ISSN:0143-1161    

DOI:10.1080/01431169308954020

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The Total Ozone Mapping Spectrometer (TOMS) on the Nimbus-7 satellite has been measuring the total column amount of ozone over the globe for more than 13 years. Recent findings from TOMS data suggest that just north of 40° N the winter trend shows an annual ozone depletion rate of just over —0-8 per cent per year. This paper reports trends derived from the TOMS reprocessed total ozone data for the case of Athens (38° N 24° E) from January 1979 to January 1992. The total depletion over the 13 year period shows a strong seasonal variation from more than 7 per cent in winter and early spring to about 2-5 per cent in summer. These trends are twice as large as expected from models.

ISSN:0143-1161    

DOI:10.1080/01431169308954021

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

This work describes spectral characteristics of fire scars in an area of intense deforestation in the Amazon tropical forest as recorded in the seven Landsat-5 TM spectral channels of an image in 1985. Ground covers were divided into four themes: natural forests, ‘capoeiras’, pastures in general and fire scars. Single-cell and maximum likelihood classification algorithms were used in the analysis. TM channel 4 was the best to identify fire scars, with digital counts differences in relation to other themes about two times higher than in other channels. Fire scars were also detected in channel 5, with the limitation that recent scars could be mistaken with water. Channels 3 and 7 also contained information about the scars. Results indicated that TM images can be used in automatic detection and assessment of biomass burning in tropical forests, contributing to the understanding of biogeochemical cycles related to the use of fire in these areas. Comparison of the results for channels 3, 4 and 5 in two more TM scenes in 1987 and 1989, showed that minor variations occurred in the spectral definition of the themes, mainly as a result of atmospheric pollution from biomass burning.

ISSN:0143-1161    

DOI:10.1080/01431169308954022

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Les enregistrements dans I'infrarouge moyen fournis par la bande 3 du senseur Advanced Very High Resolution Radiometer (AVHRR) sont utilisés, entre autre, pour la detection et la surveillance des feux en zone intertropicale. La méthode consiste à détecter les ‘points chauds’ provoquant une saturation du capteur. Certains travaux ont cependant montré que I'effet de saturation pouvail etre provoqué par des états de la surface sans lien direct avec des feux actifs.

ISSN:0143-1161    

DOI:10.1080/01431169308954023

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Development of a first-order radiative transfer model for predicting backscatter from tree canopies has been underway at the University of Michigan Radiation Laboratory for some time. This model is known as the Michigan Microwave Canopy Scattering (MIMICS) model. The first-generation model, MIMICS I, was developed for canopies with continuous (closed) crown layers and its validity has been verified in several modelling analyses. This article presents the second-generation MIMICS model (MIMICS II) which accounts for canopies with discontinuous (open) crown layer geometries. MIMICS II models open crown layers by treating the location, size and shape of the individual tree crowns as random variables. The backscattering coefficients for the canopy are then determined by introducing statistics derived from these parameters into the radiative transfer solution.

ISSN:0143-1161    

DOI:10.1080/01431169308954024

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The aim of the study was to establish remote sensing models for the estimation of canopy cover in Acacia woodlands. The models were established using Landsat-TM and MSS data and SPOT HRV XS data and based on field data from eastern Sudan. The models were derived using the Reduced Major Axis (RMA) method. Correlation coefficients between NDVI and canopy cover are for Landsat-TM 0-552, for Landsat-MSS 0-698 and for SPOT HRV XS 0-718. The confidence intervals of predicted canopy cover are also presented.

ISSN:0143-1161    

DOI:10.1080/01431169308954025

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

This article describes research related to sampling techniques for establishing linear relations between land surface parameters and remotely-sensed data. Predictive relations are estimated between percentage tree cover in a savanna environment and a normalized difference vegetation index (NDVI) derived from the Thematic Mapper sensor. Spatial autocorrelation in original measurements and regression residuals is examined using semi-variogram analysis at several spatial resolutions. Sampling schemes are then tested to examine the effects of autocorrelation on predictive linear models in cases of small sample sizes. Regression models between image and ground data are affected by the spatial resolution of analysis. Reducing the influence of spatial autocorrelation by enforcing minimum distances between samples may also improve empirical models which relate ground parameters to satellite data.

ISSN:0143-1161    

DOI:10.1080/01431169308954026

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Within the tropics, due to high cloud cover, vegetation monitoring can only be achieved by using both visible and microwave spaceborne data. In the present study, Shuttle Imaging Radar (SIR-B) data and SPOT data acquired over central Sumatra are used in a supervised classification of vegetation. Emphasis is put on SAR data utilization. Assessment of SAR data potentialities is carried out by using (1) SIR-B imagery alone, and (2) combined SJR-B and SPOT data. The article describes the methodology developed for exploiting the SIR-B image including raw data analysis, image filtering and image classification. Finally, combined filtered SIR-B imagery and SPOT data are used jointly in a supervised classification leading to a better discrimination of surface units. These results indicate the unique capabilities of combined visible and SAR data for monitoring tropical vegetation, especially for forest/non-forest discrimination.

ISSN:0143-1161    

DOI:10.1080/01431169308954027

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

This article concerns the self-similarity of sea surface temperature (SST) patterns. This study is based upon analysis of the NOAA AVHRR infrared images of the northern Japan Sea from April 1990. Calculations of isotherms lengths provide experimental evidence of the fractal properties of the SST patterns as tracers of the sea mesoscale turbulence. The isotherms fractal dimension is found to be 1.27 ± 0.07 for space scales from at least 4 km to approximately 120 km. This value is in complete agreement with that of drifting buoys trajectories in the Kuroshio extension. Estimation of sequences of the mass exponents shows that the sea surface temperature patterns exhibit monofractal rather than multifractal behaviour. Consideration of the series of the NOAA AVHRR infrared images reveals self-similar turbulent structures—the chains of vortices consisting of vortex pairs and anticyclonic eddies. Such hierarchies of these vortices, whose horizontal size grows from several kilometers to approximately 100 km, exist for at least 20 days. Their evolution and possible mechanism of formation are discussed.

ISSN:0143-1161    

DOI:10.1080/01431169308954028

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The first ERS-1 C-band SAR image of the western coast of Norway was received at Troms∅ Satellite Station, Norway, on 21 August 1991. It depicts clearly an eddy-like structure located in the coastal water. The eddy has a cyclonic spiral structure with a diameter of about 5 km. The expressions of the dark lines outlining the spiral are probably caused by the presence of natural surface slicks resulting in a damping of the Bragg scattering waves. Eddies at this particular location with the same spatial characteristics are also detected in simulations with a nonlinear, one-layer active reduced gravity model. From the model results we conclude that the eddy is formed by horizontal current shear instability associated with variations in the larger scale coastal current. A second case of an observed and simulated eddy occurred later in the Outer Oslofjord. The simultaneous observations and simulations of these eddies clearly demonstrate the potential advantage in integrated use of weather independent SA R data and model results for the monitoring and modelling of mesoscale circulation processes.

ISSN:0143-1161    

DOI:10.1080/01431169308954029

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor