河北省边界层气象要素与PM2.5关系的统计特征

为了研究河北省边界层气象要素与PM_2.5的关系,综合利用常规气象探测资料、逐小时地面自动站气象观测资料、环境监测站逐小时AQI及ρ(PM_2.5)资料等进行了统计分析.结果表明:①冬季海平面气压低于1 030 hPa、24 h变压为-3.0~-2.0 hPa、地面相对湿度高于60%、露点温度高于-10 ℃时发生全省性重污染天气的可能性较大；而海平面气压高于1 040 hPa、24 h变压在4.0 hPa以上、地面相对湿度低于40%、露点温度低于-10 ℃时,有利于清洁天气的出现.清洁天气下边界层的盛行风向多与冷空气活动有关；污染天气下盛行风向有区域性差别,边界层小风(<3.0 m/s)的风速频率高于90%. ②过程雨量达到中雨及以上量级的降水对PM_2.5具有较明显的清除作用,中雨量级降水对PM_2.5清除速率约为2 h,但优良空气质量持续时间短,平均为15 h；大雨及以上量级的降水对PM_2.5清除率达67.8%,并且优良空气质量可以持续27 h. ③与降水相比,风对PM_2.5的清除作用更为显著.较强偏南风对空气质量有一定改善,但优良空气质量仅持续16 h；大于3.0 m/s的系统性偏北风对PM_2.5清除率高达85.1%,优良空气质量持续长达32 h,空气质量的改善最为彻底.研究显示,PM_2.5与边界层气象要素关系紧密,不同级别的风和降水对PM_2.5的清除程度存在显著差异. 

Statistical Analysis of the Relationship Between Meteorological Factors and PM2.5 in the Boundary Layer Over Hebei Province

Statistical analysis was synthetically conducted using conventional meteorological observation data, hourly meteorological automatic station data, hourly AQI and PM_2.5 concentration. The purpose was to investigate the relationship between meteorological factors in the boundary layer and PM_2.5 concentrations in Hebei Province. The results indicate that there is a significant difference between the boundary layer meteorological factors during clean and heavily polluted weather. The relevant conclusions are as follows:1) The conditions of sea level pressure lower than 1030 hPa, 24 h pressure variation below -3.0--2.0 hPa, surface relative humidity over 60% and dew point temperature higher than -10 ℃ are conducive for heavily polluted weather during winter. In contrast, the conditions of sea level pressure higher than 1040 hPa, 24 h pressure variation above 4.0 hPa, surface relative humidity under 40% and dew point temperature lower than -10 ℃ are beneficial for clean weather. Prevailing wind under clean weather is relevant to cold airflows in winter. In polluted weather, prevailing wind direction varies regionally, and the frequency of thin wind (lower than 3.0 m/s) in the boundary layer is above 90%. 2) Moderate and above magnitude precipitation has comparatively obvious removal effects, demonstrating the following rules:moderate-magnitude precipitation shows a rapid removal rate of PM_2.5 (around 2 h), but with a short duration (15 h on average) of excellent air quality. Heavy and above magnitude precipitation shows a high removal rate of PM_2.5 (about 67.8%), and with relatively long duration (about 27 h) of excellent air quality. 3) Removal of wind shows a more significant effect on PM_2.5 compared to precipitation. Relatively strong southerly wind significantly improves air quality but with a short duration (around 16 h). Systematic, northerly wind above 3.0 m/s shows the most significant removal rate, longest duration (32 h in average) of excellent air quality and most complete improvement of air quality (removal rate is about 85.1%). The research shows that PM_2.5 is closely related to the meteorological factors in the boundary layer, and there are significant distinctions in removal rates on PM_2.5 among different levels of wind and precipitation.