Jupiter's auroral-related stratospheric heating and chemistry II: Analysis of IRTF-TEXES spectra measured in December 2014

ICARUS 300 (2018) 305-326

JA Sinclair, GS Orton, TK Greathouse, LN Fletcher, JI Moses, V Hue, PGJ Irwin

Ice-shelf damming in the glacial Arctic Ocean: dynamical regimes of a basin-covering kilometre-thick ice shelf

CRYOSPHERE 11 (2017) 1745-1765

J Nilsson, M Jakobsson, C Borstad, N Kirchner, G Bjork, RT Pierrehumbert, C Stranne

A rotating annulus driven by localized convective forcing: a new atmosphere-like experiment


H Scolan, PL Read

Spatial variations in Titan's atmospheric temperature: ALMA and Cassini comparisons from 2012 to 2015

Icarus (2017)

AE Thelen, CA Nixon, NJ Chanover, EM Molter, MA Cordiner, RK Achterberg, J Serigano, PGJ Irwin, N Teanby, SB Charnley

© 2017 Elsevier Inc. Submillimeter emission lines of carbon monoxide (CO) in Titan's atmosphere provide excellent probes of atmospheric temperature due to the molecule's long chemical lifetime and stable, well constrained volume mixing ratio. Here we present the analysis of 4 datasets obtained with the Atacama Large Millimeter/Submillimeter Array (ALMA) in 2012, 2013, 2014, and 2015 that contain strong CO rotational transitions. Utilizing ALMA's high spatial resolution in the 2012, 2014, and 2015 observations, we extract spectra from 3 separate regions on Titan's disk using datasets with beam sizes ranging from 0.35 × 0.28'' to 0.39 × 0.34''. Temperature profiles retrieved by the NEMESIS radiative transfer code are compared to Cassini Composite Infrared Spectrometer (CIRS) and radio occultation science results from similar latitude regions. Disk-averaged temperature profiles stay relatively constant from year to year, while small seasonal variations in atmospheric temperature are present from 2012 to 2015 in the stratosphere and mesosphere (~100-500 km) of spatially resolved regions. We measure the stratopause (320 km) to increase in temperature by 5 K in northern latitudes from 2012 to 2015, while temperatures rise throughout the stratosphere at lower latitudes. We observe generally cooler temperatures in the lower stratosphere (~100 km) than those obtained through Cassini radio occultation measurements, with the notable exception of warming in the northern latitudes and the absence of previous instabilities; both of these results are indicators that Titan's lower atmosphere responds to seasonal effects, particularly at higher latitudes. While retrieved temperature profiles cover a range of latitudes in these observations, deviations from CIRS nadir maps and radio occultation measurements convolved with the ALMA beam-footprint are not found to be statistically significant, and discrepancies are often found to be less than 5 K throughout the atmosphere. ALMA's excellent sensitivity in the lower stratosphere (60-300 km) provides a highly complementary dataset to contemporary CIRS and radio science observations, including altitude regions where both of those measurement sets contain large uncertainties. The demonstrated utility of CO emission lines in the submillimeter as a tracer of Titan's atmospheric temperature lays the groundwork for future studies of other molecular species - particularly those that exhibit strong polar abundance enhancements or are pressure-broadened in the lower atmosphere, as temperature profiles are found to consistently vary with latitude in all three years by up to 15 K.

Phase synchronization of baroclinic waves in a differentially heated rotating annulus experiment subject to periodic forcing with a variable duty cycle

Chaos 27 (2017)

