Technical Note: An empirical algorithm estimating dry deposition velocity of fine, coarse and giant particles
Item
Title (Dublin Core)
Technical Note: An empirical algorithm estimating dry deposition velocity of fine, coarse and giant particles
Description (Dublin Core)
An empirical algorithm is developed for calculating bulk dry deposition velocity (<i>V</i><sub>d</sub>) of fine (PM<sub>2.5</sub>) – particles having a diameter of ≤ 2.5 μm), coarse (PM<sub>2.5−10</sub> – particles having a diameter of 2.5–10 μm), and giant (PM<sub>10+</sub> – particles having a diameter of > 10 μm) atmospheric particles. The algorithm is developed from an empirical fit of <i>V</i><sub>d</sub> data calculated using the size-resolved <i>V</i><sub>d</sub> scheme of Zhang et al. (2001) with assumed lognormal size distributions of PM<sub>2.5</sub>, PM<sub>2.5−10</sub> and PM<sub>10+</sub>. In the new algorithm, the surface deposition velocity (<i>V</i><sub>ds</sub>) is parameterized as a simple linear function of friction velocity (<i>u</i><sub>*</sub>) for PM<sub>2.5</sub> and as a polynomial function of <i>u</i><sub>*</sub> for both PM<sub>2.5−10</sub> and PM<sub>10+</sub> over all the 26 land use categories (LUCs). An adjustment factor as an exponential function of <i>u</i><sub>*</sub> and leaf area index (LAI) is also applied to <i>V</i><sub>ds</sub> of PM<sub>2.5−10</sub> and PM<sub>10+</sub> over 9 of the 26 LUCs that have variable LAI. Constant gravitational settling velocities are provided for PM<sub>2.5</sub>, PM<sub>2.5−10</sub> and PM<sub>10+</sub>. Aerodynamic resistance between a reference height and the surface can be calculated using available analytical formulas from the literature. The bulk <i>V</i><sub>d</sub> of PM<sub>2.5</sub>, PM<sub>2.5−10</sub> and PM<sub>10+</sub> at the reference height can then be calculated by combining the gravitational settling velocity, aerodynamic resistance and the parameterized <i>V</i><sub>ds</sub>. <i>V</i><sub>d</sub> 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 <i>V</i><sub>d</sub> 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 <i>V</i><sub>d</sub> of bulk aerosol particles. <i>V</i><sub>d</sub> 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.
Creator (Dublin Core)
Zhang, L.
He, Z.
Date (Dublin Core)
2018-01-15
Type (Dublin Core)
Text
Format (Dublin Core)
application/pdf
Identifier (Dublin Core)
10.5194/acp-14-3729-2014
https://acp.copernicus.org/articles/14/3729/2014/
Source (Dublin Core)
eISSN: 1680-7324
Language (Dublin Core)
eng
