The current study represents the laboratory modelling of the microwave radiation scattering by breaking surface waves. To control the area of the whitecap coverage fraction, a specially developed optical method was used, based on the underwater illumination and digitization of images of the water surface. Microwave measurements were carried out at four polarizations in the X-band. The dependences of the received signal power on the area of the whitecap coverage fraction formed during the breaking of surface waves were obtained.

In the Barents Sea, in the presence of a polar low (polar hurricane), the wind speed distribution is obtained using the WRF atmospheric model with LES option of the planetary boundary layer and using the Polar WRF model. The test simulations of the considered case carried out with the WRF Polar the WRF LES model are compared. Further comparison between WRF Polar and WRF ARW is planned. The adjustment of the weather model in comparison with remote sensing data will help to develop methods of monitoring and forecasting of the polar hurricanes.

Numerical simulation of sea waves in Persian Gulf is performed using WAVEWATCH III model for the two different source terms. Comparison of mean square slope obtained from the Ka-band radar data and mean square slope from the model spectrum is performed. The comparison is complicated by the following details. The part of the sea wave spectrum with wavelength of decimeter band and shorter significantly contributes to the mean square slope from Ka-band radar data, while the shortest wavelength in the spectrum from WAVEWATCH III model is of the order of meter. The method to calculate mean square slope from model data is presented. It implies integrating of the composite spectrum, which long-wave part is obtained by WAVEWATCH III model, while the descending part is from the sea wave spectrum model.

The possibility of reconstructing the dynamic parameters (surface wind speed, friction velocity and roughness height) of the atmospheric boundary layer in a hurricane based on wind speed profiling by GPS dropwindsondes and collocated data of the Stepped Frequency Microwave Radiometer (SFMR) is discussed. The parameters of the atmospheric boundary layer were obtained from the data of GPS dropwindsondes with the use of the self-similarity of the velocity profile in the atmospheric boundary layer, previously proposed and successfully tested in laboratory conditions. The preliminary results of data processing showed that at surface wind speeds exceeding 35 m/s, the friction velocity saturates and the surface drag coefficient decreases accordingly. Based on the comparison of the measured dynamic parameters and the surface emissivity, empirical equations are proposed, which take into account the discovered properties of the dynamic parameters of the atmospheric boundary layer and potentially can be used for remote diagnostics of the boundary layer parameters.

The research is devoted to the problem of estimations of CO2 fluxes between the hydrosphere and atmosphere. Hurricane-force winds lead to intensive wave breaking, with formation of spray in the air, and bubbles in the water. It strongly intensifies gas flux characterizing by power dependence of the transfer rate on the 10-m height wind speed used for approximation of the empirical results. But available data demonstrate wide variation which leads large confidence limits for coefficients in empirical approximations. On the other hand, there is an obvious problem of obtaining reliable data on the wind speed. Widely used reanalysis data typically underestimate wind speed magnitude, due to the low spatial and temporal resolution. One of the most promising ways to measure near water wind speed is the use of the data of remote sensing. The present study used technique to achieve wind speed based on the processing sea surface images obtained in cross-polarized mode with C-band (5.4 GHz) radar with synthesized aperture (RSA) of Radarsat-2 satellite. To this propose geophysical model function (GMF) which binds values of wind speed and normalized radar cross section in cross-polarized mode was used. This GMF was developed in a special laboratory experiment on the wind-wave flumes for a wide range of wind speeds, including hurricanes. In turn, for parameterization of gas transfer rate results of recent laboratory experiment on high speed wind-wave flume was used.

The paper describes the first step towards development of GMF for retrieval wind speed and wind stress in hurricanes basing on calibration of the cross-polarized satellite SAR images from Sentinel-1 by the collocated NOAA GPS dropsondes data. The self-similarity of the velocity profile "defect" in the boundary layer known from the fluid dynamics was used to retrieve the parameters of the atmospheric boundary layer (the surface wind velocity and the wind friction velocity) from the dropsonde wind velocity profiles in 10 major hurricanes. Basing on preliminary data processing, the dependencies of the cross-polarized NRCS on the wind speed and wind friction velocity were obtained to be used for constructing the GMFs.

Based on laboratory experiments, the logarithmic dependence of X-band cross-polarized NRCS on wind friction velocity was found for high wind conditions. Using this dependency, surface drag parameterizations at hurricane wind and available collocated field data on radar backscattering and wind speed, the geophysical model function (GMF) as NRCS via 10-m wind speed is derived. The GMP is applicable for wind speed retrieval at stormy and hurricane conditions.

