nonlinear simulations of jupiter s 5 micron hot spots large scale nonlinear simulations of jupiter s 5 micron hot spots produce long lived coherent structures that cause subsidence in local regions explaining the low cloudiness and the dryness measured by the galileo probe inside a hot spot like observed hot spots the simulated coherent structures are equatorially confined have periodic spacing propagate west relative to the flow are generally confined to one hemisphere and have an anticyclonic gyre on their equatorward side the southern edge of the simulated hot spots develops vertical shear of up to 70 meters per second in the eastward wind which can explain the results of the galileo probe doppler wind experiment

a new look at the saturn system the voyager 2 images voyager 2 photography has complemented that of voyager i in revealing many additional characteristics of saturn and its satellites and rings saturn s atmosphere contains persistent oval cloud features reminiscent of features on jupiter smaller irregular features track out a pattern of zonal winds that is symmetric about saturn s equator and appears to extend to great depth winds are predominantly eastward and reach 500 meters per second at the equator titan has several haze layers with significantly varying optical properties and a northern polar collar that is dark at short wavelengths several satellites have been photographed at substantially improved resolution enceladus surface ranges from old densely cratered terrain to relatively young uncratered plains crossed by grooves and faults tethys has a crater 400 kilometers in diameter whose floor has domed to match tethys surface curvature and a deep trench that extends at least 270 around tethys circumference hyperion is cratered and irregular in shape iapetus bright trailing hemisphere includes several dark floored craters and phoebe has a very low albedo and rotates in the direction opposite to that of its orbital revolution with a period of 9 hours within saturn s rings the birth of a spoke has been observed and surprising azimuthal and time variability is found in the ringlet structure of the outer b ring these observations lead to speculations about saturn s internal structure and about the collisional and thermal history of the rings and satellites

planetary waves in jupiter s equatorial atmosphere abstract voyager infrared radio occultation and imaging measurements provide a variety of observational evidence and constraints for planetary scale waves latitudinally trapped within jupiter s equatorial jet the visually prominent plumes encircling the planet at 8 deg north latitude show a longitudinal organization of wavenumber n 11 13 an apparently solitary plume also appears at about 8 deg south along the with other smaller periodic cloud features deviations in cloud tracked driff speed including differences in mean values to the north and south of the equator in excess of 25 m sec 1 may be crudely indicative of the magnitude of the associated wave phase speeds radio occultation retrievals of the temperature profiles at two equatorial longitudes show harmonic variation consistent with the stratospheric propagation of two components with vertical wavelengths of approximately 3 and 0 5 scale heights these observations may be consistently interpreted in terms of specific classes of equatorially trapped wave modes the gravest equatorial rossby mode with an equivalent depth of h 2 4 km with a stratospheric wavelength of 3 4 scale heights represents the most consistent interpretation of the plumes the inferred vetical eigenmode could be ducted by a deep statically stable layer possibly imposed by a roughly solar abundant water cloud depending upon the actual details of the moist convection an estimate of the relative growth rates for the near neutral forcing of rossby modes of the inferred equivalent depth implies a maximum for zonal wavenumber 11 the solitary plume feature to the south of the equator may be interpreted as a wavenumber 1 rossby mode with the same vertical scale possibly forced by the interaction between the equatorial jet and the great red spot smaller visual features may correspond to inertia gravity modes with vertical wavelengths comparable to the small harmonic of the occultation profiles galileo orbiter and probe observations will provide an essential test of the wave analysis and substantially enhance its diagnostic utility

saturn s zonal winds at cloud level we present an analysis of new cloud motion measurements in saturn s atmosphere from voyager 1 and 2 images and define a nominal zonal wind velocity vs latitude profile for the cloud top level that can be used as reference for the upcoming cassini mission improvements over previous studies include i twice the number of wind vectors used ii independent measurements of cloud tracers iii extended latitudinal coverage iv strict error control and evaluation and v a new zonal averaging methodology mean zonal wind velocities are given for the latitude range 81 to 71 planetographic in steps of 0 5 with a gap between 0 and 10 due to ring shadowing this research also includes the study of the morphology and motions of cloud systems in the equator and in the southern hemisphere which have not been described previously we give an ephemeris motion equation for several long lived features that could be observable if they survive until cassini arrives on saturn the long term behavior of the zonal wind profile is studied by comparing it with a complete set of wind velocities compiled from historical and modern ground based and hst observations significant changes are noted in the equatorial jet between this set and the nominal voyager profile we discuss in detail the possible origin for such differences

