基于中国台湾地区主持的侵台台风之飞机侦察及下投式探空仪观测实验(Dropwindsonde Observations for Typhoon Surveillance near the Taiwan Region,DOTSTAR)获得的高分辨率下投式探空仪探测资料,分析了2003年9月—2012年8月所有发生...基于中国台湾地区主持的侵台台风之飞机侦察及下投式探空仪观测实验(Dropwindsonde Observations for Typhoon Surveillance near the Taiwan Region,DOTSTAR)获得的高分辨率下投式探空仪探测资料,分析了2003年9月—2012年8月所有发生在中国台湾地区附近海域的台风型大气波导事件,遴选出一次由0920号超强台风"卢碧"引起的强台风型海上大气波导过程作为研究对象。利用欧洲中期数值预报中心(ECMWF)再分析资料(水平分辨率0.125°×0.125°),对此次波导的生成原因进行了分析;基于WRF模式比较了不同初始化方法对台风强度、尺度和周围台风型大气波导的模拟能力。结果表明,此次强台风型大气波导发生在台风环流西北侧外围的弱下沉运动区,其形成与850 hPa高度附近北方强干空气平流导致湿度随高度锐减密切相关。在数值模拟中运用台风动力初始化方法,可以有效改进台风强度、路径和尺度的模拟效果,进而有利于改善台风型大气波导尤其是波导层所在高度的模拟效果。台风外围出现的大气波导通常以悬空波导为主,模拟效果与台风螺旋雨带和内核尺度的模拟关系密切,而与台风强度和眼墙结构关系不大。中尺度数值模式WRF具有模拟台风型大气波导的能力,是研究台风型大气波导的有力手段。展开更多
Variable thicknesses in the lowest half-ηmodel level （LML） are often used in atmospheric models to compute surface diagnostic fields such as surface latent and sensible heat fluxes.The effects of the LML on simulat...Variable thicknesses in the lowest half-ηmodel level （LML） are often used in atmospheric models to compute surface diagnostic fields such as surface latent and sensible heat fluxes.The effects of the LML on simulated tropical cyclone （TC）evolution were investigated in this study using the Weather Research and Forecasting （WRF） model.The results demonstrated notable influences of the LML on TC evolution when the LML was placed below 12 m.The TC intensification rate decreased progressively with a lowering of the LML,but its ultimate intensity change was relatively small.The maximum 10-m winds showed different behavior to minimum sea level pressure and azimuthally-averaged tangential winds,and thus the windpressure relationship was changed accordingly by varying the LML.The TC circulation was more contracted in association with a higher LML.Surface latent heat fluxes were enhanced greatly by elevating the LML,wherein the wind speed at the LML played a dominant role.The changes in the wind speed at the LML were dependent not only on their profile differences,but also the different heights they were taken from.Due to the enhanced surface heat fluxes,more intense latent heat release occurred in the eyewall,which boosted the storm＇s intensification.A higher LML tended to produce a stronger storm,and therefore the surface friction was reinforced,which in turn induced stronger boundary layer inflow together with increased diabatic heating.展开更多
远海悬空波导陷获层底的位置通常与边界层浅云的云顶有很好的对应,气溶胶与边界层浅云的相互作用及其产生的辐射强迫将改变悬空波导的结构.文中利用天气预报-化学(weather research and forecasting-chemistry,WRF-Chem)模式通过设计不...远海悬空波导陷获层底的位置通常与边界层浅云的云顶有很好的对应,气溶胶与边界层浅云的相互作用及其产生的辐射强迫将改变悬空波导的结构.文中利用天气预报-化学(weather research and forecasting-chemistry,WRF-Chem)模式通过设计不包含完整气溶胶-云-辐射的EXP0试验(相当于WRF模式)和包含完整气溶胶-云-辐射相互作用(即气溶胶直接和间接效应)的EXP1试验,对2016年5月观测到的一次珍贵的远海高压型超强悬空波导过程进行了模拟分析.结果表明:远海高压天气形势下,EXP1试验模拟的由气溶胶活化后形成的云滴数浓度比EXP0试验云滴数浓度预设常值(100个cm-3)偏低;当伴随边界层浅云出现时,EXP1试验模拟的波导顶高和强度较EXP0试验更接近于实测;夜间进行的3次观测位于高压中心附近的无云区,此时气溶胶的直接和间接效应均可忽略,因此两组试验模拟的差异极小.这一结果从侧面说明,在有边界层浅云出现的远海区域,包含完整气溶胶-云-辐射效应的WRF-Chem模式有利于提高悬空波导特征量的模拟效果.展开更多
