Polar Mesospheric Cloud Detections by TROPOMI/Sentinel-5P: First Results and Validation

We present the first results of polar mesospheric cloud (PMC) detection using ultraviolet observations from TROPOMI (TROPOspheric Monitoring Instrument). An improved retrieval algorithm, developed on the basis of the SBUV-type approach and adapted to TROPOMI UV1 (270–300 nm) measurements, combines spatial binning, iterative Rayleigh background modeling, and adaptive thresholding to extract PMC signals from the background atmosphere. The robustness of the TROPOMI retrievals is evaluated through multi-scale comparisons with PMC data from the Cloud Imaging and Particle Size experiment (CIPS) and the Ozone Mapping and Profiler Suite Nadir Profiler (OMPS-NP). Compared with CIPS, the two datasets show broadly consistent hemispheric-scale horizontal structures and a westward wave-like phase progression consistent with possible quasi-5-day planetary-wave modulation, despite local-time differences. Compared with OMPS-NP, residual albedo under matched spatiotemporal conditions shows strong agreement for bright PMCs, whereas differences in spatial resolution lead to discrepancies in the detection of faint clouds. Seasonal-scale comparisons of PMC occurrence frequency also show consistent variability among the datasets. These results demonstrate that TROPOMI can resolve PMC structures smaller than 250 km that are difficult to detect with current low-resolution instruments. TROPOMI therefore provides a bridge between long-term coarse-resolution records and high-resolution observations, offering valuable data for studies of mesospheric dynamics and climate change.