New developments in the representation of Saharan dust sources in the aerosol–climate model ECHAM6-HAM2

Abstract

Abstract. In the aerosol-climate model ECHAM6-HAM2, dust source activation (DSA) observations from Meteosat Second Generation (MSG) satellite are proposed to replace the original source area parameterization over the Sahara Desert. The new setup is tested in nudged simulations for the period 2007 to 2008. The evaluation is based on comparisons to dust emission events inferred from MSG dust index imagery, Aerosol Robotic Network (AERONET) sun photometer observations, and satellite retrievals of aerosol optical thickness (AOT).The model results agree well with AERONET measurements especially in terms of seasonal variability, and a good spatial correlation was found between model results and MSG-SEVIRI (Spinning-Enhanced Visible and InfraRed Imager) dust AOT as well as Multi-angle Imaging SpectroRadiometer (MISR) AOT. ECHAM6-HAM2 computes a more realistic geographical distribution and up to 20 % higher annual Saharan dust emissions, using the MSG-based source map. The representation of dust AOT is partly improved in the southern Sahara and Sahel. In addition, the spatial variability is increased towards a better agreement with observations depending on the season. Thus, using the MSG DSA map can help to circumvent the issue of uncertain soil input parameters.An important issue remains the need to improve the model representation of moist convection and stable nighttime conditions. Compared to sub-daily DSA information from MSG-SEVIRI and results from a regional model, ECHAM6-HAM2 notably underestimates the important fraction of morning dust events by the breakdown of the nocturnal lowlevel jet, while a major contribution is from afternoon-toevening emissions.

Identification and Characterization of Dust Source Regions Across North Africa and the Middle East Using MISR Satellite Observations

“…Furthermore, combining MISR DAOD at different wavelengths and multispectral measurements from other satellite instruments provides complementary constraints for model simulation of size-dependent dust emission (Ginoux et al, 2010;Wang et al, 2012;Xu et al, 2017). By applying the aforementioned accurate dust source map and size-dependent dust loading and emission constraints, the representation of dust aerosols and their feedbacks to the climate in coupled Earth System Models will potentially be improved Heinold et al, 2016), leading to more credible simulations of the current climate state, dust-climate feedbacks, and future projections of aerosol concentration and the impacts of dust aerosols on climate. The improved modeling capability, by incorporating the aforementioned observational constraints, will lead to a better understanding of the interannual variability in dust emission and concentration and their environmental drivers and feedbacks in key ecological regions such as Sahel and the Middle East identified by the current study.…”

Long-term profiling of mineral dust and pollution aerosol with multiwavelength polarization Raman lidar at the Central Asian site of Dushanbe, Tajikistan: case studies

“…The fieldwork of CADEX included column-integrating sun photometer measurements, vertically resolved lidar measurements, and meteorological observations in Dushanbe, Tajikistan In addition, the field experiment is accompanied by 3-D regional modeling with the regional dust model COSMO-MUSCAT (Wolke et al, 2012;Heinold et al, 2011) and the aerosol-climate model ECHAM-HAM Heinold et al, 2016). The modeling provides a perspective on the sources, transport, and the direct radiative effects of measured mineral dust and associated atmospheric feedbacks.…”

“…More observations, especially in western and Central Asia, are needed to describe global and regional dust transport and to estimate the effect of this dust on air quality (Chin et al, 2007), and climate, via direct and various indirect radiative effects. Extended investigations into Saharan dust close to its source regions (e.g., SAMUM-1, 2, Saharan Mineral Dust Experiment; Fennec climate programm; and SHADOW, Study of SaHAran Dust Over West Africa) (Heintzenberg, 2009;Ansmann et al, 2011a;Ryder et al, 2015;Veselovskii et al, 2016) as well as regarding dust longrange transport across the Atlantic ocean (e.g., SALTRACE, Saharan Aerosol Long-range Transport and Aerosol-CloudInteraction Experiment; Weinzierl et al, 2017) have been conducted to obtain novel data to reduce uncertainties in the above-mentioned estimations. However, the global dust belt, which reaches from the Sahara over the Arabian deserts to the Taklamakan and Gobi deserts, contains a lot more arid and semi-arid regions which act as sources for atmospheric mineral dust in the northern hemisphere (Darmenova et al, 2009;Ridley et al, 2016).…”

The global aerosol-climate model ECHAM6.3-HAM2.3 – Part 2: Cloud evaluation, aerosol radiative forcing and climate sensitivity

“…• Update of mineral dust emission parameterization which makes use of a satellite-based source mask for Saharan 5 dust sources (Heinold et al, 2016) • New sea salt emission parameterization based on Long et al (2011) which uses a temperature dependence following Sofiev et al (2011) • The latest version of the sectional aerosol module SALSA2.0 is implemented (described in Kokkola et al, 2018) • New emission datasets have been made available in an input file distribution for E63H23 for anthropogenic aerosol 10 emissions Aerosol-cloud interactions were improved from HAM2.0 to HAM2.3 by the following changes:…”