The Earth Clouds and Radiation Explorer (EarthCARE) is an important upcoming joint European-Japanese satellite mission scheduled for launch in 2014/2015. The mission payload consists of an advanced High Spectral Resolution Lidar (ATLID), a Doppler Cloud profiling Radar (CPR), a Multi-spectral cloud/aerosol imager (MSI) and a three-view Broad-Band Radiometer (BBR) for SW and LW Top-of-Atmosphere (TOA) flux measurements.

EarthCARE’s overarching mission objective is the improvement of “the understanding of cloud-aerosol-radiation interactions” so as to include them correctly and reliably in climate and numerical weather prediction models. Specifically, the scientific objectives are (not in order of priority):

• The observation of the vertical profiles of natural and anthropogenic aerosols on a global scale, their radiative properties and interaction with clouds.
• The observation of the vertical distributions of atmospheric liquid water and ice on a global scale, their transport by clouds and their radiative impact.
• The observation of cloud distribution (‘cloud overlap’), cloud-precipitation interactions and the characteristics of vertical motions within clouds, and
• The retrieval of profiles of atmospheric radiative heating and cooling through the combination of the retrieved aerosol and cloud properties

EarthCARE will meet these objectives by measuring simultaneously the vertical structure and horizontal distribution of cloud and aerosol fields together with outgoing radiation over all climate zones. For further information see EarthCARE.

KNMI has long been involved in supporting the development of this mission. KNMI has been instrumental in developing the EarthCARE Simulator (ECSIM). ECSIM is an example of an “end-to-end” simulation environment. That is, ECSIM starts with an input atmospheric ``scene’’, uses various radiative transfer and instrument models in order to generate synthetic observations which then can be inverted. The results of the inversions may then be compared to the input “truth”. ECSIM development has focused on fidelity and consistency between the various scientific aspects of the simulation process. In particular, instrument specific parameterizations have been avoided and instead the atmospheric inputs scenes have been defined in a “low-level” fashion so that they contain all the information necessary in order to drive a wide range of forward models. ECSIM is mainly being used as an algorithm development platform for EarthCARE. However, it is also useful for general radiative transfer studies and has even been adapted for the simulation of ground-based observations.

Since 2008 the focus of the EarthCARE related work at KNMI has been on the development of the ATLID lidar retrieval chain and the synergetic Lidar+Radar target classification product (ESA-CASPER & ESA-ATLAS projects) . Within these developments the ECSIM environment has proven to be essential for the development and testing of the retrieval algorithms. As part of this work, it was deemed essential to create a number of realistic model scenes, which show realistic extinction distributions, optical radiative properties and particle size distributions. These realistic model scenes were developed based on actual high spectral resolution lidar measurements and in-situ particle size measurements. This work has been conducted as part of the (ESA-ICAROHS project).