interpretations of observed climatological patterns in stratospheric gravity wave variance observational analyses of gravity waves in the stratosphere have revealed various climatological patterns in gravity wave activity seasonal geographical and vertical variations have all been observed in this work a linear model of gravity wave propagation is applied to investigate the underlying causes of some of the observed patterns a collection of monochromatic gravity waves that represent a broad spectrum of wavenumbers and frequencies is input at 6 km altitude in the model propagation of the waves through realistic background atmospheric wind and stability fields is treated with linear ray theory and a simple saturation condition to limit amplitudes to stable values the wave spectrum at the 6 km source height is specified to be constant at all latitudes longitudes and times so the variability that appears at higher altitudes is due entirely to background atmosphere variations before the model results are compared to the observations the spectrum of waves is filtered in a way that mimics the limitations of each of the observation techniques the filtering is described in terms of vertical wavelength and is referred to as the observational filter in a vertically varying background wind gravity waves are doppler shifted in intrinsic frequency and refracted to different vertical wavelengths as they propagate vertically through the atmosphere the observational filter and the wave refraction effects can thus couple in interesting ways that have not been explicitly considered in previous work the model shows that this coupling can give rise to geographical seasonal and vertical variations in gravity wave observations without any variations in the spectrum or amplitude of gravity wave sources in the troposphere thus careful consideration of both the background wind profile and observational filter can greatly affect the interpretation of the observed climatological patterns in gravity wave activity

tem study of in situ organic matter on continental margins occurrence and the monolayer hypothesis abstract tem photomicrographs show that organic matter in the continental margin sediments that we have examined is primarily patchy in distribution and occurs as 1 discrete discontinuous blebs and micro blebs of differentiated and undifferentiated protoplasm 2 bacterial cells and associated muco polysaccharide networks and 3 localized smears generally associated with clay minerals and domain junctions in clay rich flocs not as thin uniform grain coatings or as infillings of nicks or etch pits on sediment grains with high degrees of surface roughness this occurrence contradicts recent assertions that most organic matter in continental margins occurs as monolayer or monolayer equivalent coatings on mineral grains and inorganic bioclastic particles our results are based on tem photomicrographs of samples from the northern california continental slope that fall within the monolayer equivalent envelope defined by mayer 1994 marine snow from the overlying nepheloid layer and sediments from eckernforde bay in the baltic sea these samples were prepared specifically to preserve and image in situ sediment fabric and organic constituents textural evidence suggests that low permeabilities caused by the interaction between the organic inorganic and biologic components of the clay size fraction play a major role in determining organic matter preservation on continental margins

late holocene environments at lake mitsinjo northwestern madagascar two sediment cores from lake mitsinjo in northwestern madagascar were analysed for evidence of past environmental changes the unconformities in a 503 cm core from the centre of the lake and a 306 cm core from the shore were correlated to identify a hiatus in sedimentation that occurred just before ca 1000 bp the 3500 year stratigraphic record was analysed for fossil pollen charcoal algae organic matter and carbonate content pollen stratigraphy indicates the following vegetational changes 1 a mosaic of dry forest and grassland from ca 3500 bp until the time the lake dried up 2 a savanna from ca 1000 500 bp and 3 a highly disturbed grassland with fire adapted trees and ruderal herbs in the last 500 years pollen spectra and lithologic correlation indicate that prior to the hiatus the lake experienced a highstand and after the hiatus lake levels were lower the lake level changes probably reflect the local effective moisture pollen evidence indicates a possible human disturbance of the s

dispersal concentration and deposition of suspended matter in the north sea suspended matter comes into the north sea from the atlantic ocean from the channel rivers seafloor erosion coastal erosion the atmosphere and from primary production the contribution of the last source is temporarily large when phytoplankton growth is abundant but is soon decomposed mineralized or consumed so that over the year the net effect is small accumulation and deposition of suspended matter occurs predominantly in only a few areas the waddensea the german bight the skagerrak norwegian channel the remainder of the north sea floor consists of pleistocene and early holocene relict deposits and of reworked sands and gravels the mechanisms resulting in accumulation and deposition are discussed there are strong indications that the amount of suspended matter flowing out from the north sea into the norwegian sea along the norwegian coast is only little more or the same as the amount coming in from the north atlantic although its composition may be different

late quaternary stratigraphic charcoal records from madagascar the classic view regarding the cause of the extinction of at least 17 species of large mammals birds and reptiles in madagascar during the late holocene implicates human use of fire to modify the environment however analysis of the charcoal stratigraphy of three sediment cores from madagascar shows that late pleistocene and early to mid holocene sediments deposited prior to human settlement often contain more charcoal than postsettlement and modern sediments this observation which is confirmed by independent measurements from direct assay and palynological counting techniques suggests that widely held but previously untested beliefs concerning the importance of anthropogenic fires in late holocene environmental changes and megafaunal extinctions of madagascar may be based on an overly simplified version of actual prehistoric conditions moderate to low charcoal values characterized only the late holocene millennia immediately prior to the presumed time of arrival of the first settlers human settlement is probably indicated in the stratigraphy by the sharp rise in charcoal content observed beginning ca 1500 yr b p fire appears to be a significant natural component of prehuman environments in madagascar but some factor probably climate has modulated the extent of natural burning

characteristics of mesospheric gravity waves over the southeastern tibetan plateau region the tibetan plateau tp known as third pole of the earth has important influences on global climates and local weather an important objective in present study is to investigate how orographic features of the tp affect the geographical distributions of gravity wave gw sources three year oh airglow images november 2011 to october 2014 from qujing 25 6 n 103 7 e were used to study the characteristics of gws over the southeastern tp region along with the almost concurrent and collocated meteor radar wind measurements and temperature data from saber timed satellite the propagation conditions of three types of gws freely propagating ducted or evanescent were estimated most of gws exhibited ducted or evanescent characteristics almost all gws propagate southeastward in winter the gw propagation directions in winter are significantly different from other airglow imager observations at northern middle latitudes wind data and convective precipitation fields from the european centre for medium range weather forecasts reanalysis data are used to study the sources of gws on the edge of the tp using backward ray tracing analysis we find that most of the mesospheric freely propagating gws are located in or near the large wind shear intensity region 10 km 17 km on the southeastern edge of the tp in spring and winter the averaged value of momentum flux is 11 6 5 2 m2 s2 in winter and 7 5 3 1 m2 s2 in summer this work will provide valuable information for the gw parameterization schemes in general circulation models in tp region

late holocene environmental changes in arid southwestern madagascar a 5000 yr stratigraphic record containing fossil pollen charcoal and bones of the extinct quaternary megafauna from andolonomby a hypersaline pond in arid southwestern madagascar shows evidence for climatic desiccation beginning about 3000 yr b p pollen spectra shift at this time from primarily arboreal taxa characteristic of forests and woodlands of more mesic western madagascar to wooded savanna typical of somewhat drier localities between 3000 and 2000 yr b p the site became increasingly arid charcoal and pollen evidence indicates that increased fire and disturbance occurred at the site beginning ca 1900 yr b p probably signaling the beginning of human settlement in the area the fossil record suggests that various human and natural factors on the island may have interacted in the subsequent millennium to culminate in the extinction of the entire endemic megafauna

chronology of holocene vertebrate extinction in the galapagos islands abstract eleven conventional and 15 ams accelerator mass spectrometer radiocarbon dates establish chronologies for nine holocene vertebrate fossil sites in the galapagos islands ecuador a holocene fossil record approaching 500 000 bones more than 90 of which predate the arrival of people shows that most or all cases of extinction or extirpation in the galapagos occurred after first human contact in ad 1535 this is especially significant for two species of large rodents megaoryzomys spp that are known only from bones found in lava tubes the highest rate of background prehuman extinction interpreted from the galapagos fossil record is probably hundreds of times less than the modern rate of human related extinction

recent sedimentation and organic carbon burial in a shelf sea the north sea to obtain a carbon budget of the north sea recent sedimentation rates and organic carbon and nitrogen concentrations were determined on 27 box cores from the shallow north sea with a water depth 200 m and a surface area of 500 103 km2 the sedimentation rates in these box cores range from 5 to 35 cm 100 year 1 corg concentrations are 0 05 1 based on these numbers and published data the total amount of corg buried in the shallow north sea is calculated as 1 105 tons year 1 in large parts of the shallow north sea recent sedimentation is nearly absent reworking of relict deposits and partial mixing of these deposits with small amounts of recent fine grained sediments by biological and physical processes and human activities beam trawl fishery result in apparent sedimentation rates which are likely to exceed the real net sedimentation rates considerably the results of this study suggest that the majority of the organic matter is exported from the shelf over the shelf edge into the norwegian sea and into inner shelf deeps skagerrak and norwegian channel coarse grained shelf sediments are only of minor significance for the preservation of organic matter

stratospheric gravity waves generated by multiscale tropical convection abstract the generation of gravity waves by multiscale cloud systems evolving in an initially motionless and thermodynamically uniform environment is explored using a two dimensional cloud system resolving model the simulated convection has similar depth and intensity to observed tropical oceanic systems the convection self organizes into preferred horizontal and temporal scales involving weakly organized propagating cloud clusters the multiscale systems generate a broad spectrum of gravity waves with horizontal scales that range from the cloud system scale up to the cloud cluster scale the gravity waves with the largest horizontal scale play an important role in modifying layered tropospheric inflow and outflow to the cloud systems which in turn influence the multiscale convective organization slower moving short scale gravity waves make the strongest individual contribution to the vertical flux of horizontal momentum and cause a robust peak in the momentum flux spectrum that corresponds to the lif

radiocarbon dates on bones of extinct birds from hawaii abstract bones from a stratified sedimentary deposit in the puu naio cave site on maui hawaiian islands reveal the late holocene extinction of 19 species of birds the age of the sediment and associated fauna was determined by direct radiocarbon dating tandem particle accelerator mass spectrometer tams of amino acids extracted from bones weighing as little as 450 mg the 14c dates indicate that sediment has been accumulating in the lava tube for at least the last 7750 years a suitable time frame for testing the hypothesis that holocene extinction on islands began after human colonization despite growing evidence that a worldwide wave of extinctions coincided with human colonization of oceanic islands little radiometric data have been available to date the extinction of most small fossil vertebrates on islands the tams technique of dating purified collagen from the bones of small vertebrates could lead to vastly improved chronologies of extinction for oceanic islands where catastrophic mid to late holocene extinction is expected or known to have occurred chronologies derived from nonarcheological sites that show continuous sedimentation such as the puu naio cave deposit may also yield key evidence on the timing of earliest human settlement of oceania

gravity wave interactions with the diurnal propagating tide observations of the diurnal propagating solar tide in the mesosphere and lower thermosphere 50 150 km indicate substantial annual variations in tidal amplitudes observations and modeling efforts suggest that interactions with internal gravity waves can result in significant modifications of the diurnal tide herein a two dimensional 2 d linear steady state tidal model is used in conjunction with hybrid lindzen matsuno gravity wave parameterization to examine the role of gravity wave interactions in the seasonal variability of the diurnal tide in the mlt the analysis indicates that annual variations of the background atmosphere result in significant annual variations in the eddy diffusion and the diurnal harmonic of the momentum flux divergence wave stress produced by breaking gravity waves the seasonal variability in these two mechanisms can explain the observed semi annual variability in the diurnal tide amplitude minima at solstice and maxima at equinox the relative roles of wave stress and diffusion are examined and it is shown that both play important roles in tidal modification by damping its amplitude the effects of varying inputs to the gravity wave parameterization are explored

the seasonal variation of the propagating diurnal tide in the mesosphere and lower thermosphere part i the role of gravity waves and planetary waves abstract the seasonal variation of the propagating diurnal tide in the mesosphere and lower thermosphere is examined using results from a 2 yr simulation of the extended version of the canadian middle atmosphere model cmam the cmam is shown to be able to reproduce not only the observed semiannual amplitude variation of the tide in the lower thermosphere but also more subtle features such as amplitude maxima that are stronger in march april than in september october a 4 to 6 h shift in phase between winter and summer in the northern hemisphere and a weaker seasonal variation of phase in the southern hemisphere part i of this two part series of papers investigates the importance of two of the mechanisms that have been proposed to explain the observed variation of tidal amplitude namely 1 interactions with small scale gravity waves and 2 interactions with planetary scale waves like the quasi 2 day wave analysis of the tidal momentum and thermodynamic budgets shows that the direct effects of param

chlorophyll a and pheopigments as tracers of labile organic carbon at the central equatorial pacific seafloor high rates of primary production and fast sinking rates lead to the deposition of phytodetritus and highly reactive organic matter to the sediments of the central equatorial pacific these substances are responsible for driving important chemical fluxes and fueling benthic organisms chloropigments have proven useful as tracers of similar highly reactive organic carbon components in lacustrine and nearshore marine sediments in this study we investigate the degradation of chlorophyll a and pheopigments a at four abyssal sites on the jgofs equatorial pacific transect along 140 w and explore the usefulness of these chloropigments as tracers of the most reactive component of the deep sea particulate organic carbon poc rain first order reaction rate constants k 1 75 yr 1 half life 3 250 d and relative reactivities chlorophyll a allomer and pheophorbide a pheophytin a derived from most of the sedimentary profiles are similar to those found in laboratory and other field lake and coastal marine studies however in some profiles the rate constants determined by fitting data below 0 5 cm are slower by up to 3 orders of magnitude despite an apparent abundance of bacteria macrofauna and porewater oxygen model results assuming multi g kinetics suggest that these chloropigments degrade as two components one which accounts for at least 99 of the degradation and 11 57 of the sediment inventory degrades with a half life of 4 120 days the other component degrades with a half life of up to 440 years these results suggest that some otherwise labile poc may be protected and escape rapid degradation near the sediment water interface if phytodetritus is deposited continuously throughout the year our model calculated chlorophyll a fluxes indicate that it could account for 25 100 of the annual poc flux at sites close to the equator

extended canadian middle atmosphere model zonal mean climatology and physical parameterizations 1 this paper describes the energetics and zonal mean state of the upward extension of the canadian middle atmosphere model which extends from the ground to 210 km the model includes realistic parameterizations of the major physical processes from the ground up to the lower thermosphere and exhibits a broad spectrum of geophysical variability the rationale for the extended model is to examine the nature of the physical and dynamical processes in the mesosphere lower thermosphere mlt region without the artificial effects of an imposed sponge layer which can modify the circulation in an unrealistic manner the zonal mean distributions of temperature and zonal wind are found to be in reasonable agreement with observations in most parts of the model domain below 150 km analysis of the global average energy and momentum budgets reveals a balance between solar extreme ultraviolet heating and molecular diffusion and a thermally direct viscous meridional circulation above 130 km with the viscosity coming from molecular diffusion and ion drag below 70 km radiative equilibrium prevails in the global mean in the mlt region between 70 and 120 km many processes contribute to the global energy budget at solstice there is a thermally indirect meridional circulation driven mainly by parameterized nonorographic gravity wave drag this circulation provides a net global cooling of up to 25 k d 1

mesospheric momentum flux studies at adelaide australia observations and a gravity wave tidal interaction model abstract we present here the results of an analysis of gravity wave momentum fluxes in the mesosphere and lower thermosphere inferred using a dual beam doppler radar near adelaide australia during june 1984 our analysis reveals that over 70 of the momentum flux and of the inferred zonal drag was due to gravity waves with observed periods less than one hour this suggests that it is the gravity waves with high intrinsic frequencies and small horizontal scales that are most effective at transporting momentum into the middle atmosphere the temporal variations in the momentum flux and flux divergence due to high frequency motions were also examined in detail in addition to daily variability a strong diurnal modulation was observed to occur this was found to be correlated with the phase of large amplitude diurnal tidal motions as a result of these observations a gravity wave tidal interaction model was proposed which accounts for all of the major features of the observed data including a reduction i

mesospheric gravity waves over a tropical convective region observed by oh airglow imaging in indonesia 1 from oh airglow imaging observation carried out over one year in indonesia 74 events of gravity waves in the mlt mesosphere and lower thermosphere region were extracted observed period horizontal wavelength and observed horizontal phase speeds of gravity waves were typically 5 13 min 13 45 km and 37 75 m s respectively propagation directions were mostly southward except for the period between december and february when eastward propagation was preferential spatial distributions of tropospheric clouds estimated with gms geostationary meteorological satellite were consistent with the propagation direction of gravity waves i e these clouds mainly existed in the opposite direction to the propagation direction of waves this suggests that horizontal propagation characteristics of the short period gravity waves in the low latitude mlt region are mainly affected by the distribution of the wave sources in the troposphere and the effect of the background mean wind in the middle atmosphere is smaller as it is weaker 20 m s in the equatorial region

sensitivity of mesospheric mean flow planetary waves and tides to strength of gravity wave drag a global circulation model which extends from the surface to 125 km is used to study how the strength of gravity wave drag affects the dynamics of the mesosphere the strength of gravity wave drag has a strong influence on the zonal mean state of the mesosphere in particular the magnitude and variability of the summer mesopause temperature and the shear on the top of the mesospheric jets this change in the zonal mean state strongly affects the susceptibility of the mesosphere to baroclinic and or barotropic instability and hence the formation of the 2 day wave the 2 day wave in turn interacts nonlinearly with the diurnal tide producing secondary waves and a reduction in amplitude of the diurnal tide previous studies with quasi linear mechanistic tidal models have captured some semiannual variation in tidal amplitude through direct interactions between tides and gravity waves our fully nonlinear global circulation model results support an alternative explanation in terms of interactions between planetary waves and tides

