The meridional overturning circulation has two regimes. Under weak insolation and fast rotation, the circulation is dominantly driven by momentum forcing (including friction, eddy momentum transport etc.), and is thermally-indirect in most of the low latitudes (mechanism). Under strong insolation and slow rotation, the circulation is dominantly driven by thermal forcing (including diabatic heating, eddy heat transport etc.), and is thermally-direct.
As circulation transforms from a thermally indirect circulation to a thermally direct one, the upper air starts to be filled with low angular momentum air from the extratropics (panel c versus panel b), meanwhile, the low latitudes start to be dominated by downward motion, largely reducing the cloud fraction (panel f versus panel e).
Kang. W. 2019, Regime transition between eddy-driven and moist-driven circulation on High Obliquity Planets, Astrophysical Journal (accepted)