large amplitude mountain waves in the mesosphere observed on 21 june 2014 during deepwave 1 wave development scales momentum fluxes and environmental sensitivity

geochemical characteristics origins and model of lacustrine source rocks in the zhu 1 depression eastern pearl river mouth basin south china sea abstract variations in environmental and biological origins contributing to the heterogeneity of lacustrine source rocks can be illustrated in their diverse genetic facies the zhu 1 depression eastern pearl river mouth basin south china sea is characterized by two thick paleogene organic rich synrift units the wenchang and enping formations the integration of bulk geochemical and biomarker data with tectonic and sedimentary information provides the basis for a comprehensive assessment of the environmental and ecological changes through geologic time and their impact on the heterogeneity of these lacustrine source rocks both the wenchang and enping formations display wide variations in total organic carbon content and hydrogen index values as well as biomarker composition suggesting lateral and chronological changes in organic facies using gas chromatography mass spectrometry and hierarchical cluster analysis five genetic facies were identified within these two source horizons these facies represent different organic matter inputs and sedimentary and early diagenetic environments based on their distinctly different assemblages of 11 source dependent biomarker ratios four facies were distinguished in the wenchang formation and two facies were distinguished in the enping formation with one being common to both formations during the middle eocene the wenchang formation was deposited in a series of small deep lakes of laterally variable salinity acidity and biofacies during the deposition of the enping formation in the late eocene and early oligocene the previous lakes merged into fewer lakes with shallower depth and larger areal coverage with the biota becoming more uniform across the whole depression the coevolution of these lacustrine settings and their biota is closely associated with the development of the zhu 1 depression within which multiple separate sags produced by rapid mid eocene subsidence finally merged into a single depositional unit during slow subsidence in the late eocene and early oligocene accordingly an integrated model was established to provide an overview of the contrasting origins of lacustrine source rocks during the two paleogene epochs this model may have important implications for source rock prediction in the undrilled parts of the basins or for reference to source rock heterogeneity in other rift basins

secondary gravity wave generation over new zealand during the deepwave campaign multiple events during the deep propagating gravity wave experiment measurement program revealed mountain wave mw breaking at multiple altitudes over the southern island of new zealand these events were measured during several research flights from the national science foundation national center for atmospheric research gulfstream v aircraft utilizing a rayleigh lidar an na lidar and an advanced mesospheric temperature mapper simultaneously a flight on 29 june 2014 observed mws with horizontal wavelengths of 80 120 km breaking in the stratosphere from 10 to 50 km altitude a flight on 13 july 2014 observed a horizontal wavelength of 200 240 km mw extending from 20 to 90 km in altitude before breaking data from these flights show evidence for secondary gravity wave sgw generation near the breaking regions the horizontal wavelengths of these sgws are smaller than those of the breaking mws indicating a nonlinear generation mechanism these observations reveal some of the complexities associated with mw breaking and the implications this can have on momentum fluxes accompanying sgws over mw breaking regions

an improved boron isotope ph proxy calibration for the deep sea coral desmophyllum dianthus through sub sampling of fibrous aragonite abstract the isotopic composition of boron 11 b in marine carbonates is well established as a proxy for past ocean ph however its robust application to palaeo environments relies on the generation of species specific calibrations existing calibrations utilising the deep sea coral dsc desmophyllum dianthus highlight the potential application of this pervasive species to ph reconstructions of intermediate depth waters nevertheless considerable uncertainty remains regarding the estimation of seawater ph from these bulk skeletal 11 b measurements likely resulting from microstructural heterogeneities in 11 b of d dianthus to circumvent this problem thus improving the reliability of the d dianthus 11 b ph calibration we present a new 11 b calibration of micro sampled fibrous aragonite from this species modern coral specimens recovered from the atlantic pacific and southern oceans micro sampled using microdrilling micromilling and laser cutting extraction were analysed for trace element b ca mg ca sr ca and u ca and boron isotopic composition we find the best calibration against the 11 b of borate in local ambient seawater a function of ph and taken from hydrographic data sets ph range 7 57 to 8 05 utilises 11 b measurements of fibres with likely slow growth rates and minimal contamination from adjacent microstructures identified by low mg ca for each coral specimen this new calibration exhibits a stronger and better defined dependence on ambient seawater ph compared to bulk coral 11 b 11 b fibre 0 93 0 17 11 b borate 12 02 2 63 we suggest that the majority of the variability in measured 11 b between replicate bands of fibrous aragonite from a d dianthus specimen can be explained by small incorporation of non fibrous aragonite and surface impurities during microsampling and growth rate effects this study confirms the utility of d dianthus as an archive of precise palaeo ph 0 07 ph units provided that suitable sampling strategies are applied

significant southern ocean warming event in the late middle eocene a prominent middle eocene warming event is identified in southern ocean deep sea cores indicating that long term cooling through the middle and late eocene was not monotonic at sites on maud rise and the kerguelen plateau a distinct negative shift in 1 8 o values 1 0 is observed ca 41 5 ma this excursion is interpreted as primarily a temperature signal with a transient warming of 4 c over 600 k y affecting both surface and middle bathyal deep waters in the indian atlantic region of the southern ocean this isotopic event is designated as the middle eocene climatic optimum and is interpreted to represent a significant climatic reversal in the midst of middle to late eocene deep sea cooling the lack of a significant negative carbon isotope excursion as observed during the paleocene eocene thermal maximum and the gradual rate of high latitude warming suggest that this event was not triggered by methane hydrate dissociation rather a transient rise in pco 2 levels is suspected possibly as a result of metamorphic decarbonation in the himalayan orogen or increased ridge arc volcanism during the late middle eocene

a global view of stratospheric gravity wave hotspots located with atmospheric infrared sounder observations 1 the main aim of this study is to find and classify hotspots of stratospheric gravity waves on a global scale the analysis is based on a 9 year record 2003 to 2011 of radiance measurements by the atmospheric infrared sounder airs aboard nasa s aqua satellite we detect gravity waves based on 4 3 m brightness temperature variances our method focuses on peak events i e strong gravity wave events for which the local variance considerably exceeds background levels we estimate the occurrence frequencies of these peak events for different seasons and time of day and use the results to find local maxima or hotspots in addition we use airs radiances at 8 1 m to simultaneously detect convective events including deep convection in the tropics and mesoscale convective systems at middle latitudes we classify the gravity wave sources based on seasonal occurrence frequencies for convection but also by means of time series analyses and topographic data our study reproduces well known hotspots of gravity waves e g the andes and the antarctic peninsula however the high horizontal resolution of the airs observations also allows us to locate numerous mesoscale hotspots which are partly unknown or poorly studied so far most of these mesoscale hotspots are found near orographic features like mountain ranges coasts lakes deserts or isolated islands this study will help to select promising regions and seasons for future case studies of gravity waves

oligocene paleoceanographic changes based on an interbasinal comparison of cibicidoides spp δ18o records and a new compilation of data abstract oligocene paleoceanographic changes are useful for assessing future changes in the warming world because the levels of atmospheric pco2 in the oligocene were similar to those expected within the next century however the overall oligocene history is still unclear even though our understanding has been improved by previous studies in this paper we review the preexisting hypotheses for the eocene oligocene and oligocene miocene changes as well as the long term global changes based on newly compiled cibicidoides spp 18o 18ocib records we divide the oligocene paleoceanographic changes into five phases an abrupt increase in 18ocib values during the eocene oligocene transition eot phase 1 a gradual decrease in the early oligocene phase 2 a long term slow increase in the early to middle oligocene phase 3 a gradual decrease in the late oligocene phase 4 and an abrupt increase near the oligocene miocene transition omt phase 5 these recurring sequential changes in the global scale 18ocib profile following the eot are likely not directly connected to the strengthening and stratification of ocean currents during the oligocene as a result of the unidirectional strengthening of the antarctic circumpolar current acc and the northern component water ncw instead we suggest that the strengthened ocean currents contributed significantly to interbasinal differences in 18ocib values for a more robust explanation of oligocene long term 18ocib changes following the eot future studies will require high resolution and more reproducible records of changes in the volume of antarctic ice and atmospheric pco2 as well as information about the tectonic history

