estimates of momentum flux in the mesosphere and lower thermosphere over adelaide australia from march 1985 to february 1986 in order to balance the momentum budget of the mesosphere it is necessary to have a source of momentum in that region to drive the observed meridional circulation thus measurements of mesospheric momentum flux are fundamental to our understanding of the dynamics of the mesosphere the first measurements of momentum flux in this region did not adequately take into account the effect of aspect sensitivity on the effective pointing angle of a radar beam and were therefore incorrect by some factor in this paper a method of determining the pointing direction of a radar beam from the spatial correlation function of the echoes is presented and applied to a data set that spans a year beginning in march 1985 momentum fluxes during twelve 4 day periods thoughout the year are calculated using these improved pointing angle calculations and a new outlier rejection scheme the results representing a significant expansion of the worldwide mesospheric momentum flux data set are then presented

influence of solar and lunar tides on the mesopause region as observed in polar mesosphere summer echoes characteristics long term observations of polar mesosphere summer echoes pmse from 2002 to 2012 are investigated with the aim to statistically study the effects of solar thermal migrating and lunar gravitational tides on aerosol layers and their environment at altitudes 80 90 km the solar and lunar tidal periodicities are clearly present in pmse data for the first time both amplitudes and phases of solar and lunar tides are estimated using pmse data from the esrad radar located at esrange sweden the diurnal semidiurnal and terdiurnal solar migrating tides show pronounced periodicities in the pmse strength and wind velocity components lunar tides demonstrate clear oscillations in the pmse strength and wind velocities as well canonical lunar gravitational tides corresponding to the lunar gravitational potential produce rather large amplitudes and are comparable to the solar thermal tides whereas noncanonical lunar oscillations have minor effects on pmse layers but are still statistically significant the influence of diurnal semidiurnal tides and monthly semimonthly tidal components is studied separately our estimations of solar thermal and lunar tidal amplitudes are in good agreement with those of previous model and experimental studies a new mechanism of quadratic demodulation of the solar semidiurnal and lunar semidiurnal tides is shown to be valid at the summer mesopause and can explain periodical pmse oscillations due to the lunar synodic semimonthly tide with period of 14 77 days two harmonics with periods of 27 0 and 13 5 days supposedly representing the solar rotation cycle are also clearly present in pmse data

lunar tides in the thermosphere ionosphere electrodynamics general circulation model lunar semidiurnal tides are introduced at the lower boundary of the national center for atmospheric research thermosphere ionosphere electrodynamics general circulation model tiegcm the tides are derived from the model of vial and forbes 1994 and interesting properties of these tides are found when they are subjected to hough decomposition there is considerable hemispherical antisymmetry in the september tides and the march and september modal compositions are significantly different a differencing method is used to isolate the lunar tidal effects in the tiegcm and these are compared with lunar tidal analyses of ionospheric data the model reproduces the broad features of the lunar tide in f0f2 maximum frequency of the f region with phase changes around 7 magnetic dip latitude during daytime the model and data analysis both give variations of the amplitude and phase of the lunar tide with local time near the equator the variation of phase with local time changes with latitude as the equatorial anomaly develops during the day comparison between the model predictions and analyses of data at observatories at midlatitudes produces mixed results here the effects of the lunar components of both electrodynamic drifts and of neutral winds need to be taken into account several cases of day to night changes in the phase of the lunar tide in f0f2 are noted large nighttime amplitudes of the lunar tide in hmf2 height of the maximum density more than 4 km seem to be due to inphase action of the electrodynamic and neutral wind effects while during daytime they are out of phase the lunar tide in the ratio of oxygen to nitrogen density o n2 is estimated and found to be of relatively minor importance amplitudes of the lunar tide in f0f2 may be measured at more than 0 4 mhz at some local times but the model values are less than this comparison is also made with ion drift measurements made by the san marco d satellite the several uncertainties which underlie this work are discussed in detail

improving local earthquake locations using the l1 norm and waveform cross correlation application to the whittier narrows california aftershock sequence experiments with different earthquake location methods applied to aftershocks of the october 1 1987 whittier narrows earthquake in california ml 5 9 suggest that local event locations can be greatly improved through the use of the l1 norm station corrections and waveform cross correlation the whittier narrows sequence is a compact cluster of over 500 events at 12 to 18 km depth located within the dense station coverage of the southern california seismic network scsn a telemetered network of several hundred short period seismographs scsn travel time picks and waveforms obtained through the southern california earthquake center are examined for 589 earthquakes between 1981 and 1994 in the vicinity of the mainshock using a smoothed version of the standard southern california velocity model and the existing travel time picks improved location accuracy is obtained through use of the l1 norm rather than the conventional least squares l2 norm approach presumably due to the more robust response of the former to outliers in the data a large additional improvement results from the use of station terms to account for three dimensional velocity structure outside of the event cluster to achieve greater location accuracy waveforms for these events are resampled and low pass filtered and the p and s wave cross correlation functions are computed at each station for every event pair for those events with similar waveforms differential times may be obtained from the cross correlation functions these times are then combined with the travel time picks to invert for an adjusted set of picks that are more consistent than the original picks and include seismograms that were originally unpicked locations obtained from the adjusted picks show a further improvement in accuracy location uncertainties are estimated using a bootstrap technique in which events are relocated many times for sets of picks in which the travel time residuals at the best fitting location are used to randomly perturb each pick improvements in location accuracy are indicated by the reduced scatter in the residuals smaller estimated location errors and the increased tendency of the locations to cluster along well defined fault planes median standard errors for the final inversion are 150 m in horizontal location and 230 m in vertical location although the relative locations within localized clusters of similar events are better constrained seismicity cross sections resolve the shallow dipping fault plane associated with the mainshock and a steeply dipping fault plane associated with a ml 5 3 aftershock these fault planes appear to cross and activity began on the secondary fault plane prior to the large aftershock

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

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

a study of the equinox transition in the ionosphere above buenos aires 34 5 s 58 5 w and canberra 35 3 s 211 w as observed in the height of the f2 layer the equinox transition et in the thermosphere is analyzed on the basis of the hmf2 parameter for two southern hemisphere mid latitude ionosonde stations with 152 longitudinal separation buenos aires and canberra the period under study covers august 1 to october 31 1984 thus including the equinox transition study core period such a sample is necessary for the correct interpretation of long lasting trends et features are observed at both locations but important longitudinal differences are evident harmonic analysis of the data performed to separate 24 12 and 8 hour oscillations shows reasonable agreement with meridional tidal wind models particularly with respect to phases results indicate that the et is a gradual phenomenon not restricted to the core period but starting before it with respect to the longitudinal differences the most prominent one is the difference in the amplitude of the 12 hour oscillation which is of greater magnitude over buenos aires than canberra by at least a factor of 3 the 8 hour oscillation at both locations shows a progressive increase in amplitude fluctuations after the core period with a poor correlation between sites thus suggesting an important contribution due to local origin

analysis of sustained long period activity at etna volcano italy abstract following the installation of a broadband network on mt etna sustained long period lp activity was recorded accompanying a period of total quiescence and the subsequent onset of the 2004 2005 effusive episode from about 56000 events detected by an automatic classification procedure we analyse a subset of about 3000 signals spanning the december 17th 2003 september 25th 2004 time interval lp spectra are characterised by several unevenly spaced narrow peaks spanning the 0 5 10 hz frequency band these peaks are common to all the recording sites of the network and different from those associated with tremor signals throughout the analysed time interval lp spectra and waveforms maintain significant similarity thus indicating the involvement of a non destructive source process that we interpret in terms of the resonance of a fluid filled buried cavity polarisation analysis indicates radiation from a non isotropic source involving large amounts of shear concurrently with lp signals recordings from the summit station also depict very long period vlp pulses whose rectilinear motion points to a region located beneath the summit craters at depths ranging between 800 and 1100 m beneath the surface based on a refined repicking of similar waveforms we obtain robust locations for a selected subset of the most energetic lp events from probabilistic inversion of travel times calculated for a 3d heterogenous structure lp sources cluster in a narrow volume located beneath the summit craters and extending to a maximum depth of 800 m beneath the surface no causal relationships are observed between lp vlp and tremor activities and the onset of the 2004 2005 lava effusions thus indicating that magmatic overpressure played a limited role in triggering this eruption these data represent the very first observation of lp and vlp activity at etna during non eruptive periods and open the way to the quantitative modelling of the geometry and dynamics of the shallow plumbing system

