Numerical simulation study of the effects of foehn winds on white head incidences in Yamagata Prefecture, Japan

Abstract

Abstract Numerous studies have elucidated that white heads and chalky rice are caused by hot, dry and strong winds at night. However, these studies have only used synoptic weather charts and near‐surface observation data to confirm the role of foehn in white head occurrences. This study used a high‐resolution three‐dimensional numerical weather prediction model to show that strong foehn effects induced a significant number of white heads in rice in Yamagata Prefecture, Japan. The model accurately predicted and represented the location and timing of the observed white heads, occurring only in a limited area (87.1 ha) on the southwest side of Mt. Chokai during the nighttime. Specifically, the simulated nocturnal FTP (transpiration forcing) continuously exceeded 30 at that location. This high FTP was caused by high temperature (>24°C), strong wind speed (>8 m s−1) and low humidity (<65%) caused by the strong foehn winds descending over the southwest slope of the mountain. In the other areas, FTP did not exceed 30 because either wind speed, water vapour deficit or both were insufficiently high.

Keywords

• dynamical foehn
• forecast experiment
• rice
• white head damage
• WRF model