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The effect of breaking waves on ocean surface temperatures and surface boundary layer deepening is investigated. The modification of the Mellor–Yamada turbulence closure model by Craig and Banner and others to include surface wave breaking energetics reduces summertime surface temperatures when the surface layer is relatively shallow. The effect of the Charnock constant in the relevant drag coefficient relation is also studied.

Detailed simulations, comparisons with observations, and model sensitivity experiments are presented for the August 2011 tropical cyclone Irene and a March 2010 nor'easter that affected the New York City (NYC) metropolitan area. These storms brought strong winds, heavy rainfall, and the fourth and seventh highest gauged storm tides (total water level), respectively, at the Battery, NYC. To dissect the storm tides and examine the role of various physical processes in controlling total water level, a series of model experiments was performed where one process was omitted for each experiment, and results were studied for eight different tide stations. Neglecting remote meteorological forcing (beyond ∼250 km) led to typical reductions of 7–17% in peak storm tide, neglecting water density variations led to typical reductions of 1–13%, neglecting a parameterization that accounts for enhanced wind drag due to wave steepness led to typical reductions of 3–12%, and neglecting atmospheric pressure gradient forcing led to typical reductions of 3–11%. Neglecting freshwater inputs to the model domain led to reductions of 2% at the Battery and 9% at Piermont, 14 km up the Hudson River from NYC. Few storm surge modeling studies or operational forecasting systems incorporate the “estuary effects” of freshwater flows and water density variations, yet joint omission of these processes for Irene leads to a low‐bias in storm tide for NYC sites like La Guardia and Newark Airports (9%) and the Battery (7%), as well as nearby vulnerable sites like the Indian Point nuclear plant (23%).

Some of the results from a series of diagnostic and prognostic numerical simulations of the circulation in the South Atlantic Bight (SAB) are described. The numerical model developed for the study is a three‐dimensional, primitive equation, time dependent, σ coordinate model with an imbedded, turbulent closure submodel which should yield realistic Ekman surface and bottom layers. An implicit numerical scheme in the vertical direction and a mode‐splitting technique in time are adopted for computational efficiency. A significant portion of the paper is concerned with realistic specification of initial conditions for temperature and salinity, surface forcing, and lateral open boundary conditions. The latter are determined by a simple diagnostic (geostrophic and Ekman dynamics) model which provides dynamically consistent temperature, salinity, and velocity boundary conditions. It appears from an exaination of the numerical simulations that the full model yields results that share many features in common with our general understanding of the circulation of the South Atlantic Bight; the region includes shallow shelf waters as well as deeper water dominated by the Gulf Stream. Data for synoptic skill assessment, however, are not available.

Recent studies of flood risk at New York Harbor (NYH) have shown disparate results for the 100 year storm tide, providing an uncertain foundation for the flood mitigation response after Hurricane Sandy. Here we present a flood hazard assessment that improves confidence in our understanding of the region's present‐day potential for flooding, by separately including the contribution of tropical cyclones (TCs) and extratropical cyclones (ETCs), and validating our modeling study at multiple stages against historical observations. The TC assessment is based on a climatology of 606 synthetic storms developed from a statistical‐stochastic model of North Atlantic TCs. The ETC assessment is based on simulations of historical storms with many random tide scenarios. Synthetic TC landfall rates and the final TC and ETC flood exceedance curves are all shown to be consistent with curves computed using historical data, within 95% confidence ranges. Combining the ETC and TC results together, the 100 year return period storm tide at NYH is 2.70 m (2.51–2.92 at 95% confidence), and Hurricane Sandy's storm tide of 3.38 m was a 260 year (170–420) storm tide. Deeper analyses of historical flood reports from estimated Category‐3 hurricanes in 1788 and 1821 lead to new estimates and reduced uncertainties for their floods and show that Sandy's storm tide was the largest at NYH back to at least 1700. The flood exceedance curves for ETCs and TCs have sharply different slopes due to their differing meteorology and frequency, warranting separate treatment in hazard assessments.

A. coupled hydrodynamic and water quality model was used to examine the response of dissolved oxygen concentrations to warming of the central basin of Lake Erie. An area-averaged hydrodynamic model was used to estimate the lake temperatures and thermocline variability as forced by surface heating and winds. Vertical turbulence mixing processes were incorporated by a second-moment, turbulence closure submodel. The water quality model comprised a set of 15 mass balance equations that predicted distributions of phytoplankton biomass, nutrient concentration, and dissolved oxygen. A synthesis of the results from the coupled model forced by climate warming scenarios from three atmospheric general circulation models suggested that there will be a substantial decline in oxygen concentrations in the central basin. Although forecasts of future conditions that are beyond established experiences are uncertain, it appears likely that climate warming will lead to such a decline regardless of details in changes of lake stratification dynamics. Losses of 1 mg/L of dissolved oxygen in the upper layers and of 1-2 mg/L in the lower layers of Lake Erie's central basin can be expected, along with an increase in the area of the lake that is anoxic. The decline in dissolved oxygen is predicted to be due to warmer lake temperatures, which increase the rate of bacterial activity in the hypolimnion waters and sediment, rather than to thermocline location and volume of water below the thermocline.

Three-dimensional simulations of estuarine circulation in the New York Harbor complex, Long Island Sound, and the New York Bight have been conducted using the Estuarine, Coastal and Ocean Model (ECOM) within the framework of a single grid system. The model grid is curvilinear and orthogonal, with resolution from 100 m in rivers to about 50 km in the bight. The model forcing functions consist of (1) meteorological data; (2) water level elevation and temperature and salinity fields along the open boundary; and (3) freshwater inflows from 30 rivers, 110 wastewater treatment plants, and 268 point sources from combined sewer overflows and surface runoffs. Because the goal of this study is to maximize, to the extent possible, the predictive skill of the modeling system, the motivation for and a detailed description of the construction of these boundary forcing functions are presented. Two 12-month periods are considered: (1) October 1988 to September 1989 for model calibration; and (2) October 1994 to September 1995 for model validation. For model calibration, the results are compared with water levels at 14 stations, currents at six stations, and temperature and salinity at 35 stations. Model validation is accomplished using data from an extensive hydrodynamic monitoring program. Mean errors in predicted elevations and currents are less than 10% and 15%, respectively. Correlation coefficients for salinity and temperature are as high as 0.86 and 1.0, respectively. The level of skill shown by these statistical measures suggests that the model is capable of describing the entire spectrum of time scales for the computed quantities, from the semidiurnal to the annual scales.

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