Contamination of the Black Sea surface water layer with oil hydrocarbons

At present, the studies of the Black Sea water contamination with oil hydrocarbons have been reduced and those of coastal water areas have been limited. However, no significant trends have been revealed towards the decrease in the concentration of these hazardous substances in the water from 1978 to 2012; moreover, it may have increased due to the activation of the navigation of offshore oil-and-gas complex and oil product transshipment. Therefore, the expert evaluation of the contamination of water in the Black Sea and some coastal areas with oil hydrocarbons is carried out using the available data of in situ observations.     

Satellite monitoring of pollution in the Russian sector of the Azov and Black Seas in 2003–2007

The results of satellite monitoring of pollution in the Russian sector of the Azov-Black Sea basin in 2003–2007 are considered. Within the framework of this work, a technology of monitoring the state and pollution of the water environment from satellite information received during this period from Russian and foreign satellites has been developed. With this technology, the coastal pollution parameters and hydrometeorological characteristics of the water environment in the area of observation were mapped operationally; 14 types of different satellite information products were issued daily; and the results were generalized over 3 days, ten days, a month, and a period of observation. Long-term satellite monitoring makes it possible to determine and analyze typical situations of pollution distribution in the coastal waters and to detect new circulation elements that transport pollutants, thus purifying the water environment. For example, for the first time, it was found from satellite data that the contribution of a small-scale circulation of waters of the Russian sector of the Black Sea to the transport and distribution of pollutants is commensurable with the contribution of the Main Black Sea Current and coastal anticyclonic eddies. The regularities in the dynamics of pollution distribution promote the increased reliability of charting of the environmental situation, including the prediction of dynamics of pollution spreading.     

Paleo-evolution of the Black Sea watershed: sea level and water transport through the Bosporus Straits as an indicator of the Lateglacial–Holocene transition

The paleo-evolution of the Black Sea level during the Lateglacial–Holocene transition is still unclear, which motivates us to provide new estimates for that period based on the analysis of water budget. Hydrological conditions in the Black Sea catchment area are reconstructed here using water balance equation, available data, and constraints based on simple theory relating the runoff ratio with climatic characteristics. In order to estimate the impact of the aridity of climate we consider two alternative scenarios: (1) climate change under constant in time gradient in precipitation and evaporation over land and sea, and (2) climate change accounting for changes in the horizontal distribution of precipitation and evaporation. Hydrological data are compiled from available present-day data and paleo-observations. A number of sensitivity experiments is carried out revealing that the hydrological conditions in the Black Sea watershed should have evolved towards a very arid climate (similar to the present-day climate in the Caspian Sea area) in order to initiate a drop of sea level of ∼100 m below the sill depth of the Bosporus Straits, as speculated in some recent research. Estimates of sea level changes reveal a qualitative agreement with the coast-line evolution inferred from paleo-observations. The Younger Dryas draw down of the Black Sea starts at about 13.3 to 13 kyr BP, with a maximum low-stand of 104 m at 11.5 kyr BP. In an arid climate scenario the sea level reaches the outlet at about 8.8 to 7.4 kyr BP. Approximately at that time, Mediterranean sea level was about 10 m higher, making flooding events of the Black Sea possible. However, the nature and exact timing of the Holocene reconnection depends also on other (not well known) factors; one of them is the Bosporus sill depth, motivating further research in this field. Estimates of the water transport through the Bosporus Straits are also provided for the time of Lateglacial–Holocene transition.     

Estimation of water balance components in the Black Sea

Presented are the estimates of precipitation amount and evaporation for the Black Sea basin based on the data of numerical regional reanalysis. The spatial distribution of considered variables is compared with the results obtained before using the method of extrapolation of measurements at the coastal meteorological stations. The computed water balance components of the Black Sea compared with the available literature data are used for obtaining the estimate of the mean water discharge in the Bosphorus.     

Regional features of long-term variability of the Black Sea surface temperature

The regional features oflong-term variability ofsea surface temperature (SST) in the Black Sea are analyzed using the satellite data for 1982-2014. It is demonstrated that the maximum intraannual and interannual variability of SST is registered on the northwestern shelf of the Black Sea. The high level of interannual variability of SST and maximum linear trends are observed in the northeastern part of the sea. The qualitative connection is revealed between the long-term variability of SST and the variations in the intensity of the Black Sea Rim Current in the long-term seasonal cycle. An increase in the level of interannual variability of SST is observed in summer, when the Black Sea Rim Current weakens. The significant negative correlation is revealed between the interannual anomalies of SST and the NAO index. The highest correlation coefficients are obtained for the eastern part of the Black Sea and near the Crimean coast.     

