The Importance of Snow Sublimation on a Himalayan Glacier
The Importance of Snow Sublimation on a Himalayan Glacier
复制标题
DOI：
10.3389/feart.2018.00108
复制
发表时间：
2018-08-24
影响因子：
2.9
通讯作者：
Immerzeel, Walter W.
中科院分区：
文献类型：
--
作者：
Stigter, Emmy E.;Litt, Maxime;Immerzeel, Walter W.
雪的升华是水分从积雪流失到大气中。到目前为止，喜马拉雅山的雪升华仍然没有量化，这阻碍了对水平衡和冰川物质平衡的全面了解。因此，我们测量表面潜热通量与涡度协方差系统亚拉冰川（5,350米a.s.l）在尼泊尔喜马拉雅山量化雪升华的作用在水和冰川质量预算。观测结果显示，2016年10月至11月的32天内，累积升华量为32毫米，与世界其他地区的观测结果相比，这一数值很高。随后，针对所观察到的升华，测试了多个湍流通量参数化。整体空气动力学方法提供了最好的性能，我们随后使用该方法估计了2016-2017冬季涡度相关系统位置的累积升华和蒸发，分别为125和9 mm。这相当于年降雪量的21%。此外，本文还采用整体空气动力学方法模拟了雅拉冰川在湿润和非湿润条件下的日升华总量的空间变化。气象变量的所需空间场是从该区域的高分辨率WRF模拟结合实地观测获得的。涡度相关系统位置的累积日升华等于整个冰川的平均模拟升华。因此，这个位置似乎是亚拉冰川升华的代表。升华的空间分布主要受风速控制。靠近雅拉冰川脊的日累积升华比涡度协方差系统的位置高1.7倍，而在冰川鼻端低0.8倍。这表明，在风暴露的位置，返回大气的降雪比例可能远高于21%。这是一个相当大的水的损失，并说明了重要性和需要考虑升华在未来的水文和质量平衡研究在喜马拉雅山。
Snow sublimation is a loss of water from the snowpack to the atmosphere. So far, snow sublimation has remained unquantified in the Himalaya, prohibiting a full understanding of the water balance and glacier mass balance. Hence, we measured surface latent heat fluxes with an eddy covariance system on Yala Glacier (5,350m a.s.l) in the Nepalese Himalaya to quantify the role snow sublimation plays in the water and glacier mass budget. Observations reveal that cumulative sublimation is 32 mm for a 32-day period from October to November 2016, which is high compared to observations in other regions in the world. Multiple turbulent flux parameterizations were subsequently tested against this observed sublimation. The bulk-aerodynamic method offered the best performance, and we subsequently used this method to estimate cumulative sublimation and evaporation at the location of the eddy covariance system for the 2016-2017 winter season, which is 125 and 9mm respectively. This is equivalent to 21% of the annual snowfall. In addition, the spatial variation of total daily sublimation over Yala Glacier was simulated with the bulk-aerodynamic method for a humid and non-humid day. Required spatial fields of meteorological variables were obtained from high-resolution WRF simulations of the region in combination with field observations. The cumulative daily sublimation at the location of the eddy covariance system equals the simulated sublimation averaged over the entire glacier. Therefore, this location appears to be representative for Yala Glacier sublimation. The spatial distribution of sublimation is primarily controlled by wind speed. Close to the ridge of Yala Glacier cumulative daily sublimation is a factor 1.7 higher than at the location of the eddy covariance system, whereas it is a factor 0.8 lower at the snout of the glacier. This illustrates that the fraction of snowfall returned to the atmosphere may be much higher than 21% at wind-exposed locations. This is a considerable loss of water and illustrates the importance and need to account for sublimation in future hydrological and mass balance studies in the Himalaya.