4552035155

108 Zofia Kaczorowska

—2.0 mm/year); the central zonę extending from Olsztyn via Warszawa to Sobieszyn and, probably, further Southeastwards shows no change (—0.1 — +0.1 mm/year), whereas in the North and East of Poland a tendency of increase may be observed (1.7—1.0 mm/year). The validity of these results has been established for 5 stations only (Fig. 4).

Fig. 5 presents the results of trends developing in different parts of Poland, together with an estimation of their validity. A slight decrease in pre-cipitation has been determined in Western, Central and Southern Poland and a negligible increase in Northern and Eastern Poland; the probability is everywhere below the assumed measure expectancy.

The second part of the paper deals with attempts at determining perio-dicity.

The series of annual amounts of precipitation, observed by 5 stations, smoothed by the method of 3-year moving averages, have been shown on a graph (Fig. 6). The curves for Kraków (1920—1948) and Wrocław (1920— 1939) suggest the existence of a 10- to 11-year period.

The smoothed series of annual amounts of precipitation and of mean Wolf indices (for the number of sunspots) for the period from 1862 to 1938 were therefore subjected to a harmonie analysis by the use of an electronic Computer. The highest amplitudę for precipitation coincided with the first harmonie, — a fact indicating the existence of a 70-year periodicity (Tables 10 and 11).

A similar analysis of series of precipitation and mean Wolf indices was madę for a 95-year period (after smoothing, years 1842—1936) for Warszawa and Wrocław. For Warszawa a 16-year period distinctly appears, for Wrocław— a period of approximately 90 years.

Moreover, the curves of total precipitation for Warszawa for a period of 142 years (after interpolation and smoothing) and for Kraków for 106 years were investigated by an analogous harmonie analyzer in the State Hy-drological-Meteorological Institute. This analysis confirmed the assumption of a period of approximately 70 years for both stations, and of a 16-year period for Warszawa and a period of about 14 years for Kraków (Table 12).

Subseąuently, an investigation was madę of the trends of annual total precipitation in sub-periods showing sunspot maxima and minima (Table 13 and Fig. 7); here, however, no distinct correlation has been observed. It seems advisable to change here from annual to seasonal amounts of precipitation.

The author also verified the F. Baur [1] hypothesis according to which a threefold fluctuation in the amounts of summer precipitation occurs in the 11-year sunspot cycle. She investigated the trend of deviations from mean long-period amounts of summer precipitation for 100-year series for Warszawa and Kraków, as well as for 60-year series for the Polish Lowland and