青岛一次中到大雪过程的综合分析

2005年2月17～18日,受冷空气和较强暖湿气流共同影响,青岛发生中到大雪降雪过程。对这次过程的环流背景和雷达资料进行综合分析表明,低空暖平流、垂直风切变和高空西风急流提供了有利的动力条件,中空西南气流和近地层从黄渤海海面的水汽输送提供了降水所需的水汽。随着2．0～2．7km高度上,一个以青岛为中心的中尺度气旋性风场的出现,降雪强度迅速达到最强,该风场破坏,降雪强度也迅速减弱;雷达回波首先出现在3．0～5．5km的高度上,然后向上下扩展加强;降雪初期,0．8～3．2km高度上有弱回波区。     

东北地区一次暴雪过程的诊断分析

利用观测资料对东北地区的一次暴雪过程作了物理量场的诊断分析。分析结果表明:1.本次暴雪是受到贝加尔湖强冷空气和江淮暖湿气流的共同影响而形成的;2.稳定的地面形势和空中冷性长波槽的过境为本次暴雪过程提供了强大的动力条件;3.北上江淮暖湿气流携带来自东海和渤海两个源地的充沛水汽到达东北地区,为东北暴雪的产生提供了水汽条件;4.高低空垂直切变明显、高层辐散与低层辐合相配置导致的强上升运动以及中低层深厚的正涡度产生和维持是东北暴雪形成的动力机制。     

一次山东半岛强降雪过程的天气学分析

利用天气学方法对2003年1月3—5日山东半岛北部地区的一次强降雪过程进行了分析。结果表明：强降雪发生前，山东半岛北部地区低层大气湿度增大；在有利的大尺度环流条件下，受暖海面的热力作用和地形抬升作用，产生中尺度海岸锋，中尺度海岸锋造成局地降雪的增强。     

Simulation of a Freezing Rain and Snow Storm Event over Southern China in January 2008 using RIEMS 2.0

The Regional Integrated Environmental Model System(RIEMS 2.0) with NCEP Reanalysis II is utilized to simulate the severe freezing rain and snow storm event over southern China in January 2008,which caused severe damage in the region.The relationships between the freezing rain process and the large-scale circulation,in terms of the westerly and low-level jets,water vapor transportation,and northerly wind area/intensity indices,were analyzed to understand the mechanisms of the freezing rain occurrence.The results indicate the following:(1) RIEMS 2.0 reproduced the pattern of precipitation in January 2008 well,especially for the temporal evolution of daily precipitation averaged over the Yangtze River valley and southern China;(2) RIEMS 2.0 reproduced the persistent trough in the South Branch of the westerlies,of which the southwesterly currents transported abundant moisture into southern China;(3) RIEMS 2.0 reasonably reproduced the pattern of frequencies of light and moderate rain,although it overestimated the frequency of rain in southern China.This study shows that RIEMS 2.0 can be feasibly applied to study extreme weather and climate events in East Asia.     

Influence of October Eurasian Snow on Winter Temperature over Northeast China

This paper addresses the interannual variation of winter air temperature over Northeast China and its connection to preceding Eurasian snow cover.The results show that there is a significant negative correlation between October Eurasian snow cover and following-winter air temperature over Northeast China.The snow cover located in eastern Siberia and to the northeast of Lake Baikal plays an important role in the winter air temperature anomaly.More(less)eastern Siberia snow in October can cause an atmospheric circulation anomaly pattern in which the atmospheric pressure is higher(lower)than normal in the polar region and lower(higher)in the northern mid-high latitudes.Due to the persistence of the eastern Siberia snow from October to the following winter,the winter atmospheric anomaly is favorable(unfavorable)to the widespread movement of cold air masses from the polar region toward the northern mid-high latitudes and,hence,lower(higher)temperature over Northeast China.Simultaneously,when the October snow cover is more(less),the SST in the northwestern Pacific is continuously lower(higher)as a whole; then,the Aleutian low and the East Asia trough are reinforced(weakened),favoring the lower(higher)temperature over Northeast China.     

