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1.
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.本文进一步计算了包含广义位温的修正Q矢量方程.结果表明,锋生项对沿湿等熵线的负Q矢量散度贡献较大,而拟涡度项在暖区强风切变区域中比较显著,两项在激发上升运动中同等重要. 相似文献
2.
《大气和海洋科学快报》2021,14(2):100017
A snow burst event characterized by brief heavy snowfall affected Northeast China and caused serious social impact on 26 January 2017, with the snowband generally aligned with a northeast–southwest-oriented cold front. ECMWF reanalysis data were used to diagnose the possible trigger mechanism. Results showed there were two stages: (a) an initial stage far away from the Changbai Mountains, and (b) an enhancement stage under the influence of high terrain. During the initial stage, the coupling of low-level frontogenesis and a favorable convergence pattern caused strong upward motion, contributing to the release of instability. When the snowband approached the high terrain during the enhancement stage, the various instabilities were triggered by the low-level frontogenesis, terrain circulation, and strong wind shear associated with the low-level jet. Further, a modified Q-vector divergence including generalized potential temperature was calculated to diagnose the vertical motion. It showed that the frontogenesis terms contributed greatly to the negative Q-vector divergence along the moist isentropes, while the pseudo-vorticity terms played a role in the regions with strong wind shear associated with the low-level jet in the warm section, suggesting both were important in stimulating the ascending motion. The regions with negative Q-vector divergence had a close relationship with the vertical structure of convection, indicating the potential to track the development of the snowband in the next few hours.摘要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.本文进一步计算了包含广义位温的修正Q矢量方程.结果表明, 锋生项对沿湿等熵线的负Q矢量散度贡献较大, 而拟涡度项在暖区强风切变区域中比较显著, 两项在激发上升运动中同等重要. 相似文献
3.
以NCEP资料为初始场和侧边界条件,利用WRF模式对东、西天山地形对2015年12月9—12日大暴雪影响进行敏感性试验,从降水强度和分布等方面对比分析模拟结果,探讨地形在暴雪过程中的作用,对成因进行初步研究分析,结果表明:(1)此次强降雪发生是高空西南急流抽吸、低层风切变及风速辐合、偏北风与地形强迫抬升、地面冷锋移动缓慢等共同造成的。(2)此次暴雪天气过程,地形对强降雪的落区、强度影响很大,东、西天山高度与强降雪强度正相关,东、西天山高度降低、强降雪落区沿环流方向移动。(3)地形动力强迫整体上增强次级环流圈。近地面上升速度中心出现在迎风坡山脚至山腰区域,并向两侧递减,与此次大暴雪中心落区以及乌鲁木齐附近测站降雪量分布吻合,东、西天山地形高度降低50%,近地面上升速度中心值减少30%。地形强迫东、西天山峡谷近地面生成辐合中心和辐合线,辐合中心强度与地形高度正相关。(4)地形强迫抬升有加强水汽辐合汇聚的作用,东、西天山地形高度降低50%,水汽通量与水汽通量散度减少30%。 相似文献
4.
A coupled mesoscale atmospheric-land surface model is used to simulate a twelve-day heavy precipitation event in California. In addition to the temporal variation of the large-scale flow, local topography played a crucial role in the simulated precipitation and land-surface snow budget through orographically-generated vertical motion and a decrease of atmospheric temperature with increasing altitude. The observed and simulated heavy precipitation occurred at locations where orographic lifting is strong: western slopes of the Sierra Nevada Mountains and the Coastal Range. Due to rainshadow effects, the Central Valley area, which is located at the lee side of the Coastal Range, received only a small amount of precipitation. The snowline appeared at altitudes as low as 750 m above sea level, and most of the precipitation above the 1.8 km level was snow. Maximum rainfall was located near the 1 km elevation along the western slope of the Sierra-Nevada while snowfall maxima appeared along the ridge of the Sierra Nevada Mountains. Snow accumulation was also strongly dependent upon surface elevations. The simulation suggested that over 75% of the fresh snowfall during the study period was added to the existing snow cover at elevations above 1.5 km while much of the snowfall over lower elevations melted. 相似文献
5.
