on temperature inversions and the mesospheric surf zone 1 mesospheric thermal inversions are investigated in a numerical simulation with the whole atmosphere community climate model an upward extension of the national center for atmospheric research s community climate model the seasonal character spatial extent and magnitude of the inversion layers are realistic during winter in the model the occurrence of wintertime inversions is a direct consequence of the rapid decay with height of vertically propagating planetary waves which induces large temperature perturbations in the upper mesosphere to maintain hydrostatic equilibrium the magnitude of the inversions is highly correlated with planetary wave amplitude so that large inversions develop during episodes of planetary wave amplification gravity waves do not play a major direct role in the formation of the inversions because the largest thermal tendencies associated with gravity wave breaking occur well above the range of altitudes where inversions are found however gravity waves play an essential indirect role because they set up a critical line in the upper mesosphere where rossby waves break in the mesospheric surf zone

a seasonal climatology of rossby wave breaking in the 320 2000 k layer abstract differential advection in rossby waves can lead to potential vorticity pv p contours on isentropic surfaces folding over in latitude py 0 in a process called rossby wave breaking rwb exploring the properties of rwb may shed light on underlying dynamics and enable quantification of irreversible transport a seasonal climatology of py and rwb statistics is presented for the 320 850 k layer using ncep reanalysis data during 1979 2005 and for the 320 2000 k layer using the met office ukmo data during 1991 2003 a primary goal is to depict the spatial extent and seasonality of rwb maxima this analysis shows seven distinct rwb regimes poleward and equatorward of the subtropical westerly jets poleward and equatorward of the stratospheric polar night jets flanking the equator in the stratosphere and mesosphere equatorward of subtropical monsoon anticyclones and the summertime polar stratosphere a striking pv gradient maximum exists at the equator throughout the layer 360 2000 k flanke

an assessment of the quality of halogen occultation experiment temperature profiles in the mesosphere based on comparisons with rayleigh backscatter lidar and inflatable falling sphere measurements 1 bias errors for retrieved temperature profiles t p from the halogen occultation experiment haloe are evaluated by pairing with nearby soundings from ground based rayleigh lidar and from inflatable falling spheres findings for the mesosphere must be based on large sets of pairings because an individual haloe t p measurement is somewhat noisy and may not view the same atmospheric structure simulated estimates of total bias errors for the haloe profiles are of the order of 2 or 5 k the average biases with the lidar profiles at 44 n 6 e are within 3 k from 33 to 66 km and 4 k to 74 km at least when zonal easterlies and reduced wave activity prevail tidal effects can account for most of that difference comparisons with shipboard lidar soundings that begin near 100 km indicate no significant bias even in the 77 to 85 km range similar comparisons with falling sphere profiles at cape canaveral and wallops island indicate no significant bias from 40 to 66 km and 71 to 85 km haloe profiles are warmer than sphere values from 67 to 70 km but this is also the altitude region where the sphere profile has greater uncertainties for those months when the lidar soundings indicate inversion layers the sets of profiles paired with lidar indicate that the haloe t p is somewhat colder in the upper mesosphere in part owing to the effects of limb path averaging of horizontal structure by haloe and its inability to completely resolve the inversion layer maximum on the basis of the combined sets of findings it is concluded that most of the error in a single haloe t p is random except where there is a sharp inversion daily zonal averages of the haloe profiles are accurate and useful for defining the seasonal and longer term variations of t p in the mesosphere

a review of the mesosphere inversion layer phenomenon an active topic of current research in aeronomy is the study of the dynamics of the mesosphere and lower thermosphere mlt from 60 to 130 km especially in regard to the influences that govern variability the physical processes of this region are diverse and complex with strong coupling between the mlt and the adjacent atmospheric regions brought about largely by the propagation and dissipation of atmospheric gravity waves gws from sources above and below the measurements of mlt winds and temperatures required for such studies represent daunting technical challenges at low and midlatitudes the mesosphere inversion layer mil phenomenon a 10 km wide region of enhanced temperatures t 15 50k is observed with great regularity in both the upper mesosphere 60 70 km and the mesopause 90 100 km observations are largely based upon rayleigh and na temperature lidar systems but coherent radar observations have shown that the mil phenomenon is linked to layers of turbulence occurring in both the topside and the bottomside regions gw activity is believed to play an important role in the development of a linkage between the mil and the tidal structure through gw coupling that results in an amplification of the tidal thermal structure this linkage is readily evident for the upper mil but is seen only occasionally for the lower mil further study of mil properties should emphasize continual 24 hour temperature observations especially for the lower mil region to confirm the linkage of the development of the mil to the mlt tidal structure

a comparative study of mesospheric solar tides observed at adelaide and kyoto observations of winds in the upper mesosphere and lower thermosphere 80 110 km measured at the geographically conjugate locations of adelaide 35 s 138 e and kyoto 35 n 136 e in the years 1983 1985 are used to study hemispheric differences in the behavior of the solar diurnal and semidiurnal tides comparisons of the tidal amplitude and phase parameters show that there are distinct hemispheric asymmetries the diurnal tide is usually much larger in amplitude at adelaide and it exhibits a height structure which indicates a relatively larger contribution from the propagating 1 1 mode at this location comparisons with recent theoretical work suggest that while some of these differences may be due to hemispheric differences in forcing and or to interactions between the tide and the background winds in the middle atmosphere it is also possible that they indicate weaker turbulent induced damping of the 1 1 mode in the southern hemisphere the characteristics of the semidiurnal tide agree well at the two locations it is found that the zonal wind components are about 6 hours out of phase and the meridional components are in phase in all seasons this behavior taken together with the inferred vertical wavelengths which are greater than 100 km in summer and 45 80 km in winter indicates that there are strong contributions from the antisymmetric 2 3 mode probably forced by wind induced mode coupling from the symmetric 2 2 mode the phases near 90 km exhibit a bimodal or two state behavior with the phases being almost constant in one state near the june solstice and then making a rapid transition of between 4 and 6 hours to another phase stable state near the december solstice the duration of the state near the june solstice 6 8 months is longer than the duration of the state at the december solstice although the agreement between recent models and our observations is relatively good better agreement may be expected when more realistic wind distributions especially for the southern hemisphere are used in the models

momentum flux spectrum of convectively forced internal gravity waves and its application to gravity wave drag parameterization part ii impacts in a gcm waccm abstract impacts of a spectral parameterization of gravity wave drag gwd induced by cumulus convection gwdc in the ncar whole atmosphere community climate model waccm1b are investigated in the spectral gwdc parameterization reference wave momentum flux spectrum is launched at cloud top and analytically calculated based on the physical properties of convection and the large scale flow the cloud top wave momentum flux is strong mainly in the tropics and midlatitude storm track regions and exhibits anisotropy and spatiotemporal variability the anisotropy and variability are determined by the distributions and variations of convective activities the moving speed of convection and horizontal wind and stability in convection regions zonal mean zonal gwdc has a maximum of 13 27 37 50 m s 1 day 1 in the mesosphere in january july impacts of gwdc on zonal wind appear mainly in the low to midlatitudes of the upper stratosphere and mesosphere in these regions biases of zonal wind with respect to

high arctic observations of mesospheric inversion layers 1 rayleigh lidar measurements of middle atmospheric temperatures obtained in the high arctic at eureka 80 n 86 w are examined for evidence of mesospheric inversion layers with overlying nearly adiabatic lapse rates inversion layers are identified in 5 4 0 5 of the measurements a rate considerably lower than is observed at midlatitudes the altitude distribution for the arctic inversions is similar to that found at midlatitudes no phase progression or relationship with stratospheric gravity wave activity was found the observations have important consequences for theories of the mesospheric inversion layer

satellite observations of atmospheric variances a possible indication of gravity waves the microwave limb sounder mls on the upper atmosphere research satellite has now produced the first global maps of small scale variances in the middle atmosphere initial analyses are presented here that suggest these variances are due to gravity waves and the technique used to extract gravity wave information from saturated radiance measurements is described observations at 30 80km altitudes show that the variances of horizontal scales less than 100km are strongly correlated with upper tropospheric convection surface topography and stratospheric jetstreams mls monthly averages during solstice periods suggest that the normalized variance amplitude grows exponentially with height in the stratosphere and saturates in the mesosphere as expected from wave breaking and dissipation at these altitudes

secular change in the precambrian silica cycle insights from chert petrology chert deposits preserve a record of secular change in the oceanic silica cycle the evolutionary radiation of silica secreting organisms resulted in a transition from abiological silica deposition characteristic of the archean and proterozoic eons to the predominantly biologically controlled silica deposition of the phanerozoic comparative petrography of phanerozoic and precambrian cherts indicates that an earlier change in chert deposition occurred toward the end of the paleoproterozoic era ca 1 8 ga in neoproterozoic and mesoproterozoic strata early diagenetic chertification is largely restricted to peritidal environments these early diagenetic cherts typically occur as nodules or discontinuous beds within carbonate deposits that have similar depositional textures the cherts formed primarily by carbonate replacement with subsidiary direct silica precipitation some of the paleoproterozoic cherts associated with iron formations however are distinctly different from younger cherts and appear to have formed largely by direct silica precipitation at or just below the seabed these primary cherts lack ghosts or inclusions of carbonate precursors have fine scale grain fracturing possibly from syneresis exhibit low grain packing densities and are not associated with unsilicified carbonate deposits of similar depositional composition cherts in some paleoproterozoic iron formations e g the gunflint formation northwestern lake superior region are composed of silica types similar to those in phanerozoic sinters e g the devonian rhynie and windyfield cherts scotland such cherts may provide evidence that basinal and perhaps global oceanic silica concentrations were higher during the paleoproterozoic era than at later times

