Dear IROWG and ROMEX participants, I’m pleased to announce that the *Atmospheric Measurement Techniques (AMT)* special issue titled *“The Radio Occultation Modeling EXperiment (ROMEX): observational quality, processing, and numerical weather prediction (NWP) applications”* is now open for submissions. ROMEX <https://irowg.org/ro-modeling-experiment-romex/>, an IROWG-led initiative, aims to assess the impact of ~35,000 daily radio occultation (RO) profiles—collected from 13 missions during September–November 2022—on numerical weather prediction. This international campaign involves contributions from data providers, processing centers, and forecasting institutions across the global research and operational communities. The special issue welcomes papers using ROMEX data on topics including, but not limited to: - RO data quality and processing - Evaluation and validation of RO datasets - Impact studies in NWP and other atmospheric applications *Submission is open from 1 May 2025 to 31 December 2026* (extensions possible). Submit here: https://editor.copernicus.org/AMT/manuscript_registration Please ensure the correct special issue title is selected during submission. Editorial assignment follows a *first-come, first-served* policy. A full description of the special issue is available at: https://www.atmospheric-measurement-techniques.net/articles_and_preprints/sc... *(under 2025)* We look forward to your contributions! Hui Shao On behalf of ROMEX steering committee