Introduction to Cloud and Aerosol Products from EarthCARE's Imager focusing on the Synergy with the Atmospheric Lidar
Hünerbein, Anja1; Wandinger, Ulla1; von Hoyningen-Huene, Wolfgang2
1Leibniz-Institute for Tropospheric Research, GERMANY; 2Institute of Enviromental Physics, University of Bremen, GERMANY
The ESA's cloud and aerosol mission EarthCARE is the first satellite mission, which will provide measurements from active sounder and passive imager from one platform. The active backscatter lidar (ATLID) will provide vertical profiles of cloud and aerosol parameters with high spatial resolution. The lidar instrument measures in nadir view, while the passive multi-spectral imager (MSI) has a swath of 150km and a pixel size of 500m. The MSI observations will provide the information needed for describing the cloud and aerosol properties in the cross-track direction. Different MSI cloud and aerosol algorithms have been developed to derive cloud microphysical and macrophysical properties as well as aerosol optical thickness. The chain of the MSI retrieved cloud and aerosol products: cloud mask, cloud phase, cloud/aerosol optical thickness, cloud effective radius and cloud top height has been tested with MODIS data and synthetic MSI observations generated with the EarthCARE Simulator (ECSIM). The next step will be to combine active and passive measurements to derive a synergetic cloud product, e.g. the cloud top height. The cloud top height from ATLID have high accuracy compared to the cloud top height retrieval from the MSI, especially high level cirrus and mid-level altocumulus which typically stretch over hundreds of square kilometers. To develop a combined retrieval which use the cloud top height information from ATLID at the track and MSI over the entire swath we have used MODIS and Calipso observations as a test bed. MODIS provides observations similar to MSI. From the CALIOP lidar onboard CALIPSO the 1064-nm elastic backscatter signal is valid as a substitute for the ATLID 355-nm co-polar Mie signal. The 1064-nm signal has a negligible Rayleigh contribution and thus a similar shape in the presence of clouds as the Rayleigh-free filtered ATLID 355-nm co-polar Mie signal. Several orbits have been analyzed to obtain a correction function for the MSI cloud top height at the across track for different scenes. Further the synergistic use of ATLID and MSI to identify aerosol types has been studied based on the information of the retrieved spectral aerosol optical thickness, which consists of measurements at 355 nm (ATLID), 670 nm (MSI) and 865 nm (MSI, only ocean).