1 RAIN ALTIMETRY — PAST, PRESENT AND FUTURE

Although radar altimeters are often considered to have an "all weather " capability, this is not strictly true — rain may severely affect the ocean return signal. This paper charts the progress in understanding and modelling of rain's effect, and the various techniques used to flag rain-affected data, both for maintaining the quality of altimetric height data and for studies of rain per se. It finishes with some pointers towards the currently active research areas