Evaluation of tropospheric NO2 columns observed from the Geostationary Environment Monitoring Spectrometer (GEMS)

Abstract

<p>Nitrogen dioxide (NO<sub>2</sub>) and nitrogen oxide (NO), usually referred to as nitrogen oxides (NO<sub>x</sub>), are emitted into the atmosphere by anthropogenic and natural sources. The detection and monitoring of NO<sub>2</sub> plays a key role in air quality managements because of its effects on health and of its contribution to the increase of tropospheric ozone and nitrate aerosols. Unfortunately, up to now, observations were possible only once a day based on satellites in low-earth orbit (GOME, GOME-2, OMI and TROPOMI). However, from now on, it is possible to observe the diurnal variations over the Asia based on Geostationary Environment Monitoring Spectrometer (GEMS) in geostationary earth orbit. Here, we present results of tropospheric nitrogen dioxide column observations with high temporal (hourly) and spatial resolutions over major cities in Asia. In addition, we evaluate the GEMS NO<sub>2</sub> operational algorithm by comparing GEMS total and tropospheric NO<sub>2</sub> columns with independent observations from ground-based Pandora (total column) and MAX-DOAS (tropospheric column). Additionally, we retrieved the GEMS tropospheric NO<sub>2</sub> columns by subtracting the stratospheric NO<sub>2</sub> columns, which are assumed based on SLIMCAT model data and then scalded with the real GEMS observations, from the total NO<sub>2</sub> columns. Then we also compared the tropospheric NO<sub>2</sub> columns that are retrieved based on GEMS NO<sub>2</sub> operational algorithm and SLIMCAT model, respectively. Lastly, we compared the GEMS NO<sub>2</sub> with other low-earth orbit satellite instruments that include OMI and TROPOMI.</p>