Flow resistance in concentrated overland flow on rough slope surfaces     

J. M. Roels 《地球表面变化过程与地形》1984,9(6):541-551

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植被和气候对阿拉斯加和加拿大北部北极苔原地区多年冻土活动层厚度的影响   总被引：2，自引：4，他引：2  

Alexia M. Kelley  Howard E. Epstein  Donald A. Walker 《冰川冻土》2004,26(Z1):269-274

The active layer is the top layer of permafrost soils that thaws during the summer season due to increased ambient temperatures and solar radiation inputs. This layer is important because almost all biological activity takes place there luring the summer. The depth of active layer thaw is influenced by climatic conditions. Vegetation has also been found to have a strong impact on active layer thaw, because it can intercept incoming radiation, thereby insulating the soil from ambient conditions. In order to look at the role of vegetation and climate on active layer thaw, we measured thaw depth and the Normalized Difference Vegetation Index (NDVI; a proxy for aboveground plant biomass) along a latitudinal temperature gradient in arctic Alaska and Canada. At each site several measurements of thaw and NDVI were taken in areas with high amounts of vegetation and areas with little to no vegetation. Results show that the warmest regions, which had the greatest levels of NDVI, had relatively shallow thaw depths, and the coldest regions, which had the lowest levels of NDVI, also had relatively shallow thaw depths. The intermediate regions, which had moderate levels of NDVI and air temperature, had the greatest depth of thaw. These results indicate that temperature and vegetation interact to control the depth of the active layer across a range of arctic ecosystems. By developing a relationship to explain thaw depth through NDVI and temperature or latitude, the possibility exists to extrapolate thaw depth over large scales via remote sensing applications.  相似文献   

具有Horton及Dunne机制的径流模型在VIC模型中的应用(英)   总被引：20，自引：0，他引：20  

XIE Zhenghui  SU Fengge  LIANG Xu  ZENG Qingcun  HAO Zhenchun  GUO Yufu 《大气科学进展》2003,20(2):165-172

地表径流主要由蓄满(Dunne)和超渗产流(Horton)机制产生;土壤性质的空间变异性、前期土壤水、地形及降水的空间变异性导致不同的径流机制。在研究区域或模型网格内,蓄满产流及超渗产流可能同时出现,缺乏考虑任何一种机制以及土壤性质的次网格空间变率可能导致地表径流的过高或过低估计,从而影响土壤水的计算。利用Philip入渗公式用于时间压缩逼近(TCA)给出了一种径流参数化方法,该方法可以动态实现模型网格中的Horton及Dunne产流机理,它考虑了土壤空间变异性对Horton和Dunne径流的影响。该径流模型应用到基于水文原理的陆面过程模型VIC,在淮河流域及美国宾西法尼亚州的一个流域进行了测试,结果表明:新的参数化方法对地表径流和土壤水分含量的分配起着重要作用,对于改进径流和土壤水的模拟有重要意义。  相似文献   

Sequential assimilation of soil moisture and streamflow data in a conceptual rainfall–runoff model     

David Aubert  Ccile Loumagne  Ludovic Oudin 《Journal of Hydrology》2003,280(1-4):145-161

Soil moisture is a key hydrological variable in flood forecasting: it largely influences the partition of rain between runoff and infiltration and thus controls the flow at the outlet of a catchment. The methodology developed in this paper aims at improving the commonly used hydrological tools in an operational forecasting context by introducing soil moisture data into streamflow modelling. A sequential assimilation procedure, based on an extended Kalman filter, is developed and coupled with a lumped conceptual rainfall–runoff model. It updates the internal states of the model (soil and routing reservoirs) by assimilating daily soil moisture and streamflow data in order to better fit these external observations. We present in this paper the results obtained on the Serein, a Seine sub-catchment (France), during a period of about 2 years and using Time Domain Reflectivity probe soil moisture measurements from 0–10 to 0–100 cm and stream gauged data. Streamflow prediction is improved by assimilation of both soil moisture and streamflow individually and by coupled assimilation. Assimilation of soil moisture data is particularly effective during flood events while assimilation of streamflow data is more effective for low flows. Combined assimilation is therefore more adequate on the entire forecasting period. Finally, we discuss the adequacy of this methodology coupled with Remote Sensing data.  相似文献   

Influence of forest fires on climate change studies in the central boreal forest of Canada     

