scholarly journals Titan’s neutral atmosphere seasonal variations up to the end of the Cassini mission

2020 ◽  
Author(s):  
Athena Coustenis ◽  
Donald Jennings ◽  
Richard Achterberg ◽  
Panayotis Lavvas ◽  
Georgios Bampasidis ◽  
...  
Keyword(s):  
High Spectral Resolution ◽  
Large Temperature ◽  
Neutral Atmosphere ◽  
The North ◽  
Northern Summer ◽  
Trace Species ◽  
Northern Latitudes ◽  
Spring Equinox ◽  
Cassini Mission ◽  
Infrared Spectrometer

<p>In our recent publication [1] we reported new results concerning the seasonal atmospheric evolution near Titan’s poles and equator in terms of temperature and composition using nadir spectra acquired by the Cassini Composite Infrared Spectrometer (CIRS) at high spectral resolution during the last year of the Cassini mission in 2017 complementing previous investigations covering almost two Titan seasons. In previous papers [2,3], we reported on monitoring of Titan’s stratosphere near the poles after the mid-2009 northern spring equinox. In particular we have reported on the observed strong temperature decrease and compositional enhancement above Titan’s southern polar latitudes since 2012 and until 2014 of several trace species, such as complex hydrocarbons and nitriles, which were previously observed only at high northern latitudes. This effect accompanied the transition of Titan’s seasons from northern winter in 2002 to northern summer in 2017, while at that latter time, the southern hemisphere was entering winter. Our new data, acquired in 2017 and analyzed here, are important because they are the only ones recorded since 2014 close to the south pole in the mid-infrared nadir mode at high resolution. A large temperature increase in the southern polar stratosphere (by 10-50 K in the 0.1 to 0.01 mbar pressure range) is found associated with a change in the temperature profile’s shape. The 2017 observations also show a related significant decrease in most of the southern abundances which must have started sometime between 2014 and 2017 [1]. For the north, the spectra indicate a continuation of the decrease of the abundances which we first reported to have started in 2015 and small temperature variations [1]. We discuss comparisons with other results and with current photochemical and dynamical models which could be updated and improved by the new constraints set by the findings presented here.</p> <p>[1] Coustenis et al., 2019, Icarus 344, 1 July 2020, 113413 ; [2] Coustenis et al., 2016, Icarus 270, 409-420; [3] Coustenis et al., 2018, Astroph. J. Lett. 854, no2.</p>

Seasonal changes in Titan’s stratosphere during the Cassini mission with CIRS

2021 ◽  
Author(s):  
Athena Coustenis ◽  
Donald Jennings ◽  
Richard Achterberg ◽  
Panayotis Lavvas ◽  
Conor Nixon ◽  
...  
Keyword(s):  
Chemical Composition ◽  
High Resolution ◽  
Far Infrared ◽  
Large Temperature ◽  
Neutral Atmosphere ◽  
South Pole ◽  
The South ◽  
The North ◽  
Northern Summer ◽  
Cassini Mission

