Figure 17 – (a) global pressure belts and (b) shifting of pressure belts

4.6. Shifting of Belts

Pressure belts are not fixed. The main cause of their formation is the uneven distribution of temperature on the surface of earth. Consequently, the pressure belts swing either to the north (in July) or the south (in December) of the equator by following the apparent annual migration of the sun (figure 17(b)). Sun’s movement is recorded between tropic of Cancer and tropic of Capricorn. During the month of July, low pressure equatorial belt extends upto the tropic of

Cancer in Asian region. While in January, it extends to latitudes 100-150 S. Most profound effect of shifting of belts is seen in the temperate region. Winds blowing from the Horse latitudes in the form of westerlies create unique climatic conditions in the temperate parts of the world, especially in the Mediterranean region.