A Compile of Climatic UV-B Mesh Map in Japan

Much research has been done on the depletion of the ozone layer and consequent increase in ultraviolet B radiation (UV-B). In this study, a UV-B mesh map was compiled to show the distribution of radiation in Japan. Data on daily solar radiation and daily UV-B radiation observed in Sapporo, Tateno, Kagoshima and Naha from 1991 to 1997 were used, as well as the existing mesh data of solar radiation. First, ratios of daily UV-B to daily solar radiation were calculated for four observation sites, and then a sinusoidal curve was fitted to the annual changes in ratio for each site. The coefficients (amplitude, phase lag and mean value) of the sinusoidal functions were respectively presented as linear functions of latitude. The coefficients of correlations between the coefficients of the function and latitude were higher than 0.86. The ratio of UV-B to solar radiation can thus be calculated for any latitude by using the sinusoidal function whose coefficients are a function of latitude. Finally, monthly and annual UV-B mesh map for 1 km×1 km were obtained by multiplying this ratio by the existing mesh data of solar radiation. The procedure was done by using GTOPO30 and GRASS5.0 for the region of Japan. The state of the changes agreed well with the observed values and the standard error of estimated UV-B was 9.6%.