Spatial and temporal variations of evapotranspiration, groundwater and
precipitation in Amazonia
Abstract
The relationships and seasonal-to-annual variations among
evapotranspiration (ET), precipitation (P), and groundwater dynamics
(total water storage anomaly, TWSA) are complex across the Amazon basin,
especially the water and energy limitation mechanism for ET. To analyze
how ET is controlled by P and TWSA, we used wavelet coherence analysis
to investigate the effects of P and TWSA on ET at sub-basin, kilometer,
regional, and whole basin scales in the Amazon basin. The Amazon-scale
averaged ET has strong correlations with P and TWSA at the annual
periodicity. The phase lag between ET and P (ϕ_(ET-P)) is
~1 to ~4 months, and between ET and TWSA
(ϕ_(ET-TWSA)) is ~3 to ~7 months. The
phase pattern has a south-north divide due to the significant variation
in climatic conditions. The correlation between ϕ_(ET-P) and
ϕ_(ET-TWSA) is affected by the aridity index, of each sub-basin, as
determined using the Budyko framework at the sub-basin level. In the
southeast Amazon during a drought year (e.g., 2010), both phases
decreased, while in the subsequent years, ϕ_(ET-TWSA) increased. The
area of places where ET is limited by water continues to decrease over
time in the southern Amazon basin. These results suggest immediate
strong groundwater subsidy to ET in the following dry years in the
water-limited area of Amazon. The water storage has more control on ET
in the southeast but little influence in the north and southwest after a
drought. The areas of ET limited by energy or water are switched due to
the variability in weather conditions.