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Photochemical hazes are expected to form in hot Jupiter atmospheres and may explain the strong scattering slopes and muted spectral features observed in the transmission spectra of many hot Jupiters. Absorption and scattering by photochemical hazes have the potential to drastically alter temperature structure and atmospheric circulation of these planets but have previously been neglected in general circulation models (GCMs). We present GCM simulations of the hot Jupiter HD 189733 b that include photochemical hazes as a radiatively active tracer fully coupled to atmospheric dynamics. The influence of haze radiative feedback strongly depends on the assumed haze optical properties. For soot hazes, two distinct thermal inversions form, separated by a local temperature minimum around 10−5 bar caused by upwelling on the dayside mixing air with low haze abundance upwards. The equatorial jet broadens and slows down. The horizontal distribution of hazes remains relatively similar to simulations with radiatively passive tracers. For Titan-type hazes, the equatorial jet accelerates and extends to much lower pressures, resulting in a dramatically different 3D distribution of hazes compared to radiatively passive or soot hazes. Further experimental and observational studies to constrain the optical properties of photochemical hazes will therefore be crucial for understanding the role of hazes in exoplanetary atmospheres. In the dayside emission spectrum, for both types of hazes the amplitude of near-infrared features is reduced, while the emitted flux at longer wavelengths (>4 μm) increases. Haze radiative feedback leads to increased phase-curve amplitudes in many infrared wavelength regions, mostly due to stronger dayside emission.

The atmospheric dynamics of tidally locked hot Jupiters is characterized by strong equatorial winds. Understanding the interaction between global circulation and chemistry is crucial in atmospheric studies and interpreting observations. Two-dimensional (2D) photochemical transport models shed light on how the atmospheric composition depends on circulation. In this paper, we introduce the 2D photochemical (horizontal and vertical) transport model, VULCAN 2D, which improves on the pseudo-2D approaches by allowing for nonuniform zonal winds. We extensively validate our VULCAN 2D with analytical solutions and benchmark comparisons. Applications to HD 189733 b and HD 209458 b reveal a transition in mixing regimes: horizontal transport predominates below ∼0.1 mbar, while vertical mixing is more important at higher altitudes above 0.1 mbar. Motivated by the previously inferred carbon-rich atmosphere, we find that HD 209458 b with supersolar carbon-to-oxygen ratio (C/O) exhibits pronounced C2H4 absorption on the morning limb but not on the evening limb, due to horizontal transport from the nightside. We discuss when a pseudo-2D approach is a valid assumption and its inherent limitations. Finally, we demonstrate the effect of horizontal transport in transmission observations and its impact on the morning−evening limb asymmetry with synthetic spectra, highlighting the need to consider global transport when interpreting exoplanet atmospheres.

Convective processes are crucial in shaping exoplanetary atmospheres but are computationally expensive to simulate directly. A novel technique of simulating moist convection on tidally locked exoplanets is to use a global 3D model with a stretched mesh. This allows us to locally refine the model resolution to 4.7 km and resolve fine-scale convective processes without relying on parameterizations. We explore the impact of mesh stretching on the climate of a slowly rotating TRAPPIST-1e-like planet, assuming it is 1:1 tidally locked. In the stretched-mesh simulation with explicit convection, the climate is 5 K colder and 25% drier than that in the simulations with parameterized convection(with both stretched and quasi-uniform meshes). This is due to the increased cloud reflectivity—because of an increase in low-level cloudiness—and exacerbated by the diminished greenhouse effect due to less water vapor. At the same time, our stretched-mesh simulations reproduce the key characteristics of the global climate of tidally locked rocky exoplanets, without any noticeable numerical artifacts. Our methodology opens an exciting and computationally feasible avenue for improving our understanding of 3D mixing in exoplanetary atmospheres. Our study also demonstrates the feasibility of a global stretched-mesh configuration for LFRic-Atmosphere, the next-generation Met Office climate and weather model.

Ultrahot Jupiters (UHJs) are exceptional laboratories for studying planetary atmospheres under extreme irradiation conditions. With close-in tidally locked orbits, these planets can have daysides hot enough for metals to be significantly ionized while still maintaining nightsides cold enough for refractory species to potentially condense. We present an analysis of the UHJ HAT-P-70b taken with the MAROON-X high-resolution spectrograph. Using cross correlations, we detect 14 neutral and singly ionized species, including Fe I, Fe II, Ti I, Ca I, Ca II, Cr I, Na I, V I, Mn I, Ni I, Mg I, Ba II, O I, and Sr I, with tentative evidence for H I, Co I, and K I. The absorption signals exhibit blueshifts on the order of a few kilometers per second, consistent with day-to-night winds. We further constrain relative abundances with atmospheric retrievals and demonstrate that some inferred elemental abundance ratios depend strongly on modeling assumptions. In particular, we show that a well-mixed retrieval approach neglecting ionization can strongly bias highly ionizable elements such as Ca and Ti. Accounting for the effects of equilibrium chemistry and thermal ionization generally results in inferred elemental abundance ratios that are closer to expectations for a solar-like composition, although not in all cases. Interestingly, we find a distinct nickel enrichment on HAT-P-70b, adding to the growing number of UHJ studies where the Ni abundance is seemingly enhanced. Our results underline the importance of considering physical and chemical atmospheric processes such as ionization when interpreting high-resolution transmission spectra of UHJs.

The interior flux of a giant planet impacts atmospheric motion, and the atmosphere dictates the interior’s cooling. Here we use a non-hydrostatic general circulation model (Simulating Non-hydrostatic Atmospheres on Planets) coupled with a multi-stream multi-scattering radiative module (High-performance Atmospheric Radiation Package) to simulate the weather impacts on the heat flow of hot Jupiters. We found that the vertical heat flux is primarily transported by convection in the lower atmosphere and regulated by dynamics and radiation in the overlying radiation-circulation zone. The temperature inversion occurs on the dayside and reduces the upward radiative flux. The atmospheric dynamics relay the vertical heat transport until the radiation becomes efficient in the upper atmosphere. The cooling flux increases with atmospheric drag due to increased day–night contrast and spatial inhomogeneity. The temperature dependence of the infrared opacity greatly amplifies the opacity inhomogeneity. Although atmospheric circulation could transport heat downward in a narrow region above the radiative-convective boundary, the opacity inhomogeneity effect overcomes the dynamical effect and leads to a larger overall interior cooling than the local simulations with the same interior entropy and stellar flux. The enhancement depends critically on the equilibrium temperature, drag, and atmospheric opacity. In a strong-drag atmosphere hotter than 1600 K, a significant inhomogeneity effect in three-dimensional (3D) models can boost interior cooling several-fold compared to the 1D radiative-convective equilibrium models. This study confirms the analytical argument of the inhomogeneity effect in the companion papers by Zhang. It highlights the importance of using 3D atmospheric models in understanding the inflation mechanisms of hot Jupiters and giant planet evolution in general.

Interpretation of the ongoing efforts to simulate the atmospheres of potentially habitable terrestrial exoplanets requires that we understand the underlying dynamics and chemistry of such objects to a much greater degree than 1D or even simple 3D models enable. Here, for the tidally locked habitable-zone planet TRAPPIST-1e, we explore one effect which can shape the dynamics and chemistry of terrestrial planets: the inclusion of an Earth-like land–ocean distribution with orography. To do this we use the Earth-system model WACCM6/CESM2 to run a pair of TRAPPIST-1e models with N2–O2 atmospheres and with the substellar point fixed over either land or ocean. The presence of orography shapes atmospheric transport, and in the case of Earth-like orography, breaks the symmetry between the Northern and Southern Hemispheres which was previously found in slab ocean models. For example, peak zonal jet speeds in the Southern Hemisphere are 50%–100% faster than similar jets in the Northern Hemisphere. This also affects the meridional circulation, transporting equatorial material toward the south pole. As a result we also find significant changes in the atmospheric chemistry, including the accumulation of potentially lethal quantities of ozone at both the south pole and the surface. Future studies which investigate the effects of landmass distribution on the dynamics of exoplanetary atmospheres should pay close attention to both the dayside land fraction as well as the orography of the land. Simply modeling a flat landmass will not give a complete picture of its dynamical impact.

TRAPPIST-1e is a tidally locked rocky exoplanet orbiting the habitable zone of an M dwarf star. Upcoming observations are expected to reveal new rocky exoplanets and their atmospheres around M dwarf stars. To interpret these future observations we need to model the atmospheres of such exoplanets. We configured Community Earth System Model version 2–Whole Atmosphere Community Climate Model version 6, a chemistry climate model, for the orbit and stellar irradiance of TRAPPIST-1e assuming an initial Earth-like atmospheric composition. Our aim is to characterize the possible ozone (O3) distribution and explore how this is influenced by the atmospheric circulation shaped by orography, using the Helmholtz wind decomposition and meridional mass streamfunction. The model included Earth-like orography, and the substellar point was located over the Pacific Ocean. For such a scenario, our analysis reveals a north–south asymmetry in the simulated O3 distribution. The O3 concentration is highest at pressures >10 hPa (below ∼30 km) near the south pole. This asymmetry arises from the higher landmass fraction in the northern hemisphere, which causes drag in near-surface flows and leads to an asymmetric meridional overturning circulation. Catalytic species were roughly symmetrically distributed and were not found to be primary driver for the O3 asymmetry. The total O3 column density was higher for TRAPPIST-1e compared to Earth, with 8000 Dobson units (DUs) near the south pole and 2000 DU near the north pole. The results emphasize the sensitivity of O3 to model parameters, illustrating how incorporating Earth-like orography can affect atmospheric dynamics and O3 distribution. This link between surface features and atmospheric dynamics underlines the importance of how changing model parameters used to study exoplanet atmospheres can influence the interpretation of observations.

