Atmospheric response to the observed increase of solar UV radiation from solar minimum to solar maximum simulated by the University of Illinois at Urbana‐Champaign climate‐chemistry model

The University of Illinois at Urbana‐Champaign general circulation model with interactive photochemistry has been applied to estimate the changes in ozone, temperature and dynamics caused by the observed enhancement of the solar ultraviolet radiation during the 11‐year solar activity cycle. Two 15‐yearlong runs with spectral solar UV fluxes for the minimum and maximum solar activity cases have been performed. It was obtained that due to the imposed changes in spectral solar UV fluxes the annual‐mean ozone mixing ratio increases 3% over the southern middle latitudes in the upper stratosphere and 2% in the northern lower stratosphere. The model also shows a statistically significant warming of 1.2 K in the stratosphere and an acceleration of the polar‐night jets in both hemispheres. The most pronounced changes were found in November and March over the Northern Hemisphere and in September–October over the Southern Hemisphere. The magnitude and seasonal behavior of the simulated changes resemble the most robust features of the solar signal obtained from observational data analysis; however, they do not exactly coincide. The simulated zonal wind and temperature response during late fall to early spring contains the observed downward and poleward propagation of the solar signal, however its structure and phase are different from those observed. The response of the surface air temperature in December consists of warming over northern Europe, USA, and eastern Russia, and cooling over Greenland, Alaska, and central Asia. This pattern resembles the changes of the surface winter temperature after a major volcanic eruption. Model results for September–October show an intensification of ozone loss by up to 10% and expansion of the “ozone hole” toward South America.