selective and reversible carbonate silica replacements in lower cretaceous carbonate bearing turbidites of the eastern alps in the diagenetic history of calcareous sandstones silicacementation and silicification may be followed by carbonatecementation and replacement and vice versa and the change over from one to the other may occur more than once this is well illustrated by calcareous and siliciclastic turbidites of the gault formation aptian to albian of the eastern alps which have been interpreted as deep sea trench plain and deep sea fan deposits in these turbidites silicification selectively affects ooids and a few other biogenic carbonate fragments rich in organic matter algae and bryozoans which form a small fraction of the bulk sediment the type and sequence of diagenetic changes are largely controlled by host rock composition and may vary vertically within individual beds as a result of compositional grading in the carbonate turbidites silicification follows widespread calcite cementation the process is slow resulting in relatively coarsely crystalline replacement quartz in ooids with quartz nuclei rim quartz forms mostly monocrystalline overgrowths by outward replacement of the concentrically laminated carbonate cortex this type of silicification is often incomplete leaving parts of the ooid cortices unaffected in quartz arenites and sublitharenites silicification precedes calcite cementation there the process is rapid forming microcrystalline quartz even if the ooid nucleus consists of quartz a syntaxial overgrowth does not normally form the replacement quartz is almost always polycrystalline late stage diagenetic calcite and dolomite which develop euhedral crystal shapes and cut across grain boundaries may replace the earlier secondary rim quartz of the ooids as well as other minerals possible sources of the silica are pressure solution of quartz dissolution of opaline silica of radiolarian tests and of sponge spicules and feldspar in the host bed in a number of examples an increase in the degree of silicification can be observed towards the lower bedding planes of individual turbidites requiring an additional external source of silica which seems to necessitate cross formational flow of pore solutions silicification in both the carbonate and the siliciclastic turbidites probably took place at about the same time in the carbonate turbidites it was preceded however by calcite cementation which significantly reduced porosity and permeability before silicification took place the greater degree of alteration experienced by the gault turbidites of the falknis and tasna nappes which are more internal structural units of the alps compared to the flysch zone of the eastern alps is reflected by the growth of quartz beards and spikes from the ooids in the direction perpendicular to maximum stress this is the only case observed where the rim quartz of the ooids grows beyond the original grain boundaries

observations of intermediate scale diurnal waves in the equatorial mesosphere and lower thermosphere 1 the purpose of this study is to seek observational evidence for diurnal vertically propagating inertia gravity waves igws in the mesosphere and lower thermosphere mlt numerical modeling studies indicate that vertically propagating igws excited by tropical heating provide a significant source of momentum for the semiannual oscillation sao in the equatorial zonal mean winds the power spectrum of these waves has a strong diurnal component we analyze global patterns of ascending and descending node differences in mlt satellite temperatures which are assumed in this study to be proxies for waves of diurnal period juxtaposed upon the planetary scale features are localized variations with longitudinal wavelengths ranging from 25 to 50 and with vertical wavelengths between 13 and 25 km these intermediate scale variations are spatially coherent and persist for several weeks their amplitudes generally increase with altitude while their phase structures suggest both eastward and westward propagation the variance of wave numbers 9 17 in the mlt is examined in relation to the underlying stratospheric zonal mean zonal gradient winds stronger variances generally coincide with periods where the underlying zonal mean winds are relatively light or unidirectional the weak inverse association between variance strength and zonal wind magnitude is suggestive of a wave filtering mechanism

lidar observations of atmospheric dynamics in the troposphere and lower stratosphere over arecibo a periodic wave structure with a vertical wave length typically 2 km between 14 and 23 km altitudes has been identified in lidar measurements of relative density profiles at 589 nm that were made by the university of illinois group during the march april aida 1989 campaign effort the equivalent temperature fluctuations are several degrees in magnitude also seen are stratified aerosol layers at altitudes near 25 km with a vertical extent of 1 km both of these phenomena show a downward phase speed between 1 and 3 cm s 1 the lower periodic structure is believed to be the same phenomenon seen previously in 430 mhz measurements of winds obtained at arecibo observatory the source of this structure remains uncertain cornish and larsen 1989 and sato and woodman 1982a considered this structure to be a quasi inertial long period wave hines 1989 proposed instead the identification of this structure with a stationary wave system generated by orographic waves created through the interaction of the subtropical trade winds with the mountainous terrain of puerto rico the higher altitude feature seen in the aida lidar observations is believed to be an aerosol layer with a scattering ratio of about 1 15 an alternative explanation is clear air turbulence but the signature of the 10 k fluctuation deduced from the lidar observations was not found in the san juan balloon measurement of the temperature profile for the lower stratosphere

zonal jet structure and the leading mode of variability an observational analysis of the northern hemisphere circulation during winter reveals that the leading mode of variability depends on longitude in particular the first eof of the zonal mean circulation differs over the atlantic and pacific sectors these results provide motivation for a series of model runs where a simple gcm is used to investigate the effects of the zonal jet structure on the leading mode of variability in the northern hemisphere model results indicate that the leading mode of variability depends on the distance between the eddy driven and subtropical jets when the jets are well separated the leading mode of variability describes latitudinal shifting of the eddy driven jet however when the two jets are nearly collocated pulsing of the combined jet dominates the variability this change coincides with a weakening of the positive feedback between the eddies and zonal flow anomalies these results provide a possible explanation for the reduced amplitude of the northern annular mode in the pacific sector relative to that in the atlantic sector during northern hemisphere winter

replacement of evaporites within the permian park city formation bighorn basin wyoming usa the permian park city formation consists of cyclically bedded subtidal to supratidal carbonates cherts and siltstones early diagenesis of park city formation carbonates occurred under the influence of waters ranging from evaporative brines to dilute meteoric solutions and resulted in evaporite emplacement syndepositional nodules and cements as well as dolomitization silicification and leaching of carbonate grains major differences are seen however in the diagenetic patterns of subsurface and surface sections of park city formation rocks subsurface samples are characterized by extensively preserved evaporite crystals and nodules and preserve evidence of significant silicification chert chalcedony and megaquartz and minor calcitization of evaporites in outcrop sections the evaporites are more poorly preserved and have been replaced by silica and calcite and also leached the resultant mouldic porosity is filled with widespread very coarse blocky calcite spar these replacements appear to be multistage phenomena field and petrographic evidence indicates that silicification involved direct replacement of evaporites and occurred during the early stages of burial prior to hydrocarbon migration siliceous sponge spicules provided a major source of silica and the fluids involved in replacement were probably a mixture of marine and meteoric waters a second period of replacement and minor calcitization is inferred to have occurred during deep burial under the influence of thermochemical sulphate reduction although the presence of hydrocarbons probably retarded most other diagenetic reactions during this time interval the major period of evaporite diagenesis however occurred during late stage uplift the late stage replacement and pore filling calcites have 13c values ranging from 0 5 to 25 3 and 18o values of 16 1 to 24 30 pdb reflecting extensive modification by meteoric water vigorous groundwater flow associated with mid tertiary block faulting led to migration of meteoric fluids through the porous carbonates to depths of several kilometres these waters reacted with the in situ hydrocarbon rich pore fluids and evaporite minerals and precipitated calcite cements the tosi chert appears to have been an even more open system to fluid migration during its burial and has undergone a much more complex diagenetic history as evidenced by multiple episodes of silicification calcitization ferroan and non ferroan and hydrocarbon emplacement the multistage replacement processes described here do not appear to be restricted to the permian of wyoming similarly complex patterns of alteration have been noted in the permian of west texas new mexico greenland and other areas as well as in strata of other ages thus multistage evaporite dissolution and replacement may well be the norm rather than the exception in the geological record

managing environmental problems in cuban karstic aquifers the cuban archipelago hosts some of the most typical karst features in the caribbean and has very important and high quality resources of karst water carbonate rocks cover about 70 of the country area with a great variety of karst features and outstanding exokarstic landforms such as the cone karst in addition many caves are regarded as cultural and historical sites protection of the karst hydric resources is therefore essential in karst the intrinsic vulnerability of the environment makes it highly susceptible to pollution which may result in dramatic consequences for both the quality of karst water and the amount of water available many anthropogenic activities produce negative changes in the karst aquifers in some cases with unrecoverable effects in cuba five main sources of pollution to karst aquifers have been identified sea water intrusion agricultural practices waste disposal industrial activity and mining and oil production due to the narrow and elongated configuration of the main island wide portions of the territory are mostly affected by seawater intrusion problems exacerbated by the concentration of both population and human activities in the largest towns located along or very close to the coasts seawater intrusion however is not the only source of pollution for cuban karst aquifers the other aforementioned sources are important and may locally prevail e g pollution resulting from sugar cane factories considerations on the management of karst aquifers and a brief description of the water quality monitoring system of cuban inland waters are also provided

meteoric water participation in the genesis of jurassic cherts in the subbetic of southern spain a significant indicator of penecontemporaneous emergence abstract in the eastern sector of the betic cordillera outcrops of the internal subbetic display chert lenses in the upper parts of oolitic limestones camarena formation mid jurassic the stratigraphy indicates a sedimentary record related to synsedimentary tectonics tilting the sediments were deposited in different tectonic blocks at varying depths the camarena formation is mainly made up of shallow platform oolitic limestones and was deposited on a pelagic swell a shallow isolated platform that developed far from continental areas the chert lenses appear in those stratigraphic units deposited in the lowermost sunken fault blocks which display biosiliceous facies overlying the camarena formation the chert mainly consists of megaquartz formed by replacement of the oolitic host rocks without an opaline precursor the part of the host that has been most affected by the silicification is the carbonate cement the petrological features indicate a slow replacement from solutions which were poor in silica and cations comparing the textures and fabric of the cherts and their host rocks it is deduced that the silicification took place after compaction cementation fracturing and local dissolution of the oolitic limestones the stable isotopic data 18o 13c obtained from the chert oolitic host rock and overlain biosiliceous rocks display significant differences the host rocks camarena formation and overlying biosiliceous rocks have isotopic signatures that are typical of marine environments or shallow marine diagenesis however the chert isotopic values are interpreted to suggest meteoric water participation in the silicification process the timing of the chertification is suggested to have been between the bathonian beginning of the deposition of the biosiliceous source facies and the aptian first appearance of this chert as clasts in breccia beds in palaeogeographic terms the optimum timing would have been during emergence i e between the bathonian and tithonian the exposed areas could have acted as recharge areas of meteoric water into the regional aquifer system the involvement of meteoric water in the silicification processes gives new support to the hypothesis that pelagic swells were subjected to episodic exposure