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

numerical modeling of a multiscale gravity wave event and its airglow signatures over mount cook new zealand during the deepwave campaign a 2d nonlinear compressible model is used to simulate a large amplitude multiscale mountain wave event over mt cook nz observed as part of the deepwave campaign and to investigate its observable signatures in the hydroxyl oh layer the campaign observed the presence of a x 200km mountain wave as part of the 22nd research flight with amplitudes of 20k in the upper stratosphere that decayed rapidly at airglow heights advanced mesospheric temperature mapper amtm showed the presence of small scale 25 28km waves within the warm phase of the large mountain wave the simulation results show rapid breaking above 70km altitude with the preferential formation of almost stationary vortical instabilities within the warm phase front of the mountain wave an oh airglow model is used to identify the presence of small scale wave like structures generated in situ by the breaking of the mountain wave that are consistent with those seen in the observations while it is easy to interpret these feature as waves in oh airglow data a considerable fraction of the features are in fact instabilities and vortex structures simulations suggest that a combination of a large westward perturbation velocity and shear in combination with strong perturbation temperature gradients cause both dynamic and convective instability conditions to be met particularly where the wave wind is maximized and the temperature gradient simultaneously minimized this leads to the inevitable breaking and subsequent generation of smaller scale waves and instabilities which appear most prominent within the warm phase front of the mountain wave

gravity wave breaking and vortex ring formation observed by pmc turbo polar mesospheric cloud pmc imaging and lidar profiling performed aboard the 5 9 day pmc turbo balloon flight from sweden to northern canada in july 2018 revealed a wide variety of gravity wave

palaeo digital elevation models for use as boundary conditions in coupled ocean atmosphere gcm experiments a maastrichtian late cretaceous example abstract palaeogeography specifically palaeotopography and palaeobathymetry provides an essential boundary condition for computer based atmosphere and ocean modelling it also provides the geographic context for understanding surface processes palaeodrainage palaeoweathering and biotic interactions palaeoecology palaeobiogeography with increased model resolution coupled ocean atmosphere general circulation models gcms and the addition of vegetation soil weathering ice and chemical modules there is now a need for more robust detailed palaeotopographies and palaeobathymetries that are fully integrated with the processes being modelled especially the hydrological system here we present a new geographic information system gis based hydrologically correct palaeo digital elevation model dem for the maastrichtian late cretaceous we describe the methods and concepts used to construct the map and draw attention to the limits imposed by scale and uncertainty and how these factors must be considered as part of the error analysis of derived model results the underlying palaeogeography is one of a series of 27 global maps that represent the stages of the cretaceous and sub epochs of the cenozoic each map is generated at a scale of 1 30 million in arcview gis and arcinfo using data from the lead author s own databases of lithologic tectonic and fossil information the lithologic databases of the paleogeographic atlas project the university of chicago a survey of published literature and dsdp odp data interpretations of elevation are derived following the methods outlined in ziegler et al ziegler a m rowley d b lottes a l sahagian d l hulver m l gierlowski t c 1985 paleogeographic interpretation with an example from the mid cretaceous annual review of earth and planetary sciences 13 385 425 an understanding of the tectonic regime and evolution of each feature and the age depth relationship for the ocean the global palaeo dem was derived using the elevation contours from the paleogeography and the suite of hydrological tools available in arcinfo grid the palaeo dem has been constrained by defining areas of internal palaeodrainage palaeoriver mouths and known palaeoriver courses the maastrichtian has been completed first to provide the boundary conditions for a series of coupled atmosphere ocean experiments when integrated with the results of the coupled ocean atmosphere model the result is a powerful tool for understanding surface processes and an important step towards the development of a continuous series representing a fully evolving palaeolandscape

past co2 changes and tropical sea surface temperatures the relationship between past co2 variations and tropical climate change on time scales of millions of years is reviewed explanations for cretaceous and early cenozoic climate change often involve higher atmospheric co2 levels climate models predict that such increases should have been associated with warmer tropical sea surface temperatures ssts however sparse mid cretaceous 18o based sst estimates from low latitude calcareous plankton are 1 0 1 5 heavier than predicted initial evaluations indicate that changes in salinity may not alleviate model data discrepancies for calcareous 18o and that interpretation of altered latitudinal 18o gradients in terms of increased poleward heat transport due to warm saline bottom water wsbw formation would require very large levels of wsbw production at least 60 sv calcareous 18o records may not always record true sst patterns as 18o analyses from phosphatic groups which are less sensitive to diagenesis indicate ssts 5 c higher this latter conclusion is supported by a number of other fossil groups which indicate temperatures warmer than those estimated from calcareous 18o in order to more rigorously test the paleo co2 hypothesis and indeed the models used to forecast future climates it is desirable to intensify investigations of past climate change in low latitudes in order to determine whether these preliminary conclusions stand the test of further scrutiny

high resolution 104 years deep sea foraminiferal stable isotope records of the eocene oligocene climate transition we have constructed high resolution 104 105 years benthic foraminiferal 13c and 18o records for the upper eocene through lower oligocene of two pelagic sequences deep sea drilling project dsdp site 522 in the angola basin south atlantic ocean and ocean drilling program odp site 744 in the southern indian ocean these records provide improved constraints on both the timing and magnitude of marine oxygen and carbon isotope events from 30 to 35 ma the oxygen isotope records indicate that the ubiquitous 18o increase oi 1 which marks the rapid expansion of continental ice sheets and a minimum of 3 to 4 c of cooling of bottom waters in the earliest oligocene 33 6 ma occurred in 350 kyr more than half the transition occurred over the final 40 50 kyr this period of lower temperatures and widespread continental glaciation persisted for roughly 400 kyr i e the duration of magnetochron c13n these records also indicate that this interval was characterized by at least two 100 kyr waxing and waning cycles oi 1a and oi 1b and possibly several higher frequency events the benthic foraminiferal 13c records show a positive 0 8 excursion that is nearly isochronous with the oi 1 oxygen isotope increase similar magnitude 13c increases at other sites indicate this was a global phenomenon suggestive of an unusually large perturbation to the carbon cycle this excursion was followed by smaller amplitude 13c oscillations with periods of roughly 400 kyr we suspect that the ubiquitous oi 1 13c excursion resulted from a brief but substantial increase in export production and carbon burial

