科其喀尔冰川表碛区冰崖消融的度日因子研究

Study of the Positive Degree-day Factor of Ice Cliff Ablation in Debris-Covered Area of the Koxkar Glacier

2007年7月9日-8月30日在科其喀尔巴西冰川的表碛区进行了冰崖消融试验,通过在不同海拔、坡向和坡度冰崖的裸露冰面上栽设消融杆的方法,获得了33个有效的冰崖消融观测数据,结合观测点附近的自动气象站所获取的同期气温资料,计算了各个冰崖的度日因子,并对其变化特征进行了分析.结果表明:表碛区内冰崖的度日因子变化较大,平均为4.81 mm.℃-1.d-1,小于青藏高原及其它地区冰川的度日因子.研究区度日因子较小与冰面消融对于温度变化的敏感性及平均气温较高相关,而且这些因素通过温度随海拔的梯度效应影响表碛区内冰崖度日因子.冰崖坡向的变化也对度日因子产生了影响,总体表现为NEE-SE方向及SW-W方向的度日因子较大,NWW-N-NE方向的较小,S方向的最小,这主要与该地区的辐射、气温等气象条件的变化特征有关.研究还表明,冰崖的坡度对度日因子的影响较小.

An ice cliff ablation experiment was conducted in the debris-covered area of the Koxkar Glacier during July 9-August 30,2007.In this experiment,some ablation stakes were set up on the bare ice surface of selected ice cliffs which were distributed at various elevations and had different orientation and slope.Together with the air temperature data recorded by the neighboring Auto Weather Stations,33 sets of valid ice ablation data had been used to calculate the positive degree-day factors.Data analyses show that the positive degree-day factors range from 2.92 ～ 9.35 mm · ℃-1·d-1,with an average of 4.81 mm · ℃-1·d-1,which are smaller than those in the Tibetan Plateau and other places owing to low elevation and relatively high air temperature,because the ice ablation may be less sensitive to the change of the air temperature when the average temperature is high.It is supposed that the increasing trend of the positive degree-factor with elevation may have something to do with this reason.To minimize the influence of elevation when studying the relationship between positive degree-day factor and ice cliff orientation,the observational data are classified into three groups according to corresponding ice cliff elevations.The result shows that NEESE and SW-W oriented ice cliffs have greater positive degree-day factor,followed by that towards NWW-N-NE,and that of south-oriented ice cliffs is smaller.This characteristic of positive degree-day factor may be closely related with the regional incoming solar radiation,air temperature and other climatic conditions.This study also shows that the ice cliff slope might has less influence on the positive degree-day factor of the ice cliff in the debris-covered area of the Koxkar Glacier.