Abstract Most water balance studies in the High Arctic indicate that the weather stations underestimate annual precipitation, but the magnitude of such error is unknown. Based on up to seven years of field measurements, this study provides a comparison of snowfall at weather stations with the winter snow accumulation in their nearby drainage basins. Snowfall is the major form of precipitation in the polar region for nine months every year. Without vegetation, snowdrift is controlled by the local terrain. By establishing the snow characteristics for different terrain types, total basin snow storage can be obtained by areally weighting the snow cover for various terrain units in the basin. Such a method was successfully employed to compute total winter snowfall in the drainage basins near Resolute, Eureka and Mould Bay. Results show that the basins had 130 to 300per cent more snow than the weather stations recorded. Using revised snowfall values that are reinforced by Koerner's snow core measurements from ice‐caps, it is hoped that a more realistic precipitation map can be provided for the High Arctic. 相似文献
6.
Abstract Radar reflectivity measurements and sounding data were analyzed to investigate snowfall production in a long‐lasting snowband that formed in advance of a warm surface front moving across Alberta. The sounding data indicated that the band could have been forced by slantwise overturning during the release of moist symmetric instability combined with frontogenesis. The stability analysis presented here is novel in that it includes ice phase thermodynamics, neglected in previous studies of slantwise convection. Radar reflectivity fields were analyzed to determine the total snow content and the mass outflow rate as factors of time. The peak value of total snow content was 17 kilotons per km of snowband, and the peak mass outflow rate was 10 tons s‐1 km‐1. The snowfall rate averaged across the cloud base was about 0.8 cm h‐1, and the average snow content remained close to 0.2 g m‐1. The characteristic time (defined as the ratio of total snow content over mass outflow rate) was about 30 minutes, which is approximately the time needed for the growth of snowflakes by aggregation in the observed temperature range. The precipitation efficiency of the snowband, defined as the ratio of snow mass outflow to water vapour inflow was estimated to be 14%. The precipitation production values observed in the Alberta snowband are compared with previous estimates reported for frontal rainbands and Alberta thunderstorms. 相似文献
7.
2019年2月14日在北京海坨山地区出现了一次由低槽云系产成的降雪过程。利用飞机、Ka波段云雷达、微波辐射计、降水粒子谱仪、雪晶显微观测仪等协同观测数据集,分析了此次降雪过程的天气形势、中尺度和微观结构的演变特征。协同观测显示:（1）降雪过程由高空低槽和地面倒槽槽前西南暖湿气流与低层东风回流干冷偏东风共同影响形成,西南风厚度和强度与地面降雪量以及降雪粒子数浓度成正相关。（2）降雪云系为冰云,地面降雪形状主要为片状、枝状和柱状单晶体,冰雪晶的凝华-聚并增长是降雪的主要形成机制。（3）大量枝状雪花的攀附现象出现在地形云爬升阶段,即低层东风回流减弱,转由倒槽槽前西南暖湿气流控制。（4）过冷水的出现与地形抬升有关,地形云爬升期间存在人工增雪潜力。 相似文献
8.
A 24-h simulation with the Advanced Regional Prediction System (ARPS) nonhydrostatic model is performed for the heavy snowfall event of 3–4 February 1998 along the eastern coast of Korean Peninsula; the results are used to understand the snowfall process, including why the precipitation maxima formed along the Yeongdong coastal region rather than over the mountain slope and ridge top during. The numerical simulation with a 4-km horizontal grid spacing and 43 levels reproduces very well the narrow snowband located off the eastern Korean coast, away from, instead of over, the Yeongdong coastal mountain range. The general evolution of the snowband agrees quite well with radar observations, while the water-equivalent precipitation amount agrees reasonably well with radar precipitation estimate. The simulation results clearly show that the snow band developed due to the lifting by a coastal front that developed because of the damming of cold air against the eastern slope of the coastal mountain range. The damming was enhanced by the advection of cold air by a low-level mountain-parallel jet from the north, formed due to geostrophic adjustment as the on-shore upslope air was decelerated by the mountain blocking. As the onshore flow weakened later due to synoptic-scale flow pattern change, the cold front propagated off shore and the precipitation dissipated. 相似文献
9.
