inertia gravity waves observed in the lower stratosphere over macquarie island abstract this study examines the properties of inertia gravity waves observed in the lower stratosphere over macquarie island how these properties vary with season and the likely source of the waves the waves are observed in high resolution upper air ozonesonde soundings of wind and temperature released from macquarie island during the 1994 ashoe maesa program the properties of the inertia gravity waves observed in the soundings are quantified using hodograph and rotary spectral analyses the analyzed waves have horizontal wavelengths between 100 and 1000 km vertical wavelengths between about 1 and 7 km intrinsic frequencies between f and 2f and horizontal trace speeds between 50 and 30 m s 1 there appears to be a seasonal cycle in the inertia gravity wave activity in the lower stratosphere the minimum being in the austral winter when the background zonal flow is strong and westerly and its vertical shear is positive in contrast the variance of the horizontal perturbation winds does not show a

assessing the importance of drilling predation over the palaeozoic and mesozoic abstract plausible predatory palaeozoic and mesozoic drillholes have been reported in the literature from 62 localities mainly from north america and western europe most of which were discovered in the last 20 years twenty nine of these reports include sufficient data to be statistically valid analyses of these data suggest that there was a highly significant increase in drillhole and hence predator size in the early devonian which may reflect a change in predatory taxa as part of the mid palaeozoic marine revolution in this study frequency of drillholes in particular species has been examined examination of drilling frequency suffered by individual taxa from a range of palaeozoic and mesozoic sites showing that these are highly variable just as they are between different holocene localities nevertheless levels of up to 50 in the palaeozoic and 40 in the mesozoic suggest that at least locally drillers did exert an important selection pressure analysis of the currently available data set reveals no significant change in drilling frequency over the palaeozoic and mesozoic there are fewer records of drilling predation from the palaeozoic and mesozoic than from the cenozoic at present however it is difficult to assess whether drilling was truly less widespread than in the cenozoic or whether at least part of the problem is taphonomic loss of information in particular in the late palaeozoic and mesozoic it is striking that relatively few reports involve molluscan prey despite their attractiveness as profitable prey with high flesh yield when compared with the apparently more frequently drilled brachiopods however study of the style of preservation of drilled molluscs that were mostly originally aragonitic suggests that drillholes are only preserved in faunas which are exceptionally preserved such that the original microstructure is still observable by contrast brachiopods which were either originally phosphatic or calcitic have much better preservation potentials and therefore may be more likely to show drillholes an understanding of the preservation biases involved in the recognition of drillholes may suggest suitable localities for further research more data from a suite of localities world wide are required for a more detailed analysis of patterns of drilling predation in the palaeozoic and mesozoic

vermeij crushing analysis a new old technique for estimating crushing predation in gastropod assemblages abstract vermeij crushing analysis allows researchers to estimate frequencies of fragmentation due to crushing predation by establishing a taphonomic fragmentation baseline using shells bearing predatory drillholes we calculated the frequencies of several types of shell damage on groups of drilled and undrilled shells shells of the modern species olivella biplicata o baetica nassarius perpinguis and euspira lewisii were collected at torrey pines state beach del mar california the shells were divided into drilled and undrilled groups and examined for multiple types of damage the frequencies of damage in the drilled groups represent taphonomic damage as the cause of death of these shells is known to be naticid gastropod predation in cases where the damage frequencies were higher for the undrilled shells cause of death unknown possibly crushing the differences in fragmentation between the two categories is attributed to crushing predation the frequencies of damage due to crushing predation are used to estimate a minimum frequency of mortality due to crushing predation in the shell assemblage potential confounding factors were also examined such as potential differences in taphonomic susceptibility and hermit crab habitation between drilled and undrilled shells this technique bypasses the logistical difficulties of field predation studies and the problems of interpretation of shell repair frequencies two common methods of assessing crushing predation in shelled prey most significantly vermeij crushing analysis can be performed on both modern and fossil shell assemblages allowing the study of trends in crushing predation over both space and time

average statistical characteristics of long gravity waves observed with the middle and upper atmosphere radar in the mesosphere average statistical characteristics of internal gravity waves igws with horizontal wavelengths longer than 60 km are obtained at the altitudes 65 80 km from the observations with the middle and upper atmosphere radar at shigaraki japan 35 n 136 e in 1986 1995 the numbers of signals selected with narrow frequency band filters attributed to igw having periods 0 1 6 hours vary between 870 and 2300 for different seasons and altitudes long period igws have larger amplitudes and larger vertical wavelengths than short period igws for waves with periods 0 1 6 hours the mean values of the horizontal and vertical wavelengths are 100 300 km and 6 10 km respectively igw amplitudes and momentum fluxes have maxima in winter and summer and minima in spring and autumn distributions of the azimuths of igw horizontal wave vectors and momentum fluxes are nearly isotropic with maxima in zonal directions in summer the westward momentum flux is larger than the eastward flux in winter and is smaller than that in summer the differences between eastward and westward wave momentum fluxes are larger for long period igws the net zonal igw momentum flux is mainly directed opposite to the mean wind in the mesosphere

a new perspective on gravity waves in the martian atmosphere sources and features 1 using a mars general circulation model gcm we investigate the characteristics of gravity waves in the atmosphere of mars fluctuations due to internal gravity waves at tidal periods such as diurnal semidiurnal and terdiurnal tides are predominant in the lower atmosphere in particular the diurnal and semidiurnal tides having large zonal wave numbers s 10 are significant fluctuations associated with nontidal gravity wave components in the lower atmosphere are negligibly small except for the stationary orographic component nontidal gravity waves grow in amplitude in the middle atmosphere while tidal components remain the dominant form of gravity waves in the upper atmosphere 80 km nontidal gravity wave components and fluctuations due to the diurnal and semidiurnal tides having large zonal wave numbers are equally important we estimate the global distributions of the gravity wave energy at various altitudes and attempt to define various sources our results show that most nontidal gravity wave energy is closely related with the diurnal amplitude except in the lower atmosphere where association with orography predominates this suggests that nonorographic gravity waves are generated by the breaking and dissipation of the diurnal tide on the other hand nontidal gravity wave energy in the lower atmosphere peaks in mountainous regions and points to their source as being of orographic nature we also enumerate the major differences between gravity waves on mars and earth as simulated by global models

predatory drill holes and partial mortality in devonian colonial metazoans elliptical holes 0 2 0 3 mm in diameter with beveled edges have been found penetrating the zooids of encrusting hederellids colonial metazoans of uncertain affinity from several localities in the middle devonian givetian of north america these are the first known predatory drill holes in pre cretaceous colonial animals and a key addition to the record of paleozoic predation some drill holes were subsequently patched from within by new skeletal material proving that the drilling occurred during the life of the colony these drill holes are analogous to predatory drill holes in some modern cheilostome bryozoans which can be similarly patched in this case by the intramural budding of a new zooid into the empty chamber of the old zooid a drilling predator of unknown affinity evidently consumed hederellid zooids one at a time inflicting partial mortality on the colonies the mode of drilling suggests that the predator specialized in this type of colonial prey and the repaired drill holes show that the hederellids had a response to such damage reports of small circular holes interpreted as predatory drill holes are becoming more common in noncolonial shelled invertebrates from the paleozoic notably brachiopods bivalves and crinoids these drill holes are far less frequent than in post paleozoic shells where most are the work of gastropods and many are of questionable origin with some representing the traces of parasites and others postmortem domichnia

non predatory borings in phanerotrema gastropoda early silurian anticosti island quebec canada non predatory borings in phanerotrema gastropoda early silurian anticosti island quebec canada

global ray tracing simulations of the saber gravity wave climatology 1 since february 2002 the saber sounding of the atmosphere using broadband emission radiometry satellite instrument has measured temperatures throughout the entire middle atmosphere employing the same techniques as previously used for crista cryogenic infrared spectrometers and telescopes for the atmosphere we deduce from saber v1 06 data 5 years of gravity wave gw temperature variances from altitudes of 20 to 100 km a typical annual cycle is presented by calculating averages for the individual calendar months findings are consistent with previous results from various satellite missions based on zonal mean saber data for july and zonal mean gw momentum flux from crista a homogeneous and isotropic launch distribution for the grograt gravity wave regional or global ray tracer is tuned the launch distribution contains different phase speed mesoscale waves some of very high phase speed and extremely low amplitudes as well as waves with horizontal wavelengths of several thousand kilometers global maps for different seasons and altitudes as well as time series of zonal mean gw squared amplitudes based on this launch distribution match the observations well based on this realistic observation tuned model run we calculate quantities that cannot be measured directly and are speculated to be major sources of uncertainty in current gw parameterization schemes two examples presented in this paper are the average cross latitude propagation of gws and the relative acceleration contributions provided by saturation and dissipation on the one hand and the horizontal refraction of gws by horizontal gradients of the mean flow on the other hand

naticid drilling predation on gastropod assemblages across the k t boundary in rajahmundry india new evidence for escalation hypothesis abstract one of the important and well documented prey predator interactions in the fossil record is drilling predation done by naticid gastropods which diversified during the cretaceous although drilling frequencies showed fluctuating patterns most of the previous studies argued that naticid drilling predation was less intense during the cretaceous and the modern values were achieved since the paleocene we here present a new dataset of naticid drilling predations involving 31 929 gastropod specimens from the latest maastrichtian infratrappean bed in rajahmundry southern india these specimens belonged to 40 species of 20 families thus representing a spectacular gastropod diversity that was not known until recently from this region we examined 5884 complete or near complete specimens to quantify naticid drilling predation on this assemblage it appeared that drilling frequency was significantly higher from all previous cretaceous values this was true for both assemblage level and lower taxon level results along with high successful drilling and low unsuccessful drilling frequencies site and size stereotypy of drillholes suggest that naticid predators were highly efficient even in the cretaceous predators were prey selective and there was poor correlation between relative abundance and drilling frequency of prey taxa the present maastrichtian assemblage underlies the k t mass extinction level drilling frequency was zero in the straddler prey community in the intertrappean bed found immediately above the k t boundary the absence of any drillhole in surviving prey taxa may be due to sudden reduction in abundance of escalated predators although some prey taxa e g cerithiids continued this emphasizes the role of mass extinction in disrupting predator prey interaction we conclude that naticid drilling induced escalation was already established during the cretaceous and the present find extends the paleobiogeography of naticid predation which was previously reported from the western world up to india

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

gravity wave and equatorial wave morphology of the stratosphere derived from long term rocket soundings fluctuations in vertical profiles of atmospheric temperature and horizontal wind in the 20 60 km altitude range have been isolated from meteorological rocket measurements during 1977 87 at 15 widely separated sites the seasonal geographical and vertical variability of the variance of horizontal velocities u 2 2 and relative temperature perturbations t 2 were studied the bulk of the variance of both quantities in the 2 10 km and 2 20 km vertical wavelength bands was associated with gravity wave motions although in depth study of the wave polarization shows that planetary scale equatorial wave modes contribute to the variance at equatorial sites annual mean variances varied widely among the 15 stations suggesting appreciable geographical variability in stratospheric wave activity

simulation of inertia gravity waves in a poleward breaking rossby wave abstract poleward breaking rossby waves often induce an upper level jet streak over northern europe dominant inertia gravity wave packets are observed downstream of this jet the physical processes of their generation and propagation in such a configuration are investigated with a mesoscale model the study is focused on an observational campaign from 17 to 19 december 1999 over northern germany different simulations with the fifth generation pennsylvania state university national center for atmospheric research psu ncar mesoscale model mm5 have been performed for a high resolution process study three domains were set up that encompass the evolution of rossby waves and that of inertia gravity waves to minimize the impact of model damping the horizontal and vertical resolution has been adjusted appropriately with a novel statistical approach the properties of inertia gravity wave packets have been estimated this method uses the horizontal divergence field and takes into account the spatial e

radiosonde observations of gravity waves in the lower stratosphere over davis antarctica radiosonde observations made from davis station antarctica 68 6 s 78 0 e between 2001 and 2012 are used to compile a climatology of lower stratosphere inertial gravity wave characteristics wavelet analysis extracts single wave packets from the wind and temperature perturbations wavelet parameters combined with linear gravity wave theory allow for the derivation of a wide range of wave characteristics observational filtering associated with this analysis preferentially selects inertial gravity waves with vertical wavelengths less than 2 3 km the vertical propagation statistics show strong temporal and height variations the waves propagate close to the horizontal and are strongly advected by the background wind in the wintertime notably around half of the waves observed in the stratosphere above davis between early may and mid october propagate downward this feature is distributed over the observed stratospheric height range based on the similarity between the upward and downward propagating waves and on the vertical structure of the nonlinear balance residual in the polar winter stratosphere it is concluded that a source due to imbalanced flow that is distributed across the winter lower stratosphere best explains the observations calculations of kinetic and potential energies and momentum fluxes highlight the potential for variations in results due to different analysis techniques

mystery of naticid predation history solved evidence from a living fossil species observations of living cernina fluctuata sowerby the sole extant species of the mesozoic and cenozoic prosobranch gastropod family ampullospiridae show that this species is an algal grazer and is not a shell drilling predatory naticid gastropod all jurassic and early cretaceous gastropods previously assigned to naticidae belong to ampullo spiridae and are now inferred to be herbivores not shell drillers this finding refutes the triassic origin and favors a cretaceous origin for naticid drilling predation a preliminary revision of cenozoic and cretaceous species previously assigned to naticidae suggests that naticids were absent prior to the cretaceous campanian and diversified at a modern level in eocene time this pattern of naticid diversification from the late cretaceous onward coincides roughly with the evidence of naticid predation the fossil record of naticid drill holes once of anomalously short duration now accurately reflects the geologic history of naticid predation activity

geostrophic wind fields in the stratosphere and mesosphere from satellite data 1 daily maps of horizontally resolved zonal and meridional geostrophic wind fields in the altitude range of 20 90 km were obtained from the cryogenic infrared spectrometers and telescopes for the atmosphere crista experiment during november 1994 and august 1997 results are compared with zonal mean zonal winds from climatological sources and with assimilated data from standard analyses correlative data from ground based and balloon and rocket borne measurements are used to validate the crista winds the comparisons show that geostrophic wind fields from high spatial resolution satellite borne temperature measurements are a good approximation for the winds in the middle atmosphere up to mesopause heights therefore they may be used as input for further modeling efforts particularly in the mesosphere where no wind data from standard analyses are available

eliassen palm fluxes of the 2 day wave abstract high resolution doppler imager hrdi winds and temperatures are used to diagnose a 2 day wave event detected in the southern hemisphere during january 1994 a novel aspect of this study is the focus upon the wave fluxes throughout the 65 100 km range and their relationship to the background state a wave packet composed of zonal wavenumbers 2 3 and 4 propagates westward with a phase speed near 60 m s 1 the periods associated with zonal wavenumbers 2 3 and 4 are 3 5 2 1 and 1 7 days respectively the morphology of the 2 day temperature and wind fields is consistent with that of a developing baroclinic wave the divergence of the eliassen palm flux of zonal wavenumbers 2 4 is dominated by the vertical convergence of meridional heat flux the wave driving or eliassen palm flux divergence per unit mass is predominantly westward with magnitudes on the order of 5 m s 1 day 1 a steady state quasigeostrophic model of the mean meridionai circulation is used to estimate the mean wind respon

seasonal variation of momentum flux in the mesosphere observed with the mu radar we have regularly monitored mesospheric winds at 60 85km for three years with the mu radar 35 n 136 e and have found that the variance of wind velocity fluctuations for periods from 5 min to 2 hr shows a semi annual variation with a significant peak in summer centered in july and irregular enhancements in winter the zonal momentum flux induced by gravity waves shows eastward and westward maxima in july august and december february respectively typical eastward accelerations at the 70km altitude range from 7 to 13 m s day and from 8 to 11 m s day in summer and winter respectively which agree fairly well with theoretical predictions

statistical analysis of gravity waves observed with the middle and upper atmosphere radar in the middle atmosphere 1 method and general characteristics a statistical procedure is developed to obtain the parameters of spectral harmonics of internal gravity waves igw with horizontal wavelengths larger than 60 km using measurements of wind velocity in the middle atmosphere from the middle and upper atmosphere mu radar the method is applied to find sets of igw parameters for the winter and summer seasons of 1987 1988 for 6 km thick layers centered at 70 75 and 80 km at shigaraki japan 34 9 n 139 4 e the numbers of selected igw harmonics having periods from 5 min up to 6 hours vary between 360 and 2000 depending on the season and altitude mean vertical wave numbers are 0 6 0 9 km 1 in winter and 0 5 1 km 1 in summer and horizontal wave numbers are 3 4 10 2 km 1 and 2 4 10 2 km 1 respectively predominant azimuths of wave vectors and momentum fluxes concentrate near 64 in winter and 90 in summer at all altitudes in general the difference between the azimuths of the wave vector and momentum flux is close to zero or 180 turbulent and instrumental noise can contribute 20 30 of the observed intensity of the wind variations at altitudes of 70 85 km the igw momentum fluxes are 0 2 2 7 m 2 s 2 in winter and 0 2 1 9 m 2 s 2 in summer the wave drag of the mean flow is 0 5 45 m 2 s 1 in winter and 2 25 m 2 s 1 in summer in most cases the momentum flux and wave drag are directed oppositely to the mean wind

observations of high frequency temporal gravity wave spectra in the middle upper stratosphere there is a paucity of high frequency temporal gravity wave spectra in the middle upper stratosphere 30 40 km as most instruments that are capable of accessing this region do not have the capability to make measurements for any extended period of time the spectral analysis of density fluctuations obtained with the purple crow rayleigh scatter lidar has shown that middle upper stratospheric temporal spectra follow the expected 1 5 to 2 0 power law relationship for frequencies less than 1 10 3 s 1 at frequencies greater than 1 10 3 s 1 the shape of the temporal spectrum is much more variable with strong quasi monochromatic features appearing intermittently on certain nights these higher frequency features have been attributed to nonlinear wave interactions and suggest that estimates of gravity wave activity in the middle upper stratosphere may be larger and much more variable than previously assumed this variability also suggests that middle upper stratospheric energy dissipation and eddy diffusion values may be much larger and more variable than previously assumed current parameterizations of subgrid dynamical processes in general circulation models that resolve this region may need to be reexamined in this light

characteristics of gravity waves 10 min 6 hours at saskatoon 52 n 107 w observations by the phase coherent medium frequency radar height time cross sections of the power spectral density in two bands 10 100 min 2 6 hours for gravity waves igw are formed from horizontal u v and vertical w wind measurements made during 1989 and 1990 using the saskatoon mf radar 52n 107w these climatologies are compared with the seasonally varying mean winds and are consistent with data from previous years 1979 1984 which demonstrated semiannual variations solstitial maxima below 90 km and annual winter maximum above 90 km directions of preferred propagation are inferred by forming the wind perturbation u v covariances and fitting ellipses to the perturbation velocities the preferred orientations are closer to meridional ns than to zonal ew especially for the shorter periods finally the u w v w products which are the vertical fluxes of horizontal momenta are formed in cross section and time series formats for the longer periods the zonal momenta u w have a seasonal variation below 85 km apparently modulated by the zonal mean winds with mainly westward eastward momenta in winter summer months the divergences of the flux provide accelerations of 10 m s 1 d 1 in summer 65 80 km and 15 ms 1 d l in winter 75 90 km which are somewhat less than but often opposite in sign to the coriolis torque on the meridional flow such comparisons suggest that shorter period waves must also contribute important fluxes of momentum the fluctuations in igw intensities and covariances over time scales of several days may be considerable and will affect the sampling needed to obtain seasonal means fluctuations due to planetary waves and stratwarms are observed

