scholarly journals Atmospheric implications of the lack of H 3 + detection at Neptune

2020 ◽  
Vol 378 (2187) ◽  
pp. 20200100 ◽  
Author(s):  
L. Moore ◽  
J. I. Moses ◽  
H. Melin ◽  
T. S. Stallard ◽  
J. O’Donoghue
Keyword(s):  
Giant Planet ◽  
Atmospheric Temperature ◽  
Upper Atmosphere ◽  
Lower Atmosphere ◽  
Observational Constraints ◽  
Atmospheric Conditions ◽  
Atmospheric Escape ◽  
Upper Limits ◽  
Voyager 2 ◽  
The Impact

H 3 + has been detected at all of the solar system giant planets aside from Neptune. Current observational upper limits imply that there is far less H 3 + emission at Neptune than rudimentary modelling would suggest. Here, we explore via modelling a range of atmospheric conditions in order to find some that could be consistent with observational constraints. In particular, we consider that the upper atmosphere might be much cooler than it was during the 1989 Voyager 2 encounter, and we examine the impact of an enhanced influx of external material that could act to reduce H 3 + density. Resulting ionosphere models that are consistent with existing H 3 + observational constraints have an exospheric temperature of 450 K or less, 300 K lower than the Voyager 2 value. Alternatively, if a topside CO influx of 2 × 10 8  cm −2  s −1 is imposed, the upper atmospheric temperature can be higher, up to 550 K. The potential cooling of Neptune’s atmosphere is relevant for poorly understood giant planet thermospheric energetics, and would also impact aerobreaking manoeuvers for any future spacecraft. Such a large CO influx, if present, could imply Triton is a very active moon with prominent atmospheric escape, and/or that Neptune’s rings significantly modify its upper atmosphere, and the introduction of so much exogenic material would complicate interpretation of the origin of species observed in Neptune’s lower atmosphere. This article is part a discussion meeting issue ‘Future exploration of ice giant systems’.

Examination of Errors in Near-Surface Temperature and Wind from WRF Numerical Simulations in Regions of Complex Terrain

2013 ◽  
Vol 28 (3) ◽  
pp. 893-914 ◽  
Author(s):  
Hailing Zhang ◽  
Zhaoxia Pu ◽  
Xuebo Zhang
Keyword(s):  
Complex Terrain ◽  
Forecast Error ◽  
Wrf Model ◽  
Atmospheric Temperature ◽  
Lower Atmosphere ◽  
Forecast Errors ◽  
Atmospheric Conditions ◽  
Near Surface ◽  
System A ◽  
Synoptic Forcing

Abstract The performance of an advanced research version of the Weather Research and Forecasting Model (WRF) in predicting near-surface atmospheric temperature and wind conditions under various terrain and weather regimes is examined. Verification of 2-m temperature and 10-m wind speed and direction against surface Mesonet observations is conducted. Three individual events under strong synoptic forcings (i.e., a frontal system, a low-level jet, and a persistent inversion) are first evaluated. It is found that the WRF model is able to reproduce these weather phenomena reasonably well. Forecasts of near-surface variables in flat terrain generally agree well with observations, but errors also occur, depending on the predictability of the lower-atmospheric boundary layer. In complex terrain, forecasts not only suffer from the model's inability to reproduce accurate atmospheric conditions in the lower atmosphere but also struggle with representative issues due to mismatches between the model and the actual terrain. In addition, surface forecasts at finer resolutions do not always outperform those at coarser resolutions. Increasing the vertical resolution may not help predict the near-surface variables, although it does improve the forecasts of the structure of mesoscale weather phenomena. A statistical analysis is also performed for 120 forecasts during a 1-month period to further investigate forecast error characteristics in complex terrain. Results illustrate that forecast errors in near-surface variables depend strongly on the diurnal variation in surface conditions, especially when synoptic forcing is weak. Under strong synoptic forcing, the diurnal patterns in the errors break down, while the flow-dependent errors are clearly shown.

