ACPV-ESA-NOA-Best practice protocol for validation of Aerosol, Cloud, and Precipitation Profiles

The EarthCARE mission, implemented in cooperation with JAXA, will be the largest and most complex ESA Earth Explorer mission built to date. The satellite is expected to be ready for launch at the end of 2023 and will carry four payloads consisting of two active sensors, i.e. Atmospheric LIDar (ATLID) and Cloud Profiling Radar (CPR) and two passive instruments, i.e. Multi Spectral Imager (MSI) and Broad Band Radiometer (BBR). The mission will provide synergistic observations and unprecedented insight into aerosol, cloud, and precipitation vertical profiles, as well as radiative properties of the atmosphere. The validation of the numerous and complex synergistic products and retrieval in turn becomes a challenging and daunting task. The ESA EarthCARE Validation Team (ECVT) was established  and two such workshops were held in 2018 and 2021. The 2nd workshop included contributions from other similar (current and future) missions underlined the importance of EarthCARE as a bridge between those missions, potentially ensuring satellite data record continuity which is critical for the scientific community. The need for common guidelines on validation practices was highlighted through  clear demand for common or best practices for the validation of cloud and aerosol profiles.
One specific application of such practices is the recommended procedure to transform suborbital measurements to space-based observations, which is required to perform any meaningful intercomparisons between the measured signals applicable to the lidar, radar, and the imager observations.
The proposed activity is intended to address the need for validation common practices. There are several building blocks identified to be a valuable source of input to this activity, e.g. ongoing studies and activities under ESA. Moreover, ESA's initial effort towards convergence on common practices has managed to engage numerous scientific and validation experts in charting the way forward. These experts, collectively referred to as the Implementation Monitoring Group (IMG), together with the scientists involved in the aforementioned ESA contracts, can contribute, advise, and help review the progress of the best practice activity.
The present ESA project is contributing to the broader effort involving NASA and in the near future also JAXA and EUMETSAT. The CEOS Working Group on Calibration andValidation monitors progress of this work (CV-22-01) and the resulting document will be submitted to the CEOS-WGCV for endorsement as CEOS best practice.