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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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Record number 443986
Title Estimating ET using scintillometers and satellites in an irrigated vineyard in the Costa De Hermosillo, Sonora, Mexico
Author(s) Mulder, M.; Lopez-Ibarra, J.A.; Watts, C.J.; Rodriquez, J.C.; Hartogensis, O.K.; Moene, A.F.
Source In: Proceedings of a symposium held at Jackson Hole. - - p. 195 - 198.
Event Proceedings of a symposium held at Jackson Hole, Wyoming, USA, September 2010, 2010-09-27/2010-09-30
Department(s) Meteorology and Air Quality
WIMEK
Publication type Contribution in proceedings
Publication year 2013
Abstract Observation techniques for surface energy balance
components on kilometer scale. Several methods have been proposed to estimate ET over
large areas which combine Earth Observation Satellite data
with standard climate data. Here we use the Makkink
approach where incoming solar radiation is obtained by
calculating exoatmospheric incoming solar radiation, using
visible data from GOES West to estimate cloudiness and
16-day composite MODIS Enhanced Vegetation Index data to
estimate fractional vegetation cover. This methodology can be
used operationally at a spatial resolution of 1 km2 but
validation data are required at a similar spatial scale. Large
Aperture Scintillometers transmit and receive near infrared
radiation over distances of several kilometers and provide
measurements of the structure parameter for the refractive
index of air which is related by Monin-Obukhov Similarity
Theory to the surface sensible heat flux (H), which requires
measurements of air temperature, pressure and wind speed.
ET can then be obtained indirectly as the residual of the
energy balance, ET = Rn – G – H so that we need estimates of
Net Radiation (Rn) and Soil Heat Flux (G) as well. A
scintillometer (Scintec BLS-450) was installed over an
irrigated vineyard with area of 72 hectares (1200m x 600m) in
June 6th 2009. Net Radiation was measured in the field and
soil heat flux was estimated using G = A * Rn, where the
parameter A was obtained from 8-day composite MODIS Land
Surface Temperature data. Comparison of ET derived from
satellite and scintillometer for June 2009 showed considerable
scatter with r2 = 0.81 and ETSAT = 1.12 * ETBLS. This
apparent overestimation from the satellite-based ET is similar
to that found in previous work. However, in these initial
calculations it was assumed that unstable conditions would
prevail during the daytime but it appears that stable
conditions often occur in the late afternoon. Secondly, the
estimation of G needs to be carefully revised since this can
have a large effect on ET. These factors are being included in
the analysis of data over an entire growing season to assess
the seasonal behavior of the model.
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