Impact of photochemical hazes on the thermal structure of exoplanet atmospheres

2020 ◽  
Author(s):  
Panayotis Lavvas ◽  
Anthony Arfaux
Keyword(s):  
Chemical Composition ◽  
Gas Phase ◽  
Thermal Structure ◽  
Temperature Inversion ◽  
Upper Atmosphere ◽  
Lower Atmosphere ◽  
Cloud Formation ◽  
Electromagnetic Spectrum ◽  
Heating Efficiency ◽  
The Impact

<p>Transit observations reveal that a significant population of the detected exoplanets has hazy atmospheres (Sing et al. 2016). Although the relative contribution of clouds and photochemical aerosols is not yet fully clarified, the impact of haze particles on the thermal structure could be significant, as such particles can efficiently scatter and absorb radiation over a large part of the electromagnetic spectrum. Particularly, photochemical aerosols are anticipated to be present at pressures lower than those of cloud formation. The transit observations of HD 189733 b indicate that the haze opacity responsible for the UV-Visible slope is located at pressures between 1μbar and 1 mbar. As such low pressures, the presence of hazes could allow for strong temperature inversions due to the low atmospheric density. We investigate here the implications of such hazes on the exoplanet atmospheric thermal structure.</p> <p>We simulate the atmospheric thermal structure using a 1D radiative-convective model. The model utilizes non-equilibrium chemical composition results (Lavvas et al. 2014) for the gas phase composition, and haze particle size distributions calculated from an aerosol microphysical growth model (Lavvas & Koskinen 2017, Lavvas et al. 2019). We do not yet consider the non-LTE effects for the gases, but we do take into account the impact of temperature disequilibrium between the particles and the gas envelope that can strongly affect the heating efficiency of the particles. We consider various gas phase opacities from atomic and molecular contributions calculated through correlated-k coefficients.</p> <p>Our results demonstrate that in the lower atmosphere the simulated temperature profiles provide emission spectra that are in good agreement with the eclipse observations for the simulated targets (HD 209458 b and HD 189733 b). In the upper atmosphere of the hazy HD 189733 b the simulated haze distribution, which fits the transit observations, results in a strong temperature inversion. On the contrary, the upper atmosphere of the clear HD 209458 b, is significantly colder compared to previous evaluations based on equilibrium chemistry assumption. The implications of these results on the chemical composition will be discussed, as well as results from other exoplanet cases.</p> <p> </p>

scholarly journals Impact of Solar Activity on Global Atmospheric Circulation Based on SD-WACCM-X Simulations from 2002 to 2019

Atmosphere ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1526
Author(s):  
Chen-Ke-Min Teng ◽  
Sheng-Yang Gu ◽  
Yusong Qin ◽  
Xiankang Dou
Keyword(s):  
Solar Activity ◽  
Atmospheric Circulation ◽  
Southern Oscillation ◽  
Upper Atmosphere ◽  
Lower Atmosphere ◽  
High Solar Activity ◽  
Low Latitude ◽  
Quasi Biennial Oscillation ◽  
Global Atmospheric Circulation ◽  
The Impact

In this study, a global atmospheric model, Specified Dynamics Whole Atmosphere Community Climate Model with thermosphere and ionosphere eXtension (SD-WACCM-X), and the residual circulation principle were used to study the global atmospheric circulation from the lower to upper atmosphere (~500 km) from 2002 to 2019. Our analysis shows that the atmospheric circulation is clearly influenced by solar activity, especially in the upper atmosphere, which is mainly characterized by an enhanced atmospheric circulation in years with high solar activity. The atmospheric circulation in the upper atmosphere also exhibits an ~11 year period, and its variation is highly correlated with the temporal variation in the F10.7 solar index during the same time series, with a maximum correlation coefficient of up to more than 0.9. In the middle and lower atmosphere, the impact of solar activity on the atmospheric circulation is not as obvious as in the upper atmosphere due to some atmospheric activities such as the Quasi-Biennial Oscillation (QBO), El Niño–Southern Oscillation (ENSO), sudden stratospheric warming (SSW), volcanic forcing, and so on. By comparing the atmospheric circulation in different latitudinal regions between years with high and low solar activity, we found the atmospheric circulation in mid- and high-latitude regions is more affected by solar activity than in low-latitude and equatorial regions. In addition, clear seasonal variation in atmospheric circulation was detected in the global atmosphere, excluding the regions near 10−4 hPa and the lower atmosphere, which is mainly characterized by a flow from the summer hemisphere to the winter hemisphere. In the middle and low atmosphere, the atmospheric circulation shows a quasi-biennial oscillatory variation in the low-latitude and equatorial regions. This work provides a referable study of global atmospheric circulation and demonstrates the impacts of solar activity on global atmospheric circulation.

