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 cir- culation, in terms of the westerly and low-level jets, water vapor transportation, and northerly wind area/intensity indices, were analyzed to tmderstand the mechanisms of the freezing rain occurrence. The results indicate the fol- lowing： （1） RIEMS 2.0 reproduced the pattern of precipi- tation 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 repro- duced the persistent trough in the South Branch of the westerlies, of which the southwesterly currents trans- ported 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.

THE FEATURES OF EAST ASIAN JET STREAM IN PERSISTENT SNOWSTORM AND FREEZING RAIN PROCESSES OVER SOUTHERN CHINA IN EARLY 2008

Based on the National Centers for Environmental Prediction and National Center for Atmospheric Research(NCEP/NCAR) daily reanalysis data and the upper-level objective analysis data provided by the Meteorological Information Comprehensive Analysis and Process System(MICAPS),the feature of the spatio-temporal variation of the East Asian jet stream(EAJS) in persistent snowstorm and freezing rain processes over southern China in January 2008 have been investigated.Each of the storm events was closely linked with the extraordinarily abnormal variations of East Asian subtropical jet(EASJ) and East Asian polar front jet(EAPJ) at that time.The stronger EASJ with abnormally northward position of the jet axis corresponded to the more intense storm event with broader ranges and longer duration time.The heavy freezing-rain-and-snow event occurred over the region where a strong southerly wind of EASJ prevailed.Meanwhile,the westerly and northerly winds of the EAPJ were significantly intensified,which were also closely related to the beginning,enhancement,and ending of the heavy snowfall.The meridional component of the EAPJ was dominated by the northerly wind during the snowstorm.Thus,the intensification of the snowstorm was attributed to both the strengthening of the meridional wind of EAPJ and the southerly wind of EASJ.Further analysis indicated that wind speed and the zonal wind of the two jets exhibited precursory signals about half a month prior to this extreme event,and the precursory signals were found in the meridional components of the two jets about 20 days preceding the event.The sudden weakening of the meridional component of EASJ and the zonal component of EAPJ signified the ending of this persistent snowstorm.

Analysis on A Synoptic Process of Freezing Rain in Anshan City

Based on MICAPS(Meteorological Information Combine Analysis and Process System) and observational data in Anshan Observatory,the freezing rain event occurred rarely in Anshan on February 24 in 2010 was analyzed.The results showed that there existed the inversion layer from the ground to 850 hpa level even to 700 hPa level when the local surface temperature was below 0 ℃.The temperature stratification structure of coldness-warmth-coldness was prevailing from the upper level to the ground with the existence of the ice melting layer of a certain thickness.Thus the freezing event occurred in Anshan.

2024年2月17—23日中国大范围强寒潮雨雪冰冻强对流过程涉及的若干问题

2024年2月中下旬我国出现一次多灾种高影响天气过程。这是一次几十年一遇的过程,出现了大范围强寒潮雨雪冰冻天气并伴随强对流发生,涉及到强寒潮、沙尘、降雨、降雪、冻雨,以及强对流和伴随的大冰雹和雷暴大风,多种高影响天气在一次过程中都有所呈现,其过程之复杂异常罕见。本文针对此次过程中值得深入探讨的问题、高影响天气发生发展可能机理、相应的预报挑战等进行简要梳理,为后续对此次过程的细致和深入分析研究做一个引子。

西南地区一次典型冰冻雨雪复合极端灾害天气事件的环流特征及降水相态差异分析

在全球变暖气候背景下,复合型极端灾害天气事件频发。2008年以来我国南方冬季频发的雨雪冰冻,就是一种典型的复合型致灾极端天气事件。因此,本研究分析了西南地区一次典型大雪冻雨复合天气事件的大雪与冻雨期环流特征及降水相态差异,揭示了二者的关联特征。冻雨发生在贵州境内的云贵准静止锋锋面强斜压环境中,降雪主要发生在四川北部,位于静止锋以北的冷区。降雪区和冻雨区的垂直环流存在显著差异:降雪区以上升运动为主,温度基本随高度递减;冻雨区大气中低层存在逆温层,导致温度层结出现冷—暖—冷的分布,垂直运动呈两层环流模态,低层的上升运动受到中层下沉运动抑制,强上升运动不易发展。借助可综合表征环流特征和水汽相变的广义湿位涡理论,分别诊断大雪和冻雨发生发展时期的广义湿位涡分布特点,发现其斜压项的异常能更好体现准静止锋附近的大气斜压性,也可指示出大雪冻雨降水的落区及变化,可作为大雪冻雨区的动力识别特征量之一。通过气压扰动方程的计算分析,表明向下的扰动气压梯度力与浮力的平衡差异,是降雪与冻雨垂直环流特征差异的主要原因。本研究从环流特征入手开展雨雪冰冻复合极端灾害天气分析,可为复合降水相态预报和发电企业电力运行保障提供参考。

