Improved Satellite Retrieval of Tropospheric NO<sub>2</sub> Column Density via Updating of Air Mass Factor (AMF): Case Study of Southern China

oleh: Hugo Wai Leung Mak, Joshua L. Laughner, Jimmy Chi Hung Fung, Qindan Zhu, Ronald C. Cohen

Format: Article
Diterbitkan: MDPI AG 2018-11-01

Deskripsi

Improving air quality and reducing human exposure to unhealthy levels of airborne chemicals are important global missions, particularly in China. Satellite remote sensing offers a powerful tool to examine regional trends in NO<sub>2</sub>, thus providing a direct measure of key parameters that strongly affect surface air quality. To accurately resolve spatial gradients in NO<sub>2</sub> concentration using satellite observations and thus understand local and regional aspects of air quality, a priori input data at sufficiently high spatial and temporal resolution to account for pixel-to-pixel variability in the characteristics of the land and atmosphere are required. In this paper, we adapt the Berkeley High Resolution product (BEHR-HK) and meteorological outputs from the Weather Research and Forecasting (WRF) model to describe column NO<sub>2</sub> in southern China. The BEHR approach is particularly useful for places with large spatial variabilities and terrain height differences such as China. There are two major objectives and goals: (1) developing new BEHR-HK v3.0C product for retrieving tropospheric NO<sub>2</sub> vertical column density (TVCD) within part of southern China, for four months of 2015, based upon satellite datasets from Ozone Monitoring Instrument (OMI); and (2) evaluating BEHR-HK v3.0C retrieval result through validation, by comparing with MAX-DOAS tropospheric column measurements conducted in Guangzhou. Results show that all BEHR-HK retrieval algorithms (with <i>R</i>-value of 0.9839 for v3.0C) are of higher consistency with MAX-DOAS measurements than OMI-NASA retrieval (with <i>R</i>-value of 0.7644). This opens new windows into research questions that require high spatial resolution, for example retrieving NO<sub>2</sub> vertical column and ground pollutant concentration in China and other countries.