With the Reisner-2 bulk microphysical parameterization of the fifth-generation Pennsylvania State University-U.S. National Center for Atmospheric Research （PSU--NCAR） Mesoscale Model （MM5）, this paper investigates...With the Reisner-2 bulk microphysical parameterization of the fifth-generation Pennsylvania State University-U.S. National Center for Atmospheric Research （PSU--NCAR） Mesoscale Model （MM5）, this paper investigates the microphysical sensitivities of Typhoon Chanchu. Four different microphysical sensitivity experiments were designed with an objective to evaluate their respective impacts in modulating intensity forecasts and microphysics budgets of the typhoon. The set of sensitivity experiments were conducted that comprised （a） a control experiment （CTL）, （b） NEVPRW from which evaporation of rain water was suppressed, （c） NGP from which graupel was taken, and （d） NMLT from which melting of snow and graupel was removed. We studied the impacts of different cloud microphysical processes on the track, intensity and precipitation of the typhoon, as well as the kinematics, thermodynamics and vertical structural characteristics of hydrometeors in the inner core of the typhoon. Additionally, the budgets of the cloud microphysical processes in the fine domain were calculated to quantify the importance of each microphysical process for every sensitivity experiment. The primary results are as follows： （1） It is found that varying cloud microphysics parameters produce little sensitivity in typhoon track experiments. （2） The experiment of NGP produces the weakest storm, while the experiment of NMLT produces the strongest storm, and the experiment of NEVPRW also produces stronger storms than CTL. （3） Varying parameters of cloud rnicrophysics have obvious impacts on the precipitation, kinematics, and thermodynamics of the typhoon and the vertical structural characteristics of hydrometeors in the typhoon＇s inner core. （4） Most budgets of cloud microphysics in NMLT are larger than in CTL, while they are 20%-60% smaller in NEVPRW than in CTL.展开更多
Observational data of mesoscale surface weather stations and weather radars of Guangdong province are employed to analyze the asymmetric distribution of convection prior to, during and after landfall for tropical cycl...Observational data of mesoscale surface weather stations and weather radars of Guangdong province are employed to analyze the asymmetric distribution of convection prior to, during and after landfall for tropical cyclones of Chanchu and Prapiroon making landfall on the south China coast in 2006. The results showed that strong convection is located in the eastern and northern sectors of the landfalling Chanchu and Prapiroon, namely in the front and right portions of the TC tracks, for a period of time starting from 12 h prior to landfall to 6 h after it. Their convection also had distinct differences in the vertical direction. The analysis indicated that although the landfall of Chanchu and Prapiroon has the same asymmetric distribution of convection, the causes are not exactly the same. The asymmetric distribution of convection in the case of Chanchu is mainly correlated with the impacts of a strong environmental vertical wind shear, low-level horizontal wind shear, and low-level convergence and divergence. In the case of Prapiroon, however, the asymmetric distribution of convection is mainly associated with the impacts of low-level convergence and divergence.展开更多
With Doppler radar data from Shantou and Xiamen and the National Centers for Environmental Prediction and the National Center for Atmospheric Research （NCEP/NCAR） reanalysis data, the characteristics of a short-term...With Doppler radar data from Shantou and Xiamen and the National Centers for Environmental Prediction and the National Center for Atmospheric Research （NCEP/NCAR） reanalysis data, the characteristics of a short-term heavy rainstorm on 17 May 2006 caused by Typhoon Chanchu are studied. Doppler radar data indicates that during the period from 1800 to 1900 May 17, the azimuthal phases of the positive and negative radial wind maximums are asymmetric around the core radius of the typhoon, i.e., the radial wind on the left side of the track is anomalously larger than that on the right side. Studies show that this is induced by the intrusion of cold air （northeasterly wind）, which is primarily located at the mid-lower layers, lower than 4 kin; this is due to the