detection of migrating diurnal tide in the tropical upper troposphere and lower stratosphere using the challenging minisatellite payload radio occultation data 1 the atmospheric limb sounding technique making use of radio signals transmitted by the global positioning system gps has already proven to be a promising approach for global atmospheric measurements in this study we assess for the first time the potential of gps radio occultation soundings for detecting the migrating diurnal tide retrieved temperatures between 10 and 30 km in the tropics from the challenging minisatellite payload champ occultation observations during may 2001 to august 2005 are analyzed using space time spectrum analysis to isolate diurnal waves because of incomplete local time lt coverage of the monthly champ occultation data in any given year data from all available years are merged to obtain complete 24 h lt coverage the effects of aliasing associated with uneven data sampling and measurement noise are estimated using synthetic data the results show the feasibility of determining tidal structures from the composite champ occultation data and the vertical seasonal and latitudinal structures of the diurnal tide are presented the estimated diurnal amplitude generally increases with altitude exhibiting a maximum of order 1 k at 30 km the estimated phase indicates an upward propagating mode above 14 km with a vertical wavelength about 20 km the observed diurnal tide at 30 km exhibits a distinct seasonallatitudinal variation comparison of the observed diurnal tide to the simulated tide in the extended canadian middle atmosphere model cmam and global scale wave model version 2 gswm02 indicates that cmam overestimates the amplitude but reproduces the seasonal latitudinal variation of the diurnal tide while gswm02 simulates well the annual mean amplitude but lacks the seasonal latitudinal variation of the diurnal tide

morphological development of basin scale silica diagenetic fronts revealed with 2d seismic reflection data offshore sakhalin russian far east two dimensional 2d seismic reflection data reveal two silica diagenetic boundaries located in the north sakhalin basin offshore sakhalin island these boundaries form distinctive high amplitude seismic reflections that predominantly cross cut miocene stratigraphy the boundaries represent the opal a to opal ct cristobalite and tridymite transition and the subsequent deeper opal ct to quartz transition and cover an area of c 107 000 km 2 the reflections represent diagenetic reaction fronts that advance through silica rich host sediments during burial the oldest strata within which the diagenetic fronts have been identified are of miocene age and the fronts commonly show a parallel relationship to a late miocene unconformity these diagenetic fronts develop a variety of morphological forms in the north sakhalin basin these front geometries are probably the result of the interference of the diagenetic fronts with inclined and folded stratigraphy together with lateral changes in the composition and therefore depth of transformation of the sediment we define criteria for the recognition of these 2d cross sectional morphological elements and by so doing provide the basis for the objective description and categorization of diagenetic front geometry

shear wave logging with dipole sources laboratory measurements have verified a novel technique for direct shear wave logging in hard and soft formations with a dipole source as recently suggested in theoretical studies conventional monopole logging tools are not capable of measuring shear waves directly in particular no s waves are recorded in a soft formation with a conventional monopole sonic tool because there are no critically refracted s rays when the s wave velocity of the rock is less than the acoustic velocity of the borehole fluid the present studies were conducted in the laboratory with scale models representative of sonic logging conditions in the field we have used a concrete model to represent hard formations and a plastic model to simulate a soft formation the dipole source operating at frequencies lower than those conventionally used in logging substantially suppressed the p wave and excited a wave train whose first arrival traveled at the s wave velocity as a result one can use a dipole source to log s wave velocity

acoustic and elastic properties of calcareous sediments across a siliceous diagenetic front on the eastern u s continental slope the ocean drilling program drilled hole 904a on the upper continental slope offshore new jersey through 230 m of eocene chalks and an opal a opal ct diagenetic front in addition to a suite of standard logging tools a dipole sonic tool was deployed to determine the in situ shear sonic velocity and the elastic properties of these slow highly porous sediments while porosity decreases by 20 across the diagenetic front the compressional velocity and the density are observed to increase by 30 the shear sonic velocity and the bulk modulus by about 60 and the shear modulus by almost 300 it is shown that shear and compressional velocities are both controlled by porosity and consolidation and that existing models for the prediction of elastic properties and shear velocity from standard logs are still valid through the diagenetic front the strong effect of diagenesis on rigidity makes the shear velocity log a highly sensitive indicator of pore shape and pore filling transformations

evaluation and prediction of shear wave velocities in calcareous marine sediment and rocks shear wave velocities from full waveform acoustic logs recorded in calcareous oozes and chalks were determined using the spectral ratio inversion method data were recorded during dsdp leg 95 drilling off the east coast of the united states dsdp site 613 sampled a progression of carbonaceous siliceous oozes through partially lithified chalk discrete shear wave velocities within a 350 meter interval were calculated the results of a method for predicting shear wave velocities using wood s equation correlate well with inversion results at shear wave velocities greater than 800 m sec predictions using wood s equation provide a theoretical maximum value for shear wave velocity to compare with inversion results inverted data fall just below the predicted theoretical maximum value from wood s equation and agree quite well with trends in wood s results and other related logging measurements at slower shear wave velocities the physical contrast between borehole fluid drilling mud and the formation ooze is not enough to excite normal borehole modes used in inversion processing resulting in inversion velocities greater than wood s maximum

