A comparison of photolysis rate parameters estimated from measured and simulated actinic flux for wintertime conditions at Storm Peak Laboratory,Colorado |
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Authors: | Dongchul Kim Christopher P Loughner Melanie A Wetzel Wendy S Goliff William R Stockwell |
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Institution: | (1) Massachusetts Institute of Technology, Cambridge, MA, USA;(2) Department of Meteorology, University of Maryland, College Park, MD, USA;(3) Division of Atmospheric Sciences, Desert Research Institute, Reno, NV, USA;(4) Department of Chemistry, Howard University, 525 College Street, NW Washington, DC, 20059, USA |
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Abstract: | Photolysis rate parameters depend upon solar actinic flux and chemical species dependent quantum yields and cross sections.
Spectrally resolved measurements of actinic flux should be preferred over flux derived from models for the analysis of field
observations. Actinic flux can be difficult to derive from the irradiance measurements of flat-plate radiometers. It is also
difficult to estimate from models due to uncertainties in the ozone column, aerosol concentrations and distributions, cloud
cover, optical depth and surface albedo. A series of actinic flux measurements were performed at Storm Peak Laboratory (3,210 m
above sea level), Colorado, United States with spectroradiometers during the wintertime (January 07–10, 2004). The site is
relatively remote with a clean atmosphere and during the wintertime the ground is generally covered by fresh snow with a high
albedo. The actinic flux measurements were used to estimate the photolysis rate parameters of ozone, nitrogen dioxide and
formaldehyde. The measured actinic flux and the photolysis rate parameters derived from the flux were compared to calculations
using the Tropospheric Ultraviolet-Visible Model (TUV), version 4.2 (Madronich and Flocke, 1998). The TUV modeled actinic
flux, the measured flux and the photolysis rate parameters derived from them had similar temporal patterns. However there
were significant differences in their magnitude due to uncertainties in the data available to initialize the TUV model and
the calibration of the spectroradiometer. |
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Keywords: | Photolysis Actinic flux TUV Spectroradiometer |
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