Study On Spatial And Temporal Change Of Tropospheric NO₂Vertical Column Densities In Hebei Province Using OMI Remote Sensing Data

NO₂is one of the important trace gases in the troposphere, and it is an importantprecursor of ozone, acid rain and light chemical smoke. It is also a major atmosphericpollutants in the urban atmosphere, the concentration of NO₂is regarded as one of theindicators of air pollution strength．Satellite remote sensing monitoring is a new type ofatmospheric detection method formed in the1960s．It has the advantage of wide monitoringscope,short repetition period, high resolution, low cost, multi-platform and multispectral andgradually replaces the traditional air pollution monitoring．Measurements of the globaldistribution of the trace gas have become available with the Ozone Monitoring Instrument（OMI） onboard NASA’s Aura Mission．It provides an important basis for the study of theearth’s climate change and atmospheric environment．Hebei province lies in north China withstrong human activities. In recent years, with the rapid increase of population, the rapideconomic development, especially large-scale industrial development and the increase ofmotor vehicles，the increasing trend of tropospheric NO₂vertical column density is more andmore obvious．This paper uses the OMI NO₂column densities data provided by tropospheric emissionmonitoring network （TEMIS）, under the support of ENVI4.5, Arc GIS10.0and Excelsoftwares，to make the research on spatial and temporal distribution characteristics oftropospheric NO₂vertical column density in Hebei Province from2005to2012and itsinfluencing factors. Results show that using OMI data to study the spatial and temporalcharacteristics of tropospheric NO₂vertical column density in Hebei Province is feasible, andthis has important practical significance in North China’s atmospheric environment and airquality improvement. The main research conclusions are as follows：（1）From interannual change perspective，the tropospheric NO₂vertical column densityin hebei province from2005to2012appeared an increasing trend year by year, and NO₂value reached the maximum in2011, and it decreased in2012. From monthly changeperspective, the monthly mean of tropospheric NO₂column density in Hebei Provincepresents the annual cyclical changes, the maximum generally appeared in January orDecember, and the minimum appeared in July or August. From2005to2012, the highest NO₂value was26.072×10¹⁵molec/cm²in December2009, and the lowest NO₂value was4.3493×10¹⁵molec/cm²in August2005. About NO₂seasonal changes, the tropospheric NO₂ column density values in autumn and winter in Hebei Province were significantly higher thanthose in spring and summer. The highest NO₂value appeared in winter and the lowestappeared in summer.（2） The spatial distribution of tropospheric NO₂vertical column density in hebeiProvince was not balanced，NO₂values in northern and southern areas formed obviouscontrast, and it presented a decreasing trend from southeast to northwest. The high NO₂values in hebei province distributed in the southwest of hebei plain, including Shijiazhuang,Xingtai Handan．The medium NO₂values distributed in the north of Baoding, Langfang andHengshui, and in the south of Tangshan and Qinhuangdao．The low NO₂values distributedin the north of Taihang mountain, Zhangjiakou City and Chengde City in Bashang plateau andthe north of Zhangjiakou, Qinhuangdao and Tangshan．（3） According to average annual NO₂column densities of each city in hebei province，eleven prefecture-level cities were divided into three classes, that is, high-value city, medium-city and low-value city．NO₂change trend in these cities had almost the same as that in hebeiprovince，and presented a significant seasonal change characteristics．High values oftropospheric NO₂column densities appeared in winter, concentrated in December and January,and low values in summer, concentrated in July and August. It presented an increasing trendyear by year overall.（4） There are many factors which influence the spatial and temporal distribution oftropospheric NO₂vertical column densities． The main natural factors are terraincharacteristics，geographic location and meteorological factors, and social factors are humanNO₂emissions，population density, economic development and vehicle ownership．HebeiProvince is located in the Northern Region of strong human activities, tropospheric NO₂ismainly from human emissions. the climate characteristic and the growing number of motorvehicles in Hebei Province have the largest contribution to spatial and temporal distribution oftropospheric NO₂vertical column dendities．...