Long-term analysis of extreme wave characteristics based on the SWAN hindcasts over the Black Sea using two different wind fields

The long-term variations of wave characteristics in the Black Sea are evaluated by using a third-generation wave model (Simulating WAves Nearshore, SWAN), forced by the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim and National Centers for Environmental Prediction/Climate Forecast System Reanalysis (NCEP/CFSR) wind data, covering the period of 1979−2018. The model results were calibrated and validated with buoy measurements at seven stations along the Black Sea. The comparative study shows that the CFSR dataset predicted slightly greater significant wave heights than the ERA-Interim dataset. The greatest difference between two datasets in terms of wave characteristics was found in the northeastern part of the Black Sea. The long-term averages and the variations of long-term trends for wave characteristics show that southwestern part of the Black Sea was characterized by greater significant wave heights, longer mean wave periods and storm durations, and lower variability, while the northeastern part of the basin was characterized by lower significant wave heights, shorter mean wave periods and storm durations, and higher variability. The long-term trends indicate that the wave characteristics over the 40-year period are more likely to be exposed to higher variation on the eastern part of the Black Sea than the western part of the basin.     

Spatiotemporal long-term trends of extreme wind characteristics over the Black Sea

In this study, long-term change of wind characteristics on the Black Sea has been investigated using two widely used data sources, i.e., European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim and National Centers for Environmental Prediction/Climate Forecast System Reanalysis (NCEP/CFSR), spanning 40 years between 1979 and 2018. Spatial and seasonal variability of climatic features such as the wind speed, direction, number and duration of storms, and wind power density are discussed. Wind climate is characterized by strong, durable and stable winds in the northern and western Black Sea, and relatively weak, short-lived and highly-variable winds in the eastern Black Sea. These long-term wind patterns indicate that the eastern part of the basin is likely to be subjected to the impacts of climate change. Long-term stable and strong wind conditions in the southwest part indicate reliable, persistent and sustainable wind energy potential. Long-term and seasonal variation of wind power density (WPD) at 110 m altitude over the Black Sea is investigated. There is a significant difference in WPD values between winter and summer seasons, with around 2.8 times larger WPD in winter than that in summer. In the western Black Sea, narrow confidence intervals observed in each season indicate a low level of variation during a season and ensures stable wind power conditions.     

The Black Sea level trends from tide gages and satellite altimetry

Obtained are the estimates of the Black Sea level trends for the period of 1992–2005 as derived from the tide-gage and satellite altimetry data. An estimated rate of the mean sea level rate calculated from the averaged altimetry data is 7.6 ± 0.3 mm/year that is by 2–3 times higher than the estimates for the previous periods. Such high values of the trend are evidently associated with the sea level variability features at the 10-year temporal scale. The Black Sea level trend is characterized by the high spatial variability: it amounts to 8–9.5 mm/year in the coastal areas of the Black Sea basin that exceeds the trend in the deep-water part by 1.5–2 times (4.5–6 mm/year). Such distribution is an effect of the cyclonic Rim Current intensification. Based on the difference in the sea level trends obtained from in-situ and altimetry measurements, the velocity of the vertical crustal motion is estimated for the Ukrainian coastal stations of the Black Sea.     

Estimation of volumes of aerobic and anaerobic waters in the Black Sea and of oxygen and hydrogen sulfide contained in them

The mean depth of the upper boundary of the hydrogen sulfide zone (HSZ) in winter and summer is determined from the experimental data for the last 50 years. The estimates of aerobic and anaerobic water volumes and total oxygen and hydrogen sulfide in these seasons are derived from the data on the depth of the upper boundary of the HSZ position and more precise morphological parameters of the Black Sea. The aerobic and anaerobic water ratio is approximately 1: 10 in winter and 1: 9 in summer.     