<p>Titan’s atmosphere and surface (a complex system) evolve with season, as Titan follows Saturn in its orbit around the Sun for 30 years with an inclination of about 27°. We performed an analysis of spectra acquired by Cassini/CIRS at high resolution covering the range from 600 to 1500 cm-1 since the beginning and until the last flyby of Titan in 2017 and describe the temperature and chemical composition variations ([1-3]. By applying our radiative transfer code (ARTT) to the high-resolution CIRS spectra we study the stratospheric evolution over almost two Titan seasons [1,2], corresponding to the Cassini mission duration. CIRS nadir and limb spectral together show variations in temperature and chemical composition in the stratosphere during the Cassini mission, before and after the Northern Spring Equinox (NSE) and also during one Titan year.</p> <p>Since the 2010 equinox we have thus reported on monitoring of Titan’s stratosphere near the poles and in particular on the observed strong temperature decrease and compositional enhancement above Titan’s southern polar latitudes since 2012 and until 2014 of several trace species, such as complex hydrocarbons and nitriles, which were previously observed only at high northern latitudes. This effect followed the transition of Titan’s seasons from northern winter in 2002 to northern summer in 2017, while at that latter time the southern hemisphere was entering winter.</p> <p>Our data show a continued decrease of the abundances which we first reported to have started in 2015. The 2017 data we have acquired and analyzed here are important because they are the only ones recorded since 2014 close to the south pole in the far-infrared nadir mode at high resolution. A large temperature increase in the southern polar stratosphere (by 10-50 K in the 0.5 mbar-0.05 mbar pressure range) is found and a change in the temperature profile’s shape. The 2017 observations also show a related significant decrease in most of the abundances which must have started sometime between 2014 and 2017 [3]. In our work, we show that the equatorial latitudes remain rather constant throughout the Cassini mission.</p> <p>We have thus shown that the south pole of Titan is now losing its strong enhancement, while the north pole also slowly continues its decrease in gaseous opacities. It would have been interesting to see when this might happen, but the Cassini mission ended in September 2017. Perhaps future ground-based measurements and the Dragonfly mission can pursue this investigation and monitor Titan’s atmosphere to characterize the seasonal events. Our results set constraints on GCM and photochemical models.</p> <p> </p> <p><strong>References:</strong></p> <p> [1] Coustenis et al., 2016, Icarus 270, 409-420</p> <p>[2] Coustenis et al., 2018, Astroph. J., Lett., 854, no2</p> <p>[3] Coustenis et al., 2020. Titan’s neutral atmosphere seasonal variations up to the end of the Cassini mission. Icarus 344, 113413. https://doi.org/10.1016/j.icarus.2019.113413.<button class="clickandreadBtn" title="La ressource a été trouvée dans Unpaywall" name="CLICKANDREADLink"><img src="data:image/svg+xml;base64,PHN2ZyBpZD0iQ2FscXVlXzEiIGRhdGEtbmFtZT0iQ2FscXVlIDEiIHhtbG5zPSJodHRwOi8vd3d3LnczLm9yZy8yMDAwL3N2ZyIgdmlld0JveD0iMCAwIDUwIDI4LjE4Ij48cmVjdCB3aWR0aD0iNTAiIGhlaWdodD0iMjguMTgiIHJ4PSIxNC4wOSIgc3R5bGU9ImZpbGw6IzIxY2UyMSIvPjxwYXRoIGQ9Ik0xOC45MywxNi40NWEuMzIuMzIsMCwwLDAtLjU0LjIydjJoLTRhNS4wOCw1LjA4LDAsMCwxLDAtMTAuMTZoNS4yMlY1LjQ0SDE0LjQ0YTguMTQsOC4xNCwwLDAsMCwwLDE2LjI4aDR2MmEuMzIuMzIsMCwwLDAsLjU0LjIzbDMuNTEtMy41MWEuMzQuMzQsMCwwLDAsMC0uNDZaIiBzdHlsZT0iZmlsbDojZmZmIi8+PHBhdGggZD0iTTQyLjUyLDIxLjA3bC00Ljg0LTUuNjlhMCwwLDAsMCwxLDAsMCw1LjMsNS4zLDAsMCwwLDIuNTktNC45LDUuNDMsNS40MywwLDAsMC01LjQ4LTVIMjguNDhhMCwwLDAsMCwwLDAsMFYyMS42OWEwLDAsMCwwLDAsMCwwaDMuMDVsMCwwVjguNTVzMCwwLDAsMEgzNWEyLjI0LDIuMjQsMCwwLDEsMi4yMiwyLjUzLDIuMywyLjMsMCwwLDEtMi4zMiwySDMyLjRhLjM2LjM2LDAsMCwwLS4yOC41OWw2LjYyLDcuNzlhLjkzLjkzLDAsMCwwLC42OC4zMWgyLjgxQS4zOS4zOSwwLDAsMCw0Mi41MiwyMS4wN1oiIHN0eWxlPSJmaWxsOiNmZmYiLz48Y2lyY2xlIGN4PSIyNC4yIiBjeT0iOC4yIiByPSIyLjc2IiBzdHlsZT0iZmlsbDojZmZmIi8+PC9zdmc+" width="27" /></button></p>

