裸地蒸发过程的数值模拟   总被引：4，自引：1，他引：3  

杨邦杰  曾德超  唐登银  谢贤群 《地理学报》1988,(4)

本文以能量平衡为基础,研究了裸地蒸发过程,并提出一个用Fonran语言编写的,在IBM-PC微机上通过的裸地蒸发过程的模拟程序。这一程序能根据地表红外温度或辐射资料计算裸地蒸发量,并分析能量分配过程与土壤中的含水量、温度分布。初步的田间试验说明,计算值与实测值是比较一致的。  相似文献   

Evaluation of the ventilated chamber for measuring evaporation from a forest     

F. X. Dunin  E. A. N. Greenwood 《水文研究》1986,1(1):47-62

Evaporation from a regenerating forest was determined concurrently by atmospheric measurements of the Bowen ratio, soil water depletion, and by weighing lysimeter. The methods agreed closely over 18 days in spring and 11 days in summer. Accordingly, the Bowen ratio technique was then used as the control against which any effect on evaporation by enclosure of the lysimeter with a chamber of varied ventilation rate could be quantified hourly and daily. Accuracy of gas analysis was checked against lysimeter values. Daily evaporation by the lysimeter was generally unaffected by enclosure—on a few afternoons there was a statistically significant enhancement of hourly values by the chamber. This was accounted for by difference in turbulence between chamber and forest. The general agreement in daytime hourly values is attributed to the frequent occurrence of equilibrium evaporation (rate at which evaporation is independent of ventilation). At night, evaporation was higher during enclosure. Comparisons were not possible with rain or dew. Determination of evaporation by gas analysis agreed within about 5 per cent of lysimeter values during a dry period. We conclude that the ventilated chamber as used provides realistic estimates of evaporation by forests. We show how periods of bias can be anticipated and corrected by theory.  相似文献   

Forest-Air Fluxes Of Carbon, Water And Energy Over Non-Flat Terrain   总被引：9，自引：0，他引：9  

Xuhui Lee  Xinzhang Hu 《Boundary-Layer Meteorology》2002,103(2):277-301

A field study of surface-air exchange of carbon, water, and energy was conducted at a mid-latitude, mixed forest on non-flat terrain to investigate how to best interpret biological signals from the eddy flux data that may be subject to advective influences. It is shown that during periods of Southwest winds (sector with mild topography), the eddy fluxes are well-behaved in terms of energy balance closure, the existence of a constant flux layer, consistency with chamber observations and the expected abiotic controls on the fluxes. Advective influences are evident during periods with wind from a steep (15%) slope to the Northeast of the tower. These influences appear more severe on CO₂ flux, particularly in stable air, than on the energy fluxes. Large positive flux of CO₂ (> 23 mol m^-2 s^-1) occurs frequently at night. The annual sum of the carbon flux is positive, but the issue about whether the forest is a source of atmospheric carbon remains inconclusive.Attempts are made to assess vertical advectionusing the data collected on a single tower. Over the Southwestsector, vertical advection makes a statistically significant but small contribution to the 30-min energy imbalance and CO₂ flux variations. Contributions by horizontal advection may be larger but cannot be verified directly by the current experimental method.  相似文献   

A method for determining thermophysical properties of organic material in aqueous solutions: Succinic acid     

I. Riipinen  B. Svenningsson  M. Bilde  A. Gaman  K.E.J. Lehtinen  M. Kulmala 《Atmospheric Research》2006,82(3-4):579

A method for determining evaporation rates and thermodynamic properties of aqueous solution droplets is introduced. The method combines evaporation rate measurements using modified TDMA technique with data evaluation using an accurate evaporation model. The first set of data has been collected and evaluated for succinic acid aqueous solution droplets.Evaporation rates of succinic acid solution droplets have been measured using a TDMA system at controlled relative humidity (65%) and temperature (298 K). A temperature-dependent expression for the saturation vapour pressure of pure liquid phase succinic acid at atmospheric temperatures has been derived by analysing the evaporation rate data with a numerical model. The obtained saturation vapour pressure of liquid phase succinic acid is ln(p) = 118.41 − 16204.8/T − 12.452ln(T). The vapour pressure is in unit of Pascal and the temperature in Kelvin. A linear expression for the enthalpy of vaporization for liquid state succinic acid is also presented.According to the results presented in the following, a literature expression for the vapour pressure of liquid phase succinic acid defined for temperatures higher than 461 K [Yaws, C.L., 2003. Yaws' Handbook of Thermodynamic and Physical Properties of Chemical Compounds, Knovel] can be extrapolated to atmospheric temperatures with very good accuracy. The results also suggest that at 298 K the mass accommodation coefficient of succinic acid is unity or very close to unity.  相似文献   

