This paper studied a snow event over North China on 21 February 2017,using aircraft in-situ data,a Lagrangian analysis tool,and WRF simulations with different microphysical schemes to investigate the supercooled layer...This paper studied a snow event over North China on 21 February 2017,using aircraft in-situ data,a Lagrangian analysis tool,and WRF simulations with different microphysical schemes to investigate the supercooled layer of warm conveyor belts(WCBs).Based on the aircraft data,we found a fine vertical structure within clouds in the WCB and highlighted a 1-2 km thin supercooled liquid water layer with a maximum Liquid Water Content(LWC) exceeding0.5 g kg^(-1) during the vertical aircraft observation.Although the main features of thermodynamic profiles were essentially captured by both modeling schemes,the microphysical quantities exhibited large diversity with different microphysics schemes.The conventional Morrison two-moment scheme showed remarkable agreement with in-situ observations,both in terms of the thermodynamic structure and the supercooled liquid water layer.However,the microphysical structure of the WCB clouds,in terms of LWC and IWC,was not apparent in HUJI fast bin scheme.To reduce such uncertainty,future work may focus on improving the representation of microphysics in bin schemes with in-situ data and using similar assumptions for all schemes to isolate the impact of physics.展开更多
利用欧洲中期天气预报中心(European Center for Medium-Range Weather Forecasts,ECMWF)的ERA5再分析资料与拉格朗日分析工具(Largrangian analysis tool,LAGRANTO),对2006-2021年期间引发东北地区暴雪天气的温带气旋暖输送带进行统计...利用欧洲中期天气预报中心(European Center for Medium-Range Weather Forecasts,ECMWF)的ERA5再分析资料与拉格朗日分析工具(Largrangian analysis tool,LAGRANTO),对2006-2021年期间引发东北地区暴雪天气的温带气旋暖输送带进行统计,研究了暖输送带对气旋和降水发展的作用及其与锢囚锋的关系。结果表明:(1)气旋的加深率与暖输送带强度有明显的正相关,两者相关系数为0.63,通过α=0.01的显著性检验。大部分气旋在迅速加深24 h期间锢囚,以暖式锢囚为主。(2)强烈发展的锢囚型气旋通常具有强暖输送带,暖输送带低空入流主要位于气旋中心和气旋暖区附近,暖输送带的出流有两个分支:一支上升至气旋西北侧高空,另一支随高空西风带向气旋下游移动;气旋锢囚阶段低空正位涡异常与高空正位涡异常相互作用,形成贯穿整个对流层的位涡柱。(3)未锢囚或晚锢囚的气旋虽然有强暖输送带,但缺少对流层上层的干侵入,仅在低空有正位涡异常,气旋发展较弱。弱的锢囚型气旋存在明显干侵入,但暖输送带及降水均较弱。(4)具有强(弱)暖输送带的气旋造成的降水更多(少),且降水落区与暖输送带分布有密切关系。移动到气旋中心附近的暖输送带气块对气旋的发展有重要作用,其水平运动引起的暖平流及上升运动组织形成的低空非绝热位涡均能加强气旋式环流,进而促进气旋发展。展开更多
利用常规与加密气象观测资料、FNL再分析格点资料及FY-2G卫星云顶亮温(Temperature of Black Body,TBB)观测资料,对2015年7月14—15日湖北省梅雨期一次连续暴雨过程对流云活动的环境条件和导致短时强降雨的对流云影响方式进行了分析。...利用常规与加密气象观测资料、FNL再分析格点资料及FY-2G卫星云顶亮温(Temperature of Black Body,TBB)观测资料,对2015年7月14—15日湖北省梅雨期一次连续暴雨过程对流云活动的环境条件和导致短时强降雨的对流云影响方式进行了分析。结果表明:500 hPa位于西风槽前、850 hPa风场辐合、温度露点差较小及850—500 hPa暖平流为有利于湖北省对流云活动的环境条件。当天气尺度暖输送带云系在江南西部至长江中游地区建立,且低层暖切变线同时出现在湖北地区上空时,降雨明显增幅;当暖输送带云系明显东移后,湖北地区暴雨过程结束。当暖输送带位于湖北地区上空时,850 hPa相当位温平流项和对流项均为较大正值,且对流项大值区出现在平流项大值区的南侧。短时强降雨主要发生在降雨盛期,是构成湖北地区暴雨的重要组成部分。湖北省短时强降雨的4种对流云影响方式分别为对流云团西边界、深对流云团中心区、对流云串"列车效应"及对流云合并加强;其中,受对流云西边界、深对流云中心区或云团串影响的短时强降雨发生次数较多,受深对流云中心区和对流云合并加强影响的短时强降雨平均降雨量较大。展开更多
The Atlantic Meridional Overturning Circulation(AMOC)is part of the great ocean“conveyor belt”that circulates heat around the globe.Since the early 2000s,ocean sensors have started to monitor the AMOC,but the measur...The Atlantic Meridional Overturning Circulation(AMOC)is part of the great ocean“conveyor belt”that circulates heat around the globe.Since the early 2000s,ocean sensors have started to monitor the AMOC,but the measurements are still far from accurate and the time window does not permit the separation of short term variability from a longer term trend.Other works have claimed that global warming is slowing down the AMOC,based on models and proxies of temperatures.Some other observations demonstrate a stable circulation of the oceans.By using tide gauge data complementing recent satellite and ocean sensor observations,the stability of the AMOC is shown to go back to 1860.It is concluded that no available information has the due accuracy and time coverage to show a clear trend outside the inter-annual and multi-decadal variability in the direction of increasing or decreasing strength over the last decades.展开更多