lidar observations of the middle atmospheric thermal tides and comparison with the high resolution doppler imager and global scale wave model 1 methodology and winter observations at table mountain 34 4 n the tidal signature in the middle atmospheric thermal structure was investigated using more than 140 hours of nighttime lidar measurements at table mountain 34 4 n during january 1997 and february 1998 the lidar profiles 30 85 km revealed the presence of persistent mesospheric temperature inversions around 65 to 70 km altitude with a clear local solar time lst dependence daytime temperature profiles 65 105 km obtained by the high resolution doppler imager hrdi on board the upper atmosphere research satellite uars in january and february from 1994 to 1997 and zonally averaged at the latitude of the table mountain facility tmf were considered together with the lidar results the daytime hrdi and nighttime lidar temperature differences from their respective daytime and nighttime averages were compared to the equivalent differences predicted by the global scale wave model gswm a remarkable consistency was observed between the lidar and the hrdi upper mesospheric thermal structure with a continuous downward propagation of warm temperatures from 100 km at 1000 lst to 75 km at 2000 lst and 65 70 km at 0300 0500 lst surrounded above and below by colder temperatures this structure was predicted by gswm but with a 2 to 4 hour delay and a weaker amplitude on the lower side of this structure i e 65 70 km a thin layer characterized by early night cold temperatures and late night warm temperatures was identified as the result of the downward propagation of the temperature inversions using a new analysis technique which we have named constrained wave adjustment for convenience in future reference and assuming that the observed temperature variability was entirely driven by tides some estimations of the diurnal and semidiurnal phases and amplitudes were made from the lidar measurements between 40 and 85 km altitude although it does not allow a complete and accurate extraction of the tidal components this new method appeared to work well for the present tmf study the estimated diurnal amplitude exhibited a minimum at 63 km with a fast phase transition characteristic of the transition between the upper stratospheric trapped modes phase at 1800 lst and the upward propagating modes this transition layer was predicted by gswm to be at 5 km lower altitude this altitude shift was present throughout the middle mesosphere immediately above the transition layer the very fast growing diurnal amplitude between 65 and 72 km was followed by a substantial decrease and by the emergence of the semidiurnal component resulting in the formation of the mesospheric temperature inversion layers however the amplitude of the inversions remained large compared to the theoretical tidal predictions and a different formation mechanism should possibly be considered recent modeling studies have shown that gravity wave breaking can be significantly affected by the tidal background winds and some preferential wave breaking times could emerge that are dependent on the phase of the diurnal tide and the characteristics of the dissipating waves this lst filtering could result in lst dependent temperature inversion layers similar to those observed by lidar the new analysis technique presented in this paper was also applied to study the temperature tidal oscillations at mauna loa observatory 19 5 n the results are presented in a companion paper leblanc et al this issue

observation of a large amplitude wave and inversion layer leading to convective instability in the mesopause region over fort collins co 41 n 105 w 1 sodium resonance lidar observations on the night of nov 3 1997 ut recorded a temperature inversion with 80 k amplitude moving downward from 90 to 83 km with the maximum temperatures exceeding 280 k these are the highest temperatures and largest inversion layer observed in 10 years over fort collins colorado the inversion can be decomposed into a 50 k peak to peak amplitude oscillation with an apparent 8 hr period and 25 km vertical wavelength plus a residual 30 k inversion layer the temperature gradient above this maximum is near adiabatic from 88 100 km for 4 hours with multiple super adiabatic layers several km in depth streamlines derived from the sodium mixing ratio and the potential temperature both indicate a 10 km upward movement in the adiabatic region presumably a large amplitude upward propagating wave saturated when it reached the inversion layer just below the mesopause and broke leading to convective instabilities with large vertical and temporal scales

diagenesis of spiculites and carbonates in a permian temperate ramp succession tempelfjorden group spitsbergen arctic norway this paper explores little investigated diagenesis of spicule dominated sediments based on permian spiculites and cool water carbonates of the tempelfjorden group in central spitsbergen field observations petrography stable isotope geochemistry and mineralogical and chemical analyses reveal that the strata have been subjected to multistage diagenesis as the result of silica phase transitions at medium burial depths and deep burial overprinting the growth of silica concretions occurred during the opal a opal ct conversion and was controlled by the content and distribution of clay and spicules in the sediment resulting in a variety of megascopic silica fabrics opal ct was subsequently dissolved and all silica is now in a stable quartz stage petrographically the rocks are characterized by a variety of chalcedony and quartz cements which perfectly preserve precursor textures most cements precipitated from silica oversaturated fluids and their shapes reflect the silica saturation state and geometry of the pore space some microquartz and cryptoquartz also formed by a solid solid inversion recrystallization of chalcedony the cements have 18o values between 30 and 20 standard mean ocean water and display a systematic depletion in 18o from the first to the last crystallized interpreted to reflect gradual increase in temperature during burial the precipitation of quartz cements started in the middle triassic when the strata passed the 19 c isotherm at burial depths of ca 600 m and was completed in the mid cretaceous 2 3 km beneath the sea floor at temperatures of 75 c late diagenetic overprinting of the chert includes fracturing brecciation and cementation with carbonate cements having 18o values between 2 and 30 pee dee belemnite and 13c values between 4 and 14 pee dee belemnite they are linked to hot solutions introduced during cretaceous volcanism or palaeogene tectonism this study illustrates the diagenetic pathway during burial of spicule rich sediments in a closed system and thereby provides a baseline for studies of more complexly altered chert deposits this article is protected by copyright all rights reserved

simulation of lidar measurements of gravity waves in the mesosphere lidar measurements of mesospheric gravity wave characteristics are simulated using a simple numerical model simple theory is used to superimpose gravity wave fluctuations upon typical background densities and sodium abundances in the height range 80 100 km which we then assume are perfectly observed by a rayleigh and na lidar respectively these lidar data are then analyzed for their gravity wave content using the standard reduction and analysis methods which are routinely applied to these data sets our goal is to assess whether this analysis of lidar data faithfully recovers the underlying wave field in both quasi monochromatic and spectral wave studies the height range over which na number density can be measured and the shape of the background na profile impose a limit on the gravity wave information which can be extracted from na lidar data the limitations due to background layer shape do not exist for rayleigh lidar measurements the simulations reveal that quasi monochromatic gravity waves with vertical wavelengths larger than approximately 10 km may not be reliably retrieved from na lidar data it is also shown that there are limitations on the accurate extraction of spectral parameters from na lidar data due to the limited vertical extent of the mesospheric na layer

petrologic and geochemical constraints on the origin of subsurface dolomite enewetak atoll an example of dolomitization by normal seawater dolomite is present 1 250 1 400 m below sea level in eocene strata of enewetak atoll petrographically the deep enewetak dolomite postdates brittle compaction of rigid grains in the host eocene strata the 87 sr 86 sr ratio of these dolomites 0 70865 0 70901 indicates that they formed at one or more times between the middle miocene and the present since the top of the lower miocene is more than 900 m above the deep dolomitic interval the dolomite must have formed at a minimum burial depth of 900 m stable oxygen isotope determinations suggest dolomite precipitation from cold marine water lower miocene and eocene carbonate strata on the atoll are apparently in open communication with cold modern ocean water suggesting that those same strata were in open communication with ocean water during dolomitization at a depth of about 1 000 m modern pacific ocean water becomes undersaturated with respect to calcite but is still supersaturated with respect to dolomite therefore it is proposed that the deep enewetak dolomite precipitated from cold deep ocean water undersaturated with respect to calcite at a burial depth of more than 900 m

model measurement comparison of mesospheric temperature inversions and a simple theory for their occurrence 1 mesospheric temperature inversions are well established observed phenomena yet their properties remain the subject of ongoing research comparisons between rayleigh scatter lidar temperature measurements obtained by the university of western ontario s purple crow lidar 42 9 n 81 4 w and the canadian middle atmosphere model are used to quantify the statistics of inversions in both model and measurements inversions occur most frequently in the winter and exhibit an average amplitude of 10 k the model exhibits virtually no inversions in the summer while the measurements show a strongly reduced frequency of occurrence with an amplitude about half that in the winter a simple theory of mesospheric inversions based on wave saturation is developed with no adjustable parameters it predicts that the environmental lapse rate must be less than half the adiabatic lapse rate for an inversion to form and it predicts the ratio of the inversion amplitude and thickness as a function of environmental lapse rate comparison of this prediction to the actual amplitude thickness ratio using the lidar measurements shows good agreement between theory and measurements

propagation of enso temperature signals into the middle atmosphere a comparison of two general circulation models and era 40 reanalysis data the vertical propagation of the el nino southern oscillation enso temperature signal has been analyzed in two general circulation models the whole atmosphere community climate model and the middle atmosphere european center hamburg model and in the era 40 reanalysis data set monthly mean data have been used and composite differences el nino la nina have been computed our results show that the enso signal propagates into the middle atmosphere by means of planetary rossby waves significant wave like anomalies are observed up to around 40 km this propagation is strongly influenced by the zonal mean zonal winds being most effective in midlatitudes of the northern hemisphere because enso events tend to peak in northern winter when stratospheric winds are westerly in the northern hemisphere and allow vertical propagation of rossby waves in addition zonal mean temperature anomalies are observed in the middle atmosphere in the tropics and at polar latitudes of the northern hemisphere these anomalies are the result of changes in the residual mean meridional circulation our analysis reveals that during an el nino event vertical wave propagation and divergence of eliassen palm flux are enhanced forcing a stronger residual circulation in the stratosphere which cools the tropics and warms the higher latitudes this pattern is highly significant in the models during certain months but much less in the era 40 data where other sources of variability in particular the quasi biennial oscillation also influence the residual circulation

rayleigh lidar observations of mesosphere temperature structure ground based observations of atmospheric density profiles to 92 km were obtained for four successive seasons between summer 1989 and spring 1990 these results were obtained with a powerful rayleigh lidar facility located at wright patterson air force base dayton ohio this instrument combined a 14 w xef laser transmitter with a 2 54 m receiver mirror to observe returns from altitudes between 40 and 95 km analysis of the scale height dependence of the density profiles produced temperatures with a measurement error of about 5 k 2 5 at 90 km when the lidar data was averaged for 20 min and smoothed in height over 2 7 km examination of these profiles for the total of 18 nights showed that there often existed in the mesophere a layer of enhanced temperatures when compared with the u s standard profile the layer centroid height was about 85 km for summer and 70 to 75 km for winter data obtained for the equinoctial periods showed the amplitude of these layers to be weak the winter temperature profiles showed evidence forlong period waves passing through the region of the thermal anomaly while the equinox profiles revealed more sporadic wave activity with shorter vertical wavelengths both the winter and summer temperature data displayed regions where the observed lapse rate approached the adiabatic lapse rate in the summer the wave activity near the inversion layer was weak

