Compared to potential temperature （θ） in the dry atmosphere and equivalent potential temperature （θc） in the saturated atmosphere, generalized potential tem- perature （θ＂） has already proven a better thermod...Compared to potential temperature （θ） in the dry atmosphere and equivalent potential temperature （θc） in the saturated atmosphere, generalized potential tem- perature （θ＂） has already proven a better thermodynamic parameter in describing the non-uniformly saturated real atmosphere. To add otherwise absent graphic explanations, this paper first presents the physical definition of θ through a tephigram. Then, the utility of the measurement in identifying and forecasting the locations of precipita- tion maxima and heat wave areas with diagnostic com- parison studies and traditionally used thermodynamic parameters is shown.展开更多
The enhanced mountain-to-plain convective storms in Beijing on 22 May 2021 were simulated using the highresolution Weather Research and Forecasting model,enabling detailed analyses of convective instability characteri...The enhanced mountain-to-plain convective storms in Beijing on 22 May 2021 were simulated using the highresolution Weather Research and Forecasting model,enabling detailed analyses of convective instability characteristics and underlying causes of stability variations.Generalized potential temperature outperformed traditional potential temperature and equivalent potential temperature in capturing instability variations associated with mid-level latent heating and near-surface evaporative cooling.Local instability variance was primarily governed by potential divergence and the advection of potential instability,with these factors exhibiting out-of-phase distributions.Prior to the onset of heavy precipitation,intense downdrafts transported unstable air from higher levels into more stable regions at lower levels,increasing local near-surface instability,which contributed to the formation of heavy precipitation.During the heavy precipitation stage,vertical divergence between slantwise updrafts and downdrafts in the lowmiddle stable layers led to destabilization,supporting sustained convective development within the precipitation area.At the leading edge of the heavy precipitation,instability enhancement was primarily driven by vertical advection,and less stable air in the lower levels was transported upward,enhancing instability at higher levels.展开更多
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supported by the National Basic Research Program of China (2009CB421505)the National Natural Science Foundation of China (41075044 and 41075079)
文摘Compared to potential temperature （θ） in the dry atmosphere and equivalent potential temperature （θc） in the saturated atmosphere, generalized potential tem- perature （θ＂） has already proven a better thermodynamic parameter in describing the non-uniformly saturated real atmosphere. To add otherwise absent graphic explanations, this paper first presents the physical definition of θ through a tephigram. Then, the utility of the measurement in identifying and forecasting the locations of precipita- tion maxima and heat wave areas with diagnostic com- parison studies and traditionally used thermodynamic parameters is shown.
基金funded by the Beijing Municipal Science and Technology Commission [grant number Z221100005222012]the Department of Science and Technology of Hebei Province [grant number 22375404D]+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences [grant number XDB0760303]the National Natural Science Foundation of China [grant numbers U2233218 and 42275010]the Open Foundation of the Key Open Laboratory of Urban Meteorology,China Meteorological Administration [grant number LUM-2023-06]。
文摘The enhanced mountain-to-plain convective storms in Beijing on 22 May 2021 were simulated using the highresolution Weather Research and Forecasting model,enabling detailed analyses of convective instability characteristics and underlying causes of stability variations.Generalized potential temperature outperformed traditional potential temperature and equivalent potential temperature in capturing instability variations associated with mid-level latent heating and near-surface evaporative cooling.Local instability variance was primarily governed by potential divergence and the advection of potential instability,with these factors exhibiting out-of-phase distributions.Prior to the onset of heavy precipitation,intense downdrafts transported unstable air from higher levels into more stable regions at lower levels,increasing local near-surface instability,which contributed to the formation of heavy precipitation.During the heavy precipitation stage,vertical divergence between slantwise updrafts and downdrafts in the lowmiddle stable layers led to destabilization,supporting sustained convective development within the precipitation area.At the leading edge of the heavy precipitation,instability enhancement was primarily driven by vertical advection,and less stable air in the lower levels was transported upward,enhancing instability at higher levels.
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.
