Vol 52, No 9 (2016)

An approach to the retrieval of sea wave spatial spectra based on satellite optical imagery in linear and nonlinear approximations is described. Physical mechanisms of the formation of disturbed sea surface brightness fields recorded by remote sensing equipment are analyzed. Wave spectra retrieval methods using brightness field formation models that consider linear and nonlinear dependencies on sea surface slopes are suggested. A method for the construction of operators that retrieve the spatial spectra of surface wave slopes and elevations from aerospace imagery and take into account nonlinear modulations of disturbed sea surface brightness fields is developed. This method is based on the numerical simulation of sea surface images and the construction of a retrieving operator with respect to a set of parameters determined by aerospace imaging conditions. Examples of the use of the developed methods are given.

We consider the influence of the sea surface state on the backscattered radar cross section and the accuracy of the wind speed retrieval from the scatterometer data. We used a joint set of radars and buoys to determine the type of sea waves. Three types of sea waves were distinguished: developing wind waves, fully developed wind waves, and mixed sea. It is shown that the retrieval error of the near surface wind speed using a one-parameter algorithm is minimal in the case of fully developed wind waves. We compared these data with the results of radio-altimeter data analysis and showed that in both cases underestimation of the retrieval wind speed exists for developing wind waves and overestimation occurs for mixed sea. A variety of swell parameters (length of the dominating wave, swell height, swell age) significantly influence the backscattered radar cross section, leading to a growth in the mean square error of the retrieved wind speed during vertical sounding (radio-altimeter data), and only slightly influence the mean square error of the scatterometer data (medium incidence angles). It is necessary to include the information about the parameters of sea waves in the algorithms and take into account the regional wave properties to increase the accuracy of wind speed retrieval.

Using satellite altimetry measurement data for 1993–2013, we study the spectral characteristics of Rossby waves in the Northwestern Pacific (25°–50° N, 140°–180° E). For each latitude degree, we draw integral plots of spectral power density calculated with a two-dimensional Fourier transform (2D-FFT). We compare the dispersion equations of Rossby waves calculated from the WKB-approximation and an approximation of a two-layer ocean model with the empirical velocities determined by the slope of isopleths by the Radon method; also, we compare the dispersion equations with the spectral distributions of level variations. It is shown that the main energy of Rossby waves in the Northwestern Pacific corresponds to the first baroclinic mode. At almost all latitudes, there is good agreement between the empirical phase velocities calculated by isopleths by the Radon method and the theoretical values; also, the spectral peaks correspond to graphs of the dispersion equations for the first baroclinic mode Rossby waves, except for the Kuroshio region, where some peaks correspond to the second mode.

The possibilities of a multiangle method of radar diagnostics to determine thickness of an oil film on a sea surface by comparing the radar data with the quantitative modeling results obtained using the model of oil spreading dynamics are analyzed. The experimental results of the remote sensing of the Caspian Sea water area near the Neftyanye Kamni oil field by the Envisat-1 synthetic aperture radar (SAR) and the new Floating Objects Tracking System (FOTS) model of oil spreading are used for the analysis. The model allows to calculate the dynamics and change in the mass and size of an oil slick basing only on the available data of satellite measurements and atmospheric reanalysis.The model takes into account the main processes that influence the slick formation (gravity spreading, advective transport, dispersion, emulsification, turbulent mixing, and evaporation). This model is used to calculate the thickness evolution and dynamics of the displacement of oil slicks in the period between two consecutive radar images of this region (0.5–4 days) and to estimate the volumes of oil spilled in the field. The good consistence of the height of the oil film calculated using radar measurements and the modeling results confirms the method’s reliability.

The methodology of joint processing of the satellite altimetry and occasional hydrological observations in the Black Sea for 1993–2012 is developed. The original technique for reconstruction of the 3D temperature and salinity fields in the deep-sea part is proposed and implemented. This technique makes it possible to identify the depths at which a contribution of adiabatic processes to the deformation of the temperature and salinity profiles of the sea is predominant. Daily-averaged 3D fields of the seawater temperature and salinity in a baroclinic layer on a regular grid are reconstructed. The evaluation of accuracy of the reconstructed temperature and salinity arrays is performed by comparing them with the data of hydrological exploration. Structures of the temperature and salinity fields are correlated naturally with topography of the altimetric level and clearly indicate the synoptic variability. Seasonal and interannual variabilities of the kinetic energy (averaged over horizons of the 63–400 m layer) of the geostrophic currents calculated using the dynamic method makes it possible to reveal a sharp increase in the kinetic energy of the currents in the winter season of 2002. A high correlation is found between the interannual variability of the ERA-Interim wind stress curl averaged over the surface of the deep sea part and the kinetic energy of the geostrophic currents in the 63–400 m layer.

The waters of the Bering and Chukchi seas, as well as the De Long Strait, are investigated based on the data obtained in August 2013 during the scientific expedition of the Far Eastern Floating University on the research vessel Professor Khlyustin. Chlorophyll a concentrations calculated from MODIS-Aqua and VIIRS satellite data by ocean color and obtained by means of shipboard flow-through fluorometric measurements are comparatively analyzed. Vessel data are corrected for standard spectrophotometric measurements and the vertical depth distribution of phytoplankton. It has been found that, in the waters of the Eastern Arctic, satellite radiometers showed overestimated chlorophyll a concentrations in the upper seawater layer visible from the satellite. This is associated with the additional contribution of colored dissolved organic matter in the sea surface color. In the De Long Strait, satellite measurements incorrectly estimate the depth integrated chlorophyll a concentration, since the bulk of phytoplankton cells at a chlorophyll a concentration of 10–20 g/L is at depths of 25–30 m with luminosity of 5%.