large potential energy of gravity waves over a smooth surface with little convection simulation and observation 1 a numerical experiment is conducted using an atmospheric general circulation model agcm to investigate the presence of the large potential energy over a region of low topography and little convective activity focusing on the tropical atlantic region 10 e to 20 w 0 to 20 s it is found that gravity waves with a time period of 24 hours are excited near the equator 5 15 n in a region of large moist heating extending vertically up to 10 13 km the gravity waves propagate upward from this region with a bias toward the south and are manifested as large energy fluxes in the cross equatorial region enhanced energy fluxes are therefore simulated at 20 30 km altitude over a region with no significant source of gravity waves and are confirmed using global positioning satellite meteorology gps met experiment data

transport and mixing in the extratropical tropopause region in a high vertical resolution gcm part i potential vorticity and heat budget analysis abstract a high vertical resolution general circulation model gcm output has been analyzed to clarify transport and mixing processes in the extratropical tropopause region the high resolution gcm with a vertical resolution of about 300 m above the extratropical upper troposphere allows simulation of fine atmospheric structures near the tropopause such as the extratropical tropopause transition layer extl and the tropopause inversion layer til the high resolution gcm realistically simulates fine thermal and dynamic structures in the extratropical tropopause region the thickness and maximum stability of the simulated til are consistent with observations the high resolution output was analyzed using a zonal mean potential vorticity pv equation to identify dominant transport processes in the extratropical tropopause region in the northern hemisphere extratropics during winter mean downward advection sharpens the pv gradient between the tropopause and 20 k below it whereas latitudinal variati

characterization of in situ elastic properties of gas hydrate bearing sediments on the blake ridge during ocean drilling program leg 164 shear sonic velocity and other geophysical logs were acquired in gas hydrate bearing sediments on the blake ridge to characterize the very distinct seismic signature of such formations anomalous low amplitudes overlying a strong bottom simulating reflector bsr a comparison of the bulk moduli derived from the logs to standard elastic consolidation models shows that the sediments are overconsolidated above the bsr at 440 meters below seafloor mbsf because of the presence of hydrates below the bottom of the thermodynamic hydrate stability zone at 520 mbsf the high compressibility of the formation and the attenuation of the monopole sonic waveforms are typical of sediments partially saturated with free gas between these two depths gas hydrate and free gas seem to coexist within the gas hydrate stability zone we estimate the amount of gas hydrates using different models based on theories for wave scattering in multiphase media and for grain cementation in close agreement with measurements made on discrete in situ samples the latter describes most accurately the interactions between the matrix the pore fluids and the hydrates this model indicates that 5 to 10 of the pore space is occupied by hydrates deposited uniformly on the surface of the grains the comparison with gassmann s model also show that the amount of free gas below the bsr never exceeds 5 of the pore space but is high enough to generate the bsr the coexistence of free gas and gas hydrates below the bsr may be explained by capillary effects in the smaller pores or by remaining crystalline structures after partial hydrate decomposition

simulation of the eastward 4 day wave in the antarctic winter mesosphere using a gravity wave resolving general circulation model 1 the eastward moving 4 day wave in the antarctic winter mesosphere is investigated using a high resolution middle atmosphere general circulation model that directly simulates the spontaneous generation propagation and dissipation of gravity waves the results are also compared with the simulated seasonal march of the meridional structures of the westerly jet streams in the southern hemisphere upper stratosphere and mesosphere in order to investigate baroclinic barotropic instability as a possible excitation mechanism for the 4 day wave the model successfully reproduces the dynamically unstable double jet structure of the mesospheric westerly winds the simulated 4 day wave develops in association with the baroclinic and barotropic instability of the mesospheric mean flows and has similar characteristics to those observed at 50 60 s near the stratopause the 4 day wave has strong equatorward heat flux associated with strong baroclinicity in the antarctic winter mesosphere mainly attributable to poleward overturning circulation driven by gravity wave forcing eastward forcing due to the 4 day wave occurs within the double jet structure and offsets part of the westward forcing due to gravity waves such an effect partially acts to stabilize the unstable mean flow structure in the antarctic winter mesosphere

gravity wave characteristics in the southern hemisphere revealed by a high resolution middle atmosphere general circulation model abstractgravity wave characteristics in the middle to high latitude southern hemisphere are analyzed using simulation data over 3 yr from a high resolution middle atmosphere general circulation model without using any gravity wave parameterizations gravity waves have large amplitudes in winter and are mainly distributed in the region surrounding the polar vortex in the middle and upper stratosphere while the gravity wave energy is generally weak in summer the wave energy distribution in winter is not zonally uniform but it is large leeward of the southern andes and antarctic peninsula linear theory in the three dimensional framework indicates that orographic gravity waves are advected leeward significantly by the mean wind component perpendicular to the wavenumber vector results of ray tracing and cross correlation analyses are consistent with this theoretical expectation the leeward energy propagation extends to several thousand kilometers which explains part of the gravity wave distribution aro