Evolution of Titan’s stratosphere with Cassini/CIRS

2021 ◽  
Author(s):  
Athena Coustenis ◽  
Donald Jennings ◽  
Richard Achterberg ◽  
Panayotis Lavvas ◽  
Conor Nixon ◽  
...  
Keyword(s):  
High Resolution ◽  
Chemical Species ◽  
Far Infrared ◽  
Organic Content ◽  
Large Temperature ◽  
Neutral Atmosphere ◽  
South Pole ◽  
The South ◽  
The North ◽  
Cassini Mission

<p>Titan is a unique body in the solar system in particular because of its earth-like surface features, its putative undersurface liquid water ocean and its large organic content in the atmosphere and on the surface . These chemical species evolve with season, as Titan follows Saturn in its orbit around the Sun with an inclination of about 27°. We performed an analysis of spectra acquired by Cassini/CIRS at high resolution covering the range from 10 to 1500 cm<sup>-1</sup> since the beginning and until the last flyby of Titan in 2017 and describe the temperature and composition variations ([1-3]. By applying our radiative transfer code (ARTT) to the high-resolution CIRS spectra we study the stratospheric evolution over almost two Titan seasons [1,2]. CIRS nadir and limb spectral together show variations in temperature and chemical composition in the stratosphere during the Cassini mission, before and after the Northern Spring Equinox (NSE) and also during one Titan year.</p><p>Since the 2010 equinox we have thus reported on monitoring of Titan’s stratosphere near the poles and in particular on the observed strong temperature decrease and compositional enhancement above Titan’s southern polar latitudes since 2012 and until 2014 of several trace species, such as complex hydrocarbons and nitriles, which were previously observed only at high northern latitudes. This effect followed the transition of Titan’s seasons from northern winter in 2002 to northern summer in 2017, while at that latter time the southern hemisphere was entering winter.</p><p>Our data show a continued decrease of the abundances which we first reported to have started in 2015. The 2017 data we have acquired and analyzed here are important because they are the only ones recorded since 2014 close to the south pole in the far-infrared nadir mode at high resolution. A large temperature increase in the southern polar stratosphere (by 10-50 K in the 0.5 mbar-0.05 mbar pressure range) is found and a change in the temperature profile’s shape. The 2017 observations also show a related significant decrease in most of the abundances which must have started sometime between 2014 and 2017 [3]. In our work, we show that the equatorial latitudes remain rather constant throughout the Cassini mission.</p><p>We have thus shown that the south pole of Titan is now losing its strong enhancement, while the north pole also slowly continues its decrease in gaseous opacities. It would have been interesting to see when this might happen, but the Cassini mission ended in September 2017. Perhaps future ground-based measurements and the Dragonfly mission can pursue this investigation and monitor Titan’s atmosphere to characterize the seasonal events. Our results set constraints on GCM and photochemical models.</p><p>References:</p><p> [1] Coustenis et al., 2016, Icarus 270, 409-420; [2] Coustenis et al., 2018, Astroph. J., Lett., 854, no2; [3] Coustenis et al., 2020. Titan’s neutral atmosphere seasonal variations up to the end of the Cassini mission. Icarus 344, 113413. https://doi.org/10.1016/j.icarus.2019.113413.</p>

scholarly journals Evolution of the atmospheric organic content on Titan with seasons

2020 ◽  
Author(s):  
Athena Coustenis ◽  
Donald Jennings ◽  
Richard Achterberg ◽  
Panayotis Lavvas ◽  
Conor Nixon ◽  
...  
Keyword(s):  
High Resolution ◽  
Chemical Species ◽  
Far Infrared ◽  
Organic Content ◽  
Large Temperature ◽  
South Pole ◽  
The South ◽  
The North ◽  
Northern Summer ◽  
Cassini Mission

