Studies of the effect of stratospheric ozone depletion on tropospheric oxidising capacity over the period 1979-2010 using the UKCA Chemistry-Climate model

A grand challenge in the field of chemistry-climate modelling is to understand the connection between anthropogenic emissions, atmospheric composition and the radiative forcing of trace gases and aerosols. 

We present an analysis of the trends in tropospheric oxidising capacity in the UM-UKCA from the recent forerunner to AerChemMIP, the Chemistry-Climate Model Intercomparison project, CCMI-1, focusing on the REFC1SD and REFC1 simulations over the recent historical period.  We discuss these trends in terms of OH preconditions, such as photolysis rate and ozone concentration, and the resulting impact on methane oxidation.

Observational data provide important constraints on ozone and its precursors, as well as other radiatively important gases such as methane.  Data are available from a variety of platforms, spanning a range of spatial and temporal scales covering the past 40 years.   Recent work has highlighted the discrepancy in model and observations concerning surface ozone at key stations and the trend in tropospheric ozone levels over the past 50 years.

We will present a comparison between modelled OH and recent observational products, such as flight data from the UK ACSIS  and NASA AToM campaigns to examine how such data may be used to assess and to validate chemistry-climate models such as UKCA, and so improve the uncertainty regarding key forcing agents such as methane, ozone and aerosols.