intruding cold air that forces the atmosphere to uplift, enhancing the release of instability energy, which triggers the heavy precipitation. During the late stage of the cold air activity, the typhoon is rapidly weakened. Consistent with the radar-observed intrusion of cold air, the NCEP/NCAR reanalysis of wind data also shows that there are obvious large scalar wind values at the mid-lower layers （approximately 1-3 km） to the left of the typhoon center （1800 May 17）, and in all regions--except those affected by the intruding cold air--the wind speeds on the right side of the track remain larger than those on the left side. Furthermore, the Rankine model results confirm that northeasterly cold air is introduced to the typhoon at the mid-lower layers to the left of the track. Calculations also point out that there exists a frontal zone with high θse that tilts from southeast to northwest with height and the super heavy rainstorm occurring in the south of Fujian province lies just near the fxontal zone.展开更多
卫星红外辐射资料直接同化容易受到云的影响,大量卫星资料在有云情况下无法直接同化,其原因之一就是初始云结构难以获取,而云结构是同化系统观测算子的重要输入参数,缺乏云的结构信息,观测算子无法模拟有云环境下的亮温。热带地区以及...卫星红外辐射资料直接同化容易受到云的影响,大量卫星资料在有云情况下无法直接同化,其原因之一就是初始云结构难以获取,而云结构是同化系统观测算子的重要输入参数,缺乏云的结构信息,观测算子无法模拟有云环境下的亮温。热带地区以及台风、暴雨等极端天气系统与云密不可分,要改进卫星辐射资料特别是红外资料直接同化的效果,需要获得较高精度的云三维结构。在GRAPES-3DVAR(Global and Regional Assimilation and Prediction Enhanced System,全球/区域同化预报系统)基础上,结合WRF(Weather Research and Forecasting Model,天气研究和预报模式)对"珍珠"台风云结构的模拟,增加模拟的云参数作为GRAPES-3DVAR同化系统中RTTOV模式(fast radiative transfer model for TOVS,快速辐射传输模式)的输入参数,改进了有云环境下卫星资料直接同化的观测算子,研究了红外辐射资料直接同化的方法,并分析其对"珍珠"台风预报的影响。针对NOAA16(National Oceanic and Atmospheric Administration,美国国家海洋和大气管理局)的HIRS/3(High Resolution Infrared Radiation Sounder,高分辨率红外辐射探测仪3型)第4-8、10、13-19通道辐射亮温的同化试验表明,结合初始云结构信息改进同化系统观测算子,可以将红外辐射资料的观测信息同化到模式之中,改进台风温度、湿度结构,对短时降水预报有正面影响。展开更多
热带地区云的覆盖率高,卫星辐射资料特别是红外通道的数值模拟容易受到云的影响,提高台风等热带天气系统卫星亮温资料的模拟能力,有助于热带地区数值模式的检验以及提高卫星资料直接同化的水平。首先,利用天气研究和预报模式（Weather R...热带地区云的覆盖率高,卫星辐射资料特别是红外通道的数值模拟容易受到云的影响,提高台风等热带天气系统卫星亮温资料的模拟能力,有助于热带地区数值模式的检验以及提高卫星资料直接同化的水平。首先,利用天气研究和预报模式（Weather Research and Forecasting Model,简称WRF）对＂＂珍珠＂＂台风的三维气象场,包括云结构特征,进行了模拟,并诊断分析了总云量、云顶气压等物理量;然后,结合快速辐射传输模式（fast ra-diative transfer model for TOVS,简称RTTOV）8.7版对＂＂珍珠＂＂台风的高分辨率红外辐射探测仪3型（HighResolution Infrared Radiation Sounder,简称HIRS/3）红外辐射亮温进行了模拟,并且比较了有云和无云条件下的模拟结果。结果表明,如果不考虑云的影响,RTTOV模式无法模拟出台风的结构特征;结合三维云特征的模拟量,RTTOV模式可以较好地模拟出HIRS/3第4-10、13-19通道的辐射亮温。加入云结构特征对峰值能量高度在云层以下的红外通道的模拟有正面影响,该方案既可以作为检验模式模拟的一种手段,同时也表明红外资料在热带天气系统的资料同化领域具有潜在的应用能力。展开更多
基金National Science Foundation of China (40775066)Shanghai Typhoon Research Foundation (2008ST07)
文摘With the Reisner-2 bulk microphysical parameterization of the fifth-generation Pennsylvania State University-U.S. National Center for Atmospheric Research （PSU--NCAR） Mesoscale Model （MM5）, this paper investigates the microphysical sensitivities of Typhoon Chanchu. Four different microphysical sensitivity experiments were designed with an objective to evaluate their respective impacts in modulating intensity forecasts and microphysics budgets of the typhoon. The set of sensitivity experiments were conducted that comprised （a） a control experiment （CTL）, （b） NEVPRW from which evaporation of rain water was suppressed, （c） NGP from which graupel was taken, and （d） NMLT from which melting of snow and graupel was removed. We studied the impacts of different cloud microphysical processes on the track, intensity and precipitation of the typhoon, as well as the kinematics, thermodynamics and vertical structural characteristics of hydrometeors in the inner core of the typhoon. Additionally, the budgets of the cloud microphysical processes in the fine domain were calculated to quantify the importance of each microphysical process for every sensitivity experiment. The primary results are as follows： （1） It is found that varying cloud microphysics parameters produce little sensitivity in typhoon track experiments. （2） The experiment of NGP produces the weakest storm, while the experiment of NMLT produces the strongest storm, and the experiment of NEVPRW also produces stronger storms than CTL. （3） Varying parameters of cloud rnicrophysics have obvious impacts on the precipitation, kinematics, and thermodynamics of the typhoon and the vertical structural characteristics of hydrometeors in the typhoon＇s inner core. （4） Most budgets of cloud microphysics in NMLT are larger than in CTL, while they are 20%-60% smaller in NEVPRW than in CTL.