基金jointly supported by the China National Science Foundation under Grant Nos.41875172 and 42075192。
文摘This paper studied a snow event over North China on 21 February 2017,using aircraft in-situ data,a Lagrangian analysis tool,and WRF simulations with different microphysical schemes to investigate the supercooled layer of warm conveyor belts(WCBs).Based on the aircraft data,we found a fine vertical structure within clouds in the WCB and highlighted a 1-2 km thin supercooled liquid water layer with a maximum Liquid Water Content(LWC) exceeding0.5 g kg^(-1) during the vertical aircraft observation.Although the main features of thermodynamic profiles were essentially captured by both modeling schemes,the microphysical quantities exhibited large diversity with different microphysics schemes.The conventional Morrison two-moment scheme showed remarkable agreement with in-situ observations,both in terms of the thermodynamic structure and the supercooled liquid water layer.However,the microphysical structure of the WCB clouds,in terms of LWC and IWC,was not apparent in HUJI fast bin scheme.To reduce such uncertainty,future work may focus on improving the representation of microphysics in bin schemes with in-situ data and using similar assumptions for all schemes to isolate the impact of physics.
文摘利用欧洲中期天气预报中心(European Center for Medium-Range Weather Forecasts,ECMWF)的ERA5再分析资料与拉格朗日分析工具(Largrangian analysis tool,LAGRANTO),对2006-2021年期间引发东北地区暴雪天气的温带气旋暖输送带进行统计,研究了暖输送带对气旋和降水发展的作用及其与锢囚锋的关系。结果表明:(1)气旋的加深率与暖输送带强度有明显的正相关,两者相关系数为0.63,通过α=0.01的显著性检验。大部分气旋在迅速加深24 h期间锢囚,以暖式锢囚为主。(2)强烈发展的锢囚型气旋通常具有强暖输送带,暖输送带低空入流主要位于气旋中心和气旋暖区附近,暖输送带的出流有两个分支:一支上升至气旋西北侧高空,另一支随高空西风带向气旋下游移动;气旋锢囚阶段低空正位涡异常与高空正位涡异常相互作用,形成贯穿整个对流层的位涡柱。(3)未锢囚或晚锢囚的气旋虽然有强暖输送带,但缺少对流层上层的干侵入,仅在低空有正位涡异常,气旋发展较弱。弱的锢囚型气旋存在明显干侵入,但暖输送带及降水均较弱。(4)具有强(弱)暖输送带的气旋造成的降水更多(少),且降水落区与暖输送带分布有密切关系。移动到气旋中心附近的暖输送带气块对气旋的发展有重要作用,其水平运动引起的暖平流及上升运动组织形成的低空非绝热位涡均能加强气旋式环流,进而促进气旋发展。
文摘利用常规与加密气象观测资料、FNL再分析格点资料及FY-2G卫星云顶亮温(Temperature of Black Body,TBB)观测资料,对2015年7月14—15日湖北省梅雨期一次连续暴雨过程对流云活动的环境条件和导致短时强降雨的对流云影响方式进行了分析。结果表明:500 hPa位于西风槽前、850 hPa风场辐合、温度露点差较小及850—500 hPa暖平流为有利于湖北省对流云活动的环境条件。当天气尺度暖输送带云系在江南西部至长江中游地区建立,且低层暖切变线同时出现在湖北地区上空时,降雨明显增幅;当暖输送带云系明显东移后,湖北地区暴雨过程结束。当暖输送带位于湖北地区上空时,850 hPa相当位温平流项和对流项均为较大正值,且对流项大值区出现在平流项大值区的南侧。短时强降雨主要发生在降雨盛期,是构成湖北地区暴雨的重要组成部分。湖北省短时强降雨的4种对流云影响方式分别为对流云团西边界、深对流云团中心区、对流云串"列车效应"及对流云合并加强;其中,受对流云西边界、深对流云中心区或云团串影响的短时强降雨发生次数较多,受深对流云中心区和对流云合并加强影响的短时强降雨平均降雨量较大。
文摘The Atlantic Meridional Overturning Circulation(AMOC)is part of the great ocean“conveyor belt”that circulates heat around the globe.Since the early 2000s,ocean sensors have started to monitor the AMOC,but the measurements are still far from accurate and the time window does not permit the separation of short term variability from a longer term trend.Other works have claimed that global warming is slowing down the AMOC,based on models and proxies of temperatures.Some other observations demonstrate a stable circulation of the oceans.By using tide gauge data complementing recent satellite and ocean sensor observations,the stability of the AMOC is shown to go back to 1860.It is concluded that no available information has the due accuracy and time coverage to show a clear trend outside the inter-annual and multi-decadal variability in the direction of increasing or decreasing strength over the last decades.
