Accounting for canopy structure improves hyperspectral radiative transfer and sun-induced chlorophyll fluorescence representations in a new generation Earth System model

Three-dimensional (3D) vegetation canopy structure plays an important role in the way radiation interacts with land surface. Accurately representing this process Earth System models (ESMs) is crucial for modeling of global carbon, energy, and water cycles hence future climate projections. Despite importance accounting 3D structure, inability to represent such complexity at regional scales has impeded a successful implementation into ESMs. An alternative approach use implicit clumping index account horizontal heterogeneity representations ESMs scale. This paper evaluates how modeled hyperspectral shortwave partitioning terrestrial biosphere, as well Sun-Induced Chlorophyll Fluorescence (SIF) are impacted when parameterization incorporated radiative transfer scheme new generation ESM, Climate Model Alliance (CliMA). accurate representation within critical accurately using satellite data confront, constrain, improve model processes. The newly implemented compared Monte Carlo calculations idealized scenes from Radiation Intercomparison Project Land-Surface Parameterizations (RAMI4PILPS), open forest canopies both without snow on ground. Results indicate that it structural calculating transfer. RMSE reduced reflectance (25%), absorptance (66%), transmittance (75%) scenario considering clumping. Calculated SIF validated against remote sensing recently launched NASA Orbiting Carbon Observatory (OCO) 3, showing including vertical deriving can predictions up 51% comparison By adding CliMA-Land model, relationship between SIF, Gross Primary Productivity (GPP), transfer, viewing geometry scale be explored detail. • Horizontal included scheme. Clumping improves partitioning. Accounting calculated NASA's OCO-3 data. correlation NIR v considered. escape fraction better correlates fAPAR