Peering Inside Tropical Cyclones With the WIVERN Space-Borne Doppler Radar

The WIVERN (Wind Velocity Radar Nephoscope) mission significantly enhances the global tropical cyclone observing system. Operating from a 500 km near-polar orbit, the 3 m diameter conically scanning antenna provides an 800 km swath. The radar operated at 94 GHz (3 mm wavelength) provides high-resolution observations with a vertical resolution of 600 m and horizontal resolution finer than 1 km. With quasi-daily global coverage, WIVERN measures in-cloud tropical cyclone winds from 1 km above the surface to the upper troposphere. Simulations of the Weather Research and Forecasting model with 1.5 km grid spacing were carried out for Hurricane Milton (2024) to serve as a testbed to demonstrate the potential capabilities of the WIVERN mission and its associated data products. The high-resolution simulation successfully reproduces the hurricane's trajectory and intensification, capturing a remarkable 78-knot increase in maximum sustained wind speed during the 24-hr period from 7 October to 8 October. End-to-end simulations demonstrate that WIVERN: (a) can provide a three-dimensional view of the horizontal wind inside cyclones, in particular capturing the vertical wind shear, the upper level divergence and the in-cloud circulations inside the anvil produced by the hurricane convective towers, and some of the inflow and outflows in the lower layers of the atmosphere; (b) in presence of close-in-time overpasses, has the potential to detect the intensification of cyclone by estimating the maximum winds in the inner core; (c) can profile the tropical cyclone ice mass as a function of the distance from the eye, which will help shed light on the anvil formation and dissipation mechanisms.