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

an algorithm for extracting zonal mean and migrating tidal fields in the middle atmosphere from satellite measurements applications to timed saber measured temperature and tidal modeling 1 for a data series with grid points that do not uniformly cover a whole wave cycle in both space and time traditional least squares fitting methods will lead to biased estimates of the zonal mean and wave components as a result of aliasing between these elements we introduce a set of formal regularity conditions to select available grid points that reduce aliasing while obtaining the zonal mean and tidal components from unevenly sampled or incomplete measurements the algorithm is used to self consistently investigate the effect of the zonal mean field on the seasonal variation of diurnal tide in the upper middle atmosphere using temperature measured by the sounding of the atmosphere using broadband emission radiometry saber instrument onboard the thermosphere ionosphere mesosphere energetics and dynamics timed satellite we first unbiasly derive both the zonal mean and migrating tidal components from the measurements then simulate the seasonal variation of the migrating diurnal tide using a spectral tidal model with the measured zonal mean as input and finally compare the seasonal variation of the measured tide with the modeled one the model and measurement comparisons show self consistently and more conclusively the dominant effect of the zonal mean wind on the seasonal variation of the migrating diurnal tide in the upper middle atmosphere

multiyear observations of tidal oscillations in oh m 3 1 rotational temperatures at south pole antarctica 1 tidal amplitudes and phases deduced from austral winter observations of oh meinel 3 1 rotational temperatures at south pole antarctica over the period 1994 2007 are presented here dominant periodicities in temperature data are seen at 24 12 and 8 h the amplitude of these wave oscillations shows significant variability during the months analyzed herein april through september in contrast to 12 and 8 h waves the 24 h wave is stronger more persistent and coherent at south pole the observed amplitude variability in 24 12 and 8 h waves during the majority of the years analyzed is shown to be correlated phase variations of 24 and 8 h waves with longitudes indicate that these waves are standing zonal wave number 0 waves

large scale dynamics of the mesosphere and lower thermosphere an analysis using the extended canadian middle atmosphere model the extended canadian middle atmosphere model is used to investigate the large scale dynamics of the mesosphere and lower thermosphere mlt it is shown that the 4 day wave is substantially amplified in southern polar winter in the presence of instabilities arising from strong vertical shears in the mlt zonal mean zonal winds brought about by parameterized nonorographic gravity wave drag a weaker 4 day wave in northern polar winter is attributed to the weaker wind shears that result from weaker parameterized wave drag the 2 day wave also exhibits a strong dependence on zonal wind shears in agreement with previous modeling studies in the equatorial upper mesosphere the migrating diurnal tide provides most of the resolved westward wave forcing which varies semiannually in conjunction with the tide itself resolved forcing by eastward traveling disturbances is dominated by smaller scales nonmigrating tides and other planetary scale waves play only a minor role in the zonal mean zonal momentum budget in the tropics at these heights resolved waves are shown to play a significant role in the zonal mean meridional momentum budget in the mlt impacting significantly on gradient wind balance balance fails at low latitudes as a result of a strong reynolds stress associated with the migrating diurnal tide an effect which is most pronounced at equinox when the tide is strongest resolved and parameterized waves account for most of the imbalance at higher latitudes in summer this results in the gradient wind underestimating the actual eastward wind reversal by up to 40

observations of the diurnal tide in the mesosphere and lower thermosphere over christmas island atmospheric tidal variations in the mesosphere wind field have been studied extensively using radars most of the climatological studies of the tide have been done at middle and high latitudes previous tropical observations of the diurnal oscillation derived from campaign studies have shown the dominance of the migrating diurnal tide in the mesosphere and lower thermosphere by using wind measurements obtained with a meteor radar system located at christmas island the diurnal tidal behavior in the upper atmosphere of the equatorial pacific has been characterized over several years the data collected from august 1988 to december 1993 are presented in this paper and compared to various model results our observations show the meridional wind component of the diurnal tide maximizes in april near 94 km the observed meridional vertical wavelengths are large and indicate upward propagating energy even though the vertical wavelengths for the zonal diurnal component are also large the phase progression is upward corresponding to downward propagating energy there is considerable interannual and intraseasonal variation in the diurnal amplitudes throughout the year

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

an estimate of the momentum deposition in the lower thermosphere by the observed diurnal tide abstract this paper reports a calculation of the acceleration of the zonal mean flow induced by dissipating tides in the equatorial lower thermosphere estimates of the gravest symmetric gravitational hough mode 1 1 of the migrating diurnal tide are obtained from monthly composites of global winds observed by the upper atmosphere research satellite high resolution doppler imager using the principles of classical tidal theory the tidal momentum flux divergence is computed for a series of monthly mean 1 1 fields from january 1992 to may 1993 the contribution to the mean flow by the leading mode of the migrating tide ranges between 5 and 20 easterly m s 1 day 1 in the equatorial lower thermosphere a semiannual variation is noted in the tidal amplitudes and the inferred tidal accelerations these variations are consistent with observed trends in the zonal mean flow of the lower thermosphere

short period fluctuations of the diurnal tide observed with low latitude mf and meteor radars during cadre evidence for gravity wave tidal interactions mf and meteor radar data from four equatorial and subtropical sites hawaii christmas island jakarta and adelaide are used to examine diurnal tide amplitude and phase variability at mesosphere and lower thermosphere altitudes all sites exhibit significant seasonal variability with the largest amplitude fluctuations occurring at hawaii and adelaide shorter term variability is found to occur primarily on timescales of 5 to 30 days amplitude and phase fluctuations are well correlated among different sites on occasion but in general the amplitude and phase coherences are low and suggest significant local influences on the tidal structures the temporal behavior of height variations of the diurnal tide amplitude and phase is also examined cross correlations and cross spectra of these tidal parameters especially between the amplitude and phase are examined closely the tendency for phase maxima to lead amplitude maxima is consistent with tidal modulation of gravity wave propagation and momentum fluxes with a corresponding feedback by the gravity wave momentum flux divergences on the observed tidal structures these results substantially extend previous more limited studies of gravity wave tidal interactions and provide a statistical basis for the possible importance of this interaction and its influences on the diurnal tidal structure

empirical model of 90 120 km horizontal winds from wind imaging interferometer green line measurements in 1992 1993 an empirical model of horizontal winds is developed based on wind imaging interferometer windii green line observations between 90 and 120 km in 1992 1993 the model includes mean winds solar diurnal and semidiurnal tides and some planetary wave components as well as annual and semiannual variations in these fields its formulation is similar to that of hwm 90 and hwm 93 of hedin et al 1991 1996 but greatly modified and extended to use the higher resolution global wind measurements now available from windii while the technique will only reach fruition when results can be combined from the wind measurements of several years by the different instruments on the uars satellite this interim but updated model provides improved representation of the temporal and geographic variations of the wind fields compared to the current reference models the model generated climatological mean wind diurnal tides and some samples of the entire wind motion fields are presented and compared with the windii measurements and analysis results obtained from the data sets by different methods to check the consistencies between the model representations and the observations this study also reveals a dual cell structure in the meridional component of the diurnal tides with two amplitude maxima centered around 95 and 102 km near 20 latitude and strongly symmetric about the equator at equinox large interannual variabilities are found to exist in both diurnal wind components with maximum amplitudes of 40 and 55 m s for the zonal and meridional respectively at the vernal equinox of 1992