2024年2月我国两次雨雪冰冻过程中闪电活动特征对比分析

2024年1月31日-2月5日和2月18-25日(以下分别简称为"0131"和0218"过程)我国南方遭遇两次雨雪冰冻天气,并伴随密集的闪电发生。利用三维闪电定位数据、CLDAS-V2.0降水产品和Himawari-9号卫星红外云图资料,对比分析两次雨雪冰冻天气背景下的地闪时空分布、地闪回击数和雷电流累计概率分布特征,并研究了地闪与降水量及卫星黑体辐射亮温(TBB)间的关系。结果表明:(1)两次过程中共监测到地闪数13万余次,正、负地闪分别为2万和11万余次;两次过程的地闪均具有夜发性,正地闪较总地闪和负地闪峰值滞后约1~2h。两次过程中正地闪产生大电流的概率大于负地闪。(2)"0131"过程中地闪密度大值区出现在贵州南部及贵州、重庆、湖北三省交界处;"0218"过程中地闪密度大值区出现在湖北东部、江西北部、安徽、江苏和浙江大部。(3)"0131"过程中降水量和地闪的时空分布不一致,降水量峰值集中在白天,降水集中在湖南东南部、江西、安徽和江苏南部、浙江和福建大部;而"0218"过程中降水量和地闪的时空分布较一致,地闪出现的峰值较降水量峰值延迟2h。(4)两次过程中地闪的分布均很好地指示了对流区。地闪主要分布在对流云团发展方向的尾部且偏南处TBB变化梯度大的区域;对流合并会导致合并处地闪频数的跃增;对流发展最旺盛的冷云核心区几乎没有地闪发生。两次过程地闪密度随着TBB的增大呈现先增大后减小的变化特征。

2024年2月大气环流和天气分析

2024年2月北半球大气环流主要特征表现为极涡呈偶极型,东半球极涡中心位于鄂霍次克海到勘察加半岛上空,较常年同期偏强,影响我国的冷空气路径偏东;中纬度环流呈三波型,位于西伯利亚的平均槽较常年偏强,西风带短波槽活动频繁;南支槽位置偏东,西太平洋副热带高压显著偏强。2月全国平均气温为-1.8℃,较常年同期(-1.3℃)偏低0.5℃;平均降水量为22.5 mm,较常年同期(16.3 mm)偏多38%。月内有3次主要冷空气过程,其中2月17—22日强寒潮造成剧烈降温和显著低温。受南下冷空气和强盛的西南暖湿气流共同影响,月内出现2次大范围持续性低温雨雪冰冻天气过程,冻雨强度大、范围广,降水量具有极端性,对春运造成严重影响。此外,2月还出现了年度首次沙尘和强对流天气过程。

一次极端暴雪事件中罕见冻雨成因分析

使用常规观测、自动气象站、雷达回波及ERA5 0.25°×0.25°再分析等资料,对2021年11月8-9日发生在黑龙江省一次极端暴雪事件中罕见冻雨过程进行分析。结果表明:冻雨发生在降水强度较大时段,地面气温普遍低于0℃。垂直温度分布呈典型的“冷-暖-冷”层结特征,近地层存在强逆温层,探空温度>0℃的面积比<0℃的大。近地层冷垫是冷高压南侵时,受江淮气旋和地形阻挡,在海拔较低的松花江干流地区堆积形成。融化层在850 hPa低涡前部,西南或偏南低空急流携带暖湿空气像楔子一样插在冷空气中,持续的暖平流特征明显,地面冷垫与中层暖层之间有明显的锋区特征。电线积冰直径与融化层持续长短有很大的相关性。冻雨的形成符合“冰相融化”机制,在冻雨区具有回波强度增大的特征。

