Abstract
We derived global tropospheric ozone (O3) columns from GOME-2A (Global Ozone Monitoring Experiment) and OMI (Ozone Monitoring Instrument) O3 profiles, which were simultaneously assimilated into the TM5 (Tracer Model, version 5) global chemistry transport model for the year 2008. The horizontal model resolution has been increased by a factor of 6 for more accurate results. To reduce computational cost, the number of model layers has been reduced from 44 to 31. The model ozone fields are used to derive tropospheric ozone, which is defined here as the partial column between mean sea level and 6 km altitude. Two methods for calculating the tropospheric columns from the free model run and assimilated O3 fields are compared. In the first method, we calculate the residual between assimilated total columns and the partial model column between 6 km and the top of atmosphere. In the second method, we perform a direct integration of the assimilated O3 fields between the surface and 6 km. The results are validated against tropospheric columns derived from ozone sonde measurements. Our results show that the residual method has too large a variation to be used reliably for the determination of tropospheric ozone, so the direct integration method has been used instead. The median global bias is smaller for the assimilated O3 fields than for the free model run, but the large variation makes it difficult to make definitive statements on a regional or local scale. The monthly mean ozone fields show significant improvements and more detail when comparing the assimilated O3 fields with the free model run, especially for features such as biomass-burning-enhanced O3 concentrations and outflow of O3 rich air from Asia over the Pacific.
| Original language | English |
|---|---|
| Pages (from-to) | 8297-8309 |
| Number of pages | 13 |
| Journal | Atmospheric Chemistry and Physics |
| Volume | 19 |
| Issue number | 12 |
| DOIs | |
| Publication status | Published - 27 Jun 2019 |
Funding
Acknowledgements. The authors acknowledge all scientists and institutes who contributed their ozone sonde data to the World Ozone and Ultraviolet Radiation Data Center (WOUDC, WMO/GAW, 2016) and the Meteorological Service of Canada for hosting this important public database. EUMETSAT is acknowledged for providing the GOME-2 L1 data and Olaf Tuinder and Robert van Versendaal for their help in the retrieval of the GOME-2 ozone profiles. The Dutch–Finnish OMI instrument is part of the NASA EOS Aura satellite payload. The OMI ozone profiles (OMO3PR, v003) were retrieved at the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC) and accessed from the local storage at the Royal Netherlands Meteorological Institute (KNMI). This research was part of the Ozone_cci project (http: //www.esa-ozone-cci.org, last access: 1 December 2018), which is part of the Climate Change Initiative (CCI) programme of the European Space Agency (ESA).