man induced low frequency seismic events in italy unconventional seismic events in italy are detected by scanning three years of continuous waveforms recorded by the italian national seismic network cross correlation of signal templates with continuous seismic records has evidenced unusual events with similar low frequency characteristics in several italian regions spectral analysis and spatiotemporal distribution of these events some of which are previously interpreted as tectonic long period transients suggest that they are not natural but produced by huge cement factories since there are at least 57 full cycle cement plants operating in italy each affecting areas of about 1250 to 2800 km2 we argue that significant portions of the italian territory 23 to 51 can be affected by this man made noise seismic noise analyses such as those used for microzonation or crustal structure investigations as well as data mining techniques used to retrieve anomalous transient signals should thus take into account this peculiar and pervasive source of seismic waves

radar observations of prevailing winds and waves in the southern hemisphere mesosphere and lower thermosphere hf radar stations utilizing the spaced antenna partial reflection technique located at adelaide 35 s 138 e and mawson station 67 s 63 e have observed horizontal mesospheric winds continuously since mid 1984 observations in the period 1984 87 are compared with the northern hemisphere latitude conjugate stations of kyoto 35 n 136 e and poker flat 65 n 147 w and with satellite derived circulation models particular reference is made to the equinoctial changeovers in zonal flow and to the temporal and altitude variations in the planetary wave activity at mawson and adelaide

characteristics of semidiurnal tides observed by the kyoto meteor radar and saskatoon medium frequency radar we have compared seasonal variations of semidiurnal tides in the upper middle atmosphere observed by the kyoto meteor radar and the saskatoon medium frequency partial reflection radar in 1983 1985 amplitudes of semidiurnal tides are generally larger at saskatoon than at kyoto seasonal variations of phases at 90 km agree fairly well for both zonal and meridional components between kyoto and saskatoon the seasonal variation is mainly composed of two fundamental states appearing in summer centered april may september october and winter centered months november february march which are characterized by long and relatively short vertical wavelengths respectively clear transitions between the two states occur in equinoxes february april and october november using determinations at kyoto and saskatoon with 4 to 5 day observation intervals we have studied the behavior of semidiurnal tides during the transitions in october november in 1983 1985 and february april in 1985 precise comparisons have shown that the transitions are slightly delayed at saskatoon in both vernal and autumnal equinoxes abrupt changes in phases of semidiurnal tides coincide with reduction and pulsating fluctuations of their amplitudes suggesting the existence of interference between fundamental and higher modes which are dominant in summerlike and winterlike months respectively

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

a low angle normal fault in the umbria region central italy a mechanical model for the related microseismicity abstract in the northern apennines the upper crust is thinned by a set of east dipping low angle normal faults lanfs the easternmost and more recent of these lanfs is the altotiberina fault atf located in northern umbria the geometry of the atf has been reconstructed matching surface geology with seismic reflection profiles and borehole data the fault whose average dip is 20 borders the upper pliocene quaternary tiber basin and has a displacement of about 8 km the deeper portion of the atf is located below the axial zone of the northern apennines where the strongest instrumental and historical seismicity is recorded the microseismicity of the region m 1 to evaluate the boundary conditions for the brittle activity of the atf the fault can be reactivated for low values of differential stress 1 3 t 10 mpa and tensile fluid overpressure p f 3 e g v 0 93 in the peculiar situation of the northern apennines the deep emissions of large amounts of co 2 documented in the area can be entrapped in their ascent by structural seals e g atf favouring localised fluid overpressures the impossibility of sustaining p f 3 for wide fault portions counteracted by hydraulic fracturing increased permeability under low effective stress and load weakening behaviour for normal faulting would prevent the nucleation of moderate ruptures along the fault the short lived attainment of p f 3 along small fault portions can account for the microseismic activity located along the atf which occurs on rupture surfaces in the range of 10 1 10 3 km 2

global structure of the lunar tide in ionospheric total electron content 1 the global structure of the lunar tide in the ionosphere is studied based on observations of the global positioning system gps total electron content tec the unprecedented spatial and temporal resolution afforded by the gps tec observations enables illustration of the latitude longitude solar local time and seasonal variability of the lunar tide in the ionosphere based on analysis of the multi year mean from 1999 2008 the dominant component is generally the semidiurnal lunar tide however a significant diurnal variation is also observed in some instances the semidiurnal component achieves a maximum amplitude of 6 in the equatorial ionization anomaly crest regions and a slight hemispheric asymmetry is present with larger amplitudes in the northern hemisphere furthermore the maximum amplitudes in the semidiurnal lunar tide are found to occur during northern hemisphere winter and during 9 15 solar local time during certain years a secondary maxima in solar local time is also observed demonstrating the influence of the lunar tide on the prereversal enhancement lastly the observations reveal significant longitudinal variability in the semidiurnal lunar tide that is most prominent between november and february the presence of a longitudinal variation reveals the existence of nonmigrating components in addition to the dominant migrating semidiurnal lunar tide

seismic tremor at the 9 50 n east pacific rise eruption site ocean bottom seismic observations within the 9 50 n region of the east pacific rise indicate persistent low amplitude tremor activity throughout the october 2003 through february 2007 period of monitoring these signals exhibit either monochromatic or polychromatic spectral characteristics with a 6 hz fundamental frequency and up to two harmonics individual events cannot be correlated between nearby 1 km stations implying the presence of multiple small amplitude sources positioned within the shallow crust tremor exhibits a semidiurnal periodicity with some stations recording activity during times of increasing tidal extension and others detecting tremor signals during times of increasing compression the amplitude duration and rate of activity also correlate positively with fortnightly changes in the amplitude of the tides these spatiotemporal patterns are consistent with tremor generation in response to tidally modulated fluid flow within a network of shallow cracks tremor energy flux is spatially and temporally heterogeneous however there are extended periods of greater and lesser activity that can be tracked across portions of the array despite their shallow crustal origin changes in tremor amplitude and spectral character occur in the months prior to a major microearthquake swarm and inferred seafloor spreading event on 22 january 2006 with an increase in the degree of correlation between tremor activity and tidal strain in the weeks leading up to this event after the spreading event two eruption surviving stations near the axis continue to show high rates of tremor activity whereas these signals are suppressed at the single station recovered from the near axis flanks this off axis quiescence may result from the dike induced closing of cracks or perhaps from the emplacement of impermeable flows near the station

surface melt induced acceleration of greenland ice sheet flow ice flow at a location in the equilibrium zone of the west central greenland ice sheet accelerates above the midwinter average rate during periods of summer melting the near coincidence of the ice acceleration with the duration of surface melting followed by deceleration after the melting ceases indicates that glacial sliding is enhanced by rapid migration of surface meltwater to the ice bedrock interface interannual variations in the ice acceleration are correlated with variations in the intensity of the surface melting with larger increases accompanying higher amounts of summer melting the indicated coupling between surface melting and ice sheet flow provides a mechanism for rapid large scale dynamic responses of ice sheets to climate warming

