Evaporative Resistance Equally Important as Albedo in High Latitudes Due to Cloud Feedbacks
Abstract
It is often assumed that terrestrial surface climate in the Arctic is largely controlled by the surface albedo. As the land surface becomes darker, it will absorb more solar energy. The extra absorbed energy is then released through longwave radiation and turbulent fluxes. If the total amount of latent heating is relatively constant, the extra absorbed radiation leads to warmer temperatures. The evaporative resistance of the land surface sets the difficultly for water to evaporate, and thus changes the partitioning between the turbulent fluxes of latent and sensible heat which could lead to a different surface temperature. These effects are known; however, it is unclear what the relative contribution of evaporative resistance and albedo are for the terrestrial surface climate. We used the albedo and evaporative resistance values derived from two common vegetation types, needleleaf evergreen trees and broadleaf deciduous trees, to simulate the climate response to a change in land surface albedo and evaporative resistance in factorial combinations. We find that changing the evaporative resistance between the two plant types has a large effect on the surface energy budget that is almost if not equivalent to changing albedo alone. Lower evaporative resistances lead to an increase of low clouds relative to higher resistance. As a result, less solar radiation reaches the surface when the evaporative resistance is lower. In contrast, the albedo controls how much of the incoming solar radiation gets absorbed. The reflection of light due to the difference in albedo is of the same magnitude as the loss of incident sunlight due to increased cloud cover under lower evaporative resistance. Our results demonstrate that realistic changes in evaporative resistance can have just as large of an impact on terrestrial surface climate as changes in surface albedo and that cloud feedbacks play a first order role in determining the surface climate response to a change in Arctic land cover.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.H13H1830K
- Keywords:
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- 3307 Boundary layer processes;
- ATMOSPHERIC PROCESSESDE: 3322 Land/atmosphere interactions;
- ATMOSPHERIC PROCESSESDE: 1843 Land/atmosphere interactions;
- HYDROLOGYDE: 1866 Soil moisture;
- HYDROLOGY