Parameterization of size-resolved dust emission and validation with measurements

Abstract

[1] A critical problem in dust research is to estimate size-resolved dust emission rates. Several dust schemes have been proposed but are yet to be rigorously tested against observed data. In the recent Japan-Australia Dust Experiment (JADE), size-resolved dust fluxes were measured. In this study, the JADE data are used to test a size-resolved dust scheme. Our aim is to examine whether the scheme has the capability to predict size-resolved dust fluxes, what the ranges of the scheme parameters are, and whether the scheme is sensitive to the parameters. The JADE data show that dust emission depends linearly on saltation flux and thus confirm the basic assumption of the scheme. The magnitudes of the scheme parameters are found to be consistent with those reported in earlier studies. The estimated size-resolved dust fluxes are in satisfactory agreement with the measurements, although considerable discrepancies remain and are difficult to rectify without speculative tuning of the scheme input parameters. The discrepancies have been traced back to the uncertainties in the parent soil particle size analyses and in the dust flux observations. Ensemble tests showed both model physics uncertainties and parameter uncertainties. It is proposed that the dust scheme under consideration is not as sensitive as previously suspected and is likely to perform well if the parameters are specified within a reasonably correct range.

Impact of atmospheric dust emission schemes on dust production and concentration over the Arabian Peninsula

“…Dust is simulated in this work using two different emission scheme options, both of which generate dust emissions ''online'' during the WRF-Chem run; (1) the AFWA emission scheme adopted from the Georgia Institute of Technology-Goddard Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) model (Ginoux et al 2001), and, (2) the S11 (Shao et al 2011) emission scheme. The AFWA emissions scheme is an integration of the semiempirical MB95 dust emission parameterization (Marticorena and Bergametti 1995) with the Kok (2011) airborne dust size distributions and predicts bulk dust fluxes which are then distributed to the size-resolved sections according to observed dust size distributions.…”

“…We cover the Arabian Peninsula with a triple-nested domain configuration with the highest grid resolution over the region of Qatar. We focus on dust emissions and concentrations and unlike previous WRF-Chem applications in this region (Prakash et al 2015;Kalenderski et al 2013) we utilize the two latest dust emission schemes incorporated in the WRF-Chem model; namely (1) the AFWA (Air Force Weather Agency) and (2) the S11 (Shao et al 2011) emission schemes. We finally evaluate the model predictions of PM 10 concentrations with ambient data collected from a monitoring station at Doha, Qatar.…”

Turbulent Characteristics of Saltation and Uncertainty of Saltation Model Parameters

“…In this study, the influence of soil 371 moisture on saltation is accounted for via Equation (1) using the soil moisture measurements in 372 the top 0.05m layer (see also Fig. 4a in Shao et al 2011). The uncertainty in the wind erosion 373 parameters arising from soil moisture is most likely reflected in the stochasticity of u*t. 374 375…”

“…The essence of the saltation model 176 component is as described in Section 1. The fraction of erodible surface area, σf, used in 177 Equation (1), is estimated from photos using the technique as detailed Shao et al (2011). For 178 the site, the fraction of surface cover is about 0.02, almost negligible.…”

“…Observations of surface soil properties, including 173 soil temperature, soil moisture and surface cover were also made. The wind erosion model, as 174 detailed in Shao et al (2011), is used for computing the saltation fluxes using the JADE 175 atmospheric and surface soil measurements as input. The essence of the saltation model 176 component is as described in Section 1.…”