Long-lived contrails and convective cirrus above the tropical tropopause

Year: 2017

Authors: Schumann U., Kiemle C., Schlager H., Weigel R., Borrmann S., D’Amato F., Kramer M., Matthey R., Protat A., Voigt C., Volk CM.

Autors Affiliation: Inst Phys Atmosphere, Deutsch Zentrum Luft & Raumfahrt, D-82234 Oberpfaffenhofen, Germany; Johannes Gutenberg Univ Mainz, Inst Atmospher Phys, Mainz, Germany; Max Planck Inst Chem, Mainz, Germany; Ist Nazl Ottica, CNR, Florence, Italy; Forschungszentrum Julich, Inst Energie & Klimaforschung IEK 7, Julich, Germany; Univ Neuchatel, Lab Temps Frequence, Neuchatel, Switzerland; Australian Bur Meteorol, Res & Dev Branch, Melbourne, Vic, Australia; Univ Wuppertal, Dept Phys, Wuppertal, Germany.

Abstract: This study has two objectives: (1) it characterizes contrails at very low temperatures and (2) it discusses convective cirrus in which the contrails occurred. (1) Long-lived contrails and cirrus from overshooting convection are investigated above the tropical tropopause at low temperatures down to -88 degrees C from measurements with the Russian high-altitude research aircraft M-55 “Geophysica”, as well as related observations during the SCOUT-O3 field experiment near Darwin, Australia, in 2005. A contrail was observed to persist below ice saturation at low temperatures and low turbulence in the stratosphere for nearly 1 h. The contrail occurred downwind of the decaying convective system “Hector” of 16 November 2005. The upper part of the contrail formed at 19 km altitude in the tropical lower stratosphere at similar to 60% relative humidity over ice at -82 degrees C. The similar to 1 h lifetime is explained by engine water emissions, slightly enhanced humidity from Hector, low temperature, low turbulence, and possibly nitric acid hydrate formation. The long persistence suggests large contrail coverage in case of a potential future increase of air traffic in the lower stratosphere. (2) Cirrus observed above the strongly convective Hector cloud on 30 November 2005 was previously interpreted as cirrus from overshooting convection. Here we show that parts of the cirrus were caused by contrails or are mixtures of convective and contrail cirrus. The in situ data together with data from an upward-looking lidar on the German research aircraft “Falcon”, the CPOL radar near Darwin, and NOAA-AVHRR satellites provide a sufficiently complete picture to distinguish between contrail and convective cirrus parts. Plume positions are estimated based on measured or analyzed wind and parameterized wake vortex descent. Most of the non-volatile aerosol measured over Hector is traceable to aircraft emissions. Exhaust emission indices are derived from a self-match experiment of the Geophysica in the polar stratosphere in 2010. The number of ice particles in the contrails is less than 1% of the number of non-volatile aerosol particles, possibly because of sublimation losses and undetected very small ice particles. The radar data show that the ice water content in convective overshoots is far higher than measured along the flight path. These findings add insight into overshooting convection and are of relevance with respect to hydration of the lower stratosphere.

Journal/Review: ATMOSPHERIC CHEMISTRY AND PHYSICS

Volume: 17 (3)      Pages from: 2311  to: 2346

More Information: The authors thank all colleagues, who were engaged in the field experiments resulting in the data analyzed here. We thank all principal investigators of the aircraft instruments for permission to use their data. The SCOUT-O3, RECONCILE, and TROCCINOX projects were funded by the European Commission under grants GOCE-CT-2004-505390, RECONCILE-226365-FP7-ENV-2008-1, and EVK2-CT-2001-00122, respectively. H. Schlager and R. Weigel received funding by the German BMBF within the joint ROMIC-project SPITFIRE (01LG1205A). Additional data and information were provided by Winfried Beer, Marius Bickel, Dominik Brunner, Luca Bugliaro, Ann Mari Fjaeraa, Kaspar Graf, Andy Heymsfield, Peter Hoor, Mareike Kenntner, Boon H. Lim, Peter May, Ralf Meerkotter, Valentin Mitev, Thomas Peter, Markus Rex, Michel Rossi, Anja Schubert, Nikolay Sitnikov, Silvia Viciani, Vasily Volkov, Martin Wirth, and Vladimir Yushkov, and are gratefully acknowledged. Moreover, we thank several further colleagues for valuable comments. In particular, we thank Charmaine Franklin and Heidi Huntrieser for valuable comments on the manuscript. We deeply regret that we can no longer discuss this research with Michael J. Mahoney, Cornelius Schiller, and Genrikh Shur, who have passed away in recent years.
KeyWords: Aerosol; AVHRR; Cirrus; Contrail; Convective cloud; Convective system; Hydration; Low temperature; NOAA satellite; Relative humidity; Stratosphere; Tropical meteorology; Tropopause, Australia; Darwin; Northern Territory, Falconidae
DOI: 10.5194/acp-17-2311-2017

Citations: 6
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