Effects of the distribution of hydrological and hydrobiological parameters on the structure of transparency field in the upper layer of the Black Sea pelagic zone

Considered are the effects of suspended matter content and water mass dynamics on the formation of optical structure of water in the upper layer of the deep part of the Black Sea using the data of long-term simultaneous observations. It is demonstrated that the peculiarities of horizontal distribution of the depth of transparent and turbid optical layers depend on the distribution of hydrological parameters characterizing the dynamic processes in the upper layer of the sea. Computed and analyzed are the parameters of regression relationship between the beam attenuation coefficient and the concentration of organic and total suspension and chlorophyll-a as well as between the depth of transparent layer and the position of the lower boundary of cold intermediate layer in different dynamic formations in spring, summer, and autumn.     

一次雷暴密度流的风场结构的研究

本文利用新建325米气象塔分析了北京地区一次雷暴密度流的风场、温度场和地面诸气象要素的特征,计算了320米以下风速垂直切变、水平风速加速度、垂直风速、流函数、热通量和动量通量等物理量,着重对雷暴密度流风场结构进行了研究。得到当雷暴密度流过境时地面气压、风向、风速和温度依次均发生剧烈变化的情况。同时还证实,在雷暴密度流中存在着强烈的阵风浪涌和垂直运动,而且密度流的头部是诸气象要素变化最剧烈的区域,尤其是头的后部存在着最大的风速垂直切变和最强的下沉气流;头的前部存在着最大的水平风速加速度和最强的上升气流。这些     

Mesoscale cyclones over the Black Sea

Considered are the results of the numerical analysis of two mesoscale cyclonic vortices generated over the Black Sea near the Caucasian coast on August 3, 2007 and August 7, 2010. It is demonstrated for the axially symmetric and more long-lived vortex occurred in 2007 that the Caucasian vortices are two-dimensional structures dying out rapidly due to the turbulent friction in the near-water boundary layer, and the deviation from the strictly two-dimensional motion is associated with the presence of the secondary circulation. The difference is demonstrated in the mechanisms of the origin of vortices in 2007 and 2010. In the first case, this is the formation of cyclonic circulation over the eastern part of the Black Sea limited by the Anatolian and high Caucasian Mountains, at the intrusion of the airflow of northwestern direction. In the second case, these are the processes of the generation of cyclonic vorticity at the baroclinic airflow running around the northwestern edge of the mountain range over the land.     

Wind Waves in the Northwestern Black Sea

The study presents the results of long-term monitoring of wind waves was carried out on the offshore fixed gas production platform in the northwestern part of the Black Sea in 1995–2011. The analysis of more than 31000 wave records provided reliable statistical characteristics of wind waves in the analyzed region. It was found that the maximum wave height reached 4.8 m in summer and 8.76 m in winter. The maximum hourly wave height exceeds significant wave height by 1.9 times in the vast majority of cases. The method of annual maxima revealed that in the Karkinit Bay the maximum wave height with the return period of 50 years is equal to 9.2 m.     

Intense mesocyclones in the Black Sea region

The statistical study of intense mesoscale cyclones formed in the Black Sea region in 1979-2013 is carried out using the surface wind data of the RegCM climate model. Such cyclone parameters as intensity, lifetime, area, height, and trajectories over the sea as well as the place and time of origin are considered. The distribution of mesocyclones by months and times of day is considered. The obtained results are compared with the results of a statistical study on the Black Sea mesocyclones based on the PRECIS climate model. Possible causes for differences in data on the intensity and number of mesocyclones simulated by RegCM and PRECIS models are considered.     

Breeze circulation in the Black Sea region

The modeling of atmospheric circulation in the Black Sea region using the WRF-ARW model for 30 summer days is considered to single out the contribution of the breeze component of wind speed. Assuming the quasiperiodic nature of breeze, the speed of daytime and nighttime breeze is computed for the whole region and for five separate areas on the coast. Specific features of the formation of daytime and nighttime breeze in these areas are distinguished. It is revealed that the presence of coastal mountains and the complex coastline determine the typical features of breeze development.     