2024年2月我国两次大范围雨雪冰冻天气对比

2024年1月31日—2月7日(过程Ⅰ)和2月19—25日(过程Ⅱ)我国中东部地区先后出现两次大范围、持续性的雨雪冰冻天气过程,利用地面观测、再分析资料、双偏振雷达、雨滴谱等分析两次过程的雨雪冰冻实况、微物理特征、环流形势和层结特征,并对比二者异同。结果表明:两次过程的影响区域、持续时间和总降水量接近,但过程Ⅰ积冰更厚、积雪更深,过程Ⅱ影响范围更广、降雪量更大。过程Ⅰ降水粒子从上到下呈3层结构特征,即冰晶层-融化层-液态层,过程Ⅱ呈4层结构特征,即冰晶层-融化层-液态层-再冻结层,导致过程Ⅰ冻雨更明显、积冰更厚,过程Ⅱ冰粒更多、积雪深度较浅、积冰厚度较薄。环流形势和层结特征显示两次过程均为西伯利亚高压和南支系统的协同作用,但过程Ⅱ低层急流强度和地面西伯利亚高压更强,导致过程Ⅱ中层暖层和低层冷层的强度均强于过程Ⅰ,而冷层更强是过程Ⅱ冰粒更明显的直接原因。

How does tree age influence damage and recovery in forests impacted by freezing rain and snow?

The response and recovery mechanisms of forests to damage from freezing rain and snow events are a key topic in forest research and management. However, the relationship between the degree of damage and tree age, i.e., whether seedlings, young trees, or adult trees are most vulnerable, remains unclear and is rarely reported. We investigated the effect of tree age on the degrees of vegetation damage and subsequent recovery in three subtropical forest types-coniferous, mixed, and broad-leaved —in the Tianjing Mountains, South China, after a series of rare icy rain and freezing snow events in 2008. The results showed that damage and recovery rates were both dependent on tree age, with the proportion of damaged vegetation increasing with age(estimated by diameter at breast height, DBH) in all three forest types and gradually plateauing. Significant variation occurred among forest types. Young trees in the coniferous forest were more vulnerable than those in the broad-leaved forest. The type of damage also varied with tree age in different ways in the three forest types. The proportion of young seedlings that were uprooted(the most severe type of damage) was highest in the coniferous forest. In the mixed forest, young trees were significantly more likely to be uprooted than seedlings and adult trees, while in the broad-leaved forest, the proportion of uprooted adult trees was significantly higher than that of seedlings and young trees. There were also differences among forest types in how tree age affected damage recovery. In the coniferous forest, the recovery rate of trees with broken trunks or crowns(DBH > 2.5 cm) increased with tree age. However, in the mixed and broad-leaved forests, no obvious correlation between the recovery rate of trees with broken trunks or crowns and tree age was observed. Trees with severe root damage did not recover; they were uprooted and died. In these forests, vegetation damage and recovery showed tree age dependencies, which varied with tree shape, forest type, and damage type. Understanding this dependency will guide restoration after freezing rain and snow disturbances.

Indications of stratospheric anomalies in the freezing rain and snow disaster in South China,2008

NCEP/NCAR reanalysis data were used to characterize stratospheric temperature and water-vapor anomalies before and after the freezing rain and snow disaster of South China in 2008,and the influence of stratospheric circulation anomalies on the troposphere.Stratospheric temperature and water-vapor anomalies provided good leading indicators of this weather event.The period from December 1st 2007 to February 28th 2008 was divided into 18 pentads.During the 6th pentad,temperature decreased significantly at 10 hPa in the near-polar stratospheric region,and the decreasing trend strengthened and extended downward and southward to middle and lower latitudes.During the 14th-18th pentads,the temperature decrease reached its maximum and extended to 30°N.This coincided with the widespread freezing rain and snow event.By the end of January 2008,the temperature decrease ended in the near-polar stratospheric region,but continued in the mid-latitude area of the troposphere as the freezing rain and snow weather persisted.Similar to the temperature variations,positive anomalies of relative humidity in the stratospheric near-polar region also strengthened and extended downward and southward,coinciding with the freezing rain and snow event.Along with the significant relationship between the freezing rain and snow disaster and stratospheric circulation anomalies,the stratospheric polar vortex changed its shape in late December,intensifying and spreading downward from the top of the stratosphere and southward to the Asian continent,resulting in a deepening of the East Asian Trough and a strengthening of meridional circulation.Before the occurrence of the freezing rain and snow event,temperature and vapor increases in the stratosphere transferred downward to the troposphere,along with a stratospheric flow in the near-polar region southward to lower latitudes.

