Investigating the usefulness of satellite-derived fluorescence data in inferring gross primary productivity within the carbon cycle data assimilation system
Simulations of carbon fluxes with terrestrial biosphere models still exhibit significant uncertainties, in part due to the uncertainty in model parameter values. With the advent of satellite measurements of solar induced chlorophyll fluorescence (SIF), there exists a novel pathway for constraining s...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2015-07-01
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| Series: | Biogeosciences |
| Online Access: | http://www.biogeosciences.net/12/4067/2015/bg-12-4067-2015.pdf |
| Summary: | Simulations of carbon fluxes with terrestrial biosphere models still exhibit
significant uncertainties, in part due to the uncertainty in model parameter
values. With the advent of satellite measurements of solar induced
chlorophyll fluorescence (SIF), there exists a novel pathway for constraining
simulated carbon fluxes and parameter values. We investigate the utility of
SIF in constraining gross primary productivity (GPP). As a first test we
assess whether SIF simulations are sensitive to important parameters in a
biosphere model. SIF measurements at the wavelength of 755 nm are simulated
by the Carbon-Cycle Data Assimilation System (CCDAS) which has been augmented
by the fluorescence component of the Soil Canopy Observation, Photochemistry
and Energy fluxes (SCOPE) model.
<br><br>
Idealized sensitivity tests of the SCOPE model stand-alone indicate strong
sensitivity of GPP to the carboxylation capacity (<i>V</i><sub>cmax</sub>) and of
SIF to the chlorophyll AB content (<i>C</i><sub>ab</sub>) and incoming short wave
radiation. Low sensitivity is found for SIF to <i>V</i><sub>cmax</sub>, however the
relationship is subtle, with increased sensitivity under high radiation
conditions and lower <i>V</i><sub>cmax</sub> ranges.
<br><br>
CCDAS simulates well the patterns of satellite-measured SIF suggesting the
combined model is capable of ingesting the data. CCDAS supports the idealized
sensitivity tests of SCOPE, with SIF exhibiting sensitivity to
<i>C</i><sub>ab</sub> and incoming radiation, both of which are treated as
perfectly known in previous CCDAS versions. These results demonstrate the
need for careful consideration of <i>C</i><sub>ab</sub> and incoming radiation when
interpreting SIF and the limitations of utilizing SIF to constrain
<i>V</i><sub>cmax</sub> in the present set-up in the CCDAS system. |
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| ISSN: | 1726-4170 1726-4189 |