Open AccessOverview and conclusions of the International Photolysis Frequency Measurement and Modeling Intercomparison (IPMMI) study
Author(s) -
Cantrell Christopher A.,
Calvert Jack G.,
Bais Alkiviadis,
Shetter Richard E.,
Lefer Barry L.,
Edwards Gavin D.
Publication year - 2003
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2002jd002962
Subject(s) - photodissociation , spectroradiometer , environmental science , atmospheric sciences , downwelling , aerosol , radiative transfer , yield (engineering) , meteorology , physics , chemistry , optics , geology , reflectivity , thermodynamics , oceanography , photochemistry , upwelling
An overview is given of the International Photolysis Frequency Measurement and Modeling Intercomparison (IPMMI) study which was held at the Marshall field site of the National Center for Atmospheric Research near Boulder, Colorado, for 4 days during the period 15–19 June 1998. The major objectives of the study were (1) to compare in blind experiments the results of different techniques of measuring j (NO 2 ) and j (O 1 D ) under identical and well‐defined experimental conditions, (2) to compare results of blind theoretical modeling of j (NO 2 ) and j (O 1 D ) expected at the experimental site using several current models, (3) to compare the experimental and model results for the j values, (4) to compare the measured and modeled downwelling actinic flux, and (5) on the basis of the results, make recommendations for the choices between alternative quantum yield and cross‐section data. The findings of the IPMMI experiment are described in a series of papers in this issue [e.g., Shetter et al. , 2003; Bais et al. , 2003], and the overall conclusions are summarized here. Actinic fluxes can be measured to accuracies of ∼5% and can be estimated with radiative transfer models to ∼10%. Photolysis rate coefficients can be measured and modeled with accuracies of ∼10% for high‐sun, clear‐sky, and low‐aerosol loadings. Comparisons between chemical actinometers and spectroradiometers favor more recent, larger cross‐section and quantum yield values for NO 2 and O 3 .