Impact of Increased GNSS Radio Occultation Data Coverage on Tropical Cyclogenesis Prediction

Abstract. This study investigates the impact of increased global navigation satellite system (GNSS) radio occultation (RO) data coverage on the prediction of tropical cyclogenesis in the North Atlantic Ocean. RO data from the Radio Occultation Modelling Experiment (ROMEX) are used to construct three datasets with varying numbers of profiles and spatiotemporal coverage. The impacts of these datasets on the genesis forecasts for six selected tropical cyclones during the 2022 Atlantic hurricane season are assessed. Results show that assimilating RO datasets with higher horizontal data density and more homogeneous spatiotemporal distribution leads to improved detection of tropical cyclogenesis. Additional model diagnosis shows that the improved prediction of cyclogenesis is associated with increased specific humidity and relative vorticity, which support stronger upward motion and create a more favourable environment for tropical cyclone development. It is noted that despite the increased RO observation and data coverage, genesis was not predicted for Hurricane Lisa and Hurricane Ian. Further analysis shows that increasing the number of RO profiles and having the data more evenly distributed help improve the pre-genesis environment, with increased specific humidity and relative vorticity. These findings offer guidance for the design of future satellite observing systems: (1) increased RO profile density, beyond what is currently available operationally, is crucial for improving the representation of the pre-genesis environment, especially in data-sparse regions like the tropical North Atlantic Ocean, and (2) homogeneous data distribution minimizes data gaps and improves the accuracy of the observed atmospheric state, by minimizing the sampling errors.