high resolution cloud feature tracking on venus by galileo abstract the venus cloud deck was monitored in february 1990 for 16 hours at 400 nanometers wavelength by the galileo imaging system with a spatial resolution of about 15 km and with image time separations as small as 10 minutes velocities are deduced by following the motion of small cloud features in spite of the high temporal frequencies capable of being detected no dynamical phenomena are apparent in the velocity data except the already well known solar tides possibly altered by the slow 4 day wave and the hadley circulation there is no evidence to a level of approximately 4 m s 1 of eddy or wavelike activity the dominant size of sub global scale albedo features is 200 500 km and their contrast is approximately 5 at low latitudes there are patches of blotchy cell like structures but at most locations the markings are streaky the patterns are similar to those discovered by mariner 10 and pioneer venus m j s belton et al 1976 j atmos sci 33 1383 1393 w b rossow et al 1980 j geophys res 85 8107 8128 scaling arguments are presented to argue that the mesoscale blotchy cell like cloud patterns are caused by local dynamics driven in a shallow layer by differential absorption of sunlight it is also argued that mesoscale albedo features are either streaky or cell like simply depending on whether the horizontal shear of the large scale flow exceeds a certain critical value

life cycles of spots on jupiter from cassini images using the sequence of 70 day continuum band 751 nm images from the cassini imaging science system iss we record over 500 compact oval spots and study their relation to the large scale motions the 100 spots whose vorticity could be measured the large spots in most cases were all anticyclonic we exclude cyclonic features chaotic regions because they do not have a compact oval shape but we do record their interactions with spots we distinguish probable convective storms from other spots because they appear suddenly grow rapidly and are much brighter than their surroundings the distribution of lifetimes for spots that appeared and disappeared during the 70 day period follows a decaying exponential with time constant mean lifetime of 3 5 days for probable convective storms and 16 8 days for all other spots extrapolating the exponential beyond 70 days seriously underestimates the number of spots that existed for the entire 70 day period this and other evidences size shape distribution in latitude suggest that these long lived spots with lifetime larger than 70 days are from a separate population the zonal wind profile obtained manually by tracking individual features this study agrees with that obtained automatically by correlating brightness variations in narrow latitude bands porco et al 2003 some westward jets have developed more curvature and some have developed less curvature since voyager times but the number of westward jets that violate the barotropic stability criterion is about the same in the northern hemisphere the number of spots is greatest at the latitudes of the westward jets which are the most unstable regions according to the barotropic stability criterion during the 70 day observation period the great red spot grs absorbed nine westward moving spots that originated in the south equatorial belt seb where most of the probable convective storms originate although the probable convective storms do not directly transform themselves into westward moving spots their common origin in the seb suggests that moist convection and the westward jet compose a system that has maintained the grs over its long lifetime

