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| Titel |
Technical Note: An empirical algorithm estimating dry deposition velocity of fine, coarse and giant particles |
| VerfasserIn |
L. Zhang, Z. He |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 14, no. 7 ; Nr. 14, no. 7 (2014-04-11), S.3729-3737 |
| Datensatznummer |
250118583
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| Publikation (Nr.) |
 copernicus.org/acp-14-3729-2014.pdf |
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| Zusammenfassung |
| An empirical algorithm is developed for calculating bulk
dry deposition velocity (Vd) of fine (PM2.5) – particles having a
diameter of ≤ 2.5 μm), coarse (PM2.5−10 – particles having
a diameter of 2.5–10 μm), and giant (PM10+ – particles having a
diameter of > 10 μm) atmospheric particles. The algorithm
is developed from an empirical fit of Vd data calculated using the
size-resolved Vd scheme of Zhang et al. (2001) with assumed lognormal
size distributions of PM2.5, PM2.5−10 and PM10+. In the new
algorithm, the surface deposition velocity (Vds) is parameterized as a
simple linear function of friction velocity (u*) for PM2.5 and
as a polynomial function of u* for both PM2.5−10 and
PM10+ over all the 26 land use categories (LUCs). An adjustment factor
as an exponential function of u* and leaf area index (LAI) is also
applied to Vds of PM2.5−10 and PM10+ over 9 of the 26 LUCs
that have variable LAI. Constant gravitational settling velocities are
provided for PM2.5, PM2.5−10 and PM10+. Aerodynamic
resistance between a reference height and the surface can be calculated
using available analytical formulas from the literature. The bulk Vd of
PM2.5, PM2.5−10 and PM10+ at the reference height can then
be calculated by combining the gravitational settling velocity, aerodynamic
resistance and the parameterized Vds. Vd values calculated using the
new algorithm are within ±20% of those using the original
size-resolved scheme for fine, coarse and giant particles. Uncertainties in
Vd values from the new algorithm due to the pre-assumed size
distributions are on the order of 20% for fine particles and on the order
of a factor of 2.0 for coarse and giant particles. The new algorithm
provides an alternative approach for calculating Vd of bulk aerosol
particles. Vd of any particulate species can be simply estimated using
this scheme as long as the mass fractions in fine, coarse and giant particles
are known or can be assumed. |
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