<p>Titan is one of the most promising bodies in the solar system from the astrobiological perspective in particular because of its large organic content in the atmosphere and on the surface. These chemical species evolve with time. We performed an analysis of spectra acquired by Cassini/CIRS at high resolution which cover the far-IR range from 10 to 1500 cm-1 since the beginning and until the last year of the Cassini mission in 2017 and describe the temperature and composition variations near Titan’s poles and at the equator over almost two Titan seasons ([1-3]. By applying our radiative transfer code (ARTT) to CIRS data and to the 1980 Voyager 1 flyby values inferred from the re-analysis of the Infrared Radiometer Spectrometer (IRIS) spectra, as well as to the intervening ground- and space-based observations (such as with ISO), we study the stratospheric evolution over a Titanian year (V1 encounter Ls=9° was reached in mid-2010) [1,2]. CIRS nadir and limb spectral together show variations in temperature and chemical composition in the stratosphere during the Cassini mission, before and after the Northern Spring Equinox (NSE) and also during one Titan year.</p><p>After the 2010 equinox we have thus reported on monitoring of Titan’s stratosphere near the poles and in particular on the observed strong temperature decrease and compositional enhancement above Titan’s southern polar latitudes since 2012 and until 2014 of several trace species, such as complex hydrocarbons and nitriles, which were previously observed only at high northern latitudes. This effect followed the transition of Titan’s seasons from northern winter in 2002 to northern summer in 2017, while at that latter time the southern hemisphere was entering winter.</p><p>Our data show a continued decrease of the abundances which we first reported to have started in 2015. The 2017 data we have acquired and analyzed here are important because they are the only ones recorded since 2014 close to the south pole in the far-infrared nadir mode at high resolution. A large temperature increase in the southern polar stratosphere (by 10-50 K in the 0.5 mbar-0.05 mbar pressure range) is found and a change in the temperature profile’s shape. The 2017 observations also show a related significant decrease in most of the abundances which must have started sometime between 2014 and 2017 [3]. In our work, we show that the equatorial latitudes remain rather constant throughout the Cassini mission.</p><p>We have thus shown that the south pole of Titan is now losing its strong enhancement, while the north pole also slowly continues its decrease in gaseous opacities. It would have been interesting to see when this might happen, but the Cassini mission ended in September 2017. Perhaps future ground-based measurements can pursue this investigation and monitor Titan’s atmosphere to characterize the seasonal events. We have obtained thus significant results which set constraints on GCM and photochemical models.</p><p> [1] Coustenis et al., 2016, Icarus 270, 409-420; [2] Coustenis et al., 2018, Astroph. J., Lett., 854, no2; [3] Coustenis et al., 2019, Icarus in press, https://doi.org/10.​1016/​j.​icarus.​2019.​113413.</p>

scholarly journals Mechanisms for a remote response to Asian anthropogenic aerosol in boreal winter

2019 ◽  
Vol 19 (14) ◽  
pp. 9081-9095 ◽  
Author(s):  
Laura J. Wilcox ◽  
Nick Dunstone ◽  
Anna Lewinschal ◽  
Massimo Bollasina ◽  
Annica M. L. Ekman ◽  
...  
Keyword(s):  
North Pacific ◽  
Western Europe ◽  
Large Temperature ◽  
Boreal Winter ◽  
Far Field ◽  
Anthropogenic Aerosols ◽  
Local Circulation ◽  
The North ◽  
The North Pacific ◽  
Circulation Changes

Abstract. Asian emissions of anthropogenic aerosols and their precursors have increased rapidly since 1980, with half of the increase since the pre-industrial era occurring in this period. Transient experiments with the HadGEM3-GC2 coupled model were designed to isolate the impact of Asian anthropogenic aerosols on global climate in boreal winter. It is found that this increase has resulted in local circulation changes, which in turn have driven decreases in precipitation over China, alongside an intensification of the offshore monsoon flow. No large temperature changes are seen over China. Over India, the opposite response is found, with decreasing temperatures and increasing precipitation. The dominant feature of the local circulation changes is an increase in low-level convergence, ascent, and precipitation over the Maritime Continent, which forms part of a tropical Pacific-wide La Niña-like response. HadGEM3-GC2 also simulates pronounced far-field responses. A decreased meridional temperature gradient in the North Pacific leads to a positive Pacific–North American circulation pattern, with associated temperature anomalies over the North Pacific and North America. Anomalous northeasterly flow over northeast Europe drives advection of cold air into central and western Europe, causing cooling in this region. An anomalous anticyclonic circulation over the North Atlantic causes drying over western Europe. Using a steady-state primitive equation model, LUMA, we demonstrate that these far-field midlatitude responses arise primarily as a result of Rossby waves generated over China, rather than in the equatorial Pacific.

