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1.
In the last two decades, a number of single-source surface energy balance (SEB) models have been proposed for mapping evapotranspiration (ET); however, there is no clear guidance on which models are preferable under different conditions. In this paper, we tested five models-Surface Energy Balance Algorithm for Land (SEBAL), Mapping ET at high Resolution with Internalized Calibration (METRIC), Simplified Surface Energy Balance Index (S-SEBI), Surface Energy Balance System (SEBS), and operational Simplified Surface Energy Balance (SSEBop)—to identify the single-source SEB models most appropriate for use in the humid southeastern United States. ET predictions from these models were compared with measured ET at four sites (marsh, grass, and citrus surfaces) for 149 cloud-free Landsat image acquisition days between 2000 and 2010. The overall model evaluation statistics showed that SEBS generally outperformed the other models in terms of estimating daily ET from different land covers (e.g., the root mean squared error (RMSE) was 0.74 mm day−1). SSEBop was consistently the worst performing model and overestimated ET at all sites (RMSE = 1.67 mm day−1), while the other models typically fell in between SSEBop and SEBS. However, for short grass conditions, SEBAL, METRIC, and S-SEBI appear to work much better than SEBS. Overall, our study suggests that SEBS may be the best SEB model in humid regions, although it may require modifications to work better over short vegetation. 相似文献
2.
基于MODIS产品影像及陆面能量平衡系统(SEBS)的河北平原区域蒸散估算 总被引：5，自引：0，他引：5
地表蒸散是区域水文循环的重要组成部分之一,传统的地表蒸散估算一般基于点上的气象观测数据,当用于区域地表蒸散评价时,具有一定的局限性.随着遥感技术的发展,利用遥感影像能够对大区域进行观测的优势进行区域地表蒸散估算已成为可能.地表能量平衡系统(SEBS)是根据地表能量平衡估算地表蒸散量的一种方法,该方法由于提出了地表能量传输过程中关键制约因素热传导粗糙度的估算模型而在遥感蒸散计算方面具有较高的精度.本文在SEBS模型的基础上,以河北平原为例,采取中分辨率成像光谱辐射仪(MODIS)产品影像,根据研究区下垫面的实际情况进行了参数估算,进行了区域实际蒸发蒸腾量计算及模型精确度评价,并在SEBS模型的基础上,提出了新的"标准化温度差-反照率"特征空间分析方法,对研究区内地表土壤水分现状进行了评价;最后,对河北平原地表蒸散时空分布进行了分析.计算结果表明,在所选取的晴空乌云条件下,根据SEBS模型计算所得的地表蒸散与研究区内利用大型承重式蒸渗仪所测量的地表实际蒸散量具有很好的一致性,说明SEBS模型在遥感蒸散计算方面据有较高的可信度.然而,由于地表蒸散的遥感估算是以所获取的遥感影像单元为基础,计算误差不可避免,尤其是使用低分辨率遥感影像的时候,每个影像单元所反映的地表蒸散为单元内各种地表覆盖的综合反映,当与只反映一种地表覆盖蒸散的大型承重式蒸渗仪测量结果进行比较时,误差是显而易见的,因此,若着重考虑模型精度验证,尚需在以后的研究中考虑使用高分辨率的遥感影像.地表土壤水分或湿度状况是地表能量交换及蒸散发生的主要控制因素.利用地表温度与植被指数的关系对区域地表湿度状况进行监测在实践中被广泛利用,然而,由于不用地区地表属性的千差万别,当利用这种方法进行区域地表湿度评价时,"地表温度-植被指数"特征空间的边界很难确定.本文在SEBS模型的基础上,提出新的"标准化温度差-反照率"特征空间分析方法,对研究区内地表土壤水分现状进行评价,结果显示,由于在SEBS模型中考虑了干限和湿限两种极端情况下的能量平衡,"标准化温度差.反照率"特征空间的边界问题很容易被确定,利用修正的特征空间,可以对区域土壤水分或湿度状况进行客观的评价.下垫面的几何特征参数的精确反演是进行地表能量平衡模拟的基础,目前多根据有关经验公式利用遥感影像进行下垫面几何特征参数估算,由于已有的经验公式多基于不同研究区域获得,当应用到新的研究区时,其具体参数需要进一步调整,以获得对下垫面的几何特征的精确描述.由于缺乏相关实测资料,本研究中利用经验公式进行下垫面几何特征参数,误差不可避免,需要在以后的研究中进行深入探索.另外,地表蒸散的计算只是进行区域水资源评价、农业节水措施评价以及全球变化等研究的一个中间环节,需要在以后的研究中根据具体研究目的进行进一步研究. 相似文献
3.
