Institute for Atmospheric and Climate Science

Data Access

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Das IAC bloggt auf dem ETH-Klimablog, der Informationsplattform der ETH Zürich zum Klimawandel. Mehr auf

CATO is currently available in two different versions, including and excluding the assimilation of SBUV Version 8 vertical profiles in the uppermost layers. Please refer to the above mentioned publications for a closer description of these two versions.
The version of CATO excluding assimilation of SBUV profiles should only be used for altitudes below about 30 km because the reconstruction approach fails when ozone lifetime becomes short relative to the timescales of planetary wave motions.
The version with SBUV profile assimilation can be considered as a hybrid data set. SBUV profiles only affect the levels above 820 K potential temperature. The ozone profiles calculated with the CATO method are relaxed towards the SBUV profiles at these levels, the relaxation becoming more and more strong with altitude. At the highest levels CATO is therefore basically identical to zonal means of the SBUV Version 8 data set.
You can download monthly mean data (ASCII) format of CATO on either potential temperature levels (original vertical grid) or on pressure levels (linearly interpolated from potential temperature levels using the monthly mean pressure on the theta levels). You can also access CATO at full temporal resolution in netCDF format.
Please remember that CATO is represented on an equivalent latitude and not a geographical latitude grid.

Monthly mean data in ASCII format

Daily (6-hourly) data in netCDF format

Note: The CATO data set was reconstructed from total ozone data using a Kalman filter approach as described in Brunner et al. (JGR 2006). The state vector consists of a 2D equivalent latitude vs. potential temperature field in the stratosphere (O3_STRAT) and a 2D longitude vs. latitude field in the troposphere (O3_TROP) here defined as the atmosphere below the 320 K isentrope. Equivalent latitudes were calculated at 15 different potential temperature levels at the positions of total ozone observations using potential vorticity fields derived from ECMWF ERA-40 reanalysis data.

The file content is as follows:

Author: Dominik Brunner
Institute for Atmospheric and Climate Science (IAC)
ETH Zurich, Switzerland


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