evidence of gravity wave saturation and local turbulence production in the summer mesosphere and lower thermosphere during the state experiment this study utilizes the unique data set obtained during the structure and atmospheric turbulence environment state experiment conducted during june 1983 at poker flat alaska to examine the structure and characteristics of the wave field near the summer mesopause it is shown that the rocket and radar data together permit a much more detailed specification of wave parameters than would be possible using either data set alone the results of this analysis suggest that the wave field near the summer mesopause is composed in general of a superposition of wave motions which act collectively to produce regions in which the wave field is convectively or dynamically unstable these regions are found to correlate well with zones of enhanced turbulence and small scale wave activity suggesting the processes and effects of wave field saturation

wavelet analysis of stratospheric gravity wave packets over macquarie island 1 wave parameters we describe a technique to detect gravity wave packets in high resolution radiosonde soundings of horizontal wind and temperature the vertical profiles of meridional and zonal wind speeds are transformed using the morlet wavelet and regions of high wind variance in height wavenumber space are identified as gravity wave packets application of the stokes parameter analysis to horizontal wind and temperature profiles of the reconstructed wave packets yields the wave parameters the technique was applied to twice daily radiosonde launches at macquarie island 55 s 159 e between 1993 and 1995 a strong seasonal cycle in the total wave variance was found with a maximum in winter the amount of wave energy propagating downward from the upper stratosphere also maximized in winter waves propagated predominately toward the southwest in winter but in summer propagation directions were approximately isotropic the intrinsic frequencies were close to the inertial frequency and the waves had inferred horizontal wavelengths of several hundred kilometers

inertio gravity wave parameter estimation from cross spectral analysis we outline a method for extracting inertio gravity wave parameters using the autospectra and cross spectra of the horizontal perturbation winds in essence we define a statistical hodograph for each spectral bin thus combining the advantages of the rotary spectrum and hodograph methods furthermore we include the effects of the background vertical shear in the parameter estimation equations a step that had often been omitted in the past applying this technique to a long period data set taken with the arecibo 430 mhz radar we explore its usefulness as well as its limitations our analysis of this data set also supports the interpretation of horizontal wind perturbation rotation in the lower stratosphere over arecibo as inertio gravity waves rather than mountain waves imbedded within a background vertical shear

polar mesosphere and lower thermosphere dynamics 1 mean wind and gravity wave climatologies 1 mean wind and gravity wave climatologies are presented for the polar mesosphere and lower thermosphere mlt the data were derived using mf radars at davis 69 s 78 e and syowa 69 s 40 e in the antarctic and poker flat 65 n 147 w and andenes 69 n 16 e in the arctic the dynamics of the antarctic mlt are found to be significantly different from the arctic mlt summer maxima in both the westward and equatorward winds occur closer to the solstice in the antarctic than in the arctic the greater symmetry around the solstice suggests radiative effects may play a greater role in controlling the state of the antarctic mlt than in the arctic where dynamical effects appear to be more important gravity wave observations also suggest that wave drag may be greater in the arctic than in the antarctic the equatorward flow near the mesopause persists later in summer in the arctic than in the antarctic as do observations of polar mesospheric clouds and polar mesospheric summer echoes all three phenomena begin at about the same time in each hemisphere but end later in the arctic than in the antarctic it is proposed that the magnitude of the meridional winds can be used as a proxy for gravity wave driving and the consequent adiabatic cooling in the mlt seasonal variations in gravity wave activity are predominately combinations of annual and semiannual components significant hemispheric differences are observed for both the timing and magnitude of these seasonal variations

a review of gravity wave saturation processes effects and variability in the middle atmosphere this paper provides a review of our current understanding of the processes responsible for gravity wave saturation as well as the principal effects and variability of saturation in the lower and middle atmosphere we discuss the theoretical and observational evidence for linear and nonlinear saturation processes and examine the consequences of saturation for wave amplitude limits momentum and energy fluxes the diffusion of heat and constituents and the establishment of a near universal vertical wavenumber spectrum recent studies of gravity wave variability are reviewed and are seen to provide insights into the significant causes of wave variability throughout the atmosphere

first observational evidence of the modulation of gravity wave activity in the low latitude middle atmosphere by equatorial waves 1 evidence for the modulation of the gravity wave activity by the equatorial waves in the tropical middle atmosphere is presented using the rayleigh lidar observations of the temperature over gadanki 13 5 n 79 2 e and the rocketborne measurements of winds over shriharikota range 13 7 n 80 2 e during the period of 29 february to 31 march 2000 the potential energy per unit mass associated with the gravity wave activity in the upper stratosphere and mesosphere is found to undergo periodic fluctuations which is well correlated with the zonal and meridional wind oscillations in the stratosphere produced by the equatorial waves the most dominant modulation of the gravity wave activity due to equatorial waves is found to occur at periods around 4 days and 12 days minimum gravity wave activity in the mesosphere is observed during the southward phase of meridional wind and the westward phase of zonal wind oscillations in the lower stratosphere

advanced meteor radar installed at tirupati system details and comparison with different radars an advanced meteor radar viz sri venkateswara university svu meteor radar svu mr operating at 35 25 mhz was installed at sri venkateswara university svu tirupati 13 63 n 79 4 e india in august 2013 for continuous observations of horizontal winds in the mesosphere and lower thermosphere mlt this manuscript describes the purpose of the meteor radar system configuration measurement techniques its data products and operating parameters as well as a comparison of measured mean winds in the mlt with contemporary radars over the indian region it is installed close to the gadanki 13 5 n 79 2 e mesosphere stratosphere troposphere mst radar to fill the region between 85 and 100 km where this radar does not measure winds the present radar provides additional information due to its high meteor detection rate which results in accurate wind information from 70 to 110 km as a first step we made a comparison of svu mr derived horizontal winds in the mlt region with those measured by similar and different mst and mf radars techniques over the indian region as well as model horizontal wind model 2007 data sets the comparison showed an exquisite agreement between the overlapping altitudes 82 98 km of different radars zonal winds compared very well as did the meridional winds the observed discrepancies and limitations in the wind measurement are discussed in the light of different measuring techniques and the effects of small scale processes like gravity waves this new radar is expected to play an important role in our understanding of the vertical and lateral coupling of different regions of the atmosphere that will be possible when measurements from nearby locations are combined

low drilling frequency in norian benthic assemblages from the southern italian alps and the role of specialized durophages during the late triassic abstract drillholes represent one of the clearest lines of evidence for predation of benthic invertebrates in the fossil record and are frequently used as a primary proxy for predation intensity in the fossil record drillholes are abundant in the late cretaceous and cenozoic but their occurrence is patchy in older deposits of the mesozoic the inconsistent record of drillholes in pre cretaceous deposits of mesozoic age are problematic for interpretations of predation prey dynamics and adaptive radiations and the role of taphonomy or diagenesis have not been resolved here we present drilling percentages for assemblages of well preserved shelly benthic invertebrates mainly comprised of bivalves and rare gastropods from the upper norian upper triassic in northern italy in order to compare these values with reported drilling percentages from the carnian san cassiano formation a rare triassic sedimentary unit that has yielded many drilled fossils the norian fossil deposits reported here are comparable to those of the san cassiano in terms of depositional environment preservation and region and can be reasonably compared to the drilling percentage of fossils from the san cassiano the sampled deposits are collected from marly limestone horizons in the argillite di riva di solto in the southern italian alps deposited in the lombardian basin and which are interbedded with shale units containing well preserved fish and arthropod fossils enabling a correlation between paleoecological structure of the shelly benthos and the demersal pelagic predator diversity over four hundred bivalve fossils yielded a drilling percentage of 0 24 1 406 which is typical for fossil assemblages of this age but the single occurrence of a drillhole in this study is in marked contrast to the many drilled specimens reported from the san cassiano formation deposit in italy the drilled specimen with complete drillhole was an infaunal bivalve and no incomplete drillholes were observed in other specimens thus drilling percentages for the triassic are consistently low but present suggesting that drilling predation was an ecologically minimal influence to benthic communities and unlikely to have driven the significant ecological changes observed in benthic communities during the late triassic although drilling predation occurred during the late triassic we present an updated database of specialized durophagous predators including fishes sharks and reptiles that are likely to have been more ecologically influential on benthic communities during the norian stage fishes in particular

gravity waves in the tropical lower stratosphere an observational study of seasonal and interannual variability radiosonde observations made at cocos islands 12 s 97 e in the indian ocean between september 1992 and june 1998 are used to study seasonal and interannual variations in gravity wave activity in the lower stratosphere 18 25 km the islands are located in a region of generally strong convection that occurs at all times of the year with the period of strongest convective activity between december and july wet season the prevailing zonal winds during the observational period and height range are westward with a quasi biennial oscillation qbo superimposed time series of wave energy show that largest wave amplitudes occur during the wet season when convection is strongest but a qbo like variation is also apparent maximum energy densities of about 25 j kg 1 occur early 1993 1995 and 1997 at the times when the westward shears are largest wave energy is found to be propagating upward and in the horizontal there is considerable azimuthal anisotropy with predominate eastward propagation against the prevailing wind upward fluxes of zonal momentum flux u w are estimated by combining the temperature and wind information fluxes show a similar temporal behavior to the energy the motion and temperature fields are dominated by waves with vertical wavelengths 2 km using a stokes parameter analysis it is found that the intrinsic frequencies are on average 2 3 times the inertial frequency corresponding to intrinsic periods of 20 25 hours horizontal wavelengths between 200 and 2000 km are inferred with a mean value of about 1000 km the mean intrinsic phase speeds are about 10 ms 1 but ground based phase speeds are centered on 0 ms 1

