Surface pressure

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The term surface pressure has two distinct definitions, depending on the context.

Atmospheric science[edit]

Surface pressure often refers to the atmospheric pressure at a location on Earth's surface. It is directly proportional to the mass of air over that location.

For numerical reasons, atmospheric models such as general circulation models (GCMs) usually predict the nondimensional logarithm of surface pressure.

The average value of surface pressure on Earth is 985hPa.[1] This is in contrast to mean sea-level pressure, which involves the extrapolation of pressure to sea-level for locations above or below sea-level. The average pressure at mean sea-level (MSL) in the International Standard Atmosphere (ISA) is 1013.25hPa, or 1 atmosphere (Atm), or 29.92 inches of mercury.

Pressure (P), mass (m), and the acceleration due to gravity (g), are related by P = F/A = (m*g)/A, where A is surface area. Atmospheric pressure is thus proportional to the weight per unit area of the atmospheric mass above that location.

Physical chemistry[edit]

Surface pressure can also refer to the change of surface tension as a function of the area of water surface available to each molecule in a solution. The measurement of surface pressure is key in determining the monolayer properties of an amphiphilic material.

The surface pressure describes the depression of the surface tension below the value for an uncontaminated interface.[2][3]

See also: Pressure: Surface pressure.

References[edit]

  1. ^ Jacob, Daniel J. Introduction to Atmospheric Chemistry. Princeton University Press, 1999.
  2. ^ SHAW, D.J., (1992), Introduction to Colloid and Surface Chemistry, Fourth Edition, Butterworth–Heinemann / Elsevier Science, Oxford. Page 77.
  3. ^ PATERSON, M.P. & SPILLANE, K.T., (1969), “Surface films and the production of sea-salt aerosol”, Quarterly Journal of the Royal Meteorological Society, 95(405), 526–534.