Horizontal Distribution of Pressure - QS Study
QS Study

Horizontal Distribution of Pressure

Small differences in pressure are highly significant in terms of the wind direction and velocity. Horizontal distribution of pressure is studied by drawing isobars at constant levels. Isobars are lines connecting places having equal pressure. The distribution of atmospheric pressure across the latitudes is termed as global horizontal distribution. In order to eliminate the effect of altitude on pressure, it is measured at any station after being reduced to sea level for purposes of comparison. The sea level pressure distribution is shown on weather maps.

Figure: Isobars, pressure and wind systems in Northern Hemisphere

The figure shows the patterns of isobars corresponding to pressure systems. The low-pressure system is enclosed by one or more isobars with the lowest pressure in the center. The high-pressure system is also enclosed by one or more isobars with the highest pressure in the center. This distribution is characterized by the presence of distinctly identifiable zones of homogeneous pressure regimes or ‘pressure belts’. On the earth’s surface, there are in all seven pressure belts.

The seven pressure belts are equatorial low, the sub-tropical highs, the subpolar lows, and the polar highs. Except for the equatorial low, all others form matching pairs in the northern and southern hemispheres.