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Science 10 March 2006:
Vol. 311. no. 5766, p. 1429
DOI: 10.1126/science.1121312
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Brevia

Diffusive Separation of the Lower Atmosphere

Yosuke Adachi,* Kenji Kawamura, Laurence Armi, Ralph F. Keeling{dagger}

The separation of atmospheric constituents by gravity has been proposed theoretically for almost two centuries. However, turbulent mixing has prevented the detection of this phenomenon in the lower atmosphere. By using precise measurements of the Ar/N2 ratio of air samples taken under strong nocturnal inversions, we have detected such separation in near-surface layers. The effect is shown to be consistent with combined influence of thermal and gravimetric separation, with the thermal contribution being more important.

Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla, CA 92093–0244, USA.

* Present address: Department of Applied Chemistry, Keio University, Yokohama 223-8522, Japan.

{dagger} To whom correspondence should be addressed. E-mail: rkeeling{at}ucsd.edu

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Science. ISSN 0036-8075 (print), 1095-9203 (online)