late cretaceous early tertiary palaeoclimates of northern high latitudes a quantitative view analyses of plant community structure vegetational and leaf physiognomy and growth rings and vascular systems in wood provide qualitative and quantitative data that can be combined to define non marine palaeoclimatic parameters with better resolution than is available from other principally sedimentological methods application of these techniques to cenomanian through paleocene floras from high palaeolatitudes 75 85 n indicates a polar light regime similar to that of the present plant data suggests cenomanian sea level mean annual air temperatures mats of 10 c and mats of 13 c 5 c and 6 7 c in the coniacian maastrichtian and paleocene respectively evapotranspirational stresses at sea level were low and precipitation was in most part uniform throughout the growing season in the cenomanian with possible seasonal drying occurring by the maastrichtian maastrichtian winter freezing was likely but periglacial conditions did not exist at sea level permanent ice was likely above 1700 m at 75 n in the cenomanian and above 1000 m at 85 n in the maastrichtian these near polar data provide critical constraints on global models of late cretaceous to early tertiary climates

stable isotope stratigraphy and paleoclimatology of the paleogene bighorn basin wyoming usa abstract climatic warming from the late paleocene into the early eocene had profound effects on atmospheric and marine circulation marine thermal gradients and benthic biota in addition marine carbon isotope values decreased substantially in both surface and deep waters because carbon is rapidly exchanged between reservoirs at the earth s surface such as marine surface water the atmosphere land plants and materials that obtain carbon from plants e g soil minerals and herbivores carbon isotope fluctuations provide time lines linking the marine and continental records we analyzed the carbon isotope composition of paleosol carbonates and mammalian tooth enamel from stratigraphic sections in northwestern wyoming carbon isotope correlation demonstrates that a short interval of extreme high latitude warming coincided precisely with the first appearance of several important modern mammalian orders in addition oxygen isotope analyses of fossils and paleosol carbonates provide information about climatic conditions on land in the paleogene we reconstructed the oxygen isotope composition of local meteoric water using biogenic minerals paleocene eocene meteoric water was significantly 18 o depleted indicating substantial loss of water vapor during its transport to the region soil temperature was calculated as a proxy for mean annual temperature assuming oxygen isotope equilibrium between soil carbonate and meteoric water calculated temperatures were plausible 10 25 c but highly variable prohibiting high resolution analysis of local temperature variations in response to global climatic warming

impact of mountains on tropical circulation in two earth system models abstracttwo state of the art earth system models esms were used in an idealized experiment to explore the role of mountains in shaping earth s climate system similar to previous studies removing mountains from both esms results in the winds becoming more zonal and weaker indian and asian monsoon circulations however there are also broad changes to the walker circulation and el nino southern oscillation enso without orography convection moves across the entire equatorial indo pacific basin on interannual time scales enso has a stronger amplitude lower frequency and increased regularity a wider equatorial wind zone and changes to equatorial wind stress curl result in a colder cold tongue and a steeper equatorial thermocline across the pacific basin during la nina years anomalies associated with enso warm events are larger without mountains and have greater impact on the mean tropical climate than when mountains are present without mountains the centennial mean pacific walker circulation wea

momentum flux estimates accompanying multiscale gravity waves over mount cook new zealand on 13 july 2014 during the deepwave campaign observations performed with a rayleigh lidar and an advanced mesosphere temperature mapper aboard the national science foundation national center for atmospheric research gulfstream v research aircraft on 13 july 2014 during the deep propagating gravity wave experiment deepwave measurement program revealed a large amplitude multiscale gravity wave gw environment extending from 20 to 90 km on flight tracks over mount cook new zealand data from four successive flight tracks are employed here to assess the characteristics and variability of the larger and smaller scale gws including their spatial scales amplitudes phase speeds and momentum fluxes on each flight a large scale mountain wave mw having a horizontal wavelength 200 300 km was observed smaller scale gws over the island appeared to correlate within the warmer phase of this large scale mw this analysis reveals that momentum fluxes accompanying small scale mws and propagating gws significantly exceed those of the large scale mw and the mean values typical for these altitudes with maxima for the various small scale events in the range 20 105 m2 s 2

forcing of late cenozoic northern hemisphere climate by plateau uplift in southern asia and the american west geologic evidence indicates that net vertical uplift occurred on a large kilometer scale and at accelerating rates during the middle and late cenozoic in plateaus of southern asia and the american west based on this evidence general circulation model sensitivity tests were run to isolate the unique effects of plateau uplift on climate the experiments simulated significant climatic changes in many places some far from the uplifted regions the basic direction of most of these simulated responses to progressive uplift is borne out by changes found in the geologic record winter cooling of north america northern europe northern asia and the arctic ocean summer drying of the north american west coast the eurasian interior and the mediterranean winter drying of the north american northern plains and the interior of asia and changes over the north atlantic ocean conducive to increased formation of deep water the modeled changes result from increased orographic diversion of westerly winds from cyclonic and anticyclonic surface flow induced by summer heating and winter cooling of the uplifted plateaus and from the intensification of vertical circulation cells in the atmosphere caused by exchanges of mass between the summer heated and winter cooled plateaus and the mid latitude oceans disagreements between the geologic record and the model simulations in alaska and the southern rockies and plains may be related mainly to the lack of narrow mountain barriers in the model orography taken together the observed regional trends comprise much of the pattern of late cenozoic climatic deterioration in the northern hemisphere that culminated in the plio pleistocene ice ages the success of the uplift sensitivity experiment in simulating the correct pattern and sign of most of the observed regional climatic trends points to uplift as an important forcing function of late cenozoic climatic change in the northern hemisphere at time scales longer than orbital variations however the modest amplitude of the uplift induced cooling simulated at high latitudes indicates a probable need for additional climatic forcing

regional scale palaeoclimate modelling on soft proxy data basis an example from the upper miocene of the lower rhine embayment abstract a new method in palaeoclimatology initially proposed by mosbrugger and schilling 1992 which makes it possible to extract a maximum of information from the available proxy data is tested it possesses a capacity to produce a detailed palaeoclimate reconstruction which is consistent with both proxy data and the physics of atmospheric models since proxy data information is particularly poor on a global scale our method focuses on smaller scale regions of better proxy data coverage it consists of an iterative coupling of inverse mesoscale atmospheric modelling with proxy based palaeoclimate reconstruction using this method the palaeoclimate of the tortonian upper miocene of the lower rhine embayment northwest germany is reconstructed with a high spatial resolution the results include a physically consistent inter and extrapolation of proxy derived palaeoclimate data in space and onto variables not accessible from geological palaeontological proxies alone moreover the method delivers statistics of the large scale atmospheric flows as information on the coupling of the regional climate to global fields

miocene hominoid environments of europe and turkey abstract this study evaluates thirty six fossils hominoid site complexes from europe and turkey all belong to the middle miocene based on sedimentary faunal floral and foraminiferal evidence several patterns emerge climatic conditions in middle miocene europe and turkey were considerably warmer than during the holocene nevertheless a clear though vacillating downward temperature trend is documented from late early miocene times through the late miocene this was accompanied by increasing aridity and significant faunal floral changes water was present at nearly every site thirty two sites or 89 had some kind of water source directly at or near the site this may have been a river stream lake marsh marine coastal setting or some combination of these although all habitats were to some degree mosaics differences in species habitat associations are evident pliopithecines had strong positive associations with swamp forest and forest grassland mosaics as the dominant vegetation type by contrast dryopithecines had strong associations with fringing forest and open woodland or forest grassland mosaics while sivapithecines were strongly correlated with sites where the dominant vegetation pattern was either a forest grassland mosaic or parkland and grassland

