Large-Scale Turbulence Structures and Their Contributions to the Momentum Flux and Turbulence in the Near-Neutral Atmospheric Boundary Layer Observed from a 213-m Tall Meteorological Tower

Abstract

Large-scale turbulence structures in the near-neutral atmospheric boundary layer (ABL) are investigated on the basis of observations made from the 213-m tall meteorological tower at Tsukuba, Japan. Vertical profiles of wind speed and turbulent fluxes in the ABL were obtained with sonic anemometer-thermometers at six levels of the tower. From the archived data, 31 near-neutral cases are selected for the analysis of turbulence structures. For the typical case, event detection by the integral wavelet transform with a large time scale (180 s) from the streamwise velocity component (u) at the highest level (200 m) reveals a descending high-speed structure with a time scale of approximately 100 s (a spatial scale of 1 km at the 200-m height). By applying the wavelet transform to the u velocity component at each level, the intermittent appearance of large-scale high-speed structures extending also in the vertical is detected. These structures usually make a large contribution to the downward momentum transfer and induce the enhancement of turbulent kinetic energy. This behaviour is like that of "active" turbulent motions. From the analysis of the two-point space-time correlation of wavelet coefficients for the u velocity component, the vertical extent and the downward influence of large-scale structures are examined. Large fluctuations in the largescale range (wavelet variance at the selected time scale) at the 200-m level tend to induce the large correlation between the higher and lower levels.

On Turbulent Fluxes During Strong Winter Bora Wind Events

“…On the other hand, Helgason and Pomeroy (2012) relate these low-frequency contributions to the gustiness of the flow. Horiguchi et al (2012) also report the active role of intermittency in the spatio-temporal evolution of these large-scale, coherent structures. Additionally, Dupont et al (2008) and Horiguchi et al (2012) also observed an elevated maximum in the momentum flux (their Figs.…”

“…Horiguchi et al (2012) also report the active role of intermittency in the spatio-temporal evolution of these large-scale, coherent structures. Additionally, Dupont et al (2008) and Horiguchi et al (2012) also observed an elevated maximum in the momentum flux (their Figs. 7 and 8, respectively), similar to that found at Pometeno Brdo.…”

“…Using simple and robust conditional averaging techniques, such as quadrant analysis, variable-interval time averaging (VITA) or principal component analysis (PCA), the importance of turbulent transport below and above forest canopies has been very well documented. More so, the development of the more advanced wavelet covariance technique has enabled precise detection of coherent structures (Feigenwinter and Vogt 2005;Barthlott et al 2007; Thomas and Foken 2007;Zeri and Sá 2011;Horiguchi et al 2012;Segalini and Alfredsson 2012). Studies investigating coherent structure evolution over complex terrain are not as abundant (Cava et al 2005;Helgason and Pomeroy 2012).…”

Characteristics of the near‐surface atmosphere over the Ross Ice Shelf, Antarctica

“…Instrumented towers have been used widely around the world to study the surface layer and lower portion of the boundary layer [e.g., Van Ulden and Wieringa , ; Whiteman et al ., ; Bowen , ; Horiguchi et al ., ; Munoz et al ., ; Sorbjan and Czerwinska , ]. In addition to these midlatitude surface layer studies, instrumented towers have been used to analyze the surface layer in the polar regions, where snow and ice covered surfaces greatly influence the stability of the near‐surface atmosphere [e.g., Riordan , ; Persson et al ., ; Grachev et al ., ; Hudson and Brandt , ; Genthon et al ., ; Grachev et al ., ; Genthon et al ., ; Grachev et al ., ; Van dam et al ., ].…”

Daytime Evolution of Lower Atmospheric Boundary Layer Structure: Comparative Observations between a 307-m Meteorological Tower and a Rotary-Wing UAV

“…A meteorological observation tower provides a representative way to continuously measure vertical profiles of atmospheric variables at the site of interest for a long period. Several tall meteorological towers with heights of a few hundred meters have been installed in Boulder, USA [15], Tsukuba, Japan [16], Beijing, China [17], Boseong, South Korea [18], and Shenzhen, China [19], and have been used to observe the temporal evolution of the vertical profiles of various meteorological variables in the lower ABL. A meteorological observation tower is the most accurate in situ arrangement for obtaining meteorological data at various altitudes.…”