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

The photolytic rate constant of NO? J(NO2), has been determined using two i ndependent methods at the Ny-Angstrom lesund International Arctic Research and Monitoring Facility. At the Zeppelin mountain station the Norwegian Ins titute for Air Research (NILU) has operated a commercially available J(NO2) radiometer since 1994. Additionally, a five-channel UV irradiance radiomet er (GUV-541) was operated at Ny Angstrom lesund during 1995/1996. The resul ts of the latter, together with surface albedo measured by the Norwegian Po lar Institute (NP), are used as input in a radiative transfer model using t he discrete ordinate method to calculate J(NO2) data. Pn this paper we pres ent a detailed error discussion for the radiometer data and the quality con trolled measurements of J(NO2). J(NO2) reached an annual maximum between 19 94 and 1996 of up to 0.012 s(-1) during springtime. Surface albedo was foun d to have a large influence on the radiative balance in the Arctic. Measure d noontime data are compared with model results. Unweighted linear regressi on showed for 1996 a J(NO2)(model)/J(NO2)measure ratio of 0.90. This good a greement suggests that multichannel irradiance radiometers have the potenti al to be used to derive J values for a variety of trace gases.