Mesoscale Temperature Fluctuations and Polar Stratospheric Clouds

Abstract

Remote sensing measurements of temperature fluctuations on isentropic surfaces, as well as in situ measurements, are used to show that even high-resolution trajectory calculations seriously underestimate the rate of change of temperature experienced by air parcels. Rapid temperature fluctuations will affect the nucleation of polar stratospheric cloud (PSC) droplets and could promote the formation of metastable phases in PSCS. Mesoscale temperature fluctuations are large enough to produce significant departures from equilibrium in established PSCS. The large cooling rates experienced by air parcels have important implications for denitrification and dehydration: nearly all condensation nuclei should be activated when a PSC is first formed and mass must be redistributed to larger aerosols during the evolution of a PSC if denitrification is to occur.