ULTRAVIOLET INDEX FORECASTS ISSUED BY THE NATIONAL-WEATHER-SERVICE

The National Weather Service (NWS), in collaboration with the Environm ental Protection Agency (EPA), now issues an Ultraviolet (UV) index fo recast. The UV index (UVI) is a mechanism by which the American public is forewarned of the next day's noontime intensity of UV radiation at locations within the United States. The EPA's role in this effort is to alert the public of the dangerous health effects of overexposure to , and the accumulative effects of, UV radiation. The EPA also provides ground-level monitoring data for use in ongoing verification of the U VI. The NWS estimates the UVI using existing atmospheric measurements, forecasts, and an advanced radiative transfer model. This paper discu sses the justification for a forecasted index, the nature of UV radiat ion, the methodology of producing the UVI, and results from verifying the UVI. Since the UVI is an evolving product, a short discussion of n ecessary improvements and/or refinements is included at the end of thi s article.