The Saharan convective boundary layer structure over large scale surface heterogeneity: A large eddy simulation study

Papangelis, Georgios; Tombrou, M.; Kalogiros, John

doi:10.1016/j.atmosres.2020.105250

Cited by 4 publications

(3 citation statements)

References 53 publications

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“…6a and d). It should be noted that there is larger TKE over the patch/patches (below 0.2z i ) as the similar pattern of TKE in Papangelis et al (2021), from which the thermal internal boundary layer (TIBL) can be recognized (Fig. 6e and f).…”

Section: Effects Of the Surface Heat Flux Anomalies And Background Wind On The Tkementioning

confidence: 74%

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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Section: Effects Of the Surface Heat Flux Anomalies And Background Wind On The Tkementioning

confidence: 74%

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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“…No radiation, land surface, boundary layer, or cumulus parameterization scheme is used. Numerous LES and numerical studies conducted at model resolution across the gray zone have employed sophisticated parameterizations such as radiation schemes and/or land surface models (e.g., Connolly et al., 2021; Liu et al., 2020; Mazzaro et al., 2017; Papangelis et al., 2021; Pedruzo‐Bagazgoitia et al., 2019; Xu et al., 2021). Some were intended to improve the overall performance of LES nested within a mesoscale model.…”

Section: Numerical Experimentsmentioning

confidence: 99%

Response of Moist Convection to the Spectral Feature of the Surface Flux Field at Model Resolution Across the Gray Zone

Ryu

Kang

2022

JGR Atmospheres

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The Weather Research and Forecasting model is run at the effective resolution Δf across the gray zone, or the “terra incognita”, at which Δf ∼ l, where l is the scale of energy‐containing turbulent eddies. We examine the developments of afternoon moist convection over different multiscale features of the surface flux field as a function of the model grid spacing Δ that varies from 100 m to 1 km. Numerical experiments demonstrate that the model performs better under heterogeneous than homogeneous surface conditions in the gray zone in terms of the spatial distribution of moist convection. This improved performance is due to the explicit resolvability of the mesoscale temperature and humidity perturbations, which are critical for the growth of deep moist convection over the heterogeneous surface condition. However, under both heterogeneous and homogeneous surface conditions, the timing and intensity of moist convection vary with the model resolution. Compared with that in the large eddy simulation at Δ = 100 m, the earlier onset of moist convection at coarser resolutions appears to be related to the overestimated total buoyancy fluxes and total kinetic energy near the surface. That is, the more intense vertical mixing near the surface might induce a warmer surface layer, which yields individual cell updrafts strong enough to penetrate the capping inversion. In addition, misrepresentation of the diluting effects of entrainment on the penetrating updrafts in coarser‐resolution simulations could be responsible for the rapid development of deep convection instead of a gradual transition from shallow to deep moist convection.

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“…For example, in the Gobi Desert, it is strong thermodynamic land‐surface processes that drive the formation of deep CBL of 3,000–4,000 m (Ma et al., 2011; Zhang et al., 2011), while in the Badain Jaran Desert, the near‐neutral residual layer (RL) connected with large‐scale temperature advection is crucial for the formation of deep CBL more than 3,000 m (Han et al., 2015; Zhao et al., 2018). In addition, the deep CBL with a depth of 6,000 m in the Sahara Desert is closely associated with the heterogeneous surface albedo (Huang et al., 2010; Marsham et al., 2008; Papangelis et al., 2021). However, existing studies on the deep CBL in the TD mainly focus on the description of the phenomenon and its vertical structure, while the physical processes for its formation remain unclear.…”

Section: Introductionmentioning

confidence: 99%

Turbulent Mechanisms for the Deep Convective Boundary Layer in the Taklimakan Desert

Zhang

et al. 2022

Geophysical Research Letters

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Taklimakan Desert (TD), the second-largest shifting sand desert in the world, is located in the central Tarim Basin, north of the Tibetan Plateau, and is surrounded by high mountains in the shape of the letter C (Figure S1 in Supporting Information S1). It is characterized by an extremely arid landscape and is the main source of mineral dust. Through the dynamic coupling with the Tibetan Plateau, the TD has significant implications for the downwind areas, which makes it a key climate region in

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The Saharan convective boundary layer structure over large scale surface heterogeneity: A large eddy simulation study

Cited by 4 publications

References 53 publications

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

Response of Moist Convection to the Spectral Feature of the Surface Flux Field at Model Resolution Across the Gray Zone

Turbulent Mechanisms for the Deep Convective Boundary Layer in the Taklimakan Desert

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