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

dynamics of neptune s major cloud features abstract we used voyager 2 images of neptune to investigate the dynamics of the great dark spot gds the scooter the second dark spot ds2 and the south polar features spf relative to previous studies we covered a longer time base achieved more complete sampling of the available data and improved accuracy by using stars to correct navigation errors we tracked the gds 8 day shape oscillation for more than 2000 hr measuring amplitudes of 7 4 in longitude and 1 5 in latitude we found a surprisingly large increase in the mean latitudinal size of the gds from 8 in january 1989 to 17 in august during the same period we measured steady gds northward motion from 26 s to 17 s and found no evidence of the latitudinal limits we confirmed that the varying longitudinal drift rates of the gds and ds2 were simple functions of latitude that approximately match the zonal wind profile measurements of at least three cycles of the periodic motions of the ds2 defined a 36 day period and amplitudes of 2 4 in latitude and 47 5 in longitude relative to its mean drift longitude we found that the bright core of the ds2 varied in step with the ds2 latitudinal oscillation reaching a maximum area when the ds2 was furthest north a large increase in relative core brightness at high phase angles is consistent with forward scattering cloud particles we measured one cycle of a scooter longitudinal oscillation of 20 about its mean drift position with a period of 120 days but the scooter s latitudinal motions are too small and of the wrong frequency to be consistent with an advective model of the zonal motions we found that the highly variable spf formation region has the same mean longitudinal drift rate as the ds2 but an offset of 180 in longitude and a 20 difference in latitude the apparent synchronization of these widely separated and dramatically different features is unexplained coupling to the deep interior is ruled out by the significant difference between the radio and cloud periods observed motions of all features are described by empirical models valid over the voyager time period comparisons of voyager results with groundbased observations did not lead to conclusive constraints on the long term dynamics although much of the data seem to be consistent with a 5 8 year oscillation in gds latitude

clouds and hazes vertical structure of a saturn s giant vortex from cassini vims v data analysis abstract we studied the evolution of a giant tropospheric vortex formed in the wake of the storm that encircled saturn from december 2010 to july 2011 fletcher et al 2011a science 332 1413 1417 fletcher et al 2012 icarus 221 560 586 sanchez lavega et al 2011 nature 475 71 74 sanchez lavega et al 2012 icarus 220 561 576 sayanagi et al 2013 icarus 223 460 478 fischer et al 2011 nature 475 75 77 taking advantage of the observations acquired by the instruments on board the cassini spacecraft in particular the visual and infrared mapping spectrometer vims imaged the vortex several times in this work we analyzed two observations registered by the visual channel of vims vims v on 08 24 2011 and 01 04 2012 both after the active phase of the storm and characterized quantitatively the vertical structure of the clouds and hazes above the vortex until now vims v dataset has been scarcely exploited to perform such an analysis the ir channel of vims has always been preferred since it covers wavelengths containing spectral information on a wider range of altitudes in the atmosphere nevertheless in our analysis we investigate the information content of vims v observations and demonstrate that the covered spectral range contains valuable information that are helpful to improve our knowledge on the properties of saturn s upper atmosphere we developed a forward radiative transfer model to describe saturn s atmosphere and simulate vims v spectra in the 0 35 1 05 m wavelength range the analysis has then been performed by means of an inverse model that we built on the basis of the bayesian approach spatial distributions of effective radii column number densities and top pressures of the cloud decks have been mapped and as a by product of our analysis we also suggest a modified spectral shape for the imaginary part of the refractive index of the tropospheric haze with respect to the shape described in the study of karkoschka and tomasko 2005 icarus 179 195 221 the results suggest that the processes responsible for the formation and persistence of the vortex weakened between august 2011 and january 2012 even if the differences that we observe could be due to the fact that the vortex has moved in different positions between the two dates we found that in august 2011 the upper haze was arranged in a dome like structure with the center at 8 mbar and the boundaries at 12 mbar moreover we detected a zone in the lower haze at 135 mbar characterized by higher optical thickness with respect to the surrounding regions located at 85 mbar in january 2012 the dome in the upper layer has diluted into a more homogeneous structure and the haze appears to be overall shifted to less than 6 mbar similarly the 135 mbar high optical depth zone previously detected in the lower layer has disappeared

saturn s visible lightning its radio emissions and the structure of the 2009 2011 lightning storms visible lightning on saturn was first detected by the cassini camera in 2009 at 35 south latitude we report more lightning observations at 35 south later in 2009 and lightning in the 2010 2011 giant lightning storm at 35 north the 2009 lightning is detected on the night side of saturn in a broadband clear filter the 2011 lightning is detected on the day side in blue wavelengths only in other wavelengths the 2011 images lacked sensitivity to detect lightning which leaves the lightning spectrum unknown the prominent clouds at the west edge or the head of the 2010 2011 storm periodically spawn large anticyclones which drift off to the east with a longitude spacing of 10 15 10 000 km the wavy boundary of the storm s envelope drifts with the anticyclones the relative vorticity of the anticyclones ranges up to f 3 where f is the planetary vorticity the lightning occurs in the diagonal gaps between the large anticyclones the vorticity of the gaps is cyclonic and the atmosphere there is clear down to level of the deep clouds in these respects the diagonal gaps resemble the jovian belts which are the principal sites of jovian lightning the size of the flash illuminated cloud tops is similar to previous detections with diameter 200 km this suggests that all lightning on saturn is generated at similar depths 125 250 km below the cloud tops probably in the water clouds optical energies of individual flashes for both southern storms and the giant storm range up to 8 10 9 j which is larger than the previous 2009 equinox estimate of 1 7 10 9 j cassini radio measurements at 1 16 mhz suggest that assuming lightning radio emissions range up to 10 ghz lightning radio energies are of the same order of magnitude as the optical energies southern storms flash at a rate 1 2 per minute the 2011 storm flashes hundreds of times more often 5 times per second and produces 10 10 w of optical power based on this power the storm s total convective power is of the order 10 17 w which is uncertain by at least an order of magnitude and probably is underestimated this power is similar to saturn s global internal power radiated to space it suggests that storms like the 2010 2011 giant storm are important players in saturn s cooling and thermal evolution

