assessing adaptive mesh refinement amr in a forced shallow water model with moisture abstracttwo forced shallow water flow scenarios are explored in a 2d fourth order finite volume dynamical core with adaptive mesh refinement amr to investigate amr s ability to track and resolve

earth rotation from lunar laser ranging we have estimated the variation of latitude and uto from mcdonald observatory lunar laser ranging observations for the period october 1970 to october 1979 the typical formal uncertainties of our values are about 6 milliarcseconds marc sec and 0 5 milliseconds ms of time respectively we compared our values of variation of latitude with those derived from pole positions determined using classical astrometric satellite doppler and satellite laser ranging techniques for the period july 1976 to november 1978 when data from all of these techniques were available this comparison shows no evidence for significant high frequency fluctuations and in fact yields the smallest root mean square difference of 5 2 marc sec between the lunar laser ranging and the satellite doppler values after smoothing the latter with a gaussian shaped smoothing window with a full width at half maximum of about 70 days a comparison of our uto estimates with those calculated from the circular d smoothed pole position and ut1 values published by the bureau international de l heure 1979 system gives an rms difference of 1 5 ms for the entire 9 year span of the laser ranging data

prospects for an ancient dynamo and modern crustal remanent magnetism on venus abstract venus lacks an internally generated magnetic field today whether one existed in the past is unknown but critical to atmospheric evolution and potential habitability canonical models assume the core of venus is cooling too slowly for convection and thus a magnetic dynamo to occur today core mantle heat flow is suppressed in these models after a putative transition in mantle dynamics associated with widespread volcanic resurfacing however recent studies of impact craters and other surface features support more steady heat loss over geologic time precipitation of mgo and or sio2 from the core can also drive compositional convection even with slow cooling here we reevaluate the likelihood that venus has an earth like at least partially liquid and chemically homogeneous core using numerical simulations of the coupled atmosphere surface mantle core evolution an earth like core is only compatible with the modern lack of a dynamo if the thermal conductivity of core material is towards the higher end of modern estimates i e 100 w m 1 k 1 if lower estimates like 40 50 w m 1 k 1 are actually correct then we favor recent proposals that the core has completely solidified or preserved primordial stratification any simulation initialized with a homogeneous liquid core predicts a global magnetic field with earth like surface strength for 2 3 billion years after accretion consistent with all available observations and also sporadic activity within the surface age while temperatures remain below the curie point of magnetite therefore future spacecraft missions should prioritize the first ever magnetometer measurements below the ionosphere to search for crustal remanent magnetism

aquaplanet experiments using cam s variable resolution dynamical core abstracta variable resolution option has been added within the spectral element se dynamical core of the u s department of energy doe ncar community atmosphere model cam cam se allows for static refinement via conforming quadrilateral meshes on the cubed sphere this paper investigates the effect of mesh refinement in a climate model by running variable resolution var res simulations on an aquaplanet the variable resolution grid is a 2 222 km grid with a refined patch of 0 25 28 km resolution centered at the equator climatology statistics from these simulations are compared to globally uniform runs of 2 and 0 25 a significant resolution dependence exists when using the cam version 4 cam4 subgrid physical parameterization package across scales global cloud fraction decreases and equatorial precipitation increases with finer horizontal resolution resulting in drastically different climates between the uniform grid runs and a physics induced grid imprinting in the var res simulation

a balanced tropical cyclone test case for agcms with background vertical wind shear abstractthis paper presents a balanced tropical cyclone tc test case designed to improve current understanding of how atmospheric general circulation model agcm configurations affect simulated tc development and behavior it consists of an analytic initial condition comprising two independently balanced components the first provides a vortical tc seed while the second adds a planetary scale zonal flow with height dependent velocity and imposes background vertical wind shear vws on the tc seed the environmental flow satisfies the steady state hydrostatic primitive equations in spherical coordinates and is in balance with other background field variables e g temperature surface geopotential the evolution of idealized tcs in the test case framework is illustrated in 10 day simulations performed with the community atmosphere model version 5 1 1 cam 5 1 1 environmental wind profiles with different magnitudes directions and vertical inflection points are applied to ensure that the technique

an analytic vortex initialization technique for idealized tropical cyclone studies in agcms abstract the paper discusses the design of idealized tropical cyclone experiments in atmospheric general circulation models agcms the evolution of an initially weak warm core vortex is investigated over a 10 day period with varying initial conditions that include variations of the maximum wind speed and radius of maximum wind the initialization of the vortex is built upon prescribed 3d moisture pressure temperature and velocity fields that are embedded into tropical environmental conditions the initial fields are in exact hydrostatic and gradient wind balance in an axisymmetric form the formulation is then generalized to provide analytic initial conditions for an approximately balanced vortex in agcms with height based vertical coordinates an extension for global models with pressure based vertical coordinates is presented the analytic initialization technique can easily be implemented on any agcm computational grid the characteristics of the idealized tropical cyclone experiments are illustr

