Statistics and Evaluations of Low-Level Turbulence near Boseong, South Korea

Statistics of Low-Level Turbulence (LLT) at Boseong, South Korea was investigated using the Boseong tower data. The Boseong tower is a 300-m meteorological observation tower, operated since 2014. 3-D sonic anemometers installed on the tower measure all three components of wind with 20-Hz sampling rates at four different levels (surface, 60, 140, and 300 meters). Intensity of the LLT can be interpreted as the Eddy Dissipation Rate (EDR). After applying the Fast Fourier Transform (FFT) on the 20-Hz wind data, EDR is calculated by using the prescribed von Kármán spectral model on the individual velocity spectra for every 1-min segment. Characteristics of the EDR is investigated by the probability density functions (PDFs) of the EDR using long-term (several months) periods of the data. It is found that the EDR is generally stronger in daytime than that in nighttime, implying that the LLT is stronger in the convective boundary layer than that in stable boundary layer. EDR is getting stronger in higher altitudes than near the surface. For performance tests of the numerical simulations for the observed LLT from the Boseong tower data, entire month of October 2018 has been run by the Weather Research and Forecast (WRF) model with 3-km horizontal grid spacing and full physical packages including the Planetary Boundary Layer (PBL) schemes. Three different EDR estimates derived from the different PBL schemes are tested and compared with the observation, showing that the simulated EDR estimates are reasonably consistent with the observed EDR.