Том 52, № 3 (2016)

There were several anomalously cold winter weather regimes in Russia in the early 21st century. These regimes were usually associated with a blocking anticyclone south of the Barents Sea. Numerical simulations with an atmospheric general circulation model (AGCM) using prescribed sea-ice concentration (SIC) data for different periods during the last 50 years showed that a rapid sea-ice area decline in the Barents Sea in the last decade could bring about the formation of such a blocking anticyclone and cooling over northern Eurasia. The SIC reduction in the former period, from the second half of the 1960s to the first half of the 1990s, results in a weaker response of opposite sign. This suggests a nonlinear atmospheric circulation response to the SIC reduction in the Barents Sea, which has been previously found in the idealized AGCM simulations. An impact of the Barents Sea SIC reduction on the North Atlantic Oscillation (NAO), in particular, on the formation of the anomalously low NAO index, is found. The results indicate an important role that the Barents Sea, a region with the largest variability of the ocean–atmosphere heat exchange in the Arctic in wintertime, plays in generating anomalous weather regimes in Russia.

In this paper, a Reynolds number increase transition from self-oscillations close to single-frequency ones to the temporally chaotic regime in the flow in a cylindrical channel driven by a spatially periodic force with four half-periods is experimentally investigated. The parameter ε proportional to the mean rate of the kinetic energy dissipation in unit mass per unit time associated with perturbations in the fluid is used as a basic characteristic of self-oscillations. The Reynolds number dependence ε(Re) for single frequency self-oscillations is considered theoretically.

Water vapor is one of the basic climate gases playing a key role in various processes at different altitudes of the Earth’s atmosphere. An intercomparison and validation of different total precipitable water (TPW) measurement methods are important for determining the true accuracy of these methods, the shared use of data from multiple sources, the creation of data archives of different measurements, etc. In this paper, the TPW values obtained from measurements of solar IR spectral radiation (~8–9 μm absorption band) and thermal MW radiation of the atmosphere (1.35 cm absorption line) for 138 days of observation are compared. Measurements have been carried out from March 2013 to June 2014 at Peterhof station of the St. Petersburg State University in (59.88° N, 29.82° E). It is shown that MW measurements usually give higher TPW values than IR measurements. The bias between the two methods varies from 1 to 8% for small and large TPW values, respectively. With increasing TPW values, the bias reduces and for TPW > 1 cm it is ~1%. Standard deviation (SD) between the two methods reaches 7% for TPW < 0.4 cm and 3–5% for TPW > 1 cm. These data show the high quality of both remote sensing methods. Moreover, the IR measurements have a higher accuracy than MW measurements for small TPW values.

It has been shown by numerical simulation that the rate of formation of secondary organic aerosols (SOAs) in smoke plumes caused by vegetation and peat fires under real conditions can significantly depend on the aerosol optical thickness (AOT). The AOT determines the photodissociation rate and hydroxyl radical concentration, which in turn determines the rate of SOA generation as a result of oxidation of semivolatile organic compounds. Quantitative analysis has been carried out for the situation that took place in European Russia during the 2010 Russian wildfires. The state-of-the-art 3D chemical transport model is used in this study; the simulations are optimized and validated using the data of monitoring of the particulate matter in the Moscow region and Finland. The findings indicate that it is important to allow for this effect in studies focused on the analysis and prediction of air pollution due to wildfires, as well as climate and weather studies, whose results may depend on the assumptions about the content and properties of atmospheric carbon-containing aerosol.

We present a numerical model of Black Sea circulation based on primitive equations with improved spatial resolution in the coastal zone. The model equations are formulated in a two-pole orthogonal coordinate system with arbitrary locations of the poles and a vertical σ coordinate. Increased horizontal resolution is gained by displacing the pole into the vicinity of the separated subdomain. The problem is solved over a grid with a variable step. The northern coordinate pole is displaced to the vicinity of Gelendzhik; the grid step varies from 150 m in the coastal zone to 4.6 km in the main basin. We simulated the fields of currents, sea level, temperature, and salinity under the given atmospheric forcing in 2007. The model is capable of reproducing the large-scale Black Sea circulation and submesoscale variations in the coastal currents.

Free internal waves are considered in a Boussinesq approximation in the situation when horizontal eddy viscosity and diffusion in a vertically inhomogeneous flow are taken into account. The dispersion relation and wave damping factor are found in a linear approximation. The Stokes drift velocity is determined in the second order of smallness based on the wave amplitude. It has been indicated that the Stokes drift velocity, transverse with respect to the wave propagation direction, differs from zero if the flow-rate transverse component depends on the vertical coordinate. Vertical momentum fluxes differ from zero and can be comparable with or exceed the corresponding turbulent fluxes if eddy viscosity and diffusion are taken into account.

Based on numerical simulations, we calculate the integral water circulation of the South China Sea on the eastern Vietnam shelf in the Vietnam coastal current area. The main objective of simulations was to study the hydrodynamic structures of this current in the winter–summer interseasonal period. The calculations were performed for the period from April to June 1999, which had the necessary primary field data. Two types of atmospheric processes were considered: the first is characterized by a small pressure gradient over the South China Sea and the second includes tropical cyclones in the southern part of the sea. The simulation results showed that there are three hydrodynamic gyres in the study area during the given time period: two anticyclonic gyres and a cyclonic gyre that separates them, which together form a complex pattern of the Vietnam current. These gyres persist for the given types of atmospheric processes and are quasi-stationary structures. The Vietnam current carries coastal water masses from south to north within the anticyclonic gyres in summer and from north to south within the cyclonic gyres in winter.