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
08 Jul 2013
2Forschungszentrum Jülich, Institut für Energie und Klimaforschung 7, Jülich, Germany
†deceased 3 March 2012
Received: 31 Oct 2012 – Published in Atmos. Chem. Phys. Discuss.: 15 Nov 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 observed to be bimodal over the whole
cirrus temperature range. This bimodality is also found in ice crystal
number PDFs and might be attributed to different cirrus formation mechanisms
such as heterogeneous and homogeneous freezing.
Revised: 24 May 2013 – Accepted: 28 May 2013 – Published: 08 Jul 2013
Citation: Luebke, A. E., Avallone, L. M., Schiller, C., Meyer, J., 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., 13, 6447-6459, doi:10.5194/acp-13-6447-2013, 2013.