The Heat-Flux Imbalance: The Role of Advection and Dispersive Fluxes on Heat Transport Over Thermally Heterogeneous Terrain

Morrison, T.; Pardyjak, Eric R.; Mauder, Matthias; Calaf, Marc

doi:10.1007/s10546-021-00687-1

Cited by 15 publications

(20 citation statements)

References 37 publications

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“…To obtain representative quantities for a certain area with single point measurements, assumptions of homogeneity and ergodicity need to be made. It has recently been shown that coherent structures such as secondary circulations can violate the ergodicity assumption and lead to errors in the EC method (Mauder et al, 2020;Morrison et al, 2022). Only few experiments exist where multiple sonic anemometers have been installed over a wide area and heights above the surface layer, due to the large logistical effort.…”

Section: Introductionmentioning

confidence: 99%

Towards vertical wind and turbulent flux estimation with multicopter uncrewed aircraft systems

Wildmann

Wetz

2022

Atmos. Meas. Tech.

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Abstract. Vertical wind velocity and its fluctuations are essential parameters in the atmospheric boundary layer (ABL) to determine turbulent fluxes and scaling parameters for ABL processes. The typical instrument to measure fluxes of momentum and heat in the surface layer are sonic anemometers. Without the infrastructure of meteorological masts and above the typical heights of these masts, in situ point measurements of the three-dimensional wind vector are hardly available. We present a method to obtain the three-dimensional wind vector from avionic data of small multicopter uncrewed aircraft systems (UAS). To achieve a good accuracy in both average and fluctuating parts of the wind components, calibrated motor thrusts and measured accelerations by the UAS are used. In a validation campaign, in comparison to sonic anemometers on a 99 m mast, accuracies below 0.2 m s−1 are achieved for the mean wind components and below 0.2 m2 s−2 for their variances. The spectra of variances and covariances show good agreement with the sonic anemometer up to 1 Hz temporal resolution. A case study of continuous measurements in a morning transition of a convective boundary layer with five UAS illustrates the potential of such measurements for ABL research.

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Section: Introductionmentioning

confidence: 99%

Towards vertical wind and turbulent flux estimation with multicopter uncrewed aircraft systems

Wildmann

Wetz

2022

Atmos. Meas. Tech.

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“…(2004) a perfect balance yields a value of zero, meaning that when

I

= 1 for Morrison et al . (2021) and

I

= 0 for Kanda et al . (2004) all of the energy is contained in the turbulent contributions.…”

Section: Introductionmentioning

confidence: 90%

“…In this transformation, we introduce a reference temperature (T ref ) in the advection term to maintain the physical robustness of the expression, due to the inability to measure conservation of mass accurately with a coarse stencil (Morrison et al, 2021). Note that this reference temperature should be taken as the volumetric average temperature of the control volume.…”

Section: 𝜕T 𝜕T ⏟⏟⏟mentioning

confidence: 99%

“…Here, the dispersive flux term (⟨u ′′ T ′′ ⟩) arises as a result of the spatial averaging operation used on each face of the control volume (Morrison et al, 2021). This term provides the contribution of subgrid spatial fluctuations of the mean (i.e., time-averaged) flow, and it is therefore representative of the flux contribution by mean spatial heterogeneity in each face of the CV.…”

Section: 𝜕T 𝜕T ⏟⏟⏟mentioning

confidence: 99%

“…Note that the definition given by Morrison et al . (2021) yields a perfect balance when

I

is unity, whereas using the definition of Kanda et al . (2004) a perfect balance yields a value of zero, meaning that when

I

= 1 for Morrison et al .…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A full three‐dimensional surface energy balance over a desert playa

Morrison

Calaf

Pardyjak

2023

Quart J Royal Meteoro Soc

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For decades, closure of the surface energy balance (SEB) has remained an outstanding problem for the atmospheric boundary layer (ABL) community. Despite many attempts at achieving closure following systematic approaches, universal closure remains elusive and only on rare occasions is it achieved. In this work, data from the unique spatial deployment of sensors from the Idealized Planar Array experiment for Quantifying Spatial heterogeneity (IPAQS 2019) field campaign are used to compute the three‐dimensional SEB. Results are compared with the traditional one‐dimensional SEB approach. The three‐dimensional SEB uses an integrated approach derived from the temperature tendency equation for a 400 m prefix×$$ \times $$ 400 m prefix×$$ \times $$ 2 m control volume over near‐canonical terrain, where the only complexities arise from time‐persistent surface thermal heterogeneities. Often neglected transport terms, such as advection and dispersive fluxes, are assessed and studied. Results show that, when using a three‐dimensional approach, it is possible to obtain an improved closure of the SEB during convective periods that can attain residual values of the order of accuracy of the instrumentation. Lastly, a theoretical development to account for the flux imbalance is presented that shows a promising approach for scaling the contribution of mean advective transport using onsite measurable variables.

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Large‐eddy simulation of soil moisture heterogeneity‐induced secondary circulation with ambient winds

Zhang

Poll

Kollet

2023

Quart J Royal Meteoro Soc

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Land surface heterogeneity in conjunction with ambient winds influences the convective atmospheric boundary layer by affecting the distribution of incoming solar radiation and forming secondary circulations. This study performed coupled large‐eddy simulation (ICON‐LEM) with a land surface model (TERRA‐ML) over a flat river corridor mimicked by soil moisture heterogeneity to investigate the impact of ambient winds on secondary circulations. The coupled model employed double‐periodic boundary conditions with a spatial scale of 4.8 km. All simulations used the same idealized initial atmospheric conditions with constant incident radiation of 700 W⋅m−2 and various ambient winds with different speeds (0 to 16 m⋅s−1) and directions (e.g., cross‐river, parallel‐river, and mixed). The atmospheric states are decomposed into ensemble‐averaged, mesoscale, and turbulence. The results show that the secondary circulation structure persists under the parallel‐river wind conditions independently of the wind speed but is destroyed when the cross‐river wind is stronger than 2 m⋅s−1. The soil moisture and wind speed determine the influence on the surface energy distribution independent of the wind direction. However, secondary circulations increase advection and dispersive heat flux while decreasing turbulent energy flux. The vertical profiles of the wind variance reflect the secondary circulation, and the maximum value of the mesoscale vertical wind variance indicates the secondary circulation strength. The secondary circulation strength positively scales with the Bowen ratio, stability parameter (−Zi/L), and thermal heterogeneity parameter under cross‐river wind and mixed wind conditions. The proposed similarity analyses and scaling approach provide a new quantitative perspective on the impact of the ambient wind under heteronomous soil moisture conditions on secondary circulation.

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The Heat-Flux Imbalance: The Role of Advection and Dispersive Fluxes on Heat Transport Over Thermally Heterogeneous Terrain

Cited by 15 publications

References 37 publications

Towards vertical wind and turbulent flux estimation with multicopter uncrewed aircraft systems

Towards vertical wind and turbulent flux estimation with multicopter uncrewed aircraft systems

A full three‐dimensional surface energy balance over a desert playa

Large‐eddy simulation of soil moisture heterogeneity‐induced secondary circulation with ambient winds

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