Title
Investigation of a New Dust Emission Scheme in E3SM: High Latitude Dust
Authors
Yan Feng, Argonne National Laboratory; Douglas Hamilton and Natalie Mahowald, Cornell University
Abstract
One of the main improvements for dust physics in V3/V4 is to enable a close coupling between land and atmosphere for dust generation. In V1, dust emission is modelled based on the Dust Entrainment And Deposition model (DEAD), which requires a fixed soil erodibility map. We have recently updated it to include the brittle fragmentation theory of vertical dust flux on mineral size fractions during the V2 integration. In addition, dust aerosol absorption in the shortwave is improved by using observationally-based optical properties, resulting in a more negative aerosol forcing at TOA.
In the present study, emissions of dust are further improved to follow a physically based vertical flux theory, which calculates soil erodibility online based on the predicted soil moisture and other properties. This emission scheme has been shown to significantly improve dust emissions with CAM4 and CAM5. It allows for the removal of the soil erodibility map approach previously employed by the DEAD scheme in V1. Global dust emissions are tuned such that a global annual mean dust AOD of ~0.03 is still retained, but yield better simulation of regional dust concentrations with the new emission scheme implemented. In the high latitudes (>50º N), there are evident increases of dust emissions. Emissions of dust from >50º N are about 1~2% of the global dust total, while in V1 the high latitude dust sources were very little near the polar regions. In general, the high latitude dust concentrations peak closest to coast lines and in the summer. A few recent studies have shown that the inclusion of high latitude dust results in dust concentrations and seasonality more consistent with recent observations in the Arctic related to glacial processes. However, we found that the magnitude of the new dust emissions strongly depends on the soil moisture and surface wind predictions by the model, which have large uncertainties. As the high-latitude dust sources have the potential to significantly influence glaciation of Arctic low-level clouds, this warrants further investigation of the fidelity of the new dust emissions.