摘要:Changes of total and low cloud fraction and the occurrence of different cloud types over
Russia were assessed. The analysis was based on visual observations from more than 1600
meteorological stations. Differences between the 2001–10 and 1991–2000 year ranges were
evaluated. In general, cloud fraction has tended to increase during recent years.
A major increase of total cloud fraction and a decrease of the number of days
without clouds are revealed in spring and autumn mostly due to an increase of the
occurrence of convective and non-precipitating stratiform clouds. In contrast, the
occurrence of nimbostratus clouds has tended to decrease. In general, the ratio between
the occurrence of cumulonimbus and nimbostratus clouds has increased for the
period 2001–10 relative to 1991–2000. Over particular regions, a decrease of total
cloud fraction and an increase of the number of days without clouds are noted.