A comparison of total column ozone values derived from the Global Ozone Monitoring Experiment (GOME), the Tiros Operational Vertical Sounder (TOVS), and the Total Ozone Mapping Spectrometer (TOMS)

A comparison of total column ozone data retrieved from the Global Ozone Monitoring Experiment (GOME), the Tiros Operational Vertical Sounder (TOVS), and the Total Ozone Mapping Spectrometer (TOMS) for the years 1996, 1997, 1998, and 1999 is presented. A statistical analysis and a spatial difference analysis were performed on a range of temporally and spatially averaged datasets. An analysis of globally averaged column ozone values showed a consistent offset with TOVS and TOMS values being consistently higher than GOME by similar to 10- 13 DU averaged over the 4-yr period. A 4%-5% drift was noted between the years 1996/97 and 1998/99 in the magnitude of the offset. The drift was identified as an increased offset of +25-30 DU between TOVS/ TOMS and GOME occurring over latitudes above 70 degreesN during 1998/99, and is a result of TOVS/ TOMS ozone columns being higher during 1998/99 than in 1996/97. Seasonal and latitudinal trends were noted in the global differences. In particular, TOMS and TOVS ozone values are consistently higher than GOME in the Southern Hemisphere from 30 degrees -90 degreesS. TOVS and GOME ozone columns show good agreement between 20 degreesS and 20 degreesN, with TOMS values approximately 10-15 DU higher than both TOVS and GOME in the same region. All three sensors show reasonable agreement between 20 degrees and 60 degreesN. However, there is no agreement above 60 degreesN, where TOVS columns are higher than TOMS columns that in turn are higher than GOME columns. Results from a spatial difference analysis indicated further differences between GOME and TOVS ozone values that were not obvious from the global or latitudinal analysis owing to cancellation effects, including an area over Indonesia where GOME columns are higher than TOVS columns.