Analysis on the Long-Lasting Freezing Rain and Snowstorm Event at the Beginning of 2008

In this paper,main characteristics of the long-lasting freezing rain and snowstorm event in southern China at the beginning of 2008,features of the related atmospheric circulation and the causes thereof are analyzed.During the event,patterns of the atmospheric circulation stayed stable;the polar vortex located in the northern part of the Eastern Hemisphere was strong with little movement;the cold front from the polar region and the active warm air mass from the tropical ocean confronted each other for a long time;the blocking high to the west of Baikal remained strong and steady;the trough over central and western Asia maintained its position for quite long with a group of little troughs splitting from it frequently;the dominant wind at 700 hPa was southwesterly while shears and vortexes at 850 hPa developed continually,providing the necessary low-level convergence for subsequent precipitation.Meanwhile,in the mid troposphere,eddies were generated over the Tibetan Plateau and positive vorticity disturbances in the Sichuan Basin propagated eastward to the coastal regions of eastern China.The western Pacific subtropical high was intensive with westward and northward migrations.The subtropical frontal zone was puissant and the north-south temperature gradient was large.Quasi-stationary fronts over South China and the Yunnan-Guizhou Plateau remained stable.Warm air masses over the tropical ocean were active,so was the trough in the southern branch of the westerlies over the Bay of Bengal.There were four episodes associated with this event.The first one was featured with the interaction of strong cold and warm air,while the other three with the quasi-stationary fronts over South China and the Yunnan-Guizhou Plateau as well as vigorous penetration of cold air from the north.The existence of the inversion layer and the thick melting layer were one of the main reasons for the long-lasting freezing rains.The main reason for the snowstorms was that the positive vorticity over the Sichuan Basin propagated eastward to the coastal regions of eastern China.Abundant water vapor and intense updraft also favored the heavy snows.

中国东北地区两场罕见冻雨过程的对比分析

2020年11月17~20日(过程1)和2021年11月7~11日(过程2)在中国东北地区发生了两场历史罕见的冻雨事件,给吉林和黑龙江两省造成了异常严重的灾害。本文利用NCEP/NCAR和EC-ERA5再分析资料、地面气象要素实况和探空资料,对这两次冻雨过程进行了诊断分析。结果表明,地面关键影响系统均为北上发展加强的江淮气旋,冻雨区均位于地面暖锋北部冷空气一侧的等压线密集带中。冻雨形成过程存在差异,过程1主要表现为先有地面降温形成“冷垫”,之后气旋携带的暖空气在“冷垫”上爬升并配合850 hPa暖锋维持;过程2则表现为大量暖湿空气向北输送,地面气温回升,850 hPa暖舌发展,被抬升的暖湿空气降落在前期较冷的下垫面上形成冻雨。冻雨发生时,水汽条件丰沛,并伴有上升速度和锋区的明显加强。温度层结呈现“冷—暖—冷”三明治型垂直分布特征,即低空有逆温层且有融化层和近地面有冻结层同时存在。两次过程均符合多数北方冻雨的“冰相融化”机制。过程1逆温层顶高度、逆温强度及最大融化层厚度均强于过程2,且逆温持续时间长,导致电线积冰厚度差异明显。地形对冻雨有一定的影响。最后提炼出一个东北冻雨天气的三维结构模型。

