Comparison of ground‐based and total ozone mapping spectrometer measurements used in assessing the performance of the global ozone observing system

Abstract

Uniformly reevaluated Nimbus 7 Total Ozone Mapping Spectrometer (TOMS) total ozone data (1978–1985) are compared with data from ground‐based stations during the daily overpasses of the satellite. Existence of a drift between the two systems is identified, showing the TOMS‐derived total ozone to be decreasing nonuniformly by an average of about 0.4% per year. After removing the individual monthly biases and using the satellite as a transfer standard, the differences between 92 currently operating stations of the Global Ozone Observing System (GO 3 OS) are analyzed. About two thirds of all Dobson stations show differences of less than 2%, while only half of the M‐83 filter stations fall into this good station category; close to 20% of the Dobson stations and nearly 30% of the filter stations show differences greater than 3%. Several examples of individual station discrepancies are discussed in order to encourage the complete reevaluation of the ground‐based ozone record and to forewarn potential users from taking the published ozone data at their face value.