Radiative variables of the Earth surface

TOA Reflectance / Brightness Temperature

TOA (Top Of Atmosphere) Reflectance is defined as the ratio between the radiant exitance and the irradiance at sensor level at the top of the Earth’s atmosphere. Delivered data is defined as technical albedo, with a value range of 0-100%. This data is sensor-specific, and is based on the NOAA-OSPO calibration. The technical albedos can be transformed to re-calibrated and sensor-invariant TOA reflectances using the TIMELINE harmonization tables. TOA Brightness Temperature is the temperature of a hypothetical blackbody (emissivity = 1). It is obtained by applying the inverse of the Planck function to the measured TOA radiance of a surface.

Surface Directional Reflectance (SDR)

Surface Directional Reflectance (SDR) is defined as the ratio between the radiant exitance and the irradiance at surface level. The value range of SDR is 0-1. SDR corresponds to atmospherically corrected TOA reflectances.

Surface Reflectance (SR)

Surface Reflectance (SR) is defined as the ratio between the radiant exitance and the irradiance at earth surface level accounting for BRDF effects. The value range of SR is 0 - 1.

Albedo

The Albedo is the ratio between the radiant exitance and the irradiance at earth surface level over the shortwave spectral domain (broadband). The value range of albedo is 0 - 1. Albedo is derived from the SR (Surface Reflectance) product. Albedo is an Essential Climate Variable (ECV) as recognized by the Global Climate Observing System (GCOS).

Land Surface Temperature (LST)

Land Surface Temperature (LST) is the mean radiative skin temperature of the land surface in the instrument’s field of view. It is derived from the thermal radiation as measured by the remote sensor. LST is an Essential Climate Variable (ECV) as recognized by the Global Climate Observing System (GCOS).