scholarly journals Large eddy simulation of boundary-layer turbulence over the heterogeneous surface in the source region of the Yellow River

2021 ◽  
Vol 21 (20) ◽  
pp. 15949-15968
Author(s):  
Yunshuai Zhang ◽  
Qian Huang ◽  
Yaoming Ma ◽  
Jiali Luo ◽  
Chan Wang ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Yellow River ◽  
Source Region ◽  
Turbulent Intensity ◽  
Internal Boundary ◽  
The Yellow River ◽  
Background Wind ◽  
Boundary Layer Turbulence ◽  
Large Eddy

Abstract. Lake breezes are proved by downdrafts and the divergence flows of zonal wind in the source region of the Yellow River (SRYR) in the daytime based on ERA-Interim reanalysis data. In order to depict the effect of the circulations induced by surface anomaly heating (patches) on the boundary-layer turbulence, the UK Met Office Large Eddy Model was used to produce a set of 1D strip-like surface heat flux distributions based on observations, which were obtained by a field campaign in the Ngoring Lake basin in the summer of 2012. The simulations show that for the cases without background wind, patch-induced circulations (SCs) promote the growth of convective boundary layer (CBL), enhance the turbulent kinetic energy (TKE), and then modify the spatial distribution of TKE. Based on phase-averaged analysis, which separates the attribution from the SCs and the background turbulence, the SCs contribute no more than 10 % to the vertical turbulent intensity, but their contributions to the heat flux can be up to 80 %. The thermal internal boundary layer (TIBL) reduces the wind speed and forms the stable stratification, which produces the obvious change of turbulent momentum flux and heat flux over the heterogeneous surfaces. The increased downdrafts, which mainly occur over the lake patches, carry more warm, dry air down from the free atmosphere. The background wind inhibits the SCs and the development of the CBL; it also weakens the patch-induced turbulent intensity, heat flux, and convective intensity.

scholarly journals Large eddy simulation of boundary-layer turbulence over the heterogeneous surface in the Source Region of the Yellow River

2021 ◽  
Author(s):  
Yunshuai Zhang ◽  
Qian Huang ◽  
Yaoming Ma ◽  
Jiali Luo ◽  
Chan Wang ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Yellow River ◽  
Source Region ◽  
Turbulent Intensity ◽  
The Yellow River ◽  
Lake Basin ◽  
Convective Boundary ◽  
Boundary Layer Turbulence ◽  
Large Eddy

Abstract. Lake breezes are proved by downdrafts and the divergence flows of zonal wind in the source region of the Yellow River in the daytime based on ERA-Interim reanalysis data. In order to depict the effect of the circulations induced by surface anomaly heating (patches) on the boundary-layer turbulence, the large eddy model was used to produce a set of 1D strip-like surface heat flux distributions based on observations, which obtained by a field campaign in the Ngoring Lake Basin in the summer of 2012. The simulations show that for the cases without ambient winds, patch-induced circulations (SCs) enhance the turbulent kinetic energy (TKE) and then modify the spatial distribution of TKE. Based on phase-averaged analysis, which separates the attribution from the SCs and the background turbulence, the SCs contribute no more than 10 % to the vertical turbulent intensity, but their contributions to the heat flux can be up to 80 %. The lake patches produce consistent spatial distributions of wind speed and turbulent stress over the lake–land boundary, and the obvious change of turbulent momentum flux over the boundary of patches can not be neglected. In the entrainment layer, the convective rolls still persist under stronger geostrophic winds of 7–11 m s−1. The increased downdrafts, which mainly occur over the lake patches and carry more warm, dry air down from the free atmosphere. In general, the SCs promote the growth of convective boundary layer, while the background flows inhibit it. The background winds also weaken the patch-induced turbulent intensity, heat flux, and convective intensity.

