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A link trie structure of storing multiple attribute relationships for natural language dictionaries

INTERNATIONAL JOURNAL OF COMPUTER MATHEMATICS 1999年第4期72卷 463-476页

作者： Morita, K Koyama, M Fuketa, M Aoe, JI Univ Tokushima Fac Engn Dept Informat Sci & Intelligent Syst Tokushima 770 Japan

Word relation is primitive knowledge and it is very useful for natural language processing systems. In the traditional systems, although each knowledge dictionary is constructed in separation, recent natural language applications become more complex by integrating the above multi-attribute relationships. This paper presents an efficient data structure by introducing a trie that can define the linkage among their leaves. The linkage enables us to share the basic words required for multi-attribute relationships. Theoretical observations show that the worst-case time complexity of retrieving multi-attribute relationships is a constant. From the simulation results, it is shown that the presented method is 1/3 smaller than the competitive methods.

关键词： trie structures natural language dictionaries word relationships retrieval algorithms

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Cloud model evaluation using radiometric measurements from the airborne multiangle imaging spectroradiometer (AirMISR)

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REMOTE SENSING OF ENVIRONMENT 2007年第1-2期107卷 185-193页

作者： Ovtchinnikov, Mikhail Marchand, Roger T. Pacific NW Natl Lab Richland WA 99352 USA

Detailed information on cloud properties is needed to rigorously test retrieval algorithms for satellite and ground-based remote sensors. The inherent complexity of clouds makes this information difficult to obtain from observations alone and cloud resolving models (CRMs) are often used to generate synthetic datasets that can be used as proxies for real data. We test the ability of a CRM to reproduce the observed structure of low-level clouds detected by the Earth Observing System (EOS) validation program in north central Oklahoma on March 3, 2000. A threedimensional radiative transfer model is applied to bigh-resolution cloud fields generated by the CRM in order to simulate the top of atmosphere radiances. These synthetic radiances are then statistically compared with observations from the airborne Multiangle Imaging Spectro-Radiometer (AirMISR), flown on the NASA ER-2 high-altitude aircraft. Simulations match well the blue channel radiance distributions at oblique view angles but overestimate the minimum in reflectance at near-nadir viewing angles, The model reproduces correctly the angular change in the width of radiance distribution, as measured by the standard deviation but the change in skewness of these distributions is captured only qualitatively. The model biases are suggestive of the simulated cloud boundaries being too sharp and the distribution of the vertical liquid water path being too narrow. A power spectrum analysis shows a close agreement between simulations and observations including a break in the scaling properties of the radiance fields around 400 in. The scaling properties of the ID power spectrum of simulated radiance at smaller scales exhibit directional dependence not seen in corresponding observations. (c) 2007 Elsevier Inc. All rights reserved.

关键词： 3D radiative transfer AirMISR retrieval algorithms

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Validation and potential applications of Environment Canada Ice Concentration Extractor (ECICE) algorithm to Arctic ice by combining AMSR-E and QuikSCAT observations

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REMOTE SENSING OF ENVIRONMENT 2013年 128卷 315-332页

作者： Shokr, Mohammed Agnew, Thomas A. Environm Canada Sci & Technol Branch Toronto ON M3H 5T4 Canada

The Environment Canada's Ice Concentration Extractor (ECICE) combines observations from several different satellite sensors to resolve heterogeneous components of a given footprint To validate the algorithm and demonstrate its applicability, results are presented from combining the enhanced AMSR-E 36.5 GHz passive microwave data with dual-polarization QuikSCAT active microwave scatterometer observations of Arctic ice during September to May;2007/08. Validation is performed using comparison with results from other algorithms in addition to operational ice charts. Three ice types are resolved: young, first-year and multiyear. Total ice concentration from ECICE under cold Arctic winter conditions is in agreement with estimates from previous algorithms such as the enhanced NASA Team. Distribution of multiyear ice concentration from ECICE is presented along with evolution of daily concentration of each ice type. Events of melt-refreeze, which are common during seasonal transition periods, cause misidentification of multiyear ice as first-year ice in the fall. The reverse is observed in the spring. This is a limitation on ice type identification. ECICE is an optimal approach that minimizes the error between observations and predicted concentrations. It provides a confidence measure associated with each ice concentration estimate. It is a generic algorithm, i.e. its applications are not limited to AMSR-E and QuikSCAT. Crown Copyright (C) 2012 Published by Elsevier Inc. All rights reserved.

