How does differential heating and cooling of Earth’s surface result in global sc

Question

How does differential heating and cooling of Earth’s surface result in global scale winds like the Trade Winds and Westerlies?

What type of weather usually accompanies a drop in air pressure? What type of weather usually accompanies a rise in air pressure? Explain the relationships between vertical movement of air, air pressure, and stormy and calm weather.

Convection happens globally, most energetically lifting air at the equator, but also causes lifting on a local scale. What are three other lifting mechanisms that work on a local scale, for example, along the side of a mountain range? Name and describe the three mechanisms.

What is adiabatic temperature change and how does it occur when air rises and how does it occur when air subsides? Describe the changes with relative terms like increase and decrease.

Explanation / Answer

1. Differential cooling and heating means that some parts of earth like near the equator, receive more sunlight than some other parts like those which are on high lattitudes, e.g. polar regions.

Due to more sunlight on the equator, temperature on the earth surfaces increases. Therefore, air becomes less dense and moves upwards near the equator, creating an area of lower atmospheric pressure. While there is lower temperature on the places away from the equator, thus atmospheric pressure is high. So air is more dense there. As we all know that air goes from areas of high pressure to areas of low atmospheric pressure. So air strarts moving from colder places towards the equator near the earth surface. On the other hand, in the atmosphere the air is moving from the equator towards high lattitudes. Then it cools down, and submerges. This cycle is repeated again and again and causes global air circulation pattern or winds.

2. High pressure is associated with clear sky and fair weather while low pressure forecastes rain and stroms.

During low pressure system, air moves upwards and cools down causing the water vapors to condense thus causing rainfall.

While during high pressure, air subsides, warms up and capacity to hold moisture increases, causing high humidity and clear weather.

3. Orhographic lifting: When air is moving along a mountain range, it moves up and cools down, causing rainfall in this side of the mountain. This is called orthographic lifting.

Convergence: In the center of low pressure areas, winds converge toward the center of the low due to the effects of friction. Since the air cannot go down into the earth, it must rise up. This causes clouds and precipitation near low pressure centers.

Frontal wedging: Warmer air is lifted upwards as it interacts with cooler, more dense air. The area where the warm air interacts with the cold air is called a front.

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