The Siberian High (also Siberian Anticyclone; (Aziatsky antitsiklon); ; Pinyin Xībólìyǎ gāoyā; Kazakh Азия антициклоны (Aziya antitsiklonı)) is a massive collection of cold dry air that accumulates in the northeastern part of Eurasia from September until April. It is usually centered on Lake Baikal. It reaches its greatest size and strength in the winter when the air temperature near the center of the high-pressure area is often lower than . The atmospheric pressure is often above . The Siberian High is the strongest semi-permanent high in the northern hemisphere and is responsible for both the lowest temperature in the Northern Hemisphere outside Greenland, of on 15 January 1885 at Verkhoyansk, and the highest pressure, 1083.8 mbar (108.38 kPa, 32.01 inHg) at Agata, Krasnoyarsk Krai, on 31 December 1968, ever recorded. The Siberian High is responsible both for severe winter cold and attendant dry conditions with little snow and few or no glaciers across the Asian part of Russia, Mongolia, and China. During the summer, the Siberian High is largely replaced by the Asiatic low.
Overview
thumb|right|200px|The plot of mean sea level pressure over the winter months shows a large area of high atmospheric pressure in the South of Siberia.
The Siberian High affects the weather patterns in most parts of the Northern Hemisphere: its influence extends as far west as Italy, bringing freezing conditions also in the warm South, and as far southeast as Malaysia, where it is a critical component of the northeast monsoon. Occasionally a strong Siberian High can bring unusually cold weather into the tropics as far southeast as the Philippines.
Siberian air is generally colder than Arctic air, because unlike Arctic air which forms over the sea ice around the North Pole, Siberian air forms over the cold tundra of Siberia, which does not radiate heat the same way the ice of the Arctic does.
Genesis and variability
In general, the Siberian High-pressure system begins to build up at the end of August, reaches its peak in the winter, and remains strong until the end of April. Its genesis at the end of the Arctic summer is caused by the convergence of summer air flows being cooled over interior northeast Asia as days shorten. In the process of the Siberian High's formation, the upper-level jet is transferred across northern Eurasia by adiabatic cooling and descending advection, which in extreme cases creates "cold domes" that outbreak over warmer parts of East Asia.
In spite of its immense influence on the weather experienced by a large proportion of the world's population, scientific studies of the Siberian High have been late in coming, though variability of its behavior was observed as early as the 1960s.
Because increased snow and ice cover enhances the Siberian High, the Siberian High was both more intense and located further west during the early Middle Pleistocene as a result of the extensive glaciation of mountain ranges across Central Asia. The decrease in magnitude of the Siberian High during the Holocene enabled eastward encroachment of westerlies enriched with water vapour, precipitating an increase in low altitude afforestation of Central Asia.
See also
- Siberian Express
- Arctic dipole anomaly
- Cold wave
- North American High
- Polar vortex
- Aleutian Low