||Latitudinal and Seasonal Variation in Calculated Ultraviolet-B Irradiance for Rice-Growing Regions of Asia.
Bachelet, D. ;
Barnes, P. W. ;
Brown, D. ;
Brown, M. ;
||ManTech Environmental Technology, Inc., Corvallis, OR. ;Oregon State Univ., Corvallis. Coll. of Oceanography.;Corvallis Environmental Research Lab., OR.
Seasonal variations ;
Ultraviolet rays ;
Farm crops ;
Cloud cover ;
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Ultraviolet-B (UV-B, 280-320 nm) irradiance was calculated for more than 1200 sites in Asia to characterize the spatial and temporal variation in the present UV-B climate for rice-growing regions. The analytical model of Green et al. was used to compute UV-B irradiance for clear skies using satellite-observed ozone column thickness and local elevation data. Ground-based observations of cloud cover were then used to approximate the average effect of cloud cover on UV-B irradiance using the approach of Johnson et al. Over the geographic range of rice cultivation, the maximum daily effective UV-B irradiance (UV-B(sub BE)) when weighted according to a general plant action spectrum, was found to vary approximately 2.5-fold under both clear and cloudy sky conditions. Under a climate resulting from a doubling of atmospheric carbon dioxide, estimated UV-B using predicted cloud cover was found to change by up to 17% from present conditions in Thailand. Both latitudinal and seasonal variation in solar UV-B radiation may be important aspects of the UV-B climate for rice as cultivars differ in sensitivity to UV-B and are grown under diverse conditions and locations.