upper mesospheric lunar tides over middle and high latitudes during sudden stratospheric warming events in recent years there have been a series of reported ground and satellite based observations of lunar tide signatures in the equatorial and low latitude ionosphere thermosphere around sudden stratospheric warming ssw events this lower atmosphere ionosphere coupling has been suggested to be via the e region dynamo in this work we present the results of analyzing 6 years of hourly upper mesospheric winds from specular meteor radars over a midlatitude 54 n station and a high latitude 69 n station instead of correlating our results with typical definitions of ssws we use the definition of polar vortex weaking pvw used by zhang and forbes 2014 this definition provides a better representation of the strength in middle atmospheric dynamics that should be responsible for the waves propagating to the e region we have performed a wave decomposition on hourly wind data in 21 day segments shifted by 1 day in addition to the radar wind data the analysis has been applied to simulations from whole atmosphere community climate model extended version and the thermosphere ionosphere mesosphere electrodynamics general circulation model our results indicate that the semidiurnal lunar tide m2 enhances in northern hemispheric winter months over both middle and high latitudes the time and magnitude of m2 are highly correlated with the time and associated zonal wind of pvw at middle high latitudes m2 in the upper mesosphere occurs after before the pvw at both latitudes the maximum amplitude of m2 is directly proportional to the strength of pvw westward wind we have found that m2 amplitudes could be comparable to semidiurnal solar tide amplitudes particularly around pvw and equinoxes besides these general results we have also found peculiarities in some events particularly at high latitudes these peculiarities point to the need of considering the longitudinal features of the polar stratosphere and the upper mesosphere and lower thermosphere regions for example during ssw 2009 we found that m2 enhances many days before pvw which is not in agreement with most of our results

the semi diurnal tide at the equinoxes mf radar observations for 1978 1982 at saskatoon 52 n 107 w abstract observations of the semi diurnal atmospheric tide have been made on a continuous daily basis since september 1978 by a medium frequency mf radar the monthly mean zonal winds and tidal amplitudes and phases 70 110 km are shown here for each month of the autumn and spring equinoxes 1981 82 and compared with previous years a very regular and dramatic tidal pattern emerges with march and november being winter like and the remaining four months being more summer like wavelengths for the latter are 60 95 km intermediate between winter 45 km and summer 180 km values the less systematic and extended observations from other north american and european radar systems are consistent with these results when they are treated on a monthly rather than a seasonal basis the equinoctial spectral model of walterscheid and devore 1981 which uses improved heating rates and realistic mean winds and temperatures is compared with the new observations the model is quite successful in producing w

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

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

response of a hydrothermal system to magmatic heat inferred from temporal variations in the complex frequencies of long period events at kusatsu shirane volcano japan we investigate temporal variations in the complex frequencies frequency and quality factor q of long period lp events that occurred at kusatsu shirane volcano central japan we analyze lp waveforms observed at this volcano in the period between 1988 and 1995 which covers a seismically active period between 1989 and 1993 systematic temporal variations in the complex frequencies are observed in october november 1989 july october 1991 and september 1992 january 1993 we use acoustic properties of a crack filled with hydrothermal fluids to interpret the observed temporal variations in the complex frequencies the temporal variations in october november 1989 can be divided into two periods which are explained by a gradual decrease and increase of a gas volume fraction in a water steam mixture in a crack respectively the temporal variations in july october 1991 can be also divided into two periods these variations in the first and second periods are similar to those observed in november 1989 and in september november 1992 respectively and are interpreted as drying of a water steam mixture and misty gas in a crack respectively the repeated nature of the temporal variations observed in similar seasons between july and november suggests the existence of seasonality in the occurrence of lp events this may be caused by a seasonally variable meteoritic water supply to a hydrothermal system which may have been heated by the flux of volcanic gases from magma beneath this volcano

simulating the lunar geomagnetic variations 1 the equivalent circuit method is used to simulate the lunar semidiurnal geomagnetic tides samples of observations of the lunar geomagnetic tide are also presented derived from analyses of hourly values of the horizontal component of the magnetic field recorded at several observatories these are compared to the results of the simulations at different seasons the winds used in the simulation are derived from the global scale wave model gswm and from those determined by forbes and gillette 1982 the calculations are only carried out for a lunar age of zero new moon but this still enables a comparison to be made with the observed phases of the lunar geomagnetic tide a mostly fair agreement is obtained both for the amplitude and phase of the lunar geomagnetic tide the agreement is generally better when winds from the global scale wave model are used rather than those from the earlier forbes and gillette model the july simulation gives poorer agreement there is corroborating evidence that the phase of the winds near the equator in july should be about 3 hours earlier than that presently given by the gswm the situation in december is different from other seasons both in the simulation and the observations but agreement is difficult to achieve on account of the year to year variability in this season

subglacial recharge into the western canada sedimentary basin impact of pleistocene glaciation on basin hydrodynamics brine springs discharging from devonian carbonates of the western canada sedimentary basin have distinct water chemistry from brines in laterally equivalent units deeper in the basin stable isotope data suggest that the brine springs originated as pleistocene meltwater these waters are interpreted to originate as an influx of subglacial meltwater related to a reversal of the basin scale flow system caused by the overriding ice sheet esker distribution shows a notable relationship between shield and sedimentary rocks an integrated sedimentary basin ice sheet model supports the interpretation that high permeability carbonate units acted as preferential subglacial drains that in turn affected esker development the fluid flow history of the western canada sedimentary basin is characterized by back and forth movement through geological time in response to changing boundary conditions modern day flow systems may not then be indicative of historic movement of economic fluids through the basin

a measurement of lunar tides in the mesosphere at adelaide south australia wind measurements at adelaide 35 s at heights from 76 to 98 km are analyzed for semidiurnal or semimonthly lunar tides two data sets are used one of about 2 years 1984 1985 and one of 1 year 1986 the lunar tide amplitude generally has its largest values at the equinoxes though this pattern changes in 1984 1985 at the greatest heights to solstice maxima especially in winter july diurnal average amplitudes reach 4 m s 1 while the largest value obtained was 8 m s 1 inferred vertical wavelengths of the propagating tides were rather variable and there was evidence of possible mode coupling and interference in summer wavelengths of 25 km occurred below 92 km and were evanescent above while in winter long wavelengths were found in the 78 to 90 km range with shorter 38 km wavelengths above that height comparisons of phases with results from saskatoon and kyoto suggest that around 95 km antisymmetric modes may be dominant in june and december and symmetric modes in february diurnal variations in the lunar tide were evident and year to year changes were seen in some aspects comparison with currently available models shows several points of disagreement

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

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

deep groundwater circulation through the high arctic cryosphere forms mars like gullies we report here the discovery of the northernmost known perennial spring located in the polar desert of the canadian high arctic average precipitation 75 5 mm yr average annual air temperature 19 7 c the high discharge spring 520 l s has also anomalously high temperatures 9 0 c despite occurring in a region of low geothermal gradient and thick 400 m permafrost active erosion at the spring outlet forms gullies with alcove channel apron morphology remarkably similar to archetypal gullies observed on mid latitude regions of mars geochemical and isotopic data show a meteoric origin for the waters demonstrating that deep circulating groundwater systems can form active connections through the cryosphere to the subsurface even in the absence of thermal anomalies this discovery challenges current understanding of high latitude permafrost hydrology

upper stratospheric circulations in the two hemispheres observed by satellites a global analysis is made of upper stratospheric circulations with the aid of nimbus 5 and tiros n satellite observations in order to make a comparison of characteristics between the northern hemisphere nh and the southern hemisphere sh it is shown that the reversal of north south gradient of the zonal mean temperature at the stratopause level is always observed in higher latitudes of the sh winter while the temperature gradient of the nh winter is variable because of the occurrence of sudden warmings consequently due to the thermal wind relation the polar night westerlies of the sh stratosphere are generally stronger than those of the nh stratosphere in association with this difference the activity of transient planetary waves of wavenumber 2 is striking in the sh in contrast to the predominance of steady waves in the nh finally the interrelation between the zonal mean field and planetary waves in the upper stratosphere is briefly discussed

