How lessons learned during previous validation campaigns are guiding our airborne validation of EarthCARE

Radar and lidar are valuable active remote sensing techniques to assess global ice cloud properties from space. Recent global climate model studies are increasingly relying on ice cloud products obtained from the synergy of the radar and lidar satellites in the A-Train constellation. For the first time, the upcomingESA/JAXA satellite mission EarthCARE will acquire radar-lidar measurements from a single platform, ensuring the continuity of vertical resolved ice cloud products on a global scale. Due to additional and higher resolved measurements and a more comprehensive retrieval framework, a seamless transition from A-Train products cannot be taken for granted. In this light and with the imminent launch of EarthCARE, it is now crucial to establish a validation strategy for the EarthCARE products using airborne measurements.During the A-Train era, we learned numerous lessons and gained experience with coordinated aircraft and satellite underpasses which we performed during several airborne campaigns. During these exercises, the German research aircraft HALO was equipped with a EarthCARE-like payload consisting of a high spectral resolution lidar (HSRL) system at 532 nm, a high-power cloud radar at 35 GHz, a microwave radiometer package, and passive radiation measurements. Coordinated flights were performed with other airborne platforms carrying instruments at different wavelengths (DLR Falcon, Safire Falcon and ATR) or for validation with in-situ measurements (FAAM BAe-146) as well as below the A-Train satellite tracks.In this presentation, we will give an overview of our lessons learned and how they are guiding our airborne validation strategy. Going along with the commissioning of EarthCARE, we will employ HALO with its remote sensing payload in the PERCUSION campaign later this year. Based from multiple locations in the tropical Atlantic (Cape Verde and Barbados) and Europe (Oberpfaffenhofen), underflights of EarthCARE will be performed. The comparison with the dataset acquired during A-Train underpasses will allow us to determine if derived cloud products can be directly compared or if conversions are necessary. By sharing our knowledge and plans with the wider community, we hope to foster helpful discussions to consolidate our airborne validation strategy for EarthCARE.