Study Of Inter-product Deviations Of OMI And TROPOMI Tropospheric NO₂ Vertical Column Density In The Yangtze River Delta Region

As an important economic development city cluster in China,accurate monitoring of the tropospheric NO₂VCD in the Yangtze River Delta region will help to understand the ecological and environmental risks in the region.In the face of such management needs,meteorological monitoring satellites have become a major tool for monitoring and managing atmospheric ecosystems.However,data biases exist between different satellite products due to differences in sensors.The uncertainty of these biases and the sensitivity of the control factors need to be further investigated to provide a technical reference for the independent development and reliable application of future meteorological satellite products for high-quality tropospheric NO₂VCD.In this study,the deviations between TROPOMI and OMI NO₂VCD products are analyzed,explores the development of an R language gridding procedure for both L2 products,and the control factors that may cause the product deviations are further modeled and analyzed using a decision tree model.It was found that:1.The product distribution pattern of tropospheric NO₂VCD is generally similar for both satellites.On a time scale,the magnitude of tropospheric NO₂column concentrations is winter>autumn>spring>summer.Spatially,the tropospheric NO2VCDs are relatively high in the Shanghai region,while in the rest of the region,the NO₂concentration generally peaks only in November,December and January,which should be related to the winter heating.2.There are significant differences in the distribution of deviations between the products of NO₂VCD from the two satellites.Smaller deviations for the two sensor products in the region of high NO₂VCD values and larger deviations between products in the region of low NO₂VCD values.The mean inversion values of the OMI NO₂product can exceed those of the TROPOMI product by 1000μmol/m².3.Sensor parameters are the main control factor for the deviation of the satellite products,with meteorological factors having less influence.The sensitivity of the deviation between the two products to the difference between sensor imaging geometry is high,with a number of meteorological factors in the top ten sensitivities,with a high degree of correlation being cloudiness,cloud pressure,and easterly winds.The zenith angle is a control factor that significantly increases the deviation between the two products and is more stable in the YRD region.The azimuthal angle deviation of the sensors themselves is more related to the combined performance of the product inversion results.The results of the two sensors and different inversion algorithms are relatively stable in the face of different meteorological conditions.An increase in the value of the above control factors generally increases the difference in tropospheric NO₂VCD between the two products significantly,and the study again demonstrates that an increase in surface reflectance reduces the absolute product bias.In subsequent satellite development it is necessary to focus on zenith angle conditions in the sensor measurement area,azimuthal differences in the sensor itself,and to enhance the ability to observe meteorological conditions,especially cloud volume and pressure,from satellites.