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

equatorial pacific seismic reflectors as indicators of global oceanographic events the origin of a series of regionally correlatable seismic horizons in the neogene sediments of the central equatorial pacific is examined through seismic modeling and the detailed analyses of stratigraphic and physical property relationships in deep sea drilling project cores these regionally traceable reflectors are synchronous the younger reflectors are the direct result of carbonate dissolution events the older ones of stratigraphically selective diagenetic processes the changes in ocean chemistry associated with these events appear to be linked to global reorganizations of surface and bottom water circulation patterns the most dramatic of which are associated with reorganizations of north atlantic bottom waters these deepwater seismic horizons appear to correlate with the major events on the relative sea level curve of vail et al for the neogene

paleogene calcite compensation depth in the eastern subtropical pacific answers and questions 1 ocean drilling program leg 199 drilled a north south transect across the eocene paleoequator in the eastern pacific permitting reconstruction the calcite compensation depth ccd since earliest eocene time the ccd was relatively shallow near the early eocene pacific equator 3200 m and unlike modern latitudinal ccd gradients deepened to the north to 3600 m paleolatitude 10 n at 41 ma the ccd underwent a brief sharp transient deepening of 700 m then remained shallow until the eocene oligocene boundary at the e o boundary the ccd deepened by 1200 m in less than 300 kyr this rapid deepening served to more than double the area of seafloor subject to caco3 deposition sea level fall associated with ice volume buildup and ensuing shelf basin fractionation is unlikely to be the sole cause of the increased deep ocean caco3 burial rather a sudden rapid increase in the amount of ca entering the ocean appears necessary to explain the observations

saturn lightning recorded by cassini rpws in 2004 during 2004 the cassini rpws radio and plasma wave science instrument recorded about 5400 seds saturn electrostatic discharges which were organized in 4 storm systems and 95 episodes a computer algorithm with different intensity thresholds was applied to extract the seds from the rpws data and a statistical analysis on the main characteristics of these seds is performed compared to the seds recorded by the voyagers in the early 1980s some characteristics like sed rate intensity signal duration or power spectrum are similar but there are also remarkable differences with regard to time occurrence and frequency range the first appearance of seds storm 0 was recorded by rpws from a distance of more than 300 saturn radii at the end of may 2004 followed by storm a in mid july storm b at the beginning of august and the most prominent storm c throughout most of september there were also significant intervals of time with no detectable sed activity e g seds were practically absent from october 2004 until june 2005 no clear indication for seds below a frequency of 1 3 mhz could be found we suggest that the sed storms a b c and possibly also storm 0 originate from the same storm system residing at a latitude of 35 south which lasted for several months waxed and waned in strength and rotated with the voyager radio period of saturn the sed source might be located in the updrafting water clouds beneath the visible cloud features detected in the cassini images

cassini iss observation of saturn s north polar vortex and comparison to the south polar vortex we present analyses of saturn s north pole using high resolution images captured in late 2012 by the cassini spacecraft s imaging science subsystem iss camera the images reveal the presence of an intense cyclonic vortex centered at the north pole in the red and green visible continuum wavelengths the north polar region exhibits a cyclonically spiraling cloud morphology extending from the pole to 85 n planetocentric latitude with a 4700 km radius images captured in the methane bands which sense upper tropospheric haze show an approximately circular hole in the haze extending up to 1 5 latitude away from the pole the spiraling morphology and the eye like hole at the center are reminiscent of a terrestrial tropical cyclone in the system iii reference frame rotation period of 10h39m22 4s seidelmann et al 2007 archinal et al 2011 the eastward wind speed increases to about 140 m s 1 at 89 n planetocentric latitude the vorticity is 6 5 1 5 10 4 s 1 at the pole and decreases to 1 3 1 2 10 4 s 1 at 89 n in addition we present an analysis of saturn s south polar vortex using images captured in january 2007 to compare its cloud morphology to the north pole the set of images captured in 2007 includes filters that have not been analyzed before images captured in the violet filter 400 nm also reveal a bright polar cloud the south polar morphology in 2007 was more smooth and lacked the small clouds apparent around the north pole in 2012 saturn underwent equinox in august 2009 the 2007 observation captured the pre equinox south pole and the 2012 observation captured the post equinox north pole thus the observed differences between the poles are likely due to seasonal effects if these differences indeed are caused by seasonal effects continuing observations of the summer north pole by the cassini mission should show a formation of a polar cloud that appears bright in short wavelength filters

an objective classification of saturn cloud features from cassini iss images abstract a k means clustering algorithm is applied to cassini imaging science subsystem continuum and methane band images of saturn s northern hemisphere to objectively classify regional albedo features and aid in their dynamical interpretation the procedure is based on a technique applied previously to visible infrared images of earth it provides a new perspective on giant planet cloud morphology and its relationship to the dynamics and a meteorological context for the analysis of other types of simultaneous saturn observations the method identifies 6 clusters that exhibit distinct morphology vertical structure and preferred latitudes of occurrence these correspond to areas dominated by deep convective cells low contrast areas some including thinner and thicker clouds possibly associated with baroclinic instability regions with possible isolated thin cirrus clouds darker areas due to thinner low level clouds or clearer skies due to downwelling or due to absorbing particles and fields of relatively shallow cumulus clouds the spatial associations among these cloud types suggest that dynamically there are three distinct types of latitude bands on saturn deep convectively disturbed latitudes in cyclonic shear regions poleward of the eastward jets convectively suppressed regions near and surrounding the westward jets and baroclinically unstable latitudes near eastward jet cores and in the anti cyclonic regions equatorward of them these are roughly analogous to some of the features of earth s tropics subtropics and midlatitudes respectively this classification may be more useful for dynamics purposes than the traditional belt zone partitioning temporal variations of feature contrast and cluster occurrence suggest that the upper tropospheric haze in the northern hemisphere may have thickened by 2014 the results suggest that routine use of clustering may be a worthwhile complement to many different types of planetary atmospheric data analysis

