Context. Hot Jupiters are tidally locked gaseous exoplanets that exhibit large day-night temperature contrasts. Their cooler nightsides are thought to host clouds, as has been suggested by numerous ...observations. However, the exact nature of these clouds, their spatial distribution, and their impact on atmospheric dynamics, thermal structure, and spectra is still unclear. Aims. We investigate the atmosphere of WASP-43 b, a short period hot Jupiter recently observed with James Webb Space Telescope (JWST), to understand the radiative and dynamical impact of clouds on the atmospheric circulation and thermal structure. We aim to understand the impact of different kinds of condensates potentially forming in WASP-43 b, with various sizes and atmospheric metallicities. Methods. We used a 3D global climate model (GCM) with a new temperature-dependent cloud model that includes radiative feedbacks coupled with hydrodynamical integrations to study the atmospheric properties of WASP-43 b. We produced observables from our GCM simulations and compared them to spectral phase curves from various observations to derive constraints on the atmospheric properties. Results. We show that clouds have a net warming effect, meaning that the greenhouse effect caused by clouds is stronger than the albedo cooling effect. We show that the radiative effect of clouds has various impacts on the dynamical and thermal structure of WASP-43 b. Depending on the type of condensates and their sizes, the radiative-dynamical feedback will modify the horizontal and vertical temperature gradient and reduce the wind speed. For super-solar metallicity atmospheres, fewer clouds form in the atmosphere, leading to a weaker feedback. Comparisons with spectral phase curves observed with HST, Spitzer , and JWST indicate that WASP-43 b's nightside is cloudy and rule out sub-micron Mg 2 SiO 4 cloud particles as the main opacity source. Distinguishing between cloudy solarand cloudy super-solar-metallicity atmospheres is not straightforward, and further observations of both reflected light and thermal emission are needed.
By measuring the regular oscillations of the density of CO2 in the upper atmosphere (between 120 and 190 km), the mass spectrometer MAVEN/NGIMS (Atmosphere and Volatile EvolutioN/Neutral Gas Ion Mass ...Spectrometer) reveals the local impact of gravity waves. This yields precious information on the activity of gravity waves and the atmospheric conditions in which they propagate and break. The intensity of gravity waves measured by MAVEN in the upper atmosphere has been shown to be dictated by saturation processes in isothermal conditions. As a result, gravity waves activity is correlated to the evolution of the inverse of the background temperature. Previous data gathered at lower altitudes (∼95–∼150 km) during aerobraking by the accelerometers on board MGS (Mars Global Surveyor), ODY (Mars Odyssey) and MRO (Mars Reconnaissance Orbiter) are analyzed in the light of those recent findings with MAVEN. The anti-correlation between GW-induced density perturbations and background temperature is plausibly found in the ODY data acquired in the polar regions, but not in the MGS and MRO data. MRO data in polar regions exhibit a correlation between the density perturbations and the Brunt-Väisälä frequency (or, equivalently, static stability), obtained from Global Climate Modeling compiled in the Mars Climate Database. At lower altitude levels (between 100 and 120 km), although wave saturation might still be dominant, isothermal conditions are no longer verified. In this case, theory predicts that the intensity of gravity waves is no more correlated to background temperature, but to static stability. At other latitudes in the three aerobraking datasets, the GW-induced relative density perturbations are correlated with neither inverse temperature nor static stability; in this particular case, this means that the observed activity of gravity waves is not only controlled by saturation, but also by the effects of gravity-wave sources and wind filtering through critical levels. This result highlights the exceptional nature of MAVEN/NGIMS observations which combine both isothermal and saturated conditions contrary to aerobraking measurements.
•Gravity wave activity causes density perturbations in the Martian thermosphere.•MAVEN found a correlation between GW activity and inverse background temperature.•Lower-altitude aerobraking data do not show this correlation, except for Mars Odyssey.•Aerobraking data and GCMs suggest instead wave activity correlated with Static stability.•When no such correlation, a mix of saturation, critical levels and sources is suspected.