The Caatinga biome, located in the northeastern region of Brazil, is the most populated dryland region on the planet and extremely vulnerable to land degradation due to climatological and anthropogenic factors. Energy partitioning substantially influences the local climate and affects the water cycle, which is of utmost importance for the economy and livelihood of the region. Recently, eddy covariance (EC) towers were installed in the area; thus, the scientific community can thoroughly assess the water and energy fluxes over this unique biome. While EC towers have a high degree of accuracy, they only measure energy fluxes over a small land footprint. Given the biome spatial heterogeneity, the use of EC-based techniques has the limitation of not comprehensively representing water and energy fluxes profiles over the entire region. Incorporating remote sensing (RS) data into the landscape analysis is a feasible solution to overcome this issue, given that satellite data can capture the phenomena represented by the EC measurements across large spatial scales. Our research studied the capability of the Surface Energy Balance Algorithm for Land (SEBAL) and MOD16-ET products to represent the EC measurements regarding energy and mass exchange, with an ultimate objective of applying the best approach to assess these fluxes regionally. We applied the SEBAL model using only remote sensing data from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor. The MOD16-ET model uses a different approach but is also based on MODIS data. Our analysis was based on three years (2014–2016) of data, which was limited to the availability of the EC tower data. We found that for the EC-based measurements, energy balance closure (EBC) achieved an average of 0.84, which is considerably high for the region. This is possibly due to the EC tower being installed on a preserved Caatinga plot, with reduced heterogeneity and higher plant density. When analyzing RS-based products to represent ET profiles in the region, we found that the SEBAL model accurately represented water fluxes during the wet season but not the dry season, whereas the MOD16-ET showed a better agreement with EC-based water fluxes throughout all the seasons. SEBAL inaccuracy in drylands is partially due to the narrow range between the cold and hot pixels in an image, as the algorithm relies on this range for input parameters, especially in the dry season. Therefore, we concluded that MOD16-ET is capable of better-representing water fluxes in the Caatinga region. We analyzed the fluxes regionally and quantified annual ET for the three years. These results are especially relevant for local policymakers on dealing with water and landscape issues in a region where the livelihood and well-being of the population is inextricably bound to water availability. 相似文献
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5.
本文以新疆焉耆盆地为研究区,首先利用实测数据和Landsat 8 OLI遥感数据获取土壤调查植被指数（MSAVI）和地表温度（Ts）,构建Ts-MSAVI特征空间,拟合特征空间的干湿方程;然后利用该特征空间计算温度植被干旱指数（TVDIm）,反演9-11月的土壤湿度,探讨土壤湿度时空分布特征。试验结果表明：①遥感影像反演的TVDI与实地考察的土壤湿度显著相关（a=0.05）;不同土层中,TVDIm与10~20 cm土层湿度相关性最高（R=0.588）;②焉耆盆地湿度总体以半干旱为主（0.60.8）;土壤湿度空间分布上,焉耆盆地南侧为干旱区,西部和北部地区偏干旱,中部为湿润区域,对于该地区滨湖湿地和博斯腾湖附近小湖土壤湿度最高,博斯腾湖南部的沙地区土壤湿度最低,Ts与土壤湿度呈负相关;③10月湿地的TVDIm值最低,9月沙地的TVDIm值最高。TVDI模型应用于焉耆盆地取得较好的结果,可用于正确地估算土壤湿度,研究结果可为焉耆盆地生态环境和水资源提供重要的参数。 相似文献
6.
Sanjay Kumar Jain Sharad K. Jain V. Hariprasad Anju Choudhry 《Journal of the Indian Society of Remote Sensing》2011,39(2):259-270
Water balance of a basin involves estimation of input precipitation, runoff, infiltration and evapotranspiration (ET). Although
ET may have large variations over a big basin, it is commonly estimated using a few point measurements and this makes the
estimation error prone. Satellite based remote sensing data provides few parameters for estimation of energy fluxes, at the
land surface and atmosphere interaction in a distributed manner using the meteorological parameters. These parameters through
surface energy balance equation have been used for the estimation of ET in this study. Various spatially distributed variables
required for ET estimation; viz. NDVI, surface albedo, surface temperature etc. have been derived using remote sensing and
ancillary data for Tapi basin located in western India. Beside this field data such as rainfall, air temperature, relative
humidity, sunshine hours etc. have been used. For computation of runoff, Soil Conservation Services (SCS) approach has been
considered. Tapi basin up to Ukai dam has been selected as the study area. Satellite data from National Oceanic and Atmospheric
Administration (NOAA), Polar Orbiting Environmental Satellite, which carries the Advanced Very High Resolution Radiometer
(AVHRR), have been used for preparation of various maps required for runoff and ET analysis. The results of runoff and ET
have been compared with observed data for 2 years, 2002–2003 and the results have been found in good agreement with observed
data. 相似文献
7.
