planetary scale wave observations over a low latitude e region using simultaneous observations of vhf radar and ionosonde over sanya 18 34 n 109 62 e 1 the planetary scale oscillations of the field aligned irregularities fai and the sporadic e es layers in the low latitude e region were studied in terms of the observations from 8 june to 22 august 2009 using coherent backscatter radar and a digital ionosonde installed at sanya 18 34 n 109 62 e hainan island china quasi 2 day waves were observed both in the meridional wind and in daytime backscatter echo occurrence simultaneous observations on sporadic e layers in daytime showed a planetary scale wave signature in the low latitude region for the first time close correlation between echo occurrence and the mean critical frequency foes was found when the quasi 2 day planetary wave qtpw existed these results suggest that the es plays an important role in determining the long term variability of the low latitude e region fai to test the nonlinear interactions between tides and qtpw the hourly meridional and zonal winds are analyzed the subsidiary waves with anticipated frequencies and their height evolutions provide evidence of tide qtpw interactions bispectral analysis on the winds further validates the strong nonlinear interactions between tides and the qtpw in the meridional wind our results suggest that the mechanism proposed by pancheva et al 2003 is a reasonable explanation for the planetary scale variability of the low latitude e region fai and es the different responses of the es layers and the e region fais on the qtpw between day and night can be attributed to diurnal variations in ion densities in the region between 100 and 160 km

upper stratosphere polar jet instability in the southern hemisphere synoptic scale zonal eddies longitudinal disturbances confines to polar latitudes in the southern hemisphere sh upper stratosphere have been observed in fourier analyses of temperature measurements from the limb infrared monitor of the stratosphere lims experiment during april may 1979 eddy activity at 60 degree s 1 mb is characterized by a fourier zonal wavenumber 5 wavelength approximately 4 000 km disturbance of amplitude 2 3 k which exhibits intermittent eastward propagation substantial meridional phase tilt and little vertical phase tilt these wave properties along with evidence of pronounced latitudinal variations in the upper stratosphere zonal wind distribution suggest that the synoptic scale modes may arise from a latitudinal wind shear barotropic instability of the sh polar jet stream this analysis apparently represents the first identification of polar upper stratosphere synoptic scale disturbances from satellite based information heretofore only seen in rocketsonde measurements in northern hemisphere nh polar regions and also predicted by linear model studies the ability to discern these disturbances in satellite temperature data sets offers an opportunity for future studies of the interhemispheric and interannual variability of synoptic scale eddy activity in the stratosphere however and unambiguous determination of dominant wavelength and phase speed in such studies will be precluded by the fact that satellite data alwaysmore will suffer from a certain degree of aliasing if disturbances exist with scales unresolved by the asynoptic satellite sampling less

on the characterization of glacier response by a single time scale glacier response to climate can be characterized by a single time scale when the glacier changes sufficiently slowly then the derivative of volume with respect to area defines a thickness scale similar to that of johannesson and others and the time scale follows from it our version of the time scale is different from theirs because it explicitly includes the effect of surface elevation on mass balance rate which can cause a major increase in the time scale or even lead to unstable response the time constant has a dual role controlling both the rate and magnitude of response to a given climate change data from south cascade glacier washington u s a illustrate the ideas some of the difficulty in obtaining accurate values for the thickness and time scales and the susceptibility of all response models to potentially large errors

planetary scale variability in the low latitude e region field aligned irregularities first results from gadanki observations 1 in this paper we present for the first time planetary scale wave signatures in the low latitude e region field aligned irregularities fai observed during june 2004 to may 2005 using the gadanki mesosphere stratosphere troposphere radar we have observed a clear signature of 5 8 day variability in echo occurrence in snr and also in doppler velocity observed above 100 km concurrent temperature observations made using the sounding of the atmosphere using broadband emission radiometry saber on board the thermosphere ionosphere mesosphere energetic and dynamics timed satellite have also clearly shown the presence of 5 8 day variability similar to that of fai the temperature variations have been characterized with zonal wave numbers of 3 and 4 and vertical wavelength of 15 20 km these waves are found to have increasing amplitude with increasing height and phase progressing downward suggesting that they were of lower atmospheric origin it is emphasized that the planetary scale characteristics of neutral atmosphere in the fai observations are important in understanding the vertical coupling of the low latitude ionosphere atmosphere system these observations and the pertinent issues are discussed in the light of current understanding of the planetary scale role on the fai variability