PL Read, X Morice-Atkinson, EJ Allen, AA Castrejón-Pita

© 2017 Author(s). A series of laboratory experiments in a thermally driven, rotating fluid annulus are presented that investigate the onset and characteristics of phase synchronization and frequency entrainment between the intrinsic, chaotic, oscillatory amplitude modulation of travelling baroclinic waves and a periodic modulation of the (axisymmetric) thermal boundary conditions, subject to timedependent coupling. The time-dependence is in the form of a prescribed duty cycle in which the periodic forcing of the boundary conditions is applied for only a fraction δ of each oscillation. For the rest of the oscillation, the boundary conditions are held fixed. Two profiles of forcing were investigated that capture different parts of the sinusoidal variation and δ was varied over the range 0:1 ≤ δ ≤ 1. Reducing δ was found to act in a similar way to a reduction in a constant coupling coefficient in reducing the width of the interval in forcing frequency or period over which complete synchronization was observed (the "Arnol'd tongue") with respect to the detuning, although for the strongest pulse-like forcing profile some degree of synchronization was discernible even at δ = 0:1. Complete phase synchronization was obtained within the Arnol'd tongue itself, although the strength of the amplitude modulation of the baroclinic wave was not significantly affected. These experiments demonstrate a possible mechanism for intraseasonal and/or interannual "teleconnections" within the climate system of the Earth and other planets that does not rely on Rossby wave propagation across the planet along great circles.

Latitudinal variability in Jupiter ' s tropospheric disequilibrium species: GeH4, AsH3 and PH3

ICARUS 289 (2017) 254-269

RS Giles, LN Fletcher, PGJ Irwin

HST/WFC3 observations of Uranus' 2014 storm clouds and comparison with VLT/SINFONI and IRTF/Spex observations

ICARUS 288 (2017) 99-119

PGJ Irwin, MH Wong, AA Simon, GS Orton, D Toledo

Dynamical models to explain observations with SPHERE in planetary systems with double debris belts

ArXiv e-prints (2017)

C Lazzoni, S Desidera, F Marzari, A Boccaletti, M Langlois, D Mesa, R Gratton, Q Kral, N Pawellek, J Olofsson, M Bonnefoy, G Chauvin, AM Lagrange, A Vigan, E Sissa, J Antichi, H Avenhaus, A Baruffolo, JL Baudino, A Bazzon, JL Beuzit, B Biller, M Bonavita, W Brandner, P Bruno, E Buenzli, F Cantalloube, E Cascone, A Cheetham, RU Claudi, M Cudel, S Daemgen, V De Caprio, P Delorme, D Fantinel, G Farisato, M Feldt, R Galicher, C Ginski, J Girard, E Giro, M Janson, J Hagelberg, T Henning, S Incorvaia, M Kasper, T Kopytova, J Lannier, H LeCoroller, L Lessio, R Ligi, AL Maire, F Ménard, M Meyer, J Milli, D Mouillet, S Peretti, C Perrot, D Rouan, M Samland, B Salasnich, G Salter, T Schmidt, S Scuderi, E Sezestre, M Turatto, S Udry, F Wildi, A Zurlo

Mapping Vinyl Cyanide and Other Nitriles in Titan's Atmosphere Using ALMA


JC-Y Lai, MA Cordiner, CA Nixon, RK Achterberg, EM Molter, NA Teanby, MY Palmer, SB Chamley, JE Lindberg, Z Kisiel, MJ Mumma, PGJ Irwin

Forward and inverse kinetic energy cascades in Jupiter's turbulent weather layer

NATURE PHYSICS 13 (2017) 1135-+

RMB Young, PL Read

Sulfur dioxide in the Venus Atmosphere: II. Spatial and temporal variability

ICARUS 295 (2017) 1-15

AC Vandaele, O Korablev, D Belyaev, S Chamberlain, D Evdokimova, T Encrenaz, L Esposito, KL Jessup, F Lefevre, S Limaye, A Mahieux, E Marcq, FP Mills, F Montmessin, CD Parkinson, S Robert, T Roman, B Sandor, A Stolzenbach, C Wilson, V Wilquet

Ertel potential vorticity versus Bernoulli streamfunction on Mars


TE Dowling, ME Bradley, J Du, SR Lewis, PL Read

Orbiting a binary: SPHERE characterisation of the HD 284149 system

ArXiv e-prints (2017)

