Spatiotemporal Features of Intraseasonal Oceanic Variability in the Philippine Sea From Mooring Observations and Numerical Simulations

The Philippine Sea is located within the pathway of the propagating Madden-Julian Oscillation system and is also the destination for the North Pacific mesoscale oceanic eddies and waves. As such, the Philippine Sea is characterized by striking intraseasonal variability (ISV; 20-90 days) that plays a key role in bridging weather and climate. Spatial patterns and temporal features of intraseasonal oceanic variability along the Philippine coast are investigated using mooring observations and outputs from an eddy-resolving general circulation model. The amplitude of ISV determined from sea level anomaly is found to decrease from the northern and coastal Philippine Sea to the south and interior Pacific Ocean. In contrast, eddy kinetic energy features a northward decreasing gradient with a maximum at about 6 degrees N. The meridional distribution of sea level anomaly and eddy kinetic energy spectra indicates that the ISV period increases with latitude and is symmetrical about the equator. Mesoscale eddies in the upper layer are tracked to explore the statistical distribution. Westward propagating mesoscale eddies and intraseasonal Rossby waves related to dynamic instabilities are an important source of the oceanic ISV in the Philippine Sea. Clear coastal propagation of ISVs related to coastal Kelvin waves is detected the south of about 14 degrees N. Composite analysis shows that the Madden-Julian Oscillation is another important forcing shaping the spatial features of Philippine ISV intensity and contributes close to half of the observed total ISV.