Japan Geoscience Union Meeting 2025

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[E] Poster

A (Atmospheric and Hydrospheric Sciences ) » A-CG Complex & General

[A-CG38] Climate Variability and Predictability on Subseasonal to Centennial Timescales

Wed. May 28, 2025 5:15 PM - 7:15 PM Poster Hall (Exhibition Hall 7&8, Makuhari Messe)

convener:Takahito Kataoka(JAMSTEC Japan Agency for Marine-Earth Science and Technology), Hiroyuki Murakami(Geophysical Fluid Dynamics Laboratory), Yushi Morioka(Japan Agency for Marine-Earth Science and Technology), Nathaniel C Johnson(NOAA Geophysical Fluid Dynamics Laboratory)

5:15 PM - 7:15 PM

[ACG38-P04] Seasonal Predictability of Marine Heat Waves during Summer around Hawaii

*Naoya Takahashi1, Takeshi Doi2, Malte F Stuecker3, Kelvin J Richards3, Niklas Schneider3, Masami Nonaka2 (1.Niigata University, 2.JAMSTEC, 3.University of Hawaii at Manoa)

Keywords:Seasonal Predictability, Marine Heat Waves, Air-sea Interaction

Predicting seasonal characteristics of marine heat waves (MHWs), such as covering days of these events during a specific season, is essential for providing valuable information to marine ecosystem and coastal communities. This study focuses on the open-ocean regions around Hawaii during summer season, specifically July-August-September (JAS) when prolonged MHW events have been observed since mid-2010s. We utilize 12-month re-forecast outputs of SINTEX-F2 seasonal forecast system initialized at 1st day of each month. Adopting a metric for the seasonal characteristics of “atmospheric” heat waves which involves covering days with sea surface (SST) temperature anomalies greater than the 90th percentile for a given season (N90), we evaluate the prediction skill of MHW seasonal characteristics. SINTEX-F2 can predict N90 index in JAS accurately from the preceding April, 3-5 months in advance. The accuracy is attributed to great prediction skill of both seasonal-mean SST and the standard deviation of daily-mean SST within a given season. Heat budget analysis for the prominent MHW event in JAS 2015 around Hawaii indicates that anomalous surface forcing and vertical diffusion terms play key roles during onset and decay phase of MHW event, respectively. To further evaluate the potential predictability source of MHW events around Hawaii, we conduct composite analysis for anomalies of SST and surface wind in the years with large observed N90 index in JAS. Favorable condition of MHW events associated with a weaken of the trade wind speed is underpredicted in SINTEX-F2. In terms of the relation with the climate variability, SINTEX-F2 can accurately predict the changes in trade wind speed associated with El-Nino Southern Oscillation, but less accurately for the changes solely associated with Pacific Meridional Mode.