Spectral similarity between scalars at very low frequencies in the unstable atmospheric surface layer over the Tibetan plateau   总被引：1，自引：7，他引：1  

Jun Asanuma  Ichiro Tamagawa  Hirohiko Ishikawa  Yaoming Ma  Taiichi Hayashi  Yongqiang Qi  Jiemin Wang 《Boundary-Layer Meteorology》2007,122(1):85-103

Similarity between temperature and water vapour was investigated in the Fourier domain by using their coherency spectra, defined as the correlation coefficient between their Fourier modes, and the relative efficiency of their vertical transport. The class-averaged values of these indices were computed from the turbulence measurements over sparse grasslands on the Tibetan plateau during the intensive observations of GEWEX (Global Energy and Water Experiment) Asian Monsoon Experiment (GAME). It was found that the energy-containing eddies at scales up to 100z (z being height) are characterised by well-maintained similarity between these scalars. The scalars are highly correlated with each other, and their transport efficiencies are almost equal within this scale range. In contrast, similarity was not always maintained at scales larger than 1000z. Detailed analyses showed that this breakdown of similarity occurs occasionally or sporadically, suggesting that it is caused by events whose average return period is not much smaller than the current averaging time, i.e. 30 min. We speculate that entrainment of drier and warmer air at the top of the atmospheric boundary layer caused the scalar dissimilarity at this scale range.  相似文献   

海河及西北内陆河流域的水热平衡研究     

孙福宝  杨大文  刘志雨  丛振涛  雷志栋 《水文》2007,27(2):7-10

本文通过对海河流域的38个子流域及内陆河流域的7个子流域的逐年降水、径流及实际蒸散发和蒸发能力的分析,证明了基于Budyko假设的流域水热耦合平衡关系在海河及西北内陆河流域是成立的。根据各子流域的长期水量平衡结果,本文验证了水热耦合平衡模型中的唯一参数综合反映流域的下垫面条件且具有显著的区域分布规律,与此同时,本文还在海河流域及内陆河流域对根据流域平均坡度(tanβ),相对土壤最大蓄水能力(Smax/0)和相对土壤入渗能力(Ks/■r)估算模型参数■的经验公式进行了验证,计算结果较好。  相似文献   

Geochemical processes controlling the elevated fluoride concentrations in groundwaters of the Taiyuan Basin,Northern China   总被引：1，自引：0，他引：1  

Qinghai Guo  Yanxin WangTeng Ma  Rui Ma 《Journal of Geochemical Exploration》2007

High fluoride groundwater with F⁻ concentration up to 6.20 mg/L occurs in Taiyuan basin, northern China. The high fluoride groundwater zones are mainly located in the discharge areas, especially in places where shallow groundwater occurs (the groundwater depth is less than 4 m). Regional hydrogeochemical investigation indicates that processes including hydrolysis of silicate minerals, cation exchange, and evaporation should be responsible for the increase in average contents of major ions in groundwater from the recharge areas to the discharge areas. The concentration of F⁻ in groundwater is positively correlated with that of HCO₃⁻ and Na⁺, indicating that groundwater with high HCO₃⁻ and Na⁺ contents help dissolve some fluoride-rich minerals. The water samples with high F⁻ concentration generally have relatively higher pH value, implying that alkaline environment favors the replacement of exchangeable F⁻ in fluoride-rich minerals by OH⁻ in groundwater. In addition, the mixing of karst water along the western mountain front and the evaporation may also be important factors for the occurrence of high fluoride groundwater. The inverse geochemical modeling using PHREEQC supports the results of hydrogeochemical analyses. The modeling results show that in the recharge and flow-through area of the northern Taiyuan basin, interactions between groundwater and fluoride-rich minerals are the major factor for the increase of F⁻ concentration, whereas in the discharge area of the northern basin, the evaporation as well as the mixing of karst water has greater contribution to the fluoride enrichment in groundwater.  相似文献   