湖南冬季两次暴雪过程的对比诊断分析

利用常规地面和高空观测资料及欧洲中心ERA-5再分析数据,对2021年12月25—27日（21·12）、2022年2月21—23日（22·02）发生在湖南的两次暴雪过程进行诊断分析。两次暴雪过程有强度大、影响范围广,暴雪落区较为重合的特点。两次暴雪过程也表现出明显差异,21·12过程的累计降雪量小于22·02过程,但21·12以干雪为主,22·02以湿雪为主。分析差异的成因发现：（1）22·02过程水汽辐合强度强、延伸高度高、厚度厚,动力条件由南支槽和低涡提供;21·12过程水汽条件相对弱,动力条件由冷锋强迫抬升提供。（2）21·12过程冷空气从低层南下,云中冰相粒子比例大,温度层结满足干雪条件;22·02过程中层气温下降,云中冰相粒子与水相粒子共存,地面气温在0℃以上,故以湿雪为主。     

一次暴雨与特大暴雪并存的华北强降水过程分析

应用常规观测资料、NCEP 1°×1°再分析资料,对2012年11月3—4日华北地区产生大范围雨雪天气的成因和降水相态进行分析。结果表明:深厚的低涡和地面气旋是本次过程的直接影响系统,东南风低空急流带来东部海上的充沛水汽,使得暴雨雪区整层大气可降水量远高于当月平均值;低涡和气旋等低层辐合系统与高空辐散叠置,为强雨雪天气提供了持久强烈的上升运动,暴雨区、暴雪区分别为对流不稳定、条件性对称不稳定大气层结,而锋生作用更有利于暴雪产生;雪花形成和增长的环境条件与雪花下降过程是否融化在判断降水相态方面同等重要,二者兼具才能保证地面降雪的出现。     

黄土高原一次β中尺度大暴雨特征及成因分析

利用NCEP／NCAR逐日6h分析资料和常规观测资料,分析了2011年2月25日一28日山西连续降雪天气过程（以下简称2．25降雪）。①2．25降雪过程经历了三个阶段：2月25日为回流降雪阶段,26日一27日为倒槽冷锋与回流降雪共同影响降雪阶段,28日为低空切变线影响降雪阶段。②2．25降雪过程涵盖了华北地区大到暴雪的三个类型：回流类降雪、倒槽冷锋类降雪、低空切变线类降雪。③通过温湿场分析得出,对于低空切变线类降雪,对流层中层的湿核对降雪的开始有一定的指示意义。降雪未开始之前对流层中层有湿核,随着时间的推移,湿核向低层扩展,整个对流层中低层变为高湿区,降雪开始。当对流层中层变为干区,并向低层扩展,降雪过程结束。对于回流类降雪,低层回流对回流降雪起到冷垫的作用。④通过涡度场分析得出,对流层低层的负绝对涡度中心对其东侧的降水有指示意义,如果其东侧对流层低层配合有正涡度核,降雪强度较大,维持时间较长。⑤地面层出现的负绝对涡度中心说明近地面层有小高压系统的存在,这是因为低层回流冷垫作用形成的孤立小高压体。⑥28日降雪维持机制是条件性对称不稳定。     

一次罕见的山东暴雪天气的对称不稳定分析

采用对称不稳定判据，对发生在2001年1月6－7日的一次罕见的山东暴雪天气过程进行了分析，结果表明：暴雪产生在对称不稳定大气中，低空急流促使对流层低层暖湿气流辐合上升，触发对称不稳定能量释放，产生暴雪天气。江淮气旋和暴雪区有向对称不稳定区移动的趋势。     

A Preliminary Analysis of Features and Causes of the Snow Storm Event over the Southern Areas of China in January 2008

Four successive freezing rain/heavy snowfall processes occurred in the southern part of China from 11 January to 2 February 2008 （named ＂0801 Southern Snow Disaster＂ hereafter）, during which a large-scale blocking circulation lasted for a long time over the mid-high latitudes of the Euro-Asian continent. This severe event is featured with a broad spatial scale, strong intensity, long duration, and serious damage. During the event, the blocking situation in the mid-high latitudes maintained quasi-sationary, but weather systems in the lower latitudes were active. Abundant water vapor was supplied, and favorable weather conditions for ice storms were formed over the large areas across the southern part of China. The results in this paper demonstrate that the significant factors responsible for the abnormal atmospheric circulation and this severe event include： 1） the very active Arctic Oscillation （AO）, which helped the permanent maintenance of the planetary-scale waves; 2） the continuous transfer of negative vorticity from the upstream region around 50°E into the blocking area, which caused the blocking situation reinforced repeatedly and sustained for a long time; and 3） the active air currents south of the Tibetan Plateau, which ensured abundant moisture supply to the southern areas of China. The 0801 Southern Snow Disaster was accompanied by extremely severe icing. In this paper, the data from Cloud-Profile Radar onboard the satellite CloudSat are used to study the dynamic and microphysical features of this event. The results show that there existed a melting layer between 2 and 4 km, and ice particles could be found above this layer and in the layer near the ground surface. Surface temperature kept between -4℃ and 0℃ with relative humidity over 90%, which provided the descending supercooled waterdrops with favorable synoptic and physical conditions to form glaze and ice at the surface via freezing, deposition and/or accretion. Causes of the event might be, as a whole, traced back to the planetary-scale systems. The study on the polar vortex anomaly in this paper reveals that changes in the polar vortex in the stratosphere preceded those in the troposphere, especially in early December 2007, while the intensification of the polar vortex in the troposphere delayed dramatically until middle January and early February of 2008. This implies that changes in the polar vortex in the stratosphere may be a precursor of the ensuing severe event and a meaningful clue for extended forecasts of such a disaster.     

