Describe how atmospheric circulation gives rise to the formation of high and low pressure area? The origins of the creation of areas of differing pressures can be seen to start with the sun. As the sun gives off radiation some is absorbed by the earth, however this absorption is centred on the equator and therefore creates a disparity between the heat of the equator and tropics and the rest of the globe. Between 450 North and 300 South there is a positive heat budget whereas outside these regions annually more heat is lost than accumulated. The cause in difference between the amounts accumulated in each hemisphere is due to the north hemisphere having more land than the Southern hemisphere; land has a lesser heat capacity than water, 0.5 in comparison to 1 and therefore can absorb more radiation. As a result of the land heating up faster and more easily it gives off more heat thus creating an imbalance in pressure between the north and south hemisphere and therefore creates high and low pressure.
As we can see from this diagram the equator and surrounding areas has higher net short wave radiation than Net Longwave radiation and therefore has a radiation surplus of around 70 Watts m-2 on the equator whereas the poles have deficits of 105 Watts m-2 and 95 Watts m-2 respectively. The areas with higher levels of insolation become warmer than those with less radiation. Vertical heat transfers, primarily sensible heat transfers such as convection and conduction, cause the air in contact with the earth to warm up, as this heat is dispersed through the air, the increase in heat causes particles to expand. Becoming less dense they therefore rise leading to a reduction in air pressure. On the other hand areas with less insolation are less warm and therefore don’t warm up the surrounding air, this in turn keeps the air denser and therefore a pressure gradient is created with both areas of high and low pressure. However as soon as air tries to move down the pressure...
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