Water vapour at the tropical tropopause - and above

Aircraft data of H2O from SCOUT-O3 (Darwin), TROCCINOX (Brazil), AMMA (West Africa) and APE-THESEO (Indian Ocean) will be analyzed and compared: Formation of ultrathin cirrus clouds and freeze-drying results in very low mixing ratios, sometimes below 2 ppm. On the other hand, we observed fresh and aged signatures of overshooting convection leading to a moistening of the TTL and lower stratosphere. And at the edge to the subtropics, mixing with moister air is evident. However, the seasonality of the head of the tape recorder close to the tropopause can clearly be identified within this puzzle. Higher up, i.e. above 420 K, the regional signals are averaged-out, features as the upward propagating tape recorder become visible.