Statistical analysis and modeling of rain-generated ocean noise in the northeast Pacific Ocean

Abstract

Large scale studies of underwater ambient noise during rainfall are important for assessing the ocean environment and enabling remote sensing of rainfall rates over the open ocean. In this study, we have evaluated approximately 3.5 years of acoustical and meteorological data recorded at the northeast Pacific Ocean continental shelf and slope. The acoustic data are recorded continuously at a sample rate of 64 kHz at 81 m depth and 581 m depth at the continental shelf and slope, respectively. The wind speeds and rainfall rates are provided by a surface buoy located in the vicinity of each hydrophone. Average power spectra have been computed for different rain rates and wind speeds, and linear and non-linear regression have been performed. The results are comparted between both measurement sites to evaluate the depth dependency of rain noise at the continental margin. In contrast to previous reports, we found that the rain noise levels between 100 Hz and 10 kHz are highly dependent on the prevailing wind speed. Our findings indicate that previously proposed algorithms for estimating rainfall rates from acoustic data are not universally applicable, but rather have to be adapted for different locations.