Yang, Y., L. M. Russell, L. Xu, S. Lou, M. A. Lamjiri, R.
C. J. Somerville, A. J. Miller, D. R. Cayan, M. J. DeFlorio,
S. J. Ghan, Y. Liu, B. Singh, H. Wang, J.-H. Yoon
and P. J. Rasch,
2015:
Impacts of ENSO events on cloud radiative effects
in preindustrial conditions: Changes in cloud
fraction and their dependence on interactive
aerosol emissions and concentrations
Journal of Geophysical Research-Atmospheres, 121, 6321-6335.
Abstract.
We use three 150 year preindustrial simulations of the Community Earth System Model to
quantify the impacts of El Nino-Southern Oscillation (ENSO) events on shortwave and longwave cloud
radiative effects (CRE_SW and CRE_LW). Compared to recent observations from the Clouds and the Earth's Radiant
Energy System data set, the model simulation successfully reproduces larger variations of CRE_SW and CRE_LW
over the tropics. The ENSO cycle is found to dominate interannual variations of cloud radiative effects.
Simulated cooling (warming) effects from CRE_SW (CRE_LW) are strongest over the tropical western and central
Pacific Ocean during warm ENSO events, with the largest difference between 20 and 60 W/m2, with weaker
effects of 10-40 W/m2 over Indonesian regions and the subtropical Pacific Ocean. Sensitivity tests show that
variations of cloud radiative effects are mainly driven by ENSO-related changes in cloud fraction. The variations
in midlevel and high cloud fractions each account for approximately 20-50% of the interannual variations of
CRESW over the tropics and almost all of the variations of CRE_LW between 60S and 60N. The variation of low
cloud fraction contributes to most of the variations of CRE_SW over the midlatitude oceans. Variations in natural
aerosol concentrations explained 10-30% of the variations of both CRE_SW and CRE_LW over the tropical Pacific,
Indonesian regions, and the tropical Indian Ocean. Changes in natural aerosol emissions and concentrations
enhance 3-5% and 1-3% of the variations of cloud radiative effects averaged over the tropics.
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