Validation Of The ESA-CCI Harmonized Tropospheric Ozone Column Data Product, Using Balloon Sounding Data

Abstract

Within the ESA Ozone-CCI project, a Convective Cloud Differential (CCD) algorithm has been used to derive a harmonized dataset of 20 years (July 1995 –December 2015) of Tropical Tropospheric Ozone Column (TTOC) data for the Tropical latitude belt (20° S – 20° N). This homogenized dataset can be used in climate research studies, e.g. validating chemical transport models, helping us to understand the processes which are responsible for the variability of tropospheric ozone in the Tropical belt. The accuracy of this CCD method has been assessed by comparing the tropospheric ozone columns with ozonesonde measurements obtained from the SHADOZ network. Validation results of this Tropical Tropospheric Ozone Column (TTOC) product will be presented. The tropospheric ozone retrieval is based on the consistent ESA-CCI total ozone dataset retrieved from the successive GOME, SCIAMACHY, GOME-2A, GOME-2B and OMI sensors, applying the GODFITv3 algorithm. The TTOC product is available as monthly averages with a horizontal resolution of 1.25° latitude x 2.5° longitude. The TTOC time series will be extended in the future with the upcoming Sentinel 5 Precursor data. For S5P both the GODFIT and the TTOC will be an operational offline product. The validation results reveal that the merged TTOC product is after comparison with ozonesonde data for most of the stations within 10 % relative difference error. The correlation varies between 0.43 and 0.84 with a rmse between 3.3 and 5.1 DU. When comparing the total uncertainty among the different sensors with the harmonized dataset, it is shown that the harmonized dataset leads towards a better agreement between the different instruments.