Typhoon wind speed observation utilizing reflected signals from BeiDou GEO satellites

Typhoon monitoring utilizing reflected GNSS signals is a new application of GNSS-R technique. Coastal observations are an efficient way for the model of geophysical parameters retrieval in Typhoon and identified as a promising complementary technique with respect to the satellite instruments. However, the relationship between GNSS-R observables and the sea surface wind speed in Typhoon could not be fully described through theoretical models for the coastal regions. Meanwhile the instability of the coastal GNSS-R geometry makes it difficult to optimize an empirically calibrated model. The BeiDou GEO satellites could provide stable geometry and better coverage capability in mid- and low-latitude region where most of the typhoons occur. Based on this consideration, ocean reflected signals from BeiDou GEO satellites are exploited for coastal Typhoon observation in this paper. The relationship between reflected waveform parameters, such as coherent time, and the ocean geophysics parameters, such as wind speed is analysed. Preliminary analysis of the BeiDou reflected signal collected during the TIGRIS experiment shows good agreement between the GNSS-R measured wind speeds and the in situ measurements, the average deviation is 1.6 m/s with the root-mean-square error of 2.4 m/s.