Upscaling and Downscaling—A Regional View of the Soil–Plant–Atmosphere Continuum

Anderson, Martha C.; Kustas, William P.

doi:10.2134/agronj2003.1408

Cited by 113 publications

(77 citation statements)

References 108 publications

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“…Surface heterogeneity is fundamentally an issue of scale, in the sense of modeling and observational resolution (Brunsell and Gillies, 2003;Raupach and Finnigan, 1995;Anderson et al, 2003). Numerous efforts, ranging from the effective parameters technique (Lhomme et al, 1994;Chehbouni et al, 1995) to the mosaic approach (Koster and Suarez, 1992), have attempted to address the issue of scaling land surface parameters to ascertain areally averaged fluxes.…”

Section: Introductionmentioning

confidence: 99%

Surface heterogeneity impacts on boundary layer dynamics via energy balance partitioning

Brunsell

Mechem

Anderson³

2011

Atmos. Chem. Phys.

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Abstract. The role of land-atmosphere interactions under heterogeneous surface conditions is investigated in order to identify mechanisms responsible for altering surface heat and moisture fluxes. Twelve coupled land surface -large eddy simulation scenarios with four different length scales of surface variability under three different horizontal wind speeds are used in the analysis. The base case uses Landsat ETM imagery over the Cloud Land Surface Interaction Campaign (CLASIC) field site for 3 June 2007. Using wavelets, the surface fields are band-pass filtered in order to maintain the spatial mean and variances to length scales of 200 m, 1600 m, and 12.8 km as lower boundary conditions to the model (approximately 0.25, 1.2 and 9.5 times boundary layer height). The simulations exhibit little variation in net radiation. Rather, there is a pronounced change in the partitioning of the surface energy between sensible and latent heat flux. The sensible heat flux is dominant for intermediate surface length scales. For smaller and larger scales of surface heterogeneity, which can be viewed as being more homogeneous, the latent heat flux becomes increasingly important. The simulations showed approximately 50 Wm −2 difference in the spatially averaged latent heat flux. The results reflect a general decrease of the Bowen ratio as the surface conditions transition from heterogeneous to homogeneous. Air temperature is less sensitive to variations in surface heterogeneity than water vapor, which implies that the role of surface heterogeneity may be to maximize convective heat fluxes through modifying and maintaining local temperature gradients. More homogeneous surface conditions (i.e. smaller length scales), on the other hand, tend to maximize latent heat flux. The intermediate scale (1600 m) this does not hold, and is a more complicated interaction of scales.Correspondence to: N. A. Brunsell (brunsell@ku.edu) Scalar vertical profiles respond predictably to the partitioning of surface energy. Fourier spectra of the vertical wind speed, air temperature and specific humidity (w,T andq) and associated cospectra (wT ,wq andTq), however, are insensitive to the length scale of surface heterogeneity, but the near surface spectra are sensitive to the mean wind speed.

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Section: Introductionmentioning

confidence: 99%

Surface heterogeneity impacts on boundary layer dynamics via energy balance partitioning

Brunsell

Mechem

Anderson³

2011

Atmos. Chem. Phys.

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“…Accurate quantification of the amount of evapotranspiration and its spatial distribution is important in research in fields of hydrology, agronomy and meteorology (Avissar and Pielke, 1989;Anderson et al, 2003;Moran, 2004). This information aids in precision irrigation, determining crop water stress and water use of vulnerable ecosystems, and predicting weather and climate change.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the Surface Energy Balance System (SEBS) applied to ASTER imagery with flux-measurements at the SPARC 2004 site (Barrax, Spain)

Kwast

Timmermans

Gieske

et al. 2009

Hydrol. Earth Syst. Sci.

