InSAR observation and numerical modeling of the water vapor signal during a heavy rain: A case study of the 2008 Seino event, central Japan

This is the authors' abstract. We don't add key points for this paper.

This study reports the first detection and analysis of a localized water vapor distribution obtained using interferometric synthetic aperture radar (InSAR) during the Seino heavy rain episode. The InSAR data retrieved during the ALOS/PALSAR emergency observations for the event revealed a radar line‐of‐sight (LOS) change of up to 130 mm within 10 km. Based on the signal, we estimated the three‐dimensional water vapor distribution using the ray‐tracing method, which indicated a column of nearly saturated water vapor within a 10 km 2 area reaching from the surface to 9000 m above ground level. To geophysically confirm this signal, Weather Research and Forecasting (WRF) model simulations were performed, revealing a deep convection that was initiated by orographic lift caused by the Yoro Mountains. Another simulation that did not include the Yoro Mountains did not produce a deep convection. The WRF simulation also suggested that the effect of hydrometeors can account for approximately 20% of the maximum LOS change but this effect is even more localized than the effect of water vapor.