Abstract
Abstract. To improve the aeolian dust budget calculations with the global ECHAM/MESSy atmospheric chemistry–climate model (EMAC), which combines the Modular Earth Submodel System (MESSy) with the ECMWF/Hamburg (ECHAM) climate model developed at the Max Planck Institute for Meteorology in Hamburg based on a weather prediction model of the European Centre for Medium-Range Weather Forecasts (ECMWF), we have implemented new input data and updates of the emission scheme. The data set comprises land cover classification, vegetation, clay fraction and topography. It is based on up-to-date observations, which are crucial to account for the rapid changes of deserts and semi-arid regions in recent decades. The new Moderate Resolution Imaging Spectroradiometer (MODIS)-based land cover and vegetation data are time dependent, and the effect of long-term trends and variability of the relevant parameters is therefore considered by the emission scheme. All input data have a spatial resolution of at least 0.1∘ compared to 1∘ in the previous version, equipping the model for high-resolution simulations. We validate the updates by comparing the aerosol optical depth (AOD) at 550 nm wavelength from a 1-year simulation at T106 (about 1.1∘) resolution with Aerosol Robotic Network (AERONET) and MODIS observations, the 10 µm dust AOD (DAOD) with Infrared Atmospheric Sounding Interferometer (IASI) retrievals, and dust concentration and deposition results with observations from the Aerosol Comparisons between Observations and Models (AeroCom) dust benchmark data set. The update significantly improves agreement with the observations and is therefore recommended to be used in future simulations.
Highlights
Aeolian dust can impair everyday life and air quality especially in severe dust storms
The global ECHAM/MESSy atmospheric chemistryclimate model (EMAC) (Jöckel et al, 2005, 2010), which combines the Modular Earth Submodel System (MESSy) with the ECMWF/Hamburg (ECHAM) climate model developed at the Max Planck Institute for Meteorology in Hamburg based on a weather prediction model of the European Centre for Medium-Range Weather Forecasts (ECMWF), provides a choice of dust emission schemes (Tegen, 2002; Balkanski et al, 2004; Astitha et al, 2012) to calculate the emission flux online based on the meteorological conditions
We extend the emission scheme by including a topography factor while we strictly adhere to the global consistency concept and refrain from using regional tuning factors
Summary
Aeolian dust can impair everyday life and air quality especially in severe dust storms. Global models have different requirements regarding the dust emission scheme compared to regional models. The coarser grid spacing requires an appropriate parameterisation of subgrid processes, and, for example, reproducing individual dust events with global models may have lower priority than adequately representing the atmospheric dust budget on a longer timescale With their everincreasing resolution, global models in many regards correspond to former-generation regional models, and established emission schemes are often applied in both regional and global models. The emission mask resulting from the land cover data considerably limits emissions in the Middle East, essentially not allowing dust emissions in Syria and northern Iraq This is in conflict with the emergence of severe dust outbreaks from that region (Solomos et al, 2017) and the strong link between the soil conditions in that region and trends of atmospheric dust over the Middle East (Klingmüller et al, 2016).
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