color and the vertical structure in jupiter s belts zones and weather systems abstract radiative transfer analysis was performed with data taken by the galileo spacecraft solid state imager ssi during its nominal mission december 1995 to december 1997 the objective is to use the methane band 727 and 889 nm and color 410 and 756 nm sensitivities to identify the vertical position of cloud absorption that leads to coloration earlier work banfield et al 1998 icarus 135 230 250 with only the near ir continuum and methane band images yielded information about the vertical distribution of cloud scatterers but no information on the wavelength dependence of cloud absorption the new analysis employs the same parameter retrieval algorithm but adds the 410 nm wavelength under the assumption that the 410 nm absorption by cloud particles is indicative of spectrally broad blue absorption the new channel gives color information the primary color difference between the dark north equatorial belt neb and the brighter equatorial zone ez appears to be in the tropospheric haze layer s 410 nm single scattering albedo this layer extends through the stably stratified region approximately from 200 to 800 mbars the base of the haze layer is slightly deeper in the neb by about 200 mbars than in the ez and a variable thickness white cloud layer at the base of the haze exists in both regions but is about five times optically thicker in the ez within the ez slight color variation is seen with latitude again due to 410 nm single scattering albedo variation in the haze layer anomalous regions such as the great red spot and a 5 m hot spot are modeled showing additional variations in the structure and color of the tropospheric haze deeper clouds with pressures of 1 7 bars are seen in occasional clearings but their opacity and color are not well constrained by the data

large scale storms in saturn s atmosphere during 1994 large scale storms are rarely observed in saturn s atmosphere but their appearance traces the wind velocity field providing information on the vertical structure of the clouds and on the dynamics of the atmosphere two large scale atmospheric disturbances formed by clouds highly reflective in the visible part of the spectrum were observed on saturn during 1994 an equatorial disturbance with a longitudinal size of 27 000 kilometers drifted in longitude with a velocity of 273 6 meters per second a second disturbance a rapidly evolving convective storm with an initial size 7000 kilometers was observed at 56 degrees south moving with a zonal velocity of 15 5 meters per second

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

the evolving flow of jupiter s white ovals and adjacent cyclones abstract we present results regarding the dynamical meteorology of jupiter s white ovals at different points in their evolution starting from the era with three white ovals fa bc and de galileo continuing to the post merger epoch with only one oval ba cassini and finally to oval ba s current reddened state new horizons we demonstrate that the dynamics of their flow have similarly evolved along with their appearance in the galileo epoch oval de had an elliptical shape with peak zonal wind speeds of 90 m s 1 in both its northern and southern peripheries during the post merger epoch oval ba s shape was more triangular and less elliptical than oval de in addition to widening in the north south direction its northern periphery was 20 m s 1 slower and its southern periphery was 20 m s 1 faster than oval de s flow during the galileo era finally in the new horizons era the reddened oval ba had evolved back to a classical elliptical form the northern periphery of oval ba increased in speed by 20 m s 1 from cassini to new horizons ending up at a speed nearly identical to that of the northern periphery of oval de during galileo however the peak speeds along the southern rim of the newly formed oval ba were consistently faster than the corresponding speeds in oval de and they increased still further between cassini and new horizons ending up at 140 150 m s 1 relative vorticity maps of oval ba reveal a cyclonic ring surrounding its outer periphery similar to the ring present around the great red spot the cyclonic ring around oval ba in 2007 appears to be moderately stronger than observed in 1997 and 2001 suggesting that this may be associated with the coloration of the vortex the modest strengthening of the winds in oval ba the appearance of red aerosols and the appearance of a turbulent cyclonic feature to oval ba s northwest create a strong resemblance with the great red spot from both a dynamical and morphological perspective in addition to the white ovals we also measure the winds within two compact cyclonic regions one in the galileo data set and one in the cassini data set in the images these cyclonic features appear turbulent and filamentary but our wind field reveals that the flow manifests as a coherent high speed collar surrounding relatively quiescent interiors our relative vorticity maps show that the vorticity likewise concentrates in a collar near the outermost periphery unlike the white ovals which have peak relative vorticity magnitudes near the center of the vortex the cyclones contain several localized bright regions consistent with the characteristics of thunderstorms identified in other studies although less studied than their anticyclonic cousins these cyclones may offer crucial insights into the planet s cloud level energetics and dynamical meteorology

biogenic sedimentation in the equatorial pacific carbon cycling and paleoproduction 12 24 ma 1 the equatorial pacific is an important part of the global carbon cycle and has been affected by climate change through the cenozoic 65 ma to present we present a miocene 12 24 ma biogenic sediment record from deep sea drilling project dsdp site 574 and show that a caco3 minimum at 17 ma was caused by elevated caco3 dissolution when pacific plate motion carried site 574 under the equator at about 16 2 ma there is a minor increase in biogenic deposition associated with passing under the equatorial upwelling zone the burial rates of the primary productivity proxies biogenic silica bio sio2 and biogenic barium bio ba increase but biogenic caco3 decreases the carbonate minimum is at 17 ma coincident with the beginning of the miocene climate optimum the transient lasts from 18 to 15 ma bio sio2 and bio ba are positively correlated and increase as the equator was approached corg is poorly preserved and is strongly affected by changing carbonate burial terrestrial 232th deposition a proxy for aeolian dust increases only after the site 574 equator crossing since surface production of bio sio2 bio ba and caco3 correlate in the modern equatorial pacific the decreased caco3 burial rate during the site 574 equator crossing is driven by elevated caco3 dissolution representing elevated ocean carbon storage and elevated atmospheric co2 the length of the 17 ma caco3 dissolution transient requires interaction with a slow part of the carbon cycle perhaps elevated mantle degassing associated with the early stages of columbia river basalt emplacement

