成都地区春季一次持续性灰霾天气过程特征及预测

Characteristics of a haze weather event and prediction during spring in Chengdu

选取2013年2月25日至3月11日成都地区一次严重污染天气过程,利用成都地区环境监测中心站观测数据、成都市温江气象站观测资料、欧洲中心0.75°×0.75°再分析资料及成都信息工程学院风廓线雷达资料,对此次成都地区灰霾天气过程的特征进行了分析,研究不同气象条件对污染物扩散的影响,并建立了PM2.5浓度预测方程。结果表明:成都地区春季此次灰霾天气过程高空形势稳定,地面由均压场或弱低压控制且未形成降水时,有利于污染物的积聚与加强,但高空有低槽系统,低压一旦增强,灰霾消散的几率增大;垂直方向风速较小且为下沉气流,为灰霾天气的产生提供了有利条件。低层0—200 m之间存在较强的接地逆温,接地逆温层的结构对空气对流产生抑制作用,有利于水汽的积聚和雾的形成,出现灰霾天气的几率较大。出现灰霾天气时,混合层高度一般较低。采用逐步回归方法建立了PM2.5浓度预报模型并进行回代检验,在此基础上利用建立的模型对成都地区春季一次灰霾过程进行预报,结果表明,模型可准确的预报污染等级,预报效果较理想。

A serious haze weather event from February 25 to March 12,2013 was selected in this paper.Based on the environmental data from monitoring stations of Chengdu,meteorological data from weather stations,0.75° ×0.75° reanalysis data of ERA and wind profile radar data in Chengdu University of Information Technology,meteorological characteristics and effect of different meteorological conditions on pollutants diffusion in this process were analyzed.A forecast equation of PM2.5concentration was established.The results showthat it is stable in upper level.Surface is controlled by the uniform pressure field or weak lowpressure and no precipitation.These conditions are favorable to formation of pollution.However,there is lowtrough system in upper altitude.If lowpressure enhances on surface,haze dissipation probability increases.Lowwind speed and downdraft in vertical direction avail to product haze weather.Temperature inversion in boundary layer is another important feature.Strong ground temperature inversion exists from 0 m to 200 m,and its structure has inhibitory effect on convection current and in favor of accumulating vapor to form the mist,thus there are more chances to generate haze weather.When there is a haze weather event,the height of mixing layer is generally low.A PM2.5concentration model is established using a stepwise regression method,and its back inspection is done.Another haze weather event in spring in Chengdu is forecasted using this model.Pollution grade can be accurately forecasted,and its prediction results are relatively satisfactory.