A Multi-Instrument Best Estimate Retrieval of Clouds, Precipitation and Aerosol for EarthCARE.

The combined ESA-JAXA Earth Clouds, Aerosol and Radiation Explorer (EarthCARE) satellite aims to advance our understanding of cloud-precipitation-aerosol interactions and contribute to the improvement of their representation in numerical models. To achieve the EarthCARE objectives the satellite payload will include a cloud profiling radar with Doppler capability, a high-spectral-resolution lidar and a multispectral imager. A broadband radiometer also onboard will provide independent closure for global radiation fields computed using retrieved atmospheric profiles.

We have developed the algorithm "CAPTIVATE" that will provide the the operational EarthCARE level 2 product with realistic estimates of atmospheric vertical cross-sections for a wide range of cloud, aerosols and precipitation conditions. CAPTIVATE combines the observations from all three sensors onboard EarthCARE within a unified synergistic variational framework. The algorithm incorporates many novel features, such as explicit representation of radar and lidar multiple scattering, a new fast forward model for solar radiances, a Kalman smoother to provide robust aerosol retrievals even in the presence of noisy lidar measurements and an advanced diagnostics of retrieval confidence such as properties of the averaging kernel.

We will present a detailed evaluation of the algorithm's capability using a 6000-km swath of synthetic EarthCARE data simulated from 250-m resolution cloud-resolving model simulations. With this dataset we investigate the impact of the different observations on the retrieval of a variety of atmospheric profiles. We will also show, using the ECMWF forecast fields and A-Train data, the potential of such synergistic retrieval to evaluate global atmospheric models performance and to improve the representation of cloud, aerosol, precipitation and radiation.