An empirical algorithm is developed for calculating bulkdry deposition velocity () of fine (PM) – particles having adiameter of ≤ 2.5 μm), coarse (PM – particles havinga diameter of 2.5–10 μm), and giant (PM – particles having adiameter of > 10 μm) atmospheric particles. The algorithmis developed from an empirical fit of data calculated using thesize-resolved scheme of Zhang et al. (2001) with assumed lognormalsize distributions of PM, PM and PM. In the newalgorithm, the surface deposition velocity () is parameterized as asimple linear function of friction velocity () for PM andas a polynomial function of for both PM andPM over all the 26 land use categories (LUCs). An adjustment factoras an exponential function of and leaf area index (LAI) is alsoapplied to of PM and PM over 9 of the 26 LUCsthat have variable LAI. Constant gravitational settling velocities areprovided for PM, PM and PM. Aerodynamicresistance between a reference height and the surface can be calculatedusing available analytical formulas from the literature. The bulk ofPM, PM and PM at the reference height can thenbe calculated by combining the gravitational settling velocity, aerodynamicresistance and the parameterized . values calculated using thenew algorithm are within ±20% of those using the originalsize-resolved scheme for fine, coarse and giant particles. Uncertainties in values from the new algorithm due to the pre-assumed sizedistributions are on the order of 20% for fine particles and on the orderof a factor of 2.0 for coarse and giant particles. The new algorithmprovides an alternative approach for calculating of bulk aerosolparticles. of any particulate species can be simply estimated usingthis scheme as long as the mass fractions in fine, coarse and giant particlesare known or can be assumed.
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