冷流低云降雪成因的分析 总被引：19，自引：6，他引：19
冷流低云降雪是冬季山东半岛北部沿海地区独特的天气现象，为了研究冷流低云降雪的成因，通过对烟台１９８１－１９９０年１１月－次年３月的５０个月农日农时的降雪资料、气温资料及海面温度资料分析和探讨，认为适宜的环流形势、海－气相互作用、低层稳定度、低层风切变及地形的抬升作用是冷流低云形成并产生降雪的主要原因。 相似文献
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本文分析了1984年冬季北疆4次降水过程（11月21日、11月28日、12月1日、12月9日）的雷达观测资料、加密探空和包括1983年几次过程的飞机穿云观测、地面雪强和雪晶微物理观测以及常规观测资料等。结果表明，该区气旋锋面降水过程由频繁有秩的中小尺度降水带构成。依据观测可将它们分为两类:地形降水带和系统降水带。本文还初步研究了降水结构和降水带的生成机制，并进一步探讨了降水带的可播性。从各种降水带微结构特点和地面降水特征得知，该区冬季人工增雪催化对象主要是无高空强引晶作用的锋下层积云和浅对流、波动、爬坡等动力作用产生的降水带。 相似文献
11.
利用部分改进了的中尺度数值模式MM5V3对2006年2月7～8日祁连山一次降雪过程进行了三重双向影响嵌套模拟研究,模式对雪带分布的模拟与实测基本吻合.重点分析了此次降雪过程中的热力动力特征和云的微物理结构,并通过地形敏感性试验,研究了祁连山地形对降雪的作用.结果表明:降雪过程中有低层西北湿冷气流向祁连山区输送水汽在山前形成大值区,气流除在祁连山周围绕流外同时沿祁连山北坡爬升.降雪前期空气饱和层和上升气流区比较深厚,为祁连山北坡降雪中心的形成提供了有利的动力热力条件,降雪后期有高空干冷下沉气流侵入使降雪减弱.这次过程为冷性稳定层云降雪过程,水成物含水量大值区也主要分布于祁连山北坡和山顶附近,冰晶和雪分布在6 km以下,在冷云顶存在0.06 g·kg-1的过冷云水.祁连山高大地形对大范围降雪落区无明显影响,但对祁连山北坡降雪中心形成有直接影响.降低地形高度后,山顶无法形成上升运动和云粒子,迎风坡云体发展减弱.地形对降雪增幅中心主要位于祁连山北坡,24 h最大增幅达3 mm. 相似文献
12.
13.
2005年12月威海连续性暴雪的气候背景 总被引：2，自引：0，他引：2
利用1966—2005年NCEP/NCAR再分析资料和威海冬季降雪资料,对威海冬季降雪的时空分布特征以及2005年12月威海连续性暴雪的气候背景进行分析。结果表明：威海冬季降雪量呈明显的北多南少分布;12月降雪量和暴雪日数明显多于其他月份。威海市2005年12月的气候特征与威海12月降雪偏多年的气候特征非常相似,表现为东北亚大气环流经向型,中国东北、黄渤海到日本海一带500 hPa位势高度距平和850 hPa温度距平均为显著的负值中心,1000 hPa风场距平为气旋性弯曲;2005年12月的要素距平明显大于降雪偏多年。此外,2005年11月下旬黄渤海海温较常年显著偏高,为大气提供了充足能量,并造成边界层大气极不稳定;山东半岛地形抬升及其北岸的海陆风与环境风辐合,直接导致不稳定能量释放而形成威海连续性暴雪。 相似文献
14.
2012年锡林郭勒盟冬季雪情及灾害评估 总被引：3，自引：3，他引：0
2012年初冬,锡林郭勒盟连降暴雪,冬季总降雪量突破历史极值,具有降雪早、雪量大、积雪深和范围广的雪情特点,对草原畜牧业构成严重威胁。与历史上几次严重白灾年相比,雪情危害程度更为严重,但造成的灾害损失较小,其原因是雪灾预报预警准确,发布及时;党政领导重视,防灾措施得力;应急响应迅速,信息宣传到位;设施牧业改善,抗灾能力提高;夏季雨水充沛,牧草储备充足。 相似文献
15.
长白山地处吉林省东南部,作为国家级重点生态功能区,其降水变化特征对该地森林生态系统和水资源结构变化有重要影响。本文基于1979～2016年吉林省47个台站逐月降水资料,探究了长白山天池站夏季降水的气候特征及其相关的环流异常,并与吉林省降水进行对比。分析结果表明天池夏季降水量以及年际变率高出吉林省其它站点一倍左右。此外,天池降水年际变化对应的环流异常与吉林省降水一致,即6月东北亚气旋式异常和东亚高空急流的增强,以及7、8月西太平洋副热带高压增强和东亚高空西风急流偏北,均可引起吉林省和天池降水偏多。另一方面,天池降水变异还表现出其独特的环流异常,与吉林省降水对应的环流异常显著不同或者甚至近乎相反,究其原因为长白山地形所致。本文的结果说明山地的气候和大气环流的关系复杂、多变。 相似文献
16.
