Mirosław Darecki, Piotr Kowalczuk, Sławomir Sagan
Institute of Oceanology, Polish Academy of Sciences, Sopot

Adam Krężel
Institute of Oceanography, Gdansk University, Gdynia

Clorophyll vs AVHRR satellite data during Skagex Experiment.
Studia i Matriały Oceanologiczne 1993, No.64 pp. 49-59.

Keywords: Skagerrak, AVHRR data, Surface chlorophyll concetration, Beam attenuation. Manuscript received November 17, 1992, in final form October 1, 1993.

During Skagex Experiment (May 1990) measurements of hydrophysical, optical, chemical and biological (including chlorophyll a concentration) parameters were carried out simultaneously by several ships covering the Skagerrak area. The mesurements were synchronized with with NOAA satellite passes. The satellite data in red and near-IR light (1st and 2nd channels of AVHRR) were processed and compared with chlorophyll content.

The results show that at least qualitative desription of some spatial structures is possible. However, there is lack of theoretical premises for using the AVHRR's channels 1 and 2 for detection of optical parameters of relatively clean sea waters ( CS < mg m-3, suspended matter < 3 mg dm-3). Therefore, it seems that further development of processing algorithms is a promising line of research.

Mirosław Darecki, Jerzy Olszewski, Piotr Kowalczuk
Institute of Oceanology, Polish Academy of Sciences, Sopot

A preliminary study of the spectral characteristics of the upward radiance field in the surface layer of the Baltic. An empirical algorithm for the remote detection of chlorophyll conentration.
Studia i Matriały Oceanologiczne 1995, No.68 pp. 27-49.

Keywords: Apparent optical properties, Spectral reflectance, Remote Sensing, Chlorophyll a Manuscript received April 18, 1994, in final form Novenber 5, 1995.

The first results of experimental research into the relation between the diffuse reflectance spectra of seawater and the concentration of chlorophyll and total suspended matter in the surface layer are presented. The measurements were conducted in the southern Baltic during summer 1992 and spring and autumn 1993. The results allowed preliminary classification of these waters into two basic groups, which differ from each other in the maximum reflectance and in the concentration ranges of total suspended matter. Each of the basic groups can be divided into two sub-groups, differing in shape of the reflectace spectrum (defining the water colour), chlorophyll concetration and the level of correlation between concetrations of chlorophyll and total suspended matter.

On the basis of the above data a local algorithm for the radiometric estimation of chlorophyll content in the surface layer of the Baltic is also developed and presented. The use of the algorithm requires the reflectance just above or below the sea surface to be measured at three wavelenghts (490, 550, 620 nm) at least in order to specify the water's spectral classification group, and at two of them (490, 620 nm) to compute the chlorophyll concentration. The empirically determined choice of the 490 nm band rather than that of the chlorophyll absorption maximum (443 nm) suggests a high contribution of yellow substances to the optically active components of Baltic waters.

Jerzy Olszewski, Piotr Kowalczuk, Mirosław Darecki
Institute of Oceanology, Polish Academy of Sciences, Sopot

On the usefulness of NOAA-AVHRR satellite data for estimating the component content in Baltic Sea water.
Studia i Matriały Oceanologiczne 1995, No.68 pp. 51-60.

Keywords: Spectral reflectance, Remote Sensing, NOAA-AVHRR, Baltic Sea Manuscript received April 21, 1994, in final form December 4, 1995.

The hypothetical response of the visible channel of the NOAA satellite AVHRR detector is discussed in order to discover to what extent the content of Baltic water can be distinguished. The experimental data from the spring of 1993 shows that, the application of the detector has been proven only in the direct evaluation of totak suspended matter (TSM) concentration. The limitation ranges of TSM concetration for good and poor AVHRR detection are given. The results are illustrated with some AVHRR images, processed into spatial distribution of total suspended matter in the Baltic's surface layer.