CR 78:19-35 (2019)  -  DOI: https://doi.org/10.3354/cr01559

ABSTRACT: The main aim of the study was to determine the seasonal and long-term variability of strong high occurrence in the Arctic. The research was based on average daily air pressure values at sea level for the period 1965-2014 at grid points (2.5° x 2.5° grid) derived from NCEP/NCAR reanalyses. The Arctic was defined as an area north of 60°N. The main characteristic defining the occurrence of high pressure and strong high pressure systems was a day in which the pressure at a given grid point was ≥1020 and ≥1030 hPa, respectively. The results obtained revealed large seasonal differences in strong high occurrence in the Arctic. They occur the least frequently (usually once a month) from June to August. In subsequent months, strong highs are more frequent, and from December to February, strong highs occur even several times a month. In terms of the number of days with high pressure and the number of days with strong highs, Greenland, the Siberian part of the Arctic, and the area covering the Beaufort Sea, the East Siberian Sea, and part of the Arctic Ocean stand out. Concerning the entire Arctic, the analysis of the long-term variability of strong high occurrence demonstrated that there are signals of a decline in the number of those baric systems during the period investigated. Decreasing tendency was the strongest up to the 1990s. However, since the beginning of the 21st century, the number of strong highs has increased again.

KEY WORDS: Strong highs · Arctic · Long-term variability