jupiter new estimates of the mean zonal flow at the cloud level abstract previous estimates of the mean zonal flow on jupiter from voyager images by ingersoll et al a p ingersoll r f beebe j l mitchell g w garneau g m yagi and j p mueller 1981 j geophys res 86 8733 8743 and by limaye et al s s limaye h e revercomb l a sromovsky r j krauss v e suomi s a collins and c c avis 1982 j atmos sci 39 1413 1432 showed good agreement in the locations of the easterly and westerly jets but differed somewhat in magnitude recent measurements of the high speed jet located near 24 north plane topographic latitude by t maxworthy 1984 planet space sci 32 1053 1058 from high spatial and temporal resolution voyager images indicate that both ingersoll et al and limaye et al underestimated the magnitude of the jet by more than 30 40 msec 1 in an attempt to examine the differences in the magnitude of the jovian jets determined from voyager 1 and 2 images a new approach to determine the zonal mean east west component of motion was investigated the new technique based on simple digital pattern matching approach and applied on pairs of mapped images cylindrical mosaics yields a profile of the mean zonal component that reproduces the exact locations of the easterly and westerly jets between 60 latitude not only do the jet magnitudes but also the wings of the jets agree remarkably well from mosaic pair to pair further the latitudinal resolution is five midlatitudes to eight times equatorial greater than previous results results have been obtained for all of the voyager 1 and 2 cylindrical mosaics the correlation coefficient between voyager 1 and voyager 2 average mean zonal flow between 60 latitude determined from violet filter mosaics is 0 998 a slight latitude offset possibly due to navigation errors is detectable 0 2 latitude average in the voyager 1 data independent cloud motion measurements in two high resolution image pairs orange and violet acquired from voyager 1 cameras agree well with the average mean zonal flow for the fastest jovian jet at 23 8 n latitude comparison with maxworthy s 1984 results suggests longitudinal variations in cloud motions approaching about 20 msec 1 in particular the jet magnitude is about 163 7 rms msec 1 which compares well with 182 10 msec 1 reported by maxworthy there is excellent agreement in the location of the peak magnitude as well as its shape the time average voyager 2 mean zonal flow profile with latitude is presented in a table

cloud features and zonal wind measurements of saturn s atmosphere as observed by cassini vims 1 we present an analysis of data about saturn s atmosphere from cassini s visual and infrared mapping spectrometer vims focusing on the meteorology of the features seen in the 5 m spectral window we present vims mosaics and discuss the morphology and general characteristics of the features backlit by saturn s thermal emission we have also constructed a zonal wind profile from vims feature tracking observation sequences using an automated cloud feature tracker comparison with previously constructed profiles from voyager and cassini imaging data reveals broad similarities suggesting minimal vertical shear of the zonal wind however areas of apparent wind shear are present in the vims zonal wind profile at jet stream cores in particular our analysis shows that the equatorial jet reaches speeds exceeding 450 m s 1 similar to speeds obtained during the voyager era this suggests that recent inferences of relatively slower jet speeds of 275 375 m s 1 are confined to the upper troposphere and that the deep 1 bar jet has not experienced a significant slowdown our measurements of the numerous dark spotted features seen in the vims mosaics reveals that most of these features have diameters less than 1000 km and reside in confined zonal bands between jet stream cores we propose that these spot features are vortices and that vims and imaging science subsystem are sensing the same vortices at two different pressure levels the local structure at the zonal jet streams remains complex as vims may be sensing cloud features that are deeper than the nh3 cloud deck

global scale surface spectral variations on titan seen from cassini vims we present global scale maps of titan from the visual and infrared mapping spectrometer vims instrument on cassini we map at 64 near infrared wavelengths simultaneously covering the atmospheric windows at 0 94 1 08 1 28 1 6 2 0 2 8 and 5 m with a typical resolution of 50 km pixel or a typical total integration time of 1 s our maps have five to ten times the resolution of ground based maps better spectral resolution across most windows coverage in multiple atmospheric windows and represent the first spatially resolved maps of titan at 5 m the vims maps provide context and surface spectral information in support of other cassini instruments we note a strong latitudinal dependence in the spectral character of titan s surface and partition the surface into 9 spectral units that we describe in terms of spectral and spatial characteristics

galileo imaging of jupiter s atmosphere the great red spot equatorial region and white ovals during the first six orbits of the galileo spacecraft s prime mission the solid state imaging ssi system acquired multispectral image mosaics of jupiter s great red spot an equatorial belt zone boundary a 5 m hot spot similar to the galileo probe entry site and two of the classic white ovals we present mosaics of each region approximating their appearance at visible wavelengths and showing cloud height and opacity variations the local wind field is derived by tracking cloud motions between multiple observations of each region with time separations of roughly 1 and 10 hr vertical cloud structure is derived in a companion paper by banfieldet al icarus135 230 250 galileo s brief high resolution observations complement earth based and voyager studies and offer local meteorological context for the galileo probe results our results show that the dynamics of the zonal jets and large vortices have changed little since voyager with a few exceptions we detect a cyclonic current within the center of the predominantly anticyclonic great red spot the zonal velocity difference between 0 s and 6 s has increased by 20 m sec 1 we measure a strong northeast flow approaching the hot spot this flow indicates either massive horizontal convergence or the presence of a large anticyclonic vortex southeast of the hot spot the current compact arrangement of two white ovals and a cyclonic structure greatly perturbs the zonal jets in that region

