|Title||The MJO and global warming: a study in CCSM4|
|Publication Type||Journal Article|
|Year of Publication||2014|
|Authors||Subramanian A., Jochum M., Miller AJ, Neale R., Seo H, Waliser D., Murtugudde R.|
|Type of Article||Article|
|Keywords||Atmospheric circulation; CCSM4; climate change; climate-change; el-nino; equatorial pacific; extremes; hydrological cycle; idealized gcm; madden-julian oscillation; MJO; nino-southern-oscillation; precipitation; wide-range|
The change in Madden-Julian oscillation (MJO) amplitude and variance in response to anthropogenic climate change is assessed in the 1A degrees 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.
|Short Title||Clim. Dyn.|
"Further studies with idealized GCMs and climate models are needed to clarify the dynamical mechanisms forcing regime changes in the MJO. Links between regime changes in the MJO and other low-frequency modes of the coupled ocean-atmosphere system need to be investigated further. Since the MJO is a critical component in modulating weather variability in the tropics and extratropics of both hemispheres, knowledge of the long-term behavior of the MJO is very important in having a good understanding of future climate states and consequences for humanity."