Modeling of Dust Emission for a Crusted Surface

Download or read book Modeling of Dust Emission for a Crusted Surface written by Zahra Ghodsi Zadeh and published by . This book was released on 2018 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dust storms are frequent phenomena in the southwestern United Sates. Dust source areas in the region are often (partly) crusted. A critical prerequisite for dust aerosol modeling is an accurate representation of dust emission. While several dust emission schemes have been developed over the last decades, their applicability for crusted surfaces is not well tested. In this study, we aimed to improve the representation of magnitude, frequency, and PSD of dust emission flux from crusted surfaces. We test the applicability of Shao (2004) size-resolved dust emission scheme (S04), which estimates dust emission based on the soil volume removed by saltation particle impacts, to model PM10 dust emission from a crusted surface in New Mexico, USA, for three dust events in spring 2016. Detailed field data are available for these events which are used as scheme input (surface crust and vegetation fraction, friction velocity, minimally- and fully-dispersed particle-size distributions) and for evaluation (saltation flux and dust emission flux). Results show that the saltation flux modeled with the scheme of White (1979) was overestimated by three orders of magnitude. This is expected as the supply of particles available for saltation is limited at the site, while the model assumes an unlimited supply of saltators. As our focus is on dust emission, a constant scaling factor was applied to match modeled and observed saltation fluxes. Parameters that describe the efficiency of saltator impacts to emit dust and the degree of dispersion during erosion need to be adapted in the S04 scheme to represent the soil surface setting at the study site. Our results show that changing those parameters has little effect on the modeled dust emission and dust emission is generally underestimated when PSDs of the top ~1 cm soil layer are used as is common. The reason for this is that the crust at the site is relatively thin and the soil overall sandy, which results in only a small difference between the minimally- and fully-dispersed PSDs of parent soil. If, however, the minimally- and fully-dispersed PSDs are replaced with the PSDs of, respectively, loose erodible material and crust, then the differences increase and the scheme parameters can be well adapted to give accurate estimates of dust emission. Our tests show that the SO4 scheme is able to more accurately estimate dust emission from a crusted surface provided that sufficient input information is provided. Future research is required to investigate the parameter variability for different crusted surfaces.