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Recent field observations suggest that the air‐sea momentum flux (or the drag coefficient) is significantly reduced when the dominant wind‐forced surface waves are misaligned from local wind. Such conditions may occur under rapidly changing strong winds (such as under tropical cyclones) or in coastal shallow waters where waves are refracted by bottom topography. A recent Large Eddy Simulation (LES) study also shows that the drag coefficient is reduced by a misaligned strongly forced wave train (with a small wave age of 1.37). In order to investigate more realistic field conditions, this study employs LES to examine the effect of a misaligned (up to 90°) surface wave train over a wide range of wave age up to 10.95. For all wave ages examined, the drag coefficient is reduced compared to the flat surface condition when the misalignment angle exceeds around 22.5°–45°. The drag reduction may occur even if the form drag of the wave train is positive. Plain Language Summary: This study uses computer simulations to investigate turbulent wind blowing over ocean surface waves that are misaligned (propagate in different directions) from the wind. The study focuses on frictional wind forcing (wind stress) imparted on the ocean surface, because the wind stress is an important boundary condition for ocean, atmospheric, and surface wave models. Surface waves can be misaligned from wind when the wind field rapidly changes such as during tropical storms or in shallow water where wave directions are modified by varying water depth. When waves propagate slower than wind in the wind direction, the waves increase the wind stress compared to flat surface (no wave) conditions. However, this study finds that the wind stress is reduced, that is, the ocean surface becomes smoother, when the misalignment angle between wind and waves exceeds about 22.5°–45°. Key Points: Large eddy simulations are preformed to study wind over misaligned surface wavesDrag coefficient is reduced due to misaligned surface waves for all wave ages under wind‐driven wave conditionsDrag reduction can occur even when wave form drag is positive [ABSTRACT FROM AUTHOR]

A process study using large‐eddy simulations is carried out to explore the dominant 1‐D processes that affect mixed layer (ML) properties during an event of summer Monsoon Intra‐seasonal Oscillations (MISO) in the Bay of Bengal (BOB). These simulations use realistic air‐sea fluxes and initial conditions that were collected during the summer 2018 MISO‐BOB field experiment to explore the roles of thermal inversion layer (TIL) and Langmuir turbulence (LT) in modulating ML properties. The simulations span an active period with heavy rain and strong winds and a break period with strong solar heat flux and little rain. The mixed layer depth (MLD), sea surface temperature (SST) and sea surface salinity (SSS) are most affected by the presence of near‐inertial oscillations, solar heating and precipitation, all of which occur at different timescales. The subsurface warming induced by the TIL reduces the SST variability at the MISO timescale when compared with the simulation without TIL. Comparison of simulations with and without LT indicates that LT enhances subsurface warming during the active phase and reduces diurnal SST modulation during the break phase. Simulations with 1‐D mixing models show a wide disparity in the evolution of MLD, SST, and SSS. Plain Language Summary: Monsoon rain affects the lives of the more than a billion people in the Indian subcontinent. Increasing the prediction skill of monsoon forecasting models requires understanding how different weather events mix heat in the upper ocean. This study evaluates the different roles of observed rain, cooling, wind, solar warming and waves on mixing for two different ocean conditions. Motivated by recent observations in the Bay of Bengal, one condition includes warm water near the surface and cooler at depth and the other condition includes anomalous heat at depth. During the monsoon onset, surface cooling, winds and waves can release the anomalous heat, causing sea surface temperature to increase rather than decrease. Warmer water at the air‐sea interface leads to stronger evaporation and thus affects the intensity of monsoon rain. Our large‐eddy simulation study suggests that resolving subsurface processes and including the enhanced mixing effect of surface waves can potentially improve the prediction skill of forecast models, and thus, warrant further attention in the future studies. Key Points: Near‐inertial oscillation, solar heating and precipitation are dominant 1D processes that set mixed layer properties during the 2018 MISO eventPreconditioning by a thermal inversion inside a barrier layer during the Monsoon Intra‐seasonal Oscillations (MISO) event can reduce the sea surface temperature (SST) variability at the MISO timescaleLarge‐eddy simulations with and without Langmuir effects show enhanced subsurface warming and reduced SST variability in the mixed layer in the former [ABSTRACT FROM AUTHOR]

