Adaptation of Satellite Remote Sensing Algorithms for Retrieval of Environmental Parameters in the Caspian Sea

The state of the Caspian Sea ecosystems causes serious concern due to anthropogenic (oil and gas production and transportation) and natural reasons (climatic changes, extreme meteorological and hydrological phenomena, natural hazards and their frequency of recurrence, etc.). Climatic changes have already led to a sharp drop in the Caspian Sea level, an increase in sea surface temperature, changes in ice conditions in the Northern Caspian, the intensity of phytoplankton blooms, especially in the Southern Caspian, an increase in turbidity in coastal areas due to river runoff, and changes in the frequency and intensity of wind patterns. As a rule, such phenomena have a significant specific (more often negative) impact on the natural systems and infrastructure of the coastal zone. To understand the current state and climatic changes in the main parameters of the marine environment in the Caspian Sea and to carry out its comprehensive analysis, it is necessary to use remote sensing data and to determine correctly different environmental parameters. Our experience shows that in many cases standard algorithms for retrieval of these parameters from the remote sensing data that are elaborated, calibrated and validated for the open ocean conditions, are not valid for inland seas which have their own specific physico-geographical, oceanographic and meteorological conditions. The paper presents a review of new algorithms and techniques developed during the past decade for correct retrieval of sea surface temperature, water turbidity, suspended particulate matter concentration, as well as determination of ice cover, river plumes, and wind surge areas based first of all on Ocean Color Data: MSI Sentinel-2A, -2B; OLI/TIRS Landsat-8 and OLI-2/TIRS-2 Landsat-9. These algorithms have been introduced into the specialized information and analytical system “See the Caspian Sea” (STCS), designed for collecting, analyzing and visualizing satellite and meteorological data for the Caspian Sea region.