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

an investigation of gravity wave activity in the low latitude upper mesosphere propagation direction and wind filtering horizontal phase speeds of up to 80 m s 1 the large scale band wave patterns horizontal wavelength between 10 and 60 km exhibited a clear seasonal dependence on the horizontal propagation direction propagating toward the southeast during the summer months and toward the northwest during the winter the direction of propagation was observed to change abruptly around the equinox period in mid march and at the end of september using a numerical simulation of gravity wave propagation in a seasonally variable climatological wind field we have determined that the observed anisotropy in the wave propagation directions can be attributed to a strong filtering of the waves in the middle atmosphere by stratospheric winds index terms 0310 atmospheric composition and structure airglow and aurora 3332 meteorology and atmospheric dynamics mesospheric dynamics 3360 meteorology and atmospheric dynamics remote sensing keywords airglow winds gravity waves wind filtering imager

dating of modified femora of extinct dwarf hippopotamus from southern madagascar implications for constraining human colonization and vertebrate extinction events two significant events in the late holocene history of madagascar were a the arrival of people and b the loss of nearly two dozen species of land vertebrates in the socalled subfossil extinctions the consensus is that the faunal losses occurred shortly subsequent to human arrival but the timing of these events is poorly constrained the minimum age for initial human presence on the island may now be set at approximately 2000 bp on the basis of ams 14c dates for human modified femora of extinct dwarf hippos from sw madagascar assuming that this date also marks the beginning of deleterious human interactions with the subfossil fauna and assuming that this fauna became completely extinct by 900 bp the width of the anthropogenic extinction window may have been as long as c 1000 a this estimate nearly twice the length of previous ones is close to the unadjusted minimum for the duration of the terminal pleistocene extinction event in the americas whether or not this length of time comports with theoretical expectations of a blitzkrieg pattern of losses is uncertain but greater refinement in dating the end of the subfossil extinctions is unlikely to produce radically shorter estimates of duration

evidence of preferential directions for gravity wave propagation due to wind filtering in the middle atmosphere all sky tv images of wave structure in the near infrared hydroxyl oh nightglow emission were recorded over a 3 month period during may june and july 1988 from a high altitude site at the mountain research station 40 0 n 105 6 w 3050 m near nederland colorado well defined coherent wave patterns associated with the passage of short period 1 hour gravity waves were observed on a total of 22 occasions the wave motions exhibited similar spatial and temporal properties during each month but a distinct tendency for northward propagation 68 of the wave azimuths within 40 0 n with some eastward motion in may and june was observed throughout the campaign although it is theoretically well known that upward propagating gravity waves can be blocked at a critical layer produced by the interaction of the waves with the horizontal background wind observational evidence of this phenomenon is rare to investigate the possibility that the asymmetry in the wave propagation directions was caused by the critical layer a model based on mean climatological background winds and numerical tidal wave modes valid for any mid latitude site and time of the year was constructed to show the regions forbidden to upward gravity wave propagation from critical layer theory these blocking diagrams which vary with height and time were constructed for the oh altitude 87 km for the present paper comparison of the predicted i e least restricted and the observed directions of the wave motion show almost complete agreement this suggests that middle atmospheric winds can play an important role in determining the flux and the azimuthal distribution of short period waves reaching the upper atmosphere

statistical study of short period gravity waves in oh and oi nightglow images at two separated sites 1 using airglow images of the near infrared oh band 720 910 nm and oi 557 7 nm line we investigated seasonal latitudinal and local time variations of short period gravity waves the images were obtained at two locations in japan that are 1200 km apart rikubetsu 43 5 n 143 8 e and shigaraki 34 9 n 136 1 e between october 1998 and october 1999 our analysis has focused on small scale gravity waves with wavelengths less than 40 km and dominant phase speeds of 20 50 m s wave occurrences for both oh and oi at rikubetsu and shigaraki are significantly higher than 60 with a slightly larger value in summer the occurrences increase from evening to midnight there are no obvious local time dependencies in horizontal wavelength propagation direction and phase speed the propagation directions in summer are either northward or northeastward at both locations however in winter the propagation directions at rikubetsu are generally westward nw w and sw whereas those at shigaraki are only southwestward from simultaneous wind observation by the mf radars at wakkanai 45 4 n 141 7 e and yamagawa 31 2 n 130 6 e we discuss possible influences of doppler and thermal ducting wind filtering and source distribution of gravity waves propagating from the lower atmosphere to the airglow heights in the mesopause region

observational evidence of tidal gravity wave interactions using the uwo 2 mhz radar the degree of interaction between atmospheric gravity waves and tides is an issue which is of great importance in middle atmosphere studies it is especially important with regard to tidal variability which is frequently observed in the mesosphere and lower thermosphere but as yet has not been subject to adequate study in this paper we present some strong observational evidence of such interactions made with the uwo 2 mhz radar near london canada our observations show significant correlation between gravity waves and tides diurnal at certain times of the year and the nature of the correlation is intermittent and varies with time of year it is possible that differences between tidal amplitudes at sites with mesoscale separations may be explained in terms of such phenomena we also propose a simple model which is found to be consistent with the major features of the observed data

characteristics of ripple structures revealed in oh airglow images small scale ripple structures observed in oh airglow images are most likely induced by either dynamic instability due to large wind shear or convective instability due to superadiabatic lapse rate using the data set taken in the mesopause region with an oh all sky imager at yucca ridge field station colorado 40 7 n 104 9 w from september 2003 to december 2005 we study the characteristics and seasonal variations of ripple structures by analyzing the simultaneous background wind and temperature observed by the nearby sodium temperature wind lidar at fort collins colorado 40 6 n 105 w and a nearby medium frequency radar at platteville colorado 40 2 n 105 8 w we are able to statistically study the possible relation between ripples and the background atmosphere conditions characteristics and seasonal variations of ripples are presented in detail in this study the occurrence frequency of ripples exhibits clear seasonal variability with peak in autumn the occurrence of ripples shows a local time dependence which is most likely associated with the solar tides the lifetime and spatial scale of these ripples are typically 5 20 min and 5 10 km respectively and most of the ripples move preferentially either southward or northward however more than half of the observed ripples do not advect with background flow they have higher richardson numbers than those ripples that advect with background flow it is possible that they are not instability features but wave structures that are hard to be distinguished from the real instability features

gravity wave characteristics in the mesopause region revealed from oh airglow imager observations over northern colorado using 5 years of all sky oh airglow imager data over yucca ridge field station co 40 7 n 104 9 w from september 2003 to september 2008 we extract and deduce quasi monochromatic gravity wave gw characteristics in the mesopause region the intrinsic periods are clustered between approximately 4 and 10 min and many of them are unstable and evanescent gw occurrence frequency exhibits a clear semiannual variation with equinoctial minima which is likely related to the seasonal variation of background wind the anomalous propagation direction in january 2006 with strong southward before major warming starting in 21 january and weak southward propagation afterward was most likely affected by stratospheric sudden warming the momentum fluxes show strongly anticorrelated with the tides with 180 out of phase in the zonal component while in the meridional component the easterly maximum occurred approximately 2 6 h after maximum easterly tidal wind however the anticorrelations are both weakest during the summer the dissipating and breaking of small scale and high frequency gw s components could have a potential impact on the general circulation in the mesopause region

climatology and modeling of quasi monochromatic atmospheric gravity waves observed over urbana illinois from analyzing nine months of airglow imaging observations of atmospheric gravity waves agws over adelaide australia 35 s walterscheid et al 1999 have proposed that many of the quasi monochromatic waves seen in the images were primarily thermally ducted here are presented 15 months of observations from february 1996 to may 1997 for agw frequency and propagation direction from a northern latitude site urbana illinois 40 n as adelaide urbana is geographically distant from large orographic features similar to what was found in adelaide the agws seem to originate from a preferred location during the time period around summer solstice in conjunction with these airglow data there exists mf radar data to provide winds in the 90 km region and near simultaneous lidar data which provide a temperature climatology the temperature data have previously been analyzed by states and gardner 2000 the temperature and wind data are used here in a full wave model analysis to determine the characteristics of the wave ducting and wave reflection during the 15 month observation period this model analysis is applied to this and another existing data set recently described by nakamura et al 1999 it is shown that the existence of a thermal duct around summer solstice can plausibly account for our observations however the characteristics of the thermal duct and the ability of waves to be ducted is also greatly dependent on the characteristics of the background wind a simple model is constructed to simulate the trapping of these waves by such a duct it is suggested that the waves seen over urbana originate no more than a few thousand kilometers from the observation site

assessment of gravity wave momentum flux measurement capabilities by meteor radars having different transmitter power and antenna configurations 1 measurement capabilities of five meteor radars are assessed and compared to determine how well radars having different transmitted power and antenna configurations perform in defining mean winds tidal amplitudes and gravity wave gw momentum fluxes the five radars include two new generation meteor radars on tierra del fuego argentina 53 8 s and on king george island in the antarctic 62 1 s and conventional meteor radars at socorro new mexico 34 1 n 106 9 w bear lake observatory utah 41 9 n 111 4 w and yellowknife canada 62 5 n 114 3 w our assessment employs observed meteor distributions for june of 2009 2010 or 2011 for each radar and a set of seven test motion fields including various superpositions of mean winds constant diurnal tides constant and variable semidiurnal tides and superposed gws having various amplitudes scales periods directions of propagation momentum fluxes and intermittencies radars having higher power and or antenna patterns yielding higher meteor counts at small zenith angles perform well in defining monthly and daily mean winds tidal amplitudes and gw momentum fluxes though with expected larger uncertainties in the daily estimates conventional radars having lower power and a single transmitting antenna are able to describe monthly mean winds and tidal amplitudes reasonably well especially at altitudes having the highest meteor counts they also provide reasonable estimates of gw momentum fluxes at the altitudes having the highest meteor counts however these estimates are subject to uncertainties of 20 to 50 and uncertainties rapidly become excessive at higher and lower altitudes estimates of all quantities degrade somewhat for more complex motion fields

