Rainfall partitioning into throughfall,stemflow, and interception within a single beech (Fagus sylvatica L.) canopy: influence of foliation,rain event characteristics,and meteorology   总被引：2，自引：0，他引：2  

Jeroen Staelens  An De Schrijver  Kris Verheyen  Niko E. C. Verhoest 《水文研究》2008,22(1):33-45

While the hydrological balance of forest ecosystems has often been studied at the annual level, quantitative studies on the factors determining rainfall partitioning of individual rain events are less frequently reported. Therefore, the effect of the seasonal variation in canopy cover on rainfall partitioning was studied for a mature deciduous beech (Fagus sylvatica L.) tree over a 2‐year period. At the annual level, throughfall amounted to 71% of precipitation, stemflow 8%, and interception 21%. Rainfall partitioning at the event level depended strongly on the amount of rainfall and differed significantly (p < 0·001) between the leafed and the leafless period of the year. Therefore, water fluxes of individual events were described using a multiple regression analysis (r_a² > 0·85, n = 205) with foliation, rainfall characteristics and meteorological variables as predictor variables. For a given amount of rainfall, foliation significantly increased interception and decreased throughfall and stemflow amounts. In addition, rainfall duration, maximum rainfall rate, vapour pressure deficit, and wind speed significantly affected rainfall partitioning at the event level. Increasing maximum hourly rainfall rate increased throughfall and decreased stemflow generation, while higher hourly vapour pressure deficit decreased event throughfall and stemflow amounts. Wind speed decreased throughfall in the growing period only. Since foliation and the event rainfall amount largely determined interception loss, the observed net water input under the deciduous canopy was sensitive to the temporal distribution of rainfall. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

蒸发皿蒸发量变化及其研究进展   总被引：5，自引：0，他引：5       下载免费PDF全文

杨秀芹  钟平安 《地球物理学进展》2008,23(5):1494-1498

对近几十年蒸发皿蒸发量分析表明,许多区域平均的蒸发皿蒸发量存在持续的下降趋势,全球变暖并没有使蒸发皿蒸发量增加,蒸发皿蒸发量与人们预期的理论结果相反;总结了国内外关于蒸发皿蒸发量变化研究进展;总结了关于蒸发皿蒸发量变化成因的主要观点;并提出了需要进一步研究的问题.  相似文献   

西藏不同气候区域旱涝特征分析     

向毓意  杜军  马玉才 《气候与环境研究》2001,6(3):354-360

提出有效降水的概念,并将有效湿润度(有效降水与可能蒸发量的比值)的异常程度作为判别指标,对西藏高原不同气候区域的旱涝特征进行了研究.  相似文献   

Heating experiments relevant to the depletion of Na,K and Mn in the Earth and other planetary bodies     

《Chemie der Erde / Geochemistry》2019,79(4):125540

We have studied the evaporation of Na, K and Mn from Al-Na-K- and Mn-rich silicates at various conditions. Total alkali oxide contents ranged from 5 to 20%. The evaporation rate of Na increases with temperature and decreasing oxygen fugacity and decreases with duration of heating. The loss of K is in all cases less pronounced than for Na. Heating in an evacuated vacuum furnace is more effective in removing Na and K from melt droplets than in furnaces with one atm gas flow of air or gas mixtures controlling the oxygen fugacity. The strong pumping required to keep the vacuum removes Na and K atoms very effectively. In all experiments, the rate of evaporation is determined by quasi-equilibrium between a thin layer of Na and K rich gas above the molten silicates. The results of the experiments are in agreement with several other studies.In experiments with more than one sample in the furnace, equilibration of Na- and K-rich samples with Na- and K-poor samples occurred rapidly, mediated by the ambient gas phase.The results of experiments with Mn in starting compositions showed much stronger losses of Na than Mn under a variety of conditions.Thus the nearly chondritic Mn/Na ratios in the Earth cannot be the result of evaporation of Na and Mn in Earth-making materials, as the Mn/Na ratios in evaporation residues would be much higher than chondritic ratios. Such evaporation processes may have occurred in the parent material of Moon, Vesta and Mars.The data suggest, in agreement with earlier hypotheses, that the high and variable contents of Na and K in chondrules require a gas phase high in Na and K equilibrating with chondrule melts. The volume of nebular gas parental to a certain type of chondrites was heated and Na and K were lost from the chondrule precursors to the gas phase. Subsequently the nebular parcel was compressed leading to higher partial pressures of Na and K. Flash heating then produced chondrule melts which incorporated some of the gaseous Na and K and then cooled rapidly. The large range of Na and K contents in chondrule melts reflects very local enrichments of Na and K in the gas phase. Despite these variations bulk chondritic meteorites have well defined bulk Na and K contents, implying a closed system during formation of chondrules and matrix.  相似文献   

