From AMS Glossary
A process where one layer of the atmosphere stops interacting with an adjacent layer.
An example is a stratocumulus-topped turbulent boundary layer during the night, where infrared radiative cooling of cloud top causes cold "thermals" to sink toward the ground, causing strong turbulent coupling between the cloud and subcloud layers. During the day, these two layers can become decoupled as the combination of solar heating and infrared cooling in the cloud layer combine to make the cloud layer warmer than the subcloud layer, with a weak stable layer in between that reduces or prevents turbulent coupling of the two layers. These turbulently decoupled layers might still interact (i.e., be slightly coupled) in other ways, such as via radiation or drizzle fallout.