formation processes of basal ice at hamna glacier soya coast east antarctica inferred by detailed co isotopic analyses debris laden basal ice is exposed along an ice cliff near hamna glacier soya coast east antarctica the basal ice is about 6 8 m thick and shows conspicuous stratigraphic features the upper 5 5 m consists of alternating layers of bubble free and bubbly ice values of the bubble free ice layers are enriched by 2 4 1 0 standard deviation for 18 o compared to values of neighboring bubbly ice layers above and slopes of 18 o vs d are close to 8 such layers are suggested to have been formed by refreezing of meltwater in an open system in contrast part of the bubbly ice layers shows neutral profiles for stable isotopes suggesting that these ice masses are undisturbed ice sheet ice which was not affected by melting and freezing the massive alternating layers are thus considered to have been formed by folding of refrozen and non melted layers the lower 1 3 m consists predominantly of bubble free massive ice the profile of co isotopic values shows a change of about 3 0 o for 18 o at the interface between bubble free and bubbly ice since the isotopic change occurred over a wider thickness than the upper 5 5 m the basal ice is suggested to have been formed by refreezing of meltwater on a larger scale than the upper 5 5 m

evidence for two zones of debris entrainment beneath the greenland ice sheet investigation of the ice debris and stable isotope characteristics of basal ice exposed at the margin of the greenland ice sheet provides a means of testing and refining models of ice sheet erosion and deposition the basal ice exposed at the ice sheet margin gives evidence of the processes operating at the bed at different locations which can be used to constrain theoretical models predicting varying basal conditions1 2 improved understanding of the effects of isotope fractionation in hydrogen and oxygen caused by freezing processes at the bed which modify the isotope characteristics of the basal ice layers enables us to report evidence of two separate zones of debris entrainment beneath the ice sheet

numerical simulation of semidiurnal atmospheric tides numerical modeling of the solar and lunar semidiurnal atmospheric tides has been performed by invoking a comprehensive approach that includes both algebraic manipulation and numerical solution of the primitive equation system the effect of latitudinally varying temperature and associated mean zonal wind in a modeled atmosphere with realistic forcing are successfully incorporated to reproduce tidal variabilities at meteor heights delineated by varieties of radar observations

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

weertman regelation multiple refreezing events and the isotopic evolution of the basal ice layer a simple model is developed to s imulate the isotopic fractionation which accompanies weertman regelation at the bed of temperate based glaciers the fractionation equations of jouzel and souchez 1 982 are applied to multiple refreezing events over measured glacier bed profiles and mass balance is maintained as the basal ice and meltwater produced at one bedrock hummock enter the next s imulation results indicate that undeformed regelation ice layers are on the order of millimetres to centimetres thick often being completely melted at the stoss face of certain hummocks and exceptionally reaching a thickness in excess of 1 0 cm neither the internal morphology nor the isotopic composition of these layers is constant but both vary down glacier in accordance with bedrock configuration a glacier wide fractionation process is identified whereby heavy isotopes are preferentially removed fro m the basal meltwater film and incorporated into the basal ice this process might go some way to explaining the anomalously light isotopic composition measured in base flow waters leaving some glaciers vertical isotope profiles through undeformed basal ice layers are reconstructed and show that significant isotopic excursions can occur at a scale of millimeteres while the range of isotopic compositions within such m ulti layered regelation ice is greater than that which would occur in ice produced by a single refreezing event in circumstances where the regelation system is disrupted by removal of film waters into a network of linked cavities i t is found that the remaining basal ice may be significantly enriched in heavy isotopes relative to the composition of the initial mass inputs to the system heavy isotope enrichment of this m agnitude and consideration of the thickness of the basal ice layers concerned may explain the absence of recorded basal ice samples heavy enough to h ave been formed in equilibrium with subglacial precipitates sampled at one of the sites glacier de tsanfleuron and reported in an earlier paper

regelation of ice through debris at glacier beds implications for sediment transport results from laboratory experiments show that ice at its melting temperature regelated through dense three dimensional arrays off clasts abrading a rock bed regelation theory for an isolated stationary array of clasts successfully approximates periods when ice separated from the bed thermal gradients and clast bed contact forces despite the relative motion of clasts and incoming heat from the bed the process may entrain sediment at glacier beds and restrict deposition to zones where sediment in ice is concentrated effective pressure is low and basal melting is rapid

the deforming bed debris rich basal ice continuum and its implications for the formation of glacial landforms flutes and sediments melt out till abstract there are two potentially important shear zones at the base of the glacier the deforming layer and or the debris rich basal ice layer these two layers have a significant effect on glacier motion and glacial erosional depositional and sedimentary processes however it is shown that most of the processes operating within these two layers are very similar this includes compression at the ice margin longitudinal extension and simple shear upglacier similar styles of shear zone and associated fabric development and similar incorporation transport and depositional processes in the past many criterion have been developed to identify distinct deposition from the deforming layer and the debris rich basal ice layer however if the processes within these layers are similar then it makes the distinct identification of these two separate layers in the geological record very difficult however it is also shown that the main differences between the two layers include rates of sediment movement processes and preservation potential the later is very important as it appears that the two layers are interconnected and that material is melted out from the debris rich basal ice to form a significant component of the deforming layer in this way the final depositional imprint is from the deforming layer and there is little likelihood of the debris rich basal ice layer being preserved undeformed this is demonstrated from modern glacial environments pleistocene flute studies and studies of pleistocene melt out tills from the u k u s a and germany

