The importance of ice clouds on the Earth's radiation budget is well recognized. However due to uncertainties in their properties (i.e. optical thickness, particle effective size [Reff]), they are not well treated in climate and forecasting models. Using combined lidar and radar measurements ice cloud effective particle size profiles can be estimated [Donovan and Van Lammeren, 2001].

In this work, results from combined lidar and radar ground-based observations made at three sites (the Cabauw (Netherlands), Chilbolton (UK) and the ARM-SGP (USA) site) are presented. The European sites used in this work were part of the EU-5 CLOUDNET program [http://www.met.rdg.ac.uk/radar/cloudnet/]. Profiles of ice cloud effective particle size, extinction and ice water content (IWC) for a long time series at each site have been derived. The lidar/radar results have formed a basis for a new ice cloud effective particle size parameterization based on the cloud physical thickness. This parameterization has been tested using surface radiation measurements compared with radiative transfer calculations employing the new parameterization. Further the impact of the new parameteization in a regional climate model has been investigated.

In this paper we will briefly outline the lidar/radar method used in the study as well as discuss the new parameterization and its evaluation.

References

Donovan D.P., and van Lammeren, 2001, J. Geophys. Res., 106, 27425

Mc Farquhar, G.M., et al., 2003, J. of Climate ., 16, 1643

van Zadelhoff, G.-J., et al., 2004, J. Geophys. Res., 109, D24214