Based on prior investigation,this work defined a new thermodynamic shear advection parameter,which combines the vertical component of convective vorticity vector,horizontal divergence,and vertical gradient of generali...Based on prior investigation,this work defined a new thermodynamic shear advection parameter,which combines the vertical component of convective vorticity vector,horizontal divergence,and vertical gradient of generalized potential temperature.The interaction between waves and fundamental states was computed for the heavyrainfall event generated by landfalling typhoon“Morakot”.The analysis data was produced by ADAS[ARPS(Advanced Regional Prediction System)Data Analysis System]combined with the NCEP/NCAR final analysis data(1°×1°,26 vertical pressure levels and 6-hour interval)with the routine observations of surface and sounding.Because it may describe the typical vertical structure of dynamical and thermodynamic fields,the result indicates that the parameter is intimately related to precipitation systems.The parameter’s positive high-value area closely matches the reported 6-hour accumulated surface rainfall.And the statistical analysis reveals a certain correspondence between the thermodynamic shear advection parameter and the observed 6-hour accumulated surface rainfall in the summer of 2009.This implies that the parameter can predict and indicate the rainfall area,as well as the initiation and evolution of precipitation systems.展开更多
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 ...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.展开更多
基金National Key R&D Program of China(2017YFC1501604)Key Laboratory of South China Sea Meteorological Disaster Prevention and Mitigation of Hainan Province(SCSF202101)+1 种基金Open Grants of the State Key Laboratory of Severe Weather(2022LASW-B09)National Natural Science Foundation of China(41405049)。
文摘Based on prior investigation,this work defined a new thermodynamic shear advection parameter,which combines the vertical component of convective vorticity vector,horizontal divergence,and vertical gradient of generalized potential temperature.The interaction between waves and fundamental states was computed for the heavyrainfall event generated by landfalling typhoon“Morakot”.The analysis data was produced by ADAS[ARPS(Advanced Regional Prediction System)Data Analysis System]combined with the NCEP/NCAR final analysis data(1°×1°,26 vertical pressure levels and 6-hour interval)with the routine observations of surface and sounding.Because it may describe the typical vertical structure of dynamical and thermodynamic fields,the result indicates that the parameter is intimately related to precipitation systems.The parameter’s positive high-value area closely matches the reported 6-hour accumulated surface rainfall.And the statistical analysis reveals a certain correspondence between the thermodynamic shear advection parameter and the observed 6-hour accumulated surface rainfall in the summer of 2009.This implies that the parameter can predict and indicate the rainfall area,as well as the initiation and evolution of precipitation systems.
基金Supported by Wuhan Institute of Heavy Rain,China Meteorological Administration,under Grant No.IHR2008K03the Scientific Research Fund of Nanjing University of Iuformation Science & Technology.
文摘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.
