Toward Spectrally Consistent Solar Radiative Coupling Between the Atmosphere and the Cryosphere in Earth System Models

Components of Earth system models (ESMs) resolve solar radiative processes using independent spectral grids that do not align with one another. In the Energy Exascale Earth System Model (E3SM), the atmospheric radiative model partitions the solar spectrum into 14 bands, while solar fluxes coupled to the land component are reduced to two bands: visible (VIS) and near‐infrared (NIR). However, snow albedo within the land component is represented using one VIS and four NIR bands. As a result, the snow model adopts fixed weights to average the four NIR bands into a single NIR albedo. Here, we increase the spectral resolution of NIR fluxes passed from the atmosphere to snow‐covered land from one band to seven and align the snow albedo grid with the new coupled grid. This allows the snow model to dynamically weight the albedo based on the prognostic distribution of NIR fluxes modeled by the atmospheric component. Diagnostic experiments show that the forcing on surface absorption ranges from −1.90 to 4.73 W , with atmospheric water vapor strongly modulating the sign and magnitude of the forcing, thus allowing the forcing to be parameterized as a function of atmospheric water vapor. We show that coupling high‐resolution snow albedos from the surface to the atmosphere to calculate surface reflectance better captures the reduced reflectance at longer NIR wavelengths, decreasing lower‐atmospheric solar warming rates by up to 0.1 K . These results provide a framework for, and quantify the impacts of, implementing a high‐resolution spectrally consistent treatment of solar radiation between components in coupled ESMs.