B43H-0647
Satellite Solar-induced Chlorophyll Fluorescence Reveals Drought Onset Mechanisms: Insights from Two Contrasting Extreme Events
Thursday, 17 December 2015
Poster Hall (Moscone South)
Ying Sun1, Rong Fu2, Robert E Dickinson1, Joanna Joiner3, Christian Frankenberg4, Lianhong Gu5, Youlong Xia6 and Nelun Fernando7, (1)University of Texas at Austin, Austin, TX, United States, (2)University of Texas at Austin, Geological Sciences, Austin, TX, United States, (3)NASA Goddard SFC, Greenbelt, MD, United States, (4)NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States, (5)Oak Ridge National Laboratory, Oak Ridge, TN, United States, (6)Environmental Modeling Center, College Park, MD, United States, (7)Texas Water Development Board, Austin, TX, United States
Abstract:
This study uses the droughts of 2011 in Texas and 2012 over the central Great Plains as case studies to explore the potential of satellite-observed solar-induced chlorophyll fluorescence (SIF) for monitoring drought dynamics. We find that the spatial patterns of negative SIF anomalies from the Global Ozone Monitoring Instrument 2 (GOME-2) closely resembled drought intensity maps from the US Drought Monitor for both events. The drought-induced suppression of SIF occurred throughout 2011 but was exacerbated in summer in the Texas drought. This event was characterized by a persistent depletion of root-zone soil moisture caused by year-long below-normal precipitation. In contrast, for the central Great Plains drought, warmer temperatures and ample precipitation boosted SIF in the spring of 2012; however, a sudden drop in precipitation coupled with unusually high temperatures rapidly depleted soil moisture through evapotranspiration, leading to a rapid onset of drought in early summer. Accordingly, SIF reversed from above to below normal. For both regions, the GOME-2 SIF anomalies were significantly correlated with those of root-zone soil moisture, indicating that the former can potentially be used as proxy of the latter for monitoring agricultural droughts with different onset mechanisms. Further analyses indicate that the contrasting dynamics of SIF during these two extreme events were caused by changes in both fraction of absorbed photosynthetically active radiation (fPAR) and fluorescence yield, suggesting that satellite SIF is sensitive to both structural and physiological/biochemical variations of vegetation. We conclude that the emerging satellite SIF has excellent potential for dynamic drought monitoring.
