Vol 54, No 4 (2018)

Edge baroclinic waves are generated in a geostrophic flow with a vertical shear near a solid surface. The study investigates a new class of baroclinic waves in flows with horizontal and vertical shears and a linear distribution of potential vorticity. It is shown that taking account of the horizontal shear leads to the appearance of new features of wave dynamics. These include the nonmodal growth of energy in the initial stage of development, the time dependence of the vertical wave scale, and the possibility of generation of stationary or blocked waves. The horizontal shear makes the mechanism of generation of baroclinic waves by initial vortex perturbations more efficient. One important feature is associated with vortex paths, which are formed by the superposition of a baroclinic wave on the flow with horizontal shear.

A detailed modeling of meteorological parameters over the last 30 years (1985–2014) has been performed for the Sea of Okhotsk and Sakhalin regions in the frame of the COSMO-CLM regional mesometeorological nonhydrostatic atmospheric model. The downscaling technology is suggested and achieved with three consequent “nesting domains” (with 13.2-, 6.6-, and 2.2-km grid scales). The COSMO-CLM model reproduces (especially successfully on the 2.2-km grid scale) the extremes of wind velocity observed by meteorological stations well. Synoptic situations accompanied by extreme wind speeds are reproduced in detail.

A recently developed fully explicit algebraic model of Reynolds stress and turbulent heat flux in a thermally stratified planetary atmospheric boundary layer without stratification has been used for a numerical study of the Ekman turbulent boundary layer over a homogeneous rough surface for different dimensionless surface Rossby numbers. A comparative analysis has been conducted for a closure model of the transport term in the prognostic equation of turbulent kinetic energy dissipation including third-order moments. Dependences of the total wind rotation angle on the Rossby number have been obtained. The calculated vertical profiles of mean velocity, turbulent stress, turbulent kinetic energy, surface-friction velocity, and boundary-layer height agree satisfactorily with observational and earlier obtained LES data.

Characteristic features of changes in the vertical distribution and column content of NO₂, total ozone, and stratospheric temperature have been revealed as a result of major sudden stratospheric warmings (SSWs). Strong negative anomalies of column NO₂, total ozone and stratospheric temperature are caused by the displacement of the stratospheric circumpolar vortex aside from the pole. Strong positive anomalies of column NO₂ and total ozone are observed more frequently under SSWs accompanied by splitting of the stratospheric circumpolar vortex and are caused by the transport of stratospheric air from the low latitudes. Major SSWs can lead to significant changes in the vertical profile of NO₂. The changes in different stratospheric layers can be opposite to each other when the edge of the polar vortex is over a site of ground-based observations.

The results of instrumental studies of storm activity and parameters of lightning discharges in the south of the European part of the Russian Federation are presented. The features of spatial and temporal variations of thunderstorms and lightning parameters within a radius of 650000 km around the center of the lightning- detection network of the High-Mountain Geophysical Institute (Nalchik) covering the North Caucasus and the Black Sea coast are considered. The total number of thunderstorm days per year on the territory in question is approximately 239. The specific lightning susceptibility of the ground surface is approximately 6 discharges/km² per year in the south and 2 discharges/km² per year in the north. The share of terrestrial lightning discharges (positive and negative) on the territory is 12% of the total number of lightning; the share of cloud and intercloud discharges is 88%. According to these data, the share of positive discharges accounts for about 23% of the total number of the “cloud-to-ground” discharges. The average value of the electric currents is 13.5 kA in the negative lightning and 10.6 kA in the positive lightning. The parameters of lightning discharges over mountain terrain (altitude more than 1000 m) and over flatland terrain (altitude less than 1000 m) are considered separately. It has been found that the mean amplitude of the electric current of lightning discharges (regardless of polarity) amounts to approximately 9.29 kA over the flatland regions of the North Caucasus and 11.24 kA in the mountain part; the median value of the amplitude of the electric current reaches approximately 6.56 kA over the flatland terrain and 7.99 kA over the mountain terrain.

We study the spreading of wastewaters from an underwater source in a stratified coastal environment using the results of satellite monitoring and mathematical modeling. The problem is considered as applied to deepwater discharge in the region of Golubaya Bay of the Black Sea near Sebastopol. The main factors preventing upwelling of pollution to the sea surface are analyzed on the basis of a numerical model. It is shown that peculiarities of wastewater spreading depend on the character of stratification and velocity of the background current. The main factor influencing the uplift of these waters to the surface is the existence of water layers with high vertical gradients of water density. We reveal the structure of the wastewater field consisting of a plume and a jet extended in the direction of the background current, which is located in the density interface. If stratification is weak, the plume may reach the sea surface and form a local region of water pollution, which is recorded in multispectral satellite images. It is found that the mass of polluted waters is characterized by negative anomalies of temperature and salinity.

The results of an investigation into water mass dynamics in the northeastern sector of the middle Caspian Sea are presented. High variations of currents are observed in this region of the sea, which are caused by the influence of the Peschanomysskoye Rise (PMR) on the cyclonic gyre. This bottom elevation is an obstacle to the currents of the gyre. The Yuzhno-Buzachinskii Deflection also influences the currents. Part of the dense and cold waters from the northern Caspian Sea flows along this deflection to the Derbent Basin. This basin is also a sink for the cold waters transported on the Peschanomysskoye Rise and those that overflow it. Observations in May 2015 over a cross-shaped survey at the western basement of the PMR showed that the currents in May in the western part of the survey in the entire water column from the surface to the bottom are organized in layers in the form of an anticyclonic spiral: the bottom current is directed to the south, the middle current is directed to the west, and the surface current is directed to the north. Lenses of warm water are observed in the bottom layer.