Marina A. Evdoshenko

Bio-Optical Characteristics of the Aegean Sea Retrieved from Satellite Ocean Color Data

The specific goal of this work is to demonstrate the possibilities of new ocean color satellite sensors such as the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) for studying processes in the Eastern Mediterranean, with the Aegean Sea as an example. The Aegean Sea appears as an appropriate basin for study of contrasting ecosystems, because it is subjected to intrusion of water masses of different origin with pronounced contrast in bioproductivity: the eutrophic water from the Black Sea, and the oligotrophic water from the Levantine Basin.

Correlation of the Distribution of Normalized Spectral Radiances as an Indicator of the Features of Water Exchange in the Black Sea

A set of 128 images of the Black Sea obtained using the SeaWiFS color scanner data in 1998–2004 was processed to estimate the new capabilities of indication of the vertical inhomogeneity of the upgoing normalized radiance. The basin of the sea was divided into 430 frames with a size of 30 × 30 km. Correlation coefficients R between all the spectral radiances were calculated for all the frames of all the images. The correlation between the radiance distributions at 490 and 670 nm was most sensitive to the conditions of the radiance formation. This allowed us to find the situations in which the variations in the shortwave and long wave radiances in the frame appear opposite and are characterized by estimates R < −0.7. It was shown that such distributions are indicators of the water exchange between the coastal and open sea areas. They are caused by a special optical stratification during the events of such exchange. A conclusion is made about the prospective of applying the estimates of the correlation of spectral radiances for diagnosis of the water exchange based on the current and archive materials of ocean color scanners.

Assessment of optical characteristics of atmosphere and ocean by data from satellite ocean color sensors

At present there are half a score of satellite ocean color sensors being in operation or prepared for launch; they offer strong possibilities of providing data on spatial and temporal variability of various characteristics of atmosphere and ocean, primarily of the optical ones. As of now, data from the satellite scanner SeaWiFS (Sea-viewing Wide Field-of-view Sensor) are in most common use; they have been available since September 1997. The possibilities and problems of retrieval of optical characteristics of atmospheric aerosol, cloudiness, and sea water from SeaWiFS data are considered. The algorithms developed in the P.P. Shirshov Institute of Oceanology Russian Academy of Sciences are presented as well as some results of their validation by data of field measurements. The examples of spatial distributions and seasonal changeability of aerosol optical thickness and seawater optical characteristics derived from SeaWiFS data are given.

Optical researches for cyanobacteria bloom monitoring in Curonian Lagoon

Cyanobacteria bloom is a great ecological problem of Curonian Lagoon and Baltic Sea. The development of novel methods for the on-line control of cyanobacteria concentration and, moreover, for prediction of bloom spreading is of interest for monitoring the state of ecosystem. Here, we report the results of the joint application of hyperspectral measurements and remote sensing of Curonian Lagoon in July 2015 aimed at the assessment of cyanobacteria communities. We show that hyperspectral data allow on-line detection and qualitative estimation of cyanobacteria concentration, while the remote sensing data indicate the possibility of cyanobacteria bloom detection using the spectral features of upwelling irradiation.

Diagnostics of the mesoscale water exchange on the basis of statistical characteristics of the distribution of normalized radiance

A new approach is suggested for the diagnostics of manifestations of water exchange in the field of normalized radiance and automation of the analysis of digital images of the water surface. The approach is based on the application of a set of statistical characteristics of a radiance relief as an integral indication of local inhomogeneities in the water medium and provides for the estimate of these characteristics over small regions (frames) of the basin studied using multispectral information. Using the example of the SeaWiFS scanner data on the evolution of an eddy dipole in August 1998 in a study region with a size of 160 × 160 km in the northwestern part of the Black Sea, it was shown that the estimates of a number of statistical characteristics of spectrally different radiance reliefs found in the frames with a size of 40 × 40 km significantly depended on the presence of fragments of an eddy dipole or other structures in these frames. A set of such characteristics made possible reliable differentiation of radiance reliefs by the degree of randomness, by the orientation of the inhomogeneities that form the relief, and by other properties caused by the variability of the light scattering and light absorbing admixtures in the sea medium in the course of the water exchange. The approach does not require any preliminary information about the object of observations. It is promising in the basins with moderate water transparency and vertical inhomogeneity of the upper layer available for remote profiling.

Diagnostics of mesoscale water exchange from full mormalized radiance spectra

Potentialities of discriminating water motions and admixture transfer patterns within the surface layer and underlying thickness of the sea from the estimates of spectral-different normalized radiances are demonstrated by the example of the ocean color scanners data for the Black and Baltic Seas. The merits and limitations of the approach are discussed.