Preliminary results of measurements of atmospheric turbulence over the sea

We perform the experimental verification of the applicability of the theory of similarity to the wave boundary layer and the assessment of wave-induced perturbations of the air flow depending on various conditions of stratification of the atmosphere and the state of the sea. The measurements were carried out from a stationary platform located in the coastal part of the Black Sea. The experimental procedure is based on the simultaneous measurements of the profile and fluctuations of the wind speed at 5–6 levels in the 1.3–21-m layer, the elevations of the sea surface, the directions of waves and winds, and the mean gradients of temperature and humidity of air. The structure of the boundary layer in the region of measurements depends on the direction of the wind. For weak and moderate onshore winds (< 9 m/sec), the approximate balance is preserved between the production and dissipation of turbulent energy in the cases of unstable and neutral stratification. On the average, the estimates of friction velocity according to the profiles are higher than the dissipative estimates by 10% mainly due to the deficiency of dissipation near the surface. For the offshore wind, the structure of the boundary layer abruptly changes and is determined not by the local parameters but by strong turbulent eddies formed over the dry land. The intensity of low-frequency turbulent fluctuations and the gradient of wind velocity near the surface in the coastal zone are 1.5–2 times higher than for the open sea. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 3, pp. 42–61, May–June, 2007.     

Probability distributions of peaks,troughs and heights of wind waves measured in the black sea coastal zone

The present paper examines the adequacy of different probability density functions to describe the peaks, troughs and peak-to-trough excursions of wind waves measured in the coastal zone of the Bulgarian part of the Black sea. For that purpose various theories for non-Gaussian random process are applied. Some theories depend on the mean, variance and coefficient of skewness γ₃ of the process. Others also take the coefficient of kurtosis γ₄ into consideration. The analyzed field data are gathered in the coastal zone of the Bulgarian part of the Black sea with depth decreasing from 18 to 1.3 m. The measurements are carried out simultaneously for 11 points with time series of 20 min duration. The coefficients of skewness and kurtosis in those time series are expressed as functions of depth and spectral peak frequency. Analogous dependencies on depth of other parameters are also found. As a result of the investigation it is concluded that the probabilities of occurrence of large wave crests and heights are underpredicted by all of the theories considered.     

Detecting a response to weak sea breezes in the New South Wales coastal ocean

Current meter data from the coastal ocean at Sydney, south‐eastern Australia, were analysed to seek evidence of a response to the prevailing summer sea breeze. A response to the sea breeze was found in the currents. This is significant since the magnitude of the sea breeze was small by comparison with winds associated with large‐scale pressure systems and the East Australian Current. Responses were determined by analysing short periods (3–5 days) of sea breeze activity as opposed to the whole 2‐month data set. The correlations between the alongshore nearshore diurnal‐period currents and the local wind stress during the sea breeze periods were significantly higher than the correlations during non‐sea‐breeze periods. Despite the stronger correlations the sea breeze could only account for around one‐quarter of the variance in the diurnal‐period currents. However, the detection of the response to the sea breeze is significant since the sea breeze has never previously been identified as a process for forcing alongshore nearshore currents on this shelf.     

Coastal vulnerability assessment of the future sea level rise in Udupi coastal zone of Karnataka state, west coast of India

Udupi coast in Karnataka state, along the west coast of India, selected as a study area, is well known for sandy beaches, aquaculture ponds, lush greenery, temples and major and minor industries. It lies between 13°00′00″–13°45′00″ north latitudes and 74°47′30″–74°30′00″ east longitudes, the length of the coastline is 95 km, and is oriented along the NNW–SSE direction. It is vulnerable to accelerated sea level rise (SLR) due to its low topography and its high ecological and touristy value. The present study has been carried out with a view to calculate the coastal vulnerability index (CVI) to know the high and low vulnerable areas and area of inundation due to future SLR, and land loss due to coastal erosion. Both conventional and remotely sensed data were used and analysed through the modelling technique and by using ERDAS Imagine and geographical information system software. The rate of erosion was 0.6018 km²/yr during 2000–2006 and around 46 km of the total 95 km stretch is under critical erosion. Out of the 95 km stretch coastline, 59% is at very high risk, 7% high, 4% moderate and 30% in the low vulnerable category, due to SLR. Results of the inundation analysis indicate that 42.19 km² and 372.08 km² of the land area will be submerged by flooding at 1 m and 10 m inundation levels. The most severely affected sectors are expected to be the residential and recreational areas, agricultural land, and the natural ecosystem. As this coast is planned for future coastal developmental activities, measures such as building regulation, urban growth planning, development of an integrated coastal zone management, strict enforcement of the Coastal Regulation Zone (CRZ) Act 1991, monitoring of impacts and further research in this regard are recommended for the study area.     