paleobotanical evidence of eocene and oligocene paleoaltitudes in midlatitude western north america comparisons of the physiognomy of leaves from modern vegetation of known climates with that of eocene and oligocene fossil leaf assemblages from middle latitudes of western north america indicate paleoaltitudes comparable or higher than those at present using canonical correspondence analysis a multivariate statistical approach that includes nonlinear relationships between characters and environmental parameters we relate leaf physiognomy of fossil samples to modern vegetation of known environmental parameters including moist enthalpy of the atmosphere a thermodynamically conserved quantity of the atmosphere that varies with altitude by estimating enthalpy values for both lowland leaf assemblages and coeval interior leaf assemblages altitudes for the interior assemblages can be estimated to 890 m in northeastern washington and southern british columbia the high eocene altitudes indicate subsidence or collapse of an area undergoing crustal extension and may reflect an immediately preceding period of uplift that triggered the extension similarly other areas that have undergone cenozoic crustal extension appear to have been at least as high as they are at present three sites from the rocky mountains also indicate elevations at least as high as at present and therefore suggest subsidence either resulting from cooling of a hot upper mantle or erosion and isostatic compensation of surrounding terrain high altitudes during eocene and oligocene time in western north america appear to have been normal even in areas such as the green river basin and therefore cast doubt on the commonly inferred late cenozoic uplift of that region

the origin of stationary planetary waves in the upper mesosphere abstract satellite observations indicate that quasi stationary planetary waves often exist to at least 100 km in the winter mesosphere waves are also seen in the summer upper mesosphere a three dimensional numerical model was used to simulate these waves and to diagnose the physical processes involved the waves simulated in the model closely resemble observed waves several model runs that isolate specific processes are used to determine the relative importance of two forcing mechanisms in the model planetary waves that propagate from below are significantly damped at the altitude where gravity wave drag becomes large about 75 km in the winter midlatitudes or below if a reversal in the mean wind is encountered momentum forcing associated with breaking gravity waves that have been filtered by planetary scale wind variations below acts to generate planetary waves in the middle and upper mesosphere the amplitude from in situ forcing by gravity wave breaking exceeds the amplitude from the upward prop

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

cretaceous climate a comparison of atmospheric simulations with the geologic record abstract atmospheric simulations using realistic cretaceous geography 100 million years ago suggest that paleography is an important factor governing the nature of the circulation the simulated cretaceous atmospheric circulations are markedly different both from the present day atmospheric circulation and from the classical hypotheses of a weaker circulation and poleward displacement of circulation features e g the subtropical high therefore they pose specific questions which can be tested against the geologic record aspects of the cretaceous simulations are verified in comparisons with the geologic record the simulations serve to guide areas of future paleoclimatic research and to formulate better the nature of the problem of warm equable climates

seasonal cycle of orographic gravity wave occurrence above small islands in the southern hemisphere implications for effects on the general circulation 1 orographic gravity waves generated by flow over the topography of small islands in the southern oceans have been observed from orbit with the atmospheric infrared sounder on the aqua satellite we examine the occurrence frequencies of these waves in the stratosphere at 40km above 14 islands and examine geographical and seasonal changes our results show that these small island mountain waves occur commonly in the stratosphere in the may september season though not every day differing seasonal variations are evident at different islands and the seasonal variations are closely related to latitude and prevailing wind patterns we also examine interannual variability in 2years of data and the relationships between occurrence frequencies momentum fluxes and stratospheric and surface winds the results suggest that stratospheric winds have a first order limiting effect on the observations of these island mountain waves in atmospheric infrared sounder airs data surface wind direction and island orographic relief have an additional but secondary influence on the island mountain wave occurrence frequencies in airs data the implications are that these wave events are extremely common and that on many days when the waves are not observed in airs data they have likely dissipated and induced a drag force on the atmosphere below the 40km observation level observations of momentum flux during these wave events also permit a first estimate of their importance to the general circulation of the southern hemisphere

the late cenozoic uplift climate change paradox the geologic evidence for worldwide uplift of mountain ranges in the neogene is ambiguous estimates of paleoelevation vary according to whether they are based on the characteristics of fossil floras on the masses and grain sizes of eroded sediments or on calculations of increased thickness of the lithosphere as a result of faulting detrital erosion rates can be increased both by increased relief in the drainage basin and by a change to more seasonal rainfall patterns the geologic record provides no clear answer to the question whether uplift caused the climatic deterioration of the neogene or whether the changing climate affected the erosion system in such a way as to create an illusion of uplift we suggest that the spread of c4 plants in the late miocene may have altered both the erosion and climate systems these changes are responsible for the apparent contradictions between data supporting uplift and those supporting high elevations in the past

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

climate change on tectonic time scales abstract observational and modeling studies relevant to climate change on tectonic time scales are reviewed probably the most significant climate result from this time scale involves inferences about nearly ice free conditions for some intervals of earth history some additional results suggest relatively rapid transitions between climate states modeling studies indicate that although tectonic changes significantly modify the atmosphere and ocean circulation in most cases such modifications do not appear to be sufficient to explain ice free climates increased atmospheric co2 levels 5 10 presentvalues may be needed to completely reconcile models and data although the co2 paradigm has received widespread attention in the last few years the results summarized herein indicate that co2 is only one of several important factors influencing climate i believe the time is appropriate for contemplating climate change on tectonic time scales in terms of a post co2 synthesis in which direct tectonic factors are approximately equal in importance to co2 fluctuations in the last few years modeling studies have progressed from a state of virtually no work on the topic to one where the models are in some respect ahead of the observations in the sense that data have not been compiled to test even some of the most basic model predictions in particular information is needed on past atmospheric co2 levels tropical sea surface temperatures seasonality of continental interiors and locations and production rates of deep waters initial steps are being taken to integrate observational and modeling activities on tectonic time scales and some of these shortcomings may be rectified over the next few years

alleviation of a systematic westerly bias in general circulation and numerical weather prediction models through an orographic gravity wave drag parametrization systematic westerly biases in the northern hemisphere wintertime flow of the meteorological office 15 layer operational model and 11 layer general circulation model are described evidence that the failure to parametrize subgrid scale orographic gravity wave drag may account for such biases is presented this evidence is taken from aircraft studies surface pressure drag measurements and studies of the zonally averaged momentum budget a parametrization scheme is described in which the surface stress is proportional to the near surface wind speed and static stability and to the variance of subgrid scale orography the stress is absorbed in the vertical by considering the influence of such gravity wave activity on static stability and vertical wind shear a richardson number dependent wave breaking formulation is devised and the vertical stress profile determined by a saturation hypothesis whereby the breaking waves are maintained at marginal stability it is shown that wave breaking preferentially occurs in the boundary layer and in the lower stratosphere results from a simple zonally symmetric model show how the adjustment to thermal wind balance with a wave drag in the stratosphere warms polar regions by adiabatic descent and decelerates the mean westerlies in the troposphere the influence of the parametrization scheme on integrations of the 11 layer model is described and found to be generally beneficial in a discussion of the reasons why this problem has only recently emerged it is suggested that the satisfactory northern hemisphere winter circulations of previous coarser general circulation models were due to a compensation implied by underestimating both the surface drag and the horizontal flux of momentum by explicitly resolved large scale eddies

