Unstructured Grid-Based River–Coastal Ocean Circulation Modeling towards a Digital Twin of the Seto Inland Sea

Abstract

As computational techniques advance, the scope of digital twins (DTs) is expanding to encompass entire cities, oceans, or even the Earth. Digital twins of oceans can provide highly comprehensive insights and predictions, thus enabling better-informed decision-making regarding ocean-related activities and management. Here, a numerical model of the Seto Inland Sea (SIS), Japan, was built as a basis to establish a digital twin of the SIS. Spatially varying filtering parameters and grid resolutions were applied to facilitate the robust and accurate simulation of coastal and oceanic processes even under varying extreme conditions. The modeling results were validated using observational datasets from forty-two tidal stations, one mooring system, and thirteen water thermometers. The results represented tidal variations, with NRMSE values below 0.15 and R2 values exceeding 0.87 at all tidal stations. The NRMSE and R2 values for currents were approximately 0.14 and 0.76, respectively. The model reproduced the extreme storm surge event causing a sea level rise of 1.5 m near Osaka City resulting from Typhoon Jebi in 2018. The model was shown to enable analyses of complex circulations and hazards in the SIS by accurately replicating barotropic and baroclinic processes. After additional modules are added, this model will serve as a basis for constructing a digital twin of the SIS.

Assessment and Integration of ERA5 Reanalysis and Fujita−Takahashi Models for Storm Surge Prediction in the East China Sea

“…There was no significant rise in the water level in the central and northern coastal areas where the flow direction was S. The level rise in Yangtze River Estuary, Zhoushan Islands, and Quanzhou in Fujian Province increased significantly by more than 4 m. The flow direction of the Yangtze River Estuary and Zhoushan Islands was E, while that of Quanzhou, Fujian, was N. This spatial variation can be attributed to the complex topographic conditions near the bay. The intricate coastline and shallow shoals in this area can amplify and constrain the storm surge, resulting in higher water levels, as previous studies have also reported (Jeong et al, 2023) [21]. In contrast, the smooth and deep topography of the open sea region is unfavorable for the accumulation of storm surges.…”

Seasonal Study of the Kako River Discharge Dynamics into Harima Nada Using a Coupled Atmospheric–Marine Model

“…Much research has been performed in the entire Seto Inland Sea [7][8][9][15][16][17][18][19][20], Harima Nada [10][11][12][13][14][21][22][23][24][25][26], and its surrounding areas like Osaka Bay [14,27,28], and different numerical and simulation models and monitoring observations have been proposed, applied, and conducted to describe and study the characteristics of these regions. Until this date, all the reported ocean dynamic models for the area used offline atmospherical forcing, which means that the input of atmospheric variables was either previously calculated using an atmospheric model, belonged to reanalysis datasets, or consisted of a time series of observed data.…”