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Dry Deposition Methods Based on Turbulence Kinetic Energy: 2. Extension to Particle Deposition Using a Single-Point Model
Citation:
Cheng, B., K. Alapaty, Q. Shu, AND S. Arunachalam. Dry Deposition Methods Based on Turbulence Kinetic Energy: 2. Extension to Particle Deposition Using a Single-Point Model. JOURNAL OF GEOPHYSICAL RESEARCH: ATMOSPHERES. American Geophysical Union, Washington, DC, 127(22):e2022JD037803, (2022). https://doi.org/10.1029/2022JD037803
Impact/Purpose:
Aerosols, also known as particulate matter, in the atmosphere can affect ecosystem health through a process called dry deposition and is a loss process that can reduce human exposure to pollutants. There are several processes involved in particle dry deposition and one of the most important processes is the chaotic motions of the atmosphere, which is known as turbulence. However, turbulence is underrepresented in mathematical modeling of particle dry deposition. In this study, we introduced several turbulence parameters to improve the representation of turbulence effects on deposition and introduced new formulations. These new formulations are tested in a simple mathematical model and then field measurements are used to evaluate the performance of new formulations as well as existing formulations. Results indicate that the new formulations largely improved results and are closer to measurements while existing formulations showed large underestimations. This research offers improved capability of models in estimating particle deposition and in turn hopefully leads to better estimation of particle pollution and related exposures.
Description:
Scientific Summary Magnitude of atmospheric turbulence, a key driver of several processes that contribute to aerosol (i.e., particle) deposition, is 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 strength 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 in regional and global models.
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DOI: Dry Deposition Methods Based on Turbulence Kinetic Energy: 2. Extension to Particle Deposition Using a Single-Point Model