WP 3.2.2 • WP 3.2.2 Aircraft induced sulphur impact on UTLS ozone (UCAM-DCHEM) Start date :33 End date48 • Participant: CEA, UiO, MPICHEM and UCAM-DCHEM • Objective To estimate the effect of aircraft sulphur emissions on UTLS ozone • Description of work The impact on ozone of the increase in stratospheric aerosol density (SAD) due to aircraft sulphur emissions will be calculated. Recently published calculations of results from one model indicate (Pitari et al., 2002) that the downward transport of air depleted in ozone by the increased SAD is of the same order of magnitude as the ozone production from aircraft NOx emissions. This effect needs to be investigated with other models, because it is highly sensitive to vertical transport in the UTLS and to the microphysics implementation. A sensitivity study will be performed with several ACMs with perturbed and unperturbed stratospheric background aerosol climatologies.
SLIMCAT + SAMM • SLIMCAT (Chippefield 1999) is a 3D CTM primarily designed for stratospheric studies. The model use 18 isentropic levels from 10 to 65 km with the bottom layer at θ=350K. The model is forced by offline meteorological fields from ECMWF or UKMO. The horizontal advection scheme uses the second order moment scheme (Prather 1996). The vertical transport is calculated by the MIDRAD radiation scheme. The chemistry module calculates the behaviour of 45 species and includes more than one hundred photochemical reactions as well as nine heterogeneous reactions on PSCs and sulphur aerosols. The reaction rates are based on the JPL2002 recommendations. • The Stratospheric Aerosol Microphysical Model (SAMM, Tripathi 2004) has been added to SLIMCAT. This module simulates homogeneous binary nucleation, condensational growth, coagulation, and sedimentation of sulphuric acid-water particles in order to predict the composition and size-distribution of stratospheric aerosols. In SAMM, homogeneous nucleation and condensation are coupled in a manner that allows realistic competition between the two processes for the limited amount of vapour. With geometrically related size bins (around 40 bins for sulphuric acid-water particles in the range 0.3 nm to 1.5 m m). • Recently a new version of the SLIMCAT/TOMCAT chemical transport model has been developed in combining the existing TOMCAT (tropospheric) and SLIMCAT (straospheric) models (Chipperfield 2005). This extended version of SLIMCAT (using θ) will be used in WP 3.2.2 as we want to focus on the UTLS and the stratospheric aerosol loading.