a study of the stability of jovian zonal winds from hst images 1995 2000 abstract we present a five year study of the temporal stability of jupiter s zonal wind velocity profile at cloud level based on hubble space telescope images obtained from 1995 to 2000 we used the correlation of east west albedo scans in pairs of images separated by one jovian rotation to retrieve the zonal winds the resolution in the hst images ranged from 140 to 190 km pixel 1 independent measurements of the motions of individual cloud tracers were used to control the above profiles three wavelengths were used in this analysis 410 nm violet continuum 892 nm methane absorption band and 953 nm red continuum our study indicates that globally jupiter s zonal flow did not change during this five year interval and it does not depend on the observed wavelengths when comparing our mean profile with that obtained 16 years ago using voyager data we find a reasonable agreement we note however a small shift in the latitude of the jets poleward of latitude 30 probably due to image navigation uncertainties however true changes in the intensity of the jets at 24 n and 32 n are found results also indicate that the 7 s jet has remained stable since the voyager era in addition we extend in this paper our previous study of the 24 n with new data from year 2000 the new data confirm the jet s stability during the 1995 2000 period finally we present the average profile for this period including error estimation in a table that extends the latitudinal coverage of limaye s 1986 icarus 65 335 352 voyager profile up to latitudes 68 s and 77 n

paleogene tropical pacific clues to circulation productivity and plate motion 1 stratigraphic data from 63 deep sea drilling project and ocean drilling program odp sites that sample the lower neogene and paleogene sediments of the tropical pacific have been compiled and put on the biostratigraphic and paleomagnetic timescale refined by odp leg 199 scientists sediment accumulation rates have been calculated for ten intervals ranging in age from 10 to 56 ma and have been plotted for the midpoint of each interval at the associated paleoposition for each site used a fixed hot spot model was used for reconstruction of the pacific lithospheric plate all such reconstructed intervals show the development of a tongue of high accumulation rates associated with the oceanographic divergence at the geographic equator the development of this equatorial band is weakest between 46 and 56 ma the time of the peak warmth in paleogene climate possible motion of the hawaiian hot spot or true polar wander between 46 and 56 ma appears to have had little effect on the plate rotation estimate of the position of the equator in addition to temporal changes in the calcite compensation depth and in productivity the biggest change in the patterns of sediment accumulation rates in the eastern tropical pacific was the development of a relatively strong divergence between 6 and 10 n near the region of divergence between the modern north equatorial current and the north equatorial counter current changes in the equatorial circulation appear to be associated in time with the opening and closing of oceanic gateways particularly the complex closing of the caribbean pacific gateway

temporal behavior of cloud morphologies and motions in saturn s atmosphere saturn s atmosphere displays a variety of temporal changes in its cloud morphology at synoptic and planetary scales hemispheric long term albedo variations which are more pronounced at ultraviolet and blue wavelengths have been well established and are apparently linked to the seasonal insolation cycle short term changes of the order of months have been observed in the spectral reflectivity of the belt zone pattern mainly at mid latitudes some appear to be related to discrete spot activity but for the majority of the changes no such signs of spot activity were detected up to a resolution 2000 km in particular the ribbon structure at 45 n could have been affected by this activity and probably is a transient phenomenon the polar belts at 65 north and south and those at 75 north hexagon and south show a long term stability in their location perhaps for more than a century the most prominent belts located in the equator and the equatorial zone are persistent features of saturn s globe their main changes took place during the development of a rare planetary scale disturbance known as great white spots only five such events have been observed at repetitive regular intervals of about one saturn year since the first report in 1876 and at different latitudes from the equator to 60 n they are probably convective in origin with the seasonal heating of the upper atmosphere acting as a trigger mechanism during its life cycle of 2 3 years the disturbance shows turbulent planetary scale patterns of clouds that might be related to a wave dynamical phenomenon other distinct nonaxisymmetric cloud systems at synoptic scale are very scarce in saturn s atmosphere we observed new isolated features at several latitudes during 1990 and 1991 these spots together with those available from historical records are used as tracers for determining the latitude dependence and time variability of saturn s zonal winds the winds tend to exhibit a long term stability in their latitudinal positions and average wind speed although some significant departures from the zonal mean voyager profile have been detected during the development of the equatorial disturbance in 1990 and 1991

dynamics of saturn s polar regions we analyze data retrieved by the imaging science system onboard the cassini spacecraft to study the horizontal velocity and vorticity fields of saturn s polar regions latitudes 60 90 n in june december 2013 and 60 90 s in october 2006 and july december 2008 including the northern region where the hexagonal wave is prominent with the aid of an automated two dimensional correlation algorithm we determine two dimensional maps of zonal and meridional winds and deduce vorticity maps we extract zonal averages of zonal winds providing wind profiles that reach latitudes as high as 89 5 in the south and 89 9 in the north wind measurements cover the intense polar cyclonic vortices that reach similar peak velocities of 150 m s 1 at 88 5 the hexagonal wave lies in the core of an intense eastward jet at planetocentric latitude 75 8 n with motions that become nonzonal at the hexagonal feature in the south hemisphere the peak of the eastward jet is located at planetocentric latitude 70 4 s a large anticyclone the south polar spot sps similar to the north polar spot nps observed at the voyager times 1980 1981 has been observed in images from april 2008 to january 2009 in the south polar region at latitude 66 1 close to the eastward jet the sps does not apparently excite a wave on the jet we analyze the stability of the zonal jets finding potential instabilities at the flanks of the eastward jets around 70 and we measure the eddy wind components suggesting momentum transfer from eddy motion to the westward jets closer to the poles

the age of the steens reversal and the columbia river basalt group abstract the columbia river basalt group crbg eruptions have a well defined relative magnetostratigraphy but have not been definitively correlated to the geomagnetic polarity time scale 40 ar 39 ar ages are presented from lavas erupted in the r 0 through n 1 magnetozones of the crbg and in the transition between r 0 and n 0 four ages from transitionally magnetized lava flows at steens mountain catlow peak and poker jim ridge with a weighted mean age 16 58 0 10 ma 1 and the more precise age 16 654 0 025 ma of the normally magnetized oregon canyon tuff at the top of the catlow peak section show that the oldest crbg magnetozone r 0 correlates with the c5cr chron bayesian statistical analysis applied to data from four flows at catlow peak using the mean age of the steens reversal gives a best and preferred age of the steens reversal of 16 73 0 13 0 08 ma 95 confidence depending on the geomagnetic polarity time scale model the eruption rate from n 0 through r 2 0 34 0 45 ma in the middle and the bulk of the crbg emplacement averaged 0 30 0 41 km 3 a and peaked at a rate 1 1 2 to 4 1 2 times higher during r 2

