The contribution of haboobs to the dust direct radiative effect

Mineral dust is the most abundant type of atmospheric aerosol in terms of mass. Dust models at non-storm resolving resolutions are usually able to capture the dust load on diurnal or longer-term average, but perform worse in capturing its diurnal variability. A main reason for this deficit is the fact that phenomena smaller than the grid size cannot be represented and are therefore lacking in the simulations. A major dust-event type that can only be represented at single-digit kilometer resolution are haboobs – intense dust storms created by the cold-pool outflow of moist convection. Haboobs mostly occur during the afternoon and thus their representation in models at storm resolving resolutions increases dust emissions during the afternoon hours, especially in regions where haboobs typically occur. As a significant amount of global dust emissions can be attributed to haboobs, their impact, e.g. on interactions of dust aerosol with radiation, on the continental to global scale is of special interest.

Here we investigate the contribution of haboobs to the direct radiative effect (DRE) of dust through their modulation of the dust diurnal cycle and vertical and horizontal distributions. For this purpose, we performed a set of annual simulations of the year 2020 using the ICON-ART model at 5km and 80km grid resolution for a domain covering North Africa and the Arabian Peninsula, as these regions are strong dust sources and haboob hotspots. A radiation multiple call scheme in ICON-ART was used to assess the DRE from a single simulation. We analyze differences in DRE and the vertical and horizontal dust distribution between the simulations and link them to the spatial distribution of haboob occurrence in the high-resolution simulation.

By assessing the impact of haboobs on the radiation balance of the earth, we aim to contribute to evaluating the benefits of storm-resolving simulations on a global scale with online treatment of aerosols; and to test the importance of representing meso-scale phenomena for quantification of dust-climate impacts.