analysis of vesicular basalts and lava emplacement processes for application as a paleobarometer paleoaltimeter abstract we have developed a method for determining paleoelevations of highland areas on the basis of the vesicularity of lava flows vesicular lavas preserve a record of paleopressure at the time and place of emplacement because the difference in internal pressure in bubbles at the base and top of a lava flow depends on atmospheric pressure and lava flow thickness at the top of the flow the pressure is simply atmospheric pressure while at the base there is an additional contribution of hydrostatic lava overburden thus the modal size of the vesicle bubble population is larger at the top than at the bottom this leads directly to paleoatmospheric pressure because the thickness of the flow can easily be measured in the field and the vesicle sizes can now be accurately measured in the lab because our recently developed technique measures paleoatmospheric pressure it is not subject to uncertainties stemming from the use of climate sensitive proxies although like all measurements it has its own sou

the importance of spatial variability in the generation of secondary gravity waves from local body forces 1 we hypothesized earlier that the zonal mean body force required to close the mesospheric jets is sporadic in time and is composed of a large number of spatially and temporally localized body forces to explore the effects of such localization we randomly generate a series of localized 3d body forces in the mesosphere which create a mean acceleration of 100 m s 1 day 1 over this forcing volume secondary waves are also generated and because they have large vertical scales phase speeds and vertical group velocities they may induce important variabilities in the lower thermosphere where they dissipate we find that the secondary waves from spatially smoothed body forces have much smaller momentum fluxes frequencies and vertical group velocities thus global models having coarse resolution may be missing a significant source of sporadic wave drag and its effect throughout the middle atmosphere and lower thermosphere

too low δ18o of paleo meteoric low latitude water do paleo tropical cyclones explain it abstract isotopic analysis of rock samples showed anomalously 18 o depleted reconstructed isotopic composition of paleo meteoric water over southern israel between the late cretaceous and the early miocene with 18 o w as low as 14 smow this range is significantly lighter than the expected values for rain at the relevant paleo latitudes 8 n to 25 n it is similar or lighter than areas with meteoric water at the present climate in which rainfall contribution from tropical cyclone tc is significant rainfall from tcs is 18 o depleted because of the recirculation of the vapor into repeated precipitation or distillation cycles a paleo geographic reconstruction of the region shows that throughout the period there was a warm ocean to the east and southeast of the relevant area thus tcs formed over the ocean and made landfall on the coastline at a distance of 300 to 400 km to the east the reconstructed composition of the rainwater implies dominance of tcs at these times furthermore the combination of warmer seas and lighter rainwater than at present suggests that the tcs were more dominant than in the most tc prone coastal areas at the present climate the results of the present study suggest that climate during the relevant time periods was very different from the present with tc activity similar or exceeding the most tc prone locations in the world at the present climate this might also hint that warmer sea waters in the geological past were conducive to greater tc activity than in the present climate answering this question requires additional research

what is the source of the stratospheric gravity wave belt in austral winter abstractduring austral winter and away from orographic maxima or hot spots stratospheric gravity waves in both satellite observations and interim european centre for medium range weather forecasts ecmwf re analysis era interim data reveal enhanced amplitudes in a broad midlatitude belt extending across the southern ocean from east of the andes to south of new zealand the peak latitude of this feature slowly migrates poleward from 50 to 60 s wave amplitudes are much weaker across the midlatitude pacific ocean these features of the wave field are in striking agreement with diagnostics of baroclinic growth rates in the troposphere associated with midlatitude winter storm tracks and the climatology of the midlatitude jet this correlation suggests that these features of the stratospheric gravity wave field are controlled by geographical variations of tropospheric nonorographic gravity wave sources in winter storm tracks spontaneous adjustment emission from the midlatitude winter jet frontogenesi

planktonic and benthic foraminiferal extinction events during the last 100 m y abstract five major planktonic and benthic foraminiferal extinction events occurred during the past 100 m y at the cenomanian turonian c t boundary at the cretaceous tertiary k t boundary in the latest paleocene in the late eocene and in the early middle miocene to clarify the character of the five events i estimated 1 paleo waterdepths and paleoenvironments where foraminifera were affected 2 the duration of each extinction event and 3 evaluated possible causes for each extinction event on the basis of recent literature these extinction events can be classified into three fundamentally different types 1 the mass extinction event at the k t boundary was abrupt and concentrated among surface dwelling species 2 extinctions at the c t boundary and during the latest paleocene were abrupt and mainly affected intermediate and deep water taxa over short periods 3 the late eocene and early middle miocene events affected surface and deep water species and involved stepwise or gradual extinctions over a long period 4 m y i attributed the extinction events to 1 a bolide impact for the k t event 2 a decrease in dissolved oxygen in intermediate and deep waters due to climatic warming for the c t and latest paleocene events and 3 long term global cooling for the late eocene and early middle miocene events the following relationships exist between the causes and types of extinction events 1 large extraterrestrial impacts strongly affected surface dwelling organisms in short term extinction events 2 intermediate and deep water low oxygen conditions induced by climatic warming have severely affected intermediate and deep water organisms over medium and short terms

large amplitude mountain waves in the mesosphere accompanying weak cross mountain flow during deepwave research flight rf22 mountain wave mw propagation and dynamics extending into the upper mesosphere accompanying weak forcing are examined using in situ and remote sensing measurements aboard the national science foundation national center for atmospheric research gulfstream v gv research aircraft and the german aerospace center falcon the measurements were obtained during falcon flights ff9 and ff10 and gv research flight rf22 of the deep propagating gravity wave experiment deepwave performed over mount cook new zealand on 12 and 13 july 2014 in situ measurements revealed both trapped lee waves having zonal wavelengths of x 12 km and less and larger scale vertically propagating mws primarily at x 20 60 km and 100 300 km extending from west to 400 km east of mount cook gv rayleigh lidar measurements from 25 to 60 km altitudes showed that the weak forcing and zonal winds that increased from 12 m s at 12 km to 40 and 130 m s at 30 and 55 km respectively enabled largely linear mw propagation and strong amplitude growth with altitude into the mesosphere

reconstruction of the late miocene climate of spain using rodent palaeocommunity successions an application of end member modelling abstract end member modelling is applied to a data set of relative abundances of 67 upper miocene rodent associations 11 6 ma from spain france austria and greece the analysis results in the robust estimation of relative levels of four climatic parameters humidity temperature seasonality type and predictability in the preparatory stage species are aggregated into nine groups on the basis of ecological criteria humidity preferences and adaptations are based on actualistic and functional morphological interpretations of dentition and locomotion temperature preferences are inferred from palaeobiogeographic distributions levels of adaptation to seasonality type wet dry or cool warm seasonality are assigned on the basis of diversities in present day climate vegetation zones and the ability of extant relatives to hibernate demographic data are used to formulate adaptations to climatic un predictability in the modelling stage the compositions are unmixed into the contributions of four end members these four extreme theoretical rodent compositions are interpreted in climatic terms and their contributions to the samples are used for the estimation of climatic parameters the subset of 44 well dated rodent compositions from the calatayud daroca and teruel basins ne spain is used to construct detailed climatic curves for the late miocene while the geographical dimension in the data set is used to calculate inter basinal differences the model results for spain indicate more humid and cooler conditions between 10 5 and 8 5 ma around 7 and around 6 ma and more arid and warmer conditions before 10 5 between 8 6 and 7 5 ma and around 6 5 ma superimposed on this pattern is a shift from a more predictable cool warm seasonal climate towards a more unpredictable wet dry seasonal climate between 9 4 and 8 2 ma inter basinal comparisons per time slice show that the climate in southern europe was dryer warmer more wet dry seasonal and more unpredictable than in central europe and that the climatic and vegetational boundaries between the two regions were sharp the occurrences of more humid and cooler episodes in spain during the late miocene might be explained by southward migrations of the boundary between a temperate and subtropical dry climatic belt and their associated vegetation types various positive correlations are observed between the rodent based climatic curves for spain and other palaeoclimatic records from the mediterranean and ne atlantic region clay minerals marine fauna stable isotopes the two cooling maxima at 9 4 and 7 ma closely correspond to clusters of marine events which are generally considered to reflect maxima of global ice volume

