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What effects the climate (Seasonal Variations in pressure (Winds result…
What effects the climate
Global Circulation patterns - there are large scale wind - circulation patterns present. The global circulation pattern can be described as the world wide system of winds by which the necessary transport of heat from tropical to polar latitudes is accomplished.
Hadley Cell - The largest cells extend from the equator to between 30 and 40 degrees north to south, and are named Hadley cells. Within the trade winds blow towards the equator, then ascend near the equator as a broken line of thunderstorms, which forms the inter-tropical-convergence zone.
Ferrel Cells - In the middle cells air converges at low altitudes and then rises along the boundaries between cool polar air warmer subtropical air that generally occurs between 60 and 70 degrees north and south. This often surrounds the UK, which is why we get unsettled weather. The Ferrel cell moves in the opposite direction to the other two cells.
Polar Cell - The smallest and weakest cell, which extend between 60 and 70 degrees north and south to the poles. Air in these cells sink over the highest latitudes causing relatively dry stable conditions and flows to towards the lowest latitudes at the surface. It is why the north and south poles are deserts.
The Coriolis effect
The rotation of the earth causes an apparent of wind direction. The wind is actually blowing straight but its path when plotted on a map is curved.
Wind in the northern hemisphere deflects to the right and wind in the southern hemisphere deflects to the left.
Geostrophic Wind - However, the wind cannot go on constantly and as it cannot flow from areas of low pressure to high it will begin to flow parallel to the isobars (area of equal pressure)
Influence of altitude
Air temperature decreases as altitude increases because 1. the air becomes thinner - 2. Contains less water vapour to absorb the earth's long wave radiation leading to rapid heat loss at night.
During the day, rock surfaces exposed to the suns rays can become very warm because almost all the insolation reaches the ground but at night this is rapidly lost.
The rate of decrease in temperature with altitude for still air varies but on average is 0.65 degrees Celsius per 1000 metres. This is known as the environmental lapse rate.
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