Lecturer: Prof. Stephan Borrmann (Mainz)
Date: 2010-01-28 10:30
Place: Aniara

The tropical transition layer as phenomenon of global importance: Observations of aerosols and clouds

Stephan Borrmann

- Institute for Physics of the Atmosphere, University of Mainz, 55099 Mainz, Germany
- Particle Chemistry Department, Max-Planck-Institute for Chemistry, Mainz, Germany

The Tropical Transition Layer (TTL) is located (roughly) between the level of neutral buoyancy in the tropics and a level somewhat above the thermal tropopause. This layer has certain peculiarities which are of relevance for the global upper troposphere and lower stratosphere (UT/LS).

Between January 2005 and August 2006 in-situ measurements were performed
within the SCOUT-O3 and the AMMA-SCOUT framework in the tropical and mid-latitude UT/LS utilizing the Russian high altitude research aircraft M-55 "Geophysica" which is capable of reaching 21 km altitude. Results of ultrafine particle measurements with the COndensation PArticle measurement System (COPAS) including relevant data from other in-situ instruments- are discussed in this contribution from the TROCCINOX (2005, Aracatuba, Brazil), SCOUT-O3 (2005, Darwin, Australia) and AMMA-SCOUT (2006, Burkina Faso, West Africa) campaigns. These results are put into the context of recent WB-57 measurements from Costa Rica as well as tropical ER-2 data back until 1996.
The discussed measurements cover nucleation events in the tropical upper troposphere as well as background aerosol data from the Geophysica transfer flights to the various tropical locations. As the long distance transfer flights to Brazil, Australia and West-Africa were executed during 17 months within a period of relative volcanic quiescence the data represent a "snapshot picture" documenting the status of the "global" UT/LS ultrafine aerosol 15 years after the major Mount Pinatubo eruption. The vertical profiles measured over West-Africa significantly differ from all other tropical profiles probably due to the small albeit high reaching eruption from the Soufriere Hills volcano (Montserrat). For specific AMMA (2006) and SCOUT-O3 (2005) Geophysica flights intercomparisons with balloon data are presented. Vertical profiles of ultrafine particle volatility have been measured in the tropical campaign locations from 300 K up to 500 K. The results are compared and discussed.
Finally, in-situ data from cirrus clouds (obtained from concurrent optical particle counter and cloud imaging probe measurements) over West African MCS systems and Cb overshoots in Australia are discussed as well as thin and subvisible cirrus cloud events.

The M-55 "Geophysika" currently operates for the RECONCILE campaign out of
Arena Arctica in Kiruna. A large suite of in-situ and remote sensing instruments is implemented on board for fully automated measurements of variables relevant (among others) to stratospheric dynamics and chemistry, microphysics of aerosols and clouds, trace substances, and meteorology.

Created 2009-12-07 14:02:58 by Mats Holmström
Last changed 2009-12-21 08:41:40 by Mats Holmström