The Formation of Sharp Multi-Layered Wind Structure over Tokyo Associated with Sea-breeze Circulation

Abstract

The front of a sea breeze originating from Sagami Bay passed over Tokyo between 1300 LST and 1400 LST on August 10, 2006. Field observations of wind distributions over Tokyo by the use of a ground-based coherent Doppler lidar developed at the National Institute of Information and Communications Technology showed that a sharp multi-layered structure of vertical wind fields was gradually formed after the sea-breeze front passed the observation site. Numerical simulations using the Weather Research and Forecasting (WRF) model demonstrated that the multi-layered wind structure consisted of 1) the sea breeze at an altitude below 0.8 km above mean sea level (AMSL), 2) a layer of weak winds at an altitude of 0.8-1 km AMSL, 3) a return flow of the sea breeze, and 4) a northerly synoptic wind at an altitude above 3 km AMSL. This is the first direct observation of the formation of sharp multi-layered wind structure over Tokyo associated with sea-breeze circulation.