EXTREME COLD EVENTS: THE CASE OF BAHIA BLANCA (ARGENTINA)

The objective of this investigation is to characterize the frequency, duration, and intensity of extreme cold episodes (Period of Very Low Extreme Temperatures PVLET-, Cold Waves -CW-and Frost Days -FD0-) that occurred in Bahia Blanca and the synoptic situation associated to its development. We observed that most of the PVLET and OC had a three-day duration and occurred in June and July. About its decadic frequency, the 10-year periods 1981-1990 and 1991-2000 had the highest records of the whole period. In 2011-2020 we found the minimum frequency of PVLET and no HW were recorded. About the relationship between intensity and absolute frequency of CW, we verified that when CW where more frequent, its mean decadic intensity was higher. On the synoptic situations, CW were associated with the presence of a high-pressure system in the center of the country, which defines the dominance of cold, dry air and clear skies. Winter frosts were the most intense and frequent in all decades and late frosts were more frequent and intense than the first ones. In the highest intensity range analyzed there was only a record of occurrence for winters and only in the first three decades. During 2011-2020 we observed a decrease in the intensity of first frosts, and late frosts showed an increase in frequency of occurrence and intensity