The role of gas bubbles on the air‐sea CO2 flux during Hurricane Frances (2004) is studied using a large‐eddy simulation model that couples ocean surface boundary layer turbulence, gas bubbles, and dissolved gases. In the subtropical surface ocean where gases are slightly supersaturated, gases in bubbles can still dissolve due to hydrostatic pressure and surface tension exerted on bubbles. Under the simulated conditions, the CO2 efflux with an explicit bubble effect is less than 2% of that calculated using a gas flux formula without explicit inclusion of bubble effect. The use of a gas flux parameterization without bubble‐induced supersaturation contributes to uncertainty in the global carbon budget. The results highlight the importance of bubbles under high winds even for soluble gases such as CO2 and demonstrate that gas flux parameterization derived from gases of certain solubility may not be accurate for gases of very different solubility. Plain Language Summary: Carbon dioxide (CO2) is the primary anthropogenic greenhouse gases in the atmosphere and is the gas most responsible for global warming. The ocean is an important sink of anthropogenic atmospheric CO2, yet the exchange of CO2 between the ocean and the atmosphere is not fully understood. This study reexamines the exchange of CO2 under hurricanes over the low‐latitude ocean, using hurricane Frances (2004) as an example. Previous studies show that hurricanes significantly facilitate the outgassing of CO2 due to the extreme wind. Those studies, however, do not explicitly consider gas bubbles. Gas bubbles, entrained into the ocean when ocean wave breaks, are ubiquitous under hurricanes also due to the extreme wind. While in the ocean, gas bubbles not only move around under the influence of the chaotic wind‐driven currents and their own buoyancy, but they also exchange gases with the water. Our study, using state‐of‐the‐art computer models that concurrently simulate the chaotic ocean currents, gas bubbles, and dissolved gases, demonstrates that hurricane plays a significantly smaller role in the ocean‐atmosphere transfer of CO2 than previously estimated. Key Points: Gas bubbles reduce CO2 efflux from supersaturated water by a factor of 50 under hurricane winds for the simulated conditionsBubble‐induced supersaturation should be included in gas flux parameterization for CO2 in high wind conditionsParameterizations derived using O2, N2, and inert gases may not be accurate for CO2 that has a very different solubility [ABSTRACT FROM AUTHOR]

The Clouds, Aerosols, Precipitation, Radiation, and atmospherIc Composition Over the southeRn oceaN (CAPRICORN) experiment was carried out in March–April 2016 onboard R/V Investigator studying momentum (τ), sensible heat (Hs), and latent heat (Hl) fluxes over the Australian sector of the Southern Ocean including over one cyclonic cold‐core and one anticyclonic warm‐core mesoscale oceanic eddy. The turbulence‐based flux measurements obtained with the NOAA PSD flux system employing eddy covariance (EC) and inertial dissipation (ID) methods are compared with those obtained by the Coupled Ocean‐Atmosphere Response Experiment (COARE) 3.5 bulk model, and the neutral transfer coefficients are studied. The relative uncertainty between the turbulence‐based and COARE 3.5 estimates of τ, Hs, and Hl are 22%, 70%, and 26%, respectively, at 1‐hr time scale over the Southern Ocean. Further, the variability in bulk fluxes is investigated with respect to oceanic eddies, precipitation events, atmospheric stability, and extratropical cyclones encountered during the voyage. The main observed variability is an increase in significant wave height or γw (∼33%), τ (∼89%), Hs (∼187%), and Hl (∼79%) over the warm eddy as compared to average voyage values. During the passage of six extratropical cyclones, an increase in τ (∼62% average) and a decrease in Hs (∼235%) and Hl (∼79%) is noted in the warm sector, compared to prestorm conditions, but the pattern reverses behind the cold front. Key Points: COARE 3.5 bulk model gives lower mean estimates of wind stress and heat fluxes in the Southern Ocean when compared with observationsThe 10‐m‐neutral transfer coefficients of momentum and heat fluxes increase with wind speed >5 m/sHeat fluxes decrease in the warm sector of extratropical cyclones, but increase behind the cold front [ABSTRACT FROM AUTHOR]

