EAPS 10200 Lecture 10: EAPS 102 cyclones note n.7
31 Oct 2017
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Document Summary
A low pressure system causes an inward flow of wind (cyclonic flow) which causes convergence on the surface. The inward flowing air has no where to go but up. This rapidly rising air represents a net increase in pressure. If this happens then a cyclone cannot maintain the surface low pressure it needs and will eradicate itself. However, if the air at the top of the air column spread out (diverge) then a low pressure on the surface could be maintained. Since warm air is rising a tall column is established with clouds and precipitation. Often divergence aloft creates a surface low and if it is strong enough it acts like a powerful vacuum sucking air up. A high pressure system causes an outward flow of wind (anticyclonic flow) on the surface which is divergence. The outward flowing air on the surface is accompanied by convergence aloft. This sinking air represents a compression of the air column.
