Figure 1

Figure 1: Impact of rain on Ku- and C-band TOPEX altimeter data. (a) Rain field (mm/h) from the MIT rain radar at 17:31 UT December 12, 1992, TOPEX ground track (red line) pass 86, cycle 10, December 12, 1992 17:16 UT. (b) top: Automatic gain control in Ku (black line) and C (red line) band. Note the strong attenuation of the Ku band near 3°S associated with rain rates over 25 mm/hr. (b) bottom: the attenuation of Ku band versus C band shows several rain cells. (c) Liquid water content (Lz) estimated from the TOPEX microwave radiometer (mm). It is generally assumed that rain is present for Lz> 0.6. Average rain rate from the MIT radar in a 25-kilometer-wide swath along the satellite track and estimate of rain rate by inversion of the Ku band attenuation. (d) Sea surface height. Even if the majority of the samples within rain cells are flagged, it can be seen that the distortion of the altimeter waveforms affects the retrieval of geophysical parameters.