the great white spot and disturbances in saturn s equatorial atmosphere during 1990 a giant storm the great white spot erupted at the end of september 1990 as a localized bright cloud system close to saturn s equator its evolution produced a complex planetary disturbance which affected the whole equatorial region a month later similar spots have appeared approximately once every saturnian year about 30 earth years implying that a seasonal change in solar heating for example may be responsible for their occurrence

shallow water simulations of saturn s giant storms at different latitudes abstract shallow water simulations are used to present a unified study of three major storms on saturn nicknamed as great white spots gws at different latitudes polar 1960 equatorial 1990 and mid latitude 2010 sanchez lavega 2004 sanchez lavega et al 2011 in our model the three gws are initiated by introducing a gaussian function pulse at the latitude of the observed phenomena with controlled horizontal size and amplitude this function represents the convective source that has been observed to trigger the storm a growing disturbance forms when the pulse reacts to ambient winds expanding zonally along the latitude band of the considered domain we then compare the modeled potential vorticity with the cloud field adjusting the model parameters to visually get the closest aspect between simulations and observations simulations of the 2010 gws planetographic latitude 40o zonal velocity of the source 30 m s 1 indicate that the coriolis forces and the wind profile structure shape the disturbance generating as observed a long region to the east of the convective source with a high speed peripheral anticyclonic circulation and a long lived anticyclonic compact vortex accompanied by strong zonal advection on the southern part of the storm forming a turbulent region simulations of the equatorial 1990 gws planetographic latitude 12o 5o zonal velocity of the source 365 400 m s 1 show a different behavior because of the intense eastward jet meridional shear at the equatorial region and low latitude dynamics a round shaped source forms as observed with the rapid growth of a kelvin helmholtz instability on the north side of the source due to advection and to the strong meridional wind shear whereas at the storm latitude the disturbance grows and propagates eastward the storm nucleus is the manifestation of a rossby wave while the eastward propagating planetary scale disturbance is a gravity rossby wave trapped around the equator the simulated 1960 gws disturbance planetographic latitude 56o zonal velocity 4 m s 1 formed a chain of periodic oval spots that mimic the few available observations of the phenomenon for the mid and high latitude storms simulations predict a strong injection of negative relative vorticity due to divergence of the upwelling storm material which may produce large anticyclones on the anticyclonic side of the zonal profile and a quick turbulent expansion on the background cyclonic regions in general simulations indicate that negative relative vorticity injected by storms determines the natural reaction to zonal winds at latitudes where coriolis forces are dominant

vertical cloud structure in saturn s 1990 equatorial storm abstract we present a model study of the evolution of the vertical cloud structure and aerosol optical characteristics of the giant storm that erupted in saturn s atmosphere in september 1990 this analysis is based on the photometric measurements of the reflected intensity of the equatorial region in the optical range 336 890 nm continuum and methane absorption bands that were previously published a sanchez lavegaet al 1994 icarus108 158 168 different stages of the storm evolution are analyzed preoutburst onset and mature october november 1990 and evolved july 1991 good fits between the observations and radiative transfer calculations are found using a three layer model a gas layer a haze layer and a semiinfinite cloud deck two term henyey greenstein and mie phase functions are used for the scattering particles according to the models the main change during the evolution of the disturbance took place in the altitude of the cloud layer cloud tops elevated by 1 2 1 5 scale heights during the onset and mature storm stage relative to the undisturbed atmosphere descending later during the evolved phase by 0 7 scale heights relative to the altitude of the mature clouds the altitude location of the haze layer did not change during the storm development but the single scattering albedo of the haze particles increased significantly during the onset and mature stages in the uv blue wavelengths if the haze particles are modeled as mie spheres their mean radius varied from 0 83 to 0 64 m with real refractive index 1 5 and extreme values of the imaginary index 0 01 370 nm and 0 0005 830 nm

a comparison between excess barium and barite as indicators of carbon export 1 since dymond et al 1992 proposed the paleoproductivity algorithm based on bio ba which relies on a strong correlation between ba and organic carbon fluxes in sediment traps this proxy has been applied in many paleoproductivity studies barite the main carrier of particulate barium in the water column and the phase associated with carbon export has also been suggested as a reliable paleoproductivity proxy in some locations we demonstrate that baexcess total barium minus the fraction associated with terrigenous material frequently overestimates babarite barium associated with the mineral barite most likely due to the inclusion of barium from phases other than barite and terrigenous silicates e g carbonate organic matter opal fe mn oxides and hydroxides a comparison between overlying oceanic carbon export and carbon export derived from baexcess shows that the dymond et al 1992 algorithm frequently underestimates carbon export but is still a useful carbon export indicator if all caveats are considered before the algorithm is applied babarite accumulation rates from a wide range of core top sediments from different oceanic settings are highly correlated to surface ocean 14 c and chlorophyll a measurements of primary production this relationship varies by ocean basin but with the application of the appropriate f ratio to 14 c and chlorophyll a primary production estimates the plot of babarite accumulation and carbon export for the equatorial pacific atlantic and southern ocean converges to a global relationship that can be used to reconstruct paleo carbon export index terms 3022 marine geology and geophysics marine sediments processes and transport 4267 oceanography general paleoceanography 4825 oceanography biological and chemical geochemistry keywords paleoproductivity barite export production excess barium marine sediments citation eagle m a paytan k r arrigo g van dijken and r w murray a comparison between excess barium and barite as indicators of carbon export paleoceanography 18 1 1021 doi 10 1029 2002pa000793 2003

