full size image; 29.5K
The radiative transfer model used for this study was originally configured to execute multiple latitude/longitude gridpoints sequentially in order to accomodate all significant land areas of the world. UV dose estimates were calculated for all land areas on a 1x1 degree spacing ranging from 70N to 60S; Antarctica and the northern regions of the Arctic Circle were not included in this survey. Grid cells containing land areas covering at least 5' spatial extent were considered land covered and calculations were carried out for these cells. This small spatial scale contingency was considered so that coastal areas that may have significant population centers would not be inadvertantly excluded in the case that their geographic location lies within an area that covers only a small portion of the 1x1 degree grid cell. This data set of grid cells meeting this criteria was provided by colleagues at the Remote Sensing Research Unit at the University of California at Santa Barbara (UCSB), and totalled more than 15,000 grid cells worldwide.
This map image displays daily UV dose averaged over the June/July/August season using TOMS ozone data for the year 1991. UV dose in this context is defined as total UV-B plus UV-A weighted by the SCUP-m carcinogenic action spectrum of de Gruijl et al. (1993). Seasonally and zonally averaged cloud optical depths derived from ISCCP optical depth data (Tselioudis et al., 1992) are also employed to better estimate surface dose values. Note the effect of elevation on UV dose relative to sea level areas and between land areas of similar latitude. The most noticeable changes occur in the Himilayan Range and the Tibetian Plateau. Differences are also noticeable in the Andes Range of South America, the Rocky Mountain Range in Mexico and Southern United States, and the Zagros Mountain Range and Plateau of Iran in Southwest Asia. Variations in climatological cloud cover also contribute to variations observed in portions of the Arabian Peninsula and Sahara Desert. Elevation data were taken from the Rand 1x1 degree elevation/bathymetry data set. This data set, as well as other data used to develop these maps, are described in more detail at the model description document found on an adjoining page in the UV climatology webspace.
References:
de Gruijl, F.R., Sterenborg, H.J.C.M., Forbes, P.D., Davies, R.E., Cole, C., Kelfkens, G., van Weelden, H., Slaper, H, and J.C. van der Leun. 1993. Wavelength Dependence of Skin Cancer Induction by Ultraviolet Irradiation of Albino Hairless Mice. Cancer Research 53:53-60.Tselioudis, G., Rossow, W.B., and D. Rind. 1992. Global Patterns of Cloud Optical Thickness Variation with Temperature. Journal of Climate 5:1484-1495.
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