comparative study of short term diurnal tidal variability examination of the simultaneous temperature measurement from the sounding of the atmosphere using broadband emission radiometry saber instrument on board the thermosphere ionosphere mesosphere energetics and dynamics timed satellite not only confirms the existence of the inversion layer but also reveals the global nature of the inversion suggesting the presence of a transient planetary wave in the mesosphere the large tidal variability therefore is probably a consequence of the interaction between the transient planetary wave and tides this possibility is investigated by using the ncar thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm and by comparing model results with the lidar saber and timed doppler interferometer tidi measurements with a large transient planetary wave specified at the model lower boundary the model is able to produce strong diurnal tidal variability comparable to that from the lidar observation and the modeled temperature inversion is similar to that from the saber measurement the model results suggest that the planetary tidal wave interaction excites nonmigrating tides and modulates the gravity modes and or the rotational modes of the diurnal migrating tide among the nonmigrating tides the diurnal zonally symmetric s 0 component is the strongest and its interaction with the planetary wave leads to a strong diurnal eastward wave number 1 component

properties of the quasi 16 day wave derived from eos mls observations 1 this paper describes the use of eos microwave limb sounder mls data to observe the field of traveling planetary waves with quasi 16 day periods this study utilizes mls v2 2 temperature and geopotential data between 1 january 2005 and 31 december 2008 in the range 316 hpa to 0 001 hpa approximately 8 to 97 km to examine these waves analysis demonstrates that the quasi 16 day wavefield is made up of a number of components with westward and eastward propagating s 1 and s 2 waves generally dominant in the northern hemisphere the westward and eastward propagating s 1 waves have similar magnitudes and are larger than the other modes while in the southern hemisphere the eastward propagating s 1 and s 2 waves are larger than the westward propagating wave modes all of the modes examined display strong seasonal patterns in the temperature amplitude significant variability in the wave activity from year to year and the presence of strong pulse like patterns in the activity all of the modes also display large median temperature amplitudes poleward of 40 degrees in both hemispheres our analysis also demonstrates that the variability in winter from year to year is larger in the northern hemisphere than the southern hemisphere detailed study also suggests that the exclusion of waves from regions of negative refractive index squared likely forms much of the seasonal pattern observed thus regions of strong westward wind speeds effectively exclude vertically propagating waves as expected from theory the reflection and absorption of waves associated with critical lines is also likely to explain the frequent occurrence of standing wave patterns in the eos mls temperature observations this study highlights the potential of mls observations for observing waves from the upper troposphere to the lower mesosphere

diagenetic replacement controlled by force of crystallization many diagenetic replacements in sedimentary rocks occur along thin solution films between the authigenic and host phases rather than conventionally invoking bulk pore water undersaturation for host phase dissolution we propose that many diagenetic replacements occur by a force of crystallization controlled replacement mechanism whereby nonhydrostatic stresses resulting from authigenic crystal growth are principally responsible for host phase dissolution this model explains diagenetic features such as the restriction of host phase dissolution to authigenic host crystal contacts and euhedral authigenic crystal faces in planar contact with unreplaced host phases as well as the relative replacement tendencies of some common authigenic minerals

semidiurnal and diurnal tidal effects in the middle atmosphere as seen by rayleigh lidar the rayleigh lidar at the centre d essais des landes has been adjusted to provide continuous day and nighttime measurements when clear weather permits with high resolution in both time and space these measurements are processed to show tidal effects in the 30 to 80 km height range the observed temperature variations in two 11 day series of data from november 1988 and january 1989 are treated by spectral analysis and by least squares fitting sinusoids for 12 and 24 hour periods the observed tidal amplitudes correspond with experimental results from rocket studies and are generally consistent though somewhat larger than predicted in theoretical models observed lidar phases are roughly corroborated by radar observations and also follow the same general trends as model predicitions

mesospheric inversions and their relationship to planetary wave structure 1 mesospheric inversions are studied in vertical soundings from the french lidar at observatoire de haute provence and in synoptic global structure that was observed simultaneously by the uars satellite the latter provides the instantaneous three dimensional 3 d structure of the circulation that accompanies mesospheric inversions a numerical simulation with a 3 d primitive equation model is then shown to reproduce major features of the observed behavior both reveal an extensive pattern of inverted thermal structure the behavior is closely related to planetary waves which in the model experience strong absorption in the upper mesosphere and lower thermosphere inverted thermal structure mirrors the synoptic pattern of potential vorticity which marks the polar night vortex both are strongly distorted during stratospheric warmings when inverted thermal structure at midlatitudes is favored the region of negative lapse rate coincides with those altitudes where planetary wave temperature undergoes an abrupt phase shift wave temperature is then driven out of phase with wave geopotential this alters the vertical structure of planetary waves from westward tilt and upward amplification below the inversion to nearly barotropic structure and upward decay above the inversion accompanying the upward decay of planetary waves above the inversion is a decay of flow distortion as the disturbed vortex is gradually restored toward polar symmetry

on modeling migrating solar tides recent updates and extensions to a steady state two dimensional linearized model of global scale atmospheric waves have facilitated improved calculations of the subset of those waves which are subharmonics of a solar day and propagate with the apparent motion of the sun the model improvements are briefly described and some updated predictions of the migrating solar diurnal component are highlighted the latter represent the first numerical modeling effort to examine the seasonal variability of the migrating diurnal harmonic as it propagates into the mesosphere and lower thermosphere

chertification histories of some late mesozoic and middle palaeozoic platform carbonates a consistent pattern for the silica sources depositional environments and timing of chertification was observed in a diverse suite of five late mesozoic and middle palaeozoic carbonate sequences the 1 upper greensand cretaceous and 2 portland limestone jurassic of southern england 3 the ramp creek formation mississippian of southern indiana and the 4 lower helderberg group devonian and 5 onondaga limestone devonian of new york state nodular chert formation in all five limestone sequences occurred in sediments that were largely uncemented ghosts of pre chertification carbonate cements are present in some chert nodules but are volumetrically minor in every limestone sequence except the upper greensand chertification occurred after burial to a depth sufficient for intergranular pressure solution and mechanical grain deformation of carbonate sand nodular chert is most abundant in subtidal normal marine wackestones and mudstones that were deposited at or below fair weather wave base and is absent or rare in supratidal intertidal and high energy subtidal limestones and dolomites an intraformational sponge spicule silica source for chert nodules is suggested by direct evidence such as calcitized sponge spicules in the host limestone and circumstantial evidence such as ghosts of sponge spicules in chert nodules and a correlation of chert abundance with depositional environment most molds of siliceous sponge spicules were apparently obliterated by post chertification intergranular compaction we propose that these general trends for the depositional environments silica sources and timing of chertification are representative of most mesozoic to middle palaeozoic platform limestones

observed coupling of the mesosphere inversion layer to the thermal tidal structure rayleigh lidar observations of mesosphere temperature profiles obtained from 40 to 100 km from logan utah 41 7 111 8 w altitude 1 9 km over 10 nights in late february 1995 revealed an interesting development between 60 to 75 km of a winter mesosphere inversion layer with an amplitude of 20 30 k and a downward phase progression of 1 km hr the data also showed two altitude regions exhibiting significant cooling of 10 30 k in extent these were located below and above the peak of the inversion layer respectively at altitudes of 50 55 km and 70 80 km when these results were compared with the predictions of a global wave scale model gswm the observed thermal mesosphere structure is similar to the computed composite tidal structure based upon the semi diurnal and diurnal tides with the exception that observed amplitudes of heating and cooling are 10x larger than predicted gswm values we suggest that these events over utah are caused through a localized mechanism involving the coupling of gravity waves to the mesopause tidal structure

all sky imaging observations of mesospheric fronts in oi 557 7 nm and broadband oh airglow emissions analysis of frontal structure atmospheric background conditions and potential sourcing mechanisms 1 all sky imaging observations of distinct large horizontal transient mesospheric structures with a spatial scale of 100 km detected in images of broadband oh and oi 557 7 nm airglow emissions were made over clemson south carolina on the night of 14 15 october 2001 we designate these structures as mesospheric fronts and present a detailed summary of this night series of observations paying particular attention to the details of the different frontal structures the wave like activity seen throughout the night and the background atmospheric conditions these data are compared to other observations of similar mesospheric fronts found in the literature and we seek to understand them in relation to mesospheric bores ducted gravity waves mesospheric wall events and nonlinear gravity wave interactions we find that the observed frontal characteristics and the atmospheric background structure exhibit a close resemblance to previous observations of mesospheric bores owing to this similarity and supported by gravity wave ray tracing experiments we propose a sequence of events that generated the mesospheric fronts observed in the airglow emission furthermore we note this similarity in atmospheric structure suggests a potential means of predicting the occurrence of such mesospheric phenomena

polar mesospheric cloud structures observed from the cloud imaging and particle size experiment on the aeronomy of ice in the mesosphere spacecraft atmospheric gravity waves as drivers for longitudinal variability in polar mesospheric cloud occurrence patterns and structures in polar mesospheric clouds pmcs around the summertime mesopause region which are qualitatively similar to structures seen in noctilucent clouds nlcs from ground based photographs the structures in pmc are generally considered to be manifestations ofupward propagating atmospheric gravity waves agws variability of agw effects on pmc reported at several lidar sites has led to the notion of longitudinal differences in this relationship this studycompares thelongitudinal variability in thecips observed wave occurrence frequency with cips measured pmc occurrence frequency and albedo along with mesospheric temperatures measured by the sounding of the atmosphere using broadband emission radiometry instrument on board the thermosphere ionosphere mesosphere energetics and dynamics spacecraft our results for the latitude ranges between 70 and 80 show a distinct anticorrelation of wave structures with cloud occurrence frequency and correlations with temperature perturbations for at least two of the four seasons analyzed supporting the idea of gravity wave induced cloud sublimation the locations of the observed wave events show regions of high wave activity in both hemispheres in the northern hemisphere while the longitudinal variability in observed wave structures show changes from the 2007 2008 seasons there exist regions of both low and high wave activities common to the two seasons these persistent features may explain some of the observed differences in pmc activity reported by ground based lidar instruments distributed at different longitudes the statistical distribution of horizontal scales increases with wavelength up to at least 250 km we also discuss the possibility of atmospheric tides especially the nonmigrating semidiurnal tide aliasing our observations and affecting the results presented in this analysis

measurements of superadiabatic lapse rates in the middle atmosphere a large power aperture product rayleigh scatter lidar system has been successfully built and over 175 nights of middle atmosphere temperature measurements have been obtained the high signal to noise ratio of these measurements allows the stability of the air in the upper stratosphere and mesosphere to be determined a detailed methodology has been developed to attempt to differentiate between lapse rate variations due to photon counting errors and actual geophysical variations on nights when the geophysical variations are large compared to the photon counting errors regions of convective stability and instability can be determined at a reasonably high confidence level both statistics of the layers and an image of the layers is presented for the night of may 31 1996 the measured percentage of unstable layers is in agreement with the predictions of hines 1991 as is the apparently sporadic formation and distribution of the unstable regions