Anomalies of hydrometeorological fields in the Black Sea area associated with sea surface temperature gradients in the North Atlantic

To describe the spatial structure of hydrometeorological fields in the North Atlantic and in the Black Sea, the temperature indices (sea surface temperature gradients) representing the difference in sea surface temperature anomalies averaged throughout the water area and normalized by standard deviations are introduced. Temperature gradients between the Sargasso Sea and the tropics (STI), the Sargasso Sea and the subpolar cyclonic gyre (SNI), the Sargasso Sea and the Black Sea (SBI) are considered. The spatial structure of the sea surface temperature field anomalies in the North Atlantic and in the Black Sea at extreme values of STI and SBI is discussed. A sign-variable structure of air temperature and precipitation anomalies in the Black Sea area at extreme values of SBI is shown. Time scales of sign-variable variability of anomalies of hydrometeorological fields in the Black Sea area are estimated.     

Complex analysis of natural hydrocarbon seeps in the eastern part of the Azov and Black sea basin based on satellite observations and data of geological and geophysical researches

The radar images of the eastern part of the Azov and Black seas received from the ENVISAT satellite in the general (2009–2011) and detailed (2003) surveys are analyzed. The relationship between the surface hydrocarbon seeps and the activity of underwater geological objects (mud volcanoes and diapirs) in shallow and deep sea areas is revealed on the basis of the complex analysis of satellite radar data and geological and geophysical information using the geoinformation system. The complex analysis of information at different levels of marine and geological environment taking account of morphological features of geological objects in deep sea areas enabled to explain the forms of oil seeps on the sea surface. The estimates are given of some characteristics of hydrocarbon seep sources such as the period of activity and the area of oil seeps. The typical deciphering indications for identifying the natural oil seeps represented on radar images and their differences from anthropogenic pollution and other slick-forming phenomena are presented and systematized.     

Climate of the Black Sea region around 0 C.E.

Indications of the climate of the Black Sea Region (the region up to about 500 km from the sea) are examined for a period of a few hundred years before and after 0 C.E. Much of the information is obtained from the work of Soviet scientists, some recent discovery regarding ice conditions on a high mountain of Turkey and from archeology of the region.Levels of the Black Sea, the Caspian and that of the large Lake Van were on the rise at the time. The most plausible cause for the level rise of the latter two exitless water bodies is increased precipitation and inflow from the drainage areas; in the Black Sea's case a contributory factor must have been the level rise of the world's oceans. Pollen investigations in the southern European Soviet Union, as well as the large quantities of wine and figs grown on the northern littoral of the Black Sea at the time, suggest that the climate was a little warmer than at present. The pollen investigations intimate a temperature level about 0.5 °C higher than the cold phase around the middle of the first millenium B.C. Support to the aforementioned inference is offered by the recently discovered ice conditions on Mt. Erciyas, Turkey, as they were 2000 years ago. It is also inferred that the precipitation level of the region was, generally, somewhat higher than nowadays.Finally, a brief review is made of glacier, tree-ring density and peatbog data for Europe and North America. They all show that the period around 0 C.E. was relatively warm.In 1986–90 visiting with the Department of Meteorology, University of Copenhagen, Copenhagen, Denmark.     

Inter-comparison of long-term wave power potential in the Black Sea based on the SWAN wave model forced with two different wind fields

In this study, a long-term comparative assessment of the potential of wave power in the Black Sea was conducted using the calibrated and validated SWAN (Simulating WAves Nearshore) model forced by two well-known wind fields. The European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim and National Centers for Environmental Prediction/Climate Forecast System Reanalysis (NCEP/CFSR) wind fields were used, covering data from 1979 to 2018. In general, the wave power potential based on the results of the CFSR wind field was found to be slightly higher than that obtained with the ERA-Interim wind field. The greatest discrepancy between the results of the ERA-Interim and CFSR wind fields was observed in the northeastern Black Sea. The spatial distributions of the wave power were also evaluated on a seasonal scale using wave parameters obtained from the calibrated SWAN model. The wave climate obtained from both long-term and seasonal assessments indicates that the western Black Sea, especially the southwestern Black Sea, is characterized by higher wave power potential and lower variability, while the eastern Black Sea has lower wave power potential and higher variability. Stable and powerful long-term wave conditions in the southwestern Black Sea can indicate that this region is a suitable location for wave farms. In contrast, the effect of the long-term variability on wave power is greatest in the eastern Black Sea owing to the highly variable wave conditions in this region.     

