Observational Study of a Coastal Barrier Jet Induced by a Landfalling Tropical Cyclone

In this study, the structure and evolution of a coastal barrier jet (CBJ) along the east coast of Taiwan is documented using coastal Doppler radars. The formation of the CBJ was controlled by the flow regime associated with the approaching Tropical cyclone Haitang (2005). The prevailing strong northeasterly wind impinged on the steep coast, leading to the formation of CBJ. Once the core-region had reached the coast, the considerable curvature of the core-region circulation caused the structure of the CBJ to change, its southern branch shifting offshore. The CBJ persisted for 6 h and was approximately 140 km long and 25 km wide. The northern branch of the CBJ had stronger winds (maximum wind speed: 49–52 m s⁻¹), a greater vertical extent (the core of the jet was between 1.0 and 2.5 km in height), and a more persistent jet signal than the southern branch (maximum wind speed: 43–46 m s⁻¹; the core of the jet was between 1.0 and 2.0 km in height). An idealized model is conducted to estimate the terrain effect on CBJ formation. A vortex resembled Tropical cyclone Haitang is constructed on the basis of the circulation deduced using the Generalized Velocity Track Display (GVTD) technique. The result of a no-terrain simulation reveals wind speeds of 10–22 m s⁻¹, lower than the observed Doppler radial velocities. This difference suggests that the enhanced wind speed was most likely due to the terrain effect.

In this study, the structure and evolution of a coastal barrier jet (CBJ) along the east coast of Taiwan is documented using coastal Doppler radars. The formation of the CBJ was controlled by the flow regime associated with the approaching Tropical cyclone Haitang (2005). The prevailing strong northeasterly wind impinged on the steep coast, leading to the formation of CBJ. Once the core-region had reached the coast, the considerable curvature of the core-region circulation caused the structure of the CBJ to change, its southern branch shifting offshore. The CBJ persisted for 6 h and was approximately 140 km long and 25 km wide. The northern branch of the CBJ had stronger winds (maximum wind speed: 49–52 m s⁻¹), a greater vertical extent (the core of the jet was between 1.0 and 2.5 km in height), and a more persistent jet signal than the southern branch (maximum wind speed: 43–46 m s⁻¹; the core of the jet was between 1.0 and 2.0 km in height). An idealized model is conducted to estimate the terrain effect on CBJ formation. A vortex resembled Tropical cyclone Haitang is constructed on the basis of the circulation deduced using the Generalized Velocity Track Display (GVTD) technique. The result of a no-terrain simulation reveals wind speeds of 10–22 m s⁻¹, lower than the observed Doppler radial velocities. This difference suggests that the enhanced wind speed was most likely due to the terrain effect.