Six recent Langmuir turbulence parameterization schemes and five traditional schemes are implemented in a common single‐column modeling framework and consistently compared. These schemes are tested in scenarios versus matched large eddy simulations, across the globe with realistic forcing (JRA55‐do, WAVEWATCH‐III simulated waves) and initial conditions (Argo), and under realistic conditions as observed at ocean moorings. Traditional non‐Langmuir schemes systematically underpredict large eddy simulation vertical mixing under weak convective forcing, while Langmuir schemes vary in accuracy. Under global, realistic forcing Langmuir schemes produce 6% (−1% to 14% for 90% confidence) or 5.2 m (−0.2 m to 17.4 m for 90% confidence) deeper monthly mean mixed layer depths than their non‐Langmuir counterparts, with the greatest differences in extratropical regions, especially the Southern Ocean in austral summer. Discrepancies among Langmuir schemes are large (15% in mixed layer depth standard deviation over the mean): largest under wave‐driven turbulence with stabilizing buoyancy forcing, next largest under strongly wave‐driven conditions with weak buoyancy forcing, and agreeing during strong convective forcing. Non‐Langmuir schemes disagree with each other to a lesser extent, with a similar ordering. Langmuir discrepancies obscure a cross‐scheme estimate of the Langmuir effect magnitude under realistic forcing, highlighting limited understanding and numerical deficiencies. Maps of the regions and seasons where the greatest discrepancies occur are provided to guide further studies and observations. Key Points: Six Langmuir turbulence parameterization schemes and five non‐Langmuir schemes are compared in a common single‐column modeling frameworkA suite of test cases of various scenarios are used, including typical global ocean conditions using JRA55‐doSignificant discrepancies among schemes are found and sorted by locations, seasons, and forcing regimes [ABSTRACT FROM AUTHOR]

Bubbles play an important role in the exchange of gases between the atmosphere and ocean, altering both the rate of exchange and the equilibrium gas saturation state. We develop a parameterization of bubble-mediated gas fluxes for use in Earth system models. The parameterization is derived from a mechanistic model of the oceanic boundary layer that simulates turbulent flows and the size spectrum of bubbles across a range of wind speeds and is compared against other published formulations. Bubble-induced surface supersaturation increases rapidly with wind speed and is inversely related to temperature at a given wind speed, making the effect of bubbles greatest in regions that ventilate the deep ocean. The bubble-induced supersaturation in high-latitude surface waters compensates a substantial fraction of the undersaturation caused by surface cooling. Using a global ocean transport model, we show that this parameterization reproduces observed saturation rate profiles of the noble gas Argon in the deep Atlantic and Pacific Oceans. The abyssal argon supersaturation caused by bubbles varies according to gas solubility, ranging from ∼0.7% for soluble gases like CO2 to ∼1.7% for less soluble gases such as N2. Bubble-induced supersaturation may be significant for biologically active gases such as oxygen. [ABSTRACT FROM AUTHOR]

The marine boundary layer is known to be influenced by fast long ocean swell waves travelling away from their generation area, where they were initiated by momentum transferred to the ocean wave field during storms. The atmospheric boundary layer during wind-following swell and various stability states has been investigated using large-eddy simulation (LES) data. The dominant energy-containing motions in the near-neutral atmospheric boundary layer over flat terrain are known to be dominated by near-ground shear-induced regions of high- and low-speed flow. Wind fields and momentum fluxes from LES for swell-dominated situations have been used to interpret field measurements suggesting that these motions are disrupted by effects related to the underlying wave field in the presence of swell waves. Statistical analysis and visualization are used to further describe the effects of stratification during swell for convective boundary-layer winds and fluxes. A mechanism for transport of momentum to the upper levels of the boundary layer is suggested from interpretation of LES data. Coherent detached eddies from the directly wave-induced motions near the surface are found to maintain an upward momentum transfer. This mechanism is found to strengthen during stronger swell conditions and also during slightly convective conditions. In this way, it is argued that processes related to both the wave field and surface convection can have a significant influence on the global structure of neutral and convective boundary layers during swell. This has implication for the turbulence length-scales during wind-following swell. Copyright © 2012 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

Investigation of enteric neurobiology and development of the enteric nervous system. Neuro-immunology and the gut: characterization of the interactions between the central nervous system, enteric nervous system and immune system. Evaluation of the role of early life events in the development of functional gastrointestinal disorders. evelopment of multicenter, controlled studies aimed at evaluating epidemiology, pathophysiology and treatment of functional bowel disorders. Creation of a tissue bank for children with enteric neuromuscular disorders. Validation of the Rome II diagnostic criteria at the general practitioner and specialty level. Train physicians and researchers in performing motility, sensory, and laboratory assessment in the field of enteric neuromuscular disorders. Educate primary care physicians in the evaluation and treatment of GER and other functional bowel disorders. Educate care providers on the high incidence of enteric neuromuscular disorders and the special needs of children with neurologic handicaps. [ABSTRACT FROM AUTHOR]