Impact of new buildings on the low-level windshear at an operating runway at the Hong Kong International Airport

The impact of buildings on the low-level winds is often examined using Reynolds-averaged Navier-Stokes equations. In this study, the feasibility of simulating windshear using Large Eddy Simulation by coupling a mesoscale/microscale numerical weather prediction model with a computational fluid dynamics model that allows explicit representation of buildings is explored. The buildings in question are newly built at the Hong Kong International Airport. Low-level windshear was observed by the Doppler Light Detection and Ranging system at the airport, when strong north-northwesterly winds prevailed after the passage of a cold front. The occurrence of low-level windshear downstream of the new buildings is successfully reproduced using coupled models with a resolution down to 6 m. By considering simulations with and without the new buildings, it is demonstrated that such buildings contributed significantly to the windshear. Enhanced crosswind fluctuations are also observed in the simulation that includes the new buildings. This coupled simulation provides a detailed benchmark that can help validate other modelling approaches, such as RANS simulations, for assessing building-induced windshear.