gravity wave variability and interaction with lower frequency motions in the mesosphere and lower thermosphere over hawaii abstract radar observations of the mesosphere and lower thermosphere over kauai hawaii have provided measurements of the horizontal wind field since september 1990 horizontal velocity variances in the gravity wave band of frequencies were computed for several averaging intervals over the entire dataset the results correlated with tidal and lower frequency winds show evidence of filtering of gravity waves by tidal and other lower frequency motions spectra of gravity wave variances for two years of data display peaks at planetary wave as well as tidal periods primarily near 12 24 48 h and 16 day periods the modulation of gravity wave variance during four distinct background regimes is examined one in which the diurnal tide predominates another in which the 2 day wave is large a third in which the zonal mean wind and tidal amplitudes are large and a fourth in which the zonal mean tidal and 2 day amplitudes are all small intervals in which the diurnal tide or the 2 day wave predominates s

transtensional origin of multi order cross folds in a high grade gneiss complex southwestern grenville province formation during post peak gravitational collapse the well mapped western part of the ottawa river gneiss complex orgc new name a large metamorphic core complex hosts a system of gently plunging cross folds of outcrop to regional scale situated in the ductile detachment zone between the lower grade cover and high grade core of the complex the cross folds are buckle structures that deform the attenuated gneissic layering plunge parallel to the regional elongation lineation range from upright to recumbent and exhibit distinctive hinge parallel elongation lineations all features of extension dominated ductile transtension our l s fabric data are consistent both with kinematic modelling that predicts progressive constrictional strain in the hinge zones of transtensional folds and with dynamic modelling that predicts rotation of flattened fold limbs into moderately dipping attitudes on the basis of petrologic data we show that cross folding postdated the peak ottawan metamorphism and took place during retrogression and exhumation of the thrust sheet stack the cross folds form an inclined system that is principally developed in retrograde melt weakened amphibolite facies rocks with the transtensional origin implying that exhumation and retrogression of the high grade core of the complex took place in an oblique extensional setting a transtensional origin for the cross folds removes the need to appeal to orogen parallel regional shortening an implausible requirement of previous interpretations and is compatible with data indicating that much of the visible fabric and structure of amphibolite facies domains of the orgc developed during post peak exhumation retrogression and gravitational collapse of the thrust sheet stack

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

bending anisotropy a mechanical constraint on the orientation of fold axes in an anisotropic medium abstract bending anisotropy is the property of a layer of material whereby it bends more easily in some directions than it does in others in macroscopically homogeneous layers bending anisotropy results from the material itself being rheologically anisotropic in the plane of the layering in this paper we investigate bending anisotropy in materials with orthorhombic symmetry and linear elastic or viscous behaviour although such models are rheologically simple we believe they may provide a first approximation to the behaviour of some tectonites with linear and planar fabrics thus we predict that in rocks with strong linear fabrics folds will form with axes nearly parallel to the linear fabrics for a variety of different stress fields this has important geological consequences

two day wave observations of uars microwave limb sounder mesospheric water vapor and temperature 1 a two day wave disturbance is observed in the mesospheric temperature and water vapor on the basis of new version data from the upper atmosphere research satellite microwave limb sounder using two data segments during the austral summers january february of 1992 and 1993 and the asynoptic mapping method a strong wave signal is identified as having zonal wave number 3 and a westward period of about 2 1 days the wave amplitudes are located near the core of the summer easterly jet with strongest wave amplitudes as large as 11 k and 0 35 part per million by volume near the mesopause the temperature and water vapor wave strengths are highly correlated in time but their peaks are almost longitudinally out of phase poleward heat flux associated with upward wave energy propagation in the southern hemisphere points to baroclinic instability as the cause for the wave appearance a growing wave signature in water vapor is observed in regions of strong meridional gradient of water vapor near the mesopause wave breaking is suggested as moist polar air is displaced into the much drier subtropics and wave amplitude decays

