Because the real atmosphere is non-uniformly saturated, the generalized potential temperature is introduced. The convective vorticity vector, which can depict the occurrence and development of mesoscale deep convectiv...Because the real atmosphere is non-uniformly saturated, the generalized potential temperature is introduced. The convective vorticity vector, which can depict the occurrence and development of mesoscale deep convective systems, is modified and re-derived in a nonuniformly saturated moist atmosphere (C*). Then, a case study is performed for a frontal rainfall event which occurred near the middle and lower reaches of the Yangtze River in China. The diagnostic results of C* show that, in the lower troposphere, the vertical component of C* (Cz*) can diagnose developments and movements of precipitation and convection better than those of Cm (Cmz, in saturated moist flow) and C (Cz, in dry flow). Cz* is a good predictor for precipitation analyses as well.展开更多
A heavy rainfall process, which occurred in Shanghai during 5-6 August, 2001 from a landfalling tropical depression (TD),is examined with a control numerical experiment based on MM5 model. It is found that the contour...A heavy rainfall process, which occurred in Shanghai during 5-6 August, 2001 from a landfalling tropical depression (TD),is examined with a control numerical experiment based on MM5 model. It is found that the contours of generalized equivalent potential temperature (θ*) are almost vertical with respect to horizontal surfaces near the TD center and more densely distributed than those of equivalent potential temperature (θe).Because the atmosphere is non-uniformly saturated in reality, θ* takes the place of θe in the definition of convective vorticity vector (CVV) so that a new vector, namely the generalized convective vorticity vector (CVV*), is applied in this study. Since CVV* can reflect both the secondary circulation and the variation of horizontal moist baroclinicity, the vertical integration of vertical component of CVV* is found, in this study, to represent the rainfall areas in the TD case better than potential vorticity (PV), moist potential vorticity (MPV), generalized moist potential vorticity (Pm), and CVV, with high-value area of CVV* corresponding to heavy-rainfall area. Moreover, the analysis from CVV* implies that the Hangzhou Bay might play an important role in the heavy rain process. A sensitivity experiment without the Hangzhou Bay is then designed and compared with the control run. It is found that the CVV* becomes weaker than that in the control run, implying that the elimination of Hangzhou Bay results in reduced rainfall. Further analyses show that the Hangzhou Bay provides sufficient water vapor and surface heat flux to the TD system, which is very important to the genesis and development of mesoscale cloud clusters around the TD and the associated heavy rainfall.展开更多
The mei-yu front heavy rainstorms occurred over Nanjing on 3 5 and 8 9 July 2003 and were simulated in this paper using the Weather Research and Forecasting Model (WRFv3.1) with various mesoscale convection parameteri...The mei-yu front heavy rainstorms occurred over Nanjing on 3 5 and 8 9 July 2003 and were simulated in this paper using the Weather Research and Forecasting Model (WRFv3.1) with various mesoscale convection parameterization schemes (MCPSs). The simulations show that the temporal and spatial evolution and distribution of rainstorms can be modeled; however, there was incongruity between the comparative simulations of four different MCPSs and the observed data. These disparities were exhibited in the simulations of both the 24-hour surface rainfall total and the hourly precipitation rate. Further analysis revealed that the discrepancies of vertical velocity and the convective vorticity vector (CVV) between the four simulations were attributed to the deviation of rainfall values. In addition, the simulations show that the mid-scale convection, particularly the mesoscale convection system (MCS) formation, can be well simulated with the proper mesoscale convection parameterization schemes and may be a crucial factor of the mei-yu front heavy rainstorm. These results suggest that, in an effort to enhance simulation and prediction of heavy rainfall and rainstorms, subsequent studies should focus on the development and improvement of MCPS.展开更多
Potential vorticity (PV) has been served as a powerful and useful dynamic tracer for the understanding of the large-scale dynamics and synoptic variations in the atmosphere and oceans.Significant progress has been mad...Potential vorticity (PV) has been served as a powerful and useful dynamic tracer for the understanding of the large-scale dynamics and synoptic variations in the atmosphere and oceans.Significant progress has been made on the application of PV.In recent decades there has been a substantial amount of work done on PV in a gen-eral moist atmosphere.In this paper PV and the general-ized moist potential vorticity (GMPV) and their applica-tion in the tropical cyclones and mesoscale meteorologi-cal field are reviewed.The GMPV is derived for a real atmosphere (neither totally dry nor saturated) by intro-ducing a generalized potential temperature instead of the potential temperature or equivalent potential temperature.Such a generalization can depict the moist effect on PV anomaly in the non-uniformly saturated atmosphere.A new convective vorticity vector (CVV) is introduced in connection with GMPV in order to diagnose the devel-opment of tropical deep convections.展开更多
