Spatially Inhomogeneous Cirrus: Influence on Atmospheric Radiation
Final Report Abstract
This project was based on the former SFB 641: TROPEIS „Die troposphärische Eisphase“. The instrumental payload of the towed platform AIRTOSS was successfully extended by new technical developments for radiation sensors and in situ cloud probes. The maximum altitude which can be reached by the tandem of Learjet 35A and the AIRTOSS tow-body was extended to levels where cirrus clouds occur in mid-latitudes. Collocated radiation measurements below and above could be applied even though for a geometrically thin (200 m) cirrus caused by restrictions of the cable lengths between AIRTOSS and aircraft. The technological experience gained from implementing the AIRTOSS-ICE project proved essential for instrumenting the German Gulfstream G550 HALO research aircraft within the DFG funded Priority Program SPP 1294. In situ microphysical measurements of ice crystal shape and number distribution were used for extensive sensitivity studies estimating the effect of cirrus microphysical properties on the cloud layer optical properties and radiative forcing. Radiative transfer simulations could not reproduce the measured radiation quantities accurately partly due to a broad range of possible ice crystal shapes and the effect of variable underlying clouds. It was shown that these underlying clouds affect cloud layer properties of the cirrus but even more significantly influence the radiative forcing of cirrus which is often neglected when estimating cloud radiative effects of high level clouds. In addition to studies of radiative flux variability possibly with extended cable lengths also experiments on small scale local variability of cloud microphysical properties can be conducted with the tandem. Operating the AIRTOSS towbody at different altitudes below the aircraft allows measurements of the spatial variability of ice particle sizes and shapes. This is important -even at distances close to the aircraft- in highly variable environments like lee wave cirrus cloud fields, cirrus undulatus, jet stream cirrus, cirrus uncinus (precipitating), and frontal cirrus. Also important studies of vertical redistribution of aerosols, cloud particles and water vapor can be performed with a suitably equipped tandem. The data sets obtained during the 2013 AIRTOSS-ICE field deployments are being used (and continue to be used in the future) for analyses in these directions. The Learjet 35A AIRTOSS tandem platform so far only was used in restricted military air space over the North Sea in order to minimize risks in case the AIRTOSS is lost. However, in the future, the tandem platform can very well be used over large uninhabited areas like the rain forests, the boreal forests, the polar ice fields, and remote ocean areas. Especially when flying over ice radiation measurements are strongly influenced by ground reflection while the signal from cirrus decks can be relatively weak. Here the differential measurements from a tandem platform are highly useful. Planet E.: Abenteuer Wolkenforschung, 23 November 2014 on ZDF (http://www.zdf.de/planet-e/projekt-racepacdeutsche-wissenschaftler-erforschen-die-rolle-der-wolken-beim-klimawandel-35926184.html)
Publications
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In situ detection of stratosphere-troposphere exchange of cirrus particles in the midlatitudes, Geophys. Res. Lett., 42
S. Müller, S., P. Hoor, F. Berkes, H. Bozem, M., Klingebiel, P., Reutter, H. G. J. Smit, M. Wendisch, P. Spichtinger, and S. Borrmann
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A microphysics guide to cirrus clouds: Part I cirrus types, Atmos. Chem. Phys, 16, 3463-3483
M. Krämer, C. Rolf, A. Luebke, A. Afchine, N. Spelten. A. Costa, J. Meyer, M. Zöger, J. Smith, R. L. Herman, B. Buchholz, V. Ebert, D. Baumgardner, M. Klingebiel, and L. Avallone
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Quality assessment of MOZAIC and IAGOS capacitive hygrometers: insights from airborne field studies, Tellus B 2015, 67, 28320, 2016
Neis, P., Smit, H.G.J., Rohs, S., Bundke, U., Krämer, M., Spelten, N., Ebert, V., Buchholz, B., Thomas, K., and Petzold, A.
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Spectral optical layer properties of cirrus from collocated airborne measurements and simulations, Atmos. Chem. Phys. 16, 7681-7693, 2016
F. Finger, F. Werner, M. Klingebiel, A. Ehrlich, E. Jäkel, M. Voigt, S. Borrmann, P. Spichtinger, and M. Wendisch
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Thermodynamic correction of particle concentrations measured by underwing probes on fast flying aircraft, Atmos. Meas. Tech., 9, 5135-5162
R. Weigel, P. Spichtinger, C. Mahnke, M. Klingebiel, A. Afchine, A. Petzold, M. Krämer, A. Costa, S. Molleker, P. Reutter, M. Szakàll, M. Port, L. Grulich, T. Jurkat, A. Minikin, and S. Borrmann
