A Wind-tunnel Study on Dust-deposition Mechanics and Validation of Dust-deposition Schemes
Final Report Abstract
To understand the mechanisms of dust deposition and to develop the capacity for its quantification are important to a range of earth-environment research fields, such as global nutrient cycle and global climate change. Dust models have been under active development since the 1980s. A major challenge facing the dust modeling community is how dust deposition can be parameterized. This complex process involves a number of environmental factors. The lack of high-quality dust-deposition measurements and well-tested dust-deposition schemes and the large uncertainties in the dust-deposition predictions have been a bottle neck to the development of the entire research field. In this project, we have carried out a series of wind-tunnel experiments on dust deposition. Dust concentration and dust-particle velocity are measured using laser-based instruments for various particle-size groups, flow velocities and surface conditions. The wind-tunnel experiments produced a benchmark dataset for testing dust-deposition schemes. The measurements have been used to evaluate the performances of two existing dust-deposition schemes. The existing schemes are found to perform reasonably well for smooth surfaces, but relatively poorly for rough surfaces. A new scheme has been developed with improved performances for rough surfaces. The measurements collected in this project substantially enrich the database for the calibration of dust-deposition models. In contrast to previous studies, our data are special in that the estimates of dust dry deposition are based on direct dust-flux measurements, rather than dust-profile derived dust fluxes. We expect that the new dataset and the new dust-deposition scheme will impact upon global climate research, because dust deposition profoundly affects atmospheric dust load and size distribution, two of the key quantities which influence aerosol radiative forcing. This project has opened more questions which deserve further research. One of which is, for example, the intermittency of dust deposition. We have already developed preliminary conceptual analysis on the issue and a large-eddy simulation model has been developed the University of Cologne. A future project dedicated for studying the mechanisms of intermittent dust-deposition and for developing associated dust-deposition parameterizations will continue in future projects.
Publications
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2011: A Review on Modeling and Monitoring of Dust Dry Deposition. J Desert Res, 31(3): 639-648
Li ZQ, J Zhang, N Huang, Y Shao and XJ Zheng
