Ozone Hydroxide Research Articles

The Chemistry Climate Model ECHAM6.3-HAM2.3-MOZ1.0

The chemistry climate model ECHAM-HAMMOZ contains a detailed representation of tropospheric and stratospheric reactive chemistry and state-of-the-art parametrisations of aerorols using either a modal scheme (M7) or a bin scheme (SALSA). This article describes and evaluates the model version ECHAM6.3-HAM2.3-MOZ1.0 with a focus on the tropospheric gas-phase chemistry. A ten-year model simulation was performed to test the stability of the model and provide data for its evaluation. The comparison to observations concentrates on the year 2008 and includes total column observations of ozone (O<sub>3</sub>) and carbon monoxide (CO) from Infrared Atmospheric Sounding Interferometer (IASI) and Ozone Monitoring Instrument (OMI), Microwave Limb Sounder (MLS) observations of temperature, nitric acid (HNO<sub>3</sub>), chlorine monoxide (ClO), and O<sub>3</sub> for the evaluation of polar stratospheric processes, an ozone sonde climatology, surface ozone observations from the Tropospheric Ozone Assessment Report (TOAR) database, and surface CO data from the Global Atmosphere Watch network. Global budgets of ozone, hydroxide (OH), nitrogen oxides (NO<sub>x</sub>), aerosols, clouds, and radiation are analyzed and compared to the literature. ECHAM-HAMMOZ performs well in many aspects. However, in the base simulation, lightning NO<sub>x</sub> emissions are very low, and the impact of the heterogeneous reaction of HNO<sub>3</sub> on dust and seasalt aerosol is too strong. Sensitivity simulations with increased lightning NOx or modified heterogeneous chemistry deteriorate the comparison with observations and yield excessively large ozone budget terms and too much OH. We hypothesize that this is an impact of potential issues with tropical convection in the ECHAM model.