The Atmospheric Chemistry Suite (ACS) package is an element of the Russian contribution to the ESA-Roscosmos ExoMars 2016 Trace Gas Orbiter (TGO) mission. ACS consists of three separate infrared ...spectrometers, sharing common mechanical, electrical, and thermal interfaces. This ensemble of spectrometers has been designed and developed in response to the Trace Gas Orbiter mission objectives that specifically address the requirement of high sensitivity instruments to enable the unambiguous detection of trace gases of potential geophysical or biological interest. For this reason, ACS embarks a set of instruments achieving simultaneously very high accuracy (ppt level), very high resolving power (>10,000) and large spectral coverage (0.7 to 17 μm—the visible to thermal infrared range). The near-infrared (NIR) channel is a versatile spectrometer covering the 0.7–1.6 μm spectral range with a resolving power of ∼20,000. NIR employs the combination of an echelle grating with an AOTF (Acousto-Optical Tunable Filter) as diffraction order selector. This channel will be mainly operated in solar occultation and nadir, and can also perform limb observations. The scientific goals of NIR are the measurements of water vapor, aerosols, and dayside or night side airglows. The mid-infrared (MIR) channel is a cross-dispersion echelle instrument dedicated to solar occultation measurements in the 2.2–4.4 μm range. MIR achieves a resolving power of >50,000. It has been designed to accomplish the most sensitive measurements ever of the trace gases present in the Martian atmosphere. The thermal-infrared channel (TIRVIM) is a 2-inch double pendulum Fourier-transform spectrometer encompassing the spectral range of 1.7–17 μm with apodized resolution varying from 0.2 to 1.3 cm
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. TIRVIM is primarily dedicated to profiling temperature from the surface up to ∼60 km and to monitor aerosol abundance in nadir. TIRVIM also has a limb and solar occultation capability. The technical concept of the instrument, its accommodation on the spacecraft, the optical designs as well as some of the calibrations, and the expected performances for its three channels are described.
We present the extension to the thermosphere of a Martian general circulation model, the first able to self‐consistently study the whole Martian atmosphere from the surface to the exosphere. We ...describe the parameterizations developed to include physical processes important for thermospheric altitudes. The results of a simulation covering 1 full Martian year are presented, focusing on the seasonal, diurnal, and day‐to‐day variability of the temperatures in the exobase region. The seasonal variation of the zonal mean temperatures in the upper atmosphere is of about 100 K, mostly due to the variation of the solar forcing. The temperature of the mesopause ranges between 115 and 130 K, with little seasonal and day‐night variations. Its pressure level undergoes significant seasonal and day‐night variations. Comparisons with SPICAM observations show that the modeled mesopause is too low and too warm. A similar study for the homopause shows that it is located higher in the atmosphere during solstices, owing to reinforced mixing by a stronger circulation. Important day‐night temperature differences are found in the thermosphere, ranging from about 60 K at aphelion to 110 K at perihelion. This diurnal cycle is slightly perturbed by the day‐to‐day variations of temperature, dominated by waves with periods of 2 to 6 sols and amplitude of 30 K. The model reproduces the observed solar cycle variation in temperatures when using a UV heating efficiency of 16%, slightly lower than the theoretical value. The seasonal variation of temperatures is overestimated by the model, in comparison with the available measurements.
Global climate models (GCMs) have been successfully employed to explain the origin of many glacial deposits on Mars. However, the latitude‐dependent mantle (LDM), a dust‐ice mantling deposit that is ...thought to represent a recent “Ice Age,” remains poorly explained by GCMs. We reexamine this question by considering the effect of radiatively active water‐ice clouds (RACs) and cloud microphysics. We find that when obliquity is set to 35°, as often occurred in the past 2 million years, warming of the atmosphere and polar caps by clouds modifies the water cycle and leads to the formation of a several centimeter‐thick ice mantle poleward of 30° in each hemisphere during winter. This mantle can be preserved over the summer if increased atmospheric dust content obscures the surface and provides dust nuclei to low‐altitude clouds. We outline a scenario for its deposition and preservation that compares favorably with the characteristics of the LDM.