This paper introduces a new physical parameter -- thermodynamic shear advection parameter combining the perturbation vertical component of convective vorticity vector with the coupling of horizontal divergence perturb...This paper introduces a new physical parameter -- thermodynamic shear advection parameter combining the perturbation vertical component of convective vorticity vector with the coupling of horizontal divergence perturbation and vertical gradient of general potential temperature perturbation. For a heavy-rainfall event resulting from the landfall typhoon ＇Wipha＇, the parameter is calculated by using National Centres for Enviromental Prediction/National Centre for Atmospheric Research global final analysis data. The results showed that the parameter corresponds to the observed 6 h accumulative rainband since it is capable of catching hold of the dynamic and thermodynamic disturbance in the lower troposphere over the observed rainband. Before the typhoon landed, the advection of the parameter by basic-state flow and the coupling of general potential temperature perturbation with curl of Coriolis force perturbation are the primary dynamic processes which are responsible for the local change of the parameter. After the typhoon landed, the disturbance is mainly driven by the combination of five primary dynamic processes. The advection of the parameter by basic-state flow was weakened after the typhoon landed.展开更多
In this paper we introduce the convective vorticity vector and its application in the forecast and diagnosis of rainstorm.Convective vorticity vector is a parameter of vector field,different from scalar field,it conta...In this paper we introduce the convective vorticity vector and its application in the forecast and diagnosis of rainstorm.Convective vorticity vector is a parameter of vector field,different from scalar field,it contains more important information of physical quantities,so it could not be replaced.Considering the irresistible importance of vector field we will introduce the theory of vector field and its dynamic forecast method.With the convective vorticity vector and its vertical component's tendency equation,diagnostic analysis on the heavy-rainfall event caused by landfall typhoon“Morakot”in the year 2009 is conducted.The result shows that,the abnormal values of convective vorticity vector always changes with the development of the observed precipitation region,and their horizontal distribution is quite similar.Analysis reveals a certain correspondence between the convective vorticity vector and the observed 6-h accumulated surface rainfall,they are significantly related.The convective vorticity vector is capable of describing the typical vertical structure of dynamical and thermodynamic fields of precipitation system,so it is closely related to the occurrence and development of precipitation system and could have certain relation with the surface rainfall regions.展开更多
By using WRF mesoscale model, this paper carries out a numerical simulation and diagnostic analysis of the structural characteristics of the asymmetric spiral rain bands around the landing of Typhoon Haitang during th...By using WRF mesoscale model, this paper carries out a numerical simulation and diagnostic analysis of the structural characteristics of the asymmetric spiral rain bands around the landing of Typhoon Haitang during the period of July 19 to 20, 2005. The result indicated that the two rainbands associated with the precipitation centre was mainly located northeast of the typhoon centre. The movement and intensity of the southern rainband corresponded well with the 850-hPa positive vorticity band from 0200 to 1800 UTC July 19, 2005. Under the effect of cyclonic circulation, the positive vorticity band at 850 hPa connected with a southern rain band, leading to the intensification of rainfall in the southern centre of the precipitation. The southward rainband gradually moved toward and then merges with the northward one, strengthening the rainfall in the northern centre of the precipitation. Besides, the relationship between the heavy rainfall and the divergence field of vertical shear wind in the high altitude is analyzed. Finally, the relationship is revealed between the development of the vertical component of convective vorticity vector and the rainfall near the two centres of precipitation in the low altitude.展开更多
基金supported by the National Natural Science Foundation of China under grant Nos. 40805001 and 40433016
文摘Because the real atmosphere is non-uniformly saturated, the generalized potential temperature is introduced. The convective vorticity vector, which can depict the occurrence and development of mesoscale deep convective systems, is modified and re-derived in a nonuniformly saturated moist atmosphere (C*). Then, a case study is performed for a frontal rainfall event which occurred near the middle and lower reaches of the Yangtze River in China. The diagnostic results of C* show that, in the lower troposphere, the vertical component of C* (Cz*) can diagnose developments and movements of precipitation and convection better than those of Cm (Cmz, in saturated moist flow) and C (Cz, in dry flow). Cz* is a good predictor for precipitation analyses as well.