surface modification of venus as inferred from magellan observations of plains in sedna planitia clear stratigraphic relations can be discerned among volcanic flow units young flows exhibit sar specific cross section values similar to fresh terrestrial basalt flows whereas older flows exhibit backscatter signatures similar to degraded terrestrial basalt flows total degradation of 1 m depth over 0 6 b y is inferred for the sedna area from radar signatures impact crater abundances and ejecta superposition relations with respect to volcanic flow units analyses of parabolic ejecta deposits associated with the crater stuart imply that the material is typically centimeters in thickness a relatively small fraction 10 of venusian impact craters exhibit prominent parabolic ejecta deposits these craters are interpreted to be relatively young and parabolic deposits are interpreted to be dispersed by aeolian activity over at least tens of millions of years the inferred dispersal rate 10 3 m yr is too low to produce the degradation of flows at sedna planitia and it is concluded that the dominant flow modification process is in situ weathering in addition elevation dependent weathering is inferred in western ovda regio where plains above 6054 km radius have enhanced reflection coefficients as compared to adjacent plains at lower elevations the inferred rate of generation of high reflection coefficient materials is no more than 10 2 m yr based on the inability of aeolian activity to cover high reflectivity surfaces with normal reflection coefficient materials and the ubiquitous nature of high reflectivity surfaces at high elevations surface modification rates on venus are orders of magnitude lower than on earth venusian rates are also much lower than the inferred rate of aeolian dispersal of friable materials on mars but are comparable to the estimated rate of weathering and erosion of martian bedrock low surface modification rates imply that it will be possible to determine regional scale age variations on venus based on the degree of preservation of volcanic landforms and microwave signatures

an air sea interaction theory for tropical cyclones part ii evolutionary study using a nonhydrostatic axisymmetric numerical model abstract in part i of this study an analytical model for a steady state tropical cyclone is constructed on the assumption that boundary layer air parcels are conditionally neutral to displacements along the angular momentum surfaces of the hurricane vortex the reversible thermodynamics implied by this assumption allows the mature storm to be thought of as a simple carnot engine acquiring heat at the high temperature ocean surface and losing heat near the low temperature tropopause although the oceanic heat source is universally recognized as the sine qua non for the mature hurricane there is also wide acceptance of conditional instability of the second kind cisk which makes no specific reference to surface heat fluxes as the formative mechanism this ambivalence is seen in that all numerical simulation studies find it essential to have transfer from the ocean surface yet all start from a conditionally unstable atmosphere the hypothesis put forward in part i based on the steady state theory is t

constraints on short term mantle rheology from the j observation and the dispersion of the 18 6 y tidal love number abstract the nature of short term mantle rheology for timescales between the seismic frequency band and a few hundred years remains relatively unknown we have made use of two pieces of information which have emerged as a consequence of the recent acquisition of data from the lageos satellite to place some contraints on the rheological parameters of short term mantle rheology the first is the secular variation of the gravitational harmonic j the second is the amount of dispersion of the tidal love number for the 18 6 y tide which has been inferred to be 20 two types of rheology have been considered the first is a frequency dependent q rheology an analytical expression for the transformed shear modulus has been developed from the truncated retardation spectrum explicitly for this purpose the second anelastic rheology we have used is a standard linear solid where the parameters of importance are the relaxation strength and the short term viscosity 2 rheological parameters of the frequency dependent q model previously proposed by lambeck and nakiboglu to explain the dispersion of the tidal love number for a 18 6 y period are found to produce too much dispersion for the chandler wobble and to yield seismic q s between o 103 and o 104 for fundamental toroidal modes which are not compatible with the data we have used instead a three layer model consisting of an elastic lithosphere a mantle with a standard linear solid rheology whose debye peak lies beyond the long time cutoff of the retardation spectrum and an inviscid core for relaxation strength of around 1 and short term viscosity 2 j would result from earthquake excitation a sharp decrease of the tidal dispersion takes place for 2 5 1020 p and 1 0 for smaller values of relaxation strength 0 15 the maximum tidal dispersion is only 9 and decreases gradually as 2 is increased beyond 5 1020 p we have found that the maximum dispersion caused by the maxwell rheology is small around 5 even for asthenospheric viscosities of o 1018p these results suggest that the datum of 18 6 y tidal dispersion can be utilized eventually to place constraints on potential candidates of short term mantle rheology

