Dynamics of transport processes in the upper troposphere

Science

Volumn 276, Issue 5315, 1997, Pages 1079-1083

  Mahlman, J D ^a  

^a PRINCETON UNIVERSITY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

ARTICLE; ATMOSPHERIC TRANSPORT; ENVIRONMENTAL MONITORING; HYPOTHESIS; PHOTOCHEMISTRY; PRIORITY JOURNAL; STRUCTURE ACTIVITY RELATION; TROPOSPHERE;

ATMOSPHERIC CHEMISTRY; ATMOSPHERIC TRANSPORT; TROPOSPHERE;

EID: 0030618078     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.276.5315.1079     Document Type: Article

References (41)

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3. The troposphere is the part of the atmosphere that is generally characterized by sharply decreasing temperatures with increasing altitude, roughly 6°C/km. Its thickness ranges from roughly 8 km in higher latitudes to 16 km in the tropics. Because the cloudless atmosphere is nearly transparent to incoming solar radiation, the troposphere is essentially heated from below, with dynamically induced vertical mixing shaping the vertical temperature structure. The upper limit of the troposphere is conventionally called the tropopause.
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5. P is the specific heat of air at constant pressure. Under these idealized circumstances, the first law of thermodynamics adopts the simple form dΘ/dt = O; that is, potential temperature is conserved following an air parcel over time t. In the atmosphere, Θ generally increases with altitude, markedly so in the stratosphere. Long-term transport between the troposphere and stratosphere must be tightly constrained by the magnitude of net diabatic processes, ultimately of dynamical origin, moving air across surfaces of constant potential temperature. Static stability is defined here for convenience as the vertical pressure gradient of potential temperature (-∂θ/∂P) and is a measure of the resistance of air to vertical displacement. Use of potential temperature as a vertical coordinate allows straightforward use of the radiosonde-based meteorological network of wind, temperature, and pressure data to calculate 3D air trajectories in the troposphere, to the extent that the air moves nearly adiabatically. This substitution is a powerful diagnostic tool for addressing tracer movements, because it evades the problem that standard meteorological measurements do not measure vertical velocity directly (8-11).
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38. Nitrous oxide is an inert tracer of atmospheric motions in the troposphere and lower stratosphere. It has biological sources at Earth's surface and photochemical destruction sinks above 25-km altitude. Its global atmospheric lifetime is about 120 years. It thus is rather well mixed in the troposphere, but its small variations serve as an excellent tracer of atmospheric motions (Fig. 2).
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41. Valuable comments and assistance on this manuscript were provided by J. R. Holton, H. Levy II, W. J. Moxim, L. M. Perliski, E. M. Williams, R. J. Wilson, and an anonymous reviewer. Many excellent insights have been provided on aspects of this topic by a variety of valued colleagues. Particularly helpful were the perspective and opinions offered over the past three decades by D. G. Andrews, I. M. Held, J. R. Holton, B. J. Hoskins, M. E. McIntyre, R. A. Plumb, E. R. Reiter, and H. Riehl. This paper is dedicated to the warm personal memories of and the invaluable insights given to me on multiple aspects of this subject by E. F. Danielsen and S. B. Fels, both deceased.