Diathermancy

[1] Diathermancy was first described by German physicist and chemist Heinrich Gustav Magnus in the 1800s.

Atmospheric air is heated by long-wave thermal radiation emitted by soil, and especially, by water on the Earth's surface.

Atmospheric heat comes from long-wave radiation from the soil and, mostly, from the water surface (oceans, lakes, rivers), because water is a not diathermanous body and covers three quarters of Earth's surface.

That is because these areas tend to absorb heat radiation directly from the Sun but very slowly and also emit this radiation to the atmosphere very slowly.

Therefore, cold ocean currents have very clear skies, without clouds, because subsidence from cold and heavy air avoids or limits convection because they are opposite processes.