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

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

a link between variability of the semidiurnal tide and planetary waves in the opposite hemisphere 1 horizontal wind observations over four years from the meteor radar at esrange 68 n 21 e are analyzed to determine the variability of the semidiurnal tide simultaneous global observations of temperature and geopotential from the saber satellite instrument are used to construct time series of planetary wave amplitudes and geostrophic mean zonal wind during northern hemisphere summer and fall the temporal variability of the semidiurnal tide at esrange is found to be well correlated with the amplitude of planetary wavenumber 1 in the stratosphere in high southern latitudes i e in the opposite hemisphere the correlations indicate that a significant part of the tidal variation at esrange is due to dynamical interactions in the southern hemisphere a corresponding robust correlation pattern for the esrange tides is not apparent at other times of the multiple years analyzed

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

statistical characteristics of gravity waves observed by an all sky imager at darwin australia 1 an all sky airglow imager with a cooled charge coupled device camera in place at darwin 12 4 s 131 0 e australia since october 2001 has been used to obtain two dimensional gravity wave images in the mesopause region using airglow images of the oi 557 7 nm emission altitude 96 km and oh band 720 910 nm 86 km emissions obtained for october 2001 to august 2002 we investigated the wavelengths phase velocities and propagation directions of gravity waves wave occurrence in oh images 60 90 is higher than in oi images 30 70 for all seasons the waves have wavelengths of less than 90 km peak 30 50 km and phase velocities of less than 90 m s peak 30 60 m s most of the waves propagate in the meridional direction and the directionality strongly depends on the season in winter waves propagate both poleward and equatorward while in summer almost all waves propagate poleward an examination of airglow imaging statistics at adelaide 35 s 138 e australia obtained by walterscheid et al 1999 leads us to conclude that this clear directionality is caused by the location of the wave sources and by the wave ducting processes that is poleward waves in summer come from an equatorial convective source through a thermal duct structure the effect of wind filtering on the waves is also discussed for zonal wave propagation

concurrent oh imager and sodium temperature wind lidar observation of localized ripples over northern colorado 1 on 3 and 5 september 2002 the oh all sky imager at platteville colorado 40 2 n 104 7 w observed small scale wavelike patterns known as ripples with horizontal wavelengths of 9 km and 7 km and lifetimes of 9 min and 15 min respectively the colorado state university sodium lidar at nearby fort collins colorado 40 6 n 105 w also made concurrent observations of temperature and zonal and meridional winds which allowed us to determine the nature of the ripples observed our observations suggest that the 3 september ripple was induced by a convective instability located at 87 5 km and the 5 september ripple was induced by a dynamic instability at 88 5 km the ripples clearly advected as packets with the background wind lidar measurements also allowed us to relate the directions of wind shear to the phase front alignments of both the ripples and the nearby short period atmospheric gravity waves these spatial relationships provided a meaningful comparison with previously observed ripples as well as with current theoretical models using the 16 hour continuous lidar data set for each case we deduced that long period waves created an unusually large temperature perturbation at the ripple times on 3 september and an unusually large wind shear perturbation on 5 september these perturbations prepared the background atmosphere to be near the verge of local instability but as revealed again by lidar observation it was the superposition of smaller scale perturbations at the time of the ripples that helped to actually reach the conditions required for instability and generation of the ripples

pathways of organic carbon oxidation in three continental margin sediments we have combined several different methodologies to quantify rates of organic carbon mineralization by the various electron acceptors in sediments from the coast of denmark and norway rates of nh4 and sigma co2 liberation sediment incubations were used with o2 penetration depths to conclude that o2 respiration accounted for only between 3 6 17 4 of the total organic carbon oxidation dentrification was limited to a narrow zone just below the depth of o2 penetration and was not a major carbon oxidation pathway the processes of fe reduction mn reduction and sulfate reduction dominated organic carbon mineralization but their relative significance varied depending on the sediment where high concentrations of mn oxide were found 3 4 wt mn only mn reduction occurred with lower mn oxide concentrations more typical of coastal sediments fe reduction and sulfate reduction were most important and of a similar magnitude overall most of the measured o2 flux into the sediment was used to oxidized reduced inorganic species and not organic carbon we suspect that the importance of o2 respiration in many coastal sediments has been overestimated whereas metal oxide reduction both fe and mn reduction has probably been well underestimated

diurnal variations of temperature and winds inferred from timed and uars measurements 1 owing to their sampling properties in local solar time both the timed and uars spacecrafts provide the opportunity to quantitatively study the mesospheric thermal tides the information though is limited because it takes the timed instruments 2 months to cover the full range of 24 hours almost twice as long as uars we present here the results of an analysis in which the seasonal and global scale variations of amplitude and phase for the migrating diurnal tide are retrieved from atmospheric temperature and wind measurements on the timed saber tidi and uars mls hrdi satellites comparisons are made with results from the numerical spectral model nsm which is characterized in part by the parameterization of small scale gravity waves at 60 km and above the amplitude and phase variations of the diurnal tide from the nsm agree generally well with those derived from the saber temperatures in the saber temperature amplitudes at around 60 km there are evident asymmetries in latitude with respect to the equator which are not apparent in the mls data near 55 km or in the nsm the asymmetry in the saber temperatures disappears above 60 km for the meridional winds of the migrating diurnal tide derived from tidi the phase and relative amplitude variation with latitude and season are in qualitative agreement with the hrdi measurements and the nsm the amplitudes from tidi winds are systematically smaller but this may in part be due to interannual variations however the results for the zonal winds from tidi more often do not agree well with those from hrdi or the nsm

estimation of the equivalent rayleigh friction in mesosphere lower thermosphere region from the migrating diurnal tides observed by timed 1 we use thermosphere ionosphere mesosphere energetics and dynamics timed global temperature and wind data from 2002 to 2007 to investigate the damping of the diurnal tide horizontal winds are measured by tidi and are calculated from saber temperature measurements the determination of tidal winds from saber temperature depends on the damping and therefore the discrepancy between tidi and saber determinations of the wind tides can be used to calculate the tidal damping this damping is approximated here by an equivalent rayleigh friction erf and it is adjusted to minimize the difference in winds derived from saber and tidi data the results show that during some periods the erf coefficient can be very large over narrow vertical regions of about 5 km 10 5 s 1 in low latitudes and about 10 4 s 1 in midlatitudes the magnitude and shape of the vertical profiles change with latitude and season the peak in the vertical profile of erf is larger and located at a higher altitude in summer than in winter and the erf coefficients at 40 are stronger than at 20 in both hemispheres the erf deduced in this study without a priori assumption about the mechanism of the damping shows a seasonal variation that is clearly consistent with the seasonal variation of the zonal mean wind the maximum erf generally coincides with the altitudes of strongest wind reversal in the mesopause region

benthic organic matter supply and metabolism at depositional and non depositional areas in the north sea in 1994 four stations in the southern north sea the german bight and the skagerrak were visited with the aim to get insight into spatial and temporal variation in the supply of fresh organic matter to the benthos and its subsequent metabolic reaction stations were chosen on the basis of differences in sediment type depth and depositional regime sediments were sampled sliced and analysed for phytopigments fatty acids and nucleic acids on deck sediment core incubations provided the sediment oxygen demand sod fatty acids as well as chlorophyll a indicated a seasonal variation of phytodetritus sedimentation with highest values in may reflecting the spring bloom sedimentation the two stations in the depositional areas german bight and skagerrak had the highest input of algal detritus into the sediment these stations also contained higher concentrations of bacterial and long chain fatty acids probably related to the relatively higher proportion of fine particles in the sediment and to the input of terrestrial organic matter and or refractory marine organic matter respectively the metabolic indices viz the sod and the rna concentrations reflected the benthic metabolic reaction to the labile organic matter supply the three stations in the southern and south eastern north sea had a sod congruent with the phytodetrital inventories with highest sod measured at the german bight surprisingly the skagerrak sediment did not have a high oxygen demand although it contained the highest inventory of labile organic matter and high rna concentrations the fluxes of carbon to the sediment at station sk calculated from the chlorophyll a inventory were about four times higher than the sediment oxygen demand we hypothesise two mechanisms for this discrepancy one is the decreased mineralisation rate of labile organic matter due to sorption to clayey sediment particles the other is advection of labile organic matter from the shallower coastal waters of northern denmark to and subsequent removal from the deeper skagerrak sediments by periodically occurring high near bottom water currents

