Abstract. Vegetation optical properties have a direct impact on canopy absorption and
scattering and are thus needed for modeling surface fluxes. Although plant functional type (PFT) classification varies between different land surface
models (LSMs), their optical properties must be specified. The aim of this
study is to revisit the “time-invariant optical properties table” of the
Simple Biosphere (SiB) model (later referred to as the “SiB table”) presented
30 years ago by Dorman and Sellers (1989), which has since been adopted by
many LSMs. This revisit was needed as many of the data underlying the
SiB table were not formally reviewed or published or were based on older
papers or on personal communications (i.e., the validity of the optical
property source data cannot be inspected due to missing data sources,
outdated citation practices, and varied estimation methods). As many of
today's LSMs (e.g., the Community Land Model (CLM), the Jena Scheme of Atmosphere
Biosphere Coupling in Hamburg (JSBACH), and the Joint UK Land Environment
Simulator (JULES)) either rely on the optical properties of the SiB table or
lack references altogether for those they do employ, there is a clear need
to assess (and confirm or correct) the appropriateness of those being used
in today's LSMs. Here, we use various spectral databases to synthesize and
harmonize the key optical property information of PFT classification shared
by many leading LSMs. For forests, such classifications typically
differentiate PFTs by broad geo-climatic zones (i.e., tropical, boreal,
temperate) and phenology (i.e., deciduous vs. evergreen). For short-statured
vegetation, such classifications typically differentiate between crops, grasses, and photosynthetic pathway. Using the PFT classification of the
CLM (version 5) as an example, we found the optical properties of the
visible band (VIS; 400–700 nm) to fall within the range of measured values.
However, in the near-infrared and shortwave infrared bands (NIR and SWIR; e.g., 701–2500 nm, referred to as “NIR”) notable differences between CLM default and
measured values were observed, thus suggesting that NIR optical properties
are in need of an update. For example, for conifer PFTs, the measured mean
needle single scattering albedo (SSA, i.e., the sum of reflectance and
transmittance) estimates in NIR were 62 % and 78 % larger than the CLM
default parameters, and for PFTs with flat leaves, the measured mean leaf
SSA values in NIR were 20 %, 14 %, and 19 % larger than the CLM defaults.
We also found that while the CLM5 PFT-dependent leaf angle values were
sufficient for forested PFTs and grasses, for crop PFTs the default
parameterization appeared too vertically oriented, thus warranting an
update. In addition, we propose using separate bark reflectance values for
conifer and deciduous PFTs and demonstrate how shoot-level clumping
correction can be incorporated into LSMs to mitigate violations of turbid
media assumption and Beer's law caused by the nonrandomness of finite-sized
foliage elements.
Low Energy Electrodynamics of CrI3 Layered Ferromagnet
