A wind-induced delay pattern in SAR interferometry and numerical simulation.

Abstract

A particular delay pattern in differential synthetic aperture radar (SAR) interferometry is investigated by using upper sounding data and a numerical simulation technique. A JERS-1 pair of a humid windy summer scene and a dry autumn scene produces a large topography-correlated delay pattern. This topography-correlated delay shows linearity to topography that is mainly due to a wet delay. In this study, the static component of the atmospheric delay is calculated by using upper sounding data observed at a neighbouring station from the site. The result shows 14cm oneway delay corresponding to 3, 800m height difference, while 23cm in SAR interferogram, indicating a disagreement with SAR and meteorological data. A reason for this disagreement may be a distance between the site and the meteorological station. After removing the topography-correlated static component from the interferogram, there still remains a dynamic component caused by a wind. A numerical model, MRI-NHM, developed by Meteorological Research Institute, simulates atmosphere and the dynamic delay is evaluated. The simulation produces similar delay patterns of large scale and a wave-shaped pattern induced by a mountain wave. The simulation explains mechanisms to make these patterns. Although there are disagreements such as small-scale delay patterns and the wave length of the mountain wave, the study shows this simulation approach is promising for evaluatine the atmospheric delay, especially dynamic delay.