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

a general harmonic coordinate transformation to simulate the states of strain in inhomogeneously deformed rocks in order to investigate the possible states of strain that may exist in an inhomogeneously deformed body a general deformation is proposed in the form of a harmonic coordinate transformation this deformation differs from those previously considered by jaeger ramsay graham and hobbs in that it is capable of representing a wide variety of deformations previous efforts had inbuilt assumptions regarding the mechanism of deformation the transformation contains adjustable terms all of which have distinct geometrical significance some represent a homogeneous deformation some represent inhomogeneous shortening some represent inhomogeneous shear and others correspond to a pinch and swell type of deformation by combining these terms with different degrees of emphasis many kinds of deformation may be simulated in this paper two constraints are developed in conjunction with the general harmonic transformation these are the conditions for constant volume deformation both locally and generally and the condition for zero shear strain of lines initially normal to the distorted layer again both locally and generally

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

mean motions and tidal and two day structure and variability in the mesosphere and lower thermosphere over hawaii abstract an overview of the motion field and an analysis of the tidal and 2 day wave motions observed in the mesosphere and lower thermosphere over the central pacific from 1 october 1990 through 19 august 1992 is presented characteristics and interactions of motions at lower and higher frequencies will be addressed elsewhere wind measurements were obtained with an mf radar operating on kauai hawaii 22 n 160 w using the partial reflection drift technique results presented in this paper reveal a zonal mean motion reflecting the mesopause semiannual oscillation msao observed at more equatorial latitudes from january to july coinciding with the period during which the msao and the annual cycle of the zonal mean wind at higher latitudes are in phase eastward and westward maxima are 55 m s 1 below 80 km and 45 m s 1 near 85 km during the first year with maxima of 57 and 53 m s 1 during the second year and evidence of substantial interannual variability the second msao cycle is greatly suppresse

gravity wave induced anomalous potential vorticity gradient generating planetary waves in the winter mesosphere abstractthis study shows that gravity wave gw forcing gwf plays a crucial role in the barotropic baroclinic instability that is frequently observed in the mesosphere and considered an origin of planetary waves pws such as quasi 2 day and quasi 4 day waves simulation data from a gw resolving general circulation model were analyzed focusing on the winter northern hemisphere where pws are active the unstable field is characterized by a significant potential vorticity pv maximum with an anomalous latitudinal gradient at higher latitudes that suddenly appears in the midlatitudes of the upper mesosphere this pv maximum is attributed to an enhanced static stability that develops through the following two processes 1 strong pws from the troposphere break in the middle stratosphere causing a poleward and downward shift of the westerly jet to higher latitudes and 2 strong gwf located above the jet simultaneously shifts and forms an upwelling in the midlatitudes causing a significant increase in

evidence for a traveling two day wave in the middle atmosphere evidence is presented for the existence of a wave number 3 westward traveling 2 day oscillation in the temperature measurements made by the nimbus 5 scr and nimbus 6 pmr instruments the wave has largest amplitude in the mesosphere at low latitudes of the summer hemisphere and has a markedly asymmetrical meridional structure it is suggested that the wave may be a free wave similar to the 5 day wave identified in nimbus 5 scr data by rodgers 1976 the vertical structure shows little phase tilt and a slight indication of an increase in amplitude with height

interaction of dipole eddies with the western continental slope of the mozambique channel abstract sea level anomaly sla data were used to track a southward propagating eddy dipole along the western slope of the mozambique channel over some 6 months in april 2005 this dipole with the cyclone to the south was close to the continental slope off southern mozambique the contact zone between the contra rotating vortices and the slope was surveyed by ship using onboard s adcp and ctd lines the data showed strong 1 4 m s 1 southward geostrophic currents over the slope adjacent to the anticyclone with horizontal divergence over the shelf edge significant slope upwelling between the dipole and the shelf was evident concomitant with enhanced nutrient and chlorophyll levels enriching shelf near surface waters satellite observations depicted a 300 km long surface chlorophyll filament extending offshore in the frontal zone between the contra rotating vortices a satellite tracked drifter deployed at the coastal base of this filament confirmed the offshore advection of chlorophyll enriched shelf water which ultimately wrapped around the cyclone and filling its centre the slope upwelling was also clearly evident in hourly temperature data collected by a recorder deployed on a nearby reef zambia reef in a depth of 18 m according to the sla data the dipole took several weeks to pass zambia reef causing prolonged bouts of upwelling that finally ceased when it left the continental slope and moved southwards into the open ocean further analysis showed that lone anticyclones and cyclones against the mozambique continental shelf also induce slope upwelling as a result of horizontal divergence created by the radial circulation of the vortex in the case of cyclones the divergence occurs north of the contact zone overall this case study confirms that eddies moving southwards along the western side of the mozambique channel are the main mechanism for pumping nutrients into the otherwise oligotrophic surface waters and moreover provide a vigorous mechanism for shelf open ocean exchange

