Spectral solar UV radiation and its variability and climate responses

UV radiation is an important component in the spectral solar irradiance for Earth’s climate system. UV radiation interacts with the atmosphere to form ozone layer that prevents the harmful radiation penetrating to the surface. The absorption of UV radiation depends on the wavelength. While UV-C is completely absorbed in the upper atmosphere, only a small fraction of UV-B penetrates to the surface, UV-A suffers almost no atmospheric absorption. Observations from Spectral Irradiance Monitor (SIM) onboard the Solar Radiation and Climate Experiment (SORCE) satellite show a rather large change in the UV radiation during the descending phase of solar cycle 23 as anticipated by the reconstructed spectral solar irradiance (SSI). Here we examine implications of SIM observations on Sun climate research. To understand the climate impact of variations in UV radiation requires a 3D global climate model. We use Goddard Institute for Space Studies (GISS) Global/Middle Atmosphere Model (GCMAM) to examine the climate resp...