a time constant for hemispheric glacier mass balance the notion is developed of a mass balance time constant applicable to the northern hemispheric glacier inventory taken as a whole ice dynamics are incorporated only implicitly in its estimation which follows directly from a consideration of observed mass balance and hemispheric temperature time series while such a parameter must certainly be related to the rate at which glacier hypsometry adjusts to variations in climate as are time constants derived via dynamic considerations the parameter discussed herein differs with respect to its statistical character for an ensemble of northern hemisphere glaciers a time constant value on the order of a century is estimated it is shown that such a value is consistent with the hemispheric near equilibration of glaciers that prevailed around 1970 a reference climate is defined such that the mass balance in a given year is a function only of the difference between that year s climate and the reference this difference was small during the hemispheric near equilibrium that prevailed around 1970 implying that the glacier wastage of the late 20th century is essentially a response to post 1970 warming it is shown that precipitation fluctuations play a compensating role in the hemispheric net mass budget in that they are strongly anticorrelated with fluctuations in temperature induced melting however the contribution of precipitation does not override that of temperature which remains the dominant influence on hemisphere wide glacier fluctuations

radar observations of a 3 day kelvin wave in the equatorial mesosphere mesospheric radars are used to investigate the characteristics of a kelvin wave from two equatorial sites jakarta indonesia in the western pacific and christmas island in the central pacific our study focuses on the time span from mid january through mid october 1993 a kelvin wave with a period near 3 days was detected throughout this 9 month duration although it underwent deep amplitude modulations on a 20 day timescale a fitting procedure is applied to study the phase amplitude behavior of the wave the vertical wavenumber was measured by the radars and found to be small wandering around zero with only a weak bias toward downward phase progression the long vertical wavelength suggests that the wave was predominantly zonal wavenumber 1 the amplitude of the wave measured by the jakarta meteor scatter radar was much larger than the amplitude measured by the mf partial reflection radar at christmas island the smaller wave amplitude at christmas island could at least partially be due to a measurement bias associated with mf radars the radar at jakarta is a vhf meteor scatter radar and is not susceptible to this bias however the mean velocities and the amplitudes of the tidal and quasi 2 day wave components were in good agreement at the two sites the estimated 9 month averaged zonal acceleration was 0 67 ms 1 day 1 over jakarta at 94 98 km and only about half as large over christmas island the magnitude of the zonal acceleration occasionally showed large enhancements which suggest the importance of refractive effects associated with vertical and temporal variations in the mean winds the larger 3 day wave amplitudes and inferred acceleration at jakarta may reflect its location in the western pacific a region of high convection and hence an excitation region for equatorial waves the relative phase of the wave between the two radar sites gradually shifted over a timescale of weeks these smooth variations in relative phase are suggestive of a superposition of waves with different zonal wavenumbers perhaps radiating preferentially from one longitude the phase of the wave as a function of altitude and time was much more disordered at jakarta than at christmas island the conjecture can be made that the more chaotic phase structure observed over jakarta is due to higher order zonal wavenumber components which weaken as they propagate eastward

