Results from a new linear O 3 scheme with embedded heterogeneous chemistry compared with the parent full-chemistry 3-D CTM

• Published in: Atmospheric Chemistry and Physics
• Main Authors: W. Feng, D. Cariolle, M. P. Chipperfield, B. M. Monge-Sanz
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2011
• Subjects: Physics; QC1-999; Chemistry; QD1-999; Antarctic; The Antarctic; Antarc*
• Online Access: https://doi.org/10.5194/acp-11-1227-2011; https://doaj.org/article/69e35171ca5140c9bac15a6ef5ff415f

A detailed full-chemistry 3-D chemistry and transport model (CTM) is used to evaluate the current stratospheric O 3 parameterisation in the European Centre for Medium-Range Weather Forecasts (ECMWF) model and to obtain an alternative version of the ozone scheme implicitly including heterogeneous chemistry. The approach avoids the inaccurate treatment currently given to heterogeneous ozone chemistry in the ECMWF model, as well as the uncertainties of a cold-tracer. The new O 3 scheme (COPCAT) is evaluated within the same CTM used to calculate it. It is the first time such a comparison has been possible, providing direct information on the validity of the linear parameterisation approach for stratospheric ozone. Simulated total column and O 3 profiles are compared against Total Ozone Mapping Spectrometer (TOMS) and Halogen Occultation Experiment (HALOE) observations. COPCAT successfully simulates polar loss and reproduces a realistic Antarctic O 3 hole. The new scheme is comparable to the full-chemistry in many regions for multiannual runs. The parameterisation produces less ozone over the tropics around 10 hPa, compared to full-chemistry and observations. However, this problem can be ameliorated by choosing a different ozone climatology for the scheme. The new scheme is compared to the current ECMWF scheme in the same CTM runs. The Antarctic O 3 hole with the current ECMWF scheme is weaker and disappears earlier than with the new COPCAT scheme. Differences between the current ECMWF scheme and COPCAT are difficult to explain due to the different approach used for heterogeneous chemistry and differences in the photochemical models used to calculate the scheme coefficients. Results with the new COPCAT scheme presented here show that heterogeneous and homogeneous ozone chemistry can be included in a consistent way in a linear ozone parameterisation, without any additional tunable parameters, providing a parameterisation scheme in better agreement with the current knowledge of stratospheric O 3 chemistry than previous ...