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Jupiter's Grat Red Spot (GRS) is the largest and longest-lived vortex of all solar system planets but its lifetime is debated and its formation mechanism remains hidden. G. D. Cassini discovered in 1665 the presence of a dark oval at the GRS latitude, known as the "Permanent Spot" (PS) that was observed until 1713. We show from historical observations of its size evolution and motions that PS is unlikely to correspond to the current GRS, that was first observed in 1831. New numerical simulations rule out that the GRS formed by the merging of vortices or by a superstorm, but most likely formed from a flow disturbance between the two opposed Jovian zonal jets north and south of it. If so, the aearly GRS should have had a low tangential velocity so that its rotation velocity has increased over time as it shrunk.

Jupiters south polar region was observed by JWST Mid Infrared Instrument in December 2022. We used the Medium Resolution Spectrometer mode to provide new information about Jupiters South Polar stratosphere. The southern auroral region was visible and influenced the atmosphere in several ways. 1: In the interior of the southern auroral oval, we retrieved peak temperatures at two distinct pressure levels near 0.01 and 1 mbar, with warmer temperatures with respect to non auroral regions of 12 pm 2 K and 37 pm 4 K respectively. A cold polar vortex is centered at 65S at 10 mbar. 2: We found that the homopause is elevated to 590+25-118 km above the 1-bar pressure level inside the auroral oval compared to 460+60-50 km at neighboring latitudes and with an upper altitude of 350 km in regions not affected by auroral precipitation. 3: The retrieved abundance of C2H2 shows an increase within the auroral oval, and it exhibits high abundances throughout the polar region. The retrieved abundance of C2H6 increases towards the pole, without being localized in the auroral oval, in contrast with previous analysis. We determined that the warming at 0.01 mbar and the elevated homopause might be caused by the flux of charged particles depositing their energy in the South Polar Region. The 1 mbar hotspot may arise from adiabatic heating resulting from auroral driven downwelling. The cold region at 10 mbar may be caused by radiative cooling by stratospheric aerosols. The differences in spatial distribution seem to indicate that the hydrocarbons analyzed are affected differently by auroral precipitation.

Venus Express provided a long-term monitoring of Venus atmosphere. Several works focused on the dynamics of the upper cloud visible on the day-side in ultraviolet images sensitive to the 65-70 km altitude and in the lower cloud level (50 km height) observable in the night-side of the planet in 1.74 microns. Here we use VIRTIS-M spectral images to study the upper cloud layer in ultraviolet (360-400 nm), visible (570-680 nm) and near infrared (900-955 nm) extending in time previous analysis of VIRTIS-M data. UV images show relatively well contrasted cloud features at the cloud top. Cloud features in the visible and near infrared images lie a few kilometers below the upper cloud top, have low contrast and are distinct to the features observed in the uv. Wind measurements were obtained over a six-year period using a semi-automatic cloud correlation algorithm. Results for the upper cloud confirm analysis based on images obtained by the Venus Monitoring Camera (Khatuntsev et al. 2013). At the cloud top the mean zonal and meridional winds vary with local time accelerating towards the local afternoon. The upper branch of the Hadley cell reaches maximum velocities at 45deg latitude and local times of 14-16h. The mean zonal winds in the uv cloud accelerated in the course of the 2006-2012 period 15 ms-1. The near infrared and visible images show a more constant circulation without time variability or longitudinal variations. The meridional circulation is absent in near infrared and visible images indicating thatthe Hadley-cell circulation in Venus atmosphere is shallow or the returning branch of the meridional circulation extends to levels below levels sensed in near infrared images. At the clod tops observed in UV images there are signatures of a long-term acceleration of the zonal winds when comparing winds from 2006-2008 to 2009-2012 with a mean acceleration of 17 ms-1 between both time periods, Comment: 38 pages, 16 figures 2 tables, 1 appendix

