共查询到19条相似文献，搜索用时 494 毫秒
1.
2.
3.
E-601型蒸发器与Φ20cm蒸发皿观测资料的相关分析 总被引：1，自引：0，他引：1
摘要：通过对肯斯瓦特水文站E-601型蒸发器与Φ20cm蒸发皿14年蒸发量观测资料的相关分析，得出了两种蒸发器(皿)的折算系数，为有效利用长序列Φ20cm蒸发皿资料提供了重要依据。 相似文献
4.
5.
小河站蒸发折算系数分析 总被引：2，自引：0，他引：2
水面蒸发量的计算,是水文水利计算、水资源调查评价、水量平衡分析计算等工作中必不可少需要的资料,为了进一步提高水量平衡等分析计算的精度,更好地满足工农业生产建设的需要。以崇礼水文站1982—2008年非冰期（5-10月）E-601型[全深]蒸发器（以下简称E-601型[全深]）和结冰期11-4月E-601型[半深]蒸发器（以下简称E-601型[半深]）与D20cm口径蒸发皿（以下简称D20型）的观测值进行比较,计算分析蒸发器水面蒸发的折算系数。 相似文献
6.
7.
利用中国664个气象站1960-2000年20 cm口径蒸发皿资料,借助地理信息系统Arc GIS,分析了中国蒸发皿蒸发量的气候变化趋势.结果表明,就中国平均而言,1960-2000年中国蒸发皿蒸发量呈明显下降趋势,年蒸发皿蒸发量在20世纪80～90年代较60～70年代下降了99.8 mm,下降幅度为5.8%;不同季节对照发现,蒸发皿蒸发量的下降主要表现在春季、夏季和冬季,秋季不明显;对蒸发皿蒸发量气候变化的空间分析表明,年蒸发皿蒸发量的下降主要表现在华东和中南地区;对蒸发皿蒸发量下降的原因分析表明,日照百分率下降从而导致太阳总辐射的下降可能是近年来蒸发皿蒸发量下降的主要原因. 相似文献
8.
9.
利用长江流域107个气象站1951-2000年的20cm口径蒸发皿逐日蒸发资料,采用Mann-Kendall趋势检验法和IDW反距离权重空间插值法分析了近50年来,尤其是20世纪90年代长江流域的年和季节蒸发皿蒸发量的时空变化.50年来,长江流域以年平均、夏季和秋季蒸发皿蒸发量显著下降为主要特点,尤以20世纪90年代最为显著,是年平均和夏季蒸发皿蒸发量最小的时期,比前0年平均值分别低-25.9mm和-36.1mm,这种趋势中下游地区比上游地区明显得多,尤其是在鄱阳湖流域. 相似文献
10.
一、前言随着水文流域模型的发展,对蒸发量资料的要求随之提高,目前有关蒸发量的观测方法已有很多,所采用的观测仪器也不少,如 E-601型蒸发器、口径为80厘米和20厘米的蒸发器(皿)等,均为蒸发量的分析计算积累了宝贵 相似文献
11.
《Applied Geochemistry》2004,19(5):645-664
Sediment and water samples from 12 saline pans on the semi-arid west coast of South Africa were analysed to determine the origin of salts and geochemical evolution of water in the pans. Pans in the area can be subdivided into large, gypsiferous coastal pans with 79–150 g/kg total dissolved salt (TDS), small inland brackish to saline (2–64 g/kg TDS) pans and small inland brine (168-531 g/kg TDS) pans that have a layer of black sulphidic mud below a halite crust. The salinity of coastal pan waters varies with the seasonal influx of dilute runoff and dissolution of relict Pleistocene marine evaporite deposits. In contrast, inland pans are local topographic depressions, bordered on the north by downslope lunette dunes, where solutes are concentrated by evaporation of runoff, throughflow and groundwater seepage. The composition of runoff and seepage inflow waters is determined by modification of coastal rainfall by weathering, calcite precipitation and ion exchange reactions in the predominantly granitic catchment soils. Evaporation of pan waters leads to precipitation of calcite, Mg–calcite, dolomite, gypsum and halite in a distinct stratigraphic succession in pan sediments. Bicarbonate limits carbonate precipitation, Ca limits gypsum precipitation and Na limits halite precipitation. Dolomitisation of calcite is enhanced by the high Mg/Ca ratio of brine pan waters. Brine pan waters evolve seasonally from Na–Cl dominated brines in the wet winter months to Mg–Cl dominated brines in the dry summer months, when 5–20 cm thick halite crusts cover pan surfaces. Pan formation was probably initiated during a drier climate period in the early Holocene. More recent replacement of natural vegetation by cultivated land may have accelerated salt accumulation in the pans. 相似文献
12.
