Impact of the Pacific-Japan pattern on the tropical Indo-western Pacific Ocean surface waves

Abstract

The present study examines the impact of the Pacific-Japan (PJ) pattern on tropical Indo Western Pacific Ocean significant wave heights during the boreal summer season (June through August, JJA) for the first time. The PJ pattern is a dominant teleconnection pattern characterized by meridional propagating Rossby waves over the Western North Pacific (WNP) and East Asia. The strong southwesterly monsoon winds prevail over the North Indian Ocean (NIO) during JJA inducing strong wave heights in the mean state. The regression analysis of significant wave height anomalies on the PJ index exhibits strong negative wave height anomalies over the Bay of Bengal (BoB), the tropical WNP region and slightly weaker negative anomalies over the Arabian Sea (AS) due to a reduction in the wind-wave growth. The weakening of wave heights in the BoB and WNP regions during PJ is attributed to the anomalous low-level anticyclonic circulation accompanied by high sea-level pressure anomalies over the BoB and WNP regions. The anomalous anticyclonic circulation opposes the mean south-westerlies and reduces the wave heights over the NIO and WNP. Further, the composite analysis of positive and negative PJ patterns display significant asymmetries in their signature on the wind and wave parameters. Thus, our findings suggest that the WNP regions climate conditions strongly modulate the NIOs surface waves.