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Titel |
Correlation between satellite vegetation indices and crop coefficients |
VerfasserIn |
A. L. Russo, T. Simoniello, M. Greco, G. Squicciarrino, M. Lanfredi, M. Macchiato |
Konferenz |
EGU General Assembly 2010
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 12 (2010) |
Datensatznummer |
250043430
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Zusammenfassung |
Accurate estimations of plant evapotranspiration and its spatial distribution are fundamental
for the evaluation of vegetation water stress. Satellite remote sensing techniques represent
precious tools for the evapotranspiration estimations at large scale. Many studies are based on
the use of thermal signals as inputs for energy balance equations that are solved to estimate
evapotranspiration (e.g., Bastiaanssen et al., 1998; Ayenew, 2003). This approach requires
many inputs and a detailed theoretical background knowledge. Other works (e.g., Calera at
al., 2005; Gonzalez-Dugo and Mateos, 2008) explored a second approach based
on the FAO method that estimates the plant evapotranspiration by weighting the
reference evapotranspiration with a crop coefficient (Kc) derived from satellite
based vegetation indices. Such studies mainly investigated the usefulness of high
resolution satellite data, such as Quickbird, Ikonos, TM, that in spite of the high
spatial sampling, are not suitable for a dense temporal sampling. In order to generate
spatially distributed values of Kc that capture field-specific crop development, we
investigated the usefulness of vegetation indices derived from a time series (2005-2008) of
medium resolution MODIS data. We analyzed the spatial and temporal correlation
of different indices (NDVI, EVI, and WDVI) with crop coefficients available in
literature for different herbaceous and arboreal cultivations present in the study area
(Basilicata region, southern Italy). To take into account the background of the cultivation
covers, we weighted the Kc by considering the vegetation fraction within each
the pixel. By evaluating altogether the cultivations, we found that the correlation
increases during the growing season (R2 > 0.80) whereas it decreases during the
winter period (R2 < 0.30). Such a behaviour seems to be directly connected with the
dependence of vegetation indices on temperature that showed a specular correlation
cycle. The analysis performed for each cultivation highlighted that NDVI provided
quite high correlation for all the investigated cultivation with maximum values
for wheat (R2 = 0.89) and vineyards (R2 = 0.83). For the cultivation with more
homogeneous canopy, e.g. kiwifruit, the best performing index was the WDVI showing
a determination coefficient of 0.90; whereas its performances for vineyards and
mixed olive cultivations were not satisfactory (R2 < 0.40). The EVI showed a
behaviour similar to WDVI with slightly lower correlation values. The obtained
results highlight the capability of medium resolution satellites for dynamically
estimating crop coefficients and so for improving water balance assessment by
taking into account the actual status of vegetation instead of expected and tabulated
Kc-values.
Ayenew, T., 2003. Evapotranspiration estimation using thematic mapper spectral
satellite data in the Ethiopian rift and adjacent highlands, Journal of Hydrology, 279:
83-93
Bastiaanssen, W.G.M., Menenti, M., Feddes, R.A., Holstlag, A.A.M., 1998. A remote
sensing surface energy balance algorithm for land (SEBAL). 1. Formulation, Journal of
Hydrology, 212–213: 198-212.
Calera A., Jochum A., Cuesta Garcia A., Montoro Rodriguez A., Lopez Fuster P., 2005.
Irrigation management from space: Towards user-friendly products, Irrigation and Drainage
Systems, 19: 337-353.
Gonzalez-Dugo M.P. and Mateos L., 2008. Spectral vegetation indices for benchmarking
water productivity of irrigated cotton and sugarbeet crops, Agricultural Water Management,
95: 48-58. |
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