Alexander Myasoedov

On Dual Co-Polarized SAR Measurements of the Ocean Surface

An effective methodology using satellite high-resolution polarized information to interpret and quantitatively assess various surface ocean phenomena is suggested. Using a sample RADARSAT-2 quad-polarization ocean synthetic aperture radar (SAR) scene, the dual co-polarization (VV and HH) radar data are combined into polarization difference, polarization ratio, and nonpolarized components. As demonstrated, these field quantities provide means to distinguish Bragg scattering mechanism and radar returns from breaking waves. As shown, quantitative characteristics of the surface manifestation of ocean currents, slicks, and wind field features in these dual co-polarization properties are very different and may be effectively used in the development of new SAR detection and discrimination algorithms.

Imaging mesoscale upper ocean dynamics using synthetic aperture radar and optical data

A synergetic approach for quantitative analysis of high-resolution ocean synthetic aperture radar (SAR) and imaging spectrometer data, including the infrared (IR) channels, is suggested. This approach first clearly demonstrates that sea surface roughness anomalies derived from Sun glitter imagery compare very well to SAR roughness anomalies. As further revealed using these fine-resolution (similar to 1 km) observations, the derived roughness anomaly fields are spatially correlated with sharp gradients of the sea surface temperature (SST) field. To quantitatively interpret SAR and optical (in visible and IR ranges) images, equations are derived to relate the surface roughness signatures to the upper ocean flow characteristics. As developed, a direct link between surface observations and divergence of the sea surface current field is anticipated. From these satellite observations, intense cross-frontal dynamics and vertical motions are then found to occur near sharp horizontal gradients of the SST field. As a plausible mechanism, it is suggested that interactions of the wind-driven upper layer with the quasi-geostrophic current field (via Ekman advective and mixing mechanisms) result in the generation of secondary ageostrophic circulation, producing convergence and divergence of the surface currents. The proposed synergetic approach combining SST, Sun glitter brightness, and radar backscatter anomalies, possibly augmented by other satellite data (e.g., altimetry, scatterometry, ocean color), can thus provide consistent and quantitative determination of the location and intensity of the surface current convergence/divergence (upwelling/downwelling). This, in turn, establishes an important step toward advances in the quantitative interpretation of the upper ocean dynamics from their two-dimensional satellite surface expressions.

Sun Glitter as a "Tool" for Monitoring the Ocean from Space

A method for retrieval of the spatial variations of the sea surface mean square slope (MSS) in sun glitter imagery is proposed. Observed sun glitter brightness anomalies are converted to the MSS anomalies with use of a transfer function determined from the smoothed shape of the sun glitter brightness. The method is applied to MODIS and MERIS sun glitter imagery of natural oil seeps and the catastrophic Deep-water Horizon oil spill in the Gulf of Mexico. The results clearly demonstrate a highly feasible approach for investigation of surface signatures of the oil slicks, as well as other ocean phenomena.

SAR observations of internal waves in the Russian Arctic seas

In this work taking the advantage of high resolution spaceborne synthetic aperture radar (SAR) measurements we present first preliminary results of short-period internal waves (IW) observations in the Barents, Kara and White seas based on ENVISAT ASAR data for summer-autumn months in 2007-2011. Altogether more than 2000 IW packets were identified in about 1400 SAR images. Detailed maps of internal waves occurrences in the three Arctic seas have helped to identify main sites of regular IW generation.

Features of wind field over the sea surface in the coastal area

In this paper we analyze SAR wind field features, in particular the effects of wind shadowing. These effects represent the dynamics of the internal atmospheric boundary layer, which is formed due to the transition of the air flow arriving from the rough land surface to the “smooth” water surface. In the wind-shadowed area, the flow accelerates, and a surface wind stress increases with fetch. The width of the shadow depends not only on the wind speed and atmospheric boundary layer stratification, but also on geographic features such as windflow multiple transformations over the complex surface land–Lake Chudskoe–land–Gulf of Finland. Measurements showed that, in the area of wind acceleration, the surface stress normalized by an equilibrium value (far from the coast) is a universal function of dimensionless fetch Xf/G. Surface wind stress reaches an equilibrium value at Xf/G ≈ 0.4, which is the scale of the planetary-boundary-layer relaxation.

Detection and study of the polar lows over the arctic sea ice edge

Polar lows (PLs), emerging over the sea ice edge, are studied using multisensor data information, surface analysis maps and reanalysis data. PLs over the Western (the Greenland, the Norwegian and the Barents Seas), and the Eastern (the Chukchi, the East Siberian and the Laptev Seas) parts of the Arctic are considered. It is shown that currently operating satellite instruments, taken separately, cannot provide means for PL confident detection. Whereas multisensor satellite data, including passive and active microwave data products along with infrared and visible measurements, analyzed simultaneously, provide an opportunity to monitor PLs, developed under most environmental conditions, including the vicinity to the sea ice edge. Geophysical parameters are retrieved from satellite passive microwave data with advanced algorithms. PLs are detected using the complex geo-informational system, making advantage from simultaneous analysis of different satellite and model data.