C. Valeo  K. Beaty  R. Hesslein   《Journal of Hydrology》2003,280(1-4):91-104

This brief paper indicates that forest fires may have short and longer term effects on runoff and thus, can influence trend studies on the response of watersheds to climate change. Twenty-two watersheds at the Experimental Lakes Area in northwestern Ontario were studied to view the impacts of climatic variability and forest fires on runoff. A roughly 30 year database demonstrated few trends in climatological variables and even fewer trends in runoff data at the 5% significance level. Daily maximum temperature increased by 0.053 °C per year, while precipitation in the months of February and March showed significant decreases. Total snow showed a significant decrease over a 30 year period at the 8% significance level. The Mann Kendall test for trend was applied to the runoff indices of 19 watersheds and it was revealed that only six exhibited trends. Of these, five had been burned during the test period. Virtually all burned watersheds showed initial increases in runoff, however, long term runoff trended lower in the burned watersheds, while the one watershed that was not burned showed an increasing trend. Forest fires alter the age distribution of trees with subsequent impacts on water yields in the short and longer term.  相似文献   

乌鲁木齐河源空冰斗径流增大的原因分析   总被引：2，自引：5，他引：2  

韩添丁  李忠勤  叶柏生 《冰川冻土》2003,25(4):389-393

天山乌鲁木齐河源区空冰斗径流量自20世纪80年代中期以来增大趋势明显，尤其是1996年以来径流量一直维持在较高水平，远大于前十几年的平均值。分析其主要原因为：河源区降水自1985年以来呈增加趋势，1996年以来降水明显增多；气温自20世纪80年代以来总体呈上升趋势，其中1997～1999年气温升高显，河源区处于一个明显的向暖湿阶段的转变过程中。同时，冻土活动层内温度的升高，导致冻土活动层内地下冰和地下埋藏冰强烈消融，也是径流量增大的重要原因之一。  相似文献   

Investigations on distributions and fluxes of sea-air CO_2 of the expedition areas in the Arctic Ocean   总被引：4，自引：0，他引：4  

王伟强  陈立奇  杨绪林  黄宣宝 《中国科学D辑(英文版)》2003,46(6):569-579

揋reenhouse effect?causing global warming has been an important issue of studying climate change. In the latest 100 years, the earth surface temperature has been increased by about 0.4℃—0.8℃[1,2]. And this has been becoming a hotspot of the world[3,4]  相似文献   

浙江洪水的主要特征分析   总被引：3，自引：0，他引：3  

冯利华 《地理与地理信息科学》2003,19(2):89-92

根据大量历史和实测的洪水资料分析，提出了峰量比的概念，得出了浙江洪不泊主要特征：浙西为梅雨暴雨主控区，浙东为台风暴雨主控区；洪水暴涨暴落，最大值接近国内记录；兰江洪水与新安江洪水遭遇的情况最为严重；洪水对太阳黑子活动具有较好的响应；洪水对厄尔尼诺事件具有较好的响应。这些特征对浙江洪水的长期及超长期预测具有重要的实际意义。  相似文献   

SCICEX Investigations of the Arctic Ocean System   总被引：1，自引：0，他引：1  

Margo H. Edwards  Bernard J. Coakley 《Chemie der Erde / Geochemistry》2003,63(4):281-328

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Chlorine-36 and C chronology support a limited last glacial maximum across central chukotka, northeastern Siberia, and no Beringian ice sheet     

Julie Brigham-Grette  Lyn M. Gualtieri  Olga Yu. Glushkova  Thomas D. Hamilton  David Mostoller  Anatoly Kotov 《Quaternary Research》2003,59(3):386-398

The Pekulney Mountains and adjacent Tanyurer River valley are key regions for examining the nature of glaciation across much of northeast Russia. Twelve new cosmogenic isotope ages and 14 new radiocarbon ages in concert with morphometric analyses and terrace stratigraphy constrain the timing of glaciation in this region of central Chukotka. The Sartan Glaciation (Last Glacial Maximum) was limited in extent in the Pekulney Mountains and dates to 20,000 yr ago. Cosmogenic isotope ages > 30,000 yr as well as non-finite radiocarbon ages imply an estimated age no younger than the Zyryan Glaciation (early Wisconsinan) for large sets of moraines found in the central Tanyurer Valley. Slope angles on these loess-mantled ridges are less than a few degrees and crest widths are an order of magnitude greater than those found on the younger Sartan moraines. The most extensive moraines in the lower Tanyurer Valley are most subdued implying an even older, probable middle Pleistocene age. This research provides direct field evidence against Grosswald’s Beringian ice-sheet hypothesis.  相似文献