Wind characteristics in typhoon boundary layer at coastal areas observed via a Lidar profiler

Abstract

Information about typhoon wind characteristics provides a basis and is a prerequisite for conducting anti-typhoon studies and practices. Despite the great efforts and active exploration made in the field of typhoon measurements using various equipment over the past decades, how to effectively obtain both the mean and fluctuating components of typhoon wind especially within the atmospheric boundary layer around the inner region of the storm still remains as a challenge. In recent years, Lidar wind profilers have been attracting increasing attention and showing great promise owing to their advantages, such as wide detection range, high sampling frequency, handiness, and flexible layout. However, the results for turbulent wind components using Lidar wind profilers tend to be biased due to the intrinsic spatial average in remote sensing detection. In view of the above, this paper explores the use of the Lidar wind profiler to conduct legitimate measurements of typhoon averages and fluctuating wind field characteristics. Firstly, wind field measurements in the inner regions of two typhoons were successfully captured during their passage with the flexible deployment of equipment in coastal areas. Based on the data obtained, the mean wind field characteristics of the typhoons were examined during different transitional stages and under different exposure conditions, with a focus on the influence of inner boundary layer on the vertical wind speed profile and its key parameters, such as surface roughness and zero-plane displacement. A method based on a wind spectrum model is proposed to correct the typical fluctuating wind field parameters, which include turbulence integral length scale, turbulence intensity, and gust factor. The difference between these wind turbulence parameters before and after the correction was significant, but the corrected results were in better agreement with similar existing results, reflecting the necessity and validity of the correction work. The presented results are expected to be helpful for further understanding of the wind characteristics in the middle and upper portions of typhoon boundary layer, and contribute to the development of using Lidar profiler for observing wind turbulence.