Highs and lows

Scientists are exploiting the pitter-patter of rain to measure rainfall over oceans, till now an impossible task. Under a US Navy-sponsored research project, scientists are using underwater microphones to listen to the rhythm of the falling rain and measure rainfall as accurately as a rain gauge.

When rain hits water, microscopic bubbles form below the surface and vibrate for a split second. Large bubbles formed by the heavy splats of a thunderstorm "sing" like a baritone and small bubbles from light drizzle sound like a soprano. A computer converts these performances into rainfall estimates. This technique should lead to improved weather forecasts and make for smoother sailing for marines, scientists say.