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51.
52.
新亚欧大陆桥新疆段暴雨灾变事件的灰色预测 总被引:1,自引:1,他引:0
通过对新亚欧大陆桥新疆段水害严重区段暴雨灾变事件的分析,确定暴雨灾变事件的临界雨强,并运用灰色灾变预测方法,根据暴雨灾变序列确立相应的灾变年份序列,运用GM(1,1)模型,分别求出灾变年份序列的GM(1,1)序号响应式和灾变年份预测式。 相似文献
53.
干旱区内陆河流域的生态安全与生态需水量研究 总被引:2,自引:0,他引:2
结合对干旱区生态安全和生态需水量关键科学问题的探讨,提出干旱内陆河流域生态脆弱区的生态安全分析是以水过程研究为核心的,水文过程控制着生态过程,对流域生态系统的稳定性有着直接影响,而水资源开发利用和水循环对生态系统功能有重要影响,天然植物恢复和生长的合理地下水位的研究是确立生态需水量的基础。并实证分析和计算了维系塔里木河生态安全的生态需水量,塔里木河干流现状生态需水量为31.74×108 m3,其中,上、中、下游分别为9.95×108m3、18.47×108m3和3.32×108m3。 相似文献
54.
基于区域自然灾害发生的随机性和不确定性,运用分形、混沌理论,对新亚欧大陆桥新疆段近38年的环境灾害受损次数进行了时空分维特征研究。结果表明陆桥新疆段受损状况不仅在时间序列上具有自相似性,其容量维Df在0.8302~1.437之间,而且在空间序列上也具有自相似性,存在明显分维结构,其信息维D1在0.0997~0.1272之间。灾害严重区段的容量维值较大,并且容量维值越大,灾害事件中等级的复杂程度就越高,这一特征将有助于认识灾害发生规律和动力学特征。 相似文献
55.
塔里木河下游地下水位对植被的影响 总被引:133,自引:5,他引:128
对塔里木河下游断流河道2000~2002年9个地下水监测断面和18个植被样地的实地监测资料分析表明,地下水埋深对天然植被的组成、分布及长势有直接关系。地下水位的不断下降和土壤含水率大大丧失是引起塔里木河下游植被退化的主导因子。塔里木河下游的四次输水对其下游地下水位抬升起到了积极作用,河道附近地下水位呈逐级抬升过程,横向影响范围达1000 m左右,纵向上,表现为上段地下水抬升幅度较大 (达84%),下段抬升幅度较小 (6%)。随着地下水位的抬升,天然植被的响应范围由第一次输水后的200~250 m,扩展到第四次输水的800 m。 相似文献
56.
Potential evapotranspiration and its attribution over the past 50 years in the arid region of Northwest China 下载免费PDF全文
Evaporation paradox and its attribution have become a hot research topic in hydrology in recent years. This study estimates the potential evapotranspiration (ET0) using modified Penman–Monteith method and analyzes the corresponding trend attribution based on the long‐term meteorological data collected at 81 ground‐based meteorological stations in Northwestern arid region of China during the period 1958–2010. The analysis results show: (1) The ET0 has exhibited an obvious decreasing trend until the early 1990s; however, the downward trend has been reversed to an upward trend after then. (2) Decrease in diurnal temperature range (DTR) and wind speed (WS) may lead to the decrease of ET0 during 1956–1993. The change of dominant factors in the ET0 trend has differences after the early 1990s; observed increase in WS is the primary factor contributing to the reversion of ET0. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
57.
用涡度相关法对新疆塔里木河下游荒漠河岸柽柳(Tamarix chinensis)灌丛进行了1个生长季的实验观测,利用同步气象资料探讨了干旱胁迫环境下柽柳灌丛的近地面微气象和能量平衡特征,并运用普通最小二乘法线性回归及能量平衡比率法对比分析了不同天气条件下柽柳的日能量平衡变化和分配的差异。结果表明:观测期内柽柳灌丛的能量平衡闭合率为72.3%,地表能量通量和能量分配特征呈明显的单峰型二次曲线,地表净辐射通量和潜热通量是柽柳灌丛生长季的主要能量收入项和支出项;生长季内柽柳灌丛的能量平衡残差出现系统性、正负交替的日循环规律;在不同天气条件下,能量的分配转化和平衡程度均有明显差异,晴天的能量闭合状况好于阴天、降雨及扬沙天气,白天好于夜间;能量平衡比率在日出前与日落后的变化显著,且出现瞬时能量过闭合现象。受光合作用的影响,能量平衡闭合程度及碳通量的变化与不同天气下的温度及水分密切相关。 相似文献
58.
