Assessment of Saildrone Wind Measurements in Tropical Cyclones using Microwave Satellite Sensors

In-situ measurements of extreme winds within hurricanes are challenging and scarce at the global level. They are mostly provided by risky reconnaissance flights, most often in the tropical North Atlantic. In 2021, a novel NOAA project deployed 5 Saildrones (SDs) to monitor the tropical Atlantic storm-track areas. One of these missions, SD-1045, crossed Hurricane Sam (Cat. 4) on September 30, 2021, providing an unprecedented view of ocean surface conditions within a major hurricane, reporting surface winds as high as about 40 m/s.  New SD missions for the 2022 Atlantic hurricane season were also able to intercept the tracks of Hurricane Fiona and Ian.

Here we present a comprehensive analysis and interpretation of the Saildrone ocean surface wind measurements in these hurricanes, using the following datasets for comparison: NDBC buoys in the path of the storms, microwave (MW) radiometer wind retrievals and tropical cyclone (TC) winds from SMAP and AMSR2, wind retrievals from the ASCAT scatterometers, from the high-resolution Synthetic Aperture Radars, and the HWRF model winds. The methodology for adjusting the SD wind measurements to a 10m reference height and to the different spatial scales of satellite observations will be described in detail. In this presentation, we will address the consistency of the SD observations with the satellite data at all wind speed regimes, with special focus at extreme winds.

This study can serve as foundation for planning and monitoring the quality of wind measurements from SD missions in the tropics and extra-tropics using satellite data.  Additionally, if properly interpreted, future SD missions can provide a unique and much needed reference source of calibration/validation for satellite observations at wind speeds above 20 m/s, for which buoy data are less accurate.