J_NO2at high solar zenith angles in the lower stratosphere

In situ measurements of NO, NO2, O-3, HO2, ClO, pressure, and temperature have been made at high solar zenith angles (SZA, 70 degrees - 93 degrees) in the lower stratosphere. These measurements are used to derive the photolysis rate of NO2, J(NO2),, using a time-dependent method. The resultant J(NO2) values and the results of a multiple-scattering actinic flux model show a linear relationship throughout the SZA range. The difference of the two sets of J(NO2) values of about 11% suggests that the model scattering calculation is very accurate at high SZA conditions near sunrise and sunset.