hubble space telescope observations of the 1990 equatorial disturbance on saturn images albedos and limb darkening in september 1990 a major equatorial eruption on saturn produced a disturbance that spread in longitude until it completely girdled the planet we report here on 150 images recorded in six passbands with the wide field planetary camera wf pc aboard the hubble space telescope hst on 17 and 18 november 1990 for comparison we used hst wf pc observations of saturn obtained in three colors on 26 august 1990 before the onset of the disturbance and in six colors on 5 and 6 june 1991 when almost no evidence of the disturbance remained at both of those times the equatorial belt was normal in appearance four of the passbands with mean wavelengths of 336 435 546 and 716 nm were selected for photometric analysis and a patch of the b ring near the central meridian was used for photometric calibration using deconvolved images from all three epochs of observation we measured reflectivities i f of the disk along parallels of latitude as a function of longitudinal distance from the central meridian and also along the central meridian as a function of latitude from 0 to 90 the longitudinal measurements cover essentially the whole visible disk they were made at 1 intervals of planetographic latitude from 0 to 80 and the results are expressed in terms of minnaert coefficients k and minnaert albedos i f 0 we find that the cloud particles associated with the disturbance must differ in character from those that normally make up the visible cloud deck on saturn they were brighter and bluer they had greater limb darkening and their limb darkening was spectrally more neutral the mutual relationship of those properties is such that features which stand out strongly near the meridian fade to invisibility when near the limb

potential vorticity and layer thickness variations in the flow around jupiter s great red spot and white oval bc layer thickness variations in jupiter s atmosphere are investigated by treating potential vorticity as a conserved tracer starting with the horizontal velocity field measured from voyager images fluid trajectories around the great red spot grs and white oval bc are calculated the flow is assumed to be frictionless adiabatic hydrostatic and steady in the reference frame of the vortex absolute vorticity is followed along each trajectory its magnitude is assumed to vary directly as the thickness which is defined as the mass per unit area between potential temperature surfaces to the accuracy of the observations the inferred thickness is a separable function of trajectory and latitude the latitude dependence has positive curvature near the grs and bc the relative variations of thickness with respect to latitude are generally larger than the relative variations of coriolis parameter with respect to latitude the beta effect the data are a useful diagnostic which will help differentiate between models of jovian vortices the present analysis employs a quasi geostrophic model in which a thin upper weather layer which contains the vortex is supported hydrostatically by a much deeper lower layer in this model the upper free surface does not contribute to the observed variation of thickness along trajectories such variations are due exclusively to bottom topography flow of the deep lower layer relative to the vortex the observation are used to infer the form of the deep zonal velocity profile vs latitude the magnitude of the profile depends on the unknown static stability the principal result is the existence of horizontal shear in the deep layer zonal velocity profile i e the lower layer is not in solid body rotation and does not act like a flat solid surface in this respect the data support the hypothesis of ingersoll and cuong concerning motions in the deep layer however at some latitudes the data violate ingersoll and cuong s criterion governing the compactness of the vortices at these latitudes the topography allows standing rossby waves wakes extending far downstream to the west observed wavelike features the filamentary regions are possibly formed by this mechanism

the origin and evolution of saturn s 2011 2012 stratospheric vortex the planet encircling springtime storm in saturn s troposphere december 2010 july 2011 fletcher l n et al 2011 science 332 1413 1414 sanchez lavega a et al 2011 nature 475 71 74 fischer g et al 2011 nature 475 75 77 produced dramatic perturbations to stratospheric temperatures winds and composition at mbar pressures that persisted long after the tropospheric disturbance had abated thermal infrared ir spectroscopy from the cassini composite infrared spectrometer cirs supported by ground based ir imaging from the visir instrument on the very large telescope and the mirsi instrument on nasa s irtf is used to track the evolution of a large hot stratospheric anticyclone between january 2011 and march 2012 the evolutionary sequence can be divided into three phases i the formation and intensification of two distinct warm airmasses near 0 5 mbar between 25 and 35 n b1 and b2 between january april 2011 moving westward with different zonal velocities b1 residing directly above the convective tropospheric storm head ii the merging of the warm airmasses to form the large single stratospheric beacon near 40 n b0 between april and june 2011 disassociated from the storm head and at a higher pressure 2 mbar than the original beacons a downward shift of 1 4 scale heights approximately 85 km post merger and iii the mature phase characterised by slow cooling 0 11 0 01 k day and longitudinal shrinkage of the anticyclone since july 2011 peak temperatures of 221 6 1 4 k at 2 mbar were measured on may 5th 2011 immediately after the merger some 80 k warmer than the quiescent surroundings from july 2011 to the time of writing b0 remained as a long lived stable stratospheric phenomenon at 2 mbar moving west with a near constant velocity of 2 70 0 04 deg day 24 5 0 4 m s at 40 n relative to system iii longitudes no perturbations to visible clouds and hazes were detected during this period with no direct tracers of motion in the stratosphere we use thermal windshear calculations to estimate clockwise peripheral velocities of 200 400 m s at 2 mbar around b0 the peripheral velocities of the two original airmasses were smaller 70 140 m s in august 2011 the size of the vortex as defined by the peripheral collar was 65 longitude 50 000 km in diameter and 25 latitude stratospheric acetylene c2h2 was uniformly enhanced by a factor of three within the vortex whereas ethane c2h6 remained unaffected the passage of b0 generated a new band of warm stratospheric emission at 0 5 mbar at its northern edge and there are hints of warm stratospheric structures associated with the beacons at higher altitudes p 0 1 mbar than can be reliably observed by cirs nadir spectroscopy analysis of the zonal windshear suggests that rossby wave perturbations from the convective storm could have propagated vertically into the stratosphere at this point in saturn s seasonal cycle one possible source of energy for the formation of these stratospheric anticyclones

glacial interglacial variability in the delivery of dust to the central equatorial pacific ocean abstract fluxes of continental mineral aerosols dust were greater during glacial periods than during interglacials throughout most regions of the earth the equatorial pacific ocean was a possible exception to this pattern in that previous studies have reported either greater dust fluxes during interglacials or no consistent glacial interglacial pattern of dust flux we have applied the 230th normalization technique to derive five new records of dust flux from central equatorial pacific ocean sediments in contrast to previous studies which relied on stratigraphic accumulation rates the 230th normalization technique produces internally consistent results revealing fluxes to this region of continental lithogenic material that were positively correlated with global ice volume throughout the past 300 000 yr maximum glacial fluxes of continental mineral aerosols exceed minimum interglacial fluxes by about a factor of 2 similar to changes found elsewhere at low and mid latitudes this amplitude of variability is substantially smaller than that seen in some recent models and these observations provide a calibration point for future model development

