Pavel Toropov

Hydrodynamic aspects of the Novorossiysk bora episodes in 2012–2013

The spatial and time variability of the surface wind field during the bora episodes, including the events of January 27 and February 7, 2012, which were accompanied by windstorms on the coast and Markotkhsky ridge downwind slopes, has been analyzed based on the meteorological parameters observed during the winter expeditions in 2012–2013 to the Novorossiysk—Gelendzhik region. The dependence of the wind velocity on the background atmospheric parameters and incident-flow blocking conditions has been studied for the cases of strong and weak bora. It is assumed that bora is of a wave nature in the considered episodes and the wave drag effect predominated in the observed wind-flow acceleration on a downwind slope. Partial blocking of an incident wind flow by mountains also affects the wind regime in the downwind zone, especially near Gelendzhik, where mountains are higher than in the Novorossiysk region.

The Black Sea and the Caspian Sea paleolevel changes: links to simulated runoff of rivers and global climate change

Introduction To assess the link between climate variability and hydrological regime, we focused our study on the mid-Holocene (6 ka years BP) and the last cold period of the Late Quaternary (21 ka BP). We discuss how well current general circulation models (GCMs) can reproduce river runoff changes and, consequently, variations in closed lake level under contrasting climate conditions. The Paleoclimate Modeling Intercomparison Project (PMIP) (Joussaume and Taylor, 1995) has run simulations that are used in this study. The rivers of the East European Plane (EEP) were selected for analysis. Feed of rivers is determined by the balance of precipitation and evaporation in the catchment, hence river runoff change responds immediately to climate changes. It is important that both precipitation and evaporation are calculated by a GCM. Moreover, on large planes, such as the EEP, GCM data much better refl ect the state of climate compared to areas with complex mosaic surface conditions. Additionally, large amounts of paleoclimate data exist on the EEP for selected periods of the past.

Hydraulic and Wave Aspects of Novorossiysk Bora

Bora in Novorossiysk (seaport on the Black Sea coast of the Caucasus) is one of the strongest and most prominent downslope windstorms on the territory of Russia. In this paper, we evaluate the applicability of the hydraulic and wave hypotheses, which are widely used for downslope winds around the world, to Novorossiysk bora on the basis of observational data, reanalysis, and mesoscale numerical modeling with WRF-ARW. It is shown that mechanism of formation of Novorossiysk bora is essentially mixed, which is expressed in the simultaneous presence of gravity waves breaking and a hydraulic jump, as well as in the significant variability of the contribution of wave processes to the windstorm dynamics. Effectiveness of each mechanism depends on the elevated inversion intensity and mean state critical level height. Most favorable conditions for both mechanisms working together are moderate or weak inversion and high or absent critical level.

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.

Using isotope methods to study alpine headwater regions in the Northern Caucasus and Tien Shan

High mountain areas provide water resources for a large share of the world’s population. The ongoing deglaciation of these areas is resulting in great instability of mountainous headwater regions, which could significantly affect water supply and intensify dangerous hydrological processes.The hydrological processes in mountains are still poorly understood due to the complexity of the natural conditions, great spatial variation and a lack of observation. A knowledge of flow-forming processes in alpine areas is essential to predict future possible trends in hydrological conditions and to calculate river runoff characteristics. The goal of this study is to gain detailed field data on various components of natural hydrological processes in the alpine areas of the North Caucasus and Central Tien Shan, and to investigate the possibility that the isotopic method can reveal important regularities of river flow formation in these regions. The study is based on field observations in representative alpine river basins in the North Caucasus (the Dzhankuat river basin) and the Central Tien Shan (the Chon-Kyzyl-Suu river basin) during 2013–2015. A mixing-model approach was used to conduct river hydrograph separation. Isotope methods were used to estimate the contribution of different nourishment sources in total runoff and its regime. d18О, dD and mineralization were used as indicators. Two equation systems for the study sites were derived: in terms of water routing and runoff genesis. The Dzhankuat and Chon-Kyzyl-Suu river hydrographs were separated into 4 components: liquid precipitation/meltwaters, surface routed/subsurface routed waters.