meteor wind radar observations of gravity wave momentum fluxes and their forcing toward the mesospheric semiannual oscillation 1 wind measurements from continuous meteor radar observations during june 2004 may 2007 are used to estimate the gravity wave momentum fluxes in the mesosphere lower thermosphere mlt region over trivandrum 8 5 n 76 9 e a low latitude station in india the radial velocity variances in the 82 98 km height region which are mainly caused by gravity waves measured by the meteor radar are used to determine the gravity wave momentum fluxes using a novel method proposed by hocking 2005 altitude profiles of momentum fluxes of short period less than 2 3 h gravity waves are estimated for three continuous years seasonal variation in the gravity wave momentum fluxes showed semi annual variation with equinoctial maximum and solstitial minimum by using estimated gravity wave momentum fluxes an attempt is made to quantify their contribution in driving the mesospheric semi annual oscillation msao the mean flow acceleration estimated from the divergence of gravity wave momentum fluxes is compared with the observed mean flow acceleration computed from monthly mean zonal winds during six msao cycles over three years this comparison reveled that the gravity wave contribution toward the westerly phase of msao varies from 20 60 while that toward the easterly phase varies from 30 70 variations are observed from cycle to cycle in the gravity wave forcing toward both phases of msao the significance of the present study lies in estimating the gravity wave momentum fluxes in the mlt region and quantifying their contribution toward the generation of msao over the low latitude for the first time

simultaneous na lidar and hf radar observations of vertical velocities in the mesosphere above urbana illinois the first simultaneous na lidar and medium frequency 2 66 mhz doppler radar observations of vertical winds in the mesosphere 79 5 100 km above urbana illinois are reported the lidar and radar systems were operated simultaneously for a 24 h period during january 1989 the lidar measured na density profiles and the radar measured the vertical component of velocity the na density data was used to derive the vertical velocity using the continuity equation this data set provides a unique opportunity to check the consistency of parameters measured by the two very different experimental techniques excellent agreement is found between the radar velocities and the velocities inferred from the na density on the bottomside of the na layer significant differences are found between the velocities obtained with the two techniques on the top side of the na layer possible reasons for this discrepancy are discussed

falling sphere observations of anisotropic gravity wave motions in the upper stratosphere over australia a study of inertial scale gravity wave motions in the region of the atmosphere between 30 and 60 km has been undertaken using wind and temperature data derived from rocket borne falling sphere density experiments performed over woomera australia between 1962 nad 1976 the gross features of the wave field compare favorably with those found in similar northern hemispheric studies wave propagation is found to be both vertically and horizontally anisotropic a rotary spectral analysis indicates predominately upgoing wave energy suggesting that the majority of sources of these waves lie below 30 km a detailed statistical investigation of the waves made using the stokes parameters technique reveals that phase progression is also highly directional in the horizontal with a significant zonal component in summer but with a strong meridional component in winter propagation towards the southeast is inferred in summer with the waves possibly emanating from tropospheric sources in equatorial regions to the north of australia the technique also shows that on average the waves appear to have mean ellipse eccentricities f around 0 4 0 45 indirect estimates of a number of important wave parameters are made in particular v andw flux estimates are made over several height intervals the vertical gradient of density weighted flux implies wave induced mean flow accelerations of the order 0 1 1 ms 1day 1 this suggests that dissipating gravity waves are a significant source of the momentum residuals that are encountered in studies of satellite data from this region

the use of hydrogeochemical analyses and multivariate statistics for the characterization of groundwater resources in a complex aquifer system a case study in amyros river basin thessaly central greece the present study investigates the hydrogeochemical regime of a complex aquifer system in a highly cultivated area of thessaly central greece to do so totally forty 40 groundwater samples were collected for three aquifer units with diverse geological and hydrogeological attributes and analyzed for 77 parameters data processing was accomplished with the joint use of classic hydrogeochemical techniques including major ion molar ratios and graphical interpretation as well as multivariate statistical methods including r mode factor fa and hierarchical cluster analysis hca results showed that major ion hydrogeochemistry is characterized by the prevalence of calcium median 81 mg l and bicarbonates median 308 mg l in the following descending order of concentrations for cations ca2 mg2 na k and anions hco3 no3 so42 cl respectively nitrate values are elevated median 23 mg l especially in the porous quaternary aquifer indicating the ongoing agricultural impact from the excessive use of nitrogen fertilizers and manure the results of multivariate statistics highlighted four factors that chiefly control 81 4 of overall hydrogeochemistry related with both geogenic and anthropogenic impacts the geogenic impact is mainly attributed to the geological substrate and secondarily to the ongoing geochemical redox conditions which in turn enrich or deplete groundwater solution with different ions anthropogenic impact is mainly related with the extensive agricultural practices which favor nitrate enrichment and salinization due to irrigation water return flow

a climatology of gravity wave motions in the mesopause region at adelaide australia abstract a statistical study of gravity wave motions in the mesosphere and lower thermosphere measured with a mf partial reflection radar located at buckland park new adelaide 35 s 138 e in the period november 1933 to december 1984 is presented the analyses am confined to waves with ground based periods between 1 and 24 h time height cross sections show that the mean square amplitudes u 2 and v 2 of the zonal and meridional perturbation velocities respectively vary in a predominantly semiannual manner such that the minima in wave activity coincide with the reversals in the zonal circulation in the middle atmosphere in most instances v 2 is greater than u 2 which together with the small but nonzero u v fluxes shows that the gravity wave field is partially polarized a technique similar to that used to analyse partially polarized electromagnetic waves suggests that on a seasonal basis the wave field is polarized by about 10 to 20 but for shorter periods the degree of polarization may be signi

correlative radar and airborne sodium lidar observations of the vertical and horizontal structure of gravity waves near the mesopause in november 1986 joint radar and na lidar observations were conducted in colorado to study mesopause dynamics the radar observations were conducted at platteville colorado with a stratosphere troposphere st radar in a meteor echo detection mode the na lidar observations included ground based observations at broomfield and denver colorado and airbome observations during three flights over the great plains rocky mountains and pacific coast both radar and lidar identified a 6 hour wave that was remarkably coherent during the november campaign the vertical wavelength of the 6 hour wave estimated from the radar data was 8 to 9 km the amplitude of the zonal wind component was 10 m s 1 and the amplitude of the meridional wind component was 4 m s 1 the vertical wavelength estimated from the ground based and airborne lidar data was 7 3 km and the amplitude of the scalar horizontal wind ranged from 13 to 16 m s 1 the zonal wavelength of this wave was approximately 772 km and the intrinsic zonal phase velocity was 35 m s 1 westward the 6 hour wave was dominant in the height range of 80 90 km which corresponds to the bottomside of the na layer an additional 2 hour wave was observed with the na lidar during both the ground based and airborne observations the vertical wavelength of this wave was about 12 km and the zonal wavelength was 260 km the intrinsic zonal phase velocity was 43 m s 1 westward this 2 hour wave was also present only on the bottomside of the na layer

meteor radar observations of short term tidal variabilities in the low latitude mesosphere lower thermosphere evidence for nonlinear wave wave interactions 1 short term tidal variabilities in the mesosphere lower thermosphere mlt region using the meteor radar observations over trivandrum 8 5 n 77 e during march 2006 to february 2007 are discussed spectral analysis of daily averaged zonal and meridional winds revealed the presence of planetary waves with periods ranging from 2 to 30 days in the height region of 82 98 km the hourly zonal and meridional wind measurements are then used to estimate day to day diurnal tide amplitudes in the mlt region for the first time over this latitude spectral analysis of zonal and meridional diurnal tide amplitudes revealed tidal modulations at periods ranging from 2 to 30 days further during a strong episode of tidal modulation which is identified from the wavelet spectra a group of subsidiary spectral components around the diurnal tide is observed the presence of subsidiary spectral components around the diurnal tide has provided evidence for nonlinear interaction between tides and planetary waves to substantiate this result bispectral analysis is carried out which showed the nonlinear tide planetary wave interactions by revealing the presence of secondary waves exactly at the anticipated periods as the present observational site is very near to dip equator it is envisaged that the present results will have important implications in interpreting day to day variabilities in the equatorial ionosphere

gravity waves in the troposphere and stratosphere during the macwave midas summer rocket program 1 combining data taken during the macwave summer rocket campaign at the andoya rocket range 69 3 n 16 0 e with a lidar radiosondes falling spheres and vhf radars at andoya and at the esrange the gravity wave content of the troposphere and stratosphere during the campaign nights was analyzed the lidar yielded vertical wavelengths and periods of gravity waves in the stratosphere a stokes parameter analysis was performed for the radiosonde and falling sphere data to estimate propagation directions of the gravity waves the wave content in the troposphere was inferred by applying wavelet and cross spectral methods to the radar data we found propagation conditions and spectra of the waves to vary with height following the change in the background wind the waves were excited both at the ground and in the tropopause lower stratosphere region

