The formation of raindrops releases latent heat, which is one of the primary sources of energy that drives atmospheric circulation. Thus, scientists need to improve their understanding of the global distribution and intensity of rainfall to improve weather and climate forecasts. Unfortunately, rainfall is very difficult to measure, especially over the ocean where few people live and where rain gauges commonly used on land don't work. But we know that rain falling onto a tin roof makes a lot of noise, and so does rain falling onto water. In fact, rain falling onto water is one of the loudest sources of underwater sound, therefore we can measure oceanic rain by listening to it from below the ocean surface.
Scientists use the distinct sounds made underwater by different size raindrops to measure rainfall.
Hydrophones in remote stretches of ocean record the sound of rain falling on water and transmit it to laboratories where the recordings are analyzed to augment our undersdtanding of global rainfall patterns.