文摘基于中国台湾地区主持的侵台台风之飞机侦察及下投式探空仪观测实验(Dropwindsonde Observations for Typhoon Surveillance near the Taiwan Region,DOTSTAR)获得的高分辨率下投式探空仪探测资料,分析了2003年9月—2012年8月所有发生在中国台湾地区附近海域的台风型大气波导事件,遴选出一次由0920号超强台风"卢碧"引起的强台风型海上大气波导过程作为研究对象。利用欧洲中期数值预报中心(ECMWF)再分析资料(水平分辨率0.125°×0.125°),对此次波导的生成原因进行了分析;基于WRF模式比较了不同初始化方法对台风强度、尺度和周围台风型大气波导的模拟能力。结果表明,此次强台风型大气波导发生在台风环流西北侧外围的弱下沉运动区,其形成与850 hPa高度附近北方强干空气平流导致湿度随高度锐减密切相关。在数值模拟中运用台风动力初始化方法,可以有效改进台风强度、路径和尺度的模拟效果,进而有利于改善台风型大气波导尤其是波导层所在高度的模拟效果。台风外围出现的大气波导通常以悬空波导为主,模拟效果与台风螺旋雨带和内核尺度的模拟关系密切,而与台风强度和眼墙结构关系不大。中尺度数值模式WRF具有模拟台风型大气波导的能力,是研究台风型大气波导的有力手段。
基金supported by the National Public Benefit (Meteorology) Research Foundation of China (Grant No. GYHY201106004)the National Natural Science Foundation of China (Grant Nos. 41005029, 41105065 and 41230421)
文摘Variable thicknesses in the lowest half-ηmodel level （LML） are often used in atmospheric models to compute surface diagnostic fields such as surface latent and sensible heat fluxes.The effects of the LML on simulated tropical cyclone （TC）evolution were investigated in this study using the Weather Research and Forecasting （WRF） model.The results demonstrated notable influences of the LML on TC evolution when the LML was placed below 12 m.The TC intensification rate decreased progressively with a lowering of the LML,but its ultimate intensity change was relatively small.The maximum 10-m winds showed different behavior to minimum sea level pressure and azimuthally-averaged tangential winds,and thus the windpressure relationship was changed accordingly by varying the LML.The TC circulation was more contracted in association with a higher LML.Surface latent heat fluxes were enhanced greatly by elevating the LML,wherein the wind speed at the LML played a dominant role.The changes in the wind speed at the LML were dependent not only on their profile differences,but also the different heights they were taken from.Due to the enhanced surface heat fluxes,more intense latent heat release occurred in the eyewall,which boosted the storm＇s intensification.A higher LML tended to produce a stronger storm,and therefore the surface friction was reinforced,which in turn induced stronger boundary layer inflow together with increased diabatic heating.
文摘远海悬空波导陷获层底的位置通常与边界层浅云的云顶有很好的对应,气溶胶与边界层浅云的相互作用及其产生的辐射强迫将改变悬空波导的结构.文中利用天气预报-化学(weather research and forecasting-chemistry,WRF-Chem)模式通过设计不包含完整气溶胶-云-辐射的EXP0试验(相当于WRF模式)和包含完整气溶胶-云-辐射相互作用(即气溶胶直接和间接效应)的EXP1试验,对2016年5月观测到的一次珍贵的远海高压型超强悬空波导过程进行了模拟分析.结果表明:远海高压天气形势下,EXP1试验模拟的由气溶胶活化后形成的云滴数浓度比EXP0试验云滴数浓度预设常值(100个cm-3)偏低;当伴随边界层浅云出现时,EXP1试验模拟的波导顶高和强度较EXP0试验更接近于实测;夜间进行的3次观测位于高压中心附近的无云区,此时气溶胶的直接和间接效应均可忽略,因此两组试验模拟的差异极小.这一结果从侧面说明,在有边界层浅云出现的远海区域,包含完整气溶胶-云-辐射效应的WRF-Chem模式有利于提高悬空波导特征量的模拟效果.
