Changes in the amount of low clouds in Estonia (1955–1995)

Abstract

Based on data from 16 meteorological stations, trends in the amount of low clouds in Estonia have been investigated for the period 1955-1995. Analysis shows that the amount of low clouds has increased in March at all stations, in June at 12 stations and in September at eight stations. The amount of low clouds has decreased in May at seven stations and in October at five stations. Only trends that are significant at at least the 0.1 level were taken into account. Regression analysis shows that the increase in the amount of low clouds in March can be ascribed to changes in the frequencies of occurrence of European circulation patterns and/or to an increase in the amount of low clouds within the zonal circulation.

Long‐term variability of the cloud amount and cloud genera and their relationship with circulation (Kraków, Poland)

“…() reported an upwards trend for overcast weather and low cloud cover in Moscow in 1955–1995. In the same period, the amount of cloud in the low étage in Estonia increased in 10 out of the 16 locations included in the study and decreased in two of them (Keevallik and Russak, ). In Lithuania, the low‐level cloud cover was showing a declining trend from the 1940s until the end of the 20th century during the cold part of the year, while positive trends were recorded in the warm part of the year (Stankūnavičius, ).…”

“…In the temperate zone, the greatest determinant of cloud formation is deemed to be macro‐scale circulatory processes and radiation factors, as well as local conditions (Henderson‐Sellers, ; Huth, ; Keevallik and Russak, ; Matuszko, ; Żmudzka, ; Cahynova and Huth, ; Lewik et al ., ). Also, there are a number of studies concerning the effects of aerosols on cloud cover (e.g.…”

North‐Atlantic surface winds examined as the source of winter warming in Europe

“…Moisture is available, and enhanced cloud‐cover (especially high clouds) is a corollary effect to the steeper lapse rate [ Otterman et al , 2002]. Indeed, increased cloudiness is reported for this period, see Keevallik and Russak [2001], for instance. That these two trends, which inherently accompany near‐surface warming by low‐level warm advection, are actually observed, strengthens the case for attributing the warming to this process.…”

Shifts in early spring wind regime in North-East Europe (1955–2007)

“…Most of the relevant analysis has been concentrated on extracting linear trends in local meteorological parameters. A decrease in snow cover during the second half of the winter (Tooming and Kadaja, 2000), an increase in the amount of low clouds in March (Keevallik and Russak, 2001), warming tendencies in late winter and spring (Jaagus, 2006;Keevallik, 2003a), and decreases in the duration of ice cover (Sooäär and Jaagus, 2007), among other things, have been noticed in Estonia.…”