climatological statistics of stratospheric inertia gravity waves deduced from historical rocketsonde wind and temperature data ten years of rocketsonde observations of wind and temperature in the 28 57 km height range at 12 stations spanning 8os to 76on were analyzed the aim was to determine the geographical and seasonal variation of statistics relating to the propagation of inertia gravity waves as noted by earlier investigators there is a clear tendency for the rocketsonde hodographs to display clockwise rotation with height in the extratropical northern hemisphere this is consistent with the notion that the variations are dominated by inertia gravity waves with upward energy propagation by using the wind and temperature data simultaneously it was possible to determine a dominant direction of horizontal wave propagation for each profile this quantity has an impressive seasonal variation in mid latitudes with strong eastward propagation apparent in summer and generally westward propagation in winter this seasonal cycle is consistent with theoretical notions of how the mean flow ought to affect wave propagation two stations within 10 o of the equator are included in this analysis the results at these near equatorial stations contrast strongly with those at higher latitudes there is a clear tendency for the hodographs at these stations to display quite linear polarization rather than the systematic rotation generally seen at higher latitudes the wind variations also show a remarkable tendency to align themselves in the zonal direction when the wind and temperature variations are used together it can be shown that the variations seen are consistent with a clear dominance of eastward propagation indirect observational inferences e g hartmann 1976 hamilton 1983 smith and lyjak 1985 and results from simple theoretical models e g lindzen 1981 holton 1982 suggest that inertia gravity ig waves of less than planetary scales play a significant role in the general circulation of the stratosphere it is quite clear that in at least some comprehensive general circulation models gcms the vertical momentum transports associated with resolved ig waves

characteristics of gravity waves in the mesosphere observed with the middle and upper atmosphere radar 1 momentum flux we observed wind motions from 60 to 90 km altitudes with the mu radar 35 n 136 e in the four observation periods october 1986 june 1987 july 1990 and january february 1991 mean wind profiles were fairly consistent with results of kyoto meteor radar observations 35 n 136 e collected in 1983 1985 at 80 to 110 km altitudes and zonal mean winds generally agreed well with cira 1986 except for the profiles below 70 km in january february 1991 although discrepancy of amplitudes sometimes ranged up to 10 to 20 m s characteristics of frequency spectra of radial wind velocities were basically similar among results determined in four observation periods that is oblique spectra had a logarithmic slope of about 5 3 in the frequency range lower than 4 5 10 4 s 1 gravity waves with periods longer than 20 50 min to 5 hours the lowest limit of the spectral analysis were found to carry a large part of the zonal momentum flux while a dominant frequency component was not detected for the meridional flux zonal and meridional drag of mean winds induced by the gravity wave with periods from 5 min to 8 10 hours were 51 m s d and 4 m s d in june at 75 km and 4 0 m s d and 7 4 m s d in october at 70 km respectively the major part of the drag force was also found in the wave component with periods larger than 30 min the day to day variation in the zonal momentum flux showed a good correlation with the vertical shear of the zonal mean wind which suggests effects of the gravity wave activities on mean wind fields or the effect of shear variation on the gravity wave activity

occurrence characteristics of medium scale gravity waves observed in oh and oi nightglow over adelaide 34 5 s 138 5 e 1 this paper presents a 7 year climatology describing medium scale gravity waves observed in the menopause region covering the years from 1995 to 2001 the data comes from the oi and oh airglow observations of the three field photometer employed at the university of adelaide s buckland park australia 34 5 s 138 5 e about 1300 gravity wave events agw are identified during the years 1995 2001 these agw events usually persist for between 40 min and 4 hours the magnitudes range from 1 to 14 of the background intensities and peak at 2 for oi observations and at 3 for oh observations the observed periods range from 10 to 30 min and the horizontal phase speeds range from 20 to 250 m s 1 with dominant wave scales of 17 min 70 m s 1 for oi observations and 20 min 40 m s 1 for oh observations the intrinsic parameters are obtained by using medium frequency mf wind data observed at the same place the occurrence frequency of agw events peaks at 13 min 40 m s 1 for both oi and oh observations the occurrence rate of gravity waves has a major peak in summer and a minor peak in winter there is an obvious dominating southeastward direction for gravity waves with azimuths of 160 in summer and 130 in winter studies for gravity waves observed in various locations show a similar tendency of propagating meridionally toward the summer pole this implies that the tendency of propagating toward the summer pole may be a global trend for medium scale gravity waves observed in the mesopause region during summer gravity waves propagate against winds measured by mf radar in their dominating direction using the ray tracing method we found that the seasonal variation of winds limits the access of gravity waves to the observation height through reflection and critical coupling which is one of the causes leading to the seasonal behavior of gravity waves observed over adelaide

paleoecological patterns in molluscan extinctions and recoveries comparison of the cretaceous paleogene and eocene oligocene extinctions in north america abstract exposures across the cretaceous tertiary k t and eocene oligocene e o boundaries in texas and mississippi respectively probably represent the most complete and best preserved fossil molluscan sequences across these boundary intervals in the world outcrops from both boundaries contain pristine aragonitic and calcitic molluscan shells which were deposited in fine grained sediments from open marine environments the k t and the e o extinctions exhibit very different recovery patterns probably reflecting very different causes as well as magnitudes of extinction the k t sequence contains a molluscan fossil record that is consistent with an abrupt extinction event at the k t boundary and a prolonged initial recovery in hostile oceanographic conditions the uppermost 10 m of upper cretaceous sediments contain a diverse approximately 40 species molluscan fauna dominated by suspension feeders the earliest paleocene sediments immediately above the tsunami bed contain an impoverished fauna dominated by deposit feeders the paleocene fauna slowly climbs in diversity but remains relatively impoverished and dominated by deposit feeders for several hundred thousand years after the extinction in conjunction with anomalous 13c values that suggest prolonged suppression of marine primary productivity diverse suspension feeder dominated molluscan assemblages reappear with the resumption of normal conditions of primary production in the long term early to middle paleocene gamma diversity includes evolutionary bloom taxa families that exhibit unusual speciation bursts that subside in the eocene total diversity for the gulf coast does not approach cretaceous levels until the late eocene representing a total recovery interval of nearly 25 million years while the e o event also reflects a molluscan extinction rate of over 90 in the gulf of mexico there are no signs of hostile environmental conditions in the recovery fauna early oligocene molluscan assemblages are diverse and dominated by suspension feeders characteristic of normal marine conditions the hiatus at the e o boundary however could have obscured a short term recovery fauna there is also no sign of long term perturbation by the e o extinction there are no bloom taxa and gamma diversity approaches pre extinction levels within a few million years the overall pattern of the e o extinction is consistent with extinction and or migration associated with long term cooling

a review of the source behaviour and distribution of arsenic in natural waters the range of as concentrations found in natural waters is large ranging from less than 0 5 g l 1 to more than 5000 g l 1 typical concentrations in freshwater are less than 10 g l 1 and frequently less than 1 g l 1 rarely much higher concentrations are found particularly in groundwater in such areas more than 10 of wells may be affected defined as those exceeding 50 g l 1 and in the worst cases this figure may exceed 90 well known high as groundwater areas have been found in argentina chile mexico china and hungary and more recently in west bengal india bangladesh and vietnam the scale of the problem in terms of population exposed to high as concentrations is greatest in the bengal basin with more than 40 million people drinking water containing excessive as these large scale natural as groundwater problem areas tend to be found in two types of environment firstly inland or closed basins in arid or semi arid areas and secondly strongly reducing aquifers often derived from alluvium both environments tend to contain geologically young sediments and to be in flat low lying areas where groundwater flow is sluggish historically these are poorly flushed aquifers and any as released from the sediments following burial has been able to accumulate in the groundwater arsenic rich groundwaters are also found in geothermal areas and on a more localised scale in areas of mining activity and where oxidation of sulphide minerals has occurred the as content of the aquifer materials in major problem aquifers does not appear to be exceptionally high being normally in the range 1 20 mg kg 1 there appear to be two distinct triggers that can lead to the release of as on a large scale the first is the development of high ph 8 5 conditions in semi arid or arid environments usually as a result of the combined effects of mineral weathering and high evaporation rates this ph change leads either to the desorption of adsorbed as especially as v species and a range of other anion forming elements v b f mo se and u from mineral oxides especially fe oxides or it prevents them from being adsorbed the second trigger is the development of strongly reducing conditions at near neutral ph values leading to the desorption of as from mineral oxides and to the reductive dissolution of fe and mn oxides also leading to as release iron ii and as iii are relatively abundant in these groundwaters and so4 concentrations are small typically 1 mg l 1 or less large concentrations of phosphate bicarbonate silicate and possibly organic matter can enhance the desorption of as because of competition for adsorption sites a characteristic feature of high groundwater as areas is the large degree of spatial variability in as concentrations in the groundwaters this means that it may be difficult or impossible to predict reliably the likely concentration of as in a particular well from the results of neighbouring wells and means that there is little alternative but to analyse each well arsenic affected aquifers are restricted to certain environments and appear to be the exception rather than the rule in most aquifers the majority of wells are likely to be unaffected even when for example they contain high concentrations of dissolved fe

drill hole analysis reveals evidence of targeted predation on modern brachiopods abstract if drill holes are made in prey either by mistaken or opportunistic predators or parasites rather than those which do so on a more regular basis we might predict that such drill holes will commonly be incomplete or repaired and show no evidence of behavioural familiarity such as size selection or constancy of attack site these predictions were used to examine the patterns of drill holes found in bulk samples of death assemblages of modern rhynchonelliform brachiopods from around new zealand four samples yielding data for five different taxa four terebratulides and one rhynchonellide were examined in each the proportion of incomplete or repaired holes was low samples of terebratella sanguinea fiordland and gyrothyris mawsoni antipodes islands show statistically significant evidence of both size selection and preferential drill hole siting the sample of notosaria nigricans waikawa shows only evidence of size selection examination of drill hole morphology and the co occurring gastropod fauna suggests that the distinctive countersunk holes in t sanguinea and g mawsoni were likely made by the trophonid gastropod xymene ambiguus aquarium experiments demonstrate that the ranellid gastropod argobuccinum tumidum is also capable of feeding on brachiopods but that the resulting hole is not likely to be readily recognisable in death assemblages