Convective storms (CS) on Saturn appear as bright clouds, irregular in shape and rapidly changing over time, accompanied by lightning phenomena. They cover a wide range of size scales, from 500 km or less and up to sizes that encircle the planet. In this chapter we focus on medium or synoptic-scale events (typical sizes 2,000 - 7,000 km) and planetary-scale major storms known as Great White Spots (GWS). In general, the storms emerge in westward jets and in the peak of the strong eastward equatorial jet. They have been observed preferentially in the northern hemisphere and seem to occur in the same latitude in intervals of 30 and 60 years coinciding with the times of maximum insolation within the seasonal cycle. Moist convection models locate the origin of the storms in the water clouds (at about 10 bars of pressure) and to some extent in ammonia clouds, and their thermodynamics explain the possible periodicity of the phenomena. Once triggered, the storms grow and expand, and their interaction with the zonal wind system gives rise to anticyclonic ovals and to disturbances that propagate zonally covering an entire latitude band in the case of the GWS., Comment: Peer reviewed and accepted for publication as Chapter 14 of a multi-volume work edited by Kevin Baines, Michael Flasar, Norbert Krupp, and Thomas Stallard, entitled Cassini at Saturn: The Grand Finale, to be published by Cambridge University Press. 31 pages, 15 figures

This review presents an insight into our current knowledge of the atmospheres of the planets Venus, Mars, Jupiter, Saturn, Uranus and Neptune, the satellite Titan, and those of exoplanets. It deals with the thermal structure, aerosol properties (hazes and clouds, dust in the case of Mars), chemical composition, global winds and selected dynamical phenomena in these objects. Our understanding of atmospheres is greatly benefitting from the discovery in the last three decades of thousands of exoplanets. The exoplanet properties span a broad range of conditions, and it is fair to expect as much variety for their atmospheres. This complexity is driving unprecedented investigations of the atmospheres, where those of the solar systems bodies are the obvious reference. We are witnessing a significant transfer of knowledge in both directions between the investigations dedicated to Solar System and exoplanet atmospheres, and there are reasons to think that this exchange will intensity in the future. We identify and select a list of research subjects that can be conducted at optical and infrared wavelengths with future and currently available ground-based and space-based telescopes, but excluding those from the space missions to solar system bodies., Comment: 129 pages

Spectral observations of Neptune made in 2019 with the MUSE instrument at the Very Large Telescope in Chile have been analysed to determine the spatial variation of aerosol scattering properties and methane abundance in Neptune's atmosphere. The darkening of the South Polar Wave (SPW) at $\sim$ 60$^\circ$S, and dark spots such as the Voyager 2 Great Dark Spot is concluded to be due to a spectrally-dependent darkening ($\lambda < 650$nm) of particles in a deep aerosol layer at $\sim$ 5 bar and presumed to be composed of a mixture of photochemically-generated haze and H$_2$S ice. We also note a regular latitudinal variation of reflectivity at wavelengths of very low methane absorption longer than $\sim$ 650 nm, with bright zones latitudinally separated by $\sim$ 25$^\circ$. This feature, similar to the spectral characteristics of a discrete deep bright spot DBS-2019 found in our data, is found to be consistent with a brightening of the particles in the same $\sim$5-bar aerosol layer at $\lambda > 650 $ nm. We find the properties of an overlying methane/haze aerosol layer at $\sim$ 2 bar are, to first-order, invariant with latitude, while variations in the opacity of an upper tropospheric haze layer reproduce the observed reflectivity at methane-absorbing wavelengths, with higher abundances found at the equator and also in a narrow `zone' at $80^\circ$S. Finally, we find the mean abundance of methane below its condensation level to be 6--7% at the equator reducing to $\sim$3% south of $\sim$25$^\circ$S, although the absolute abundances are model dependent., Comment: 32 pages, 13 figures. Accepted in JGR: Planets

Previous observations of dark vortices in Neptune's atmosphere, such as Voyager-2's Great Dark Spot, have been made in only a few, broad-wavelength channels, which has hampered efforts to pinpoint their pressure level and what makes them dark. Here, we present Very Large Telescope (Chile) MUSE spectrometer observations of Hubble Space Telescope's NDS-2018 dark spot, made in 2019. These medium-resolution 475 - 933 nm reflection spectra allow us to show that dark spots are caused by a darkening at short wavelengths (< 700 nm) of a deep ~5-bar aerosol layer, which we suggest is the H$_2$S condensation layer. A deep bright spot, named DBS-2019, is also visible on the edge of NDS-2018, whose spectral signature is consistent with a brightening of the same 5-bar layer at longer wavelengths (> 700 nm). This bright feature is much deeper than previously studied dark spot companion clouds and may be connected with the circulation that generates and sustains such spots., Comment: 1 table. 3 figures. Nature Astronomy (2023)