the origin of fold abutments in the map pattern of the westernmost grenville province central ontario abstract the westernmost part of the proterozoic grenville orogen widely interpreted as an aggregate of structural domains and subdomains has been subjected to superimposed disharmonic buckling on the scale of kilometres the domain boundaries are characterized by abutments of upright to overturned folds attributed by others to thrust induced truncation of inherited structures the present study shows that abutments on geological maps are fold termination lines which mark narrow zones of adjustment flow caused by buckle strain heterogeneity on the kilometre scale such adjustment zones are ductile equivalents of fold decollement surfaces in the brittle upper crust and are normally characterized by high strain gradients prominent adjustment zones may be located within strain softened rocks at domain boundaries coincident with major ductile thrusts

the 2 day wave in the middle atmosphere observations and theory a recurrent global scale 2 day oscillation in the middle atmosphere is well documented in a variety of data sources meteor wind partial reflection satellite and rocketsonde the observed period is almost invariably near 2 1 days and the zonal structure has been established as a westward propagating wave number 3 mode observations also indicate that the meridional wind component maximizes near the equator and dominates the wind field at low latitudes these features suggest the disturbance s identification with the wave number 3 rossby gravity normal mode of a windless isothermal atmosphere such modes are found to exist largely independent of the mean fields the eigenperiods are only modestly altered by mean wind variations on the lowest three scale heights and the influence on the mode structure is local the vertical growth of amplitude is enhanced in regions of weak westerly wind relative to the wave and equatorward temperature gradient while the vertical growth rate is retarded and amplitudes may even decay in regions of strong westerlies or poleward temperature gradient in realistic mean fields the third rossby gravity mode has magnified responses very near 2 25 days in both equinox and solstice conditions the horizontal structure remains largely intact in the lowest levels however considerable asymmetry is introduced in the solstice upper stratosphere and mesosphere by the magnified vertical growth of amplitude in the summer hemisphere the latter results from the moderate easterlies and equatorward temperature gradient characteristic of the region as for the simple eigenstructure the meridional wind component in this region maximizes near the equator and dominates the wind field up to mid latitudes

the quasi 2 day wave observed in the polar mesosphere 1 using mf radar data obtained at tromso 69 6 n 19 2 e for 37 months between 1 november 1998 and 8 december 2001 we have examined characteristics of the quasi 2 day wave q2dw in the polar mesosphere in the height range from 70 to 91 km the activity of the q2dw is higher in winter months november february than in summer months may august over this height region the maximum values of the amplitude are 25 m s 1 in winter and 15 m s 1 in summer between 70 and 82 km the amplitude appears to maximize near winter solstice over the 3 years the average ratio of meridional to zonal amplitudes is 1 1 1 2 over the height region thus there is no significant preference towards either components the variations of the periods of maximum amplitude are also examined and periods with 45 2 and 54 9 hours occur more frequently than those with 48 0 and 51 2 hours however no clear seasonal trend of the variation of the period is found in addition the amplitude is modulated at 4 10 day rate with simultaneous observational data from the mf radar and the eiscat uhf radar colocated in tromso we have examined whether or not the q2dw was able to penetrate to the lower thermosphere for the period of 1 9 july 1999 it is found that the amplitude of the q2dw with period of 51 2 hours maximized at 95 km height with values of 25 m s 1 in both meridional and zonal components the q2dw was attenuated above 95 km but it appears to survive up to 108 km height in the meridional component between 85 and 95 km for the meridional component during this 8 day interval the q2dw and semidiurnal tide were the strongest among the periodic components