a diurnal modulation of the lunar tide in the upper atmosphere analysis of geomagnetic data from several stations in the equatorial region shows that the amplitude of the lunar semimonthly tide frequently does not have the expected symmetry about noon in its diurnal variation there is a distinct tendency for larger amplitudes in the morning at many stations this effect is largest in equinoctial months though there are regional differences analysis of data from different years confirms its presence the interaction between solar and lunar tides in the middle atmosphere may be responsible for the observed modulation

lunar tidal winds measured in the upper atmosphere 78 105 km at saskatoon canada abstract six years of winds data measured by the partial reflection drifts technique have been analyzed for lunar tides data are available at 3 km intervals of height and are separately analyzed in two year datasets to cheek consistency a month by month seasonal variation is derived largest amplitudes of the lunar tide occur in january february with a smaller maximum in summer the vertical wavelength is longest in summer and the tide then resembles that predicted for a pure 2 2 mode in winter vertical wavelengths range from 25 to 81 km in different years several of these results do not agree with the model of forbes an o1 component of the lunar tide could not be detected

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

lunar tides at meteor heights we determined lunar semidiurnal m2 and diurnal luni solar o1 tides of the meridional winds observed for two years between 1979 and 1980 by the kyoto meteor radar at 95 km altitude the m2 and o1 tidal wind of 2 2 m sec and 1 2 m sec were observed from the downward phase progression with altitude the vertical wavelength was estimated as 60 and 25 km for the m2 and o1 component respectively seasonal variation of the m2 tidal wind was detected lunar variation has also been detected in the mean height of meteor echoes the amplitude for the m2 and o1 component was 0 22 and 0 18 km with the maximum height occurring at 9 4 and 14 1 hrs lunar time respectively

variability of the equatorial electrojet its relations to the sq current system and semidiurnal tides average diurnal and seasonal variations of the horizontal geomagnetic element delta h are examined the semiannual variation in equatorial electrojet strength is found to disappear in afternoon hours this may be related to changes in the latitude of the sq current system focus during the day this in turn may be caused by a superposed semidiurnal tide and may also explain delta h variations at stations near the focus

lunar tidal winds at adelaide and saskatoon at 80 to 100 km heights 1985 1990 winds data from the two sites were analyzed for lunar tides in 2 year groups the variation with height of the phase and amplitude of the tide showed considerable variability from year to year yet in general seasonal variations at particular heights were similar to those determined previously phases of the tide at the two sites were compared in order to estimate whether the tide was symmetric or antisymmetric for this purpose it was found necessary to use only 1 year data sets the predominance of symmetric tides during solstice months and antisymmetric tides at the equinox came as a surprise yet the result is in broad agreement with phase relations of the lunar geomagnetic tide

narrow band transient signals in central apennines italy hints for underground fluid migration summary in this paper we investigate nature and properties of narrow band transient seismic signals observed by a temporary array deployed in the val tiberina area central apennines italy these signals are characterized by spindle shaped harmonic waveforms with no clear s wave arrivals the first portion of the seismograms exhibits a main frequency peak centred at 4 5 hz while the spectrum of the slowly decaying coda is peaked at about 2 hz events discrimination is performed using a matched filtering technique resulting in a set of 2466 detections spanning the 2010 january march time interval from a plane wave fitting procedure we estimate the kinematic properties of signals pertaining to a cluster of similar events the repetition of measurements over a large number of precisely aligned seismograms allows for obtaining a robust statistics of horizontal slownesses and propagation azimuths associated with the early portion of the waveforms the p wave arrival exhibits horizontal slownesses around 0 1 s km 1 thus suggesting waves impinging at the array almost vertically separately we use traveltimes measured at a sparse network to derive independent constraints on epicentral location ray parameters and azimuths are calibrated using slowness measurements from a local well located earthquake after this correction the joint solution from traveltime inversion and array analysis indicates a source region spanning the 1 3 km depth interval considerations related to the source depth and energy and the occurrence rate which is not related to the daily and weekly working cycles play against a surface artificial source instead the close resemblance of these signals to those commonly observed in volcanic environments suggest a source mechanism related to the resonance of a fluid filled fracture likely associated with instabilities in the flux of pressurized co2

crustal shortening and duplication of the moho in the northern apennines a view from seismic refraction data abstract a reappraisal of the dss refraction seismic campaigns of 1978 and 1974 in the northern apennines and the northern tyrrhenian sea after digitization of the original analog data and a new interpretation of crustal structures are presented in this paper the layering of the adria crust consists of a low velocity lower crust topped by a 6 7 km s horizon and an upper crust again formed by a low velocity layer capped by a faster one in the tuscany sector the crust mantle boundary and lower crust show attenuated velocities and a reduced thickness with respect to the adriatic counterpart these differences are due to the extensional tectonics restricted to tuscany and occurred in a high heat flow regime related to an uplifting astenosphere it has been confirmed that a deep thrust is responsible for moho doubling in correspondence with the zero bouguer anomaly line the tuscan moho overlaps the umbro marchean one for a length of about 30 km it is hypothesized that another shallower thrust involves upper crust in the mid tuscany range mt cetona and perugia massifs had their roots in the mantle and that subsequent extensional tectonics obliterated every trace of thrusting in lower crust and mantle rocks no conclusive proof of the existence of a european moho below a tuscan one in the area underneath elba has yet been found revision of dss data excludes the presence of a refractor reflector 60 km deep the same data however are compatible with the existence of a crust mantle boundary at 30 35 km depth

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

highly localized cooling in daytime mesopause temperature over the dip equator during counter electrojet events first results the first observations of lowering of mesopause temperature during counter electrojet cej events over a narrow region of 150 km centered at around magnetic equator are presented the daytime mesopause temperature is measured over trivandrum 8 5 n 77 e dip lat 0 5 n india using the ground based multiwavelength dayglow photometer the unique meridional scanning capability of the instrument is extensively used in this study a lowering of temperature by as much as 25 k has been observed during certain cej events which includes a few partial cejs the gravity wave tidal interaction through vertically upward wind is proposed to be manifesting as lowering in the mesopause temperature and also as cej these observations are new and address to the issues concerning the vertical coupling processes prevailing in the equatorial mesosphere lower thermosphere ionosphere mlti region citation vineeth c t k pant c v devasia and r sridharan 2007 highly localized cooling in daytime mesopause temperature over the dip equator during counter electrojet events

cold springs in permafrost on earth and mars 1 perennial springs located on west central axel heiberg island in the canadian high arctic occur in a region with a mean annual air temperature of 15 c and flow through continuous permafrost 600 m thick the spring water is a low temperature up to 6 c brine that maintains constant discharge temperatures and flow rates throughout the year here we report on observations of temperature and discharge rate of these springs and develop a combined flow and thermal model of the subsurface flow using the measured geothermal gradient we also consider the implications these springs have for the search for similar environments past or present on mars

