Observations of UV doses and Ozone amounts near New York City using the NILU-UV instrument

At Stevens Institute of Technology, Hoboken, NJ we have operated a site with NILU-UV instruments for nearly two years. For most of this time only one instrument has been in operation, but we also have data for extended periods of time when up to three instruments have been working in parallel. The site is in close proximity to New York City and it is equipped with basic radiation sensors in addition to the NILU-UV sensors. In a companion paper¹ we present results from intercomparisons between filter-based instruments, such as the NILU-UV. and the Dobson and Brewer instruments. Here we describe our experience operating filter-based radiation instruments. In particular, we discuss data quality issues and describe how one can detect and correct for drift in filter- based instruments. We also investigate the effect of elevated detector temperatures due to over-heating of the instrument by solar radiation on very warm days. Our experience with the newer versions of the filter instruments is that most of them have only minor problems with filter drift over time, and that this drift (if any) is easily detectable and can be corrected for. A potential problem is that varying detector temperature can degrade the instrument performance. Since filter UV instruments are normally set to operate with detector temperatures much higher than ambient temperatures this is a minor issue for most locations, and one that can easily be prevented.