TOMCAT CTM total ozone column and passive ozone columns.

Title TOMCAT Total Ozone Column Data

The TOMCAT/SLIMCAT 3-D chemical transport model (CTM) simulations were performed for the period January 1977 through March 2026. The model runs at a horizontal resolution of 2.8° × 2.8° with 32 altitude levels and is forced by ERA5 meteorological reanalysis fields. The simulations include a comprehensive description of stratospheric gas-phase and heterogeneous chemistry, including reactions on polar stratospheric clouds (PSCs). Surface mixing ratios of long-lived source gases are specified based on the WMO (2022) scenario, with the model also accounting for time-varying solar fluxes and aerosol surface area density (SAD) changes. 

To isolate the drivers of ozone variability, the dataset includes:  CNTL (Control Simulation): Uses time-varying ODS levels following the WMO (2022) scenario.  ODS95 (Sensitivity Simulation): Keeps ODS levels fixed at 1995 levels (corresponding to peak halogen loading) to quantify the impact of ozone recovery.  Passive Ozone Tracer: Both simulations include a passive ozone tracer that is re-initialized on December 1st of each year to distinguish dynamical replenishment from chemical ozone depletion.

### Dataset DescriptionThe dataset contains monthly mean total column ozone data (3D fields) derived from the TOMCAT CTM. These data are used to diagnose interannual variability, chemical loss, and dynamical transport efficiency, particularly for the Arctic polar cap (60°N–90°N). Each file contain two variables: tco- total column ozone (active) and tpo (total passive ozone). There are 128 longitude, 64 latitudes and 279 months (starting from January 2003).

File List:   column_ozone_CNTL_2003_2026.nc: Monthly mean total column ozone from the control simulation (RUN781).   column_ozone_ODS95_2003_2026.nc: Monthly mean total column ozone from the ODS95 simulation (RUN790).stics.

The data can be used to quantify ozone variability  drivers such as chemical ozone loss (the difference between active and passive tracers) and transport effect (e.g. difference in passive ozone column from December (year-1) to March (year)) the dynamical increase in column ozone from December to March. Note: For specific high-resolution analysis, daily 3D profiles are available upon request (emails : [e-mail] or [e-mail]).

For more details about TOMCAT see: https://tomcat.leeds.ac.uk/tomcat/