Impacts of the Pacific meridional mode on rainfall over the maritime continent and australia: potential for seasonal predictions
This study assesses whether, the extent to which and why the Pacific Meridional Mode (PMM) modulates rainfall in Australia and the Maritime Continent. We find a statistically significant time-lagged association between March-to-May (MAM) PMM and September-to-November (SON) rainfall in the Maritime Continent and Australia. The association is largely caused by the contribution of PMM to the El Niño Southern Oscillation (ENSO). Positive (negative) MAM PMM is generally followed by El Niño (La Niña) events in the following SON and December-to-February (DJF), which then suppresses (enhances) rainfall in the Maritime Continent and Australia. The suppression (enhancement) of rainfall is closely tied to the dynamical changes of moisture flux using moisture flux potential and its divergent components. Following the positive (negative) PMM phases, there is a strong moisture flux potential sink (source) in SON over the Maritime Continent and Australia, which act to suppress (enhance) rainfall there. Using MAM PMM as a predictor for SON rainfall in the Maritime Continent and Australia, the prediction skill is comparable to the North American Multimodel Ensemble project (NMME) forecasts initialized in June over the period 1981–2014. This suggests that MAM PMM may be used as a predictor for SON rainfall in the Maritime Continent and Australia.
The authors are grateful to four anonymous reviewers for insightful comments. The authors thank the NMME program partners and acknowledge the help of NCEP, IRI and NCAR personnel in creating, updating and maintaining the NMME archive, with the support of NOAA, NSF, NASA and DOE. This study was partly supported by NOAA’s Climate Program Office’s Modeling, Analysis, Predictions, and Projections Program, Grant #NA15OAR4310073, and Award NA14OAR4830101 from the National Oceanic and Atmospheric Administration, US Department of Commerce.
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