Variability of cirrus clouds in a convective outflow during the Hibiscus campaign F. Fierli1, G. Di Donfrancesco2, F. Cairo1, V. Marécal3, M. Zampieri1, E. Orlandi1, and G. Durry4,5 1Istituto di Scienze dell'Atmosfera e del Clima, CNR, Italy 2Ente Nazionale Energia e Ambiente, Dipartimento Clima, Italy 3Laboratoire de Physique et Chimie de l'Environnement, CNRS and Université d'Orléans, France 4Groupe de Spectroscopie Moléculaire et Atmosphérique, CNRS and Université de Reims, France 5Service d'Aéronomie, CNRS and Institut Pierre et Simon Laplace, France
Abstract. Light-weight microlidar and water vapour measurements were taken on-board a
stratospheric balloon during the HIBISCUS 2004 campaign, held in Bauru,
Brazil (49° W, 22° S). Cirrus clouds were observed throughout
the flight between 12 and 15 km height with a high mesoscale variability in
optical and microphysical properties. It was found that the cirrus clouds
were composed of different layers characterized by marked differences in
height, thickness and optical properties. Simultaneous water vapour
observations show that the different layers are characterized by different
values of the saturation with respect to ice. A mesoscale simulation and a
trajectory analysis clearly revealed that the clouds had formed in the
outflow of a large and persistent convective region and that the observed
variability of the optical properties and of the cloud structure is likely
linked to the different residence times of the convectively-processed air in
the upper troposphere.
Citation: Fierli, F., Di Donfrancesco, G., Cairo, F., Marécal, V., Zampieri, M., Orlandi, E., and Durry, G.: Variability of cirrus clouds in a convective outflow during the Hibiscus campaign, Atmos. Chem. Phys., 8, 4547-4558, doi:10.5194/acp-8-4547-2008, 2008.