High-resolution wave climate analysis in complex tropical straits using triple-nested unstructured WW3 modeling

Abstract

We investigate the seasonal, interannual, and long-term behaviour of waves in and around the Malacca–Singapore Strait using a nested, high-resolution WAVEWATCH III hindcast forced by 8-km downscaled ERA5 through SINGV-RCM for 1981–2014, rigorously validated against multi-mission altimetry. The regional climatology features a persistent offshore–inshore gradient shaped by fetch alignment and bathymetry, with the most energetic conditions in boreal winter. Interannually, significant wave height anomalies are positively linked to ENSO and organize into a winter dipole that enhances waves in the straits while weakening or reversing the response east of Singapore; this structure is captured by a dominant, in-phase leading EOF (explaining the vast majority of interannual variance) and a secondary cross-shore mode governed by directional winds and island/topographic sheltering. Long-term tendencies indicate a modest rise in mean wave conditions from spring to autumn alongside a wintertime weakening of extremes over the eastern shelf, indicating a redistribution of risk from rare peaks toward more frequent moderate states. Generalized extreme-value analysis provides a coherent exposure gradient in present-climate design levels, with 100-year significant wave heights reaching $\sim 6$ m on the outer shelf and substantially lower values in the straits ($\sim 3$ m) and harbours ($\sim 1$ m). Thus, these mechanism-consistent diagnostics provide exposure-aware guidance for navigation, port operations, and coastal design in the Singapore region.