Winter cloudiness variability over Northern Eurasia related to the Siberian High during 1966–2010

Abstract

This letter presents an assessment of winter cloudiness variability over Northern Eurasia regions related to the Siberian High intensity (SHI) variations during 1966–2010. An analysis of cloud fraction and the occurrence of different cloud types was carried out based on visual observations from almost 500 Russian meteorological stations. The moonlight criterion was implemented to reduce the uncertainty of night observations. The SHI was defined based on sea-level pressure fields from different reanalyses. We found a statistically significant negative correlation of cloud cover with the SHI over central and southern Siberia and the southern Urals with regression coefficients around 3% hPa−1 for total cloud fraction (TCF) for particular stations near the Siberian High center. Cross-wavelet analysis of TCF and SHI revealed a long-term relationship between cloudiness and the Siberian High. Generally, the Siberian High intensification by 1 hPa leads to a replacement of one overcast day with one day without clouds, which is associated mainly with a decrease in precipitating and stratiform clouds. These changes point to a positive feedback between cloudiness and the Siberian High.