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

observations of long period earthquakes accompanying hydraulic fracturing waveforms of most seismic events accompanying hydraulic fracturing have been reported to contain clear p and s waves and have fault plane solutions consistent with shear displacement across a fault this observation is surprising since classical hydraulic fracturing theory predicts the creation of a tensile opening of a cavity in response to fluid pressure very small long period events similar to long period earthquakes observed at volcanoes were found to occur during four hydraulic fracturing experiments carried out at fenton hill new mexico since the long period earthquakes occur in the same region as the shear type events it is concluded that the unusual character of the long period earthquake waveforms is due to a source effect and not a path effect the occurrence of long period earthquakes during hydraulic fracturing could indicate tensile fracturing many waveforms of these events are identical which implies that these events represent repeated activation of a given source a proposed source for these long period events is the sudden opening of a channel that connects two cracks filled with fluid at different pressures the sizes of the two cracks differ which causes two or more peaks to appear in the spectra each peak beingmore associated with one physical dimension of each crack from the frequencies at which spectral peaks occur crack lengths are estimated to be between 3 and 20m less

ice sheet derived submarine groundwater discharge on greenland s continental shelf 1 isotopically light 1 to 8 and fresh pore fluids 300 520 mm cl were found in continental shelf sediments up to 100 km offshore of southeastern se greenland suggesting infiltration and mixing of ice sheet meltwater with seawater to depths of 260 m these geochemical anomalies may be associated with ice sheet derived submarine groundwater discharge smgd we present a continental scale reconstruction of the late pleistocene hydrogeology of se greenland using finite element analysis that incorporates ice sheet loading and solute and isotope transport results indicate that subglacial infiltration and smgd are of the same order of magnitude and are highly dependent on the permeability of the subaerial basalt simulated infiltration and smgd almost doubled during the last glacial maximum compared to ice free conditions much of the present day glacially induced groundwater discharge occurs on land subice infiltration on the continental shelf likely represents a mixture of seawater and meltwater during past glacial maximums simulated smgd during the most recent interval of glacial retreat is about 4 of the total ice sheet melting at present the simulated rate of smgd is about 11 of the estimated current melting rate

observations of mean winds and tides in the upper mesosphere during 1980 1984 using the poker flat alaska mst radar as a meteor radar a postprocessing selection algorithm is used to determine the meteor echoes detected on the poker flat alaska mst radar 65 n 147 w from a composite data base consisting of meteor and turbulence echoes the echo distributions depend on the geometry of the antenna beams the presence of strong turbulence echoes average power transmitted and the number of coherent averages used in the signal processing winds are derived from the meteor echoes and are used to compute monthly mean winds and tides in the upper mesosphere these results are consistent with previous high latitude observations tidal amplitudes are largest in summer and weakest in winter the tides exhibit large month to month variability although the seasonal averages in 1983 are in agreement with those of 1984 the semidiurnal tide exhibits a dramatic phase shift of approximately 180 from october to november in both years results suggest future enhancement of the mst wind data can be achieved with real time meteor echo detection

carbon dioxide earth degassing and seismogenesis in central and southern italy 1 we present the first regional map of co2 earth degassing from a large area most of central and south italy derived from the carbon of deep provenance dissolved in the main springs of the region the investigation shows that a globally significant amount of deeply derived co2 10 of the estimated global co2 emitted from subaerial volcanoes is released by two large areas located in western italy the anomalous flux of co2 suddenly disappears in the apennine in correspondence to a narrow band where most of seismicity concentrates here at depth the gas accumulates in crustal traps generating co2 overpressurized reservoirs which induce seismicity

transient nature of arctic spring systems driven by subglacial meltwater 1 in the high arctic supra and proglacial springs occur at borup fiord pass ellesmere island spring waters are sulfur bearing and isotope analysis suggests springs are fed by deeply circulating glacial meltwater however the mechanism maintaining spring flow is unclear in these areas of thick permafrost which would hamper the discharge of deep groundwater to the surface it has been hypothesized that fracture zones along faults focus groundwater which discharges initially underneath wet based parts of the ice with thinning ice the spring head is exposed to surface temperatures tens of degrees lower than temperatures of pressure melting and permafrost starts to develop numerical modeling of coupled heat and fluid flow suggest that focused groundwater discharge should eventually be cut off by permafrost encroaching into the feeding channel of the spring nevertheless our model simulations show that these springs can remain flowing for millennia depending on the initial flow rate and ambient surface temperature these systems might provide a terrestrial analog for the possible occurrence of martian springs recharged by polar ice caps

sensitivity to long term climate change of subpermafrost groundwater systems in svalbard deep subpermafrost aquifers are highly climate dependent with the permafrost as an aquitard preventing groundwater recharge and discharge a study from the high arctic island of spitsbergen svalbard shows that during a glacial to interglacial phase both the permafrost and the glacier regime will respond to climatic changes and a glacier fed groundwater flow system will vary accordingly a full glaciation results in the melting of permafrost and groundwater can flow through pores and fracture systems in the rocks and sediments below the temperate zones of glaciers these groundwater flow systems will mainly be localized to fjords and valleys and form low lying terrestrial springs when the relative sea level drops during deglaciation due to glacio isostatic rise during an interglaciation permafrost develops and thickens and the groundwater recharge and discharge areas will thereby be gradually reduced to a minimum reached at the warmest part of an interglaciation an already frozen spring system cannot reopen before the permafrost melts only groundwater springs related to permanently warm based glacial ice will persist into the next glaciation during a new glaciation flow systems that terminated during the previous interglaciation may become revitalized if overridden by warm based ice causing permafrost thawing

rayleigh lidar observations of mesosphere temperature structure ground based observations of atmospheric density profiles to 92 km were obtained for four successive seasons between summer 1989 and spring 1990 these results were obtained with a powerful rayleigh lidar facility located at wright patterson air force base dayton ohio this instrument combined a 14 w xef laser transmitter with a 2 54 m receiver mirror to observe returns from altitudes between 40 and 95 km analysis of the scale height dependence of the density profiles produced temperatures with a measurement error of about 5 k 2 5 at 90 km when the lidar data was averaged for 20 min and smoothed in height over 2 7 km examination of these profiles for the total of 18 nights showed that there often existed in the mesophere a layer of enhanced temperatures when compared with the u s standard profile the layer centroid height was about 85 km for summer and 70 to 75 km for winter data obtained for the equinoctial periods showed the amplitude of these layers to be weak the winter temperature profiles showed evidence forlong period waves passing through the region of the thermal anomaly while the equinox profiles revealed more sporadic wave activity with shorter vertical wavelengths both the winter and summer temperature data displayed regions where the observed lapse rate approached the adiabatic lapse rate in the summer the wave activity near the inversion layer was weak

ionospheric variability over indian low latitude linked with the 2009 sudden stratospheric warming in this paper we analyze radar observations of e b drift and plasma irregularities ionosonde observations of e and f layer parameters including spread f and magnetic field observations made from indian low latitudes linked with the 2009 sudden stratospheric warming ssw event e b drift variations presented here are the first of their kind from the indian sector as far as the effect of ssw is concerned difference of magnetic fields observed from the equator and low latitude h and e b drift show linear relation and both show remarkably large positive values in the morning and negative values in the afternoon exhibiting semidiurnal behavior remarkable changing patterns in the critical frequency of f2 layer fof2 and f3 layer fof3 were observed after the occurrence of ssw large variations with quasi 16 day periodicity were observed in h fof2 and fof3 both semidiurnal and quasi 16 day wave modulation observed after the 2009 ssw event are consistent with those reported earlier we also noted quasi 6 day variations in h and fof2 soon after the ssw commencement not much reported before during the counterelectrojet events linked with the ssw event while equatorial es esq disappeared as expected there were no blanketing es esb a finding not reported and discussed earlier esb was also not formed at the off equatorial location indicating the absence of required vertical wind shear but e region plasma irregularities were observed by the ionosonde and radar with a close relationship between the two weak f region irregularities were observed in the postmidnight hours and case studies suggest the possible role of ssw related background electric field in the manifestation of postmidnight f region irregularities

lunar tidal winds in the upper atmosphere over jakarta 1 winds have been measured at heights from 70 to 120 km by means of a meteor wind radar near jakarta 6 4s 106 7e from 1993 to 1997 these data have been analysed for the lunar semidiurnal tide using a least squares fitting method generally lunar tidal amplitudes in the winds are about 2 m s 1 though the northward wind amplitude reaches 6 m s 1 in southern summer variations with height and season are shown and compared with the global scale wave model gswm often the agreement with the model is good but there is a difference in phase of the eastward wind in southern winter the gswm predicts a more rapid increase in northward wind magnitude with height than is observed year to year changes are examined for different seasons and these reveal sometimes consistent results and sometimes a variation in phase from year to year often the phase relations between eastward and northward winds at jakarta are more characteristic of a northern hemisphere tide as predicted by classical tidal theory particularly in southern spring and summer

