Global Wind Explained

The illustration below portrays the global wind belts, 3 in every hemisphere. Note that the U.S. Lies primarily in the Westerly Wind Belt with prevailing winds indigenous the west. Every of these wind belts to represent a "cell" that circulates air through the environment from the surface to high altitudes and ago again. The cell on either next of the Equator are dubbed Hadley cells and give climb to the trade Winds at Earth"s surface. Exactly how do we describe this sample of an international winds and how does it affect precipitation?


Figure 20. An international Winds
Source: NASA

We"ll begin at Earth"s equator, wherein solar radiation is the greatest year around. Air near the equator is warmed and rises due to the fact that it is less dense (mass/unit volume) than the air roughly it as shown in figure 21 below.

You are watching: Describe the main global wind systems give characteristics of each


Figure 21. Air close to the equator is heated and rises as shown by the red arrows.
Source: Mike Arthur and Demian Saffer

The rising air create a circulation cell, called a Hadley Cell, in i beg your pardon the wait rises and cools at high altitudes moves outward (towards the poles) and, eventually, descends back to the surface. The continual heating and rise that air at the equator create low push there, which causes air to move (wind) towards the equator to take the ar of the air the rises. Top top the other hand, sinking air create high press at the surface where it descends. A gradient of pressure (high to low) is formed that reasons air to circulation away native the high and also towards the low push at the surface.


Figure 22. Hadley Cells, displayed as red circles, are formed as the wait rises.
Source: Mike Arthur and Demian Saffer

Figure 23. Hadley Circulation Cells cause a gradient of pressure displayed in this figure.
Source: Mike Arthur and also Demian Saffer

The earth would have actually two large Hadley cells if the did no rotate. But, since it does rotate, the rotation the the planet leads come the Coriolis effect. You have to view the short video clip on this so-called "effect" or "force." (The Coriolis Effect). Without going into detail regarding why rotation creates this apparent force, the Coriolis effect causes winds (and all relocating objects) to be deflected:

to the appropriate in the north Hemisphereto the left in the southern Hemisphere

The Coriolis effect causes winds to deflect together they travel within circulation cells and results in the two huge hypothetical Hadley cell breaking right into six smaller sized cells, which looks something like the diagram below (and the first figure in this series).


Figure 24. The rotation the the planet is responsible because that the Coriolis effect which breaks the two big Hadley Cells right into six smaller ones presented as 6 red one in this figure.
Source: Mike Arthur and Demian Saffer

Ok, so, us now have some idea about the beginning of global wind solution that result from pressure gradients in ~ Earth"s surface. How does this create precipitation, and where? Precipitation occurs where moisture-laden wait rises, one of two people by heating at the equator or by to run up and over a much more dense air mass. Together the rising air cools its volume to hold water to reduce (relative humidity increases) and, at some point, saturation v respect to water vapor is reached. Then, condensation--clouds and also rain!

Figure 25. This number demonstrates how the wind moves at the surface as it concerned Hadley cell circulation.
Source: Mike Arthur and Demian Saffer

The diagrams over and below portray just the Hadley cabinet circulation, that is propelled by heater in the equatorial region. ~ above the surface, wind moves away from high pressure (High) and toward low press (Low). Convergence occurs close to the equator (winds punch in in the direction of one another) and Divergence occurs under the descending air that forms high-pressure belts. The final figure (Figure 26) mirrors all 6 cells diagrammatically, together with the press variations at the surface ar of the Earth and zones of typical wet and also dry belts. Note particularly the dry belts close to 30 levels North and South.

Figure 26. This figure display divergent and convergent winds together they related to Hadley cell circulation.
Source: Mike Arthur and also Demian Saffer
Figure 27. This number shows all six cells diagrammatically, in addition to the press variations in ~ the surface of the Earth and also zones of common wet and dry belts.
Click below for Text alternate of number 27.
Air circulation patternsLatitudeBarometric PressurePrecipitationSurface winds

Source: Mike Arthur and Demian Saffer
‹ worldwide Wind increase Unit 2: physical Hydrology ›
Earth 111: Water: Science and also Society

Logged in together Anonymous.


Unit 1: new Water: Scarcity or Surfeit?Module 2: Climatology of WaterRelative HumidityGlobal Wind

Authors: Michael Arthur and Demian Saffer Professors, The Pennsylvania State university - university Park, Patrick Belmont Assistant Professor, Utah State University.

Team Lead: Maureen Feineman, combine Professor, The Pennsylvania State University. Discovering Designer: April Millet, The Pennsylvania State University

This courseware module is part of penn State"s university of Earth and also Mineral Sciences" OER Initiative.

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