an eastward propagating two day wave evidence for nonlinear planetary wave and tidal coupling in the mesosphere and lower thermosphere 1 temperature observations from the saber instrument on the timed spacecraft are used to investigate the structure and evolution of an eastward propagating zonal wavenumber 2 disturbance with a period near two days this oscillation obtains a maximum amplitude of nearly 10 k in the southern hemisphere mid latitudes during late january the timing and location of this planetary wave is coincident with the regular quasi two day wave intensification that occurs annually in late january the period wavenumber and spatial structure of the eastward propagating two day wave are consistent with a wave that results from a nonlinear interaction between the quasi two day wave and the migrating diurnal tide the existence of an eastward propagating wave with a period near two days coincident with the westward propagating two day wave will have an impact on the interpretation of ground based observations analysis of the saber temperature observations are utilized to determine the structure and evolution of both this eastward propagating two day wave and the classic westward propagating zonal wavenumber 3 quasi two day wave during january 2005

mesospheric temperature inversions with overlying nearly adiabatic lapse rate an indication of a well mixed turbulent layer the rayleigh lidar technique was applied to study the thermal structure of the middle atmosphere observations were carried out on a routine basis for one year 130 clear nights at the main campus of york university near toronto 44 n 80 w mesospheric temperature inversions were generally found to occur below a height of 70 km during winter and above during summer the most interesting aspect of our observations was that the inversions were often associated with an overlying nearly adiabatic lapse rate which extended for several kilometres we interpret this as being an indication or signature of a well mixed turbulent layer a one dimensional numerical model was applied to demonstrate that a well defined turbulent layer within the mesosphere can bring about a thermal structure quite similar to that which was commonly observed an inversion with overlying nearly adiabatic lapse

coordinated investigation of midlatitude upper mesospheric temperature inversion layers and the associated gravity wave forcing by na lidar and advanced mesospheric temperature mapper in logan utah mesospheric inversion layers mil are well studied in the literature but their relationship to the dynamic feature associated with the breaking of atmospheric waves in the mesosphere lower thermosphere mlt region are not well understood two strong mil events t 30 k were observed above 90 km during a 6 day full diurnal cycle na lidar campaign conducted from 6 august to 13 august logan utah 42 n 112 w colocated advanced mesospheric temperature mapper observations provided key information on concurrent gravity wave gw events and their characteristics during the nighttime observations the study found both mils were well correlated with the development and presence of an unstable region 2 km above the mil peak altitudes and a highly stable region below implicating the strengthening of mil is likely due to the increase of downward heat flux by the enhanced saturation of gravity wave when it propagates through a highly stable layer each mil event also exhibited distinct features one showed a downward progression most likely due to tidal gw interaction while the peak height of the other event remained constant during further investigation of atmospheric stability surrounding the mil structure lidar measurements indicate a sharp enhancement of the convective stability below the peak altitude of each mil we postulate that the sources of these stable layers were different one was potentially triggered by concurrent large tidal wave activity and the other during the passage of a strong mesospheric bore

diagenetic evolution of the eocene ramp carbonates a paradigm from the nile valley egypt petrographical and geochemical attributes abstract carbonate rocks of east nile valley in egypt have been investigated as a paradigm for revealing the diagenetic evolution of the eocene ramp carbonates the integration of petrographical elemental geochemical and stable isotopic data revealed that the studied carbonates have been influenced by a sequence of diagenetic processes which are included in three diagenetic episodes i e eogenesis mesogenesis and telogenesis and are related to four diagenetic environments i e marine phreatic meteoric phreatic burial and uplifting environments the paragenetic sequence of the studied carbonates commences with the eodiagenetic episode which includes the marine and meteoric phreatic diagenetic environments the marine phreatic diagenetic environment comprises micritization glauconitization pyritization marine cementation fibrous calcite and syntaxial overgrowth rim cements early dolomitization formation of fine crystalline matrix replacive dolomites and early stages of mechanical compaction before significant burial the meteoric phreatic diagenetic environment includes the neomorphism dissolution meteoric cementation earlier phases of sparry calcite cements and precipitation of megaquartz in the void spaces of the peritidal carbonates during the mesogenesis episode the studied carbonates were exposed to burial diagenesis the shallow burial diagenesis resulted in the creation of point tangenetial contacts between the allochemical constituents and the precipitation of a medium coarse crystalline dolomite cement filling the dissolved fossils and dissolution pores the deep burial diagenetic processes embody the chemical compaction condensed fitted interpeneteration and pressure dissolution fabrics fracturing and burial cementation the telodiagenesis represents the last episode in the diagenetic history of the studied carbonates it witnessed the fracturing meteoric vadose cementation and hematitization processes

mechanism and controls of silicification of fossils in limestones silicification of calcitic fossils occurs along thin solution films at which calcite dissolves and silica precipitates the mechanism is replacement controlled by force of crystallization whereby the growth of the silica phase exerts pressure across the silica carbonate contact increasing the gibbs free energy and hence solubility of shell calcite physical evidence for force of crystallization controlled replacement includes restriction of carbonate dissolution to the silica carbonate contact and euhedral quartz terminations at some quartz calcite contacts correlations among some replacement quartz types and fossil taxa indicate that shell microstructure and bulk pore water silica concentration control replacement quartz type

biogenic chert in the cow head group cambro ordovician western newfoundland chert in the cow head group is mainly a replacement of limestone and shale and to a lesser extent an interparticle cement its field occurrences are distinct as 1 silicified margins on coarse conglomerates and thinly bedded limestones 2 nodules within limestone and shale 3 pervasively silicified beds of limestone and shale and 4 clasts or partial replacement of clasts within conglomerate radiolarians and sponge spicules are composed of microquartz or calcite and are particularly common in the ordovician part of the succession where most chert occurs in limestone spatially associated with chert the use of cathodoluminescence demonstrates that calcite replaced radiolarians and spicules are volumetrically more important than realized through transmitted light petrography petrographic relations between siliceous and rare pyritized radiolarians further indicate that these particles may be dissolved prior to compaction no trace of their former existence remains other than indirectly through the presence of silicified limestone and shale crushed grains cemented by chalcedony indicate that chert was precipitated during or after compaction the history of silicification and the replacement or dissolution of siliceous bioclasts is protracted ranging from near the sediment water interface where it is concomitant with early limestone lithification to deeper burial postdating mechanical compaction

mesospheric temperature inversion and gravity wave breaking more than 500 nightly mean temperature profiles have been obtained since 1981 by two rayleigh lidars located in south of france 550 km apart in the mesosphere a temperature inversion a feature persisting for several days is frequently observed simultaneously at both sites from a statistical study of the inversion characteristics it is shown that its altitude ranges from 55 72 km in winter to 70 83 km in summer while its probability of occurrence presents a semi annual variation with a maximum higher in winter than in summer and a minimum lower in may than in september the seasonal variation of the temperature inversion is shown to be very similar to that of the mst radar echoes in the mesosphere associated to turbulent layers generated by the breaking of gravity waves a crude estimate of the amplitude growth with height of a gravity wave in the presence of an inversion layer indicates that the wave will break preferably inside and above this layer the persistence of a temperature inversion during several days with amplitude as large as 40 k is tentatively explained by the heating of the turbulent layers generated by the continuous breaking of gravity waves above the secondary minimum of temperature

timed saber observations of lower mesospheric inversion layers at low and middle latitudes we present the global distribution seasonal and interannual variations of the lower mesospheric inversion layers mils using saber sounding of the atmosphere using broadband emission radiometry temperature data we show that both the characteristics and the formation mechanisms of large spatiotemporal scale lower mils are latitude dependent at low latitudes the monthly zonal mean amplitude of the lower mils exhibits a semi annual cycle and reaches a maximum of similar to 40 k in spring and a secondary maximum of similar to 30 k in autumn on the equator the semi annual oscillations in the background and diurnal migrating tide temperatures could contribute more than 12 and 25 k respectively suggesting they are the key causes of large spatiotemporal scale lower mils at low latitudes at middle latitudes the monthly zonal mean amplitude of the lower mils exhibits an annual cycle with its maximum in the range 24 33 k in winter in addition their longitudinal distribution and daily variation in winter are closely correlated with the transient structure of a composite wave composed of stationary and westward propagating quasi 16 day planetary waves with zonal wave number 1 the correlation coefficient between the lower mils and the composite wave can sometimes reach unity the composite planetary wave could contribute temperature enhancements of at least 15 20 k to the lower mils thus we believe that the transient structure of planetary waves is also an important cause of the large spatiotemporal scale lower mils in winter at middle latitudes in addition to previously proposed mechanisms

multidisciplinary approach for assessment of the factors affecting geohazard in karst valley the case study of gravina di petruscio apulia south italy management plans actions and strategies for preventing and mitigating natural disasters require detailed information on natural and human induced geohazards for the area under evaluation karst areas are particularly prone to instability due to the natural fragility of their environment but are also vulnerable due to human activity in depth studies of the factors controlling mass movement processes including land use over time become crucial for understanding instability mechanisms and future landscape evolution as well as for designing preventive measures and control techniques the murge area in the central part of apulia south italy is crossed by a vast network of dry valleys locally named lame and gravine whose morphology may resemble the most well known canyons and gorges of the world the genesis of these dry valleys is controversial and still the subject of continued debate although their origin is directly related to the geostructural setting and the uplift of the apulia foreland since the middle pleistocene each of these karst valleys has particular morphometric characteristics as well as their own morpho evolutionary history strongly linked to the different types of fault or fracture on which they developed also geological and geotechnical characteristics of the rock substrate channel and historic human made slope excavation or remodeling play an important role unfortunately several tragic events which occurred during the last decades have shown the susceptibility of the apulian dry valleys to natural hazards sometimes caused by human activities this paper proposes by means of a case study on a dry valley called gravina di petruscio in the arco ionico tarantino subregion a multidisciplinary approach using traditional methods of investigation and combining results to arrive at a critical appraisal of information that are suitable for a geohazard susceptibility analysis in karst environments geological geostructural and geomechanical surveys together with petrographic observations in thin sections of the outcropping materials allow to understand the genesis of the valley and then its evolution mainly due to slope retreat processes both sides of the valley have been found to be affected by planar slides wedge slides direct toppling and falls while the caves mostly modified by humans are affected by thinning spalling and crushing of pillars and partial or total collapse of cave roofs the predisposing and triggering factors of the most common mass movements are presented and discussed mitigation and prevention measures for future planning and remedial engineering structures are reported

