scholarly journals Atmospheric Dynamics of Hot Giant Planets and Brown Dwarfs

2020 ◽  
Vol 216 (8) ◽  
Author(s):  
Adam P. Showman ◽  
Xianyu Tan ◽  
Vivien Parmentier
Keyword(s):  
Radiative Forcing ◽  
Large Scale ◽  
Brown Dwarfs ◽  
Global Scale ◽  
Giant Planets ◽  
External Irradiation ◽  
Night Temperature ◽  
Hot Jupiters ◽  
Wide Range ◽  
Radiative Feedbacks

AbstractGroundbased and spacecraft telescopic observations, combined with an intensive modeling effort, have greatly enhanced our understanding of hot giant planets and brown dwarfs over the past ten years. Although these objects are all fluid, hydrogen worlds with stratified atmospheres overlying convective interiors, they exhibit an impressive diversity of atmospheric behavior. Hot Jupiters are strongly irradiated, and a wealth of observations constrain the day-night temperature differences, circulation, and cloudiness. The intense stellar irradiation, presumed tidal locking and modest rotation leads to a novel regime of strong day-night radiative forcing. Circulation models predict large day-night temperature differences, global-scale eddies, patchy clouds, and, in most cases, a fast eastward jet at the equator—equatorial superrotation. The warm Jupiters lie farther from their stars and are not generally tidally locked, so they may exhibit a wide range of rotation rates, obliquities, and orbital eccentricities, which, along with the weaker irradiation, leads to circulation patterns and observable signatures predicted to differ substantially from hot Jupiters. Brown dwarfs are typically isolated, rapidly rotating worlds; they radiate enormous energy fluxes into space and convect vigorously in their interiors. Their atmospheres exhibit patchiness in clouds and temperature on regional to global scales—the result of modulation by large-scale atmospheric circulation. Despite the lack of irradiation, such circulations can be driven by interaction of the interior convection with the overlying atmosphere, as well as self-organization of patchiness due to cloud-dynamical-radiative feedbacks. Finally, irradiated brown dwarfs help to bridge the gap between these classes of objects, experiencing intense external irradiation as well as vigorous interior convection. Collectively, these diverse objects span over six orders of magnitude in intrinsic heat flux and incident stellar flux, and two orders of magnitude in rotation rate—thereby placing strong constraints on how the circulation of giant planets (broadly defined) depend on these parameters. A hierarchy of modeling approaches have yielded major new insights into the dynamics governing these phenomena.

scholarly journals The Iso2k Database: A global compilation of paleo-δ<sup>18</sup>O and δ<sup>2</sup>H records to aid understanding of Common Era climate

2020 ◽  
Author(s):  
Bronwen L. Konecky ◽  
Nicholas P. McKay ◽  
Olga V. Churakova (Sidorova) ◽  
Laia Comas-Bru ◽  
Emilie P. Dassié ◽  
...  
Keyword(s):  
Large Scale ◽  
Climate Model ◽  
Global Environmental Change ◽  
Global Scale ◽  
Proxy Records ◽  
Global Environmental ◽  
Past 2000 Years ◽  
Wide Range ◽  
Terrestrial Sediments ◽  
Common Era

Abstract. Reconstructions of global hydroclimate during the Common Era (CE; the past ~ 2000 years) are important for providing context for current and future global environmental change. Stable isotope ratios in water are quantitative indicators of hydroclimate on regional to global scales, and these signals are encoded in a wide range of natural geologic archives. Here we present the Iso2k database, a global compilation of previously published datasets from a variety of natural archives that record the stable oxygen (δ18O) or hydrogen (δ2H) isotopic composition of environmental waters, which reflect hydroclimate changes over the CE. The Iso2k database contains 756 isotope records from the terrestrial and marine realms, including: glacier and ground ice (205); speleothems (68); corals, sclerosponges, and mollusks (145); wood (81); lake sediments and other terrestrial sediments (e.g., loess) (158); and marine sediments (99). Individual datasets have temporal resolutions ranging from sub-annual to centennial, and include chronological data where available. A fundamental feature of the database is its comprehensive metadata, which will assist both experts and non-experts in the interpretation of each record and in data synthesis. Key metadata fields have standardized vocabularies to facilitate comparisons across diverse archives and with climate model simulated fields. This is the first global-scale collection of water isotope proxy records from multiple types of geological and biological archives. It is suitable for evaluating hydroclimate processes through time and space using large-scale synthesis, model-data intercomparison and (paleo)data assimilation. The Iso2k database is available for download at: https://doi.org/10.6084/m9.figshare.11553162 (McKay and Konecky, 2020).

