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The belts of sub-polar low pressure are located between 60°-65° latitudes in both the hemispheres. Ordinarily, these cold regions having very low temperature throughout the year should have been high pressure areas, areas of sinking air. Instead, these are regions of rising air. The envelop of air is thin, since rotation swings the bulk of the air towards the Equator. Moreover, the cold Polar winds, as they creep towards the Equator, become thinner and warmer and meet the warm ‘Westerlies’ in the sub polar belts. Being lighter, the westerlies override the heavier Polar winds and rise up to create these low pressure belts.
As these two zones are marked by ascent of warm Sub-Tropical air over cold polar air blowing from poles, and there is a great contrast between the temperatures of the winds from sub-tropical and polar source regions, these regions are marked by violent storms in winter.
The Polar High Pressure Belts are small in area, that lie around the Poles between 80º -90ºN and S latitudes. These regions are the realm of extreme cold and are remarkably characterized by permanent IceCaps. The intense cold makes the polar air extremely cold and dense.
This cold and heavy air tends to settle near the ground. Apart from that, a part of air rising from the Sub Polar Lows that moves mainly towards the Poles, also gradually becomes colder and heavier and comes down around the Poles to form the high pressure belts. From here cold surface winds creep towards the Equator as Polar winds.
