Abstract:
HAPEX-Sahel: the Hydrology-Atmosphere Pilot Experiment in the Sahel,
1990-1992.
(The following text is an extract of : Geographical, biological and
remote sensing aspects of the Hydrologic Atmospheric Pilot Experiment
in the Sahel (HAPEX SAHEL) by S.D. Prince, Y.H. Kerr, J.-P. Goutorbe,
T. Lebel, A. Tinga, J. Brouwer, A.J. Dolman, E.T. Engman,
J.H.C. Gash, M. Hoepffner, P. Kabat, B. Monteny, F. Said, P. Sellers,
J. Wallace, to be published in RSE)
HAPEX-Sahel (Hydrological and Atmospheric Pilot Experiment in the
Sahel) is an international land-surface-atmosphere observation program
that was undertaken in western Niger, in the west African Sahel
region. The overall aims were to improve our understanding of the role
of the Sahel on the general circulation, in particular the effects of
the large interannual fluctuations of land surface conditions in this
region and, in turn, to develop ideas about how the general
circulation is related to the persistent droughts that have affected
the Sahel during the last 25 years. The field program obtained
measurements of atmospheric, surface and certain sub-surface processes
in a 1deg x1deg area that incorporates examples of many of the major
land surface types found throughout the Sahel. An important
consideration was that the data must to be applicable to the scales of
current general circulation models (GCM).
In order to obtain data for this large area, an extensive measurement
program was undertaken including field, aircraft, and satellite remote
sensing measurements, mainly between mid1990 and late1992. An
intensive operations period was undertaken for 8 weeks from mid to
late growing season of 1992. HAPEX- Sahel was initiated in response
to the World Climate Research Programme (WCRP) Global Energy and Water
Cycles Experiment (GEWEX) which aims to determine the fluxes of water
and energy globally in order to quantify the energetic processes of
the Earth's climate system and the forcing functions on the ocean,
land, ice and vegetation. GEWEX recognizes the need for more realistic
measurements of major global environments, especially critical areas
that are thought to have strong influences on the general circulation.
It is possible to have on-line information: 'http://www.ird.fr/hapex/'
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