cold trap

cold trap (plural cold traps)

1. In vacuum applications, a device that condenses all vapours except the permanent gases into a liquid or solid, typically to prevent contamination of a vacuum pump.
2. (astronomy) An atmospheric layer that is significantly colder than the adjacent layers both deeper and higher. It keeps ascending gases that have high melting points from escaping the atmosphere by freezing them to a solid which then drops back to the planet surface.
   • 1983, Christopher P. McKay, Gary E. Thomas, “Formation of noctilucent clouds by an extraterrestrial impace”, in Geological Implications of Impacts of Large Asteroids and Comets on the Earth, →ISBN:

     The impact of a large body in the oceans would inject large quantities of water through the tropopause cold trap into the stratosphere and lower mesosphere.

   • 2009, Patrick Irwin, Giant Planets of Our Solar System: Atmospheres, Composition, and Structure, →ISBN, page 97:

     Since the tropopauses of these planets are very cold, there is effectively a cold trap, which in the absence of any other sources should keep the stratospheric water abundance very low, as discussed in Section 4.3.3.

   • 2008, Donald Rapp, Assessing Climate Change, →ISBN, page 24:

     The heat input to polar areas prevents this global cold trap catastrophe from happening, but during ice ages, significant capture of the Earth's water in polar areas will occur.

   • 2010, Raymond T. Pierrehumbert, Principles of Planetary Climate, →ISBN, page 547:

     The tropopause acts as a cold trap, dehumidifying the upper atmosphere and strongly limiting the opportunity for water vapor to escape or for hydrogen to build up in Earth's upper atmosphere through decomposition of water vapor.