Trends and Spatiotemporal Patterns of Tropospheric NO2 over China During 2005–2014
2017
Yu, Shumei | Yuan, Jinguo | Liang, Xingyin
Nitrogen dioxide (NO₂) is one of the major atmospheric pollutants, and the concentration of NO₂ is regarded as one of the indicators of air quality. In the past decades, China has experienced rapid economic growth and severe NO₂ pollution to match. We evaluate the trends and spatiotemporal patterns of tropospheric NO₂ over mainland China from 2005 to 2014 using vertical column density (VCD) datasets retrieved from the Ozone Monitoring Instrument (OMI). Results show that from 2005 to 2014, NO₂ pollution regions have enlarged at the national scale, and high NO₂ VCDs are mainly concentrated over highly populated regions in eastern China. The year 2011 is the turning point. Tropospheric NO₂ VCDs first significantly increase by 0.19 × 10¹⁵ molec cm⁻² year⁻¹ (R ² = 0.94, P = 0.002) from 2005 to 2011, and then decrease by 0.21 × 10¹⁵ molec cm⁻² year⁻¹ (R ² = 0.97, P = 0.016) from 2011 to 2014. Since 2011, tropospheric NO₂ VCDs over central-east China decrease remarkably. Tropospheric NO₂ VCDs is higher in November (3.630 × 10¹⁵ molec/cm²), December (4.758 × 10¹⁵ molec/cm²), and January (4.863 × 10¹⁵ molec/cm²), while lower in July (1.684 × 10¹⁵ molec/cm²), August (1.627 × 10¹⁵ molec/cm²), and September (1.703 × 10¹⁵ molec/cm²), indicating that winter and spring are the most polluted seasons. Due to the huge gap in population density and industry development between western and eastern China, the spatial pattern of tropospheric NO₂ VCDs shows large west-east difference.
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