Assessment of different Synthetic Aperture Radar (SAR) systems for mapping floating pumice rafts after submarine volcanic eruptions

Kurzfassung

Floating pumice rafts from submarine eruptions threaten maritime activities, fisheries, tourism, and coastal populations. Effective tracking is essential to mitigate impacts. While previous approaches have primarily relied on optical satellite data, we investigated the potential of cloud penetrating Synthetic Aperture Radar (SAR) that has not been evaluated for this purpose yet. We analyzed amplitude data from TerraSAR-X (X-band), Sentinel-1 (C-band), and ALOS-2 (L-band). We observed that the co-pol channel proves more suitable for mapping than the cross-pol channel for all investigated SAR bands due to higher contrast between volcanic debris and water and less influence of system noise, which distorts backscatter and makes this channels data unusable for image-based processing. A limiting scenario for SAR were partially or fully submerged pumice rafts after a longer period following the eruption, suggesting that SAR data are not suited for long-term tracking of floating pumice. This finding indicates that SAR data are primarily effective for short-term tracking, as mapping reliability decreases with time once pumice begins to waterlog, submerge or disperse. Nevertheless, SAR imagery captured consolidated pumice rafts well during eruption events and under cloudy conditions, highlighting its value as a complementary data source to optical sensors when visibility is often limited.