Article

Climate Dynamics

, Volume 42, Issue 7, pp 2019-2031

The MJO and global warming: a study in CCSM4

  • Aneesh SubramanianAffiliated withSIO, UCSD Email author 
  • , Markus JochumAffiliated withClimate and Geophysics Division, The Niels Bohr Institute
  • , Arthur J. MillerAffiliated withSIO, UCSD
  • , Richard NealeAffiliated withClimate and Global Dynamics Division, National Center for Atmospheric Research
  • , Hyodae SeoAffiliated withPhysical Oceanography Department, Woods Hole Oceanographic Institution
  • , Duane WaliserAffiliated withJet Propulsion Laboratory, California Institute of Technology
  • , Raghu MurtuguddeAffiliated withEarth System Science Interdisciplinary Center, University of Maryland

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Abstract

The change in Madden–Julian oscillation (MJO) amplitude and variance in response to anthropogenic climate change is assessed in the 1° nominal resolution community climate system model, version 4 (CCSM4), which has a reasonable representation of the MJO characteristics both dynamically and statistically. The twentieth century CCSM4 run is compared with the warmest twenty-first century projection (representative concentration pathway 8.5, or RCP8.5). The last 20 years of each simulation are compared in their MJO characteristics, including spatial variance distributions of winds, precipitation and outgoing longwave radiation, histograms of event amplitude, phase and duration, and composite maps of phases. The RCP8.5 run exhibits increased variance in intraseasonal precipitation, larger-amplitude MJO events, stronger MJO rainfall in the central and eastern tropical Pacific, and a greater frequency of MJO occurrence for phases corresponding to enhanced rainfall in the Indian Ocean sector. These features are consistent with the concept of an increased magnitude for the hydrological cycle under greenhouse warming conditions. Conversely, the number of active MJO days decreases and fewer weak MJO events occur in the future climate state. These results motivate further study of these changes since tropical rainfall variability plays such an important role in the region’s socio-economic well being.

Keywords

MJO Climate change CCSM4