the 2 day wave during the boreal summer of 1994 1 the 2 day wave during the boreal summer of 1994 was observed using stratospheric analyses from the british met office and at mesospheric heights using medium frequency mf radars and the microwave limb sounder mls and high resolution doppler imager hrdi satellite instruments most of the evidence from our study points to a high latitude source for the boreal 2 day wave event we observed we found little evidence for a connection between the 2 day wave event in the mesosphere and activity at lower altitudes instead we contend that the 2 day wave observed at upper mesospheric heights was excited in situ this event was predominantly zonal wave number 2 was highly localized in time and the disturbance propagated equatorially from high northern latitudes at stratopause and lower mesospheric heights the largest 2 day wave amplitudes were seen at high southern hemisphere latitudes i e in the winter hemisphere however the austral winter 2 day wave was trapped and did not penetrate to upper mesospheric heights

coordinated global radar observations of tidal and planetary waves in the mesosphere and lower thermosphere during january 20 30 1993 a multi instrument global campaign involving incoherent scatter medium frequency and meteor wind radars was conducted during the period of january 20 30 1993 to study the dynamics of the mesosphere and lower thermosphere data obtained from 15 radar stations covering a wide latitude range have been used to determine the global distribution of planetary and tidal waves during this 10 day campaign spectral analysis of the neutral winds measured by the radars in the altitude range from 80 to 130 km indicates the existence of a strong 48 hour wave near 90 km at latitudes between 40 n and 40 s that is present up to 108 km at 18 n the semidiurnal tide is large at middle and high latitudes near 90 km and is predominant above 110 km while the diurnal tide is observed to be particularly important in the upper mesosphere near 40 latitude a least squares fit to the radar data is performed to obtain the amplitudes and phases of the tidal and 48 hour waves comparison with national center for atmospheric research thermosphere ionosphere mesosphere general circulation model shows that the predictions from the model agree reasonably well with the observed global morphology of tidal wave amplitudes

a statistical analysis of the propagating quasi 16 day waves at high latitudes and their response to sudden stratospheric warmings from 2005 to 2018

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

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

observations of the 2 day wave in nmc stratospheric analyses abstract observational characteristics of the 2 day wave a westward propagating zonal wave 3 oscillation in the summer subtropical upper stratosphere and mesosphere are studied based on five years of national meteorological center nmc operational stratospheric analyses these data show episodic occurrence of the 2 day wave in the upper stratosphere in january centered near 20 s and july august centered near 20 n these episodes are strongly correlated with observed reversals of the zonal mean potential vorticity gradient near the core of the summer easterly jet consistent with previous suggestions that the 2 day wave is generated by an in situ instability of this jet on the other hand the horizontal and vertical structure of the waves is very similar to that calculated by salby for a global normal mode rossby wave the combination of normal mode structure and instability signature suggests that the 2 day wave is a near resonant mode forced by dynamical instability

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

the solid body tilt of deformed paleohorizontal planes application to an archean transpression zone southern canadian shield abstract the solid body tilt sbt of deformed paleohorizontal planes is equal to the angle between their unstrained top direction and an upward pointing vertical axis kinematic models of important tectonic processes such as transpression and ductile thrusting have specific sbt requirements these models can be tested in ancient and modern orogens by determining the actual sbt of strata early magmatic sills and late horizontal intrusions with relict primary layering classical transpression models predict that except for sheath structures all folds in bedding be upright and horizontal i e that sbt values be close to zero within the hinge zones moreover all passive folding is accomplished by amplification of asperities and caused by the pure shear component of the transpression tensor nine sbt analyses were made in the archean crust of northwest ontario to test the transpression hypothesis north of the quetico wabigoon boundary western superior province central canada the nine sbt values do not discredit the hypothesis that the quetico fault marks an archean transpression zone which included the wabigoon rocks adjacent to the quetico metasediments

