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Spatial and temporal variations of evapotranspiration, groundwater and precipitation in Amazonia
  • +5
  • Juan Zhang,
  • Jie Niu,
  • Chaopeng Shen,
  • John Melack,
  • Jin Zhang,
  • Han Qiu,
  • Bill Hu,
  • William Riley
Juan Zhang
Jinan University
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Jie Niu
Jinan University
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Chaopeng Shen
Pennsylvania State University
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John Melack
University of California Santa Barbara
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Jin Zhang
Jinan University
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Han Qiu
Pacific Northwest National Laboratory
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Bill Hu
Jinan University
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William Riley
Lawrence Berkeley National Laboratory
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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.