london

Credit: NASA

Three forms of data have been used to provide a dramatic three-dimensional visualization of increased sea level height and raised sea temperatures in the eastern Pacific linked to the El Niño event (above). Data from three separate instruments, including the US National Aeronautics and Space Administration's (NASA)'s Topex radar altimetry satellite, released last week, show a 34-cm rise in the height of the eastern Pacific Ocean between January 1997 and March this year. Sea surface temperature increased by 5.4 °C during the same period.

The height of the sea is indicated by the bumps in the images. Sea surface temperature is represented by the colour, with red being 10 °C above normal, and blue 10 °C below normal. The large area of blue in the final frame indicates colder than normal water being left behind as warmer water moves further eastwards.

The winter El Niño forecast of warmer waters moving eastwards across the Pacific Ocean was issued last summer. Data from the instruments show that the 1997-98 El Niño arrived earlier than the last comparable event in the winter of 1982-83. But projections of drier than normal weather in parts of Asia have not quite materialized (see Nature 388, 108; 1997). India, for example, experienced a near-normal monsoon.

The frames, as well as a computer simulation of the movement of water, can be viewed on the NASA El Niño Web site, http://nsipp.gsfc.nasa.gov/enso/nino_update.