Evaluation of CAS-ESM2 in simulating the spring dust activities in the Middle East

Abstract

The assessment of Earth System Models (ESMs) in simulating long-term dust activities is a prerequisite for the applications of ESMs to the projection of future dust change. Middle East is the second largest dust source region in the world after North Africa, and our knowledge of the ESMs' ability in simulating regional dust cycle in this region is still limited. Here we examine the ability of the Chinese Academy of Sciences Earth System Model version 2 (CAS-ESM2) in simulating the spatiotemporal variations of dust activity over the Middle East region (30°E to 65°E, 10°N to 42°N). CAS-ESM2 simulations are compared with station observations, satellite observations, the Dust Constraints from joint Experimental-Modeling-Observational Analysis (DustCOMM) dataset, and the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2). The results show that CAS-ESM2 captures the main dust sources extending from the south of the Persian Gulf to the Arabian Peninsula, Iraq, and Sudan. CAS-ESM2 also simulates similar patterns of dust optical depth (DOD) with referential data, although there is some uncertainty in DOD observation. Further analysis shows that the model is able to reproduce the temporal variations of dust event frequency with the temporal correlation coefficient between model and station observations reaching 0.39. Simulations of dust-relevant variables such as surface wind, precipitation, and soil moisture are also evaluated. The biases including weaker surface wind speed and larger soil moisture as well as their impacts on the dust emission and transport are also noted for future model improvements. Overall, CAS-ESM2 demonstrates a good ability to simulate the spatio-temporal variations of spring dust activity over the Middle East, yet some biases remain to be improved.