海洋光学遥感器的辐射定标与数据真实性检验综述   总被引：9，自引：0，他引：9  

陈清莲  唐军武 《海洋技术学报》1998,17(3):13-26

遥感数据定量化应用遥感技术深入发展亟须解决的重要课题,对遥感器进行辐射定标,对遥感数据进行真实性检验的工作已在深入开展,本文介绍了国际关于定标／真实性检验的组织及分工概况,简要阐述了定标／真实性检验的概念与做法,着重讨论了与海洋光学遥感器有关的辐射定标／真实性检验,综述了国外在这方面的若干做法,并在我们工作的基础上提出了开展此项工作的几个关键问题及中能解决的途径。  相似文献   

NEAT approach for testing and validation of geospatial network agent-based model processes: case study of influenza spread     

Taylor Anderson  Suzana Dragićević 《International journal of geographical information science》2020,34(9):1792-1821

ABSTRACT

Agent-based models (ABM) are used to represent a variety of complex systems by simulating the local interactions between system components from which observable spatial patterns at the system-level emerge. Thus, the degree to which these interactions are represented correctly must be evaluated. Networks can be used to discretely represent and quantify interactions between system components and the emergent system structure. Therefore, the main objective of this study is to develop and implement a novel validation approach called the NEtworks for ABM Testing (NEAT) that integrates geographic information science, ABM approaches, and spatial network representations to simulate complex systems as measurable and dynamic spatial networks. The simulated spatial network structures are measured using graph theory and compared with empirical regularities of observed real networks. The approach is implemented to validate a theoretical ABM representing the spread of influenza in the City of Vancouver, Canada. Results demonstrate that the NEAT approach can validate whether the internal model processes are represented realistically, thus better enabling the use of ABMs in decision-making processes.  相似文献   

Validation of AIRS-Retrieved atmospheric temperature data over the Taklimakan Desert     

YuFen Ma  RuQi Li  Men Zhang  MinZhong Wang  Mamtimin Ali 《寒旱区科学》2020,12(4):242-251

The Taklimakan Desert, the world's second largest desert, plays an important role in regional climate change. Previous studies on its spatial temperature features suffered from sparse conventional detection data, but the Atmospheric Infrared Sounder(AIRS) provides excellent temperature retrievals with high spatiotemporal resolution. Validation of AIRS temperature retrievals over desert regions with high land-surface emissivity, the key contributor to inversion error, is essential before using these data in regional weather/climate modeling. This paper examines the correlation coefficients, root mean square error(RMSE) and mean BIAS between AIRS-retrieved atmospheric temperature data and radiosonde observations(RAOBs) in the Taklimakan Desert hinterland and oases in the morning and at dusk. Firstly, the AIRS retrievals are consistent with RAOBs and are more consistent in the morning than at dusk. The consistency is better over a small-scale desert oasis than over a large-scale oasis in the morning and exhibits the opposite trend at dusk. The correlation coefficient over the hinterland is high in the morning but negative at dusk due to high desert-surface emissivity. Second, the RMSEs, which are all smaller than 3 K, are generally higher over desert sites than over oasis sites and slightly lower over a small-scale oasis than over a large-scale oasis in the morning. At dusk, the RMSEs are higher over desert sites than over oases and slightly higher over a small-scale oasis than over a large-scale oasis. Furthermore, the RMSEs are generally higher in the morning than at dusk over a large-scale oasis and lower in the morning than at dusk over a small-scale oasis. Third, the absolute mean BIAS values are mostly lower than 1 K. In the morning, relative to RAOB temperatures, the retrieval temperatures are higher over desert sites but lower over oasis sites. At dusk, the retrieval temperatures are lower than RAOB temperatures over both desert and oasis sites. The retrieval temperatures are higher than RAOB temperatures over desert sites in the morning but slightly lower at dusk. Most absolute mean BIAS values are higher in the morning than at dusk over both oasis and desert sites. Finally, the consistency between the AIRS and RAOB temperature data is high from 700 hPa to 100 hPa in the morning and from 700 hPa to 300 hPa at dusk. The difference between the AIRS and RAOB temperature data is generally higher in the morning than that at dusk. The RMSE differences between the AIRS and RAOB data are slightly lower in the morning than at dusk and are lower in the middle layers between 700 hPa and 150 hPa than in the layers above 150 hPa during both the morning and night. The BIAS is lower in the morning than at dusk below 300 hPa but higher in the upper layers. Moreover, the BIAS value is positive in the middle layers between 500 hPa and 150 hPa and negative at other levels at both times. Generally, the AIRS retrieval temperatures are reliable and can be used in further studies in the Taklimakan Desert.  相似文献   