First geophysical and shallow ice core investigation of the Kazbek plateau glacier, Caucasus Mountains

First-ever ice core drilling at Mt. Kazbek (Caucasus Mountains) took place in the summer of 2014. A shallow ice core (18xa0m) was extracted from a plateau at ~4500xa0m a.s.l. in the vicinity of the Mt. Kazbek summit (5033xa0m a.s.l.). A detailed radar survey showed that the maximum ice thickness at this location is ~250xa0m. Borehole temperature of −7xa0°C was measured at 10xa0m depth. The ice core was analyzed for oxygen and deuterium isotopes and dust concentration. From the observed seasonal cycle, it was determined that the ice core covers the time interval of 2009–2014, with a mean annual snow accumulation rate of 1800xa0mm w. eq. Multiple melt layers have been detected. δ18O values vary from −25 to −5‰. The dust content was determined using a particle sizing and counting analyzer. The dust layers were investigated using scanning electron microscopy and X-ray diffraction analysis. Dust can be separated into two categories by its origin: local and distant. Samples reflecting predominantly local origin consisted mainly of magmatic rocks, while clay minerals were a characteristic of dust carried over large distances, from the deserts of the Middle East and Sahara. The calculated average dust flux over three years at Kazbek was of 1.3xa0mg/cm2 a−1. Neither δ18O nor dust records appear to have been affected by summer melting. Overall, the conditions on Kazbek plateau and the available data suggest that the area offers good prospects of future deep drilling in order to obtain a unique environmental record.

Present-day variations and paleodynamics of the Caspian Sea level as a standard for climate modeling data verification

Long-term variations of the Caspian Sea level occur mainly due to river runoff variations (the variations of the Volga River runoff is of primary importance here). In this case, the observed and reconstructed variations of the Caspian Sea level can serve as a standard for assessing the quality of the model runoff simulated by climate models. To solve this problem, a number of detailed maps of the Caspian Sea are prepared for the series of regression and transgression stages. These data are used for verifying the results of some numerical experiments carried out within the framework of CMIP5/PMIP3. It is demonstrated that the model data can be verified depending on how well the models simulate the present-day (instrumentally observed) variations of the decadal scale reconstructed in recent 1000 years of variations: the transition from the Derbent regression to the New Caspian transgression (the 5th phase) with the insignificant sea level drop in the late 19th century and under conditions of large regression during the period of the late Pleistocene glaciation maximum.

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.

Djankuat Glacier Station in the North Caucasus, Russia: A Database of complex glaciological, hydrological, meteorological observations and stable isotopes sampling results during 2007-2017

The study presents a dataset on long-term complex glaciological, hydrological, meteorological observations and isotopes sampling in an extremely underreported alpine zone of the North Caucasus. The Djankuat research basin is of 9.1 km2, situated on elevations between 2500 – 4000 m, and covered with glaciers by 30%. The largest in the basin, the Djankuat 20 glacier, was chosen as representative of the central North Caucasus during the International Hydrological Decade and is one of 30 ‘reference’ glaciers in the world which have annual mass balance series longer than 50 years (Zemp et al., 2009). The dataset reported here covers 2007–2017 and contains the result of yearly measurements of snow depth and density; dynamics of snow and ice melting; measurements of water runoff, conductivity, turbidity, temperature, δ18O, δD at the main gauging station (844 samples in sum) with a one-hour or several-hours’ time step depending on the parameter; data on δ18O and δ2H 25 sampling of liquid precipitation, snow, ice, firn, groundwater in different parts of the watershed taken regularly in time during melting season (485 samples in sum); precipitation amount, air temperature, relative humidity, shortwave incoming and reflected radiation, longwave downward and upward radiation, atmospheric pressure, wind speed and direction – measured at several automatic weather stations within the basin with 15 min to one-hour step; gradient meteorological measurements to estimate turbulent fluxes of heat and moisture, measuring three components of wind speed at a frequency of 10 hertz to estimate 30 the impulse of turbulent fluxes of sensible and latent heat over the glacier surface by the eddy covariance method. All the observations were done during the ablation period (June–September) and were interrupted in winter. The dataset was published on knb.ecoinformatics.org long-term repository (doi:10.1594/PANGAEA.894807) and will be further updated. The dataset can be useful for developing and verifying hydrological, glaciological and meteorological models for high elevation territories,

Erratum to: Using isotope methods to study alpine headwater regions in the Northern Caucasus and Tien Shan

The original version of this article unfortunately contained a mistake. The spelling of the Yu.K. VASILCHUK’s name was incorrect. The correct name is given below.n Yu.K. VASIL’CHUK