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The North Atlantic High appears notably weakened from the beginning of the examined period until the beginning of this century. From then until 1930, it exhibits an increased central pressure. From the beginning of the period until 1914, the North Atlantic High exhibits a significant trend of intensification and at the same time a trend of displacement to the west. From 1915 until 1963 it exhibits a trend ofweakeningand a trend ofeastward displacement. The North Atlantic Low has not exhibited a significant trend of its central pressure, but it has shown a small trend of displacement to the west. There is generally a negative correlation between the pressures of these two centres ofaction and a positive correlation between latitudinal position of the centres. The meridional component of the pressure gradient created between the two action centres, appears to have low values during epochs of low frequency of westerlies and high values when the westerlies are more frequent.

The presence of the Siberian Anticyclone is continuous from October until March in an area defined by longitude 90"-110"E and latitude 40"-55"N. From the point of view of central pressure, this anticyclone is much more intense than the permanent anticyclones in the Atlantic and Pacific Oceans. During the last 116 years there have been periods during which the anticyclone appeared stronger and periods when it appeared weaker. Since 1970 a continuous decrease in central pressure of the anticyclone is observed, and is related to a continuous temperature rise of the 1000-500 hPa layer for the same time interval. Their correlation is found to be negative. After 1950, maximum values of central pressure are observed corresponding to maximum values of solar activity. In some of the time series of the anticyclone central pressure, periodicities of 58, 4.5, 3.5, and 3 years are observed, as well as the Quasi-biennial Oscillation.

Sunshine duration fluctuation in this century is studied from annual values for 26 stations in central and south-eastern Europe. Possible sources of inhomogeneity are identified: ageing of the glass ball in the sunshine recorder, changes in instruments, the recording tape and its evaluation, and location of the station, and exposure to air pollution, Long-term changes of annual sunshine duration are presented using a smoothed Gauss filter and principal component analysis. The main feature of sunshine duration fluctuation in this century is its sharp decrease after a maximum at the end of the 1940s. Principal component 1 shows, with small exceptions, positive loadings for the year and its seasons (for the period of . Principal component 2 divides the region studied into two parts, with positive loadings in the western and northern parts of central Europe and negative loadings over the rest of area analysed. A contradictory situation occurs only in autumn. Statistically significant cycles occur at intervals of about 2.3-2.4 years (western Germany), 3 years (Greece), 3.5-3.7 years (central Europe and Bucharest) and 3.7-4.0 years (Bulgaria). Some of the stations used indicate longer cycles (44-1 10 years). Comparison of coldest (1901Comparison of coldest ( -1920 and warmest (19341953) 20-year periods in the Northern Hemisphere shows for the warmest period an important increase in sunshine duration, with the exception of Athens and Bucharest and some other stations in winter. In the warmer period sunshine duration variability is generally higher in spring and winter and less in summer and autumn.