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Model code and tools associated with "The influence of simulated surface dust lofting and atmospheric loading on radiative forcing"




Saleeby, Stephen

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This high-resolution numerical modeling study investigates the potential range of impact of surface-lofted dust aerosols on the mean radiative fluxes and temperature changes associated with a dust lofting episode over the Arabian Peninsula (2-5 August 2016). Assessing the potential for lofted dust to impact the radiation budget and temperature response in regions of the world that are prone to intense dust storms is important due to the impact of such temperature perturbations on thermally driven mesoscale circulations such as sea-breezes and convective outflows. As such, sensitivity simulations using various specifications of dust erodible fraction were performed using two high-resolution mesoscale models that use similar dust lofting physics based on threshold friction wind velocity and soil characteristics. The dust erodible fraction, which represents the fraction (0.0 to 1.0) of surface soil that could be mechanically lifted by the wind and controls the location and magnitude of surface dust flux, was varied for three experiments with each model. The "Idealized" experiments, which used an erodible fraction of 1.0 over all land grid cells, represent the upper limit on dust lofting within each modeling framework, the "Ginoux" experiments used a 1-degree resolution, spatially-varying erodible fraction dataset based on topographic depressions, and the "Walker" experiments used satellite-identified, 1-km resolution data with known lofting locations given an erodible fraction of 1.0. These simulations were compared to a "No-Dust" experiment in which no dust aerosols were permitted. The use of erodible fraction databases in the Ginoux and Walker simulations produced similar dust loading which was more realistic than that produced in the Idealized lofting simulations. Idealized lofting in this case study generated unrealistically large amounts of dust compared to observations of aerosol optical depth (AOD), due to the lack of locational constraints. Generally, the simulations with enhanced dust mass via surface lofting experienced reductions in daytime insolation due to aerosol scattering effects, as well as reductions in nighttime radiative cooling due to aerosol absorption effects. These radiative responses were magnified with increasing amounts of dust loading. In the Idealized simulation with "extreme" (AOD > 5) dust amounts, these radiative responses suppressed the diurnal temperature range. In the Ginoux and Walker simulations with "moderate" (AOD ~ 1-3) amounts of lofted dust, the presence of dust still strongly impacted the radiative fluxes but only marginally modified the low-level temperature. The dust-induced near-surface temperature change was limited due to competing thermal responses to changes in the net radiative fluxes and the dust layer radiative heating rates. Compared to the Ginoux simulation, the use of increased resolution in dust erodible fraction inventories in the Walker simulations led to enhanced fine-scale horizontal variability in lofted dust and a modest increase in the mean dust concentration profile and radiative/thermal responses. This study discusses the utility of using high-resolution dust source databases for simulating lofted dust, the need for greater spatial coverage of in situ aerosol observations in dust prone regions, the impacts of dust on the local radiation budget and surface thermal conditions, and the potential dust radiative impacts on thermally driven mesoscale features.


File is a gzipped tarball containing the RAMS model code, namelists, tools, and documentation needed for reproducing simulations associated with the noted manuscript.
The model output dataset associated with this paper is too large to store in a repository. As such, we are archiving the RAMS model code, namelists, and documentation required to reproduce the simulations created for this study. This study involved analyzing simulations run for a surface dust lofting event over the Arabian Peninsula from Aug 2-5, 2016. Simulations were run at 15km and 2km grid spacing. We were analyzing the impacts of dust storms on the radiation budget and its impacts on low-level thermodynamics.
Department of Atmospheric Science

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Associated Publications

Saleeby, S. M., van den Heever, S. C., Bukowski, J., Walker, A. L., Solbrig, J. E., Atwood, S. A., Bian, Q., Kreidenweis, S. M., Wang, Y., Wang, J., and Miller, S. D.: The influence of simulated surface dust lofting erodible fraction on radiative forcing, Atmos. Chem. Phys., 19, 10279-10301,, 2019.