scholarly journals Temperature structure and vertical mixing of water mass in mesocosms in Lake Suwa.

1989 ◽  
Vol 50 (4) ◽  
pp. 299-311 ◽  
Author(s):  
Motoaki KISHINO ◽  
Masayuki TAKAHASHI ◽  
Hidetake HAYASHI
Keyword(s):  
Water Mass ◽  
Vertical Mixing ◽  
Temperature Structure ◽  
Lake Suwa

Circulation and Temperature Structure in Large Marine Enclosures

1977 ◽  
Vol 34 (8) ◽  
pp. 1095-1104 ◽  
Author(s):  
J. H. Steele ◽  
D. M. Farmer ◽  
E. W. Henderson
Keyword(s):  
Vertical Mixing ◽  
Temperature Structure ◽  
Temperature Profiles ◽  
Turbulent Diffusivity ◽  
Mixing Energy ◽  
Physical Measurements ◽  
Average Coefficient ◽  
Different Depths ◽  
External Fluctuations ◽  
Shed Light

Certain physical measurements intended to shed light on the circulation in large plastic enclosures (60–2000 m3) induced by the changing environment in which they are moored are described. Layers of dye were generally seen to diffuse vertically although some important advection effects were also observed. Estimates of an average coefficient of turbulent diffusivity yielded values in the range.05–.26 cm2∙s−1.Measurements taken with recording thermistor chains both inside and outside the enclosures show strong damping of external fluctuations with periods significantly less than 1 day. Various possible sources of mixing energy are considered and it is concluded that thermal forcing through the wall may be significant and could account for the observed range of coefficients.The significance of the observed mixing and circulation to the ecology of the enclosures is discussed. Of particular importance is the vertical mixing of nutrients that influences phytoplankton sinking rates and thus plays a crucial role in determining variations in algal concentration at different depths. Key words: mixing, enclosures, controlled ecosystem pollution experiment, circulation, temperature profiles

scholarly journals Assessing spectra and thermal inversions due to TiO in hot Jupiter atmospheres

2020 ◽  
Vol 496 (3) ◽  
pp. 3870-3886 ◽  
Author(s):  
Anjali A A Piette ◽  
Nikku Madhusudhan ◽  
Laura K McKemmish ◽  
Siddharth Gandhi ◽  
Thomas Masseron ◽  
...  
Keyword(s):  
Near Infrared ◽  
Vertical Mixing ◽  
Emission Spectra ◽  
Primary Source ◽  
Temperature Structure ◽  
Atmospheric Conditions ◽  
Atmospheric Models ◽  
Line List ◽  
Hot Jupiters ◽  
Work First

ABSTRACT Recent detections of thermal inversions in the dayside atmospheres of some hot Jupiters are motivating new avenues to understand the interplay between their temperature structures and other atmospheric conditions. In particular, TiO has long been proposed to cause thermal inversions in hot Jupiters, depending on other factors such as stellar irradiation, C/O, and vertical mixing. TiO also has spectral features in the optical and near-infrared that have been detected. However, interpretations of TiO signatures rely on the accuracy of TiO opacity used in the models. The recently reported toto TiO line list provides a new opportunity to investigate these dependences, which is the goal of this work. First, we investigate how the toto line list affects observable transmission and emission spectra of hot Jupiters at low and high resolutions. The improvement in the toto line list compared to a previous line list results in observable differences in the model spectra, particularly in the optical at high resolution. Secondly, we explore the interplay between temperature structure, irradiation, and composition with TiO as the primary source of optical opacity, using 1D self-consistent atmospheric models. Among other trends, we find that the propensity for thermal inversions due to TiO peaks at C/O ∼ 0.9, consistent with recent studies. Using these models, we further assess metrics to quantify thermal inversions due to TiO, compared to frequently used Spitzer photometry, over a range in C/O, irradiation, metallicity, gravity, and stellar type.

scholarly journals South Adriatic Recipes: Estimating the Vertical Mixing in the Deep Pit

2020 ◽  
Vol 7 ◽  
Author(s):  
Vanessa Cardin ◽  
Achim Wirth ◽  
Maziar Khosravi ◽  
Miroslav Gačić
Keyword(s):  
Time Series ◽  
Heat Equation ◽  
Gravity Current ◽  
Vertical Mixing ◽  
Temperature Structure ◽  
Temperature Profiles ◽  
Eof Analysis ◽  
Vertical Temperature ◽  
Current Events ◽  
Sill Depth

