We used temperature data from the Michelson Interferometer for Passive Atmospheric Sounding on board ESA's Envisat satellite to analyze the temperature responses in the mesosphere and thermosphere up ...to 170 km to a major stratospheric sudden warming (SSW) which occurred in January 2009. The temperature observations show clear signatures of a mesospheric cooling and a thermospheric warming, the latter peaking at 120–140 km in agreement with model predictions. From the analysis of the zonal temperature structure during the SSW a pronounced wave 1 pattern was found in the entire middle and upper polar atmosphere with maximum amplitudes around 50 and 140 km. In the mesosphere, the wave amplitude is significantly damped. The wave amplification above is most likely produced by in situ forced planetary waves in the mesosphere and lower thermosphere region. Our observations represent the first experimental evidence of a dynamical coupling of the lower atmosphere and the thermosphere in the 120–150 km range by means of satellite data.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The vast set of near‐global and continuous atmospheric measurements made by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument since 2002, including daytime and ...nighttime kinetic temperature (Tk) from 20 to 105 km, is available to the scientific community. The temperature is retrieved from SABER measurements of the atmospheric 15 μm CO2 limb emission. This emission separates from local thermodynamic equilibrium (LTE) conditions in the rarefied mesosphere and thermosphere, making it necessary to consider the CO2 vibrational state non‐LTE populations in the retrieval algorithm above 70 km. Those populations depend on kinetic parameters describing the rate at which energy exchange between atmospheric molecules take place, but some of these collisional rates are not well known. We consider current uncertainties in the rates of quenching of CO2(υ2) by N2, O2 and O, and the CO2(υ2) vibrational‐vibrational exchange to estimate their impact on SABER Tk for different atmospheric conditions. The Tk is more sensitive to the uncertainty in the latter two, and their effects depend on altitude. The Tk combined systematic error due to non‐LTE kinetic parameters does not exceed ±1.5 K below 95 km and ±4–5 K at 100 km for most latitudes and seasons (except for polar summer) if the Tk profile does not have pronounced vertical structure. The error is ±3 K at 80 km, ±6 K at 84 km and ±18 K at 100 km under the less favorable polar summer conditions. For strong temperature inversion layers, the errors reach ±3 K at 82 km and ±8 K at 90 km. This particularly affects tide amplitude estimates, with errors of up to ±3 K.
The quality of the retrieved temperature-versus-pressure (or T(p)) profiles is described for the middle atmosphere for the publicly available Sounding of the Atmosphere using Broadband Emission ...Radiometry (SABER) Version 1.07 (V1.07) data set. The primary sources of systematic error for the SABER results below about 70 km are (1) errors in the measured radiances, (2) biases in the forward model, and (3) uncertainties in the corrections for ozone and in the determination of the reference pressure for the retrieved profiles. Comparisons with other correlative data sets indicate that SABER T(p) is too high by 1-3 K in the lower stratosphere but then too low by 1 K near the stratopause and by 2 K in the middle mesosphere. There is little difference between the local thermodynamic equilibrium (LTE) algorithm results below about 70 km from V1.07 and V1.06, but there are substantial improvements/differences for the non-LTE results of V1.07 for the upper mesosphere and lower thermosphere (UMLT) region. In particular, the V1.07 algorithm uses monthly, diurnally averaged CO2 profiles versus latitude from the Whole Atmosphere Community Climate Model. This change has improved the consistency of the character of the tides in its kinetic temperature (T(sub k)). The T(sub k) profiles agree with UMLT values obtained from ground-based measurements of column-averaged OH and O2 emissions and of the Na lidar returns, at least within their mutual uncertainties. SABER T(sub k) values obtained near the mesopause with its daytime algorithm also agree well with the falling sphere climatology at high northern latitudes in summer. It is concluded that the SABER data set can be the basis for improved, diurnal-to-interannual-scale temperatures for the middle atmosphere and especially for its UMLT region.
In this paper, we analyze the strong unidentified emission near 3.28 micron in Titan's upper daytime atmosphere recently discovered by Dinelli et al.We have studied it by using the NASA Ames PAH IR ...Spectroscopic Database. The polycyclic aromatic hydrocarbons (PAHs), after absorbing UV solar radiation, are able to emit strongly near 3.3 micron. By using current models for the redistribution of the absorbed UV energy, we have explained the observed spectral feature and have derived the vertical distribution of PAH abundances in Titan's upper atmosphere. PAHs have been found to be present in large concentrations, about (2-3) × 10(exp 4) particles / cubic cm. The identified PAHs have 9-96 carbons, with a concentration-weighted average of 34 carbons. The mean mass is approx 430 u; the mean area is about 0.53 sq. nm; they are formed by 10-11 rings on average, and about one-third of them contain nitrogen atoms. Recently, benzene together with light aromatic species as well as small concentrations of heavy positive and negative ions have been detected in Titan's upper atmosphere. We suggest that the large concentrations of PAHs found here are the neutral counterpart of those positive and negative ions, which hence supports the theory that the origin of Titan main haze layer is located in the upper atmosphere.
Observations from the SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) instrument on the TIMED (Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics) satellite show ...interannual variations of mesospheric ozone in the NH late winter. Ozone in the mid‐January to mid‐March period is significantly different in 2004, 2006, and 2009 than in other years (2002, 2003, 2005, 2007, 2008). The altitudes of the ozone secondary maximum (∼90–95 km), the minimum (∼80 km) and the tertiary maximum (∼72 km) are all lower by 3–5 km during the three anomalous winters. The ozone anomalies indicate enhanced downward motion and are consistent with other observations of unusual profiles of trace species. The ozone perturbations extend to at least 100 km while temperatures above 90 km are within the range found in the other years.
