Research of cloudiness variations and cosmic ray intensity

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Results of research of cloudiness variations over the North Asia during Forbush-decrease of cosmic ray
intensity for the summer of 2000 (the year of maximum of solar activity), carried out by the method of epoch
imposing, are presented. The area covered by cloudiness with continental climate is considered: 34 degrees at the
latitude (40-74N) and 95 degrees at the longitude (80-175E). The cloudiness was calculated for three latitudinal
zones defined by orographical features (by basic latitudinal watersheds): southern zone 40-56N; central zone
56-66N; northern zone 66-74N.
It was shown that for AE > 300 nT (12 events) the decrease of cloud cover was observed after the beginning
of Forbush-decrease of cosmic ray intensity which corresponds to the positive correlation; the anti-correlation
of cloud cover density and the intensity of cosmic ray flux was registered for 18 events when AE < 300 nT. In
particular, correlation coefficient for the total cloudiness of all three zones for Forbush-decrease event on May
21, 2000 was R = -0,68.
Under Forbush-decreases the variations of ratio between cloudiness of zones are observed. It can be explained
by latitudinal displacement of western cyclone tracks depending on solar activity.
Investigation is supported by grants of the Russian Foundation for Basic Research 08-02-00348, 09-05-98540
and by programs of Presidium of the RAS 16, FANI 02-740-11-0248 and RNP 2-1-1-2555.