The available historical oxygen data show that the deepest part of the South Adriatic Pit remains well-ventilated despite the winter convection reaching only the upper 700 m depth. Here, we show that the evolution of the vertical temperature structure in the deep South Adriatic Pit (dSAP) below the Otranto Strait sill depth (780 m) is described well by continuous diffusion, a continuous forcing by heat fluxes at the upper boundary (Otranto Strait sill depth) and an intermittent forcing by rare (several per decade) deep convective and gravity-current events. The analysis is based on two types of data: (i) 13-year observational data time series (2006–2019) at 750, 900, 1,000, and 1,200 m depths of the temperature from the E2M3A Observatory and (ii) 55 vertical profiles (1985–2019) in the dSAP. The analytical solution of the gravest mode of the heat equation compares well to the temperature profiles, and the numerical integration of the resulting forced heat equation compares favorably to the temporal evolution of the time-series data. The vertical mixing coefficient is obtained with three independent methods. The first is based on a best fit of the long-term evolution by the numerical diffusion-injection model to the 13-year temperature time series in the dSAP. The second is obtained by short-time (daily) turbulent fluctuations and a Prandtl mixing length approximation. The third is based on the zero and first modes of an Empirical Orthogonal Function (EOF) analysis of the time series between 2014 and 2019. All three methods are compared, and a diffusivity of approximately κ = 5 · 10−4m2s−1 is obtained. The eigenmodes of the homogeneous heat equation subject to the present boundary conditions are sine functions. It is shown that the gravest mode typically explains 99.5% of the vertical temperature variability (the first three modes typically explain 99.85%) of the vertical temperature profiles at 1 m resolution. The longest time scale of the dissipative dynamics in the dSAP, associated with the gravest mode, is found to be approximately 5 years. The first mode of the EOF analysis (85%) represents constant heating over the entire depth, and the zero mode is close to the parabolic profile predicted by the heat equation for such forcing. It is shown that the temperature structure is governed by continuous warming at the sill depth and deep convection and gravity current events play less important roles. The simple model presented here allows evaluation of the response of the temperature in the dSAP to different forcings derived from climate change scenarios, as well as feedback on the dynamics in the Adriatic and the Mediterranean Sea.

scholarly journals A new set of atmosphere and evolution models for cool T–Y brown dwarfs and giant exoplanets

2020 ◽  
Vol 637 ◽  
pp. A38 ◽  
Author(s):  
M. W. Phillips ◽  
P. Tremblin ◽  
I. Baraffe ◽  
G. Chabrier ◽  
N. F. Allard ◽  
...  
Keyword(s):  
Near Infrared ◽  
Vertical Mixing ◽  
Emission Spectra ◽  
Brown Dwarfs ◽  
Atmospheric Temperature ◽  
Temperature Structure ◽  
Surface Boundary ◽  
Quantum Molecular Dynamics ◽  
Solar Metallicity ◽  
The Impact

We present a new set of solar metallicity atmosphere and evolutionary models for very cool brown dwarfs and self-luminous giant exoplanets, which we term ATMO 2020. Atmosphere models are generated with our state-of-the-art 1D radiative-convective equilibrium code ATMO, and are used as surface boundary conditions to calculate the interior structure and evolution of 0.001–0.075 M⊙ objects. Our models include several key improvements to the input physics used in previous models available in the literature. Most notably, the use of a new H–He equation of state including ab initio quantum molecular dynamics calculations has raised the mass by ~1−2% at the stellar–substellar boundary and has altered the cooling tracks around the hydrogen and deuterium burning minimum masses. A second key improvement concerns updated molecular opacities in our atmosphere model ATMO, which now contains significantly more line transitions required to accurately capture the opacity in these hot atmospheres. This leads to warmer atmospheric temperature structures, further changing the cooling curves and predicted emission spectra of substellar objects. We present significant improvement for the treatment of the collisionally broadened potassium resonance doublet, and highlight the importance of these lines in shaping the red-optical and near-infrared spectrum of brown dwarfs. We generate three different grids of model simulations, one using equilibrium chemistry and two using non-equilibrium chemistry due to vertical mixing, all three computed self-consistently with the pressure-temperature structure of the atmosphere. We show the impact of vertical mixing on emission spectra and in colour-magnitude diagrams, highlighting how the 3.5−5.5 μm flux window can be used to calibrate vertical mixing in cool T–Y spectral type objects.

