Measurements of J(NO 2 ) at Ny‐Ålesund, Svalbard

The photolytic rate constant of NO 2 , J(NO 2 ), has been determined using two independent methods at the Ny‐Ålesund International Arctic Research and Monitoring Facility. At the Zeppelin mountain station the Norwegian Institute for Air Research (NILU) has operated a commercially available J(NO 2 ) radiometer since 1994. Additionally, a five‐channel UV irradiance radiometer (GUV‐541) was operated at Ny‐Ålesund during 1995/1996. The results of the latter, together with surface albedo measured by the Norwegian Polar Institute (NP), are used as input in a radiative transfer model using the discrete ordinate method to calculate J(NO 2 ) data. In this paper we present a detailed error discussion for the radiometer data and the quality controlled measurements of J(NO 2 ). J(NO 2 ) reached an annual maximum between 1994 and 1996 of up to 0.012 s −1 during springtime. Surface albedo was found to have a large influence on the radiative balance in the Arctic. Measured noontime data are compared with model results. Unweighted linear regression showed for 1996 a J(NO 2 ) model /J(NO 2 ) measure ratio of 0.90. This good agreement suggests that multichannel irradiance radiometers have the potential to be used to derive J values for a variety of trace gases.