Reference Measurements (RM)
|RM-1||Direct/Diffuse visible radiation|
|RM-2||Direct/Diffuse thermal radiation
Corresponds to the TIR upwelling and downwelling radiances (W.m2) measured in the field from radiometers (directional, narrowband measurements) or pyrgeometers (hemispheric, broadband, measurements). The Planck Function is used to derive radiances when Brightness Temperatures are measured in the field.
|RM-4||Transmission through canopy
Corresponds to the Fraction of Transmitted Photosynthetically Active Radiation (FTPAR) which is the amount of photosynthetically active radiation (PAR) that is transmitted through the canopy. PAR is defined as the radiation at wavelengths of between 400 nm and 700 nm, and is measured as Photosynthetic Photon Flux Density (PPFD) in units of μmol m-2 s-1. It is the radiation within this region of the electromagnetic spectrum that is absorbed by photosynthetic pigments in plants for the purposes of photosynthesis. FTPAR is a dimensionless quantity that ranges from 0 to 1, and depends on illumination geometry and the proportion of direct and diffuse radiation. Thus, FTPAR can be defined as instantaneous or integrated depending on the time period over which it is computed, and black-sky or white-sky depending on whether direct or diffuse radiation is considered.
Corresponds to the Fraction of Intercepted Photosynthetically Active Radiation (FIPAR) which is the amount of PAR that is intercepted by the canopy. Like FTPAR, FIAPR is a dimensionless quantity that ranges from 0 to 1, and depends on illumination geometry and the proportion of direct and diffuse radiation. Thus, FIPAR can be defined as instantaneous or integrated depending on the time period over which it is computed, and black-sky or white-sky depending on whether direct or diffuse radiation is considered. The Fraction of Absorbed Photosynthetically Active Radiation (FAPAR), which is designated an Essential Climate Variable (ECV), is more typically the parameter of interest. However, the difference between FAPAR and FIPAR is considered minimal in most circumstances, making measurements of FIPAR suitable for validating satellite-derived FAPAR products.
Corresponds to the Leaf Area Index (LAI) which is the one-sided leaf area per unit ground surface area, and describes the amount of leaf material in a vegetation canopy. It is an important descriptor of canopy structure, determining the size of the interface for biogeochemical fluxes between vegetation and the atmosphere. As such, it is designated an ECV. LAI a dimensionless quantity that typically varies between 0 and 10, and as an intrinsic property of the canopy, is not dependent on observation conditions such as illumination geometry.
Corresponds to the Land Surface Emissivity (LSE). LSE is the average emissivity of an element of the surface of the Earth calculated from measured radiance and land surface temperature (LST) (Norman and Becker, 1995). This variable is not routinely observed in the field but can be obtained from auxiliary data sources such as the CIMMS Baseline Fit Emissivity Database (Seemann et al. 2008).
|RM-9||Ground and Surface Temperature
Corresponds to the Land Surface Temperature (LST). LST is derived from direct or diffuse thermal radiation (RM-2) and LSE (RM-8).
|RM-10||Soil moisture at 5 cm
Corresponds to hourly Soil Moisture (SM) at 5 cm depth. It is expressed in m3.m-3.
Corresponds to several meteorological parameters:
Land Products (LP)
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