Climate Continentality in Cisbaikalia in Different Circulation Epochs

The dynamics of the continentality index over 90 years has been studied on the basis of data on air temperature obtained at meteorological stations of Cisbaikalia. The dynamics of the continentality index is performed for four circulation epochs in the Siberian sector (two zonal and two meridional epochs). The continentality is assessed by the Gorczyński Continentality Index (GCI). The mean long-term values of GCI in the study area are in the range from 51 to 86, which corresponds to the continental (33 < GCI < 67) and extreme continental (67 < GCI < 100) climate. A latitudinal rise in the GCI is clearly manifested. Minimal values were recorded at weather stations on the coast of Lake Baikal and at weather stations in the central and southern parts of Irkutsk oblast located on the coast of the reservoirs of the Angara cascade of hydroelectric power stations. It is found that, in case of the zonal form of circulation, the continentality index either moderately increases or decreases at a slower rate when compared to the meridional form of circulation. An increase in the continentality index is observed at all weather stations in the second zonal circulation epoch (1977‒2005). It is established that this is related to elementary circulation mechanisms (ECMs) of the meridional northern group, the frequency of which in the second zonal epoch is twice as high as in the first epoch. The greatest contribution was made by sediment-forming ECM 12a, the duration of which since the late 1980s is twice as large as the long-term mean. One distinctive feature of the weather stations on the Baikal coast is in the positive trend of the continentality index in the last meridional epoch, while a negative dynamics is observed at the continental stations.