This is a review of methods of passive microwave satellite monitoring of the sea-ice cover in polar regions. We briefly describe the microwave radiometers launched into the Earth’s orbit and provide data used in studies of Arctic and Antarctic sea ice. We give a detailed description of currently used algorithms for determining the sea-ice concentration and cover in polar regions according to satellite microwave radiometry. The methods for constructing these algorithms and their related drawbacks are considered. The final section of this paper briefly analyzes the studies that compare current algorithms with each other, with radar data, infrared data, and data of visual ship observations.

Application of satellite passive microwave sensing for the retrieval of key climatic parameters in the Barents Sea is considered. Fields of surface wind, atmosphere water vapor content and cloud liquid water content were found from MTVZA-GY radiometer onboard the Meteor-M N1 satellite and AMSR2 onboard the GCOM-W1 satellite with the use of original algorithms. The fields are in a good agreement with the ancillary remote and in situ measurements, which follows from the analysis of the evolution of the extra tropical and polar cyclones and cold air outbreaks with storm winds leading to intense air-sea interaction, and the formation and drift of sea ice.

We discuss the possibility of detecting deep convection in the Lofoten Basin of the Norwegian Sea based on the eddy structures revealed from the satellite data. Satellite altimetry, SAR imagery, and MODIS satellite spectral radiometer sea-surface temperature (SST) data are used in the analysis, along with the data of oceanographic Argo floats. It is shown that the eddies identified from the satellite data correspond to the convective cells in the same region according to the data of the Argo floats. We consider several examples of the summer eddy and one winter eddy and the corresponding structures in the ocean measured by the Argo floats when they were located close to the identified eddies. As this method develops and improves, it can be used for the analysis of the dynamic of oceanic eddies in the region of the Lofoten Basin, and possibly in other regions with active deep convection.

Peculiarities of the formation of carbon gas and fine aerosol emissions into the atmosphere during wildfires are analyzed. A prompt satellite monitoring system and technique for the assessment of burnt areas and volumes of CO₂, CO, and PM_2.5 emissions from wildfires are described. The results of satellite monitoring of the Russian Federation and some Russian regions for different months over 2010–2014 are given; burnt areas and volumes of carbon gas and aerosol emissions throughout the entire territory are assessed. The peculiarities of seasonal frequencies of wildfires and volumes of hazardous gas and fine aerosol emissions in the regions under study are identified.

Two multispectral threshold techniques have been developed and tested for the automatic classification of AVHRR/NOAA and SEVIRI/Meteosat-10 data. They provide day-and-night detection and the assessment of cloud-cover parameters, as well as the discrimination of precipitation zones and severe weather phenomena. The validation of output information products, which has been performed with ground-based conventional meteorological observations and radar data, as well as with independent satellite-based estimates of cloud cover and precipitation parameters, confirms the feasibility of developed techniques and reasonable accuracy of output products. Therefore, the technique is concurrent to those implemented in current foreign satellite centers.

International investigations into the correlation between tropical cyclones (TCs) and the ionosphere are associated with great difficulties in proving the influence of possible TC mechanisms on the ionosphere. In this paper, the ionospheric parameters obtained by ground-based and satellite sensing over the TC and at a certain distance from it are analyzed. This paper is a brief presentation of the main areas of research on the TC–ionosphere interaction problem by different international teams of scientists from the formulation of the problem to the present. The main conclusion of the paper is that internal gravity waves are the main factors that influence the ionosphere from the active cyclones.

It is especially important to know the character and the intensity level of tropical cyclone (TC) activity when the system for estimating the cyclonic danger and risk is formed. During seasons of increased cyclonic activity, when several TCs are simultaneously active, the total energy effect of the cyclone group joint action is not estimated numerically. Cyclonic activity is as a rule characterized by the number of TCs that occur in the considered zone. A variant of the criterion, according to which relative cyclonic activity is estimated, is presented.

The present work is devoted to the development of a retrieval algorithm for the sea surface temperature from the two-channel measurements of the Landsat-8 satellite on the basis of a comparison with MODIS satellite data. The algorithm makes it possible to reconstruct the surface temperature with a 100 m resolution, which enables analysis of the spatial structure of various phenomena on the ocean surface at small scales (upwelling, submesoscale vortices, etc.). The magnitude of the standard deviation between the reconstructed temperature and the temperature derived from the MODIS satellite is ~0.58°C. The sources of inconsistency between temperatures retrieved from the MODIS and Landsat-8 measurements were investigated: diurnal temperature variation, which leads to an increase in the standard deviation in the summer period because of the mismatch in time (~2 hours) between measurements; the presence of specific bands in the Landsat data, which is probably related to instrumental errors of the device.

A multisensory algorithm of satellite radiothermovision has been proposed that makes it possible to combine the data of satellite radiothermal monitoring of the Earth from different sources within a single method of spatiotemporal interpolation taking into account the differences in time of measurements and in the spatial resolution of different instruments. The new algorithm was tested in a series of measurements with SSMIS instruments onboard F16, F17 satellites of DMSP and AMSR-2 instruments onboard the GCOMW1 satellite in November 2013, as well as a series of measurements with the same instruments in August 2012 supplemented with data from WindSat. The parameters of the spatiotemporal interpolation of total precipitable water fields are improved nearly twofold (with a time step of 1.5 h on a regular grid with 0.125° sampling) compared with the method that previously used only SSM/I data. The achieved spatial sampling exceeds known world analogues while maintaining a high accuracy of interpolation. In addition, the problem of the transition from the fields at a fixed local time to the fields at a fixed universal time is briefly considered. It has been shown that this transition is mainly relevant in the study of the fast atmospheric processes on a global scale with high temporal resolution.