NaCl-X-H2O三元体系25℃等温蒸发石盐流体包裹体均一温度实验研究     

李俊  程怀德  张西营  李雯霞  海擎宇  张星  周同亮 《矿床地质》2019,38(1):120-128

复杂卤水组分对于石盐流体包裹体均一温度的影响尚不明确,文章基于NaCl-X-H_2O(X=KCl, MgCl_2,CaCl_2, Na_2SO_4)三元卤水体系,尝试探讨K~+、Mg~(2+)、Ca~(2+)、SO_4~(2-)对石盐流体包裹体均一温度测试结果的影响。不同卤水体系最大均一温度分析结果表明,K~+、Mg~(2+)、Ca~(2+)的存在总体上会导致石盐流体包裹体均一温度偏大,SO_4~(2-)的存在对均一温度的影响很小。以NaCl-H_2O体系为参照,NaCl-Na_2SO_4-H_2O体系平均均一温度较之要低,而NaCl-KCl-H_2O、NaCl-MgCl_2-H_2O和NaCl-CaCl_2-H_2O体系与其相反。NaCl-KCl-H_2O体系中的KCl浓度与平均均一温度呈现负相关关系,NaCl-MgCl_2-H_2O、NaCl-CaCl_2-H_2O、NaCl-Na_2SO_4-H_2O体系中的w(MgCl_2)、w(CaCl_2)和w(Na_2SO_4)与平均均一温度则呈现正相关关系。平均和最大均一温度分析结果都显示出复杂卤水体系中不同离子及其浓度对石盐流体包裹体均一温度会产生影响。本研究对于具有复杂化学组分卤水结晶析出石盐均一温度的研究具有重要的参考价值。  相似文献   

一里坪矿区卤水自然蒸发试验研究   总被引：4，自引：0，他引：4       下载免费PDF全文

李俊德  石天成  王英孝  吴蝉  付建龙 《盐湖研究》2008,16(4)

在青海省重点科技攻关项目"柴达木盆地一里坪凹陷开采方法及找矿方向研究"(2005-G-131)基础上,对一里坪锂硼钾矿区卤水进行了自然蒸发试验研究。  相似文献   

遥感反演土壤蒸发/植被蒸腾二层模型在华北地区的应用   总被引：5，自引：2，他引：3  

田静  苏红波  孙晓敏  陈少辉 《地理研究》2009,28(5):1297-1306

利用一种可操作的地表蒸散遥感反演二层模型,以我国华北平原为研究区,选择2004年的3月至6月华北地区主要农作物冬小麦的生长季节作为研究时段,利用MODIS遥感卫星数据,结合地面130多个气象台站的空气温湿度实测数据,实现了土壤蒸发和植被蒸腾的反演。采用国家生态网络禹城综合试验站利用涡度相关系统观测的地表总蒸散半小时平均的数据进行了模型验证,结果表明模型估算的地表可利用能量与地面实测数据的相关系数可以达到0.92,均方差为30.4w.m^-2;模型估算的地表总蒸散值与地面实测数据的相关系数为0.85,均方差为21.3 w.m^-2,由此证明了模型的可用性。  相似文献   

