Representation of aerosol particles and associated transport pathways in regional climate modelling in Africa

Abstract

Aerosol particles can have large impacts on air quality and on the climate system. Regional climate models for Africa have not been well-tested and validated for their representation and simulation of aerosol particles. This study aimed to validate the current representation of aerosol particles in the Conformal Cubic Atmospheric Model (CCAM), using the CMIP5 historical emissions inventory, to monitored data over Africa. In this study, CCAM was used to produce historical regional climate model simulations at 50 km horizontal resolution, globally, through the dynamical downscaling of ERA Interim reanalysis data. CCAM has a prognostic aerosol scheme for organic carbon, black carbon, sulphate, and dust, and non-prognostic sea salt. The aerosol optical depth (AOD) at 550nm from CCAM was compared to the AOD values (observed at 440nm and adjusted to 550nm using the Ångström exponent) from AERONET stations across Africa for 1999-2012. For this validation with AERONET, sites that are strongly impacted by aerosols from natural sources were prioritized. In general, the model captures well the monthly trends of the AERONET data. In addition, a climatology of simulated aerosol transport during the southern African biomass burning season was developed using self-organizing maps. This presentation will provide, through comparisons to monitored data, a basis for understanding how well aerosol particles are represented over Africa in regional climate modelling using the emissions inventory from the latest Intergovernmental Panel on Climate Change assessment report.