Statistics and spectra of turbulence under different roughness in the near‐neutral atmospheric surface layer

Abstract

Accurate knowledge of the contacts between surface roughness and the resultant wind speed are important for climatic models, wind power meteorology, agriculture and erosion hazards especially on sand saltation in arid and semi‐arid environments, where vegetation cover is scarce. In this study, synchronous measurements of three‐dimensional wind speed below 5 m are carried out in three different surface roughness conditions in Minqin, China, and the difference in the turbulence statistics and the structure of the very large‐scale motions (VLSMs) were revealed. The results show that the slope of the mean wind profile (MVP), the turbulent kinetic energy (TKE) and Reynolds stress increase with the surface roughness. The roughness seems to suppress the ejection events and the surface roughness will not only weaken the energy of the VLSMs, but also reduce the scale values of VLSMs near the wall. These influences may cause some changes regarding the dust transportation in streamwise and vertical directions during the sand and dust storm (SDS). That is, the decrease of the mean velocity near the ground will reduce the dust transportation in the streamwise direction and influence of the roughness on the ejection and sweep events will change the dust transportation in the vertical direction. Furthermore, the increase of roughness will weaken the scale and energy of VLSMs, which will lead to the decrease of the capacity of dust transportation. © 2019 John Wiley & Sons, Ltd.

High-frequency observation during sand and dust storms at the Qingtu Lake Observatory

“…Characteristics of coherent structures were investigated under near-neutral and stratified conditions (e.g., Wang and Zheng, 2016;Liu et al, 2019;Li and Bo, 2019a;Li et al, 2021b). Roughness effects were explored to illustrate the features in the near-surface layer (e.g., Li and Bo, 2019b;Li et al, 2021c). (ii) Sandladen flows are wind-blown sand movements that are topically two-phase flows in arid and semiarid regions, where the interaction between flow features and PM 10 concentration were previously discussed (e.g., Wang et al, 2017Wang et al, , 2020.…”

High frequency observation during the sand and dust storms in the Qingtu Lake Observatory

“…Characteristics of coherent structures were investigated under near-neutral and stratified conditions (e.g., Wang and Zheng, 2016;Liu et al, 2019;Li and Bo, 2019a;Li et al, 2021b). Roughness effects were explored to illustrate the features in the near surface layer (e.g., Li and Bo, 2019b;Li et al, 2021c). ii) Sand-laden flows: Wind-blown sand movements are topically two-phase flow in the arid and semiarid regions, where the interaction between flow features and PM 10 concentration were previously discussed (e.g., Wang et al, 2017Wang et al, , 2020.…”

Size Distribution of Mineral Dust Emissions From Sparsely Vegetated and Supply‐Limited Dryland Soils

“…Conditions that could induce variability in emission‐flux PSD with u * include changes in availability and PSD of LEM that can be entrained by wind (Gillette & Chen, 2001; Klose et al., 2017), variability in cohesive properties of soil that influence surface deformation, and abrasion during saltation (Houser & Nickling, 2001; Rice et al., 1999; Shao, Ishizuka, et al., 2011), and variability in turbulent momentum fluxes from surface roughness and buoyancy in the ABL (Dupont et al., 2019; X. Li & Bo, 2019). These conditions are found in many drylands, including agricultural landscapes, where vegetation is present and soils contain sufficient silt and clay to promote sediment supply limitation through aggregation and crusting (Webb & Strong, 2011).…”

“…Conditions that could induce variability in emission-flux PSD with u * include changes in availability and PSD of LEM that can be entrained by wind (Gillette & Chen, 2001;Klose et al, 2017), variability in cohesive properties of soil that influence surface deformation, and abrasion during saltation (Houser & Nickling, 2001;Rice et al, 1999;Shao, Ishizuka, et al, 2011), and variability in turbulent momentum fluxes from surface roughness and buoyancy in the ABL (Dupont et al, 2019;X. Li & Bo, 2019).…”