Ultraviolet Index Forecasts Issued by the National Weather Service

Abstract

The National Weather Service (NWS), in collaboration with the Environmental Protection Agency (EPA), now issues an Ultraviolet (UV) index forecast. 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 UVI. The NWS estimates the UVI using existing atmospheric measurements, forecasts, and an advanced radiative transfer model. This paper discusses the justification for a forecasted index, the nature of UV radiation, the methodology of producing the UVI, and results from verifying the UVI. Since the UVI is an evolving product, a short discussion of necessary improvements and/or refinements is included at the end of this article.

An empirical model to predict the UV‐index based on solar zenith angles and total ozone

“…At some locations cloud properties can be predicted with some success (see e.g. Long et al 1996;Burrows 1997). At many places the spatial and temporal variability of the clouds is so high that forecasters prefer to issue 'clear sky' and 'overcast' UVI forecasts instead, thus eliminating this source of error.…”

The effect of varying ozone concentration on surface UV-B radiation: a Fiji perspective

“…Despite this, some animals are known to be UV-B tolerant (Callaghan et al 2004). Over 34,100 people suffered from melanoma in the USA alone since 1973 and these cases are increasing by 4% each year (Long et al 1996;UNEP 1998).…”

“…UV-B studies have shown the effects of cloud cover on the magnitude of UV-B radiation reaching the ground to vary from 70% reductions with dense heavy clouds to an increasing effect with broken clouds (Long et al 1996;McKenzie et al 1997). The effects of clouds (cloud type and percentage cover) on the UV-B radiation are essential in determining its relationship to the total column ozone.…”

“…of the aerosols. Anthropogenic sulfate aerosols associated with fossil fuel burning were observed to decrease surface UV-B irradiance by a maximum of 5 -18% in highly industrialized regions of the Northern Hemisphere (Li et al 1995;Long et al 1996;UNEP 1998). Despite these natural means of reducing the levels of UV-B radiation from reaching the Earth's surface, there are sufficient rays penetrating these obstacles to cause harm to life.…”

Effects of model chemistry and data biases on stratospheric ozone assimilation

“…The observations can correct forecast errors, thereby providing accurate ozone initial conditions for the next forecast and analysis cycle. In addition to improving derived forecast products such as surface ultraviolet (UV) indices (Long et al, 1996), ozone assimilation and forecasting improve model stratospheric heating rates (and hence temperatures) and can be used to diagnose transport in the lower stratosphere, thereby improving wind assimilation (Peuch et al, 2000;Jang et al, 2003). These and other motivations for ozone assimilation, as well as previous work on the problem, are summarized by Rood (2005).…”