rayleigh lidar observations of a mesospheric inversion layer during night and day a narrow field of view rayleigh lidar has been constructed at millstone hill mit haystack observatory 42 6 n 71 5 w for observations of middle atmospheric temperatures throughout the diurnal cycle during a 31 5 h measurement on 19 21 march 2001 a mesospheric thermal inversion layer was observed in both the night and day it developed near 60 km in altitude progressed downward at 0 40 0 06 km h and had an overlying adiabatic lapse rate the inversion amplitude correlated with the evolution of stratospheric gravity wave activity although the mesospheric perturbations were too large to be due to conservative gravity wave growth alone the 24 h mean temperature profile shows no evidence of a residual inversion layer

mesosphere inversion layers and stratosphere temperature enhancements 1 it has been known for at least 30 years that vertically narrow thermal layers form within the middle atmosphere two types of temperature enhancements the low latitude to midlatitude mesosphere inversion layer mil and the high latitude winter stratosphere temperature enhancement ste have both received much attention within the atmospheric science community because of their unexplained formation mechanisms and potential impacts on the middle atmosphere global circulation numerous experimental numerical and theoretical studies have attempted to explain certain aspects of these respective thermal layers but no one theory consistently and satisfactorily describes all the features observed we present a review of the literature and explicitly propose a classification scheme based on the different formation mechanisms suspected to cause these events for the mil we demonstrate that there are two subtypes the first one is tidally driven and tends to occur above 85 km this mil originates from large amplitude tidal waves propagating into the mesosphere and their subsequent nonlinear interactions with gravity waves which can often create the appearance of a double mil separated by approximately one vertical tidal wavelength 25 km the other subtype of mil is formed by a climatological planetary wave dissipation mechanism that occurs at a zero wind line the dissipation of the planetary wave tends to generate a mesoscale 1000 km inversion layer in the range of 65 80 km these two formation mechanisms explain a host of observed characteristics including the reason behind the downward progression of some mils and not others the different climatological nature of the two forms of mil events and the relative scarcity of mil observations at high latitudes the ste is believed to be generated by an altogether different process namely the nonlinear interaction between the polar vortex and planetary waves aleutian high the induced temperatures typically peak around 40 km and often exceed 300 k generating what appears to be a low hot stratopause when vertical temperature profiles are combined with synoptic analyses one observes that the ste is the consequence of high latitude vortex interactions creating a baroclinic atmosphere i e a downward adiabatic compression induced by an ageostropic flow we summarize the details of the relationship between this feature and sudden stratospheric warmings as well as the potential for in situ gravity wave generation we close with a review of currently unexplained mil ste features and offer new directions for future middle atmosphere thermal layer research

rayleigh lidar observations of gravity wave activity in the upper stratosphere at urbana illinois abstract during 13 nights of rayleigh lidar measurements at urbana illinois in 1984 86 thirty six quasi monochromatic gravity waves were observed in the 35 50 km altitude region of the stratosphere the characteristics of the waves are compared with other lidar and radar measurements of gravity waves and with theoretical models of wave saturation and dissipation phenomena the measured vertical wavelengths 2 ranged from 2 to 11 5 km and the measured vertical phase velocities cz ranged from 10 to 85 cm s 1 the vertical wavelengths and vertical phase velocities were used to infer observed wave periods tob which ranged from 100 to 1000 min and horizontal wavelengths x which ranged firm 70 to 2000 km there may be errors in the inferred values of the horizontal wavelengths because they were calculated by assuming that the observed period inferred the intrinsic period dominant wave activity was found at vertical wavelengths between 2 4 km and 7 10 km no significant seasonal variations were evide

double peaked hydroxyl airglow profiles observed from windii uars the windii instrument onboard the uars satellite made many thousands of measurements of the apparent brightness of the hydroxyl airglow as a function of tangent height during the night the measurements were mainly at latitudes between 42 s and 42 n most of the profiles of volume emission rate indicate a simple layer with a peak between 85 and 90 km however from 5 to 25 of the measured profiles have a more complex structure for the layer profile most frequently with two peaks separated by 4 to 6 km the horizontal extent varies from 200 to several thousand kilometers and the duration may be as long as 1 hours here the windii data from november 1991 to april 1995 are used to study the frequency of occurrence of the double peaked layers as a function of latitude season and local time and to explore possible causes of the unusual profiles early in the night the double peaked layers occur preferentially at low to medium latitudes migrating toward the equator by midnight where they remain for the rest of the night there is a pronounced asymmetry between the hemispheres which reverses between the march april equinox and the september october equinox the solstice behavior is similar though not so pronounced through simulation three possible causes to the observed oh double peaked layers were identified gravity waves are a likely source of isolated small scale events but the large horizontal scale long duration structures are more likely to result from temperature inversion layers or mixing events or a combination of the two

radiative influence of antarctica on the polar night vortex abstract temperatures over the antarctic plateau are sharply colder than those over its maritime surroundings the sharp temperature contrast due to antarctica is conveyed upward through 9 6 m absorption by ozone which shapes the thermal structure in the stratosphere the radiative impact of antarctica on the polar stratosphere is investigated in three dimensional integrations of the nonlinear primitive equations coupled to a full radiative transfer calculation that is performed with and without clouds cooling associated with antarctica depresses radiative equilibrium temperatures by as much as 10 k this direct radiative influence emerges clearly at high latitudes of the lowermost stratosphere it is accompanied elsewhere by temperature changes of opposite sign which result indirectly through adiabatic warming by the induced residual meridional circulation collectively these influences reinforce the polar night vortex shift the jet axis poleward and intensify downward transport over the polar ca

global distribution and variability of quasi 2 day waves based on the nogaps alpha reanalysis model this study presents the analysis of 14 months january 2009 february 2010 of continuous hourly nogaps alpha reanalysis data used for examining the quasi 2 day wave otdw the global structure and seasonal variability of the eastward and westward traveling qtdws in all meteorological fields geopotential height zonal and meridional wind and temperature have been studied the use of hourly reanalysis data allows a comprehensive understanding of the global spatial temporal qtdw distribution by simultaneous separations of all tides and planetary waves the wave characteristics amplitudes and phases are presented in latitude range 80 and altitudes from 15 to 95 km two different types of eastward traveling waves are identified i waves at middle and high latitudes with zonal wave numbers 2 and 3 which are observed in the local winters and ii waves observed predominantly over the equator with zonal wave number 2 which do not have a well defined seasonal variability but show some enhancement between june and august while the first type waves are seen in all meteorological fields the second ones are not seen in the meridional wind and belong to the ultra fast kelvin waves two different types of westward traveling waves have been identified as well i waves at middle and high latitudes with zonal wave numbers 2 3 and 4 which are observed mainly in summer hemisphere and ii waves observed predominantly over the equator with zonal wave numbers 1 2 and 3 enhanced predominantly at both solstices but are seen in other seasons as well while the first type waves are seen in all meteorological fields the second ones are observed in the meridional wind and are rossby gravity normal modes

implementation of a gravity wave source spectrum parameterization dependent on the properties of convection in the whole atmosphere community climate model waccm 1 this article describes the implementation of a new source spectrum parameterization for convectively generated gravity waves in the whole atmosphere community climate model version 2 waccm2 this parameterization is active in the tropics and is interactive with the underlying convection the gravity wave spectrum at each model grid point and time step is determined based on the convective heating depth tropospheric wind and the convective heating rate this parameterization introduces more realistic spatial and temporal distributions of gravity wave activity and yields gravity wave characteristics related to the underlying wave source we present the estimated gravity wave momentum flux phase speed spectra at 100 hpa as well as the gravity wave drag in the middle and upper atmosphere using the new source spectrum representation we also show the effects of this more physically based parameterization on the structure of the stratospheric and mesospheric semi annual oscillations of the zonal wind compared to a simulation with uniform gravity wave distribution we conclude that the interaction of the gravity wave parameterization with tropospheric characteristics is a positive step toward a more physical representation of the middle and upper atmosphere

multi instrumental observations of the quasi 16 day variations from the lower thermosphere to the topside ionosphere in the low latitude eastern asian sector during the 2017 sudden stratospheric warming event

effect of el nino southern oscillation on the dynamical thermal and chemical structure of the middle atmosphere 1 a simulation of the middle atmosphere is presented using a general circulation model gcm forced with observed sea surface temperature for the period 1950 2000 the gcm extends to the lower thermosphere and reproduces realistic dynamical and temperature distributions the period contains several el nino and la nina events which are identified using the nino3 index composite anomalies of relevant meteorological fields are obtained by stratifying the northern winter season according to the nino3 index these anomalies have the structure of vertically propagating planetary waves extending from the troposphere to the mesosphere circulation anomalies in the middle atmosphere are accompanied by large temperature anomalies that are of opposite sign in the stratosphere and mesosphere the former being warmer and the latter colder during el nino events near the summer mesopause changes in momentum deposition by parameterized gravity waves results in warming during el nino detailed statistical analysis is used to determine the significance of these anomalies a chemical transport simulation is carried out using output from the gcm it shows that when the lower stratosphere is colder as during la nina events some ozone depletion takes place conversely when the lower stratosphere is warmer and more disturbed as is the case during el nino events heterogeneous chemical processes are inhibited

a survey of paleozoic microbial fossils in chert abstract non acritarch microbial fossils from paleozoic marine cherts exhibit generally poor preservation with rare exceptional preservation microbial microfossils were discovered in 11 out of 17 stromatolitic and non stromatolitic paleozoic units containing replacement cherts from the continental united states many microfossils likely have a cyanobacterial affinity having both coccoid and filamentous morphotypes examined units range in age from middle cambrian to late permian and were deposited in peritidal open shelf and basinal settings all of which have preserved microbial assemblages cherts from the examined units generally formed during early diagenesis and the quality of microbial preservation does not seem to have changed during the paleozoic which is a period that experienced significant secular changes in the mode of marine silica formation

