The Temporal–Spatial Characteristics of Column NO2 Concentration and Influence Factors in Xinjiang of Northwestern Arid Region in China

Abstract

This paper investigates the temporal–spatial characteristics of column NO2 concentration and influence factors in Xinjiang based on the Tropospheric Monitoring Instrument (TROPOMI) aboard the EU/ESA Sentinel-5 Precursor satellite. The findings indicate that there is a high linear correlation between TROPOMI NO2 data and ground-based data, with Yining having the highest correlation (R2 = 0.8132) and Aksu having the lowest correlation (R2 = 0.7307). The TROPOMI NO2 data can be used to approximate the characteristics of near-surface atmospheric NO2 concentration. NO2 VCD in the troposphere varies greatly geographically, with a noticeable ‘island’ pattern. The high-value zones are mostly found on the northern slope of Tianshan Mountain, in the capital cities of several prefectures, and occasionally in the industrial parks. Urumqi has the highest annual average NO2 VCD of 553.9 × 10−6 mol·m−2. The NO2 VCD is characterized by seasonal shifts and cyclical swings of “low in spring, high in winter, and transition in summer and autumn”. The monthly mean value is highest in December (27.14 × 10−6 mol m−2) and lowest in March (12.66 × 10−6 mol m−2). Meteorological factors can influence the temporal and spatial distribution of NO2 VCD. The GRA in Urumqi is 0.774 between the monthly mean of NO2 VCD and relative humidity. The main causes of the increase in NO2 VCD are man-made emissions. The annual GDP of the secondary industry and its annual average NO2 VCD in fifteen key cities in Xinjiang have a correlation coefficient of 0.78. TROPOMI NO2 data can provide strong support for the fine control of air pollution and air quality in early warning forecast in Xinjiang.