Key Points
Simulations of recent ice ages are performed using an improved climate model
Cloud radiative effect and coupling to the dust cycle control snow deposition
The location of predicted ice deposits is consistent with geologic evidence
Airborne dust modifies the thermal structure of the Martian atmosphere. The Mars Climate Sounder (MCS) first revealed local maxima of dust mass mixing ratio detached from the surface, not reproduced ...by global climate models (GCM). In this paper, the thermal signature of such detached layers is detected using data assimilation, an optimal combination of a GCM and observations. As dust influences the atmospheric temperatures, MCS temperature profiles are used to estimate the amount of dust in the atmosphere. Data assimilation of only MCS temperature information reproduces detached dust layers, independently confirming MCS's direct observations of dust. The resulting analyzed state has a smaller bias than an assimilation that does not estimate dust. This makes it a promising technique for Martian data assimilation, which is intended to support weather forecasting and weather research on Mars.
Key Points
Dust field is reconstructed from its thermal signature onlyInclusion of detached dust layers in model produces better temperatureDust improves Martian temperature data assimilation
The recently discovered exoplanet Gl 581d is extremely close to the outer edge of its system’s habitable zone, which has led to much speculation on its possible climate. We have performed a range of ...simulations to assess whether, given simple combinations of chemically stable greenhouse gases, the planet could sustain liquid water on its surface. For best estimates of the surface gravity, surface albedo and cloud coverage, we find that less than 10 bars of CO2 is sufficient to maintain a global mean temperature above the melting point of water. Furthermore, even with the most conservative choices of these parameters, we calculate temperatures above the water melting point for CO2 partial pressures greater than about 40 bar. However, we note that as Gl 581d is probably in a tidally resonant orbit, further simulations in 3D are required to test whether such atmospheric conditions are stable against the collapse of CO2 on the surface.
•A seasonal radiative–convective model of Saturn’s atmosphere is built and evaluated.•Sensitivity to composition, aerosols, internal heat flux and ring shadow’s is assessed.•Strong cooling is ...expected under the ring’s shadow, but is not observed by Cassini.•Model-data mismatches are reviewed and reveal departures from radiative equilibrium.•The radiative cooling of the warm beacon formed after the 2010 storm is discussed.
We have developed and optimized a seasonal, radiative–convective model of Saturn’s upper troposphere and stratosphere. It is used to investigate Saturn’s radiatively-forced thermal structure between 3 and 10−6bar, and is intended to be included in a Saturn global climate model (GCM), currently under development. The main elements of the radiative transfer model are detailed as well as the sensitivity to spectroscopic parameters, hydrocarbon abundances, aerosol properties, oblateness, and ring shadowing effects. The vertical temperature structure and meridional seasonal contrasts obtained by the model are then compared to Cassini/CIRS observations. Several significant model-observation mismatches reveal that Saturn’s atmosphere departs from radiative equilibrium. For instance, we find that the modeled temperature profile is close to isothermal above the 2-mbar level, while the temperature retrieved from ground-based or Cassini/CIRS data continues to increase with altitude. Also, no local temperature minimum associated to the ring shadowing is observed in the data, while the model predicts stratospheric temperatures 10K to 20K cooler than in the absence of rings at winter tropical latitudes. These anomalies are strong evidence that processes other that radiative heating and cooling control Saturn’s stratospheric thermal structure. Finally, the model is used to study the warm stratospheric anomaly triggered after the 2010 Great White Spot. Comparison with recent Cassini/CIRS observations suggests that the rapid cooling phase of this warm “beacon” in May–June 2011 can be explained by radiative processes alone. Observations on a longer timeline are needed to better characterize and understand its long-term evolution.
