Influence of cloud radiative effects on the large-scale climate variability in the extratropics

Influence of cloud radiative effect on the tropical circulation and precipitation have been investigated extensively, but relatively little research effort has been placed on understanding the impact of cloud radiative effect on the large-scale variability in the extratropical atmospheric circulation. Extratropical clouds over the storm track regions exert a large net radiative cooling effect at the top of the atmosphere. Making clouds transparent to the radiation, the amplitude of the annual-mean eddy kinetic energy is significantly reduced by a factor of 3. Such reduction in the amplitude of the eddy kinetic energy is not simulated in the numerical experiments in which only planetary boundary layer clouds are made transparent to the radiation. Possible physical processes explaining the changes in eddy kinetic energy in the absence of cloud-radiative effects are examined. Impacts of the removal of atmospheric cloud radiative effect on the large-scale patterns of climate variability and surface climate are discussed.