Isentropic advection and convective lifting of water vapor in the UT – LS as observed over Brazil (22° S) in February 2004 by in situ high-resolution measurements of H₂O, CH₄, O₃ and temperature

Abstract. The micro-SDLA balloonborne diode laser spectrometer was flown twice from Bauru (22° S, Brazil) in February 2004 during HIBISCUS to yield in situ H₂O measurements in the Upper Troposphere (UT) and Lower Stratosphere (LS) and in particular in the Tropical Tropopause Layer (TTL). The overall TTL was found warmer (with a subsaturated cold point near –79°C) and the LS moister compared to former measurements obtained in tropical oceanic conditions. The use of specific balloons with a slow descent, combined with the high-resolution of the laser sensor, allowed us to observe in situ in the UT, the TTL and the LS several thin layers correlated on H₂O, CH₄, O₃, temperature and PV. A component of these layers is associated with the isentropic transport into the UT- LS of extratropical stratospheric air masses. Moreover, the examination of temperature and tracer (CH₄, O₃) profiles gives insights on the potential contribution of convective transport of H₂O in the TTL.