Task: Class Definition Understanding (ontology: Earth_Environment/OBOE)

Which of the following definitions best describes 'SpectralIrradiance'?

A. Unit of pressures often used in meteorology. One the concept is equivalent to one millibar; one standard atmosphere is exactly equal to 1013.25 hPa. One the concept corresponds to about 0.1% of atmospheric pressure near sea level (Wikipedia).
B. Irradiance, radiant emittance, and radiant exitance are radiometry terms for the power per unit area of electromagnetic radiation at a surface. "Irradiance" is used when the electromagnetic radiation is incident on the surface. "Radiant exitance" or "radiant emittance" is used when the radiation is emerging from the surface. The SI units for all of these quantities are watts per square meter (W/m2) (wikipedia). All of these quantities characterize the total amount of radiation present, at all frequencies. It is also common to consider each frequency in the spectrum separately. When this is done for radiation incident on a surface, it is called spectral irradiance, and has SI units W/m3, or commonly W·m−2·nm−1.
C. A the concept is one nautical mile per hour, which is equal to exactly 1.852 km/h and approximately 1.151 mph.
D. the concept amount of substance of solute B in a solution divided by the mass of the solvent: Often favored because measurements of mass are more precise than measurements of volume.

Answer: Irradiance, radiant emittance, and radiant exitance are radiometry terms for the power per unit area of electromagnetic radiation at a surface. "Irradiance" is used when the electromagnetic radiation is incident on the surface. "Radiant exitance" or "radiant emittance" is used when the radiation is emerging from the surface. The SI units for all of these quantities are watts per square meter (W/m2) (wikipedia). All of these quantities characterize the total amount of radiation present, at all frequencies. It is also common to consider each frequency in the spectrum separately. When this is done for radiation incident on a surface, it is called spectral irradiance, and has SI units W/m3, or commonly W·m−2·nm−1.