 |
| Titel |
The impact of in-canopy wind profile formulations on heat flux estimation in an open orchard using the remote sensing-based two-source model |
| VerfasserIn |
C. Cammalleri, M. C. Anderson, G. Ciraolo, G. D'Urso, W. P. Kustas, G. Loggia, M. Minacapilli |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1027-5606
|
| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 14, no. 12 ; Nr. 14, no. 12 (2010-12-22), S.2643-2659 |
| Datensatznummer |
250012537
|
| Publikation (Nr.) |
 copernicus.org/hess-14-2643-2010.pdf |
|
|
|
|
|
| Zusammenfassung |
| For open orchard and vineyard canopies containing significant fractions of
exposed soil (>50%), typical of Mediterranean agricultural regions, the
energy balance of the vegetation elements is strongly influenced by heat
exchange with the bare soil/substrate. For these agricultural systems a
"two-source" approach, where radiation and turbulent exchange between the
soil and canopy elements are explicitly modelled, appears to be the only
suitable methodology for reliably assessing energy fluxes. In strongly
clumped canopies, the effective wind speed profile inside and below the
canopy layer can strongly influence the partitioning of energy fluxes
between the soil and vegetation components. To assess the impact of
in-canopy wind profile on model flux estimates, an analysis of three
different formulations is presented, including algorithms from Goudriaan
(1977), Massman (1987) and Lalic et al. (2003). The in-canopy wind profile
formulations are applied to the thermal-based two-source energy balance
(TSEB) model developed by Norman et al. (1995) and modified by Kustas and
Norman (1999). High resolution airborne remote sensing images, collected
over an agricultural area located in the western part of Sicily (Italy)
comprised primarily of vineyards, olive and citrus orchards, are used to
derive all the input parameters needed to apply the TSEB. The images were
acquired from June to October 2008 and include a relatively wide range of
meteorological and soil moisture conditions. A preliminary sensitivity
analysis of the three wind profile algorithms highlights the dependence of
wind speed just above the soil/substrate to leaf area index and canopy
height over the typical range of canopy properties encountered in these
agricultural areas. It is found that differences among the models in wind
just above the soil surface are most significant under sparse and medium
fractional cover conditions (15–50%). The TSEB model heat flux estimates
are compared with micro-meteorological measurements from a small aperture
scintillometer and an eddy covariance tower collected over an olive orchard
characterized by moderate fractional vegetation cover (≈35%)
and relatively tall crop (≈3.5 m). TSEB fluxes for the 7
image acquisition dates generated using both the Massman and Goudriaan
in-canopy wind profile formulations give close agreement with measured
fluxes, while the Lalic et al. equations yield poor results. The Massman
wind profile scheme slightly outperforms that of Goudriaan, but it requires
an additional parameter accounting for the roughness sub-layer of the
underlying vegetative surface. The analysis also suggests that within-canopy
wind profile model discrepancies become important, in terms of impact on
modelled sensible heat flux, only for sparse canopies with moderate
vegetation coverage. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|