temperatures winds and composition in the saturnian system stratospheric temperatures on saturn imply a strong decay of the equatorial winds with altitude if the decrease in winds reported from recent hubble space telescope images is not a temporal change then the features tracked must have been at least 130 kilometers higher than in earlier studies saturn s south polar stratosphere is warmer than predicted from simple radiative models the c h ratio on saturn is seven times solar twice jupiter s saturn s ring temperatures have radial variations down to the smallest scale resolved 100 kilometers diurnal surface temperature variations on phoebe suggest a more porous regolith than on the jovian satellites

sedimentology and stratigraphy of tidal sand ridges southwest florida inner shelf abstract detailed investigation of linear shelf sand ridges located off the southwest coast of florida shows them to be tide dominated sand bodies these ridges are remarkably similar to the large sand ridges of the north sea and they have abundant apparent analogs in the stratigraphic record many of which are important petroleum producers the florida ridges are asymmetric in profile about 10 km long 1 km wide with relief of 3 4 m with the adjacent sea bed extensive tidal current monitoring sediment distribution patterns and side scan sonar surveys permit characterizing their morphodynamics tidal currents show distinct bidirectional patterns with speeds up to 70 cm s there is slight flood dominance and currents show much higher velocities in the troughs as compared to the crests of he ridges megaripples and sand waves are widespread and migrate obliquely across the ridges at opposite directions on the gentle and steep sides of the ridge shallow high resolution seismic data and 39 vibracores in the area of the ridges show a consistent sequence characterized by three ascending holocene lithofacies 1 muddy quartz sand with limestone clasts 2 bioturbated muddy shelly quartz sand and 3 well sorted cross stratified quartz sand that characterizes the sand ridges themselves each of the tidal sand ridges displays a coarsening upward sequence of fine well sorted sand small scale multidirectional cross stratification dominates the stratigraphy of the cores in this facies but megaripple cross stratification is also present all data indicate that these tidal ridges are good modern analogs for many of the shelf sand bodies in the ancient record especially the mesozoic of the mid continent area

constraints on saturn s tropospheric general circulation from cassini iss images abstract an automated cloud tracking algorithm is applied to cassini imaging science subsystem high resolution apoapsis images of saturn from 2005 and 2007 and moderate resolution images from 2011 and 2012 to define the near global distribution of zonal winds and eddy momentum fluxes at the middle troposphere cloud level and in the upper troposphere haze improvements in the tracking algorithm combined with the greater feature contrast in the northern hemisphere during the approach to spring equinox allow for better rejection of erroneous wind vectors a more objective assessment at any latitude of the quality of the mean zonal wind and a population of winds comparable in size to that available for the much higher contrast atmosphere of jupiter zonal winds at cloud level changed little between 2005 and 2007 at all latitudes sampled upper troposphere zonal winds derived from methane band images are 10 m s 1 weaker than cloud level winds in the cores of eastward jets and 5 m s 1 stronger on either side of the jet core i e eastward jets appear to broaden with increasing altitude in westward jet regions winds are approximately the same at both altitudes lateral eddy momentum fluxes are directed into eastward jet cores including the strong equatorial jet and away from westward jet cores and weaken with increasing altitude on the flanks of the eastward jets consistent with the upward broadening of these jets the conversion rate of eddy to mean zonal kinetic energy at the visible cloud level is larger in eastward jet regions 5 2 10 5 m 2 s 3 and smaller in westward jet regions 1 6 10 5 m 2 s 3 than the global mean value 4 1 10 5 m 2 s 3 overall the results are consistent with theories that suggest that the jets and the overturning meridional circulation at cloud level on saturn are maintained at least in part by eddies due to instabilities of the large scale flow near and or below the cloud level