基金The State 973 Program (2009CB421505)National Natural Sciences Foundation of China (40921160381,40875039,40905020,41005033,40905029)+2 种基金Projects for Public Welfare (Meteorology) of China (GYHY200906002,GYHY201006008)Shanghai Meteorological Bureau (MS201202)Fund for Graduate Renovative Education of Jiangsu Province
文摘A heavy rainfall process, which occurred in Shanghai during 5-6 August, 2001 from a landfalling tropical depression (TD),is examined with a control numerical experiment based on MM5 model. It is found that the contours of generalized equivalent potential temperature (θ*) are almost vertical with respect to horizontal surfaces near the TD center and more densely distributed than those of equivalent potential temperature (θe).Because the atmosphere is non-uniformly saturated in reality, θ* takes the place of θe in the definition of convective vorticity vector (CVV) so that a new vector, namely the generalized convective vorticity vector (CVV*), is applied in this study. Since CVV* can reflect both the secondary circulation and the variation of horizontal moist baroclinicity, the vertical integration of vertical component of CVV* is found, in this study, to represent the rainfall areas in the TD case better than potential vorticity (PV), moist potential vorticity (MPV), generalized moist potential vorticity (Pm), and CVV, with high-value area of CVV* corresponding to heavy-rainfall area. Moreover, the analysis from CVV* implies that the Hangzhou Bay might play an important role in the heavy rain process. A sensitivity experiment without the Hangzhou Bay is then designed and compared with the control run. It is found that the CVV* becomes weaker than that in the control run, implying that the elimination of Hangzhou Bay results in reduced rainfall. Further analyses show that the Hangzhou Bay provides sufficient water vapor and surface heat flux to the TD system, which is very important to the genesis and development of mesoscale cloud clusters around the TD and the associated heavy rainfall.
基金supported jointly by the Projects of Jiangsu Key Lab of Meteorological Disaster (Grant No. Klme060207)the National Natural Science Foundation of China (Grant No. 40875031)
文摘The mei-yu front heavy rainstorms occurred over Nanjing on 3 5 and 8 9 July 2003 and were simulated in this paper using the Weather Research and Forecasting Model (WRFv3.1) with various mesoscale convection parameterization schemes (MCPSs). The simulations show that the temporal and spatial evolution and distribution of rainstorms can be modeled; however, there was incongruity between the comparative simulations of four different MCPSs and the observed data. These disparities were exhibited in the simulations of both the 24-hour surface rainfall total and the hourly precipitation rate. Further analysis revealed that the discrepancies of vertical velocity and the convective vorticity vector (CVV) between the four simulations were attributed to the deviation of rainfall values. In addition, the simulations show that the mid-scale convection, particularly the mesoscale convection system (MCS) formation, can be well simulated with the proper mesoscale convection parameterization schemes and may be a crucial factor of the mei-yu front heavy rainstorm. These results suggest that, in an effort to enhance simulation and prediction of heavy rainfall and rainstorms, subsequent studies should focus on the development and improvement of MCPS.
文摘Potential vorticity (PV) has been served as a powerful and useful dynamic tracer for the understanding of the large-scale dynamics and synoptic variations in the atmosphere and oceans.Significant progress has been made on the application of PV.In recent decades there has been a substantial amount of work done on PV in a gen-eral moist atmosphere.In this paper PV and the general-ized moist potential vorticity (GMPV) and their applica-tion in the tropical cyclones and mesoscale meteorologi-cal field are reviewed.The GMPV is derived for a real atmosphere (neither totally dry nor saturated) by intro-ducing a generalized potential temperature instead of the potential temperature or equivalent potential temperature.Such a generalization can depict the moist effect on PV anomaly in the non-uniformly saturated atmosphere.A new convective vorticity vector (CVV) is introduced in connection with GMPV in order to diagnose the devel-opment of tropical deep convections.