subfossil lemur discoveries from the beanka protected area in western madagascar a new fossil site in a previously unexplored part of western madagascar the beanka protected area has yielded remains of many recently extinct vertebrates including giant lemurs babakotia radofilai palaeopropithecus kelyus pachylemur sp and archaeolemur edwardsi carnivores cryptoprocta spelea the aardvark like plesiorycteropus sp and giant ground cuckoos coua many of these represent considerable range extensions extant species that were extirpated from the region e g prolemur simus are also present calibrated radiocarbon ages for 10 bones from extinct primates span the last three millennia the largely undisturbed taphonomy of bone deposits supports the interpretation that many specimens fell in from a rock ledge above the entrance some primates and other mammals may have been prey items of avian predators but human predation is also evident strontium isotope ratios 87sr 86sr suggest that fossils were local to the area pottery sherds and bones of extinct and extant vertebrates with cut and chop marks indicate human activity in previous centuries scarcity of charcoal and human artifacts suggests only occasional visitation to the site by humans the fossil assemblage from this site is unusual in that while it contains many sloth lemurs it lacks ratites hippopotami and crocodiles typical of nearly all other holocene subfossil sites on madagascar

diurnal variation of gravity wave momentum flux and its forcing on the diurnal tide 1 the diurnal variation of gravity wave gw momentum flux is derived from the 5 years of meteor radar wind measurements at maui hawaii the amplitude and phase relationships between the gw forcing and the diurnal tide are analyzed by calculating their equivalent rayleigh frictions the results show that the gw momentum flux is clearly modulated by the diurnal tide the forcing from the momentum flux convergence has strong effects on both the amplitude and phase of the diurnal tide they can reach 80 ms 1 day 1 for the amplitude and 15 h day 1 for the phase the gw forcing tends to increase the diurnal tide amplitude above 90 km but has a small damping effect below 90 km it tends to increase the phase of the diurnal tide throughout all altitudes seasonal variations of the gw forcing exist which result in differences in their effects on the diurnal tide the magnitudes of the forcing are in agreement with recent results from satellite observations but are much larger than values used in general circulation models this work also demonstrates that meteor radar measurements can provide a valuable data set for the study of gw tide interactions

the amino acid and stable isotope biogeochemistry of elephant bird aepyornis eggshells from southern madagascar abstract a diverse suite of animals became extinct on madagascar during the late holocene as observed on landmasses elsewhere the extinction process broadly coincided with the arrival of people our research on the amino acid racemisation and the carbon and oxygen isotope biogeochemistry of elephant bird aepyornis eggshells from southern madagascar refines models that attempt to explain the extinction process a correlation between the extent of isoleucine epimerisation aile ile and radiocarbon age of eggshells allows aile ile to serve as a proxy for eggshell age the aile ile values indicate the majority 87 of eggshells in this study are holocene with the remainder representing pleistocene aepyornis populations and that further amino acid analyses would help to constrain the timing of aepyornis extinction carbon isotope ratios in the organic and calcite fractions of eggshells indicate that aepyornis primarily browsed c3 vegetation oxygen isotope values are more negative and less variable than in eggshells of ostriches living in semi arid environments suggesting that aepyornis populations relied upon groundwater fed coastal wetlands for their drinking water the isotope results require that the changing abundances of c3 vegetation and groundwater fed watering points be considered in models that aim to understand the extinction of aepyornis in southern madagascar

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

palaeoenvironmental reconstruction and evidence of marine influence in permian coal bearing sequence from lalmatia coal mine rajmahal basin jharkhand india a multi proxy approach abstract lalmatia coal bearing sequences belong to the barakar formation permian of lower gondwana the well developed coal bearing sequences approx 52 m exposed along the mine section have been studied to understand the depositional environment along with this a cuticle study was performed to understand the palaeoclimate with the help of the stomatal index the distribution of n alkanes n c15 to n c31 suggests major higher plant and algal dominant source input although variations are seen in the relative input steranes identified include c29 regular sterane and 4 methylsteranes the pr ph ratio varied from 0 43 to 4 26 warm temperate to subtropical palaeoclimate with fresh to brackish water bodies and reducing oxygen poor environment were inferred from the rb sr sr cu th u sr ba v v ni mean 13c value measured is 23 0 0 60 for coal and 22 6 for shale these values are well correlated with typical 13c values of the permian coal and shale the stomatal index of glossopteris leaves 280 million years was taken into account and it showed a value of 10 7 that assumes a higher level of atmospheric co2 during the barakar formation artinskian age the result also shows that permian taxon glossopteris can be used for co2 proxy during permian age the geochemical evidence suggests that towards the middle part middle coal seam of the studied section the depositional milieu was under a marine influenced marginal condition the geochemical studies and carbon isotopic ratios unequivocally suggest that fluctuating climatic conditions existed during the deposition of the lalmatia coal bearing sequence

short term variability in the migrating diurnal tide caused by interactions with the quasi 2 day wave 1 the migrating diurnal tide is one of the dominant dynamical features in the low latitudes of the earth s mesosphere and lower thermosphere mlt region representing the atmospheric response to the largest component of solar forcing ground based observations of the tide have resolved short term variations attributed to nonlinear interactions between the tide and planetary waves that are also in the region using the ncar thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm we simulate a quasi 2 day wave qtdw event under late january conditions in this case sideband sum and difference child waves are resolved indicating that a nonlinear interaction is occurring between the qtdw and the tide the migrating diurnal tide in the mlt displays local amplitude decreases of 20 40 as well as a shortening of vertical wavelength by roughly 4 km examining the physical mechanisms driving the interaction nonlinear advection is found to result in amplification of the tide in some regions and damping in others manifesting as increased smoothing of the tidal structure when the qtdw is present in the mlt additionally the qtdw also enhances the easterly summer mean wind jet that can also account for changes in tidal amplitude and vertical wavelength we find that qtdw induced background atmosphere changes in time gcm can drive tidal variability at levels greater than nonlinear advection a possibility not previously considered

flow induced uptake of particulate matter in permeable sediments we demonstrate the fast transfer of suspended particles from the boundary layer into the upper strata z 2 x 10 l l m2 incubated in a laboratory flume increased pressure up and downstream of small mounds z 2 5 cm drove water 5 5 cm into the core carrying suspended particles 1 pm to 2 2 cm sediment depth within 10 h simultaneously decreased pressure at the downstream slope of the protrusions drew pore fluid from deeper layers z 5 10 cm to the surface in the sediment friction reduced the velocity of the particulate tracers resulting in size fractionation and layers of increased particle concentration ripple topography 0 8 2 8 cm high enhanced interfacial particle 1 pm flux by a factor 2 3 when compared to a level control core the pathways of the particle and solute tracers below a sediment ripple are explained with a source sink model that describes the pore flow velocity field our results suggest that bedform induced interfacial flows are important for the uptake of particulate organic matter into permeable shelf sediments

tidal perturbations and variability in the mesopause region over fort collins co 41n 105w continuous multi day temperature and wind lidar observations 1 an unusually long data set was acquired at the sodium lidar facility at colorado state university 41n 105w between sep 18 and oct 01 2003 including a 9 day continuous observation this time is long enough to average out the perturbations of gravity waves and short period planetary waves as such it can be used to define tidal period perturbations in temperature and horizontal wind assuming the sodium mixing ratio is a constant of motion the observed tidal period oscillation in sodium density follows that of vertical wind thus the data set defines tidal period perturbations of temperature and wind vector the observed amplitudes and phases were compared to global scale wave model predictions both gswm00 and gswm02 we found excellent agreement in diurnal phases and reasonable agreement in semidiurnal phases however gswm02 overestimates diurnal amplitudes and both model versions underestimate observed semidiurnal amplitudes since the data period is long enough for the study of planetary waves and of tidal variability we perform spectral analysis of the data revealing a strong quasi 3 day wave in meridional wind a 14 hour perturbation in zonal wind and both 14 hour and 10 hour periods in meridional wind likely the result of nonlinear interactions the observed semidiurnal amplitudes are much larger than the corresponding diurnal amplitudes above 85 km and over a few days the diurnal and semidiurnal amplitudes vary by factors of 2 3 causes for the observed tidal variability in terms of planetary wave modulation and tide gravity wave interaction are explored qualitatively