saturn s magnetospheric planetary period oscillations neutral atmosphere circulation and thunderstorm activity implications or otherwise for physical links 1 suggestions that the planetary period oscillations ppos observed in saturn s magnetosphere may be driven or influenced by neutral atmospheric perturbations motivate an exploratory comparison of ppo rotation periods with available tropospheric and stratospheric determinations nonpolar atmospheric rotation periods occupy the range 10 2 10 7 h associated with the latitudinal jet structure are similar north and south and are independent of season while ppo periods lie in a narrower partly overlapping range 10 6 10 8 h are persistently shorter north than south and undergo a seasonal cycle in this cycle widely separated north south ppo periods during southern summer converge across equinox to values lying within the atmospheric west jet band remaining well separated from east jet periods closest convergence occurred 1 year post equinox contemporaneously with the switch in seasonal thunderstorm activity from southern to northern hemispheres since most large scale atmospheric phenomena are related to the west jets rotating with closely similar periods they also rotate with periods close to the ppos under post equinoctial conditions but not otherwise specifically post equinox northern ppos rotate with a period close to the southern thunderstorms as well as the north polar spot and hexagon features while the post equinox southern ppos rotate with a period close to the pre equinox northern string of pearls and the first colocated post equinox northern thunderstorm the great white spot event however even under these conditions no consistent correspondences in period are found at a detailed level which taken together with the lack of correspondence at other times does not suggest a direct physical link exists between these phenomena

saturn s northern hemisphere ribbon simulations and comparison with the meandering gulf stream voyager observations of saturn in 1980 81 discovered a wavy feature engirdling the planet at 47 n planetographic latitude its latitude coincides with that of an eastward jet stream which is the second fastest on saturn after the equatorial jet the 47 n jet s wavy morphology is unique among the known atmospheric jets on the gas giant planets since the voyagers it has been seen in every high resolution image of this latitude for over 25 years and has been termed the ribbon the ribbon has been interpreted as a dynamic instability in the jet stream this study tests this interpretation and uses forward modeling to explore the observed zonal wind profile s stability properties unforced initial value numerical experiments are performed to examine the nonlinear evolution of the jet stream parameter variations show that an instability occurs when the 47 n jet causes reversals in the potential vorticity pv gradient which constitutes a violation of the charney stern stability criterion after the initial instability development the simulations demonstrate that the instability s amplitude nonlinearly saturates to a constant when the eddy generation by the instability is balanced by the destruction of the eddies when the instability saturates the zonal wind profile approaches neutral stability according to arnol d s second criterion and the jet s path meanders in a ribbon like manner it is demonstrated that the meandering of the 47 n jet occurs over a range of tropospheric static stability and background wind speed the results here show that a nonlinearly saturated shear instability in the 47 n jet is a viable mechanism to produce the ribbon morphology observations do not yet have the temporal coverage to confirm the creation and destruction of eddies but these simulations predict that this is actively occurring in the ribbon region similarities exist between the behaviors found in this model and the dynamics of pv fronts studied in the context of meandering western boundary currents in earth s oceans in addition the simulations capture the nonlinear aspects of a new feature discovered by the cassini visual and infrared mapping spectrometer vims the string of pearls which resides in the equatorward tip of the 47 n jet the explicit planetary isentropic coordinate epic model is used herein

the sequence and correlation of early ordovician arenig graptolite faunas in the richardson trough and misty creek embayment yukon territory and district of mackenzie canada four graptolite biozones are recorded from the arenig portion of the road river group in the richardson and mackenzie mountains in the yukon and northwest territories in ascending order these zones are tetragraptus approximatus pendeograptus fruticosus didymograptus bifidus and parisograptus caduceus australis new the castlemainian stage may be represented by nongraptolitic massive bedded chert the arenig llanvirn boundary is drawn below the first occurrence of undulograptus austrodentatus fifty four graptolite taxa are present and 16 of these species and subspecies are recorded for the first time in this deep water biotope namely didymograptus cf adamantinus d asperus d dilatans d cf kurcki d validus communis holmograptus aff leptograptoides h sp a isograptus sp nov a i dilemma keblograptus geminus pseudisograptus manubriatus harrisi ps m koi ps m janus ps cf tau xiphograptus lofuensis and zygograptus cf abnormis

