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 spectroradio metry (SR) and chemical actinometry (CA) was performed in summer 1997 in Ju lich, Germany. During this experiment (JCOM97) a large set of data was coll ected with a time resolution of similar to 1 min, showing a high linear cor relation (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 recommen ded by NASA/JPL (1997) and recently published data of the NO2 absorption sp ectrum (sigma(NO2)) is used for the evaluation of the SR-data. The influenc e 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%.