Intercomparison of NO2 photolysis frequency measurements by actinic flux spectroradiometry and chemical actinometry during JCOM97

A first intercomparison of J(NO2) measurements by actinic flux spectroradiometry (SR) and chemical actinometry (CA) was performed in summer 1997 in Julich, Germany. During this experiment (JCOM97) a large set of data was collected with a time resolution of similar to 1 min, showing a high linear correlation (R = 0.998) in J(NO2) Linear regression indicates a good absolute agreement with the CA being 6% higher than SR if the quantum yield recommended by NASA/JPL (1997) and recently published data of the NO2 absorption spectrum (sigma(NO2)) is used for the evaluation of the SR-data. The influence of using previously published (sigma(NO2)) data is discussed. Overall the comparison suggests that J(NO2) can be measured by either CA or SR with an accuracy of better than 10%