气象要素与蒸发密切相关,通过室内外不同气象条件下的器皿水蒸发实验,获得了水面蒸发氢氧稳定同位素分馏因子与气象要素的关系。实验结果表明,随着蒸发的进行,剩余水体中逐渐富集重同位素;自由水体蒸发同位素分馏在垂线上有分层现象,表层水体同位素值比垂线平均的同位素值略富集;不同温度条件下的室内蒸发实验中,温度越高,液-气间分馏系数越小,相应于同一剩余水体体积比,剩余水体稳定同位素值则越低。室外器皿水自由蒸发实验中得出的蒸发线方程斜率较大地偏离了当地降水线,表明实验期间水体蒸发分馏作用较明显。该研究为进一步揭示水体蒸发分馏规律提供了可靠的实验依据。 相似文献
13.
Free fatty acids make up the bulk (50–84% wt/wt) of lipid materials recovered from artificial gypsum precipitates and crystals collected from sea salt evaporation pans. Both the fatty acids and hydrocarbons associated with artificial gypsum tend to be of longer mean chain length than organic materials dissolved in the mother liquor. Increased specific adsorption of n-fatty acids at Ca2+ sites on gypsum surfaces is positively correlated with alkyl chain length. Neutral lipids were not significantly enriched in either type of gypsum precipitates. The fatty acids associated with gypsum from sea salt evaporation pans are branched fatty acids in contrast to the predominantly normal acids associated with artificial gypsum samples. Differences in the two adsorbed acid distributions are attributed to the unique lipids of hypersaline biota. 相似文献
14.
利用全国353个气象站1956-2005年的气象资料,系统分析了过去50年间蒸发皿蒸发量、气温及降水的变化趋势,重点对"蒸发悖论"在中国的规律进行分析,并研究了蒸发皿蒸发量与降水的长期变化趋势的关系。研究结果表明:(1)过去50年间,全国范围内气温增加显著、蒸发皿蒸发量呈下降趋势,总体上存在"蒸发悖论";(2)"蒸发悖论"具有空间上和时间上的不一致,表现在:随着气温增加,东北地区蒸发皿蒸发量呈上升趋势,20世纪80年代中期以后全国范围蒸发皿蒸发量呈上升趋势;(3)过去50年间,降水量变化趋势不明显,降水量与蒸发皿蒸发量变化趋势在空间分布上大体呈逆向关系。 相似文献
15.
在气候变化背景下,许多地区蒸发皿蒸发量出现持续减少现象。淮河流域是中国南北方气候分界线,研究蒸发问题对认识淮河流域水分循环和水资源状况有重要作用。利用淮河流域实测蒸发皿蒸发量、气温、降水等7种气象要素、英国CRU月平均云量资料和NCEP/NCAR的再分析资料,分析了淮河流域近50年来蒸发皿蒸发量的变化及其原因。结果表明,淮河流域蒸发皿蒸发量存在显著的下降趋势。在一年的四季中,春夏季节蒸发量最大,下降趋势最强;淮河流域北部和西部蒸发量最大,下降趋势最强。究其原因,蒸发皿蒸发量下降与下垫面风速和日照时数减少、相对湿度和降水量增多有关;大气对流层相对湿度和比湿的增加致使地面相对湿度增大,天空云量和降水量增多,从而减弱了太阳辐射的强度,缩短了日照时间,结果使蒸发皿蒸发量下降。 相似文献
16.
Albert Günter Herrmann Doris Knake Jürgen Schneider Heide Peters 《Contributions to Mineralogy and Petrology》1973,40(1):1-24
Seawater at different stages of evaporation from the salt works of Seovlje near Portoro (Yugoslavia) was analyzed geochemically. The seawater there passes through 20 stages of concentration until the first halite crystallizes. All important parameters were determined at all stages: concentrations of Cl, SO4, Na, K, Ca, Mg, and Br, temperature, pH, Eh, oxygen content and titration alkalinity. With increasing evaporation calcium carbonate crystallizes first followed by calcium sulphate as gypsum and after these halite. All three components crystallize from supersaturated solutions. The pH of the initial seawater is 8.32; it falls abruptly to 6.65 when the first calcium carbonate precipitates. Eh in the original seawater is +393 mv; negative values were found in the halite crystallization pans, which contain an anaerobic mud as a reducing agent. The oxygen content of the solution decreases parallel to the drop in Eh. In the pans in which NaCl crystallizes Eh is zero. Apparently the mud also adsorbs K, as can be inferred from a change in the Mg/K ratio.The bromine partition between crystallizing halite and the brine in the salt pans of Seovlje is discussed with regard to some genetic problems of marine salt deposits. In the conditions in the salt pans the bromine partition coefficient at the beginning of NaCl crystallization from seawater—expressed as b=wt.-% Br (mineral)/wt.-% Br (solution)—is 0.12 to 0.14 or—expressed as D=Br/Cl(mineral)/Br/Cl(solution)—0.030 to 0.034 at temperatures between 33° C and 42° C. The conclusion is that a Br content of about 60 to 75 ppm is to be expected for the first halite that crystallizes from evaporating seawater. 相似文献
17.