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Hydrocarbon species, and in particular CH4, play a key role in the stratosphere-thermosphere boundary of Jupiter, which occurs around the μ-bar pressure level. Previous analyses of solar occultation, ...He and Ly-α airglow, and ISO/SWS measurements of the radiance around 3.3 μm have inferred significantly different methane concentrations. Here we aim to accurately model the CH4 radiance at 3.3 μm measured by ISO/SWS by using a comprehensive non-local thermodynamic equilibrium model and the most recent collisional rates measured in the laboratory for CH4 to shed new light onto the methane concentration in the upper atmosphere of Jupiter. These emission bands have been shown to present a peak contribution precisely at the μ-bar level, hence directly probing the region of interest. We find that a high CH4 concentration is necessary to explain the data, in contrast with the most recent analyses, and that the observations favour the lower limit of the latest laboratory measurements of the CH4 collisional relaxation rates. Our results provide precise constraints on the composition and dynamics of the lower atmosphere of Jupiter.
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FMFMET, NUK, UL, UM, UPUK
Using a ground‐to‐exosphere general circulation model for Mars we have simulated the variability of the dayside temperatures at the exobase during eight Martian years (MY, from MY24 to MY31, ...approximately from 1998 to 2013), taking into account the observed day‐to‐day solar and dust load variability. We show that the simulated temperatures are in good agreement with the exospheric temperatures derived from Precise Orbit Determination of Mars Global Surveyor. We then study the effects of the solar variability and of two planetary‐encircling dust storms on the simulated temperatures. The seasonal effect produced by the large eccentricity of the Martian orbit translates in an aphelion‐to‐perihelion temperature contrast in every simulated year. However, the magnitude of this seasonal temperature variation is strongly affected by the solar conditions, ranging from 50 K for years corresponding to solar minimum conditions to almost 140 K during the last solar maximum. The 27 day solar rotation cycle is observed on the simulated temperatures at the exobase, with average amplitude of the temperature oscillation of 2.6 K but with a significant interannual variability. These two results highlight the importance of taking into account the solar variability when simulating the Martian upper atmosphere and likely have important implications concerning the atmospheric escape rate. We also show that the global dust storms in MY25 and MY28 have a significant effect on the simulated temperatures. In general, they increase the exospheric temperatures over the low latitude and midlatitude regions and decrease them in the polar regions.
Key Points
Eight Martian years simulated with global model including day‐to‐day variable solar flux and dust
Important effect of solar cycle and solar rotation on simulated exobase temperatures
Significant effects of planetary‐encircling dust storms on simulated exobase temperatures
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
A comprehensive interpretation of single and multichannel seismic reflection profiles integrated with biostratigraphical data and log information from nearby DSDP and ODP wells has been used to ...constrain the late Messinian to Quaternary basin evolution of the central part of the Alboran Sea Basin. We found that deformation is heterogeneously distributed in space and time and that three major shortening phases have affected the basin as a result of convergence between the Eurasian and African plates. During the Messinian salinity crisis, significant erosion and local subsidence resulted in the formation of small, isolated, basins with shallow marine and lacustrine sedimentation. The first shortening event occurred during the Early Pliocene (ca. 5.33–4.57 Ma) along the Alboran Ridge. This was followed by a major transgression that widened the basin and was accompanied by increased sediment accumulation rates. The second, and main, phase of shortening on the Alboran Ridge took place during the Late Pliocene (ca. 3.28–2.59 Ma) as a result of thrusting and folding which was accompanied by a change in the Eurasian/African plate convergence vector from NW‐SE to WNW‐ESE. This phase also caused uplift of the southern basins and right‐lateral transtension along the WNW‐ENE Yusuf fault zone. Deformation along the Yusuf and Alboran ridges continued during the early Pleistocene (ca. 1.81–1.19 Ma) and appears to continue at the present day together with the active NNE‐SSW trending Al‐Idrisi strike‐slip fault. The Alboran Sea Basin is a region of complex interplay between sediment supply from the surrounding Betic and Rif mountains and tectonics in a zone of transpression between the converging African and European plates. The partitioning of the deformation since the Pliocene, and the resulting subsidence and uplift in the basin was partially controlled by the inherited pre‐Messinian basin geometry.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Jupiter's atmosphere has been sounded in transmission from the UV to the IR, as if it were a transiting exoplanet, by observing Ganymede while passing through Jupiter's shadow. The spectra show ...strong extinction due to the presence of aerosols and haze in Jupiter's atmosphere and strong absorption features of methane. Here, we report a new detailed analysis of these observations, with special emphasis on the retrievals of the vertical distribution of the aerosols and their sizes, and the properties and distribution of the stratospheric water ice. Our analysis suggests the presence of aerosols near the equator in the altitude range of 100 hPa up to at least 0.01 hPa, with a layer of small particles (mean radius of 0.1 m) in the upper part (above 0.1 hPa), an intermediate layer of aerosols with a radius of 0.3 m, extending between ∼10 and 0.01 hPa, and a layer with larger sizes of ∼0.6 m at approximately 100-1 hPa. The corresponding loads for each layer are ∼2 × 10−7 g cm−2, ∼3.4 × 10−7 g cm−2, and ∼1.5 × 10−6 g cm−2, respectively, with a total load of ∼2.0 × 10−6 g cm−2. The lower and middle layers agree well with previous measurements; but the finer particles of 0.1 m above 0.01 hPa have not been reported before. The spectra also show two broad features near 1.5 and 2.0 m, which we attribute to a layer of very small (∼10 nm) H2O crystalline ice in Jupiter's lower stratosphere (∼0.5 hPa). While these spectral signatures seem to be unequivocally attributable to crystalline water ice, they require a large amount of water ice to explain the strong absorption features.
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