Editorial Type:
Article
Article Type:
Research Article

Examining Photolysis Rates with a Prototype Online Photolysis Module in CMAQ

Francis S. Binkowski Carolina Environmental Program, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina

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Saravanan Arunachalam Carolina Environmental Program, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina

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Zachariah Adelman Carolina Environmental Program, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina

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Joseph P. Pinto U.S. Environmental Protection Agency, Research Triangle Park, North Carolina

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Print Publication:
01 Aug 2007
Collections:
NOAA/EPA Golden Jubilee
DOI:
https://doi.org/10.1175/JAM2531.1
Page(s):
1252–1256
Restricted access

Abstract

A prototype online photolysis module has been developed for the Community Multiscale Air Quality (CMAQ) modeling system. The module calculates actinic fluxes and photolysis rates (j values) at every vertical level in each of seven wavelength intervals from 291 to 850 nm, as well as the total surface irradiance and aerosol optical depth within each interval. The module incorporates updated opacity at each time step, based on changes in local ozone, nitrogen dioxide, and particle concentrations. The module is computationally efficient and requires less than 5% more central processing unit time than using the existing CMAQ “lookup” table method for calculating j values. The main focus of the work presented here is to describe the new online module as well as to highlight the differences between the effective cross sections from the lookup-table method currently being used and the updated effective cross sections from the new online approach. Comparisons of the vertical profiles for the photolysis rates for nitrogen dioxide (NO2) and ozone (O3) from the new online module with those using the effective cross sections from a standard CMAQ simulation show increases in the rates of both NO2 and O3 photolysis.

Corresponding author address: Francis S. Binkowski, UNC-Chapel Hill Carolina Environmental Program, Bank of America Plaza, 137 E. Franklin St., CB 6116, Chapel Hill, NC 27599-6116. Email: frank_binkowski@unc.edu

This article included in the NOAA/EPA Golden Jubilee special collection.

Abstract

A prototype online photolysis module has been developed for the Community Multiscale Air Quality (CMAQ) modeling system. The module calculates actinic fluxes and photolysis rates (j values) at every vertical level in each of seven wavelength intervals from 291 to 850 nm, as well as the total surface irradiance and aerosol optical depth within each interval. The module incorporates updated opacity at each time step, based on changes in local ozone, nitrogen dioxide, and particle concentrations. The module is computationally efficient and requires less than 5% more central processing unit time than using the existing CMAQ “lookup” table method for calculating j values. The main focus of the work presented here is to describe the new online module as well as to highlight the differences between the effective cross sections from the lookup-table method currently being used and the updated effective cross sections from the new online approach. Comparisons of the vertical profiles for the photolysis rates for nitrogen dioxide (NO2) and ozone (O3) from the new online module with those using the effective cross sections from a standard CMAQ simulation show increases in the rates of both NO2 and O3 photolysis.

Corresponding author address: Francis S. Binkowski, UNC-Chapel Hill Carolina Environmental Program, Bank of America Plaza, 137 E. Franklin St., CB 6116, Chapel Hill, NC 27599-6116. Email: frank_binkowski@unc.edu

This article included in the NOAA/EPA Golden Jubilee special collection.

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Journal of Applied Meteorology and Climatology

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