Continuous calculations of evapotranspiration (LE) using eddy covariance
method and energy budget were performed over more than one year above the
heterogeneous canopy of an arid oasis ecosystem in the central Syrian desert.
Irrigation practice wa
s traditional flooding with a 28 days turn of water
delivery. The work focuses on seasonal variations of energy budget over a 2
years period with emphasis on effects of rainfall, wind speed and radiative
budget on evapotranspiration. Maximum evapotranspiration was only
5mm/day. Even under irrigation practices, winter rainfall seems to have an
important impact on LE: comparisons of two situations in June 2002 and June
2003 showed an increase of 13% in values of LE/Rn-G. Maximum averaged
hourly values of evapotranspiration were found for wind speed values closed to
3m/s. This suggests that when the evaporative demand from the air (or vapour
pressure deficit (vpd) ) is increasing above a certain limit, the vegetation closes
its stomata and reduces transpiration. Results from the energy balance closure
showed significant differences in the slope of H+LE against Rn-G relationships
between cold and hot month which was explained by specific radiative budget
of desert areas.