volcanic degassing of argon and helium and the history of crustal production on venus we develop a new methodology linking 40ar and 4he degassing to crustal production on venus in order to examine two different scenarios for the history of magmatism on that planet both consistent with recent analyses of the cratering record of the venus surface the first scenario includes episodic global resurfacing events and modest levels of magmatism between such events while the second scenario invokes different rates of steady magmatism before and after a given transition time our degassing models include distinct mantle crustal and atmospheric reservoirs diffusive transfer of 40ar and 4he from the crust to the atmosphere is also taken into account the 40ar abundance in the present atmosphere reflects the integrated degassing and magmatism over most of planetary history in contrast helium escapes from the planetary atmosphere within a characteristic residence time of 200 myr to 1 8 gyr so the present atmospheric 4he abundance is relevant to the volume of magma produced during the last global resurfacing event and the rate of the magmatism subsequent to that event under the first scenario and to the two steady rates of magmatism and the transition time under the second unfortunately large uncertainties in mineral partition coefficients and in the ar and he mixing ratios in the lower atmosphere of venus presently prevent the use of our degassing models to distinguish among crustal formation history models we therefore explore the influence of these uncertain parameters on the degassing history in order to identify those new laboratory and in situ measurements that will most strongly constrain crustal production history as an important step in the development of the ar degassing model the k budget in the bulk silicate fraction of venus is re examined on the basis of venera and vega ray measurements of k u and th concentrations in surface materials for u and th concentrations in the bulk silicate planet of 18 29 ppb and 64 94 ppb respectively the degree of mantle melting that formed the surface materials at the venera 9 and 10 and vega 1 and 2 landing sites is calculated to lie between 0 02 and 0 16 the degree of melting calculated for materials at each landing site is combined with measurements of surface k concentration to estimate the k concentration in the bulk silicate portion of the planet at between 100 and 300 ppm these results suggest that venus and earth have similar heat production

sensitivity of equatorial convection to horizontal resolution in aquaplanet simulations with a variable resolution gcm abstract climate simulations using idealized zonally symmetric boundary conditions an aquaplanet are performed in order to highlight possible deviations from zonality introduced by the spatial variations in resolution caused by the variable resolution technique simulations at three different uniform resolutions with spectral truncations t21 t63 and t106 are used as control simulations and analyzed in order to describe the zonal climate simulated by this version of the arpege climat general circulation model and establish its sensitivity to varying spatial resolution the model simulates a single equatorial precipitation maximum in which the activity of the convective cells is modulated by westward and eastward propagating equatorial waves depending on the resolution a simulation with the variable resolution technique using a truncation t63 and a stretching factor of 3 with the maximum resolution pole placed at the equator is then compared to the uniform resolution simulations deviations from the

spectroscopic analysis of global tide gauge sea level data summary yearly and monthly tide gauge sea level data from around the globe are fitted to numerically generated tidal data to search for the 18 6 yr lunar nodal tide and 14 month pole tide both tides are clearly evident in the results with amplitudes and phases that are consistent with a global equilibrium response global atmospheric pressure data are fitted to global monthly sea level data to study the response of the ocean to pressure fluctuations the global response of sea level to pressure is found to be inverted barometer at periods greater than 2 months a large coherence at 437 days between pressure and sea level data is found for the north sea baltic sea and the gulf of bothnia the results are not entirely conclusive but they tend to support o connor s 1986 suggestion that the apparent enhanced pole tide in these basins may be due to meteorological forcing rather than to a basin scale resonance finally global averages of tide gauge data after correcting for the effects of post glacial rebound on individual station records reveal an increase in sea level over the last 80 yr of between 1 1 and 1 9 mm yr as part of the process of removing the effects of post glacial rebound we fit those effects to the global tide gauge data and obtain very good agreement with results predicted from post glacial rebound models this tends to support the post glacial model results and it suggests that the global tide gauge data are indeed capable of resolving changes in sea level at the mm yr level

using variable resolution meshes to model tropical cyclones in the community atmosphere model abstracta statically nested variable mesh option has recently been introduced into the community atmosphere model s cam s spectral element se dynamical core that has become the default in cam version 5 3 this paper presents a series of tests of increasing complexity that highlight the use of variable resolution grids in cam se to improve tropical cyclone representation by dynamically resolving storms without requiring the computational demand of a global high resolution grid as a simplified initial test a dry vortex is advected through grid transition regions in variable resolution meshes on an irrotational planet with the cam subgrid parameterization package turned off vortex structure and intensity is only affected by grid resolution and no spurious artifacts are observed cam se model simulations using an idealized tropical cyclone test case on an aquaplanet show no numerical distortion or wave reflection when the cyclone interacts with an abrupt transition region using the same test case th