a method for the near source anisotropy by the pair event inversion of rayleigh wave radiation patterns summary a novel method is proposed for retrieving the 3 d orientation of axes of symmetry of near source anisotropy by a non linear inversion of observed radiation patterns of seismic displacement spectra of rayleigh waves if faulting is generated within an anisotropic source region body force equivalents for the faulting are in general not a double couple but the sum of three orthogonal dipole forces kosevich kawasaki tanimoto as a result of the third dipole force radiation patterns of rayleigh waves are deformed the deformation amounting to several per cent of those for an isotropic source medium the non linear inversion is carried out to find the optimum fault plane solutions giving the minimum square residual between observed and theoretical radiation patterns in some period range in order to remove effects of heterogeneity along propagation paths a pair event scheme is involved in the inversion which denotes taking spectral amplitude ratios and differential phases of the seismic displacement spectra of the pair events having close hypocentres and different fault plane solutions the uniqueness of the fault plane solutions of the non linear inversion is afforded a proof by the monte carlo experiment the non linear inversion is repeated for some possible types of symmetry of the near source orthotropic anisotropy due to the preferred orientation of olivine crystals as mantle materials square residuals thus obtained are compared with each other to see which orientation gives the minimum the method is applied to pair events which occurred in the anomalous mantle beneath the mid atlantic ridge this leads to a discovery that one type of symmetry of the preferred orientations with a b and c axes aligned vertical parallel to and perpendicular to the trend n11e of the ridge axis respectively is most likely existing in the anomalous mantle

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

revisiting nutrient utilization in the glacial antarctic evidence from a new method for diatom bound n isotopic analysis holocene in the indian sector is smaller than in previous measurements these data suggest no change in the degree of nitrate utilization in the atlantic sector and at most a 20 increase from 25 to 45 in the indian sector the new measurements suggest that during the last ice age in the atlantic sector of the antarctic the atmospheric source of biologically available iron was not so great as to become significant relative to the iron supply from below given the apparent spatial variability in the degree of nitrate drawdown more work is required to develop an adequate picture of the glacial antarctic nutrient field index terms 4806 oceanography biological and chemical carbon cycling 4845 oceanography biological and chemical nutrients and nutrient cycling 4894 oceanography biological and chemical instruments and techniques 9310 information related to geographic region antarctica

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

missing organic carbon in eocene marine sediments is metabolism the biological feedback that maintains end member climates 1 ocean chemistry is affected by pco2 in the atmosphere by increasing the dissolution of solid calcium carbonate and elevating the dissolved inorganic carbon concentrations in seawater positive feedbacks between the ocean and atmosphere can maintain high atmospheric pco2 and affect global climate we report evidence for changes in the oceanic carbon cycle from the first high quality organic carbon corg data set of eocene sediments beneath the equatorial pacific upwelling region leg 199 of the ocean drilling program eocene corg mass accumulation rates mars are 10 times lower than holocene rates even though expected corg mars estimated from biogenic barium mars an indicator of biological production equal or exceed modern fluxes what happened to the missing corg recent advances in ecology and biochemical kinetics show that the metabolism of nearly all animals marine and terrestrial is positively correlated by first principles to environmental temperatures the approximately 10 c abyssal temperature difference from eocene to holocene should have radically reduced pelagic corg burial as we observe we propose that higher basal metabolism and nutrient utilization recycling rates in the eocene water column and surface sediments precluded corg sediment burial in the pelagic ocean increased rates of metabolism nutrient utilization and lowered corg sedimentation caused by increased temperature may have acted as a biological feedback to maintain high atmospheric pco2 and hothouse climates conversely these same parameters would reverse sign to maintain low pco2 when temperatures decrease thereby maintaining icehouse conditions during cold climate regimes

dynamical features in the northern hemisphere of saturn from voyager 1 images results of the analysis of voyager measurements of divergence and inferred vertical velocity of convective cloud features in the northern hemisphere of saturn are presented here the winds in this region have been measured by tracking the cloud elements observed in sequences of images the derived zonal winds imply that these convective features reside at the maximum of strong easterly jets centred at 41 n planetocentric latitude and that the jet is barotropically unstable the divergences and local dynamics of the saturn features are found to differ from those of the jovian equatorial plumes

the onset and growth of the 1990 equatorial disturbance on saturn abstract the development of cloud structures at low saturnian latitudes in september 1990 can be divided into three phases the onset and expansion of the initial disturbance popularly known as the great white spot the eastward and westward expansion of the bright cloud and the eventual formation of wave like structures encircling the equator the three phases of this storm are consistent with a single convective event this event is evaluated within the historical context of previous occurrences and general seasonal mechanisms are considered

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

the south equatorial belt of jupiter i its life cycle abstract the south equatorial belt seb of jupiter located between latitudes 10 s and 20 s represents the archetype of a cyclically changing band between the belt and zone stages a new analysis of the historical records has been performed using various published observations and additional data in visual wavelengths which permit characterization of cloud morphology patterns the zonal and meridional motions the zonal wind velocities and the spatial and temporal scales of the variability of the seb for uniformity and clarity each phase of the cycle has been denoted with its proper nomenclature based on the traditional one the following sequential stages can be distinguished i zone like global fade aspect sebf ii outbreak of activity with one or more independent sources in different longitudes but fixed latitudes sebd0 followed by the development and zonal expansion of a disturbance to planetary scale within the cyclonic band sebd iii propagation of the activity and formation of new disturbances in adjacent regions tropical 20 s to 26 s strzd and equatorial 5 s to 10 s ezs activity this phase denoted globally as sebd1 does not always develop after the sebd iv normal belt like stage seb a period during which secondary outbursts simulating in some respects the sebd can take place also the strzd and ezs disturbances can be present v the cycle is completed with a rapid return to the sebf phase a new comprehensive list that includes quantitative data and detailed commentaries of all the documented events has been compiled we propose and discuss possible dynamical scenarios involved in each one of these phases in an accompanying paper part ii the recent sebd phase whose onset occurred on april 6 1993 is described in detail the data presented in that paper describes the most thoroughly documented event to date and is based on our observations in the specral range from 400 to 890 nm which will serve as a guide for comparisons with simultaneous observations by other teams performed at other wavelengths

