遥感数据在水文模拟中的应用研究进展

水文模型已成为水文研究中不可或缺的重要部分。水文模型在经过黑箱模型阶段和集总式模型阶段后,现已发展到分布式水文模型阶段。相比于传统的站点观测,遥感技术由于能够获取面源信息、资料相对易获取并有稳定的较长时序观测等优势在水文模型中获得越来越广泛的应用。同时,近年来遥感数据产品在观测能力、可靠性和准确性、多源融合技术、卫星组网技术等方面取得了长足进展。遥感数据在水文模型中的应用主要有获取驱动数据,获取参数和边界条件,获取状态变量等3种方式。近些年来由于数据同化技术的发展,通过同化遥感观测数据改善水文模型模拟结果已成为遥感数据在水文应用中的一大研究热点。当前,遥感观测仍存在不确定性较高、时空尺度问题、瞬时观测、难以获取深层土壤信息等问题需要克服,如何在水文模型中充分利用不同来源、不同尺度的观测数据将是未来水文学研究的一个重要方向。     

Uncertainty estimates for the FAPAR operational products derived from MERIS — Impact of top-of-atmosphere radiance uncertainties and validation with field data

This paper discusses the accuracy of the operational Medium Resolution Imaging Spectrometer (MERIS) Level 2 land product which corresponds to the Fraction of Absorbed Photosynthetically Active Radiation (FAPAR). The FAPAR value is estimated from daily MERIS spectral measurements acquired at the top-of-atmosphere, using a physically based approach. The products are operationally available at the reduced spatial resolution, i.e. 1.2 km, and can be computed at the full spatial resolution, i.e. at 300 m, from the top-of-atmosphere MERIS data by using the same algorithm. The quality assessment of the MERIS FAPAR products capitalizes on the availability of five years of data acquired globally. The actual validation exercise is performed in two steps including, first, an analysis of the accuracy of the FAPAR algorithm itself with respect to the spectral measurements uncertainties and, second, with a direct comparison of the FAPAR time series against ground-based estimations as well as similar FAPAR products derived from other optical sensor data. The results indicate that the impact of top-of-atmosphere radiance uncertainties on the operational MERIS FAPAR products accuracy is expected to be at about 5-10% and the agreement with the ground-based estimates over different canopy types is achieved within ± 0.1.     

Mapping the potential annual total nitrogen load in the river basins of Japan with remotely sensed imagery

The increase of nutrient loads such as nitrogen and phosphorus to a river due to land cover changes in surrounding areas has been one of the major sources of water pollution or eutrophication. Monitoring the influent nutrient load from river basins to rivers is now crucial in the management of river basin environments. The monitoring is not easy, however, because it requires spatial and temporal measurement tools for land cover changes in the river basin and water qualities, and also it requires models relating them.In this study, we first analyzed the relation between the land cover types estimated from monthly maximum Normalized Difference Vegetation Index (NDVI) imagery calculated from NOAA Advanced Very High Resolution Radiometer (AVHRR) imagery and the annual total nitrogen load discharged from river basins. We found that the runoff load factor from urban areas is higher than those of forested areas. We also found that the impacts of land cover such as plantation and field weed communities on the total nitrogen load of each river are higher than the impacts of other land cover types such as Beech and Camellia japonica community type.Finally, we produced two advanced maps of the potential annual total nitrogen load (PTNL) index and the potential annual total nitrogen load for each river basin area (PTNL/area) index by considering the relationship between the land cover types and the annual total nitrogen load discharged from river basins in Japan. The PTNL map will be useful for the risk assessment of total nitrogen load impact on lakes and the sea through rivers from each basin. The PTNL/area index, which considers the effects of river basin areas, will allow evaluation of the state of river basins.     

A comprehensive modeling environment for the simulation of groundwater flow and transport

A comprehensive graphical modeling environment has been developed to address the needs of the computer simulation of groundwater flow and transport. The Department of Defense Groundwater Modeling Systems (GMS), developed at the Engineering Computer Graphics Laboratory at Brigham Young University, is part of a multi-year project funded through the Department of Defense, Department of Energy and Environmental Protection Agency. GMS is a graphically based software tool providing facility through all aspects of the groundwater flow and transport modeling process. Facilities include geometric modeling of hydrostratigraphy, two- and three-dimensional mesh generation, graphically based model input for specific flow and transport codes, interpolation and geostatistics as well as complete three-dimensional scientific visualization.     