evidence of mesospheric gravity waves generated by orographic forcing in the troposphere 1 we report on the first imaging observations of stationary mesospheric gravity waves in the three nightglow emissions of oh 695 1050 nm na 589 3 nm and o 1s 557 7 nm the waves were observed in all sky images at the el leoncito observatory elo argentina 31 8 s 69 3 w during the period of 1 8 july 2008 over the course of each night the band like wave features exhibited a zero or near zero observed horizontal phase speed and had lifetimes of several hours these factors coupled with the winds measured locally and the orientation of the waves to the andes mountain range located nearby suggested that the waves were mountain waves generated by 70 ms 1 eastward winds flowing over the andes

control of north atlantic deep water circulation by the greenland scotland ridge coherent bathymetric features along the reykjanes ridge indicate that there were significant changes in the flux of buoyant material within the icelandic hot spot during the neogene the radial extent of the topographic swell associated with this hot spot is of the order of 1000 to 2000 km and therefore these changes affected the greenland scotland ridge gsr at present sill depths along the gsr are generally less than 500 m with the deepest passage being less than 1000 m making the overflow water sensitive to even small changes in the ridge depths reconstructions of neogene mantle plume activity correlate with the deepwater circulation patterns in the north atlantic times of high mantle plume activity caused northern component water ncw production to cease ncw fluxes resumed once this phase of high mantle plume activity slowed the long term climate change during the neogene must be controlled by factors other than ncw production however climatic optima during the late early miocene and early pliocene appear to have been augmented by high ncw fluxes while subsequent middle miocene and middle pliocene coolings correlate with uplifts on the gsr and reduced ncw flux we suggest that reductions in ncw may have contributed to both of these cooling events

seismic stratigraphy of the west shetland drift implications for late neogene paleocirculation in the faeroe shetland gateway 1 the morphology and anatomy of a late neogene contourite drift on the british margin of the faeroe shetland channel is investigated in unprecedented detail using industrial two dimensional and three dimensional seismic data the west shetland drift is constructed by a succession of mounded asymmetric strata that in the basin and on the midslope has accumulated on a regional unconformity of early pliocene age the midslope component of the drift system forms a 400 m thick convex elongate sedimentary body that can be traced from the outlet of the norwegian channel and 250 km southwest along the shetland margin contourite drifts occupying the basin are evident as a succession of sheeted mounded and wavy migrating units intercalated by three mega debrite sequences the seismic architecture of the west shetland drift and tentative age estimates of its bounding surfaces suggests that it formed rapidly 5 10 cm kyr 1 by alongslope transport of hemipelagic sediments derived from the nw european shelf the change from erosion nondeposition to enhanced contourite drift accumulation during the early pliocene suggests that a moderate thermohaline current regime prevailed in the faeroe shetland channel prior to the main phase of northern hemisphere glaciation at 3 0 2 5 ma a reduction in meridional heat transport associated with a decrease in the flux of north atlantic deep waters may have been an important factor for the growth of northern hemisphere ice sheets

gravity waves and ionospheric irregularities over tropical convection zones observed by gps met radio occultation gps met observations of the tropical atmo sphere of the southern hemisphere 5 st o 25 s during february 1997 are analysed when a high amount of con vective tropospheric water vapor is at these latitudes en hanced gravity wave activity of the lower stratosphere at h 22 28 km is associated to areas of increased tropospheric water vapor pressure at h 4 6 km regarded as a measure of tropical convection sporadic e and other ionospheric irregularities vertical scales less than 7 km of the meso sphere lower thermosphere are observed to be highly cor related to gravity wave activity in the lower stratosphere and to tropical convection zones we find 4 areas of en hanced ionospheric irregularities and stratospheric wave ac tivity over pacific around 140 w brazil 50 w africa 40 e and indonesia australia 110 e

sensitivity of climate to late cenozoic uplift in southern asia and the american west numerical experiments experiments with general circulation models with no mountains half mountains and full modern mountains show the sensitivity of atmospheric circulation patterns to progressive amounts of uplift the experiments were motivated by geologic evidence for large kilometer scale uplift in the late cenozoic in southern asia and the american west particularly within the last 10 m y in january the amplitude of the mid latitude upper tropospheric planetary waves increased with uplift and the low level winds were progressively blocked or diverted around the topographic features in july the progressive uplift caused monsoonlike circulations to develop in the vicinity of the colorado and tibetan plateaus atmospheric heating rates midtroposphere vertical motion and upper tropospheric planetary wave amplitudes varied approximately linearly with progressive uplift these results suggest that geologically recent kilometer scale uplift may have had climatic consequences comparable in magnitude and pattern to those of earlier stages of uplift comparison of the simulated climatic effects of uplift with the geologic evidence for late cenozoic climatic change especially for the last 10 m y is given in accompanying papers

evolution of early cenozoic marine temperatures the equator to high southern latitude sea surface and vertical temperature gradients are reconstructed from oxygen isotope values of planktonic and benthic foraminifers for the following five time intervals late paleocene early eocene early middle eocene late eocene and early oligocene paleotemperatures are calculated using standard oxygen isotope temperature equations with adjustments to account for 1 variations in sea water 18o related to changes in global ice volume over time and 2 latitudinal gradients in surface water 18o these reconstructions indicate that sea surface temperatures sst of the southern oceans in the early eocene were as high as 15 c whereas temperatures during the late paleocene and early middle eocene reached maximum levels of 10 12 c by the late eocene and early oligocene high latitude sst had declined to 6 and 4 c respectively for most of the early paleogene low latitude sub tropical temperatures remained constant and well within the range of holocene temperatures 24 ndash 25 c but by the late eocene and early oligocene declined to values in the range of 18 to 22 c the late paleogene apparent decline in tropical temperatures however might be artificial because of dissolution of near surface foraminifera tests which biased sediment assemblages toward deeper dwelling foraminifera moreover according to recent plate reconstructions it appears that the majority of sites upon which the late eocene and early oligocene tropical temperatures were previously established were located either in or near regions likely to have been influenced by upwelling global deepwater temperature on average paralleled southern ocean sst for most of the paleogene we speculate based on the overall timing and character of marine sea surface temperature variation during the paleogene that some combination of both higher levels of greenhouse gases and increased heat transport was responsible for the exceptional high latitude warmth of the early eocene