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

strain patterns of crescentic granitoid plutons in the archean greenstone terrain of ontario abstract granitoid plutons of crescentic outcrop pattern in the archean terrain of northwestern ontario are dominated by constrictive strains that are interpreted to be due to intrusion rather than regional deformation the strain patterns of antiformal plutons are characterized by subvertical lineations in contrast the strain patterns of synformat plutons are characterized by subhorizontal lineations presumably only the last flow increments were recorded by the deformed mineral aggregates employed as strain gauges and occurred when the granitoid magma was largely crystalline simple kinematic models are capable of explaining many but not all elements of the natural strain patterns

strain in an archean greenstone belt of minnesota abstract we measured strain at more than 60 locations in metasedimentary and metavolcanic rocks of the vermilion district an e w trending archean greenstone belt in minnesota strain ellipsoid orientations and shapes correlate strongly with n s location in the belt but magnitudes do not flattening strains occur near the present vermilion fault which bounds the greenstone belt to the north with constrictional strains to the south the observed strain patterns can be mathematically modeled by deformation paths which produce the flattening strains with west plunging 1 axes by dextral shear of the constrictional strains with east plunging 1 axes using reasonable geologic constraints the shear plane must dip to the north with a subhorizontal shear direction structures throughout the district also indicate dextral shear a geometrical finite element program uses the measured strains to destrain the rocks and find the configuration which most closely satisfies strain compatibility equations the linear e w strain patterns and minor rotations about horizontal axes during the deformation preclude origin of the greenstone belt by infolding and shear off the flanks of a rising granitic diapir by accounting for rotations which result in the deformed curvature of the original surface a true estimate of 50 n s shortening across the belt can be made the data and deformation models favor the origin of the vermilion district rocks at a convergent margin most likely as a n dipping subduction zone complex with shallow slab dip the origin of the constrictional strains remains enigmatic

radar observations of longitudinal variability of tidal planetary waves and mean motions in the tropical mesosphere during the summer of 1995 two mf radars located at hawaii and puerto rico were in operation to measure mesospheric motions we use the data obtained at the two sites to study the longitudinal variability of mean winds planetary waves and tides on average the winds at puerto rico were more westward and equatorward than those at hawaii quasi 2 day planetary wave activity was evident most of the time from june 28 to july 25 the quasi 2 day wave had a zonal wave number m of 3 during one occasion and 4 during another and the periods of the two planetary waves were 56 and 48 hours respectively the diurnal tide at puerto rico was stronger than that at hawaii above 86 km and the semidiurnal tide at hawaii was strongly damped in the altitude range of 90 98 km both the semidiurnal and the diurnal tides were apparently modulated by longer period waves which was perhaps the most important factor in accounting for their large spatial and temporal variability the phase difference at the two sites deviates considerably from the expectation of purely migrating tides

measurement of momentum fluxes near the summer mesopause at poker flat alaska abstract observations of the motion field near the summer mesopause using the poker flat mst radar in a symmetric six beam configuration during 8 days of july 1986 were used to examine the mean structure the wave variances and the momentum fluxes due to gravity wave and tidal motions our results reveal a mean horizontal wind structure generally consistent with previous observations but with considerable daily variability and large mean shears particularly significant is a mean downward eulerian vertical velocity of 0 3 m s 1 which implies a significant upward flux of wave energy horizontal and vertical velocity variances are found to be 1500 and 6 m2 s 2 and to remain nearly constant with height momentum flux measurements reveal a largely zonal mean flux of 5 to 15 m2 s 2 that achieves a maximum just below the height of wind reversal daily mean values on the other hand exhibit large variability with maxima as large as 30 to 40 m2 s 2 hourly momentum flux profiles were found to achieve m

nappe emplacement direction in the central gneiss belt grenville province ontario canada evidence for oblique collision abstract the proterozoic grenville province in canada is widely regarded as a compressional orogen in which thrust transport occurred towards the northwest perpendicular to the orogenic front new structural data from an area near parry sound ontario lead to a re evaluation of this interpretation nappe structures in this area are consistent with northeast rather than northwest directed thrusting and imply that the southwestern part of the province experienced an early sinistral oblique collision which predated the emplacement of the 1 24 ga sudbury dike swarm two nappe piles which contain different rock types and have distinct stacking sequences are separated by a lateral ramp or ductile tear fault that coincides with the interior of the parry sound domain of davidson et al 1982 early nappes and associated structures f 1 are overprinted by nw se striking upright folds f 2 that formed between about 1 16 and 1 12 ga these later folds partially reorient rotated feldspar porphyroclast systems that formed during nappe emplacement and have axes that are consistently parallel to a well developed mineral lineation the orientation of this lin lineation reflects the two stage deformation history of the area rather than the thrusting direction during a single orogenic event

