CONVECTIVE PROCESSES IN NEAR-WATER LAYERS OF THE ATMOSPHERE FROM RADAR IMAGERY OF THE OCEAN SURFACE

Atmospheric boundary-layer stratification exerts a considerable influence on side-looking radar imagery of the sea surface in the centimeter range. Characteristic cellular structures present on the imagery under conditions of instability in the atmospheric boundary layer do not appear on images recorded under stable atmospheric conditions. The possibility of observation of dry and moist convection in the atmospheric layer above the water surface is examined.     

Manifestation specifics of hydrodynamic processes in satellite images of intense phytoplankton bloom areas

The paper summarizes the results of the long-term complex satellite monitoring of the Black and Baltic seas. Data from synthetic aperture radars (SARs) constitute the experimental basis for the investigation of satellite. In addition to radar data, the data of the visible and infrared bands from MODIS Terra/Aqua, MERIS Envisat, Landsat series sensors are used. The features of the manifestation of hydrodynamic processes, submesoscale eddies in particular, in satellite radar and optical images in a period of intense phytoplankton bloom are discussed. A relationship is established between the intensity and duration of the phytoplankton bloom in the regions of observation and the frequency of the appearance of long-lasting wakes behind moving ships in SAR images. These wakes appear as long narrow bright bands of enhanced backscattered signal extending for tens and sometimes hundreds of kilometers. It is proposed to consider the wakes of this type as indicators of the areas and duration of intense phytoplankton bloom. Satellite observations over the Black and Baltic Seas conducted for more than ten years have shown that long-lasting ship wakes are influenced by powerful jet streams, such as those associated with the passage of eddies that leads to shifts and deformations. By comparing the true route of a ship with its wake in the satellite image, it is possible to obtain detailed information about the parameters of currents.     

Study of internal wave generation and propagation features in non-tidal seas based on satellite synthetic aperture radar data

Despite the intense attention paid to internal wave (IW) investigation, the most experimentally studied and theoretically described are internal gravitational waves in shelf zones of oceans and tidal seas appearing during the interaction of tidal currents with the margin of the shelf. Information on surface manifestations of internal waves in enclosed seas, such as the Black and Caspian seas, is almost absent. In this paper, the results of study of the peculiarities of generation and propagation of nontidal internal waves are presented; the study is carried out on the basis of combined analysis in data of marine surface radiolocation and data of optical and infrared satellite-borne sensors. The experimental basis of investigation is radar images of the marine surface derived with the help of Synthetic Aperture Radars, onboard the Envisat and ERS-2 satellites. Additionally, the data of the following sensors belonging to the optical and infrared ranges were used for the purpose of radar image interpretation: MODIS (onboard the Aqua/Terra satellite), MERIS (Envisat), and AVHRR (NOAA). Surface manifestations of IWs in the northeastern part of the Black Sea and in the Caspian Sea have been found in radar imagery for the first time, their pattern of spatial and temporal variation has been reconstructed. The possible factors leading to generation of the observed nontidal IWs are determined and suppositions about the corresponding generation mechanisms are made. In particular, the IW manifestations recorded in the northeastern part of the Black Sea are localized in the vicinity of the boundaries of eddies or hydrological fronts; this fact evidences for the frontal mechanism of generation, at which IWs are radiated by a nonstationary (moving and/or inertially oscillating) front. The most probable main sources of generation of IWs detected in the Caspian Sea are longitudinal one-knot seiches, whose knot point is located near the Apsheron sill.     

Satellite observations of surface manifestations of internal waves in the Caspian Sea

Results of satellite observations of surface manifestations of internal waves in the Caspian Sea are presented. It is proposed that the possible cause of generation of the revealed internal waves is uninodal seiches with a nodal line located in the vicinity of the Apsheron Sill. The basic parameters of internal waves in the Caspian Sea, having the form of classical soliton trains, are determined. Seasonal variability of surface manifestations of the internal waves is revealed. The horizontal current velocity of the solitons is assessed. According to the estimation, velocity is about 0.2 m/s, which is sufficient for wind ripple modulation.     

Satellite monitoring of oil slicks on the Black Sea surface

This paper summarizes the results of perennial combined satellite monitoring of the Black Sea conducted in order to detect sea-surface oil and oil-product pollution, as well as biogenic and anthropogenic surfactant films. A joint analysis of data obtained by various remote sensing techniques has been performed. The large amount of data has resulted in generalizations and reliable statistics on the spatial and temporal variability of different film manifestations in radar images of the sea surface. Regions most severely polluted by petroleum products have been identified. A hypothesis is suggested linking the surface manifestations of certain types of polluting films with natural gas and oil seeps and mud volcanism in the Black Sea. Improvements in the reliability of interpreting satellite data are discussed.