TY - GEN AU - Sean Healy AU - Niels Bormann AU - Alan Geer AU - Elias Holm AU - Bruce Ingleby AU - Katie Lean AU - Katrin Lonitz AU - Cristina Lupu AB - We review the assessment of existing observations with Observing System Experiments (OSEs) and the Forecast Sensitivity to Observation Impact (FSOI) approach. Although care is needed when interpreting their results, the information they provide is largely consistent. The Ensemble of Data Assimilations (EDA) provides an affordable and manageable framework for simulating the impact of future observing systems. Recent experience comparing EDA predictions with the subsequent impact of real measurements gives us some confidence that, with appropriate interpretation and care, they provide useful information that can help guide the future evolution of the global observing system. BT - ECMWF Technical Memoranda CY - Reading DA - 04/2024 DO - 10.21957/2f240fe55f M1 - 916 N2 - We review the assessment of existing observations with Observing System Experiments (OSEs) and the Forecast Sensitivity to Observation Impact (FSOI) approach. Although care is needed when interpreting their results, the information they provide is largely consistent. The Ensemble of Data Assimilations (EDA) provides an affordable and manageable framework for simulating the impact of future observing systems. Recent experience comparing EDA predictions with the subsequent impact of real measurements gives us some confidence that, with appropriate interpretation and care, they provide useful information that can help guide the future evolution of the global observing system. PB - ECMWF PP - Reading PY - 2024 T2 - ECMWF Technical Memoranda TI - Methods for assessing the impact of current and future components of the global observing system UR -   ER -