Wind Speed, Vertical Wind Shear, and Stability in the Lower Troposphere Revealed in High-Resolution Radiosonde Data in South Korea

다국어 초록 (Multilingual Abstract)

In this study, high-resolution radiosonde data at five stations in South Korea are analyzed to understand characteristics of vertical structure of wind speed, vertical wind shear (VWS), squared Brunt-Vaisala frequency (N²), and Richardson number (Ri) in the lower troposphere (below z=1500 m) for 4 years (July 2016-June 2020). Wind speed, VWS, N² and Ri show large spatial and temporal variabilities. In the analysis of 3 layers of equal height (500 m) up to 1500 m, wind speed increases with increasing height and strong VWS is confined to the lowest layer. The ratio of convective instability (Ri<0) to Kelvin-Helmholtz (KH) instability (0<Ri<0.25) to stable condition (Ri>0.25) is 3:1:6 for the whole height range below z=1500 m, and the proportions of convective and KH instabilities decrease with increasing height. Ri less than 0.25 has seasonal variations with larger occurrences in winter than in summer. In power spectral density (PSD) analysis, it is found that the annual cycle is predominant for all variables and 1 day cycle is also significant for VWS and N2 below z=500 m. In addition, there are relatively strong variations among stations below z=1000 m at which geographical features such as islands and mountains are highly influential, while common features are more evident above z=1000 m.