Implications from Subseasonal Prediction Skills of the Prolonged Heavy Snow Event over Southern China in Early 2008

An exceptionally prolonged heavy snow event(PHSE) occurred in southern China from 10 January to 3 February2008, which caused considerable economic losses and many casualties. To what extent any dynamical model can predict such an extreme event is crucial for disaster prevention and mitigation. Here, we found the three S2 S models(ECMWF,CMA1.0 and CMA2.0) can predict the distribution and intensity of precipitation and surface air temperature(SAT)associated with the PHSE at 10-day lead and 10-15-day lead, respectively. The success is attributed to the models' capability in forecasting the evolution of two important low-frequency systems in the tropics and mid-latitudes [the persistent Siberian High and the suppressed phase of the Madden-Julian Oscillation(MJO)], especially in the ECMWF model. However, beyond the 15-day lead, the three models show almost no skill in forecasting this PHSE.The bias in capturing the two critical circulation systems is responsible for the low skill in forecasting the 2008 PHSE beyond the 15-day lead. On one hand, the models cannot reproduce the persistence of the Siberian High, which results in the underestimation of negative SAT anomalies over southern China. On the other hand, the models cannot accurately capture the suppressed convection of the MJO, leading to weak anomalous southerly and moisture transport, and therefore the underestimation of precipitation over southern China.The Singular Value Decomposition(SVD) analyses between the critical circulation systems and SAT/precipitation over southern China shows a robust historical relation, indicating the fidelity of the predictability sources for both regular events and extreme events(e.g., the 2008 PHSE).     

东北一次雪飑事件的触发机制研究

2017年1月26日,中国东北地区发生了一次短时强降雪过程.本文利用ECMWF再分析数据诊断该过程的可能触发机制.分析表明,该过程可分两个阶段:初生阶段降雪远离高地形,低层锋生和有利的辐散场配置激发上升运动释放不稳定;增强阶段雪带接近长白山,低层锋生,地形环流以及与低空急流有关的风切变共同释放锋前不稳定.本文进一步计算...     

2008年广西严重低温雨雪冰冻天气过程分析

利用T213、ECMW F数值预报资料和MICAPS提供的常规观测资料,对这次极端天气事件成因进行分析,表明造成这次长时间低温雨雪冰冻天气的主要原因有:(1)北半球东亚倒Ω流型使大气环流长时间稳定,使北支、南支锋区偏南,极地冷空气不断补充南下影响到江南、华南,华南静止锋在沿海长时间维持,锋区强度大;(2)南支槽活跃,西南暖湿气流持续向我国南方输送,冷暖空气在华南上空交汇,导致广西出现长时间的降水;(3)逆温层维持时间长,长时间的降水普遍以小雨为主,容易形成过冷水滴,雨淞范围从贵州、湖南南扩至广西北部,造成道路结冰、电线积冰等次生灾害,灾情严重。     

辐射雾发展的爆发性特征

根据1996年12月27日沪宁高速公路上雾的观测资料分析，揭示了辐射雾的双层结构和爆发性发展的特征，分析了辐射雾发展的物理过程，讨论了影响辐射雾生消过程的逆温结构和湍流混合问题。     