scholarly journals Evaluation of the Moisture Sources in two Extreme Landfalling Atmospheric River Events using an Eulerian WRF-Tracers tool

2017 ◽  
Author(s):  
Jorge Eiras-Barca ◽  
Francina Dominguez ◽  
Huancui Hu ◽  
A. Daniel Garaboa-Paz ◽  
Gonzalo Miguez-Macho
Keyword(s):  
Cross Sections ◽  
North Atlantic ◽  
Cold Front ◽  
Wrf Model ◽  
Atmospheric River ◽  
The North ◽  
Northern Latitudes ◽  
The Pacific ◽  
Low Level Jet ◽  
Tropical Moisture

Abstract. A new 3D Tracer tool is coupled to the WRF model to analyze the origin of the moisture in two extreme Atmospheric River (AR) events: the so-called Great Coast Gale of 2007 in the Pacific Basin, and the Great Storm of 1987 in the North Atlantic. Results show that between 80 % and 90 % of the moisture advected by the ARs, as well as between 70 % and 80 % of the associated precipitation have a tropical or subtropical origin. Local convergence transport is responsible for the remaining moisture and precipitation. The ratio of tropical moisture to total moisture is maximized as the cold front arrives to land. Vertical cross sections of the moisture suggest that the maximum in humidity does not necessarily coincide with the Low-Level Jet (LLJ) of the extratropical cyclone. Instead, the amount of tropical humidity is maximized in the lowest atmospheric level in southern latitudes, and can be located above, below or ahead the LLJ in northern latitudes in both analyzed cases.

scholarly journals Fingerprints of changes in the terrestrial carbon cycle in response to large reorganizations in ocean circulation

2010 ◽  
Vol 6 (5) ◽  
pp. 1811-1852 ◽  
Author(s):  
A. Bozbiyik ◽  
M. Steinacher ◽  
F. Joos ◽  
T. F. Stocker
Keyword(s):  
Carbon Cycle ◽  
Ocean Circulation ◽  
North Atlantic ◽  
Climate Model ◽  
Carbon Stocks ◽  
Meridional Overturning Circulation ◽  
Climate Conditions ◽  
Tropical Regions ◽  
The North ◽  
Northern Latitudes

Abstract. CO2 and carbon cycle changes in the land, ocean and atmosphere are investigated using the comprehensive carbon cycle-climate model NCAR CSM1.4-carbon. Ensemble simulations are forced with freshwater perturbations applied at the North Atlantic and Southern Ocean deep water formation sites under pre-industrial climate conditions. As a result, the Atlantic Meridional Overturning Circulation reduces in each experiment to varying degrees. The physical climate fields show changes that are well documented in the literature but there is a clear distinction between northern and southern perturbations. Changes in the physical variables affect, in return, the land and ocean biogeochemical cycles and cause a reduction, or an increase, in the atmospheric CO2 by up to 20 ppmv, depending on the location of the perturbation. In the case of a North Atlantic perturbation, the land biosphere reacts with a strong reduction in carbon stocks in some tropical locations and in high northern latitudes. In contrast, land carbon stocks tend to increase in response to a southern perturbation. The ocean is generally a sink of carbon although large re-organizations occur throughout various basins. The response of the land biosphere is strongest in the tropical regions due to a shift of the Intertropical Convergence Zone. The carbon fingerprints of this shift, either to the south or to the north depending on where the freshwater is applied, can be found most clearly in South America. For this reason, a compilation of various paleoclimate proxy records of Younger Dryas precipitation changes are compared with our model results.

