摘要:

We use snow surface temperatures obtained from thermal infrared (TIR) satellite imagery, together with radiosonde profiles of free-air temperature and high-resolution topographic data to study the thermal structure of the atmospheric boundary layer in a coastal region ofEast Antarctica. Surface temperatures over a coastal ice shelf are shown to be significantly lower than those observed on the lower part of the adjoining coastal slopes as a result of the strong surface temperature inversion that forms over the ice shelf. Between 400 and 1500 m elevation the surface temperature lapse rate is close to the dry adiabatic value while the free-air temperature profile is significantly stable over this height range. We argue that this implies that the strength of the surface inversion increases with increasing elevation. Above 1500 m the surface temperature lapse rate becomes significantly superadiabatic and the coldest surface temperatures are found a few 10s of kilometres inland of the highest topography. The technique may prove useful for studying boundary layer structure in other regions of Antarctica where suitable high-resolution topographic data are available.

ISSN:0143-1161    

DOI:10.1080/014311698214028

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A laboratory experiment was conducted to determine the spectral characteristics of different types of sediment under suspension in water and to select an optimal wavelength for the quantification of suspended sediment concentration and secchi depth (water clarity) in the Tawa reservoir, using the Indian Remote Sensing Satellite-1A Linear Imaging Self Scanning Scanner-I (IRS-1A LISS-I) data. It was noted that the correlation between suspended sediment concentration and reflected radiance varied with colour, mineral composition of sediment and grain size. The clay minerals of low specific gravity had a larger value of reflected radiance than those from high specific gravity non-clay minerals. The laboratory results indicated that an algorithm to quantify suspended sediment concentration and secchi depth in the reservoir can be developed from reflected radiance received by the satellite. For this purpose the Tawa reservoir on the Tawa river of the Narmada basin in Central India was selected. Tawa reservoir water samples were collected on 20 October, 1988 concurrent with an IRS-1A overpass. The secchi depth, pH, and conductivity measurements were made at all the sampling points. The samples were analysed to determine the concentration of total suspended matter, grain size and mineralogy. A positive functional relation exists between the concentration of suspended solids and the visible wavelength bands 1, 2 and 3 (0.45 to 0.68 mu m). On the other hand, the secchi depth of water increases with the decrease in reflected radiance. It has been observed that concentration, mineralogy and grain size of the suspended solids are the main factors which influence the reflected radiance.

ISSN:0143-1161    

DOI:10.1080/014311698214037

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Quality controlled wind speed observations from merchant ships have been compared with ERS-1 scatterometer data. The ship and satellite wind speed pairs were well correlated at 120 km separation in the open ocean, reducing to 40 km in the North Sea. The maximum allowed separation of ship and scatterometer wind speed pairs had to be further reduced to 20 km in the North Sea to avoid matching of coastal ship wind speed data with scatterometer data from more exposed regions. Spurious biases in the comparisons were caused by the error variability of the scatterometer data (0.5 m s-1) being significantly less than that for the ships (2.0 m s-1). The unbiased regression was: U10n(ship)=1.025 U10n(satellite)+0.255 No significant enhancement of the scatterometer wind speeds occurred in the coastal region.

ISSN:0143-1161    

DOI:10.1080/014311698214046

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

An original scheme to detect shoreline changes using multi-temporal satellite images and tidal measurements is presented here. First, the basic idea behind this investigation is to reconstruct a reference digital terrain model (DTM) for tideland areas from a set of SPOT satellite images sampled over a short period. Each image corresponds to a tidal measurement. Then, the shoreline, as interpreted from a historical satellite image, is compared with one traced from the reference DTM, according to the associated tidal elevations. Experimental results indicate that the area error of the test sand barriers ranges between 7.6% and 12.5%.

ISSN:0143-1161    

DOI:10.1080/014311698214055

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This paper presents applications of Synthetic Aperture Radar (SAR) image classification using morphological texture features. The texture features are based on morphological residues of opening and closing by reconstruction. It is shown that this set of features shows high 'robustness' to speckle perturbation in SAR images compared with those derived from traditionalmorphological residues. An algorithm based on estimating the divergence between and within classes was constructed in order to search for a discriminating feature subset. Higher classification accuracy was obtained by the optimized feature subset than by using other feature subsets derived from some well known texture characterization approaches. The classification accuracy was continuously improved by the introduction of post-processing filtering.

ISSN:0143-1161    

DOI:10.1080/014311698214064

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In crop production estimation using remotely sensed data, it is necessary to estimate the crop area and its yeild per unitarea in a particular administrative division. Two approaches were adopted: (1) the target image of the study area was cut with the administrative boundary, land cover/use classification was processed and crop identification and area calculation were carried out, (2) land cover/use classification was carried out first and then the study area was cut from the image with administrative boundary, and area was estimated. We call these two methods strategy A (cut and classify) and strategy B (classify and cut), respectively. In this paper, the two strategies were applied to rice crop area estimation. The results indicate that strategy B is better than strategy A in the unsupervized classification-cluster process and the rice crop area was estimated with an accuracy over 81% for semi-late rice and 90% for early rice.

ISSN:0143-1161    

DOI:10.1080/014311698214073

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0143-1161    

DOI:10.1080/014311698214082

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Maximum likelihood classification (MLC) is compared with unsupervised classification (USC) for operational cover mapping from airborne imagery. Data from the Compact Airborne Spectrographic Imager (CASI) were clustered into a large number of unsupervised subclasses then amalgamated into target classes. For extensive operational classification of coastal imagery, USC proved an acceptable alternative to MLC due to the wide spectral variation between surface classes. However, for river corridors containing a variety of vegetated surfaces with similar reflectances, USC did not produce consistent results.

ISSN:0143-1161    

DOI:10.1080/014311698214091

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A methodology is described for detecting and classifying burned forests in Amazonia. Linear mixture models using three image endmembers (vegetation, soil, shade) were used to separate forest from non-forest. Forested areas were unmixed using vegetation, non-photosynthetic vegetation (NPV) and shade endmembers and reclassified as unburned, recently burned and older burned forests. The NPV fraction provided the greatest separability of the forest classes and has potential for subclassification of burned areas into damage classes. For 184 km2 of burned forest, a conservative estimate of 9% (22 metric tons ha-1) of living biomass was lost due to forest fires between 1991-1993.

ISSN:0143-1161    

DOI:10.1080/014311698214109

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

There is a need for a consistent time-series of NDVI data for vegetation monitoring in Africa. In this work, we explore the compatibility of the FAOARTEMIS and NASA Pathfinder AVHRR Land NDVI archives. Values from the two archives were found to be significantly and systematically different even for the recently corrected form of the Pathfinder archive. Differences are attributable to the different processing chains used on essentially the same raw data. The two archives should not be mixed together for time-series analysis of NDVI, without correction. Although differences varied for periods of the record covered by different satellites, these were practically small and we present a single linear relation to correct one series values to the same basis as the other.

ISSN:0143-1161    

DOI:10.1080/014311698214118

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor