Pub Date : 2021-06-01DOI: 10.22449/0233-7584-2021-3-333-349
A. Chukharev, M. Pavlov
Purpose. The study is aimed at qualitative and quantitative analysis (based on the updated previously proposed multiscale model) of the experimental data on turbulence intensity and their comparison with theoretical and semi-empirical relationships for the purpose of describing the contributions of various turbulence sources. Methods and Results. A comparative analysis of experimental data and model calculations of turbulence characteristics near the sea surface was performed. The methods of theoretical assessing generation of turbulence in the near-surface sea layer by various physical processes are considered. The results of calculations by the well-known models of turbulent exchange were compared with the experimental data collected by the scientists of the Turbulence Department of MHI, RAS, using the specialized equipment. The analysis results made it possible to determine the possibility of applying the considered models for calculating turbulence intensity under different hydrometeorological conditions. At light winds, none of the models yielded the results which matched the measurement data. At moderate winds, the simulation results showed quite satisfactory agreement with the experiment data; and for strong winds, the multiscale model results were the best. This model was modified to assess the contributions of two other mechanisms of turbulence generation: the Stokes drift and the Langmuir circulations. Conclusions. Objective assessment of the turbulent exchange intensity requires taking into account of three main mechanisms of turbulence generation, namely flow velocity shear, wave motions and wave breaking. Depending on the hydrometeorological situation, each of these mechanisms can dominate in a certain depth range. The calculations performed using the updated model showed that the Stokes drift added 2–17 % to the total dissipation in the upper 30-meter layer, whereas the contribution of the Langmuir circulations calculated through dependence of the vertical velocity of kinetic energy transfer upon the Langmuir number, can reach 15 % for small Langmuir numbers.
{"title":"Model and Experimental Estimates of Vertical Mixing Intensity in the Sea Upper Homogeneous Layer","authors":"A. Chukharev, M. Pavlov","doi":"10.22449/0233-7584-2021-3-333-349","DOIUrl":"https://doi.org/10.22449/0233-7584-2021-3-333-349","url":null,"abstract":"Purpose. The study is aimed at qualitative and quantitative analysis (based on the updated previously proposed multiscale model) of the experimental data on turbulence intensity and their comparison with theoretical and semi-empirical relationships for the purpose of describing the contributions of various turbulence sources. Methods and Results. A comparative analysis of experimental data and model calculations of turbulence characteristics near the sea surface was performed. The methods of theoretical assessing generation of turbulence in the near-surface sea layer by various physical processes are considered. The results of calculations by the well-known models of turbulent exchange were compared with the experimental data collected by the scientists of the Turbulence Department of MHI, RAS, using the specialized equipment. The analysis results made it possible to determine the possibility of applying the considered models for calculating turbulence intensity under different hydrometeorological conditions. At light winds, none of the models yielded the results which matched the measurement data. At moderate winds, the simulation results showed quite satisfactory agreement with the experiment data; and for strong winds, the multiscale model results were the best. This model was modified to assess the contributions of two other mechanisms of turbulence generation: the Stokes drift and the Langmuir circulations. Conclusions. Objective assessment of the turbulent exchange intensity requires taking into account of three main mechanisms of turbulence generation, namely flow velocity shear, wave motions and wave breaking. Depending on the hydrometeorological situation, each of these mechanisms can dominate in a certain depth range. The calculations performed using the updated model showed that the Stokes drift added 2–17 % to the total dissipation in the upper 30-meter layer, whereas the contribution of the Langmuir circulations calculated through dependence of the vertical velocity of kinetic energy transfer upon the Langmuir number, can reach 15 % for small Langmuir numbers.","PeriodicalId":43550,"journal":{"name":"Physical Oceanography","volume":"1 1","pages":""},"PeriodicalIF":0.8,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68624845","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-04-28DOI: 10.22449/1573-160X-2021-2-180-190
A. Vidnichuk, S. Konovalov
Purpose. Assessing changes in the oxygen regime of the deep-water part of the Black Sea under the influence of climatic and anthropogenic factors over the past 40 years is the goal of the work. Methods and Results. For the analysis, the expedition data (2015–2019) and those from the Databank of the Marine Hydrophysical Institute, Russian Academy of Sciences, (1980–2013) were used. The data for the deep-water part of the Black Sea (the depths exceeding 200 m) were selected from the array. The data on hydrophysical and hydrochemical parameters were subjected to expert assessment, and those including random errors in the values were excluded from the array. Then the average profiles of temperature, salinity, oxygen concentration, oxygen saturation, and nitrates concentration were plotted in the density scale (σt). Averaging was carried out by the inverse distance method followed by additional smoothing by the low-frequency filtering method. Conclusions. Against the background of the tendency of temperature increase in the upper layers of the water column and decrease of winter convective mixing intensity, the oxygen supply diminishes in all the layers of the Black Sea aerobic zone. Having been analyzed, of the data for the 1980–2019 period showed that at the present stage, a "regime shift" resulting from the joint effect of climate changes and anthropogenic load took place in the ecosystem of the deep-water part of the Black Sea. Decrease in the oxygen saturation of water throughout the entire thickness of the aerobic zone shows that the process of the Black Sea basin eutrophication constitutes a significant factor affecting oxygen dynamics in the Black Sea waters.
{"title":"Changes in the Oxygen Regime in the Deep Part of the Black Sea in 1980–2019","authors":"A. Vidnichuk, S. Konovalov","doi":"10.22449/1573-160X-2021-2-180-190","DOIUrl":"https://doi.org/10.22449/1573-160X-2021-2-180-190","url":null,"abstract":"Purpose. Assessing changes in the oxygen regime of the deep-water part of the Black Sea under the influence of climatic and anthropogenic factors over the past 40 years is the goal of the work. Methods and Results. For the analysis, the expedition data (2015–2019) and those from the Databank of the Marine Hydrophysical Institute, Russian Academy of Sciences, (1980–2013) were used. The data for the deep-water part of the Black Sea (the depths exceeding 200 m) were selected from the array. The data on hydrophysical and hydrochemical parameters were subjected to expert assessment, and those including random errors in the values were excluded from the array. Then the average profiles of temperature, salinity, oxygen concentration, oxygen saturation, and nitrates concentration were plotted in the density scale (σt). Averaging was carried out by the inverse distance method followed by additional smoothing by the low-frequency filtering method. Conclusions. Against the background of the tendency of temperature increase in the upper layers of the water column and decrease of winter convective mixing intensity, the oxygen supply diminishes in all the layers of the Black Sea aerobic zone. Having been analyzed, of the data for the 1980–2019 period showed that at the present stage, a \"regime shift\" resulting from the joint effect of climate changes and anthropogenic load took place in the ecosystem of the deep-water part of the Black Sea. Decrease in the oxygen saturation of water throughout the entire thickness of the aerobic zone shows that the process of the Black Sea basin eutrophication constitutes a significant factor affecting oxygen dynamics in the Black Sea waters.","PeriodicalId":43550,"journal":{"name":"Physical Oceanography","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2021-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44280080","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-04-28DOI: 10.22449/1573-160X-2021-2-238-254
I. Timchenko, E. M. Igumnova, S. V. Svishchev
Purpose. The work is aimed at constructing an adaptive model of the ecological-economic system of the sea coastal zone intended to control the volume of consumption of marine assimilation and biological resources by the coastal socio-economic system. Methods and Results. The model based on tracking the integral balance of the rates of marine environment pollution and its purification due to the natural physical and biogeochemical processes and to the environmental actions is proposed. The average multi-year values of the ecosystem variables are used in the applied concept of stationary state of the marine ecosystem. To describe the conditions forming the polluted area in the coastal marine environment, proposed is the algorithm taking into account the ratio between the rate of growth of concentration of the pollutants inflowing from the coastal sources and the rate of their destruction resulting from natural purification of marine environment. Coastal pollution runoff was managed by the penalties imposed on the economic system, which was forced to reduce the generalized product output simultaneously increasing its prime cost. In the marine ecosystem model, the main lower links of the food chain were used: concentrations of phytoplankton, zooplankton and bacterioplankton. Their weighted sum constituted the marine biodiversity index, which was taken as a concentration of bio-resource consumed by the coastal economic system. It was believed that there was an inverse relationship between the biodiversity index and the pollution concentration. Therefore, the maximum permissible pollution concentration was assessed based on the permissible values of the biodiversity index. Along with control of the economic efficiency of marine resource consumption, the model provided for the biodiversity index monitoring so that it did not fall below its permissible vales. In this case, the management agent included in the model, limited production. The model equations are constructed by the method of adaptive balance of causes, which preserved the material balances resulting from the interaction between the environmental and economic processes. The modular equations of the method permitted to use the known stationary state of the ecosystem to obtain the estimates of the influence coefficients. It is shown that the forecasted scenarios provide the compromises between the efficiency of the coastal economic system and the ability of marine ecosystem to restore the consumed assimilation and biological resources. Conclusions. The proposed model makes it possible to forecast the scenarios of the ecological and economic processes that provide a balance of consumption and reproduction of marine resources.
{"title":"Managing the Balance of Consumption and Reproduction of Marine Resources in the “Coast – Sea” Ecological-Economic System","authors":"I. Timchenko, E. M. Igumnova, S. V. Svishchev","doi":"10.22449/1573-160X-2021-2-238-254","DOIUrl":"https://doi.org/10.22449/1573-160X-2021-2-238-254","url":null,"abstract":"Purpose. The work is aimed at constructing an adaptive model of the ecological-economic system of the sea coastal zone intended to control the volume of consumption of marine assimilation and biological resources by the coastal socio-economic system. Methods and Results. The model based on tracking the integral balance of the rates of marine environment pollution and its purification due to the natural physical and biogeochemical processes and to the environmental actions is proposed. The average multi-year values of the ecosystem variables are used in the applied concept of stationary state of the marine ecosystem. To describe the conditions forming the polluted area in the coastal marine environment, proposed is the algorithm taking into account the ratio between the rate of growth of concentration of the pollutants inflowing from the coastal sources and the rate of their destruction resulting from natural purification of marine environment. Coastal pollution runoff was managed by the penalties imposed on the economic system, which was forced to reduce the generalized product output simultaneously increasing its prime cost. In the marine ecosystem model, the main lower links of the food chain were used: concentrations of phytoplankton, zooplankton and bacterioplankton. Their weighted sum constituted the marine biodiversity index, which was taken as a concentration of bio-resource consumed by the coastal economic system. It was believed that there was an inverse relationship between the biodiversity index and the pollution concentration. Therefore, the maximum permissible pollution concentration was assessed based on the permissible values of the biodiversity index. Along with control of the economic efficiency of marine resource consumption, the model provided for the biodiversity index monitoring so that it did not fall below its permissible vales. In this case, the management agent included in the model, limited production. The model equations are constructed by the method of adaptive balance of causes, which preserved the material balances resulting from the interaction between the environmental and economic processes. The modular equations of the method permitted to use the known stationary state of the ecosystem to obtain the estimates of the influence coefficients. It is shown that the forecasted scenarios provide the compromises between the efficiency of the coastal economic system and the ability of marine ecosystem to restore the consumed assimilation and biological resources. Conclusions. The proposed model makes it possible to forecast the scenarios of the ecological and economic processes that provide a balance of consumption and reproduction of marine resources.","PeriodicalId":43550,"journal":{"name":"Physical Oceanography","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2021-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46643397","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-04-28DOI: 10.22449/1573-160X-2021-2-205-214
V. S. Suetin, S. Korolev
Purpose. he work is aimed at studying the effects of light absorption in the Black Sea waters with due regard for the variations of its individual components, and how they are manifested in the NASA archival results of calculating the chlorophyll a concentration obtained by processing satellite data using the universal operational method. Methods and Results. The NASA archival data of the MODIS and SeaWiFS satellite instruments, and the values of the light absorption components (determined by the method of Generalized ocean color inversion model for retrieving marine inherent optical properties (GIOP)) related to yellow substance and phytoplankton were analyzed. In order to avoid possible manifestations of various distortions in the results of determining the remote sensing reflectance of the sea and in the products resulted from application of the GIOP method, only the specially selected and sufficiently reliable test data from two areas located near the Crimea Southern Coast and south of the Danube estuary were used. Conclusions. In the considered examples with low content of chlorophyll a in the seawater, the yellow substance plays a predominant role in light absorption in the spectrum blue part, whereas if the chlorophyll a content is high, the phytoplankton contribution is dominant. The revealed relationship between the light absorption components related to yellow substance and phytoplankton significantly differs from that implicitly preset as a basis of the universal method (applied in NASA for the satellite data operational processing) for determining the chlorophyll a concentration. This, in its turn, is manifested in the fact that the data on the chlorophyll a concentration in the Black Sea stored in the NASA archive may be overestimated in case the chlorophyll a concentration is low, and underestimated – in case it is high.
{"title":"Application of Satellite Data for Retrieving the Light Absorption Characteristics in the Black Sea Waters","authors":"V. S. Suetin, S. Korolev","doi":"10.22449/1573-160X-2021-2-205-214","DOIUrl":"https://doi.org/10.22449/1573-160X-2021-2-205-214","url":null,"abstract":"Purpose. he work is aimed at studying the effects of light absorption in the Black Sea waters with due regard for the variations of its individual components, and how they are manifested in the NASA archival results of calculating the chlorophyll a concentration obtained by processing satellite data using the universal operational method. Methods and Results. The NASA archival data of the MODIS and SeaWiFS satellite instruments, and the values of the light absorption components (determined by the method of Generalized ocean color inversion model for retrieving marine inherent optical properties (GIOP)) related to yellow substance and phytoplankton were analyzed. In order to avoid possible manifestations of various distortions in the results of determining the remote sensing reflectance of the sea and in the products resulted from application of the GIOP method, only the specially selected and sufficiently reliable test data from two areas located near the Crimea Southern Coast and south of the Danube estuary were used. Conclusions. In the considered examples with low content of chlorophyll a in the seawater, the yellow substance plays a predominant role in light absorption in the spectrum blue part, whereas if the chlorophyll a content is high, the phytoplankton contribution is dominant. The revealed relationship between the light absorption components related to yellow substance and phytoplankton significantly differs from that implicitly preset as a basis of the universal method (applied in NASA for the satellite data operational processing) for determining the chlorophyll a concentration. This, in its turn, is manifested in the fact that the data on the chlorophyll a concentration in the Black Sea stored in the NASA archive may be overestimated in case the chlorophyll a concentration is low, and underestimated – in case it is high.","PeriodicalId":43550,"journal":{"name":"Physical Oceanography","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2021-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45819388","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-04-28DOI: 10.22449/1573-160X-2021-2-215-227
E. Skorokhod, T. Churilova, T. Efimova, N. Moiseeva, V. Suslin
Purpose. The purpose of the work is to evaluate accuracy of the satellite products for the coastal waters near Sevastopol, generated by the standard algorithms based on the MODIS and VIIRS (installed at the artificial Earth satellites Aqua and Terra, and at Suomi NPP, respectively) data. Methods and Results. In situ sampling was carried out at the station (44°37’26" N and 33°26’05" E) located at a distance of two miles from the Sevastopol Bay. The chlorophyll a concentration was measured by the spectrophotometric method. The spectral light absorption coefficients by optically active components were measured in accordance with the current NASA protocol. The spectroradiometers MODIS and VIIRS Level-2 data with spatial resolution 1 km in nadir around the in situ station (44°37’26"±0°00’32" N and 33°26’05"±0°00’54" E) were used. The satellite products were processed by the SeaDAS 7.5.3 software developed in NASA. The research showed that the standard NASA algorithms being applied to the MODIS and VIIRS data, yielded incorrect values of the optically active components’ content in the Black Sea coastal waters near Sevastopol as compared to the data of in situ measurements in the same region: the satellite-derived “chlorophyll a concentration” was on average 1.6 times lower in spring, and 1.4 times higher in summer; the contribution of phytoplankton to total light absorption at 443 nm was underestimated in 8.7 times; the light absorption by colored detrital matter was overestimated in 2.2 times. Conclusions. The NASA standard algorithms are inapplicable to calculating bio-optical indices in the coastal waters of the Black Sea near Sevastopol since they provide incorrect values of the satellite products (Ca-s, aph-s(443) and aCDM-s(443)). Operative ecological monitoring based on satellite data requires development of a regional algorithm taking into account the seawater optical features in the region and in the coastal zone, in particular.
{"title":"Bio-Optical Characteristics of the Black Sea Coastal Waters near Sevastopol: Assessment of the MODIS and VIIRS Products Accuracy","authors":"E. Skorokhod, T. Churilova, T. Efimova, N. Moiseeva, V. Suslin","doi":"10.22449/1573-160X-2021-2-215-227","DOIUrl":"https://doi.org/10.22449/1573-160X-2021-2-215-227","url":null,"abstract":"Purpose. The purpose of the work is to evaluate accuracy of the satellite products for the coastal waters near Sevastopol, generated by the standard algorithms based on the MODIS and VIIRS (installed at the artificial Earth satellites Aqua and Terra, and at Suomi NPP, respectively) data. Methods and Results. In situ sampling was carried out at the station (44°37’26\" N and 33°26’05\" E) located at a distance of two miles from the Sevastopol Bay. The chlorophyll a concentration was measured by the spectrophotometric method. The spectral light absorption coefficients by optically active components were measured in accordance with the current NASA protocol. The spectroradiometers MODIS and VIIRS Level-2 data with spatial resolution 1 km in nadir around the in situ station (44°37’26\"±0°00’32\" N and 33°26’05\"±0°00’54\" E) were used. The satellite products were processed by the SeaDAS 7.5.3 software developed in NASA. The research showed that the standard NASA algorithms being applied to the MODIS and VIIRS data, yielded incorrect values of the optically active components’ content in the Black Sea coastal waters near Sevastopol as compared to the data of in situ measurements in the same region: the satellite-derived “chlorophyll a concentration” was on average 1.6 times lower in spring, and 1.4 times higher in summer; the contribution of phytoplankton to total light absorption at 443 nm was underestimated in 8.7 times; the light absorption by colored detrital matter was overestimated in 2.2 times. Conclusions. The NASA standard algorithms are inapplicable to calculating bio-optical indices in the coastal waters of the Black Sea near Sevastopol since they provide incorrect values of the satellite products (Ca-s, aph-s(443) and aCDM-s(443)). Operative ecological monitoring based on satellite data requires development of a regional algorithm taking into account the seawater optical features in the region and in the coastal zone, in particular.","PeriodicalId":43550,"journal":{"name":"Physical Oceanography","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2021-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44820247","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-04-28DOI: 10.22449/1573-160X-2021-2-191-204
D. Kremenchutskii, K. Gurov
Purpose. The aim of the work is to study spatial variability of the 137Cs and 40K concentrations in the bottom sediments of the Balaklava Bay, and to estimate the sedimentation rate and relative content of the biogenic fraction. Methods and Results. The results of the 137Cs and 40K concentration measurements in 5 columns of the bottom sediments sampled in various parts of the Balaklava Bay are represented. Activity of 137Cs and 40K in the samples was determined by the gamma spectrometric analysis. Based on the measurement data, spatial variability of the 137Cs and 40K concentration fields in the bottom sediments was studied, and the sedimentation rate was quantitatively estimated. Application of the balance equation provided quantitative estimates of the relative biogenic fraction content; its spatial variability was described. Quantitative estimates of the relationship between the biogenic fraction estimates resulted from use of the direct and indirect methods are represented. Conclusions. According to the obtained results, the 137Cs and 40K concentrations in the upper 5 cm layer of bottom sediments varied in space from 11 to 62 and from 155 to 562 Bq/kg, respectively. The maximum radionuclide concentrations were characteristic of the northern part of the bay, the minimum ones – of its southern part. The sedimentation average rate was 0.51 ± 0.06 cm/year. Relative biogenic fraction content in the sediments varied in space from 30 to 89% and averaged 46 ± 25%. The maximum values were observed in the southern part of the bay, the minimum ones – in the northern part.
{"title":"Distribution of 137Cs and 40K in the Bottom Sediments of the Balaklava Bay (the Black Sea)","authors":"D. Kremenchutskii, K. Gurov","doi":"10.22449/1573-160X-2021-2-191-204","DOIUrl":"https://doi.org/10.22449/1573-160X-2021-2-191-204","url":null,"abstract":"Purpose. The aim of the work is to study spatial variability of the 137Cs and 40K concentrations in the bottom sediments of the Balaklava Bay, and to estimate the sedimentation rate and relative content of the biogenic fraction. Methods and Results. The results of the 137Cs and 40K concentration measurements in 5 columns of the bottom sediments sampled in various parts of the Balaklava Bay are represented. Activity of 137Cs and 40K in the samples was determined by the gamma spectrometric analysis. Based on the measurement data, spatial variability of the 137Cs and 40K concentration fields in the bottom sediments was studied, and the sedimentation rate was quantitatively estimated. Application of the balance equation provided quantitative estimates of the relative biogenic fraction content; its spatial variability was described. Quantitative estimates of the relationship between the biogenic fraction estimates resulted from use of the direct and indirect methods are represented. Conclusions. According to the obtained results, the 137Cs and 40K concentrations in the upper 5 cm layer of bottom sediments varied in space from 11 to 62 and from 155 to 562 Bq/kg, respectively. The maximum radionuclide concentrations were characteristic of the northern part of the bay, the minimum ones – of its southern part. The sedimentation average rate was 0.51 ± 0.06 cm/year. Relative biogenic fraction content in the sediments varied in space from 30 to 89% and averaged 46 ± 25%. The maximum values were observed in the southern part of the bay, the minimum ones – in the northern part.","PeriodicalId":43550,"journal":{"name":"Physical Oceanography","volume":"1 1","pages":""},"PeriodicalIF":0.8,"publicationDate":"2021-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41333321","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-04-28DOI: 10.22449/1573-160X-2021-2-135-148
G. V. Zhegulin, A. Zimin
Purpose. The aim of the work is to test the bispectral wavelet analysis being applied as a tool for studying resonance interactions between the frequency components in the spectrum of internal waves (based on the example both of the model signals, the shape of which is similar to that of the solitons and boras, and the field observations data on temperature fluctuations resulted from the internal waves in the Gorlo Strait of the White Sea). Methods and Results. The paper represents a technique for detecting three-wave interactions in the internal waves’ spectrum. The method is based on the bispectral wavelet analysis. It permits to identify the interharmonic correlation and the magnitude of the quadratic phase relationship arising as a result of nonlinear interactions between the signal frequency components. In the first part of the paper, efficiency of the applied method was evaluated using the example of various artificial signals with quadratic nonlinearity in order to demonstrate the method features and advantages. In its second part, the method was used to analyze the temperature profiles obtained by scanning thermohaline sounding, in which the oscillations related to passing of the internal wave groups were recorded. It is shown that the waves with the 40 min period are generated due to quadratic nonlinearity. The auto-bicoherence function values confirm the fact that the higher harmonics are formed in the 60–120 min range as a result of the three-wave interactions. They change synchronously in time, and their amplitudes are proportional, that is typical of the initial stage of the waves’ nonlinear transformation. Absence of a periodic change in the biphase sign in the considered range indicates insignificant influence of the dispersion effects upon the short-period internal waves’ structure. Conclusions. The example of observations in the Gorlo Strait of the White Sea shows that the recorded asymmetric structure of the isotherm oscillations was formed being influenced by the three-wave interaction. Possibility of further application of the method for studying the processes of the internal waves’ nonlinear transformation and breaking is discussed.
{"title":"Application of the Bispectral Wavelet Analysis for Searching Three-Wave Interactions in the Spectrum of Internal Waves","authors":"G. V. Zhegulin, A. Zimin","doi":"10.22449/1573-160X-2021-2-135-148","DOIUrl":"https://doi.org/10.22449/1573-160X-2021-2-135-148","url":null,"abstract":"Purpose. The aim of the work is to test the bispectral wavelet analysis being applied as a tool for studying resonance interactions between the frequency components in the spectrum of internal waves (based on the example both of the model signals, the shape of which is similar to that of the solitons and boras, and the field observations data on temperature fluctuations resulted from the internal waves in the Gorlo Strait of the White Sea). Methods and Results. The paper represents a technique for detecting three-wave interactions in the internal waves’ spectrum. The method is based on the bispectral wavelet analysis. It permits to identify the interharmonic correlation and the magnitude of the quadratic phase relationship arising as a result of nonlinear interactions between the signal frequency components. In the first part of the paper, efficiency of the applied method was evaluated using the example of various artificial signals with quadratic nonlinearity in order to demonstrate the method features and advantages. In its second part, the method was used to analyze the temperature profiles obtained by scanning thermohaline sounding, in which the oscillations related to passing of the internal wave groups were recorded. It is shown that the waves with the 40 min period are generated due to quadratic nonlinearity. The auto-bicoherence function values confirm the fact that the higher harmonics are formed in the 60–120 min range as a result of the three-wave interactions. They change synchronously in time, and their amplitudes are proportional, that is typical of the initial stage of the waves’ nonlinear transformation. Absence of a periodic change in the biphase sign in the considered range indicates insignificant influence of the dispersion effects upon the short-period internal waves’ structure. Conclusions. The example of observations in the Gorlo Strait of the White Sea shows that the recorded asymmetric structure of the isotherm oscillations was formed being influenced by the three-wave interaction. Possibility of further application of the method for studying the processes of the internal waves’ nonlinear transformation and breaking is discussed.","PeriodicalId":43550,"journal":{"name":"Physical Oceanography","volume":"28 1","pages":""},"PeriodicalIF":0.8,"publicationDate":"2021-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43766094","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-04-28DOI: 10.22449/1573-160X-2021-2-165-179
I. Shokurova, A. Kubryakov, M. Shokurov
Purpose. The paper is aimed at studying the relationship between the wind regime and the wind stress curl in the Black Sea and the long-term changes in the large-scale sea level pressure field in winter months. Methods and Results. The data on wind speed and sea level pressure in January – February from the NCEP/NСAR reanalysis for 1948–2018 are used. Based on the 6-hour data, the synoptic conditions accompanied by high and low values of the wind stress curl in the sea were determined. The synoptic situations in which a vast anticyclone is located north and northeast of the sea, and the area of low pressure – to the southwest of the sea in the Mediterranean region, are accompanied by the northeast and east winds, and by the cyclonic curl predominance. On the contrary, passing of the cyclones to the north of the sea and increase of pressure to the southwest are followed by the westerly and southwesterly winds, and by the anticyclonic curl predominance. Extremely high monthly mean values of the cyclonic curl were observed in those years, when the area occupied by the Siberian anticyclone increased and expanded westward, so that the Black Sea was on the southwestern periphery of its spur. Extremely low values of the anticyclonic curl were noted when the Azores anticyclone area expanded to the Mediterranean region. The wind stress curl changes on the multidecadal scales have shown its relation to the global changes in the field of the sea level pressure and the sign of the pressure anomalies at the low latitudes. Conclusions. The opposite sign of the surface pressure anomalies to the northeast and southwest of the sea is accompanied by the highest values of the wind stress curl.
{"title":"Influence of Long-Term Changes in the Large-Scale Sea Level Pressure Field on the Wind Regime and the Wind Stress Curl in the Black Sea","authors":"I. Shokurova, A. Kubryakov, M. Shokurov","doi":"10.22449/1573-160X-2021-2-165-179","DOIUrl":"https://doi.org/10.22449/1573-160X-2021-2-165-179","url":null,"abstract":"Purpose. The paper is aimed at studying the relationship between the wind regime and the wind stress curl in the Black Sea and the long-term changes in the large-scale sea level pressure field in winter months. Methods and Results. The data on wind speed and sea level pressure in January – February from the NCEP/NСAR reanalysis for 1948–2018 are used. Based on the 6-hour data, the synoptic conditions accompanied by high and low values of the wind stress curl in the sea were determined. The synoptic situations in which a vast anticyclone is located north and northeast of the sea, and the area of low pressure – to the southwest of the sea in the Mediterranean region, are accompanied by the northeast and east winds, and by the cyclonic curl predominance. On the contrary, passing of the cyclones to the north of the sea and increase of pressure to the southwest are followed by the westerly and southwesterly winds, and by the anticyclonic curl predominance. Extremely high monthly mean values of the cyclonic curl were observed in those years, when the area occupied by the Siberian anticyclone increased and expanded westward, so that the Black Sea was on the southwestern periphery of its spur. Extremely low values of the anticyclonic curl were noted when the Azores anticyclone area expanded to the Mediterranean region. The wind stress curl changes on the multidecadal scales have shown its relation to the global changes in the field of the sea level pressure and the sign of the pressure anomalies at the low latitudes. Conclusions. The opposite sign of the surface pressure anomalies to the northeast and southwest of the sea is accompanied by the highest values of the wind stress curl.","PeriodicalId":43550,"journal":{"name":"Physical Oceanography","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2021-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46767070","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-04-28DOI: 10.22449/1573-160X-2021-2-228-237
А. L. Chikin, L. Chikina
Purpose. Numerical study based on the model example is aimed at examining the process of the salt water inflow to the Stary Don sleeve from the Taganrog Bay due to the wind water surge. Methods and Results. Complex mathematical model of the flow and salt distribution in the open riverbed is described. The section of the River Don, consisting of the Stary Don sleeve and a part of the main channel was considered. Salt is delivered through the host reservoir – the Taganrog Bay. The model is described by the system of Saint-Venant equations and the convection-diffusion equation. The problem is solved by the finite-difference methods. The results of the numerically studied influence of the sea surface level in the Taganrog Bay both on the flow nature in the Don Delta area and the degree of salt penetration upstream of the river are obtained. It was numerically established that the flow rate did not significantly affect salt concentration in the Don main channel. Conclusions. The computational experiments showed that the decisive factor in the process of the salt water inflow to the Don Delta from the Taganrog Bay consisted in the sea level significant increase resulting from extreme wind surges; and the preceding runoffs enhanced this effect even greater. The represented model gives an idea of the general trend in the process of the Don Delta possible salinization as a result of the surge phenomena.
