As improved and accumulated satellite records become available, it is significant to provide up-to-date perspectives on the spatiotemporal signatures of tropospheric nitrogen dioxide (NO2) over China, the knowledge of which is helpful for air pollution control. In this study, the Ozone Monitoring Instrument NO2 dataset for the last 10 years (2005–14) was retrieved to examine multiple aspects of NO2 columns, including distributions, trends, and seasonal cycle. The pattern of average NO2 suggests five hotspots with column density higher than 20 × 1015 molec cm?2: Jing-Jin-Tang; combined southern Hebei and northern Henan; Jinan; the Yangtze River Delta; and the Pearl River Delta. Furthermore, substantial and widespread NO2 growths are distributed over the North China Plain. By contrast, downward trends in NO2 amounts prevail in the megacities of Beijing, Shanghai, and Guangzhou, despite generally high loading levels. Except for the Pearl River Delta, there appears to be temporally consistent behaviors across all regions considered, where NO2 had an abrupt decline during 2008 to 2009, then a drastic increase up to 2013, before beginning to reduce again after 2013. However, the NO2 over the Pearl River Delta is not coevolving with the rest, having experienced a moderate rise from 2005 to 2007, followed by a reduction thereafter. A marked seasonality is apparent, with a maximum in winter and a minimum in summer, regardless of the region. The annual amplitude of NO2 is less pronounced over the Pearl River Delta, whereas the largest range is observed over the combined Southern Hebei and Northern Henan region, induced by enhanced NO2 emission in wintertime due to intense domestic heating.
NO2是我国空气三大主要污染物之一，给居民健康带来极大的危害。虽然针对中国区域NO2的分布特征已经开展了一系列的研究工作，但这些文献反映的基本是2009年之前的状况。伴随着卫星监测NO2资料的不断补充和积累，以及卫星数据反演精度的提高，有必要重新评估现今中国区域NO2的时空分布特征，从而为我国大气环境质量的评价和污染防治提供科学依据。本研究基于OMI(Ozone Monitoring Instrument)传感器反演的最近十年(2005-2014)的对流层NO2柱总量，分析其空间分布、长期变化趋势和季节循环特征。NO2浓度大于20×1015molec cm-2的区域有5个，分别是京津唐地区、河北南部和河南北部地区、济南地区、长江三角洲地区和珠江三角洲地区。同时，华北平原的NO2增长趋势最为显著。但是，北京、上海和广州等特大城市的NO2浓度却呈现逐渐下降的趋势。除珠江三角地区外，其它4个地区的NO2演变的时间序列有共同的特征，即在2008-2009年浓度大幅降低，随后稳定增加至2013年，2013后又再次减少；珠江三角洲地区的NO2演变则表现为2005-2007年缓慢增加，之后持续下降。最后，中国区域的NO2具有明显的季节变化：冬季浓度高，夏季浓度低。NO2浓度最小的年较差位于珠江三角洲，而最大的年较差位于河北南部和河南北部区域，其原因是由于北方冬季取暖增加了NO2的排放量。