Using In Situ Measurements to Validate CYGNSS Wind Speed Observations

Many phenomena in the atmosphere and the ocean can be detected by sea surface winds. High quality, high temporal and spatial resolution sea surface wind data products are needed to study these phenomena. In this paper, sea surface winds from the Cyclone Global Navigation Satellite System (CYGNSS) mission between 35°N and 35°S are validated against in situ observations in order to evaluate the performance of CYGNSS mission. The in situ wind measurements are from the Xisha flux tower in South China Sea (SCS) and from moored buoy data in the Global Tropical Moored Buoy Array (GTMBA). The results indicate that the mean bias of in situ and CYGNSS wind is 0.13 m/s. The mean root-mean-square-difference (RMSD) of in situ and CYGNSS wind is 2.19 m/s. When the wind speed is less than 10 m/s, the RMSD is generally less than 2 m/s and the RMSD increases when the wind speed is larger than 10 m/s. Part of this discrepancy may come from instrument error, and part of it may come from representative error because of the non-exact spatiotemporal match of in situ and satellite measurements. The time evolution of CYGNSS winds, however, is consistent with that of in situ winds, suggesting potential applications toward understanding the multi-scale processes of the atmosphere and ocean in tropical regions.