Multi‐GNSS Airborne Radio Occultation Observations as a Complement to Dropsondes in Atmospheric River Reconnaissance

Abstract Variations in the water vapor that atmospheric rivers (ARs) carry toward North America within Pacific storms strongly modulates spatiotemporal distribution of west‐coast precipitation. The “AR Recon” program was established to improve forecasts landfalling Pacific‐coast ARs and their associated Dropsondes are deployed from weather reconnaissance aircraft pressure sensors have been added drifting ocean buoys fill a major gap standard observations, while research is being conducted on potential for airborne Global Navigation Satellite System (GNSS) radio occultation (ARO) also contribute forecast improvement. ARO further expands spatial coverage data collected during AR Recon flights. This study provides first description these data, which provide temperature information typically as far 300 km side aircraft. refractivity profiles European Galileo satellites provided accuracy evaluated using dropsondes. It shown variations anomaly (difference climatological background) modulated by features, including low‐level jet tropopause fold, illustrating RO measurements represent key characteristics. demonstrated assimilation can influence moisture used initial conditions high‐resolution model. While dropsonde precise, situ wind, vertical beneath aircraft, surface pressure, complementary thermodynamic aloft broad areas not otherwise sampled at no additional expendable cost.