general aspects of a t213l256 middle atmosphere general circulation model 1 a high resolution middle atmosphere general circulation model gcm developed for studying small scale atmospheric processes is presented and the general features of the model are discussed the gcm has t213 spectral horizontal resolution and 256 vertical levels extending from the surface to a height of 85 km with a uniform vertical spacing of 300 m gravity waves gws are spontaneously generated by convection topography instability and adjustment processes in the model and the gcm reproduces realistic general circulation in the extratropical stratosphere and mesosphere the oscillations similar to the stratopause semiannual oscillation and the quasi biennial oscillation qbo in the equatorial lower stratosphere are also spontaneously generated in the gcm although the period of the qbo like oscillation is short 15 months the relative roles of planetary waves large scale gws and small scale gws in maintenance of the meridional structures of the zonal wind jets in the middle atmosphere are evaluated by calculating eliassen palm diagnostics separately for each of these three groups of waves small scale gws are found to cause deceleration of the wintertime polar night jet and the summertime easterly jet in the mesosphere while extratropical planetary waves primarily cause deceleration of the polar night jet below a height of approximately 60 km the meridional distribution and propagation of small scale gws are shown to affect the shape of the upper part of mesospheric jets the phase structures of orographic gws over the south andes and gws emitted from the tropospheric jet stream are discussed as examples of realistic gws reproduced by the t213l256 gcm

fossilisation of a silica diagenesis reaction front on the mid norwegian margin the diagenetic transformation of biogenic silica from opal a to opal ct was recognised on seismic reflection data over an area of 78 103 km2 on the mid norwegian margin the opal a ct diagenetic boundary appears as a positive high amplitude reflection that generally cross cuts the hosting stratigraphy we demonstrate that it is not a sea bottom simulating reflection bsr and also that is not in thermal equilibrium with the present day isotherms we present arguments that three styles of deformation associated with the opal a ct reflection polygonal faulting regional anticlines and synclines and differential compaction folding indicate that the silica diagenesis reaction front is fossilised at a regional scale isochore maps demonstrate the degree of conformity between the opal a ct reflection and three seismic horizons of late miocene to early pliocene age that potentially represent the paleo seabed when fossilisation of the reaction front took place the seismic interpretational criteria for recognition of a fossilised diagenetic front are evaluated and the results of our study are integrated with previous studies from other basins of the ne atlantic in order to determine if the arrest of silica diagenesis was diachronous along this continental margin

tidal variability in the ionospheric dynamo region 1 the seasonal and interannual variability of migrating sun synchronous and nonmigrating solar atmospheric tides at altitudes between 100 and 116 km are investigated using temperature measurements made with the saber instrument on the timed spacecraft during 2002 2006 quasi biennial variations of order 10 15 in migrating diurnal and semidiurnal tidal amplitudes are found presumably due to modulation by the quasi biennial oscillation qbo as the tides propagate from their troposphere and stratospheric sources to the lower thermosphere a number of nonmigrating tidal components are found that have the potential to produce significant longitudinal variability of the total tidal fields the most prominent of these i e those that appear at amplitudes of order 5 10 k in a 5 year mean climatology include the zonally symmetric s 0 diurnal tide d0 the eastward propagating diurnal and semidiurnal tides with zonal wave numbers s 2 de2 and se2 and s 3 de3 and se3 and the following westward propagating waves diurnal s 2 dw2 semidiurnal s 1 sw1 s 3 sw3 and s 4 sw4 and terdiurnal s 5 tw5 these waves can be plausibly accounted for by nonlinear interaction between migrating tidal components and stationary planetary waves with s 1 or s 2 or by longitudinal variations of tropospheric thermal forcing additional waves that occur during some years or undergo phase cancellation within construction of a 5 year climatology include dw5 se1 se4 sw6 te1 tw1 and tw7 it is anticipated that the winds that accompany all of these waves in the 100 170 km region will impose longitudinal variability in the electric fields produced through the ionospheric dynamo mechanism thereby modulating vertical motion of the equatorial ionosphere and the concomitant plasma densities in addition to the wave 4 modulation of the equatorial ionosphere that has recently been discovered and replicated in modeling studies the waves revealed here will generate wave 1 sw1 sw3 d0 dw2 wave 2 sw4 tw1 wave 3 de2 se1 wave 4 de3 se2 dw5 sw6 te1 tw7 wave 5 se3 and wave 6 se4 components of this ionospheric variability depending on year and time of year however the absolute and relative efficiencies with which these waves produce electric fields remains to be determined

effect of depth dependent shear modulus on tsunami generation along subduction zones estimates of the initial size of tsunamis generated by subduction zone earthquakes are significantly affected by the choice of shear modulus at shallow depths analysis of over 360 circum pacific subduction zone earthquakes indicates that for a given seismic moment source duration increases significantly with decreasing depth bilek and lay 1998 1999 under the assumption that stress drop is constant the increase of source duration is explained by a 5 fold reduction of shear modulus from depths of 20 km to 5 km this much lower value of shear modulus at shallow depths in comparison to standard earth models has the effect of increasing the amount of slip estimated from seismic moment determinations thereby increasing tsunami amplitude the effect of using depth dependent shear modulus values is tested by modeling the tsunami from the 1992 nicaraguan tsunami earthquake using a previously determined moment distribution ihmle 1996a we find that the tide gauge record of this tsunami is well matched by synthetics created using the depth dependent shear modulus and moment distribution because excitation of seismic waves also depends on elastic heterogeneity it is important particularly for the inversion of short period waves that a consistent seismic tsunami shear modulus model be used for calculating slip distributions

