Explain the direction of the six surface wind belts in Fig. 6.24C. Be sure to use the concept of pressure gradient force and the Coriolis effect in your answer.
To explain the direction of the six surface wind belts in Fig. 6.24C, we need to consider two important factors: the pressure gradient force and the Coriolis effect.
The pressure gradient force is the force that drives air from areas of high pressure to areas of low pressure. In the context of global wind patterns, air near the equator tends to be warm and rises, creating a region of low pressure. Meanwhile, air near the poles tends to be cold and sinks, creating a region of high pressure. This temperature difference between the equator and the poles leads to the establishment of six major surface wind belts.
Now, let's analyze the direction of the wind belts using the pressure gradient force and the Coriolis effect.
1. Equatorial Low Pressure Belt (Doldrums):
The Equatorial Low Pressure Belt is located near the equator, where air rises due to intense heating. Air flows horizontally from both the Northern and Southern Hemispheres, creating a low-pressure zone. Due to the weakening of the Coriolis effect near the equator, the wind in this belt is generally weak and exhibits variable direction.
2. Subtropical High Pressure Belt (Horse Latitudes):
Moving away from the equator towards the subtropics, the air from both hemispheres gradually descends, giving rise to the Subtropical High Pressure Belt. The pressure gradient force causes air to flow from this high-pressure region towards the low-pressure areas near the Equatorial Low Pressure Belt. However, the Coriolis effect deflects the flow to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. This causes the prevailing winds in this belt to blow from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere.
3. Subpolar Low Pressure Belt:
The Subpolar Low Pressure Belt is located near the poles. As cold air sinks at the poles, it flows horizontally towards the equator, creating a low-pressure area. The pressure gradient force drives air from the higher latitudes towards this low-pressure zone. However, the Coriolis effect deflects the flow to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. As a result, the prevailing winds in this belt blow from the southwest in the Northern Hemisphere and from the northwest in the Southern Hemisphere.
4. Polar High Pressure Belt:
Moving closer to the poles, the sinking cold air creates the Polar High Pressure Belt. As the air flows from this high-pressure region towards the Subpolar Low Pressure Belt, the Coriolis effect deflects it to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. Consequently, the prevailing winds in this belt blow from the east in both hemispheres.
In summary, the direction of the six surface wind belts can be explained by the combined effects of the pressure gradient force and the Coriolis effect. The pressure gradient force drives the air from areas of high pressure to areas of low pressure, while the Coriolis effect deflects the flow to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. These two forces working together give rise to the specific wind directions observed in the six wind belts.