威海PM_(2.5)和PM_(10)造成重污染个例的气象条件对比分析

Comparative Analysis of Meteorological Conditions of Heavy Pollution Cases Caused by PM_(2.5) and PM_(10) in Weihai

通过对比分析2017年1月1日PM_(2.5)和4月30日PM_(10)造成重污染个例的气象条件发现,两者在低层都有暖脊,但天气形势背景差异较大。分析其物理量特征发现,在925 hPa两者都发生在20%~30%的相对湿度条件下,T-Td冬季大于12℃,春季大于20℃;两个个例都是上湿下干的浅对流大气层结,在低层都有逆温,但湿层和逆温层高度不同,风垂直切变也不同;两者在700 hPa上都是下沉运动,在925 hPa上都有弱的上升运动,但上升运动大小有差别。地面风向都存在南风和北风,风速都在4级以下。相对湿度PM_(2.5)在70%~98%,PM_(10)在10%~40%。

By comparing and analyzing the meteorological conditions of heavy pollution cases caused by PM_(2.5)on January 1 and PM_(10)on April 30,2017,it is found that both of them have warm ridges in the lower layer,but the weather situation background is quite different.By analyzing the characteristics of physical quantities,it is found that at 925 hPa,both of them occur at 20%~30%relative humidity,T-Td is greater than 12℃in winter and 20℃in spring;both of them are shallow convective atmospheric stratification with upper humidity and lower dryness,and there is inversion in the lower layer,but the height of wet layer and inversion layer is different,and the wind vertical shear is also different;both of them sink at 700 hPa,and at 925 hPa there is a weak ascending motion,but the ascending motion is different.There are south wind and north wind in the surface wind direction,and the wind speed is below grade 4.The relative humidity is 70%~98%for PM_(2.5)and 10%~40%for PM_(10).