Mixed Layer Cooling in Mesoscale Oceanic Eddies during Hurricanes Katrina and Rita

2009 ◽  
Vol 137 (12) ◽  
pp. 4188-4207 ◽  
Author(s):  
Benjamin Jaimes ◽  
Lynn K. Shay
Keyword(s):  
Mixed Layer ◽  
Water Mass ◽  
Vertical Mixing ◽  
Current Response ◽  
Atmospheric Conditions ◽  
Warm Core ◽  
Velocity Response ◽  
Inertial Wave ◽  
Hurricanes Katrina And Rita ◽  
Cold Core

Abstract During favorable atmospheric conditions, Hurricanes Katrina and Rita deepened to category 5 over the Loop Current’s (LC) bulge associated with an amplifying warm core eddy. Both hurricanes subsequently weakened to category 3 after passing over a cold core eddy (CCE) prior to making landfall. Reduced (increased) oceanic mixed layer (OML) cooling of ∼1°C (4.5°C) was observed over the LC (CCE) where the storms rapidly deepened (weakened). Data acquired during and subsequent to the passage of both hurricanes indicate that the modulated velocity response in these geostrophic features was responsible for the contrasts in the upper-ocean cooling levels. For similar wind forcing, the OML velocity response was about 2 times larger inside the CCE that interacted with Katrina than in the LC region affected by Rita, depending on the prestorm OML thickness. Hurricane-induced upwelling and vertical mixing were increased (reduced) in the CCE (LC). Less wind-driven kinetic energy was available to increase vertical shears for entrainment cooling in the LC, as the OML current response was weaker and energy was largely radiated into the thermocline. Estimates of downward vertical radiation of near-inertial wave energies were significantly stronger in the LC (12.1 × 10−2 W m−2) than in the CCE (1.8 × 10−2 W m−2). Katrina and Rita winds provided O(1010) W to the global internal wave power. The vertical mixing induced by both storms was confined to the surface water mass. From a broader perspective, models must capture oceanic features to reproduce the differentiated hurricane-induced OML cooling to improve hurricane intensity forecasting.

scholarly journals Vertical Mixing and Heat Fluxes Conditioned by a Seismically Imaged Oceanic Front

2021 ◽  
Vol 8 ◽  
Author(s):  
Kathryn L. Gunn ◽  
Alex Dickinson ◽  
Nicky J. White ◽  
Colm-cille P. Caulfield
Keyword(s):  
Water Mass ◽  
Vertical Mixing ◽  
Three Dimensional ◽  
Heat Fluxes ◽  
Water Masses ◽  
Mixing Rate ◽  
Southwest Atlantic ◽  
Cross Sectional ◽  
Mean Values ◽  
Mixing Rates

The southwest Atlantic gyre connects several distinct water masses, which means that this oceanic region is characterized by a complex frontal system and enhanced water mass modification. Despite its significance, the distribution and variability of vertical mixing rates have yet to be determined for this system. Specifically, potential conditioning of mixing rates by frontal structures, in this location and elsewhere, is poorly understood. Here, we analyze vertical seismic (i.e., acoustic) sections from a three-dimensional survey that straddles a major front along the northern portion of the Brazil-Falkland Confluence. Hydrographic analyses constrain the structure and properties of water masses. By spectrally analyzing seismic reflectivity, we calculate spatial and temporal distributions of the dissipation rate of turbulent kinetic energy, ε, of diapycnal mixing rate, K, and of vertical diffusive heat flux, FH. We show that estimates of ε, K, and FH are elevated compared to regional and global mean values. Notably, cross-sectional mean estimates vary little over a 6 week period whilst smaller scale thermohaline structures appear to have a spatially localized effect upon ε, K, and FH. In contrast, a mesoscale front modifies ε and K to a depth of 1 km, across a region of O(100) km. This front clearly enhances mixing rates, both adjacent to its surface outcrop and beneath the mixed layer, whilst also locally suppressing ε and K to a depth of 1 km. As a result, estimates of FH increase by a factor of two in the vicinity of the surface outcrop of the front. Our results yield estimates of ε, K and FH that can be attributed to identifiable thermohaline structures and they show that fronts can play a significant role in water mass modification to depths of 1 km.

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