mountain waves entering the stratosphere using the national science foundation nsf ncar gulfstream v and the nsf wyoming king air research aircraft during the terrain induced rotor experiment t rex in march april 2006 six cases of sierra nevada mountain waves were surveyed with 126 cross mountain legs the goal was to identify the influence of the tropopause on waves entering the stratosphere during each flight leg part of the variation in observed parameters was due to parameter layering heaving up and down in the waves diagnosis of the combined wave layering signal was aided with innovative use of new gps altitude measurements the ozone and water vapor layering correlated with layered bernoulli function and cross flow speed gps corrected static pressure was used to compute the vertical energy flux confirming for the first time

a warm equable cretaceous the nature of the problem abstract the nature of the problem of warm equable paleoclimates is defined by investigating the mid cretaceous period the problem consists of three components 1 defining precisely the climatic state during any specified interval of geologic time 2 specifying the external climatic forcing factors which may have been important and 3 understanding the climatic response to any specific modifying influence these components are characterized by limitations of critical importance in understanding paleoclimates the nature of the problem of a warm cretaceous is defined both qualitatively and quantitatively within these limits

asthenospheric ice load effects in a global dynamical system model of the pleistocene climate in a previous dynamical model the late cenozoic climate variations were simulated taking into account free and forced variations of atmospheric carbon dioxide acting in concert with changes in global ice mass and the deep ocean thermal state all under the influence of the known earth orbital radiative changes this model is now extended by adding another relevant variable bedrock asthenosphere depression including its associated ice calving effects within the context of this extended model we 1 demonstrate the main results of previous bedrock ice sheet models in what we believe is the simplest possible manner 2 show how these previous models can exhibit the mid pleistocene transition with the inclusion of co2 effects 3 discuss the limitations of these previous bedrock models and 4 illustrate the possibility of removing some of these limitations and accounting for further aspects of the paleoclimate record by using the full dynamical system that includes forced and free effects of co2 as well as effects of bedrock depression and milankovitch forcing as one example of a new possibility with bedrock effects included in the full system we can obtain a solution characterized by irregularly spaced intermittent episodes in which the behavior is dominated either by near 40 kyr period oscillations or by near 100 kyr periods such as prevailed over the pleistocene

possible role of oceanic heat transport in early eocene climate increased oceanic heat transport has often been cited as a means of maintaining warm high latitude surface temperatures in many intervals of the geologic past including the early eocene although the excess amount of oceanic heat transport required by warm high latitude sea surface temperatures can be calculated empirically determining how additional oceanic heat transport would take place has yet to be accomplished that the mechanisms of enhanced poleward oceanic heat transport remain undefined in paleoclimate reconstructions is an important point that is often overlooked using early eocene climate as an example we consider various ways to produce enhanced poleward heat transport and latitudinal energy redistribution of the sign and magnitude required by interpreted early eocene conditions our interpolation of early eocene paleotemperature data indicate that an approximately 30 increase in poleward heat transport would be required to maintain eocene high latitude temperatures this increased heat transport appears difficult to accomplish by any means of ocean circulation if we use present ocean circulation characteristics to evaluate early eocene rates either oceanic processes were very different from those of the present to produce the early eocene climate conditions or oceanic heat transport was not the primary cause of that climate we believe that atmospheric processes with contributions from other factors such as clouds were the most likely primary cause of early eocene climate

a search for mountain waves in mls stratospheric limb radiances from the winter northern hemisphere data analysis and global mountain wave modeling 1 despite evidence from ground based data that flow over mountains is a dominant source of gravity waves gws for the northern hemisphere winter middle atmosphere gw related signals in global limb radiances from the microwave limb sounder mls on the upper atmosphere research satellite uars have shown little direct evidence of mountain waves we address this issue by combining a renewed analysis of mls limb track and limb scan radiances with global mountain wave modeling using the naval research laboratory mountain wave forecast model mwfm mls radiance variances show characteristics consistent with mountain waves such as enhanced variance over specific mountain ranges and annual variations that peak strongly in winter however direct comparisons of mls variance maps with mwfm simulated mountain wave climatologies reveal limited agreement we further develop a detailed mls gw visibility function that accurately specifies the three dimensional in orbit sensitivity of the mls limb track radiance measurement to a spectrum of gws with different wavelengths and horizontal propagation directions on postprocessing mwfm generated mountain wave fields through these mls visibility filters we generate mwfm variance maps that agree substantially better with mls radiance variances this combined data analysis and mls filtered mwfm modeling leads us to conclude that many mls variance enhancements can be associated with mountain waves forced by flow over specific mountainous terrain these include mountain ranges in europe e g scandinavia alps scotland ural putoran altai hangay and sayan mountains yablonovyy stanovoy khingan verkhoyansk and central ranges north america e g brooks range mackenzie mountains colorado rockies southeastern greenland and iceland our results show that given careful consideration of the in orbit sensitivity of the instrument to gws middle atmospheric limb radiances measured from uars mls as well as from the new mls instrument on the earth observing system eos satellite can provide important global information on mountain waves in the extratropical northern hemisphere stratosphere and mesosphere

explanations of the tertiary global cooling trend abstract a series of general circulation model experiments are performed to examine the role of paleogeography as an explanation of the tertiary global cooling trend systematic long term variations in topography and land sea distribution are potential causes of long term climate change however climate model sensitivity experiments indicate a geographically related cooling during the last 20 million years but not a long term cenozoic trend coarse resolution changes in geography throughout the tertiary may not be the explanation of the tertiary global cooling trend either a series of events some geographically related or another forcing factor most probably atmospheric co2 concentration are offered as alternative explanations of the tertiary global cooling trend

dynamics of orographic gravity waves observed in the mesosphere over the auckland islands during the deep propagating gravity wave experiment deepwave abstracton 14 july 2014 during the deep propagating gravity wave experiment deepwave aircraft remote sensing instruments detected large amplitude gravity wave oscillations within mesospheric airglow and sodium layers at altitudes z 78 83 km downstream of the auckland islands located 1000 km south of christchurch new zealand a high altitude reanalysis and a three dimensional fourier gravity wave model are used to investigate the dynamics of this event at 0700 utc when the first observations were made surface flow across the islands terrain generated linear three dimensional wave fields that propagated rapidly to z 78 km where intense breaking occurred in a narrow layer beneath a zero wind region at z 83 km in the following hours the altitude of weak winds descended under the influence of a large amplitude migrating semidiurnal tide leading to intense breaking of these wave fields in subsequent observations starting at 1000 utc the linear fourier model constrained by upstream reanalysis

late cenozoic environmental changes and uplift on the northern side of the central himalaya a reappraisal from field data abstract the extreme view that uplift of the tibetan plateau and the adjacent himalayan range occurred mainly during the quaternary cannot be further sustained as discussed in the light of available field data palaeobiogeography sedimentary environments and tectonic evidence comparison with other independent sources such as the loess records of central china and data on the post orogenic sedimentation and geochronology of the himalayan and south asian oceanic fans shows that the tibetan plateau certainly reached an elevation close to its present one before the climatic changes of the quaternary as such this elevated himalaya tibet ensemble was probably one of the major causes of the late tertiary general cooling of the northern hemisphere as suggested by global modelling of climate palaeoenvironmental changes observed during the quaternary were certainly governed by orbital parameters yet they were also regionally influenced by both the uplift of the greater himalaya with respect to tibet and by the disruption of the northern himalaya and south tibet into horsts and grabens uncertainty still surrounds the periods during which critical elevations were achieved to induce both the monsoon circulation and e w extension

