直流电阻率测深曲线解释中的直接反演法     

阮百尧  徐世浙 《物探化探计算技术》1996,18(2):118-124

本文根据在电导率随深度变化梯度不大的情况下，ＤａｒＺａｒｒｏｕｋ曲线与视电阻率曲线基本重合这一性质，通过各种变换，在电阻率测深中导出了一种可与大地电磁测深中Ｂｏ－ｓｔｉｃｋ反演方法相比美的直接反演方法，将视电阻率随极距变化曲线转换为电阻率随深度变化曲线。  相似文献   

Root controls on water redistribution and carbon uptake in the soil–plant system under current and future climate     

《Advances in water resources》2013

Understanding photosynthesis and plant water management as a coupled process remains an open scientific problem. Current eco-hydrologic models characteristically describe plant photosynthetic and hydraulic processes through ad hoc empirical parameterizations with no explicit accounting for the main pathways over which carbon and water uptake interact. Here, a soil–plant-atmosphere continuum model is proposed that mechanistically couples photosynthesis and transpiration rates, including the main leaf physiological controls exerted by stomata. The proposed approach links the soil-to-leaf hydraulic transport to stomatal regulation, and closes the coupled photosynthesis–transpiration problem by maximizing leaf carbon gain subject to a water loss constraint. The approach is evaluated against field data from a grass site and is shown to reproduce the main features of soil moisture dynamics and hydraulic redistribution. In particular, it is shown that the differential soil drying produced by diurnal root water uptake drives a significant upward redistribution of moisture both through a conventional Darcian flow and through the root system, consistent with observations. In a numerical soil drying experiment, it is demonstrated that more than 50% of diurnal transpiration is supplied by nocturnal upward water redistribution, and some 12% is provided directly through root hydraulic redistribution. For a prescribed leaf area density, the model is then used to diagnose how elevated atmospheric CO₂ concentration and increased air temperature jointly impact soil moisture, transpiration, photosynthesis, and whole-plant water use efficiency, along with compensatory mechanisms such as hydraulic lift using several canonical forms of root-density distribution.  相似文献   

Responses of canopy transpiration and canopy conductance of peach (Prunus persica) trees to alternate partial root zone drip irrigation     

Daozhi Gong  Shaozhong Kang  Jianhua Zhang 《水文研究》2005,19(13):2575-2590

We investigated canopy transpiration and canopy conductance of peach trees under three irrigation patterns: fixed 1/2 partial root zone drip irrigation (FPRDI), alternate 1/2 partial root zone drip irrigation (APRDI) and full root zone drip irrigation (FDI). Canopy transpiration was measured using heat pulse sensors, and canopy conductance was calculated using the Jarvis model and the inversion of the Penman–Monteith equation. Results showed that the transpiration rate and canopy conductance in FPRDI and APRDI were smaller than those in FDI. More significantly, the total irrigation amount was greatly reduced, by 34·7% and 39·6%, respectively for APRDI and FPRDI in the PRDI (partial root zone drip irrigation) treatment period. The daily transpiration was linearly related to the reference evapotranspiration in the three treatments, but daily transpiration of FDI is more than that of APRDI and FPRDI under the same evaporation demand, suggesting a restriction of transpiration water loss in the APRDI and FPRDI trees. FDI needed a higher soil water content to carry the same amount of transpiration as the APRDI and FPRDI trees, suggesting the hydraulic conductance of roots of APRDI and FPRDI trees was enhanced, and the roots had a greater water uptake than in FDI when the average soil water content in the root zone was the same. By a comparison between the transpiration rates predicted by the Penman–Monteith equation and the measured canopy transpiration rates for 60 days during the experimental period, an excellent correlation along the 1:1 line was found for all the treatments (R² > 0·80), proving the reliability of the methodology. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

非饱和黏性土的电阻率特性及其试验研究   总被引：9，自引：0，他引：9  

查甫生  刘松玉  杜延军  崔可锐 《岩土力学》2007,28(8):1671-1676

在讨论黏性土导电特性的基础上,假定非饱和黏性土中存在3种电流流通路径,针对已有的非饱和土电阻率结构模型存在的缺陷,推导了适用于非饱和黏性土的电阻率结构模型,探讨了土电阻率的主要影响因素,并将其归纳为3类。最后,通过对合肥膨胀土相关试验研究,分析了含水率、孔隙水电阻率、温度以及孔隙率对膨胀土的电阻率的影响特征,探讨了非饱和膨胀土的电阻率基本特性。  相似文献   

基于小波分析的TEM快速成像   总被引：2，自引：2，他引：0  

马宇  张陪强 《地质与勘探》2005,41(2):72-76

在信号分析、处理领域,出现了号称为"数学显微镜"的小波分析,给我们带来了新的信号分析工具.小波分析是针对非平稳信号的处理方法,特别适用于动态、瞬态的信号处理.而利用视纵向电导参数进行测深资料解释具有一定的优越性,在以上基础上提出了基于小波分析的TEM快速成像,并在Windows操作平台下开发了绘制微分电导图的软件,软件的功能丰富、界面友好、操作简单,图形能以直观、形象的面貌清晰的展示电性界面的分布形态.  相似文献   

