Title Evidence for ice particles in the tropical stratosphere from in-situ measurements
Author de Reus, M.; Borrmann, S.; Bansemer, A.; Heymsfield, A.J.; Weigel, R.; Schiller, C.; Mitev, V.; Frey, W.; Kunkel, D.; Kürten, A.; Curtius, J.; Sitnikov, N.M.; Ulanovsky, A.; Ravegnani, F.
Author Affil de Reus, M., Max Planck Institute for Chemistry, Particle Chemistry Department, Mainz, Germany. Other: Mainz University, Germany; National Center for Atmospheric Research; Research Centre Jülich, Germany; Swiss Centre for Electronics and Microtechnology, Switzerland; Goethe University of Frankfurt, Germany; Central Aerological Observatory, Russian Federation; CNR Institute of Atmospheric Sciences and Climate, Italy
Source Atmospheric Chemistry and Physics, 9(18), p.6775-6792, . Publisher: Copernicus, Katlenburg-Lindau, International. ISSN: 1680- 7316
Publication Date 2009
Notes In English. Part of special issue no. 124, SCOUT-O3 Tropics, edited by Brunner, D. et al., http://www.atmos-chem- phys.net/special_issue124.html; published in Atmospheric Chemistry and Physics Discussions: 14 November 2008, http://www.atmos-chem-phys- discuss.net/8/19313/2008/acpd-8-19313- 2008.html ; accessed in May, 2011. 60 refs. GeoRef Acc. No: 310157
Index Terms aerosols; clouds (meteorology); condensation; crystals; density (mass/volume); evaporation; ice; ice crystals; measurement; particles; pressure; remote sensing; solar radiation; stratosphere; temperature; microelement content; water vapor; vapor pressure; chemical reactions; Cloud Imaging Probe; clouds; density; Forward Scattering Spectrometer Probe; in situ; size; trace elements; tropical environment; troposphere
Abstract In-situ ice crystal size distribution measurements are presented within the tropical troposphere and lower stratosphere. The measurements were performed using a combination of a Forward Scattering Spectrometer Probe (FSSP-100) and a Cloud Imaging Probe (CIP), which were installed on the Russian high altitude research aircraft M55 "Geophysica" during the SCOUT-O3 campaign in Darwin, Australia. One of the objectives of the campaign was to characterise the Hector convective system, which appears on an almost daily basis during the pre-monsoon season over the Tiwi Islands, north of Darwin. In total 90 encounters with ice clouds, between 10 and 19 km altitude were selected from the dataset and were analysed. Six of these encounters were observed in the lower stratosphere, up to 1.4 km above the local tropopause. Concurrent lidar measurements on board "Geophysica" indicate that these ice clouds were a result of overshooting convection. Large ice crystals, with a maximum dimension up to 400 µm, were observed in the stratosphere. The stratospheric ice clouds included an ice water content ranging from 7.7×10-5 to 8.5×10- 4 g m-3 and were observed at ambient relative humidities (with respect to ice) between 75 and 157%. Three modal lognormal size distributions were fitted to the average size distributions for different potential temperature intervals, showing that the shape of the size distribution of the stratospheric ice clouds are similar to those observed in the upper troposphere. In the tropical troposphere the effective radius of the ice cloud particles decreases from 100 µm at about 10 km altitude, to 3 µm at the tropopause, while the ice water content decreases from 0.04 to 10-5 g m-3. No clear trend in the number concentration was observed with altitude, due to the thin and inhomogeneous characteristics of the observed cirrus clouds. The ice water content calculated from the observed ice crystal size distribution is compared to the ice water content derived from two hygrometer instruments. This independent measurement of the ice water content agrees within the combined uncertainty of the instruments for ice water contents exceeding 3×10-4g m-3. Stratospheric residence times, calculated based on gravitational settling, and evaporation rates show that the ice crystals observed in the stratosphere over the Hector storm system had a high potential of humidifying the stratosphere locally. Utilizing total aerosol number concentration measurements from a four channel condensation particle counter during two separate campaigns, it can be shown that the fraction of ice particles to the number of aerosol particles remaining ranges from 1:300 to 1:30 000 for tropical upper tropospheric ice clouds with ambient temperatures below - 75°C.
URL http://www.atmos-chem-phys.net/9/6775/2009/acp-9-6775-2009.pdf
Publication Type journal article
Record ID 65006696