Performance Assessment of Simulated CYGNSS Measurements in the Tropical Cyclone Environment

The capability of the cyclone global navigation satellite system (CYGNSS) to observe winds within tropical cyclones (TCs) is assessed by using simulated CYGNSS observations over 43 cyclones from 2010 to 2011. The CYGNSS end-to-end simulator (E2ES) is utilized to generate delay-Doppler maps from which wind speeds are then retrieved. These wind speeds are first compared to the high-resolution model winds input into the E2ES. For range corrected gain (RCG) values greater than 20, the CYGNSS winds have a standard deviation of 0.57 m/s relative to these model winds. An error probability lookup table is developed to improve performance for RCG values lower than 20, as well as minimizing data loss (up to 4.4%). Since actual TCs are utilized in this study, the CYGNSS winds are also compared to winds from the advanced SCATterometer (ASCAT), the Oceansat-II scatterometer, GPS dropsondes, the stepped frequency microwave radiometer, and the H*wind model analysis. The CYGNSS winds compared best to the ASCAT winds with an overall bias around -0.4 m/s, and a standard deviation less than 1.54 m/s. GPS dropsonde winds compared less favorably with a standard deviation around 7.36 m/s, which can be partially attributed to spatial and temporal sampling differences. The CYGNSS ability to retrieve the TC maximum wind is also evaluated using the national hurricane center best track maximum winds. Although the CYGNSS overall bias varied from season to season (from -4.7 m/s in the Atlantic basin-2011 to -13.0 m/s in the Atlantic basin-2010), the standard deviation remained fairly consistent.