华北一次浓雾过程爆发性增强的微物理特征

基于华北雾-霾综合观测试验资料,分析了2011年12月4日河北涿州一次浓雾过程爆发性增强的微物理特征及形成机理。结果表明：此次浓雾过程除具有均压场、地面辐射降温、逆温层、静稳天气等特征外,还具有雾微物理过程出现爆发性增强的特征,10 min内,小雾滴浓度显著增加,含水量增大了3个量级,雾滴谱由15 μm拓宽到35 μm,能见度由500 m骤降至70 m。夜间地面长波辐射冷却效应导致近地层雾的形成,而近地层雾的形成反过来快速地增强了地面长波辐射冷却效应,促使大量小雾滴的形成和碰并过程的产生,这是一种正反馈效应;大量雾滴形成释放的潜热,促使雾体抬升和向下长波辐射增强,又使地面长波辐射冷却效应减弱,产生负反馈效应。相对于南京辐射雾过程,此次涿州浓雾的小雾滴粒子数浓度高,液态水含量明显偏小,这与华北高浓度气溶胶和弱水汽输送有关。     

2018年夏季东北极端高温事件物理机制分析

基于观测资料和再分析资料,研究分析了2018年夏季中国东北地区持续多日出现高温异常事件的形成机理。首先分析了整个夏季该地区观测台站逐日的温度资料,计算了观测台站的超热因子(Excess Heat Factor,EHF)指数,发现东北地区出现高温异常的时段主要是7月和8月,异常高温的发生区域集中在东北南部。在此期间,东亚大气环流形势的异常主要表现为南亚高压和西太平洋副热带高压强度异常增强,作用相互重叠和位置持续偏北。进一步的分析可以注意到,二者的重叠造成研究区域内有负涡度异常增强,使得南亚高压和西太平洋副热带高压在北推的过程中不断带动东北南部上空负涡度异常增强,并伴随有异常下沉气流,下沉绝热增温与晴空辐射增温,这可能是东北南部地表增温的一个重要原因。相关分析证实,在整个夏季东北南部地表气温与其上空300 hPa至500 hPa涡度异常都有显著的负相关关系。因此,南亚高压和西太平洋副热带高压之间的相互叠加组合是导致东北南部在2018年夏季7、8月份出现高温异常的主要原因。进一步的研究发现,夏季副热带西风急流中准定常Rossby波能量的传播与南亚高压和西太平洋副热带高压异常增强有密切联系,同时夏季西太平洋暖池的显著增暖导致了菲律宾地区异常旺盛的对流活动,进而在500 hPa高度场上激发出PJ(太平洋—日本涛动)波列,从另一个路径上促进了西太平洋副热带高压偏强偏北。     

冬季积雪对我国夏季降水预测的评估分析

根据高原积雪和高纬积雪与我国夏季降水相关分析的结果，将高原积雪和高纬积雪作为独立因子分别对我国夏季降水预测做了检验，结果表明：高原积雪较高纬积雪效果要好，冬季高原积雪异常偏多时，长江流域夏季易发生洪涝，这也是预测汛期降水的一个重要信号。     

南方大到暴雪的一种预报方法

对构成南方大到暴雪的两个特征量：降水量和积雪深度用多种预报方法从晴雨、降水性质、降水量级、冰冻及积雪厚度等不同角度分别进行预报，然后通过推理组合，最终建立暴雪预报方法。该方法除了可以得出有无大到暴雪的预报结果外，还可以得到多种中间预报结果，从而适应预报服务的多种需要。在近３年的实际使用中获得了很好的效果。     

热源异常对2008年初中国南方低温雨雪天气的影响

利用资料诊断和全球大气原始方程模式(Intermediate General Circulation Model,IGCM),研究了2008年1月中国南方地区出现罕见的持续性雨雪事件的成因.结果表明,2008年1月大气非绝热加热场的主要异常出现在热带海洋、青藏高原及中亚地区以及北大西洋.用全球异常热源强迫IGCM得到的...     

中国近50a积雪变化时空特征

利用1961～2012年中国1400个站点逐日积雪增量、积雪日数和气温稳定通过0℃日数资料,对我国积雪时空变化特征进行了分析研究。结果表明：我国积雪主要分布在新疆北部地区、东北和内蒙古东北部地区及青藏高原地区,年积雪增量均超过50era;在年代际变化中,1991～2000年我国大部分地区积雪增量偏少;在对我国5个区域的趋势分析中,新疆北部地区、东北和内蒙古东北部地区积雪量有显著增加趋势,积雪日数的变化趋势均不显著,气温稳定通过0oC日数均呈显著减少。