polar motion and earth rotation during the period from 1979 through 1982 polar motion and earth rotation activity centered on the development of new observation techniques and the investigations of the relation between the observed motions and geophysical phenomena determinations of polar motion through classical techniques continued but the number of united states observing sites was reduced however significant advances in alternate methods for polar motion and earth rotation determination were achieved regular polar motion and length of day determinations are being reported now by groups analyzing satellite doppler laser ranging and very long baseline interferometry vlbi data and preliminary determinations of ut1 by these methods are now being reported

the 0 125 degree finite volume general circulation model on the nasa columbia supercomputer preliminary simulations of mesoscale vortices 1 the nasa columbia supercomputer was ranked second on the top500 list in november 2004 such a quantum jump in computing power provides unprecedented opportunities to conduct ultra high resolution simulations with the finite volume general circulation model fvgcm during 2004 the model was run in realtime experimentally at 0 25 degree resolution producing remarkable hurricane forecasts atlas et al 2005 in 2005 the horizontal resolution was further doubled which makes the fvgcm comparable to the first mesoscale resolving general circulation model at the earth simulator center ohfuchi et al 2004 nine 5 day 0 125 degree simulations of three hurricanes in 2004 are presented first for model validation then it is shown how the model can simulate the formation of the catalina eddies and hawaiian lee vortices which are generated by the interaction of the synoptic scale flow with surface forcing and have never been reproduced in a gcm before

chemical dieferentiation of a convecting planetary interior consequences for a one plate planet such as venus partial melting to generate the crust of a planet creates compostionally buoyant residual mantle in the absence of mantle flow associated with plate tectonics this buoyant refractory layer may collect at the top of the mantle with important implications for the evolution of the interior and surface in this study models of the thermal and chemical evolution of a planetary interior demonstrate the possible consequences of a chemically buoyant depleted mantle layer as the depleted layer thickens the melting temperature at the top of the underlying convecting mantle also increases and the degree of partial melting of mantle added to the depleted layer decreases as less depleted mantle with less positive compositional buoyancy is added negative thermal buoyancy of the layer eventually exceeds its positive compositional buoyancy the depleted layer then sinks into and mixes with the convecting interior the top of the convecting mantle then moves to a shallower depth larger degrees of melting resume and a new depleted layer accumulates this accumulation and instability of the depleted layer occurs repeatedly over a substantial portion of the planet s evolution with a period of 300 500 myr on venus the population of impacts craters is indistinguishable from a random distribution over the surface and give a surface age of about 500 myr we speculate that the mechanism described above may explain this episodic global resurfacing of venus

true polar wander abstract a re evaluation of the existence of true polar wander tpw since the late cretaceous and a comparison among the various approaches are made using updated paleomagnetic hotspot and relative motion datasets previous attempts to determine the existence of tpw had resulted in different conclusions comparison of hotspot locations and paleomagnetic poles required significant pole motion although lithospheric plate displacement analysis yielded insignificant motion however these earlier determinations cannot be directly compared to find the reason for the discrepancies because each used different datasets for this study the different approaches are applied to a single updated model with three alternative relative motions of east and west antarctica although the results are model dependent in general there was not significant motion of the pole relative to the lithosphere 1 5 since the early tertiary but a large motion 10 12 relative to the hotspot framework it is unlikely that errors in the determinations could account for this disagreement the a95 of the plate reconstruction is about 3 the uncertainty in antarctica motion is estimated to no larger than 3 and cumulative errors in the relative plate motions may also amount to 3 only if all these errors are present in the maximum estimated amount and in the same direction could they account for the 10 12 gap between the two approaches this conclusion of pole motion relative to the hotspots but not the lithosphere may indicate an independent shift of the mesosphere relative to the lithosphere or mantle roll of hargraves and duncan

long period tidal variations in the length of day a new model of long period tidal variations in length of day is developed the model comprises 80 spectral lines with periods between 18 6 years and 4 7 days and it consistently includes effects of mantle anelasticity and dynamic ocean tides for all lines the anelastic properties follow wahr and bergen experimental confirmation for their results now exists at the fortnightly period but there remains uncertainty when extrapolating to the longest periods the ocean modeling builds on recent work with the fortnightly constituent which suggests that oceanic tidal angular momentum can be reliably predicted at these periods without data assimilation this is a critical property when modeling most long period tides for which little observational data exist dynamic ocean effects are quite pronounced at shortest periods as out of phase rotation components become nearly as large as in phase components the model is tested against a 20 year time series of space geodetic measurements of length of day the current international standard model is shown to leave significant residual tidal energy and the new model is found to mostly eliminate that energy with especially large variance reduction for constituents sa ssa mf and mt