植被光合有效辐射吸收比率遥感研究进展     

田定方  范闻捷  任华忠 《遥感学报》2020,24(11):1307-1324

植被光合有效辐射吸收比率FPAR（Fraction of absorbed Photosynthetically Active Radiation）反映了植被冠层的光学特性，是表征植被光合作用水平和生长状态的重要参量，因此成为全球变化研究中多种过程模型的重要输入参数。随着定量遥感研究的深入和新型传感器的使用，从区域到全球尺度上的FPAR遥感估算方法不断提出，多样化的遥感FPAR产品越来越多地应用于碳循环、能量循环、生产力估算及作物估产等研究领域。本文梳理了遥感估算的植被光合有效辐射的相关概念和算法，并着重对过去十年间遥感估算FPAR的新进展进行了系统总结和探讨。研究表明，近年来FPAR遥感的研究工作一方面聚焦于对现有算法的改进与各类型产品的验证，更多的研究则侧重于FPAR概念体系的拓展，叶片、叶绿素水平的FPAR估算，直射光、散射光的FPAR建模等新方向逐渐成为研究热点。  相似文献   

Nitrogen Mass Fraction and Stable Isotope Ratios for Fourteen Geological Reference Materials: Evaluating the Applicability of Elemental Analyser Versus Sealed Tube Combustion Methods     

Toby J. Boocock  Sami Mikhail  Julie Prytulak  Tommaso Di Rocco  Eva E. Stüeken 《Geostandards and Geoanalytical Research》2020,44(3):537-551

Thirteen commercially available silicate reference materials (RM) and one in‐house reference material, eleven of which have no previously published values, were analysed for nitrogen mass fraction and isotopic ratios with an Elemental Analyser (EA), and a Sealed Tube Combustion line, coupled to a continuous flow isotope ratio mass spectrometer (IRMS). These materials ranged from < 10 μg g^?1 to 1% m/m nitrogen mass fractions and δ¹⁵N of ?0.5 to +19.8‰. Existing nitrogen RM BHVO‐2, MS#5 and SGR‐1b were used to assess the accuracy of the data from the sealed tube combustion line, which was found to be in good agreement with existing published values. In contrast, the EA‐IRMS failed to fully liberate nitrogen from all silicate rocks and minerals (achieving a mean of 44 ± 10% nitrogen yield) resulting in kinetic fractionation of isotope values by ?1.4‰ on average. Therefore, sealed tube combustion is better suited for analyses of silicate‐bound nitrogen. The EA worked reliably for organic samples, but care should be taken when using the EA for silicate nitrogen research. Moving forward, it is recommended that BHVO‐2, Biotite‐Fe, FK‐N and UB‐N be used as quality control materials as they appear to be most reproducible in terms of nitrogen mass fraction (relative error < 10%, 1s), and isotopic composition (< 0.6‰, 1s).  相似文献   

An assessment of large-scale flood modelling based on LiDAR data     

Guénolé Choné  Pascale M. Biron  Thomas Buffin-Bélanger  Iulia Mazgareanu  Jeff C. Neal  Christopher C. Sampson 《水文研究》2021,35(8):e14333