on the origins of mesospheric gravity waves 1 using hourly data from a three year simulation based on a gravity wave resolving general circulation model we have first inferred a global view of gravity wave sources and propagation affecting significantly the momentum balance in the mesosphere the meridional cross section of momentum fluxes suggests that there are a few dominant propagation paths originating from the subtropics in summer and the middle to high latitudes in winter these gravity waves are focused into the mesospheric jets in their respective seasons acting effectively to decelerate the jets the difference in the source latitudes likely contributes to the hemispheric asymmetries of the jets the horizontal distribution of the momentum fluxes indicates that the dominant sources are steep mountains and tropospheric westerly jets in winter and vigorous monsoon convection in summer the monsoon regions are the most important window to the middle atmosphere in summer because of the easterlies associated with the monsoon circulation

deep ocean paleo seafloor erosion in the northwestern pacific identified by high resolution seismic images abstract the deposition and diagenesis of pelagic marine sediments together play important roles in global geochemical cycles by returning elements such as silica from the hydrosphere to the geosphere and stably sequestering them within deep ocean sedimentary sections around the world here we present new high resolution vertical resolution 2 5 m seismic reflection data from the northwestern pacific that we interpret to indicate a period of erosional activity that has returned silica to the hydrosphere and thus represents a departure from uniform sequestration by pelagic sediment deposition the interpreted erosional features are observed as a 200 to 300 m wide horizontal variation in reflection character within the 20 m interval overlying the regional chert porcellanite layer this reflection character variation is not consistent with uniform pelagic sedimentation and it has not previously been noted in the northwestern pacific where most seismic data are lower resolution erosion of seafloor sediments may have been caused by bottom current activity but the geometry of the observed features suggests that fluid expulsion erosion from diagenesis of primarily siliceous sediment played some role in driving this mass transfer this period of erosional activity occurred after this portion of the pacific plate left the equatorial zone of high biological productivity 75 ma and ended between approximately 35 and 55 ma regardless of the details of the process erosion of deep ocean seafloor sediments represents a return of silica and other chemicals from the sediment to the bottom water and if pervasive in the oceans these processes should be accounted for in models of global geochemical cycles

connections between deep tropical clouds and the earth s ionosphere 1 we report on a series of simulations with the national center for atmospheric research ncar thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm which were designed to replicate and facilitate the interpretation of the longitudinal structure discovered in image satellite airglow observations of the equatorial ionization anomaly eia at the far ultraviolet fuv 135 6 nm wavelength during march april 2002 equinox our time gcm results indicate that the four peaked longitudinal variation in the eia observed by image fuv near 20 00 local solar time can be explained by the effects of an eastward propagating zonal wavenumber 3 diurnal tide de3 that is excited by latent heat release associated with raindrop formation in the tropical troposphere

porosity reduction during diagenesis of diatomaceous rocks with lithification and burial diatomaceous rock transforms from opal a to opal ct and then quartz this study documents two different patterns of porosity reduction and their associated mineralogical and density changes using samples from the monterey formation california samples that have one set of properties are called group 1 and those showing other trends are assigned to group 2

solar tides as revealed by measurements of mesosphere temperature by the mls experiment on uars abstract temperatures between 25 and 86 km measured by the microwave limb sounder mls experiment on the upper atmosphere research satellite uars are analyzed to delineate diurnal semidiurnal and terdiurnal tidal structures and stationary planetary waves these fourier components are determined from temperatures averaged in bins covering 5 latitude 30 longitude and 1 h in local time this study confirms the presence of diurnal nonmigrating tides with zonal wavenumbers s 0 2 3 s 0 s 0 implying westward eastward propagation and semidiurnal tides with s 1 and 3 and some components of lesser importance that were previously determined from uars wind measurements near 95 km the seasonal latitudinal and height structures of these components are now revealed and utilized to aid in interpreting their behaviors and ascertaining their origins new discoveries include the terdiurnal s 2 and s 4 components and trapped nonmigrating diurnal tides with s 0 and s 2 the former are like

global distribution of atmospheric waves in the equatorial upper troposphere and lower stratosphere agcm simulation of sources and propagation 1 the global distribution sources and propagation of atmospheric waves in the equatorial upper troposphere and lower stratosphere were investigated using an atmospheric general circulation model with t106l60 resolution 120 km horizontal and 550 m vertical resolution the quasibiennial oscillation qbo with a period of 1 5 2 years was simulated well without gravity wave drag parameterization the zonal wave number versus the frequency spectra of simulated precipitation represent realistic signals of convectively coupled equatorial trapped waves eqws the temperature spectra in the stratosphere also indicate dominant signals of eqws eqws with equivalent depths in the range of 8 90 m from the n 1 mode to n 2 mode were extracted separately each eqw in the stratosphere generally corresponded well with the source of each convectively coupled eqw activity in the troposphere the propagations of kelvin waves and n 0 eastward westward propagating eqws are strongly influenced by the walker circulation and the phase of the qbo potential energy associated with eqws is generally larger in the westerly than in the easterly shear phase of the qbo eqws with vertical wavelengths 7 km contribute up to 30 of total potential energy 7 km over the equator at an altitude of 20 30 km gravity waves generated by cumulus convection with periods 24 h are clearly visible over areas of africa the amazon and around indonesia and result in localized pe distributions in areas short distances from the source region comparisons of the model results and recent satellite observations are discussed

