Abstract. Drought is a devastating natural hazard that is difficult
to define, detect and quantify. The increased availability of both
meteorological and remotely sensed data provides an opportunity to develop
new methods to identify drought conditions and characterize how drought changes
over space and time. In this paper, we applied the surface energy balance
model, SEBS (Surface Energy Balance System), for the period 2001–2018, to
estimate evapotranspiration and other energy fluxes over the dehesa area of the
Iberian Peninsula, with a monthly temporal resolution and
0.05∘ pixel size. A satisfactory agreement was found between
the fluxes modeled and the measurements obtained for 3 years by two
flux towers located over representative sites (RMSD = 21 W m−2 and
R2=0.76, on average, for all energy fluxes and both sites). The
estimations of the convective fluxes (LE and H) showed higher deviations,
with RMSD = 26 W m−2 on average, than Rn and G, with RMSD = 15 W m−2. At both sites, annual evapotranspiration (ET) was very close to total precipitation,
with the exception of a few wet years in which intense precipitation events
that produced high runoff were observed. The analysis of the anomalies of
the ratio of ET to reference ET (ETo) was used as
an indicator of agricultural drought on monthly and annual scales.
The hydrological years 2004/2005 and 2011/2012 stood out for their negative
values. The first one was the most severe of the series, with the highest
impact observed on vegetation coverage and grain production. On a monthly
scale, this event was also the longest and most intense, with peak negative
values in January–February and April–May 2005, explaining its great
impact on cereal production (up to 45 % reduction). During the drier
events, the changes in the grasslands' and oak trees' ground cover allowed for a
separate analysis of the strategies adopted by the two strata to cope with
water stress. These results indicate that the drought events characterized
for the period did not cause any permanent damage to the vegetation of
dehesa systems. The approach tested has proven useful for providing insight into
the characteristics of drought events over this ecosystem and will be
helpful to identify areas of interest for future studies at finer
resolutions.
Regional Estimation of Remotely Sensed Evapotranspiration Using the Surface Energy Balance-Advection (SEB-A) Method