基金National Basic Research Program of China (973 program) (2009CB421500)National Natural Science Foundation of China (90715031+3 种基金 40875026 and 40730948)Project of City University of Hong Kong (7001994)Natural Science Foundation of Guangdong Province of China (8351030101000002)
文摘Observational data of mesoscale surface weather stations and weather radars of Guangdong province are employed to analyze the asymmetric distribution of convection prior to, during and after landfall for tropical cyclones of Chanchu and Prapiroon making landfall on the south China coast in 2006. The results showed that strong convection is located in the eastern and northern sectors of the landfalling Chanchu and Prapiroon, namely in the front and right portions of the TC tracks, for a period of time starting from 12 h prior to landfall to 6 h after it. Their convection also had distinct differences in the vertical direction. The analysis indicated that although the landfall of Chanchu and Prapiroon has the same asymmetric distribution of convection, the causes are not exactly the same. The asymmetric distribution of convection in the case of Chanchu is mainly correlated with the impacts of a strong environmental vertical wind shear, low-level horizontal wind shear, and low-level convergence and divergence. In the case of Prapiroon, however, the asymmetric distribution of convection is mainly associated with the impacts of low-level convergence and divergence.
基金Project for Social Development from Xiamen Science and Technology Bureau (3502Z200520103502Z20064022)
文摘With Doppler radar data from Shantou and Xiamen and the National Centers for Environmental Prediction and the National Center for Atmospheric Research （NCEP/NCAR） reanalysis data, the characteristics of a short-term heavy rainstorm on 17 May 2006 caused by Typhoon Chanchu are studied. Doppler radar data indicates that during the period from 1800 to 1900 May 17, the azimuthal phases of the positive and negative radial wind maximums are asymmetric around the core radius of the typhoon, i.e., the radial wind on the left side of the track is anomalously larger than that on the right side. Studies show that this is induced by the intrusion of cold air （northeasterly wind）, which is primarily located at the mid-lower layers, lower than 4 kin; this is due to the intruding cold air that forces the atmosphere to uplift, enhancing the release of instability energy, which triggers the heavy precipitation. During the late stage of the cold air activity, the typhoon is rapidly weakened. Consistent with the radar-observed intrusion of cold air, the NCEP/NCAR reanalysis of wind data also shows that there are obvious large scalar wind values at the mid-lower layers （approximately 1-3 km） to the left of the typhoon center （1800 May 17）, and in all regions--except those affected by the intruding cold air--the wind speeds on the right side of the track remain larger than those on the left side. Furthermore, the Rankine model results confirm that northeasterly cold air is introduced to the typhoon at the mid-lower layers to the left of the track. Calculations also point out that there exists a frontal zone with high θse that tilts from southeast to northwest with height and the super heavy rainstorm occurring in the south of Fujian province lies just near the fxontal zone.
文摘卫星红外辐射资料直接同化容易受到云的影响,大量卫星资料在有云情况下无法直接同化,其原因之一就是初始云结构难以获取,而云结构是同化系统观测算子的重要输入参数,缺乏云的结构信息,观测算子无法模拟有云环境下的亮温。热带地区以及台风、暴雨等极端天气系统与云密不可分,要改进卫星辐射资料特别是红外资料直接同化的效果,需要获得较高精度的云三维结构。在GRAPES-3DVAR(Global and Regional Assimilation and Prediction Enhanced System,全球/区域同化预报系统)基础上,结合WRF(Weather Research and Forecasting Model,天气研究和预报模式)对"珍珠"台风云结构的模拟,增加模拟的云参数作为GRAPES-3DVAR同化系统中RTTOV模式(fast radiative transfer model for TOVS,快速辐射传输模式)的输入参数,改进了有云环境下卫星资料直接同化的观测算子,研究了红外辐射资料直接同化的方法,并分析其对"珍珠"台风预报的影响。针对NOAA16(National Oceanic and Atmospheric Administration,美国国家海洋和大气管理局)的HIRS/3(High Resolution Infrared Radiation Sounder,高分辨率红外辐射探测仪3型)第4-8、10、13-19通道辐射亮温的同化试验表明,结合初始云结构信息改进同化系统观测算子,可以将红外辐射资料的观测信息同化到模式之中,改进台风温度、湿度结构,对短时降水预报有正面影响。
文摘热带地区云的覆盖率高,卫星辐射资料特别是红外通道的数值模拟容易受到云的影响,提高台风等热带天气系统卫星亮温资料的模拟能力,有助于热带地区数值模式的检验以及提高卫星资料直接同化的水平。首先,利用天气研究和预报模式（Weather Research and Forecasting Model,简称WRF）对＂＂珍珠＂＂台风的三维气象场,包括云结构特征,进行了模拟,并诊断分析了总云量、云顶气压等物理量;然后,结合快速辐射传输模式（fast ra-diative transfer model for TOVS,简称RTTOV）8.7版对＂＂珍珠＂＂台风的高分辨率红外辐射探测仪3型（HighResolution Infrared Radiation Sounder,简称HIRS/3）红外辐射亮温进行了模拟,并且比较了有云和无云条件下的模拟结果。结果表明,如果不考虑云的影响,RTTOV模式无法模拟出台风的结构特征;结合三维云特征的模拟量,RTTOV模式可以较好地模拟出HIRS/3第4-10、13-19通道的辐射亮温。加入云结构特征对峰值能量高度在云层以下的红外通道的模拟有正面影响,该方案既可以作为检验模式模拟的一种手段,同时也表明红外资料在热带天气系统的资料同化领域具有潜在的应用能力。