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

two facies interpretation of the basal layer of the greenland ice sheet contributes to a unified model of basal ice formation two exposures of basal ice in alaska and greenland which have previously provided the basis for contrasting models of basal ice development are in fact directly comparable reinterpretation of previous field descriptions combined with new structural and sedimentological data from west greenland facilitates a simple unification of previous models of basal ice development and a common terminology for the field description of basal ice sequences the stratigraphy of the basal ice sequence at any site indicates the subglacial conditions and processes operating up glacier of that site presented here are interpretations of the major sequence types

generation of secondary waves arising from nonlinear interaction between the quasi 2 day wave and the migrating diurnal tide theory and past observations have provided evidence that atmospheric tides and other global scale waves interact nonlinearly to produce additional secondary waves throughout the space atmosphere interaction region however few studies have investigated the generation region of nonlinearly generated secondary waves and as a result the manifestation and impacts of these waves are still poorly understood this study focuses on the nonlinear interaction between the quasi 2 day wave 2dayw3 and the migrating diurnal tide dw1 two of the largest global scale waves in the atmosphere the fundamental goals of this effort are to characterize the forcing region of the secondary waves and to understand how it relates to their manifestation on a global scale first the fast fourier synoptic mapping method is applied to thermosphere ionosphere mesosphere energetics and dynamics sounding of the atmosphere using broadband emission radiometry satellite observations to provide new evidence of secondary waves these results show that secondary waves are only significant above 80 km the nonlinear forcing for each secondary wave is then computed by extracting short term primary wave information from a reanalysis model the estimated nonlinear forcing quantities are used to force a linearized tidal model in order to calculate numerical secondary wave responses model results show that the secondary waves are significant from the upper mesosphere to the middle thermosphere highlighting the implications for the atmosphere space weather coupling the study also concludes that the secondary wave response is most sensitive to the nonlinear forcing occurring in the lower and middle mesosphere and not coincident with the regions of strongest nonlinear forcing

long term variability in the equatorial middle atmosphere zonal wind the high resolution doppler imager hrdi on the upper atmosphere research satellite uars has provided measurements of the horizontal wind field in the stratosphere mesosphere and lower thermosphere since november 1991 this data set which spans a period of more than 3 years has facilitated an investigation of the long term behavior of the background circulation on a nearly global basis at middle and high latitudes the zonal circulation is characterized by an annual oscillation at low latitudes 30 the most prominent long term variation above the stratopause is the mesosphere semiannual oscillation msao which maximizes near the equator at an altitude of between 80 and 85 km further analysis of the time series reveals an additional strong variation with an amplitude near 30 ms 1 and a period of about 2 years this feature shows the same altitude and latitude structure as the msao and exhibits a phase relationship with the stratospheric quasi biennial oscillation qbo observations from the christmas island mf radar 2 n 130 w confirm the presence of this mesospheric qbo mqbo these observations support recent findings from a modeling study which generates an mqbo via the selective filtering of small scale gravity waves by the underlying winds they traverse

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

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

the effects of source and receiver motion on seismic data1 the effects of source and receiver motion on seismic data are considered using extensions of the standard convolutional model in particular receiver motion introduces a time variant spatial shift into data while source motion converts the effect of the source signature from a single channel convolution in time to a multichannel convolution in time and space these results are consistent with classical doppler theory and suggest that doppler shifting can introduce distortions into seismic data even at relatively slow acquisition speeds it is shown that while both source and receiver motion are known to be important for marine vibroseis acquisition receiver motion alone can produce significant artifacts in marine 3d data fortunately the convolutional nature of the distortions renders them amenable to correction using simple deconvolution techniques specifically the effects of receiver motion can be neutralized by applying an appropriate reverse time variant spatial shift while those due to source motion can be addressed by introducing time variant spatial shifts both before and after standard deterministic signature deconvolution or correlation

nonmigrating diurnal tides in mesospheric and lower thermospheric winds and temperatures abstract this paper presents analyses of nonmigrating diurnal tide signatures in high resolution doppler imager mesospheric and lower thermospheric winds and temperatures a global comparison of both winds and temperature reveals equatorial features corresponding to nonmigrating tides structures interpreted as zonal mean and eastward nonmigrating diurnal tides display consistency between horizontal winds and temperatures the second symmetric mode is prominent in the zonal mean and wavenumber 1 the gravest antisymmetric mode and the gravest symmetric or kelvin mode are the main features in zonal wavenumbers 2 and 3 the amplitudes of the tides generally increase with altitude and maximize within 90 110 km

intraseasonal variability of high resolution doppler imager winds in the equatorial mesosphere and lower thermosphere analyses of high resolution doppler imager hrdi daytime equatorial zonal winds indicate significant variability on time scales of 20 121 days these appear as transient oscillations in the equatorial zonal mean zonal wind between 70 and 100 km the oscillations are characterized by two maxima near 75 and 95 km that are out of phase separated by a minimum near 80 km these features move downward in time and exhibit equatorial symmetry with maximum values at the equator during 1994 maximum amplitudes of the intraseasonal oscillation are 20 m s 1 in january and 30 m s 1 in june the intraseasonal variability present in hrdi winds is qualitatively consistent with variations on similar timescales reported at christmas island it has been hypothesized that the wind patterns at christmas island result from modulated gravity wave driving eckermann et al 1997 the results of the present study strongly support this view

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

direct observations of nonmigrating diurnal tides in the equatorial thermosphere 1 we present direct observations of nonmigrating diurnal tides in the 90 270 km range inferred from the upper atmosphere research satellite uars wind imaging interferometer windii a prominent zonal wavenumber 4 appears in daytime zonal winds extending to 180 km we interpret this signature as an eastward propagating diurnal wavenumber 3 de3 viewed from the satellite perspective this evidence of the extended upward propagation of de3 demonstrates that it acts as a direct coupling agent between the troposphere and the thermosphere and f region in addition to its role in the e region dynamo

stationary planetary waves in upper mesospheric winds abstract quasi stationary planetary scale longitudinal variations are found in the upper mesospheric winds measured during winter by the hrdi satellite instrument these are negatively correlated with eddy winds in the stratosphere two different mechanisms are proposed to explain the mesospheric perturbation winds and their anticorrelation with stratospheric winds 1 planetary waves propagate through the stratosphere and into the mesosphere with a phase shift of one half cycle and 2 mesospheric perturbations are forced in situ by gravity waves whose spectrum has longitudinal asymmetries due to filtering by planetary waves in the stratosphere the first mechanism is more consistent with the observations during southern hemisphere late winter august and also may explain the observations during northern hemisphere early winter december the second mechanism gives a more consistent explanation for the northern hemisphere late winter observations as previously shown by the author the hemispheric diff

satellite observations of mean winds and tides in the lower thermosphere 2 wind imaging interferometer monthly winds for 1992 and 1993 1 satellite observations of monthly i e 60 d averages centered on the 15th of each month zonal mean and migrating tide winds in the region of 90 120 km and 40 s 40 n from the wind imaging interferometer are presented the zonal mean zonal winds are characterized by annually varying eastward winds at midlatitudes with a maximum in summer and semiannually varying westward winds in the tropics with maxima at equinox below 105 km the zonal mean meridional winds are characterized by a summer to winter flow below 100 km at solstice and by a cell like structure at equinox the latter is the first such global observation of this tidally driven structure two distinct types of diurnal tide are observed an upward propagating one and an evanescent one of comparable magnitude the propagating tide which is dominant in the subtropics below about 105 km exhibits a semiannual variation with a primary maximum in march april and a secondary maximum in september october the evanescent tide which is dominant poleward of 20 n s and above 100 km has an annual variation with a maximum in the summer months the coupling of the two produces a double peaked structure in the vertical profile of the diurnal amplitude the semidiurnal tide is generally weaker than the diurnal tide the maximum semidiurnal winds are at 30 40 n s and at 105 110 km both zonal and meridional components are stronger in april september than in october march in both hemispheres but in the equatorial region in april september the meridional component has a maximum whereas the zonal component has a minimum

observations of the 6 5 day wave in the mesosphere and lower thermosphere previous observations of atmospheric oscillations with zonal wave number 1 have consistently located waves of periods between 5 and 7 days this study presents a global and seasonal analysis of the 6 5 day wave in high resolution doppler imager daytime mesosphere and lower thermosphere horizontal winds temperatures and nighttime atomic oxygen at 95 km the horizontal structures of all these atmospheric variables are similar to the gravest symmetric wave number 1 rossby wave i e the 1 1 mode the seasonal and spatial analysis displays possible modification by the zonal mean wind finally the observed vertical structures of the 6 5 day wave indicate that it is an internal rossby wave not an external or lamb wave

