On the Estimation of Wind Speed Diurnal Cycles Using Simulated Measurements of CYGNSS and ASCAT

Due to solar heating, many geophysical quantities, such as precipitation, sea surface temperature, and wind, have distinct diurnal signatures in the tropical region. To explore the potential of wind speed measurements of the Cyclone Global Navigation Satellite System (CYGNSS) mission launched in December 2016, we examine the degree to which wind diurnal cycles can be estimated from the surface wind speed data provided by CYGNSS along with data from the ASCAT mission. Ocean wind speed measurements are simulated based on the Cross-Calibrated Multi-Platform analysis fields of surface wind vectors. We estimate the amplitude and phase of diurnal wind speed based on a discrete Fourier transform generalized to analyze unevenly sampled time series of wind speed anomalies. The results show that the combination of CYGNSS and ASCAT measurements can provide some ability to observe diurnal wind information, but that additional time samples (e.g., from other measurement sources) would likely provide further benefits in estimation performance.