scholarly journals Opposite long-term trends in aerosols between low and high altitudes: a testimony to the aerosol–PBL feedback

2017 ◽  
Vol 17 (12) ◽  
pp. 7997-8009 ◽  
Author(s):  
Zipeng Dong ◽  
Zhanqing Li ◽  
Xing Yu ◽  
Maureen Cribb ◽  
Xingmin Li ◽  
...  
Keyword(s):  
Air Pollution ◽  
Atmospheric Stability ◽  
Atmospheric Temperature ◽  
Upper Atmosphere ◽  
Lower Atmosphere ◽  
Surface Cooling ◽  
Vertical Diffusion ◽  
Aerosol Loading ◽  
Wide Range ◽  
Absorbing Aerosols

Abstract. Interactions between absorbing aerosols and the planetary boundary layer (PBL) play an important role in affecting air pollution near the surface. In this study, a unique feature of the aerosol–PBL interaction is identified that has important implications in monitoring and combating air pollution. Opposite trends in aerosol loading between the lower and upper PBL are shown on a wide range of timescales and data acquired by various platforms: from a short-term field experiment to decadal satellite observations and multidecadal ground observations in China. A novel method is proposed to obtain the vertical profiles of aerosol loading from passive sensors by virtue of varying elevations. The analyses of visibility, aerosol optical depth, and extinction with different temporal scales exhibit the similar trend, i.e., increasing in the lower atmosphere but decreasing in the upper atmosphere. Integration of the reversal aerosol trend below and above the PBL resulted in a much less change in the column-integrated quantities. The surface cooling effect, together with the change in the heating rate induced by the absorbing aerosol, unevenly modifies the atmospheric temperature profile, causing a more stable atmosphere inside the PBL but a destabilized atmosphere above the PBL. Such a change in the atmospheric stability favors the accumulation of pollutants near the surface and the vertical diffusion of aerosol particles in the upper atmosphere, both of which are consistent with the observed reversal aerosol trends. These findings have multiple implications in understanding and combating air pollution, especially in many developing countries with high emissions of light-absorbing aerosols.

scholarly journals Global heating of Jupiter's upper atmosphere by auroral energy circulation

2021 ◽  
Author(s):  
James O'Donoghue ◽  
Luke Moore ◽  
Tanapat Bhakyapaibul ◽  
Henrik Melin ◽  
Tom Stallard ◽  
...  
Keyword(s):  
Giant Planet ◽  
Upper Atmosphere ◽  
Lower Atmosphere ◽  
Planetary Scale ◽  
Global Circulation ◽  
Global Circulation Models ◽  
Auroral Emissions ◽  
Global Increase ◽  
Magnetic Poles ◽  
Coupling Processes

Abstract Giant planet upper atmospheres have long been observed to be significantly hotter than expected. Magnetosphere-atmosphere coupling processes give rise to auroral emissions and enormous energy deposition near the magnetic poles, explaining high temperatures for narrow regions of the planet. However, global circulation models have difficulty redistributing auroral energy globally due to the strong Coriolis forces and ion drag. Heating by solar photons is insufficient at giant planets, and yet other proposed processes, such as heating by waves originating from the lower atmosphere, also fail to explain the warm equatorial temperature. There remains no self-consistent explanation for measured non-auroral temperatures at present, mostly due to a lack of definitive observational constraints. Here, using high-resolution maps capable of tracing global temperature gradients at Jupiter, we show that upper-atmosphere temperatures decrease steadily from the aurora to the equator. During a period of enhanced auroral activity, likely driven by a coincident solar wind compression event, we also find a global increase in temperature accompanied by a high temperature planetary-scale structure that appears to emanate from the auroral region. These observations indicate that Jupiter's upper atmosphere is predominantly heated via the redistribution of auroral energy.