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

solar tides in the middle atmosphere i description of satellite observations and comparison with theoretical calculations at equinox in recent years several refinements have been made in the numerical computation of solar atmospheric tides between 30 and 60 km although comparisons have been made with winds observed by rockets it has not been possible until now to test these predictions against a globally extensive set of observations in this paper we describe techniques for obtaining such observations from measurements made by the stratospheric sounding units ssu on the tiros n series of satellites these unique data are compared with calculations of the radiance variations expected from the ssu based on classical tidal theory at equinox

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

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

on the isotopic composition in δd and δ18o of water and ice during freezing experiments on progressive unidirectional freezing are coi1 ducted to determine rhe evol ution in 00 and 51 bo of successive water samples and ice layers ta ken during the course of freezing r es ults indicate t hal lhi s evoluti on takes pl ace in a bd bibo diagram a long a strai ght line wi th a characteri sti c slope this slope different from that due to the precip itation effec t gives a finger print of the occurrence of a freezing or of a melt ing refreez ing process in the stud ied reservoir residual water was sampled at the beginning of the experiment after 40 80 85 90 and 95 of the material had frozen when the freezing process was complete the ice core was recovered and sectioned the samples covered the freezing ranges from 0 to 10 10 to 20 20 to 50 50 to 60 60 to 70 70 to 80

nonmigrating semidiurnal and diurnal tides at 95 km based on wind measurements from the high resolution doppler imager on uars 1 for more than a decade derived results from the high resolution doppler imager hrdi on uars have provided an enormous amount of new and invaluable information on the global variability of atmospheric winds these and other results have given added impetus to theoretical modeling efforts until recent years the large majority of investigations have focused on migrating tides and now more results on nonmigrating tides have become available we provide new results for semidiurnal and diurnal nonmigrating tides based on data from hrdi at 95 km much of these results have not been obtained before and they are substantially different from those that have been previously reported our amplitudes are usually significantly larger with more periodicities in both day of year and latitude than results that have previously appeared in the literature we also find components up to longitude wave number 3 that are significant and have not been presented before and that traveling components of larger longitude wave numbers 4 5 and 6 can reach several m s in amplitude we compare our results with earlier results based on hrdi measurements and from selected models

global mesospheric tidal winds observed by the high resolution doppler imager on board the upper atmosphere research satellite this paper presents preliminary results of a study of mesospheric and lower thermosphedc diurnal tidal winds obtained with the high resolution doppler imager hi on the upper atmosphere research satellite uars zonal averages of the meddional and zonal wind fields are performed at fixed local times these analyses reveal tidal structures in the mean meridional wind field during the months of february and march 1992 results are presented for a typical day in february 1992 the observed maximum amplitude of meridional wind is approximately 75 m s 1 the observed vertical wavelength is about 20 km with amplitudes increasing linearly with height in addition to the tides the zonal wind field reveals many features of the mesospheric

observations of the quasi 2 day wave from the high resolution doppler imager on uars a strong westward traveling oscillation with a period of 2 days and zonal wave number 3 is observed in the mesospheric and lower thermospheric winds from the high resolution doppler imager on the upper atmosphere research satellite the important events happen in january july and september october of which the occurrence in january is the strongest with an amplitude over 60ms 1 detailed analyses for the periods of january 1992 and january 1993 reveal a cause and effect relationship in the wave developing process at 95km the global structures of the wave amplitude and phase are also presented

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

tidal gravity wave interactions and their influence on the large scale dynamics of the middle atmosphere model results results from a modified version of the quasi geostrophic model of mclandress and mcfarlane 1993 in combination with the tidal model of forbes 1982a b are used to delineate the role of tides in modulating gravity wave momentum fluxes and the ensuing effects on the large scale circulation of the middle atmosphere for solstice conditions the influence of the tidal wind fields on the location and strength of the gravity wave drag is strongest in the mesosphere and lower thermosphere where the tidal winds are of the same order as the zonal mean component due to the nonlinear dependence on the local wind speed the daily mean gravity wave drag in the model can differ significantly depending on whether or not tidal variations are included at middle and low latitudes these differences are largest and occur as a result of the filtering effects of the shorter vertical wavelength diurnal tide at more polar latitudes where the longer wavelength semidiurnal tide dominates a slight increase in drag occurs the interaction between the tidal wind fields and the localized orographic gravity wave momentum flux has important consequences for the in situ generation of planetary scale disturbances in particular the amplification of stationary planetary wavenumber 1 is enhanced by the presence of tides in addition forcing of nonmigrating tidal modes is predicted to occur as a result of the localized drag

equivalent current systems for the annual and semiannual sq variations observed along the 210 mm cpmn stations 1 we analyzed ground magnetometer data for the 10 international quiet days during 1996 2007 the data were obtained from 19 stations along 210 magnetic meridian mm of the circum pan pacific magnetometer network cpmn covering both the northern hemisphere and southern hemisphere from the daily variations of the geomagnetic field we deduced the latitude local time lat lt diagram of the equivalent sq current system which can be regarded as the superposition of the following three current systems sq0 sq1 and sq2 the sq0 sq1 and sq2 current systems are equivalent current systems for the yearly average annual variation and semiannual variation of the sq field respectively we have examined temporal and spatial features of these current systems the principal features are as follows 1 the total current intensities of the sq1 and sq2 current systems are about 35 and 15 of that of the sq0 current system respectively 2 the sq0 and sq2 current systems have a dayside vortex in each hemisphere while the sq1 current system has a single vortex centered at the equatorial region in the morning sector 1000 lt

basal glacier ice and massive ground ice different scientists same science whilst glaciologists and permafrost researchers investigate ice bodies using similar techniques there has been surprisingly little collaboration between the two communities this paper examines the potential benefits of interdisciplinary research into the formation of basal ice beneath glaciers and the origin of massive ice in glaciated permafrost regions active collaboration in these areas has already improved our understanding of the formation of basal ice beneath cold based glaciers the critical role played by basal freezing in controlling the dynamic behaviour of stagnating ice streams and the significance of glacier permafrost interactions at the margins of pleistocene ice sheets however in order to promote future collaboration certain obstacles need to be overcome the contrasting ice classification schemes employed by glaciologists and permafrost scientists for example need to be unified in order to allow detailed comparisons of ice rich sequences in both environments this could in turn enable exciting research advances most notably by facilitating the identification of preserved remnants of pleistocene ice sheets within permafrost regions that provide a potentially invaluable and currently largely untapped source of palaeoglaciological information