scholarly journals Atmospheric Circulation of Hot Jupiters

2004 ◽  
Vol 202 ◽  
pp. 261-268 ◽  
Author(s):  
Tristan Guillot
Keyword(s):  
Large Scale ◽  
Circulation Model ◽  
Giant Planets ◽  
Large Temperature ◽  
Strong Wind ◽  
Temperature Variations ◽  
Hot Jupiters ◽  
Stellar Radiation ◽  
Synchronous Rotation ◽  
Night Side

About 40% of the extrasolar giant planets discovered so far have orbital distances smaller than 0.2 AU. These “hot Jupiters” are expected to be in synchronous rotation with their star. The ability to measure their radii prompts a careful reexamination of their structure. I show that their atmospheric structure is complex and that thermal balance cannot be achieved through radiation only but must involve heat advection by large-scale circulation. A circulation model inspired from Venus is proposed, involving a relatively strong zonal wind (with a period that can be as short as 1 day). It is shown that even this strong wind is incapable of efficiently redistributing heat from the day side to the night side. Temperature variations of 200 K or more are to be expected, even at pressures as large as 10 bar. As a consequence, clouds should be absent on the day side, allowing more efficient absorption of the stellar light. The global chemical composition of the atmosphere should also be greatly affected by the presence of large temperature variations. Finally, stellar tides may also be important in their ability to deposit heat at levels untouched by stellar radiation, thereby slowing further the cooling of the planets.

scholarly journals Cloud Inhomogeneity from MODIS

2005 ◽  
Vol 18 (23) ◽  
pp. 5110-5124 ◽  
Author(s):  
Lazaros Oreopoulos ◽  
Robert F. Cahalan
Keyword(s):  
Optical Thickness ◽  
Large Scale ◽  
Spatial Scales ◽  
Temporal Variations ◽  
Global Scale ◽  
Time Of Day ◽  
Wide Range ◽  
Level 3 ◽  
Inhomogeneity Parameter ◽  
Moderate Resolution Imaging Spectroradiometer

Abstract Two full months (July 2003 and January 2004) of Moderate Resolution Imaging Spectroradiometer (MODIS) Atmosphere Level-3 data from the Terra and Aqua satellites are analyzed in order to characterize the horizontal variability of vertically integrated cloud optical thickness (“cloud inhomogeneity”) at global scales. The monthly climatology of cloud inhomogeneity is expressed in terms of standard parameters, initially calculated for each day of the month at spatial scales of 1° × 1° and subsequently averaged at monthly, zonal, and global scales. Geographical, diurnal, and seasonal changes of inhomogeneity parameters are examined separately for liquid and ice phases and separately over land and ocean. It is found that cloud inhomogeneity is overall weaker in summer than in winter. For liquid clouds, it is also consistently weaker for local morning than local afternoon and over land than ocean. Cloud inhomogeneity is comparable for liquid and ice clouds on a global scale, but with stronger spatial and temporal variations for the ice phase, and exhibits an average tendency to be weaker for near-overcast or overcast grid points of both phases. Depending on cloud phase, hemisphere, surface type, season, and time of day, hemispheric means of the inhomogeneity parameter ν (roughly the square of the ratio of optical thickness mean to standard deviation) have a wide range of ∼1.7 to 4, while for the inhomogeneity parameter χ (the ratio of the logarithmic to linear mean) the range is from ∼0.65 to 0.8. The results demonstrate that the MODIS Level-3 dataset is suitable for studying various aspects of cloud inhomogeneity and may prove invaluable for validating future cloud schemes in large-scale models capable of predicting subgrid variability.

scholarly journals The Iso2k database: a global compilation of paleo-<i>δ</i><sup>18</sup>O and <i>δ</i><sup>2</sup>H records to aid understanding of Common Era climate

