Answer to Reviewer’s Comments 1 (RC1) (Anonymous referee #3) of the manuscript (acp-2016-714): Integrating canopy and large-scale atmospheric effects in convective boundary-layer dynamics during CHATS experiment

Abstract. By characterizing the dynamics of a convective boundary layer above a relatively sparse and uniform orchard canopy, we investigated the impact of the roughness sublayer (RSL) representation on the predicted diurnal variability of surface fluxes and state variables. Our approach combined numerical experiments, using an atmospheric mixed-layer model including a land surface-vegetation representation, and measurements from the Canopy Horizontal Array Turbulence Study (CHATS) field experiment near Dixon, California. The RSL is parameterized using an additional factor in the standard Monin-Obukhov Similarity Theory flux-profile relationships that takes into account the canopy’s influence on the atmospheric flow. We selected a representative case characterised by southerly wind conditions to ensure well-developed RSL over the orchard canopy. We then investigated the sensitivity of the diurnal variability of the boundary-layer dynamics to the changes in the RSL key scales, the canopy adjustment length scale, Lc, and the β = u*/|U| ratio at the top of the canopy, due to their stability and dependence on canopy structure. We found that the inclusion of the RSL parameterisation resulted in improved prediction of the diurnal evolution of the near-surface mean quantities (e.g. up to 50 % for the wind velocity) and transfer (drag) coefficients. We found relatively insignificant effects on the modelled surface fluxes (e.g. up to 5 % for the friction velocity, while 3 % for the sensible and latent heat), which is due to the compensating effect between the mean gradients and the drag coefficients, which are both largely affected by the RSL parameterisation. When varying Lc (from 10 to 20 m) and β (from 0.25 to 0.4), based on observational evidence, the predicted friction velocity is found to vary by up to 25 % and the modeled surface energy fluxes (SH and LE) vary up to 2 % and 9 %, respectively. Consequently, the boundary-layer height varies up to 6 %. Furthermore, our analysis indicated that to interpret the CHATS measurements above the canopy, the contributions of non-local effects such as entrainment, subsidence and the advection of heat and moisture over the CHATS site need to be taken into account.

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

Atmospheric Research ◽

10.1016/j.atmosres.2020.105250 ◽

2021 ◽

Vol 248 ◽

pp. 105250

Author(s):

Georgios Papangelis ◽

Maria Tombrou ◽

John Kalogiros

Keyword(s):

Boundary Layer ◽

Simulation Study ◽

Convective Boundary Layer ◽

Large Scale ◽

Layer Structure ◽

Surface Heterogeneity ◽

Convective Boundary ◽

Eddy Simulation ◽

Large Eddy ◽

Scale Surface

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Characterization of a boreal convective boundary layer and its impact on atmospheric chemistry during HUMPPA-COPEC-2010

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-9335-2012 ◽

2012 ◽

Vol 12 (19) ◽

pp. 9335-9353 ◽

Cited By ~ 30

Author(s):

H. G. Ouwersloot ◽

J. Vilà-Guerau de Arellano ◽

A. C. Nölscher ◽

M. C. Krol ◽

L. N. Ganzeveld ◽

...

Keyword(s):

Boundary Layer ◽

Atmospheric Chemistry ◽

Convective Boundary Layer ◽

Large Scale ◽

Spatial Scales ◽

Potential Temperature ◽

Chemical Species ◽

Convective Boundary ◽

The Impact

Abstract. We studied the atmospheric boundary layer (ABL) dynamics and the impact on atmospheric chemistry during the HUMPPA-COPEC-2010 campaign. We used vertical profiles of potential temperature and specific moisture, obtained from 132 radio soundings, to determine the main boundary layer characteristics during the campaign. We propose a classification according to several main ABL prototypes. Further, we performed a case study of a single day, focusing on the convective boundary layer, to analyse the influence of the dynamics on the chemical evolution of the ABL. We used a mixed layer model, initialized and constrained by observations. In particular, we investigated the role of large scale atmospheric dynamics (subsidence and advection) on the ABL development and the evolution of chemical species concentrations. We find that, if the large scale forcings are taken into account, the ABL dynamics are represented satisfactorily. Subsequently, we studied the impact of mixing with a residual layer aloft during the morning transition on atmospheric chemistry. The time evolution of NOx and O3 concentrations, including morning peaks, can be explained and accurately simulated by incorporating the transition of the ABL dynamics from night to day. We demonstrate the importance of the ABL height evolution for the representation of atmospheric chemistry. Our findings underscore the need to couple the dynamics and chemistry at different spatial scales (from turbulence to mesoscale) in chemistry-transport models and in the interpretation of observational data.

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Role of the residual layer and large-scale subsidence on the development and evolution of the convective boundary layer

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-13-31527-2013 ◽

2013 ◽

Vol 13 (12) ◽

pp. 31527-31562 ◽

Cited By ~ 3

Author(s):

E. Blay-Carreras ◽

D. Pino ◽

A. Van de Boer ◽

O. De Coster ◽

C. Darbieu ◽

...