遥感监测土壤湿度综述及其在新疆的应用展望 总被引：3，自引：1，他引：2
土壤湿度在全球水循环运动中扮演着非常重要的角色,是水文、气象和农业研究中的重要参数,国内外都极为重视对土壤湿度的研究。国外利用可见光、红外、热红外、微波遥感监测土壤水分已有三、四十年的历史,随着研究的深入和技术的发展,现已形成地面、航空、航天、多星的立体干旱遥感监测格局。国内遥感监测土壤湿度的方法主要有微波遥感、热红外遥感、距平植被指数法、植被供水指数、作物缺水指数等方法。本文通过对国内外已有的土壤湿度遥感监测方法的介绍和总结,对比分析了各种方法的原理、适用领域及其研究进展,并针对新疆的具体情况,认为借助Mod is影像进行新疆地区土壤湿度的监测是较为可行的一种方法。 相似文献
8.
农田水分生产率估算方法及应用 总被引：5，自引：1，他引：4
水分生产率是评价农业灌溉用水管理水平和节水效果的一个重要指标.本文利用遥感数据定量估算了流域平原区的蒸散量和干物质量,采用经验的收获指数计算了海河流域2003-2008多年平均水分生产率.通过在水资源三级分区的统计结果分析表明：遥感估算的水分生产率可以反映单方水产出的空间差异,海河流域平原平均水分生产率为0.99kg/m3,变化范围为0.02-2.13kg/m3,总体水平较低,南北差异较大。通过ET,产量和水分生产率关系的分析表明水分生产率与产量线性相关(R＝0.97),提高产量将一直是流域提高水分生产率的重要研究方向。水分生产率与产量随ET变化均为先线性增加后减小的特点,在两季作物区当年耗水量在335-575mm范围变化时,水分是影响产量和水分产出效益的关键因子,要着重提高中低产区域的水分生产率; 当耗水量超过575mm,水分不是唯一的限制因子,以提高作物的收获指数为重点。 相似文献
9.
Evapotranspiration is a key parameter for water stress assessment as it is directly related to the moisture status of the soil-vegetation system and describes the moisture transfer from the surface to the atmosphere. With the launch of the Meteosat Second Generation geostationary satellites and the setup of the Satellite Application Facilities, it became possible to operationally produce evapotranspiration data with high spatial and temporal evolution over the entire continents of Europe and Africa. In the frame of this study we present an evaluation of the potential of the evapotranspiration (ET) product from the EUMETSAT Satellite Application Facility on Land Surface Analysis (LSA-SAF) for drought assessment and monitoring in Europe.To assess the potential of this product, the LSA-SAF ET was used as input for the ratio of ET to reference evapotranspiration (ET0), the latter estimated from the ECMWF interim reanalysis. In the analysis two case studies were considered corresponding to the drought episodes of spring/summer 2007 and 2011. For these case studies, the ratio ET/ET0 was compared with meteorological drought indices (SPI, SPEI and Sc-PDSI for 2007 and SPI for 2011) as well as with the anomalies of the fraction of absorbed photosynthetic active radiation (fAPAR) derived from remote sensing data. The meteorological and remote sensing indicators were taken from the European Drought Observatory (EDO) and the CARPATCLIM climatological atlas.Results show the potential of ET/ET0 to characterize soil moisture variability, and to give additional information to fAPAR and to precipitation distribution for drought assessment. The main limitations of the proposed ratio for drought characterization are discussed, including options to overcome them. These options include the use of filters to discriminate areas with a low percentage vegetation cover or areas that are not in their growing period and the use of evapotranspiration without water restriction (ETwwr), obtained as output of the LSA-SAF model instead of ET0. The ET/ETwwr ratio was tested by comparing its accumulated values per growing period with the winter wheat yield values per country published by Eurostat. The results point to the potential of using the remote sensing based LSA-SAF evapotranspiration and the ET/ETwwr ratio for vegetation monitoring at large scale, especially in areas where data is generally lacking. 相似文献
10.