关键词： Sea ice retrieval algorithms Ice concentration Arctic ice QuikSCAT AMSR-E Multiyear ice

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GCOM-W1 AMSR2 and MetOp-A ASCAT wind speeds for the extratropical cyclones over the North Atlantic

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REMOTE SENSING OF ENVIRONMENT 2014年 147卷 89-98页

作者： Zabolotskikh, Elizaveta Mitnik, Leonid Chapron, Bertrand State Hydrometeorol Univ Satellite Oceanog Lab St Petersburg 195196 Russia VI Ilichev Pacific Oceanol Inst Vladivostok 690041 Russia IFREMER Ctr Brest F-29280 Plouzane France

This study presents the results of the comparison between sea surface wind speed (SWS) estimates made by MetOp-A scatterometer ASCAT and GCOM-W1 Advanced Microwave Sounding Radiometer 2 (AMSR2) relating to winds developing in the extratropical cyclones (ECs) over the North Atlantic. One season of winter ECs of 2012-2013 is considered in which 33 most intensive ECs are selected for the study. ASCAT Level 2 operational coastal wind vector product is used for the comparison, whereas AMSR2 SWS values are calculated with newly developed algorithms. Two algorithms for SWS retrieval from AMSR2 are based on numerical simulation of AMSR2 brightness temperatures (T-B) over the oceans and their following inversion with Neural Networks. The first algorithm uses T-B measurements at higher frequency AMSR2 channels (HF algorithm), the second one uses T-B measurements at lower frequency channels (LF algorithm). It is demonstrated that both AMSR2 SWS estimates are highly correlated with ASCAT SWS for the range of low and moderate wind speeds which opens new potential for possible merging of active and passive microwave SWS products. It is shown also that LF AMSR2 algorithm overestimates ASCAT winds greater than 15 m/s. To support the comparison results SWS estimates by AMSR2 are validated against in-situ wind speed measurements from platform weather stations in the North Sea and Norwegian Sea, including high wind events. (C) 2014 Elsevier Inc. All rights reserved.

关键词： Active and passive sea surface wind speeds MetOp-A ASCAT GCOM-W1 AMSR2 retrieval algorithms Intercomparison Validation

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Aerosol retrievals over the ocean by use of channels 1 and 2 AVHRR data: sensitivity analysis and preliminary results

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APPLIED OPTICS 1999年第36期38卷 7325-7341页

作者： Mishchenko, MI Geogdzhayev, IV Cairns, B Rossow, WB Lacis, AA NASA Goddard Inst Space Studies New York NY 10025 USA Columbia Univ Dept Appl Phys & Appl Math New York NY 10025 USA

We outline the methodology of interpreting channels 1 and 2 Advanced Very High Resolution Radiometer (AVHRR) radiance data over the oceans and describe a detailed analysis of the sensitivity of monthly averages of retrieved aerosol parameters to the assumptions made in different retrieval algorithms. The analysis is based on using real AVHRR data and exploiting accurate numerical techniques for computing single and multiple scattering and spectral absorption of light in the vertically inhomogeneous atmosphere-ocean system. We show that two-channel algorithms can be expected to provide significantly more accurate and less biased retrievals of the aerosol optical thickness than one-channel algorithms and that imperfect cloud screening and calibration uncertainties are by far the largest sources of errors in the retrieved aerosol parameters. Both underestimating and overestimating aerosol absorption as well as the potentially strong variability of the real part of the aerosol refractive index may lead to regional and/or seasonal biases in optical-thickness retrievals. The Angstrom exponent appears to be the aerosol size characteristic that is least sensitive to the choice of aerosol model and should be retrieved along with optical thickness as the second aerosol parameter. (C) 1999 Optical Society of America OCIS codes: 010.1100, 010.1110, 010.1310, 010.7030.