the limited suitability of silica diagenetic boundaries as isothermal markers insights from seismic reflection imaging offshore sakhalin russian far east abstract in many sedimentary basins the seismic reflections that mark the conversion of opal a to opal ct and the subsequent conversion of opal ct to quartz are parallel to the present day seabed as the reactions are in part thermally activated these boundaries have been proposed as potential isothermal markers and could have utility for hydrocarbon exploration we describe opal a to opal ct and opal ct to quartz diagenetic boundaries using 2d seismic data from the north sakhalin basin nsb these are not parallel to the present day seabed but for 80 of the area of the basin are parallel to an unconformity of late miocene age and may represent palaeo isotherms that were parallel to the late miocene seabed this characteristic has been identified in other basins and may indicate silica diagenetic boundaries do not make reliable present day isothermal boundaries we propose diagenetic boundaries which are not parallel to the seabed are not present day isothermal boundaries this characteristic could result from 1 temperature decrease such as through a declining geothermal gradient or erosion of the overburden which will cause the rate of conversion to slow 2 variations in the burial rate that would cause changes to the rate of conversion and 3 a change in the rate of conversion as a result of variation in the physico chemical factors influencing the silica diagenetic reactions

troposphere thermosphere tidal coupling as measured by the saber instrument on timed during july september 2002 1 coupling between the troposphere and lower thermosphere due to upward propagating tides is investigated using temperatures measured from the saber instrument on the timed satellite the data analyzed here are confined to 20 120 km altitude and 40 latitude during 20 july to 20 september 2002 apart from the migrating sun synchronous tidal components the predominant feature seen from the satellite frame during this period is a wave 4 structure in longitude with extrema of up to 40 50 k at 110 km amplitudes and longitudes of maxima of this structure evolve as the satellite precesses in local time and as the wave s responsible for this structure vary with time the primary wave responsible for the wave 4 pattern is the eastward propagating diurnal tide with zonal wave number s 3 de3 its average amplitude distribution over the interval is quasi symmetric about the equator similar to that of a kelvin wave with maximum of about 20 k at 5 s and 110 km de3 is primarily excited by latent heating due to deep tropical convection in the troposphere it is demonstrated that existence of de3 is intimately connected with the predominant wave 4 longitude distribution of topography and land sea difference at low latitudes and an analogy is drawn with the strong presence of de1 in mars atmosphere the predominant wave 2 topography on mars and the wave 2 patterns that dominate density measurements from the mars global surveyor mgs spacecraft near 130 km additional diurnal semidiurnal and terdiurnal nonmigrating tides are also revealed in the present study these tidal components are most likely excited by nonlinear interactions between their migrating counterparts and the stationary planetary wave with s 1 known to exist in the southern hemisphere during this period just prior to the austral midwinter stratospheric warming of 2002

acoustic and related properties of calcareous deep sea sediments abstract three expeditions to the ontong java plateau and the eastern equatorial pacific obtained unusually good samples of calcareous sediment from box and piston cores water depths ranged from 1600 m to 4900 m two sedimentary environments are represented dissolution dilution and winnowing cause reductions with increasing water depth of caco3 percent sand mean grain size sediment rigidity and sound velocity the best indices to predict sound velocity are percent sand mean grain size and the velocity ratio this ratio varies from about 1 05 on top of the plateau to about 1 00 at 4400 m hollow tests of foraminifera act as solid particles in transmitting sound density and porosity are good predictors of velocity in the east pacific but not in the plateau area because of large amounts of hollow foraminifera there is no significant increase in sound velocity as caco3 increases from 35 to about 75 percent above that percent increases in velocity are mainly due to increases in sand size particles eastern pacific sediment has higher porosities and lower densities than the plateau samples because of less caco3 and more biogenous silica biogenous silica content causes good correlation between density and caco3 content in the eastern pacific but not in the plateau sediment density or impedance cannot be used to determine caco3 content in sediment lacking significant amounts of biogenous silica as water depth increases from 1600 m to 4900 m percent sand and mean grain size decrease markedly but total porosity increases only 1 to 3 percent this is due to dissolution and breakdown of hollow tests of foraminifera and transfer of intraparticle porosity within the tests to interparticle porosity between the grains new estimates of intraparticle porosity range from 13 percent in clayey sand to zero in silty clay new relations between the frame bulk modulus and porosity allow computations of elastic properties which indicate very small differences in bulk moduli or densities over wide ranges of grain sizes and water depths but large changes in dynamic rigidities cause both shear and compressional wave velocities to decrease with increasing water depth

