上海海陆风分类特征、环流背景及对O_(3)的影响

Classification characteristics,circulation background and its effect on O_(3) of land and sea breeze in Shanghai

针对2013~2019年上海三类海陆风(北支、南支和双支)过程,从气象要素(温度、湿度和风)、形成海陆风的六种环流背景及对O_(3)浓度的影响等方面进行了对比分析.结果表明:2013~2019年上海共出现海陆风237d,其中北支天数最多(209d),双支天数最少(88d),南支出现双支海陆风的比例最高(75.9%);三类海陆风中北支的起始时间最早,维持时间最长,海风强度最强,南支的平均温度最高,平均湿度较低,风场最分散;与无海陆风相比,北支、南支和双支海陆风的O_(3)浓度分别上升了20.5,26.4,25.1μg/m^(3),O_(3)污染浓度上南支与无海陆风持平,北支和双支均略低于无海陆风;在形成上海海陆风的6种弱环流背景中,高压中心型、无系统型和均压场型是最主要的三种类型,合计占比70%;环流背景和海陆风类型组合结果显示,上海海陆风中O_(3)污染概率最高的组合是均压场型的南支海陆风,达到40.0%,O_(3)浓度和O_(3)污染浓度最高的组合分别是无系统型的南支海陆风和高压前部型的双支海陆风,平均浓度分别为146.6,211.3μg/m^(3).

A comparative analysis was made from meteorological factors(temperature,humidity and wind),six circulation backgrounds that formed sea land breeze and their impacts on O_(3)concentration of three types of land and sea breeze(North Branch,South Branch and Double Branch)in Shanghai from 2013 to 2019.The results show that there were 237 days of land and sea breeze in Shanghai from 2013 to 2019,of which the North Branch had the most days(209d)and the Double Branch had the least days(88d).The proportion of Double Branch land and sea breeze with the South Branch was the highest(75.9%);Among the three types of land and sea breeze,the North Branch had the earliest starting time,the longest maintenance time and the strongest sea breeze intensity.The South Branch had the highest average temperature,lower average humidity,and the most dispersed wind field;Compared with no sea and land breeze condition,O_(3)concentration in North Branch,South Branch and Double Branch increased by 20.5,26.4 and 25.1μg/m^(3) respectively.O_(3)pollution concentration in South Branch was the same as that in no sea and land breeze condition,while that in North Branch and Double Branch were slightly lower than that in no land and sea breeze condition.Among the six weak circulation backgrounds forming Shanghai land and sea breeze,the high-pressure central type,the unsystematic type and the pressure equalizing field type were the most important three types,accounting for 70%in total;The results of the combination of circulation backgrounds and land and sea breeze types show that the highest probability of O_(3)pollution was the South Branch land and sea breeze of pressure equalization field type,reaching 40.0%.The highest combination of O_(3)concentration and O_(3)pollution concentration was South Branch land and sea breeze with the unsystematic type and the Double Branch land and sea breeze with the high pressure front type,with the average concentration of 146.6μg/m^(3) and 211.3μg/m^(3),respectively.