Use of satellite leaf area index estimating evapotranspiration and gross assimilation for Australian ecosystems

Abstract

Accurate quantification of terrestrial evapotranspiration and ecosystem productivity is of significant merit to better understand and predict the response of ecosystem energy, water, and carbon budgets under climate change. Existing diagnostic models have different focus on either water or carbon flux estimates with various model complexity and uncertainties induced by distinct representation of the coupling between water and carbon processes. Here, we propose a diagnostic model to estimate evapotranspiration and gross primary production that is based on biophysical mechanism yet simple for practical use. This is done by coupling the carbon and water fluxes via canopy conductance used in the Penman–Monteith–Leuning equation (named as PML_V2 model). The PML_V2 model takes Moderate Resolution Imaging Spectrometer leaf area index and meteorological variables as inputs. The model was tested against evapotranspiration and gross primary production observations at 9 eddy‐covariance sites in Australia, which are spread across wide climate conditions and ecosystems. Results indicate that the simulated evapotranspiration and gross primary production by the PML_V2 model are in good agreement with the measurements at 8‐day timescale, indicated by the cross site Nash–Sutcliffe efficiency being 0.70 and 0.66, R2 being 0.80 and 0.75, and root mean square error being 0.96 mm d−1 and 1.14 μmol m−2 s−1 for evapotranspiration and gross primary production, respectively. As the PML_V2 model only requires readily available climate and Moderate Resolution Imaging Spectrometer vegetation dynamics data and has few parameters, it can potentially be applied to estimate evapotranspiration and carbon assimilation simultaneously at long‐term and large spatial scales.

Flavonol Profile Is a Reliable Indicator to Assess Canopy Architecture and the Exposure of Red Wine Grapes to Solar Radiation

“…The exposure of a single cluster was indicative of the local estimations of canopy architecture parameters, canopy porosity and LAI. These are relevant ecophysiological parameters as they are related light interception efficiency (Oyarzun et al, 2007), but also estimated LAI, can be used to model carbon assimilation or evapotranspiration in plant communities when the scale is too large to take actual measurements of leaf area (Gan et al, 2018). Flavonol profile was also related to satellite NDVI, a widely used remote sensing estimator of canopy size based on the specific spectral reflectance of chlorophyll tissues respect to the ground.…”

LUCC‐Driven Changes in Gross Primary Production and Actual Evapotranspiration in Northern China

“…This study uses PML‐V2 for modeling. It is a coupled GPP‐ET model, developed by Gan et al (2019) and Zhang et al (2019). The main feature of this model is that it uses GPPrs and atmospheric CO 2 concentration to calculate canopy conductance, which is then used to calculate transpiration.…”

A Comparison of SSEBop-Model-Based Evapotranspiration with Eight Evapotranspiration Products in the Yellow River Basin, China

“…Leuning et al (2008) [56] and Zhang et al (2010) [57] developed the biophysical model for Gs to account for canopy physiological processes and soil evaporation (resulting in PMLv1). Gan et al (2018) [58] coupled vegetation transpiration with gross primary productivity using a biophysical canopy conductance (Gc) model in the PML model (resulting in PMLv2). Zhang et al applied the PMlv2 model [59] at the global scale with 0.25 • resolution and 3-h Global Land Data Assimilation System (GLDAS-2.1 meteorological data, monthly atmospheric (CO2) concentration, LAI (MCD15A3H), albedo (MCD43A3), and surface emissivity data (MOD11A2) inputs.…”