In 2019, the southern region of Eastern Siberia (located between 45° N and 60° N) experienced heavy floods, while the northern region (between 60° N and 75° N) saw intense forest fires that lasted for almost the entire summer, from 25 June to 12 August. To investigate the causes of these natural disasters, we analyzed the large-scale features of atmospheric circulation, specifically the Rossby wave breaking and atmospheric blocking events. In the summer of 2019, two types of Rossby wave breaking were observed: a cyclonic type, with a wave breaking over Siberia from the east (110° E–115° E), and an anticyclonic type, with a wave breaking over Siberia from the west (75° E–90° E). The sequence of the Rossby wave breaking and extreme weather events in summer, 2019 are as follows: 24–26 June (cyclonic type, extreme precipitation, flood), 28–29 June and 1–2 July (anticyclonic type, forest fires), 14–17 July (both types of breaking, forest fires), 25–28 July (cyclonic type, extreme precipitation, flood), 2 and 7 August (anticyclonic type, forest fires). Rossby wave breaking occurred three times, resulting in the formation and maintenance of atmospheric blocking over Eastern Siberia: 26 June–3 July, 12–21 July and 4–10 August. In general, the scenario of the summer events was as follows: cyclonic Rossby wave breaking over the southern part of Eastern Siberia (45° N–60° N) caused extreme precipitation (floods) and led to low gradients of potential vorticity and potential temperature in the west and east of Lake Baikal. The increased wave activity flux from the Europe–North Atlantic sector caused the anticyclonic-type Rossby wave breaking to occur west of the area of a low potential vorticity gradient and north of 60° N. This, in turn, contributed to the maintenance of blocking anticyclones in the north of Eastern Siberia, which led to the intensification and expansion of the area of forest fires. These events were preceded by an increase in the amplitude of the quasi-stationary wave structure over the North Atlantic and Europe during the first half of June.

This paper studies the long-term variability of frequency of atmospheric blockings over Western Siberia in 1948–2015 based on the data of three reanalysis projects. We revealed a decreasing blocking...

Western Siberia is a large area in Northern Eurasia, which lies between the Urals and the Yenisei River. The atmospheric blocking events are not a frequent phenomenon in this region. Nevertheless, they noticeably affect the weather and living conditions of people there. We have investigated 14 winter blocking events, identified over Western Siberia, over 2004–2016, and have studied their effect on the surface temperature in this region. We have compared each of the 14 blocking events to the corresponding surface temperature anomalies in the north and in the south of Western Siberia. As a result, the temperature anomalies were separated into two groups: (1) dipole, with a positive surface temperature anomaly (or close to the norm) in the north, and with a negative anomaly (or close to the norm) in the south, and (2) non-dipole. Ten events were attributed to Group 1, four events were referred to Group 2. Analyzing the potential temperature on the dynamic tropopause (advection characteristic) showed that the Group 1 events feature strong advection over the investigated territory. In the non-dipole situations from Group 2 Western Siberia are away from strong blocking events.

Based on the NCEP/NCAR and ERA-Interim reanalysis archives, we investigated different methods to detect atmospheric blocking events in Western Siberia. Two criteria were studied that are based on calculating meridional gradients of the 500 hPa height and potential temperature at the dynamic tropopause. A situation is considered blocking, when it features a gradient inversion of the investigated characteristics. Additionally, we performed a synoptic analysis of individual blocking events.

We studied moisture content/aridity conditions in Buryatia (Russia) in summertime for the period of 1979–2019. Selyaninov’s hydrothermal coefficient (HTC) was used as the aridity criterion. The HTC was calculated on the basis of precipitation and 2 m temperature data from two datasets: meteorological stations and the ECMWF ERA5 project. A comparison of the HTC calculations for these two datasets was performed. The ERA5 data showed underestimated HTC values compared to the observations. The inconsistencies found are mainly related to the underestimation of precipitation in the ERA5 project compared to the observational data. The air temperature obtained from the two datasets agrees well for most stations, both in value and in long-term dynamics. It has been shown that at the stations in central and southern Buryatia, the increase in aridity (and decreased HTC) in 1979–2019 is mainly due to the increase in air temperature.