Large eddy simulation of boundary-layer turbulence over different underlying surfaces in the Source Region of the Yellow River, northeastern Tibetan Plateau

2020 ◽  
Author(s):  
Yunshuai Zhang ◽  
Qian Huang ◽  
Yaoming Ma
Keyword(s):  
Boundary Layer ◽  
Tibetan Plateau ◽  
Turbulence Intensity ◽  
Yellow River ◽  
Source Region ◽  
Horizontal Resolution ◽  
The Yellow River ◽  
Lake Basin ◽  
Small Range ◽  
Large Eddy

<p>In order to study the characteristics of turbulence over the homogeneous and inhomogeneous underlying surfaces and its effects on the transport of material and energy in the Source Region of the Yellow River (SRYR), northeast of the Tibetan Plateau. We use the GPS sounding data and eddy covariance data observed during a field experiment in the Ngoring Lake Basin in summer 2012, and for the first time large eddy simulations are performed to investigate the characteristics of the fine turbulence structure in the convective boundary layer (CBL) of the two different underlying surfaces (grassland and lake) in the SRYR. It shows that the simulated CBLs of grassland and lake in the SRYR is in good agreement with the observations, but the characteristics of the turbulence structure in the CBLs are obviously different. The spatio-temporal distribution of turbulence energy and the structure characteristics of thermal bubbles in the CBL above the grassland are consistent with those of the typical thermally driven CBL above the land. Convective rolls are simulated in the shear dominant CBL above the lake. Turbulence intensity in the surface layer above the grassland is higher, while it is larger at the top of CBL above the lake due to the strong entrainment. We also found that the simulations are sensitive to the horizontal resolution on the two different homogeneous underlying surfaces. The higher horizontal resolution should applied to the CBL above the lake to improve the accuracy in the simulation of turbulence kinetic energy and turbulence flux of the surface layer and the entrainment layer, while avoiding underestimating the turbulence flux due to the small range of the waves simulated at low resolution. For the CBL of the grassland, it is suggested that the grid distance should be between 200 m-300 m, which can save the calculation time, also can give the turbulence flux and the fine turbulence structure. In addition, 3-D simulations are also performed to figure out the differences of turbulence intensity over homogeneous and inhomogeneous underlying surfaces. It is found that lake breeze induced by surface inhomogeneity would enhance the wind shear, decreasing the intensity of vertical turbulence and increasing that of horizontal turbulence.</p>

scholarly journals Estimates of Daily Evapotranspiration in the Source Region of the Yellow River Combining Visible/Near-Infrared and Microwave Remote Sensing

2020 ◽  
Vol 13 (1) ◽  
pp. 53
Author(s):  
Rong Liu ◽  
Jun Wen ◽  
Xin Wang ◽  
Zuoliang Wang ◽  
Yu Liu ◽  
...  
Keyword(s):  
Heat Flux ◽  
Surface Energy ◽  
Energy Distribution ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Yellow River ◽  
Source Region ◽  
The Yellow River ◽  
Effective Energy ◽  
Meteorological Satellite

The spatial variation of surface net radiation, soil heat flux, sensible heat flux, and latent heat flux at different times of the day over the northern Tibetan Plateau were estimated using the Surface Energy Balance System algorithm, data from the FY-2G geostationary meteorological satellite, and microwave data from the FY-3C polar-orbiting meteorological satellite. In addition, the evaporative fraction was analyzed, and the total evapotranspiration (ET) was obtained by the effective evaporative fraction to avoid the error from accumulation. The hourly change of latent heat flux presented a sound unimodal diurnal variation. The results showed the regional ET ranged between 2.0 and 4.0 mm over the Source Region of the Yellow River. The conditional expectations of surface energy components during the experimental period of the study area were statistically analyzed, and the correspondence between different surface temperatures and the effective energy distribution was examined. The effective energy distribution of the surface changed significantly with the increase in temperature; in particular, when the surface temperature exceeded 290 K, the effective energy was mainly used for surface ET. The aim of this study was to avoid the use of surface meteorological observations that are not readily available over large areas, and the findings lay a foundation for the commercialization of land surface evapotranspiration.

scholarly journals Key technologies and optimization model for ecological protection and grass-based livestock husbandry in the source region of the Yellow River

资源科学 ◽  
2020 ◽  
Vol 42 (3) ◽  
pp. 508-516
Author(s):  
Tianwei XU ◽  
Xinquan ZHAO ◽  
Yuanyue GENG ◽  
Xungang WANG ◽  
Shaojuan MAO ◽  
...  
Keyword(s):  
Optimization Model ◽  
Yellow River ◽  
Source Region ◽  
The Yellow River ◽  
Ecological Protection ◽  
Key Technologies ◽  
Livestock Husbandry
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