Air pressure on the map is represented by the Isobars. Just like temperature, for determining the air pressure also, two months of the year (January and July) are selected.
The condition of air pressure in January: In January, the Sun shines almost vertically on the tropic of Capricorn in the Southern Hemisphere. Because of this, there is high temperature and low air pressure. The areas of low air pressure lie in the interior parts of South America, South Africa and Australia. Fully developed sub tropical high air pressure regions are found in the continents of the Northern Hemisphere.
The condition of air pressure in July: In July, the sun shines almost vertically on the Tropic of Cancer in the northern hemisphere. Due to the land becoming hotter in the northern hemisphere, the area of low air pressure develops there, and in the southern hemisphere, high air pressure belt develops.