late holocene vegetational change in central madagascar abstract a sediment core from lake kavitaha central madagascar provides a stratigraphic record of changes in pollen spectra and charcoal influx in the late holocene the earliest pollen spectra distantly resemble the modern pollen rain of a vegetational mosaic in northern madagascar although results of principal component analysis suggest no close modern analog at about 1300 yr b p a marked rise in charcoal is followed by a decline in pollen of woody taxa culminating in a change to grass dominated pollen spectra within about 4 centuries pollen of woody taxa decline below 15 of total terrestrial pollen and spores beginning about 600 yr b p the influx of charcoal from graminoid sources remains high until recent centuries the late holocene changes in vegetation and fire ecology at the site were approximately contemporaneous with the latest 14 c dates for the extinct megafauna and the earliest dates for human occupation

oh emission and gravity waves including a breaking wave in all sky imagery from bear lake ut a new type of all sky imager using a high resolution bare ccd was operated at utah state university observatory at bear lake utah during fall winter 1991 2 on clear nights the purpose was to image oh airglow in the 7500 9000 a spectral region for correlative measurements with uars satellite instrumentation examination of some 20 nights of data some oh wave activity interpreted as gravity wave phenomena has been observed on all images and the spatial extent of the waves typically covered the entire viewing field including overhead images are presented including examples of multiple wave sources and a one time observed complex breaking wave the unique chaotic structure which evolved over an hour developed a distorted phase front followed by a very short wavelength rippled structure

seasonal variations of the diurnal tide induced by gravity wave filtering wind measurements with the uars spacecraft show that between 90 and 100 km altitude the fundamental diurnal tide is modulated semi annually with peak amplitudes of almost 100 m s near equinox more than a factor of two larger than during solstice applying hines doppler spread parameterization dsp for small scale gravity waves gw we present results from a numerical spectral model nsm to describe the seasonal variations in the mean zonal circulation interacting self consistently with the diurnal tide with the dsp the gw momentum source increases the amplitude of the tide at altitudes above 70 km in contrast to the rayleigh friction parameterization that causes damping since the tide absorbs gw momentum it reduces the wave generated semi annual oscillations sao in the mean zonal winds at equatorial latitudes outside the tropics gw momentum is absorbed by the mean zonal winds that peak near the summer and winter solstices as a result the gw reach the upper mesosphere with more momentum during equinox periods and thus cause a seasonal modulation of the tide that is predominately semi annual

winter temperature tides from 30 to 110 km at mcmurdo 77 8 s 166 7 e antarctica lidar observations and comparisons with wam we provide the first characterization of diurnal and semidiurnal thermal tides in temperature from 30 to 110 km in the winter season may through august at mcmurdo 77 8 s 166 7 e antarctica the observations were made with an fe boltzmann temperature lidar in 2011 and 2012 over 330 h of winter data are compiled into a composite day of temperature perturbations that significantly reduce the incoherent wave effects while preserving the coherent tidal signatures both diurnal and semidiurnal tides have small amplitudes less than 3 k below 100 km with vertical wavelengths of 29 and 23 km respectively a new finding of this study is the fast growth of diurnal and semidiurnal tidal amplitudes above 100 km to at least 15 k near 110 km exceeding that of the freely propagating tides originating from the lower atmosphere such fast growth exists for all kp index cases and diurnal amplitude increases to 15 30 k at 110 km with larger kp indices corresponding to larger tidal amplitudes and faster growth rates the slopes of diurnal tidal phases become steeper above 100 km and the tidal phases barely change with altitude from 100 to 106 km the tidal growth behavior is reproduced in the whole atmosphere model wam with phases comparable to the observations but magnitudes significantly underestimated wam compares reasonably well with the observations below 100 km the observed significant amplitude increases and phase structure changes suggest additional tidal sources near or above 100 km which deserve future investigation

organic facies of surface sediments in the north sea abstract surface sediments of the north sea were investigated by organic geochemical and sedimentological methods including organic carbon and nitrogen determination rock eval pyrolysis protokerogen microscopy gas chromatography of aliphatic hydrocarbons grain size fractionation and clay mineral analysis the total organic matter was found to be a mixture of mostly reworked or oxidized marine and terrestrial constituents with a generally strong influence of the latter throughout the platform locally improved hydrodynamic conditions yielded an incorporation of more freshly produced marine organic matter differences in water current velocities and turbulence also appeared to determine whether this supplement is incorporated into the fine or coarse fractions of the sediments a general constancy of the organic carbon contents within the individual size fractions was recognized independently of sediment type and age i e in recent and pre recent deposits this suggested that the latter have been effectively overprinted by the shelf processes operating at present or that these processes have been of comparable intensity since about the beginning of the holocene transgression the major factors controlling the spatial variations in the organic facies are the sediment grain size and the present day hydraulic regime

laboratory studies of oxic and anoxic degradation of chlorophyll a in long island sound sediments abstract laboratory incubations of long island sound lis sediments show that chlorophyll a chla degradation generally follows first order kinetics but that the rates and mechanisms of degradation differ under oxic and anoxic conditions chl a in fresh sediment can be operationally defined as being present in three pools bound chl a nonextractable by acetone free acetone extractable anoxically degradable chl a and free anoxically stable chl a a major pathway of degradation is initial release of bound chl a into the free pool the release rate constants of bound chl a into free chl a are remarkably faster 10 under oxic 4 d 1 compared to anoxic 0 1 d 1 conditions and a much greater fraction of total chl a degrades under oxic conditions however the apparent degradation rate constants of free chl a are two to three times higher in the absence of oxygen in sediments with high bound chla 0 2 0 3 d 1 for anoxic 0 1 d 1 for oxic and about seven times higher in sediments without bound chl a 0 3 d 1 for anoxic 0 04 d 1 for oxic the differences between anoxic and oxic decomposition in incubation experiments together with naturally observed concentration profiles which reach low levels of chl a imply that chl a in natural sediments degrades during the oscillation between oxic and anoxic conditions caused by physical and biological mixing processes oscillation experiments oxic vs anoxic and anoxic vs oxic suggest that the activities of aerobic organisms may be an important factor affecting chl a degradation examination of effects of meiofauna on chl a degradation under oxic conditions implies that microorganisms may play a stronger role in chl a degradation than meiofauna 0 125 mm the relative temperature independence of anoxic degradation and temperature dependence of oxic degradation suggest that anoxic degradation may be controlled largely by chemical factors while oxic degradation may be more strongly controlled by biophysical and biochemical processes

long term oscillations of the wind field in the tropical mesosphere and lower thermosphere from hawaii mf radar measurements 1 wind measurements in the mesosphere and lower thermosphere obtained with a medium frequency mf radar in hawaii 22 n 160 w spanning 16 years are employed to examine the intra annual and interannual variability of the mean and tidal motions at altitudes between 84 and 94 km intra annual periodicities range from 3 to 12 months with significant coherence in altitude and between the zonal and meridional components of each motion field interannual variations confirm the dominant periodicities identified previously at this site and elsewhere in particular the significant diurnal and less significant semidiurnal tidal responses at periods of 28 and 48 months amplitudes of these long period oscillations of the diurnal tide increase with altitude below 92 km and are larger than the amplitudes of the 12 month oscillations above 90 km phases of the 28 and 48 month oscillations show a downward progression with a slightly larger altitude variation in the meridional diurnal tide for the 28 month oscillation and a significantly larger altitude variation in the zonal diurnal tide for the 48 month oscillation the long and nearly continuous hawaii data set also enables characterization of the responses of the wind fields to the 11 year solar cycle both wind and tidal fields exhibit this periodicity but these responses display interesting and different relations to the phase of the solar cycle the 11 year oscillation of the meridional wind is nearly in phase with the solar cycle while the 11 year oscillation of the zonal wind is in approximate quadrature with the solar cycle the 11 year oscillations of the semidiurnal tidal amplitudes and the meridional diurnal amplitude are all in approximate quadrature with the solar cycle with the tidal amplitudes leading by 29 to 37 months while the 11 year oscillation of the zonal diurnal amplitude is somewhat nearer an antiphase than a quadrature relation to the solar cycle leading by 54 months

recent sediment accumulation organic carbon burial and transport in the northeastern north sea abstract organic carbon and nitrogen and sedimentation rate determinations were made of boxcores from the norwegian channel north sea the geographical distribution of recent sedimentation areas were defined by analysis of published data and 3 5 khz penetrating echo sounder data the annual dry bulk sediment accumulation in the northeastern north sea is established at 74 10 6 tons as the average organic carbon content for the norwegian channel and skagerrak kattegat sediments is 0 6 and 1 8 respectively the organic carbon accumulation rate in the northeastern north sea could be calculated the total organic carbon accumulation in the norwegian channel and skagerrak northern kattegat is 0 17 10 6 tons yr 1 and 0 83 10 6 tons yr 1 respectively less than 10 of this is accounted for by local primary production this means that more than 90 of the organic carbon buried in the sediments of the northeastern north sea must have been supplied from different sources terrigenous sources supply 20 of the organic carbon the remainder is marine organic matter produced elsewhere in the north sea or imported from the atlantic ocean norwegian sea and the baltic sea storm wave and current induced near bottom nepheloid layers are the main likely mechanism to transport fine grained sediments and associated organic matter from the north sea plateau into the kattegat skagerrak and norwegian channel

hypoxia in the lower st lawrence estuary how physics controls spatial patterns 1 a laterally integrated advection diffusion two dimensional model was implemented to simulate the spatial distribution of dissolved oxygen and the development of hypoxic conditions in the deep waters of the laurentian channel estuary and gulf of st lawrence eastern canada our simulations reveal that the horizontal distribution of dissolved oxygen in the bottom waters of the laurentian channel is determined by a combination of physical and biogeochemical processes whereas its vertical distribution is governed by the deep water circulation this result strongly suggests that the physics of the system and the source water properties are mostly responsible for the generation of a mid water column oxygen minimum and the oxygen distribution pattern in the deep water column

