Globally the cooling of the atmosphere by radiation is balanced by its heating from condensation and heat transfer from the Earth’s surface. This study is the first to investigate this so-called Radiative Convective Equilibrium – or RCE – from observations.

It finds that RCE is a strongly non-local equilibrium that intimately involves the circulation of the atmosphere to connect regions of strong cooling in the subtropics with regions of heavy rainfall in the tropics.

We also find that the equilibrium breaks down once the area considered decreases to sizes less than a few thousand kilometres on a side.

This implies that cloud model simulations using the RCE assumption should be carried out for areas larger than this threshold.

We also show that RCE usually combines a mixture of large areas covered with low clouds and little precipitation with small areas of convection.