A transitioning Arctic surface energy budget: the impacts of solar zenith angle, surface albedo and cloud radiative forcing
A transitioning Arctic surface energy budget: the impacts of solar zenith angle, surface albedo and cloud radiative forcing
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DOI：
10.1007/s00382-010-0937-5
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发表时间：
2011-10
期刊：
影响因子：
4.6
通讯作者：
J. Sedlar;M. Tjernström;T. Mauritsen;M. Shupe;I. Brooks;P. Persson;C. Birch;C. Leck;A. Sirevaag;M. Nicolaus;M. Nicolaus
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文献类型：
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作者：
J. Sedlar;M. Tjernström;T. Mauritsen;M. Shupe;I. Brooks;P. Persson;C. Birch;C. Leck;A. Sirevaag;M. Nicolaus;M. Nicolaus
2008年8月至9月初，在北极夏季云海洋研究期间，在87.5°N附近测量了雪面和海冰能量收支。地表温度显示了四种不同的温度状态，其特征在于不同的云，热力学和太阳能特性。最初温暖的融化季节被一个为期3天的寒冷状态所打断，温度从接近零度下降到-7 °C。随后，平均能量预算残差在1周内保持较小且接近零，直到气温再次迅速下降且能量预算残差变为负值。能量收支转换主要由净辐射通量决定，而云量则是主要的控制因素。变化的热量、湿度和云的分布与不断变化的空气质量有关。地面云辐射强迫，云在地面上相对于晴朗天空的净辐射效应，估计。短波云强迫的范围在−50 W m− 2和0之间，并随地面太阳辐射、太阳天顶角和云液态水的变化而显著变化。长波云强迫较大，通常在65到85 W m−2之间，除非云部分是稀薄的或含有很少的液态水;因此云的净效应是使地表变暖。这两个寒冷的时期都发生在稀薄的，或完全没有，含有少量液态水的低空云层下，有效地减少了云的温室效应。冻结的进展，提高了太阳天顶角和表面反射的组合，而抑制了一个大的，积极的表面云强迫，直到一个新的空气质量与相当少的云量平流在实验区。
Snow surface and sea-ice energy budgets were measured near 87.5°N during the Arctic Summer Cloud Ocean Study (ASCOS), from August to early September 2008. Surface temperature indicated four distinct temperature regimes, characterized by varying cloud, thermodynamic and solar properties. An initial warm, melt-season regime was interrupted by a 3-day cold regime where temperatures dropped from near zero to −7°C. Subsequently mean energy budget residuals remained small and near zero for 1 week until once again temperatures dropped rapidly and the energy budget residuals became negative. Energy budget transitions were dominated by the net radiative fluxes, largely controlled by the cloudiness. Variable heat, moisture and cloud distributions were associated with changing air-masses. Surface cloud radiative forcing, the net radiative effect of clouds on the surface relative to clear skies, is estimated. Shortwave cloud forcing ranged between −50 W m−2and zero and varied significantly with surface albedo, solar zenith angle and cloud liquid water. Longwave cloud forcing was larger and generally ranged between 65 and 85 W m−2, except when the cloud fraction was tenuous or contained little liquid water; thus the net effect of the clouds was to warm the surface. Both cold periods occurred under tenuous, or altogether absent, low-level clouds containing little liquid water, effectively reducing the cloud greenhouse effect. Freeze-up progression was enhanced by a combination of increasing solar zenith angles and surface albedo, while inhibited by a large, positive surface cloud forcing until a new air-mass with considerably less cloudiness advected over the experiment area.