ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-7-6737-2007 Cirrus clouds in convective outflow during the HIBISCUS campaign Fierli F. 1 Di Donfrancesco G. 2 Cairo F. 1 Zampieri M. 1 3 Orlandi E. 1 Istituto di Scienze dell'Atmosfera e del Clima, CNR, Italy Ente Nazionale Energia e Ambiente, Dipartimento Clima, Italy Laboratoire de Meteorologie Dynamique, Ecole Normale Superieure, France 16 05 2007 7 3 6737 6765 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys-discuss.net/7/6737/2007/acpd-7-6737-2007.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/7/6737/2007/acpd-7-6737-2007.pdf

Light-weight microlidar measurements were taken on-board a stratospheric balloon during the HIBISCUS 2004 campaign, held in Bauru, Brazil (22 S, 49 W). Tropical cirrus observations showed high mesoscale variability in optical and microphysical properties. The cirrus clouds were observed throughout the flight between 12 and 15 km height. It was found that the clouds were composed of different layers, characterized by a marked variability in height, thickness and optical properties. Trajectory analysis and mesoscale transport simulations clearly revealed that the clouds had formed in the outflow of a large and persistent convective region, while the observed optical properties and cloud structure variability could be linked to different residence times of convective-processed air in the upper troposphere. Mesoscale simulations were able to reproduce the supersaturation due to recent outflow, while it was necessary to consider the presence of other formation processes than convective hydration for cirrus forming in aged detrained anvils.

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