Surface energy balance and katabatic flow over glacier and tundra during GIMEX-91
Surface energy balance and katabatic flow over glacier and tundra during GIMEX-91
复制标题
GIMEX-91 期间冰川和苔原上的表面能量平衡和下降流
DOI：
10.1016/0921-8181(94)90004-3
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发表时间：
1994
影响因子：
3.9
通讯作者：
M. Broeke
中科院分区：
文献类型：
--
作者：
P. Duynkerke;M. Broeke
本文描述了1991年夏季格陵兰冰架试验（gmex -91）观测到的能量平衡。沿着一条垂直于冰缘的横断面，竖起了几根桅杆；从冰帽上方90公里处，穿过消融带，到冻土带内5.8公里处。讨论了摩擦速度、感热通量和潜热通量在一天（7月22日）和整个观测期间的日平均值的变化。在大部分观测期内，由于冰在融化，冰面上的感热通量（正向上）的日平均值为负（约为- 30 W/m2）。潜热通量平均为正，湿润了沿冰盖向下流动的边界层空气。在距离冰缘约20公里以上的冰盖上方，能量平衡由净辐射驱动，导致白天的潜热通量高于夜间。夜间感热通量越小（越负），加速了滑水流；这导致风在深夜或清晨最大。这种能量平衡的日循环与在南极洲斜坡上观察到的非常相似。在冰的边缘，冰和冻土带的辐射和热特性之间的巨大差异对垂直流动施加了强烈的热强迫，类似于陆地-海风环流。在白天，热风加速了滑水流，导致湍流交换率和湍流通量的增强。
The energy balance observed in the summer of 1991 during the Greenland Ice Margin EXperiment (GIMEX-91) is described. Several masts were erected along a transect perpendicular to the ice edge; from a point 90 km up the ice cap, through the ablation zone, down to a point 5.8 km within the tundra zone.The diurnal variation of the friction velocity, sensible heat flux and latent heat flux, both on a single day (22 July) and averaged over the complete observational period are discussed. The mean daily values of the sensible heat flux (positive upwards) over the ice were negative (about — 30 W/m2), as the ice was melting during most of the observational period. On average the latent heat flux was positive, which moistened the boundary layer air flowing down the ice cap.Up the ice cap, more than about 20 km from the ice edge, the energy balance is driven by the net radiation which causes higher fluxes during the day than during the night. The smaller (more negative) sensible heat fluxes during the night accelerate the katabatic flow; this leads to a wind maximum late at night or early in the morning. This diurnal cycle in energy balance is very similar to that observed on the slopes of Antarctica.At the ice edge, the large difference between the radiative and thermal properties of the ice and the tundra exerts a strong thermal forcing on the katabatic flow, analogous to the land-sea breeze circulation. During day-time the thermal wind accelerates the katabatic flow, which leads to an enhancement of the turbulent exchange rate and turbulent fluxes.