Spaceborne synthetic aperture radar (SAR) and ground-based radar interferometers (GBRIs) can be used to detect spatially detailed crustal deformations that are difficult to detect by on-site observations, the Global Navigation Satellite System, tiltmeters, and so on. To make such crustal deformation information readily available to those engaged in evaluating volcanic activities and researching the mechanisms, we are preparing a database within the Japan Volcanological Data Network data sharing system to store crustal deformation detected by spaceborne SAR and GBRIs (Subtheme 2-1, Project B, the Integrated Program for Next Generation Volcano Research and Human Resource Development). In this study, we examined methods to reduce atmospheric delay noise in SAR interferometry using the numerical weather model and determined the methods for resampling the analytical values of the numerical weather model and estimating atmospheric delay to efficiently determine atmospheric delay. We show that the atmospheric delay can be estimated with higher accuracy by properly combining the isobaric surface and ground surface data of the mesoscale model (MSM) provided by the Japan Meteorological Agency. We are developing a multi-type portable SAR system as a GBRI system such that it would allow campaign observations whenever increased volcanic activities are observed and acquire crustal deformation with a higher temporal resolution than spaceborne SAR for storage in the database. This system employs L-band radar, which has a higher penetrability against vegetation. Two modes of observations are possible: ground-based SAR and car-borne SAR. The prototype was fabricated to conduct experiments necessary to develop a working model. The experimental observations was carried out around Asama volcano, and we confirmed that clear fringe was obtained.

1. [1] H. Ueda, T. Kozono, E. Fujita, Y. Kohno, M. Nagai, Y. Miyagi, and T. Tanada, “Crustal deformation associated with the 2011 Shinmoe-dake eruption as observed by tiltmeters and GPS,” Earth Planets Space, Vol.65, pp. 517-525, 2013.
2. [2] Y. Miyagi, T. Ozawa, and Y. Kohno, “Crustal deformation associated with the 2011 Eruption of Shinmoe-dake in Kirishima volcano group, southwestern Japan, detected by DInSAR and GPS Measurements,” Bull. Vol. Soc. Japan (Kazan), Vol.58, Issue 2, pp. 341-351, 2013 (in Japanese with English abstract).
3. [3] D. Massonnet, M. Rossi, C. Carmona, F. Adragna, G. Peltzer, K. Feigl, and T. Rabaute, “The displacement field of the Landers earthquake mapped by radar interferometry,” Nature, Vol.364, pp. 138-142, 1993.
4. [4] Y. Miyagi, T. Ozawa, T. Kozono, and M. Shimada, “Long-term lava extrusion after the 2011 Shinmoe-dake eruption detected by DInSAR observations,” Geophys. Res. Lett., Vol.41, pp. 5855-5860, doi: 10.1002/2014GL060829, 2014.
5. [5] T. Ozawa, E. Fujita, and H. Ueda, “Crustal deformation associated with the 2016 Kumamoto Earthquake and its effect on the magma system of Aso volcano,” Earth Planets Space, Vol.68, Articl No.186, doi: 10.1186/s40623-016-0563-5, 2016.
6. [6] R. F. Hanssen, “Radar interferometry, Data interpretation and error analysis,” Kluwer Academic Publishers, 308pp., 2001.
7. [7] M. Shimada, “Imaging from spaceborne and airborne SARs, calibration, and applications,” CRC Press, 391pp., 2018.
8. [8] H. Ueda, T. Yamada, T. Miwa, M. Nagai, and T. Matsuzawa, “Development of a data sharing system for Japan Volcanological Data Network,” J. Disaster Res., Vol.14, No.4, pp. 571-579, doi: 10.20965/jdr.2019.p0571, 2019.
9. [9] Council for Science and Technology, “About subjects and correspondences in the volcano observation research following the eruption of the Ontake volcano,” http://www.mext.go.jp/b_menu/shingi/gijyutu/gijyutu6/toushin/1353717.htm, 2014 (in Japanese) [accessed June 19, 2019]
10. [10] F. Gatelli, A. M. Guamieri, F. Parizzi, P. Pasquali, C. Prati, and F. Rocca, “The wavenumber shift in SAR interferometry,” IEEE Trasn. Geosci. Remote Sensing, Vol.32, No.4, pp. 855-865, doi: 10.1109/36.298013, 1994.