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 meteor radar and na doppler lidar measurements of winds in the mesopause region above maui hawaii 1 simultaneous sodium na doppler lidar and meteor radar measurements of horizontal winds in the mesopause region over maui hawaii were collected in july 2002 and october november 2003 the coincident measurements span 96 hours and altitudes between 80 and 100 km statistical comparisons are carried out on radar lidar winds with 1 hour and 4 km time and height resolution respectively the rms radar lidar wind component differences observed in this study are in the range 12 17 m s at altitudes below 96 km this is smaller than the rms differences observed in a previous na lidar and meteor radar comparison lidar wind component variances exceed radar variances and radar lidar covariance is nearly equal to the radar variance excess variance observed by the lidar is consistent with the fact that the meteor radar cannot resolve wind perturbations with horizontal scales smaller than 200 km whereas the lidar will respond to all horizontal scales close correspondence between the radar wind variance and radar lidar covariance suggests that measurement errors associated with the radar winds are swamped by geophysical variation furthermore the excess lidar variance exceeds lidar estimation errors by a large factor indicating that the lidar measurement errors are also insignificant relative to geophysical variations together these observations suggest that the observed radar lidar differences are a consequence of the different horizontal wave number filters associated with the techniques and hence the differences are determined by the strength and shape of the horizontal wave number spectrum for wind perturbations at scales smaller than 200 km

ams 14c dates for extinct lemurs from caves in the ankarana massif northern madagascar abstract an extensive late quaternary fauna including many extinct giant lemurs has been collected recently in a 110 km system of caves in the ankarana massif of northern madagascar ams 14c dates for the acid insoluble collagen gelatin fraction of bones of the giant lemur megaladapis 26 150 400 and 12 760 70 yr b p confirm its presence in the area during the late pleistocene and provide the first pleistocene 14 c ages from bones of the extinct megafauna of the island the first date from bones of the recently described extinct babakotia radofilai 4400 60 yr b p shows that it was present in northern madagascar in mid holocene times a comparatively recent age of 1020 50 yr b p for the extinct archaeolemur indicates survival of this genus for at least a millennium after the first direct evidence for humans in madagascar this suggests that the island s extinction window may have represented a longer time span than would have been expected under the blitzkrieg model of late quaternary extinctions a mid holocene age 4560 70 yr b p for a bone sample of the small extant lemur hapalemur simus indicates that the disappearance of this now restricted species from the ankarana occurred after this date new data from the ankarana and other sites on the island add to the consensus that major biotic changes occurred on madagascar in the late holocene

maui mesosphere and lower thermosphere maui malt observations of the evolution of kelvin helmholtz billows formed near 86 km altitude 1 small scale less than 15 km horizontal wavelength structures known as ripples have been seen in oh airglow images for nearly 30 years the structures have been attributed to either convective or dynamical instabilities the latter are mainly due to large wind shears while the former are produced by superadiabatic temperature gradients dynamical instabilities produce kelvin helmholtz kh billows which have been known for many years however models and laboratory experiments suggest that these billows often spawn a secondary instability that is convective in nature while laboratory investigations see evidence of such structures the evolution of these instabilities in the atmosphere has not been well documented the maui mesosphere and lower thermosphere maui malt observatory located on mt haleakala is instrumented with a na wind temperature lidar that can detect dynamic or convective instabilities with 1 km vertical resolution over the altitude region from about 85 to 100 km the observatory also includes a fast oh airglow camera sensitive to emissions coming from approximately 82 to 92 km altitude which obtains images every 3 s at sufficient resolution and signal to noise to see the ripples on 15 july 2002 ripples were observed moving at an angle to their phase fronts after a few minutes structures appeared to form approximately perpendicular to the main ripple phase fronts the lidar data showed that a region of dynamical instability existed from approximately 85 5 to 87 km and that the direction of the wind shear in this region was consistent with the phase fronts of the ripple features the motion of the ripples themselves was consistent with the wind velocity at 85 9 km thus in this case the observed ripple motion was the advection of kh billows by the wind the perpendicular structures were seen to be associated with the kh billows they formed at the time when the atmosphere briefly became convectively unstable within the region where the kh billows most likely formed because of this and because the ripples were oriented approximately perpendicular to and moved with the billows we speculate that they are the secondary instabilities predicted by models of kh evolution the primary and perpendicular features were seen to decay into unstructured regions suggestive of turbulence while the formation and decay time appear consistent with models the horizontal wavelength of the perpendicular structures seems to be larger than models predict for the secondary instability features

early diagnesis of carbohydrates in the marine environment ii composition and origin of carbohydrates in skagerrak sediments abstract the distribution and composition of carbohydrates were determined for the upper 15 cm of four cores from the southern slope of the skagerrak high concentrations were found in the upper bioturbated layers rapidly decreasing at sediment depths 3 cm total contents appear to be controlled by bioturbation application of various biomarker criteria suggests that carbohydrates originated from terrestrial macroalgal and planktonic sources input from these sources might be by episodic events rather than by continuous sedimentation as can be hypothesised from the irregular occurrence of marine and terrestrial signals

origin distribution and accumulation of organic carbon in the skagerrak abstract organic carbon contents have been determined in grain size fractions of sediments from the skagerrak southern slope and basin c org concentrations were generally inversely related to grain size the 62 63 m fraction in surface sediments from deeper waters had higher contents attributable to agglutination of fine material by tube forming benthic organisms especially in the clay and fine silt fractions c org increased with increasing fraction content presumably as a result of higher grazing pressure on fine material in coarse sediments a comparison of high resolution age 210 pb porosity and grain size composition profiles indicates that deviations in the 210 pb curves are due both to bioturbation and sedimentation events porosity profiles also show high regional variability on a small scale when primary production c org vertical fluxes and accumulation rates are compared an excess of organic carbon stored in skagerrak sediments becomes apparent potential sources for this carbon such as river input dumping or sea floor erosion are examined

satellite observations of thermospheric tides results from the wind imaging interferometer on uars thermospheric winds measured by the wind imaging interferometer windii on the upper atmosphere research satellite are analyzed for migrating solar tides the data cover a 2 year period commencing february 1992 and are obtained from the atomic oxygen o 1s 557 7 nm emission which provides observations of the 90 to 200 km altitude range during daytime and the 90 to 110 km range at night the subtropical lower thermosphere is dominated by the diurnal propagating tide which exhibits a vertical wavelength of approximately 22 km grows in amplitude up to 95 km and decays rapidly above where molecular diffusion greatly reduces the vertical shears although the phase remains fairly uniform throughout the year a pronounced semiannual oscillation is observed in the diurnal tide amplitude at both 20 n and 20 s the meridional and zonal wind components attain their maximum values at equinox of approximately 70 and 40 m s respectively while the solstitial minima are nearly a factor of 2 smaller at 35 n the diurnal tide semiannual amplitude oscillation is still present in the lower thermosphere but above 100 km it is replaced by an annual cycle with a maximum in july and august this contrasts with 35 s where the july august peak is absent and the semiannual oscillation extends to 110 km at midlatitudes the zonal and meridional winds are of similar magnitude and no significant hemispheric asymmetries in amplitudes are observed in the lower thermosphere the semidiurnal tide amplitude exhibits an annual oscillation with maximum values of 30 to 40 m s occurring in june july near 100 km at 35 n 35 s and the equator a bimodal structure in the seasonal variation of the semidiurnal phase is observed this feature is characterized by rapid equinoctial transitions and is particularly well defined at the equator examination of the equatorial middle thermosphere indicates that the semidiurnal tide attains its maximum amplitude at 140 km and exhibits a vertical wavelength of approximately 60 km these findings indicate the predominance of the antisymmetric 2 3 hough mode in the tropics

sediment oxygen consumption and benthic organic carbon mineralization on the continental shelves of the east china sea and the yellow sea abstract sediment oxygen consumption soc rates on the shelves of the east china sea ecs and the yellow sea ys were measured during five field studies in the period april 2010 to may 2011 using the batch intact core incubation technique the measured soc rates ranged from 1 73 to 17 56 mmol o2 m 2 d 1 which are comparable to values reported for other typical continental shelves worldwide for the shelves of both the ecs and the ys there was a remarkable spatial and temporal variation in soc rates soc was used as a proxy to assess the benthic organic carbon mineralization in the ecs and the ys and to prepare simple organic carbon budget for the ys it was found that on average approximately 90 of the organic carbon derived from primary productivity was decomposed in the water column and 8 was decomposed in the sediment resulting in