magnetic fabric and remanent magnetization of pyroclastic surge deposits from vulcano aeolian islands italy abstract tufi di grotte dei rossi inferiori are unwelded fine grained pyroclastic deposits of hydromagmatic origin emplaced between 21 and 11 8 6 ka at vulcano aeolian islands italy by deposition through surges spreading laterally from inside the la fossa caldera in this study the deposit s magnetic properties were investigated and interpreted in terms of eruptive and emplacement dynamics rock magnetism data were supplemented by grain size and textural characteristic analyses as well as scanning electron microscope sem investigations curie point measurements isothermal remanent magnetization and microprobe analyses showed that magnetization is carried by low ti titanomagnetite the size of the grains ranges from about 20 to 300 micrometres their shape from equidimensional to highly elongated the magnetic fabric is typical of fine grained pyroclastics foliation is well developed and in most sites lineation is directed towards the source area of the la fossa caldera the remanent magnetization consists of two components whose blocking temperature spectra partially overlap the direction of the low temperature component is close to that of the axial dipole and consistent with the palaeosecular variation curve for the aeolian islands the high temperature component is systematically shallowed and close to the direction of the magnetic lineation the overall results suggest that the high temperature component was acquired before and the low temperature component after the actual deposition of grains immediately after eruption the grains cooled and moved as free particles in the turbulent cloud during the expansion of the surge flows those particles with high blocking temperatures acquired a thermal remanence they were then deposited and shear at the very base of the flow oriented them and imprinted the rock s fabric and high temperature magnetization component volcanological and magnetic data suggest turbulent transportation and traction deposition of particles finally the rock cooled down and acquired the low temperature magnetization according to this model remanence acquisition in pyroclastic rocks deposited at temperatures lower than the curie point of their ferromagnetic grains depends on both the fluid dynamic forces and cooling history and must therefore be more complex than in pyroclastics deposited at higher temperatures such as welded ignimbrites

reconstruction of the annual balance of vadret da morteratsch switzerland since 1865 we have reconstructed the annual balance of vadret da morteratsch engadine switzer land with a two dimensional energy balance model for the period 1865 2005 the model takes into account a parameterization of the surface energy fluxes an albedo that decreases exponentially with snow depth as well as the shading effect of the surrounding mountains the model was first calibrated with a 5 year record of annual balance measurements made at 20 different sites on the glacier between 2001 and 2006 using meteorological data from surrounding weather stations as input to force the model for the period starting in 1865 we employed monthly temperature and precipitation records from nearby valley stations the model reproduces the observed annual balance reasonably well except for the lower part during the warmest years most crucial to the results is the altitudinal precipitation gradient but this factor is hard to quantify from the limited precipitation data at high elevations the simulation shows an almost continuous mass loss since 1865 with short interruptions around 1920 1935 and 1980 a trend towards a more negative annual balance can be observed since the beginning of the 1980s the simulated cumulative mass balance for the entire period 1865 2005 was found to be 46 m w e

evidence of a role for modulated atmospheric tides in the dependence of sporadic e layers on planetary waves 1 a large amplitude 7 day period westward propagating s 1 planetary wave pw of global response has been reported from ground radar and satellite wind measurements in the mesosphere lower thermosphere mlt during the second half of august and well into september 1993 following recent suggestions that pw might play a role in the formation of midlatitude sporadic e layers es haldoupis and pancheva 2002 found a strong 7 day periodicity present in all stations concurrently with the 7 day planetary wave reported elsewhere by analyzing sporadic e critical frequency foes time series from eight midlatitude ionosonde stations covering a longitudinal zone from about 58 e to 157 w this study provided the first direct proof in favor of a pw role on es formation in the present paper we further investigate this role by considering the same pw event and correlating the 7 day periodicity in foes directly with concurrent variations in the mesospheric neutral wind measured with atmospheric radars in saskatoon canada and in sheffield united kingdom although our analysis cannot exclude a direct pw role on es formation it shows clearly that es is affected indirectly by the pw through the action of the diurnal and semidiurnal tides which are strongly modulated by the same pw apparently through a nonlinear interaction process at altitudes below 100 km this 7 day pw modulation was found to be clearly present simultaneously in the amplitude of the zonal 12 hour tidal wind the meridional 24 hour tidal wind and in both the 12 hour and 24 hour periodicities which existed in the foes time series the results here provide a new physical explanation for the observed relation between sporadic e layers and planetary waves