the meridional wind component of the thermospheric tide observed by windii on uars thermospheric meridional winds measured by the wind imaging interferometer windii on the upper atmosphere research satellite uars are analyzed for migrating solar tides for march april 1993 tidal signatures are extracted by zonally averaging and binning the data in equally spaced intervals of local time latitude and altitude an examination of the binned data reveals vertically propagating tides in the lower thermosphere with the diurnal tide dominating at low latitudes above 120 km evidence of vertical propagation ceases and the vertical gradients are significantly reduced in regions where both daytime and nighttime data are available fourier decomposition of the binned winds is used to extract the diurnal component of the tide this analysis reveals that the propagating diurnal tide attains a maximum amplitude of 65 m s at 20 n and 20 s at 95 km and exhibits a vertical wavelength of about 25 km

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

simulation of large scale dynamics in the mesosphere and lower thermosphere with the doppler spread parameterization of gravity waves 2 eddy mixing and the diurnal tide turbulence is thought to be produced by gravity waves that become unstable in the upper atmosphere owing to a relatively short vertical wavelength of the solar diurnal tide turbulent viscous type mixing is expected to be particularly important for tidal dissipation in the mesosphere and lower thermosphere mlt within the doppler spread parameterization dsp of gravity waves the vertical eddy exchange coefficients may be calculated from the gw energy deposition rate the dsp as implemented in the spectral mesosphere lower thermosphere model is shown to provide realistic simulations of both the diurnal tide and turbulent mixing in the mlt in particular the vertical structure and seasonal variations of eddy mixing agree well with in situ observations and independent estimates from global thermal balance the seasonal variations of turbulence are found to be primarily responsible for a strong semiannual variation of the diurnal tide in agreement with recent satellite observations

climatology of upward propagating diurnal and semidiurnal tides in the thermosphere 1 a major challenge in delineating and understanding the space weather of the ionosphere thermosphere system is the lack of global tidal observations in the 120 400 km thermospheric gap between satellite remote sensing and in situ tidal diagnostics this paper aims to close this gap by presenting an observation based climatological tidal model of the thermosphere ctmt of self consistent upward propagating migrating and nonmigrating diurnal and semidiurnal tides from 80 400 km and pole to pole for moderate f10 7 110 sfu solar flux conditions ctmt includes the 6 8 most important diurnal semidiurnal tidal components for temperature density and zonal meridional and vertical winds and is based on hough mode extension fits to 2002 2008 mean timed satellite tidal diagnostics in the mesosphere lower thermosphere mlt validation with independent 2002 2008 champ tidal diagnostics f10 7 105 sfu around 400 km proves that the approach captures nonmigrating tides well indicating that these waves propagate directly upward without significant tidal forcing occurring in the thermosphere notable exceptions are the dw2 and d0 components that are most likely generated in situ by nonlinear interaction forcing in the upper thermosphere ctmt is suitable for driving upper atmosphere models that require self consistent tidal fields in the mlt region as a lower boundary condition it does not include migrating tides due to in situ euv absorption in the upper thermosphere but allows us to quantitatively assess thermospheric variability due to tides from the lower atmosphere this is done by discussing longitude latitude maps of reconstructed diurnal and semidiurnal tidal variations as function of altitude and local time

fidelity and repeatability of wave fields reconstructed from multicomponent streamer data wave field reconstruction the estimation of a three dimensional 3d wave field representing upgoing downgoing or the combined total pressure at an arbitrary point within a marine streamer array is enabled by simultaneous measurements of the crossline and vertical components of particle acceleration in addition to pressure in a multicomponent marine streamer we examine a repeated sail line of north sea data acquired by a prototype multicomponent towed streamer array for both wave field reconstruction fidelity or accuracy and reconstruction repeatability data from six cables finely sampled in line but spaced at 75 m crossline are reconstructed and placed on a rectangular data grid uniformly spaced at 6 25 m in line and crossline benchmarks are generated using recorded pressure data and compared with wave fields reconstructed from pressure alone and from combinations of pressure crossline acceleration and vertical acceleration we find that reconstruction using pressure and both crossline and vertical acceleration has excellent fidelity recapturing highly aliased diffractions that are lost by interpolation of pressure only data we model wave field reconstruction error as a linear function of distance from the nearest physical sensor and find for this data set with some mismatched shot positions that the reconstructed wave field error sensitivity to sensor mispositioning is one third that of the recorded wave field sensitivity multicomponent reconstruction is also more repeatable outperforming single component reconstruction in which wave field mismatch correlates with geometry mismatch we find that adequate repeatability may mask poor reconstruction fidelity and that aliased reconstructions will repeat if the survey geometry repeats although the multicomponent 3d data have only 500min line aperture limiting the attenuation of non repeating multiples the level of repeatability achieved is extremely encouraging compared to full aperture pressureonly time lapse data sets at an equivalent stage of processing

satellite observations of mean winds and tides in the lower thermosphere 1 aliasing and sampling issues 1 the canadian middle atmosphere model a general circulation model extending up to 200 km is used to analyze the impact of aliasing and data gaps on satellite observations of zonal mean winds and migrating tides in the lower thermosphere focus is placed on measurements from the wind imaging interferometer windii mock data sets are constructed by sampling daily zonal mean and migrating tides from the model like the satellite previously unverified assumptions that satellite observations of the zonal mean zonal winds and the meridional component of the diurnal tide winds are largely unaffected by aliasing are confirmed of the two the meridional component of the diurnal tide is more robust the amplitude of the zonal component of the diurnal tide is not strongly affected by aliasing tidal phase is nearly unaffected gaps in the windii data do not adversely affect the results provided sufficient local time coverage is available the analysis suggests that more subtle features in the windii observations such as the tidally driven cell like structures in the zonal mean meridional wind at low latitudes may be observable issues pertaining to the sampling interval and the use of daytime only data are also addressed sampling every second or third day provides nearly as good results as sampling every day and that using daytime only data results in substantial biases in the zonal mean zonal winds in the lower thermosphere the latter underscores the importance of the accurate removal of the migrating diurnal tide from climatologies generated from daytime only satellite data

