成渝地区空气重污染天气形势分析

Analysis of the synoptic situation of heavy polluted weather in Chengdu-Chongqing region

利用Lamb-Jenkinson客观环流分型法,对成渝地区及4个子区域2014—2018年高度场和海平面气压场进行了环流分型,并探讨了环流型与空气污染的关系.结果表明,成渝地区海平面气压场的最高频率环流型为东北气流型(NE),850 hPa上为高压型(A),500 hPa上为平直西风气流型(W).综合来看,成渝地区易发生污染天气形势是:高空500 hPa为平直西风(W),地面和850 hPa上为低压(C)或东南气流型(SE);易出现优良天气的环流形势是:高空500 hPa为平直西风(W),地面和850 hPa上为高压(A)或东北气流型(NE).对个例进行分析后发现,当地面为气旋或东南气流,同时风速较小时,不利于污染物的水平扩散;若高空为弱脊控制或者为槽后西北气流,则在下沉气流的作用下,不利于污染的垂直扩散,地面污染进一步加重.

In this article,Lamb-Jenkinson objective circulation classification method is used to analyze the height field and sea level pressure field of the Chengdu-Chongqing area and its four sub-areas from 2014 to 2018,and the relationship between circulation pattern and air pollution is explored.The following conclusions are obtained:The highest frequency circulation patterns of sea level pressure field in Chengdu-Chongqing region are northeast airflow pattern(NE),high pressure pattern(A)at 850 hPa,and westerly airflow pattern(W)at 500 hPa;Overall,the circulation situations that are likely to cause pollution over the Chengdu-Chongqing region include:it is the westerly airflow(W)at 500 Pa,and it is the low pressure(C)or the southeast airflow(SE)at the sea level pressure field and 850 hPa.The circulation situations that are prone to good weather include:it is westerly airflow(W)at 500 hPa,it is the high pressure(A)or northeast airflow(NE)at sea level pressure field and 850 hPa.After analyzing the cases,the results show that when the sea level pressure field is cyclone or southeast airflow,and the wind speed is small,it will suppress the horizontal diffusion of pollutants;when the upper layer is controlled by weak ridges or the northwest airflow behind the trough,it will suppress the vertical diffusion of pollutants,and the ground pollution is further aggravated underneath the effect of the downdraft.