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Atmos. Chem. Phys. Discuss., 12, 29443-29474, 2012
www.atmos-chem-phys-discuss.net/12/29443/2012/ doi:10.5194/acpd-12-29443-2012 © Author(s) 2012. This work is distributed under the Creative Commons Attribution 3.0 License. |
Ice water content of arctic, midlatitude, and tropical cirrus – Part 2: Extension of the database and new statistical analysis
1University of Colorado, Laboratory for Atmospheric and Space Physics, Boulder, Colorado, USA
2Forschungszentrum Jülich, Institut für Energie und Klimaforschung 7, Jülich, Germany
†deceased, 3 March 2012
Abstract. Ice clouds are known to be major contributors to radiative forcing in the Earth's atmosphere, yet describing their microphysical properties in climate models remains challenging. Among these properties, the ice water content (IWC) of cirrus clouds is of particular interest both because it is measurable and because it can be directly related to a number of other radiatively important variables such as extinction and effective radius. This study expands upon the work of Schiller et al. (2008), extending a climatology of IWC by combining datasets from several European and US airborne campaigns and ground-based lidar measurements over Jülich, Germany. The relationship between IWC and temperature is further investigated using the new merged dataset and probability distribution functions (PDFs). A PDF-based formulation allows for representation of not only the mean values of IWC, but also the variability of IWC within a temperature band. The IWC-PDFs are found to be bimodal over the whole cirrus temperature range, which might be attributed to different cirrus formation mechanisms such as heterogeneous and homogeneous freezing. The PDFs of IWC are further compared to distributions of cirrus ice crystal number and mass mean radius, which show that the general relationship between IWC and temperature appears to be influenced much more by particle number than by particle size.
Citation: Luebke, A. E., Avallone, L. M., Schiller, C., Rolf, C., and Krämer, M.: Ice water content of arctic, midlatitude, and tropical cirrus – Part 2: Extension of the database and new statistical analysis, Atmos. Chem. Phys. Discuss., 12, 29443-29474, doi:10.5194/acpd-12-29443-2012, 2012.