Spatial structure of local winds “Rokko‐oroshi”: A case study using Doppler lidar observation and <scp>WRF</scp> simulation

Abstract Rokko‐oroshi is a northerly local wind blowing in the mega‐city Kobe, Japan. This wind blows from the Rokko Mountains. This study analyzed the three‐dimensional structure of Rokko‐oroshi observed with a near‐surface anemometer and Doppler lidar on January 16, 2023. Furthermore, numerical simulations using the Weather Research and Forecasting (WRF) model revealed the factors responsible for the strong winds. The results showed that Rokko‐oroshi on January 16, 2023 was a bora‐type downslope windstorm. The Doppler lidar observed the strong winds of Rokko‐oroshi and a stagnant layer immediately above them. Numerical simulation results indicated the stagnant layer was formed by mountain‐wave breaking. Under this stagnant layer, the airflow transitioned from subcritical to supercritical, resulting in the strong winds of Rokko‐oroshi. This Rokko‐oroshi was accompanied by a hydraulic jump. The occurrence of the Rokko‐oroshi was supported by an upper‐level critical layer and a lower‐level strong stable layer on the windward side of the Rokko Mountains.