two day wave structure and mean flow interactions observed by radar and high resolution doppler imager data obtained with four mf and meteor radars at equatorial and subtropical sites and with the high resolution doppler imager hrdi instrument aboard the uars satellite were used to examine the structure wave mean flow interactions and potential sources of the 2 day wave in the middle atmosphere during three southern hemisphere summers the three wave events were highly transient having typical durations of 20 to 30 days and exhibiting modulation at shorter periods temporal variations were found to exhibit good correlations between radar and hrdi data radar and hrdi data were used to estimate those components of the eliassen palm flux that could be assessed with these data meridional fluxes of momentum and heat were computed using hrdi data and agree reasonably with the momentum fluxes computed from radar data at discrete locations these fluxes were found to exhibit consistent latitudinal structures each year suggesting systematic wave excitation and wave mean flow interactions meridional momentum flux gradients were seen to be anticorrelated with zonal wind accelerations in a manner consistent with wave forcing of the large scale circulation the apparent wave mean flow interactions suggest that the 2 day wave could be a transient response to baroclinic instability of the summer hemisphere mesospheric jet a calculation of the meridional gradient of quasi geostrophic potential vorticity using hrdi winds and the cospar international reference atmosphere cira 1986 temperatures exhibits a region of instability in the lower and middle mesosphere extending into subtropical latitudes and provides additional evidence of a possible source of this motion via baroclinic instability of the summer hemisphere jet structure

recognition of pervasive prestrain in the total strain pattern of large folds abstract two methods are introduced for identifying states of pervasive prefold strain in the total strain field of large domes or basins the first method relies on the symmetry rule and is restricted to structures in which the planes of effective symmetry of the total strain field are non coincident with those of the fold form the second method seeks to demonstrate the existence of a strain induced anisotropy foliation or lineation prior to upright folding and utilizes narrow decollement zones within homogeneous rock units of domes or basins the methods are applied to large oval structures in two precambrian gneiss terranes of ontario

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

a connection between the south equatorial current north of madagascar and mozambique channel eddies 1 combining high resolution model output and geostrophic currents derived from satellite altimeter data it is shown that the formation of mesoscale eddies in the mozambique channel mzc is connected to variability in the transport of the south equatorial current sec lagged cross correlations of the currents north of madagascar and vorticities in the mzc combined with a composite analysis of the model output show that eddies form in the narrows of the channel approximately 20 weeks following a westward transport pulse in the sec a relationship between mzc eddies and the large scale variability of the south indian ocean may have downstream impacts on the agulhas leakage the atlantic meridional overturning circulation and thus climate

the quasi two day wave event of january 1984 and its impact on the mean mesospheric circulation abstract studies of the quasi two day wave show that it is a summertime phenomenon in the summer of 1983 84 at adelaide 35 s 138 e the main phase of the wave appeared as a pulse in mid january which lasted about seven cycles 14 days coincident with the onset of the pulse a temporary but substantial change occured in the prevailing circulation throughout a deep layer of the upper mesosphere a perturbation of more than 10 m s 1 occurred in the northward flow whereas the change in the zonal flow about 30 m s 1 westward actually caused a reversal of the prevailing eastward simulation above 84 km it is suggested that these changes in the prevailing circulation were a response to the wave pulse a simple calculation is performed to estimate the anticipated response to the observed wave event under plausible assumptions about the magnitude of mean and eddy dissipation processes predicted circulation changes agree reasonably well with those observed it is concluded that such events have a substan

interplay between folding and ductile shearing in the proterozoic crust of the muskoka parry sound region central ontario grenville gneiss of the central georgian bay region was subjected to ductile deformation that produced narrow mylonite zones as well as three sets of superimposed folds differing greatly in structural signature size and orientation some mylonite zones are concordant to gneissosity and are repeatedly folded others cut gneissosity and postdate the folding gneissosity was generated as a regionally subhorizontal feature either by crustal thinning or like the early mylonite zones by low angle reverse shearing an attempt is made to account for the initially subhorizontal gneissosity the mylonite zones and the folds in a regime of large scale reverse shearing that strikes parallel to the grenville front upright northwest southwest to north south buckle folds dominate the map pattern and are subperpendicular to the reverse grenville front boundary fault these set 2 folds cannot be attributed to reverse simple shearing but require a large component of east west compression such stress could have been

