Deriving tropospheric ozone from assimilated profiles

van Peet, Jacob C. A.; van der A, Ronald J.

We derived global tropospheric ozone (inline-formulaO3) columns from GOME-2A (Global Ozone Monitoring Experiment) and OMI (Ozone Monitoring Instrument) inline-formulaO3 profiles, which were simultaneously assimilated into the TM5 (Tracer Model, version 5) global chemistry transport model for the year inline-formula2008. The horizontal model resolution has been increased by a factor of inline-formula6 for more accurate results. To reduce computational cost, the number of model layers has been reduced from inline-formula44 to inline-formula31. The model ozone fields are used to derive tropospheric ozone, which is defined here as the partial column between mean sea level and inline-formula6inline-formulakm altitude. Two methods for calculating the tropospheric columns from the free model run and assimilated inline-formulaO3 fields are compared. In the first method, we calculate the residual between assimilated total columns and the partial model column between inline-formula6inline-formulakm and the top of atmosphere. In the second method, we perform a direct integration of the assimilated inline-formulaO3 fields between the surface and inline-formula6inline-formulakm. 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 inline-formulaO3 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 inline-formulaO3 fields with the free model run, especially for features such as biomass-burning-enhanced inline-formulaO3 concentrations and outflow of inline-formulaO3 rich air from Asia over the Pacific.

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Zitierform:

van Peet, Jacob C. A. / van der A, Ronald J.: Deriving tropospheric ozone from assimilated profiles. 2019. Copernicus Publications.

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Rechteinhaber: Jacob C. A. van Peet

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