revisiting an old concept the gradient wind abstractthe gradient wind is defined as a horizontal wind having the same direction as the geostrophic wind but with a magnitude consistent with a balance of three forces the pressure gradient force the coriolis force and the centrifugal force arising from the curvature of a parcel trajectory this definition is not sufficient to establish a single way of computing the gradient wind different results arise depending upon what is taken to be the parcel trajectory and its curvature to clarify these distinctions contour and natural gradient winds are defined and subdivided into steady and nonsteady cases contour gradient winds are based only on the geostrophic streamfunction natural gradient winds are obtained using the actual wind even in cases for which the wind field is available along with the geostrophic streamfunction it may be useful to obtain the gradient wind for comparison to the existing analyzed or forecast wind or as a force balanced reference state it is shown that the nonanomalous

solubility of water in magmas to 2 kbar high water concentrations 4 6 wt are found in the quenched glass inclusions of phenocrysts of explosive silicic and intermediate eruptions accordingly we have measured the solubility of water in a wide range of natural liquids up to 2 kbar with data from the literature we have developed a simple thermodynamically based empirical model for the solubility of water as a function of temperature 700 1200 c pressure 1 2000 bar and composition the model works well for both pure h 2 o and mixed fluid compositions fits the data to 0 5 wt 2 and may be used to successfully model the degassing and eruption behavior in most volcanic systems as well as the magmatic exsolution processes that lead to ore deposition due to the nature of the regression however it should not be extrapolated to conditions beyond the range of the data

station coordinates baselines and earth rotation from lageos laser ranging 1976 1984 satellite laser range slr measurements to lageos from may 1976 to january 1984 have been used to compute earth rotation parameters and the geocentric positions of 57 laser tracking station sites occupied during this interval the station position determinations were part of a simultaneous solution which includes lageos orbit elements in 15 day arcs and earth rotation parameters in 3 day subarcs using residuals from a 7 7 year lageos long arc lla 8402 systematic differences between the terrestrial reference frames implied by the university of texas station coordinate solution lsc 8402 and by previous solutions computed at the university of texas ut and at goddard space flight center gsfc are reviewed the new solution resolves a 0 72 m z axis difference between the terrestrial reference system origins inferred from the gsfc solution sl5 and the previous ut solution lsc 8112 the implied origins of the lsc 8402 solution and the sl5 solution are consistent to less than 60 mm in all components and after removing orientation and scale differences the coordinates for 26 common tracking stations have an rms difference of less than 80 mm the rms difference in baseline length for 22 station pairs used in the recent crustal dynamics project very long baseline interferometry vlbi slr intercomparison experiment is 50 mm between the gsfc and ut laser solutions and 40 mm between the ut laser solution and the vlbi solution the earth rotation parameters computed in 3 day intervals have an internal precision of 2 marc sec 62 mm at the earth s surface for xp and yp and 0 15 ms 70 mm at the equator for ut1 the estimated accuracy of the series based on dual baseline vlbi intercomparisons is approximately 2 marc sec for xp and yp and 0 2 ms for ut1 the effects of plate motion on the determination of the secular drift in polar motion using the 7 7 year series is shown to be at the level of 1 marc sec yr finally baseline changes have been investigated by repeated station coordinate determinations using 60 day subsets of the 7 7 year interval of the lageos data set in each 60 day solution interval orbit elements were estimated at 15 day intervals and earth rotation parameters were determined at 5 day intervals for the 4 year period beginning in january 1980 baseline length changes inferred by the successive 60 day solutions were found to be in general agreement with the motions predicted by the am1 2 plate motion model of minster and jordan

the period and q of the chandler wobble summary we have extended our calculation of the theoretical period of the chandler wobble to account for the non hydrostatic portion of the earth s equatorial bulge and the effect of the fluid core upon the lengthening of the period due to the pole tide we find the theoretical period of a realistic perfectly elastic earth with an equilibrium pole tide to be 426 7 sidereal days which is 8 5 day shorter than the observed period of 435 2 day using rayleigh s principle for a rotating earth we exploit this discrepancy together with the observed chandler q to place constraints on the frequency dependence of mantle anelasticity if q in the mantle varies with frequency u as u between 30 s and 14 months and if q in the lower mantle is of order 225 at 30 s we find that 0 04 5 a 5 0 1 1 if instead q in the lower mantle is of order 350 near 200 s we find that 0 11 5 a 0 19 in all cases these limits arise from exceeding the 68 per cent confidence limits of 2 6 day in the observed period since slight departures from an equilibrium pole tide affect the q much more strongly than the period we believe these limits to be robust