jupiter s cloud structure from galileo imaging data the vertical structure of aerosols on jupiter is inferred from data obtained by the nasa galileo solid state imaging system during the first six orbits of the spacecraft images at 889 nm a strong methane band 727 nm a weaker methane band and 756 nm continuum taken at a variety of lighting and viewing angles are used the images are displayed and described in the companion paper by vasavada et al 1998 icarus 135 265 275 conservative scattering cloud particles with laterally uniform single scattering properties are assumed in the analysis and are shown to be consistent with the data at these wavelengths particles are bright and the darkest locations on jupiter correspond to the smallest optical thickness of aerosols optical depths and vertical positions of aerosol layers vary from place to place and are the retrieved quantities in the analysis only mid and low latitudes are sampled in this data set a stratospheric haze with an optical depth of roughly a tenth and an upper tropospheric haze with an optical depth of 2 to 6 exist over all regions both are consistent with previous conclusions based on data of lower spatial resolution e g west et al 1986 icarus 65 161 217 the new data show that these layers contain little lateral structure on scales smaller than the planetary jets on scales of the jets and ovals the top and bottom of the upper tropospheric haze vary in elevation the concentration of particles optical depth per pressure interval varies less than does the total optical depth near the base of the upper tropospheric haze is a third cloud component usually at pressure p 750 200 mb which is less than a scale height in geometric thickness its optical depth varies from zero to about 20 on regional scales and often varies by 50 on scales of a few tens of kilometers optical depth variations in this cloud are the principal cause of the features in jupiter s atmosphere seen at red and longer wavelengths it is probably composed of ammonia the expected nh 4sh cloud has not been identified in this work perhaps because it exists only at locations where it is concealed beneath higher clouds our retrievals also cannot rule out a pervasive deep haze without small scale structure finally in one region northwest of the great red spot a deeper cloud is identified parts of it lie at a pressure greater than four bars it is associated with a rapidly changing storm system with optical depth of several tens or more and a range of cloud heights between p 4 bars to p 400 mb it is probably composed of water

moist convection and the 2010 2011 revival of jupiter s south equatorial belt fletcher was supported by a royal society research fellowship at the university of leicester giles was supported by a royal society research grant at the university of oxford the uk authors acknowledge the support of the science and technology facilities council stfc a portion of this work was performed by orton and payne at the jet propulsion laboratory california institute of technology under a contract with nasa this research used the alice high performance computing facility at the university of leicester we are extremely grateful for the combined efforts of the numerous amateur observers including those listed in the figure captions for sharing their data and for the jupos software developed by grischa hahn and hans jorg mettig to reproject the visible light data this investigation was partially based on thermal infrared observations acquired at i the eso very large telescope paranal ut3 melipal observatory using directors discretionary time program id 286 c 5009 and regular service time program id 087 c 0024 ii the subaru telescope which is 27 operated by the national astronomical observatory of japan program id o11154 iii nasa s infrared telescope facility which is operated by the university of hawaii under contract nnh14ck55b with the national aeronautics and space administration program ids 2010b010 2011a010 2011b027 and iv observations obtained at the gemini observatory program ids gn 2010b dd 3 gs 2010b q 8 and gs 2011aq 11 which is operated by the association of universities for research in astronomy inc under a cooperative agreement with the nsf on behalf of the gemini partnership the national science foundation united states the national research council canada conicyt chile ministerio de ciencia tecnolog ia e innovacion productiva argentina and ministerio da ci encia tecnologia e inovac ao brazil we wish to recognise and acknowledge the very significant cultural role and reverence that the summit of mauna kea has always had within the indigenous hawaiian community we are most fortunate to have the opportunity to conduct observations from this mountain

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

record breaking storm activity on uranus in 2014 abstract in spite of an expected decline in convective activity following the 2007 equinox of uranus eight sizable storms were detected on the planet with the near infrared camera nirc2 coupled to the adaptive optics system on the 10 m w m keck telescope on ut 5 and 6 august 2014 all storms were on uranus northern hemisphere including the brightest storm ever seen in this planet at 2 2 m reflecting 30 as much light as the rest of the planet at this wavelength the storm was at a planetocentric latitude of 15 n and reached altitudes of 330 mbar well above the regular uppermost cloud layer methane ice in the atmosphere a cloud feature at a latitude of 32 n that was deeper in the atmosphere near 2 bar was later seen by amateur astronomers we also present images returned from our hst too program that shows both of these cloud features we further report the first detection of a long awaited haze over the north polar region

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

atmospheric dynamics of saturn s 2010 giant storm great white spot a rare planet encircling storm raged on saturn in 2010 2011 analyses of high resolution spacecraft imagery and numerical modelling reveal a dynamic storm head powered by sustained convection in the zonal flow of saturn s atmosphere

thermal structure and dynamics of saturn s northern springtime disturbance saturn s slow seasonal evolution was disrupted in 2010 2011 by the eruption of a bright storm in its northern spring hemisphere thermal infrared spectroscopy showed that within a month the resulting planetary scale disturbance had generated intense perturbations of atmospheric temperatures winds and composition between 20 and 50 n over an entire hemisphere 140 000 kilometers the tropospheric storm cell produced effects that penetrated hundreds of kilometers into saturn s stratosphere to the 1 millibar region stratospheric subsidence at the edges of the disturbance produced beacons of infrared emission and longitudinal temperature contrasts of 16 kelvin the disturbance substantially altered atmospheric circulation transporting material vertically over great distances modifying stratospheric zonal jets exciting wave activity and turbulence and generating a new cold anticyclonic oval in the center of the disturbance at 41 n