Application of a satellite-retrieved sheltering parameterization (v1.0) for dust event simulation with WRF-Chem v4.1

Abstract

Abstract. Roughness features (e.g., rocks, vegetation, furrows) that shelter or attenuate wind flow over the soil surface can considerably affect the magnitude and spatial distribution of sediment transport in active aeolian environments. Existing dust and sediment transport models often rely on vegetation attributes derived from static land use datasets or remotely sensed greenness indicators to incorporate sheltering effects on simulated particle mobilization. However, these overly simplistic approaches do not represent the three-dimensional nature or spatiotemporal changes of roughness element sheltering. They also ignore the sheltering contribution of non-vegetation roughness features and photosynthetically inactive (i.e., brown) vegetation common to dryland environments. Here, we explore the use of a novel albedo-based sheltering parameterization in a dust transport modeling application of the Weather Research and Forecasting model with Chemistry (WRF-Chem). The albedo method estimates sheltering effects on surface wind friction speeds and dust entrainment from the shadows cast by subgrid-scale roughness elements. For this study, we applied the albedo-derived drag partition to the Air Force Weather Agency (AFWA) dust emission module and conducted a sensitivity study on simulated PM10 concentrations using the Georgia Institute of Technology–Goddard Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) model as implemented in WRF-Chem v4.1. Our analysis focused on a convective dust event case study from 3–4 July 2014 for the southwestern United States desert region discussed by other published works. Previous studies have found that WRF-Chem simulations grossly overestimated the dust transport associated with this event. Our results show that removing the default erodibility map and adding the drag parameterization to the AFWA dust module markedly improved the overall magnitude and spatial pattern of simulated dust conditions for this event. Simulated PM10 values near the leading edge of the storm substantially decreased in magnitude (e.g., maximum PM10 values were reduced from 17 151 to 8539 µg m−3), bringing the simulated results into alignment with the observed PM10 measurements. Furthermore, the addition of the drag partition restricted the erroneous widespread dust emission of the original model configuration. We also show that similar model improvements can be achieved by replacing the wind friction speed parameter in the original dust emission module with globally scaled surface wind speeds, suggesting that a well-tuned constant could be used as a substitute for the albedo-based product for short-duration simulations in which surface roughness is not expected to change and for landscapes wherein roughness is constant over years to months. Though this alternative scaling method requires less processing, knowing how to best tune the model winds a priori could be a considerable challenge. Overall, our results demonstrate how dust transport simulation and forecasting with the AFWA dust module can be improved in vegetated drylands by calculating the dust emission flux with surface wind friction speed from a drag partition treatment.

A new process-based and scale-aware desert dust emission scheme for global climate models – Part II: evaluation in the Community Earth System Model (CESM2)

“…Furthermore, although many ESMs include the impacts of dust on ice cloud formation (Storelvmo, 2017) Finally, while many dust modeling studies focused on improving and evaluating the spatial representation of modeled dust, the importance of evaluating the temporal variability of modeled dust is likely undervalued. Relatively few dust studies (e.g., Zhang et al, 2013;Klose et al, 2021;LeGrand et 1120LeGrand et al, 2023 provide evaluation of the temporal changes in dust emissions and DAOD. This study represents one of the early attempts to conduct a global-scale evaluation of the day-to-day variability (Figs.…”

“…3.4; Kok et al, 130 2012;Comola et al, 2019). Nevertheless, most dust emission schemes in global and regional models employ 𝑢 * "# as the single threshold for both the initiation and termination of dust emission flux in models (Menut et al, 2013;Klose et al, 2021;Tai et al, 2021;Li et al, 2022;LeGrand et al, 2023), which could be problematic (see Sect. 3.4).…”

Reducing Resolution Dependency of Dust Emission Modeling Using Albedo‐Based Wind Friction

“…It enables correctly upscaled, area‐weighted estimates of u s * for calculating Q and F demonstrated using MODIS albedo daily, every 500 m across Earth (Chappell and Webb, 2016; Chappell et al., 2019; Hennen et al., 2022). This albedo‐based approach improves regional dust model performance with better representation of roughness (LeGrand et al., 2023). This approach offers the opportunity to investigate the extent to which existing regional and global Q and F models are resolution dependent, constrained by the incompatibility of the grain‐scale model and the areal wind fields.…”

The Wind‐Blown Sand Experiment in the Empty Quarter Desert: Roughness Length and Saltation Characteristics

“…; play an important role (Bagnold, 1941; Chepil, 1951; Fécan et al., 1999; Gillette et al., 2001; Iversen & White, 1982). In fact, in commonly used dust parameterization schemes, a threshold value of roughness length is used above which no emission occurs so as to prevent dust emission in urban and vegetated regions (LeGrand et al., 2023). What is more, the soil water content and clay mass fraction, the terrain elevation and the surface albedo also typically modulate the threshold speed for dust emission in numerical models (LeGrand et al., 2023).…”

“…In fact, in commonly used dust parameterization schemes, a threshold value of roughness length is used above which no emission occurs so as to prevent dust emission in urban and vegetated regions (LeGrand et al., 2023). What is more, the soil water content and clay mass fraction, the terrain elevation and the surface albedo also typically modulate the threshold speed for dust emission in numerical models (LeGrand et al., 2023). Field measurements show that saltation (the horizontal sand motion) is a prerequisite for significant dust emissions (Gunn et al., 2021; Shao et al., 2011; Sow et al., 2009).…”