Dust-Infused Baroclinic Storm Clouds: The Evidence, Meteorology, and Some Implications

Desert mineral dust is a critical yet still poorly understood component of atmospheric composition, weather, and climate. Long-range transport of dust is well known yet uncertainty persists regarding the pathway from the desert floor to the free troposphere. Here we will show that a recurrent pathway for dust into the uppermost troposphere involves passage through an extratropical baroclinic cyclonic storm. The evidence derives from a synergistic use of satellite-based, multi-spectral nadir-image data and lidar. The dust-infused baroclinic storm (DIBS) exhibits peculiar cirrus cloud-top reflected and emitted radiance from the UV through thermal IR, involving positive UV absorbing aerosol index, muted visible reflectivity, visible cumuliform texture, and systematically intense visible lidar backscatter on a synoptic scale. Proof that the DIBS is microphysically impacted by storm-scale dust infusion is the occurrence of anomalously large daytime 3.9-11 micron brightness temperature difference indicative of small ice crystals. We present multi-spectral snapshots of two DIBS, over two desert source regions, in comparison with a pristine baroclinic storm cloud. Each storm snapshot is presented in the context of the baroclinic cyclone’s lifetime and dust-source region (the Gobi Desert and the Sahara). These and other cases discussed show that the DIBS is a recurring conduit for long-range transport and a natural experiment in dust-related aerosol indirect effects.