Aerosol and Cloud Changes during the Corona Lockdown in 2020 – First highlights from the BLUESKY campaign

2021 ◽  
Author(s):  
Christiane Voigt ◽  
Jos Lelieveld ◽  
Hans Schlager ◽  
Johannes Schneider ◽  
Daniel Sauer ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Atmospheric Composition ◽  
Data Set ◽  
The North ◽  
Aerosol Mass ◽  
Trace Species ◽  
Research Aircraft ◽  
Fine Mode ◽  
Cloud Modeling ◽  
Fine Mode Aerosol

<p>Worldwide regulations to control the COVID-19 pandemic caused significant reductions in ground and airborne transportation in spring 2020. This unprecedented situation provided the unique opportunity to directly measure the less perturbed atmosphere, notably near the tropopause, and derive the effects of anthropogenic emissions on atmospheric composition, aerosol, clouds and climate. These changes were investigated during the BLUESKY experiment by the two research aircraft HALO and the DLR Falcon, satellite observations and models. From 16 May to 9 June 2020, the two research aircraft performed 20 flights over Europe and the North Atlantic. Profiles of trace species were measured with an advanced in-situ trace gas, aerosol and cloud payload from the boundary layer to 14 km altitude. Here, we present an overview and selected highlights of the BLUESKY experiment. Continental aerosol profiles show significant reductions in aerosol mass in the boundary layer. The reduced aerosol optical thickness above Germany has also been detected by MODIS and its impact on the colour of the sky is investigated. A specific focus was the detection of aerosol and cirrus changes caused by up to 90% reductions in air traffic. We find reductions in fine mode aerosol in the UTLS at various levels compared to CARIBIC data. In addition, we derive reductions in contrail and cirrus cover using passive and active remote sensing from satellite combined with cloud modeling. The comprehensive data set acquired during the 2020 lockdown period allows better understanding and constraining the anthropogenic influence on the composition of the atmosphere and its impacts on air quality and climate.</p>

Stomach contents of northern bottlenose whales Hyperoodon ampullatus stranded in the North Sea

2001 ◽  
Vol 81 (1) ◽  
pp. 143-150 ◽  
Author(s):  
M.B. Santos ◽  
G.J. Pierce ◽  
C. Smeenk ◽  
M.J. Addink ◽  
C.C. Kinze ◽  
...  
Keyword(s):  
The Netherlands ◽  
Stomach Contents ◽  
Important Species ◽  
North East ◽  
The North ◽  
Northern Latitudes ◽  
The North Sea ◽  
Fish Remains ◽  
Northern Bottlenose Whales ◽  
Hyperoodon Ampullatus

This paper presents information on the stomach contents of four northern bottlenose whales Hyperoodon ampullatus (Odontoceti: Ziphiidae) from the north-east Atlantic, an area for which there are few recent data on the feeding ecology of this species. Two of these whales were relatively recent strandings, a female stranded in August 1993 at Hargen (the Netherlands) and a male stranded in February 1997 on the island of Tåsinge (Denmark). Stomach content samples were also examined from a juvenile male stranded in November 1885 at Dunbar (Scotland) and a female stranded in August 1956 on the island of Texel (the Netherlands).  Food remains from the four samples consisted almost entirely of cephalopod beaks. Some fish remains were also found in the stomach of the Hargen and Tåsinge whales, and the latter also had crustacean remains in the stomach. The cephalopod prey consisted mainly of oceanic cephalopods: Gonatus sp. (probably G. fabricii, Cephalopoda: Teuthoidea), Taoniuspavo and Histioteuthis sp. for the Dunbar whale; Gonatus and Teuthowenia megalops for the Texel whale; Gonatus for the Hargen whale and Gonatus, T. megalops and Taonius pavo for the Tåsinge whale. Other prey species found in the Tåsinge specimen included the squid Histioteuthis reversa, H. arcturi, and the octopods Vampiroteuthis infernalis and Vitreledonella richardi. Based on the size of the lower beaks, the squid eaten included juvenile and mature individuals of the most important species (Gonatus and Teuthowenia megalops). The fish remains consisted of vertebrae of Gadidae and fish eye lenses (Hargen whale) and two Trisopterus otoliths (Tåsinge whale).  The results from this study are in agreement with those of previous authors in that cephalopods in general, and G. fabricii in particular, are the main prey of the northern bottlenose whale and other toothed whales in northern latitudes.

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