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

the quasi two day wave observed in the equatorial middle atmosphere an oscillation with a period near 2 days is found in radar wind measurements made in the upper mesosphere and lower thermosphere at christmas island 2 n 157 w in the central pacific the oscillation is particularly strong in the meridional wind component and seems to be present almost continuously ir the 80 100 km height region although some intermittency is evident wave amplitudes are especially large about one month after the solstices in july august and in january february at times coincident with large 2 day wave events in the summer mesosphere at extratropical latitudes power spectral and complex demodulation techniques are used to study the amplitude and frequency variations of the oscillation as a function of height and time downward phase propagation is found consistent with upward energy propagation and with a vertical wavelength of about 70 km an unusual feature is a shift in wave period from near 50 hours in july august to 48 hours in january february when the largest amplitudes up to 45 m s 1 are observed a 16 hour oscillation is also found at times when the 2 day wave amplitudes are largest the observations are consistent with the 2 day wave being a manifestation of the 3 0 rossby gravity normal mode another weaker oscillation is also found in the meridional wind field at a period near 44 hours this oscillation may be due to the 2 0 normal mode

basal debris entrainment and transport in glaciers of southwestern bylot island canadian arctic abstract glaciers on southwestern bylot island in the canadian arctic flow from an alpine setting in high grade crystalline archean terrane on to coastal lowlands underlain by clastic sedimentary

semidiurnal tidal climatology of the e region theoretical predictions of global monthly and seasonally averaged semidiurnal temperatures and winds between 80 and 150 km are presented and compared with seasonal means from measurements at the arecibo chatanika millstone hill and sondrestrom incoherent scatter radars the model values above 100 km are obtained by utilizing a set of tabulated hough mode extension functions to extrapolate the 2 2 2 3 2 4 and 2 5 propagating tidal modes at 100 km from a spectral model not valid in the e region due to the way molecular dissipation is parameterized to higher altitudes and by superimposing a component driven by in situ excitation important mainly above 140 km the monthly simulations demonstrate the close coupling that exists between seasonal and latitudinal structures and argue for an observational program emphasizing adequate seasonal and latitudinal coverage despite constraints imposed by the distributions of existing data with respect to month and year comparisons with the model reveal several trends that appear to be real 1 the model amplitudes are usually 20 50 smaller than those observed 2 vertical wavelengths are well predicted by the model but model phases generally lead the observations at middle and low latitudes by approximately 2 3 hours at all heights for both winds and temperatures 3 semidiurnal temperatures at middle and low latitudes in both the observations and model indicate significant seasonal changes in the phase of the temperature oscillation but not in the winds and 4 the seasonal trends in the model and observations are consistent with summer leading winter at millstone hill while the reverse is true at arecibo the sources of the absolute amplitude and phase discrepancies in the model which are probably connected with the adopted mean wind and thermal excitation specifications need to be investigated in addition a concerted effort must be made within the coupling energetics and dynamics of atmospheric regions cedar program to better delineate the seasonal latitudinal thermal structure and dynamics of the e region following the example of the extensive f region observational data base which has been accumulated over the last decade

atmospheric tide 2 the solar and lunar semidiurnal components solar and lunar semidiurnal wind and temperature oscillations from the surface to 400 km are simulated for average solar activity conditions utilizing the numerical tidal model described in part 1 hough mode decomposition of the solstitial solar semidiurnal tide excited by h2o and o3 insolation absorption below 80 km indicates that it is characterized by a predominance of 2 2 below 60 km about equal contributions of 2 2 2 3 and 2 4 between 70 and 90 km mostly 2 4 with some 2 5 and 2 2 between 90 and 120 km and a predominance of 2 2 above 140 km with secondary contributions from 2 3 and 2 5 the solstitial lunar semidiurnal tide is characterized by a predominance of 2 2 below 70 km 2 4 with secondary contributions from 2 2 2 3 and 2 5 between 80 and 110 km and by 2 2 with a fairly strong secondary contribution from 2 3 above 120 km similar descriptions for both the solar and lunar oscillations apply at equinox except that the asymmetric 2 3 and 2 5 modes are absent relative to the solar component lunar temperature and wind amplitudes are sufficiently large 20 in the lower and upper thermosphere to account for some of the observed variability previously attributed to the solar tide amplitudes of the 2 4 and 2 5 modes above 100 km are significantly affected by mesospheric eddy diffusion coefficients in excess of 2 106 cm s 1 the total solar semidiurnal exospheric temperature oscillation for average solar conditions ranges from 10 20 k poleward of 40 n to 40 60 k equatorward of 30 n and has its origin in three sources of excitation all of comparable importance 1 euv solar radiation absorption in the lower thermosphere 100 200 km 2 in situ momentum coupling due to the interaction of diurnal winds and diurnally varying ion drag and 3 tides propagating upwards from below 100 km in addition the calculations are compared with rocket meteor radar partial reflection thomson scatter and satellite data to evaluate the consistency of the model with observations

observations of tidal temperature and wind perturbations in the mesopause region above urbana il 40 n 88 w na lidar and mf radar measurements of temperature and horizontal winds were conducted simultaneously during several continuous 24 h periods in march and april 1996 at the urbana atmospheric observatory the data are used to determine the amplitude and phase profiles of the 24 and 12 h tides in the mesopause region between about 82 and 100 km the measured amplitudes and phases of the tidal components of the horizontal winds are generally consistent with the predictions of the global scale wave model gswm the measured 24 h temperature amplitude is comparable to the gswm predictions between 85 and 96 km but is significantly larger than gswm above 96 km the measured phase progression is downward below 94 km with an inferred vertical wavelength of 14 1 km above 94 km the temperature phase progression is upward with a vertical wavelength of 12 1 km the measurements suggest the presence of a diurnal heat source in the lower thermosphere which is generating a strong downwardly propagating 24 h wave

δd δ18o relationships and the thermal history of basal ice near the margins of two glaciers in lyngen north norway les resultats des mesures combinees d et 18 o pour 2 glaciers en norvege du nord sont rapportes ainsi que leurs implications pour l histoire thermique de la glace et les variations observees dans l entrainement des debris

seasonal changes in ground penetrating radar signature observed at a polythermal glacier bylot island canada in recent years ground penetrating radar gpr has been increasingly used for characterization of subglacial and englacial environments at polythermal glaciers the geophysical method is able to exploit the dielectric difference between water air sediment and ice allowing delineation of subsurface hydrological thermal and structural conditions more recent gpr research has endeavoured to examine temporal change in glaciers in particular the distribution of the cold ice zone at polythermal glaciers however the exact nature of temporal change that can be identified using gpr has not been fully examined this research presents the results of three gpr surveys conducted over the course of a summer ablation season at a polythermal glacier in the canadian arctic a total of approximately 30 km of gpr profiles were collected in 2002 repeatedly covering the lower 2 km of stagnation glacier bylot island 72 58 n 78 22 w comparison between profiles indicated changes in the radar signature including increased noise appearance and disappearance of englacial reflections and signal attenuation in the latter survey further an area of chaotic returns in up glacier locations which was interpreted to be a wet temperate ice zone showed marked recession over the course of the ablation season combining all the temporal changes that were detected by gpr results indicate that a polythermal glacier may exhibit strongly seasonal changes in hydrological and thermal characteristics throughout the ice body including the drainage of 17 000 m 3 of temporarily stored intra glacial meltwater it is also proposed that the liquid water content in the temperate ice zone of polythermal glaciers can be described as a fraction of a specific retention capacity copyright 2006 john wiley sons ltd

