Relationships between mineral dust and cloud properties in the West African Sahel.

Abstract

Aerosol cloud interactions are known to be of great importance to many parts of the climate system. Five years of observations from three different satellites (Aqua, ENVISAT and Meteosat Second Generation) are used to statistically analyse the relationship of mineral dust aerosol, separated from other aerosol species, with monsoon season cloud state in the West African Sahel domain. Additionally, observations of the Tropical Rainfall Measuring Mission are used for discrimination of dry and wet seasons. The aerosolcloud- interactions are analysed separately by season and air mass in order to minimise spurious correlations with meteorological conditions. The detailed analysis uncovers different counteracting relationships of the mineral dust aerosol with the cloud state, which is also evident from an analysis of the spatial distribution patterns of cloud properties changes with dust activity. The aerosol-cloud relationships found from the analysis of this multiple year dataset are mainly consistent with the hypothesis of a suppression of convective activity, but also indications of lifetime enhancement and thus increased cloud cover and convective intensity are found in some subsets.