关键词： .aerosol size Aerosol retrievals radiance data averages retrieved aerosol retrieval algorithms atmosphere–ocean one-channel ngstro exponent

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The development of new algorithms for remote sensing of snow conditions based on data from the catchment of vre Heimdalsvatn and the vicinity

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HYDROBIOLOGIA 2010年第1期642卷 35-46页

作者： Solberg, Rune Koren, Hans Amlien, Jostein Malnes, Eirik Schuler, Dagrun Vikhamar Orthe, Nils Kristian Norwegian Comp Ctr NR N-0314 Oslo Norway No Res Inst Norut N-9294 Tromso Norway Norwegian Meteorol Inst N-0313 Oslo Norway Norwegian Water Resources & Energy Directorate NVE N-0301 Oslo Norway

The catchment of vre Heimdalsvatn and the surrounding area was established as a site for snow remote sensing algorithm development, calibration and validation in 1997. Information on snow cover and snowmelt are important for understanding the timing and scale of many lake ecosystem processes. Field campaigns combined with data from airborne sensors and spaceborne high-resolution sensors have been used as reference data in experiments over many years. Several satellite sensors have been utilised in the development of new algorithms, including Terra MODIS and Envisat ASAR. The experiments have been motivated by operational prospects for snow hydrology, meteorology and climate monitoring by satellite-based remote sensing techniques. This has resulted in new time-series multi-sensor approaches for monitoring of snow cover area (SCA) and snow surface wetness (SSW). The idea was to analyse, on a daily basis, a time series of optical and radar satellite data in multi-sensor models. The SCA algorithm analyses each optical and synthetic aperture radar (SAR) image individually and combines them into a day product based on a set of confidence functions. The SSW algorithm combines information about the development of the snow surface temperature and the snow grain size (SGS) in a time-series analysis. The snow cover algorithm is being evaluated for application in a global climate monitoring system for snow variables. The successful development of these algorithms has led to operational applications of snow monitoring in Norway and Sweden, as well as enabling the prediction of the spring snowmelt flood and thus the initiation of many lake production processes.

关键词： Remote sensing retrieval algorithms Fractional snow cover Snow surface wetness Snow surface temperature

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Surface Meteorological Conditions and Boundary Layer Height Variations During an Air Pollution Episode in Nanjing, China

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JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 2019年第6期124卷 3350-3364页

作者： Yin, J. Gao, C. Y. Hong, J. Gao, Z. Li, Y. Li, X. Fan, S. Zhu, B. Nanjing Univ Informat Sci & Technol Sch Atmospher Phys Climate & Weather Disasters Collaborat Innovat Ct Key Lab Aerosol Cloud PrecipitatChina Meteorol A Nanjing Jiangsu Peoples R China Columbia Univ Dept Earth & Environm Sci New York NY USA Yonsei Univ Dept Atmospher Sci Seoul South Korea Chinese Acad Sci Inst Atmospher Phys State Key Lab Atmospher Boundary Layer Phys & Atm Beijing Peoples R China

The evolution of planetary boundary layer (PBL) was investigated using observations from a laser ceilometer, an eddy covariance system, and an automatic meteorological station in the north of Nanjing city during an air pollution episode in 2016-2017 winter. Based on 7-day observation under clean to polluted day, we recorded the temporal variations of backscatter signals observed by the ceilometer, and then intercompared the planetary boundary layer height (PBLH) retrieved from individual methods. The results show that backscatter signal gradient, standard deviation, and wavelet transform analysis methods generated similar PBLH values and PBL diurnal variation patterns. Moreover, the PBL structure varied diurnally, with distinct patterns corresponding to clean and polluted days. Based on these measurements, the relationships between PBLH, weather conditions, and contaminants were analyzed. Results show that on clean days, strong surface turbulence exchange makes the PBL fully developed and makes the PBLH increase sharply after sunrise, with a maximum of 1,483m;on polluted days, stable synoptic conditions and the weaker wind speeds facilitated the accumulation of air pollutants, leading to smaller net surface radiation and weaker turbulence. Consequently, these conditions during polluted days led to lower PBLH values, which were typically less than 900m.

