Experimental investigations of the spatial and temporal variability of temperature in the near-surface layer with weak wind blowing

In situ data compiled during Cruise 52 of the R/VMikhail Lomonosov in May 1990 have been used to study the space-time variability of the near-surface temperature, with weak wind blowing. Temperature fluctuations within the layer of diurnal warming are shown to be primarily controlled by the heterogeneity of the wind-induced mixing and to be capable of indicating internal waves. The data on the manifestation of internal waves over a bottom rise are submitted, along with the statistical characteristics of temperature fluctuations in a cycle of solar warming. Translated by Vladimir A. Puchkin.     

Determination of the surface temperature and the temperature drop in the skin layer from a moving vessel using IR data

In this paper methods are given of the IR radiometric determination of the temperature of the radiating oceanic layer,T _s, and the determination on its basis of the temperature drop in the skin layer,dt, from on board a ship underway, which allows for the emissivity of the sea surface and the contribution of the atmosphere to the upward radiation of the sea surface. The seawater temperatureT _w was registered by a contact sensor towed along the ship at a depth of 0.1–0.4 m. The valuedt=T _s–T _w was found to be within the limits of 0.07 to –0.85 K, being on average 0.33 K. The near-surface wind speedv (v=1–13 m s^–1) had the best relationship withdt;dt=–0.66+0.06v. The empirical values ofdt were compared with the model ones obtained by the well-known formulae for the conditions of forced and free convection of the surface layer.Translated by Mikhail M. Trufanov.     

Estimating the quality of the retrieval of the surface geostrophic circulation of the Black Sea by satellite altimetry data based on validation with drifting buoy measurements

Combined measurements of satellite altimeters make it possible to determine anomalies of the sea level of the Black Sea on a regular grid with a high spatial resolution 1/8°. In this work arrays of total geostrophic velocities of currents in the Black Sea basin are retrieved and compared with drifter measurements of current velocities for 1999–2007. The comparison is performed both for the whole array of drifter measurements (～110000 measurements) and individually for each drifter. To retrieve the velocities, two different arrays of mean dynamic topography (MDT) are used: synthetic and climatic mean dynamic topography. The comparison results demonstrate that using synthetic MDT is preferable for calculating geostrophic velocities. Velocities calculated by from satellite altimetry data agree with velocities obtained by in-situ data.     

A two-channel method for retrieval of the Black Sea surface temperature from Landsat-8 measurements

Izvestiya, Atmospheric and Oceanic Physics - The present work is devoted to the development of a retrieval algorithm for the sea surface temperature from the two-channel measurements of the...     

Comparing satellite and meteorological data on wind velocity over the Black Sea

Wind-velocity data obtained from in situ measurements at the Golitsyno-4 marine stationary platform have been compared with QuikSCAT scatterometer data; NCEP, MERRA, and ERA-Interim global reanalyses and MM5 regional atmospheric reanalysis. In order to adjust wind velocity measured at a height of 37 m above the sea surface to a standard height of 10 m with stratification taken into account, the Monin–Obukhov theory and regional atmospheric reanalysis data are used. Data obtained with the QuikSCAT scatterometer most adequately describe the real variability of wind over the Black Sea. Errors in reanalysis data are not high either: the regression coefficient varies from 0.98 to 1.06, the rms deviation of the velocity amplitude varies from 1.90 to 2.24 m/s, and the rms deviation of the direction angle varies from 26° to 36°. Errors in determining the velocity and direction of wind depend on its amplitude: under weak winds (<3 m/s), the velocity of wind is overestimated and errors significantly increase in determining its direction; under strong winds (>12 m/s), its velocity is underestimated. The influence of these errors on both spatial and temporal estimates of the characteristics of wind over the Black Sea is briefly considered.     

The North Atlantic Oscillation: A dominant factor in variations of oceanic circulation systems of the Atlantic Ocean

On the basis of altimetry data, the dynamics of the interaction between the subtropical anticyclonic (SA) and subpolar cyclonic (SC) gyres of the North Atlantic is considered. It is shown that the westerlies in the lower troposphere represented by the North Atlantic Oscillation (NAO) index are the main factor responsible for the dynamics of the gyres, which controls the inflow of warm Atlantic water into the Polar basin.     

Formation of the coastal current in the Black Sea caused by spatially inhomogeneous wind forcing upon the upper quasi-homogeneous layer

A poorly known mechanism of formation of a warm coastal current by spatially nonstationary and nonuniform wind forcing in the northeastern part of the Black Sea is described. Owing to the blocking influence of the Caucasian Mountains, the northeasterly wind (nordost) west and east of Tuapse is characterized by a spatially nonuniform speed distribution over the Russian sector of the sea. In the first half of the year, during the nordost wind, the intense wind forcing upon the upper quasi-homogeneous layer (UQL) leads to its fast cooling due to the turbulent entrainment of cold waters from the shallow seasonal thermocline. Satellite data and measurements from ships obtained at the end of June-beginning of July 2006 showed that, during two days, the temperature of the UQL west of Tuapse dropped by 7–10°C, whereas, east of Tuapse where the wind was weak, it practically did not change. As a result, a narrow frontal zone between the warm (less dense) and cold (denser) upper layer waters oriented quasi-normally to the shore was formed. A hydrodynamic analysis showed that, in such situation, an intense jet of a near-shore density current is developed that transports warm waters to the northwest at a velocity of 40–60 cm/s. This estimate agrees well with satellite data and observations from ships. The satellite data allowed us to find that this jet reached the Kerch Strait region in a few days. During the time of its existence (approximately 2 weeks), the jet transports a large volume of water and can change the functioning regime of the coastal ecosystem. The mechanism of the near-shore current formation revealed may also function in other seas and oceanic regions.     

Properties of the Vertical Distribution of Diurnal Temperature Variations in Different Seasons in the Black Sea Based on the NEMO Model Data

Izvestiya, Atmospheric and Oceanic Physics - A study has been performed for the Black Sea basin investigating the properties of the vertical distribution of the daily temperature variation in...     

Reconstruction of mean dynamic topography of the Black Sea for altimetry measurements

In this study a new approach for reconstructing the Mean Dynamic Topography of the Black Sea is applied. Constant observations (SVP measurements), drifters, and data of vertical sounding of the temperature and salt content together with measurements of sea level anomalies received from Topex/Poseidon mission satellite data were used. The absolute sea level received by altimetry data using the mean dynamic topography received during work was compared to the dynamic level received according to independent marine surveys. The comparison showed that the method represented in the study permits one to define more exactly the dynamic topography of the Black Sea when compared with the studies of previous authors. The results of this study will be useful to reconstruct the areas of the geostrophic currents according to satellite altimetry.