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

diurnal migrating tide as seen by the high resolution doppler imager uars 1 monthly mean global meridional winds the high resolution doppler imager hrdi instrument on board the upper atmosphere research satellite measures global winds in the mesosphere and lower thermosphere on a day to day basis the horizontal coverage of the hrdi data is excellent and provides a unique opportunity to study global scale dynamic phenomena however the local time resolution and coverage are limited because of the nature of the satellite sampling the lack of local time coverage makes conventional methods of data analysis e g fourier analysis both difficult and erroneous an original method of analysis based on a numerical model of atmospheric thermal tides is proposed and applied to the hrdi data the tidal model is solved for the tidal oscillations in the meridional wind component the simulated diurnal meridional tidal winds are used as a first guess in the analysis the results of the model are adjusted to give meridional migrating tidal winds that have maximum consistency with hrdi measurements this technique is used to derive monthly mean tidal oscillations of the meridional velocity the derived tidal amplitudes show profound seasonal changes that seem to be consistent with gravity wave breaking theory the results are compared with mf radar data it is found that in the upper mesosphere and lower thermosphere the tidal amplitudes obtained by hrdi can be bigger than those from mf radars by a factor of 2

marine vibrators and the doppler effect marine seismic data acquired with a moving vibrator suffer phase dispersion caused by doppler shifting of the source sweep function the dispersion for a particular reflection event depends upon frequency the type of sweep function and the doppler factor associated with that event synthetic vibrator data show that at typical ship speeds the doppler factors for steeply dipping events are big enough to cause phase dispersion as large as several hundred degrees if unaccounted for such dispersive effects could make a moving marine vibrator unacceptable for imaging steep dips in a constant offset section the doppler factor for a reflection event is the product of ship speed and the event s time dip that key simple relationship allows a two dimensional f k filter to remove the phase dispersion caused by the doppler effect comparisons of both synthetic data and gulf of mexico field data before and after application of the phase correcting filter show that the filter improves steep dip imaging in ma

diurnal tide in the equatorial middle atmosphere as seen in lims temperatures abstract the distribution of day night temperature differences in the middle atmosphere determined by the nimbus 7 lims experiment is described day night differences maximize at and are approximately symmetric about the equator successive centers of opposite sign increase in amplitude with altitude the pattern having a vertical wavelength of 25 km profiles of rocket meridional wind at kwajalein 8 7 n and ascension island 8 0 s taken near local noon and averaged over the lims data period exhibit maxima which support the tidal interpretation of the equatorial temperature pattern these characteristics are in general agreement with previous observational and theoretical results for the solar driven diurnal tide substantial time variations in amplitude and in location of the temperature maxima are observed the diurnal tide near the equatorial stratopause appears to be influenced by the phase of the semiannual oscillation

mean winds tides and gravity waves during the westward phase of the mesopause semiannual oscillation msao mf radar observations of mean winds tides and gravity waves in the period range 30 120 min over tirunelveli 8 7 n 77 8 e during april 1993 when the mesopause semiannual oscillation msao was in the westward phase are presented in this work the focus herein is on the observed relationship between these dynamical parameters which is explained in the context of the current understanding of the behavior of msao winds tidal dissipation and gravity wave tide interactions the observed diurnal tide amplitude and phase variations with height indicate 1 1 wave damping and subsequent westward momentum deposition the gravity wave variances are shown to be modulated by the diurnal tide though the analysis does not lead to an estimation of gravity wave contributions to the time mean zonal flow and its shears the observations do suggest that the short term tidal variability contributes either directly or indirectly through the gravity wave tidal interactions to the variation of the strength of the time mean westward flow associated with the msao

tidal signatures in temperature data from crista 1 mission temperature measurements in the stratosphere and mesosphere were taken during the first cryogenic infrared spectrometers and telescopes for the atmosphere crista 1 mission using co2 emissions these measurements range from 13 to close to 100 km and individual temperature measurements have a precision of 1 k the crista orbit was circular at an inclination of 57 so local time variations during the 7 day mission were small for a given latitude and orbit leg zonal averages of the data show significant structure in the vertical and as a function of latitude temperature differences between the zonal mean data from the ascending and descending portions of the orbit are of the form expected from the diurnal tide the maximum zonal mean difference is 20 k and occurs over the equator at an altitude of 75 km zonal variations in the temperature difference indicate that the tidal amplitude is not uniform at all longitudes at the equator the maximum amplitude 30 k appears over the african sector and the minimum 10 k over the pacific sector this variation is most likely a nonmigrating wavenumber 2 diurnal tide although other less plausible possibilities exist to facilitate comparisons with model results the temperature variations are converted to equivalent vertical displacements assuming the tidal motions are adiabatic such an approach is appropriate in the mesosphere where diurnal variations due to radiative effects are small and reduces the dependence of the measured temperature amplitude on the background temperature profile equivalent vertical displacements are also calculated using results from the global scale wave model for the most part the model results and observations are in excellent qualitative and good quantitative agreement from the tropopause to the mesopause however the observed vertical wavelength is smaller and its amplitude in terms of equivalent displacement is smaller in the upper mesosphere than that in the model the decrease in amplitude is consistent with that expected from the transition from equinox to solstice conditions

seasonal variations of mlt tides revealed by a meteor radar chain based on hough mode decomposition seasonal variations of different tides in the mesosphere and lower thermosphere are investigated from wind observations of a meteor radar chain on the basis of hough mode decomposition first the observed winds are decomposed into different diurnal semidiurnal and terdiurnal tidal components different seasonal patterns are revealed for each component pronounced semiannual oscillation sao is presented in the diurnal component while latitude dependent seasonal variation is found in the semidiurnal and terdiurnal components at the low midlatitude stations the semiannual annual oscillation is relatively stronger then hough mode decomposition is utilized to extract the dominant tidal modes of each decomposed component it is found that each component is dominated by one of its symmetric tidal modes with strong seasonal dependency apparent sao is observed in the dominant 1 1 mode 2 4 mode is strong in the autumn and winter months after the september equinox based on the extracted results we further map the three dimensional distribution latitude altitude season of each tidal component the mapped results are finally compared with the corresponding values observed by the thermosphere ionosphere mesosphere energetics and dynamics doppler interferometer tidi and modeled from the global scale wave model gswm each mapped tidal component agrees well with corresponding tidi observation in the seasonal variation meanwhile coincidences are found in the seasonal dependency of the diurnal component between the mapped values and the modeled results from gswm while difference between them exists in that of the semidiurnal one

