The fifth North American Intercomparison of Ultraviolet Monitoring Spectroradiometers was held June 13 to 21, 2003 at Table Mountain outside of Boulder, Colorado, USA. 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 NOAA and included participants from six national and international agencies. The UV measuring instruments included scanning spectroradiometers, spectrographs, and multi-filter radiometers. Synchronized spectral scans of the solar irradiance were performed between June 16 and 20, 2003. The spectral responsivities were determined for each instrument using the participants' lamps and calibration procedures and with NOAA/CUCF standard lamps. This paper covers the scanning spectroradiometers and the one spectrograph. The solar irradiance measurements from the different instruments were deconvolved using a high resolution extraterrestrial solar irradiance and reconvolved with a 1-nm triangular band-pass to account for differences in the bandwidths of the instruments. The measured solar irradiance from the spectroradiometers using the rivmSHIC algorithm on a clear-sky day on DOY 172 at 17.0 UTC (SZA = 30o) had a relative 1- standard deviation of +/-2.6 to 3.4% for 300- to 360-nm using the participants' calibration.
The design and optical characteristics of a polychromatic ultraviolet radiation exposure system are described. The system uses a Xe lamp and long-pass cutoff filters to provide exposures to plankton suspensions in quartz cuvettes. Up to 80 simultaneous exposures can be made for eight spectral regimes with ten irradiance levels for each regime. Treatment spectra are presented for a system configured for the study of UV responses of biological and chemical processes in the Chesapeake Bay. Experimental exposures bracket full solar spectral irradiance for the site.
The fluorescence of chlorophyll a (Chl) nm can be detected in water leaving radiance and related quantitatively to the concentration of Chl. Solar-induced fluorescence has also been related to photosynthesis in deeper waters. However, little is known about the relationships between Chl, fluorescence, photosynthesis, and irradiance near the sea surface. Quantum yields of fluorescence and photosynthesis, as well as the ratio of fluorescence to photosynthesis, change during exposures to bright light. Several physiological processes are at play. Consequently, it is difficult to construct models of near-surface quantum yields. Experimentation and comprehensive sampling in the field are required for critical information. Some approaches are presented here. Radiometer buoys that measure downwelling irradiance at 490 nm, Ed(490), and upwelling spectral radiance, Lu(lambda) are good tools for measuring solar-stimulated fluorescence during studies of near-surface biology. Results can be compared with experimental measurements using a fluorometer with a very weak measuring beam that does not perturb the balance between fluorescence and photosynthesis. Comparisons indicate that relationships between near-surface Chl, fluorescence, photosynthesis and irradiance can vary widely for reasons that are not yet well resolved. Still, Lu(683), corrected for backscatter and normalized to Ed(490), is a useful measure of near-surface Chl in many environments.
Conference Committee Involvement (3)
Ultraviolet Ground- and Space-based Measurements, Models, and Effects IV
5 August 2004 | Denver, Colorado, United States
Ultraviolet Ground- and Space-based Measurements, Models, and Effects III
4 August 2003 | San Diego, California, United States
Ultraviolet Ground- and Space-based Measurements, Models, and Effects II
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.