Evapotranspiration (ET) is a vital process in land surface atmosphere research. In this study, Surface Energy Balance Algorithm for Land (SEBAL) for the assessment of ET (for 23 December 2010, 8 January 2011, 24 January 2011, 9 February 2011, 25 February 2011, 29 March 2011 and 14 April 2011) from LANDSAT7-ETM+ and validation with Lysimeter data set is illustrated. It is based on the evaporative fraction concept, and it has been applied to LANDSAT7-ETM + (30 m resolution) data acquired over the Indian Agricultural Research Institute’s agricultural farm land. The ET from SEBAL was compared with Lysimeter ET using four statistical tests (root-mean-square error (RMSE), relative root-mean-square error (R-RMSE), mean absolute error (MAE), and normalized root-mean square error (NRMSE)), and each test showed a good correlation between the predicted and observed ET values. Results from this study revealed that the RMSE of crop-growing period was 0.51 mm d?1 for ETSEBAL, i.e. ETSEBAL having good accuracy with respect to observed ETLysimeter. Results were also validated using R-RMSE test, which also proved that ETSEBAL data are having good accuracy with respect to observed ETLysimeter as R-RMSE of crop-growing period is 0.19 mm d?1. MAE (0.19), NRMSE (0.21) and r2 (0.91) tests indicated that model prediction is significant, and model can be effectively used for the estimation of ET from SEBAL as input of remote sensing data sets. Finally, the SEBAL has been useful for remote agricultural land where ground-based data (Lysimeter data) are not available for daily ET (ET24 h) estimation. The temporal study of the ET24 h values analysed has revealed that the highest ET24 h values are owing to the higher development (high greenness) of crops, whereas the lower values are related to the lower development (low greenness) or null crop. 相似文献
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12.
Integrating terrain and vegetation indices for identifying potential soil erosion risk area 总被引：1，自引：0，他引：1
Arabinda Sharma 《地球空间信息科学学报》2010,13(3):201-209
The present paper offers an innovative method to monitor the change in soil erosion potential by integrating terrain and vegetation
indices derived from remote sensing data. Three terrain indices namely, topographic wetness index (TWI), stream power index
(SPI) and slope length factor (LS), were derived from the digital elevation model. Normalized vegetation index (NDVI) was
derived for the year 1988 and 2004 using remote sensing images. K-mean clustering was performed on staked indices to categorize the study area into four soil erosion potential classes. The
validation of derived erosion potential map using USLE model showed a good agreement. Results indicated that there was a significant
change in the erosion potential of the watershed and a gradual shifting of lower erosion potential class to next higher erosion
potential class over the study period. 相似文献
13.
Jonas Ardö Meelis Mölder Bashir Awad El-Tahir Hatim Abdalla Mohammed Elkhidir 《Carbon balance and management》2008,3(1):1-18
Background
Large spatial, seasonal and annual variability of major drivers of the carbon cycle (precipitation, temperature, fire regime and nutrient availability) are common in the Sahel region. This causes large variability in net ecosystem exchange and in vegetation productivity, the subsistence basis for a major part of the rural population in Sahel. This study compares the 2005 dry and wet season fluxes of CO2 for a grass land/sparse savanna site in semi arid Sudan and relates these fluxes to water availability and incoming photosynthetic photon flux density (PPFD). Data from this site could complement the current sparse observation network in Africa, a continent where climatic change could significantly impact the future and which constitute a weak link in our understanding of the global carbon cycle.Results
The dry season (represented by Julian day 35–46, February 2005) was characterized by low soil moisture availability, low evapotranspiration and a high vapor pressure deficit. The mean daily NEE (net ecosystem exchange, Eq. 1) was -14.7 mmol d-1 for the 12 day period (negative numbers denote sinks, i.e. flux from the atmosphere to the biosphere). The water use efficiency (WUE) was 1.6 mmol CO2 mol H2O-1 and the light use efficiency (LUE) was 0.95 mmol CO2 mol PPFD-1. Photosynthesis is a weak, but linear function of PPFD. The wet season (represented by Julian day 266–273, September 2005) was, compared to the dry season, characterized by slightly higher soil moisture availability, higher evapotranspiration and a slightly lower vapor pressure deficit. The mean daily NEE was -152 mmol d-1 for the 8 day period. The WUE was lower, 0.97 mmol CO2 mol H2O-1 and the LUE was higher, 7.2 μmol CO2 mmol PPFD-1 during the wet season compared to the dry season. During the wet season photosynthesis increases with PPFD to about 1600 μmol m-2s-1 and then levels off.Conclusion
Based on data collected during two short periods, the studied ecosystem was a sink of carbon both during the dry and wet season 2005. The small sink during the dry season is surprising and similar dry season sinks have not to our knowledge been reported from other similar savanna ecosystems and could have potential management implications for agroforestry. A strong response of NEE versus small changes in plant available soil water content was found. Collection and analysis of flux data for several consecutive years including variations in precipitation, available soil moisture and labile soil carbon are needed for understanding the year to year variation of the carbon budget of this grass land/sparse savanna site in semi arid Sudan. 相似文献14.
