Diurnal signals in satellite sea surface temperature measurements

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Abstract
During the daytime, solar heating may lead to the formation of a near‐surface diurnal warm layer, particularly in regions with low wind speeds. This effect can be clearly seen in global, satellite‐derived, maps of the difference between daytime and nighttime SSTs. Analysis of TMI and AVHRR SSTs revealed that the onset of warming begins as early as 8 AM and peaks near 3 PM., with a magnitude of 2.8 C during favorable conditions. After this peak, the signal decays gradually until 11 PM, when the skin temperature approaches the bulk temperature. An empirical model is calculated from satellite SST and wind speed data, then used to derive daily global maps of diurnal warming. When modeled warming is removed from daytime SSTs, the mean and standard deviation of day minus night SST differences are diminished.