2018年1月杭州市连续雨雪过程中雨雪转换气象条件分析

利用2018年1月下旬杭州及周边地区各气象观测站的逐小时地面气象要素观测资料、ERA-Interim逐6 h再分析资料,以及同时期微波辐射计、风廓线雷达和双偏振雷达资料,采用等熵位涡分析、物理量诊断等方法,分析了杭州市一次长时间连续雨雪过程的天气成因,并讨论了雨雪转换前后的气象要素特征。天气背景分析表明,200 hPa脊后辐散区和强西风急流提供了强上升运动,500 hPa倒“Ω”阻塞形势和以295 K等熵面高位涡值代表的低层冷空气提供了持续冷源。分析雨雪转换前后的气象要素发现,当700 hPa温度在-1℃以下,850—925 hPa为东北风,冷层温度低于-4℃时,杭州以降雪为主,反之将出现雨雪转换。不同的暖层和冷层厚度是造成27日降水相态不同的原因。温度高于-1℃暖层和温度低于-3.5℃冷层的厚度,可作为雨雪相态的判断指标。微波辐射计和风廓线雷达探测资料分析结果表明,雪转雨时,温度的变化开始于700 hPa高度,并逐渐向下传导,700 hPa温度的变化时间较850—925 hPa的提前约4~6 h,待低层冷层强度明显减弱后由降雪转为降雨。双偏振雷达差分反射率(Z_(DR))、零阶滞后相关系数(CC)和相态识别产品(HCL)分析结果表明,25日、27日两次雪转雨过程中25日层结温度较27日的低,冷层强度也较27日的强,是25日未出现纯雨的原因。通过分析雷达产品可大致分辨层结气温分布特征,并判断降水相态。

贵州省2008年与2022年年初低温雨雪冻雨天气过程对比分析

为了解贵州2008年与2022年年初低温雨雪天气过程差异,该文选取常规气象观测资料以及NCEP再分析资料,采用时空分布统计,环流背景、相关性分析等方法,对2008年和2022年年初贵州省低温雨雪冻雨天气过程进行对比分析。结果表明:2022年低温雨雪与2008年相比偏轻,气温偏低程度和冻雨、降雪站数与2008年相比均偏低偏少,尤其是冻雨站数与2008年相比明显偏少,但2022年最大雪深超过2008年。2008年和2022年低温雨雪期间,副高异常增强、阻塞高压形势稳固,北极明显升温,孟加拉湾和南海持续的水汽输送以及逆温层的存在,拉尼娜事件的影响,为这2次雨雪冰冻灾害提供重要的环流背景。2008年低温雨雪过程中副高位置比2022年偏北偏西,持续时间长,海平面气压高压中心强度更大;2022年副高最强强度指数和面积指数较2008年偏强,但持续时间短,鄂霍次克海低涡强度和逆温与2008年相比偏弱。

复杂环境下CL型外墙免拆复合保温模板力学及热工性能试验

CL(Composite Light-weight, CL)型外墙免拆复合保温模板在工程中得到广泛应用,在长期受复杂环境如反复受到冷冻和热冷雨等环境作用后,其力学性能及热工性能会降低。分析免拆复合保温模板受冻融循环、热冷及热雨循环环境作用下的力学及热工性能,结果表明:常温环境模板抗弯模量E为980Mpa,模板抗弯强度σc为3.03Mpa;冻融循环30次后,模板抗弯模量为767Mpa,降低约22.0%;模板抗弯强度为1.72Mpa,降低约43.3%;热冷雨循环试验后模板的抗弯模量为733Mpa,降低约25.2%;抗弯强度为1.59Mpa,降低约47.5%。同时进行耐冻融和耐候性试验得出平均导热系数分别为0.0478587W/(m·k)以及0.043668106W/(m·k),比正常条件下导热系数分别增加49.98%以及36.87%。

1951—2020年中国南方地区低温雨雪冰冻危险性评估

基于1951—2020年中国南方12个省(市、区)258个气象站的平均温度和降水量日数据,提取低温雨雪冰冻事件及其过程负积温、累积降水量及日最大降水量等指标,表征不同重现期下(5 a、10 a、30 a、50 a)的低温、雨雪、冰冻灾害危险性分布,再依据交通线路数据评估暴露风险。结果表明,发生次数较多地区集中在海拔较高的贵州、湖北、安徽、江苏等。平均持续时间的空间分布呈条带状,高值区边界较清晰,其中持续时间较长的区域在贵州和湖南。50 a一遇下的低温、雨雪、冰冻的负积温最低值为−78.2℃,累积降水量最大值为83.2 mm,日降水量最大值为38.9 mm。湖北、湖南、贵州、安徽及江西等地危险性较高,上述高危险区均存在高风险路段。