Temperature and Humidity Regime Changes on the Black Sea Coast in 1982-2014

Specific features of climate change in the Black Sea and on its northeastern coast for the period of 1982-2014 are investigated based on weather station data, ERA-Interim reanalysis, and satellite data on sea surface temperature. The main trends in air temperature and precipitation are revealed from weather station data and are compared with reanalysis data. The spatial peculiarities of variations in air temperature, integrated water vapor, moisture flux divergence, CAPE, and vertical velocity are analyzed. It is shown that air temperature variations on the coast highly correlate with sea surface temperature. In general, surface air temperature in the region has risen, especially in summer. Despite the increase in integrated water vapor and CAPE, no statistically significant increase was revealed for the mean amount of precipitation, for its intensity and maximum values. This fact might be associated with the moisture flux divergence increase in the region due to the intensification of large-scale downdrafts.     

Circulation over Bulgaria and its connection with NAO indices and Sea Surface Temperatures

Trends in atmospheric pressure, circulation and some relationships between North Atlantic Oscillation (NAO) indices, sea surface temperatures, and atmospheric circulation over Bulgaria are discussed in this article. Data for measured atmospheric pressure at stations Burgas, Pleven, and Sandanski are used. Information about atmospheric circulation over Bulgaria was obtained using sea level pressure and 700 hPa Omega (vertical velocity) reanalysis daily data for grid cells covering the territory of Bulgaria for the period 1948–2010. Zonal and meridional indices for Bulgaria were also calculated based on the data for sea level pressure. NAO index calculated by NOAA and NCAR is correlated with atmospheric pressure and circulation. A total of 12 areas in three major water basins influencing Bulgarian climate—North Atlantic, Mediterranean, and Black Seas—were studied. Main methods employed in the article are statistical—trend analysis, multiple linear regression, correlation, nonparametric tests, etc. There is no change in the mean values of atmospheric pressure over Bulgaria. Circulation over Bulgaria during the research period increases its anticyclonal patterns mainly due to the decrease of the number of cyclones. Dynamics in zonal and meridional indices for Bulgaria result in an increase of the northwest transport in the winter and an increase of the northeast transport in the summer. Cyclones over Bulgaria determine the values of atmospheric pressure. Influence of the NAO on atmospheric pressure and circulation is stronger in winter. Atmospheric processes, expressed by the number of cyclones and anticyclones, are most active in spring. Current trends are towards increasing of sea surface temperatures (SSTs) at all investigated places. Temporally, the effect of SSTs on the number of cyclones, anticyclones, zonal and meridional indices for Bulgaria during the different seasons comes with a delay of 1 to 3 months. Constructed multiple linear regression (MLR) models with predictors SSTs adequately describe the atmospheric circulation over Bulgaria. There is a clear pattern of SSTs distribution, which leads to a higher number of cyclones over Bulgaria in winter—lower than normal temperatures in the Aegean Sea and higher than normal in the Black Sea. A decrease in the difference of temperatures between the Gulf Stream and western colder parts leads to higher values of winter zonal transport over Bulgaria. Higher than normal temperatures in Black Sea lead to a higher number of cyclones in spring. Higher difference in temperatures of the North Atlantic leads to a stronger cyclogenesis and enhanced zonal transport, which affects autumn circulation over Bulgaria.     

Simulation of Extreme Surges in the Taganrog Bay with Atmosphere and Ocean Circulation Models

The simulation the most extreme surges over the period of instrumental observations in the Taganrog Bay since 1881, the surges occurred on March 24, 2013 and September 24, 2014. The objective of the simulation is to study surge formation features and to reveal requirements for the accuracy of simulating atmospheric and oceanic circulation in the Sea of Azov. For this purpose, the Institute of Numerical Mathematics Ocean Model (INMOM) with the spatial resolution of ~4 km and ~250 m was used. The atmospheric forcing over the Black Sea region was specified using ERA-Interim reanalysis data and WRF model data with the spatial resolution of 80 and 10 km, respectively. It is shown that the quality of simulation of extreme surges in the Sea of Azov is more dependent on the quality of the input atmospheric forcing than on the spatial resolution of the ocean circulation model. The usage of WRF data as atmospheric forcing allows the more accurate simulation of extreme surges. However, the simulation of the extreme surge of 2014 overestimates, and simulations for the 2013 surge underestimate the surge level. Evidently, as the used version of INMOM does not take into account the coastal zone flooding, the maximum surge value is overestimated.     

