Cross-verification of simulated GEMS tropospheric ozone retrievals and ozonesonde measurements over Northeast Asia

Abstract

Abstract. The Geostationary Environment Monitoring Spectrometer (GEMS) is scheduled to be launched in 2019 on board the GEO-KOMPSAT (GEOstationary KOrea Multi-Purpose SATellite)-2B, contributing as the Asian partner of the global geostationary constellation of air quality monitoring. To support this air quality satellite mission, we perform the cross-verification of simulated GEMS ozone profile retrievals based on the Optimal Estimation and ozonesonde measurements within the GEMS domain, covering from 5° S (Indonesia) to 45° N (south of the Russian border) and from 75° E to 145° E. The comparison between ozonesonde and GEMS shows a significant dependence on ozonesonde types. Ozonesonde data measured by Modified Brewer-Master (MB-M) at Trivandrum and New Delhi show inconsistent seasonal-variabilities in the tropospheric ozone, compared to latitudinally adjacent stations with Carbon Iodine (CI) and Electrochemical Condensation Cell (ECC). CI ozonesonde measurements are biased relative to ECC measurements by 2–4 DU; a better agreement with GEMS simulations is achieved with ECC measurements. ECC ozone data at Hanoi, Kuala Lump, and Singapore show abnormally worse agreements with simulated GEMS retrievals among ECC measurements. Therefore, ECC ozonesonde measurements at Hong Kong, Pohang, Naha, Sapporo, and Tsukuba are finally identified as an optimal reference. The accuracy of simulated GEMS retrievals is estimated to be ~ 5.0 % for both tropospheric and stratospheric column ozone with the precision of 15 % and 5 %, which meet the GEMS ozone requirements.