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The annual distribution of the planetary geomagnetic Ap index monthly meanvalues on visually cloudless days and nights at the Abastumani AstrophysicalObservatory (41.75N, 42.82E) in 1957-1993 is analyzed. Cloudless days wereselected from day-time observations of the total ozone content and cloudlessnights from night-time measurements of the mesosphere-thermosphere nightglowintensity. Both series of observations were carried out almost uninterruptedduring the referred time period. The distribution of long-term monthly mean Apvalues on cloudless days shows a semi-annual variation with maxima on theequinoctial months (March and September), while on cloudless nights it displaysa seasonal-like character. The semi-annual and seasonal-like variations of Apmodulate the annual distribution of long-term monthly numbers of cloudless dayswith maximum in August and that of cloudless nights with maximum in September.The lowest monthly mean Ap value for cloudless days and its highest value forcloudless nights fall on June. Different annual distributions of long-termmonthly numbers of cloudless days and nights, when sudden storm commencementsare present, have been found. This coupling between the visually cloudlessdays/nights and the magnetically disturbed days may be considered as amanifestation of the influence of space weather/cosmic factors on the regionaland global climate.

About the annual distribution of magnetically disturbed cloudless days and nights over Abastumani (41.75N, 42.82E)