11. [11] R. M. Goldstein and C. L. Werner, “Radar interferogram filtering for geophysical applications,” Geophys. Res. Lett., Vol.25, pp. 4035-4038, doi: 10.1029/1998GL900033, 1998.
12. [12] C. W. Chen and H. A. Zebker, “Phase unwrapping for large SAR interferograms: Statistical segmentation and generalized network models,” IEEE Trans. Geosci. Remote Sensing, Vol.40, pp. 1709-1719, 2002.
13. [13] S. Okuyama, “Correction of unwrapping errors caused by branch-cut algorithm,” J. Geod. Soc. Japan, Vol.56, pp. 149-153, 2010 (in Japanese with English abstract).
14. [14] G. D. Thayer, “An improved equation for the radio refractive index of air,” Radio Sci., Vol.9, pp. 803-807, 1974.
15. [15] M. Bevis, S. Businger, S. Chisewell, T. A. Herring, R. A. Anthes, C. Roken, and R. H. Ware, “GPS meteorology: Mapping zenith wet delays onto precipitable water,” J. Appl. Meteor., Vol.33, pp. 379-386, 1994.
16. [16] T. Hobiger, R. Ichikawa, T. Takasu, Y. Koyama, and T. Kondo, “Ray-traced troposphere slant delays for precise point positioning,” Earth Planets Space, Vol.60, pp. e1-e4, 2008.
17. [17] S. Fujiwara, M. Tobita, M. Murakami, H. Nakagawa, and P. A, Rosen, “Baseline determination and correction of atmospheric delay induced by topography of SAR interferometry for precise surface change detection,” J. Geod. Soc. Japan, Vol.45, Issue 4, pp. 315-325, 1999 (in Japanese with English abstract).
18. [18] T. Ozawa and S. Shimizu, “Atmospheric noise reduction in InSAR analysis using numerical eather model,” J. Geod. Soc. Japan, Vol.56, No.4, pp. 137-147, 2010 (in Japanese with English abstract).
19. [19] W. C. Skamarock, J. B. Klemp, J. Dudhia, D. O. Gill, D. M. Barker, M. G Duda, X.-Y. Huang, W. Wang, and J. G. Powers, “A Description of the Advanced Research WRF Version 3,” NCAR Tech. Note NCAR/TN-475+STR, 113pp., doi: 10.5065/D68S4MVH, 2008.
20. [20] T. Ozawa, H. Munekane, H. Yarai, and M. Murakami, “Local deformation around Iwo-yama, Kirishima volcanic complex derived from JERS-1/InSAR,” Bull. Vol. Soc. Japan (Kazan), Vol.48, Issue 6, 507-512, 2003 (in Japanese with English abstract).
21. [21] D. Tarchi, N. Casagli, S. Moretti, D. Leva, and A. J. Sieber, “Monitoring landslide displacements by using ground-based synthetic aperture radar interferometry: Application to the Ruinon landslide in the Italian Alps,” J. Geophys. Res., Vol.108, Issue B8, doi: 10.1029/2002JB002204, 2003.
22. [22] C. Werner, T. Strozzi, A. Wiesmann, and U. Wegmüller, “A real-aperture radar for ground-based differential interferometry,” Proc. of 2008 IEEE Int. Geoscience and Remote Sensing Symp. (IGARSS’08), pp. 210-213, 2008.
23. [23] F. D. Traglia, M. Battaglia, T. Nolesini, D. Lagomarsino, and N. Casagli, “Shifts in the eruptive styles at Stromboli in 2010–2014 revealed by ground-based InSAR data,” Nature, Scientific Reports Vol.5, Article No.13569, doi: 10.1038/srep13569, 2015.
24. [24] T. Ozawa and H. Nohmi, “Effect of vegetation on surface deformation measurement using InSAR investigated from laboratory experiments,” J. Geod. Soc. Japan, Vol.64, pp. 81-88, doi: 10.11366/sokuchi.64.81, 2019 (in Japanese with English abstract).
25. [25] X. Wang and Y. Aoki, “Post-eruptive thermoelastic deflation of intruded magma in Usu volcano, Japan, 1992-2017,” J. Geophys. Res. Solid Earth, doi: 10.1029/2018JB016729, 2019.
26. [26] P. Wessel and W. H. F. Smith, “New, improved version of generic mapping tools released,” EOS Trans. AGU, Vol.79, Issue 47, p. 579, 1998.