Microphysical properties of cirrus clouds as derived from CloudSat/CALIPSO

Through their interaction with solar and thermal radiation, ice clouds are important in determining atmospheric and surface heating rates. To derive microphysical properties of ice clouds, we adapted a combined radar and lidar approach for ground-based measurements, developed at the KNMI, to data from CloudSat and CALIPSO. To validate the KNMI Lidar/Radar algorithm we performed an error assessment/sensitivity study using synthetic test cases generated by the Earth Care Simulator (ECSIM), based on in-situ measurements from the EUCREX campaigne. The aim of this study is to develop an ice cloud effective size parameterization suitable for application in climate and forecast models. An earlier study, using ground-based lidar and radar measurements, showed limitations of a global description of the particle size (Reff) as a function of temperature (T) and ice water content (IWC) and showed a possible solution to globally describe Reff as a function of depth into cloud Reff(ΔZ/H).
Using the CloudSat and CALIPSO data the retrieved microphysical properties of ice clouds at high-, mid- and low-latitudes have been analysed. The effective particle size and ice water content were derived and correlated to temperature and depth into the cloud from cloud top (ΔZt). It is shown that the relation of Reff to ΔZt, for different classes of total cloud thicknesses (H), allows for a single parameterization valid in all three latitude regimes.
The resulting ice cloud effective size parameterization is therefore valid on a global scale and thus applicable in global models.