05 July 2016

Impacts of El Niño and Aerosols on Cloud Radiative Effects

El Niño dominates inter-annual variations of cloud radiative effects contributing up to 30% of the effects over the tropics.

Science

Inter-annual variability in cloud radiative effects is driven by mid-level and high clouds. Both natural aerosol emissions and concentrations enhance the variability.

Impact

This study reveals the importance of aerosols to the inter-annual variability of cloud radiative effects.

Summary

A research team, including scientists from the Department of Energy’s Pacific Northwest National Laboratory, used three 150-year pre-industrial simulations of the Community Earth System Model to quantify the impacts of El Niño events on shortwave and longwave cloud radiative effects. They found that the El Niño cycle dominates inter-annual variations of cloud radiative effects. Sensitivity tests showed that variations of cloud radiative effects are mainly driven by El Niño-related changes in the cloud fraction. Aerosols contribute to 10–30% of the inter-annual variability of cloud radiative effects over the tropics.

Contact
Steven J. Ghan
Pacific Northwest National Laboratory (PNNL)
Publications
Yang, Y, LM Russell, L Xu, S Lou, MA Lamjiri, RC Somerville, AJ Miller, DR Cayan, MJ DeFlorio, SJ Ghan, Y Liu, B Singh, H Wang, J Yoon, and PJ Rasch.  2016.  "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, doi:10.1002/2015JD024503.