water vs. carbon: an evaluation of smap soil moisture...
TRANSCRIPT
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Punch Line
Water vs. carbon: An evaluation of SMAP soil moisture, evapotranspiration, & OCO-2 solar induced fluorescence to characterize global plant stress
•Projected changes in climate indicate shifts towards warmer and drier conditions in certain regions with potential to increase the frequency of vegetation stress.
•Understanding how vegetation responds to regulate photosynthesis and evapotranspiration (ET) is important to quantify potential feedback between the carbon and water cycles.
•Despite its importance, to what extent plants respond to stressful conditions is an open science question.
•This study links the carbon and water cycles from space to determine if satellite observations of soil moisture, ET and solar induced fluorescence (SIF) can address this uncertainty by answering questions such as:
• How do plants control water loss and carbon uptake under hotter and drier years?
• How do these responses vary across climates and biomes?
Motivation
Purdy, A.J.1, Fisher, J.B.2, Goulden, M.L.1, Randerson, J.T1, Famiglietti, J.S.2 1: Department of Earth System Science University of California, Irvine. 2: Jet Propulsion Laboratory
•Vegetation stress, as seen by negative SIF and transpiration anomalies, occurs with simultaneous decreases in water availability and increases in temperature.
•For regions where plant growth is limited by water availability or cold temperature, we find strong coupling of plant control on the water cycle and the carbon cycle.
•For regions less obviously limited by water and temperature, plant control on these cycles becomes decoupled and a contrasting response is observed with lower SIF and higher transpiration.
•Future work will focus on regions of disagreement between changes in SIF and transpiration.
Contact & Acknowledgements AJ Purdy | [email protected] This project was supported by the NASA Earth and Space Science Fellowship 17-EARTH17R-0062
Objectives
Results
Figure 3) Climate scatter plots showing changes in SIF (top) and transpiration (bottom) for each of the study regions from Fig. 2. Similar responses (decrease in SIF & decrease in transpiration) are observed in Southern Africa and Australia while contrasting responses (decrease in SIF & increase in transpiration) are observed in the Amazon and the Sunda Islands.
Transpiration and GPP
CO2H2O
Canopy observablesLeaf scale regulation
future climate drying only
Mortality
Threshold
Vegetation Stre
ss
future climate
warming only
Reproduced from Allen et al., 2015
current climate
Hot
Col
d
Dry WetPrecipitation
Tem
pera
ture
Data & Methods
•We capitalize on the 2015-2016 El Niño to evaluate how climate perturbations in temperature, precipitation, and water availability impact changes of ET and GPP as seen from satellite observations.
•We map changes in ET and SIF to identify vegetation stress.
•We characterize vegetation stress using time series and climate scatter plots.
Figure 2) Top and bottom rows: Time series analysis of precipitation, temperature, soil moisture, transpiration and SIF. Middle plots: A) 2-year change in SIF and B) PT-JPL transpiration.
A B
C D
Figure 1) 2-year change in precipitation (A) and temperature (B) normalized by 30 year inter annual variability, and 2-year change in surface soil moisture (C) and root zone soil moisture (D).
future climate drying only
Mortality
Threshold
Vegetation Stre
ss
future climate
warming only
Reproduced from Allen et al., 2015
current climate
Hot
Col
d
Dry WetPrecipitation
Tem
pera
ture
Amazon
Sunda Islands
Russia
Southern Africa
Australia
Eastern Africa
A B
The goals of the project are 1) to identify geographic regions vulnerable to decreases in water availability and increases in temperature, and 2) to characterize the effect of vegetation stress on the land-atmosphere exchange of carbon and water.