Projections of Aerosol Effect on Diurnal Cycle of Precipitation Amount and Frequency Over Central Africa

ABSTRACT Atmospheric aerosols disturb the Earth's radiative balance through their direct effects (scattering and absorption of solar radiation) and their indirect effects (interaction with clouds). It is now widely recognised that the effect of aerosols on climate change is significant when compared to greenhouse gases. Despite the intensification of studies on this subject, the estimation of the radiative forcing of aerosols and their impact on precipitation remain highly uncertain. This article examines the projected effects of aerosols on the diurnal cycle of precipitation amount and frequency in Central Africa using the latest version of RegCM5 regional climate model from the Abdus Salam International Centre for Theoretical Physics (ICTP), coupled with the Community Land Model version 4.5 as the land surface scheme. RegCM5 is used to dynamically downscale the global climate model that participated in phase 5 of the Coupled Model Intercomparison Project (CMIP5) (HadGEM2‐ES) for both past (1991–2005) and near‐future (2035–2049) periods under the Representative Concentration Pathway (RCP) emission scenarios 2.6, 4.5, and 8.5. For a better analysis of the results, three sub‐regions have been considered based on their land cover and climatic characteristics. Diurnal cycle of precipitation characteristics, as well as the amplitude, and phase of both precipitation amount and frequency, have been investigated. The analyses show that the responses to anthropogenic forcings vary depending on the season and RCP. It emerges that all experiments with RCP forcings, without aerosol effects, show a decrease in both precipitation amount and frequency compared to the historical period. This decrease in precipitation intensifies with the presence of atmospheric aerosols. This suggests that precipitation in Central Africa will be negatively affected by the aerosols present in the surrounding environment. In the presence of aerosols, changes in the amplitudes of precipitation amount and frequency decrease by nearly 5%. In contrast, the changes in phases show both increases or decreases in precipitation across Central Africa and its three sub‐zones with small amounts ( 10 mm/h). The projected changes in the variation of the diurnal cycle of precipitation are nearly identical across all RCP scenarios, which justifies the high similarity obtained between different RCPs for precipitation amount and frequency, except for Zone 1 in DJF, which shows a low similarity.