Vectorized simulation of groundwater flow and streamline transport

We describe a modeling suite of Matlab functions for simulating nonpoint source (NPS) pollution in groundwater aquifers. The NPS model simulates groundwater flow and contaminant transport from a large array (order of 10² – 10⁷) of spatially distributed sources with time-varying pollution strength to a similarly large array of spatially distributed production wells (receptors) using the streamline transport approach. The code solves three equations: steady-state groundwater flow, particle tracking, and transient advection dispersion contaminant transport. The code performs convolution integration in its predictive step. Written in highly efficient vectorized form to avoid time consuming “for/while” loops, the code is also suitable for other groundwater flow and transport problems. The code is verified against analytical solutions and finite element software Comsol. An application illustrates 200 years of transient nitrate transport in the 2000 km² Tule River aquifer sub-basin of the Central Valley, California, with 9000 individual nitrate sources and 1920 wells.     

Spectroscopic characterization of oils yielded from Brazilian offshore basins: Potential applications of remote sensing

Spectroscopy is the basis to detect and characterize offshore hydrocarbon (HC) seeps through optical remote sensing. Diagnostic spectral features of HCs are linked to their chemical composition and fundamental molecular vibrations (SWIR-TIR features), as well as overtones and combinations of these vibrations (VNIR-SWIR). These features allow for the characterization of oil, oil on water and emulsified oil. This work shows the results of lab and field spectral measurements of 17 petroleum samples yielded from key, oil-rich sedimentary basins in Brazil. Measurements comprised reflectance data (VNIR- SWIR), Attenuated Total Reflectance (ATR), Directional Hemispherical Reflectance (DHR), and emissivity data (TIR). These spectra were analyzed by multivariate techniques, such as Principal Components Analysis (PCA) and Partial Least-Square analysis (PLS). The experimental results indicate that for the VNIR-SWIR range: (i) spectral features can be recognized for crude oil, emulsified oil and oil on ocean water; (ii) different oil types can be qualitatively distinguished based on these features (i.e. light or heavy), even considering oil on water; (iii) the same applies for oil measurements simulated at the spectral resolution of hyperspectral (357-bands/ProSpecTIR) and multispectral (9-bands/ASTER) sensors. Within TIR wavelengths (3-14 μm), typical HC spectral features can also be resolved and oil types qualitatively discriminated using PCA/PLS, including both full-resolution spectra and spectra resampled to hyperspectral sensor (128-bands/SEBASS). However, despite the fact that oil emissivity is always lower than that of water, such separation seems unfeasible using 8-12 μm TIR features only; emissivity spectra are essentially flat for all samples in this interval. This research demonstrated that oil can be qualitatively distinguished based on both VNIR-SWIR and TIR spectroscopy data, with important implications for remote off-shore oil exploration and classification of oil leakages.     

Development and evaluation of GIS-based ArcPRZM-3 system for spatial modeling of groundwater vulnerability to pesticide contamination

The objectives of this study were to develop and evaluate a GIS-based modeling system called ArcPRZM-3 for spatial modeling of pesticide leaching potential from soil surface towards groundwater. The ArcPRZM-3 was developed by coupling a commonly used FORTRAN-based Pesticide Root Zone Model version 3 (PRZM-3) with user-friendly input and output interfaces through links to GIS using customized programming. A Visual PRZM-3 interface simplifies the entry of model inputs and links to the databases of crops, soils, and pesticides. The ArcPRZM-3 produces user-friendly outputs from the PRZM-3 batch simulations in the form of tables, charts, and maps. The Visual PRZM-3 can be used to run a single simulation for site-specific studies or simultaneous multiple simulations for spatial distributed modeling. The ArcPRZM-3 was applied to simulate maximum dissolved bentazon concentration at 0.75 m soil depth for a period of 2 years. These simulation results were used to develop a health risk map for Woodruff County, Arkansas, based on the U.S. Environmental Protection Agency's Lifetime Health Advisory Level (USEPA-LHA) of bentazon in drinking water. The ArcPRZM-3 was evaluated by comparing the bentazon detection data from monitoring wells from the same area with the predicted bentazon health risk map. The results showed that 100% of the wells where bentazon was detected were within the high risk category based on the ArcPRZM-3 predictions. However, uncertainty in the ArcPRZM-3 model and the timing of groundwater well monitoring could both complicate the interpretations of the ArcPRZM-3 simulation results.     