Keyword(s):

Boundary Layer ◽

Mixed Layer ◽

Convective Boundary Layer ◽

Large Scale ◽

Temporal Evolution ◽

Residual Layer ◽

Mixing Ratio ◽

Convective Boundary ◽

Previous Night ◽

Morning Transition

Abstract. Observations, mixed-layer theory and the Dutch Large-Eddy Simulation model (DALES) are used to analyze the dynamics of the boundary layer during an intensive operational period (1 July 2011) of the Boundary Layer Late Afternoon and Sunset Turbulence campaign. Continuous measurements made by remote sensing and in situ instruments in combination with radio soundings, and measurements done by remotely piloted airplane systems and two aircrafts probed the vertical structure and the temporal evolution of the boundary layer during the campaign. The initial vertical profiles of potential temperature, specific humidity and wind, and the temporal evolution of the surface heat and moisture fluxes prescribed in the numerical simulations are inspired by some of these observations. The research focuses on the role played by the residual layer during the morning transition and by the large-scale subsidence on the evolution of the boundary layer. By using DALES, we show the importance of the dynamics of the boundary layer during the previous night in the development of the boundary layer at the morning. DALES numerical experiments including the residual layer are capable to model the observed sudden increase of the boundary-layer depth during the morning transition and the subsequent evolution of the boundary layer. The simulation shows a large increase of the entrainment buoyancy heat flux when the residual layer is incorporated into the mixed layer. We also examine how the inclusion of the residual layer above a shallow convective boundary layer modifies the turbulent kinetic energy budget. Large-scale subsidence mainly acts when the boundary layer is fully developed and, for the studied day, it is necessary to be considered to reproduce the afternoon observations. Additionally, we investigate how carbon dioxide (CO2) mixing ratio stored the previous night in the residual layer plays a fundamental role in the evolution of the CO2 mixing ratio during the following day.

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Integrating canopy and large-scale effects in the convective boundary-layer dynamics during the CHATS experiment

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-1623-2017 ◽

2017 ◽

Vol 17 (3) ◽

pp. 1623-1640 ◽

Cited By ~ 5

Author(s):

Metodija M. Shapkalijevski ◽

Huug G. Ouwersloot ◽

Arnold F. Moene ◽

Jordi Vilà-Guerau de Arrellano

Keyword(s):

Boundary Layer ◽

Latent Heat ◽

Convective Boundary Layer ◽

Friction Velocity ◽

Surface Fluxes ◽

Convective Boundary ◽

Diurnal Variability ◽

Drag Coefficients ◽

Boundary Layer Dynamics ◽

The Impact

Abstract. By characterizing the dynamics of a convective boundary layer above a relatively sparse and uniform orchard canopy, we investigated the impact of the roughness-sublayer (RSL) representation on the predicted diurnal variability of surface fluxes and state variables. Our approach combined numerical experiments, using an atmospheric mixed-layer model including a land-surface-vegetation representation, and measurements from the Canopy Horizontal Array Turbulence Study (CHATS) field experiment near Dixon, California. The RSL is parameterized using an additional factor in the standard Monin–Obukhov similarity theory flux-profile relationships that takes into account the canopy influence on the atmospheric flow. We selected a representative case characterized by southerly wind conditions to ensure well-developed RSL over the orchard canopy. We then investigated the sensitivity of the diurnal variability of the boundary-layer dynamics to the changes in the RSL key scales, the canopy adjustment length scale, Lc, and the β = u*/|U| ratio at the top of the canopy due to their stability and dependence on canopy structure. We found that the inclusion of the RSL parameterization resulted in improved prediction of the diurnal evolution of the near-surface mean quantities (e.g. up to 50 % for the wind velocity) and transfer (drag) coefficients. We found relatively insignificant effects on the modelled surface fluxes (e.g. up to 5 % for the friction velocity, while 3 % for the sensible and latent heat), which is due to the compensating effect between the mean gradients and the drag coefficients, both of which are largely affected by the RSL parameterization. When varying Lc (from 10 to 20 m) and β (from 0.25 to 0.4 m), based on observational evidence, the predicted friction velocity is found to vary by up to 25 % and the modelled surface-energy fluxes (sensible heat, SH, and latent heat of evaporation, LE) vary up to 2 and 9 %. Consequently, the boundary-layer height varies up to 6 %. Furthermore, our analysis indicated that to interpret the CHATS measurements above the canopy, the contributions of non-local effects such as entrainment, subsidence and the advection of heat and moisture over the CHATS site need to be taken into account.

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A New Mixing-Length Formulation for the Parameterization of Dry Convection: Implementation and Evaluation in a Mesoscale Model

Monthly Weather Review ◽

10.1175/mwr2808.1 ◽

2004 ◽

Vol 132 (11) ◽

pp. 2698-2707 ◽

Cited By ~ 11

Author(s):

J. Teixeira ◽

J. P. Ferreira ◽

P. M. A. Miranda ◽

T. Haack ◽

J. Doyle ◽

...

Keyword(s):

Boundary Layer ◽

Convective Boundary Layer ◽

Large Scale ◽

Mesoscale Model ◽

Climate Impact ◽

Layer Growth ◽

Mixing Length ◽

Convective Boundary ◽

Realistic Representation ◽

New Formulation

Abstract A realistic representation of the evolution of the dry convective boundary layer in mesoscale and large-scale atmospheric models has been an elusive goal for many years. In this paper the performance of a new mixing-length formulation for the dry convective boundary layer is evaluated in the context of the Coupled Ocean– Atmosphere Mesoscale Prediction System (COAMPS). In this new formulation, the mixing length is proportional to a time scale and to the square root of the turbulent kinetic energy. The model results are tested against observations from the Climate Impact of Changes in Land Use (CICLUS) field experiment in the south of Portugal. It is shown that COAMPS with the new formulation produces a more realistic simulation of the boundary layer growth. A data assimilation experiment performed with COAMPS shows that the improvements provided by the new formulation are significant, particularly in terms of the humidity vertical distribution. Finally, one-dimensional simulations are used to confirm that the new formulation provides more accurate results because of a more realistic representation of the entrainment and of the vertical mixing in general.

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