山东一次大范围持续性霾过程的气象条件分析

Meteorological Characteristics of a Continuous Haze Process in Shandong

2016年12月30日至2017年1月8日,山东出现了以PM2.5为首要污染物、持续几天、大部地区重度以上污染的霾天气。基于多种实况观测资料和ERA-Interim再分析资料,分析了此次过程天气背景和边界层特征等。结果发现:高空平直纬向环流、地面弱气压场、典型的静稳天气,有利于霾维持较长时间。此次过程期间有3次冷空气影响,冷空气的强度影响霾的变化,弱冷空气难以破坏近地层逆温结构,并会从上游向下输送污染物,有利于污染物的累积;较强冷空气带来较强的垂直运动,破坏了静稳天气形势,有利于污染物的扩散及清除。此次过程稳定层结形势下,边界层高度是一个对霾有指示意义的物理量。边界层高度和AQI的变化呈滞后负相关关系,边界层高度降低之后对应AQI指数升高。逆温层长时间的存在是此次霾持续的重要条件,另外由于地理原因东南风增湿和逆温层顶高度降低都会导致污染物浓度增大,使霾加重。

From 30 December 2016 to 8 January 2017,a haze weather with PM2.5 as the main pollutant lasted for several days and severe pollution appeared in most areas of Shandong Province.Based on the observational data and ERA-Interim reanalysis data,the weather background and boundary layer characteristics of the process are analyzed.The results show that the condition of horizontal zonal circulation at high altitude,the weak pressure field on the ground and the typical stable weather patterns,were conducive to the continuous haze.During the process,three cold air processes appeared.The intensity of cold air affected the change of haze.Weak cold air could not destroy the inversion structure near the surface.At the same time,weak cold air transported pollutants from upstream,which was favorable for the accumulation of pollutants.Strong cold air brought strong vertical movements and destroyed the stable weather situation,which facilitated the diffusion and the removal of pollutants.Under the stable weather condition,the boundary layer height was an indicative physical quantity for the haze.The change of boundary layer height and AQI had a lag negative correlation relationship,and thus the AQI index increased when the boundary layer height decreased.The existence of an inversion layer for a long time was an important condition for the continuation of the haze.In addition,due to geographical reasons,the low layer southeast wind increased the humidity and the reduction of inversion layer top height,which both led to the increase of pollutant concentration,so to aggravate the haze.