saturn s zonal wind profile in 2004 2009 from cassini iss images and its long term variability abstract five years of cassini imaging science subsystem images from 2004 to 2009 are analyzed in this work to retrieve global zonal wind profiles of saturn s northern and southern hemispheres in the methane absorbing bands at 890 and 727 nm and in their respective adjacent continuum wavelengths of 939 and 752 nm a complete view of saturn s global circulation including the equator at two pressure levels in the tropopause 60 mbar to 250 mbar with the mt filters and in the upper troposphere from 350 mbar to 500 mbar with the cb filter set is presented both zonal wind profiles available at the supplementary material section show the same structure but with significant differences in the peak of the eastward jets and the equatorial region including a region of positive vertical shear symmetrically located around the equator between the 10 c

dynamics of saturn s great storm of 2010 2011 from cassini iss and rpws saturn s quasi periodic planet encircling storms are the largest convecting cumulus outbursts in the solar system the last eruption was in 1990 sanchez lavega a 1994 chaos 4 341 353 a new eruption started in december 2010 and presented the first ever opportunity to observe such episodic storms from a spacecraft in orbit around saturn fischer g et al 2011 nature 475 75 77 sanchez lavega a et al 2011 nature 475 71 74 fletcher l n et al 2011 science 332 1413 here we analyze images acquired with the cassini imaging science subsystem iss which captured the storm s birth evolution and demise in studying the end of the convective activity we also analyze the saturn electrostatic discharge sed signals detected by the radio and plasma wave science rpws instrument the storm s initial position coincided with that of a previously known feature called the string of pearls sops at 33 n planetocentric latitude intense cumulus convection at the westernmost point of the storm formed a particularly bright head that drifted at 26 9 0 8 m s 1 negative denotes westward motion on january 11 2011 the size of the head was 9200 km and up to 34 000 km in the north south and east west dimensions respectively rpws measurements show that the longitudinal extent of the lightning source expanded with the storm s growth the storm spawned the largest tropospheric vortex ever seen on saturn on january 11 2011 the anticyclone was sized 11 000 km by 12 000 km in the north south and east west directions respectively between january and september 2011 the vortex drifted at an average speed of 8 4 m s 1 we detect anticyclonic circulation in the new vortex the vortex s size gradually decreased after its formation and its central latitude shifted to the north the storm s head moved westward and encountered the new anticyclone from the east in june 2011 after the head vortex collision the rpws instrument detected that the sed activities became intermittent and declined over 40 days until the signals became undetectable in early august in late august the sed radio signals resurged for 9 days the storm left a vast dark area between 32 n and 38 n latitudes surrounded by a highly disturbed region that resembles the mid latitudes of jupiter using iss images we also made cloud tracking wind measurements that reveal differences in the cloud level zonal wind profiles before and after the storm

saturn atmospheric dynamics one year after cassini long lived features and time variations in the drift of the hexagon abstract we examine saturn s atmospheric dynamics with observations in the visible range from ground based telescopes and hubble space telescope hst we present a detailed analysis of observations acquired during 2018 obtaining drift rates of major meteorological systems from the equator to the north polar hexagon a system of polar storms that appeared in the planet in march 2018 and remained active with a complex phenomenology at least until september is analyzed elsewhere sanchez lavega et al 2019 many of the regular cloud features visible in 2018 are long lived and can be identified in saturn images in 2017 and in some cases for up to a decade using also cassini iss images without considering the polar storms the most interesting long lived cloud systems are i a bright white spot in the equatorial zone that can be tracked continuously since 2014 with minimal changes in its zonal velocity which was 444 3 3 1 m s 1 in 2014 and 452 4 1 7 m s 1 in 2018 this velocity is remarkably different from the zonal winds at the cloud level at its latitude during the cassini mission and is closer to zonal winds obtained at the time of the voyagers flybys and to zonal winds from cassini vims infrared images of the lower atmosphere ii a large long lived anticyclone vortex here av that formed after the great white spot of 2010 2011 this vortex has changed significantly in visual contrast drift rate and latitude with minor changes in size over the last years iii a system of subpolar vortices at latitudes 60 65 n present at least since 2011 these vortices and additional atmospheric features here studied follow drift rates consistent with zonal winds obtained by cassini we also present a study of the positions of the vertices of saturn s north polar hexagon from 2015 to 2018 these measurements are compared with previous analyses during the cassini mission 2007 2014 observations with hst in the 90s and data from the voyagers in 1980 1981 to explore the long term variability of the hexagon s drift rate we find variations in the drift rate of the hexagon through these epochs that can not be fit by seasonal changes in the polar area instead the different drift rates reinforce the role of the north polar spot that was present in the voyager epoch and in the early 90s to cause a faster drift rate of the hexagon at that time compared with the current slower one

