Because the ocean, land, atmosphere, and clouds have relatively similar temperatures, all of these sources emit energy primarily in the infrared portion of the electromagnetic spectrum. Therefore, a satellite sensor used to determine temperature from measurements of infrared electromagnetic energy will actually receive this energy from several sources as shown in Figure 2.02, where
1 = surface (skin) emissions
2 = direct cloud emissions
3 = direct atmospheric emissions
4 = reflected cloud or atmosphere emissions.
Were interested in inferring sea surface temperature from measurements of the surface emissions of infrared electromagnetic energy from the ocean. To do this we must either minimize or correct for the energy arriving at the satellite from the other sources shown in Figure 2.02. Well look first at how to minimize the influence of absorption and emissions from atmospheric gases. A discussion on how to correct for the presence of clouds will follow. Finally, correcting for other atmospheric influences will be discussed.