A New Sensitivity Analysis and Solution Method for Scintillometer Measurements of Area-Averaged Turbulent Fluxes

Gruber, Matthew A.; Fochesatto, G. J.

doi:10.1007/s10546-013-9835-9

Cited by 10 publications

(24 citation statements)

References 28 publications

(36 reference statements)

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“…This result is the average value of the sensitivity along the whole length of the path, and it converges to the same result for all paths. The sensitivity function in figure 7 is compatible with the one-dimensional sensitivity function for flat terrain seen in Gruber and Fochesatto (2013).…”

Section: Resultssupporting

confidence: 60%

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Sensitivity of large-aperture scintillometer measurements of area-average heat fluxes to uncertainties in topographic heights

Gruber¹,

Fochesatto²,

Hartogensis³

2014

Preprint

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Displaced-beam scintillometer measurements of the turbulence innerscale length lo and refractive index structure function C 2 n resolve area-average turbulent fluxes of heat and momentum through the Monin-Obukhov similarity equations. Sensitivity studies have been produced for the use of displaced-beam scintillometers over flat terrain. Many real field sites feature variable topography. We develop here an analysis of the sensitivity of displaced-beam scintillometer derived sensible heat fluxes to uncertainties in spacially distributed topographic measurements. Sensitivity is shown to be concentrated in areas near the center of the beam and where the underlying topography is closest to the beam height. Uncertainty may be decreased by taking precise topographic measurements in these areas.

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Section: Resultssupporting

confidence: 60%

“…The sensitivity function S H S ,z for this measurement strategy over flat terrain has been evaluated in Gruber and Fochesatto (2013).…”

Section: Introductionmentioning

confidence: 99%

Sensitivity of large-aperture scintillometer measurements of area-average heat fluxes to uncertainties in topographic heights

Gruber¹,

Fochesatto²,

Hartogensis³

2014

Preprint

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“…For instance, from 1000 to 1700 AKST, it is typical for the temperature at SC 1 m to be most similar to DC 3 m, while SC 2 m is most similar to DC 12 m and 7 m, and SC 4 m and 8 m are most similar to DC 24 m (Figure , inset). Therefore, changes in canopy height and density impact the temperature distribution within and above the forest, consequently affecting thermodynamic processes at small scales; thus, upscaling local processes requires accurate spatial data on canopy architecture [ Gruber and Fochesatto , ; Gruber et al ., ].…”

Section: Resultsmentioning

confidence: 99%

Temperature regimes and turbulent heat fluxes across a heterogeneous canopy in an Alaskan boreal forest

et al. 2015

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We evaluate local differences in thermal regimes and turbulent heat fluxes across the heterogeneous canopy of a black spruce boreal forest on discontinuous permafrost in interior Alaska. The data were taken during an intensive observing period in the summer of 2013 from two micrometeorological towers 600 m apart in a central section of boreal forest, one in a denser canopy (DC) and the other in a sparser canopy, but under approximately similar atmospheric boundary layer (ABL) flow conditions. Results suggest that on average 34% of the half-hourly periods in a day are nonstationary, primarily during night and during ABL transitions. Also, thermal regimes differ between the two towers; specifically between midnight and 0500 Alaska Standard Time (AKST) it is about 3°C warmer at DC. On average, the sensible heat flux at DC was greater. For midday periods, the difference between those fluxes exceeded 30% of the measured flux and over 30 W m À2 in magnitude more than 60% of the time. These differences are due to higher mechanical mixing as a result of the increased density of roughness elements at DC. Finally, the vertical distribution of turbulent heat fluxes verifies a maximum atop the canopy crown (2.6 h) when compared with the subcanopy (0.6 h) and above canopy (5.1 h), where h is the mean canopy height. We argue that these spatial and vertical variations of sensible heat fluxes result from the complex scale aggregation of energy fluxes over a heterogeneous canopy.

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“…Sensible heat flux was measured locally (i.e., ecosystem scale) by means of and eddy-covariance (EC) instrument and processed considering signal distortions under all weather conditions [27] and, at landscape scale, based on a large aperture scintillometer (LAS) [28][29][30].…”

Section: Field Experimentsmentioning

confidence: 99%

Evapotranspiration in Northern Agro-Ecosystems: Numerical Simulation and Experimental Comparison

Ruairuen¹,

Fochesatto²,

Bittelli³

et al. 2017

Current Perspective to Predict Actual Evapotranspiration

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Evapotranspiration and near-surface soil moisture dynamics are key-entangled variables regulating flux at the surface-atmosphere interface. Both are central in improving mass and energy balances in agro ecosystems. However, under the extreme conditions of high-latitude soils and weather pattern variability, the implementation of such coupled liquid and vapor phase numerical simulation remain to be tested. We consider the nonisothermal solution of the vapor flux equation that accounts for the thermally driven water vapor transport and phase changes. Fully coupled flux model outputs are compared and contrasted against field measurements of soil temperature, heat flux, water content, and evaporation in a subarctic agroecosystem in Alaska. Two welldefined hydro-meteorological situations were selected: dry and wet periods. Numerical simulation was forced by time series of incoming global solar radiation and atmospheric surface layer thermodynamic parameters: surface wind speed, ambient temperature, relative humidity, precipitation, and soil temperature and soil moisture. In this simulation, soil parameters changing in depth and time are considered as dynamically adjusted boundary conditions for solving the set of coupled differential equations. Results from this evaluation give good correlation of modeled and observed data in ) during the dry period. On the other hand, a poor agreement was obtained in the radiative fluxes and turbulent fluxes during the wet period due to the lack of representation in the radiation field and differences in soil dynamics across the landscape.

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A New Sensitivity Analysis and Solution Method for Scintillometer Measurements of Area-Averaged Turbulent Fluxes

Cited by 10 publications

References 28 publications

Sensitivity of large-aperture scintillometer measurements of area-average heat fluxes to uncertainties in topographic heights

Sensitivity of large-aperture scintillometer measurements of area-average heat fluxes to uncertainties in topographic heights

Temperature regimes and turbulent heat fluxes across a heterogeneous canopy in an Alaskan boreal forest

Evapotranspiration in Northern Agro-Ecosystems: Numerical Simulation and Experimental Comparison

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