We investigated upwelling events in the pelagic area of Lake Baikal that developed during summer stratification (July–November) using a combination of in situ and satellite observations. These upwellings appear in the centres of local cyclonic macrovortices with compensatory downwelling located on their periphery in coastal areas. The average duration of upwelling events was 5 weeks, with an observed maximum of 16 weeks. The most stable upwellings in Southern Baikal and over the Academician Ridge covered areas of up to 4,400 km² (59 % of Southern Baikal’s surface) and 1,550 km², respectively. Water was ascending in the upwelling zones at velocities of 1 × 10⁻⁴ to 1.2 × 10⁻² cm s⁻¹. Temperature differences of 1–4 °C and 2–13 °C were observed between the downwelling and upwelling zones in the epilimnion and metalimnion, respectively. On the surface of the lake, water temperature can drop 4–7 °C for water ascending from depths of 10–75 m, but the observed thickness of the layer within which water was ascending reached a depth of 280 m in August–September and 380 m in October; i.e. the ascending water included the entire upper layer (0–300 m). Geostrophic currents reached up to 24–38 cm s⁻¹ on the boundary between up- and downwelling zones (usually 5–7 km offshore), but did not exceed 6–10 cm s⁻¹ in the centres of upwelling zones. Comparison with other large lakes of the world is carried. This study is important for understanding the upwelling process that develops in Lake Baikal during summer stratification and can influence the heterogeneity of nutrients and primary production.

The investigation is aimed to determine the boundaries and intensity of urban heat islands in the Irkutsk region and assess the change in these parameters over a long-term period. The formation of an urban heat island is an example of anthropogenic influence on the urban climate. Land surface temperature and its spatial and temporal variations can be used to study urban heat islands, since the difference between the land surface temperature within the city and its surroundings is the result of the transformation of the underlying surface, heat capacity and three-dimensional structure of urban buildings in the process of urbanization. In order to study the phenomenon of urban heat islands of cities of the Irkutsk region, the land surface temperature data reconstructed from AVHRR-based thermal infrared imagery for 1998-2019 was used. As a result of the study, multi-temporal maps showing the urban heat islands of the agglomeration of Irkutsk-Angarsk-Shelekhov and the city of Bratsk were obtained. The investigated heat islands are characterized by a significant diurnal dynamic, so the difference in temperature values between the city and the suburbs in summer daytime reached 8-10 °C, in the evening and at night in summer this parameter decreases to 3-5 °C. The dimensions of the urban heat islands of the cities under investigation in the daytime exceed the dimensions of these heat anomalies in the evening and at night. Interannual variability in the intensity of urban heat islands did not show statistically significant trends from 1998 to 2019, the areas of urban heat islands increased significantly over the study period. The observed increase in area was probably associated with the development of the cities under study, with the transformation of landscapes and a decrease in the density of vegetation in the suburbs. In order to assess the contribution of the lack of vegetation to the formation of the urban heat islands in summer daytime, the values of the land surface temperature were compared with the values of the vegetation index NDVI. An analysis of the relationships between these parameters found that daytime land surface temperature was in close inverse relationship with the NDVI value, while this relationship was less pronounced at night and in the evening.

Основная цель настоящего исследования – разработка методик долгосрочного прогнозирования сроков полного очищения ото льда Красноярского, Иркутского, Братского и Усть-Илимского водохранилищ с использованием значений телеконнекционного индекса AO (Arctic Oscillation). Установленные в ходе исследования прогнозные зависимости позволяют предвидеть характер развития данного ледового явления со средней заблаговременностью от 29 до 46 сут., максимальной заблаговременностью – от 38 до 58 сут. Величина обеспеченности допустимой погрешности полученных прогностических зависимостей составляет от 89,5 до 94,7%, индекс корреляции имеет значения от 0,89 до 0,91, что определяет категорию качества предложенных методик прогнозирования сроков полного очищения ото льда Красноярского, Иркутского, Братского и Усть- Илимского водохранилищ как хорошую. Значения коэффициента прогностической информативности выше 0,82 демонстрируют временную устойчивость и возможность практического использования полученных методик прогнозирования. doi 10.17072/2079-7877-2017-1-66-72 Поступила в редакцию: 14.12.2016

Межгодовая изменчивость и прогноз весенних ледовых явлений на оз. Байкал и водохранилищах Ангарского каскада