Development of a Solar-Induced FluorescenceCanopy Conductance Model and Its Application to Stomatal Reactive Nitrogen Deposition

The
bidirectional exchange of gases between vegetation and the
atmosphere is controlled by a variety of environmental factors and
feedbacks that are entangled and difficult to quantify. As a result
of this complexity, parameterizations of canopy conductance (Gc) in atmospheric models introduce large uncertainties
and likely biases into representations of atmosphere–biosphere
gas exchange. We present a novel representation of canopy conductance
derived from measurements of solar-induced fluorescence (SIF) from
the TROPOspheric Monitoring Instrument (TROPOMI). We show a strong
linear correlation between GPP and Gc,
calculated using the Penman–Monteith theory, across a variety
of ecosystem types in the AmeriFlux network. We couple this Gc–GPP correlation to previous research
showing a strong linear correlation between SIF and GPP and estimate Gc at a 500 m spatial resolution across the continental
United States. We also combine our model with surface estimates of
NO2 and PAN from WRF-Chem to estimate stomatal deposition
fluxes of these gases. Our results suggest that satellite measurements
of SIF can provide important constraints on model representations
of stomatal activity and canopy gas exchange on regional and global
scales.