15.
Umit Haluk Atasever Coskun Ozkan 《Journal of the Indian Society of Remote Sensing》2018,46(8):1213-1222
Actual evapotranspiration is one of the most important component for efficient water management and planning. Until recently, evapotranspiration computations and measurements have been performed locally. But, in recent years, actual evapotranspiration computations can be calculated regionally thanks to improvements on remote sensing discipline and satellites. Surface Energy Balance Algorithm for Land (SEBAL) is one of the most commonly preferred technics for actual evapotranspiration mapping. However, this algorithm has some difficulties such as mismatch with Landsat 8 and hot–wet pixel selection which require expert knowledge. In this paper, a novel SEBAL based approach (SEBAL-BSA), which can use Landsat 8 images as data and can automatically perform hot–wet pixel selection using Backtracking Search Algorithm (BSA) with ground control points, has been proposed. SEBAL-BSA was developed and tested using January 22–2015, April 28–2015 and July 01–2015 dated Landsat 8 images in Akarsu Irrigation Water User Association command area in the Çukurova Region of Turkey and actual evapotranspiration mapping was realized without albedo measurements. Accuracy of SEBAL-BSA has been examined by comparing values of predefined ground truth points and values obtained from proposed approach. According to results of parametric matched pairs T test and nonparametric Wilcoxon sign rank test, SEBAL-BSA is highly successful. Applications also show that the SEBAL-BSA is a user-friendly approach for institutions and organizations related to water authorization and management. 相似文献
16.
蒸散发是水圈、大气圈和生物圈中水分循环和能量交换的纽带。在全球尺度上,蒸散发约占陆地降水总量的60%;作为其能量表达形式,潜热通量约占地表净辐射的80%。随着通量观测技术的发展,全球长期持续的观测数据得以获取和共享,近年来基于数据驱动的蒸散发遥感反演方法取得了较好的研究进展。本文针对数据驱动的蒸散发遥感反演方法和产品,从经验回归、机器学习和数据融合3个方面展开,对现有的研究进展进行了梳理、归纳和总结,并从驱动数据、反演方法、已有产品等方面指出目前仍存在的问题和不足。未来仍需开展数据驱动的高时空分辨率的蒸散发遥感反演方法的研究,有效考虑地表温度和土壤水分等可以指示地表蒸散发短期变化的重要信息,同时加强基于过程驱动的物理模型与数据驱动的模型的结合,使两类模型能互为补充、各自发挥所长,共同推动蒸散发遥感反演研究水平的进步。 相似文献
17.
穆西晗 阎广建 周红敏 庞勇 邱凤 张乾 张永光 谢东辉 周盈吉 赵天杰 仲波 宋金玲 孙睿 蒋玲梅 尹思阳 李凡 焦子锑 屈永华 张吴明 程顺 崔同祥 《遥感学报》2021,25(4):888-903
遥感综合试验对于遥感科学技术的发展起到重要作用,无论是基础研究还是遥感应用都需要试验提供支撑。从2018年开始,遥感科学国家重点实验室针对遥感自身发展和遥感面向地表圈层深化应用面临的科学问题,在滦河上游流域组织了小滦河流域复杂地表碳循环遥感综合观测试验,本文旨在介绍该试验的目标、区域、观测参数、观测方法以及对未来研究的展望,以期望为今后开展其他遥感试验及相关研究提供有益的参考和帮助。该试验采用星机地协同综合观测的方式,选择主要的在轨运行卫星数据及覆盖此流域的遥感产品作为主要数据;针对典型区域开展航空及无人机遥感试验,搭载光学传感器设备,获取典型区域水热循环、碳循环等关键参数;并同步开展地面观测试验,在典型实验区开展大气、植被和土壤关键参数的精细观测。目前已系统的开展了地面测量试验、无人机遥感试验及航空遥感试验,并同步收集了卫星遥感数据,形成了一套丰富的星—机—地配套遥感实测数据集。在试验的推动下,遥感科学国家重点实验室于2020年在试验区架设了多座综合观测塔,并配置了多种观测设备,开启了长时间序列观测任务,虚拟试验场的构建和机理生态模型的运行也在同步开展。小滦河流域复杂地表碳循环遥感综合试验利用星—机—地一体化的监测方法有效获取了地表水、能量和碳循环的关键参数,为遥感机理模型发展、反演方法检验和尺度转换研究提供了关键的基础数据。目前已用来建立遥感机理模型的综合检验平台,分析和改进传统模型和遥感产品在复杂地表的适用性,阐明流域尺度碳水耦合的物理过程。 相似文献
18.