diurnal nonmigrating tidal oscillations forced by deep convective clouds the global distribution of latent heat released by the diurnal oscillations in deep convective precipitating clouds is investigated as a forcing mechanism of diurnal nonmigrating atmospheric tidal modes the seasonal distribution of this forcing is deduced from 3 hour temporal resolution infrared 11 m radiance measured by four geostationary and two polar orbiting satellites which was transformed into the zonal wavenumber domain yielding migrating and non migrating oscillations the dominant wavenumbers in the forcing include the westward propagating 5 2 and 1 oscillations the eastward propagating 3 oscillation and the standing oscillation these dominant wavenumber oscillations were decomposed into hough functions to describe their meridional structure a vertical profile of latent heating rate was estimated and the dominant 22 tidal modes were used in an f plane model to determine the middle atmospheric response to this tropospheric forcing the f plane model was also excited using heating rates associated with the solar insolation absorption by water vapor the magnitude of the model atmosphere diurnal winds from both water vapor and latent heat is similar at certain locations this response suggests that the superposition of many nonmigrating tidal modes forced by the latent heat release of precipitating clouds is important in understanding the middle atmospheric circulation

ultrasonic velocities of opaline rocks undergoing silica diagenesis experimental results of laboratory measurements at ultrasonic frequencies on dry opaline rocks are documented from the monterey formation a siliceous unit in the san joaquin basin in these samples the silica is primarily biogenic opal a in origin but progressively alters to opal ct and then quartz with depth the diagenetic transitions are accompanied by a marked porosity reduction compressional and shear wave velocities were measured on core plugs at effective reservoir pressure experimental results on samples from the opal a opal ct transition and the opal ct quartz transition show very little pressure dependence of elasticwave velocities when their elastic moduli are normalized by those of the solid phase the moduli porosity trend is very close to that of chalk and in the lower porosity domain of some clean sandstones

the role of equatorial waves forced by convection in the tropical semiannual oscillation abstract recent satellite observations suggest that convection over the tropical continents is capable of exciting wave motions over a wide range of spatial and temporal scales an equatorial beta plane model was used to investigate the forcing by convective heating of equatorial waves with zonal wavenumbers from 1 to 15 and a wide range of periods including diurnal oscillations also studied are the propagation of these waves in the equatorial middle atmosphere and their role in driving the tropical semiannual oscillation sao specification of the heating distribution used to force the model is guided by observations and analyses of tropical convection it was found that intermediate scale kelvin and inertia gravity waves provide between 25 and 50 of the forcing necessary to drive the westerly phase of the sao near the stratopause while the remainder is supplied by planetary scale kelvin waves in the mesosphere intermediate scale waves account for an even larger fraction of the force required to

sources of nonmigrating tides in the tropical middle atmosphere 1 temperature measurements from the cryogenic infrared spectrometers and telescopes for the atmosphere crista experiment taken during the u s space shuttle mission sts 66 in november 1994 provide a variety of zonally symmetric and asymmetric tidal signatures in the altitude range from 40 90 km the most prominent zonally asymmetric tidal pattern is identified to be the westward propagating nonmigrating diurnal tide of zonal wavenumber 2 s 2 this mode has an amplitude of approximately half the amplitude of the migrating s 1 component of the diurnal tide the observational findings are compared to model results from the global scale wave model gswm and from the thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm gswm and time gcm account for different tidal sources and therefore allow an analysis of the tidal forcing responsible for the observed signatures the gswm tidal forcing in the model version used is based upon latent heat release associated with tropical deep convection while nonmigrating tides in the time gcm are predominantly forced by nonlinear interactions between the migrating diurnal tide and stationary planetary waves it is shown that the latter mechanism forces a large part of the s 2 mode while the stationary zonally uniform s 0 diurnal nonmigrating tide is mainly driven by latent heat release this result suggests that dynamical models for the mesosphere lower thermosphere mlt region need to account for the tropospheric latent heat source and stationary planetary wave activity in order to predict realistic longitudinal diurnal tidal variability

structure of a silica diagenetic transformation zone the gjallar ridge offshore norway three dimensional seismic data from the gjallar ridge were used together with x ray diffraction data scientific boreholes and wireline logs to analyse the seismic structure of a silica diagenetic transformation zone the following features were identified i an interval some 150 to 300 m thick that contains anomalously high amplitude reflections ii a strong reflection event at the top of this interval which cross cuts stratigraphy interpreted as the transformation boundary between opal a rich and opal ct rich sediment iii amplitude variations on stratigraphic reflections within the interval attributed to variations in the proportions of opal a and opal ct and iv a second deeper cross cutting reflection event within the interval interpreted as the transformation boundary between opal ct rich and quartz rich sediment the base of the interval containing the anomalously high amplitude reflections is interpreted as a stratigraphic reflection demarcating the base of the silica rich strata on a stratigraphic reflection within the interval of high amplitudes roughly circular regions of anomalously high amplitude with diameters of 0 8 to 2 5 km are separated by lower amplitude regions this pattern is similar to the cells previously identified at the opal a to opal ct transformation boundary and probably results from more complete transformation of opal a to opal ct all of these observations provide the first recognition from seismic data that silica diagenetic transformations are not always narrow boundaries represented by single cross cutting seismic reflection events as implied previously but can be heterogeneous and hundreds of metres in thickness as observed at outcrop

combined controls of sedimentology and diagenesis on seismic properties in lacustrine and palustrine carbonates upper miocene samos island greece