Using near-infrared observations of Neptune from the Keck and Lick Observatories, and the Hubble Space Telescope in combination with amateur datasets, we calculated the drift rates of prominent infrared-bright cloud features on Neptune between 2018 and 2021. These features had lifespans of $\sim 1$ day to $\geq$1 month and were located at mid-latitudes and near the south pole. Our observations permitted determination of drift rates via feature tracking. These drift rates were compared to three zonal wind profiles describing Neptune's atmosphere determined from features tracked in H band (1.6 $\mu m$), K' band (2.1 $\mu m$), and Voyager 2 data at visible wavelengths. Features near $-70 \deg$ measured in the F845M filter (845nm) were particularly consistent with the K' wind profile. The southern mid-latitudes hosted multiple features whose lifespans were $\geq$1 month, providing evidence that these latitudes are a region of high stability in Neptune's atmosphere. We also used HST F467M (467nm) data to analyze a dark, circumpolar wave at $- 60 \deg$ latitude observed on Neptune since the Voyager 2 era. Its drift rate in recent years (2019-2021) is $4.866 \pm 0.009 \deg $/day. This is consistent with previous measurements by Karkoschka (2011), which predict a $4.858 \pm 0.022 \deg$/day drift rate during these years. It also gained a complementary bright band just to the north., Comment: 29 pages, 13 figures, accepted to Icarus

ESA's Jupiter Icy Moons Explorer (JUICE) will provide a detailed investigation of the Jovian system in the 2030s, combining a suite of state-of-the-art instruments with an orbital tour tailored to maximise observing opportunities. We review the Jupiter science enabled by the JUICE mission, building on the legacy of discoveries from the Galileo, Cassini, and Juno missions, alongside ground- and space-based observatories. We focus on remote sensing of the climate, meteorology, and chemistry of the atmosphere and auroras from the cloud-forming weather layer, through the upper troposphere, into the stratosphere and ionosphere. The Jupiter orbital tour provides a wealth of opportunities for atmospheric and auroral science: global perspectives with its near-equatorial and inclined phases, sampling all phase angles from dayside to nightside, and investigating phenomena evolving on timescales from minutes to months. The remote sensing payload spans far-UV spectroscopy (50-210 nm), visible imaging (340-1080 nm), visible/near-infrared spectroscopy (0.49-5.56 $\mu$m), and sub-millimetre sounding (near 530-625\,GHz and 1067-1275\,GHz). This is coupled to radio, stellar, and solar occultation opportunities to explore the atmosphere at high vertical resolution; and radio and plasma wave measurements of electric discharges in the Jovian atmosphere and auroras. Cross-disciplinary scientific investigations enable JUICE to explore coupling processes in giant planet atmospheres, to show how the atmosphere is connected to (i) the deep circulation and composition of the hydrogen-dominated interior; and (ii) to the currents and charged particle environments of the external magnetosphere. JUICE will provide a comprehensive characterisation of the atmosphere and auroras of this archetypal giant planet., Comment: 83 pages, 24 figures, accepted to Space Science Reviews special issue on ESA's JUICE mission

