2026-10-14T06:29:46Z https://api.figshare.com/v2/oai

oai:figshare.com:article/33770914 2026-09-15T04:28:11Z category_62 portal_316 item_type_3 month_year_09_2026

Data Sheet 1_Estimation and interpretation of spatially varying bottom friction coefficients in Bohai Bay using A-4DEnVar.docx Yang Zhang (30734) Wei Li (7081) Guijun Han (13228641) Xuan Wang (55634) Hong Li (20183) Haowen Wu (9955526) Lige Cao (20380194) Gongfu Zhou (480506) Xudong Cui (1670146) Qingyu Zheng (17737497) Yicong Tong (24912139) Jianxin He (120804) Marine Biology A−4DEnVar Bohai Bay bottom friction coefficient data assimilation suspended sediment form drag tidal modeling Introduction<p>The bottom friction coefficient (BFC) is critical for numerical simulations of tides and coastal ocean engineering. In situ observations indicate that BFC is spatially variable; however, it is challenging to represent it accurately in tidal models.</p>Methods<p>In this study, two principal tidal constituents (M2 and K1) were synchronously simulated in Bohai Bay using the Princeton Ocean Model with a generalized coordinate system. The tidal harmonic constants obtained from the NAO.99jb tidal harmonic constants dataset and tidal gauge stations are assimilated into the tidal model. An analytical four-dimensional ensemble variational data assimilation scheme is used to jointly estimate the open boundary conditions, BFCs, and bathymetry of the tidal model. Additionally, a random forest approach is applied to quantify the relative contributions of form drag, suspended sediment concentration, tidal current speed, and water depth to the spatial distribution of BFC in Bohai Bay.</p>Results<p>The tidal model performance improved after data assimilation, and the multi-parameter joint optimization scheme outperformed optimizing BFC alone. The spatial distributions of BFCs estimated through different observations were nearly consistent and robust, as verified by sensitivity experiments. The model explains approximately 76% of the BFC spatial variance, with suspended sediment concentration and form drag identified as the dominant controlling factors. The relationships between BFC and each influencing factor, as derived from partial dependence analysis, are consistent with the conclusions reported in existing studies.</p>Discussion<p>The results are beneficial for determining accurate spatially varying BFCs in the tidal model of Bohai Bay.</p> 2026-09-15T04:28:11Z Dataset Dataset 10.3389/fmars.2026.1864155.s001 https://figshare.com/articles/dataset/Data_Sheet_1_Estimation_and_interpretation_of_spatially_varying_bottom_friction_coefficients_in_Bohai_Bay_using_A-4DEnVar_docx/33770914 CC BY 4.0