| Taking the best use of meteorological data (mainly the temperature and precipitation observation data), basic geographic information, dataset of China glacier information system (1:100000), digital elevation model (DEM), remote sensing images collected in the Yarlung Zangbo River basin in association with the reference of the relevant achievements obtained in the past by pioneer studies in the region, comprehensive and systematic studies concerning with spatial and temporal variation characteristics of climate (focus on rainfall and temperature index) and their future tendency over the Yarlung Zangbo river basin during the past30years were conducted by means of the GIS spatial interpolation techniques, meteorological statistics method and R/S analysis...etc. First of all, by using RS and GIS techniques, the orientational and the altitudinal distribution of glacier areas in the Yarlung Zangbo River basin were comprehensively analyzed, and the seasonal fluctuation and interannual variation of typical glaciers were quantitatively studied. In combination of the research results concerning with glacier fluctuations and glacier inventory materials, the glacier variations related to equivabrium line fluctuations, glacier area and volume changes in long term as well as the long term climatic spatial and temporal variations were studied. Based on the above research results and the previous studies, the responses of glaciers and river water resources to the climate change in the Yarlung Zangbo river basin were systematically studied. The main conclusions obtained through this study can be summarized as follows:(1) From1978to2009, precipitation within the watershed roughly increased from west to east, and the basin scale averaged precipitation insignificantly increased at the speed of7.935mm/10a. Annual mean temperature increased gradually from the river source area to down-streams and from the basin boundary to hinterland with an exception for a local high-temperature zone emerged over the Lhasa city and the Naidong area. In32years from1978 to2009, annual mean temperature increased about2.2℃with the increase rate of0.489℃/10a (through99%significance test), which is obviously higher than the reported global temperature increase rate as well as for whole China. Over the past10years, the basin scale averaged precipitation notably reduced with a speed of-139mm/10a, while the temperature tended to increase with a speed of1.14℃/10a, which implies the whole watershed tended to be much warm and dry in the recent decade. In addition, according to the R/S analyses, Hurst index of the32years (from1978to2009) predicted that air temperature and precipitation would increase in some period in the future, and the climate over the basin would tend to be much warm and wet.(2) The distribution of glacier areas in the Yarlung Zangbo River basin from large to small is found orientated in order northeast, north, south, east, northwest, southeast and southwest, west. The altitudinal range in the partial north and west are respectively smaller than in the partial south and east. The altitudinal distribution of the glacier in the basin is about4600m, and the altitudinal interval between5300and5500m has the biggest glacier area developed. Taking No.5O258A0023glacier as a typical example, the glacier ablation period mainly concentrated from May、June to October while the accumulated phase mainly taken place from November to next year’s April、May. From1976to1988,21large maritime glaciers in the eastern river basin retreated, and the total glacier areas shrunk from1434.4km2to1283.4km2, with the annual diminution rate of0.810%. But from1988to2005, this group of large glaciers exhibited the reverse fluctuation trend with glacier areas increased from1283.4km2to1416.5km2in total at the annual rise rate of0.810%. On the whole, however, from1976to2005, the area of21large maritime glaciers reduced17.9km2, accounting for1.25%of the total area of glaciers in1976, so glacier appeared no significant retreat. Summarizing the results of previous studies and my research results, we can find out that most glaciers in the basin tended to slight retreat in general.(3) Taking21maritime glaciers as example, of climate change, the response of glaciers to climate change was analyzed. The conclusion is as following. Though the increasing temperature over the Yarlung Zangbo river basin tended to result in these glaciers retreat in general, but the increase of precipitation over the same period weaken or even offset the negative influence of the rising temperature. Increasing temperature plus increasing precipitation may be the main reason accounts for the glacier changes in the studied basin exhibited non-significant progress or retreat from1976to2005. Glacier change is influenced by accumulative temperature, precipitation, and there is inevitable response relationship among these three factors, which is found different in diverse regions. Some glaciers have been found changed more sensitive to the precipitation than to temperature.(4) According to the water balance equation of the Yarlung Zangbo river basin, its river runoff is affected by climate (temperature, precipitation, snow, and evaporation) and glacier change. For decades in the background of the rising temperature, the increasing precipitation and snow and decreasing evaporation over the basin, river runoff presented the increasing trend to response the climate and glacier changes. |
PDF Full Text Request