遥感技术在考古中的应用

随着考古研究工作的扩展和研究区域的扩大,考古学家们逐渐从更加宏观的角度去研究历史文化,认识古代文明,追溯历史进程,这些仅仅依靠传统的考古方法是不可能实现的,这就决定了遥感在考古研究中不可替代的作用。遥感应用于考古,是一门新兴的学科,是自然科学、技术科学和社会科学相结合的结果,是遥感技术和野外考古的整合。通过研究近几十年来遥感考古在国内外发展的情况,详细系统地探讨了用于考古的卫星遥感技术的原理和方法,并归纳总结出遥感在考古研究的各个领域的应用情况及技术方法。     

Modeling spectral reflectance of optically complex waters using bio-optical measurements from Tokyo Bay

This study presents an approach for optimally parameterizing a reflectance model. A parameterization scheme is realized based on a comprehensive bio-optical data set, including subsurface downwelling and upwelling irradiance spectra, absorption spectra of particle and dissolved substances, as well as chlorophyll and total suspended matter concentrations at 45 stations near Tokyo Bay between 1982 and 1984. The irradiance reflectance model is implemented with three-component inherent optical property submodels.In this parameterization scheme, an unsupervised classification was applied in the hyper-spectral space of reflectance, leading to three spectrally distinct optical water types. The reflectance model was parameterized for the entire data set, and then parameterized for each of the water types. The three sets of type-specific model parameters, which define corresponding IOP submodels, are believed to accommodate differences in the optical properties of the in-water constituents. The parameterized reflectance model was evaluated by both reconstructing measured reflectance spectra and solving for the nonlinear inverse problem to retrieve in-water constituent concentrations. The model accuracy was significantly improved in the forward direction for classified waters over that of non-classified waters, but no significant improvement was achieved in the retrieval accuracy (inverse direction). A larger data set with greater resolution of constituent inherent optical properties would likely improve the modeling results.     

Evaluating environmental influences of zoning in urban ecosystems with remote sensing

The influence of zoning on Normalized Difference Vegetation Index (NDVI) and radiant surface temperature (T_s) measurements is investigated in the City of Indianapolis, IN, USA using data collected by the Enhanced Thematic Mapper Plus (ETM+) remote sensing system. Analysis of variance indicates statistically significant differences in mean T_s and NDVI values associated with different types of zoning. Multiple comparisons of mean T_s and NDVI values associated with specific pairings of individual zoning categories are also shown to be significantly different. An inverse relationship between T_s and NDVI was observed across the city as a whole and within all but one zoning category. A range of environmental influences on sensible heat flux and urban vegetation was detected both within and between individual zoning categories. Examples for implementing these findings in urban planning applications to find examples of high and low impact development are demonstrated.     

Effects of channel morphology and sensor spatial resolution on image-derived depth estimates

The utility of remote sensing in the study of fluvial systems depends upon the extent to which image data can be used to derive quantitative information of sufficient accuracy and precision for specific applications. In this study, we evaluate the effects of channel morphology on depth retrieval by coupling a radiative transfer model to various morphologic scenarios. Upwelling radiance L_u spectra generated for a range of depths (2-150 cm) and benthic cover types (limestone, periphyton, and gravel) were linearly mixed to simulate sub-pixel bed topography and substrate heterogeneity. For sloping bottoms, solar-streambed geometry modified L_u relative to a level bottom, especially for beds sloping steeply away from the sun. Aggregate pixel scale L_u spectra were compared to a database of simulated spectra to determine the radiance-equivalent depth of a uniform bottom (REDUB). REDUB spectra for hypothetical stepped streambeds indicated underestimation of the actual area-weighted mean depth, but the ln (L_u,560/L_u,690) REDUB ratio consistently reproduced the pixel-scale mean for beta distributions of depths. Similarly, when both dark periphyton and bright limestone substrates occurred within a pixel, REDUB spectra produced large errors while the ratio proved robust. Along channel banks, pixels will inevitably be mixed, and our simulations indicated that although bank fractions estimated by spectral mixture analysis were highly accurate for vegetated cutbanks, gravel bars were sensitive to the selection of both aquatic and terrestrial end members and subject to relatively large fraction errors. These theoretical results were tested using a ratio-based relative depth map and two-end member mixture models derived from a hyperspectral image of the Lamar River in Yellowstone National Park, which also served to illustrate the importance and applicability of our simulations. The primary conclusions of this study are that 1) the ratio-based algorithm is well-suited to complex river channels; 2) channel morphology and sensor spatial resolution must be considered jointly during data collection and analysis; and 3) the accuracy and precision of depth estimates are influenced by channel morphology and thus vary spatially.     