atmosphere mantle coupling and feedbacks on venus we investigate the coupled evolution of the atmosphere and mantle on venus here we focus on mechanisms that deplete or replenish the atmosphere atmospheric escape to space and volcanic degassing of the mantle these processes are linked to obtain a coupled model of mantle convection and atmospheric evolution including feedback of the atmosphere on the mantle via the surface temperature during early atmospheric evolution hydrodynamic escape is dominant while for later evolution we focus on nonthermal escape as observed by the analyzer of space plasma and energetic atoms instrument on the venus express mission the atmosphere is replenished by volcanic degassing from the mantle using mantle convection simulations based on those of armann and tackley 2012 and include episodic lithospheric overturn the evolving surface temperature is calculated from the amount of co2 and water in the atmosphere using a gray radiative convective atmosphere model this surface temperature in turn acts as a boundary condition for the mantle convection model we obtain a venus like behavior episodic lid for the solid planet and an atmospheric evolution leading to the present conditions co2 pressure is unlikely to vary much over the history of the planet with only a 0 25 20 postmagma ocean buildup in contrast atmospheric water vapor pressure is strongly sensitive to volcanic activity leading to variations in surface temperatures of up to 200 k which have an effect on volcanic activity and mantle convection low surface temperatures trigger a mobile lid regime that stops once surface temperatures rise again making way to stagnant lid convection that insulates the mantle

deep submarine pyroclastic eruptions theory and predicted landforms and deposits submarine pyroclastic eruptions at depths greater than a few hundred meters are generally considered to be rare or absent because the pressure of the overlying water column is sufficient to suppress juvenile gas exsolution so that magmatic disruption and pyroclastic activity do not occur consideration of detailed models of the ascent and eruption of magma in a range of sea floor environments shows however that significant pyroclastic activity can occur even at depths in excess of 3000 m in order to document and illustrate the full range of submarine eruption styles we model several possible scenarios for the ascent and eruption of magma feeding submarine eruptions 1 no gas exsolution 2 gas exsolution but no magma disruption 3 gas exsolution magma disruption and hawaiian style fountaining 4 volatile content builds up in the magma reservoir leading to hawaiian eruptions resulting from foam collapse 5 magma volatile content insufficient to cause fragmentation normally but low rise speed results in strombolian activity and 6 volatile content builds up in the top of a dike leading to vulcanian eruptions we also examine the role of bulk interaction steam explosivity and contact surface steam explosivity as processes contributing to volcaniclastic formation in these environments we concur with most earlier workers that for magma compositions typical of spreading centers and their vicinities the most likely circumstance is the quiet effusion of magma with minor gas exsolution and the production of somewhat vesicular pillow lavas or sheet flows depending on effusion rate the amounts by which magma would overshoot the vent in these types of eruptions would be insufficient to cause any magma disruption the most likely mechanism of production of pyroclastic deposits in this environment is strombolian activity due to the localized concentration of volatiles in magma that has a low rise rate magmatic gas collects by bubble coalescence and ascends in large isolated bubbles which disrupt the magma surface in the vent producing localized blocks bombs and pyroclastic deposits another possible mode of occurrence of pyroclastic deposits results from vulcanian eruptions these deposits being characterized by the dominance of angular blocks of country rocks deposited in the vicinity of a crater should be easily distinguishable from strombolian and hawaiian eruptions however we stress that a special case of the hawaiian eruption style is likely to occur in the submarine environment if magmatic gas buildup occurs in a magma reservoir by the upward drift of gas bubbles in this case a layer of foam will build up at the top of the reservoir in a sufficient concentration to exceed the volatile content necessary for disruption and hawaiian style activity the deposits and landforms are predicted to be somewhat different from those of a typical primary magmatic volatile induced hawaiian eruption specifically typical pyroclast sizes might be smaller fountain heights may exceed those expected for the purely magmatic hawaiian case cooling of descending pyroclasts would be more efficient leading to different types of proximal deposits and runout distances for density flows would be greater potentially leading to submarine pyroclastic deposits surrounding vents out to distances of tens of meters to a kilometer in addition flows emerging after the evacuation of the foam layer would tend to be very depleted in volatiles and thus extremely poor in vesicles relative to typical flows associated with hawaiian style eruptions in the primary magmatic gas case we examine several cases of reported submarine volcaniclastic deposits found at depths as great as 3000 m and conclude that submarine hawaiian and strombolian eruptions are much more common than previously suspected at mid ocean ridges furthermore the latter stages of development of volcanic edifices seamounts formed in submarine environments are excellent candidates for a wide range of submarine pyroclastic activity due not just to the effects of decreasing water depth but also to 1 the presence of a summit magma reservoir which favors the buildup of magmatic foams enhancing hawaiian style activity and episodic dike emplacement which favors strombolian style eruptions and 2 the common occurrence of alkalic basalts the co2 contents of which favor submarine explosive eruptions at depths greater than tholeiitic basalts these models and predictions can be tested with future sampling and analysis programs and we provide a checklist of key observations to help distinguish among the eruption styles

