Besides the considerable latitudinal differences in pressure and atmospheric circulations, there are significant longitudinal variations, particularly in the subtropical high-pressure belts, in both the hemispheres.
As discussed earlier, the subtropical high pressure cells are generally more persistent over the oceans and they are more intense on their eastern than their western sides. That is why in the subtropical regions subsidence and divergent airflow are characteristic of the eastern parts of warm oceans.
The anticyclones near the earth’s surface are capped by upper-air temperature inversion layers. The resultant weather is clear and fine.
The highs of the horse-latitudes are much weaker over the western portions of the oceans. This part of the oceans is characterized by weaker subsidence. The upper-air inversion layer is found at higher elevations.
ADVERTISEMENTS:
Weather is often stormy. There is pole-ward movement of air in the western portions of these subtropical anticyclones. Trade winds in these regions are, therefore, weak and, at times, non-existent.
In the northern hemisphere there is a greater contrast in the pressure and temperature of land areas and oceans in the higher latitudes. Such contrasts persist throughout the year. In the interior of the continents there are strong anticyclones with out blowing cold and dry winds during the low sun period.
In summer, the pressure gradient is reversed. At this time of the year, the heated land masses develop low pressure which results in the reversal of the wind direction. Now, the winds blow from the oceans to the continents.