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Evaluation of An Advanced Ozone Dry Deposition Model
Citation:
Alapaty, Kiran, J. Bash, B. Cheng, S. Arunachalam, AND J. Munger. Evaluation of An Advanced Ozone Dry Deposition Model. American Geophysical Union Fall Meeting, Chicago, IL, December 12 - 16, 2022.
Impact/Purpose:
An innovative method for improved estimation of dry depostion is proposed and evaluated helping to better estimate human helath impacts due to ozone exposure.
Description:
Literature indicates that turbulence strength is under-represented in almost all dry deposition models and the different types of stability functions used are contributing to biases in the estimated dry deposition of ozone (O3) and are also a source for differences among models’ simulations. To alleviate these issues, we developed new and revised resistance formulations based on turbulence kinetic energy to accurately represent turbulence strength to improve estimation of O3 deposition fluxes. New formulations developed are for the aerodynamic and cuticle resistances, and relevant formulations for other resistances (e.g., leaf boundary layer resistance) were revised to include improved representation of turbulence strength. A revised stomatal resistance includes impacts of dew formation on adaxial surface and particle blockage of abaxial stoma. Decadal measurements (1991-2000) (referred to as OBS) available from the Harvard Forest site are used to drive a single-point (box) model and to evaluate O3 deposition flux estimation by STAGE (referred to as STAGE) as well as the revised STAGE (referred to as TKE-STAGE) formulations. We hypothesized and proved that a new turbulence velocity scale can effectively avoid the usage of stability functions, and that inclusion of an improved estimate of turbulence strength along with other revisions leads to a more representative simulation of O3 deposition. Decadal averaged monthly & hourly variations of simulated O3 fluxes by TKE-STAGE are much closer to OBS when compared to STAGE. For example, decadal averaged hourly minimum measured fluxes (ppb ms-1) occurred at midnight with OBS=0.18; STAGE=0.21; TKE-STAGE=0.17 while maximum measured fluxes occurred at local noon with OBS=0.6; STAGE=0.8; TKE-STAGE=0.7. We found that the bias reduction is attributable to improved representation of processes in the TKE-STAGE formulations. The findings from the research may help improve the capability of dry deposition schemes for better estimation of dry deposition fluxes and opens doors for the development of a community dry deposition model for use in regional/global air quality models. The TKE-STAGE formulations will be available as an additional option to choose from in a future release of Box model and CMAQ model. Disclaimer: The views expressed in this article are those of the authors and do not necessarily represent the views or policies of US EPA.