dolomitization and chertification of the early eocene rus formation in abu dhabi united arab emirates abstract the early eocene carbonates of the rus formation in the jabal hafit area near al ain united arab emirates were sampled to study their diagenetic history these carbonates were cyclically deposited in a shallow water environment alternating with marls or marly limestones and are characterized by extensive dolomitization and chertification with associated glauconitization the cyclic nature of sedimentation suggests that deposition was eustatically driven the diagenetic history of the limestones proceeded through the following path 1 marine cementation of allochems concomitant with formation of micrite envelopes 2 micritization of peloids ooids and skeletal grains 3 neomorphism of formerly high mg calcite and aragonite grains to low mg calcite 4 partial to complete dolomitization 5 partial chertification of both calcite and dolomite 6 glauconitization of chert 7 fracturing during shallow burial and 8 precipitation of late coarse calcite spar or mosaic and saddle baroque dolomite spar filling voids and fractures porosity is virtually nil in these rocks except for infrequent unfilled fractures vugs and oomolds due primarily to cementation and chertification biogenic grains are abundant in the limestones with nummulites sp alveolinid and miliolid foraminifera and crinoid ossicles and other echinoderm fragments being most common the tests of nummulites sp are commonly replaced by length fast chalcedony fibers which are occasionally later replaced by glauconite spherulitic and zebraic chalcedony and more rarely megaquartz occur as void filling cements and fringing chalcedonic fibers frequently rim the tests of skeletal grains all except the fringing chalcedonic fibers were subject to glauconitization prior to the chertification process is an extensive dolomitization period rhombic and sucrosic dolomite partially to completely replaced calcite at a relatively early diagenetic stage silicification caused the replacement of calcite by chert at a much more rapid rate than that of dolomite which was found floating within a chertified matrix fractures occurred both early and late in the rus and are usually filled by a late coarse mosaic calcite spar or coarse mosaic and saddle dolomite spar in completely dolomitized samples

global variability of mesospheric temperature planetary scale perturbations at equatorial and tropical latitudes 1 the study examines the source of a cold temperature perturbation observed in the wind imaging interferometer windii daytime daily zonal mean temperatures at 87 km height during march april 1993 also seen to some extent in 1995 and 1997 over the latitude range 25 s to 25 n the perturbation appears centered at 10 s as a departure of 10k to 35k below the semiannual climatological mean which peaks at equinox after accounting for tidal contributions to the observations by adopting tidal parameters determined from the microwave limb sounder mls temperature observations the cold temperature signature still remained in the residual data the perturbation is a global phenomenon immediately following march equinox and lasts over a period of 2 weeks the period is marked by the presence of mesospheric temperature inversions over the altitude range of 70 90 km harmonic analysis reveals the presence of planetary waves of wave number 1 with periods of 3 days 4 5 days and 7 days a cross section of the temperature monthly zonal mean data and month of the year over the period from january 1992 to december 1995 revealed a distinct msao modulated by a qbo with strong cold anomalies in march april 1993 1995 and 1997 in excellent agreement with the msao easterly phase of correlative mf radar wind observations at tirunelveli 8 7 n 77 8 e it is shown that the observed temperature anomalies can be produced by the residual circulation associated with the wave driving of the msao itself

mesospheric inversion layers at chatanika alaska 65 n 147 w rayleigh lidar observations and analysis rayleigh lidar observations at poker flat research range chatanika alaska 65 n 147 w have yielded density and temperature measurements from 40 km to 80 km these measurements have been made under clear skies at night between november 1997 and may 2009 we have identified and characterized 79 mesospheric inversion layers mils in the 40 70 km altitude region on 56 of 117 nights of observations between august and may these 79 mils have an average amplitude of 13 k peak altitude of 61 km topside lapse rate of 6 k km depth or thickness of 3 km base altitude of 58 km bottomside gradient of 5 k km and downward vertical velocity of 0 1 km h based on the 2 h temperature profiles mils occur with a nightly occurrence rate of 48 more frequently than previously reported at arctic sites but less frequently than at lower latitude sites mils are embedded in the larger planetary wave structure mils are found to occur most commonly in january as has been reported from lower latitude sites we find that the planetary wave 1 amplitudes are a factor 1 3 larger at an altitude of 5 0 6 5 scale heights 32 39 km on days when mils are observed than when they are not observed the planetary wave 2 amplitudes are not significantly different when mils are present and absent we find that eliassen palm flux divergences at an altitude of 7 8 scale height 45 52 km are a factor 2 0 larger on nights when mils are observed than when they are not observed we also find that gravity wave potential energy densities are a factor 1 3 larger on nights when mils are observed than on nights when they are not observed

silurian thalassinoides in an offshore carbonate community wisconsin usa abstract silicified boxwork of the ichnogenus thalassinoides in the silurian wenlockian racine formation milwaukee wisconsin usa represents open burrow systems that extended decimeters below the sediment surface in offshore carbonate muds of an intracratonic basin the most completely silicified burrows contain a core of organic rich spiculitic chert a surrounding zone of chert and an outer zone of mixed chert and dolomite burrows reach 3 cm in diameter and include larger turning chambers they were probably produced by an arthropod bioturbation affected the epibenthic fauna by extensive vertical mixing of skeletal material and possibly by construction of small mounds at the sediment surface the same skeletal fauna of siliceous sponge spicules silicified crinozoan ossicles and a diverse array of other groups occurs in both burrows and surrounding dolomite matrix brachiopods including dicoelosia and skenidioides indicate silurian benthic assemblage 5 which represents an outer shelf setting trilobite sclerites are more common within thalassioides burrows than in the surrounding matrix two enrolled calymenid individuals and one molted calymenid exoskeleton occur within thalassinoides suggesting that commensal trilobites occupied the burrow systems

accreted mesozoic pelagic seamount in chirai quarry hokkaido japan petrographic evidence of flint limestone cycles abstract the jurassic to cretaceous cyclic sequences of nodular flints and micritic limestones of the nikoro group in chirai quarry eastern hokkaido were studied petrographically and geochemically they were compared with the cretaceous to eocene cycles of nodular flints and pelagic carbonates on the crests of three pelagic seamounts in the north pacific the nodular flints and micritic limestones in chirai quarry were shown to be deposited in a pelagic environment from the fe mg plots of the non calcareous fractions the flint nodules were formed due to the dissolution of pelagic carbonates and three kinds of dissolution are possible 1 dissolution by deep bottom waters 2 dissolution by organisms to form burrows and 3 dissolution by meteoric groundwaters although nodules formed due to 2 and 3 can be recognized at some horizons in the quarry most of the nodules are interpreted to be formed by dissolution due to upwelling bottom waters on the crest of the seamount the nodules on the crests of modern pelagic seamounts in the pacific are restricted in distribution on the seamount to places where the water depth on the crest at the time of deposition was in the range 2 4 km this may suggest that the upwelling bottom water undersaturated with calcium carbonate is not found at depths shallower than 2 km the cycles of flints and pelagic carbonates are interpreted to denote the facies on the crest of the pelagic seamount therefore the jurassic to cretaceous cycles found in chirai quarry can be recognized as an accreted pelagic seamount

episodic accumulation and the origin of formation boundaries in the helderberg group of new york state at any single locality in the helderberg group of new york state most formation and member boundaries coincide with boundaries of punctuated aggradational cycles in each case of coincidence the boundary is a discontinuity that was produced by a rapid rise of relative base level rather than a facies contact representing gradual migration of contiguous paleoenvironments apparently diachronous formation boundaries in the sequence are not single continuous surfaces instead each diachronous boundary is actually a stratigraphic series of isochronous surfaces that are separate punctuated aggradational cycles pac boundaries produced by distinct geologically instantaneous base level rises these conclusions about the origin of formation boundaries suggest that the concept of the formation as a fundamental unit of stratigraphic description and interpretation may need revision if the stratigraphic record accumulated episodically on a small scale

nodular chert from the arbuckle group slick hills sw oklahoma a combined field petrographic and isotopic study nodular chert from the middle and upper arbuckle group early ordovician in the slick hills sw oklahoma was formed by selective replacement of grainstones burrow fillings algal structures and evaporite nodules chert nodules are dominantly microquartz with minor fibrous quartz both quartzine and chalcedony megaquartz and microflamboyant quartz lepisphere textures of an opal ct precursor are preserved in many especially in finely crystalline chert nodules the 18o values of microquartz chert range from 23 4 to 28 80 00 smow significantly lower than those of cenozoic and mesozoic microquartz chert formed both in the deep sea and from near surface sea water the 18o values of chert decrease with increasing quartz crystal size silicification in the arbuckle group occurred during early diagenesis with the timing constrained by the relative temporal relationships among silicification burial compaction and early dolomite stabilization silica for initial chert nucleation may have been derived from both dissolution of sponge spicules and silica enriched sea water chert nucleation appears to have been controlled by the porosity permeability and organic matter content of precursor sediments this conclusion is based on the fact that chert selectively replaced both porous grainstones and burrows and algal structures enriched in organic matter growth of chert probably occurred by a maturation process from opal a to opal ct to quartz as indicated by the presence of opal ct precursor textures in many chert nodules although field and petrographic evidence argues for an early marine origin for chert in the arbuckle group the light 18o values are inconsistent with this origin meteoric resetting of the 18o values of the chert during exposure of the carbonate platform best explains the light 18o values because i the 18o values of chert nodules decrease with decreasing 18o values of host limestones and ii chert nodules from early dolomite which underwent more extensive meteoric modification than associated limestones have lighter 18o values than chert nodules from limestones increasing recrystallization of chert nodules by meteoric water resulted in progressive 18o depletion and quartz crystal enlargement

mesospheric temperature inversions as seen by isams in december 1991 a large number of mesospheric temperature inversion layers have been observed locally in recent decades notably by the network of french lidars it is shown in this paper that the improved stratospheric and mesospheric sounder on board the upper atmosphere research satellite is able to detect the presence of temperature inversions and thus allows the study of their occurrence and characteristics on a global scale during december 1991 inversions of large amplitude greater than 20 k are seen almost every day especially in mid latitudes with extent varying typically from 105 to 106 km several particularly large inversions were observed at the end of the month their correlation with assimilated stratospheric winds is consistent with the interpretation that gravity waves propagate unfiltered through the stratosphere in the regions of strong winds and break in the mesosphere the combination of high resolution lidar measurements and global satellite coverage is expected to lead to a better understanding of this significant feature of the winter mesosphere at middle latitudes

rayleigh lidar observations of mesospheric inversion layers at poker flat alaska 65 n 147 w rayleigh lidar measurements of the stratosphere and mesosphere have been made on an ongoing basis over a three year period at poker flat alaska 65 n 147 w these observations have yielded 27 nightly measurements of the middle atmosphere temperature profile 40 80 km these nighttime measurements are distributed between august and april mesospheric inversion layers have been observed on five occasions the average altitude of the inversion layer peak is 60 km with average amplitude of 18 k the temperature gradients on the topside of the inversion layers approach the adiabatic lapse rate the inversion layers do not exhibit the apparent downward phase velocities that are commonly observed at lower latitudes furthermore the inversion layers appear significantly less frequently than at lower latitudes the observations are discussed in terms of current models and observations at other sites

