Parameterization of dust flux emitted by convective turbulent dust emission (CTDE) over the Horqin Sandy Land area

Publication date: August 2018
Source:Atmospheric Environment, Volume 187
Author(s): Tingting Ju, Xiaolan Li, Hongsheng Zhang, Xuhui Cai, Yu Song
A new convective turbulent dust emission (CTDE) empirical parameterization scheme was developed and validated using the observational data of dust concentrations and meteorological parameters over the Horqin Sandy Land area. Moreover, different CTDE schemes were compared and discussed. The statistical results from the observations in 2016 showed that the proportion of dust emission fluxes emitted by CTDE is 27% for all dust emission which indicates that the significance of CTDE events for the contribution of atmospheric dust aerosols. In addition, dust emission fluxes emitted by CTDE constituted up to 78% of the total dust emission fluxes due to direct aerodynamic entrainment, which verified that CTDE is indeed the most important and major form of aerodynamic entrainment dust emission. A new CTDE empirical parameterization scheme (Fmod=2.93×w∗1.5, where w∗ is the convective velocity scale), was established and validated based on nine typical CTDE events observed at the Horqin site in 2016, and the model predictions of the new CTDE scheme were in a good agreement with the observations both in magnitude and variation. The results of the model predictions using the MK14 scheme and Li scheme were also good, but their schemes exaggerated the impact of shear-driven turbulence, which caused discrepancies between the new empirical parameterization scheme and the MK14 scheme. Moreover, effects of soil moisture on CTDE were investigated in this study, and the results showed that there was no obvious relationship between soil moisture content and Fobs during CTDE events. This finding was likely because only dust particles in the upper few millimeters of the soil surface, where soil moisture content was relatively low in semi-arid region, can be emitted into the atmosphere during CTDE events due to weak wind speeds. In addition, compared with the saltation-bombardment and/or aggregation-disintegration dust emission (SADE) event, the process of a CTDE event may be aerodynamic lift limitation, not supply limitation.



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