We present ground-based high-resolution spectroscopic pre-eclipse observations of the hot Jupiter CoRoT-2b obtained with the IGRINS spectrograph on Gemini South. Using cross-correlation analysis, we detect the Doppler-shifted signature of the planet’s thermal emission with a signal-to-noise ratio of 4.32. Our independent analyses confirm the presence of H2O with a confidence level of 2.6σ and an abundance of log10 −5.08−0.43+0.43 , as well as CO with 2.3σ confidence and an abundance of log10 −4.21−0.81+0.48 in CoRoT-2b’s atmosphere, using two fully independent data reduction and retrieval pipelines. No significant detections of CH4, CO2, TiO, or VO are reported. While our cross-correlation analysis tentatively suggests the presence of HCN and OH, retrieval analysis does not confirm these molecules. The detected H2O and CO features indicate that CoRoT-2b’s dayside spectrum is not featureless, as previously inferred from lower-resolution observations, but instead reveals a complex atmospheric structure. Interestingly, we find a lack of significant molecular features at wavelengths shorter than 1.7 μm, potentially due to high-altitude absorbers such as H−, clouds, or observational systematics. From our retrieved abundances of CO and H2O, we constrain a supersolar C/O ratio of 0.91−0.17+0.08 and a subsolar metallicity. This study provides the first high-resolution constraints on the atmospheric composition of CoRoT-2b and serves as the foundation for future investigations into its peculiar westward hot spot offset. Further phase-resolved observations will be required to explore the underlying atmospheric dynamics in more detail.

We perform high-resolution atmospheric flow simulations of hot and warm giant exoplanets that are tidally locked. The modeled atmospheres are representative of those on KELT-11 b and WASP-39 b, which possess markedly different equilibrium temperatures but reside in a similar dynamical regime. In this regime, their key dynamical numbers (e.g., Rossby and Froude numbers) are comparable. Despite their temperature difference, both planets exhibit qualitatively similar atmospheric circulation patterns, which are characterized by turbulent equatorial flows, anticyclonic polar vortices, and large-scale Rossby waves that give rise to quasi-zonal flows in the extratropics (i.e., near ±20∘). Quantitative differences between the KELT-11 b and WASP-39 b atmospheres are consistent with their different Rossby deformation scales, which influence the horizontal length scale of wave–vortex interactions and the overall structure of the circulation.

Young planetary-mass objects and brown dwarfs near the L–T spectral transition exhibit enhanced spectrophotometric variability over field brown dwarfs. Patchy clouds, auroral processes, stratospheric hot spots, and complex carbon chemistry have all been proposed as potential sources of this variability. Using time-resolved, low- to mid-resolution spectroscopy collected with the JWST/NIRISS and NIRSpec instruments, we apply harmonic analysis to SIMP J013656.5+093347.3, a highly variable, young, isolated planetary-mass object. Odd harmonics (k = 3) at pressure levels (≳1 bar) corresponding to iron (Fe) and forsterite (Mg2SiO4) cloud formation suggest a potential north–south hemispheric asymmetry in the cloudy, and likely equatorial, regions. We use the inferred harmonics, along with 1D substellar atmospheric models, to map the flux variability by atmospheric pressure level. These vertical maps demonstrate robust interaction between deep convective weather layers and the overlying stratified and radiative atmosphere. We identify distinct time-varying structures in the near-infrared that we interpret as planetary-scale wave-associated (e.g., Rossby or Kelvin) cloud modulation. We detect deviations from bulk (composite) variability in water (maximum signal-to-noise ratio (S/Nmax)=14.0 ), carbon monoxide ( S/Nmax=13.0 ), and methane ( S/Nmax=14.9 ) molecular signatures. Forsterite cloud modulation is anticorrelated with the overlying carbon monoxide and water abundances and correlated with deep methane absorption, suggesting complex interaction between cloud formation, atmospheric chemistry, and temperature structure. Furthermore, we identify distinct harmonic behavior between methane and carbon monoxide absorption bands, providing evidence for time-resolved disequilibrium carbon chemistry. At the lowest pressures (≲100 mbar), we find that the mapped methane lines transition from absorption to emission, supporting evidence of high-altitude auroral heating via electron precipitation.