discriminating glacier thermal and dynamic regimes in the sedimentary record abstract this paper provides a description and evaluation of the sedimentary facies and environments associated with a range of glacier thermal and dynamic regimes with additional consideration given to the tectonic context new and previously published data are evaluated together and are presented from modern terrestrial and marine glacial sedimentary environments in order to identify a set of criteria that can be used to discriminate between different glacier thermal regimes and dynamic styles in the sedimentary record sedimentological data are presented from a total of 28 glaciers in 11 geographical areas that represent a wide range of contemporary thermal dynamic and topographic regimes in the context of landsystems representatives from terrestrial environments include temperate glaciers in the european alps patagonia new zealand the cordillera blanca peru cold glaciers in the dry valleys of antarctica and the antarctic peninsula region and polythermal valley glaciers in svalbard northern sweden the yukon and the khumbu himal nepal the glaciomarine environment is illustrated by data from cold and polythermal glacier margins on the east antarctic continental shelf and from a polythermal tidewater glacier in svalbard along with general observations from temperate glaciers in alaska these data show that temperate glacial systems particularly in high relief areas are dominated by rockfall and avalanche processes although sediments are largely reworked by glaciofluvial processes debris in polythermal glaciers is both thermally and topographically influenced in areas of moderate relief debris is mainly of basal glacial origin and the resulting facies association is dominated by diamicton in high relief areas such as the himalaya the debris load in polythermal glaciers is dominated by rockfall and avalanche inputs resulting in extensive accumulations of sandy boulder gravel cold glaciers are dominated by basal debris entrainment but sediments are little modified from the source materials which are typically sandy boulder gravel from older till and sand from glaciofluvial glaciolacustrine and aeolian sources similar facies associations but with different facies geometry and thickness occur in equivalent glaciomarine settings application of these concepts can aid the interpretation of glacier thermal regime and hence palaeoclimate in quaternary and ancient glacial systems

doppler imager wind measurements with simulations from the ncar thermosphere ionosphere mesosphere electrodynamics circulation model in this paper a comparison is presented between simulations of the diurnal and semidiurnal tides in the middle and upper atmosphere from the thermosphere ionosphere mesosphere electrodynamics general circulation model timegcm and satellite observations from the upper atmosphere research satellite uars high resolution doppler imager hrdi reasonable agreement is found between the model and observations for a march condition when a strong diurnal tide was observed the model is able to reproduce many tidal features at altitudes between 65 and 110 km as observed in the hrdi wind measurements of interest in these features is the shortening vertical wavelength of the 1 1 tide in the upper mesosphere and lower thermosphere which appears in both model simulations and the wind observations the hrdi data also show large longitudinal variations in the diurnal tide of which the amplitude can be as high as 50 of the migrating tide the wavelike structures in latitude and altitude dimensions suggest that the longitudinal variations are likely due to the presence of propagating nonmigrating tides in the upper mesosphere and lower thermosphere for further investigations of the observed tidal variability the model demonstrates great potential with the use of more realistic heating cooling and wave forcing schemes

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

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

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

tides in the mesopause region over fort collins colorado 41 n 105 w based on lidar temperature observations covering full diurnal cycles 1 eighteen sets of 24 hour continuous lidar temperature observation well distributed throughout the year have been analyzed to reveal the mean amplitude and phase of oscillations with 24 12 8 and 6 hour periods for four seasons the amplitude and phase of both 24 and 12 hour components are compared to the prediction of the most recent global scale wave model gswm 00 the variability of diurnal and semidiurnal oscillations is examined by comparing the amplitude and phases of each observed day in autumn winter and spring even with the limited data sets reported here surprisingly good general agreement between the observed and model tidal phases can be established implicating the prevalence of migrating diurnal and semidiurnal tides compared to the diurnal and semidiurnal phases which typically show clear downward phase progression the 8 and 6 hour components exhibit small amplitude and show unorganized phase propagation as a function of altitude the advantage of having coverage over complete diurnal cycle and entire mesopause altitudes as demonstrated here would hopefully stimulate future tidal studies with lidar temperature and zonal and meridional wind observations

latitude and seasonal dependence of the semidiurnal tide observed by the high resolution doppler imager the high resolution doppler imager hrdi on the upper atmosphere research satellite uars has provided measurements of the horizontal wind field in the mesosphere and lower thermosphere mlt since november 1991 the observed dynamical patterns are dominated by the 1 1 diurnal tide but semidiurnal perturbations are also very prominent in the hrdi data particularly at latitudes greater than 40 this paper presents a preliminary study of the semidiurnal tide and discusses latitudinal and seasonal variations in the phenomenon regular seasonal changes are clearly detected and significant interhemispheric asymmetries have been identified in general the observed features are consistent with previous measurements and model results but some discrepancies have been found this new technique which brings a global perspective to the observation of mlt dynamics is complementary to the very detailed but localized radar data sets currently available and should provide important constraints for numerical models

interannual variations of the diurnal tide in the mesosphere generated by the quasi biennial oscillation 1 we report results from a study with the numerical spectral model nsm which produces significant interannual variations in the diurnal tide applying hines s doppler spread parameterization small scale gravity waves gws drive the quasi biennial oscillation qbo and semiannual oscillation with a gw source that peaks at the equator and is taken to be isotropic and independent of season the nsm generates a qbo with variable periods around 26 months and zonal wind amplitudes close to 25 m s 1 at 30 km as reported earlier the nsm reproduces the observed equinoctial maxima in the diurnal tide at altitudes around 95 km in the present paper it is shown that the qbo also modulates the tide such that the seasonal amplitude maxima can vary from one year to another by as much as 30 to shed light on the underlying mechanisms the relative importance of the linearized advection terms is discussed which involve the meridional and vertical winds of the diurnal tide these interactions generate pronounced qbo modulations of the tide at altitudes below 50 km in the mesosphere between 50 and 80 km the signature is not well defined because of interference from the seasonal variations at altitudes above 80 km however the qbo related interannual variations of the tide are again relatively large but they are generated primarily by gw momentum deposition since the period of the qbo is variable and its phase is relative to the seasonal cycle changes the magnitude of the qbo modulation of the tide in the upper mesosphere varies considerably as our long term model simulation shows this intermittency must be attributed to nonlinear interactions and gw drag momentum deposition is discussed as a potential candidate

entrainment at cold glacier beds here we present measurements of the gas content and isotopic composition of debris rich basal layers of a polar glacier meserve glacier antarctica which has a basal temperature of 17 c these measurements show that debris entrainment has occurred without alteration of the glacial ice and provide the most direct evidence to date that active entrainment occurs at the beds of cold glaciers without bulk freezing of water entrainment at subfreezing temperatures may have formed the u shaped trough containing meserve glacier in addition to possibly allowing some cold based glaciers to be important geomorphic agents entrainment at subfreezing temperatures provides a general mechanism for formation of the dirty basal layers of polar glaciers and ice sheets which are rheologically distinct and can limit the time span of ice core analyses furthermore accumulating evidence suggests that geomorphologists should abandon the assumption that cold based glaciers do not slide and abrade their beds