Tropospheric ozone columns from TROPOMI/S5P, related nadir sensors and GEMS

TROPOspheric Monitoring Instrument (TROPOMI) on board the Sentinel 5 P instrument was launched into space in October 2017. Meanwhile the analysed data from several research institutes offer a variety of trace gases columns, including different tropospheric ozone data set. One based on the Convective Cloud Differential algorithm is an official TROPOMI data product. The algorithm in an improvement of the algorithm developed for the ESA ozone CCI project. It uses the offline (OFFL) ozone total columns and the cloud data sets. The data agree well with data from other satellite missions, i.e. GOME-2 or OMI. Therefore they will extent the time series started in 1995 with GOME / ERS2 developed during the CCI project. However despite the long time series of the CCD data set, the CCD algorithm can only be applied within the tropics (20°S -20°N).

A completely different approach uses data assimilation to constrain the stratospheric ozone and subtract the stratosphere from the total column. This offers the possibility to study tropospheric ozone on a global scale. We developed an algorithm for the scientific product that will be presented as well. Ozone observation from the microwave limb sounder (MLS) on the AURA satellite constrain the ozone distribution in the BASCOE (Belgian Assimilation System for Chemical ObsErvations) assimilation model. The BASCOE ozone concentrations are integrated above the tropopause to calculate the stratospheric column. Interpolated stratospheric columns are subtracted from the TROPOMI total ozone columns. The tropospheric ozone data agree reasonable well with comparable data from NASA using OMPS total columns, and within the tropics also with the CCD data. The algorithm was extend to be used also for other total ozone column observations like from GOME-2, OMI. But also geostationary observers like GEMS can in principal be used and might give intersting insight in the daily cycle of tropospheric ozone.