An ozone climatology is presented, based entirely on ozone observations over a target period 1980-1991. The climatology gives zonal mean ozone values, as well as the corresponding inter-annual standard deviation, for 17 zonal bands 80S - 80N) at 19 pressure levels (1000-0.3 hPa), for each month of the year. It is intended mainly for climate simulations with GCM's. For the troposphere and lower stratosphere (1000-10 hPa), the climatology is compiled from ozonesonde observations of 30 ozonesonde stations located around the world. To account for tropospheric longitudinal variability within a zonal band, a dataset giving tropospheric total ozone values between 50S-50N is used. For stations within this latitude range, the tropospheric profile is scaled with a factor derived from this dataset to make it more representative of the zonal mean. Consequently, the corrected profiles of the individual stations are combined within each zonal band, using weighted averaging. These zonal profiles are then attached to zonal monthly mean SBUV-SBUV/2 observations in the stratosphere (30-0.3 hPa). Three overlap layers at 30, 20 and 10 hPa give an indication of how well these two datasets match. Where possible, the integral of the combined ozone profiles are made consistent with TOMS, by applying a correction factor to the ozonesonde part of the profile, derived from TOMS minus the integrated SBUV-SBUV/2 profile. The resulting climatology is compared to three other ozone climatologies: the predecessor of this one, a climatology compiled by the State University of New York, and a climatology used in the GCM at the Max Planck Institute in Hamburg, Germany. Apparent improvements are a better consistency with TOMS (compared to the first climatology) and more realistic ozone values in the Tropics and polar regions (compared to the first and second climatology). There is an overall strong improvement compared to the third climatology, which was generated from an analytical formula and old ozone observations in the seventies. A unique further advantage of the current climatology is the accompanying standard deviation climatology, giving an indication of the natural variability and reliability of the mean ozone values.

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