A technology of waterspout monitoring over the Russian part of the Black Sea

The technology of waterspout monitoring over the Russian part of the Black Sea is presented. The technology was developed using the foreign experience of tornado and waterspout prediction and the data from the meteorological observation network of the Russian Federation. The technology is based on the software for the organization and maintenance of operational database including the data of satellite imagery, numerical weather prediction models, lightning detection systems, and weather radars. It was found that the results of the use of the presented technology for analyzing waterspout-risk conditions during the waterspout season are of the greatest interest. The waterspout season in the Black Sea area usually begins in May and ends in September. The review of waterspout occurrence over the Russian part of the Black Sea in 2014 is presented.     

On the Black Sea circulation with very strong and weak winds

With a baroclinic prognostic model of sea dynamics, the annual cycle of the Black Sea hydrological regime is modeled for constantly changing atmospheric circulation types characteristic of the Black Sea. Emphasis is placed on the hydrological structure of the upper sea layer in two extreme meteorological situations, storm and near-calm conditions over the sea basin. A significant difference is found in the character of the sea currents, and the main sea circulation features are determined for such situations. The system of model equations is solved using a method of two-cycle splitting on a grid with a 5-km horizontal step and 32 levels in the vertical.     

天山南坡暖季暴雨过程的水汽来源及输送特征

利用1981—2020年5—9月天山南坡16个气象站逐日降水资料和NCEP/NCAR GDAS再分析资料,分析天山南坡暖季暴雨过程的环流形势,并采用HYSPLIT模式,模拟追踪水汽源地及输送特征。结果表明:天山南坡暖季暴雨主要发生在南亚高压双体型、500 hPa以上西南急流(气流)、700 hPa切变辐合以及天山地形辐合抬升的重叠区域。水汽主要源自中亚、大西洋及其沿岸、地中海和黑海及其附近,经TKAP(塔吉克斯坦、吉尔吉斯坦、阿富汗东北部、巴基斯坦北部和印度西北部)、南疆、北疆关键区,分别从偏西、偏南、偏北通道输入暴雨区,700 hPa以上偏西通道、以下偏北通道占主导地位,且贡献最大的是南疆关键区。源自中亚的水汽主要输送至暴雨区700 hPa及以下,对暴雨的贡献较大,且沿途损失较大;源自大西洋及其沿岸、地中海和黑海及其附近的水汽主要输送至暴雨区700 hPa以上,对暴雨的贡献较小。另外,中低层还存在源自北疆、南疆、北美洲东部、蒙古的水汽。基于上述特征,建立了天山南坡暖季暴雨过程水汽三维精细化结构模型。     

天山南坡暖季暴雨过程的水汽来源及输送特征

利用1981—2020年5—9月天山南坡16个气象站逐日降水资料和NCEP/NCAR GDAS再分析资料,分析天山南坡暖季暴雨过程的环流形势,并采用HYSPLIT模式,模拟追踪水汽源地及输送特征。结果表明:天山南坡暖季暴雨主要发生在南亚高压双体型、500 hPa以上西南急流(气流)、700 hPa切变辐合以及天山地形辐合抬升的重叠区域。水汽主要源自中亚、大西洋及其沿岸、地中海和黑海及其附近,经TKAP(塔吉克斯坦、吉尔吉斯坦、阿富汗东北部、巴基斯坦北部和印度西北部)、南疆、北疆关键区,分别从偏西、偏南、偏北通道输入暴雨区,700 hPa以上偏西通道、以下偏北通道占主导地位,且贡献最大的是南疆关键区。源自中亚的水汽主要输送至暴雨区700 hPa及以下,对暴雨的贡献较大,且沿途损失较大;源自大西洋及其沿岸、地中海和黑海及其附近的水汽主要输送至暴雨区700 hPa以上,对暴雨的贡献较小。另外,中低层还存在源自北疆、南疆、北美洲东部、蒙古的水汽。基于上述特征,建立了天山南坡暖季暴雨过程水汽三维精细化结构模型。