Brewer–Dobson circulation refers to the global atmospheric circulation pattern of tropical

tropospheric The troposphere is the first and lowest layer of the atmosphere of the Earth, and contains 75% of the total mass of the planetary atmosphere, 99% of the total mass of water vapour and aerosols, and is where most weather phenomena occur. From ...

air rising into the

stratosphere The stratosphere () is the second layer of the atmosphere of the Earth, located above the troposphere and below the mesosphere. The stratosphere is an atmospheric layer composed of stratified temperature layers, with the warm layers of air ...

and then moving poleward as it descends. The basics of the circulation were first proposed by

Gordon Dobson Gordon Miller Bourne Dobson (25 February 1889 – 10 March 1976) was a British physicist and meteorologist who did important work on ozone. Education He was educated at Sedbergh School and Gonville and Caius College, Cambridge, graduating with ...

and Alan Brewer. The term "Brewer-Dobson circulation" was first introduced in 1963. This circulation pattern explains observations of

ozone Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the lo ...

and

water vapor (99.9839 °C) , - , Boiling point , , - , specific gas constant , 461.5 J/( kg·K) , - , Heat of vaporization , 2.27 MJ/kg , - , Heat capacity , 1.864 kJ/(kg·K) Water vapor, water vapour or aqueous vapor is the gaseous pha ...

distribution, and has been accelerating in recent decades, likely due to

climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...

Circulation

Brewer–Dobson circulation is driven by planetary scale

atmospheric waves An atmospheric wave is a periodic disturbance in the fields of atmospheric variables (like surface pressure or geopotential height, temperature, or wind velocity) which may either propagate (''traveling wave'') or not (''standing wave''). Atmosp ...

, namely Rossby waves, with results in westward drag and therefore poleward pumping action to conserve

angular momentum In physics, angular momentum (rarely, moment of momentum or rotational momentum) is the rotational analog of linear momentum. It is an important physical quantity because it is a conserved quantity—the total angular momentum of a closed syst ...

Global impacts

Because it moves air into and out of the stratosphere, Brewer–Dobson circulation determines the mean age and

residence time The residence time of a fluid parcel is the total time that the parcel has spent inside a control volume (e.g.: a chemical reactor, a lake, a human body). The residence time of a set of parcels is quantified in terms of the frequency distribution ...

of stratospheric gases, as well as tropical tropopause temperatures and stratospheric

. Brewer-Dobson circulation directly impacts the distribution and abundance of

stratospheric ozone The ozone layer or ozone shield is a region of Earth's stratosphere that absorbs most of the Sun's ultraviolet radiation. It contains a high concentration of ozone (O3) in relation to other parts of the atmosphere, although still small in relat ...

by moving it from the tropics towards the poles. This transport helps to explain why tropical air has less

than polar air, even though the tropical

is where most atmospheric

is produced. Brewer-Dobson circulation also influences the lifetime of ozone-degrading substances and some greenhouse gases.

Acceleration due to greenhouse effect

Interest in Brewer–Dobson circulation has increased in the 21st century due to predictions of general circulation models and chemistry-climate models that the circulation will accelerate due to greenhouse-gas induced

. Observations have recently confirmed that Brewer-Dobson circulation has accelerated at ~2.0% per decade for the past four decades, leading to a cooling of the tropical lower

and warming in high latitudes.

Reference

External links

* {{DEFAULTSORT:Brewer-Dobson circulation Atmospheric circulation

Circulation

Global impacts

Acceleration due to greenhouse effect

See also

Reference

External links