Toward Understanding the Diverse Impacts of Air-Sea Interactions on Madden-Julian oscillation Simulations Journal of Geophysical Research: Oceans

The role of air-sea interactions on Madden-Julian oscillation simulations has long been recognized. However, the reasons for the variation of the impacts of air-sea coupling among different models are still elusive. In this study, we used NCEP GFS under different cumulus schemes and SST conditions to explore this issue. We focused on the Oct-Madden-Julian oscillation and Nov-Madden-Julian oscillation during the DYNAMO IOP. We show that the effects of SST-feedback on Madden-Julian oscillation simulations not only vary between these two Madden-Julian oscillation events, but are also very sensitive to the specifics of cumulus schemes and intraseasonal SST forcing. The Oct-Madden-Julian oscillation basically reinvigorates over Indian Ocean in association with the arrival of global circumnavigating mode. The Nov-Madden-Julian oscillation is largely reinvigorated by a robust intraseasonal SST anomaly over Indian Ocean. We found that SST-feedback is crucial for the existence of the Nov-Madden-Julian oscillation, but has little effect on the Oct-Madden-Julian oscillation. This finding raises the possibility that the occurrence of some Madden-Julian oscillation events may be rooted in air-sea interactions. These results suggest that the diverse impacts of air-sea coupling on Madden-Julian oscillation simulations can be attributed to at least the following three potential causes: (i) diverse responses of ocean to individual Madden-Julian oscillation events in nature; (ii) diverse behaviors of various cumulus parameterizations; and (iii) diverse intraseasonal SST anomalies in coupled models. Either a too weak internal Madden-Julian oscillation mode in atmospheric models or a too weak intraseasonal SST anomaly in coupled models would lead to the underestimation of the impacts of air-sea coupling on Madden-Julian oscillation simulations. Grant no. NA15OAR4310175 Grant no. NA16NWS4680019 Grant no. NA17OAR4310256