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TROPOMI reveals dry-season increase of solar-induced chlorophyll fluorescence in the Amazon forest

Doughty, Russell and Köhler, Philipp and Frankenberg, Christian and Magney, Troy S. and Xiao, Xiangming and Qin, Yuanwei and Wu, Xiaocui and Moore, Berrien, III (2019) TROPOMI reveals dry-season increase of solar-induced chlorophyll fluorescence in the Amazon forest. Proceedings of the National Academy of Sciences of the United States of America, 116 (44). pp. 22393-22398. ISSN 0027-8424. PMCID PMC6825294. doi:10.1073/pnas.1908157116.

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Photosynthesis of the Amazon rainforest plays an important role in the regional and global carbon cycles, but, despite considerable in situ and space-based observations, it has been intensely debated whether there is a dry-season increase in greenness and photosynthesis of the moist tropical Amazonian forests. Solar-induced chlorophyll fluorescence (SIF), which is emitted by chlorophyll, has a strong positive linear relationship with photosynthesis at the canopy scale. Recent advancements have allowed us to observe SIF globally with Earth observation satellites. Here we show that forest SIF did not decrease in the early dry season and increased substantially in the late dry season and early part of wet season, using SIF data from the Tropospheric Monitoring Instrument (TROPOMI), which has unprecedented spatial resolution and near-daily global coverage. Using in situ CO_2 eddy flux data, we also show that cloud cover rarely affects photosynthesis at TROPOMI’s midday overpass, a time when the forest canopy is most often light-saturated. The observed dry-season increases of forest SIF are not strongly affected by sun-sensor geometry, which was attributed as creating a pseudo dry-season green-up in the surface reflectance data. Our results provide strong evidence that greenness, SIF, and photosynthesis of the tropical Amazonian forest increase during the dry season.

Item Type:Article
Related URLs:
URLURL TypeDescription Information CentralArticle
Doughty, Russell0000-0001-5191-2155
Köhler, Philipp0000-0002-7820-1318
Frankenberg, Christian0000-0002-0546-5857
Magney, Troy S.0000-0002-9033-0024
Xiao, Xiangming0000-0003-0956-7428
Qin, Yuanwei0000-0002-5181-9986
Moore, Berrien, III0000-0001-7870-8920
Additional Information:© 2019 National Academy of Sciences. Published under the PNAS license. Edited by Gregory P. Asner, Arizona State University, Tempe, AZ, and approved September 27, 2019 (received for review May 13, 2019). PNAS first published October 14, 2019. This study was supported by research grants through the Geostationary Carbon Cycle Observatory (GeoCarb) Mission from NASA (GeoCarb Contract 80LARC17C0001) and the US National Science Foundation Established Program to Stimulate Competitive Research (EPSCoR) program (IIA-1301789). P.K. and C.F. were funded by the Earth Science U.S. Participating Investigator (Grant NNX15AH95G). Author contributions: R.D., X.X., and B.M. designed research; R.D., P.K., C.F., T.S.M., X.X., Y.Q., X.W., and B.M. performed research; R.D., P.K., and C.F. contributed new reagents/analytic tools; R.D. and P.K. analyzed data; and R.D., P.K., C.F., T.S.M., X.X., Y.Q., and X.W. wrote the paper. The authors declare no competing interest. This article is a PNAS Direct Submission. This article contains supporting information online at
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Subject Keywords:photosynthesis; productivity; MODIS; EVI; geometry
Issue or Number:44
PubMed Central ID:PMC6825294
Record Number:CaltechAUTHORS:20191015-073430505
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Official Citation:TROPOMI reveals dry-season increase of solar-induced chlorophyll fluorescence in the Amazon forest. Russell Doughty, Philipp Köhler, Christian Frankenberg, Troy S. Magney, Xiangming Xiao, Yuanwei Qin, Xiaocui Wu, Berrien Moore. Proceedings of the National Academy of Sciences Oct 2019, 116 (44) 22393-22398; DOI: 10.1073/pnas.1908157116
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:99265
Deposited By: Tony Diaz
Deposited On:15 Oct 2019 15:02
Last Modified:15 Feb 2022 23:21

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