基于加密观测的一次极端雨雪过程积雪特征分析  

Study on Snow Cover Characteristic of Extreme Rain-snow Event based on Intensive Observation Data

作　　者：杨成芳 赵宇[3] YANG Chengfang;ZHAO Yu(Laboratory for Meteorological Disaster Prevention and Mitigation of Shandong,Jinan 250031,Shandong,China;Shandong Meteorological Observatory,Jinan 250031,Shandong,China;Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters(CIC-FEMD)/Key Laboratory of Meteorological Disaster,Ministry of Education(KLME),Nanjing University of Information Science&Technology,Nanjing 210044,Jiangsu,China)

机构地区：[1]山东省气象防灾减灾重点实验室,山东济南250031 [2]山东省气象台,山东济南250031 [3]南京信息工程大学气象灾害预报预警与评估协同创新中心/气象灾害教育部重点实验室,江苏南京210044

出　　处：《高原气象》2021年第4期853-865,共13页Plateau Meteorology

基　　金：国家自然科学基金项目(41975055,41475038);中国气象局预报员专项(CMAYBY2018-042)。

摘　　要：利用降水现象仪、地面自动站、人工加密积雪深度逐时观测资料及NCEP/NCAR 1°×1°再分析资料,对山东2020年1月5-7日罕见雨雪过程的积雪特征及温度影响机制进行了分析。结果表明:(1)降水量突破同期历史极值导致此次雨雪过程成为极端天气事件,地面影响系统为江淮气旋,冷平流较弱,积雪深度是预报难点。(2)整个过程全省各站的平均降雪含水比为0.46 cm·mm^(-1),低于过去20年间的江淮气旋暴雪过程。(3)积雪深度与高空温度、相对湿度和垂直速度的配置有关,在最大上升运动与90%以上相对湿度的叠置层次内,如果环境温度有利于树枝状冰晶增长则积雪深度和降雪含水比大,而环境温度适合空心柱状冰晶增长的则积雪深度小;云下温度高于0℃使得积雪深度减小。(4)积雪深度与近地面温度的关系表现为:气温低于0.5℃可形成有量积雪;0 cm地温对积雪的影响表现在积雪产生之前,降至0.4℃以下可形成有量积雪;雪面温度在产生积雪前后的2 h内维持在0℃左右,其他时段变化与气温类似。(5)降雪含水比基本上随着气温的升高而减小,在0.5 cm·mm^(-1)以上时一般降雪期间气温低于0.4℃。该个例揭示了积雪深度和降雪含水比的预报需要综合考虑高低空气象条件。Diagnostic analysis has been performed to study the characteristics of snow cover and contributing factor of temperature in an extreme rain-snow event over Shandong Province during 5-7 January 2020 by hourly precipitation measurement instrument,automatic weather stationintensive snow depth observation data and NCEP/NCAR 1°×1°reanalysis data.Main results are as follows:(1)The rain-snow process is an extreme weather event caused by Jianghuai cyclone with weak cold advection and severe precipitation.So snow depth has presented a challenge to forecasters.(2)The averaged snow-liquid ratio in Shandong Province is 0.46 cm·mm^(-1),less than that average of all snowstorms produced by Jianghuai cyclone over the past 20 years.(3)Snow depth is related to configuration of temperature,relative humidity and vertical velocity in upper level.The environment temperature at the level where maximum ascending motion accompanied relative humidity larger than 90%is favorable to branch ice crystal growth,while that with large snow depth and snow-liquid ratio is favorable to hollow columnar ice crystal growth.Temperature under the cloud higher than 0℃can decrease snow depth.(4)The relationship between surface temperature and snow depth shows that obvious snow cover can form with the temperature of most stations lower than 0.5℃and ground surface temperature at 0 cm lower than 0.4℃.The impact of ground surface temperature occurs before snow cover forms.Snow surface temperature maintains about 0℃in 2 h prior to or after the formation of obvious snow cover,similar to air temperature in other time.(5)Generally,snow-liquid ratio decreases with air temperature increasing,with air temperature lower than 0.4℃when the snow-liquid ratio is larger than 0.5 cm·mm^(-1) during snowfall.The analysis of this snowstorm event revealed that forecasting snow depth and snow-liquid ratio need to consider various meteorological conditions.

关 键 词：暴雪 积雪深度 降雪含水比 温度 

分 类 号：P426.63[天文地球—大气科学及气象学]