青藏高原东部和西南地区低温冰冻雨雪事件的时空变化特征

利用国家气象信息中心1961-2020年青藏高原东部和我国西南地区157个站点逐日最低气温和降水量数据,定义了一个低温冰冻雨雪事件的标准,采用Mann-Kendall突变检验、滑动t检验和EOF等方法分析了两个地区低温冰冻雨雪事件的气候特征和时空变化特征。结果表明:(1)青藏高原东部和西南地区低温冰冻雨雪发生的频次及其降水量的年变化的气候特征有明显的不同。青藏高原呈现出明显的双周期年变化,初春3月达最大值,秋季10月达第二峰值;西南地区则是U型的单周期年变化,在冬季1月最多。(2)高原上发生频次最多的区域在青海三江源和藏北怒江源地区,西南地区发生频次最多的区域在贵州的西部。(3)EOF分解得到的前3个模态表明不同季节低温冰冻雨雪频次的时空间变化有明显的不同。青藏高原春季和秋季第一空间分布模态呈全区一致变化,时间系数具有明显年代际振荡特征,春季在20世纪70年代末到2000年发生的频次较多,经历了“偏少-偏多-偏少”的演变过程;秋季在20世纪60~70年代低温冰冻雨雪频次偏多,在1981年前后发生年代际突变,之后发生的频次偏少;冬季第一空间分布模态以西南地区冬季变化为主,表明西南地区冬季在1985年前后有明显的突变特征,经历了“偏多-偏少”的变化过程;冬季第二空间分布模态以高原地区冬季变化为主,其时间变化特征与高原春季时间变化类似,2009年左右有明显的突变特征。

2023年2月大气环流和天气分析

2023年2月,大气环流的主要特征为,北半球极涡呈偶极型,次中心位于鄂霍次克海,强度较常年偏强;欧亚中高纬地区由多槽型转变为“两槽一脊”型。我国中高纬度大部处于高压脊前锋区内,槽前为正距平,冷空气活动较多但强度偏弱,南支槽位置强度接近常年同期,导致我国北方地区多雨雪天气过程,南方地区出现阶段性阴雨寡照天气。全国平均气温为0.3℃,较常年同期偏高1.6℃,全国平均降水量为15.5 mm,较常年同期偏少5%。

冷垫背景下冻雨和极端大暴雪成因机制分析

利用常规气象资料、通辽市和赤峰市多普勒雷达资料、气候极端降雪以及NCEP的FNL(1°×1°)逐6 h再分析资料,对2020年11月17-19日内蒙古中东部极端回流大暴雪天气进行分析。研究表明:500 hPa东移高空槽前暖湿气流、700 hPa西南急流以及暖式切变线为降雪提供了丰富的水汽和动力辐合抬升机制,地面至850 hPa均为偏东风冷垫,中高空西南暖湿空气沿低层冷垫爬升产生锋生,是造成此次大暴雪的主要原因。降雪最强时段,从低层到高层均为上升运动,中低层水汽几乎接近饱和状态,深厚湿层有利于产生高效率的强降雪;通辽探空图有冰相层、逆温层、融化层、中性层等多种特殊层结,并有明显表征冻雨的“象鼻”层结曲线;低层东北风急流与中高层西南急流形成强的垂直风切变和温度差,动力锋生在降雪期间一直维持,动力锋生最强阶段和降雪最强时刻相对应。雷达反射率有0℃层亮带,50~55 dBz带状强回波;基本径向速度低层长时间维持东北急流构成的冷垫,并有一对正负速度中心的风速核,形成“牛眼”结构,“牛眼”结构代表边界层出现急流核;雷达基本径向速度图低层东北风,中高层西南急流,很好地反映了西南暖湿急流在冷垫上爬升的天气学结构特征,通过多普勒雷达实时监测弥补了普通降雪短时观测的不足,这对暴雪短时预报预警具有非常好的指示意义。