中国对流层臭氧的时空变化及影响因素研究

Spatiotemporal Dynamics and Driving Factors of Tropospheric Ozone in China

近年来臭氧(O_(3))浓度的升高给人类健康和气候变化带来了许多负面影响,因此迫切需要认识对流层O_(3)柱浓度的时空演变特征及影响因子。本研究基于OMI-MLS数据,分析了2005-2020年我国对流层O_(3)柱浓度的时空分布特征及变化趋势,采用随机森林模型量化了我国对流层O_(3)柱浓度影响因子的重要性。结果表明:①在月尺度上,我国OMI-MLS对流层O_(3)柱浓度与站点近地面O_(3)浓度显著相关,87.81%站点的近地面O_(3)浓度与OMI-MLS对流层O_(3)柱浓度的皮尔逊相关系数大于0.50(P<0.05)。在季尺度上,我国OMI-MLS对流层O_(3)柱浓度与站点近地面O_(3)浓度在春、秋两季相关性较高,在夏、冬两季相关性较差。②我国对流层O_(3)柱浓度多年平均值为34.42DU,整体呈东高西低的分布格局。2005-2020年我国对流层O_(3)柱浓度呈波动上升的趋势(0.228 DU/a),但各地区对流层O_(3)柱浓度的年际变化存在差异,华南地区的对流层O_(3)柱浓度增速(0.272 DU/a)最快,西南地区增速(0.209DU/a)最慢。③我国对流层O_(3)柱浓度季节性变化明显,表现为夏季>春季>秋季>冬季,并且对流层O_(3)柱浓度的季节变化趋势存在差异,对流层O_(3)柱浓度在夏季增速(0.265 DU/a)最快,春季、秋季(均为0.217 DU/a)次之,冬季(0.213DU/a)最慢。④对流层O_(3)柱浓度年际和季节变化的影响因子在重要性排序上存在差异,总体上,气象因子对我国对流层O_(3)柱浓度的影响程度最大,排放因子的影响程度较小。研究显示,我国对流层O_(3)柱浓度的时空分布存在显著差异,形成该时空分布格局的影响因子不同。

In recent years,increased ozone concentrations had many negative impacts on human health and climate change.Therefore,there is an urgent need to understand the spatiotemporal changes in tropospheric ozone column concentration and its influencing factors.Based on OMI-MLS satellite data,this study analyzed the distribution characteristics and temporal trends of tropospheric ozone column concentration from 2005 to 2020.The random forest model was used to further identify the contributions of factors affecting tropospheric ozone column concentration in China.The results showed that there was a strong agreement between the OMI-MLS tropospheric O_(3) column concentration and the surface ozone concentration from the sites in China at the monthly scale,with the Pearson correlation coefficient greater than 0.50(P<0.05)for 87.81% of the sites.At a seasonal scale,the correlation between OMI-MLS data and groundbased data in China was higher in spring and autumn,but weaker in summer and winter.There were significant spatial changes in multiyear average ozone column concentration,showing a pattern of high in the east and low in the west.From 2005 to 2020,the ozone concentration in China showed a fluctuating upward trend,with a growth rate of 0.228 DU/a.However,the interannual variations of tropospheric O_(3) column concentration exhibited the remarkable regional difference,with the fastest growth rate in South China(0.272 DU/a)and the slowest in Southwest China(0.209 DU/a).The seasonal variation in ozone column concentration was obvious,with the highest value in summer,followed by spring,autumn,and winter.In addition,the growth rate of ozone column concentration changed with seasons,with the fastest growth rate in summer(0.265 DU/a),followed by spring and autumn(both 0.217 DU/a),and the slowest growth rate in winter(0.213 DU/a).Factors influencing the interannual and seasonal variations of tropospheric O_(3) column concentration varied in their importance.Overall,meteorological factors had the greatest influence on tropospheric O_(3) column concentration in China,while emission factors had a relatively smaller impact The results show that there are significant differences in the spatiotemporal distribution characteristics of tropospheric ozone column concentration in China,and the influencing factors that cause these differences are different.