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

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

a deep groundwater origin for recurring slope lineae on mars the recurring slope lineae on mars have been hypothesized to originate from snow melting deliquescence dry flow or shallow groundwater except for the dry flow origin these hypotheses imply the presence of surficial or near surface volatiles placing the exploration and characterization of potential habitable environments within the reach of existing technology here we present observations from the high resolution imaging science experiment heat flow modelling and terrestrial analogues which indicate that the source of recurring slope lineae could be natural discharge along geological structures from briny aquifers within the cryosphere at depths of approximately 750 m spatial correlation between recurring slope lineae source regions and multi scale fractures such as joints and faults in the southern mid latitudes and in valles marineris suggests that recurring slope lineae preferably emanate from tectonic and impact related fractures we suggest that deep groundwater occasionally surfaces on mars in present day conditions observations and heat flow modelling suggest that briny groundwater surfacing from fractures forms recurring slope lineae on mars

deep circulation of groundwater in overpressured subglacial aquifers and its geological consequences abstract it is generally assumed that meltwater from the base of ice sheets is discharged in a relatively thin subglacial zone whereas this may be true for ice sheets resting on impermeable beds many ice sheets such as the glacial period ice sheets of north america and europe flowed over extensive aquifers a theory is developed which suggests that high rates of meltwater discharge into these aquifers would have completely reorganised their flow fields producing intergrated patterns of glacially pressurised flow controlled by the continental scale form of the ice sheet surface rather than the small scale topographic basins which determine modern aquifer extent the theory is applied to the aquifers which underlay the saalian ice sheet in the netherlands where it is shown that potential gradients and groundwater flow velocities would have developed which were two orders of magnitude greater than modern values and that the dominant flow vectors would have been normal to those of the modern flow thus glacial interglacial cycling in areas which have suffered periodic glaciation during the late cenozoic may have experienced alternating phases of greater and lesser flow energy it represents another example of climatically driven cyclical change in the earth under highly energised glacial conditions potential gradients much larger than modern values may have produced many common features of sediment disruption such as diapirs liquifaction structures and pipes and forms such as glacial doughnuts and pock marks which have hitherto been explained by other processes deep and penetrative flushing of aquifers by glacial meltwater may have left a distinctive geochemical signal in them which may be used to test the theory gases such as methane generated at shallow depth may have been trapped beneath the glacial cap rock and may also have played an important role in these processes

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

first observations of non volcanic long period seismicity in the central apennines italy 1 we report unprecedented observations of long period lp seismicity in non volcanic setting our data are from the central northern sector of the apennine chain italy for this area intense co2 circulation of mantle origin has been documented by either groundwater composition and borehole measurements we perform waveform correlation and stacking to obtain reliable epicenter estimates following chouet s crack model we find that both the quality factor and dominant frequency of lp oscillations are consistent with the sustained resonance of a wet crack filled by a water co2 mixture

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

a calculation of ionospheric currents due to semidiurnal antisymmetric tides the fully developed equivalent circuit method is used to calculate the ionospheric electric current flow due to the 2 3 and 2 5 tidal modes the 2 5 mode currents are of negligibly small amplitude the 2 3 current pattern has meridional currents in the same direction at a given local time in both north and south hemispheres there is also sometimes a minimum in the zonal current around 10 degree dip latitude and the equatorial electrojet pattern may be different in different longitude zones these features may be possible explanations of 1 the meridional current pattern observed at saint santin 2 current flows on abnormal quiet days aqds 3 the reverse equatorial electrojet 4 the seasonal phase anomaly in the lunar geomagnetic tide and 5 the invasion of one hemisphere s current pattern by that from the opposite hemisphere the recent detection of antisymmetric semidiurnal winds just below the dynamo region further demonstrates the importance of these modes

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

the role of advective heat transport in talik development beneath lakes and ponds in discontinuous permafrost 1 regions of warm thin discontinuous permafrost have been observed to be experiencing rapid changes in lake and pond dynamics in recent decades even though surface water and groundwater interactions are thought to play a significant role in heat transport in these regions the effect of these interactions on permafrost remains largely unquantified in order to examine the influence of groundwater flow on permafrost dynamics we modeled the development of a sub lake talik under permafrost conditions similar to those observed in the southern central seward peninsula region of alaska using a numerical solution that couples heat transport and groundwater flow including the effect of water phase changes on soil permeability and latent heat content a comparison of model simulations with and without near surface subpermafrost groundwater flow indicates that stable permafrost thicknesses are 2 to 5 times greater in the absence of groundwater flow simulations examining the thermal influence of lakes on underlying permafrost suggest that a through going talik can develop in a matter of decades and that the incorporation of advective heat transport reduces the time to complete loss of ice beneath the lake by half relative to heat transport by conduction alone this work presents the first quantitative assessment of the rates of sub lake permafrost response to thermal disturbances such as talik development in systems with near surface groundwater flow the results highlight the importance of coupled thermal and hydrologic processes on discontinuous permafrost dynamics

magnitude scale for lp events a quantification scheme for volcanic quakes summary the peculiar source characteristics of long period seismic events time persistency of the source low frequency peaks in the source spectrum absence of high frequency radiation prevent the formation of a definite high frequency coda in the seismograms in contrast this is well formed in volcano tectonic quakes for this reason the widely used duration magnitude scale that is based on the proportionality between the energy and the coda duration cannot be used for long period estimation in observatory practice the long period magnitude is sometimes estimated using the same duration magnitude scale leading to confusing results in this report we show a new method to estimate the magnitude of long period events that generally occur for volcanoes with some application examples from data for mt etna italy colima volcano mexico and campi flegrei italy

former dynamic behaviour of a cold based valley glacier on svalbard revealed by basal ice and structural glaciology investigations large numbers of small valley glaciers on svalbard were thicker and more extensive during the little ice age lia demonstrated by prominent ice cored moraines up to several kilometres beyond present day margins the majority of these glaciers have since experienced a long period of strongly negative mass balance during the 20th century and are now largely frozen to their beds indicating they are likely to have undergone a thermal transition from a polythermal to a cold based regime we present evidence for such a switch by reconstructing the former flow dynamics and thermal regime of tellbreen a small cold based valley glacier in central spitsbergen based on its basal sequence and glaciological structures within the basal sequence the underlying matrix supported diamict is interpreted as saturated subglacial traction till which has frozen at the bed indicating that the thermal switch has resulted in a cessation of subglacial sediment deformation due to freezing of the former deforming layer this is overlain by debris poor dispersed facies ice interpreted to have formed through strain induced metamorphism of englacial ice the sequential development of structures includes arcuate fracture traces interpreted as shear planes formed in a compressive transpressive stress regime and fracture traces interpreted as healed extensional crevasses the formation of these sediment ice facies and structures is indicative of dynamic warm based flow most likely during the lia when the glacier was significantly thicker

