摘要:

Computation of phytoplankton pigment concentrations from the radiances received by the coastal zone color scanner (CZCS) is a complicated process. Water-leaving radiance, a small portion of the total signal, controls the pigment content, but fully 80–90 per cent of the total radiance is due to Rayleigh and aerosol scattering. These effects must be accurately modelled if reasonable pigment concentrations are to be computed. Rayleigh radiance is relatively easy to determine from either single or multiple scattering algorithms. Several examples of the effects of single versus multiple Rayleigh scattering on pigment content are given. The aerosol component varies both spatially and temporally and is poorly determined. Historically, the ratios of aerosol radiance in channels 1–3 to that in channel 4 have been assumed to be constant for an entire image. The proportionality constants are found by assuming values of water-leaving radiance for low pigment waters and theoretically should be independent of aerosol magnitude. However, a single ratio often is not representative of an entire image and a strong correlation may exist between aerosol magnitude and the aerosol ratio, especially when Rayleigh radiance is computed from multiple-scattering theory. These variations can produce large differences in derived pigment concentration. Hence aerosol ratios generally may not be reliable estimates of aerosol radiance. These considerations must be addressed before accurate pigment concentrations can be obtained from an arbitrary CZCS image.

ISSN:0143-1161    

DOI:10.1080/01431169108929637

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0143-1161    

DOI:10.1080/01431169108929641

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The effects of the addition of sediments on the upwelling radiance from pure algal cultures is examined. Upwelling reflectance signatures for both algae and suspended sediments are determined by the reflectance of the particles themselves, as well as absorbance by the water surrounding the particles. The addition of sediments to pure cultures of algae increased the reflectance at wavelengths longer than 550 nm. This effect was equal for wavelengths longer than 600 nm and subtraction of reflectance at 660–720 nm is suggested as a means of compensating for these effects.

ISSN:0143-1161    

DOI:10.1080/01431169108929642

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A system is described, for the on-line retrieval of information about satellite overpasses recorded at the Natural Environment Research Council (NERC) Satellite Receiving Station at the University of Dundee.

ISSN:0143-1161    

DOI:10.1080/01431169108929643

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The local observing time of the sensor on National Oceanic and Atmospheric Administration (NOAA) satellites is discussed and a strategy is recommended for maintaining relatively constant time of afternoon observations by the Advanced Very High Resolution Radiometer (AVHRR) over the satellite lifetime. The NOAA current orbital strategy is shown to be very conservative and a re-examination of the problem is recommended.

ISSN:0143-1161    

DOI:10.1080/01431169108929644

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Aircraft synthetic aperture radar (SAR) measurements from seven flight paths at two different altitudes were acquired over a tri-modal ocean wave system off the coast of Norway on 11 March 1988. These three-wave systems travelling in different directions were also measured by a directional buoy with the buoy spectra rotated into the radar coordinates for comparison with SAR spectra. Fifteen subspectra were averaged to obtain the measured SAR spectra and sixteen spectral bands were averaged to obtain the measured buoy spectra. The seven flight paths in conjunction with the three wave systems resulted in a nearly uniform distribution, of azimuth peak directions varying from 0° to 83° and R/Vvarying from 28 to 110 s. The SAR spectra derived and buoy peak wavelength and direction comparison show the expected variation, however some scatter and bias are present. The r.m.s. scatter was about 10 per cent or less for the peak wavelength and 10° or less for the peak direction. We consider the scatter as primarily due to the statistical uncertainty in the spectral estimates, the wave-number resolution and differences in the temporal and spatial averaging.

ISSN:0143-1161    

DOI:10.1080/01431169108929645

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

This is the first attempt to test the results of wind-induced current modelling for the northern Adriatic (Kuzmić and Orlić 1987) using space-borne Coastal Zone Colour Scanner (CZCS) data. In particular, new remotely sensed empirical evidence has been sought for the previously studied effect of the spatially heterogeneous bura (gusty, katabatic wind of north-easterly direction) by observing changes in spectral reflectance of the northern Adriatic waters. To that end, an existing hydrodynamical model has been extended to include a simple two-dimensional random walk dispersion model. The CZCS measured radiance has been processed to estimate pigment concentration. Remotely sensed data corroborate mathematical model findings. Comparison of model-generated and sensor-collected information strongly suggests that bura-induced gyre is the mechanism responsible for particular spatial pattern change observed in the CZCS detected radiance and estimated pigment concentration.

ISSN:0143-1161    

DOI:10.1080/01431169108929646

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A laboratory study was used to determine the form of the relationship between the suspended sediment concentration (SSC) and the spectral reflectance (Rλ). It was hypothesized that when the SSC was high the relationship would belog-linearat short,visiblewavelengths (where only a small portion of the radiation would be absorbed by water and the reflectance asymptote would be reached at low levels of SSC) andlinearat long,near-infraredwavelengths (where a large portion of the radiation would be absorbed by water and the reflectance asymptote would be reached at high levels of SSC). The data comprised spectral reflectance recorded in 875 wavebands from 350 to 2500 nm for eighteen sediment type/grain size samples, each at up to thirty SSC concentrations over a range of 0 to 1300 mg I−1. The strong relationship between SSC and Rλwas, as hypothesized, log-linear for wavelengths from 450 to 700 nm and linear from 700 to 1050 nm. The applicability of this information was illustrated in relation to the collection of data by the Daedalus 1268 multispectral scanner. It was recommended that in situations where a limited number of SSC measurements is available for the calibration of the SSC/Rλrelationship, a log-linear relationship be assumed for wavebands 1 to 5 and a linear relationship for wavebands 6 to 8.

ISSN:0143-1161    

DOI:10.1080/01431169108929647

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The results of drought stress on a crop of soybean have been observed using laser-induced fluorescence kinetics of individual leaves in two wavelength bands. Thisin vivochlorophyll fluorescence is particularly useful for early stress detection in plants recorded in the field. In the context of remote sensing, measurements on leaves sampled from different levels in the canopy and a mathematical simulation have shown the importance of the ratio of fluorescence peaks in the wavelength bands 690 and 730 nm. This index is not very sensitive to the leaf area and structure of the vegetation.

ISSN:0143-1161    

DOI:10.1080/01431169108929648

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor