文章摘要
渤海海效应降雨的统计特征及形成机理*
Statistical characteristics and mechanism of Bohai ocean-effect rain
投稿时间:2021-09-09  修订日期:2021-10-07
DOI:
中文关键词: 海效应降雨  山东半岛  统计特征  形成机理
英文关键词: ocean-effect rain  Shandong peninsula  statistical characteristics  mechanism
基金项目:国家自然科学基金项目(面上项目,重点项目,重大项目)
作者单位邮编
杨成芳 山东省气象防灾减灾重点实验室山东省气象台 250031
曹玥瑶 山东省气象防灾减灾重点实验室山东省气象台 250031
摘要点击次数: 161
全文下载次数: 0
中文摘要:
   海效应降雨是指强冷空气流经暖海面所产生的降雨过程,是海效应事件天气现象之一,其发生发展机理与内陆地区降雨有明显区别。利用综合观测资料统计分析了1999—2020年31次渤海海效应降雨过程的基本特征,通过典型个例分析揭示了海效应降雨的形成机理,并与渤海海效应降雪进行了比较。结果表明:1)渤海海效应降雨发生在10月中旬至11月,以11月中上旬发生频率最高;10月为纯雨,11月可产生纯雨,也有雨转雨夹雪(雪)或雨雪共存的天气过程;海效应降雨分布在山东半岛北部沿海地区,站点过程降雨量均为小雨;每次降雨过程持续时间不超过1 d。2)海效应降雨发生时的冷空气强度比海效应降雪弱,降雨时山东半岛850 hPa的温度10月在-1 ℃左右,11月在-6 ℃左右;11月发生雨转雨夹雪或雪时850 hPa的温度一般在-9~-8 ℃,地面气温集中在2~4 ℃。3)典型渤海海效应降雨过程环流形势表现为500 hPa冷涡、850 hPa西北冷平流和地面冷高压,强冷空气入侵渤海和山东半岛,对流层低层的温度和海面的温度差明显增大,暖海面向上输送感热通量,790 hPa以下北部沿海地区产生浅层对流不稳定;海陆不同下垫面和低山丘陵地形影响形成风向风速辐合,触发不稳定能量而产生海效应降雨;自动站风场和雷达径向速度均表现出强海效应降雨时段北部沿海地区对流层低层存在偏东北风与西北风之间的切变线及明显的风速辐合,最大雷达反射率因子为45~50 dBz。4)本文分析表明渤海效应降雨的形成机理与海效应降雪类似,其环流形势、水汽来源、热力、动力及雷达径向速度特征基本相同,主要差异在于海温和冷空气强度。渤海海效应降雨的预报关键期为10月下旬至11月。
英文摘要:
   Ocean-effect rain occurs when strong cold air flows through warm sea surface, as one of the ocean-effect events. There are remarkable differencesin the mechanisms betweenocean-effect rain and other types rain inland. Based on various observed data, characteristics of 31 Bohai ocean-effect rain events from 1999 to 2020 are statistically analyzed, and typical ocean-effect rain event study reveals the mechanisms. Moreover, the comparative analysis on Bohai ocean-effect rain and ocean-effect snow are conducted. The results are as follows.1) Bohai ocean-effect rain usually occurs between the middle ten-day period of October and November. It remains the highest frequency in the first and middle ten-day period of November. As precipitation types, rain occurs in October; while rain, sleet or snow occurs in November. Bohai ocean-effect rain is distributed in the north coastal area of Shandong peninsula with light rain and duration less than 1 day.2)The cold air intensity of ocean-effect rain is weaker than ocean-effect snow.To rain, temperature is about -1 ℃ at 850 hPa in Shandong peninsula in October, while it’s -6 in November. To sleet or snow during ocean-effect rain process, the temperatureat 850 hPa is usually -9 to -8 , and air temperature at surface is 2 to 4 . 3) There is cold vortex at 500 hPa, north-west cold advection at 850 hPa and cold high pressure system at surface for typical Bohai ocean-effect rain event. Strong cold air affects Bohai and Shandong peninsula. It leads to distinct temperature between low troposphere and sea surface. Sensible heat flux comes from warm sea surface, which produces shallow instability below 790 hPa layer in the north coastal area. Because of different surface and hill topography, wind direction and wind speed becomes convergent. So it triggers unable unstable energy to rain. Obvious wind speed convergence and shear of north-east wind and north-westwind at low troposphere can be observed easily by automatic station wind and Doppler radial velocity field. Maximum radarSreflectivitySfactor is 45 to 50 dBz when it rains. 4) This study shows that mechanism of ocean-effect rain is similar to ocean-effect snow, with the major same circulation, water vapor source, thermal conditions, dynamic conditions and Doppler radial velocity field. Their obvious difference lies in sea surface temperature and cold air intensity. In the end,the last ten-day of October and November is forecast critical period for Bohai ocean-effect rain.
View Fulltext   查看/发表评论  下载PDF阅读器
关闭