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

influence of pre or post diapiric deformation on the foliation and strain pattern of a diapiric ridge abstract foliation and total strain patterns of diapiric structures are very sensitive to pre or post diapiric deformation this is illustrated quantitatively by superimposing homogeneous pure and simple shear on mareschal and west s 1977 finite element model of an antiformal diapiric ridge in models with post diapiric homogeneous deformation type 1 the foliation patterns typical for diapirism are obliterated in models with pre diapiric homogeneous deformation type 2 diapiric deformation was too weak to overprint pre diapiric foliation patterns however total strain patterns can be used successfully for identifying a diapiric component in the deformation history of both type 1 and type 2 models provided post or pre diapiric deformation is not too high

the quasi 2 day wave observed in the polar mesosphere comparison of the characteristics observed at tromso and poker flat 1 a comparison of the quasi 2 day wave q2dw observed at tromso 69 6 n 19 2 e and poker flat 65 2 147 6 w is presented at four heights of 70 76 82 and 88 km using wind data taken for 4 years from 1 november 1998 to 7 november 2002 the characteristics of the q2dw such as seasonal variation occurrence of period of maximum amplitude ratio of meridional to zonal amplitudes shape of altitude profile of phase and modulation of amplitude at a 4 10 days rate found at poker flat are very similar to those found at tromso reported by nozawa et al 2003 the activity of the q2dw is higher in winter than in summer for meridional and zonal components at the two sites long term variation i e seasonal variation of the q2dw is found to be similar between the two sites while short term variations i e over several days do not synchronize well with each other the ratio of amplitudes of the q2dw between the two sites varies mainly between 0 5 and 2 and there is no significant preference toward either site phase differences of q2dws between the two sites are examined and it is found that in phase like events are more frequently seen than out of phase like events at 76 82 and 88 km in winter and at 88 km in summer this can be interpreted to mean that the zonal wave number of the q2dw appears to be 2 or 4 more often than 3 in the polar upper mesosphere these results suggest that observed q2dws have features consistent with the rossby gravity wave mode but the amplitude and phase of the q2dw are affected significantly by local sources a possibility that the observed q2dw is an eastward moving wave is also discussed

estimated obliquities between the horizontal traces of x y surfaces and foliation trajectories in strained orthogneiss abstract the geometrical style of mineral foliation varies greatly within deformed metaplutonic masses and the angle between foliation trajectories and horizontal traces of x y surfaces of total strain depends largely on this variation in laminated orthogneiss derived from protoliths with isolated megacrysts or polycrystalline aggregates the foliation trajectories can be markedly oblique to the traces of the x y surface the obliquity angle depends on 1 the boundary migration of mineral aggregates 2 the finite strain accumulated during the production of laminae and 3 the finite deformation imposed on laminated gneiss prediction of the obliquity angle is difficult because 1 and 2 are effectively unknown and 3 varies greatly with position by assuming that i all isolated aggregates behave as if they deform coaxially while being transformed into laminae and ii all laminae rotate as passive markers we were able to calculate the obliquity angle for a range of laminae producing strains and a spectrum of imposed plane deformations these results apply to rocks located on the symmetry planes of large folds and x z sections of shear zones here the obliquity between foliation trajectory and the horizontal trace of x y plane is 2 4 even if the laminae producing strain is as low as 2 0

the two day wave in eos mls temperature and wind measurements during 2004 2005 winter 1 two day wave observations during january march 2005 are reported using the recently launched microwave limb sounder mls aboard nasa s earth observing system aura mission wave induced disturbances in temperature water vapor carbon monoxide and mls line of sight wind appear in early january peak near the end of january and persist until late february temperature and wind amplitudes as large as 9 k and 50 m s are observed near 90 km the wave disturbance is initially confined in the mid to low summer latitudes where the climatological summer easterly jet exhibits strong shear the wave then develops features akin to the third rossby gravity global normal mode with a weak temperature disturbance in the winter hemisphere anti symmetric about the equator and wind disturbance over the equator strong wind perturbation episode around 17 23 january 2005 in the mid latitude southern hemisphere coincides with a particularly intense solar proton event