We performed a unique Venus observation campaign to measure the disk brightness of Venus over a broad range of wavelengths in August and September 2020. The primary goal of the campaign is to investigate the absorption properties of the unknown absorber in the clouds. The secondary goal is to extract a disk mean SO$_2$ gas abundance, whose absorption spectral feature is entangled with that of the unknown absorber at the ultraviolet (UV) wavelengths. A total of 3 spacecraft and 6 ground-based telescopes participated in this campaign, covering the 52 to 1700~nm wavelength range. After careful evaluation of the observational data, we focused on the data sets acquired by 4 facilities. We accomplished our primary goal by analyzing the reflectivity spectrum of the Venus disk over the 283-800 nm wavelengths. Considerable absorption is present in the 350-450 nm range, for which we retrieved the corresponding optical depth by the unknown absorber. The result shows a consistent wavelength dependence of the relative optical depth with that at low latitudes during the Venus flyby by MESSENGER in 2007 (P\'erez-Hoyos et al. 2018), which was expected because the overall disk reflectivity is dominated by low latitudes. Last, we summarize the experience obtained during this first campaign that should enable us to accomplish our second goal in future campaigns., Comment: Accepted for publication in PSJ, 45 pages, 13 figures

In meteor physics the luminous efficiency ${\tau}$ is used to convert the meteor's magnitude to the corresponding meteoroid's mass. However, lack of sufficiently accurate verification methods or adequate laboratory tests leave this parameter to be controversially discussed. In this work meteor/fireball data obtained by the Fireball Recovery and InterPlanetary Observation Network (FRIPON) was used to calculate the masses of the pre-atmospheric meteoroids which could in turn be compared to the meteor brightnesses to assess their luminous efficiencies. For that, deceleration-based formulas for the mass computation were used. We have found ${\tau}$-values, as well as the shape change coefficients, of 294 fireballs with determined masses in the range of $10^{-6}$ kg - $100$ kg. The derived ${\tau}$-values have a median of ${\tau}_{median}$ = 2.17 %. Most of them are on the order of 0.1 % - 10 %. We present how our values were obtained, compare them with data reported in the literature, and discuss several methods. A dependence of ${\tau}$ on the pre-atmospheric velocity of the meteor, $v_e$, is noticeable with a relation of ${\tau}=0.0023 \cdot v_e^{2.3}$. The higher luminous efficiency of fast meteors could be explained by the higher energy released. Fast meteoroids produce additional emission lines that radiate more efficiently in specific wavelengths due to the appearance of the so-called second component of higher temperature. Furthermore, a dependence of ${\tau}$ on the initial meteoroid mass, $M_e$, was found, with negative linear behaviour in log-log space: ${\tau}=0.48 \cdot M_e^{-0.47}$. This implies that the radiation of smaller meteoroids is more efficient.

Martian planet-encircling dust storms or global dust storms (GDS), resulting from the combined influence of local and regional storms, are uncommon aperiodic phenomena: with an average frequency of approximately one every 3-4 MY, they produce a substantial rise in the atmospheric dust loading that lasts from weeks to months and have a significant impact on the atmospheric properties, energy budget, and global circulation. During the 2018/MY34 global dust storm, initiated at L_S = 185$^\circ$ (30-31 May 2018), an intensive atmospheric science campaign was carried out by the Mars Science Laboratory (MSL) rover to monitor the environmental parameters at Gale Crater. We contribute to previous studies with independent retrievals to constrain the dust opacity and characterise the aerosol particle properties, including: size, shape and single scattering phase function. An iterative radiative transfer retrieval procedure was implemented to determine the aerosol parameters that best fit the angular distribution of sky radiance at forward and backward scattering regions observed by MSL Navigation Cameras (Navcams) during the 2018/MY34 GDS., Comment: 23 pages, 6 figures

On 7th August 2019, an impact flash lasting $\sim1$s was observed on Jupiter. The video of this event was analysed to obtain the lightcurve and determine the energy release and initial mass. We find that the impactor released a total energy of $96-151$ kilotons of TNT, corresponding to an initial mass between $190-260$ metric tonnes with a diameter between $4-10$m. We developed a fragmentation model to simulate the atmospheric breakup of the object and reproduce the lightcurve. We model three different materials: cometary, stony and metallic at speeds of $60$, $65 $ and $70$ km/s to determine the material makeup of the impacting object. The slower cases are best fit by a strong, metallic object while the faster cases require a weaker material., Comment: 10 pages, 8 figures, 2 tables, Accepted for publication in MNRAS