Floodplain water storage in the Negro River basin estimated from microwave remote sensing of inundation area and water levels

The objective of this study is to determine spatio-temporal variations of water volume over inundated areas located in large river basins using combined observations from the Synthetic Aperture Radar (SAR) onboard the Japanese Earth Resources Satellite (JERS-1), the Topex/Poseidon (T/P) altimetry satellite, and in-situ hydrographic stations. Ultimately, the goal is to quantify the role of floodplains for partitioning water and sediment fluxes over the great fluvial basins of the world. SAR images are used to identify the type of surface (open water, inundated areas, forest) and, hence, the areas covered with water. Both radar altimetry data and in-situ hydrographic measurements yield water level time series. The basin of the Negro River, the tributary which carries the largest discharge to the Amazon River, was selected as a test site. By combining area estimates derived from radar images classification with changes in water level, variations of water volume (focusing on a seasonal cycle) have been obtained. The absence of relationship between water volume and inundated area, reflecting the diverse and widely dispersed floodplains of the basin, is one of the main result of this study.     

Integration of GRACE,ground observation,and land-surface models for groundwater storage variations in South Korea

Terrestrial water storage (TWS) comprises all forms of water stored in the Earth’s surface. The gravity recovery and climate experiment (GRACE) twin satellite provides an efficient method of assessing TWS changes (TWSCs) by measuring variations in the Earth’s gravity. GRACE-derived TWS is equivalent to the sum of all forms of water such as surface water, soil moisture, snow water equivalent, and groundwater. Therefore, groundwater storage and its variations can be estimated when other variables are determined. We used Level-3 data (RL 05) to estimate monthly TWSC in South Korea. Data were obtained from land-surface models (LSMs) of global land data assimilation system (GLDAS), ground observations from water management information system (WAMIS) and rural agricultural water resources information system (RAWRIS). GRACE-derived groundwater storage changes (GWSCs) were ?0.18 ± 6.5 cm month^?1 on average, indicating the decrease of groundwater. We validated the GRACE-derived GWSC by comparing the changes with well-derived GWSC obtained from in situ groundwater observation wells of Korean national groundwater monitoring networks (NGMNs). This satellite-based remote-sensing methodology can provide an efficient tool for the nationwide planning and management of groundwater.     

Building a geodatabase for mapping hydrogeological features and 3D modeling of groundwater systems: Application to the Saguenay-Lac-St.-Jean region, Canada

Understanding and managing groundwater resources require the integration of a large amount of high-quality data from a variety of sources. Due to the limitations in accessing information related to groundwater and subsurface conditions, the gathering of available existing information is of crucial importance when conducting a successful hydrogeological study. Here, we present an approach for the development of an exhaustive and comprehensive groundwater database through (1) the gathering of relevant sources of information relating to groundwater, and (2) the application of a quality control process in order to screen the data for accuracy and quality. This hydrogeological database is then implemented within a GIS (geographic information system) framework coupled to a Relational Database Management System (RDBMS) as a personal geodatabase (ESRI format) GIS technology. Once established, the spatial database allows a user to request the relevant data required for a specific hydrogeological study. In addition, stratigraphic data stored within the spatial database may be utilized for constructing 3D subsurface hydrostructural models. In order to achieve this objective, the software Arc Hydro Groundwater combined with the ArcGIS spatial database is shown to be appropriate for the 3D structural representation of aquifers (groundwater reservoirs). The innovative contribution of this approach in building 3D hydrostructural subsurface models from a spatial database resides in simplifying the required step-by-step processes by considering a unified compatible combination of “RDBMS-ArcGIS-Arc Hydro Groundwater” technologies. The proposed methodology is illustrated using data from an ongoing project aimed at developing an inventory of the groundwater resources of the Saguenay-Lac-Saint-Jean region, Quebec (Canada).     

