ISSN:0143-1161    

DOI:10.1080/01431168808954858

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Reported in this article are research results pertaining to an assessment of remote sensing and image processing technology for supplying useful information to numerical models which derive estimates of a hydrodynamic surface flow field. The role of remote sensing and image processing in this research is to provide time-sequential tracer distribution information over a water surface which is used as input to the flow estimating numerical model. Technical and scientific considerations concerning remote sensing tracers, platforms and sensors, as well as image processing procedures involving atmospheric corrections, geometric/radiometric processing and spatial aggregation are discussed. Results from the remote sensing/image processing component of this multidisciplinary exploratory research are encouraging, suggesting that remote sensing methods are at this time technologically (if not operationally) appropriate for supplying hydrodynamic tracer data useful for estimating spatially contiguous surface flow fields.

ISSN:0143-1161    

DOI:10.1080/01431168808954859

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The unified full-wave solution for electromagnetic wave scatter from a rough surface is expressed as an integral similar in form to physical optics solutions. However it correctly predicts return for small and intermediate roughness scales where the physical optics approach fails. This full-wave solution is used here to evaluate microwave sea surface backscatter at normal incidence for both the like-and cross-polarized linear components. Surface heights and slopes are assumed to be Gaussian, the sea is characterized by its surface height spectral density function and both perfectly and finitely conducting surfaces are considered. Results from this complete full-wave evaluation are compared with approximations, involving single-scale (specular point) and two-scale models. For both of these models, however, it is necessary to assume a spectral wavenumber, νd, where spectral splitting between the large and the small scales of the rough surface occurs. The full-wave solution is used as a guide in the selection of νdand to study the accuracy and sensitivity of the different approximations to νd. It is also shown that results for cross-polarized backscatter based on the physical optics or two-scale models are totally inadequate.

ISSN:0143-1161    

DOI:10.1080/01431168808954860

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Landsat multispectral scanner (MSS) data for 27 dates between January 1983 and June 1985 for Moon Lake in Coahoma County, Mississippi, were analysed to determine if Landsat MSS digital data could be used to estimate suspended sediment concentrations in the surface waters of a small agricultural lake. Field measurements of suspended sediment concentration in the surface water and other water quality variables were available for five locations in Moon Lake within 0 to 13 days of each of the 27 Landsat overpass dates. Pixel values, radiance and reflectance measurements from Landsat MSS data from 14 scenes were compared with field data and used to develop simple and multiple regression equations to estimate suspended sediment concentration in the surface water of the lake. The best equations were used to estimate the suspended sediment concentrations for the 13 other Landsat scenes. The coefficient of determination for the relationship between measured and estimated suspended sediment concentrations was greater than 0·80 and the root mean square error was less than 40 mg l−1when equations using either the radiance and reflectance data were used to estimate suspended sediment concentrations. This study shows that good estimates of suspended sediment concentrations can be made using Landsat MSS data especially in the range of concentrations between 50 and 250mg l−1which are the critical concentrations for assessing conservation needs. Suspended sediment concentrations greater than 250mg l−1were underestimated by most of the equations indicating a saturation of reflected solar radiation at higher suspended sediment concentrations. Thus a technique using Landsat MSS digital data can be developed to monitor the landscape to locate those reservoirs with critical suspended sediment concentrations quickly. Soil and water conservation efforts can then be concentrated on the watershed of those reservoirs where suspended sediment is greatest.

ISSN:0143-1161    

DOI:10.1080/01431168808954861

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Tropical seas are major sites for extensive cyanobacterial ( = blue-green algal) developments. The oceanic nitrogen fixation caused by such blooms may be of relatively great importance in regard to the global nitrogen budget. A Nimbus-7 Coastal Zone Colour Scanner (CZCS) image on 4 January 1982 shows a large phytoplankton bloom (90000 km2) around New Caledonia and the Vanuatu archipelago, located east of Australia in the Coral Sea (165° E, 20° S). The bloom is caused by cyanobacteria, presumably Oscillatoria (=Trichodesmium) spp. which occur systematically in this region. This assertion was not controlled by simultaneous sea-truths, but several indices and current knowledge of the region indicate that our hypothesis is reasonable. By using the CZCS image, an estimation is made for the nitrogen fixation of the bloom. It suggests that such a biological event plays a significant role in the global nitrogen oceanic budget.