Christopher Potter Steven Klooster Robert Crabtree Shengli Huang Peggy Gross Vanessa Genovese 《Carbon balance and management》2011,6(1):1-16
Background
A simulation model based on remote sensing data for spatial vegetation properties has been used to estimate ecosystem carbon fluxes across Yellowstone National Park (YNP). The CASA (Carnegie Ames Stanford Approach) model was applied at a regional scale to estimate seasonal and annual carbon fluxes as net primary production (NPP) and soil respiration components. Predicted net ecosystem production (NEP) flux of CO2 is estimated from the model for carbon sinks and sources over multi-year periods that varied in climate and (wildfire) disturbance histories. Monthly Enhanced Vegetation Index (EVI) image coverages from the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) instrument (from 2000 to 2006) were direct inputs to the model. New map products have been added to CASA from airborne remote sensing of coarse woody debris (CWD) in areas burned by wildfires over the past two decades.Results
Model results indicated that relatively cooler and wetter summer growing seasons were the most favorable for annual plant production and net ecosystem carbon gains in representative landscapes of YNP. When summed across vegetation class areas, the predominance of evergreen forest and shrubland (sagebrush) cover was evident, with these two classes together accounting for 88% of the total annual NPP flux of 2.5 Tg C yr-1 (1 Tg = 1012 g) for the entire Yellowstone study area from 2000-2006. Most vegetation classes were estimated as net ecosystem sinks of atmospheric CO2 on annual basis, making the entire study area a moderate net sink of about +0.13 Tg C yr-1. This average sink value for forested lands nonetheless masks the contribution of areas burned during the 1988 wildfires, which were estimated as net sources of CO2 to the atmosphere, totaling to a NEP flux of -0.04 Tg C yr-1 for the entire burned area. Several areas burned in the 1988 wildfires were estimated to be among the lowest in overall yearly NPP, namely the Hellroaring Fire, Mink Fire, and Falls Fire areas.Conclusions
Rates of recovery for burned forest areas to pre-1988 biomass levels were estimated from a unique combination of remote sensing and CASA model predictions. Ecosystem production and carbon fluxes in the Greater Yellowstone Ecosystem (GYE) result from complex interactions between climate, forest age structure, and disturbance-recovery patterns of the landscape. 相似文献19.
土壤有机物质对土壤介电常数的影响 总被引：4，自引：0，他引：4
土壤介电常数是开展微波土壤水分和冻融状态的监测的基础,也是植被和积雪的下垫面边界条件,然而目前已有的介电常数研究都没有对高有机质含量的土壤开展系统观测。本文将土壤中的自然有机物质分为腐殖质和植物性残留物两类。采用控制变量实验方法,通过测量5种不同有机质含量的东北黑土和加入不同比例毛白杨碎屑的扁都口草甸土,研究了腐殖质和植物性残留物的对土壤介电常数的影响。结果表明,腐殖质会降低干燥土壤的容重,从而发挥间接作用,使介电常数降低;而对于相同容重下观测的潮湿土壤,腐殖质含量较多的土壤介电常数更大。与Dobson模型的比较显示,在29℃室温下,腐殖质对25%重量含水量潮湿土壤实部的影响在±2左右,虚部能达到1。与腐殖质相比,植物性残留物对风干土壤和潮湿土壤的影响都十分明显。植物性残留物能有效地疏松土壤并代入植物组分的介电特征。当重量含水量为30%时,含毛白杨含量为20%的混合土壤比纯扁都口土壤在实部平均减小3—7左右,虚部减小 1—3左右。因此,根据实验观测以及和模型的比较,土壤中的有机物质会改变土壤介电性质,对微波遥感造成影响。 相似文献