longitudinal variation of the lunar tide in the equatorial electrojet the atmospheric lunar tide is one known source of ionospheric variability the subject received renewed attention as recent studies found a link between stratospheric sudden warmings and amplified lunar tidal perturbations in the equatorial ionosphere there is increasing evidence from ground observations that the lunar tidal influence on the ionosphere depends on longitude we use magnetic field measurements from the champ satellite during july 2000 september 2010 and from the two swarm satellites during november 2013 february 2017 to determine for the first time the complete seasonal longitudinal climatology of the semidiurnal lunar tidal variation in the equatorial electrojet intensity significant longitudinal variability is found in the amplitude of the lunar tidal variation while the longitudinal variability in the phase is small the amplitude peaks in the peruvian sector 285 e during the northern hemisphere winter and equinoxes and in the brazilian sector 325 e during the northern hemisphere summer there are also local amplitude maxima at 55 e and 120 e the longitudinal variation is partly due to the modulation of ionospheric conductivities by the inhomogeneous geomagnetic field another possible cause of the longitudinal variability is neutral wind forcing by nonmigrating lunar tides a tidal spectrum analysis of the semidiurnal lunar tidal variation in the equatorial electrojet reveals the dominance of the westward propagating mode with zonal wavenumber 2 sw2 with secondary contributions by westward propagating modes with zonal wavenumber 3 sw3 and 4 sw4 eastward propagating waves are largely absent from the tidal spectrum further study will be required for the relative importance of ionopsheric conductivities and nonmigrating lunar tides

earth s atmosphere in dynamic coupling envisaged through atmospheric tides and atmospheric gravity waves a view on the past present future research in 1982 1985 an international scientific endeavor was attempted as the middle atmosphere program contributing successfully to exploring the last unknown part of the atmosphere on the planet earth the middle atmosphere now it seems timely for us to consider the whole atmosphere which extends from the ground to the upper atmosphere and further into space as an entity each part of the atmosphere couples not only horizontally globally but also vertically while the horizontal coupling is mainly important for conventional meteorology the vertical one is significant say for space physics and probably future meteorology and will be the present topic atmospheric waves play an important role for the dynamic coupling of the atmosphere transporting energy momentum and material mainly from below and releasing on the way in their propagation upward already in the last century the existence of the tidal dynamo for the geomagnetic sq variation in the upper atmosphere was known as a manifestation of the dynamic coupling by atmospheric tides atmospheric internal gravity waves are now found to play an important role among many others in the general circulation of the middle atmosphere which is another manifestation of the dynamic coupling of the atmosphere reviewing remarkable progress in the last 40 years in the research of this subject the author has suggested that frontiers of the future research would be to develop a gcm general circulation model to include the upper atmosphere and to establish an equatorial atmosphere observation system

impact of sudden stratospheric warming of 2009 on the equatorial and low latitude ionosphere of the indian longitudes a case study using the equatorial electrojet eej induced surface magnetic field and total electron content tec measurements we investigated the impact of the sudden stratospheric warming ssw of january 2009 on the equatorial electrodynamics and low latitude ionosphere over the indian longitudes results indicate that the intensity of eej and the tec over low latitudes extending up to 30 n exhibit significant perturbations during and after the ssw peak one of the interesting features is the deviation of eej and tec from the normal quiet time behaviour well before the onset of the ssw this is found to be coincided with the beginning of enhanced planetary wave pw activity over high latitudes the substantial amplification of the semidiurnal perturbation after the ssw peak is seen to be coinciding with the onset of new and full moon the response of tec to ssw is found to be latitude dependent as the near equatorial ne stations show the semidiurnal perturbation only after the ssw peak another notable feature is the presence of reduced ionization in the night sector over the ne and low latitude regions appearing as an ionization hole well after the ssw peak the investigation revealed the existence of a quasi 16 day wave in the tec over low latitudes similar to the one present in the eej strength these results have been discussed in the light of changes in the dynamical background because of enhanced pw activity during ssw which creates favourable conditions for the amplification of lunar tides and their subsequent interaction with the lower thermospheric tidal fields

spherical harmonic analysis of geomagnetic tides 1964 1965 the mathematical forms chosen for analyses of s q and l by seventeen different authors are reviewed on the basis of the review and on consideration of the ionospheric dynamo theory and the hough function structure of wind velocities in the upper atmosphere a mathematical model is chosen that includes two more terms than the recent analysis by malin 1973 hourly mean values from 130 magnetic observatories for the i q s ys international quiet solar years 1964 and 1965 were prepared in machine readable form and analysed the solar and lunar transient magnetic variations were evaluated together with the lunar elliptic magnetic tide and the seasonal change at one and two cycles per year for all magnetic tides spherical harmonic analyses were made of the phase law tides and the smaller partial tides altogether 94 different spherical harmonic analyses were completed for a total of ten different magnetic tides two of the ten tides are the solar and lunar magnetic tides usually denoted s and l respectively the results are tabulated in a form that distinguishes between eastward and westward moving terms which is suitable for the evaluation of phase angle differences and amplitude ratios between internal and external parts malin s ocean dynamo calculation has been applied to the lunar and lunar elliptic magnetic tides the spherical harmonic coefficients are compared in some detail with those of malin 1973 for years of high sunspot activity the magnetic tidal potential associated with a given atmospheric tidal mode is derived theoretically and used to obtain an estimate of the hough function components of the solar and lunar semi diurnal atmospheric tides at ionospheric levels from the corresponding magnetic tidal potential

slow earthquakes and nonvolcanic tremor nonvolcanic tremor is observed in close association with geodetically observed slow slip events in subduction zones accumulating evidence points to these events as members of a family of slow earthquakes that occur as shear slip on the downdip extensions of fault zones in a regime that is transitional between a frictionally locked region above and a freely slipping region below by virtue of their locations and their properties slow earthquakes are certain to provide new insights into the behavior of earthquakes and faulting and into the hazard they embody

a conjugate study of mean winds and planetary waves employing enhanced meteor radars at rio grande argentina 53 8 s and juliusruh germany 54 6 n 1 two meteor radars with enhanced power and sensitivity and located at closely conjugate latitudes 54 6 n and 53 8 s are employed for interhemispheric comparisons of mean winds and planetary wave structures at periods of 8 to 20 days our study uses data from june 2008 through may 2010 during which both radars provided nearly continuous wind measurements from 80 to 100 km monthly mean winds at 53 8 s exhibit a stronger westward zonal jet in spring and early summer at lower altitudes and no westward winds at higher altitudes in contrast westward mean winds of 5 10 ms 1 at 54 6 n extend to above 96 km during late winter and early spring each year equatorward mean winds extend approximately from spring to fall equinox at both latitudes with amplitudes of 5 10 ms 1 meridional mean winds are more variable at both latitudes during fall and winter with both poleward and equatorward monthly means indicating longer period variability planetary waves seen in the 2 day mean data are episodic and variable at both sites exhibit dominant periodicities of 8 10 and 16 20 days and are more confined to late fall and winter at 54 6 n at both latitudes planetary waves in the two period bands coincide closely in time and exhibit similar horizontal velocity covariances that are positive negative at 54 6 n 53 8 s during peak planetary wave responses

the structure of the lunar semi diurnal pressure tide l2 the hough structure of the lunar semi diurnal tide l2 p in surface pressure is estimated using joint weightings by area and probable error structure on annual and lloyd seasonal scales with new data global representations on seasonal and annual scales of the l2 wave in both spherical harmonic and hough function forms are presented for the haurwitz cowley dataset enlarged by the more recent tidal determinations of hutchings and palumbo these are mainly for southern hemiphere island locations the asymmetric hough eigenfunction terms h32 are considerably larger than previously estimated both annually and seasonally a possible artefact of the earlier data analysis technique they are consistent and identified with the well known difference in phasing and amplitude of l2 by hemisphere the dependence of the hough structure on the order of the fitting and on the more extreme residuals is examined it is stable for the smallest models spherical harmonic terms up to degree 6 and order 3 to removal of the largest residuals from a first fitting and to the two largest datasets seasonal changes in the hough structure are discussed the asymmetric results appear consistent with early frictional thermal interpretations on the seasonal variation of l2 but the sensitivity of l2 to upper air temperature structure is not consistently shown in the analyses for the main mode h 2 2 copyright 2005 royal meteorological society

