inDust Webinar: The mysterious abundance of coarse desert dust in earth’s atmosphere

Abstract

Aircraft measurements have revealed that coarse dust (diameter > 5 mm) is surprisingly abundant in Earth’s atmosphere. In this seminar, I estimate the global load of coarse dust using a framework that leverages dozens of measurements of atmospheric dust size distributions. I find that the atmosphere contains 17 (10 – 29) Tg of coarse dust, which surprisingly accounts for approximately a third of all aerosol mass in the atmosphere. However, current global models on average account for only about a quarter of this large loading of coarse dust, thereby missing a warming effect of 0.15 (0.10 – 0.24) Wm-2. I explore the causes of this model underestimation of coarse dust and derive a new parameterization for the size distribution of emitted dust aerosols that matches measurements of coarse dust close to source regions. Despite this improvement in the accuracy of coarse dust emissions, models still greatly underestimate super coarse dust in dust outflow regions. Thus, the model underestimation of super coarse atmospheric dust is in part due to the underestimation of super coarse dust emission and likely in part due to errors in deposition processes.