Solar Radiation, Heat Balance and Temperature | Class 11 Geography Notes

Vertical Variation of Pressure

The atmospheric pressure decreases rapidly with height in the lower atmosphere. This vertical pressure gradient is much stronger than the horizontal pressure gradient. For example, pressure drops from 1,013.25 mb at sea level to 898.76 mb at 1 km elevation, 540.48 mb at 5 km, and 265 mb at 10 km, as shown in the standard atmosphere table. Temperature also decreases with height, which affects the rate of pressure change. Despite the strong vertical pressure gradient force, we do not experience strong upward winds because this force is nearly balanced by the gravitational force pulling air downward. This balance is known as hydrostatic equilibrium. The vertical pressure gradient force acts perpendicular to the Earth's surface and is responsible for the vertical structure of the atmosphere, but it does not cause significant vertical air movement under normal conditions.

📊 Diagram: Table on page 1 (5×3) showing pressure and temperature at different altitudes.

🔗 Connection: This section sets the stage for understanding horizontal pressure variations and their role in wind formation.

Table on page 1 (5×3)