The 1997 North American Interagency Intercomparison of Ultraviolet Spectroradiometers Including Narrowband Filter Radiometers

Abstract

The fourth North American Intercomparison of Ultraviolet Monitoring Spectroradiometers was held September 15 to 25, 1997 at Table Mountain outside of Boulder, Colorado, USA. Concern over stratospheric ozone depletion has prompted several government agencies in North America to establish networks of spectroradiometers for monitoring solar ultraviolet irradiance at the surface of the Earth. The main purpose of the Intercomparison was to assess the ability of spectroradiometers to accurately measure solar ultraviolet irradiance, and to compare the results between instruments of different monitoring networks. This Intercomparison was coordinated by NIST and NOAA, and included participants from the ASRC, EPA, NIST, NSF, SERC, USDA, and YES. The UV measuring instruments included scanning spectroradiometers, spectrographs, narrow band multi-filter radiometers, and broadband radiometers. Instruments were characterized for wavelength accuracy, bandwidth, stray-light rejection, and spectral irradiance responsivity. The spectral irradiance responsivity was determined two to three times outdoors to assess temporal stability. Synchronized spectral scans of the solar irradiance were performed over several days. Using the spectral irradiance responsivities determined with the NIST traceable standard lamp, and a simple convolution technique with a Gaussian slit-scattering function to account for the different bandwidths of the instruments, the measured solar irradiance from the spectroradiometers excluding the filter radiometers at 16.5 h UTC had a relative standard deviation of ±4 % for wavelengths greater than 305 nm. The relative standard deviation for the solar irradiance at 16.5 h UTC including the filter radiometer was ±4 % for filter functions above 300 nm.

2003 North American interagency intercomparison of ultraviolet spectroradiometers: scanning and spectrograph instruments.

“…This is closer to results observed during previous intercomparisons and to the participants' calibrations given in Fig. 8(a) [5]. The EPA participants believe there was a calculation error in their processing routines that needs to be evaluated.…”

“…In this paper, the results are presented for five scanning spectroradiometers and one spectrograph. The Brewer spectrophotometer, the USDA U111 spectroradiometer, and earlier versions of the BSI spectroradiometer and RSS Spectrograph have been described in previous Intercomparison papers [2,3,4,5]. Several of the instruments have been described in other intercomparison campaigns or cited references [13,14,15,16,17].…”

“…The U Series Ultraviolet spectroradiometers were designed and built by the Atmospheric Science Research Center and Instruments SA for use in the USDA UV Network (USDA_U11) and this instrument resides permanently at the Table Mountain Test. The design and data processing of this instrument are described further in several references [5,16,22]. …”

“…The main reason is that most instruments have been fully characterized in previous studies and/or have participated previously in North American Intercomparisons where instrument characterization occurred (i.e. ASRC_RSS, EPA_BRW, USDA_U11) [2,3,4,5]. Instruments that have not participated in previous North American Intercomparisons (NSF_SUV, IMUK_BEN, NOAA_NIWA) have been characterized fully elsewhere.…”

Sensitivity of Dobson and Brewer Umkehr ozone profile retrievals to ozone cross-sections and stray light effects

“…Unfortunately, some of the design features lead to instability of its optical system due to the degradation of one of the optical filters used in MKII, MKIV and MKV versions of the instrument (Bennet and McBride, 1964;Kimlin et al, 2003). Therefore, regular calibration of the Brewer instruments in the network and post-correction of measurements is done every 2 yr (Early et al, 1998;Lantz et al, 2002;Kimlin et al, 2005;Petropavlovskikh et al, 2007). The NEUBrew operational network (http://www.esrl.noaa.…”