How do westerlies form

At this point, the warm air rises and most of it flows back towards the 30 degree latitude mark. This creates the Ferrel cells of Figure 1. The final regions are at the poles, from 60 degrees latitude to 90 degrees latitude. This wind cools towards the poles and sinks to the surface, and recirculates.

This creates what is known as the Polar Hadley cell or Polar cell. The video from Keith Meldahl [5] below illustrates each of the described winds, along with a visualization of each. Fossil Fuels. Nuclear Fuels. Acid Rain. Climate Change. Climate Feedback. The Gulf Stream continues in a northeastern direction, but is stopped by the westerly winds before it can reach the islands of Antigua and Barbuda.

The same behavior is seen in the northwestern region of the Pacific Ocean. As the dominant winds in the middle latitude regions, the westerly winds have had a significant impact on trade routes throughout history. Not only did the westerly winds help direct sailors along the correct path, but they also made the journey faster than previous methods had been. According to some sources, the time it took to get between these two places by using the westerly winds was cut in half. Hendrick Brouwer, a Dutch explorer, is credited with discovering the route.

The significance of the westerly winds helped shape the face of trade for roughly two centuries. Additionally, using these winds led to the European discovery of Australia which was inhabited by indigenous peoples prior to this discovery. In fact, sailboats often continue to follow the westerly winds route, particularly those participating in racing competitions. Researchers have recently made a connection between the westerly blowing winds and global climate change.

Human activity has led to a change in the temperatures and climate patterns in certain areas of the world. This change is particularly noticeable over the Antarctic, where temperatures tend to be cooler than historic trends indicate, and in the southern hemisphere in general, where temperatures are heating up. The human activity believed to be responsible for this is ozone depletion and CFC pollution.

The area between the pole and the westerly winds in the southern hemisphere is experiencing increased temperatures as a result of the combination of these two weather patterns. In turn, this warmer temperature causes the westerly winds to grow in strength and speed.

As these winds become stronger, they prevent the warm air from making its way to the south pole. The winds in each of the southern circulation cells are known by the same names as those in the north. The bulk of air mass movement and transfer of solar heat energy occurs in the Hadley circulation cells located directly north and south of the equator.

The sun warms the tropical ocean and causes evaporation of seawater into water vapor in the air. At the equator, hot air saturated with water vapor, a low-pressure system, rises and moves at a high altitude toward the North and South Poles.

As the water vapor rises it forms clouds. This is why the tropics get a lot of rain Fig. The high-altitude air from the tropics gradually becomes cool, dry, and denser as it flows from the tropics to higher latitudes.

The trade wind belt blows towards the equator from the northeast in the Northern Hemisphere due to the combined effects of the Coriolis effect and the global north-south patterns of atmospheric circulation Fig.

At each pole, a cold polar air mass creates a region of high air pressure. The rotational speed of the polar air mass as it travels towards the equator is slower than the rotational speed of the land and water beneath it.

The cold air mass cannot keep up with the rotating earth. Therefore, air flowing from the North Pole towards the equator produces cold, surface-level winds that blow from the northeast toward the southwest. These winds are called the polar easterlies. Winds are named by the direction from which they blow. As the polar easterlies move toward the equator, they become warmer and less dense. This circulation cell is called the polar cell.

The Hadley cell distributes heat away from the equator, and the polar cell absorbs this heat. Hadley cell and polar cell circulation is straightforward as they are driven by the differential heating of the earth at the equator compared to the poles. This differential heating produces a relatively stable atmosphere and weather system. The Ferrel cell is located between the Hadley and polar circulation cells Fig. Thus, the Ferrel cell is like an atmospheric gear driven by the Hadley and polar circulation cells.

In the Ferrel cell in the Northern Hemisphere, the surface winds blow from the southwest and are called the prevailing westerlies. The prevailing westerlies blow from the southwest to the northeast because of the Coriolis effect—the air mass is moving faster than the rotational speed of the land and water beneath. Prevailing westerlies are the dominant winds blowing across most of the continental United States.

The areas where the circulation cells come together have no steady prevailing winds.