Ocean–atmosphere dynamics during Hurricane Ida and Nor’Ida : an application of the coupled ocean–atmosphere–wave–sediment transport (COAWST) modeling system

This paper is not subject to U.S. copyright. The definitive version was published in Ocean Modelling 43-44 (2012): 112–137, doi:10.1016/j.ocemod.2011.12.008.The coupled ocean–atmosphere–wave–sediment transport (COAWST) modeling system was used to investigate atmosphere–ocean–wave interactions in November 2009 during Hurricane Ida and its subsequent evolution to Nor’Ida, which was one of the most costly storm systems of the past two decades. One interesting aspect of this event is that it included two unique atmospheric extreme conditions, a hurricane and a nor’easter storm, which developed in regions with different oceanographic characteristics. Our modeled results were compared with several data sources, including GOES satellite infrared data, JASON-1 and JASON-2 altimeter data, CODAR measurements, and wave and tidal information from the National Data Buoy Center (NDBC) and the National Tidal Database. By performing a series of numerical runs, we were able to isolate the effect of the interaction terms between the atmosphere (modeled with Weather Research and Forecasting, the WRF model), the ocean (modeled with Regional Ocean Modeling System (ROMS)), and the wave propagation and generation model (modeled with Simulating Waves Nearshore (SWAN)). Special attention was given to the role of the ocean surface roughness. Three different ocean roughness closure models were analyzed: DGHQ (which is based on wave age), TY2001 (which is based on wave steepness), and OOST (which considers both the effects of wave age and steepness). Including the ocean roughness in the atmospheric module improved the wind intensity estimation and therefore also the wind waves, surface currents, and storm surge amplitude. For example, during the passage of Hurricane Ida through the Gulf of Mexico, the wind speeds were reduced due to wave-induced ocean roughness, resulting in better agreement with the measured winds. During Nor’Ida, including the wave-induced surface roughness changed the form and dimension of the main low pressure cell, affecting the intensity and direction of the winds. The combined wave age- and wave steepness-based parameterization (OOST) provided the best results for wind and wave growth prediction. However, the best agreement between the measured (CODAR) and computed surface currents and storm surge values was obtained with the wave steepness-based roughness parameterization (TY2001), although the differences obtained with respect to DGHQ were not significant. The influence of sea surface temperature (SST) fields on the atmospheric boundary layer dynamics was examined; in particular, we evaluated how the SST affects wind wave generation, surface currents and storm surges. The integrated hydrograph and integrated wave height, parameters that are highly correlated with the storm damage potential, were found to be highly sensitive to the ocean surface roughness parameterization.Primary funding for this study was furnished by the US Geological Survey, Coastal and Marine Geology Program, under the Carolinas Coastal Processes Project

Mid-Breton Sediment Diversion (MBrSD) Assessment – Final Report

The purpose of this project is to provide managers at the Mississippi Department of Marine Resources (MDMR) with the scientific information needed to accurately address public concerns regarding the potential effects of the Louisiana Coastal Master Plan / Coastal Protection and Restoration Authority (CPRA) Mid-Breton Sediment Diversion (MBrSD) on the jurisdictional waters and resources of Mississippi. The stated design purpose of the MBrSD is to reconnect and re-establish the deltaic sediment deposition process between the Mississippi River and the Breton Sound Basin through a diversion that will deliver up to 75,000 cfs of sediment-laden freshwater. The report presented herein provides model-based guidance on the impact that the introduction of the MBrSD will have on salinity conditions in the Mississippi Sound (MSS) and Mississippi\u27s jurisdictional waters that encompass oyster reef locations. Oysters are key ecosystem health indicators and economic drivers for the State of Mississippi and freshwater diversions into the western MS Sound (WMSS) have recently led to significant, unprecedented environmental impacts resulting in oyster mortality. The potential addition of a new pathway for additional freshwater to be introduced into the MSS requires careful assessment of the potential impacts that may be incurred. This project is designed to assess the impact of implementing the MBrSD on the physical environment in the WMSS. The primary aim is to understand the connectivity between MBrSD-derived freshwater input to Breton Sound on the environmental conditions impacting the oyster reefs of the WMSS near Bay St. Louis. A physical ocean modeling system based on the Coupled Ocean Atmosphere Wave Sediment Transport (COAWST) has been used to simulate the circulation and dynamics over the entire MSS with the analysis presented herein focusing particularly on the western to central MSS. This project demonstrates the importance of applying modeling-based scientific research and the capability of physical ocean circulation models for assessing aquatic ecosystem health, particularly in key oyster reef areas

Storm-induced inner-continental shelf circulation and sediment transport : Long Bay, South Carolina

