摘要
利用高时空分辨率T6390场预报资料、FY—2C卫星资料和Doppler雷达产品,详细分析了2010年2月23日发生在新疆天山北坡中部致灾大暴雪的多尺度系统和物理量场配置以及发生时间和落区。结果表明,南北支短波槽的合并、加强使得冷暖空气强烈交汇是造成大暴雪的主要环流背景,低空急流、辐合线和切变线是大暴雪的主要触发机制,低空急流输送的大量水汽和高低空急流的有利配合有助于低层上升运动加强,为暴雪强度的增强提供了有利条件。大暴雪发生在南北支短波槽交汇处、高空急流入口区右后方辐散区、低空西南暖湿急流出口区左侧辐合区、辐合线前部、切变线南侧以及地面冷锋附近的重叠区域内。大暴雪期间中高层辐散大于中低层辐合,上升运动强盛且深厚,水汽辐合强烈、湿层深厚。中—α和中-β尺度冷云团是造成大暴雪的主要系统,降雪强度、范围和持续时间与冷云团强度、面积及其生命史呈正相关,大暴雪发生在冷云团内部局地增强及强中心维持阶段,并位于TBB≤-65℃的中—α尺度和TBB≤-70℃的中-β尺度冷云团边缘的TBB梯度最大处。强降雪时段雷达回波呈带状分布,回波移动方向与带状长轴方向一致,使得降雪时间较长;回波强度演变、强中心范围与降雪量分布及强降雪中心范围基本一致,强降雪中心的回波强度达35～40dBz,回波强度梯度大,"S"形速度场曲率大,垂直累积液态水含量有短时的跃增过程,回波演变具有短时弱对流特征。
Using the high spatial and temporal resolutions of T6a9, FY-2C and Doppler radar products, the multi-scale system and physical field configurations and districts of the rare snowstorm in the centre of Tian Mountain north slope, Xinjiang on February 23 were analyzed, The results showed that the merger and enhancement of North-south trough resulting in the intersection of cold and warm air was main circula- tion background in the snowstorm process. The main trigger mechanism of the snowstorm was the low-lev- el jet, convergence and shear line. The low-level jet transported a large number of water vapor. And the upper-and lower-jet streams contributed to strengthen the upward motion on low level. These all provided the favorable conditions for the enhancement of snowfall intensity. The snowstorm appeared in the junc- tion where north and south short-wave trough join up, the divergence zone of right behind the jet stream entrance area, the convergence zone on the left side of low level southwest warm jet exit area, in the front of convergence line, on the south side of shear line and the overlapping region near the surface cold front. During the snowfall, there were strong increased movement and thick layer of wet, moisture convergence. Meso-a and meso-fl scale cold clouds were the main system resulting in the severe snowstorm. The intensi- ty, scope and duration of snowfall were positively correlated with the enhanced intensity range, area and life history of cold cloud. And the great blizzard occurred during the phase when the internal cold clouds part enhanced, which located the maximum gradient of TBB within the meso-a scale cloud with TBB-65 ℃ and the meso-fl scale clouds with TBB≤-70℃. The radar echo was zonal distribution during the heavy snowfall. The direction of echo movement was consistent with the direction of long axis of ribbon, resul- ting in a longer duration of snowfall. The range of echo intensity evolution and echo intensity center were consistent with the range of snowfall distribution and heavy snowfall center. The echo intensity of heavy snowfall center was 35 - 40 dBZ. The echo intensity gradient was large. The curvature of velocity field with ＇ S＇ type was also large. The content of vertical accumulation of liquid water had a short-term growth. The evolution of echo had a short-term weak convection characteristic.
出处
《高原气象》
CSCD
北大核心
2013年第1期201-210,共10页
Plateau Meteorology
基金
中国气象局预报员专项"天山北坡中部罕见大暴雪发生时间及落区研究"(CMAYBY2012-071)
公益性行业(气象)科研专项"新疆北部致灾暴雪成因分析和预报技术研究"(GYHY201106007)共同资助
关键词
致灾大暴雪
多尺度系统
物理场配置
Disaster snowstorm
Multi-scale system
Physical field configuration
