Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 14, 13223-13240, 2014
https://doi.org/10.5194/acp-14-13223-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
11 Dec 2014
Tropical deep convective life cycle: Cb-anvil cloud microphysics from high-altitude aircraft observations
W. Frey1,2, S. Borrmann1,3, F. Fierli4, R. Weigel3, V. Mitev5, R. Matthey6, F. Ravegnani7, N. M. Sitnikov8, A. Ulanovsky8, and F. Cairo4 1Max Planck Institute for Chemistry, Mainz, Germany
2School of Earth Sciences and ARC Centre of Excellence for Climate System Science, University of Melbourne, Melbourne, Australia
3Institute for Atmospheric Physics, Johannes Gutenberg University, Mainz, Germany
4Institute of Atmospheric Sciences and Climate, ISAC-CNR, Rome, Italy
5Swiss Centre for Electronics and Microtechnology, Neuchâtel, Switzerland
6Laboratoire Temps-Fréquence, Institute de Physique, Université de Neuchâtel, Neuchâtel, Switzerland
7Institute of Atmospheric Sciences and Climate, ISAC-CNR, Bologna, Italy
8Central Aerological Observatory, Dolgoprudny, Moscow Region, Russia
Abstract. The case study presented here focuses on the life cycle of clouds in the anvil region of a tropical deep convective system. During the SCOUT-O3 campaign from Darwin, Northern Australia, the Hector storm system has been probed by the Geophysica high-altitude aircraft. Clouds were observed by in situ particle probes, a backscatter sonde, and a miniature lidar. Additionally, aerosol number concentrations have been measured. On 30 November 2005 a double flight took place and Hector was probed throughout its life cycle in its developing, mature, and dissipating stage. The two flights were four hours apart and focused on the anvil region of Hector in altitudes between 10.5 and 18.8 km (i.e. above 350 K potential temperature). Trajectory calculations, satellite imagery, and ozone measurements have been used to ensure that the same cloud air masses have been probed in both flights.

The size distributions derived from the measurements show a change not only with increasing altitude but also with the evolution of Hector. Clearly different cloud to aerosol particle ratios as well as varying ice crystal morphology have been found for the different development stages of Hector, indicating different freezing mechanisms. The development phase exhibits the smallest ice particles (up to 300 μm) with a rather uniform morphology. This is indicative for rapid glaciation during Hector's development. Sizes of ice crystals are largest in the mature stage (larger than 1.6 mm) and even exceed those of some continental tropical deep convective clouds, also in their number concentrations. The backscatter properties and particle images show a change in ice crystal shape from the developing phase to rimed and aggregated particles in the mature and dissipating stages; the specific shape of particles in the developing phase cannot be distinguished from the measurements. Although optically thin, the clouds in the dissipating stage have a large vertical extent (roughly 6 km) and persist for at least 6 h. Thus, the anvils of these high-reaching deep convective clouds have a high potential for affecting the tropical tropopause layer by modifying the humidity and radiative budget, as well as for providing favourable conditions for subvisible cirrus formation. The involved processes may also influence the amount of water vapour that ultimately reaches the stratosphere in the tropics.


Citation: Frey, W., Borrmann, S., Fierli, F., Weigel, R., Mitev, V., Matthey, R., Ravegnani, F., Sitnikov, N. M., Ulanovsky, A., and Cairo, F.: Tropical deep convective life cycle: Cb-anvil cloud microphysics from high-altitude aircraft observations, Atmos. Chem. Phys., 14, 13223-13240, https://doi.org/10.5194/acp-14-13223-2014, 2014.
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Short summary
This study presents in situ cloud microphysical observations obtained during a double flight in a Hector thunderstorm during the SCOUT-O3 campaign from Darwin, Northern Australia, in 2005. The measurements show a change of the micophysics with the storm's evolution. The clouds in the dissipating stage possess a high potential for affecting the humidity in the tropical tropopause layer.
This study presents in situ cloud microphysical observations obtained during a double flight in...
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