Solid precipitation on a tropical glacier in Bolivia measured with an ultrasonic depth gauge
Solid precipitation on a tropical glacier in Bolivia measured with an ultrasonic depth gauge
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用超声波深度计测量玻利维亚热带冰川上的固体降水
DOI：
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
E. Berthier
中科院分区：
文献类型：
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作者：
J. Sicart;P. Ribstein;J. Chazarin;E. Berthier
使用超声波深度计测量玻利维亚（16°S）Zongo冰川（2.4平方公里）平衡线附近两年的降雪量。通过研究风、气温和空气湿度对测量结果的影响，可以在3小时的时间步长内量化降雪量，灵敏度为1 cm的雪。新雪的密度是通过与雨量计测量结果进行比较来估计的。一年的特点是从5月到8月的旱季和从12月到4月的雨季，在此期间，冰川上的积累和融化同时发生。降雪事件与来自山谷的中速风（小于4 m s−1）有关。大量的潮湿空气起源于亚马逊盆地。地形效应会在安第斯山谷的中午和高山的下午产生降水。夜间降雪事件发生在与区域大气环流有关的恶劣天气期间，并持续数天。新雪的密度很高，约为250 kg m−3，这是因为降雪时气温很高（超过−3°C）。高雪密度和中等风速防止雪漂流的条件，这导致热带冰川上的积累空间变异性低。准确记录短时间步长的降雪对于研究冰川表面的能量通量非常重要，因为降雪事件大大增加了反照率，而太阳辐射通常是融化能量的主要来源。
An ultrasonic depth gauge was used to measure snowfall over a 2‐year period near the equilibrium line of the Zongo glacier (2.4 km2), Bolivia (16°S). Study of the influence of wind, air temperature, and air moisture on the measurements gives a quantification of snowfall at a 3‐hour time step, with a sensitivity of 1 cm of snow. The density of fresh snow is estimated by comparison with rain gauge measurements. The year is marked by a dry season from May to August and a wet season from December to April, during which accumulation and melting coincide on the glacier. Snowfall events are associated with a wind of moderate speed from the valley (less than 4 m s−1). Masses of moist air originate in the Amazon basin. The orographic effect produces precipitation at midday in the Andean valleys and in the afternoon in the high mountains. Nighttime snowfall events occur during periods of bad weather related to the regional atmospheric circulation and last several days. The density of fresh snow is high, about 250 kg m−3, because of the high air temperature during snowfall events (over −3°C). The high snow density and the moderate wind speeds prevent snow drifting conditions, which results in low spatial variability of the accumulation on tropical glaciers. Accurate recording of snowfall at a short time step is important for the study of energy fluxes at the glacier surface because snowfall events greatly increase the albedo and solar radiation is generally the main source of melting energy.