Cloud effects on surface energy and mass balance in the ablation area of Brewster Glacier, New Zealand

The Cryosphere

N. J.Cullen¹  J. P.Conway¹ 

DOI  :  10.5194/tc-10-313-2016

学科分类：地球科学(综合)

来源: Copernicus Publications

【 摘 要 】

The effect of clouds on glacier surface energy balance (SEB) has receivedincreased attention in the last decade, but how clouds interact with othermeteorological forcing to influence surface mass balance (SMB) is not as wellunderstood. This paper resolves the SEB and SMB at a site in the ablationzone of Brewster Glacier over a 22-month period, using high-quality radiationdata to carefully evaluate SEB terms and define clear-sky and overcastconditions. A fundamental change in glacier SEB in cloudy conditions wasdriven by increased effective sky emissivity and surface vapour pressure,rather than a minimal change in air temperature and wind speed. Duringovercast conditions, positive net long-wave radiation and latent heat fluxesallowed melt to be maintained through a much greater length of time comparedto clear-sky conditions, and led to similar melt in each sky condition. Thesensitivity of SMB to changes in air temperature was greatly enhanced inovercast compared to clear-sky conditions due to more frequent melt andchanges in precipitation phase that created a strong albedo feedback. Duringthe spring and autumn seasons, the sensitivity during overcast conditions wasstrongest. To capture these processes, future attempts to exploreglacier–climate interactions should aim to resolve the effects ofatmospheric moisture (vapour, cloud, and precipitation) on melt as well asaccumulation, through enhanced statistical or physically based methods.

【 授权许可】

Unknown