浙江臭氧污染特征及与气象条件关系分析

Characteristics and its relationship with meteorological conditions of ozone pollution in Zhejiang

臭氧是光化学污染的主要污染物之一,开展近地面臭氧浓度变化特征及其与气象条件相关性分析对防治大气污染十分重要。利用2014—2019年浙江112个环境监测站点的臭氧观测资料、欧洲中期数值预报中心ERA-Interim再分析资料分析发现:浙江春、夏季臭氧污染较重,杭州、嘉兴、金华、衢州5—9月臭氧浓度高,宁波4—5月臭氧浓度高。臭氧浓度日变化特征明显,一般14:00达到日最高值。利用K均值聚类法对春夏季全省性臭氧高浓度日分型,Ⅰ型为浙东北型,Ⅱ型为全省型。春季Ⅰ型占70.3%,Ⅱ型占29.7%;夏季Ⅰ型占67.7%,Ⅱ型占32.3%。臭氧浓度受风向、风速影响明显。杭州在西北风控制下,嘉兴在西南风控制下,金华在西南、东南风控制下,衢州在偏西、东南风控制下,容易造成臭氧浓度增高。浙江在500 hPa高度场为弱负距平,附近区域850 hPa风场为偏北风,相对湿度偏低,下沉运动偏强等天气特征下,容易导致全省臭氧浓度偏高。

Ozone is one of the main factors of photochemical pollution.To better prevent the air pollution,it is very important to analyze the variation characteristics of near-surface ozone concentration and its correlation with meteorological conditions.Based on ozone observations from 112 stations of Zhejiang from 2014 to 2019 and ERA-Interim reanalysis from the European Centre for Medium-Range Weather Forecasts,analysis was carried out to investigate ozone characteristics of Zhejiang.Results showed that ozone pollution in spring and summer was heavier than the other seasons.Ozone concentrations from May to September were high in Hangzhou,Jiaxing,Jinhua and Quzhou,and those from April to May in Ningbo.Ozone concentrations displayed an obvious diurnal variation,and reached its peak at about 14:00.K-means clustering method was used to do classification on high ozone concentration days in spring and summer,and two types,namely typeⅠand typeⅡ,were reasonable.For typeⅠ,stations with high ozone concentrations were mainly located in northeastern Zhejiang,and for typeⅡlocated all over the whole province.TypeⅠandⅡcovered percentage of 70.3%and 29.7%respectively in spring,while 67.7%and 32.3%in summer.Ozone concentrations were obviously affected by wind directions and speeds.They tended to go up easily when under northwesterly winds in Hangzhou,southwesterly winds in Jiaxing,southwesterly and southeasterly winds in Jinhua,and westerly and southeasterly winds in Quzhou.It was favorable to result in high ozone concentrations when Zhejiang was under control of weak negative anomaly field at 500 hPa,northerly winds at 850 hPa,as well as low relative humidity and strong sinking motion and so on.