An experiment to examine the detectability of volcanic ash cover and its thickness by using L-band synthetic aperture radar (SAR) was carried out. Test sites with 0, 10, 20, and 40 cm ash layers were developed. PALSAR-2 and Pi-SAR-L2 observations were carried out several times with and without the ash cover. The PALSAR-2 backscatter coefficients in HH polarization, σ HH  0 , for soil with ash layers are on average 1.7 to 3.5 dB lower than that for soil without ash layers. On the other hand, the 0 cm site shows almost the same value throughout the experiment. The ash layer was also measured by ground based radar operated in C-band. The reflectivity-frequency plot obtained from the soil with 2 to 6 cm ash layers appears as a sine-like curve, indicating the reflection from two layers (soil plus ash). It indicates that no linear correlation is expected between σ 0  and thickness of ash layer. Correlations between the ash thickness and representative parameters obtained from L-band SAR observation are examined. It indicates that volume scattering component shows the highest correlation with R 2  of 0.7143.
['Manabu Watanabe', 'Masashi Sonobe', 'Ryo Natsuaki', 'Shinichi Suzuki']
Trial of volcanic ash detection using L-band synthetic aperture radar (SAR)