100

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Abstract. Accurate quantification of the amount and spatial variation of evapotranspiration is important in a wide range of disciplines. Remote sensing based surface energy balance models have been developed to estimate turbulent surface energy fluxes at different scales. The objective of this study is to evaluate the Surface Energy Balance System (SEBS) model on a landscape scale, using tower-based flux measurements at different land cover units during an overpass of the ASTER sensor over the SPARC 2004 experimental site in Barrax (Spain). A sensitivity analysis has been performed in order to investigate to which variable the sensible heat flux is most sensitive. Taking into account their estimation errors, the aerodynamic parameters (h c , z 0M and d 0 ) can cause large deviations in the modelling of sensible heat flux. The effect of replacement of empirical derivation of these aerodynamic parameters in the model by field estimates or literature values is investigated by testing two scenarios: the Empirical Scenario in which empirical equations are used to derive aerodynamic parameters and the Field Scenario in which values from field measurements or literature are used to replace the empirical calculations of the Empirical Scenario. In the case of a homogeneous land cover in the footprints of the measurements, the Field Scenario only resulted in a small improvement, compared to the Empirical Scenario. The Field Scenario can even worsen the result in the case of heterogeneous footprints, by creating sharp borders related to the land cover map. In both scenarios modelled fluxes correspond Correspondence to: J. van der Kwast (hans.vanderkwast@vito.be) better with flux measurements over uniform land cover compared to cases where different land covers are mixed in the measurement footprint. Furthermore SEBS underestimates sensible heat flux especially over dry and sparsely vegetated areas, which is common in single-source models.

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“…The primary radiometric signal is the morning surface temperature rise, while the ABL model component uses only the general slope (lapse rate) of the atmospheric temperature profile (Anderson et al, 1997), which is more reliably analyzed from synoptic radiosonde data than is the absolute temperature reference. To map fluxes at higher resolution than afforded by geostationary satellites (typically 5-10 km) a flux disaggregation technique referred to as DisALEXI (Norman et al, 2003) can be applied. DisALEXI is a nested modeling approach that uses air temperature diagnosed by ALEXI along with high resolution LAI and T rad information from polar orbiting instruments like Landsat or MODIS or aircraft, normalized to conserve H at the GOES pixel scale.…”

Section: Model Descriptionmentioning

confidence: 99%

Characterizing the multi–scale spatial structure of remotely sensed evapotranspiration with information theory

Brunsell

Anderson²

2011

Biogeosciences

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Abstract.A more thorough understanding of the multi-scale spatial structure of land surface heterogeneity will enhance understanding of the relationships and feedbacks between land surface conditions, mass and energy exchanges between the surface and the atmosphere, and regional meteorological and climatological conditions. The objectives of this study were to (1) quantify which spatial scales are dominant in determining the evapotranspiration flux between the surface and the atmosphere and (2) to quantify how different spatial scales of atmospheric and surface processes interact for different stages of the phenological cycle. We used the ALEXI/DisALEXI model for three days (DOY 181, 229 and 245) in 2002 over the Ft. Peck Ameriflux site to estimate the latent heat flux from Landsat, MODIS and GOES satellites. We then applied a multiresolution information theory methodology to quantify these interactions across different spatial scales and compared the dynamics across the different sensors and different periods. We note several important results: (1) spatial scaling characteristics vary with day, but are usually consistent for a given sensor, but (2) different sensors give different scalings, and (3) the different sensors exhibit different scaling relationships with driving variables such as fractional vegetation and near surface soil moisture. In addition, we note that while the dominant length scale of the vegetation index remains relatively constant across the dates, the contribution of the vegetation index to the derived latent heat flux varies with time. We also note that length scales determined from MODIS are consistently larger than those determined from Landsat, even at scales that should be detectable by MODIS. This may imply an inability of the MODIS sensor to accurately determine the fine scale spaCorrespondence to: N. A. Brunsell (brunsell@ku.edu) tial structure of the land surface. These results aid in identifying the dominant cross-scale nature of local to regional biosphere-atmosphere interactions.

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Upscaling and Downscaling—A Regional View of the Soil–Plant–Atmosphere Continuum

Cited by 113 publications

References 108 publications

Surface heterogeneity impacts on boundary layer dynamics via energy balance partitioning

Surface heterogeneity impacts on boundary layer dynamics via energy balance partitioning

Evaluation of the Surface Energy Balance System (SEBS) applied to ASTER imagery with flux-measurements at the SPARC 2004 site (Barrax, Spain)

Characterizing the multi–scale spatial structure of remotely sensed evapotranspiration with information theory

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