Cases-97: Late-Morning Warming And Moistening Of The Convective Boundary Layer Over The Walnut River Watershed

LeMone, Margaret A.; Grossman, Robert L.; McMillen, R. T.; Liou, Kuo‐Nan; Ou, S. C.; McKeen, S. A.; Angevine, W. M.; Ikeda, Kyoko; Chen, Fei

doi:10.1023/a:1015569104180

Cited by 58 publications

(57 citation statements)

References 51 publications

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“…This is consistent with the result of the LEMs study by Kang and Davis (2009) and is also supported by observations (e.g. Mahrt et al, 1994;LeMone et al, 2002;Kang et al, 2007;Lenschow and Sun, 2007;Taylor et al, 2007). However, this weak mesoscale circulation may not be considered negligible, as stressed by Ek and Mahrt (1991).…”

Section: Experiments Surface Stylessupporting

confidence: 91%

Properties of a simulated convective boundary layer over inhomogeneous vegetation

Wang

Tian

Parker

et al. 2010

Quart J Royal Meteoro Soc

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Using a high-resolution boundary-layer model, effects of heterogeneity over a mesoscale flat domain are investigated through a series of idealised model simulations. In these simulations two different land surface types (bare soil and vegetation) are arranged in two different patterns. It is found that the effect of heterogeneity remains significant with geostrophic winds of 10 m s −1 . However, when the geostrophic wind direction is perpendicular to the alignment of the surface heterogeneities (with alignment here defined as the direction along the edges of a sequence of surface patches), higher winds tend to weaken the coherent circulations caused by the surface heterogeneities. The vertical winds generated by the mesoscale circulations associated with the surface heterogeneities are on the order of 0.5 cm s −1 . When the geostrophic wind direction is perpendicular to the alignment of the surface heterogeneities over a three-strip surface type, the mesoscale pattern in horizontal velocity is also pronounced, with significant fluctuations at the interfaces between two different surface patches. The heights at which the heterogeneity effects on potential temperature and winds vanish are well above the convective boundary layer top and reach at least 3.3 Z i under light winds, but depend on the wind speed and directions as well as the orientation of surface heterogeneities.Finally, the implications of the surface heterogeneity for initiation of deep convection have been explored for a surface consisting of two-dimensional strips of alternating soil and vegetated surfaces aligned in the north-south direction. For this surface pattern, the interaction between westerly background winds and the secondary circulation sets up conditions which favour the initiation of deep convection at the eastern, downwind edge of the soil strip.

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Section: Experiments Surface Stylessupporting

confidence: 91%

Properties of a simulated convective boundary layer over inhomogeneous vegetation

Wang

Tian

Parker

et al. 2010

Quart J Royal Meteoro Soc

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“…In contrast with previous analysis of the morning transition (e.g., Angevine et al, 2001;LeMone et al, 2002;Lapworth, 2006;Beare, 2008), we use a sensitivity analysis of the the numerical experiments to study the influence of the two processes in the evolution of the convective boundary layer.…”

Section: Discussionmentioning

confidence: 99%

“…LeMone et al (2002) analyzed data recorded during CASES-97 to study the warming and moistening of the atmosphere due to boundary-layer depth, wind direction, and surface heterogeneity during this period. Other authors (Sorbjan, 1996;Beare, 2008) analyzed the morning transition by using numerical models, such as LES, to study the relevance of different temperature lapse rate or the importance of domain sizes and grid length or by using MLM to study the impact of the atmospheric boundary layer dynamics on the atmospheric chemistry (Ouwersloot et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2014

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Abstract. Observations, mixed-layer theory and the DutchLarge-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 aircraft systems and two manned 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 models runs 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 of modeling the observed sudden increase of the boundary-layer depth during the morning transition and the subsequent evolution of the boundary layer. These simulations show a large increase of the entrainment buoyancy 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.Finally, we also investigate how carbon dioxide (CO 2 ) mixing ratio stored the previous night in the residual layer plays a fundamental role in the evolution of the CO 2 mixing ratio during the following day.

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“…Surface turbulent fluxes and boundary layer dynamics determine the daily evolution of temperature, moisture and other scalar quantities in the atmospheric boundary layer (Lemone et al, 2002). Focusing on the diurnal variability of CO 2 , some studies have improved our understanding about the influence of surface processes such as photosynthesis and respiration (Kim and Verma, 1990;Lloyd and Taylor, 1994;Jacobs and De Bruin, 1992;Baldocchi et al, 2001) but boundary layer development plays also a main role in determining the horizontal and vertical distribution of CO 2 (Denning et al, 1995;Wofsy et al, 1988;Yi et al, 2004;McGrathSpangler and Denning, 2010).…”

Section: Introductionmentioning

confidence: 99%

A conceptual framework to quantify the influence of convective boundary layer development on carbon dioxide mixing ratios

et al. 2012

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Abstract. Interpretation of observed diurnal carbon dioxide (CO 2 ) mixing ratios near the surface requires knowledge of the local dynamics of the planetary boundary layer. In this paper, we study the relationship between the boundary layer dynamics and the CO 2 budget in convective conditions through a newly derived set of analytical equations. From these equations, we are able to quantify how uncertainties in boundary layer dynamical variables or in the morning CO 2 distribution in the mixed-layer or in the free atmosphere (FA) influence the bulk CO 2 mixing ratio.We find that the largest uncertainty incurred on the midday CO 2 mixing ratio comes from the prescribed early morning CO 2 mixing ratios in the stable boundary layer, and in the free atmosphere. Errors in these values influence CO 2 mixing ratios inversely proportional to the boundary layer depth (h), just like uncertainties in the assumed initial boundary layer depth and surface CO 2 flux. The influence of uncertainties in the boundary layer depth itself is one order of magnitude smaller. If we "invert" the problem and calculate CO 2 surface exchange from observed or simulated CO 2 mixing ratios, the sensitivities to errors in boundary layer dynamics also invert: they become linearly proportional to the boundary layer depth.We demonstrate these relations for a typical well characterized situation at the Cabauw site in The Netherlands, and conclude that knowledge of the temperature and carbon dioxide profiles of the atmosphere in the early morning are of vital importance to correctly interpret observed CO 2 mixing ratios during midday.

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Cases-97: Late-Morning Warming And Moistening Of The Convective Boundary Layer Over The Walnut River Watershed

Cited by 58 publications

References 51 publications

Properties of a simulated convective boundary layer over inhomogeneous vegetation

Properties of a simulated convective boundary layer over inhomogeneous vegetation

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

A conceptual framework to quantify the influence of convective boundary layer development on carbon dioxide mixing ratios

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