scholarly journals Grid of upper atmosphere models for 1–40 M⊕ planets: application to CoRoT-7 b and HD 219134 b,c

2018 ◽  
Vol 619 ◽  
pp. A151 ◽  
Author(s):  
D. Kubyshkina ◽  
L. Fossati ◽  
N. V. Erkaev ◽  
C. P. Johnstone ◽  
P. E. Cubillos ◽  
...  
Keyword(s):  
Mass Loss Rate ◽  
Atmospheric Temperature ◽  
High Energy ◽  
Physical Models ◽  
Upper Atmosphere ◽  
Heating Rates ◽  
Planetary Evolution ◽  
Atmospheric Escape ◽  
Theoretical Evidence ◽  
Atmospheric Loss

There is growing observational and theoretical evidence suggesting that atmospheric escape is a key driver of planetary evolution. Commonly, planetary evolution models employ simple analytic formulae (e.g. energy limited escape) that are often inaccurate, and more detailed physical models of atmospheric loss usually only give snapshots of an atmosphere’s structure and are difficult to use for evolutionary studies. To overcome this problem, we have upgraded and employed an existing upper atmosphere hydrodynamic code to produce a large grid of about 7000 models covering planets with masses 1–39 M⊕ with hydrogen-dominated atmospheres and orbiting late-type stars. The modelled planets have equilibrium temperatures ranging between 300 and 2000 K. For each considered stellar mass, we account for three different values of the high-energy stellar flux (i.e. low, moderate, and high activity). For each computed model, we derived the atmospheric temperature, number density, bulk velocity, X-ray and EUV (XUV) volume heating rates, and abundance of the considered species as a function of distance from the planetary centre. From these quantities, we estimate the positions of the maximum dissociation and ionisation, the mass-loss rate, and the effective radius of the XUV absorption. We show that our results are in good agreement with previously published studies employing similar codes. We further present an interpolation routine capable to extract the modelling output parameters for any planet lying within the grid boundaries. We used the grid to identify the connection between the system parameters and the resulting atmospheric properties. We finally applied the grid and the interpolation routine to estimate atmospheric evolutionary tracks for the close-in, high-density planets CoRoT-7 b and HD 219134 b,c. Assuming that the planets ever accreted primary, hydrogen-dominated atmospheres, we find that the three planets must have lost them within a few Myr.

scholarly journals Upper limit of hydrogen and helium concentrations on Titan

1971 ◽  
Vol 40 ◽  
pp. 394-400
Author(s):  
Wayne E. McGovern
Keyword(s):  
Upper Atmosphere ◽  
Lower Atmosphere ◽  
Mixing Ratios ◽  
Upper Limit ◽  
Upper Limits

The satellite Titan is commonly quoted as possessing an atmosphere consisting of at least 2 × 104 cm atm of methane. Plausible additional atmospheric constituents like hydrogen and helium are assumed to have completely escaped from the satellite. However, the employment of recent techniques to the upper atmosphere of Titan permits an improved estimate of the upper limits of the hydrogen to methane and helium to methane mixing ratios existing in the lower atmosphere of Titan, namely 10−6±1 and 10−3.5±0.5.

Effects of atmospheric temperature and pressure on the performance of a vehicle

2002 ◽  
Vol 216 (6) ◽  
pp. 473-477 ◽  
Author(s):  
S M C Soares ◽  
J R Sodre
Keyword(s):  
Ambient Temperature ◽  
Sea Level ◽  
Fuel Injection ◽  
Atmospheric Temperature ◽  
Intake Manifold ◽  
Atmospheric Conditions ◽  
Fixed Temperature ◽  
Vehicle Performance ◽  
The Road ◽  
On The Road

This paper describes the influence of the atmospheric conditions on the performance of a vehicle. Tests were carried out on the road, under different conditions of ambient temperature, pressure and humidity, measuring the acceleration time. The tested vehicle featured a gasoline-fuelled four-cylinder engine, with variable intake manifold length and multipoint fuel injection. The vehicle was tested at sea level and at an altitude of 827 m above sea level, with the ambient temperature ranging from 20 to 30°C. The times required for the vehicle to go from 80 to 120 km/h, from 40 to 100 km/h and to reach distances of 400 and 1000 m leaving from an initial speed of 40 km/h at full acceleration were recorded. The results showed the vehicle performance to be more affected by changes in the atmospheric pressure than in the temperature. An average difference of 3 per cent in the time to reach 1000 m, leaving from the speed of 40 km/h at full acceleration, was found between the atmospheric pressures tested, for a fixed temperature.

