Unique multispectral cloud properties of cyclones entrained with large amounts of desert dust

In late winter and early spring in the northern hemisphere, baroclinic cyclones are responsible for entraining desert dust aerosols to high altitudes where they can influence ice cloud properties. One region that regularly produces these entrainments is the Sahara Desert as cyclones transition over northern Africa to the Mediterranean Sea and Europe. This presentation focuses on instruments from geostationary (Meteosat Second Generation) and polar orbiting (A-Train) satellites to show that these types of cyclones possess unusual multispectral characteristics when compared with similar non-dust-entrained cyclones.

Using radiative transfer simulations as a basis for comparison, it is found that both passive and active satellite observations indicate an increase in the particle number concentrations and a reduction in the particle effective radius when a large amount of desert dust is entrained into the cloud tops. Other interesting characteristics of these clouds are also in contrast with "regular" cirrus clouds, such as longer cloud lifetimes (defined by parameters including brightness temperature) and well-defined cellular cloud top structures (normally associated with altocumulus). The climate impacts of these aerosol indirect effects on ice clouds remain largely unknown, and this study takes the important first steps to quantify the spatiotemporal properties of this interaction.