Comparison between CZCS data from 10 July 1979 and simultaneous in situ measurements for south-eastern Scottish waters

Abstract

This paper presents an analysis of coastal zone colour scanner (CZCS) data for a date for which simultaneous in situ measurements exist.Using CZCS data of 10 July 1979 for the vicinity of Dundee, the inflight slope and intercept for all spectral bands were calculated. Comparison of these results with the pre-flight values show that the deviations of the inflight slopes from the pre-flight slopes for the visible bands are within II per cent, whereas the deviations in the intercepts are found to be rather larger. The contribution to the satellite-recorded radiance from the atmospheric interplay was removed using Sturm's atmospheric correction method which incorporates the iteration procedure described by Smith and Wilson.Many algorithms have been used for comparing the upwelling radiance with the in situ chlorophyll-like pigment concentrations. Although, some of the algorithms gave good correlation coefficients, the constants in the algorithms used turn out to be quite different from the values which have been obtained by other investigators. We have also computed the sea-surface temperatures from the infrared band data and the inflight calibration constants, but no atmospheric correction was applied to the infrared band data.We have used NASA's.chlorophyll algorithms (with given parameters), one for low chlorophyll concentrations and the other for high chlorophyll concentrations for calculating the chlorophyll concentrations for those pixels within which the in situ measurements were made. The low-chlorophyll algorithm gives the chlorophyll concentrations which are smaller by a factor of about 4 than the in situ data. The results obtained from the high-chlorophyll concentration algorithm are within a factor of about 2 of the measured values.The error in the determination of chlorophyll-like pigment concentrations from the CZCS data due to factors hitherto ignored in practice by other workers is shown to be as large as the error due to the inherent signal-to-noise ratio. The factors considered here are (a) the wavelength dependence of the refractive index of seawater, (b) the variation in the temperature and salinity of seawater and (c) the choice of different values of the refractive index of seawater by individual investigators. The results are presented in such a manner that an investigator having no in situ data can estimate the errors due to these factors in the chlorophyll-like pigment concentrations computed from the CZCS data alone.We have also investigated the effect of the revised values of the solar irradiances on the chlorophyll-like pigment algorithm and we recommend that all those algorithms which are based on the original values of the solar irradiances must be revised using the new recommended values of the solar irradiances. If this is not done then the error in the derived product is shown to be about 169 per cent. Downloaded by [Massachusetts Institute of Technology] at 10:05 26 November 2014 756 S. M. Singh et al.

Satellite ocean color algorithms: A review of applications to the Great Lakes

“…Intended as a proof-of-concept instrument, the CZCS operated from October 1978 through June 1986 when the sensor failed. Although many studies used the data collected in the 91-month life of the system to examine the distribution of phytoplankton in the oceans (Gordon et al, 1983;Singh et al, 1983;Pan et al, 1988) no similar applications were done in the Great Lakes, probably because of problems with the atmospheric correction algorithm (Tanis, 1984). A major result of the CZCS mission was the conclusion that although it was a successful proof-of-concept experiment, uncertainties in the quality of the radiometric data indicated that future ocean color sensors needed to be more stable and have more reliable radiometric calibrations (Evans and Gordon, 1994).…”

The marine environment

“…(See, for example, Morel 1980, Viollier er a/. 1980, Sturm 1981, Singh et a/. 1983, Viollier and Sturm 1984, Robinson 1983.…”

Εκτίμηση παραμέτρων του παράκτιου οικοσυστήματος (συγκέντρωση χλωροφύλλης-α διαφάνεια του νερού θερμοκρασία της επιφάνειας της θάλασσας) της ανατολικής Λέσβου από δορυφορικές εικόνες landsat- tm

“…Με κατάλληλες μεθόδους επεξεργασίας των δορυφορικών δεδομένων επιτυγχάνεται η μέτρηση διαφόρων θαλάσσιων παραμέτρων (Manikiam 1989). Μέχρι σήμερα έχει αναπτυχθεί σε αρκετά μεγάλο βαθμό η χρήση δορυφορικών δεδομένων στην ωκεανογραφία (Gower 1981, Cracknell 1983, Robinson 1985, Maul 1985, Stewart 1985, Geraci 1991, Robinson 1994, Bucata et al 1995, Gorgon 1998, Kondratyev et al 1998, και η έρευνα συνεχίζεται με αποτέλεσμα να βελτιώνονται συνεχώς οι τεχνικές μέτρησης και η ακρίβεια των αποτελεσμάτων.…”

“…Περισσότερες λεπτομέρειες για τις παραμέτρους που μπορούν να μετρηθούν από δορυφορικούς δέκτες αναφέρονται και στους Gower 1981, Cracknell 1983, Robinson 1985, Stewart 1985, Saltzman 1985, Maul 1986, Robinson 1994. Μία αναδρομή στην βιβλιογραφία σχετικά με τις παραμέτρους του θαλασσίου περιβάλλοντος που μπορούν να μετρηθούν με τηλεπισκοπικές τεχνικές, με έμφαση στους παθητικούς δέκτες έγινε και από τους Γαζή & Χατζόπουλο 1990.…”