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.     

浙江省沿海海面日极大风预报

利用浙江海岛站1天4次的平均风速作为人工神经网络的输入层,相对应的日极大风为输出层,建立日极大风速人工神经网络预报模型,试报表明夏季大风天气系统和秋冬季大风天气系统的预报拟合率为89%~90%,春季大风天气系统的预报拟合率为87%~88%,夏季大风天气系统和秋冬季系统6~9级极大风预报准确率较高,基本在70%左右,对预报员有较好的参考价值。与以前大风预报方法相比,它具有简单、有效的优点,可以不受地域限制在各地推广使用。     

Field studies of the motion of sediments in the coastal zone of the sea

We present the results of measurements carried out with the help of the “Donnaya Stantsiya” complex of equipment in the coastal zone of the Crimean shelf near Evpatoriya and near the southeast end of the Kosa Tuzla Island. For the same intensity of winds in these regions, the intensities of waves and turbulence in the coastal zone near Evpatoriya are much higher and, hence, the fluxes of suspended sediments are more intense. The accumulated data are intended for the correction of the kinetic model used for the evaluation of the characteristics of the field of suspended sediments in the shallow-water areas.     

A stochastic model of the atmospheric precipitation in the coastal zone of the Tropical Atlantic

A stochastic prognostic model of the atmospheric precipitation in the tropical area of the Atlantic Ocean is developed on the basis of a large data array. The data represent a series of monthly precipitation rates for 31 towns in the Republic of Guinea covering a period of 35–64 years as well as satellite data on the meridional displacement of the Intertropical Convergence Zone during 11 years. The model takes into account major regularities of the tropical precipitation: their impulsive periodic regime, trends, and the modulation of the stochastic component by the determined variability.Translated by Mikhai M. Trufanov.     

Spatio-temporal variability in sea surface wind stress near and off the east coast of Korea

Sea surface wind stress variabilities near and off the east coast of Korea, are examined using 7 kinds of wind datasets from measurements at 2 coastal (land) stations and 2 ocean buoys,satellite scatterometer (QuikSCAT), and global reanalyzed products (ECMWF,NOGAPS,and NCEP/NCAR). Temporal variabilities are analyzed at 3 frequency bands; synoptic (2-20 d), intra-seasonal (20-90 d),and seasonal (>90 d).Synoptic and intra-seasonal     

Information-and-measuring drifter system for the monitoring of currents in the coastal zone of the sea

The autonomous drifting buoys equipped with satellite link turn into one of the most important components of the global system of operative observations of the ocean and the surface layer of the atmosphere. However, on the regional level, the problem of analysis of the surface circulation of waters in the coastal zone and sea straits remains quite urgent because the available drifters cannot be used in this case due to their sizes and long intervals between measurements. We present the results of development and testing of a new drifter system aimed at measuring currents. The system is based on the use of buoys operating at depths less than 1 m. To improve the space-and-time resolution of measurements, the buoys are equipped with receivers of the global positioning system (GPS) and GSM modems for the data transfer via cellular communication networks. The drifter system guarantees the possibility of determination of the coordinates of buoys with a resolution of 3 min in time and 14 m in space. We describe the specific features of the design of the proposed information-and-measuring drifter system and present the first results of application of new buoys called “minidrifters” for the pilot monitoring of currents in the Kerch Strait.     

Effects of sea roughness and atmospheric stability on wind wave growth

The paper considers the effects of sea roughness and atmospheric stability on the wind wave growth by using the logarithmic boundary layer profile including a stability function, as well as adopting Toba et al.'s [J. Phys. Ocean. 34 (1990) 705] significant wave height formula combined with some commonly used sea surface roughness formulations. The wind wave growth is represented by the non-dimensional total wave energy relative to that for neutral stability used by Young [Coast. Engng 34 (1998) 23]. For a given velocity at the 10 m elevation, spectral peak period and stability parameter, the wind wave growth is determined.     