关键词： planetary boundary layer height ceilometer retrieval algorithms air pollution Nanjing

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Evaluation of regression algorithms for estimating leaf area index and canopy water content from water stressed rice canopy reflectance

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Information Processing in Agriculture 2021年第2期8卷 284-298页

作者： Niranjan Panigrahi Bhabani Sankar Das Agricultural and Food Engineering Department Indian Institute of Technology KharagpurWest Bengal 721302India School of Water Energy and EnvironmentCranfield UniversityCranfield MK430ALUK

Optical remote sensing(RS)with robust algorithms is needed for accurate assessment of crop canopy *** intensive studies on algorithms,their performance using RS needs to be *** evaluated five different algorithms(partial-least-squares regression(PLSR),support vector regression(SVR),random forest regression(RFR),locally-weighted-PLSR(PLSRLW)and PLSR with feature selection(PLSRFS))for rapid assessment of leaf area index(LAI)and canopy water content(CWC)for rice canopies using canopy reflectance spectra over visible to short-wave infrared *** pooled datasets of LAI(600)and CWC(480)were collected from two replicated field experiments during 2014–15 and 2015–16 rice growing *** performance of each algorithm was evaluated using coefficient of determination(R^(2)).Results showed that PLSRLW performed more accurately than other algorithms with R^(2) values 0.77 and 0.66 for LAI and CWC,*** also used a bootstrapping approach to generate a kernel density estimator of root mean squared error values for each *** results suggested that the improvement in prediction accuracy of LAI and CWC can be achieved if a suitable algorithm is selected by assigning higher weights to calibration samples,which has similar canopy structure as the test *** of the canopy spectral data results large error values in test dataset,therefore the use of entire season canopy spectral data should be used for model calibration.

关键词： Rice canopy Reflectance spectroscopy Calibration retrieval algorithms Partial-least-squares regression

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Effective Scattering Albedo of Forests Retrieved by SMOS and a Three-Parameter Algorithm

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IEEE GEOSCIENCE AND REMOTE SENSING LETTERS 2017年第12期14卷 2260-2264页

作者： Vittucci, C. Ferrazzoli, P. Richaume, P. Kerr, Y. Tor Vergata Univ Rome Dipartimento Ingn Civile & Ingn Informat I-00133 Rome Italy Ctr Etud Spatiales BIOsphere F-31401 Toulouse France

This letter illustrates results obtained using brightness temperature data collected by the Soil Moisture and Ocean Salinity radiometer and a three-parameter algorithm, retrieving soil moisture, vegetation optical depth, and the effective albedo of vegetation. Four eight-day time intervals have been considered. Only areas with a forest cover higher than 90% have been selected. For tropical forests, the retrieved albedo is in a range 0.05-0.07 and tends to decrease with an increasing optical depth. For these forests, the results are scarcely influenced by seasonal variations. For boreal forests of North America, the range of retrieved albedo is again 0.05-0.07 in July, but lower values are found in November for needleleaf forests of Canada and Northern U.S. For forests with higher optical depth, retrieved values of effective albedo show a lower spread.

关键词： Forests microwave radiometry retrieval algorithms

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How Many Parameters Can Be Maximally Estimated From a Set of Measurements?

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IEEE GEOSCIENCE AND REMOTE SENSING LETTERS 2015年第5期12卷 1081-1085页

作者： Konings, Alexandra G. McColl, Kaighin A. Piles, Maria Entekhabi, Dara MIT Dept Civil & Environm Engn Cambridge MA 02139 USA Univ Politecn Cataluna Dept Teoria Senyal & Comunicac Remote Sensing Lab ES-08034 Barcelona Spain SMOS Barcelona Expert Ctr Barcelona 08003 Spain

Remote sensing algorithms often invert multiple measurements simultaneously to retrieve a group of geophysical parameters. In order to create a robust retrieval algorithm, it is necessary to ensure that there are more unique measurements than parameters to be retrieved. If this is not the case, the inversion might have multiple solutions and be sensitive to noise. In this letter, we introduce a methodology to calculate the number of (possibly fractional) "degrees of information" in a set of measurements, representing the number of parameters that can be retrieved robustly from that set. Since different measurements may not be mutually independent, the amount of duplicate information is calculated using the information-theoretic concept of total correlation (a generalization of mutual information). The total correlation is sensitive to the full distribution of each measurement and therefore accounts for duplicate information even if multiple measurements are related only partially and nonlinearly. The method is illustrated using several examples, and applications to a variety of sensor types are discussed.

关键词： Algorithm design mutual information retrieval algorithms total correlation

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