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

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

geochemical evidence for and characterization of co2 rich gas sources in the epicentral area of the abruzzo 2009 earthquakes abstract we describe the results of a detailed hydrogeochemical campaign on the groundwater circulating in two regional aquifers located in the area of the abruzzo 2009 earthquakes the influx of deeply derived co2 rich gases into the two aquifers is highlighted by the 13c isotopic composition of dissolved carbon species the source of the gas is roughly localised beneath the epicentral area of the earthquakes where the presence of sources of fluids under high pressure is suggested by seismological investigations the carbon isotopic mass balance of the aquifers indicates that the amount of the deep co2 dissolved and transported by the groundwaters is 530 t day the chemical and isotopic composition of the gas entering the aquifers named abruzzo gas has been derived by comparing the data measured in the springs with the results of a gas water rock reaction model that simulates the evolution of the chemical and isotopic composition of groundwater affected by the input of a deeply derived co2 rich gas phase the composition of abruzzo gas is compared to that of 40 large gas emissions located in central italy the gas becomes progressively richer in radiogenic elements 4he and 40ar and in n2 from the volcanic complexes in the west to the apennines in the east the abruzzo gas in agreement with its location well matches the composition of the gases emitted in the pre apennine region these geochemical features consistent with the structural setting of the region indicate increasing residence times of the gas in the crust moving from west to east in particular we suggest that the strong increase in radiogenic crustal gases reflects the occurrence of deep traps where the gas is stored at high pressures for a long time and that such high pressure gas pockets play a major role in the generation of apennine earthquakes

a numerical investigation of ice lobe permafrost interaction around the southern laurentide ice sheet permafrost existed around and under marginal parts of the southern laurentide ice sheet during the last glacial maximum the presence of permafrost was important in determining the extent form and dynamics of ice lobes and the landforms they produced because of influences on resistance to basal motion and subglacial hydrology we develop a two dimensional time dependent model of permafrost and glacier ice dynamics along a flowline to examine i the extent to which permafrost survives under an advancing ice lobe and how it influences landform development and hydrology and ii the influence of permafrost on ice motion and surface profile the model is applied to the green bay lobe which terminated near madison wisconsin during the last glacial maximum simulations of ice advance over permafrost indicate that the bed upstream of the ice sheet margin was frozen for 60 200 km at the glacial maximum permafrost remained for centuries to a few thousand years under advancing ice and penetrated sufficiently deep tens of meters into the underlying aquifer that drainage of basal meltwater became inefficient likely resulting in water storage beneath the glacier our results highlight the influence of permafrost on subglacial conditions even though uncertainties in boundary conditions such as climate exist

mean winds and tidal components during counter electrojet events the first observations of mean winds and the amplitude and phases of the tidal components measured with a meteor wind radar located at trivandrum 8 5 n 77 e during five consecutive days of counter electrojet events identified in the horizontal component of the earth s magnetic field from january 27 31 1987 are described the mean zonal winds in the altitude region of 90 105 km are in general westward during counter electrojet days and eastward during no counter electrojet days the amplitudes and phases of the tidal components on the counter electrojet days are found to be substantially different from those on the no counter electrojet days

lunar tides in total electron content over brazil using data from global navigation satellite systems dual frequency receivers the lunar tides were studied in the ionospheric total electron content tec over brazil from 2011 to 2014 in order to calculate the amplitudes and phases of the lunar tides quiet magnetic days within a 27 day window has been used to remove the solar rotation effects relative residuals tec were calculated by performing a spectral analysis by removing the solar tide contributions lastly a lunar month size window was used to calculate the amplitude and phase of the lunar components lunar diurnal tide amplitudes showed a semiannual variation with maximum in the equinox months for almost all latitudes while lunar semidiurnal amplitudes were larger in december and january and may be related to sudden stratospheric warming events both components did not display significant longitudinal variation what could be due to the short range of longitude 30 degrees lunar diurnal amplitudes were basically uniform over brazil while lunar semidiurnal amplitudes showed some peaks over the equatorial ionization anomaly crest and minimum values near the magnetic equator

upper atmosphere wind systems during reverse equatorial electrojet events days of reversed equatorial electrojet were identified at trivandrum india and in order to seek a global wind change in the dynamo region responsible for these events upper atmosphere winds at a height of 99 km at saskatoon canada were examined during northern winter and also in april and september the reversed electrojets were accompanied by reversals of the eastward wind at saskatoon the winter events generally occurred during a stratwarm no changes in the winds were detected during summer reversed electrojets

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

lunar tides in the mesosphere over christmas island 2 n 203 e this paper reports the first measurement of the lunar tide in upper atmosphere winds at an equatorial site wind velocities have been measured at christmas island in the pacific ocean from 1990 to 1993 over the height range 82 to 98 km and hourly values have been used to deduce the lunar tide using a least squares method amplitudes are 1 to 3 m s with only small changes in phase with season a large phase change over the early part of 1990 was found in the northward wind generally the phase difference between northward and eastward winds was about 6 hours and good agreement was obtained with a tidal model developed from that of forbes 1982a

characterization of a sulfur rich arctic spring site and field analog to europa using hyperspectral data abstract a unique glacial spring system exists at borup fiord pass in the canadian high arctic emerging from a glacial surface and depositing elemental sulfur gypsum and calcite across a portion of the glacier the presence of sulfur springs associated with glacial ice is extremely rare in a terrestrial context and the resulting deposits may provide a field analog to non ice materials on the surface of europa spectral characterization of the supraglacial deposits in the visible near infrared vis nir range 0 4 2 5 m was carried out using reflectance spectra collected in situ using a field spectrometer during the 2006 field season these spectra while dominated by melting snow ice and sulfur show that some absorption features of the sulfates are shifted in wavelength with respect to library spectra due to the effects of mixing or temperature absorption features of calcite are largely absent potentially due to mineral partitioning effects within the deposits investigations into changes in mineralogy within the deposits over the course of the active season using data collected by the hyperion hyperspectral visible infrared spectrometer aboard the earth observing 1 spacecraft eo 1 were limited by low signal to noise snr ratios in the data although they indicate that sulfur is remaining stable this is confirmed by seasonal data on the extent of the deposits obtained using a classification algorithm running onboard the satellite which continued to detect the presence of sulfur until snow obscured the site ground truth for the observations is provided by mineralogical analyses obtained by x ray diffraction xrd measurements and laboratory reflectance spectra from 0 2 25 m obtained of samples returned from the site in 2006 we show that while sulfur the main constituent of the deposits is well represented in hyperion data minor constituents such as calcite and gypsum can be partially or entirely masked in the data in spite of these effects autonomous detection methods can be utilized to monitor the generation and extent of the deposits whose spectral properties show similarities with those of europa s non ice materials

geodetic strain in peninsular italy between 1875 and 2001 1 we determine geodetic strain in peninsular italy by the gps reoccupation of the first order triangulation network of italy installed from 1860 the uncertainties in the original measurements about 3 ppm and the time span between the two observations imply that tectonic signals larger than about 0 03 ppm yr are resolvable along the apenninic belt where the largest earthquakes are concentrated the geodetic deformation has a clear and consistent strain pattern between adjacent regions well above the uncertainties and shows a pervasive ne sw extension along the tyrrhenian and adriatic coasts the geodetic signal is not homogeneous and is comparable with the uncertainty in the original measurements seismic deformation calculated over the same time interval agrees well with estimated extensional direction but the magnitudes of geodetic and seismic strain differ suggesting that in part of the apennines significant strain accumulation over the past 130 years may not have been released in earthquakes