2020 ◽  
Vol 12 (3) ◽  
pp. 2261-2288 ◽  
Author(s):  
Bronwen L. Konecky ◽  
Nicholas P. McKay ◽  
Olga V. Churakova (Sidorova) ◽  
Laia Comas-Bru ◽  
Emilie P. Dassié ◽  
...  
Keyword(s):  
Large Scale ◽  
Climate Model ◽  
Global Environmental Change ◽  
Global Scale ◽  
Proxy Records ◽  
Global Environmental ◽  
Past 2000 Years ◽  
Wide Range ◽  
Terrestrial Sediments ◽  
Common Era

Abstract. Reconstructions of global hydroclimate during the Common Era (CE; the past ∼2000 years) are important for providing context for current and future global environmental change. Stable isotope ratios in water are quantitative indicators of hydroclimate on regional to global scales, and these signals are encoded in a wide range of natural geologic archives. Here we present the Iso2k database, a global compilation of previously published datasets from a variety of natural archives that record the stable oxygen (δ18O) or hydrogen (δ2H) isotopic compositions of environmental waters, which reflect hydroclimate changes over the CE. The Iso2k database contains 759 isotope records from the terrestrial and marine realms, including glacier and ground ice (210); speleothems (68); corals, sclerosponges, and mollusks (143); wood (81); lake sediments and other terrestrial sediments (e.g., loess) (158); and marine sediments (99). Individual datasets have temporal resolutions ranging from sub-annual to centennial and include chronological data where available. A fundamental feature of the database is its comprehensive metadata, which will assist both experts and nonexperts in the interpretation of each record and in data synthesis. Key metadata fields have standardized vocabularies to facilitate comparisons across diverse archives and with climate-model-simulated fields. This is the first global-scale collection of water isotope proxy records from multiple types of geological and biological archives. It is suitable for evaluating hydroclimate processes through time and space using large-scale synthesis, model–data intercomparison and (paleo)data assimilation. The Iso2k database is available for download at https://doi.org/10.25921/57j8-vs18 (Konecky and McKay, 2020) and is also accessible via the NOAA/WDS Paleo Data landing page: https://www.ncdc.noaa.gov/paleo/study/29593 (last access: 30 July 2020).

scholarly journals Theory of low mass stars, brown dwarfs and extra-solar giant planets

1997 ◽  
Vol 189 ◽  
pp. 331-340 ◽  
Author(s):  
Gilles Chabrier ◽  
Isabelle Baraffe
Keyword(s):  
Equations Of State ◽  
Galactic Disk ◽  
Brown Dwarfs ◽  
Reaction Rates ◽  
Point Of View ◽  
Giant Planets ◽  
Substantial Contribution ◽  
Mechanical And Thermal Properties ◽  
Low Mass Stars ◽  
Wide Range

Accurate modeling of the mechanical and thermal properties of very-lowmass stars (VLMS), Brown Dwarfs (BD) and Extra-solar Giant Planets (EGP) is of prior importance for a wide range of physical and astrophysical problems, from the fundamental physics point of view to the astrophysical and cosmological implications. They provide natural laboratories to test the different theories, equations of state, nuclear reaction rates, model atmospheres aimed at describing the physics of dense and cool objects. They represent the largest stellar population in the Galaxy, and thus provide a substantial contribution to the Galactic (disk) mass budget. Finally they represent one of the most intriguing questions in our understanding of the formation of star-like objects: are planet and star formation processes really different? Is there, and if so what is, a minimum mass for the formation of star-like objects? This field has blossomed recently with the discovery of several brown dwarfs (Nakajima et al, 1995; Rebolo et al., 1995) and numerous exoplanets since 51 Pegasi (Mayor and Queloz 1995; Mayor, this conference), which provide important information to challenge the theory.

scholarly journals Evaluating the hydrological consistency of satellite based water cycle components

2016 ◽  
Author(s):  
Oliver López ◽  
Rasmus Houborg ◽  
Matthew F. McCabe
Keyword(s):  
Land Surface ◽  
Water Budget ◽  
Large Scale ◽  
Water Cycle ◽  
Satellite Observation ◽  
Global Scale ◽  
Satellite Observations ◽  
Arid Environments ◽  
Basin Scale ◽  
Wide Range

