摘要
To better describe the stability of a moist atmosphere,a new Richardson number,the Richardson number in a non-uniformly saturated moist atmosphere（Ri^＊）,is defined in this paper.Ri^＊ is the same as the Richardson number（Ri） except that the generalized potential temperature introduced by Gao et al.in 2004 is used to calculate the Brunt-Vaisala frequency.Then,with outputs from simulations of two heavy rainfall events,Ri^＊ is applied to diagnosing instabilities of rainfall areas.The results show that convective instability is concentrated in the lower troposphere while instability determined by Ri^＊1 is mainly located in the middle and upper troposphere above the rainfall areas.The Ri^＊ is more appropriate than the Richardson number in a dry or uniformly saturated moist atmosphere for describing instability of rainfall areas.Moreover,in the two cases here,instability represented by Ri^＊ emerged a few hours prior to the rainfall occurrence,suggesting that Ri^＊ may be used to indicate the occurrence of rainfall.Thus,Ri^＊ could be a helpful index in estimating rainfall occurrence and development.
To better describe the stability of a moist atmosphere,a new Richardson number,the Richardson number in a non-uniformly saturated moist atmosphere（Ri^＊）,is defined in this paper.Ri^＊ is the same as the Richardson number（Ri） except that the generalized potential temperature introduced by Gao et al.in 2004 is used to calculate the Brunt-Vaisala frequency.Then,with outputs from simulations of two heavy rainfall events,Ri^＊ is applied to diagnosing instabilities of rainfall areas.The results show that convective instability is concentrated in the lower troposphere while instability determined by Ri^＊1 is mainly located in the middle and upper troposphere above the rainfall areas.The Ri^＊ is more appropriate than the Richardson number in a dry or uniformly saturated moist atmosphere for describing instability of rainfall areas.Moreover,in the two cases here,instability represented by Ri^＊ emerged a few hours prior to the rainfall occurrence,suggesting that Ri^＊ may be used to indicate the occurrence of rainfall.Thus,Ri^＊ could be a helpful index in estimating rainfall occurrence and development.
基金
Supported by Wuhan Institute of Heavy Rain,China Meteorological Administration,under Grant No.IHR2008K03
the Scientific Research Fund of Nanjing University of Iuformation Science & Technology.
