Evapotranspiration & Water Use Efficiency

Evapotranspiration

Evapotranspiration (ET) is the combined process of water evaporation from soil and surface water bodies, and transpiration through plant stomata. ET is important for understanding the water cycle, which impacts water security and vegetation health. ET products derived from remote sensing observations can help with conservation, fire risk assessment, water management, and agricultural practices (among other things). The PIE lab works closely with NASA's ECOSTRESS mission, which measures thermal infrared radiation (TIR) and uses it to map ET from space.

Water use efficiency

The relationship between ecosystem carbon gain (gross primary production; GPP) and water loss (ET), also known as water use efficiency (WUE), is a key variable that can help us better understand and constrain the response of ecosystems to changes in climate. Combining solar-induced chlorophyll fluorescence (SIF) and TIR-derived ET has potential to constrain the highly dynamic nature of WUE across space and time and yield critical insights into global carbon and water cycles. The PIE lab explores the connections between remotely sensed SIF and TIR and WUE across scales.

Diagram of stomatal conductance controlling CO2, H2O, and O2 exchange at the leaf scale, linked to tower- and satellite-derived GPP, ET, and WUE at the ecosystem scale — Stomata regulate the tradeoff between carbon uptake and water loss at the leaf scale, linking to ecosystem-scale GPP, ET, and WUE via eddy-covariance, SIF, and TIR observations from towers and satellites.

Related Publications

Pierrat, Z. A., Purdy, A. J., Halverson, G., Fisher, J. B., Mallick, K., Pascolini-Campbell, M., Ryu, Y., Anderson, M. C., Villanueva-Weeks, C., Johnson, M. C., Hatch, B., Davis, E., Yang, Y., & Cawse-Nicholson, K., 2025. Evaluation of ECOSTRESS Collection 2 Evapotranspiration Products: Strengths and Uncertainties for Evapotranspiration Modeling. Water Resources Research, 61(6), e2024WR039404. doi.org/10.1029/2024WR039404
Preprint: doi.org/10.22541/essoar.173193420.03623709/v1
Pierrat, Z. A., Gustine, R.N., Boser, A., Ruehr, S., Lee, C.M., Reager, J.T., Cawse-Nicholson, K., 2026. Human contributions to evapotranspiration mitigate swings in dry-to-wet year transitions. Communications Sustainability. 1, 8. doi.org/10.1038/s44458-025-00002-w
Pierrat, Z. A., Kurosu, T. P., Chatterjee, A., Fisher, J. B., Johnson, M., Kuai, L., Mallick, K., Parazoo, N., Wiebe, B., & Cawse-Nicholson, K., 2026. OCO-3 meets ECOSTRESS: Insights into ecosystem diurnal water-use efficiency from co-located solar-induced fluorescence and thermal observations. Geophysical Research Letters, 53(18), e2026GL124105. doi.org/10.1029/2026GL124105

Related Datasets

Four-panel map of co-located ECOSTRESS latent heat flux, OCO-3 solar-induced fluorescence, ECOSTRESS land surface temperature, and IGBP surface type over Osaka, Japan — Co-located ECOSTRESS and OCO-3 observations — latent heat flux (a measure of ET) and solar-induced fluorescence (a proxy for GPP) — capable of mapping diurnal changes in water use efficiency.

Kurosu, T. P., Chatterjee, A., Cawse-Nicholson, K., Pierrat, Z. A., & Hook, S. J. (2026). ECOSTRESS/OCO-3 Co-Located Observations V2.0. Greenbelt, MD, USA, Goddard Earth Sciences Data and Information Services Center (GES DISC). doi.org/10.5067/UWL1Q909EOZ8
Version 2.0 is based on ECOSTRESS Collection 2 and OCO-3 Version 11.2 products and covers August 2019 through June 2026.

Kurosu, T. P., Chatterjee, A., Cawse-Nicholson, K., Pierrat, Z. A., & Hook, S. J. (2025). ECOSTRESS/OCO-3 Co-Located Observations V1.0. Greenbelt, MD, USA, Goddard Earth Sciences Data and Information Services Center (GES DISC). doi.org/10.5067/JY21I1T22RCA