Evaluation of Ice cloud retrievals using CloudSat/CALIPSO/MODIS/AIRS and EarthCARE
Abstract:We analyzed characterization of ice water content and ice water path and discussed the uncertainties of these quantities. We developed the retrieval algorithms that use CloudSat and CALIOP on CALIPSO and also the one for CloudSat, CALIOP and MODIS on Aqua. There are several possible sources of uncertainties in the retrieved values. The backscattering properties of ice particles have not been yet fully understood in lidar wavelengths. There are also uncertainties in the retrieval results in radar- or lidar-only detected cloud regions where only one of the two sensors detected clouds. Multiple scattering contribution in space-borne lidar observations has not been fully evaluated too.
In order to assess and reduce these uncertainties, we introduced two approaches. Analyses of independent physical quantities based on the same physical ice particle models used in the retrievals of microphysics might be useful in order to test consistency in the ice particle model and its scattering properties. Second approach is to develop a new type of ground-based active sensor system. Concerning the first approach, backscattering color ratio of ice particles was derived from the backscattering coefficient at 532nm and 1064nm for periods before and after the change of the laser tilt angle from 0.3 degrees off nadir to 3 degrees off nadir. Then we examined relationships between the retrieved color ratio and the retrieved microphysics and found the relations agreed with the theoretically estimated ones.For the second approach, Multi-Field of view Multiple Scattering Polarization Lidar has been developed to resolve the angular dependence of backscattering and depolarization ratio and has been employed to evaluate the uncertainties in the retrievals. We performed global evaluation of ice microphysical properties and examined relationships between ice microphysics and ice super saturation information from AIRS on Aqua.
Finally we introduced the JAXA-ESA satellite mission EarthCARE that will be launched in 2016. There are four sensors on the EarthCARE, i.e., Doppler cloud profiling radar (CPR), high spectral resolution lidar at 355nm (ATLID), multi-spectral imager (MSI) and broad band radiometer (BBR). We discussed the possible improvements in the ice cloud retrievals.