One of the centres of action that tend to control large scale weather patterns around the globe. This centre forms over Siberia during the winter and is centred around Lake Baikal. The sea level pressure exceeds 1030 millibars from late November to early March. The resulting anticyclonic circulation pattern is enhanced by the tendency of the surrounding mountains to prevent the cold air from easily flowing away. This pattern is replaced by a low pressure pattern in the summer related to the monsoon circulation.