A5081437956- Climate variability and models
- Oceanographic and Atmospheric Processes
- Meteorological Phenomena and Simulations
- Atmospheric and Environmental Gas Dynamics
- Wind and Air Flow Studies
- Fluid Dynamics and Turbulent Flows
- Arctic and Antarctic ice dynamics
- Tropical and Extratropical Cyclones Research
- Marine and coastal ecosystems
- Methane Hydrates and Related Phenomena
- Hydrology and Drought Analysis
- Solar and Space Plasma Dynamics
- Electromagnetic Scattering and Analysis
- Particle physics theoretical and experimental studies
- Hydrology and Watershed Management Studies
- Astrophysics and Star Formation Studies
- Engineering Applied Research
- Numerical methods for differential equations
- Geomagnetism and Paleomagnetism Studies
- Black Holes and Theoretical Physics
- Geology and Paleoclimatology Research
- Astro and Planetary Science
- Electromagnetic Simulation and Numerical Methods
- Cosmology and Gravitation Theories
- Geophysics and Gravity Measurements
Goddard Institute for Space Studies
2005-2020
Medgar Evers College
2009-2020
City University of New York
2018-2020
Columbia University
2005-2019
Massachusetts Institute of Technology
2004-2008
Planetary Science Institute
2003-2006
IIT@MIT
2005
Princeton University
1994
Ocean mixing processes have traditionally been formulated using one-point turbulence closure models, specifically the Mellor and Yamada (MY) which were pioneered in geophysics 1980 state-of-the-art modeling. These models widely applied over years, but underlying core physical assumptions hardly improved since 1980s; yet, meantime, modeling has made sufficient progress to allow four improvements be made. 1) The value of Ricr. MY-type yield a low for critical Richardson number, Ricr = 0.2 (the...
Second-order turbulence models of the Mellor and Yamada type have been widely used to simulate planetary boundary layer (PBL). It is, however, known that these several deficiencies. For example, assuming production turbulent kinetic energy equals its dissipation, they all predict a critical Richardson number is about four times smaller than large eddy simulation (LES) data in stably stratified flows are unable distinguish vertical lateral components neutral PBLs, height lower expected. In...
A Reynolds stress–based model is used to derive algebraic expressions for the vertical diffusivities Kα(α = m, h, s) momentum, heat, and salt. The are expressed as KαRρN,Tϵ in terms of density ratio Rρ αs∂S/∂z(αT∂T/∂z)−1, Brunt–Väisälä frequency N2 −gρ−10∂ρ/∂z, Richardson number RiT N2/Σ2 (Σ shear), dissipation rate kinetic energy ϵ. valid both mixed layer (ML) below it. Here N computed everywhere using large-scale fields from an ocean general circulation while contributed by resolved...
Abstract A large set of laboratory, direct numerical simulation (DNS), and eddy (LES) data indicates that in stably stratified flows turbulent mixing exists up to Ri ∼ O(100), meaning there is practically no Ri(cr). On the other hand, traditional local second-order closure (SOC) models entail a critical Ri(cr) O(1) above which turbulence ceases exist are therefore unable explain data. The authors suggest how modify recent SOC model Cheng et al. reproduce for arbitrary Ri.
Turbulent convection is inherently a nonlocal phenomenon and primary condition for successful treatment of the convective boundary layer reliable model nonlocality. In dynamic equations governing flux, turbulent kinetic energy, etc., nonlocality represented by third-order moments (TOMs). Since simplest form, so-called down gradient approximation (DGA), severely underestimates TOMs (up to an order magnitude), more physical needed. 1994, analytical was presented that derived directly from...
Abstract The standard approach to studying the planetary boundary layer (PBL) via turbulence models begins with first-moment equations for temperature, moisture, and mean velocity. These entail second-order moments that are solutions of dynamic equations, which in turn third-order moments, so on. How where terminate (close) has not been a generally agreed upon procedure variety differ precisely way they sequence. This can be viewed as bottom-up approach. In this paper, top-down is suggested,...
