气象条件对河北廊坊城市空气质量的影响

气象条件是影响大气污染的重要因子.利用2013年3月—2014年2月廊坊颗粒物质量浓度监测资料、自动气象站观测资料和欧洲中期天气预报中心再分析资料,采用多种统计方法分析气象与污染的关系,量化天气形势和局地气象条件对城市颗粒物质量浓度变化的贡献.结果表明:天气形势是决定局地气象要素和城市空气质量的重要因子.当廊坊位于高压中心或高压后部时,大气层结稳定,易造成重污染；当廊坊位于高压前部(气压梯度较大)时,大气层结不稳定,易于污染物输送和扩散.利用客观天气分型结合污染物质量浓度统计分析方法,可以量化天气形势对城市空气质量的影响.在局地气象要素中,能见度与ρ(PM_2.5)、ρ(PM₁₀)相关性最高(相关系数分别为-0.75和-0.53,下同),其次依次为风速(-0.45和-0.31)、相对湿度(0.41和0.25)和温度(-0.15和-0.06).通过污染物浓度与局地风场关系分析发现,廊坊颗粒物质量浓度受天津市、河北省南部区域输送的影响明显,受北京区域输送的影响相对较弱.研究显示,气象条件可以解释廊坊ρ(PM_2.5)和ρ(PM₁₀)日均值变化的56%和49%,其在冬季对颗粒物质量浓度影响最为显著,春秋季次之,夏季影响最小. 

Impacts of Meteorological Conditions on Air Quality in Urban Langfang, Hebei Province

Abstract: Meteorological conditions are an important factor affecting air pollution. The effects of weather type and local meteorological conditions on pollutant concentrations in Langfang, a city in Northern China, were quantified based on statistical relationships established using observed particulate matter (PM) concentration, local meteorological conditions, and European Center for Medium Range Weather Forecasting (ECMWF) reanalysis data for the period March 2013-February 2014. Weather type was an important factor determining local meteorological conditions and urban air quality. Severe pollution occurred when Langfang was located in the center or the back of high pressure, while it was clean when Langfang was located in the front of high pressure with large pressure gradient. For local meteorological conditions, PM_2.5 and PM₁₀ concentrations were found to be highly correlated with atmospheric visibility (-0.75 and -0.53), followed by wind speed (-0.45 and -0.31), relative humidity (0.41 and 0.25) and temperature (-0.15 and -0.06). The relationship between PM concentrations and local wind revealed that air quality in Langfang was significantly affected by regional transport from Tianjin and southern Hebei Province, but less affected by pollutants transported from Beijing. Meteorological conditions could explain 56% and 49% of the day-to-day variation in PM_2.5 and PM₁₀ respectively, and their effects on PM concentration were the most significant in winter, followed by autumn, spring, and summer.