Abstract. Advances in multi-satellite based observations of the earth system have provided the capacity to retrieve information across a wide-range of land surface hydrological components and provided an opportunity to characterize terrestrial processes from a completely new perspective. Given the spatial advantage that space-based observations offer, several regional-to-global scale products have been developed, offering insights into the multi-scale behaviour and variability of hydrological states and fluxes. However, one of the key challenges in the use of satellite-based products is characterizing the degree to which they provide realistic and representative estimates of the underlying retrieval: that is, how accurate are the hydrological components derived from satellite observations? The challenge is intrinsically linked to issues of scale, since the availability of high-quality in-situ data is limited, and even where it does exist, is generally not commensurate to the resolution of the satellite observation. Basin-scale studies have shown considerable variability in achieving water budget closure with any degree of accuracy using satellite estimates of the water cycle. In order to assess the suitability of this type of approach for evaluating hydrological observations, it makes sense to first test it over environments with restricted hydrological inputs, before applying it to more hydrological complex basins. Here we explore the concept of hydrological consistency, i.e. the physical considerations that the water budget impose on the hydrologic fluxes and states to be temporally and spatially linked, to evaluate the reproduction of a set of large-scale evaporation (E) products by using a combination of satellite rainfall (P) and Gravity Recovery and Climate Experiment (GRACE) observations of storage change, focusing on arid and semi-arid environments, where the hydrological flows can be more realistically described. Our results indicate no persistent hydrological consistency in these environments, suggesting the need for continued efforts in improving satellite observations, particularly for the retrieval of evaporation, and the need to more directly account for anthropogenic influences such as agricultural irrigation into our large scale water cycle studies.

scholarly journals A simple model of ozone–temperature coupling in the tropical lower stratosphere

2021 ◽  
Vol 21 (24) ◽  
pp. 18531-18542
Author(s):  
William J. Randel ◽  
Fei Wu ◽  
Alison Ming ◽  
Peter Hitchcock
Keyword(s):  
Large Scale ◽  
Radio Occultation ◽  
Lower Stratosphere ◽  
Strong Correlations ◽  
Continuity Equations ◽  
Wide Range ◽  
Radiative Feedbacks ◽  
Seasonal And Interannual Variations ◽  
Balloon Measurements ◽  
Phase Relationships

Abstract. Observations show strong correlations between large-scale ozone and temperature variations in the tropical lower stratosphere across a wide range of timescales. We quantify this behavior using monthly records of ozone and temperature data from Southern Hemisphere Additional Ozonesonde (SHADOZ) tropical balloon measurements (1998–2016), along with global satellite data from Aura microwave limb sounder and GPS radio occultation over 2004–2018. The observational data demonstrate strong in-phase ozone–temperature coherence spanning sub-seasonal, annual and interannual timescales, and the slope of the temperature–ozone relationship (T / O3) varies as a function of timescale and altitude. We compare the observations to idealized calculations based on the coupled zonal mean thermodynamic and ozone continuity equations, including ozone radiative feedbacks on temperature, where both temperature and ozone respond in a coupled manner to variations in the tropical upwelling Brewer–Dobson circulation. These calculations can approximately explain the observed (T / O3) amplitude and phase relationships, including sensitivity to timescale and altitude, and highlight distinct balances for “fast” variations (periods < 150 d, controlled by transport across background vertical gradients) and “slow” coupling (seasonal and interannual variations, controlled by radiative balances).

scholarly journals Evaluation of the absolute regional temperature potential

2012 ◽  
Vol 12 (6) ◽  
pp. 13813-13825 ◽  
Author(s):  
D. T. Shindell
Keyword(s):  
Radiative Forcing ◽  
Large Scale ◽  
Climate Models ◽  
Climate Model ◽  
Temperature Response ◽  
Global Scale ◽  
Large Set ◽  
Temperature Potential ◽  
Regional Temperature ◽  
The Absolute

Abstract. The Absolute Regional Temperature Potential (ARTP) is one of the few climate metrics that provides estimates of impacts at a sub-global scale. The ARTP gives the time-dependent temperature response in four latitude bands (90–28° S, 28° S–28° N, 28–60° N and 60–90° N) as a function of the regional forcing imposed in those bands. It is based on a large set of simulations performed with a single atmosphere-ocean climate model. Here I evaluate ARTP estimates of regional temperature responses due to historic aerosol forcing in three independent climate models and show that the ARTP metric provides results in good accord with the actual responses in those models. Nearly all ARTP estimates fall within ±20% of the actual responses, and in particular for the tropics and the Northern Hemisphere mid-latitudes this range appears to be roughly consistent with the 95% confidence interval. Land areas within these two bands respond 41 ± 6% and 19 ± 28% more than the latitude band as a whole. The ARTP, presented here in a slightly revised form, thus appears to provide a relatively robust estimate for the responses of large-scale latitude bands and land areas within those bands to inhomogeneous radiative forcing.

