The UV<unk>  is a linear scale; each increase in value corresponds to a constant decrease in time to sunburn. Higher values represent a greater risk of sunburn (which is correlated with other health risks) due to UV exposure. An<unk>  of 0 corresponds to zero UV radiation, as is essentially the case at night. An<unk>  of 10 corresponds roughly to midday summer sunlight with a clear sky when the UV<unk>  was originally designed; now summertime<unk>  values in the tens are common for tropical latitudes, mountainous altitudes, areas with ice/water reflectivity and areas with above-average ozone layer depletion. While the UV<unk>  can be calculated from a direct measurement of the UV spectral power at a given location, as some<unk> pensive portable devices are able to approximate, the value given in weather reports is usually a prediction based on a computer model. Although this may be in error (especially when cloud conditions are unexpectedly heavy or light), it is usually within ±1 UV<unk>  unit as that which would be measured. Typical variation of UV<unk>  by time of day and time of year, around 40.71 -74.01, based on FastRT UV Calculator When the UV<unk>  is presented on a daily basis, it represents UV intensity around the sun's highest point in the day, called solar noon, halfway between sunrise and sunset. This typically occurs between 11:30 and 12:30, or between 12:30 and 13:30 in areas where daylight saving time is being observed. Predictions are made by a computer model that accounts for the effects of Sun elevation and distance, stratospheric ozone, cloud conditions, air pollutants, surface albedo, and ground altitude, all of which influence the amount of UV radiation at the surface. The calculations are weighted in favor of the UV wavelengths to which human skin is most sensitive, according to the CIE-standard McKinlay–Diffey erythemal action spectrum. The resulting UV<unk>  cannot be expressed in pure physical units, but is a good indicator of likely sunburn damage. Because the<unk>  scale is linear (and not logarithmic, as is often the case when measuring things such as brightness or sound level), it is reasonable to assume that one hour of exposure at<unk>  5 is approximately equivalent to a half-hour at<unk>  10.
Ultraviolet index
Dermal equivalent
NC ratio
Color vision
Biochemistry
Titer
Eagle score
Killing Season