The winter months make the largest contribution to the trend of increasing average annual air temperature in the Russian Federation. This feature is especially important for Siberia, since the period of rapid temperature increase in the region by 85–90% was due to the softening of winters. The paper analyzes winter surface air temperature anomalies over Siberia and the circulation causes of their appearance. The sign of temperature anomalies at different circulation epochs was determined. It was revealed that an increase in the duration of zonal circulation forms usually leads to the formation of large positive temperature anomalies, as a rule, and an increase in the duration of meridional circulation - negative. The dynamics of the temperature field anomaly index (according to V.G. Tokarev) for the territory enclosed within 50-70° N (north latitude) and 60-120° E (east longitude) was analyzed for the period 1947-2019.
The article deals with the structure of summer climate season, settled according to meteorological observations at the Irkutsk station. The dynamics of dates of air temperature stable transition above and below 10°C are considered. We compared the dates of the onset of summer climate season for the period during 1976-2017 with the climate data sheets. Calculations of dates of air temperature stable transition over 10°С showed its shift to a later date on June 6. We revealed that, starting from 2000, there has been a change in the long-term trend, i.e. the shift of the starting date of summer climate season to earlier periods, and the end of summer to later ones had been noted. Consequently, the duration of summer climate season has increased. We analyzed the dynamics of the climate index, i.e. the number of hot days. The number of days with a maximum air temperature in excess of 25°C is rapidly increasing, and therefore, can lead to drought hazard and forest fires in the vicinity of Irkutsk. In the period from 1976 to 1985 the average number of hot days was 25. Note, that in the past two decades, hot days have been observed 48 times per season. The record-holder for the number of hot days was 2002. An assessment of changes in thermal resources is important in a comprehensive study of agroclimatic conditions of a territory, for solving applied issues of agricultural production, including for assessing plant heat, determining the time of sowing of various crops, evaluating the heat accumulated.
The article considers the long-term dynamics of heavy rains and snowfalls on the territory of Irkutsk oblast for the period from 1950 to 2015. The share of extreme precipitations in the total amount of atmospheric precipitation is estimated. Seasonal features of changes in the frequency of extreme events, manifested in the insignificantly increased precipitation in autumn, typical for the Western synopticoclimatic region, and in winter increase within the Upper Lena and Southern regions of the investigated region are studied. The emerging trends may affect the seasonal changes in the hydrological regime in the watersheds of large rivers. The paper presents the analysis in the relationship between the extreme precipitation events and the macrocirculation mechanisms. Precipitation-forming elementary circulation mechanisms (ECMs) for Irkutsk oblast are identified. It was revealed that the maximum contribution to the extreme precipitation is made by ECM 13l (latitudinal western circulation), 13s (latitudinal western circulation and stationary position) and 12a (longitude northern).
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