Explain the factors that influence/affect the atmospheric pressure of a place.
- Temperature differences: An increase in temperature leads to a fall in pressure & a decrease in temperature leads to rise in pressure. For example equatorial region which have hot temperatures due to the sun’s effect have low pressure. This is because hot air expands leading to reduction of its mass per unit area.
- Altitude: This is the height of land above the sea level. Air pressure is created due to weight of air therefore sea level has highest air pressure. Moving above sea level air pressure decrease because the proportion of lighter gases (like nitrogen) leading to the decrease in air density decreases. For example air pressure at Mombasa (sea Level is greater than at higher altitude like Kampala or Kasese.
- Moisture in Air (Humidity): As humidity increases pressure decreases because water vapor is less dense than dry air at the same temperature; the addition of water vapor decreases the overall density of the air and lowers its pressure.
- Gravitation of Earth: Atmosphere glues around the Earth due to its gravitation. The intensity of gravitational pull decreases as we get away from core of Earth. Another fact is that as Earth rotates round its axis, average distance of Polar Regions and equatorial regions varies from the core of Earth. For example Polar Regions are nearer to core of the Earth as compared to Equatorial regions and hence have higher air pressure.
- Rotation of Earth: Rotation of Earth produces centrifugal force which has more effect in Equatorial region while lesser effect on Polar Regions. Centrifugal force pushes things away from its core. Same is the effect on air pressure which results into lesser pressure in Equatorial regions as compared to that in Polar Regions.
- Latitudinal variation: Along the equator there is much more heat and therefore low pressure, towards the pole temperature decreases & therefore there is high pressure.
- Nature of the Earth’s surface/ land & Sea breeze. During day the land heats up faster than water. Hot temperature over land leads to low pressure. During night the land lose its heart very rapidly while the sea is warmer. This creates hot temperature on the sea hence low pressure.
- Time of day. At noon air pressure decreases due to an increase in temperature. During the evening and night temperature drop leading to an increase in atmospheric pressure.
- Motion or stability of the air. At the same temperature and vapour concentration, an air mass moving on the surface will exert less pressure than an air mass with similar charateristics but which is simply rests on the surface..
- Seasonal changes: During winter its cold and so pressure rise and summer temperature are hot and so pressure reduces.
CATEGORIES Geography
TAGS Dr. Bbosa Science