Preferences of coastal zone user groups regarding the siting of offshore wind farms

Offshore wind power has a large potential as a vast resource for delivering clean and abundant energy on a global scale. However, the siting of offshore wind farms in the coastal zone has negative effects on the seascape. This might be particularly evident in the case if offshore wind farms are located close to areas with recreational activities in the coastal zone. Extending the analysis from a previous investigation of the preference for reducing visual impacts from offshore wind farms, the present paper utilises the same sample representing the Danish population. Based on the stated preferences from a Choice Experiment in a mail survey the preferences for reducing visual disamenities from offshore wind farms among different types of coastal zone users are compared to the preferences of less frequent users of the coastal zone. The results strongly indicate that in addition people who can see offshore wind farms from their residence, anglers and recreational boaters, i.e. users of the coastal zone, significantly perceive the visual impacts to be more negative compared to people who do not use the coastal area for those specific purposes. Furthermore, the results also indicate that respondents who visit the beach on a frequent basis also have stronger preferences for reducing the visual disamenities, when compared to less frequent visitors. As a consequence, the specific users and frequent visitors of the coastal zone are willing to pay approximately twice as much to have future offshore wind farms moved further away from the coast, when compared to less frequent users and visitors. These results display that, given the wind farms are not located at relative large distance from the shore, the recreational value of the coastal use is potentially jeopardised by visual impacts from offshore wind farms. From an energy planner's point of view, these results are noteworthy, as they – everything else being equal – point towards that potential gains in capital cost (investment, construction and running costs) by locating offshore wind farms at relative close distances from the shore might be outweighed by the visual disamenity costs in coastal areas with a large recreational activity. As such, the optimal location, i.e. distance from the shore, of offshore wind farms might be closer to the coast in areas with little recreational activities compared to coastal areas with a higher level of recreational activities.     

Manifestations of water dynamics in the coastal zone in the field of breaking of wind waves

In the coastal zone, as a result of mixing of waters, it is difficult to identify turbulent phenomena with a spatial scale of 0.1–1 km accompanied by strong vertical flows according to the data of measuring temperature. On the basis of the data of direct measurements, it is shown that turbulent structures are well pronounced in the field of breaking of wind waves. We deduce empirical estimates of the response of the intensity of wave breaking to the magnitude of divergence of the current and develop a theoretical model of the influence of inhomogeneities of currents on wave breaking capable of describing the experimental data. Translated by Peter V. Malyshev and Dmitry V. Malyshev     

Control over the ecological-economic processes in the integral model of the coastal zone of the sea

We consider integral dynamic models of the ecological-economic systems of the coastal zone of the sea aimed at the establishment of balance between the consumption and reproduction of marine bioresources. The models are constructed with the help of the systems approach according to which the economic aims of the consumption of bioresources depend on the ecological state of marine media. Examples of control over the balance of ecological-economic processes based on the use of the integral criteria of biodiversity and the level of pollution of marine media are presented. It is shown that the information technology of control over the scenarios of ecological-economic processes enables us to estimate the profitability of production of seafood under the conditions of use of a part of the profit for the preservation of marine bioresources.     

基于合成孔径雷达的长江口海表流场反演

Range Doppler velocities derived from the Envisat advanced synthetic aperture radar（ASAR） wide swath images are analyzed and assessed against the numerically simulated surface current fields derived from the finite volume coastal ocean model（FVCOM） for the Changjiang Estuary. Comparisons with the FVCOM simulations show that the European Space Agency（ESA） Envisat ASAR based Doppler shift anomaly retrievals have the capability to capture quantitative information of the surface currents in the Changjiang Estuary. The uncertainty analysis of the ASAR range Doppler velocity estimates are discussed with regard to the azimuthal and range bias corrections, radar incidence angles, inaccuracy in the wind field corrections and the presence of rain cells.The corrected range Doppler velocities for the Changjiang Estuary area are highly valuable as they exhibit quantitative expressions related to the multiscale upper layer dynamics and surface current variability around the East China Sea, including the Changjiang Estuary.     

On the effect of the coastal zone wind regime on the optical characteristics of haze

Based on an experimental study of directed dissipation coefficients and aerosol microstructure in the coastal area the problem of wind regime manifestation is considered. It is shown that the main changes of parameters of dissipation indicatrix form near angles =15°–165°, which are conditioned by submicron fractions of aerosol particles, take place without regard for wind regime. Usually they are defined by effect of relative air humidity. It is found that specific manifestations of wind regime are observed close to small dissipation angles and are conditioned by the effect of coarse-dispersed aerosol fractions.UDK 551.593     

Flow resistance in the coastal zone

The apparent bed roughness, the roughness value experienced by a mean flow outside the wave-boundary layer, is deduced from the physical bed roughness and the wave–current interaction mechanism. Both the physical bed roughness and the wave–current interaction are described by a (combination of) model(s). Modelling of the apparent bed roughness leads to realistic results, however, the final results are rather sensitive to the particular choice of these models. Four bed form models and two wave–current interaction models were implemented in a 1-DV flow model to calculate near-bed velocities. A comparison between measured and predicted velocities shows that reasonable results can be obtained in this way. A constant bed roughness of 0.1 m, however, leads to even better results at this site during all conditions. This can be explained by the reversed influence of the form roughness and the wave–current interaction on the apparent bed roughness value for varying wave conditions.