microearthquake seismicity at the intersection between the kazerun fault and the main recent fault zagros iran summary seismicity and fault plane solutions of earthquakes at the intersection between the main recent fault a right lateral strike slip fault that bounds the zagros to the ne and the kazerun fault system another right lateral zone that crosses the zagros show slip to be partitioned into nearly pure strike slip at shallow depths and nearly pure thrust slip below 12 km such slip partitioning is commonly observed where oblique convergence occurs but in general faults of different styles lie adjacent to one another not at different depths with one below the other we provide evidence for this partitioning in a microearthquake study in which we deployed a temporary network of 29 seismographs for 7 weeks we located no activity north of the main zagros reverse fault mzrf which separates the zagros fold belt from central iran most earthquakes occurred between the northern termination of the kazerun fault and the mzrf but not near to known major faults activity is limited to the upper crust between 2 and 16 km most of the focal mechanisms show strike slip faulting dextral if the ns striking plane is the active plane but a few for the deepest events show reverse faulting distributed between the kazerun fault and the mzrf with p axis trending consistently ns this partitioning of the deformation with depth suggests that the brittle upper crust deforms by slip on pre existing faults that strike obliquely but that the lower crust accommodates the shortening by reverse faulting we infer that the deformation in the upper part of the crust reflects a stiffer medium in which pre existing faults localize the deformation the largest event recorded during this experiment located at the same place as the destructive 1977 naghan earthquake mw 5 9 348 victims shows reverse faulting likely related to the dopolan high zagros fault the crustal thickness deduced from receiver function analysis does not show a marked difference across the kazerun fault which suggests a pure strike slip motion on the fault

seismic analysis of polygonal fault systems in the great south basin new zealand abstract polygonal fault systems pfs consisting of networks of layer bound normal faults are analyzed for eocene strata in the great south basin new zealand an advanced fault enhancement and skeletonization method is applied to delineate faults using 3d seismic data from the great south basin the process sharpens structural and stratigraphic discontinuities and smears the incoherent noise on coherence to obtain a skeletonized fault probability volume which can be directly used to extract and map fault geometries the characteristics of the polygonal faults in cross section planform and 3d space were studied the faults dip approximately 50 with displacements on a single fault ranging from tens of meters to a hundred meters the fault planform patterns are polygonal but also related to the regional horizontal stress anisotropy caused by slope changes of the basal unit the patterns vary from linear for high slopes rectangular for moderate slopes and polygonal for low slopes two preferred orientations may reflect the superposition of deep cretaceous trends on the polygonal system in the eocene strata a local concentric pattern with outward dipping normal faults is related to passive or active draping above a circular plutonic volcanic structure the genetic mechanism of the polygonal fault systems is interpreted to be related to volume loss and shear failure related to opal a ct transition within the sediments

initiation and propagation of polygonal fault arrays by thermally triggered volume reduction reactions in siliceous sediment abstract polygonal fault arrays have been documented in sedimentary basins from around the world and several theories exist as to how they initiate and propagate three dimensional seismic data from polygonal fault arrays from offshore norway are used to develop a new process model for polygonal fault development we propose that in siliceous sediment polygonal fault arrays can be triggered thermally due to the conversion of opal a to opal ct at depths of 100 1000 m this conversion causes differential compaction and shear failure and therefore fault initiation the location of the earliest faults is dependent on where opal a to opal ct conversion and compaction occur first this is controlled by which strata have a favourable bed composition local fluid chemistry and temperature or because the strata reach the depth of the reaction front first due to the presence of pre existing structural relief folds or faults subsidence of biosiliceous sediment through the opal a to opal ct reaction front causes fault propagation because of continued localised differential compaction fault initiation and propagation due to silica conversion generate polygonal fault arrays at significantly deeper burial depths than previously thought possible

growth of planetary waves and the formation of an elevated stratopause after a major stratospheric sudden warming in a t213l256 gcm 1 recovery processes after a major stratospheric sudden warming ssw with the formation of an elevated stratopause and a strong polar night jet are investigated using a gravity wave resolving gcm the major ssw that occurred in the gcm bears a strong resemblance to observations in january 2006 and january 2009 the recovery phase of the ssw in the gcm is divided into two stages in the first stage during about five days just after the ssw a large positive eliassen palm e p flux divergence associated with the growth of planetary waves contributes to the quick recovery of eastward wind above 2 hpa about 42 km which is likely due to baroclinic and or barotropic instabilities in the second stage over the next three weeks a prolonged westward wind in the lower stratosphere blocked upward propagation of gravity waves with westward intrinsic phase velocities it reduces the deceleration of eastward wind in the upper mesosphere and raises the breaking height of gravity waves since the height of westward gravity wave forcing also rises the polar stratopause created by the gravity wave driven meridional circulation is formed at an elevated height about 75 km compared to that before the ssw 55 65 km in addition the weaker westward gravity wave forcing in the upper mesosphere drives weaker downwelling around 1 hpa and forms a cold layer consequently the strong polar night jet forms at a higher altitude than before the ssw as a result of adjustment toward the thermal wind balance this indicates that these two stages provide eastward acceleration in different ways