Remote sensing observations suffer significant limitations when used to study the bulk atmospheric composition of the giant planets of our solar system. This impacts our knowledge of the formation of these planets and the physics of their atmospheres. A remarkable example of the superiority of in situ probe measurements was illustrated by the exploration of Jupiter, where key measurements such as the determination of the noble gases' abundances and the precise measurement of the helium mixing ratio were only made available through in situ measurements by the Galileo probe. Here we describe the main scientific goals to be addressed by the future in situ exploration of Saturn, Uranus, and Neptune, placing the Galileo probe exploration of Jupiter in a broader context. An atmospheric entry probe targeting the 10-bar level would yield insight into two broad themes: i) the formation history of the giant planets and that of the Solar System, and ii) the processes at play in planetary atmospheres. The probe would descend under parachute to measure composition, structure, and dynamics, with data returned to Earth using a Carrier Relay Spacecraft as a relay station. An atmospheric probe could represent a significant ESA contribution to a future NASA New Frontiers or flagship mission to be launched toward Saturn, Uranus, and/or Neptune., Comment: 27 pages, 9 figures, White Paper submitted in response to ESA's Call for Voyage 2050 Science Themes. arXiv admin note: substantial text overlap with arXiv:1708.00235

We analyze the onset and initial expansion of the 2018 Martian Global Dust Storm (GDS 2018) using ground-based images in the visual range. This is the first case of a confirmed GDS initiating in the Northern Hemisphere. A dusty area extending about 1.4x10e5 km^2 and centered at latitude +31.7{\deg} $\pm$ 1.8{\deg} and west longitude 18{\deg} $\pm$ 5{\deg}W in Acidalia Planitia was captured on 30 and 31 May 2018 (Ls = 184.9{\deg}). From 1 to 8 June, daily image series showed the storm expanding southwards along the Acidalia corridor with velocities of 5 m/s, and simultaneously progressing eastwards and westwards with horizontal velocities ranging from 5 to 40 m/s. By 8 June the dust reached latitude -55{\deg} and later penetrated in the South polar region, whereas in the North the dust progression stopped at latitude +46{\deg}. We compare the onset and expansion stage of this GDS with the previous confirmed storms., Comment: Accepted in Geophysical Research Letters. Main article and Supporting Information

The Cassini spacecraft made a gravity assist flyby of Jupiter in December 2000. The Imaging Science Subsystem (ISS) acquired images of the planet that covered the visual range with filters sensitive to the distribution of clouds and hazes, their altitudes and color. We use a selection of these images to build high-resolution cylindrical maps of the planet in 9 wavelengths. We explore the spatial distribution of the planet reflectivity examining the distribution of color and altitudes of hazes as well as their relation. A variety of analyses is presented: a) Principal Component Analysis (PCA); b) color-altitude indices; and c) chromaticity diagrams (for a quantitative characterization of Jupiter "true" colors as they would be perceived by a human observer). PCA of the full dataset indicates that six components are required to explain the data. These components are likely related to the distribution of cloud opacity at the main cloud, the distribution of two types of hazes, two chromophores or coloring processes and the distribution of convective storms.

We analyse the potential vorticity of Saturn's polar regions, as it is a fundamental dynamical tracer that enables us to improve our understanding of the dynamics of these regions and their seasonal variability. In particular, we present zonally averaged quasi-geostrophic potential vorticity maps between 68{\deg} planetographic latitude and the poles at altitudes between 500 mbar and 1mbar for three different epochs: (i) June 2013 (early northern summer) for the north polar region, (ii) December 2008 (late northern winter) for both polar regions and (iii) October 2006 (southern summer) for the south, computed using temperature profiles retrieved from Cassini Composite Infrared Spectrometer (CIRS) data and wind profiles obtained from Cassini's Imaging Science Subsystem (ISS). The results show that quasi-geostrophic potential vorticity maps are very similar at all the studied epochs, showing positive vorticities at the north and negative at the south, indicative of the dominance of the Coriolis parameter 2${\Omega}sin{\phi}$ at all latitudes, except near the pole. The meridional gradients of the quasi-geostrophic potential vorticity show that dynamical instabilities, mainly due to the barotropic term, could develop at the flanks of the Hexagon at 78{\deg}N, the jet at 73.9{\deg}S and on the equatorward flank of both polar jets. There are no differences in potential vorticity gradients between the two hemispheres that could explain why a hexagon forms in the north and not in the south. No seasonal variability of the potential vorticity and its meridional gradient has been found, despite significant changes in the atmospheric temperatures over time., Comment: 21 pages, 9 figures. Accepted in Journal of Geophysical Research