Data assimilation is carried out for the Martian atmosphere with the Mars Climate Sounder (MCS) retrievals of temperature, dust, and ice. It is performed for the period Ls = 180° to Ls = 320° of Mars ...Year 29 with the Local Ensemble Transform Kalman Filter scheme and the Laboratoire de Météorologie Dynamique (LMD) Mars Global Climate Model (GCM). In order to deal with the forcings of aerosols (dust and water ice) on atmospheric temperatures, a framework is given for multivariate analysis. It consists of assimilating a GCM variable with the help of another GCM variable that can be more easily related to an observation. Despite encouraging results with this method, data assimilation is found to be intrinsically different for Mars and more challenging, due to the Martian atmosphere being less chaotic and exhibiting more global features than on Earth. This is reflected in the three main issues met when achieving various data assimilation experiments: (1) temperature assimilation strongly forces the GCM away from its free‐running state, due to the difficulty of assimilating global atmospheric thermal tides; (2) because of model bias, assimilation of airborne dust is not able to reproduce the vertical diurnal variations of dust observed by MCS, and not present in the GCM; and (3) water ice clouds are nearly impossible to assimilate due to the difficulty to assimilate temperature to a sufficient precision. Overall, further improvements of Martian data assimilation would require an assimilation that goes beyond the local scale and more realism of the GCM, especially for aerosols and thermal tides.
Key Points
Data assimilation of the Martian atmosphere is tackled with a multivariate approach
Assimilation is found to be distinctively challenging on Mars
Despite this challenge, temperature can be predicted for a few Martian days in dusty conditions
Ozone (O3) in the atmosphere of Mars is produced following the photolysis of CO2 and is readily destroyed by the hydrogen radicals (HOx) released by the photolysis and oxidation of water vapor. As a ...result, an anti‐correlation between ozone and water vapor is expected. We describe here the O3‐H2O relationship derived from 4 Martian years of simultaneous observations by the SPICAM spectrometer onboard the Mars Express spacecraft. A distinct anti‐correlation is found at high latitudes, where the O3 column varies roughly with the −0.6 power of the H2O column. The O3 and H2O columns are uncorrelated at low latitudes. To evaluate our quantitative understanding of the Martian photochemistry, the observed O3‐H2O relationship is then compared to that predicted by a global climate model with photochemistry. For identical model and observed abundances of H2O, the model underpredicts observed ozone by about a factor of 2 relative to SPICAM when using the currently recommended gas‐phase chemistry. Sensitivity studies employing low‐temperature CO2 absorption cross sections, or adjusted kinetics rates, do not solve this bias. Taking into account potential heterogeneous processes of HOx loss on clouds leads to a significant improvement, but only at high northern latitudes. More broadly, the modeled ozone deficits suggest that the HOx‐catalyzed photochemistry is too efficient in our simulations. This problem is consistent with the long‐standing underestimation of CO in Mars photochemical models, and may be related to similar difficulties in modeling O3 and HOx in the Earth's upper stratosphere and mesosphere.
Plain Language Summary
The thin ozone layer on Mars is produced when the solar ultraviolet light breaks the CO2 molecules that compose 95% of its atmosphere. Conversely, ozone on Mars is readily destroyed by the hydrogen species released by water vapor. An inverse relationship is therefore expected between the quantities of ozone and water vapor. Quantifying this relationship provides important insight into the hydrogen chemistry that stabilizes the composition of the Mars atmosphere. We describe here the ozone and water vapor measurements performed during 4 Martian years (7.5 Earth years) by the SPICAM instrument onboard the Mars Express spacecraft. We then attempt to reproduce these measurements with a Mars climate model with photochemistry. Although the model reproduces the inverse relationship observed between ozone and water vapor, the ozone amount is underestimated by about a factor of 2 in the simulations. The ozone deficit suggests that the destruction by hydrogen species is too strong when one uses the currently recommended reaction rates. This problem is consistent with the long‐standing underestimation in Mars models of carbon monoxide, also destroyed by hydrogen species, and can be related to similar difficulties in modeling ozone in the Earth's upper atmosphere.
Key Points
The relationship between the O3 and H2O columns on Mars is quantified from 4 Martian years of simultaneous measurements
The O3 and H2O columns are distinctly anti‐correlated at high latitudes but are uncorrelated at low latitudes
Model simulations using the observed amount of H2O and the currently recommended kinetics underpredict O3 by about a factor of 2
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