Abstract
Abstract. We present the dust module in the Multiscale Online Non-hydrostatic AtmospheRe CHemistry model (MONARCH) version 2.0, a chemical weather prediction system that can be used for regional and global modeling at a range of resolutions. The representations of dust processes in MONARCH were upgraded with a focus on dust emission (emission parameterizations, entrainment thresholds, considerations of soil moisture and surface cover), lower boundary conditions (roughness, potential dust sources), and dust–radiation interactions. MONARCH now allows modeling of global and regional mineral dust cycles using fundamentally different paradigms, ranging from strongly simplified to physics-based parameterizations. We present a detailed description of these updates along with four global benchmark simulations, which use conceptually different dust emission parameterizations, and we evaluate the simulations against observations of dust optical depth. We determine key dust parameters, such as global annual emission/deposition flux, dust loading, dust optical depth, mass-extinction efficiency, single-scattering albedo, and direct radiative effects. For dust-particle diameters up to 20 µm, the total annual dust emission and deposition fluxes obtained with our four experiments range between about 3500 and 6000 Tg, which largely depend upon differences in the emitted size distribution. Considering ellipsoidal particle shapes and dust refractive indices that account for size-resolved mineralogy, we estimate the global total (longwave and shortwave) dust direct radiative effect (DRE) at the surface to range between about −0.90 and −0.63 W m−2 and at the top of the atmosphere between −0.20 and −0.28 W m−2. Our evaluation demonstrates that MONARCH is able to reproduce key features of the spatiotemporal variability of the global dust cycle with important and insightful differences between the different configurations.
Highlights
The Multiscale Online Non-hydrostatic AtmospheRe CHemistry model (MONARCH) is a chemical weather modeling system that can be used at multiple spatial scales, ranging from regional scales at single-digit kilometer resolutions with explicit convection to coarse-resolution global scales with parameterized convection (Pérez et al, 2011; Badia et al, 2017)
The MODIS FoObased map is linked with fractions of anthropogenic land use, following the approach described in Ginoux et al (2012), but using an updated land-use data set (Klein Goldewijk et al, 2017)
We presented the description of mineral dust in the Multiscale Online Non-hydrostatic AtmospheRe CHemistry model (MONARCH) version 2.0
Summary
The Multiscale Online Non-hydrostatic AtmospheRe CHemistry model (MONARCH) is a chemical weather modeling system that can be used at multiple spatial scales, ranging from regional scales at single-digit kilometer resolutions with explicit convection to coarse-resolution global scales with parameterized convection (Pérez et al, 2011; Badia et al, 2017). The more simplified dust emission schemes are typically constrained by “preferential” source scaling functions and are commonly used in global and in regional models. Physics-based dust emission parameterizations are very sensitive to such changes but need more detailed input This detailed input has traditionally been difficult to observe and/or estimate, in particular globally, and errors in the description of, for example, surface properties, translate non-linearly into errors in emitted and transported dust. How such errors compare with those arising when neglecting dust emission sensitivities entirely remains a subject of research and discussion. We demonstrate and evaluate MONARCH’s dust modeling capabilities based on four annual global model runs
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