Measurements of J(NO2) at Ny-Alesund, svalbard

The photolytic rate constant of NO? J(NO2), has been determined using two independent methods at the Ny-Angstrom lesund International Arctic Research and Monitoring Facility. At the Zeppelin mountain station the Norwegian Institute for Air Research (NILU) has operated a commercially available J(NO2) radiometer since 1994. Additionally, a five-channel UV irradiance radiometer (GUV-541) was operated at Ny Angstrom lesund 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(NO2) data. Pn this paper we present a detailed error discussion for the radiometer data and the quality controlled measurements of J(NO2). J(NO2) 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(NO2)(model)/J(NO2)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.