We consider the hypothesis that galactic magnetic fields are primordial. also discuss various objections to this hypothesis. To test properly we assume there was a field present in plasma before galaxy formed and explore how such would evolve assuming specific model for interstellar medium disk. After disk formed, lines of force thread through it remain connected external cosmic medium. They enter one side disk, proceed horizontally distance l then leave other side. find stretched by...
Abstract We formulate a new second-order closure turbulence model by employing recent for the pressure–temperature correlation at equation level. As result, we obtain heat flux equations that avoid long-standing issue of finite critical Richardson number. The new, structurally simpler improves on Mellor–Yamada and Galperin et al. models; key feature includes enhanced mixing under stable conditions facilitating agreement with observational, experimental, high-resolution numerical datasets....
Available models of Double Diffusion (DD) processes (Salt Fingers, SF and Diffusive Convection, DC) are primarily based on laboratory experiments that do not include turbulence which is however always present in the ocean. A reliable DD model for use OGCMs (ocean global circulation models) therefore still lacking a true assessment role oceanic yet to be made. Here, we derive validate new + Turbulence using second‐order closure differs significantly from previous ones ratios correlation time...
Abstract Recently, we presented a parameterization of an arbitrary tracer 3D mesoscale flux that describes both diabatic and adiabatic regimes without using tapering functions. However, did not parameterize the diffusivity, which is subject this work. A key difference between present previous diffusivity parameterizations in latter, two main ingredients, drift velocity eddy kinetic energy, were parameterized but determined data, deprives models predictive power. Since winds, stratification,...
The cosmic microwave anisotropies in a scenario of large-scale structure formation with cold dark matter (CDM) and texture are discussed compared recent observational results the COBE satellite. A couple important statistical parameters determined. fluctuations slightly non-Gaussian. quadrupole anisotropy is 1.5\ifmmode\pm\else\textpm\fi{}1.2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}5}$ on an angular scale 10\ifmmode^\circ\else\textdegree\fi{}...
Abstract It has been known for three decades that in the case of buoyancy-driven flows widely used second-order closure (SOC) level-2.5 turbulence models exhibit divergences render them unphysical certain domains. This occurs when dimensionless temperature gradient Gh (defined below) approaches a critical value Gh(cr) order 10; thus far, have treated with ad hoc limitations typewhere τ is eddy turnover time scale, g gravitational acceleration, α coefficient thermal expansion, T mean...
In most ocean general circulation models (OGCM), mixing in the pycnocline is treated with a constant background diffusivity. This creates following problem. To obtain observed sharp equatorial thermocline, OGCMs must adopt diffusivity ten times smaller than at mid‐latitudes. The conflict can only be resolved by switching to spatially variable mixing. this work we present GISS model supplemented Gregg et al. 's [2003] finding that rate of dissipation internal gravity waves latitude dependent....
Abstract In 2011, Chelton et al. carried out a comprehensive census of mesoscales using altimetry data and reached the following conclusions: “essentially all observed mesoscale features are nonlinear” “mesoscales do not move with mean velocity but their own drift velocity,” which is “the most germane nonlinear metrics.” Accounting for these results in parameterization presents conceptual practical challenges since linear analysis no longer usable one needs model nonlinearity. A presented...
Corresponding author address: Dr. V. M. Canuto, NASA GISS, 2880 Broadway, New York, NY 10025. Email: vcanuto@giss.nasa.gov
Abstract The goal of this paper is to derive the equation for turbulence dissipation rate ɛ a shear-driven flow. In 1961, Davydov used one-point closure model from first principles but final result contained undetermined terms and thus lacked predictive power. Both in 1987 (Schiestel) 2001 (Rubinstein Zhou), attempts were made using two-point closure, their methods relied on phenomenological assumption. standard practice has been employ heuristic form that contains three empirical...
Abstract Several studies have demonstrated the relevance of submesoscales (SM) to production phytoplankton and ocean absorption anthropogenic CO 2 . One variable that thus far has not been fully quantified is SM‐induced rates subduction obduction at bottom mixed layer. In this work, we use an SM parameterization had previously assessed estimate subduction‐obduction using a coarse resolution stand‐alone code compute large‐scale fields. To separate contributions baroclinic instabilities from...