airglow imaging of gravity waves 2 critical layer filtering images of the variations of oh intensities have been recorded by a three station network of scanning radiometers in southwestern ontario during the period from may until september 1998 the ensemble of gravity waves seen in all three instruments is analyzed and observed to have a strong dependence in their propagation direction with the majority of waves seen at each of the three sites having a horizontal wave vector in the northeast direction in order to understand these results a model of the transmission of gravity waves through the atmosphere was employed the gravity waves observed by the oh scanning radiometers ohscrs are assumed to originate in the troposphere with an isotropic spectrum meaning that the average wave amplitudes are equal in all directions the gravity waves propagate upward where they will undergo a selection process owing to the effect of the background winds using the horizontal winds from the horizontal wind model hwm 93 the transmission of gravity waves from a tropospheric source is modeled and shown to be consistent with the observations the strong zonal winds account for the summer eastward and winter westward propagation but it is the tidal components of the meridional wind that account for the northward tendency of wave propagation and the corresponding relative absence of southward propagating waves in order to further validate the transmission model winter measurements from the ohscr data set are examined and shown to be consistent

accelerator radiocarbon dating at the molecular level molecular level 14c dating is the isolation of specific classes of molecules for their 14c dating by accelerator mass spectrometry ams complex matrices such as fossil bone are difficult to date due to their extreme chemical heterogeneity by isolating individual amino acids contaminants humates are removed and crystalline amino acids result bones with 0 1 0 2 n and collagenous compositions can be dated accurately because structural collagen is present contaminants are removable with xad resin bones with 0 1 n and non collagenous compositions yield dates hundreds to thousands of years too young because most of the preserved organic matter is exogenous accelerator 14c dates on collagenous and non collagenous bones are not comparable due to intrinsic dating inaccuracies ams 14c dating of amino acids demonstrated that 1 post 10 800 year ages for north american megafauna are due to sample contamination not holocene ages on extinct fauna 2 a clovis age 10 900 years was established for a human fossil from the anzick site montana 3 holocene ages cannot be established absolutely for many north american human fossils because the bones were non collagenous 4 accurate ages are attainable on vertebrate fossils as small as passerine birds from pacific island localities 5 well preserved bones are datable without their destruction by extracting protein with water at high temperatures and 6 stratigraphic anomalies to 45 000 years in european upper paleolithic rock shelters are recognizable by dating bone directly

quantification of the gravity wave forcing of the migrating diurnal tide in a gravity wave resolving general circulation model 1 the interaction of gravity waves gws and the migrating diurnal tide are studied in a gw resolving general circulation model gcm by calculating the tidal components of zonal wind accelerations and equivalent rayleigh friction due to tidal induced gw dissipation two 15 day periods for perpetual equinoctial and solstice simulations are analyzed which are performed with the japanese atmospheric general circulation model for upper atmosphere research jaguar high resolution gcm the model can directly simulate gws with horizontal wavelengths greater than about 190 km and thus reproduce the general features of the mean winds and temperatures from the surface to the mesosphere and lower thermosphere mlt the amplitudes of the migrating diurnal tide are successfully simulated during both seasons and the tidal winds affect the altitudes of gw dissipation in the low latitude mlt the tidal component of gw forcing has maximal values of about 15 m s 1 d 1 near the maximal vertical shears of the tidal winds and generally works to shorten the vertical wavelength of the migrating diurnal tide the phase relationship between the tidal winds and the tidal induced gw forcing is not exactly 90 out of phase causing amplification suppression of the tide the gw forcing amplifies the migrating diurnal tide during the equinox while during the solstice it suppresses the tidal winds in the upper mesosphere of both hemispheres this difference in behavior can be attributed to a seasonal variation of the mean zonal winds because combination of the mean and tidal winds affects the altitudes of gw dissipation

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

momentum budget of the migrating diurnal tide in the whole atmosphere community climate model at vernal equinox 1 the momentum budget of the migrating diurnal tide dw1 at the vernal equinox is studied using the whole atmosphere community climate model version 4 waccm4 classical tidal theory provides an appropriate first order prediction of the dw1 structure while gravity wave gw forcing and advection are the two most dominant terms in the momentum equation that account for the discrepancies between classical tidal theory and the calculation based on the full primitive equations it differs from the conclusion by mclandress 2002a that the parameterized gw effect is substantially weaker than advection terms based on the canadian middle atmosphere model cmam in the region where dw1 maintains a large amplitude gw forcing in the wave breaking region always damps dw1 and advances its phase the linear advection largely determined by the latitudinal shear of the zonal mean zonal wind makes a dominant contribution to the phase change of dw1 in the zonal wind compared to the gw forcing and nonlinear advection however nonlinear advection is more important than gw forcing and linear advection in modulating the amplitude and phase of dw1 in the meridional wind the dw1 amplitudes in temperature and winds are smaller than the timed observations suggesting that gw forcing is overestimated in the waccm4 and results in a large damping of dw1

momentum budget of the migrating diurnal tide in the mesosphere and lower thermosphere 1 the leading terms of the momentum budget of the migrating diurnal tide are diagnosed from temperatures and geopotential height provided by thermosphere ionosphere mesosphere energetics and dynamics timed sounding of the atmosphere using broadband emission radiometry saber and the horizontal wind vector provided by timed doppler interferometer tidi the wave drag upon the tide is inferred as a residual of the classical and linear advective terms in the zonal and meridional momentum equations between 85 and 100 km the migrating diurnal tide is generally far from the classical description of chapman and lindzen 1970 the leading nonclassical terms are the meridional advection of zonally averaged momentum and wave drag effects encapsulated in the momentum residuals the magnitudes of the momentum residuals range between 50 and 150 m s 1 d 1 for the zonal component and 100 250 m s 1 d 1 for the meridional component the zonal momentum residual is generally in quadrature with the zonal wind tide while the meridional momentum residual is in antiphase with the meridional wind above 95 km winds and temperatures exhibit maximum amplitudes during the vernal equinox season but only a minor reduction in wave damping is observed our results suggest that rayleigh damping is inadequate to describe the relationship between the tide and the forces acting upon it

observations of the phase locked 2 day wave over the australian sector using medium frequency radar and airglow data 1 the quasi 2 day wave with a nominal mean period just above 50 h is a significant feature of the 80 100 km altitude region in both hemispheres it becomes particularly prominent in the southern hemisphere summer at midlatitudes where a short time after summer solstice its amplitude rapidly increases and its mean period is found to be approximately 48 h producing an oscillation phase locked in local time this lasts for a few weeks presented here are observations of the meridional winds and airglow over two sites in australia for 4 years during the austral summers of 2003 2006 we show that during those times when the large amplitude phase locked 2 day wave pl tdw is present the diurnal tide greatly decreases this is consistent with the walterscheid and vincent 1996 model in which the pl tdw derives its energy from a parametric excitation by the diurnal tide these data also show that the diurnal tide is more suppressed and the pl tdw amplitude is larger in odd numbered years suggesting a biannual effect the airglow data indicated that for the pl tdw the winds and temperature are nearly out of phase when the pl tdw is present airglow amplitudes can become quite large a result dependent on the local time of the pl tdw maximum the airglow intensity response was in general much larger than what would be expected from the airglow temperature response suggesting that the pl tdw is causing a significant composition change possibly due to minor constituent transport

global distribution and interannual variations of mesospheric and lower thermospheric neutral wind diurnal tide 1 migrating tide 1 using the timed doppler interferometer tidi mesospheric and lower thermospheric neutral wind multiyear data set 2002 2007 and ncar time general circulation models gcm 1 2 annual run results 2002 2005 at the tidi sampling points we study the migrating diurnal tide s global distribution interannual and seasonal variations in connection with the mean zonal wind interannual variations a strong quasi biennial oscillation qbo effect on the diurnal tide was observed in the tidi data and reproduced to a lesser degree in the time gcm run the migrating diurnal tide amplitude is larger during the eastward phase of the stratospheric qbo and weaker during the westward phase westward mesospheric equatorial mean zonal winds appeared during the eastward phase of the stratospheric qbo in 2002 2004 and 2006 the strongest qbo effect on both the migrating diurnal tide and mean zonal winds was observed during the march equinox the stronger tides may be related to the weaker gravity wave filtering in the stratosphere during the eastward phase stratospheric qbo the tidi data also exhibit large interhemispheric asymmetry the westward mean zonal winds in the mesosphere appeared to be associated with the enhanced diurnal tide the time gcm 1 2 diurnal tide amplitudes are in general smaller than those observed by the tidi instrument limited vertical spatial resolution for the time cgm 1 2 is suggested as the cause future improvements are expected with a higher spatial resolution in the model