PNNL

Abstract

Dust aerosols are important for global energy balance since they can scatter and absorb radiation directly and interact with radiation indirectly by acting as efficient ice nuclei to alter cold cloud properties. However, estimate of dust indirect effect remains highly uncertain due to large uncertainties in model simulated dust spatial distributions, especially in the upper troposphere, as well as due to lack of reliable dust observations. Here we use an improved global dust dataset derived from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and an air parcel trajectory model to characterize and understand upper troposphere dust source and transport. We identify distinct “upper troposphere dust belt” over northern hemisphere middle and high latitudes with its column loading strongest during March-April-May (MAM) and show that the out-phased mid-level dust concentration and westerly wind over source regions control the strong seasonal variations of column dust loading. We also find that Africa desert contributes the most (46.3%) to the “upper troposphere dust belt” in MAM and the synoptic trough is the leading (49%) dust lifting mechanism. These results provide essential guidance for model improvements.