S. V. Loginov

Climate variability over the Asian territory of Russia during 1975–2012

Observational data for 1975–2012 have been used in analyzing the formation of air temperature and atmospheric pressure fields over the Asian territory of Russia (ATR). The climatic trends at the end of the 20th — beginning of the 21st centuries for the ATR as a whole as well as for its separate regions were assessed through comparison of temperature and pressure variability indices for two time intervals: 1975–2005, and 1982–2012. It was established that climatic changes during 1982–2012 continued to manifest themselves in a rise of mean annual surface air temperature; however, the warming process was less intense than during 1975–2005. A large role in the decrease of the temperature growth rates is played by the winter months when the warming process is replaced by the cooling process. Furthermore, the latter time interval showed a tendency for an increase in pressure.

Spatio-temporal variability of heat balance components and CO2 radiation forcing for the territory of West Siberia

The analysis of regional climate changes and variability of heat balance components was carried out for the territory of West Siberia over the period of 1976-2014. It was revealed that the beginning of XXI century is characterized by decelerating of warming rates, and in winter season the temperature decrease is accompanied with the tendency of pressure rise. Dominating role in the variability of understudy parameters belongs to heat balance components: effective radiation and heat fluxes. According to numeric modelling results, CO2 radiaton forcing became less during last two decades.

Impact of non-Gaussian statistics of atmospheric variables on extreme intramonth anomalies

The analysis of asymmetry of probability distribution functions (PDF) is carried out for key atmospheric variables using the JRA-55 reanalysis data in the troposphere of the Northern Hemisphere for 1976–2014. The nonzero asymmetry of the PDF indicates the deviation of the PDF from the normal distribution. The analysis was carried out for two time-scale intervals: synoptic variability (SV) of 2–7 days and low-frequency variability (LV) of 9–30 days. Statistically significant deviations from the normal probability distribution occur in the regions of the most frequent formation of atmospheric baroclinic perturbations, i.e., over the western parts of the oceans in midlatitudes and downstream in the atmosphere. In the SV time-scale interval, a negative asymmetry of the vertical velocity is revealed in isobaric coordinates for the entire thickness of the free troposphere, which agrees with the overall dominance of cyclonic anomalies in this interval of time scales. In the LV interval, the asymmetry of this variable in the entire free troposphere is positive, which indicates the dominance of anticyclonic anomalies at these time scales. For the zonal velocity, temperature, and geopotential, the asymmetry sign of the PDF for variability with time scales of 2–7 days is different for the upper and lower free troposphere. The asymmetry of the PDF for atmospheric variables indicates the important role of the intermode interaction in the formation of baroclinic perturbations. The corresponding deviations of synoptic variability from the normal distribution, which is found in the upper troposphere of the subpolar and polar latitudes, can be related to the interaction of these perturbations with the winter polar vortex. These deviations of PDF from the normal distribution substantially increase the probability of the appearance of large (in absolute value) anomalies as compared to the case of the Gaussian PDF.

Spatio-temporal variability of atmospheric precipitation in West Siberia over last decades using observational data

In the framework of this study the analysis of spatio-temporal variability in atmospheric precipitation characteristics in West Siberia was carried out using observational data by means of comparison two time intervals: 1976-1998 – the period of intensive global warming and 1999-2015 – the period of slowdown in the temperature growth. Features in precipitation amount variability in the northern and southern parts of the territory during warm and cold periods of a year are also described. Thus, in the beginning of XXI century the tendency to atmospheric precipitation increase is observed. Furthermore, the highest statistically significant growth is in the northern part of West Siberia in warm period.

Influence of radiation and circulation factors on climate change in Western Siberia at the end of the 20th century and beginning of the 21st century

An analysis of the air-temperature and atmospheric-pressure fields in Western Siberia is performed based on observations in 1976–2014; a comparison of temperature and pressure variability in two temporal intervals, 1976–2005 and 1985–2014, is carried out. The estimation of contributions from such climate-forming factors as radiation and circulation is performed for the same intervals. It is revealed that an increase in the annual mean ground–air temperature in the investigated region of Western Siberia was still taking place in the period of 1985–2014; however, the warming process was less active than in the 1976–2005 period. Winter months play the largest role in decreasing the temperature growth rate; during these months, the warming process was replaced by a cooling one in the second time interval. It is shown that the circulation factors, that is, the mechanisms described by indices of global circulation, played the dominant role in the period from 1985 to 2014.

Forecasting estimates of surface air temperature changes by the wavelet transformation method

Analysis of a series of average annual surface air temperature (SAT) shows that they consist of three major components: a long-term trend, a set of harmonic components, and anomalies whose characters are close to a random process. We propose to use wavelet transformation of the source series to set aside quasi-periodic fluctuations. In this case, the distribution of the transformation coefficients enables one to set aside fluctuations of various scales, both the ones that are almost harmonic and those characterized as nonstationary fluctuation process. Then, forward extrapolation is performed by wavelet transformation coefficients for the set-aside scales in view of their temporal dynamics. The series’ fluctuation component is restored by inverse wavelet transformation. The proposed approach is demonstrated by the example of average annual SAT series registered by stations in the towns of Syktyvkar and Tomsk with an instrumental observation period of more than 100 years.