We report the discovery of a large ($\sim$8500 km diameter) infrared-bright storm at Neptune's equator in June 2017. We tracked the storm over a period of 7 months with high-cadence infrared snapshot imaging, carried out on 14 nights at the 10 meter Keck II telescope and 17 nights at the Shane 120 inch reflector at Lick Observatory. The cloud feature was larger and more persistent than any equatorial clouds seen before on Neptune, remaining intermittently active from at least 10 June to 31 December 2017. Our Keck and Lick observations were augmented by very high-cadence images from the amateur community, which permitted the determination of accurate drift rates for the cloud feature. Its zonal drift speed was variable from 10 June to at least 25 July, but remained a constant $237.4 \pm 0.2$ m s$^{-1}$ from 30 September until at least 15 November. The pressure of the cloud top was determined from radiative transfer calculations to be 0.3-0.6 bar; this value remained constant over the course of the observations. Multiple cloud break-up events, in which a bright cloud band wrapped around Neptune's equator, were observed over the course of our observations. No "dark spot" vortices were seen near the equator in HST imaging on 6 and 7 October. The size and pressure of the storm are consistent with moist convection or a planetary-scale wave as the energy source of convective upwelling, but more modeling is required to determine the driver of this equatorial disturbance as well as the triggers for and dynamics of the observed cloud break-up events., Comment: 42 pages, 14 figures, 6 tables; Accepted to Icarus

We present measurements of the wind speeds at the nightside lower clouds of Venus from observations by JAXA's mission Akatsuki during 2016, complemented with new wind measurements from ground-based observations acquired with TNG/NICS in 2012 and IRTF/SpeX in 2015 and 2017. Zonal and meridional components of the winds were measured from cloud tracking on a total of 466 Akatsuki images of Venus acquired by the camera IR2 using the 2.26-$\mathrm{\mu m}$ filter, with spatial resolutions ranging 10--80 km per pixel and covering from 2016 March 22 to October 31. More than 149,000 wind vectors were obtained with an automatic technique of template matching, and 2,947 wind vectors were inferred with the manual procedure. The meridional profiles for both components of the winds are found to be consistent with results from the Venus Express mission during 2006--2008, although stronger wind variability is found for the zonal component at equatorial latitudes where Akatsuki observations have better viewing geometry than Venus Express. The zonal winds at low latitudes also suggest a zonal variability that could be associated with solar tides or vertically propagating orographic waves. Finally, the combination of our wind measurements from TNG/NICS, IRTF/SpeX and Akatsuki images with previously published and based in data from 1978 to 2017 suggests variations of up to 30 m s$^{-1}$ in the winds at the lower clouds of the Venus nightside., Comment: 20 pages, 13 figures, Supplemental Material available at ApJS

Small-scale waves were observed along the boundary between Jupiter's North Equatorial Belt and North Tropical Zone, ~16.5{\deg} N planetographic latitude in Hubble Space Telescope data in 2012 and throughout 2015 to 2018, observable at all wavelengths from the UV to the near IR. At peak visibility, the waves have sufficient contrast (~10%) to be observed from ground-based telescopes. They have a typical wavelength of about 1.2{\deg} (1400 km), variable-length wave trains, and westward phase speeds of a few m/s or less. New analysis of Voyager 2 data shows similar wave trains over at least 300 hours. Some waves appear curved when over cyclones and anticyclones, but most are straight, but tilted, shifting in latitude as they pass vortices. Based on their wavelengths, phase speeds, and faint appearance at high-altitude sensitive passbands, the observed NEB waves are consistent with inertia-gravity waves at the 500-mbar pressure level, though formation altitude is not well constrained. Preliminary General Circulation Model simulations generate inertia-gravity waves from vortices interacting with the environment and can reproduce the observed wavelengths and orientations. Several mechanisms can generate these waves, and all may contribute: geostrophic adjustment of cyclones; cyclone/anticyclone interactions; wind interactions with obstructions or heat pulses from convection; or changing vertical wind shear. However, observations also show that the presence of vortices and/or regions of convection are not sufficient by themselves for wave formation, implying that a change in vertical structure may affect their stability, or that changes in haze properties may affect their visibility., Comment: Astronomical Journal, accepted

