I'm trying to understand what causes the sea-surface temperature (in the open ocean and coastal areas) and the air temperature immediately above it to be different. I know very little about the subject, as I have not taken a class on boundary layers. I would think that in the winter, air is colder than the ocean (and vice-versa in the summer) because the ocean has a higher heat capacity than air. Am I right? What other factors contribute to the differences between SST and local air temperature, and are there notable exceptions to what I say above?

If there are relevant papers or texts on this topic, please let me know...

  • $\begingroup$ SST can be warmer or colder than air temperature. One common effect of SST<Tair is the formation of sea fog. For instance, along the California upwelling, moist air encounters cooler waters and results in intense fog (e.g., San Francisco). $\endgroup$
    – arkaia
    Dec 16, 2015 at 15:25

2 Answers 2


You're right. Water has a much higher specific heat capacity than air, so will change temperature much more slowly. This means that,

  • the sea surface tends not to reach the same extremes as the air (hence the seasonal effect that you mentioned)
  • the sea tends to lag behind the air in seasonal changes
  • the air readily heats and cools with day and night, while the sea does this much less; so which one is warmer can vary on a diurnal as well as a seasonal basis.

All this can then be greatly complicated by sea and air currents, especially vertical circulation in the ocean - but you have the right idea.


I think you're overestimating the amount of knowledge you need to really understand it.

The short answer is basically exactly what you said: air and water have extremely different heat capacities. How the water itself behaves is a whole other can of worms, but you don't need to worry about the nuances of ocean circulation (which I've forgotten myself! undergrad was quite a while ago) to understand the basics of how SST and air temperature are different.

There are certainly many, many exceptions to the general patterns you mention, but to answer that you have to delve into the intricacies of circulation in the region you're studying. Wind patterns have strong effects on surface circulation (e.g. https://en.wikipedia.org/wiki/Sverdrup_balance), but Salinity plays a major factor as well in areas of intense rainfall or ice melting for example.

TL;DR: you're right. :)


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