Depth Hoar Development Under Different Shading Conditions in Seasonal Snow Cover
Received date: 2011-08-29
Request revised date: 2011-11-10
Online published: 2012-07-13
Copyright
Depth hoar (DH) under different shading conditions in seasonal snow cover was studied in Tianshan Station Snow Cover and Avalanche Research Station in the winter of 2009-2010. Optical stereo microscope and the portable equipment Snow Fork were used to observe the grain size and shapes as well as water content and density of DH in the open ground (0 % shaded), canopy edge (50 % shaded) and canopied zone(90 % shaded). Results showed that: 1) DH growth primarily depends on temperature, and secondarily on temperature gradient. Temperature condition, caused by snow thickness depends on the snow accumulation and solar radiation, is the fundamental reason of DH’s differences under different shading conditions. 2) Both the snow depth and DH thickness indicate a diminishing sequence of open ground>canopy edge>canopied zone. In the snowmelt period, the decreasing rate of DH thickness shows canopied zone>open ground>canopy edge. 3) The DH grain size shows a decreasing trend at first stage (stable accumulation period - transition period) and then increase at the following stage (-snowmelt period). The rank of grain size keeps in the order of open ground>canopy edge> canopied zone after the stable accumulation period. 4) Due to the large snow thickness in the winter of 2009-2010, rounding depth hoar(DHxr) and rounding faceted particles(FCxr) are the two predominant grain shapes in DH, which accounted for 70%-80%. Hollow cups (DHcp) prefer to develop at open ground, while large striated crystals(DHla), hollow prisms(DHpr) and faceted particles (FCso) incline to grow at canopy edge and canopied zone. There are approximately 10%-30% congregate crystals in DH. The ratio declines at open ground and rises at canopy edge and canopied zone along time scale.
HONG Wen , WEI Wen-shou , LIU Ming-zhe , LU Heng , HAN Xi . Depth Hoar Development Under Different Shading Conditions in Seasonal Snow Cover[J]. SCIENTIA GEOGRAPHICA SINICA, 2012 , 32(8) : 979 -985 . DOI: 10.13249/j.cnki.sgs.2012.08.979
Fig. 1 Variations of air temperature, snow depth and snowmelt runoff in the observation period图1 观测期内积雪站气温、雪深和融雪径流的变化曲线 |
Fig.2 Comparison of snow and DH (Depth Hoar) depth图2 雪深与深霜厚度的比较 |
Fig.3 The temperature and temperature gradient of DH in open ground图3 开阔地深霜层雪温(a)与温度梯度(b) |
Fig.4 Variation of grain size of DH图4 深霜冰晶粒径的变化 |
Fig. 5 Variation of mean water content(a) 、and porosity(b) of DH图5 深霜层平均含水率(a)和孔隙率(b)的变化趋势 |
Fig. 6 Main grain shapes of DH in study area图6 研究区主要深霜晶型 |
Fig. 7 Proportion variation of grain shapes of DH图7 深霜晶型比例的变化 |
The authors have declared that no competing interests exist.
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