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.     

Effect of Moon phases in riometer absorption and in the ionospheric and geomagnetic parameters

Variations in the frequency of occurrence of riometer absorption, minimum frequency of reflection of the ionospheric F layer, minimum height, and height of maximum electron density of the ionospheric F layer near the solar minimum have been studied. Application of the superposed epoch technique has detected the Moon phase effect on these ionospheric parameters. This effect was: three events per day in the occurrence of riometer absorption, 0.056 MHz in the minimum frequency of reflection of the F layer, and 2.6 and 6.7 km, in the change of the minimum height of reflection and height of reflection from the region with maximum electron density of the ionospheric F layer, respectively. The lunar tide action changes the ionospheric conductivity and, thus, influences the current systems of the magnetosphere. Through changes of magnetospheric currents, the Moon phase effect is exhibited in the Ap and Dst indices and is 4.3 and 4.25 nT, respectively.     

Characteristic features of energy exchange between sea and atmosphere in the Black Sea coastal zone in summer

Characteristic features of energy exchange between sea and atmosphere in the coastal zone are considered with allowance for the wind direction in the surface layer and at 500 hPa in the summertime. Principal characteristics of distributions of the energy-exchange parameters are found. It is demonstrated that large-scale air flows directed from the land in the daytime are accompanied by increased stability of the marine surface layer, decreased sensible heat fluxes, and evaporation intensification. In the nighttime, on the contrary, such tendencies are observed when flows at 500 hPa are directed from the sea. When mesoscale circulation with surface wind directed parallel to the large-scale flow is developed, the sensible heat transfer increases both in the daytime and at night, while the evaporation increases in the nighttime and decreases in the daytime.     

Sedimentary Waves of the Southeastern Barents Sea Shelf (Kanin Peninsula–Cheshskaya Bay)

Oceanology - Sedimentary waves are represented by a series of wavelike accumulative features with various degrees of morphological expression. These morphological forms are superimposed on the...     

Patterns of spatial distribution of positive thunderstorm discharges in Eastern Siberia

Patterns of spatial distributions of the thunderstorm positive discharges, which were obtained by using a one-point storm direction and distance finder with observation radius of ～1200 km in Eastern Siberia in 2003–2007, are considered in this paper. It was found that distributions of positive discharges reflect, in general, overall patterns of thunderstorm activity. Two centers corresponding to maximum activity of the negative storm discharges are located in southwest; however, they were dominating (in terms of their intensity) only in 2005. Two other centers are more intense: the northeastern one was especially strong in 2003, 2004, 2006 and the eastern one was dominating in 2003 and 2007. The northeastern centers are the most active in the beginning and the end of the season. In these areas, ratio of positive and negative discharge fluxes can exceed 1. Activity of the eastern center, whose large part is situated in mountains, can be explained by neighborhood of the Sea of Okhotsk. The mentioned patterns of spatial distributions of positive storm discharges indicate that the geographic conditions play a significant role in their origination in the eastern part of Siberia. In the southern and western regions, a typical electric structure of thunderstorm clouds develops with main negative charge in the lower part of a cloud. At the same time, in the high latitudes, in the mountains, evidently, a different mechanism is realized, leading to the inverted location of charges in a cloud.     

Detection Statistics of Pulse Signals at Declinations from +42° to +52° at the Frequency 111 MHz

Astronomy Reports - A search for pulse signals was carried out in a new sky area included in the monitoring program for the search for pulsars and transients. Processing of several months data...     

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.     

Some results of observations of positive lightning discharges and relative phenomena in the east of Siberia

We have considered spatial distributions of positive lightning discharges in the east of Siberia for the summer seasons of 2003–2007 and properties of their electromagnetic signals with the ELF “slow tail”, which, as is known, can be accompanied by sprites. There are two main regions of positive discharges located in the south and west of Yakutsk. Two other “centers” (the northeastern and the eastern) are located in high-mountainous regions. In these regions the positive discharges intensity can exceed the negative discharge intensity.The electromagnetic signals in the ELF range (usually in the form of two half-cycles) were observed after the VLF atmospherics were recorded in the high-latitude regions. The delay of ELF pulses relative to the corresponding atmospherics was 0–7 ms. The long (up to 350 ms) events of quasi-periodic ELF oscillations with the period of about 7 ms (which corresponds to the quasi-period of ELF pulses) were revealed.     

Modeling of variations in river runoff on the East European Plain under different climates of the past

The results of modeling of the annual river runoff on the East European Plain, performed with the help of atmospheric general circulation models for the conditions of the present-day climate, the Atlantic Optimum of the Holocene, and the Cryochrone of the Late Pleistocene, are analyzed. The quality of modeling the present-day climate is assessed; the spatial scales, within which the model results are appropriate for using in hydrological calculations, are determined. The genesis of variations in the river runoff on the East European Plain in the epochs of the Holocene Optimum and Late-Pleistocene Cryochrone is investigated.