Nature of long-term correlations between cloud state and variations in galactic cosmic ray flux

The nature of long-term correlations between low cloud anomalies and galactic cosmic ray (GCR) intensity, as well as possible causes of variations in the character of these correlations in the early 2000s, were studied. It was shown that the influence of GCRs on a cloud state at midlatitudes is closely related to GCR effects on variations in extratropical cyclogenesis intensity. The high positive correlation coefficients between low clouds and GCR fluxes observed in 1983–2000 were caused by the fact that increases in GCR fluxes during this period were accompanied by an intensification of cyclonic activity at midlatitudes. The correlation between clouds and GCR fluxes in the early 2000s was possibly violated, because the sign of GCR effects on the development of extratropical baric systems reversed as a result of a change in the stratospheric polar vortex state.