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Keywords:

  • clouds;
  • radiation;
  • ITCZ;
  • circulation changes

Abstract

Whereas it is well established that clouds are important to changes in Earth's surface temperature, their impact on changes of the large-scale atmospheric circulation is less well understood. Here we study the radiative impact of clouds on the shift of the Intertropical Convergence Zone (ITCZ) in response to hemispheric surface albedo forcings. The problem is approached using aquaplanet simulations with four comprehensive atmosphere models. The radiative impact of clouds on the ITCZ shift differs in sign and magnitude across models and is responsible for half of the model spread in the ITCZ shift. The model spread is dominated by tropical clouds whose radiative impact is linked to the dependence of their cloud radiative properties on the circulation. The simulations not only demonstrate the importance of clouds for circulation changes but also propose a way to reduce the model uncertainty in ITCZ shifts.