This paper is not subject to U.S. copyright. The definitive version was published in Continental Shelf Research 42 (2012): 51–63, doi:10.1016/j.csr.2012.05.001.Long Bay is a sediment-starved, arcuate embayment located along the US East Coast connecting both South and North Carolina. In this region the rates and pathways of sediment transport are important because they determine the availability of sediments for beach nourishment, seafloor habitat, and navigation. The impact of storms on sediment transport magnitude and direction were investigated during the period October 2003–April 2004 using bottom mounted flow meters, acoustic backscatter sensors and rotary sonars deployed at eight sites offshore of Myrtle Beach, SC, to measure currents, water levels, surface waves, salinity, temperature, suspended sediment concentrations, and bedform morphology. Measurements identify that sediment mobility is caused by waves and wind driven currents from three predominant types of storm patterns that pass through this region: (1) cold fronts, (2) warm fronts and (3) low-pressure storms. The passage of a cold front is accompanied by a rapid change in wind direction from primarily northeastward to southwestward. The passage of a warm front is accompanied by an opposite change in wind direction from mainly southwestward to northeastward. Low-pressure systems passing offshore are accompanied by a change in wind direction from southwestward to southeastward as the offshore storm moves from south to north. During the passage of cold fronts more sediment is transported when winds are northeastward and directed onshore than when the winds are directed offshore, creating a net sediment flux to the north–east. Likewise, even though the warm front has an opposite wind pattern, net sediment flux is typically to the north–east due to the larger fetch when the winds are northeastward and directed onshore. During the passage of low-pressure systems strong winds, waves, and currents to the south are sustained creating a net sediment flux southwestward. During the 3-month deployment a total of 8 cold fronts, 10 warm fronts, and 10 low-pressure systems drove a net sediment flux southwestward. Analysis of a 12-year data record from a local buoy shows an average of 41 cold fronts, 32 warm fronts, and 26 low-pressure systems per year. The culmination of these events would yield a cumulative net inner-continental shelf transport to the south–west, a trend that is further verified by sediment textural analysis and bedform morphology on the inner-continental shelf.This research was funded by the South Carolina Coastal Erosion Project(http://pubs.usgs.gov/fs/2005/3041/), a cooperative study supported by the US Geological Survey and the South Carolina Sea Grant Consortium(Sea Grant Project no:R/CP-11)

Development of a Coupled Ocean–Atmosphere–Wave–Sediment Transport (COAWST) Modeling System

This paper is not subject to U.S. copyright. The definitive version was published in Ocean Modelling 35 (2010): 230-244, doi:10.1016/j.ocemod.2010.07.010.Understanding the processes responsible for coastal change is important for managing our coastal resources, both natural and economic. The current scientific understanding of coastal sediment transport and geology suggests that examining coastal processes at regional scales can lead to significant insight into how the coastal zone evolves. To better identify the significant processes affecting our coastlines and how those processes create coastal change we developed a Coupled Ocean–Atmosphere–Wave–Sediment Transport (COAWST) Modeling System, which is comprised of the Model Coupling Toolkit to exchange data fields between the ocean model ROMS, the atmosphere model WRF, the wave model SWAN, and the sediment capabilities of the Community Sediment Transport Model. This formulation builds upon previous developments by coupling the atmospheric model to the ocean and wave models, providing one-way grid refinement in the ocean model, one-way grid refinement in the wave model, and coupling on refined levels. Herein we describe the modeling components and the data fields exchanged. The modeling system is used to identify model sensitivity by exchanging prognostic variable fields between different model components during an application to simulate Hurricane Isabel during September 2003. Results identify that hurricane intensity is extremely sensitive to sea surface temperature. Intensity is reduced when coupled to the ocean model although the coupling provides a more realistic simulation of the sea surface temperature. Coupling of the ocean to the atmosphere also results in decreased boundary layer stress and coupling of the waves to the atmosphere results in increased bottom stress. Wave results are sensitive to both ocean and atmospheric coupling due to wave–current interactions with the ocean and wave growth from the atmosphere wind stress. Sediment resuspension at regional scale during the hurricane is controlled by shelf width and wave propagation during hurricane approach

The genetic architecture of the human cerebral cortex

The cerebral cortex underlies our complex cognitive capabilities, yet little is known about the specific genetic loci that influence human cortical structure. To identify genetic variants that affect cortical structure, we conducted a genome-wide association meta-analysis of brain magnetic resonance imaging data from 51,665 individuals. We analyzed the surface area and average thickness of the whole cortex and 34 regions with known functional specializations. We identified 199 significant loci and found significant enrichment for loci influencing total surface area within regulatory elements that are active during prenatal cortical development, supporting the radial unit hypothesis. Loci that affect regional surface area cluster near genes in Wnt signaling pathways, which influence progenitor expansion and areal identity. Variation in cortical structure is genetically correlated with cognitive function, Parkinson's disease, insomnia, depression, neuroticism, and attention deficit hyperactivity disorder