M Bonavita, V D Orazi, D Mesa, C Fontanive, S Desidera, S Messina, S Daemgen, R Gratton, A Vigan, M Bonnefoy, A Zurlo, J Antichi, H Avenhaus, A Baruffolo, JL Baudino, JL Beuzit, A Boccaletti, P Bruno, T Buey, M Carbillet, E Cascone, G Chauvin, RU Claudi, V De Caprio, D Fantinel, G Farisato, M Feldt, R Galicher, E Giro, C Gry, J Hagelberg, S Incorvaia, M Janson, M Jaquet, AM Lagrange, M Langlois, J Lannier, H Le Coroller, L Lessio, R Ligi, AL Maire, F Menard, C Perrot, S Peretti, C Petit, J Ramos, A Roux, B Salasnich, G Salter, M Samland, S Scuderi, J Schlieder, M Surez, M Turatto, L Weber

Jupiter's para-H-2 distribution from SOFIA/FORCAST and Voyager/IRIS 17-37 mu m spectroscopy

ICARUS 286 (2017) 223-240

LN Fletcher, I de Pater, WT Reach, M Wong, GS Orton, PGJ Irwin, RD Gehrz

Observational evidence against strongly stabilizing tropical cloud feedbacks


IN Williams, RT Pierrehumbert

Linking the Climate and Thermal Phase Curve of 55 Cancri e

Astrophysical Journal 849 (2017)

M Hammond, RT Pierrehumbert

© 2017. The American Astronomical Society. All rights reserved. The thermal phase curve of 55 Cancri e is the first measurement of the temperature distribution of a tidally locked super-Earth, but raises a number of puzzling questions about the planet's climate. The phase curve has a high amplitude and peak offset, suggesting that it has a significant eastward hot-spot shift as well as a large day-night temperature contrast. We use a general circulation model to model potential climates, and investigate the relation between bulk atmospheric composition and the magnitude of these seemingly contradictory features. We confirm theoretical models of tidally locked circulation are consistent with our numerical model of 55 Cnc e, and rule out certain atmospheric compositions based on their thermodynamic properties. Our best-fitting atmosphere has a significant hot-spot shift and day-night contrast, although these are not as large as the observed phase curve. We discuss possible physical processes that could explain the observations, and show that night-side cloud formation from species such as SiO from a day-side magma ocean could potentially increase the phase curve amplitude and explain the observations. We conclude that the observations could be explained by an optically thick atmosphere with a low mean molecular weight, a surface pressure of several bars, and a strong eastward circulation, with night-side cloud formation a possible explanation for the difference between our model and the observations.

Jupiter's auroral-related stratospheric heating and chemistry I: Analysis of Voyager-IRIS and Cassini-CIRS spectra

ICARUS 292 (2017) 182-207

JA Sinclair, GS Orton, TK Greathouse, LN Fletcher, JI Moses, V Hue, PGJ Irwin

Moist convection and the 2010-2011 revival of Jupiter's South Equatorial Belt

ICARUS 286 (2017) 94-117

LN Fletcher, GS Orton, JH Rogers, RS Giles, AV Payne, PGJ Irwin, M Vedovato

Reconstructing Climate from Glaciers

Annual Review of Earth and Planetary Sciences 45 (2017) 649-680

AN Mackintosh, BM Anderson, RT Pierrehumbert

Copyright © 2017 by Annual Reviews. All rights reserved. Glaciers offer the potential to reconstruct past climate over timescales from decades to millennia. They are found on nearly every continent, and at the Last Glacial Maximum, glaciers were larger in all regions on Earth. The physics of glacier-climate interaction are relatively well understood, and glacier models can be used to reconstruct past climate from geological evidence of past glacier extent. This can lead to significant insights regarding past, present, and future climate. For example, glacier modeling has demonstrated that the near-ubiquitous global pattern of glacier retreat during the last few centuries resulted from a global-scale climate warming of ∼1°C, consistent with instrumental data and climate proxy records. Climate reconstructions from glaciers have also demonstrated that the tropics were colder at the Last Glacial Maximum than was originally inferred from sea surface temperature reconstructions. Future efforts to reconstruct climate from glaciers may provide new constraints on climate sensitivity to CO2 forcing, polar amplification of climate change, and more.



JK Barstow, S Aigrain, PGJ Irwin, DK Sing