VDatum for the Long Island Sound, Narragansett Bay, and New York Bight: Tidal Datums and Sea Surface Topography.

摘要

An application of the vertical datum transformation software tool, VDatum, is developed for the Long Island Sound (LIS), Narragansett Bay, New York Harbor and New York Bight areas. It performs conversions between various tidal datum fields and mean sea level as well as between mean sea level and the North American Vertical Datum of 1988 (NAVD88). The tidal datums fields were created using an unstructured, two-dimensional, barotropic hydrodynamic model, the ADvanced CIRCulation (ADCIRC) model. A triangular finiteelement grid consisting of 181,798 nodes and 333,910 cells was created for this tide model application. The model run was forced with seven tidal constituents (M2, S2, N2, K2, K1, O1, Q1) and tidal-induced water level undulations were simulated for 37 days. Various tidal datum fields, including mean lower low water (MLLW), mean low water (MLW), mean high water (MHW), and mean higher high water (MHHW), were computed based on water level time series from the final 30 days of the simulation. Model results were validated by comparing modeled and accepted datums from 123 water level stations maintained by NOAAs Center for Operational Oceanographic Products and Services (CO-OPS). Discrepancies between model results and accepted datums were attributed to model errors and were interpolated over the whole model domain using the tidal constituent and residual interpolation (TCARI) software to obtain a domain-wide error field for each tidal datum. The error fields were applied to the model results to achieve error-corrected tidal datums on the unstructured model grid. Finally, tidal datum fields were interpolated onto a regular VDatum grid of 0.0017 degree by 0.0017 degree (approximately 185 m by 185 m) resolution. A topography of the sea surface (TSS), defined as the elevation of NAVD88 relative to local mean sea level (LMSL), was derived based on data from the most recent National Tidal Datum Epoch (1983-2001). The NAVD88-to-LMSL spatially-varying transformations were computed using orthometric-to-tidal datum relationships at NOAA tidal gauges and at tide station benchmarks. Results from both methodologies were coupled to create a final TSS grid using spatial interpolation techniques.