Spatial and temporal dynamics of river channel migration and vegetation in central Amazonian white-water floodplains by remote-sensing techniques

We investigated spatial and temporal migration of the Solimões, the Japurá, and the Aranapu River channels in western Brazilian Amazonia with Landsat TM imagery over a 21-year period. Additionally, we classified and monitored how channel migrations affect the distribution of pioneer vegetation and old-growth forest. The cloud-free study area was 153,032 ha — open water plus 3 km inland on each margin. The channel migration rates, expressed as percent dislocation of the open water body of the river year^− 1, were lowest in the Japurá River (1.2%), and highest in the Aranapu channel (2.5%), the point bars at river confluence being the most affected landforms subject to geomorphic changes. Annual rates of lateral erosion and accretion of vegetated land along the three rivers were well-balanced. They averaged 0.79 and 0.83% of the cloud-free channel area over the 21 years. The Solimões River was more dynamic than the Japurá River, which can be traced to higher water discharge and sediment load. During the 21 years, the area covered by pioneer vegetation increased by 5.8% of the study area, while late-succession areas decreased by a similar amount (5.5%). According to local biomass estimates of the different vegetation types, these values suggest that C-releases by alluvial erosion would be much higher than C-sequestration caused by the creation of areas suitable for colonization by pioneer vegetation at our study site.     

我国南方红壤分布区1:20万水土流失遥感调查方法探讨

介绍了水土流失区土壤流失1:20万比例尺遥感调查过程,建立了权重模型和判别条件,可用来评估土壤流失强度。认为所获得的 Landsat TM3,4,7波段的假彩色合成影像是解译和识别影响因子的主要手段。在流失区面积估测中,利用大比例尺航片,解译量算流失区中的“非流失区系数”,通过非流失区系数扣除,可大大提高面积量算的精度。     

三维结构真实遥感像元场景的生成

遥感像元场景模型是遥感机理研究的关键组成,通过调查光与遥感像元场景的相互作用,可以帮助人们理解遥感信号产生的机理,并验证遥感物理模型。从植被野外测量、三维结构真实遥感像元场景的参数化描述、场景数据结构、场景生成方法和流程等方面阐释了遥感像元场景模型。植被的野外测量和统计是结构真实场景的基础;场景生成方法为：（1）使用L系统生成结构真实植株,进而生成遥感像元场景;（2）按统计规则直接生成遥感像元场景。试验表明该遥感像元场景模型可以生成符合遥感像元统计规律的三维场景,是准确和便捷地计算光与植被相互作用的可靠基础。     

GIS在环境影响评价中的应用探析

自1979年我国的EIA制度正式建立以来,其评价原理,方法和技术不断发展,但目前EIA中的许多研究领域还不成熟。没有制定出正式的导则和规范,还需要引进其它学科的技术,使其不断完善和提高,首先论述了GIS在EIA中应用的必要性和可能性,然后介绍了GIS在EIA中应用的领域,在对国内外现状进行分析的基础上,又对GIS在EIA中的应用前景做了展望。     

基于COM的混合编程及在遥感中的应用

光学遥感成像仿真系统存在各模块耦合性强的问题,不利于仿真系统的扩展和复用,另外,现有的Visual C 与Fortran混合编程主要基于DLL库和基于文件操作的方式,基于COM的Visual C 与Fortran混合编程未见报道.针对以上问题,提出了一种以COM技术为基础的光学遥感成像仿真系统的建模方法,根据光学遥感成像仿真系统的功能要求,按照COM接口规范对仿真系统进行结构划分,设计各模块的对外接口,结合VC与Fortran混合编程实现了大气辐射传输组件,并应用于光学遥感成像模拟软件进行测试.结果表明,采用该方法可以较好地解决上述问题,减弱各模块间的耦合性,使仿真系统具备良好的可复用性和可扩展性.     

Remote sensing estimates of boreal and temperate forest woody biomass: carbon pools, sources, and sinks

The relation between satellite measurements of the normalized difference vegetation index (NDVI), cumulated over the growing season, and inventory estimates of forest woody biomass carbon is estimated statistically with data from 167 provinces and states in six countries (Canada, Finland, Norway, Russia and the USA for a single time period and Sweden for two periods). Statistical tests indicate that the regression model can be used to represent the relation between forest biomass and NDVI across spatial, temporal and ecological scales for relatively long time scales. For the 1.42 billion ha of boreal and temperate forests in the Northern Hemisphere, the woody biomass carbon pools and sinks are estimated at a relatively high spatial resolution (8×8 km). We estimate the carbon pool to be 61±20 gigatons (10⁹) carbon (Gt C) during the late 1990s and the biomass sink to be 0.68±0.34 Gt C/year between the 1982 and 1999. The geographic detail of carbon sinks provided here can contribute to a potential monitoring program for greenhouse gas emission reduction commitments under the Kyoto Protocol.