silicification in the belt supergroup mesoproterozoic glacier national park montana usa nodular cherts can provide a window on the original sediment composition diagenetic history and biota of their host rock because of their low susceptibility to further diagenetic alteration the majority of phanerozoic cherts formed by the intraformational redistribution of biogenic silica particularly siliceous sponge spicules radiolarian tests and diatom frustules in the absence of a biogenic silica source precambrian cherts necessarily had to have had a different origin than phanerozoic cherts the mesoproterozoic belt supergroup in glacier national park contains a variety of chert types including silicified oolites and stromatolites which have similar microtextures and paragenesis to phanerozoic cherts despite their different origins much of the silicification in the belt supergroup occurred after the onset of intergranular compaction but before the main episode of dolomitization the belt supergroup cherts probably had an opal ct precursor in the same manner as many phanerozoic cherts although it is likely that precambrian seas had higher silica concentrations than at present because of the absence of silica secreting organisms no evidence was observed that would suggest that high dissolved silica concentrations in the belt sea had a significant widespread effect on silicification the rarity of microfossils in belt supergroup cherts indicates that early silicification if it occurred was exceptional and restricted to localized environments the similarity of microtextures in cherts of different ages is evidence that the silicification process is largely controlled by host carbonate composition and dissolved silica concentration during diagenesis regardless of the source of silica

vhf echoes from the midlatitude mesosphere and the thermal structure observed by lidar observations with a 46 5 mhz radar system at aberystwyth wales 52 n 4 w over the period february 1990 to may 1994 have shown a pronounced seasonal variation in the height range of mesospheric echoes these were observed over the range 64 84 km in all seasons but those at still greater heights were confined to summer months coordinated radar and lidar observations at the same site during 1993 have shown that these intense echoes in summer analogous to polar mesosphere summer echoes pmse are associated with low mesopause temperatures the weaker echoes observed in winter seem to be associated with regions of superadiabatic lapse rates and echoes are observed both above and below the maxima in temperature inversions commonly observed below the mesopause the types of instability implied in these associations of echo height and temperature structure are considered

observations of the diurnal tide from space abstract this study presents a climatology of mesospheric and lower thermospheric diurnal tidal winds obtained with the high resolution doppler imager hrdi on the upper atmosphere research satellite uars the observations reveal that although tidal structures are present at all times like the prevailing zonal winds they exhibit significant semiannual as well as other shorter term variations in amplitude results are presented for a period extending over more than one year from november 1991 to july 1993 the 1 1 diurnal tidal amplitude of the meridional component characterized by the value at an altitude of 90 km and a latitude of 22 ranges from a minimum at solstice of less than 20 m s 1 to an equinox maximum of over 70 m s 1 the vertical wavelength and phase of the tide show only slight variations throughout the year with a suggestion of semiannual variations in both

na doppler temperature lidar initial mesopause region observations and comparison with the urbana medium frequency radar meteoric ablation in the upper atmosphere is the source of a dense layer of atomic na between about 80 and 105 km altitude peak densities are typically several thousand atoms cm3 and the total abundance varies seasonally at mid latitudes with the maximum in winter the na layer is a sensitive tracer of the thermal and density structure of this region of the atmosphere and can be probed with exceptional accuracy and resolution using resonance fluorescence lidar techniques we report the first observations of vertically resolved na density temperature and wind profiles in the mesopause region using a new four frequency doppler temperature lidar the initial zonal wind and temperature observations were obtained with a resolution of 30 min and 1 5 km and rms accuracies of 12 m s and 2 k these measurements were conducted simultaneously with the medium frequency mf radar at the urbana atmospheric observatory 40 n 88 w during the night of march 14 15 1991 the mean temperature profile exhibits a well defined mesopause at 95 5 km with a temperature of 181 k the mean zonal wind profile exhibits a strong 58 m s westward jet at 97 km which appears to be related to the mesopause during the 6 hour and 45 min observation period the na doppler winds averaged between 88 and 98 km exhibit the same general trends as the mf radar apparent and true winds in this same region however the lidar and radar velocity estimates differ by as much as 40 m s at some times during the night

mesospheric inversion layer and sprites 1 the vertical structure of temperature observed by sounding of atmosphere using broadband emission radiometry saber aboard thermosphere ionosphere mesosphere energetics and dynamics timed and sprites observations made during the eurosprite 2003 2007 observational campaign were analyzed sprite observations were made at two locations in france namely puy de dome 45 46 19 2 n 02 57 44 64 e 1 464 km altitude in the french massif central and at the pic du midi 42 56 11 n 00 08 34 e 2 877 km altitude in the french pyrenees it is observed that the vertical structure of temperature shows evidence for a mesospheric inversion layer mil on those days on which sprites were observed a few events are also reported in which sprites were not recorded although there is evidence of a mil in the vertical structure of the temperature it is proposed that breaking gravity waves produced by convective thunderstorms facilitate the production of 1 sprites by modulating the neutral air density and 2 mils via the deposition of energy the same proposition has been used to explain observations of lightings as well as both mils and lightning arising out of deep convections

effects of the quasi biennial oscillation and stratospheric semiannual oscillation on tracer transport in the upper stratosphere usingsatelliteobservationstogetherwitha chemistry climatemodel ccm theeffect ofthestratospheric semiannual oscillation sao and quasi biennial oscillation qbo on the equatorial double peak in observed ch4 and no2 is reexamined it is concluded that the lower equatorial halogen occultation experiment haloe ch4 mixing ratio of the april double peak in 1993 and 1995 was associated with the prominent first cycle of the sao westerlies which causes local vertical downwelling in the upper equatorial stratosphere the observational evidences imply that the strong westerlies of the first cycle of the stratospheric sao in 1993 and 1995 were driven by enhanced lower stratospheric gravity wave activity in the early parts of those years the ccm simulations further verify that the gravity wave source strength has a large impact on the development and strength of the sao westerlies this result suggests that the equatorial longlived tracer mixing ratio near the stratopause which is associated with the strength of the sao westerlies was not only modulated by the qbo phase but was also significantly influenced by interannual variation in the gravity waves it is also found that the deeper equatorial trough of the double peak is unlikely to be always accompanied by the more prominent northern hemispheric lobe and the northern hemispheric lobe of the double peak can be mainly attributed to subtropical upwelling the altitude of greatest chemical destruction anomalies associated with the sao and qbo is below the trough of the double peak implying that the effect of the chemical process on the double peak is insignificant

sodium lidar observed gravity wave breaking followed by an upward propagation of sporadic sodium layer over hefei china the university of science and technology of china ustc sodium temperature wind lidar observed a strong zonal wind shear 60 m s km near 98 km between 1315 and 1330 ut on 29 july 2013 and a cooling near 96 100 km above a warming near 90 95 km between 1330 and 1430 ut this suggests a possible gravity wave gw breaking event comparison of the lidar results with observations from a nearby meteor radar and with satellite results indicated that the gw likely broke down over a large horizontal area in addition the sodium number density suddenly increased by 10 12 times 13 000 atmos cm3 near 95 km at 1400 ut immediately following the gw breaking this sporadic sodium layer ssl which is different from most previously observed ssl events which propagate downward tended to propagate upward and also appeared 2 minutes earlier in the west channel than in the east channel the horizontal propagation direction of the ssl was aligned with the horizontal wind direction which was likely due to the propagation of a high density sodium layer from the northwest of the lidar site and was possibly related to the earlier gw breaking event

observations of horizontal and vertical wave number spectra of gravity wave motions in the stratosphere and mesosphere over the mid pacific we present vertical and horizontal wave number spectra of density perturbations in the upper stratosphere 25 40 km and the upper mesosphere 80 105 km inferred from 45 hours of airborne na rayleigh lidar observations in the vicinity of hawaii the mean density variance is 0 92 2 for the upper stratosphere and 6 1 2 and for the upper mesosphere the mean vertical shear variance and richardson s number for the upper mesosphere are 6 1 km 2 and 0 69 respectively the observed vertical wave number m and horizontal wave number k spectra exhibit power law dependencies the mean slopes of the vertical wave number spectra are 2 5 for the upper stratosphere and 3 1 for the upper mesosphere the mean slope of the horizontal wave number spectra is 1 9 for the upper mesosphere the mean characteristic vertical and horizontal wavelengths inferred from the spectra are 13 4 and 5810 km respectively in all cases the magnitudes of the upper stratosphere m spectra are more than an order of magnitude smaller than those of the upper mesosphere at all observable scales in the stratosphere the m spectra exhibit significant energy at low wave numbers that are less than the values expected for the characteristic wave numbers this suggests the presence of gravity wave sources capable of generating significant energy at long vertical scales the source is believed to be geostrophic adjustment of the jet stream a large amplitude highly coherent quasi monochromatic short horizontal scale h 16 km oscillation in the na layer was observed on the march 22 flight the oscillation resembled short horizontal scale structures often observed in oh airglow images and was found to be consistent with a gravity wave interpretation

chert occurrences in carbonate turbidites examples from the upper jurassic of the betic mountains southern spain in upper jurassic carbonate turbidites of the betic mountains southern spain chert occurs in three morphologies bedded chert nodular chert and mottled chert the last refers to a weak dispersed and selective silification which gives a speckled appearance to the rock the three types of chert are formed by replacement of limestones and are associated with different calcareous facies turbidite packstones of saccocoma and peloids and turbidite lime mudstones of pelagic material contain bedded and nodular cherts the silicification textures are mainly micro and cryptocrystalline quartz with local chalcedonic quartz both length fast and length slow which is more common in the packstones only mottled chert is produced where calcareous breccia beds are silicified mottled chert consists of micro and cryptocrystalline quartz length slow chalcedonic quartz and mosaics or individual crystals of euhedral megaquartz beds and nodules are the result of early diagenetic silicification with silica derived from the calcitization and dissolution of radiolarians and subordinately sponge spicules whereas mottled chert is the consequence of later silicification in a probably mg rich environment early silicification is mainly confined to turbidite beds and only rarely occurs in the interbedded pelagic limestones turbidite sedimentation favours silicification because rapid burial of the transported siliceous tests prevents silica from the dissolution of tests passing into overlying sea water a silica rich interstitial fluid develops in the turbidite layer and this migrates to more permeable zones giving rise to bedded and nodular chert