parameterization of strong stratospheric inertia gravity waves forced by poleward breaking rossby waves abstract the link between poleward breaking rossby waves and stratospheric inertia gravity waves is examined with a visual inspection of ertel s potential vorticity maps based on ecmwf analyses it was found that rossby wave breaking events occurred over northern europe in about 40 of the winter days in 1999 2003 the majority of them were breaking poleward downstream a total of 10 field campaigns were performed in the winters of 1999 2002 at kuhlungsborn germany 54 n 12 e they are related to such events and can be considered as representative for poleward breaking rossby waves inertia gravity wave properties are diagnosed from radiosonde observations they appeared to be shallower slower and stronger than the climatological mean for the north german lowlands hence rossby wave breaking events are linked with strong stratospheric inertia gravity wave activity a novel parameterization of inertia gravity wave generation and propagation is proposed the stratospheric inertia gravity wave action i

a fossil record full of holes the phanerozoic history of drilling predation the evolutionary history of drilling predation despite a long and rich fossil record precambrian holocene contains a 120 m y gap late triassic early cretaceous drilled bivalve and brachiopod shells from jurassic deposits of hungary india and four localities documented in the literature indicate that drillers may have existed continuously throughout the mesozoic they may have been descendants of paleozoic predators unknown mesozoic carnivores or precursors of modern drillers a literature database suggests three major phases in the phanerozoic history of drilling predators 1 the paleozoic phase latest precambrian carboniferous dominated by rare to moderately frequent drillings in brachiopods and sessile echinoderms 2 the mesozoic phase permian early cretaceous with very rare or even facultative drillers that had little impact on marine benthic communities but nevertheless may have been present continuously and 3 the cenozoic phase late cretaceous holocene dominated by frequent gastropod drillings in mollusks

trends of mesospheric gravity waves at northern middle latitudes during summer 1 recent investigations of the seasonal variation of the activity of gravity waves in the mesosphere lower thermosphere mlt at middle and high latitudes suggest a semiannual variation with maxima during winter and summer and minima during the equinoxes it is generally assumed that this annual cycle is determined by filtering processes due to the background winds in the stratosphere and lower mesosphere on the other side long term observations of mesospheric winds at juliusruh 55 n 13 e since 1990 indicate a stable increase of westward directed winds below 80 km negative trends during summer as e g clearly evident in monthly means in july here we are studying how these long term changes of winds are related to trends of the activity of gravity waves gw with periods between 3 6 hours our results show that the observed zonal wind trend at about 75 km during july goes along with an enhancement of the gw activity at altitudes above 80 km indeed also the year to year variation of maxima of the observed westward directed winds at altitudes near 75 km and the gw activity at about 80 km are significantly correlated our results stimulate the further study of long term wind changes and corresponding gravity wave trends

balloon borne observations of short vertical wavelength gravity waves and interaction with qbo winds the quasi biennial oscillation qbo a ubiquitous feature of the zonal mean zonal winds in the equatorial lower stratosphere is forced by selective dissipation of atmospheric waves that range in

drilling predation on gryphus vitreus brachiopoda off the french mediterranean coasts abstract a total of 145 valves of gryphus vitreus with naticid drillholes have been recorded from samples during 21 cruises in the northwestern mediterranean out of about 30 000 empty valves drilling was lower than 1 in all stations except in one station where it reached up to 25 5 selectivity of drillhole site by the naticid euspirella pulchella seems to apply in g vitreus as drillholes are mainly concentrated in the relatively meaty distal half of the shell which is also the thickest part of the valve about 0 6 2 mm attacks occur generally on the ventral valve 86 2 according to the life position of gryphus the predation pressure on g vitreus by drilling appears exceptional in that it has hardly any influence on the evolution of the species this contradicts several previous statements on the fossil record

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

palaeoecology and evolution of marine hard substrate communities abstract marine organisms have occupied hard substrates since the archaean shells rocks wood and sedimentary hardgrounds offer relatively stable habitats compared to unconsolidated sediments but the plants and animals which inhabit them must develop means to gain and defend this premium attachment space hard substrate communities are formed by organisms with a variety of strategies for adhering to and or excavating the substrates they inhabit while mobile grazers organically attached and even soft bodied organisms may leave evidence of their former presence in ancient hard substrate communities a superior fossil record is left by sessile encrusters with mineralised skeletons and by borers which leave trace fossils furthermore encrusters and borers are preserved in situ retaining their spatial relationships to one another and to the substrate spatial competition ecological succession oriented growth and differential utilisation of exposed vs hidden substrate surfaces can all be observed or inferred hard substrate communities are thus excellent systems with which to study community evolution over hundreds of millions of years here we review the research on modern and ancient hard substrate communities and point to some changes that have affected them over geological time scales such changes include a general increase in bioerosion of hard substrates particularly carbonate surfaces through the phanerozoic this is at least in part analogous to the infaunalisation trends seen in soft substrate communities encrusting forms show an increase in skeletalisation from the palaeozoic into the mesozoic and cenozoic which may be a response to increasing levels of predation hard substrate communities considering borers and encrusters together show a rough increase in tiering through the phanerozoic which again parallels trends seen in soft substrate communities this extensive review of the literature on living and fossil hard substrate organisms shows that many opportunities remain for large scale studies of trends through time at the community and clade levels palaeontologists will especially benefit by closer integration of their work with that of neontologists particularly in aspects of ecology such as larval recruitment competition and succession

record of intense predatory drilling from upper jurassic bivalves of kutch india implications for the history of biotic interaction abstract the study of past biotic interactions is important not only to understand the paleoecological history of a community but also to test the evolutionary role of such interactions drill holes in invertebrate exoskeletons provide one of the very few scenarios where biotic interaction could be studied directly and the related hypotheses could be tested with statistical rigor hence the documentation and interpretation of the spatio temporal patterns of drill hole frequencies has been the subject of extensive paleontological research the two main gastropod groups responsible for the drilling predation in modern marine environment arose in cretaceous as supported by their body fossil however the drill holes have been reported from the fossils of as far back as precambrian age the trend shows an overall low but variable intensity in paleozoic and mesozoic and a significant increase in cenozoic there are few reported cases of drilled bivalves from the mesozoic although in those instances frequencies are fairly low most of the previous records of drilling predation during paleozoic and mesozoic come from north america and western europe here we report 148 drilled bivalve specimens of a single species from the upper jurassic horizon in western india this is highest in number for any taxon ever recorded since precambrian to cretaceous the frequency of drilling constitutes 30 of shells of the same species examined this drilling frequency is highest when compared to all the reported mesozoic drilling frequencies in bivalves the shapes of the drill holes are indicative of gastropod predation the drilling gastropods responsible for these lethal attacks are also similar to their modern counterparts in terms of their highly selective prey choice and site specificity these results suggest that 1 mesozoic bivalves were preyed upon by drilling gastropods often with high intensities and 2 the specialized characters of modern drilling predators were also present in mesozoic this largely unexplored record of bivalve drill holes from the middle mesozoic contradicts the general trend of mesozoic quiescence as claimed by most researchers

subaerial hunting behaviour in natica gualteriana naticid gastropod natica gualteriana as observed on intertidal sand bars in bantayan island philippines emerges from the sand at low tide when the bottom is exposed to the air and hunts epifaunally for the trochacean gastropod umbonium vestiarium n gualteriana captures u vestiarium with a quick extension of the foot triggered by direct contact with the prey the shell aperture of the prey is subsequently plugged with a small amount of mucus that forces u vestiarium to remain retracted inside its shelf chemically benumbed but neither kills nor permanently affects it drilling of the prey takes place infaunally after burrowing this seems to be the first record of subaerial hunting in naticid gastropods

boring predation and mesozoic articulate brachiopods abstract a systematic survey of all the mesozoic brachiopods in the large collections of the sedgwick museum cambridge university has revealed more than 213 predatory boreholes from a wide range of largely british localities it seems likely that this type of predation was not infrequent at least locally as evidenced by the proportion of bored valves at some localities and the degree of stereotypy shown in borehole positioning the size of the boreholes and their neat circular cross sections suggest that they were made by large epifaunal predators using chemical attack and those of post albian age may be comfortably if not confidentally assigned to muricid gastropods although it is likely that bivalves with their greater flesh yields were the preferred prey item in most mesozoic shelly benthic communities it is apparent that boring predators may have resulted in a significant predation pressure on articulate brachiopods

gravity wave tidal interactions in the mesosphere and lower thermosphere over rothera antarctica 68 s 68 w 1 a simple technique for measuring gravity wave activity has been used to investigate gravity wave tidal interactions in the polar mesosphere and lower thermosphere mlt the technique uses the radial velocities of individual meteors recorded by meteor radar to derive a statistical measure variance of the activity of the high frequency gravity wave field this technique can measure gravity waves with horizontal wavelengths of up to about 400 km and periods up to approximately 3 hours interactions between the observed gravity wave field and the background wind are investigated using data collected between february 2005 and december 2008 by a meteor radar based at rothera antarctica 68 s 68 w the results reveal the presence of significant modulations of the observed gravity wave field at tidal periods of 12 and 24 hours correlations between the hourly zonal winds and the gravity wave field measured by the meteor radar reveal an in phase relationship between the hourly zonal winds and gravity wave variance in winter and an anti phase relationship in summer this is consistent with the theory of filtering by tidal winds acting on a zonally asymmetric gravity wave field in which westward waves dominate in winter and eastward waves dominate in summer the limitations of the technique and the effect this has on the interpretation of these results are also considered the effects of the diurnal cycles in meteor count rates the uncertainty in recorded radial velocities and the uncertainty in the measured heights of meteors are considered

