Wednesday, 9 July 2014
Deep convective processes involve complex interactions across a range of scales. In addition, the response of deep convective clouds to changing levels of cloud condensation nuclei (CCN) remains poorly quantified. The Congo basin is home to some of the most intense convective activity on the planet, yet has been the focus of very few previous studies, especially when compared to the neighbouring, relatively well-understood West African climate system. Ground-based observations of convection and precipitation in the Congo region are sparse, and there has been a sharp decline in the number of rain gauges in the region over the past few decades [Washington, 2013]. Seasonal agricultural burning is a strong source of aerosol in the Congo basin. Satellite observations of aerosol optical depth (AOD) made by the MISR instrument show that there is a strong seasonal variation in AOD over the Congo region, with persistent cloud cover and high aerosol concentrations particularly apparent in the June-August season.
We focus on the Congo basin in order to characterise the nature of deep convection in this area of intense convective activity and in order to investigate the response of convection and precipitation to regional CCN sources. We present high-resolution convection-permitting simulations of deep convection over the Congo Basin. Simulations are performed with the WRF model using a 2-moment bulk microphysics scheme. We quantify the characteristics of convection and precipitation in the region on timescales much longer than that of individual cloud lifecycles. Our findings are compared with satellite observations of the Congo region, allowing us to evaluate our simulations despite the lack of in-situ observational data. We investigate the response of the convective and precipitation processes within our modelling framework to aerosol and microphysical parameters, allowing us to identify and quantify the processes that dominate the nature of convection in this region.
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