The influence of wind speed on surface layer stability and turbulent fluxes over southern Indian peninsula station

Patil, M. N.; Waghmare, R.T.; Dharmaraj, T.; Chinthalu, G. R.; Siingh, Devendraa; Meena, G. S.

doi:10.1007/s12040-016-0735-5

Cited by 8 publications

(3 citation statements)

References 35 publications

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“…Equation indicates that C DN should be independent of wind speed for a fixed z 0 . However, observations show that C DN increases sharply with the decrease of wind speed in light winds (Al‐Jiboori, 2010; Grachev et al., 2006; Mahrt et al., 2015; Patil et al., 2016; Rao, 2004; Rao et al., 1996). The behavior of C DN in light winds, which is in excess of that expected by MOS theory and may affect the performance of the weather and climate numerical models, has attracted increasing attention (Katz & Zhu, 2017; Mahrt, 2008; Srivastava & Sharan, 2015; Zhu & Furst, 2013).…”

Section: Introductionmentioning

confidence: 99%

Improvement of Drag Coefficient Calculation Under Near‐Neutral Conditions in Light Winds Over land

Liu

Gao

et al. 2020

JGR Atmospheres

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By analyzing the data collected over a rice paddy field in China, the occurrence of large drag coefficient in light winds (U ≤ 1ms −1) under near-neutral conditions (−0.1 ≤ z/L ≤ 0.1) is analyzed in this study. It is found that, with the use of either vector-or scalar-averaged wind speed, the drag coefficient under near-neutral conditions (C DN) always increases with the decrease of wind speed. Such behavior of C DN cannot be interpreted by the change of aerodynamic roughness length z 0 because it would need to be enlarged by an order of magnitude. While in light winds, the nonlocal transport, which is caused by large-scale eddies and overlooked by traditional Monin-Obukhov Similarity theory, is found to be the main cause of increased C DN. At last, a fixing term related to nonlocal effects is proposed based on our observation, and its applicability is verified with two AmeriFlux observation sites with a landscape of forest and savanna, respectively. Plain Language Summary According to the Monin-Obukhov Similarity (MOS) theory, the drag coefficient over land under near-neutral conditions (C DN) should be a constant and independent of wind speed because of the static surface roughness elements. However, the abnormal increase of C DN in light winds has been reported in many observations. In this study, we first examine the characteristics and mechanisms of the increased C DN in light winds. We conclude that the nonlocal transport caused by large-scale eddies is the major cause for the increased C DN in light winds. Furthermore, to successfully predict the variation of C DN with wind speed within MOS framework, we propose a fixing term related to nonlocal effects with our rice paddy observations, and the applicability of this fixing term is verified by two AmeriFlux observation sites with a landscape of forest and savanna, respectively. LIU ET AL.

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Section: Introductionmentioning

confidence: 99%

Improvement of Drag Coefficient Calculation Under Near‐Neutral Conditions in Light Winds Over land

Liu

Gao

et al. 2020

JGR Atmospheres

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“…the surface, and it plays an important role in the transport of momentum in the boundary layer. Patil et al (2016) reported that the frictional velocity increases with increasing wind speed under lower wind speed conditions in the surface layer. Thus, we focused on the variations in the wind speed (Figs.…”

Section: Effects Of Patch-induced Circulation On the Turbulent Intensity And Heat Fluxmentioning

confidence: 99%

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

Zhang

Huang

et al. 2021

Preprint

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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.

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“…The frictional velocity (u * ) is a critical parameter in the turbulence exchange near the surface, and it plays an important role in the transport of momentum in the boundary layer. Patil et al (2016) reported that the frictional velocity increases with wind speed under lower wind speed conditions in the surface layer. Thus, we focused on the variations in the wind speed (Fig.…”

Section: Turbulence In the Surface Layermentioning

confidence: 99%

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

Zhang

Huang

et al. 2021

Atmos. Chem. Phys.

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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.

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The influence of wind speed on surface layer stability and turbulent fluxes over southern Indian peninsula station

Cited by 8 publications

References 35 publications

Improvement of Drag Coefficient Calculation Under Near‐Neutral Conditions in Light Winds Over land

Improvement of Drag Coefficient Calculation Under Near‐Neutral Conditions in Light Winds Over land

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

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

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