Laboratory experiments directed to investigation of dependencies of the X-band normalized co-polarized and de-polarized radar cross-section on wind speed (U10) and incident angle (θ) are presented. Parameters of air-flow velocity and surface wind waves were measured simultaneously. It was shown that both co-polarized and depolarized radar return depend on incidence angle; the depolarized return is less sensitive. Analysis of the Doppler spectra of the radar backscatter enabled us to conclude that the radar return is formed by resonant scatters moving with the velocity exceeding in 20% the phase velocity of the energy containing surface waves. Basing on the measurements the X-band and C-band geophysical model functions (GMF) were derived for U10=10-40 m/s and θ=30°-60°. Examples of hurricane wind speed retrieval with the use of the new GMF are discussed.

This work aims to development of a simple method for distinction between open water and ice cover on the base of geophysical data record (GDR) of altimetry satellite Jason-2 for large and middle-sized freshwater inland water bodies. The method is applied for six reservoirs at the Volga and Don Rivers. It was shown earlier [1, 2] that the retracking of the Jason-1, 2 satellite data allow us to determine with sufficient accuracy the water level variations either for the large Rybinsk reservoir, or for the middle-sized Volga reservoirs (the Gorky reservoir and others). Ice and snow conditions of inland waters are of interest since they influence the life and economic activity of people and are significant indicators of climate changes. Satellite methods of ice-snow cover observations have certain advantages, connected with the global coverage, instantaneous observations of large water areas and relatively low cost. However, the use of satellite methods for inland waters is often limited by their spatial resolution comparable to or greater than the size of water reservoirs. Satellites carrying instruments of high spatial resolution often have large repeat periods (ICESat), either the data quality strongly depend on weather conditions (Landsat). In this regard, the use of Jason -1, 2 satellites, equipped with a dual-frequency (13.6 GHz and 5 GHz) radar altimeters and three-channel (18, 21 and 37 GHz) microwave radiometers is of great interest, because the footprint diameter of their altimeters in Ku-band is about 10 Km and the repeat period of observations is ten days, that make them suitable for observations of large and medium-sized inland waters.

Laboratory experiments directed to investigation of co-polarized and de-polarized X-band microwave radar return from the water surface at strong and hurricane wind were carried out in the high-speed wind-wave flume. Microwave measurements were accompanied by the measurements of air-flow and wave field parameters. Experiments showed that alternatively to the co-polarized return, the dependency of the de-polarized return on the wind speed do not saturate, although the growth rate decreases at wind speed exceeding 30 m/s. Comparison of the of the experimental data with the composite-surface Bragg scattering model for the measured parameters of the wind and waves showed, that the model is in agreement with measurements of microwave co-polarized return, but fails to describe the de-polarized radar return. The obtained dependency of de-polarized radar return was compared with the empirical geophysical model function based on collocated airborne and satellite data.

Altimetry data processing algorithms developed for the open ocean may be inapplicable for the case of coastal and inland waters. The problems of inland water data processing are very similar to those arising in the coastal zone of the ocean from contamination of the received signal by reflection from the land. An adaptive retracking algorithm was developed by the authors for inland waters and proved on the base of Jason-1 data for Gorky reservoir of the Volga River. This work is about our experience of retrieving the water level in the Volga River Reservoirs by an adaptive retracking algorithm for the SGDR data of Jason-2 satellite. It is shown that the algorithm essentially increases the number of data involved in monitoring and improves accuracy of water level retrieval from altimetry.

The problem of minimization of the errors in the water level retrieving for the Gorky reservoir from altimetry measurements can be resolved by re-tracking of Jason-1 satellite altimeter data. For justification of the optimal re-tracking algorithm the average impulse response of the statistically inhomogeneous surface were calculated theoretically for the model of the terrain in the vicinity of Gorky reservoir. The modeled waveforms are in good agreement with the Jason-1 ,2 waveforms for the same area. Comparing of the data with in situ measurements shows that re-tracking significantly improves measurements of the water level. General principles of re-tracking algorithms for complex areas (land, coastal zone, inland waters, etc) based on calculations of the waveforms taking into account statistical inhomogeneity of the reflecting surface adjusted to a certain geographic region, are discussed.

Wind-wave interaction at extreme wind speed is of special interest now in connection with the problem of explanation of the sea surface drag saturation at the wind speed exceeding 30 m/s. The main objective of this work is investigation of factors determining momentum exchange under high wind speeds (up to U10>;40 m s-1) basing on the laboratory experiment in a well-controlled environment. Air flow velocity measurements were complemented by measurements of the wind wave spectra. The tendency to saturation of the surface drag was observed for wind speeds exceeding 25 m s-1, accompanied by the saturation of wind wave slopes. The effect of surface drag saturation can be explained quantitatively within the quasi-linear model of the air boundary layer above the waved water surface, when the contribution of the short-wave part of the wind wave spectrum to aerodynamic resistance of the water surface is taken into account.

Space-time variability of current field characteristics, surface waves, and parameters of the near-surface atmospheric layer above the shelf zone of the Black Sea in the Gelendzhik-city region are studied. A joint analysis of the field measurement data obtained on August, 2007, September, 2008 and of the synchronous SAR images made by the Envisat satellite of the European Space Agency is carried out.