ON THE DERIVATION OF TROPOSPHERIC COLUMN OZONE FROM RADIANCES MEASURED BY THE TOTAL OZONE MAPPING SPECTROMETER

We have developed a new algorithm to retrieve tropospheric column ozone on a daily basis directly from the measured total ozone mapping spectrometer (TOMS) albedos at a spatial resolution of about 50 km. This new algorithm is applied to the retrieval of tropospheric ozone over the region bounded by 20 degrees W and 60 degrees E longitude and 20 degrees S and 0 degrees S latitude during the 1989 biomass burning season when tropospheric ozone approaches 20% of total ozone. We find that for the conditions of high tropospheric ozone during biomass burning, the archived TOMS data underestimates total ozone over cloud free regions and overestimates ozone over the marine stratocumulus cloud off the west coast of Africa. This error can be as high as 15 Dobson units. Thus previous methods which derive tropospheric ozone from the TOMS archived ozone data are subject to error. Details of the algorithm and an analysis of the expected error are presented.