{"title":"Numerical Study of the Process of Salt Water Inflow to the Don Mouth from the Taganrog Bay","authors":"А. L. Chikin, L. Chikina","doi":"10.22449/1573-160X-2021-2-228-237","DOIUrl":"https://doi.org/10.22449/1573-160X-2021-2-228-237","url":null,"abstract":"Purpose. Numerical study based on the model example is aimed at examining the process of the salt water inflow to the Stary Don sleeve from the Taganrog Bay due to the wind water surge. Methods and Results. Complex mathematical model of the flow and salt distribution in the open riverbed is described. The section of the River Don, consisting of the Stary Don sleeve and a part of the main channel was considered. Salt is delivered through the host reservoir – the Taganrog Bay. The model is described by the system of Saint-Venant equations and the convection-diffusion equation. The problem is solved by the finite-difference methods. The results of the numerically studied influence of the sea surface level in the Taganrog Bay both on the flow nature in the Don Delta area and the degree of salt penetration upstream of the river are obtained. It was numerically established that the flow rate did not significantly affect salt concentration in the Don main channel. Conclusions. The computational experiments showed that the decisive factor in the process of the salt water inflow to the Don Delta from the Taganrog Bay consisted in the sea level significant increase resulting from extreme wind surges; and the preceding runoffs enhanced this effect even greater. The represented model gives an idea of the general trend in the process of the Don Delta possible salinization as a result of the surge phenomena.","PeriodicalId":43550,"journal":{"name":"Physical Oceanography","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2021-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42662131","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-04-28DOI: 10.22449/1573-160X-2021-2-149-164
I. D. Rostov, E. Dmitrieva, N. Rudykh
Purpose. The study is aimed at identifying the regional features of the surface air temperature in the coastal zone and over the Pacific Ocean (to the north of 40° N) manifested as a result of global climate changes at the turn of the XX–XXI centuries, and at assessing their trends and possible causal relationships with the processes in the atmosphere and on the ocean surface. Methods and Results. Based on the Global Meteorological Network and NOAA reanalysis data, the regional features of interannual oscillations of the surface air temperature and their relationship with variations in the fields of pressure, wind and water temperature on the ocean surface, and with climate indices over the past 4 decades were identified. In order to determine the temperature field spatial-temporal structure and to zone the water area according to the features of climate changes, the methods of cluster, correlation analysis and the apparatus of empirical orthogonal functions were used. The results obtained made it possible to characterize the degree of heterogeneity of the studied area response to the ongoing global changes, to identify different domains and to assess quantitatively the warming rate in these water areas. Conclusions. The tendencies of modern warming are manifested in the trends of interannual air temperature variability, on the average, by ~0.20°C/10 years in the subarctic, and indicate significant regional differences (1.5–2 times) in the ongoing changes. In the west of the region, the warming rate is higher than in the east, where the temperature trends are minimal or statistically insignificant. In the warm period of a year, their values are higher than those in the cold period. The alternation phases of the warm and cold periods are consistent with the variation tendencies in the characteristics both of the atmospheric action centers and various climatic parameters. The corresponding correlations are most widely manifested in variations in the empirical orthogonal functions modes of the H500 geopotential field, and the PDO, NP, SOI, PTW, AD and EP/NP indices. Stable anomalies and trends of the ocean surface temperature in the North Atlantic also play an important role in formation of the Та anomalies in the western subarctic.
{"title":"Climatic Changes of Thermal Conditions in the Pacific Subarctic at the Modern Stage of Global Warming","authors":"I. D. Rostov, E. Dmitrieva, N. Rudykh","doi":"10.22449/1573-160X-2021-2-149-164","DOIUrl":"https://doi.org/10.22449/1573-160X-2021-2-149-164","url":null,"abstract":"Purpose. The study is aimed at identifying the regional features of the surface air temperature in the coastal zone and over the Pacific Ocean (to the north of 40° N) manifested as a result of global climate changes at the turn of the XX–XXI centuries, and at assessing their trends and possible causal relationships with the processes in the atmosphere and on the ocean surface. Methods and Results. Based on the Global Meteorological Network and NOAA reanalysis data, the regional features of interannual oscillations of the surface air temperature and their relationship with variations in the fields of pressure, wind and water temperature on the ocean surface, and with climate indices over the past 4 decades were identified. In order to determine the temperature field spatial-temporal structure and to zone the water area according to the features of climate changes, the methods of cluster, correlation analysis and the apparatus of empirical orthogonal functions were used. The results obtained made it possible to characterize the degree of heterogeneity of the studied area response to the ongoing global changes, to identify different domains and to assess quantitatively the warming rate in these water areas. Conclusions. The tendencies of modern warming are manifested in the trends of interannual air temperature variability, on the average, by ~0.20°C/10 years in the subarctic, and indicate significant regional differences (1.5–2 times) in the ongoing changes. In the west of the region, the warming rate is higher than in the east, where the temperature trends are minimal or statistically insignificant. In the warm period of a year, their values are higher than those in the cold period. The alternation phases of the warm and cold periods are consistent with the variation tendencies in the characteristics both of the atmospheric action centers and various climatic parameters. The corresponding correlations are most widely manifested in variations in the empirical orthogonal functions modes of the H500 geopotential field, and the PDO, NP, SOI, PTW, AD and EP/NP indices. Stable anomalies and trends of the ocean surface temperature in the North Atlantic also play an important role in formation of the Та anomalies in the western subarctic.","PeriodicalId":43550,"journal":{"name":"Physical Oceanography","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2021-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43745339","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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