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Wind Sensitivity Analysis In a COAWST Model of the Mississippi Sound

The University of Southern Mississippi (USM) Ocean Modeling Group developed a high spatial resolution (400-m) Coupled Ocean Atmosphere Wave Sediment Transport (COAWST) modeling system with the Regional Ocean Modeling System (msbROMS) at its core during the Gulf of Mexico Research Initiative (GoMRI)-funded the Consortium for Coastal River-Dominated Ecosystems (CONCORDE) project. High spatial and temporal resolution wind forcing is necessary to resolve highly variable atmospheric circulation over complicated coastal features like those found in the Mississippi Sound. In this study, sensitivity of the ocean model predictions to atmospheric forcing with different spatial and temporal resolutions is examined to evaluate the impact on inlet exchange and estuarine dynamics. The hourly 1-km resolution output of the CONCORDE Meteorological Analysis (CMA) product developed at the USM, hourly 3-km resolution National Oceanic and Atmospheric Administration High-Resolution Rapid Refresh (HRRR) product with radar assimilation, and 3-hourly 32-km resolution North American Regional Reanalysis (NARR) product were used as atmospheric forcing to run the COAWST model for a period in the summer of 2016. We show that COAWST model results of coastal ocean variability significantly improve when forced with high temporal and spatial resolution CMA atmospheric product that captures diurnal sea breeze. This inclusion of sea breeze impacts on near shore circulation is critical for accurately representing estuarine exchanges of hydrographic and biogeochemical properties, hypoxia onset and intensity, and pathways of submarine groundwater discharge

Assessment of the Impact of the Variability of Freshwater Input and Land-Sea Breeze On the Mississippi Sound Using a Modeling Approach

The Mississippi Sound located on the northeastern Gulf of Mexico is greatly influenced by freshwater inflow and diurnal wind breeze. The Mississippi Sound shows the greatest variation in salinity from January to June due to the dynamics of high river water inflow and shelf water mixing. Besides the river water inflow, Bonnet Carré Spillway contributes a high influx of freshwater into the Mississippi Sound through its opening when it is operated to avoid flooding in New Orleans. After becoming operational in 1931, Bonnet Carré Spillway has been opened in 3 years consecutively (2018,2019, & 2020) for the first time and 2019 is the only year in which Bonnet Carré Spillway was opened twice in a calendar year which caused about 38.1 km 3 freshwater input into the Mississippi Sound. In addition to freshwater inflow, diurnal wind breeze acts as a primary source of hydrographic variability in the Mississippi Sound. As 2019 was a major year for Bonnet Carré Spillway opening impacts, the main objective of this study is to hindcast the combined effects of freshwater variability and diurnal land-sea breeze on salinity using observed and hypothetical numerical model scenarios. The main difference between these simulations is using two types of wind forcing in the COAWST modeling framework. Hourly NOAA High-Resolution Rapid Refresh (HRRR) output which captures the diurnal landsea breeze is used as atmospheric forcing for a simulation that represents the real scenario in 2019 and 24-hour low-pass filtered HRRR forcing which smooths out the wind in the diurnal frequency range is used for the hypothetical scenario. These twin experiments show the distinctive variation in salinity because of the effects of diurnal land-sea breeze on freshwater inflow and shelf water mixing. As the diurnal land-sea breeze is strong during late spring, summer, and the beginning of the fall season, salinity variability has been analyzed from March to October 2019 to understand the role of these diurnal effects. It is observed that the hypothetical simulation using filtered wind forcing overestimates the salinity in the month of June to October in the Mississippi Sound. It could be because using filtered wind forcing can shorten the flushing time and affect the shelf-water inflow in the Mississippi Sound. Salinity variation between these two simulations is evident in the central and eastern Mississippi Sound. For quantitative analysis, the sound has been divided into four north-south transects. In terms of surface salinity, the western and central-western transects are mostly affected by the Bonnet Carré Spillway opening and diurnal wind forcing does not play a dominating role here. But significant differences have been found in the central-eastern and eastern transect in the month of August. Filtered wind simulation is 2.4 ppt and 5 ppt saltier than the HRRR wind simulation along the central-eastern and eastern transect respectively during this month. The bottom salinity is less affected than the surface salinity observed in these twin experiments which is expected. As diurnal land-sea breeze plays a key role in the dynamics of freshwater and shelf water mixing in the Mississippi Sound, it can be concluded that high-resolution wind forcing data should be used for more accurate simulations of salinity in the Mississippi Sound