利用张家口市崇礼1960-2014年逐日降水和天气现象资料,分析了雪季与冬奥会赛期(2月4-20日)的降雪特征。结果显示：崇礼最早降雪初日为10月13日,最迟降雪终日为4月30日,初、终雪日多年平均为11月2日和4月6日;雪季长度最长和最短分别为190 d和123 d,多年平均为156 d。雪季间最长连续无降雪时段多出现在12月末到1月下旬。冬奥会赛期前的11月上旬降雪日数少,但降雪量较大;此后各旬降雪日数、雪量差异不大。2月4-20日间平均4~5 d出现一次降雪,且主要为中小雪,出现大雪的概率极低。这些结果为冬奥会赛场充分利用降雪资源、制定赛事计划和赛事期间的气象条件预测及预报等保障提供参考依据。 相似文献
17.
选取青藏高原东部地区1967~2010年61个测站的积雪数据,分析比较了整年和不同季节高原积雪的年代际变化特征及其与降雪和气温的关系,结果表明:除了秋季以外,高原东部积雪表现出“少雪-多雪-少雪“的显著年代际变化特征,80年代末发生的由少到多突变仅在冬季积雪中表现显著,20世纪末发生的由多到少突变在冬春两季积雪中均表现显著;降雪和气温的变化是影响高原东部积雪的重要因素,降雪变化的影响更加显著,尤其是秋季降雪;在冬春季降雪偏多时段,降雪的变化主导着积雪的变化;在冬春季降雪偏少时段,气温变化的影响增大,某些时段会超过降雪,甚至达到主导积雪变化的程度。 相似文献
18.
利用实况资料,分析了2004年12月20日-22日出现在华北地区的大到暴雪天气的干侵入特征,得出：a）此次降雪主要受中层切变线影响,降雪带与切变线相对应,强降雪中心就出现在切变线交汇的东南到东侧.b）此次降雪过程中,干冷空气主要来自对流层高层,分3路持续入侵,与3条切变线密切对应,而中低层西南和南2支暖湿气流在对流层中层耦合加强,与于冷空气交汇,产生强降雪;强降雪落区位于相对湿度梯度最大处的湿区一侧且有强风辐合的区域.c）随着中层切变线的东移发展,湿不稳定增强并向下延伸,高位涡区向东输送并向下传播,从而触发不稳定能量释放,导致强降雪.d）对流层高层持续的干侵入,使得中低层切变线稳定维持,有利于其前方西南急流的稳定加强和对流性不稳定的持续发展,是导致强降雪持续、增幅的重要原因. 相似文献
19.
利用1961—2019年冬季北疆45个国家站逐日降水观测资料,采用统计分析方法,对不同等级降雪的气候变化特征进行了分析。结果表明:近59 a北疆降雪日数、降雪量、降雪强度分别以0.41 d/10 a、3.13 mm/10 a、0.15(mm·d~(-1))/10 a的速率增加,其中降雪量对全年降水量的贡献以1.3%/10 a的速率增长。降雪日数、降雪量主要表现为中雪和大雪的增加,降雪强度主要表现为暴雪强度的增加。小雪对降雪日数、降雪量的贡献呈减少趋势,其余等级为增加趋势,以中雪降雪日和大雪降雪量的贡献最为明显。北疆降雪日数仅在1月表现为减少趋势,主要是小雪日数显著减少;冬季各月降雪量均表现为增加趋势,主要是中雪和大雪降雪量显著增加。21世纪前10 a是降雪日数和降雪量最多的时期,20世纪60年代和21世纪10年代是降雪日数较少的时期。北疆降雪量在1985年发生突变,突变后年平均降雪量增加了12.4 mm。对比丰雪年和枯雪年,丰雪年降雪量偏多主要是小雪以上等级降雪日数的增多。 相似文献
20.
降雪量和积雪深度的关系是降雪预报及相关科研工作中的重要参数,加密降雪资料的出现为分析这种关系提供了新的支持。利用2009—2011年冬季加密降雪资料并采用线性拟合方法,分析得出我国冬季积雪深度变化值和相应降雪量的比值大体为0.75 cm·mm-1,该比值随气温上升呈明显减小趋势,且有明显的地区差异,但未体现出显著的时间变化特征。降雪量和积雪深度的关系仍需深入分析,并需要更高质量降雪资料的支持,以便能应用到实际业务和科研工作中。 相似文献