基金supported by the National Basic Research Program of China (Grant No. 2009CB421505)the Main Direction Program of Knowledge Innovation of Chinese Academy of Sciences (KZCX2-YW-206-4)+2 种基金the National Natural Science Foundation of China(Grant Nos. 40875032 and 40875002)the Major Foreland Project of IAP (IAP07201)the National Science and Technology Project,China (GYH200706042)
文摘This paper introduces a new physical parameter -- thermodynamic shear advection parameter combining the perturbation vertical component of convective vorticity vector with the coupling of horizontal divergence perturbation and vertical gradient of general potential temperature perturbation. For a heavy-rainfall event resulting from the landfall typhoon ＇Wipha＇, the parameter is calculated by using National Centres for Enviromental Prediction/National Centre for Atmospheric Research global final analysis data. The results showed that the parameter corresponds to the observed 6 h accumulative rainband since it is capable of catching hold of the dynamic and thermodynamic disturbance in the lower troposphere over the observed rainband. Before the typhoon landed, the advection of the parameter by basic-state flow and the coupling of general potential temperature perturbation with curl of Coriolis force perturbation are the primary dynamic processes which are responsible for the local change of the parameter. After the typhoon landed, the disturbance is mainly driven by the combination of five primary dynamic processes. The advection of the parameter by basic-state flow was weakened after the typhoon landed.
基金supported by the Key Project of National Natural Science Foundation of China(41930972)the key special projects plan in key areas of Guangdong Province(2019B111101002)+2 种基金National Natural Sciences General Foundations of China(Grant Nos.41875056)China Meteorological Administration forecaster project(cmayby2019-143)the National Natural Science Foundation of China of China(Grant Nos.41405049).
文摘In this paper we introduce the convective vorticity vector and its application in the forecast and diagnosis of rainstorm.Convective vorticity vector is a parameter of vector field,different from scalar field,it contains more important information of physical quantities,so it could not be replaced.Considering the irresistible importance of vector field we will introduce the theory of vector field and its dynamic forecast method.With the convective vorticity vector and its vertical component's tendency equation,diagnostic analysis on the heavy-rainfall event caused by landfall typhoon“Morakot”in the year 2009 is conducted.The result shows that,the abnormal values of convective vorticity vector always changes with the development of the observed precipitation region,and their horizontal distribution is quite similar.Analysis reveals a certain correspondence between the convective vorticity vector and the observed 6-h accumulated surface rainfall,they are significantly related.The convective vorticity vector is capable of describing the typical vertical structure of dynamical and thermodynamic fields of precipitation system,so it is closely related to the occurrence and development of precipitation system and could have certain relation with the surface rainfall regions.
基金National Program on Basic Research Project (973 Program) (2009CB421503)National Natural Science Foundation of China (40775033)National Natural Science Foundation of China (40975037)
文摘By using WRF mesoscale model, this paper carries out a numerical simulation and diagnostic analysis of the structural characteristics of the asymmetric spiral rain bands around the landing of Typhoon Haitang during the period of July 19 to 20, 2005. The result indicated that the two rainbands associated with the precipitation centre was mainly located northeast of the typhoon centre. The movement and intensity of the southern rainband corresponded well with the 850-hPa positive vorticity band from 0200 to 1800 UTC July 19, 2005. Under the effect of cyclonic circulation, the positive vorticity band at 850 hPa connected with a southern rain band, leading to the intensification of rainfall in the southern centre of the precipitation. The southward rainband gradually moved toward and then merges with the northward one, strengthening the rainfall in the northern centre of the precipitation. Besides, the relationship between the heavy rainfall and the divergence field of vertical shear wind in the high altitude is analyzed. Finally, the relationship is revealed between the development of the vertical component of convective vorticity vector and the rainfall near the two centres of precipitation in the low altitude.
