Mapping the Dynamics of the South Asian Monsoon Using CYGNSS's Level-1 Signal Coherency

A method for mapping the dynamics of the South Asian monsoon season is proposed based on the use of the coherence of CYGNSS Level 1 delay-Doppler Map measurements. Because the apparent coherence of the specular forward scattering observed by CYGNSS provides information on the presence of inland water, it can be related to different phases of the monsoon season. Results reported from 2017 to 2020 illustrate inter-annual variations in the seasonal monsoon, and show high degrees of correlation with SMAP soil moisture maps over the Indian subcontinent. Comparisons with precipitation information from the global precipitation measurement mission also show relationships indicative of the monsoon's dry and wet phases. The analysis presented in this work highlights the potential of using spaceborne GNSS-R systems for the operational mapping of monsoon dynamics.