第八届青年地学论坛

Not only total solar irradiance (TSI) but also spectral solar irradiance (SSI) matter for our climate. Different

surfaces can have different reflectivity for the visible (VIS) and near-infrared (NIR). The recent NASA Total and Spectral

Solar Irradiance Sensor (TSIS-1) mission has provided more accurate SSI observations than before. The TSI observed by

TSIS-1 differs from the counterpart used by climate models by no more than 1Wm22. However, the SSI difference in a

given VIS (e.g., 0.44–0.63 mm) and NIR (e.g., 0.78–1.24 mm) band can be as large as 4Wm22 with opposite signs. Using the

NCAR CESM2, we study to what extent such different VIS and NIR SSI partitions can affect the simulated climate. Two

sets of simulations with identical TSI are carried out, one with SSI partitioning as observed by the TSIS-1 mission and the

other with what has been used in the current climate models. Due to different VIS-NIR spectral reflectance contrasts

between icy (or snowy) surfaces and open water, the simulation with more SSI in the VIS has less solar absorption by the

high-latitude surfaces, ending up with colder polar surface temperature and larger sea ice coverage. The difference is more

prominent over the Antarctic than over the Arctic. Our results suggest that, even for the identical TSI, the surface albedo

feedback can be triggered by different SSI partition between the VIS and NIR. The results underscore the importance of

continuously monitoring SSI and the use of correct SSI in climate simulations.