Changes of δ<Superscript>18</Superscript>O and δD along the Dousitu River,Inner Mongolia,China, and their evidence of river water evaporation     

Qian Hui  Li Mengyao  Ji Yadong  Yang Bingchao  Zhao Zhenhong 《Aquatic Geochemistry》2007,13(2):127-142

On the basis of the hydrogeology of the Dousitu River drainage basin, the changes of water flow rate, δ¹⁸O and δD along the Dousitu River are discussed according to measured and analytical results. Changes of flow rate along the Dousitu River agree well with groundwater level contours and the recharge and discharge of groundwater to the river. When compared with other types of water in the area, it is obvious that the ¹⁸O and D of river waters have experienced evaporation. The changes of δ¹⁸O and δD along the Dousitu River are mainly caused by combined effects of groundwater recharge and river water evaporation. The recharge of groundwater makes δ¹⁸O and δD of the river water decrease. Evaporation makes δ¹⁸O and δD of the river water increase. The evaporation fractions of the river water are calculated using the kinetic fractionation theory. Results showed as much as 10–30% of water was evaporated in different segments of Dousitu River.  相似文献   

Comparative analysis of groundwater formation in arid and super-arid deserts (with examples from Central Asia and northeastern Arabian Peninsula)     

Vladimir N. Ostrovsky 《Hydrogeology Journal》2007,15(4):759-771

Groundwater formation within arid and super-arid deserts is discussed through comparative analysis. Although fresh groundwater is being formed in both types of deserts, mainly from infiltrated surface runoff, in arid deserts, infiltration is currently taking place, whereas in super-arid areas, it occurred mainly in the Pleistocene pluvial epoch. Groundwater discharge conditions are also different. In arid deserts, the discharge occurs mainly through transpiration by phreatophytes, which form phyto-hydrogeological ecosystems where the dominant factor is an interaction between groundwater and vegetation, with transpiration reaching over hundreds of mm/year and the thickness of the groundwater evaporation zone extending over 10 m. Active subsurface water exchange does not favor the preservation of Pleistocene fossil groundwater. Super-arid deserts, however, have an extremely scarce vegetative cover (low, if any), physical evaporation, a thin zone of evaporation influence, and slow water outflow. Favorable conditions therefore exist for the preservation of relict low-mineralized waters. Furthermore, arid and super-arid deserts differ by types of groundwater accumulation and horizontal and vertical zonalities. In arid deserts, hydrogeological problems are connected with the anthropogenic influence upon groundwater, and with control on rational use of surface water and groundwater. In super-arid deserts, the basic problem is depletion of fossil groundwater.  相似文献   

Experimental study on moisture evaporation of lime wastes and marine clay: implications for landfill storage management     

J. Y. Lee  J. Y. Cheon  D. Hwang 《Environmental Geology》2006,50(7):963-975

A large quantity of by-product lime wastes with high water content produced from chemicals manufacturing processes has been stacked in an open area in Incheon, Korea. Highly alkaline leachate and fine dust emanating from the stacked lime wastes caused an environmental concern in the city. So evaporative drying and stabilization of the fine-grained wastes and use of the on site marine clay as a natural geomembrane liner using drying hardening were considered as a part of a landfill construction plan. Treatment of the lime wastes and marine clay was focused on maximizing the evaporative drying and the density. Evaporation experiments were conducted in field condition to understand evaporation characteristics and to evaluate actual evaporation rate of the lime wastes and marine clay. Local Class A pan evaporation data from a nearby weather station for last 30 years indicated that mean annual and monthly evaporations were 1,178.5 and 98.2 mm, respectively. Relative evaporations of the sludge lime, cake lime, and marine clay compared with the pan evaporation were 114.9, 61.9, and 119.0%, respectively. Estimates of annual evaporations from storage surfaces in the field based on the relative evaporation data were 1,353.6, 729.1, and 1,402.2 mm for the sludge lime, cake lime, and the marine clay, respectively. And annual net evaporations considering rainfall effect were estimated as between 879.9 and 1,082.9 mm for the lime sludge, between 473.9 and 583.3 mm for the lime cake, and between 981.5 and 1,191.9 mm for the marine clay. It was expected that the actual field evaporation rate would be varied with the moisture contents of the lime and the clay. Results of these experiments will provide useful implications for the drying behavior of the by-product lime and the marine clay and landfill or management plan of the storages.  相似文献