The Effects of Dust–Radiation–Cloud Interactions on Cloud Development over North Africa

This study investigates impacts of dust-radiation-cloud effects on cloud development. A mesoscale convective system (MCS) case during 6-7 July 2010 is chosen due to the high likelihood for interaction between the MCS and a massive dust plume over Northwest Africa. The WRF-dust model was used to produce numerical simulations, for which NCEP Final Operational Global Analysis data provided initial and boundary condition. Four numerical experiments were conducted by activating or deactivating dust-radiation and/or dust-cloud interactions. Each experiment was allowed to integrate for four days, from 1200 UTC 4 July to 1200 UTC 8 July 2010. To ensure that each experiment’s dust field at the initial time was both non-zero and consistent with the reanalysis meteorology, the WRF-dust model was run with four-dimensional data assimilation (FDDA) starting on 0000UTC 26 June 2010.

Despite the formation of a weaker-than-observed simulated MCS, the experiment run with both dust-cloud and dust-radiation effects activated, named as DirInd, placed the storm reasonably close to its observed location around 0200 UTC 6 July 2010 as CloudSat passed over the storm. The preliminary comparison among experiments shows that DirInd has the most organized storm structure and strongest strength. The dust-cloud interactions influence largely on the storm’s convective structure; the dust-radiation impacts are able to modulate environment and influence the characteristic of cloud clusters. Further analysis for the relative importance of dust-radiation and dust-cloud effects on cloud development, storm intensity, and the storm’s large-scale environment by comparing results between all four experiments will be performed.