates that LFC changes in CAPE calculation with virtual temperature correction,since two temperature profiles of air parcel and the environment change after correction,and their crossing point（LFC） also changes.The altitude of LFC is usually decreased using virtual temperature correction.Case study shows that although the CAPE increment is not so obvious when using the revised LFC in CAPE calculation with virtual temperature correction,it will be more reasonable in graphical representation and more precise for its physical meaning when considering the variation of LFC.

关 键 词：对流有效位能(CAPE) 虚温订正 自由对流高度(LFC) 

分 类 号：P401[天文地球—大气物理学与大气环境] P458[天文地球—大气科学及气象学]