山东省极端降雪天气事件特征分析

Analysis on Characteristics of Extreme Snowfall Events in Shandong Province

应用常规地面和高空观测资料、NCEP/NCAR 1°×1°再分析资料以及山东省122个国家自动站日降水量和小时降水量资料,从日积雪深度和过程总降水量两个角度分别定义第一和第二类极端降雪事件,并进一步对其基本特征进行分析总结。结论如下:(1)山东省极端降雪事件发生在江淮气旋和回流天气形势下,出现在11月(初冬)和2月(早春)的可能性最大,江淮气旋类多出现在2月,回流类多出现在11月。(2)极端降雪事件中鲁东南、鲁西北西部和鲁中北部地区降雪量大且出现极端降雪次数多。江淮气旋类极端降雪过程降水量大值中心出现在鲁东南、鲁中北部和半岛地区,而回流类过程降水量呈现出"南多北少"的分布特征。(3)相比较于江淮气旋类降雪过程,回流类极端降雪过程出现的单站最大降水量更大,且大雨以上量级降水范围更广。通常极端降雪过程中,降水量最大为50.0~59.9 mm,多数站点过程降水量为10.0~29.9 mm。(4)不同天气系统影响下的两类极端降雪过程地面气旋初生时中心气压值、冷高压中心强度和位置、低空急流的厚度和强度等特征有所不同。(5)回流类极端降雪过程,水汽辐合层次深厚,700 h Pa与850 h Pa均有明显的水汽辐合,江淮气旋类极端降雪过程中水汽辐合层次较低,主要位于850 h Pa附近。对于过程降水量超过50.0 mm的极端降雪事件,700 h Pa和850 h Pa比湿均达到并超过5 g·kg^(-1)。(6)回流类极端降雪过程伴有不同范围寒潮。

Based on the conventional observations,NCEP/NCAR 1° × 1° reanalysis data,daily and hourly precipitation data from 122 national automatic stations in Shandong Province in recent years,the first and the second kind extreme snowfall events were defined firstly from two aspects of daily snow cover depth and total precipitation of snowfall process,and 12 extreme snowfall events were selected according to these standards,then fundamental characteristics of extreme snowfall events occurring in Shandong Province were studied. The results are as follows:( 1) Extreme snowfall events mainly occurred under the situations of return-flow in November and Jiang-huai cyclone in February.( 2) The largest snowfall during extreme snowfall processes appeared in southeast Shandong,the western part of northwest Shandong and the northern part of middle Shandong and extreme snowfall occurred more frequently there. The centers of maximum precipitation of Jiang-huai cyclone extreme snowfall events located in southeast Shandong,the northern part of middle Shandong and Shandong Peninsula,while the precipitation of return-flow extreme snowfall events was more in south and less in north.( 3) The total precipitation of return-flow extreme snowfall events was larger and the area of heavy rain was wider compared with those of Jiang-huai cyclone snowfall. Usually,the largest precipitation of extreme snowfall events could be up to 50. 0-59. 9 mm,and in most stations the precipitation ranged from 10. 0 to 29. 9 mm.( 4) The central pressure of newborn cyclones,the location and intensity of surface cold high were different from the first and the second kind extreme snowfall events under the influence of both Jiang-huai cyclone and return-flow,and the strength and depth of low level jets were also different.( 5) There was significant convergence of water vapor on 700 h Pa and 850 h Pa during return-flow extreme snowfall processes,while for Jiang-huai cyclone extreme snowfall events,the water vapor converged only on 850 h Pa. For the extreme snowfall events with total precipitation more than 50. 0 mm,the specific humidity could reach up to and even exceed 5 g·kg^(-1) on both 700 h Pa and 850 h Pa.( 6) Return-flow extreme snowfall events were always accompanied by cold waves.