cassini imaging of saturn southern hemisphere winds and vortices high resolution images of saturn s southern hemisphere acquired by the cassini imaging science subsystem between february and october 2004 are used to create maps of cloud morphology at several wavelengths to derive zonal winds and to characterize the distribution frequency size morphology color behavior and lifetime of vortices nonequatorial wind measurements display only minor differences from those collected since 1981 and reveal a strong prograde flow near the pole the region just southward of the velocity minimum at 40 7 s is especially active containing numerous vortices some generated in the proximity of convective storms the two eastward jets nearest the pole display periodicity in their longitudinal structure but no direct analogs to the northern hemisphere s polar hexagon or ribbon waves were observed characteristics of winds and vortices are compared with those of saturn s northern hemisphere and jupiter s atmosphere

saturn s cloud structure inferred from cassini iss abstract using high resolution cassini iss images with wavelengths ranging from the ultraviolet to the near infrared we have retrieved saturn s atmospheric aerosol structure and properties for a broad range of latitudes in the southern hemisphere the observations are consistent with two distinct layers of haze above a scattered cloud each layer is characterized by a vertical location an optical thickness and an effective mean particle size all of which vary with latitude the tropospheric haze is optically thickest and extends to the greatest heights 40 mbar over the equator its top surface is at significantly greater depths 150 mbar at mid latitudes the height of the haze correlates well with position of the tropopause as indicated by the temperature field beneath this haze we find a scattered denser cloud responsible for small scale contrasts at an average depth of 1 75 0 4 bar with some features as deep as 2 5 bar or greater

general circulation and transport in saturn s upper troposphere and stratosphere abstract we present a model for the general circulation and dynamical transport in saturn s upper troposphere and stratosphere and derive the effective advective circulation and eddy transport coefficients required for use in two dimensional latitude altitude photochemistry transport models a three dimensional outer planet general circulation model opgcm is used to generate the transport data we find that the opgcm adequately captures the global scale pole to pole temperature contrast but overestimates mid and high latitude temperatures in the summer hemisphere by 5 k in addition the model reproduces the local temperature minimum seen at the equator in cassini composite infrared spectrometer cirs 0 1 mbar data but not the local maximum in 1 mbar temperatures suggesting that it is capturing the phase of saturn s semiannual oscillation associated with a temperature minimum at the equator but not the opposite phase the meridional circulation at low latitudes is found to be dominated by a seasonally reversing hadley circulation characterized by upwelling near the equator cross equatorial flow from summer to winter hemisphere and strong subsidence centered near 25 latitude in the winter hemisphere the cross equatorial flow induces an asymmetry in which the equatorial jet is found to be stronger in the winter than in the summer stratosphere the location of the subsidence near 25 n for l s 310 coincides with local maxima in acetylene diacetylene and methylacetylene mixing ratios measured by cassini cirs guerlet s fouchet t bezard b moses j i fletcher l n simon miller a a flasar f m 2010 icarus 209 682 695 this result supports the suggestion by guerlet et al 2010 that the hydrocarbon abundances are enhanced at this latitude by pronounced downward transport of hydrocarbon rich air from above the lateral eddy diffusion coefficient is found to typically be 10 5 10 6 m 2 s 1 at mid latitudes implying meridional eddy transport time scales of order 100 1000 years