comparison of the mesospheric gravity waves observed with the mu radar 35 n and the adelaide mf radar 35 s mesospheric gravity waves observed with the mu radar located near kyoto 35 n 136 e and the adelaide mf radar 35 s 138 e are compared for two campaigns in summer and winter the frequency spectral densities of the horizontal wind motions were larger in summer than in winter at both locations while the spectral density was almost identical if the summers or winters in both hemispheres are compared the total variances of the waves with periods of 2 hours 30 minutes observed in the 70 80 km height range were almost the same at the two sites this suggests that eddy dissipation processes due to turbulence caused by breaking gravity waves are almost the same magnitude between the hemispheres which is different from the previous suggestion of the much larger dissipation in the northern hemisphere derived from the tidal observations at adelaide and kyoto the propagation directions of the different frequency components was also investigated they seem to be similar at both locations in summer but the directions were rather widely spread in winter at both locations the mu radar results showed more preferential zonal directions for the gravity wave propagation compared to the results from adelaide these results indicate a difference in the propagation directions between the hemispheres or the difference at the two locations of adelaide and kyoto which might be caused by differences in topography around the sites

geochemical evidence for suppression of pelagic marine productivity at the cretaceous tertiary boundary the normal biologically productive ocean is characterized by a gradient of the 13c 12c ratio from surface to deep waters here we present stable isotope data from planktonic and benthic micro fossils across the cretaceous tertiary boundary in the north pacific which reveal a rapid and complete breakdown in this biologically mediated gradient the fluxes of barium a proxy for organic carbon and caco3 also decrease significantly at the time of the major marine plankton extinctions the implied substantial reduction in oceanic primary productivity persisted for 0 5 myr before the carbon isotope gradient was gradually re established in addition the stable isotope and preservational data indicate that environmental change including cooling began at least 200 kyr before the cretaceous tertiary boundary and a peak warming of 3 c occurred 600 kyr after the boundary event

vertical fluctuation energy in united states high vertical resolution radiosonde data as an indicator of convective gravity wave sources 1 convectively generated internal gravity waves at extratropical latitudes are difficult to identify by climatological analysis of the temperature and horizontal wind fields from radiosonde profiles using traditional analysis methods here we show that by analyzing ascent rate profiles we define a new variable vertical fluctuation energy ve we can identify convection sources in climatological analyses analysis of a 9 year time series 1998 2006 of united states high vertical resolution radiosonde data shows that ve maximizes in summer in midlatitudes within the troposphere 2 8 9 km and peaks at local afternoon early evening during the summer over most of the contiguous united states furthermore the apparent dominant vertical wavelength based on fourier analysis of the low pass filtered ascent rate fluctuations also increase and decrease with ve both on diurnal and seasonal timescales ve in the lower stratosphere however does not show this same relationship to convection but analysis of the vertical wavelength does show some of the features seen in tropospheric ve unlike midlatitude stations ve within both the troposphere and the lower stratosphere over tropical western pacific island stations is highly correlated with convective precipitation and inversely correlated with outgoing longwave radiation we interpret this difference by using the 4 d gravity wave regional or global ray tracer ray tracing model with a source spectrum representative of a convection source

convectively generated gravity waves observed from radiosonde data taken during mctex the properties of gravity waves generated by deep tropical convective systems are analysed from radiosonde soundings taken during the maritime continent thunderstorm experiment and the results compared against recent cloud scale numerical modelling of convectively generated waves fluctuations in the ascent rate of the radiosonde are used to characterize the high frequency waves whereas the zonal wind fluctuations are used to determine the properties of the inertia gravity waves the density weighted vertical velocity variance shows a pronounced diurnal cycle with the largest amplitude gravity waves developing during the early afternoon following the development of deep convection in contrast the density weighted horizontal velocity variance and by implication the inertia gravity wave activity shows no diurnal variation simple theoretical analysis shows that the observations on 27 november 1995 are consistent with a westward propagating gravity wave with a horizontal wavelength of 17 km and a source frequency equal to 0 007 rad s 1 these findings are consistent also with a high resolution numerical model simulation for the same day nonetheless the character of the high frequency gravity waves cannot be uniquely determined from a single radiosonde sounding copyright 2003 royal meteorological society

circum mediterranean oligo miocene biogeographic evolution the gastropods point of view based on studies in iran qom basin esfahan sirjan basin zagros mountains in turkey mut and sivas basins in the mesohellenic basin and in northeastern egypt a new palaeobiogeographic concept for the oligocene and miocene in the circum mediterranean area with special emphasis on the distribution patterns of gastropod faunas is presented a very strict biogeographic terminology is proposed to avoid the common fusion of geographic faunistic and geodynamic terms in the palaeontologists jargon our main interest focuses on the affinities and the faunistic interactions between the early mediterranean and the early indo pacific regions during the oligo miocene especially the role of the early indo pacific faunas as the mythic centre of origination of early neogene european mollusc faunas as often vaguely indicated in the literature is critically evaluated this leads to the establishment of a mediterranean iranian province and a western indian eastern african province as palaeobiogeographic subunits of the western tethys region during the oligocene due to major geodynamic and related biogeographic changes in the early miocene the western tethys region no longer existed and was replaced by the proto mediterranean atlantic region for the area of the paratethys the palaeobiogeographic unit danubian province which includes the protocaspian subprovince is proposed furthermore the underrated transatlantic communication of the oligo miocene nearshore mollusc faunas is demonstrated altogether this paper is a contribution to the discussion on the biogeographic concepts classification and nomenclature in palaeontology as initiated by westermann palaeogeogr palaeoclimatol palaeobiogeogr 158 2000 1 13 163 2000 49 68 2002 elsevier science b v all rights reserved

morphometric analysis of predatory drillholes abstract quantitative studies of post jurassic predatory drillholes assume that drill holes were made by either naticid or muricid gastropods however other potential predators can leave similar traces and the traditional method of discrimination based on differences in vertical shape of drillholes cylindrical vs countersunk is not always applicable poor preservation or thin shells may prevent identification a multivariate morphometric approach including principal component analysis pca canonical variate analysis cva and size free discriminant analysis is suggested here as a supplementary method i test the approach by analyzing 98 drillholes made in the valves of the thin shelled bivalve mulinia coloradoensis collected from subfossil deposits in northeastern baja california using traditional criteria 10 10 2 of 98 drillholes were not correctly identified morphometric analyses indicate that in planar view muricid and naticid drillholes do not differ in shape however they perfectly discriminate in size the cylindrical drillholes oichnus simplex attributed to muricid predators are significantly smaller than countersunk ones oichnus paraboloides made most likely by naticid gastropods the results do not necessarily undermine the validity of the traditional ichnotaxonomy muricids tend to produce smaller drillholes than naticids nevertheless the vertical shape of a drillhole may be a function of both the type of predator and the size of hole drilled more than half of the unidentified drillholes 6 out of 10 from an independent group characterized by a more oval shape octopod drilling the traditional method supported by the morphometric methods employed here is a powerful tool for analysis of drillholes it may be valuable not only as a tool for analysis of muricid and naticid drillholes but also as a method for comparative analysis of drillholes of unknown source found throughout the phanerozoic fossil record

characteristics of gravity waves in the mesosphere observed with the middle and upper atmosphere radar 2 propagation direction we studied the characteristics of dominant component of gravity waves z 10 km in the vertical profile of the wind velocities observed in the mesosphere at around 70 75 km with the middle and upper atmosphere mu radar in the four observation campaigns june 1987 july 1990 october 1986 and january february 1991 and the monthly mesosphere observations carried out 4 5 days a month in december 1985 to december 1988 by assuming linear dispersion relations of gravity waves both vertical and horizontal propagation directions of gravity waves were determined most of the dominant waves propagated upward except that they sometimes propagated downward mainly in summer a typical vertical wavelength and intrinsic period of the dominant gravity waves were 4 15 km and 4 15 hours respectively the mean values of the vertical wavelength horizontal wavelength and intrinsic periods were 8 2 km 1200 km and 10 2 hours respectively which did not show significant seasonal variations most of the waves were found to be dissipated by the eddy diffusion of 15 100 m2 s which does not agree with mf radar observations 10 to 120 min observed periods but is rather consistent with sodium lidar observations 36 300 m2 s the mean horizontal phase velocity was 33 m s the horizontal propagation direction was generally eastward throughout a year except for the westward propagation in early winter november to december this suggests that the dominant gravity waves are less sensitive to a change in the mean zonal wind direction in the middle atmosphere than the short period gravity waves 2 hours to 5 min momentum flux carried by the dominant gravity waves was estimated to be 0 5 1 m2 s2 which was generally smaller than the momentum flux of gravity waves with periods ranging from 8 hours to 5 min the amplitude of the momentum flux of the dominant gravity waves had an autumn maximum while the momentum flux with periods of 8 hours to 5 min had equinoctial minima thus in september and october the momentum flux due to the dominant gravity waves became significant we further pointed out that the possibility that depends on the wave periods and therefore the major frequency component of is not easily determined from simple dispersion relation only

dynamics of the equatorial mesosphere first results with a new generation partial reflection radar the first observations of mesospheric winds made between january august 1990 with an mf partial reflection radar located on christmas island 2 n 157 w in the central pacific are described the mean zonal winds are in general westward but show clear evidence for a wave driven circulation power spectral studies indicate that waves are present over a wide range of periods ultra fast kelvin waves are especially evident in january march with peak amplitudes 20 ms 1 and intrinsic phase speeds of 150 ms 1 indicated the kelvin waves are estimated to contribute an eastward acceleration of up to 10 ms 1 day 1 gravity wave amplitudes are also found to be almost as large as those observed at mid latitude sites which suggests that convection is a major source of gravity wave activity

