Typhoon In-Fa (2021) Near Surface Wind Field Characteristics Based on Lidar Observations

Abstract

This study analyzes the surface winds of Typhoon In-fa during landfall at a coastal area using Doppler wind lidar (DWL) observations in the Plane Position Indicator (PPI) scanning mode. High-resolution (30 m) wind field structures in the lower boundary layer at the land-sea interface were derived using the velocity-azimuth display technique. This approach captures the wind field structure in unprecedented detail at the scale of tens of meters, providing a fine-scale view of the coastal wind field during typhoon landfall. It was found that stronger winds were predominantly located at the periphery of the scanning area, where the underlying surface is water, whereas weaker winds tended to occur near the radar, where the underlying surface is land. Analysis of vorticity and divergence revealed small-scale vortex structures, approximately 100 m in size, embedded within the large-scale circulation of the typhoon. These structures became less distinct as the typhoon center approached. Furthermore, the turbulent energy spectrum derived from the directly observed radial winds followed Kolmogorov's −5/3 law, indicating that the turbulence was generally isotropic. Additionally, the turbulent kinetic energy (TKE) calculated from the DWL data showed good agreement with previous tower-based observations, particularly in terms of the relationship between TKE and wind speed, confirming the reliability of DWL measurements in capturing turbulence characteristics. These results suggest that DWL can serve as an effective alternative for future turbulence observations during typhoon landfall.