Range-height indicator (RHI) scans from the Doppler Light Detection And Ranging (LIDAR) systems at the Hong Kong International Airport (HKIA) reveal vortices associated with Kelvin-Helmholtz (KH) instability, jump-like features and mountain waves associated with lower kills and a gap on Lantau Island nearby HKIA. These novel features of terrain-disrupted airflow at HKIA that has not been documented before. This paper analyzes such flow features by considering some parameters of the airflow based on the upper air sounding in Hong Kong, such as Richardson number, Scorer parameter, and Froude number. An attempt has also been made to simulate these novel flow phenomena at HKIA using a high resolution mesoscale numerical weather prediction (NWP) model. The modeling results are found to be a mixed success. Some features, such as mountain waves and jump-like feature, are readily reproduced. However, vortices associated with KH instability are difficult to reproduce, and the vortex shedding simulation does not fully reproduce the observational data based on the Doppler LIDARs. The results in this paper are considered to be useful for the study of mountain meteorology in Hong Kong and elsewhere in the world.
Yu-Ting Leung, Pak-Wai Chan, M. Chong et al.· Idojaras - Quarterly journal...· 0 citations
Micrometeorological studies of a bridge and the urban area of Hong Kong under south to southwesterly winds associated with tropical cyclone Wutip in June 2025 were conducted using computational fluid dynamic simulation driven by a mesoscale model. For mean winds, such as 1-min or 10-min averages (as in the application to road traffic management on a bridge), the use of mesoscale meteorological models alone may be sufficient to capture the general wind trend, since the RMSEs of the mean wind speeds were comparable and mostly in the range of 1–5 m s⁻¹. However, if fluctuations in winds are considered and turbulence intensity is a concern for operation (such as the operation of drones in low-altitude economic activities), the coupling of mesoscale meteorological models with computational fluid dynamics models must be considered. However, the measured turbulence intensity could be rather high (40–50% for turbulence intensity), which may not be achieved with mesoscale coupled computational fluid dynamic models. Numerous issues remain to be resolved for this type of micro-meteorological studies, especially for studies and applications in urban meteorology. Future directions for these studies are also discussed.
Ka-Wai Lo, K. Lai, P. Chan· Idojaras - Quarterly journal...· 0 citations
Doppler Light Detection and Ranging (LIDAR) systems and a mesoscale meteorological model coupled with computational fluid dynamics (CFD) for the monitoring of low-level wind and turbulence have been extensively applied for the Hong Kong International Airport. This study represents the first application in Hong Kong to apply such techniques for the exploration of providing meteorological support for the operation of Unmanned Aircraft Systems (UASs) in a sandbox project in Hong Kong. The flight route under consideration is between the western coast of Hong Kong Island and an outlying island called Lamma Island, with a sea channel in between. Based on the LIDAR observations in three different prevailing wind directions, low-level turbulence may arise from wind flow disruptions by natural terrain and human-made buildings. Simulations of the wind and turbulence are attempted using the GPU-based FastEddy, with the turbulent kinetic energy equation being used to output the eddy dissipation rate (EDR). Comparisons between observed and simulated fields showed broadly consistent patterns across wind speed, wind direction, and EDR. Quantitative validation yielded RMSE of 1.35 m/s for wind speed, 28.4° for wind direction, and 0.032 m2/s2 for EDR, with corresponding R2 values of 0.72, 0.48, and 0.07, respectively. However, point-to-point comparison as in the scatter plot of the two datasets is still challenging, due to low correlation for EDR. Nonetheless, FastEddy is found to shed preliminary insights to generate reasonable simulations of low-level winds and turbulence to support the operation of UASs for the cases under study. These findings should be considered preliminary and exploratory given the limited number of case studies analyzed. More cases would need to be studied to find out the performance of FastEddy in other meteorological conditions.
K. Lai, Shuk M. Tse, P. Chan· Applied Sciences· 0 citations
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