2023年和2005年山东两次极端海效应暴雪的对比

利用常规气象观测资料、降水天气现象仪资料、美国国家海洋和大气管理局（National Oceanic and Atmospheric Administration，NOAA）资料、欧洲中期天气预报中心（European Centre for Medium-Range Weather Forecasts，ECMWF）第五代大气再分析（ECMWF Reanalysis v5，ERA5）资料等对2023年12月山东半岛的海效应特大暴雪和2005年12月持续性海效应强降雪过程的高空形势、海气温差、低层切变线、大气水凝物等进行了综合分析。结果表明：（1）亚欧大陆强大的经向高压脊和脊前冷涡环流是发生海效应暴雪的大尺度环流背景。2005年高压脊宽广、稳定少动是海效应强降雪持续时间长的主要原因，2023年高压脊、冷涡的经向特征更加显著，冷空气爆发力强。（2）2005、2023年渤海海面温度较常年偏高；2023年偏高2.5 ℃的范围更广，12月20—21日海气温差超过30 ℃。（3）出现暴雪时，山东半岛北部存在偏西风和北—东北风之间的风场辐合；荣成站出现暴雪时，低层需要更强劲的引导气流。（4）2023年12月20—21日，云体主要由冰晶和雪晶构成，较多雪晶位于上升气流上方，与冰粒子分布区域重叠，说明除了水汽凝华外，冰雪晶粒子之间的聚合作用对雪粒子的增长有很大帮助，聚合产生的枝状雪粒子有利于积雪深度增大，文登站雨滴谱也表明，21—22日雪粒子直径偏大的特征更明显。

Comparative analysis on two extreme sea-effect snowstorms in Shandong in 2023 and 2005

Based on the data of conventional meteorological observation, precipitation weather phenomenon instrument, NOAA (National Oceanic and Atmospheric Administration), and ECMWF (European Centre for Medium-Range Weather Forecasts) Reanalysis v5 (ERA5), the upper-level synoptic situations, air-sea temperature difference, low-level shear lines, and atmospheric hydrometeors of the heavy sea-effect snowstorm in December 2023 and the continuous sea-effect heavy snowfall in December 2005 over Shandong Peninsula are comprehensively analyzed. The results are shown below. (1) The strong meridional ridge in Eurasia and the cold vortex circulation in front of the ridge are the large-scale circulation background of sea-effect snowstorm. The broad and stable ridge is the main reason for the long duration of the strong sea-effect snowfall in 2005. The meridional characteristics of ridge and cold vortex are more significant in 2023, so the cold air is stronger. (2) The SST (sea surface temperature) of the Bohai Sea in 2005 and 2023 is higher than that in the normal years. In 2023, the range of temperature 2.5 ℃ higher than the normal years is wider, and the air-sea temperature difference exceeds 30 ℃ from 21 to 22 December. (3) When a snowstorm occurs, there is wind field convergence between westerly and northerly-northeasterly in the north of Shandong Peninsula; the snowstorm at Rongcheng station requires stronger steering flow in the low level. (4) The cloud body is mainly composed of ice crystals and snow crystals, and more snow crystals above the updraft overlap with ice particles from 20 to 21 December 2023, which indicates that the aggregation of snow-ice crystals contributes to the growth of snow particles besides water vapor deposition. The dendritic snow particles produced by the aggregation are conductive to the increase of snow depth. The raindrop size distribution at Wendeng station also shows that the diameter of the snow particles is larger from 21 to 22 December.