statistical analysis of inertial gravity wave parameters in the lower stratosphere over northern china to determine the morphology of inertial gravity wave igw activity in the lower stratosphere 18 25 km over northern china and provide observational data constraints for igw parameterization in atmospheric circulation models the seasonal variation and longitudinal distribution of igw parameters were analyzed statistically using 4 years 2010 2013 of radiosonde data from 20 sites distributed throughout northern china 80 2 e 122 3 e the results are as follows 1 the seasonal variation in the monthly mean igw energy strong in winter and weak in summer is consistent with the results for other regions in the northern hemisphere however the energy shows a significant longitudinal increase from west to east in winter and the opposite pattern in summer which has rarely been reported 2 the monthly mean intrinsic frequency exhibits clear seasonal variation large in winter and small in summer the annual average ratio with the coriolis frequency is 2 47 while the degree of polarization exhibits the opposite seasonal variation with an annual average of 0 71 the monthly mean vertical and horizontal wavelengths are 2 5 and 481 3 km in northern china respectively 3 the annual mean magnitude of the intrinsic horizontal group speed 7 0 m s is much larger than that of the vertical group speed 0 08 m s and both have maxima in winter and minima in summer the frequency of occurrence of the westward propagated igw is larger than that of the eastward propagated igw year round and it is isotropic in the north south direction this phenomenon is related to the filtering effect of the tropospheric westerly jet the annual mean fraction of upward propagation is 75 9 with a minimum in winter 4 the momentum flux exhibits a similar temporal and spatial distribution to energy showing preferred propagation in the northwest direction 5 the correlation of the monthly mean total energy of the igw with the westerly jet and the dynamic instability were studied the results suggest that the westerly jet near the tropopause has a strong influence on the igws activity in the lower stratosphere in northern china and the height region of the westerly jet is a possible source region for igws the maxima regions of the occurrence rates of dynamic instability at the upper and lower edges of the westerly jet in winter are also the possible source region for igws

vhf radar observations of the dynamics of the summer polar mesopause region observations of the dynamics of the mesopause region over the norwegian island of andoya 69 n 16 e made during 2 days in summer 1987 using the mobile sousy vhf 53 5 mhz doppler radar are reported measurements of the three mean wind components and the 12 and 24 hour horizontal tidal components as well as preliminary estimates of the component of the total upward flux of density normalized horizontal momentum in the sw ne plane and the anisotropy of the horizontal wind are presented for the 83 to 90 km height interval values of the component of the density normalized flux in the sw ne plane for the 10 min to 48 hour period range after the 12 and 24 hour tidal components have been removed vary from 1 m2 s 2 near 84 km to 16 m2 s 2 near 89 km the major contribution is from the 10 min to 12 hour period range the corresponding mean flow acceleration takes a mean value of 136 m s 1 d 1over the 83 90 km height interval the anisotropy is considerable and may suggest the presence of standing waves

climatology of mesospheric gravity wave activity over urbana illinois 40 n 88 w a 5 year 1991 1995 climatology of mesospheric gravity wave activity observed with the urbana medium frequency mf radar is presented we focus on the monthly mean horizontal wind variances associated with gravity waves with observed periods between 10 min and 8 hours these results are compared with the seasonal characteristics from other gravity wave observations the total wave variance displays a dominant semiannual variation maxima summer winter minima spring fall below 87 km with little seasonal variation above 87 km the zonal wave variance exceeds the meridional wave variance except around regions of zonal wind reversal in all seasons the observed variance scale height is greater than that of a nondissipating wave field a simple zero mean wind model based on linear saturation theory is found to be inadequate in reproducing the seasonal characteristics of the observed wave variances an alternative model based on critical layer filtering by a height dependent wind field can reproduce the observed semiannual oscillation in the wave variance given a specific source input

mesospheric gravity waves at saskatoon 52 n kyoto 35 n and adelaide 35 s the gravity waves with periods of 10 min to 8 hours in the mesosphere 67 80 km are studied using observations from the adelaide mf radar 35 s saskatoon mf radar 52 n and the middle and upper atmosphere mu radar at shigaraki near kyoto 35 n the seasonal variations of the gravity wave intensity deduced from the horizontal wind velocities showed semiannual variations with solstitial maxima and equinoctial minima at all three locations but the month of maximum intensity in the year depends on the locations and wave frequency the kinetic energy due to gravity waves showed similar amplitude between kyoto and adelaide but smaller at saskatoon which agrees well with the results of the preliminary comparison using a limited frequency range and limited observation periods by nakamura et al 1993a b the horizontal propagation direction of these gravity waves showed small seasonal variations and significant dependency with wave periods at saskatoon but showed more frequent variation without a large frequency dependency at kyoto and adelaide these characteristics indicate that at the lower latitudes gravity wave activity is larger as pointed out by tsuda et al 1994 from various observational techniques also the frequent changes of the gravity wave intensities at the lower latitudes suggest that there are strong influences of the background wind variation in the middle atmosphere such as semiannual oscillation mesospheric semiannual oscillation and other wind variations in the low latitudes

gravity wave flux retrievals using meteor radars 1 the ability of all sky interferometric meteor radars to measure mean wind and high frequency gravity wave wind perturbations from meteor radial velocities is assessed a monte carlo technique that models line of sight meteor wind measurements with realistic errors in angle of arrival and range is used to investigate uncertainties in mean wind and gravity wave wind parameters as a function of meteor echo rate it is shown that mean horizontal wind speeds are recovered with reasonable accuracy at meteor rates as low as 10 hr 1 mean square horizontal wind perturbation can be derived with relatively little averaging but momentum fluxes are recovered with much less accuracy which means that considerable averaging is required to produce meaningful values results are illustrated using meteor wind radar observations taken over a 30 day period in january february 2006 in northern australia

a three year gravity wave climatology of the mesosphere and lower thermosphere over kauai a 3 year study of gravity wave variability covering 1991 1992 and 1993 was conducted using horizontal wind measurements collected by a partial reflection mf radar located on the island of kauai hawaii 22 n 160 w high echo return rates between 70 and 98 km provided ample time resolution for the study of gravity wave variability in this height range horizontal wind measurements were band pass filtered for periods between 20 min and 6 hours establishing a gravity wave band time series gravity wave variance and polarization calculations were carried out over various time frames and examined with regard to their response to season and background environment among the more interesting observed phenomena were the annual and semiannual oscillations in the gravity wave variances a significant diurnal and semidiurnal variability in the variances and an extended enhancement of these variances during the latter half of 1992 and the beginning of 1993

multibeam radar observations of winds in the mesosphere we present the results of a statistical analysis of mesospheric wind fluctuations with periods in the range 5 min to 8 hours the data were collected with the sousy vhf radar by observing line of sight doppler velocities sequentially in three directions the temporal spectrum is computed for the vertical fluctuations as well as for line of sight fluctuations on two oblique beams at 3 6 zenith angle separated by 90 in azimuth the observed spectra are shown to be mutually consistent if interpreted in terms of a field of propagating gravity waves using the three beam data the temporal spectrum for the underlying gravity waves is obtained the height dependence of the line of sight component of the mean square wave amplitudes is also studied

the influence of geology and land use on arsenic in stream sediments and ground waters in new england usa population statistics for as concentrations in rocks sediments and ground water differ by geology and land use features in the new england region usa significant sources of as in the surficial environment include both natural weathering of rocks and anthropogenic sources such as arsenical pesticides that were commonly applied to apple blueberry and potato crops during the first half of the 20th century in the region the variation of as in bedrock ground water wells has a strong positive correlation with geologic features at the geologic province lithology group and bedrock map unit levels the variation of as in bedrock ground water wells also has a positive correlation with elevated stream sediment and rock as chemistry elevated as concentrations in bedrock wells do not correlate with past agricultural areas that used arsenical pesticides on crops stream sediments which integrate both natural and anthropogenic sources have a strong positive correlation of as concentrations with rock chemistry geologic provinces and ground water chemistry and a weaker positive correlation with past agricultural land use although correlation is not sufficient to demonstrate cause and effect the statistics favor rock based as as the dominant regional source of the element in stream sediments and ground water in new england the distribution of bedrock geology features at the geologic province lithology group and map unit level closely correlate with areas of elevated as in ground water stream sediments and rocks

gravity wave characteristics in the lower atmosphere at south pole a 4 year 1993 1996 temperature and wind data set obtained from over 2000 high resolution balloon soundings at south pole is used to study gravity wave characteristics in the troposphere and lower stratosphere extensive analyses of energy density spectra and static stability are performed to present a comprehensive view of the gravity wave characteristics in the lower atmosphere at south pole our results show that the gravity waves are ubiquitous and often fairly strong at south pole even though the generation mechanisms are not clear gravity wave characteristics are in general similar to those obtained at other high latitude southern hemisphere stations potential energies vary between about 0 5 j kg and 5 j kg with season and altitude variations in kinetic energies are not well correlated with potential energy variations and range from 1 j kg to 11 j kg we observe significant seasonal variations of the slope and magnitude of the vertical wavenumber spectrum of temperature fluctuations especially in the stratosphere in general the gravity waves in the stratosphere are stronger weaker in austral spring fall wave activity in the troposphere has little seasonal dependence stability analysis shows that instabilities are more likely to occur in the troposphere than in the stratosphere the probability of wave instability is 13 7 in the troposphere and 5 4 in the stratosphere this is due to the less stable stratification in the troposphere where the buoyancy period averages 8 3 min compared to 4 9 min in the stratosphere dynamic shear instability is more likely to occur than convective instability 11 versus 2 6 in the troposphere and 4 7 versus 0 7 in the stratosphere due to the prevailing strong wind shear the instability probabilities vary seasonally with the austral winter exhibiting the highest probability of instabilities dynamic and convective instabilities combined in both the troposphere and stratosphere