Impact of Spectral Solar Irradiance Variations on the Energy Balance of the Earth

The total solar irradiance is usually adopted when studying the solar impact on the energy balance of the Earth at present. However, based on the Solar Radiation and Climate Experiment irradiance record, the impact of solar spectral variations on the global energy balance between December 2007 and the First Half 2010, which were in the descending and ascending solar phase respectively, is studied. The results show that the relatively larger total solar output in the First Half 2010 was mainly caused by the radiation enhancements in ultraviolet and infrared regions, with increments of 0.11% in 200～400nm and 0.05% in 760～4000nm respectively, while the radiation in visible region of 400～760nm decreased by 0.05%. According to the reanalysis of the daily ozone data from MLS Version 2.2, the concentration of stratospheric ozone also increased in the First Half 2010 at the same time. Especially, in February and March whose ultraviolet enhancements are relatively higher than those in other months, the ozone increments are also higher, with maximum of 0.6mL·m^-3 and 0.62mL·m^-3 respectively at altitudes of 33km and 40km. As a result, the radiation reduction in visible region and concentration increase in stratospheric ozone together contributed to the smaller solar radiation at the tropopause in the First Half 2010 as compared with that in December 2007, with the maximum reduction of 0.15W·m^-2 in March 2010. The results mean that the increase in solar activity or total output may also cool the Earth-Troposphere system.