nonmigrating diurnal tides in the thermosphere 1 horizontal wind measurements from the hrdi and windii instruments on the upper atmosphere research satellite are analyzed to reveal the most prominent nonmigrating diurnal tidal components at 95 km the eastward propagating diurnal tide with zonal wave number s 3 de3 the standing s 0 diurnal oscillation d0 and the westward propagating diurnal tide with s 2 dw2 the strongest de3 occurs primarily during northern hemisphere summer fall with maximum eastward winds near the equator of order 15 ms 1 and is a vertical extension of the s 3 kelvin wave the first antisymmetric mode of de3 dominates during october april with maximum meridional winds near the equator of order 8 ms 1 d0 exists during nearly all months and is nonsymmetric about the equator with maximum northward wind amplitudes in the southern hemisphere of order 7 10 ms 1 dw2 closely resembles the first symmetric propagating mode from classical tidal theory with maximum northward wind amplitudes of order 10 12 ms 1 during september through february the combination of de3 d0 and dw2 with dw1 gives rise to significant longitude variations in the diurnal tide between 40 latitude forcing in the global scale wave model gswm is calibrated according to the above observations thus enabling global estimates of nonmigrating tidal temperatures and other fields for instance it is estimated that the temperature and eastward wind perturbations associated with de3 may be as large as 20k and 35 ms 1 at 145 km and 115 km respectively over the equatorial region during july

impact of silica diagenesis on the porosity of fine grained strata an analysis of cenozoic mudstones from the north sea silica diagenesis has the potential to drastically change the physical and fluid flow properties of its host strata and therefore plays a key role in the development of sedimentary basins the specific processes involved in silica diagenesis are however still poorly explained by existing models this knowledge gap is addressed by investigating the effect of silica diagenesis on the porosity of cenozoic mudstones of the north viking graben northern north sea through a multiple linear regression analysis first we identify and quantify the mineralogy of these rocks by scanning electron microscopy and x ray diffraction respectively mineral contents and host rock porosity data inferred from wireline data of two exploration wells are then analyzed by multiple linear regressions this robust statistical analysis reveals that biogenic opal a is a significant control and authigenic opal ct is a minor influence on the porosity of these rocks these results suggest that the initial porosity of siliceous mudstones increases with biogenic opal a production during deposition and that the porosity reduction during opal a ct transformation results from opal a dissolution these findings advance our understanding of compaction dewatering and lithification of siliceous sediments and rocks moreover this study provides a recipe for the derivation of the key controls e g composition on a rock property e g porosity that can be applied to a variety of problems in rock physics

three dimensional structures of tropical nonmigrating tides in a high vertical resolution general circulation model this paper investigates nonmigrating tides from the ground to the lower mesosphere using data from a high resolution general circulation model kanto gcm as well as observational data from the sounding of the atmosphere using broadband emission radiometry instrument on board the thermosphere ionosphere mesosphere energetics and dynamics satellite and from gps radio occultation measurements obtained with the cosmic formosat 3 mission we extract nonmigrating tides using a composite as a function of universal time in physical space without performing a zonal wave number decomposition the kanto gcm clearly demonstrates that tropical nonmigrating tides are regarded as gravity waves excited by diabatic heating enhanced over two major continents specifically africa and south america they propagate zonally in a direction away from their sources that is west and eastward propagating waves are dominant on the western and eastern sides of the continents respectively these characteristics are observed in two satellite data sets as well except that the amplitudes in the kanto gcm are larger than those in the observations seasonal variations of nonmigrating tides are also investigated it is suggested that filtering owing to the stratopause semiannual oscillation as well as diabatic heating in the troposphere is important for the seasonal variations of nonmigrating tides in the stratosphere and the lower mesosphere

nonmigrating diurnal tides in the equatorial middle atmosphere abstract data from the nimbus 7 limb infrared monitor of the stratosphere lims are used to extend the analysis of diurnal tides in the middle atmosphere to include the zonally symmetric and eastward propagating components these modes show vertical and meridional structures that are generally consistent with the predictions of linear tidal theory the zonal and meridional wind fields are calculated from the tidal temperatures diurnal perturbations in lims temperature and derived winds agree well with equinoctial model calculations comparisons with day night differences of radiosonde temperature and rocket winds show qualitative agreement in vertical structure and amplitude the zonally symmetric and eastward migrating tidal components show a higher degree of temporal variability than the sun synchronous component these modes at times contribute substantially to the diurnal signal in wind and temperature with combined amplitudes equal to or in excess of the amplitude of the main migrating diurnal tid

the role of downhole measurements in marine geology and geophysics during the last 25 years downhole measurements have been increasingly used for scientific applications in marine geology and geophysics particularly in deep sea drilling operations used mostly by the oil industry to map promising formations for exploration and production of hydrocarbons a variety of instruments have been developed that can be lowered down drill holes to extract information about the subsurface geology in the last decade advances in computers software and data transmission have greatly increased the amount and quality of data that such instruments can provide relatively new instruments that image the borehole wall with high resolution can reveal layers and faults that previously could be seen only in core sections downhole measurements play a crucial role in linking core data with regional geophysical surveys and in providing data where core sections could not be obtained examples of recent scientific applications and approaches are presented that address previous problems with data quality and changes in properties over time after a hole is drilled the role of downhole measurements is discussed for two broad areas of research the structure and composition of the earth s crust most of which is formed at mid ocean ridges and past changes in earth s environment recorded in the deep sea sediments overlying the crust finally new emerging technologies and experiments that promise significant advantages over current methods for downhole measurements in marine geology and geophysics are discussed