生长季流动沙地水量平衡研究   总被引：4，自引：3，他引：1  

刘新平  赵哈林  何玉惠  张铜会  赵学勇  李玉霖 《中国沙漠》2009,29(4):663-667

利用水分分配箱对流动沙地土面蒸发量和入渗补给量的月动态特征及其水量平衡作了定量研究。结果表明:①生长季流动沙地土面蒸发量从４月开始逐渐增大,至８月达到蒸发的最高点,９月蒸发量开始回落;5月、6月受气温的影响蒸发量相对较小,只占到同期降水量的30%~40％,有利于土壤储存更多的水分;生长季总蒸发量为167.42 mm,占同期降水量的76.07％,远小于固定沙地小叶锦鸡儿灌丛蒸散量占同期降水量的135.83％的比值。②补给量从4月开始逐渐增大,8月达到最大值16.79 mm,进入9月,随着降水量的减少以及8月较大的蒸发消耗,补给量迅速减少。补给系数从5月至8月逐渐增大,最大值可达到26.73％,平均值为15.09％。  相似文献   

Orographic controls on rain water isotope distribution in the Mount Lofty Ranges of South Australia     

Huade Guan  Craig T. Simmons  Andrew J. Love 《Journal of Hydrology》2009,374(3-4):255-264

Hydrogen and oxygen isotopes of water are common environmental tracers used to investigate hydrological processes, such as evaporation, vegetation water use, surface water–groundwater interaction, and groundwater recharge. The water isotope signature in surface water and groundwater evolves from the initial rain signature. In mountain terrain, rain water stable isotope composition spatially varies due to complex orographic precipitation processes. Many studies have examined the isotope–elevation relationships, while few have quantitatively investigate the terrain aspect and slope effect on rain isotope distribution. In this paper, we examine the orographic effects more completely, including elevation, terrain slope and aspect, on stable isotope distribution in the Mount Lofty Ranges (MLR) of South Australia, using a multivariate regression model. The regression of precipitation isotope composition suggests that orographic effects are the dominant controls on isotope spatial variability. About 75% of spatial variability in δ¹⁸O and deuterium excess is represented by the regression using solely orography-related variables (elevation, terrain aspect and slope), with about 25% of δ¹⁸O spatial variability attributed to the terrain aspect and slope effect. The lapse rate is about −0.25‰ for every 100 m at both windward and leeward slopes. However, at the same elevation, δ¹⁸O at the leeward slope (eastern MLR) is 0.5‰ larger than that at the windward slope. The difference can be explained by different mechanisms – continuous rain-out processes on the windward side and sub-cloud evaporation on the leeward side. Both δ¹⁸O and deuterium excess maps (1 km resolution) are constructed based on the regression results for the MLR. Both maps are consistent with groundwater of local precipitation origin, and useful to examine groundwater recharge.  相似文献   

甘肃省不同气候区蒸发量变化特征及其影响因子研究   总被引：8，自引：2，他引：6  

王素萍  张存杰  韩永翔 《中国沙漠》2010,30(3):675-680

蒸发量是研究水分平衡和气候变化的一个非常重要的参数。众多研究普遍认为,近几十年来,国内外大部分区域蒸发量总体上呈下降趋势,且认为太阳总辐射、净辐射、日照时数以及风速的减小是造成蒸发下降的主要原因。研究也发现,在不同的区域,因地形、地理位置以及气候的差异,蒸发量的变化趋势、变化幅度和主要影响因子也存在差异。利用甘肃省4个不同气候区代表站1970—2007年的实测气象资料,分析了近38 a来各站潜在蒸发量及20 cm蒸发皿蒸发量的变化特征,同时,通过分析各站主要气象要素的变化特征,探讨了影响各站蒸发量变化的主要气象因子。结果表明,与国内外大多数区域不同,近38 a来,甘肃省4个不同气候区代表站的蒸发皿蒸发量均呈增加趋势,且从暖干区向冷湿区,蒸发皿蒸发量依次由明显的增加趋势逐渐转变为不变或微弱的增加趋势;位于亚热带湿润区的文县和暖干区的敦煌站潜在蒸发量均呈下降趋势;位于高寒湿润区的玛曲站,潜在蒸发量表现为微弱的上升趋势;中温带干旱区马鬃山站潜在蒸发量表现为明显的上升趋势;各气候区中蒸发的影响因子有所不同,但无论是干旱区还是湿润区,动力因子——风速的显著减小是导致潜在蒸发量显著减少的最重要原因,而热力因子是影响蒸发皿蒸发量的主要因子。  相似文献