Manifestations of the Indian Ocean tsunami of 2004 in satellite nadir-viewing radar backscatter variations

The paper reports on the first experimental evidence for space‐observed manifestation of the open ocean tsunami in the microwave radar backscatter (in C‐ and Ku‐bands; electromagnetic wave lengths 6cm and 2 cm respectively). Significant (a few dB) variations of the radar cross section synchronous with the sea level anomaly were found in the geophysical data record of the altimetry satellite Jason‐1 for the track which crossed the head wave of the catastrophic tsunami of 26 December 2004. The simultaneous analysis of the available complementary data provided by the satellite three‐channel radiometer enabled us to exclude meteorological factors as possible causes of the observed signal modulation. A possible physical mechanism of modulation of short wind waves due to transformation of the thin boundary layer in the air by a tsunami wave is discussed. The results open new possibilities of monitoring tsunamis from space.