Assessment of CMIP6 model performance in simulating atmospheric aerosol and precipitation over Africa

Abstract

Recent studies have shown that east African region experiences both extreme rainfall and droughts due to presence of atmospheric absorbing aerosols. As such, it is important to understand the Global Climate Models (GCMs) phase6 of Coupled Model Intercomparison Project (CMIP6) performance in capturing the climatological precipitation over the region. This study evaluates the ability of nineteen CMIP6 models in simulating the presence of aerosols and precipitation in both annual and seasonal variation over Africa and east Africa respectively from 1980 to 2014. The Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) aerosol reanalysis data and Global Precipitation Climatology Project (GPCP) rainfall data have been used against CMIP6 datasets for validation. Model performance metrics were employed namely bias, root mean square error, spatial correlation coefficient, standard deviation and percentage bias (PBias) to assess the ability of individual models in simulating the two parameters over the study region. The quantitative analysis shows that most models are able to simulate both aerosols and precipitation over the study domain. Among the nineteen models evaluated, five (CMCC-CM2-SR5, E3SM-1-0, E3SM-1-1-ECA, NorESM2-LM and KACE-1-0-G) are showing good performance in reproducing aerosols over Africa. For precipitation, all the models are performing good except BCC-ESM1, CESM2-FV2, CMCC-CM2-SR5 and E3SM-1-1. In general, out of the nineteen models, no single model performs best in relation to observation. The performance of the models varies from season to season. Hence climate users are strongly advised to use projections of atmospheric aerosols and precipitation over the study area from CMIP6 models with caution for decision making on the mitigation or even adaptation of climate change.