Atmospheric circulation

Earth Global Circulation - en

Atmospheric circulation is the large-scale movement of air through the troposphere, and the means (with ocean circulation) by which heat is distributed on the surface of the Earth. The patterns of atmospheric circulation can vary from year to year, but the basic structure remains fairly constant. This is because they are determined by the Earth's rotation and the difference in solar radiation between the equator and the poles.

Overview

Atmospheric circulation is a key topic in meteorology and climatology. It is driven by the energy from the sun, which heats the Earth's surface unevenly, creating temperature differences that cause the movement of air masses. The rotation of the Earth also influences circulation patterns through the Coriolis effect, which causes moving air to turn to the right in the northern hemisphere and to the left in the southern hemisphere.

Cells and Belts

The global atmospheric circulation can be described as a series of belts and cells that encircle the planet. These include the Hadley Cell, Ferrel Cell, and Polar Cell, which operate in both the northern and southern hemispheres.

Hadley Cell

The Hadley Cell is a tropical circulation feature with warm air rising near the equator, moving poleward at high altitudes, sinking at the subtropics, and then returning equatorward near the surface. This cell is responsible for the trade winds in the tropics and the subtropical jet streams.

Ferrel Cell

The Ferrel Cell lies between the Hadley and Polar Cells. It is characterized by air that moves poleward and eastward at the surface and equatorward and westward at higher altitudes. This cell is associated with the mid-latitude westerlies and the formation of many of the weather systems in the mid-latitudes.

Polar Cell

The Polar Cell is the smallest and weakest cell, with air sinking over the highest latitudes and moving equatorward near the surface. This cell is associated with the polar easterlies and the polar front.

Jet Streams

Jet streams are relatively narrow bands of strong wind in the upper levels of the atmosphere. They are located near the top of the troposphere and are westerly winds (flowing west to east). Their paths typically have a meandering shape, and they can have profound effects on the weather, including the development and movement of low-pressure systems.

Monsoons

Monsoons are seasonal wind patterns that occur in tropical and subtropical regions, which result in pronounced wet and dry seasons. The Asian monsoon is the most well-known example, bringing significant rainfall to the Indian subcontinent during the summer.

Impact on Climate and Weather

Atmospheric circulation is a critical component in determining the climate of a region as well as the weather patterns that occur from day to day. Changes in the circulation patterns can lead to significant weather events, such as hurricanes, droughts, and floods.

Climate Change and Atmospheric Circulation

Changes in atmospheric circulation are expected as a result of climate change. These changes can lead to shifts in weather patterns, including more intense storms, longer drought periods, and changes in the distribution of rainfall. Understanding these patterns is crucial for predicting future climate conditions and for preparing for their impacts.