Perturbing and constraining Norway’s surface water and energy balance

Abstract

The interplay of the land surface and atmosphere has been studied for a thousand years. Yet, we are still unsure how changes on the land surface impact the atmosphere and vice versa. Further, present-day models rely on a number of simplifications. This thesis takes on these issues in three studies, combining novel model experiments and observational data. In one study we conducted experiments in a regional climate model centered on South Norway. We perturbed the surface, either forest extent, snow cover, or sea surface temperature (SST). Annual precipitation and runoff were sensitive to both forest extent and SST changes. Another study considers two drivers of the land surface: near-surface humidity and incident radiation. It presents a new method producing a high-resolution data-set of these variables. Exciting estimates and the new data-set were compared with observations. The new data set was exploited in a third study. In a gridded hydrological model we let snowmelt and evaporation also react to humidity and radiation. Comparison with previous studies showed uncertainty about Norway's average annual precipitation and evaporation.