石家庄市周边秸杆焚烧导致云凝结核变化的特征

Characteristics of CCN concentration change caused by straw burning around Shijiazhuang City

摘要:

利用DMTCCN仪定点观测的云凝结核(cloud condensation nuclei,CCN)粒子浓度资料,对2007年6月11-13日石家庄市出现的一次空气质量和能见度均十分差的灾害性极端天气事件进行了分析。结果表明,这次极端事件与周边地区焚烧秸杆的人为活动密切相关;对流层中、高层维持的下沉气流,迫使烟雾聚集在近地面层而使得CCN粒子数相对增加;垂直湍流交换微弱抑制了近地面层烟雾的垂直扩散,从而加剧低能见度的恶化,并导致霾天气形成;逆温层的厚度和地面静风、风速偏小同样使形成的烟雾在特殊地形作用下聚集。

关键词:秸杆焚烧;空气质量;CCN数浓度;霾

Abstract:

Based on the fixed-point observation data of CCN(cloud condensation nuclei) concentration fr om DMT(Droplet Measurement Technologies), an extreme disastrous weather occurred during June 11-13, 2007 in Shijiazhuang, with the air quality and visibility being both bad, is analyzed.Results show that the extreme weather is closely related to the straw burning(one of the human activities) around Shijiazhuang City.The persistent downward flow in the middle and high troposphere forces the smog to gather near the ground layer, and makes the number of CCN particles increases.The weak exchange of vertical turbulence restrains the vertical diffusion of smog near the ground layer, which makes the visibility much worse and leads to the formation of haze weather.The thickness of temperature inversion and the low wind velocity on the ground jointly enable the smog to accumulate over the special terrain.

Key words:straw burning;air quality;CCN concentration;haze