A comment about the seasonal cycle of air pressure

The most notable feature of sea level pressure for winter months is the low pressure over the Atlantic sector corresponding to the Icelandic Low. Standard deviations are also high in this region, due to variations in the number and strength of cyclones from year to year. (Although not within the area covered by the Atlas grid, low pressure and high standard deviation are also found south of Alaska, corresponding to the Aleutian Low.) The high winter pressures over Siberia correspond to the Siberian High. During spring the Icelandic and Aleutian lows weaken, as do the Siberian and Alaskan highs. An anticyclone develops over the Beaufort Sea. This Beaufort Sea High is strongest in March and April. In general, standard deviations are lower than for winter. The pressure field in summer is quite flat. Pressures are actually lowest over the central Arctic Ocean, as it is in this season that cyclone activity in this area is most common. The fairly high standard deviations largely manifest variations in cyclone activity in this area. The fields for autumn capture the transition back to the winter pattern. Note in particular the redevelopment of the Icelandic Low.