The impact of improving ocean surface albedo on hydrological responses in the community earth system model

Surface albedo is a major influence on climate over a wide range of time scales. Despite the known importance of surface albedo, its representation in comprehensive global climate models and its influence on simulated climate remain poorly characterized. This study incorporates an improved ocean surface albedo parameterization into the Community Earth System Model (CESM), version 2.1.3, and evaluates its impact on hydrological response. We conduct two comparative types of climate simulations with forcing based on recent climate averages: A modified albedo CESM run (M-CESM) and a control CESM run (C-CESM). Results from comparison of monthly mean net freshwater flux (NFW; precipitation (P) minus evaporation (E)), between M-CESM and C-CESM show that the NFW pattern of M-CESM tends to detrain more water (E) in the subtropics where the dry, subsiding air comes out of the subtropical high-pressure centers to feed the trade-wind systems. There is a tendency to evaporate more water (P) into the Intertropical Convergence Zone (ITCZ) where the air ascends, releasing the moisture to form the high precipitation band in the tropics. This feature appears more remarkable, particularly, in the Northern Hemisphere summer. High-latitude precipitation zones are caused by poleward moisture transport by westerlies. The hydrological response to modified albedo is the result of readjusted energy flow such as changes in the spatial pattern and magnitude of air temperature, moisture, and clouds in the tropical meridional overturning circulation induced by the placement of the ocean albedo modification.