Evidence of mineral dust altering cloud microphysics and precipitation

Qilong Min
SUNY Albany


Multi-platform and multi-sensor observations are employed to investigate the impact of mineral dust on cloud microphysical and precipitation processes in mesoscale convective systems. For a given convective strength, small hydrometeors were more prevalent in the stratiform rain regions with dust than in those regions that were dust free. Evidence of abundant cloud ice particles in the dust sector, particularly at altitudes where heterogeneous nucleation of mineral dust prevails, further supports the observed changes of precipitation. The consequences of the microphysical effects of the dust aerosols were to shift the precipitation size spectrum from heavy precipitation to light precipitation and ultimately suppressing precipitation. In addition to microphysical changes in clouds and precipitation, changes in nucleation processes of ice cloud due to aerosols would result in substantial changes in cloud top distribution. We found that the ice cloud effective temperature increases with mineral dust loading with a slope of +3.06℃ per unit AOD. The macrophysical changes in ice cloud top distributions as a consequence of mineral dust-cloud interaction exert a strong cooling effect (up to 16 wm-2) of thermal infrared radiation on cloud systems. Induced changes of ice particle size by mineral dusts influence cloud emissivity and play a minor role in modulating the outgoing longwave radiation for optically thin ice clouds.