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 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.

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 Impacts of the Two Biggest Lakes on Local Temperature and Precipitation in the Yellow River Source Region of the Tibetan Plateau

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Lijuan Wen ◽  
Shihua Lv ◽  
Zhaoguo Li ◽  
Lin Zhao ◽  
Nidhi Nagabhatla
Keyword(s):  
Tibetan Plateau ◽  
Yellow River ◽  
Source Region ◽  
Maximum Temperature ◽  
The Yellow River ◽  
The Tibetan Plateau ◽  
Lake Area ◽  
Local Climate ◽  
Community Land Model ◽  
Yellow River Source

The Tibetan Plateau harbors thousands of lakes; however few studies focus on impacts of lakes on local climate in the region. To investigate and quantify impacts of the two biggest lakes (Ngoring Lake and Gyaring Lake) of the Yellow River source region in the Tibetan Plateau on local climate, two simulations (with and without the two large lakes) from May 2010 to July 2011 are performed and analyzed using the WRF-CLM model (the weather research and forecasting model coupled with the community land model). Differences between simulated results show that the WRF-CLM model could provide realistic reproduction of surface observations and has better simulation after considering lakes. Lakes mostly reduce the maximum temperature all year round and increase the minimum temperature except in March due to the large heat capacity that makes lakes absorb (release) more energy for the same temperature change compared to land. Lakes increase precipitation over the lake area and in the nearby region, mostly during 02–14 BT (Beijing Time) of July to October when the warm lake surface induces the low level horizontal convergence and updraft over lake and provides energy and vapor to benefit the development of the convection for precipitation.

scholarly journals A first investigation of hydrogeology and hydrogeophysics of the Maqu catchment in the Yellow River source region

2021 ◽  
Vol 13 (10) ◽  
pp. 4727-4757
Author(s):  
Mengna Li ◽  
Yijian Zeng ◽  
Maciek W. Lubczynski ◽  
Jean Roy ◽  
Lianyu Yu ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Water Cycle ◽  
Yellow River ◽  
Source Region ◽  
The Yellow River ◽  
Mountainous Area ◽  
The Tibetan Plateau ◽  
Soil Thickness ◽  
Eastern Area ◽  
Yellow River Source

Abstract. The Tibetan Plateau is the source of most of Asia's major rivers and has been called the Asian Water Tower. Detailed knowledge of its hydrogeology is paramount to enable the understanding of groundwater dynamics, which plays a vital role in headwater areas like the Tibetan Plateau. Nevertheless, due to its remoteness and the harsh environment, there is a lack of field survey data to investigate its hydrogeology. In this study, borehole core lithology analysis, soil thickness measurement, an altitude survey, hydrogeological surveys, and hydrogeophysical surveys (e.g. magnetic resonance sounding – MRS, electrical resistivity tomography – ERT, and transient electromagnetic – TEM) were conducted in the Maqu catchment within the Yellow River source region (YRSR). The hydrogeological surveys reveal that groundwater flows from the west to the east, recharging the Yellow River. The hydraulic conductivity ranges from 0.2 to 12.4 m d−1. The MRS sounding results, i.e. water content and hydraulic conductivity, confirmed the presence of an unconfined aquifer in the flat eastern area. Based on TEM results, the depth of the Yellow River deposits was derived at several places in the flat eastern area, ranging from 50 to 208 m. The soil thickness measurements were done in the western mountainous area of the catchment, where hydrogeophysical and hydrogeological surveys were difficult to be carried out. The results indicate that most soil thicknesses, except on the valley floor, are within 1.2 m in the western mountainous area of the catchment, and the soil thickness decreases as the slope increases. These survey data and results can contribute to integrated hydrological modelling and water cycle analysis to improve a full-picture understanding of the water cycle at the Maqu catchment in the YRSR. The raw dataset is freely available at https://doi.org/10.17026/dans-z6t-zpn7 (Li et al., 2020a), and the dataset containing the processed ERT, MRS, and TEM data is also available at the National Tibetan Plateau Data Center with the link https://doi.org/10.11888/Hydro.tpdc.271221 (Li et al., 2020b).

Holocene hydroclimate in the source region of the Yellow River: A new sediment record from Lake Gyaring, NE Tibetan Plateau

2021 ◽  
Vol 205 ◽  
pp. 104601
Author(s):  
Wenwei Zhao ◽  
Chunzhu Chen ◽  
Qingfeng Jiang ◽  
Ming Ji ◽  
Jianan Zhen ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Yellow River ◽  
Source Region ◽  
The Yellow River ◽  
Sediment Record ◽  
Ne Tibetan Plateau
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