Solar Ultraviolet Irradiance Variations and the Earth’s Atmosphere

Abstract

Solar ultraviolet (UV) irradiance variations are frequently invoked as a source of variance in atmospheric parameters, and as a possible cause of climate change. Recent observations have established that the solar ultraviolet irradiance does indeed vary with time. However, the extent to which these variations modulate the earth’s middle and lower atmosphere is not well known. Not all correlations observed between solar activity and atmospheric variability are consistent with model calculations of the atmosphere’s response to solar UV irradiance variations. Physical mechanisms postulated to explain a UV-climate connection require that solar induced variations in the stratosphere be coupled to the troposphere. To date, such coupling mechanisms have been explored only qualitatively. One difficulty in establishing the magnitude of any solar UV-climate link is the lack of detailed information about the temporal behaviour of the solar UV fluxes. In this paper, the interaction of solar UV radiation with the earth’s atmosphere is described, solar UV irradiance variability is examined, and possible links between solar UV irradiance variations and atmospheric variability are discussed.