Motion Of Sea-Salt Aerosol In Coastal Atmospheric Boundary Layer

Sea-salt aerosol is a kind of fine suspended particles which widespreads in coastal atmospheric boundary layer.It plays a significant role in radiation balance,atmospheric environment,construction corrosion,injuring people and plant health,soil salinization and so on.Constrained by the research methods and some other factors,some features of the motion and aerodynamics of sea-salt aerosol in the coast zone still remain unknown.Consequently,a large-eddy simulation is first performed for the purpose of further investigating the inland transport of sea-salt aerosol and how some different kinds of urderlying surface influence it in a more micro scale.As the current empirical formulas based on observation data disable to describe the exact inland deposition patternsof sea-salt aerosol,we introduced a current exist theoretical solution,which is futher modified based on the simulation result in this work.The new model is validated by comparing with experiment favorably and shows good work in estimating the inland deposition regimes of heavy sea-salt particles.Our work illustrates the inland deposition of sea-salt aerosols should be obtained from the integration of deposition curves for all sizes of deposited particleswhich statisfy the modified theory framework,which means the deposition rate is relatively steady near the shoreline while decays in power-law futher inland.Moreover,the roughness,thermal condition,canopy covered of the coastal underlying surface would also influence the inland transport and deposition of sea-salt aerosol.First,the sudden increase of roughness on the coastal underlying surface leads the maximum of the concentration profile rise aloft as the sea salt aerosols are transported inland.When the coastal air becomes convective,the enchanment of atmospheric turbulent would accelerate this raising process.The present work shows both in neutral and convective coast,the sea salt aerosols' concentration depletion profiles are self-preserved when they are transported inland.When the coast atmosphere becomes more unstable,the position of maximal turbulent induced sea-salt aerosol flux more coincides with that of the maximal vertical velocity fluctuation and the decay of aerosol's inland deposition rate becomes faster.Second,the existence of forest or urban canopy would make the inland sea wind go through two main stages,i.e.,leading edge flow and equilibrium canopy flow.In the leading edge flow region,the mean ascending airflow transport large amount of sea salt aerosols out of the canopy to the internal boundary layer above while the interception of canopy largly enhances the deposition of large sea-salt particles.In the equilibrium canopy flow region,the shear eddies generated above the canopy top play a more important role in transporting the sea-salt aerosols downward to the canopy then enhance the deposition rate especially for the light particles.In addition,some canopy features like the forest density,city's height may also influence on the inland transport of sea-salt aerosols.In this case,some special phenomenon of sea-slat aerosols like concentration accumulation,changing the dynamic scale of aerosol's exchange inside and outside the canopy may also occur.