Brewer-Dobson Circulation
Overview
The Brewer-Dobson circulation (BDC) is a model in atmospheric sciences that describes the transport of air and trace gases in the stratosphere. Named after the scientists Alan Brewer and Gordon Dobson who first described it, the BDC is a fundamental concept in understanding the chemistry and dynamics of the stratosphere.
History
The concept of the BDC was first proposed by Alan Brewer in 1949. Brewer's work was based on observations of the distribution of ozone and water vapor in the stratosphere. He proposed that air in the stratosphere circulates from the tropics to the poles in a slow, upward motion. This was later confirmed by Gordon Dobson, who used measurements of total ozone to infer the existence of this circulation.
Mechanism
The BDC is driven by the differential heating of the Earth's surface. The tropics receive more solar radiation than the poles, creating a temperature gradient that drives the circulation. The warm air in the tropics rises and moves towards the poles, where it cools and descends. This creates a loop of air movement known as the BDC.
The BDC is also influenced by the Coriolis effect, which causes the air to be deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. This results in a net transport of air from the tropics to the poles in the stratosphere.
Role in Atmospheric Chemistry
The BDC plays a crucial role in the distribution of trace gases in the stratosphere. These gases, which include ozone, water vapor, and other greenhouse gases, are transported from the tropics to the poles by the BDC. This transport process is important for the chemistry of the stratosphere, as it determines the distribution of these gases and their interaction with solar radiation.
The BDC also plays a role in the depletion of the ozone layer. The transport of ozone-depleting substances (ODSs) from the tropics to the poles is facilitated by the BDC. These ODSs, once in the polar regions, can lead to the formation of the ozone hole.
Current Research
Current research on the BDC focuses on understanding its variability and response to climate change. Changes in the BDC can have significant impacts on the distribution of trace gases in the stratosphere, and hence on the Earth's climate. Researchers use a combination of observations, numerical models, and theoretical studies to investigate these aspects of the BDC.
