Impacts of Carbonaceous Aerosol on Hydrological Cycle over the Northern Africa

The Northern Africa has exhibited extensive drought in the late 20^th century.  Most of the variability in rainfall has been attributed to change in the Sea Surface Temperature (SST) in both the Atlantic and Indian Oceans.  However, most of the climate models have difficulty in reproducing magnitude of rainfall reduction.  Various climate feedback processes such as Vegetation-Albedo feedback were suggested as amplifying mechanisms which are typically missing in most of current climate models.  In this study, aerosol indirect effects (AIE) are analyzed with a focus on its impact on hydrological cycle over the Northern Africa.  Previously various pathways were suggested to explain how aerosols can affect the hydrological cycle and climate.  However, most of them were based on climate models with capability of simulating only the aerosol direct effect through changes in radiative properties of the atmosphere.

The Community Atmosphere Model (CAM) version 5 has fully predictive aerosol life cycle, which actively interacts with both radiative property and cloud microphysics.  Therefore, we can investigate how the carbonaceous aerosols from biomass burning can affect rainfall over the Northern Africa due to aerosol indirect and direct effects using sets of sensitivity experiments.  Our goal is to explore how the AIE may alter the atmospheric hydrological cycle over the Northern Africa.