Directional Infrared 
Temperature 
Hemispherical Emissivity 
Hemispherical Infrared 
Temperature 
Kinetic Temperature 
Skin Temperature 
Surface Temperature 
The temperature from a given view direction that is calculated 
from the thermal radiance in a given wavelength interval consid 
ering appropriate surface emissivity and reflected thermal irra- 
diance. It may be estimated by setting the measured radiance 
divided by the surface directional emissivity equal to the integral 
over wavelength of the product of the Planck’s function times 
the sensor response; then inverting the equation for the tempera 
ture in the Planck’s function. 
Emissivity of surface integrated over the hemisphere of view. 
For purposes of the thermal radiation in the surface energy 
budget, a broadband (3-100 pm) hemispherical emissivity is 
used. A narrowband hemispherical emissivity can be defined 
for particular sensors, but it rarely is useful. 
A temperature of the radiating surface that provides an estimate 
of the broadband emitted flux density when the temperature is 
raised to the fourth power and multiplied by the Stefan- 
Boltzman constant and broadband hemispherical emissivity. 
A weighted average thermodynamic temperature of all the ele 
ments comprising the surface. For a heterogeneous surface 
composed of objects with a range of temperatures, the kinetic 
temperature depends on the weighting and thus is not unique; 
further, the kinetic temperature of a canopy-soil system probably 
is not directly measurable except when it is near isothermal. 
For a Lambertian surface with a uniform temperature in thermo 
dynamic equilibrium, the kinetic temperature, hemispherical 
infrared temperature and directional infrared temperature from 
any direction are identical. A mean kinetic temperature may be 
the arithmetic average of all the objects, or an area weighted 
mean. A directional kinetic temperature may weight the fourth 
power of temperatures of objects by the fraction of view they 
occupy from some particular view direction. 
A nonspecific term that may refer to the directional brightness 
or infrared temperature for a sensor with particular wavelength 
and view characteristics. 
A general, nonspecific term referring to the aggregate tempera 
ture of all objects comprising the surface. It might be an infra 
red temperature, kinetic temperature or aerodynamic tempera 
ture, or it may be directional or hemispherical.