Dry Deposition Methods Based on Turbulence Kinetic Energy: Part 2.
Extension to Particle Deposition Using a Single-Point Model
Abstract
Magnitude of atmospheric turbulence, a key driver of several processes
that contribute to aerosol (i.e., particle) deposition, is typically
underrepresented in current models. Various formulations have been
developed to model particle dry deposition; all these formulations
typically rely on friction velocity and some use additional ad hoc
factors to represent enhanced impacts of turbulence. However, none were
formally linked with the three-dimensional (3-D) turbulence. Here, we
propose a set of 3-D turbulence-dependent resistance formulations for
particle dry deposition simulation and intercompare the performance of
new resistance formulations with that obtained from using the existing
formulations and measured dry deposition velocity. Turbulence parameters
such as turbulence velocity scale, turbulence factor, intensity of
turbulence, effective sedimentation velocity, and effective Stokes
number are newly introduced into two different particle deposition
schemes to improve turbulence representation. For an assumed particle
size distribution, the newly proposed schemes predict stronger diurnal
variation of particle dry deposition velocity and are comparable to
corresponding measurements while existing formulations indicate large
underpredictions. We also find that the incorporation of new turbulence
parameters either introduced or added stronger diurnal variability to
sedimentation velocity and collection efficiencies values, making the
new schemes predict higher deposition values during daytime and
nighttime when compared to existing schemes. The findings from this
research may help improve the capability of dry deposition schemes and
help fostering the community dry deposition modeling system for use in
regional and global models.