The research results of the long-term change trends of seasonal average air humidity within the atmospheric boundary layer of Siberian region over last 30 years (1981-2010) estimated by the observed data of 25 aerological stations for winter, spring, summer, and autumn are presented. It has been found that changes of seasonal average humidity observed within the atmospheric boundary layer over the territory of Siberia for the last 30 years depend on the geographical position of the station and make a different contribution to the long-term fluctuations of annual average humidity in the different seasons. Namely, while the negative trends making for annual average humidity fall within all atmospheric boundary layer predominate in winter and in a small degree in summer (only in the subpolar and the moderate zones of Western Siberia), the positive trends are typical in spring and autumn for all regions. It is shown as well that in the last ten years almost everywhere seasonal average air humidity fall was observed in the atmospheric boundary layer of the most part of Siberian region for every season, especially in winter. Seasonal average air humidity rises predominates only in the polar regions of Siberia (for every season) and in the subpolar zone of Eastern Siberia (in spring, summer and autumn), and at every altitude of the atmospheric boundary layer.
long-term changes, linear trends, average seasonal air humidity, the atmospheric boundary layer, Siberian region