| Summary: | Ocean surface albedo (OSA), the ratio of the upward to the downward radiation just above the air-sea interface, is of primary importance in quantifying the solar energy exchange between the atmosphere and the ocean. In current climate models, many OSA schemes depend only on the solar zenith angle (SZA) or both SZA and wind speed, are only valid for broadband, and commonly ignore considering ocean surface-layer optical properties. Oversimplified OSA in most climate models leads to less accurate estimation of the net shortwave energy in the coupled atmosphere-ocean system. This dissertation develops an improved OSA algorithm by considering multiple influential factors, including additional oceanic light attenuation effects and appropriate treatment of spectral variations of the reflective properties for incident direct and diffuse solar beams at the sea surface. The proposed OSA method shows robust performance compared to the in-situ measurements from the Clouds and the Earth's Radiant Energy System (CERES) Ocean Validation Experiment on a regional scale, and the CERES OSA products on a global scale. The new OSA is then added in the fully coupled mode of the Community Earth System Model2 to explore responses of Arctic surface temperature and the subsiding edges of the Hadley Circulation (HC) due to the OSA changes. Incorporation of light attenuation in OSA increases absorbed solar radiation and warms the ocean, enhancing seasonal heat storage and release across the Arctic Ocean, and increasing sea ice reduction and other positive climate feedback that amplify Arctic surface warming. Surface air warming is induced primarily through positive heating anomalies of vertical advection, latent heat release, and longwave radiative forcing. Warmer skin temperature is driven predominantly by increased downward longwave radiation, another positive surface albedo feedback. The warming effect not only occurs at the surface, but it also extends through most of the atmosphere, subsequently setting up corresponding atmospheric ...
|
|---|