基于GIS的西藏南部雪线场的建立及其空间分布特征

CREATING THE DISTRIBUTION FIELD OF EQUILIBRIUM LINE ALTITUDE BASED ON GIS IN THE SOUTHERN OF TIBET AND ANALYZING ITS DISTRIBUTION CHARACTERS

采用中国冰川编目最新数据资料,求出西藏南部冰川系统中所有冰川样点的计算雪线高度(ELAhc),并将计算雪线高度导入ArcGIS 9中。在ArcGIS 9中调用ETgoW izard软件生成10'×10'的格网后,对格网内冰川样点的经度、纬度和计算雪线高度进行算术平均,得到每个网格里只有一个虚拟冰川数据。然后在ArcG IS 9中用Kriging插值,生成一定间隔的雪线分布图,即雪线场。经分析,发现它除受全球规律控制外,还能突出地反映西藏南部雪线场的较详尽的分布规律和受地形影响极大的区域特点,具体表现在以下3个方面:(1)雪线从南向北增高,具有反纬度地带性规律;(2)雪线由东向西逐步升高,具有经度地带性规律;(3)南部雪线分布密集、复杂,而北部雪线相对稀疏和较平缓。

On the basis of the data out of glacier inventory of china, the equilibrium line attitude （ELAhc） of the southern Tibet glacier system could be obtained. And the ELAhc was added into the software of ArcGIS 9. Then the graticule mesh of 10＇×10＇, which was produced by the software of ETgoWizard in the ArcGIS 9, overlaid the data points in the region of the southern Tibet. And arithmetic average values of all the data points＇ longitude, latitude and ELAhc in every square could be calculated with such software as ArcGIS 9, excel, word, etc. Thus the new data from calculating showed an invented glacier system that could really show some laws. Then an ELAhc distribution map of the interval of some distance, namely, the field of equilibrium line attitude, was produced by Kriging interpolation. By analyzing the recently equilibrium line attitude field, glacier＇s more detailed distribution＇s law of the southern Tibet glacier system could be found besides the global regular patterns accepted by people. And the region characteristic, which was produced by influence of topography, was more apparent. There were three such distribution characteristics as the following in the result. Firstly, the field gradient of ELAhc is steeper in south than in north of the Southern of Tibet, furthermore the phenomenon is contrary to the variety law of latitudinal direction zonality; Secondly, the ELAhc progressively increases westward, and the variation tallies with the variety law of longitude direction zonality; Thirdly, the south＇s ELAhc distribution of this region is denser and more complex, but the north＇s is relatively sparser and gentler.