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

tropospheric The troposphere is the lowest layer of the atmosphere of Earth. It contains 80% of the total mass of the planetary atmosphere and 99% of the total mass of water vapor and aerosols, and is where most weather phenomena occur. From the planetary s ...

air rising into the

stratosphere The stratosphere () is the second-lowest layer of the atmosphere of Earth, located above the troposphere and below the mesosphere. The stratosphere is composed of stratified temperature zones, with the warmer layers of air located higher ...

and then moving poleward as it descends. The basics of the circulation were first proposed by Gordon Dobson 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 compound, 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 , break ...

and

water vapor Water vapor, water vapour, or aqueous vapor is the gaseous phase of Properties of water, water. It is one Phase (matter), state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from th ...

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

climate change Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...

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 be stationary (''standing wave'' ...

, namely

Rossby wave Rossby waves, also known as planetary waves, are a type of inertial wave naturally occurring in rotating fluids. They were first identified by Sweden-born American meteorologist Carl-Gustaf Arvid Rossby in the Earth's atmosphere in 1939. They ...

s, with results in westward drag and therefore poleward pumping action to conserve

angular momentum Angular momentum (sometimes called moment of momentum or rotational momentum) is the rotational analog of Momentum, linear momentum. It is an important physical quantity because it is a Conservation law, conserved quantity – the total ang ...

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 distribu ...

of stratospheric gases, as well as tropical

tropopause The tropopause is the atmospheric boundary that demarcates the lowest two layers of the atmosphere of Earth – the troposphere and stratosphere – which occurs approximately above the equatorial regions, and approximately above the polar regi ...

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 rela ...

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 model A general circulation model (GCM) is a type of climate model. It employs a mathematical model of the general circulation of a planetary atmosphere or ocean. It uses the Navier–Stokes equations on a rotating sphere with thermodynamic terms for ...

s and chemistry-climate models that the circulation will accelerate due to

greenhouse-gas Greenhouse gases (GHGs) are the gases in the atmosphere that raise the surface temperature of planets such as the Earth. Unlike other gases, greenhouse gases Absorption (electromagnetic radiation), absorb the Electromagnetic spectrum, radiat ...

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.

References

External links

* {{DEFAULTSORT:Brewer-Dobson circulation Atmospheric circulation

Circulation

Global impacts

Acceleration due to greenhouse effect

See also

References

External links