The Scientific Committee on Solar-Terrestrial Physics (SCOSTEP) and Predictability of the Variable Solar-Terrestrial Coupling (PRESTO) Online Seminar will be held on 13 February 2024 from 11:00 PM to 12:00 AM CET.
Not only total solar irradiance (TSI) but also spectral solar irradiance (SSI) matter for our climate. On top of spectrally dependent gas absorptions in the atmosphere, different surfaces can have different reflectivity for the visible (VIS) and near-infrared (NIR). The TSI observed by the most recent NASA SSI monitoring mission, TSIS-1, differs from the counterpart used by the CMIP6 climate models by no more than 1 W m−2; however, the SSI difference in a given VIS band (e.g., 0.44–0.63 μm) and NIR band (e.g., 0.78–1.24 μm) can be as large as 4 W m−2 but with opposite signs. We recently showed that such a difference in the spectral partitioning of TSI can cause noticeable differences in the simulated high-latitude surface climate. Using the CESM 2.1.3, we continue this line of research to understand the underlying physical mechanisms for the SSI partitioning to affect the simulated climate. We carried out a series of sensitivity runs by varying the partitioning between the VIS and NIR SSI while keeping the TSI unchanged. Radiative kernels are used to diagnose radiative feedback in response to such configuration (i.e., the different partitioning configurations of the VIS and NIR SSI). Our results show that the surface albedo feedbacks derived from different sensitivity runs are consistent regarding the magnitude and the spatial map. However, the hemispherical averaged broadband albedo changes little throughout all the sensitivity runs. The implications of our findings on future climate-change projection and paleoclimate studies are then discussed.
Professor Xianglei Huang
Photo by Zoltan Tasi on Unsplash