Observations of a quasi-tropical cyclone over the Black Sea

A rare atmospheric phenomenon in the Black Sea region is described: a mesoscale cyclone with all main properties of tropical cyclones. The cyclone developed in the southwestern part of the sea and existed for about five days. General characteristics of the cyclone are presented along with its effect on thermodynamic structure of the sea upper layer.     

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.     

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.     

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.     

Numerical simulation of storm waves near the northeastern coast of the Black Sea

The results ofnumerical simulation of storm waves near the northeastern coast ofthe Black Sea using different wind forcing (CFSR reanalysis, GFS forecast, and WRF reanalysis and forecast) are presented. The wave modeling is based on the SWAN spectral wave model and the high-resolution unstructured grid for the Tsemes Bay. The quality estimates of wave simulation results for various wind forcing are provided by comparing the model results with the instrumental data on wind waves in the Tsemes Bay. It is shown that the forecast of the maximum wave height for some storms using the WRF wind forcing is more accurate than that based on the GFS forcing.     

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.     

Annual variation of the southern boundary current in the Banda Sea

ADCP measurements in the southern Banda Sea, obtained with the bulk carrier “MS First Jupiter” from 1997 until 2000, have been analysed. The observations reveal the presence of an eastward flowing southern boundary current, bringing water from the Indonesian throughflow towards the connections with the Indian Ocean in Ombai Strait and the Timor Sea. The mean transport in the upper 300 m is estimated to be about 5 Sv, over 50% of the outflow towards the Indian Ocean in this layer through the eastern passages near Timor. The velocity in the boundary current shows a clear annual variation, more or less in phase with the annually varying inflow through Makassar Strait and the outflow near Timor. The phase of the annual variation cannot be explained by the monsoonal variation of the local winds. Therefore this annual variation of the throughflow is probably generated by large-scale forcing. A considerable reduction of the strength of the boundary current was observed in 1998, following the 1997–1998 El Niño with a delay of about half a year. On shorter time scales, Kelvin waves, entering the Banda Sea from the Indian Ocean, cause flow reversals of the boundary current.     

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.     

River Runoff Effects on the Coastal Water Transparency in the Western Black Sea

Using the data of long-term observations of the Secchi disk visibility depth and water salinity (1947-2000) and satellite monitoring of chlorophyll a concentration (1978-1986), their seasonal spatial distributions and intraannual variability in the coastal waters of the western Black Sea are considered. The estimates of seasonal variations are obtained for the coastal zone of the sea. A good agreement is demonstrated between intraannual variations in the salinity of transformed river water, chlorophyll a concentration, and transparency in the areas where these waters propagate. We studied the effects of the Danube River runoff and transformed river water on the phytoplankton development and chlorophyll a concentration which largely define water transparency.     

Performance of gridded precipitation products in the Black Sea region for hydrological studies

Theoretical and Applied Climatology - Gridded precipitation products are becoming good alternative data sources for regions with limited weather gauging stations. In this study, four climate...     

Decadal variability of characteristics of the Black Sea pycnocline and geostrophic circulation in the wintertime

The Black Sea density fields and geostrophic circulation in the 0–300-dbar layer are reconstructed from the February archive hydrological data for several decades from 1951 to 1995 and then their interdecadal variability is studied. A gradual rise of the pycnocline is noted in the dome region of large-scale cyclonic gyrals from 5 m at the top of the pycnocline to 10–15 m at 100–300-m levels. Differently directed tendencies of long-term variability of the winter circulation are revealed: circulation intensification in the upper 0–50-m layer (except for the southwestern sea) and weakening in the lower pycnocline 200–300-m layer. The connection with the wind vorticity variability, river runoff, precipitation, and air temperature is analyzed. Strengthening of the cyclonic wind vorticity in the 1960s and the early 1970s is in good agreement with the circulation intensification of that time in the eastern sea.