Climatology and trends of surface UV radiation: Survey article

Abstract

An improved understanding of the global ultraviolet (UV) climate has recently become of great interest. A number of stations are now making regular measurements of spectrally-resolved UV-B irradiance. Despite the lack of long-term records RÉSUMÉ [traduit par la rédaction] On cherche récemment à améliorer nos connaissances de la climatologie mondiale de l'ultraviolet (UV). Plusieurs stations mesurent périodiquement l'irradiance UV-B résolue spectralement. Malgré la pénurie de données à long terme, il est possible de décrire la climatologie à court terme de l'irradiance UV-B au sol ainsi que plusieurs de ses caractéristiques et des facteurs dont elle dépend. Le présent article décrit l'état actuel des mesures des UV-B et présente une climatologie de l'irradiance UV-B au sol, notamment pour le Canada. L'irradiance UV est fonction de l'ozone et d'autres variables climatiques; cette relation est examinée en détail en faisant appel aux observations. Une comparaison des résultats fournis par les modèles de transfert radiatif et des mesures récentes révèle qu'il est possible d'inférer l'irradiance UV-B à la surface à partir d'enregistrements plus anciens de l'ozone total et de mesures accessoires (irradiance avec IntroductionThe ultraviolet (UV) solar spectrum is, by common convention, divided into three regions. Solar radiation of less than 280 nm wavelength (the UV-C region) is so strongly absorbed by ozone and (at shorter wavelengths) molecular oxygen that it is undetectable at the Earth's surface. Surface UV irradiance † therefore consists of UV-A (315-400 nm) and UV-B (280-315 nm). While the former comprises a much larger portion of the total solar energy (7% of the extraterrestrial solar constant versus 1.5% for the UV-B portion) it has much less capacity to affect biological systems because the individual photons themselves are less energetic.

Variable phytoplankton response to enhanced UV-B and nitrate addition in mesocosm experiments at three latitudes (Canada, Brazil and Argentina)

“…While incident solar radiation is generally highest in the tropics, there is a more pronounced seasonal in-crease in ozone-induced UV-B flux from mid-to highlatitudes (Tarasick et al 2003). It has been suggested that tropical species are less sensitive to enhanced UV-B, because they have an evolutionary history of exposure to high and more constant PAR (photosynthetically available radiation, 400 to 700 nm), UV-A (320 to 400 nm) and UV-B flux that permits the development of adaptation processes (Hazzard et al 1997, Helbling et al 1992.…”

Surface ultraviolet radiation

“…A multi-year climatology of daily maximum surface UV Index values was reported by Tarasick et al (2003) for 14 stations ranging in latitude from 69°S (Syowa) to 82.5°N (Alert).…”

Stratospheric ozone, ultraviolet radiation and climate change

“…As a result there are few reliable long-term records of surface UV radiation covering several decades. For instance, broadband radiometers used in the United States since the 1970s proved not to have the stability required to detect UV trends (Tarasick et al, 2003). A worldwide monitoring network -Network for the Detection of Atmospheric Composition Change -is now operational and already provides useful measurements to study the long-term evolution of surface UV radiation.…”