Recent measurements of high supersaturations and thin cirrus in the tropical tropopasue layer (Invited Speaker)

Measurements from recent field campaings (including CRYSTAL-FACE, Pre-AVE, CR-AVE, and TC-4) have provided a wealth of information about supersaturation and thin cirrus in the tropical tropopause layer. This presentation will review measurements indicating large ice supersaturations (both within thin cirrus clouds and in clear air). The presence of large (~100 microns) ice crystals just below the tropopause seems to be consistent with the persistence of large ice supersaturations. These observations have important implications for our understanding of ice nucleation at low temperatures, as well as processes controlling the water vapor concentration in the stratosphere.