There are several main ways of atmospheric motion

There are several main ways of atmospheric motion

Atmospheric motion
In theory, the atmospheric motion should be in the form of three circulations
1. Single loop circulation
Assuming that the earth's surface is uniform, and there is no rotation of the earth, that is, the motion of the air has neither friction nor geostrophic bias force. Then, the air in the equatorial region expands and rises, the polar air cools and shrinks and sinks, and the pressure at a certain height above the equator is higher than that at a similar height above the polar region, When the air above the equator flows over the polar region, the mass of the air column on the equator decreases, causing the equatorial ground pressure to decrease and forming a low pressure region, which is called the equatorial low pressure; when there is air flowing over the polar region, the surface pressure increases and forming a high pressure region, which is called the polar high pressure, In this way, a closed atmospheric circulation between the equator and the polar region is formed
In fact, the earth rotates all the time. If the surface of the earth is uniform, the circulation becomes more complicated because the air flow is affected by the geostrophic force
2. Three circle circulation
At first, the effect of geostrophic deflection force is very small, and the air basically moves along the meridional circle in the direction of pressure gradient force. With the increase of latitude, the effect of geostrophic deflection force gradually increases, and the air flow gradually deflects to the latitudinal circle. At about 30 ° n, the geostrophic deflection force increases to equal to the pressure gradient force, At this time, the air flow in the northern hemisphere is almost westerly along the zonal direction, which hinders the air flow to the polar region. Therefore, the air flow accumulates and sinks over 30 ° n, resulting in a high pressure belt in the lower layer, called the subtropical high belt. The equatorial low pressure belt is formed due to the air rising at the equator, which causes the air to flow from the subtropical high belt to the equator and the high latitude region respectively, Under the influence of geostrophic bias force, it becomes northeast wind in the northern hemisphere and southeast wind in the southern hemisphere, which are called northeast trade wind and southeast trade wind respectively. These two trade winds converge near the equator and compensate the air flowing out of the equator, so the upper and lower air currents in the tropical region form the first circulation circle (I), which is called trade wind circulation circle or tropical circulation circle
Three circle circulation
In the northern hemisphere, the air flows out of the polar high and deflects to the right to become easterly. When the air flows out of the subtropical high northward, it also deflects to the right to become westerly in the lower middle latitudes. The two air flows converge near 60 ° n, and the warm air is lifted by the cold air, At latitude 60 ° n, due to the outflow of air, the lower layer forms the sub polar low pressure zone. The air flowing to the polar region and the lower layer from the polar region to the low latitude form the polar circulation circle, which is the second circulation circle (II); the air flowing from the upper layer to the sub tropical zone and the air flowing from the subtropical high belt to the high latitude form the middle latitude circulation circle, This is the third circulation circle (Ⅲ). The circulation circle formed only by the influence of solar radiation and earth rotation is called the three circulation circle. It is an ideal model of atmospheric circulation
Due to the different underlying surface conditions, the three circle circulation pattern is broken, forming monsoon, sea land wind, valley wind, foehn wind and Canyon wind
All these motions are atmospheric motions