observation and analysis of a large amplitude mountain wave event over the antarctic peninsula 1 we use measurements from the atmospheric infrared sounder airs on the aqua satellite to observe the 3 dimensional structure of a gravity wave event over the antarctic peninsula and determine the horizontal and vertical wavelengths propagation direction and temperature amplitude and from these we estimate wave momentum flux using theoretical knowledge of the weighting functions and radiative transfer for airs radiance measurements at temperature sensitive channels in the infrared we derive a method of estimating wave temperature amplitude directly from the radiance measurements comparison of the radiance based temperature amplitudes to the temperature amplitude in airs retrieved temperature fields shows close agreement because the radiances have 3 times better horizontal resolution than the retrievals our analysis suggests we can routinely observe important geophysical properties of waves with horizontal wavelengths as short as 80 km using airs radiances we further analyze a nearly identical wave event appearing in the european centre for medium range forecasts ecmwf temperature and wind fields from both assimilation and forecast data analysis of the ecmwf data and nearby radiosonde wind profiles allows the interpretation as a mountain wave event forced by flow over the topography of the antarctic peninsula

three dimensional characteristics of stratospheric mountain waves during t rex abstract measurements from the national science foundation national center for atmospheric research nsf ncar gulfstream v g v obtained during the recent terrain induced rotor experiment t rex indicate marked differences in the character of the wave response between repeated flight tracks across the sierra nevada which were separated by a distance of approximately 50 km observations from several of the g v research flights indicate that the vertical velocities in the primary wave exhibited variations up to a factor of 2 between the southern and northern portions of the racetrack flight segments in the lower stratosphere with the largest amplitude waves most often occurring over the southern flight leg which has a terrain maximum that is 800 m lower than the northern leg multiple racetracks at 11 7 and 13 1 km altitudes indicate that these differences were repeatable which is suggestive that the deviations were likely due to vertically propagating mountain waves that varied systematically in am

the influence of true polar wander on glacial inception in north america abstract the impact that long term changes in earth s rotation axis relative to the surface geography or true polar wander tpw and continental drift have had in driving cooling of high latitude north america since the eocene is explored recent reanalyses of paleomagnetic pole positions suggest a secular drift in earth s rotation axis of 8 over the last 40 myr in a direction that has brought north america to increasingly higher latitudes using modern temperature data in tandem with a simple model a reduction in the annual sum of positive degree days pdds driven by this polar and plate motion over the last 20 myr is quantified at sites in baffin island the tpw and continental drift driven decrease in insolation forcing over the last 20 myr rivals changes in insolation forcing caused by variations in earth s obliquity and precession using conservative pdd scaling factors and an annual snowfall equal to modern station observations the snowiest location in baffin island 20 myr ago had a mass balance deficit of 0 75 2 m yr 1 water equivalent thickness relative to its projected mass balance at 2 7 ma this mass balance deficit would have continued to increase as one goes back in time until 40 myr ago based on adopted paleopole locations tpw and continental drift that moved arctic north america poleward would have strongly promoted glacial inception in baffin island at 3 ma a location where the proto laurentide ice sheet is thought to have originated

a comparison of eocene climate model results to quantified paleoclimatic interpretations abstract the integration of climate model results and geologic information offers considerable potential for deriving greater insight into the geologic record in this study climate model results and quantified climatic interpretations derived from proxy data are compared to assess model capabilities and to examine proxy data interpretations atmospheric general circulation model experiments were used to produce a range of possible representative eocene climate states based on current knowledge of the eocene record the climate model experiments incorporate two idealized endmembers of eocene ocean surface temperature distributions characterized by very different latitudinal gradients model results are compared to quantified interpretations of the climate of early eocene north america in an attempt to identify one of the sea surface temperature distributions as more likely to have existed during the eocene the comparisons do not produce a conclusive match between inferred paleoclimatic information and any single case of model results but some interesting insights become apparent model predictions of mean annual temperature and mean annual precipitation compare favorably to interpretations from geologic evidence but there are large differences between model results and interpreted paleoclimatic parameters of minimum surface temperature and mean annual temperature range several possible causes for these differences are discussed

late miocene climate in the circum alpine realm a quantitative analysis of terrestrial palaeofloras abstract selected mega and microfloras from central and southern europe have been analysed for the time interval tortonian pannonian mn 9 12 with the coexistence approach to obtain quantitative palaeoclimate data the results give a geographically differentiated picture of the late miocene climate in the circum alpine area spatial patterns are presented in maps for mean annual temperature temperature of the coldest month temperature of the warmest month mean annual precipitation and mean annual range of temperature the obtained data show an overall warm humid and homogenous climate with very low latitudinal and longitudinal gradients there is no indication of a mediterranean type of climate palaeogeographic influences on climate patterns are evident the pannonian lake caused mild winters and a lower seasonality of temperature in the pannonian basin

oxygen isotope evidence for high altitude snow in the laramide rocky mountains of north america during the late cretaceous and paleogene the 18 o values of river waters in late cretaceous and paleogene basins of alberta montana wyoming and colorado are calculated from the isotopic composition of unaltered aragonite mollusk fossils the isotopic composition of these river waters has significant implications for the uplift and climate history of the mountains surrounding the basins our data show that the 18 o values of river water varied dramatically ranging from 23 to 5 relative to vienna standard mean ocean water with an uncertainty of 2 close stratigraphic association of river deposits with very different isotopic values indicates two different water sources rainfall in the warm low elevation basins and snowfall in surrounding mountains the 18 o difference between basinal and highland precipitation suggests that local relief was similar to today9s on the order of 2 5 3 km seasonal variation in shell 18 o values also indicates that there are times when large snow fields in the maastrichtian and paleocene mountains of montana and wyoming survived summer melting and were multiannual features

atmospheric circulation during warm geologic periods is the equator to pole surface temperature gradient the controlling factor paleoclimatologists have hypothesized that the equator to pole surface temperature gradient is a dominant control on the paleocirculation of the oceans and the atmosphere atmospheric simulations using realistic cretaceous 100 m y ago geography are used to examine quantitatively the relationships between paleogeography surface temperature gradients and the nature of the atmospheric circulation these results raise questions concerning the classical theories and interpretations of warm paleoclimates and suggest that paleogeography is an important factor governing the nature of the circulation

terrestrial palaeclimatology in the tertiary a methodological critique abstract the state of discussion on tertiary climate is reviewed with emphasis on the lower rhine embayment lre serious methodological deficits and the absence of climate reconstructions by utilizing limited area models seem to be major drawbacks to present tertiary paleoclimate reconstruction efforts since close cooperation of modern quantitative evaluation and estimation of palaeontological geological remains and numerical experiments with mostly global and rarely regional climate models proves to be very fruitful in the quaternary climate reconstruction context we propose a combined approach using mesoscale climate modeling and palaeontological geological analyses for regional tertiary climate studies this being applicable when a locally dense net of relevant probes related to one comparatively homogeneous time slice of about 1 ma e g in the miocene is available this data base enables optimal estimates of surface climate parameters by combining tolerance bounds of different taxa and stable regression techniques when possible using a trial and error method the model s output is fitted to the data base by minimizing an error function the computed model climatic statistics in turn serve as a guideline for critical examination of the palaeontological geological data base by determining inconsistencies an a posteriori by product is a ranking of different estimation methods using climate parameters from palaeontological indicators we discuss the advantages drawbacks and a possible setup of our proposed combined approach