excitation of the earth s polar motion a reassessment with new data a comparison of a revised ils polar motion series for the years 1901 to 1970 with an atmospheric time series shows evidence for coherence near the period of the 14 month chandler motion the same ils series and two other bih series have also been used to compute shifts in the apparent pole position near the times of the 1960 chilean and 1964 alaskan earthquakes these shifts are not convincingly similar to those predicted by other investigators from earthquake source parameters in addition there is disagreement among the shifts computed from the various polar motion data sets thus a conclusive determination of the relative roles of atmospheric earthquake and other sources in the excitation of polar motion will probably require improved observations of both the proposed excitation phenomena and the earth s polar motion

magnetic petrology of the 1991 1995 dacite lava of unzen volcano japan degree of oxidation and implications for the growth of lava domes abstract to understand the oxidation state and process of oxidation of lava domes we carried out magnetic petrological analyses of lava samples obtained from domes and block and ash flow deposits associated with the 1991 1995 eruption of unzen volcano japan as a result we recognize three different types of magnetic petrology each related to deuteric high temperature oxidation during initial cooling type a oxides are characterized by homogenous titanomagnetite and titanohematite indicating a low oxidation state and high titanomagnetite concentrations type b oxides are weakly exsolved and contain titanohematite laths and rutile lenses indicating a higher oxidation state type c oxides which represent the highest oxidation state are completely exsolved and composed of ti poor titanomagnetite titanohematite rutile and pseudobrookite indicating high hematite concentrations some grains in types a and b show indications of reduction which was related to interaction with volcanic gases subsequent to high temperature oxidation in terms of geological occurrence the oxidation processes probably differed for endogenous and exogenous domes endogenous dome lavas are oxidized concentrically and are classified into the three types according to their location within the dome samples from the surface are strongly oxidized and classified as type c while the inner part is unoxidized and classified as type a exogenous dome lavas are unoxidized and assigned to type a some samples show signs of reduction which may have occurred around fumaroles we propose that location within the dome and the process of dome growth are the factors that control oxidation

a consistent picture of early hydrodynamic escape of venus atmosphere explaining present ne and ar isotopic ratios and low oxygen atmospheric content abstract a time dependent model of hydrogen hydrodynamic escape powered by solar euv flux and solar wind and accounting for oxygen frictional escape has been implemented in primitive venus conditions the model is constrained by the present 20 ne 22 ne and 36 ar 38 ar ratios in venus atmosphere it suggests that the net total amount of water delivered to the planet during accretion 10 100 myr is not in excess of the content of 5 terrestrial oceans 5 to in our preferred scenario 60 of the oxygen 3 to is left behind the hydrogen during the first 100 myr from a comparison with earth s case we suggest that hydrodynamic escape has dried up venus atmosphere early in its history 70 myr triggering the crystallization of the magma ocean and leaving no available water in the atmosphere to condense out and form an earth size water ocean on the contrary earth possibly endowed with more water and subject to a weaker hydrodynamic escape would have remained wet after the crystallization of its magma ocean we suggest that the oxygen left behind the escaping hydrogen during the main hydrodynamic phase on venus has been dissolved in the magma ocean and lost through oxidation in the proposed scenario the dense venus co 2 atmosphere doesn t result from an initial episode of runaway or moist greenhouse but has been formed during the crystallization of the magma ocean by progressive exsolution of carbon dioxide at a time when the atmospheric partial pressure of water was of a few hundred bar in the subsequent period from 100 to 500 myr the hydrogen of the water delivered by comets may have been removed by continuing thermal escape resulting at 500 myr in a water global equivalent layer gel of a few meters depth or less probably under the form of water vapor in the atmosphere and a molecular oxygen atmosphere of 10 bar or so at later times pick up ion escape may have removed most of the remaining water and led to the present d h atmospheric enhancement factor of 150 the 10 bar of oxygen may have been absorbed by crustal oxidation

the rotation of the ocean solid earth system it is shown that the long period highly elliptical markowitz wobble can be viewed as a natural wobble of the coupled mantle ocean system from a rotational point of view oceanic wobble is possible even if the oceans respond in an equilibrium manner to wobble because the oceans are nonglobal and a thin layer either of the latter conditions or an oceanic response which is nonequilibrium can maintain the separation of rotation and figure axes constituting wobble characteristics of the uncoupled bodies are first determined the inertia tensor of the oceans yields an oceanic body whose free wobble is retrograde and short period under the assumption of an equilibrium fluid response it also yields an oceanless earth whose precessional constant more nearly equals the hydrostatic rather than the observed whole earth value the equations governing wobbles of a coupled two body system rigid or deformable are developed and referred to the same wobbling coordinate system solutions are found for various general types of coupling for a deformable system the retrograde character of the free oceanic wobble leads to coupled motions which are at best undamped and at worst unstably damped those types of coupling which avoid unstable rotational behavior and also generate one wobble mode with the characteristics of the chandler wobble predict a second wobble mode with the period and retrograde or marginally prograde sense of the markowitz wobble since those couples are nondissipative attenuation of the wobbles is presumably achieved by a combination of shallow sea interactions and internal friction within mantle and oceans some of the amplitude characteristics predicted for the wobble modes fail to match observations adequately resolution of these disparities within the coupled system framework may enhance our understanding of wobble excitation and the open ocean pole tide

