The regression relationships between terrestrial water storage/discharge and evapotranspiration minus precipitation represented by observations and the isotope-enabled Community Atmosphere Model (iCAM)
![[Shi et al., 2022] The regressions of ET-P on δD_004 from both observations and isotope enabled Community Atmosphere Model (iCAM). Panel (a) represents the regressions of GRACE terrestrial water storage (TWS)/discharge on AIRS δD_004 and panel (b) represents the regressions of ET-P on δD_004 from iCAM for three Amazon river basin groups during 2013–2015.](https://ngee-tropics.lbl.gov/wp-content/uploads/sites/16/2024/07/shi-2-1024x435.png)
The regressions of ET-P on δD_004 from both observations and isotope-enabled Community Atmosphere Model (iCAM). Panel (a) represents the regressions of GRACE terrestrial water storage (TWS)/discharge on AIRS δD_004 and panel (b) represents the regressions of ET-P on δD_004 from iCAM for three Amazon river basin groups during 2013–2015. Image courtesy of authors
The Science
Changes in the drivers of evapotranspiration (ET), such as above-ground biomass, could have a larger impact on soil moisture and humidity in the dry Amazon relative to the wet Amazon. The Atmospheric Infrared Sounder (AIRS) observations of the HDO/H2O ratio of water vapor are sensitive to spatiotemporal variations of the difference between two moisture fluxes, evapotranspiration minus precipitation (ET-P) over the Amazon. Thus, this study uses the AIRS HDO/H2O ratio of water vapor to investigate the spatial, seasonal, and interannual variability of ET-P over the Amazon.
The Impact
The results show that AIRS deuterium measurements can be used to quantify the spatiotemporal Amazon water balance at monthly to seasonal and interannual time scales. In the Amazon, rainfall controls wet Amazon water balance variability, but ET becomes important in regulating water balance and its variability in the dry Amazon.
Summary
Atmospheric humidity and soil moisture in the Amazon forest are tightly coupled to the region’s water balance, or the difference between two moisture fluxes, evapotranspiration minus precipitation (ET-P). This study calibrates the isotopic data to ET-P at river-basin scales using GRACE TWS and river discharge (TWS/discharge) measurements and quantifies their spatial biases and precision with a global climate model enabled with water isotopes. The relationship between precipitation and water balance in the wet and dry Amazon is quantified. The results demonstrate that rainfall controls wet Amazon water balance variability, but ET becomes important in regulating water balance and its variability in the dry Amazon.
Contact
Mingjie Shi
Pacific Northwest National Laboratory
mingjie.shi@pnnl.gov
Funding
This research was partly conducted at Pacific Northwest National Laboratory, operated for the U.S. Department of Energy by Battelle Memorial Institute under contract DE-AC05-76RL01830. This study was partly supported by the Department of Energy’s (DOE) Office of Biological and Environmental Research as part of the Terrestrial Ecosystem Science program through the Next-Generation Ecosystem Experiments (NGEE)-Tropics project.
Publications Citation:
Shi, M., Worden, J. R., Bailey, A., Noone, D., et al. “Amazonian terrestrial water balance inferred from satellite-observed water vapor isotopes”. Nature Communications, 13(1), 2686, (2022). https://doi.org/10.1038/s41467-022-30317-4