In December 2010, a major storm erupted in Saturn's northern hemisphere near 37 degree planetographic latitude. This rather surprising event, occurring at an unexpected latitude and time, is the sixth "Great White Spot" (GWS) storm observed over the last century and a half. Such GWS events are planetary-scale atmospheric phenomena that dramatically change the typically bland appearance of the planet. Occurring while the Cassini mission was on-orbit at Saturn, the Great Storm of 2010-2011 was well-suited for intense scrutiny by the suite of sophisticated instruments onboard the Cassini spacecraft as well by modern instrumentation on ground-based telescopes and onboard the Hubble Space Telescope. This GWS erupted on December 5th and generated a major dynamical disturbance that affected the whole latitude band from 25 deg to 48 deg N. Lightning events were prominent and detected as outbursts and flashes at both optical and radio wavelengths. The activity of the head ceased after about seven months, leaving the cloud structure and ambient winds perturbed. The tops of the optically dense clouds of the storm's head reached the 300 mbar altitude level where a mixture of ices was detected. The energetics of the frequency and power of lightning, as well as the estimated power generated by the latent heat released in the water-based convection, both indicate that the power released for the storm was a significant fraction of Saturn's total radiated power. The effects of the storm propagated into the stratosphere forming two warm airmasses at the 0.5-5 mbar pressure level altitude. Related to the stratospheric disturbance, hydrocarbon composition excesses were found. The decades-long interval between storms is probably related to the insolation cycle and the long radiative time constant of Saturn's atmosphere, and several theories for temporarily storing energy have been proposed., Comment: Chapter 13 in the book "Saturn in the 21st Century"

This book chapter, Saturn's Polar Atmosphere, is to be published by Cambridge University Press as part of a multi-volume work edited by Kevin Baines, Michael Flasar, Norbert Krupp, and Thomas Stallard, entitled "Saturn in the 21st Century." This chapter reviews the state of our knowledge about Saturn's polar atmosphere that has been revealed through Earth- and space-based observation as well as theoretical and numerical modeling. In particular, the Cassini mission to Saturn, which has been in orbit around the ringed planet since 2004, has revolutionized our understanding of the planet. The current review updates a previous review by Del Genio et al (2009; Saturn Atmospheric Structure and Dynamics, Chapter 7 of "Saturn from Cassini-Huygens"), written after Cassini's primary mission phase that ended in 2008, by focusing on the north polar region of Saturn and comparing it to the southern high latitudes. Two prominent features in the northern high latitudes are the northern hexagon and the north polar vortex; we extensively review observational and theoretical investigations to date of both features. We also review the seasonal evolution of the polar regions using the observational data accumulated during the Cassini mission since 2004 (shortly after the northern winter solstice in 2002), through the equinox in 2009, and approaching the next solstice in 2017. We conclude the current review by listing unanswered questions and describing the observations of the polar regions planned for the Grand Finale phase of the Cassini mission between 2016 and 2017., Comment: 2016-10-03: Typo in the spelling of co-author Agustin S\'anchez-Lavega's name has been corrected, and moved the first sentence now of the abstract from the comments section

This white paper examines the benefit of the upcoming James Webb Space Telescope for studies of the Solar System's four giant planets: Jupiter, Saturn, Uranus, and Neptune. JWST's superior sensitivity, combined with high spatial and spectral resolution, will enable near- and mid-infrared imaging and spectroscopy of these objects with unprecedented quality. In this paper we discuss some of the myriad scientific investigations possible with JWST regarding the giant planets. This discussion is preceded by the specifics of JWST instrumentation most relevant to giant planet observations. We conclude with identification of desired pre-launch testing and operational aspects of JWST that would greatly benefit future studies of the giant planets.