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Synergistic use of SMAP and OCO-2 data in assessing the responses of ecosystem productivity to the 2018 U.S. drought

Li, Xing and Xiao, Jingfeng and Kimball, John S. and Reichle, Rolf H. and Scott, Russell L. and Litvak, Marcy E. and Bohrer, Gil and Frankenberg, Christian (2020) Synergistic use of SMAP and OCO-2 data in assessing the responses of ecosystem productivity to the 2018 U.S. drought. Remote Sensing of Environment, 251 . Art. No. 112062. ISSN 0034-4257.

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Soil moisture and gross primary productivity (GPP) estimates from the Soil Moisture Active Passive (SMAP) and solar-induced chlorophyll fluorescence (SIF) from the Orbiting Carbon Observatory-2 (OCO-2) provide new opportunities for understanding the relationship between soil moisture and terrestrial photosynthesis over large regions. Here we explored the potential of the synergistic use of SMAP and OCO-2 based data for monitoring the responses of ecosystem productivity to drought. We used complementary observational information on root-zone soil moisture and GPP (9 km) from SMAP and fine-resolution SIF (0.05°; GOSIF) derived from OCO-2 SIF soundings. We compared the spatial pattern and temporal evolution of anomalies of these variables over the conterminous U.S. during the 2018 drought, and examined to what extent they could characterize the drought-induced variations of flux tower GPP and crop yield data. Our results showed that SMAP GPP and GOSIF, both freely available online, could well capture the spatial extent and dynamics of the impacts of drought indicated by the U.S. Drought Monitor maps and the SMAP root-zone soil moisture deficit. Over the U.S. Southwest, monthly anomalies of soil moisture showed significant positive correlations with those of SMAP GPP (R² = 0.44, p < 0.001) and GOSIF (R² = 0.76, p < 0.001), demonstrating strong water availability constraints on plant productivity across dryland ecosystems. We further found that SMAP GPP and GOSIF captured the impact of drought on tower GPP and crop yield. Our results suggest that synergistic use of SMAP and OCO-2 data products can reveal the drought evolution and its impact on ecosystem productivity and carbon uptake at multiple spatial and temporal scales, and demonstrate the value of SMAP and OCO-2 for studying ecosystem function, carbon cycling, and climate change.

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Frankenberg, Christian0000-0002-0546-5857
Additional Information:© 2020 Elsevier. Received 9 March 2020, Revised 25 August 2020, Accepted 30 August 2020, Available online 10 September 2020. This study was supported by the National Aeronautics and Space Administration (NASA) (PI Jingfeng Xiao: Climate Indicators and Data Products for Future National Climate Assessments - Grant No. NNX16AG61G and Carbon Cycle Science Program - Grant No. NNX14AJ18G) and National Science Foundation (NSF) (PI Jingfeng Xiao: Macrosystem Biology & NEON-Enabled Science program - Grant No. DEB-2017870). The contribution of J.S.K. was supported by NASA Grant No. NNH15ZDA001N and NNX15AT74A. R.R. was supported by the SMAP project. We thank the OCO-2 and SMAP science teams for making OCO-2 SIF and SMAP root-zone soil moisture and GPP data available and USDA-NASS for providing crop yield data. We also thank the principal investigators and other research personnel of the four AmeriFlux sites for making the flux data available. Funding for AmeriFlux data resources was provided by the U.S. Department of Energy's Office of Science. We thank the five anonymous reviewers for their two rounds of insightful and constructive comments on our manuscript. Author contributions. X. Li and J. Xiao designed the research, conducted the analysis, and wrote the manuscript. J.S. Kimball, R.H. Reichle, R.L. Scott, M.E. Litvak, G. Bohrer, and C. Frankenberg contributed data and to the writing of the manuscript. Declaration of Competing Interest. None.
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Department of Energy (DOE)UNSPECIFIED
Subject Keywords:Soil Moisture Active Passive; Orbiting Carbon Observatory-2; GOSIF; Soil moisture; Sun-induced chlorophyll fluorescence; Gross primary production; Water stress; Dryland; Carbon cycle; Crop yield; Enhanced vegetation index
Record Number:CaltechAUTHORS:20200911-133136605
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Official Citation:Xing Li, Jingfeng Xiao, John S. Kimball, Rolf H. Reichle, Russell L. Scott, Marcy E. Litvak, Gil Bohrer, Christian Frankenberg, Synergistic use of SMAP and OCO-2 data in assessing the responses of ecosystem productivity to the 2018 U.S. drought, Remote Sensing of Environment, Volume 251, 2020, 112062, ISSN 0034-4257,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:105344
Deposited By: George Porter
Deposited On:14 Sep 2020 14:20
Last Modified:14 Sep 2020 14:20

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