ISSN:0143-1161    

DOI:10.1080/01431168808954862

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Spectral data (gathered using a hand-held radiometer) and harvest data were collected from four salt marsh vegetation types in Brittany, France, to develop equations predicting live aerial biomass from spectral measurements. Remote sensing estimates of biomass of the general salt marsh community (GSM) and of Spartina alternifiora can be obtained throughout the growing season if separate biomass prediction equations are formulated for different species mixtures (for the GSM) and for different canopy types (for S. alternifiora). Results suggest that remote sensing will not be useful for predicting Halimione portulacoides biomass, but can be used to estimate Puccinellia maritima biomass early in the growing season.

ISSN:0143-1161    

DOI:10.1080/01431168808954863

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The northern region of Baffin Bay (74°-79° N and 70°-78° W) is known as the North Water Polynya—a region of inhomogeneous ice cover during the winter and spring months. During the winters of 1978/79 and 1980/81, a series of low-level aircraft flights were conducted over the North Water covering a length of 2300 km. Surface thermal infrared (TIR) temperatures were measured and visual surface ice characteristics photographed with the aid of a searchlight attached to the aircraft. Corrections procedures were applied to the TIR data which produced a temperature accuracy of ± 0·15°C. A matching was made between visual ice types and ice surface temperatures along with ice properties using the aircraft and ice/meteorological data collected at a base station near Resolute Bay, Northwest Territories. Also, surface temperatures outside the spatial extent of the aircraft measurements were extrapolated by means of NOAA-VHRR TIR imagery. From the two sets of data, regional surface temperature maps were constructed. Results indicated that grey-white ice for thicknesses of 0·15-0·3 m was the dominant type of ice especially during January and Feburary with a marked increase of white ice percentage towards the end of the ice season. Ice-free areas or warm water actually constituted only a very small percentage of the total area for both winter seasons.

ISSN:0143-1161    

DOI:10.1080/01431168808954864

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Operational sea surface temperature (SST) monitoring was tested with the study of large-scale SST features in Indonesia from July 1981 to June 1985. Digital data were provided by digitizing 208 weekly SST charts of NOAA-NESS. The pixel size corresponded to 1 ° 15' longitude and latitude. These data displayed a 0·5 deg K. r.m.s. error compared with 1985in situmeasurements. Iterative interactive factorial analyses combined with a parallelepiped classifier as a clustering technique enhanced the SST spatio-temporal features. The study area was divided into zones in which pixels had similar SST profiles and dates of occurrence of thermal anomalies were pointed out. Sea fronts and upwellings were mapped through spatio-temporal analyses of thermal gradients. This study stresses the possibility of operational SST monitoring for Indonesia, allowing simple data manipulation with hardware easily maintained locally.

ISSN:0143-1161    

DOI:10.1080/01431168808954865

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The surface current in the spring of 1984 off the west coast of Ireland has been mapped from NOAA-8 thermal infrared images. The “feature-tracking method” has been used to derive flow vectors from advective sea surface temperature feature displacements and elapsed time. This feature-tracking method has a great advantage which gives a synoptic and spatial view of the velocity distribution over in situ measurements. Sequential images obtained on orbits 5596, 5610 and 5627 during the period 25-27 April 1984 have been used and geometrically corrected. With the 24 hours and 48 hours differences, the measurement accuracy achieved in the speed of sea features was ±1 8cm/s. The surface current pattern agrees with the main current pattern obtained by ships and drift bottles. A cyclonic eddy centred at 57° 04′ N 10° 59′ W has been studied. A very pronounced feature recognized is the sea surface front between mixed coastal water and stratified Atlantic water along the whole west coast of Ireland. The front is characterized by cyclonic and anticyclonic eddies which have time scales of the order of 1 day to 7 days and length scales of the order of 30 km.

ISSN:0143-1161    

DOI:10.1080/01431168808954866

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Several methods of deriving Arctic cloud information, primarily from satellite imagery, have been intercompared. The comparisons help in establishing what cloud information is most readily determined in polar regions from satellite data analysis. The analyses for spring-summer conditions show broad agreement, but subjective errors affecting some geographical areas and cloud types are apparent. The results suggest that visible and thermal infrared data may be insufficient for adequate cloud mapping over some Arctic surfaces.

ISSN:0143-1161    

DOI:10.1080/01431168808954867

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor