Solar ultraviolet irradiance: Origins, measurements, and models

Solar ultraviolet (UV) irradiance and its variation significantly affects the evolution of the Earth, particularly its atmosphere. Because a large portion of the solar UV irradiance is absorbed well above the Earth's surface, it must be measured above the atmosphere. Starting with the earliest observations at mid-century, more accurate observations of longer time series have become the focus of our continued investigations. The goals are to characterize its behavior and to understand its causes so that the future impact on humanity can be assessed.