Ground-based validation of the MetopA and B GOME-2 OClO measurements

• Main Authors: Pinardi, G., Roozendael, M., Hendrick, F., Richter, A., Valks, P., Alwarda, R., Bognar, K., Frieß, U., Granville, J., Gu, M., Johnston, P., Prados-Roman, C., Querel, R., Strong, K., Wagner, T., Wittrock, F., Gonzalez, M.
• Format: Report
• Language: English
• Published: 2021
• Subjects: Arctic; Antarctic; Antarc*
• Online Access: http://hdl.handle.net/21.11116/0000-000A-7970-0

This paper reports on ground-based validation of the atmospheric OClO data record produced in the framework of EUMETSAT’s Satellite Application Facility on Atmospheric Chemistry Monitoring (AC SAF) using the GOME2-A and -B instruments over the 2007–2016 and 2013–2016 periods, respectively. OClO slant column densities are compared to correlative measurements collected from 9 NDACC Zenith-Scattered-Light DOAS (ZSL-DOAS) instruments distributed in both the Arctic and Antarctic. Sensitivity tests are performed on the ground-based data to estimate the impact of the different OClO DOAS analysis settings. On this basis, we infer systematic uncertainties of about 25 % between the different ground-based data analysis, reaching total uncertainties ranging from about 26 % to 33 % for the different stations. Time-series at the different sites show good agreement between satellite and ground-based data, both for the inter-annual variability and the overall OClO seasonal behavior. GOME-2A results are found to be nosier than those of GOME-2B, especially after 2011, probably due to instrumental degradation effects. Daily linear regression analysis for OClO activated periods yield correlation coefficients of 0.8 for GOME-2A and 0.87 for GOME-2B, with slopes of 0.64 and 0.72, respectively. Biases are within 8 x 1013 molec/cm2 with some differences between GOME-2A and GOME-2B, depending on the station. Overall, considering all the stations, a median bias of about −2.2 x 1013 molec/cm2 is found for both GOME-2 instruments.