Yanfang Wang Yanjun Shen Fubao Sun Yaning Chen 《Theoretical and Applied Climatology》2014,118(3):569-579
Temperature has long been accepted as the major controlling factor in determining vegetation phenology in the middle and higher latitudes. The influence of water availability is often overlooked even in arid and semi-arid environments. We compared vegetation phenology metrics derived from both in situ temperature and satellite-based normalized difference vegetation index (NDVI) observations from 1982 to 2006 by an example of the arid region of northwestern China. From the satellite-based results, it was found the start of the growing season (SOS) advanced by 0.37 days year?1 and the end of the growing season (EOS) delayed by 0.61 days year?1 in Southern Xinjiang over 25 years. In the Tianshan Mountains, the SOS advanced by 0.35 days year?1 and the EOS delayed by 0.31 days year?1. There were almost no changes in Northern Xinjiang. Compared with satellite-based results, those estimates based on temperature contain less details of spatial variability of vegetation phenology. Interestingly, they show different and at times reversed spatial patterns from the satellite results arising from water limitation. Phenology metrics derived from temperature and NDVI conclude that water limitation of onset of the growing season is more severe than the cessation. Phenology spatial patterns of four oases in Southern Xingjiang show that, on average, there is a delay of the SOS of 1.6 days/10 km of distance from the mountain outlet stations. Our results underline the importance of water availability in determining the vegetation phenology in arid regions and can lead to important consequences in interpreting the possible change of vegetation phenology with climate. 相似文献
59.
Changes of stomatal conductance (g s), net photosynthetic rates (P N) and water use efficiency (WUE) were investigated in Populus euphratica grown on sites with different groundwater depths (GDs) under two CO2 concentrations in the lower reaches of Tarim River, Xinjiang, northwestern China. P N in P. euphratica only slightly decreased when the groundwater depth increased from 4.12 to 7.74 m below the ground surface. P N values significantly increased in response to an elevated CO2 concentration at all GDs except at GD of 4.12 m for its good availability of groundwater. WUE values decreased with an initial increase in the groundwater depth, but increased when the groundwater depth reached 7.74 m especially under the elevated CO2 concentration. The g s values measured at 4.12 and 4.74 m both decreased indistinctively by only 3% due to CO2 enrichment; however, when GDs increased to 5.54 and 7.74 m, the g s values decreased significantly by about 10%. It shows that the response of g s in P. euphratica to elevated CO2 is weaker under lower groundwater depth (mild drought stress) but stronger under deeper groundwater depth (moderate drought stress). Results from this study suggest that groundwater depth could determine the response of photosynthesis to future CO2 enrichment in P. euphratica in arid desert areas. 相似文献
60.
Quantifying the effects of climate variability and human activities on runoff for Kaidu River Basin in arid region of northwest China 总被引:2,自引:0,他引:2
Much attention has recently been focused on the effects that climate variability and human activities have had on runoff. In this study, data from the Kaidu River Basin in the arid region of northwest China were analyzed to investigate changes in annual runoff during the period of 1960–2009. The nonparametric Mann–Kendall test and the Mann–Kendall–Sneyers test were used to identify trend and step change point in the annual runoff. It was found that the basin had a significant increasing trend in annual runoff. Step change point in annual runoff was identified in the basin, which occurred in the year around 1993 dividing the long-term runoff series into a natural period (1960–1993) and a human-induced period (1994–2009). Then, the hydrologic sensitivity analysis method was employed to evaluate the effects of climate variability and human activities on mean annual runoff for the human-induced period based on precipitation and potential evapotranspiration. In 1994–2009, climate variability was the main factor that increased runoff with contribution of 90.5 %, while the increasing percentage due to human activities only accounted for 9.5 %, showing that runoff in the Kaidu River Basin is more sensitive to climate variability than human activities. This study quantitatively distinguishes the effects between climate variability and human activities on runoff, which can do duty for a reference for regional water resources assessment and management. 相似文献