Elbers, J.A.

Gieske, A.

Jia, L.

Jin, X.

Kwast, H., van der

Moreno, J.

Nerry, F.

Olioso, A.

Sabol, D.

Sobrino, J.A.

Su, B.

Timmermans, W.

Wageningen Yield 

Z. (Bob) Su, L. Jia, X. Jin, J. Elbers, A. Gieske, W. Timmermans, H. van
der Kwast, A. Olioso, J.A. Sobrino, J. Moreno, F. Nerry, and D. Sabol
(2004), Land-atmosphere exchanges of water and energy in space and
time over a heterogeneous land surface, in Proceedings of the 2nd inter-
national CAHMDA workshop on: The Terrestrial Water Cycle: Modelling
and Data Assimilation Across Catchment Scales, edited by A.J. Teuling, H.
Leijnse, P.A. Troch, J. Sheffield and E.F. Wood, pp. 129–130, Princeton,
NJ, October 25–27
CAHMDA-II workshop Session 3 Su
Land-atmosphere exchanges of water and energy in space and time
over a heterogeneous land surface
Z. (Bob) Su1, L. Jia2, X. Jin2, J. Elbers3, A. Gieske1, W. Timmermans1, H. van der
Kwast4, A. Olioso5, J.A. Sobrino6, J. Moreno6, F. Nerry8, D. Sabol8
1International Institute for Geo-Information Science and Earth Observation (ITC), Enschede, The
Netherlands
2Wageningen University, Wageningen, The Netherlands
3Alterra, Wageningen University and Research Centre, Wageningen, The Netherlands
4University of Utrecht, Utrecht, The Netherlands
5INRA, Avignon, France
6University of Valencia, Valencia, Spain
7TRIO/ULP, Strasbourg, France
8University of Washington, Seattle, U.S.A
In order to advance our understanding of land-atmosphere exchanges of water and energy
in space and time over heterogeneous land surfaces, an intensive field campaign was carried
out at the Barrax agricultural test site in Spain in the period 12–21 July involving multiple
field, satellite and airborne instruments for characterizing the state of the atmosphere, the
vegetation and the soil from visible to microwave range of the spectrum. Part of the exper-
imental area is a core site of a 25 km2 area within which numerous crops are grown - on
both irrigated and dry land - alongside fields of bare soil. This campaign formed part of
the preparatory study for a proposed ESA Earth Explorer mission called SPECTRA (Sur-
face Processes and Ecosystem Changes Through Response Analysis) of the European Space
Agency, thus was named as SPARC-2004 (SPECTRA Barrax Campaign-2004) in combina-
tion with the EU 6FP EAGLE Project.
Used for the first time during SPARC-2004 was the new Airborne Hyperspectral System (AHS),
operated by Spain’s Instituto Nacional de Técnica Aeroespacial (INTA). The AHS has a total of
80 spectral channels available in the visible, short wave infrared and thermal infrared. A total of
16 multiangular acquisition flight lines were obtained over Barrax with spatial resolutions vary-
ing from 2.5 to 6.8 m. Several satellite sensors, including the Compact High Resolution Imaging
Spectrometer (CHRIS) on the Proba spacecraft, with two days of consecutive multiangular acqui-
sitions over the campaign site, as well as sensors from several other satellites (ENVISAT, TERRA,
MSG) were deployed for image data acquisition.
A large number of ground based instruments were also deployed including lidars and balloon-
based radio sondes to sample atmospheric variables, sun photometers to measure sky radiance and
sensors mounted on mobile towers to record local vegetation characteristics. Several mobile instru-
ment towers, including four eddy correlation devices and two scintillometers, were deployed in the
field to monitor the individual components of the energy, water and carbon dioxide flux exchanged
between land and the atmosphere. In addition to CHRIS data, two ENVISAT overpasses enabled
acquisitions from that spacecraft’s Medium Resolution Imaging Spectrometer (MERIS) and Ad-
vanced Along Track Scanning Radiometer (AATSR), as part of parallel ENVISAT data product
validation activities. Data from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI)
instrument aboard MSG-1 (Meteosat Second Generation) were acquired during the campaign as
part of the validation activities for MSG vegetation products, alongside data from Landsat and also
129
Su Session 3 CAHMDA-II workshop
the Moderate Resolution Imaging Spectroradiometer (MODIS) and Advanced Spaceborne Ther-
mal Emission and Reflection Radiometer (ASTER) on Terra, collected to complete the SPARC
dataset.
In the CHRIS configuration available to the SPARC-2004 campaign, 62 spectral bands were avail-
able for five angular acquisitions with 34 m spectral resolution. The higher resolution data, in
combination with data from other sensors (spatial resolution from 90 m of ASTER, 300 m of
MERIS, to 1 km of AATSR and MODIS, and to over 3 km of MSG data) provide unprecedented
opportunity for studying of the scaling behavior of the land-atmosphere exchanges of water and
energy.
A total of 80 people from 21 different institutions in five different countries were involved in
the SPARC-2004 activity, with around 50 people directly participating in the daily field measure-
ments. Participants included Spanish teams from Universities in Valencia, Albacete and Castellon
along with national research institutes (INTA, INM, CSIC, CIEMAT, CEDEX, ITAP and CE-
CAF), French teams from LURE-Paris, INRA-Avignon and the University of Strasbourg, Italian
teams from the University of Naples and the National Research Council and a large team from the
Netherlands involving Alterra, Wageningen University, ITC and the University of Utrecht, plus
ESA participants. A team from the University of Washington in Seattle also took part in the cam-
paign, as part of a NASA project related to validation of Terra/ASTER data over the Barrax site.
The SPARC-2004 activity has been funded by ESA and the European Commission with additional
contributions from Eumetsat and national projects.
The in-situ data relevant to land-atmosphere exchanges included the following measurements:
• Turbulence, H2O, CO2 fluxes and CO2 concentrations using an eddy correlation system
(Gill 3D sonic + closed path Licor gasanalyser: CO2 and H2O + nitrogen reference gas
+pneumatic mast + dataloggers);
• Soil heat flux, soil temperatures (two levels), air temperature and humidity
• Leaf temperatures (thermal couples);
• Radiation balance (shortwave and longwave incoming and outgoing radiation, wind, air tem-
perature, radiometric surface temperature) and sensible heat flux (using two scintillometer
systems);
• Photosynthesis, conductance and transpiration measurements at leaf level (using a CIRAS
from PP systems);
• Radiometric surface temperature measurements using a hand-held radiometer (Everest);
• Roughness measurements using stereo photogrammetry with the NEar Sensing CAmera
Field Equipment (NESCAFE);
• Emissivity measurements with the "two-lid box method";
• LAI measurements with hemispherical photographs, which will be processed with Win-
Phot∗.
Digital photos are taken to document the actual field situations. These data and part of the satel-
lite data have undergone preliminary analysis in space and time, the results and findings will be
presented at the workshop.
∗http://www.bio.uu.nl/~herba/Guyana/winphot/wp_index.htm
130


Land-atmosphere exchanges of water and energy in space and time over a heterogeneous land surface

Su, Zhongbo

Jin, Xiaomei

Elbers, J.

Gieske, A.S.M.

Timmermans, W.J.

van der Kwast, H.

University of Twente Research Information

Land - atmosphere exchanges of water and energy in space and time over a heterogeneous land surface

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Land-atmosphere exchanges of water and energy in space and time over a heterogeneous land surface

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