Brightness Temperature vs. Sea Surface Temperature

Description: Microwave radiometers measure the emitted power of a surface in terms of a parameter called the brightness temperature which is proportional to the ideal black body radiation. This graph shows brightness temperature (degrees Kelvin) versus sea surface temperature (SST; degrees Celsius) at the frequency of the NASA Aquarius instrument (1.41 GHz). Each blue line represents a specific salinity value (12, 17, 22, etc.) measured as Practical Salinity Units (psu) which is roughly equivalent to parts per thousand. The teal area labeled "Open Ocean" indicates salinity values commonly found at the sea surface (i.e., 32 - 37 psu). Credit: Klein & Swift, 1977.