scholarly journals Microwave temperature and pressure measurements with the Odin satellite: I. Observational method

2002 ◽  
Vol 80 (4) ◽  
pp. 443-454 ◽  
Author(s):  
J R Pardo ◽  
M Ridal ◽  
D Murtagh ◽  
J Cernicharo
Keyword(s):  
Radiative Transfer ◽  
Outer Space ◽  
Atmospheric Temperature ◽  
Upper Atmosphere ◽  
Operational Mode ◽  
Altitude Range ◽  
Molecular Lines ◽  
Temperature And Pressure ◽  
Radiative Transfer Modeling ◽  
Temperature Vertical Profile

The Odin satellite is equipped with millimetre and sub-millimetre receivers for observations of several molecular lines in the middle and upper atmosphere of our planet (~25–100 km, the particular altitude range depending on the species) for studies in dynamics, chemistry, and energy transfer in these regions. The same receivers are also used to observe molecules in outer space, this being the astrophysical share of the project. Among the atmospheric lines that can be observed, we find two corresponding to molecular oxygen (118.75 GHz and 487.25 GHz). These lines can be used for retrievals of the atmospheric temperature vertical profile. In this paper, we describe the radiative-transfer modeling for O2 in the middle and upper atmosphere that we will use as a basis for the retrieval algorithms. Two different observation modes have been planned for Odin, the three-channel operational mode and a high-resolution mode. The first one will determine the temperature and pressure on an operational basis using the oxygen line at 118.75 GHz, while the latter can be used for measurements of both O2 lines, during a small fraction of the total available time for aeronomy, aimed at checking the particular details of the radiative transfer near O2 lines at very high altitudes (>70 km). The Odin temperature measurements are expected to cover the altitude range ~30–90 km. PACS Nos.: 07.57Mj, 94.10Dy, 95.75Rs

scholarly journals R-BPMV-Mediated Resistance to Bean pod mottle virus in Phaseolus vulgaris L. Is Heat-Stable but Elevated Temperatures Boost Viral Infection in Susceptible Genotypes

Viruses ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1239
Author(s):  
Chouaïb Meziadi ◽  
Julie Lintz ◽  
Masoud Naderpour ◽  
Charlotte Gautier ◽  
Sophie Blanchet ◽  
...  
Keyword(s):  
Elevated Temperature ◽  
Phaseolus Vulgaris ◽  
Elevated Temperatures ◽  
Heat Waves ◽  
Dominant Gene ◽  
Atmospheric Temperature ◽  
Mottle Virus ◽  
Bean Pod Mottle Virus ◽  
Heat Stable ◽  
The Impact

In the context of climate change, elevated temperature is a major concern due to the impact on plant–pathogen interactions. Although atmospheric temperature is predicted to increase in the next century, heat waves during summer seasons have already become a current problem. Elevated temperatures strongly influence plant–virus interactions, the most drastic effect being a breakdown of plant viral resistance conferred by some major resistance genes. In this work, we focused on the R-BPMV gene, a major resistance gene against Bean pod mottle virus in Phaseolus vulgaris. We inoculated different BPMV constructs in order to study the behavior of the R-BPMV-mediated resistance at normal (20 °C) and elevated temperatures (constant 25, 30, and 35 °C). Our results show that R-BPMV mediates a temperature-dependent phenotype of resistance from hypersensitive reaction at 20 °C to chlorotic lesions at 35 °C in the resistant genotype BAT93. BPMV is detected in inoculated leaves but not in systemic ones, suggesting that the resistance remains heat-stable up to 35 °C. R-BPMV segregates as an incompletely dominant gene in an F2 population. We also investigated the impact of elevated temperature on BPMV infection in susceptible genotypes, and our results reveal that elevated temperatures boost BPMV infection both locally and systemically in susceptible genotypes.

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