Characteristics of Energy Dissipation Rate Observed from the High-Frequency Sonic Anemometer at Boseong, South Korea

Jeonghoe Kim,Robert D Sharman,Jung-Hoon Kim

doi:10.3390/atmos12070837

Jeonghoe Kim, Robert D Sharman + Show 1 more

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https://doi.org/10.3390/atmos12070837

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Abstract

The characteristics of low-level turbulence at Boseong, located on the southern coast of South Korea, were investigated in terms of eddy dissipation rate (EDR) using 1-year (2018) of wind data obtained from the Boseong Meteorological Observatory (BMO), a World Meteorological Organization testbed. At BMO, a 307 m tall tower is installed on which four high-frequency (20 Hz) sonic anemometers are mounted at 60, 140, and 300 m above ground level (AGL). In addition, a sonic anemometer at 2.5 m AGL is located to the south of the tower. EDRs are estimated from the wind measurements based on three different EDR estimation methods. The first two methods use the inertial dissipation method derived from Kolmogorov turbulence theory, and the third uses a maximum likelihood estimation assuming a von Kármán spectral model. Reasonable agreement was obtained between the three methods with various fluctuations, including diurnal variations for all seasons, while the EDR calculated from the third method displayed slightly higher EDR values than the other two methods. The result of the analysis showed that the mean (standard deviations) of logarithms of EDR had larger values as height decreased (increased), and the means were higher in the unstable planetary boundary layer (PBL) than in the stable PBL for this heterogeneous location adjacent to the coastlines. The probability density functions (PDFs) of the EDRs showed that the distribution was well-represented by a lognormal distribution in both the stable and unstable PBL, although the PDFs at the lowest level (2.5 m) deviated from those at other levels due to surface effects. Seasonal variations in the PDFs showed that there was less difference in the shape of the PDFs depending on atmospheric stability in the wintertime. Finally, we calculate the 1-yr statistics of the observed EDR, which will be used for future LLT forecast systems in Korea.

Highlights

The energy dissipation rate (ε) is the rate at which turbulent kinetic energy (TKE) cascades down to smaller scales
Time series of eddy dissipation rate (EDR) in the four seasons at the four levels were obtained using the above three different EDR estimation methods
EDR2 and EDR3 were almost perfectly correlated for all levels because the Kolmogorov spectra and the von Kármán spectra are theoretically identical within the predefined inertial range (IR) in this study

Summary

Introduction

The energy (or eddy) dissipation rate (ε) is the rate at which turbulent kinetic energy (TKE) cascades down to smaller scales. Has been the subject of many investigations, including the effect on the frontogenesis [3], in the evaluations of the PBL parameterizations [4], in the energy production from the wind farms [5], and in the development of low-level turbulence (LLT) forecasting systems [6] These and other studies have been based on sonic anemometer data [3,4,5,6,7,8], aircraft data [9,10,11], lidars [7,12,13,14,15,16,17], and radars [10,18,19]. Based on the lognormality observed in the commercial aircraft in-situ EDR observations, the lognormal mapping technique (LMT) has been recently used in the development of numerical weather prediction (NWP) model-based turbulence forecast systems such as the Graphical

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