In late July 2001, SPIE held 3 days of UV sessions in San Diego that attracted more than 50 papers written by authors from 12 countries. We have collected 11 of those papers in this special section of Optical Engineering. Another 22 of the papers given at the SPIE sessions dealing with the effects of UV on plants and ecosystems will be found in a special issue of Agricultural and Forest Meteorology. The papers in this special section focus on the measurement and modeling of solar ultraviolet (UV) radiation reaching the Earth’s surface and penetrating into the ocean. One of the most widely used models for predicting the amount of UV radiation at the Earth’s surface is the discrete ordinate model described by Stamnes et al.;1 An overview of UV modeling issues relating to both surface irradiance and irradiance penetrating into the oceans is presented by Stamnes. Vasilkov et al.; present modeling results using NASA Total Ozone Mapping Spectrometer (TOMS)-derived column ozone and cloud cover to predict the amount of UV reaching various depths of the ocean. Krotkov et al.; outline the improvements that have been made to the TOMS surface UV retrieval procedure. Schmalwieser et al.; provide global validation of the Austrian UV Index Forecast for clear skies by comparing model results with broadband irradiances measured over four continents. Fioletov et al.; compare Canadian Brewer UV spectrometer data from 10 sites with TOMS retrievals. The authors determine that TOMS overestimates UV at all but the cleanest site. Long-term time series of UV are reported by Sasaki et al.;, and Chubarova et al.; Sasaki et al.; analyze a ten-year broadband time series from Japan and find modest positive trends in UV. Chubarova et al.; document a twenty-year broadband UV-B plus UV-A (300 to 380-nm) time series from Moscow and determine a slight positive trend, which the authors attribute to decreases in cloud cover and aerosols. In addition to ozone decreases due to chlorine and bromine free radicals causing catalytic destruction of ozone in polar regions, there have recently been many documented events of ozone poor from low latitudes air being advected to mid latitudes resulting in large increases in surface UV. Siana et al.; report on such an event that occurred in Italy in November 2000. Another factor known to have a strong influence on the UV reaching the ground is the surface albebo. Schmucki and Philopona make a careful study of the influence of varying snowfields on the UV reaching several stations in the Swiss Alps. Science moves ahead by relating measurements of the physical world made by new instrumentation using ever more comprehensive models. Harrison et al.; describe the new USDA reference spectrometer that is being used to calibrate all of the 44 USDA broadband UV radiometers. Heath and Ahmad demonstrate the utility of a multi-channel narrowband radiometer which, when used in conjunction with a portable scanning spectrometer, can calibrate other UV radiometric instruments and derive column ozone. These papers represent some of the latest UV research that continues to benefit from the combination of new instrumentation, analysis of well-calibrated time series, and comparisons to radiative transfer models. The editors of this special section wish to express our thanks to SPIE, especially to Jonica Todd-Gallery, Jinxue Wang, and Karolyn Labes. Finally we wish to thank the reviewers for their time and expertise. They, as well as the authors, contributed to the high quality of the research that is presented here. REFERENCES
K. Stamnes
,
S. C. Tsay
,
W. Wiscombe
, and
K. Jayaweera
,
“Numerically stable algorithm for discrete-ordinate-method radiative transfer in multiple scattering and emitting layered media,”
Appl. Opt. , 27 2502
–2509
(1988). Google Scholar
|