scholarly journals Mapping the Pressure-dependent Day–Night Temperature Contrast of a Strongly Irradiated Atmosphere with HST Spectroscopic Phase Curve

2021 ◽  
Vol 163 (1) ◽  
pp. 8
Author(s):  
Ben W. P. Lew ◽  
Dániel Apai ◽  
Yifan Zhou ◽  
Mark Marley ◽  
L. C. Mayorga ◽  
...  
Keyword(s):  
White Dwarf ◽  
Near Infrared ◽  
Brown Dwarfs ◽  
Phase Curve ◽  
Brown Dwarf ◽  
Night Temperature ◽  
Flux Variation ◽  
Hot Jupiters ◽  
Temperature Contrast ◽  
Hot Jupiter

Abstract Many brown dwarfs are on ultrashort-period and tidally locked orbits around white dwarf hosts. Because of these small orbital separations, the brown dwarfs are irradiated at levels similar to hot Jupiters. Yet, they are easier to observe than hot Jupiters because white dwarfs are fainter than main-sequence stars at near-infrared wavelengths. Irradiated brown dwarfs are, therefore, ideal hot Jupiter analogs for studying the atmospheric response under strong irradiation and fast rotation. We present the 1.1–1.67 μm spectroscopic phase curve of the irradiated brown dwarf (SDSS1411-B) in the SDSS J141126.20 + 200911.1 brown dwarf–white dwarf binary with the near-infrared G141 grism of the Hubble Space Telescope Wide Field Camera 3. SDSS1411-B is a 50M Jup brown dwarf with an irradiation temperature of 1300 K and has an orbital period of 2.02864 hr. Our best-fit model suggests a phase-curve amplitude of 1.4% and places an upper limit of 11° for the phase offset from the secondary eclipse. After fitting the white dwarf spectrum, we extract the phase-resolved brown dwarf emission spectra. We report a highly wavelength-dependent day–night spectral variation, with a water-band flux variation of about 360% ± 70% and a comparatively small J-band flux variation of 37% ± 2%. By combining the atmospheric modeling results and the day–night brightness temperature variations, we derive a pressure-dependent temperature contrast. We discuss the difference in the spectral features of SDSS1411-B and hot Jupiter WASP-43b, as well as the lower-than-predicted day–night temperature contrast of J4111-BD. Our study provides the high-precision observational constraints on the atmospheric structures of an irradiated brown dwarf at different orbital phases.

scholarly journals Diagnosing oceanic nutrient deficiency

2016 ◽  
Vol 374 (2081) ◽  
pp. 20150290 ◽  
Author(s):  
C. Mark Moore
Keyword(s):  
Large Scale ◽  
Nutrient Deficiency ◽  
Global Scale ◽  
Nutrient Ratios ◽  
Upper Ocean ◽  
Key Indicator ◽  
Trace Element Chemistry ◽  
Wide Range ◽  
Climatic Impacts ◽  
Microbial Systems

The supply of a range of nutrient elements to surface waters is an important driver of oceanic production and the subsequent linked cycling of the nutrients and carbon. Relative deficiencies of different nutrients with respect to biological requirements, within both surface and internal water masses, can be both a key indicator and driver of the potential for these nutrients to become limiting for the production of new organic material in the upper ocean. The availability of high-quality, full-depth and global-scale datasets on the concentrations of a wide range of both macro- and micro-nutrients produced through the international GEOTRACES programme provides the potential for estimation of multi-element deficiencies at unprecedented scales. Resultant coherent large-scale patterns in diagnosed deficiency can be linked to the interacting physical–chemical–biological processes which drive upper ocean nutrient biogeochemistry. Calculations of ranked deficiencies across multiple elements further highlight important remaining uncertainties in the stoichiometric plasticity of nutrient ratios within oceanic microbial systems and caveats with regards to linkages to upper ocean nutrient limitation. This article is part of the themed issue ‘Biological and climatic impacts of ocean trace element chemistry’.

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