陆地植被二氧化碳通量尺度扩展研究进展   总被引：2，自引：0，他引：2  

王培娟  孙睿  朱启疆 《遥感学报》2005,9(6):751-759

定量的估计陆地植被的光合作用,是估算作物产量和净初级生产力的基础。简要介绍了当前国内外CO2通量观测研究的方法以及与尺度问题有关的一些地学问题,重点阐述了陆地植被气孔导度模型和光合作用模型的尺度扩展以及尺度转化方法,总结了从植被叶片尺度到冠层尺度的4种尺度扩展模型(大叶模型、多层模型、两片大叶模型以及多层—两片大叶模型)以及从冠层尺度到群落尺度的尺度扩展方法,并对上述模型和方法的适用范围、应用优势以及存在的问题等进行了分析和讨论,指出对不同的研究对象,选择合适尺度的模型和参数是研究成败的关键。  相似文献   

基于自适应收缩可行域的遗传算法反演TEM导电薄层   总被引：6，自引：2，他引：6  

Li Xiu Xue Guoqiang Song Jianping Guo Wenbo Wu Junjie Shen Meifang 《应用地球物理》2005,2(4):204-210

将自适应收缩可行域的遗传算法与视纵向电 导微分成像法相结合,反演瞬变电磁测深中的导电 薄层,计算结果证明:该算法通过对可行域的自适 应收缩,加快了计算速度、提高了计算精度;并在 一定程度上克服了瞬变电磁测深的等值性,缩小了 等值范围。通过对导电薄层模型的模拟计算和实例 分析,并与常规反演曲线进行对比,使用本法反演 成像的结果,明显地显示出导电薄层的存在。  相似文献   

黑河流域几个主要植物种光合特征的比较研究   总被引：11，自引：6，他引：11  

龚吉蕊  赵爱  苏培玺  黄承 《中国沙漠》2005,25(4):587-592

对自然生长在沙丘上的旱生植物沙拐枣、梭梭和防护林带的中生植物沙枣和杨树在大气干燥,土壤干旱下的光合响应机制进行了比较研究。结果表明,4种植物气孔导度的变化主要受空气相对湿度和饱和水蒸汽压差的影响,气孔的关闭是对空气湿度的急剧降低、饱和水蒸汽压差的急剧升高的前馈反应,只是响应程度不同。沙拐枣、沙枣和梭梭具有高光合,杨树为低光合。沙拐枣、梭梭、沙枣的光合速率日变化曲线呈双峰型,有午睡现象出现;杨树的呈单峰型。沙拐枣的午睡主要由非气孔因素引起,光化学效率的降低可能是非气孔因素之一;梭梭的光合午睡也是由非气孔因素引起。而气孔关闭是沙枣光合午睡的一个原因。沙枣的光合速率的日变化曲线与气孔导度的变化呈平行下降趋势,其他3种植物没有表现此现象。4种植物在强光时都发生了不同程度的光抑制,只是出现的时间不同;沙拐枣和沙枣出现低谷后恢复很快,梭梭和杨树起伏比较大,杨树恢复相对较慢,但到晚上都得到恢复。4种植物对沙区高光强表现出不同程度的可调控的保护性机制。  相似文献   

Simulation of crop growth and energy and carbon dioxide fluxes at different time steps from hourly to daily   总被引：2，自引：0，他引：2  

Jing Wang  Qiang Yu  Xuhui Lee 《水文研究》2007,21(18):2474-2492

Understanding the exchange processes of energy and carbon dioxide (CO₂) in the soil–vegetation–atmosphere system is important for assessing the role of the terrestrial ecosystem in the global water and carbon cycle and in climate change. We present a soil–vegetation–atmosphere integrated model (ChinaAgrosys) for simulating energy, water and CO₂ fluxes, crop growth and development, with ample supply of nutrients and in the absence of pests, diseases and weed damage. Furthermore, we test the hypotheses of whether there is any significant difference between simulations over different time steps. CO₂, water and heat fluxes were estimated by the improving parameterization method of the coupled photosynthesis–stomatal conductance–transpiration model. Soil water evaporation and plant transpiration were calculated using a multilayer water and heat‐transfer model. Field experiments were conducted in the Yucheng Integrated Agricultural Experimental Station on the North China Plain. Daily weather and crop growth variables were observed during 1998–2001, and hourly weather variables and water and heat fluxes were measured using the eddy covariance method during 2002–2003. The results showed that the model could effectively simulate diurnal and seasonal changes of net radiation, sensible and latent heat flux, soil heat flux and CO₂ fluxes. The processes of evapotranspiration, soil temperature and leaf area index agree well with the measured values. Midday depression of canopy photosynthesis could be simulated by assessing the diurnal change in canopy water potential. Moreover, the comparisons of simulated daily evapotranspiration and net ecosystem exchange (NEE) under different time steps indicated that time steps used by a model affect the simulated results. There is no significant difference between simulated evapotranspiration using the model under different time steps. However, simulated NEE produces large differences in the response to different time steps. Therefore, the accurate calculation of average absorbed photosynthetic active radiation is important for the scaling of the model from hourly steps to daily steps in simulating energy and CO₂ flux exchanges between winter wheat and the atmosphere. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

瞬变电磁测深的微分电导成像   总被引：4，自引：0，他引：4  

李貅  全红娟  许阿祥  马宇 《煤田地质与勘探》2003,31(3):59-61

通过对等效导电平面方法原理的阐述,指出了利用视纵向电导参数进行瞬变电磁测深资料解释的优越性。同时,为了提高对电性层位的分辨能力,在明确电导及其导数曲线物理含义的基础上,采用B样条函数对实测数据进行处理,实现了电导参数的微分成像。实践证明,采用该方法的成像结果与其他反演结果吻合较好,其“电性同相轴”以直观、形象的面貌清晰地展示了电性界面的分布形态。   相似文献