Large-scale flood modelling approaches designed for regional to continental scales usually rely on relatively simple assumptions to represent the potentially highly complex river bathymetry at the watershed scale based on digital elevation models (DEMs) with a resolution in the range of 25–30 m. Here, high-resolution (1 m) LiDAR DEMs are employed to present a novel large-scale methodology using a more realistic estimation of bathymetry based on hydrogeomorphological GIS tools to extract water surface slope. The large-scale 1D/2D flood model LISFLOOD-FP is applied to validate the simulated flood levels using detailed water level data in four different watersheds in Quebec (Canada), including continuous profiles over extensive distances measured with the HydroBall technology. A GIS-automated procedure allows to obtain the average width required to run LISFLOOD-FP. The GIS-automated procedure to estimate bathymetry from LiDAR water surface data uses a hydraulic inverse problem based on discharge at the time of acquisition of LiDAR data. A tiling approach, allowing several small independent hydraulic simulations to cover an entire watershed, greatly improves processing time to simulate large watersheds with a 10-m resampled LiDAR DEM. Results show significant improvements to large-scale flood modelling at the watershed scale with standard deviation in the range of 0.30 m and an average fit of around 90%. The main advantage of the proposed approach is to avoid the need to collect expensive bathymetry data to efficiently and accurately simulate flood levels over extensive areas.  相似文献   

Evaluation of WaPOR V2 evapotranspiration products across Africa     

Megan L. Blatchford  Chris M. Mannaerts  Sammy M. Njuki  Hamideh Nouri  Yijian Zeng  Henk Pelgrum  Steven Wonink  Poolad Karimi 《水文研究》2020,34(15):3200-3221

The Food and Agricultural Organization of the United Nations (FAO) portal to monitor water productivity through open-access of remotely sensed derived data (WaPOR) offers continuous actual evapotranspiration and interception (ETIa-WPR) data at a 10-day basis across Africa and the Middle East from 2009 onwards at three spatial resolutions. The continental level (250 m) covers Africa and the Middle East (L1). The national level (100 m) covers 21 countries and 4 river basins (L2). The third level (30 m) covers eight irrigation areas (L3). To quantify the uncertainty of WaPOR version 2 (V2.0) ETIa-WPR in Africa, we used a number of validation methods. We checked the physical consistency against water availability and the long-term water balance and then verify the continental spatial and temporal trends for the major climates in Africa. We directly validated ETIa-WPR against in situ data of 14 eddy covariance stations (EC). Finally, we checked the level consistency between the different spatial resolutions. Our findings indicate that ETIa-WPR is performing well, but with some noticeable overestimation. The ETIa-WPR is showing expected spatial and temporal consistency with respect to climate classes. ETIa-WPR shows mixed results at point scale as compared to EC flux towers with an overall correlation of 0.71, and a root mean square error of 1.2 mm/day. The level consistency is very high between L1 and L2. However, the consistency between L1 and L3 varies significantly between irrigation areas. In rainfed areas, the ETIa-WPR is overestimating at low ETIa-WPR and underestimating when ETIa is high. In irrigated areas, ETIa-WPR values appear to be consistently overestimating ETa. The relative soil moisture content (SMC), the input of quality layers and local advection effects were some of the identified causes. The quality assessment of ETIa-WPR product is enhanced by combining multiple evaluation methods. Based on the results, the ETIa-WPR dataset is of enough quality to contribute to the understanding and monitoring of local and continental water processes and water management.  相似文献   

Evolution of river-routing schemes in macro-scale models and their potential for watershed management     