tidal variations of earth rotation we have rederived the periodic variations of the earth s rotation due to the tidal deformation of the earth by the sun and moon and included all terms with amplitudes 0 002 milliseconds 1 mm this series applies to the mantle plus crust and oceans which rotate together for characteristic tidal periods the parameter which scales the rotational series is k c where k is that fraction of the love number which causes the tidal variation in the moment of inertia of the coupled mantle and oceans while c is the dimensionless polar moment of inertia of the coupled units if the whole earth minus oceans were coupled rotationally then k 0 30 and c 0 33 ocean tides increase k by 0 04 decoupling of the fluid core from the mantle decreases k by 0 06 while c cmantle 0 29 since neither pressure viscous nor hydromagnetic coupling locks the fluid to the mantle for periods less than 5 to 25 years from the analysis of lunar laser ranging data we find that k c at monthly and fortnightly frequencies equals 0 99 0 15 and 0 99 0 20 as compared with a theoretical value of 0 94 0 04 in addition we have estimated theoretically the effects of ocean tides on earth rotation nutation and polar motion using models based on the laplace tidal equations

the rotation of the earth studies of the earth s rotation provide one of the best means of probing the interactions of the atmosphere oceans and solid earth as well as the structure of the core and mantle since the last report of the u s national report to the iugg tapley 1983 two developments have led to significant improvement in the measurement of the rotation the upgrading of the laser network of the national aeronautics and space administration nasa and the expansion of vlbi observations coordinated by the national geodetic survey ngs with the support of nasa and the u s naval observatory both of these developments have been complemented by strong contributions from other countries the availability of more accurate measurements together with healthy research support in this field by federal agencies has also created a ripe environment for progress in theoretical studies of the rotation

impact of physical parameterizations on idealized tropical cyclones in the community atmosphere model 1 this paper explores the impact of the physical parameterization suite on the evolution of an idealized tropical cyclone within the national center for atmospheric research s ncar community atmosphere model cam the cam versions 3 1 and 4 are used to study the development of an initially weak vortex in an idealized environment over a 10 day simulation period within an aqua planet setup the main distinction between cam 3 1 and cam 4 lies within the physical parameterization of deep convection cam 4 now includes a dilute plume convective available potential energy cape calculation and convective momentum transport cmt the finite volume dynamical core with 26 vertical levels in aqua planet mode is used at horizontal grid spacings of 1 0 0 5 and 0 25 it is revealed that cam 4 produces stronger and larger tropical cyclones by day 10 at all resolutions with a much earlier onset of intensification when compared to cam 3 1 at the highest resolution cam 4 also accounts for changes in the storm s vertical structure such as an increased outward slope of the wind contours with height when compared to cam 3 1 an investigation concludes that the new dilute cape calculation in cam 4 is largely responsible for the changes observed in the development strength and structure ofthetropicalcyclone citation reed k a andc jablonowski 2011 impact of physical parameterizations on idealized tropical cyclonesinthecommunityatmospheremodel geophys res lett

effect of a single large impact on the coupled atmosphere interior evolution of venus abstract we investigate the effect of a single large impact either during the late veneer or late heavy bombardment on the evolution of the mantle and atmosphere of venus we use a coupled interior exterior numerical code based on stagyy developed in gillmann and tackley gillmann c tackley p j 2014 j geophys res 119 1189 1217 single vertical impacts are simulated as instantaneous events affecting both the atmosphere and mantle of the planet by i eroding the atmosphere causing atmospheric escape and ii depositing energy in the crust and mantle of the planet the main impactor parameters include timing size mass velocity and efficiency of energy deposition we observe that impact erosion of the atmosphere is a minor effect compared to melting and degassing triggered by energy deposition in the mantle and crust we are able to produce viable pathways that are consistent with present day venus especially considering large late veneer impacts small collisions

venus a thick basal magma ocean may exist today basal magma oceans develop in earth and venus after accretion as their mantles solidify from the middle outwards fractional crystallization of the basal mantle is buffered by the core and radiogen