为比较一次性灌溉和间歇灌溉在盐分淋洗效率方面的优劣,采用HYDRUS-1D两区模型模拟分析了不同频次灌溉条件下的土壤水盐运移过程。结果表明存在一个间歇灌溉具有更高淋洗效率的最大深度,并将其称为临界深度。对砂土的模拟显示在灌水总量为20 cm时,随着潜在蒸发强度从0 mm/d升高至6 mm/d,临界深度从60 cm以上降为0 cm;而在潜在蒸发强度为2 mm/d时,随着灌水总量从10 cm增加至40 cm,临界深度相应从20 cm增加至接近80 cm。比较而言,透水性好、不动水体占比高、两部分孔隙之间水分和溶质交换能力差的土壤,临界深度更大;对黏土、黏壤土、壤土、砂壤土和砂土分别进行模拟显示偏砂性土壤具有更大的临界深度,在灌水总量和潜在蒸发强度分别为30 cm和2 mm/d时,黏土和砂土的临界深度分别为56 cm和大于100 cm。总的来看,对于间歇灌溉是否能提高盐分淋洗效率不能一概而论,引入临界深度可以在一定程度上解释研究者们对于间歇灌溉是否能提高盐分淋洗效率的不同认识。 相似文献
18.
René M. Price William K. Nuttle Bernard J. Cosby Peter K. Swart 《Estuaries and Coasts》2007,30(3):497-506
Variation and uncertainty in estimated evaporation was determined over time and between two locations in Florida Bay, a subtropical
estuary. Meteorological data were collected from September 2001 to August 2002 at Rabbit Key and Butternut Key within the
Bay. Evaporation was estimated using both vapor flux and energy budget methods. The results were placed into a long-term context
using 33 years of temperature and rainfall data collected in south Florida. Evaporation also was estimated from this long-term
data using an empirical formula relating evaporation to clear sky solar radiation and air temperature. Evaporation estimates
for the 12-mo period ranged from 144 to 175 cm yr−1, depending on location and method, with an average of 163 cm yr−1 (±9%). Monthly values ranged from 9.2 to 18.5 cm, with the highest value observed in May, corresponding with the maximum
in measured net radiation. Uncertainty estimates derived from measurement errors in the data were as much as 10%, and were
large enough to obscure differences in evaporation between the two sites. Differences among all estimates for any month indicate
the overall uncertainty in monthly evaporation, and ranged from 9% to 26%. Over a 33-yr period (1970–2002), estimated annual
evaporation from Florida Bay ranged from 148 to 181 cm yr−1, with an average of 166 cm yr−1. Rainfall was consistently lower in Florida Bay than evaporation, with a long-term average of 106 cm yr−1. Rainfall considered alone was uncorrelated with evaporation at both monthly and annual time scales; when the seasonal variation
in clear sky radiation was also taken into account both net radiation and evaporation were significantly suppressed in months
with high rainfall. 相似文献
19.
Climatic causes of ecological and environmental variations in the source regions of the Yangtze and Yellow Rivers of China 总被引：1，自引：0，他引：1
In the source regions of the Yangtze and Yellow Rivers of China, glaciers, frozen ground, the hydrological system, and alpine
vegetation have changed over the past decades years. Climatic causes of these variations have been analyzed using mean monthly
air temperature and monthly precipitation between 1956 and 2000, and monthly evaporation from φ20 evaporation pans between
1961 and 1996. In the source region of the Yangtze River, lower temperature and plentiful precipitation during the 1960s and
continuing into the early 1980s triggered a glacier advance that culminated in the early 1990s, while a robust temperature
increase and precipitation decrease since 1986 has forced glaciers to retreat rapidly since 1995. Permafrost degradation is
another consequence of the climatic warming. The variations in the hydrological system and alpine vegetation are controlled
mainly by the climate during the warm season. Warmer and drier summer climate is the major cause of a degradation of the vegetation,
desiccation of the high-cold marshland, a decrease in the areas and numbers of lakes and rivers in the middle and north source
regions of the Yangtze and Yellow Rivers, and a reduction in surface runoff in the source region of the Yangtze River for
the last 20 years. The causes of eco-environmental change in Dari area, near the outlet from the source area of the Yellow
River, are different from those elsewhere in the study area. A noticeable reduction in runoff in the source region of the
Yellow River and degradation of alpine vegetation in Dari area are closely related to the permafrost degradation resulting
from climate warming. 相似文献