Kashif Shaad 《水文科学杂志》2018,63(7):1062-1077

Macro-scale river-routing schemes first emerged to channel runoff generated as a by-product from land surface models to oceans. In the past decade, as discharge of major rivers was identified as a suitable parameter to test the performance of the macro-scale land surface models, river-routing received significant attention, with development of multiple schemes. As resolution improves, the possibility of river-routing schemes connecting the global models with watershed issues has emerged as an option. Yet, even as results from these schemes become easily available, a comprehensive overview of their scope and limitation when considering regional or watershed-centric applications is lacking. To address this gap, 18 published river-routing schemes are compared by examining their structure, rationale and limitations. Due to the diverse nature of scheme implementations, a direct comparison of performance is not yet possible. However, features and studies geared towards watershed-scale applications are highlighted. Issues of global to local integration are discussed.  相似文献   

Evaluation of intermediate TanDEM-X digital elevation data products over Tasmania using other digital elevation models and accurate heights from the Australian National Gravity Database     

M. Rexer  C. Hirt 《Australian Journal of Earth Sciences》2016,63(5):599-609

The successful operation of the TanDEM-X satellite mission is the start of a new era of globally consistent and accurate digital elevation data for planet Earth. In this work available 12 m-resolution intermediate TanDEM-X products (DEM: digital elevation model; HEM: height error map; COV: coverage map; WAM: water indication mask) are evaluated over Tasmania. Elevations from the TanDEM-X intermediate digital elevation model (IDEM) are compared with (a) other global DEMs (30 m-resolution SRTM1 USGS v3 and 30 m-resolution Advanced Spaceborne Thermal Emission Reflectometer (ASTER GDEM2), (b) the local 25 m-resolution DEM made available by Tasmanian environmental authority (DPIPWE), and (c) over 15 000 accurate ground-control-points (GCPs) from the Australian National Gravity Database (ANGD). The comparison with ASTER and SRTM over the area of Tasmania involves over 500 million valid TanDEM-X IDEM elevations. The root-mean-square (RMS) of 8.8 m indicates a reasonable to good agreement of TanDEM-X IDEM and SRTM, while ASTER shows almost twice the disagreement in terms of RMS (～16.5 m). Both, ASTER and SRTM show a (mean) offset of –1.9 m and –2.3 m w.r.t. TanDEM-X IDEM, respectively. By comparisons with GCPs, we find that SRTM and ASTER overestimate the terrain height. The comparison with the AGND GCPs also allows an estimate of the absolute accuracy of the IDEM, which is found to be superior to that of SRTM or ASTER. The RMS error of 6.6 m shows that the IDEM is close to the officially denoted 4 m absolute vertical accuracy considering that the GCPs are not error free. The height error map information layer is found to a suitable first indicator of the (local) accuracy of the IDEM in a relative sense. However, we find that the HEM tends to underestimate observed differences to the GCPs. Terrain-type analyses reveal that the TanDEM-X IDEM is a very consistent elevation database over Tasmania. In conclusion, our study demonstrates that the new TanDEM-X elevation data sets provide improved high-resolution terrain information over Tasmania and beyond.  相似文献   

Growing Operational Use of FY-3 Data in the ECMWF System     

Niels BORMANN  David DUNCAN  Stephen ENGLISH  Sean HEALY  Katrin LONITZ  Keyi CHEN  Heather LAWRENCE  Qifeng LU 《大气科学进展》2021,38(8):1285-1298

This paper reviews the data quality and impact of observations from the FY-3 satellite series used operationally in the ECMWF system. This includes data from the passive microwave radiometers MWHS-1, MWHS-2 and MWRI, as well as observations from the radio occultation receiver GNOS. Evaluations against background equivalents show that the quality of the observations is broadly comparable to that of similar instruments on other polar-orbiting satellites, even though biases for the passive microwave observations can be somewhat larger and more complex for some channels. An observing system experiment shows that the FY-3 instruments jointly contribute significantly to the forecast skill in the ECMWF system. Positive impact of up to 2% is seen for most variables out to the day-2 forecasts over hemispheric scales, with significant benefits for total column water vapor or for temperature and wind in the stratosphere out to day 4.  相似文献