the 5 day wave in the arctic and antarctic mesosphere and lower thermosphere 1 the 5 day planetary wave in the polar mesosphere and lower thermosphere has been investigated using meteor radars at esrange 68 n 21 e in the arctic and rothera 68 s 68 w in the antarctic the measurements span the 9 year interval from october 1999 to december 2008 and the 4 year interval from february 2005 to december 2008 respectively the height range covered is approximately 80 100 km horizontal wind variance within a wave period range of 4 7 days is used as a proxy for the activity of the 5 day wave strong wave activity is seen in winter and late summer however there is a high degree of interannual variability and in some individual years wave activity is almost absent the data are used to construct a representative climatology for the arctic and antarctic the seasonal cycle of the 5 day wave is found to be very similar in both polar regions wave activity in winter is present across the entire height range observed wintertime wave variance can reach about 65 m2 s2 the wave is largely absent around the equinoxes wave activity is also very strong in late summer reaching about 75 m2 s2 but occurs only for 1 2 months and is confined to heights above about 90 km and excluded from the stronger westward winds at lower heights summertime wave activity peaks at a height of about 95 km and decays rapidly above and below that height during this summer maximum the wave cannot have ascended to the mesosphere and lower thermosphere from below and so must have been generated in situ and or ducted across the equator from the winter hemisphere the seasonal cycle of the 5 day wave is remarkably similar to that observed for the 2 day wave at these latitudes

verification of large scale rapid transport in the lower thermosphere tracking the exhaust plume of sts 107 from launch to the antarctic 1 new analysis of the doppler shift of o2 airglow spectra recorded by the timed doppler interferometer tidi and the high resolution doppler imager hrdi have provided conclusive evidence that the shuttle main engine exhaust plume generated in the lower thermosphere by the launch of sts 107 and imaged by the global ultraviolet imager guvi instrument on timed was transported to the antarctic in 80 h supporting a key inference from the initial study by stevens et al 2005 these new results were aided by improved knowledge of the effects of instrumental and satellite artifacts imposed on the doppler spectra sts 107 launched on 16 january 2003 and the neutral wind near its launch trajectory and nearby volume was sampled within minutes by tidi these initial observations suggested that the northernmost end of the shuttle s exhaust plume would move northeast and that the southern end would move southeast motions that were identified in imagery acquired during the next orbit of timed the direction and magnitude of plume motion inferred from guvi images obtained 12 26 and 50 h after launch were again confirmed by tidi and hrdi the appearance of the plume over the antarctic 80 h after launch inferred from earlier work by the appearance of iron ablated from the shuttle s main engines was consistent with neutral winds measured by the satellite doppler instruments over the antarctic the transport of the plume from the coast of florida to the antarctic was aided by the favorable phase and strong amplitude of a 2 day planetary wave of wave number three in the southern hemisphere on 18 january 2003 the existence of the 2 day wave was deduced from zonally averaged and combined tidi and hrdi neutral wind observations we conclude that the existence of strong and sustained winds in the mlt significantly greater than expected from empirical and theoretical models is indisputable and provides compelling evidence supporting the global scale nature of thermospheric winds with magnitude greater than 100 m s observed by larsen 2002 from 40 years of sounding rocket chemical release experiments

annual and interannual variations in global 6 5dws from 20 to 110 km during 2002 2016 observed by timed saber

quasi periodic radar echoes from midlatitude sporadic e and role of the 5 day planetary wave using measurements of magnetic aspect sensitive radar echoes from midlatitude sporadic e collected over a two month period from tanegashima japan we show that while their occurrence duration from night to night did not exhibit any systematic variation that of the so called quasi periodic qp echoes varied sinusoidally with a period of 5 days we have interpreted this behavior in terms of effects produced by a planetary wave and identified its presence through neutral wind measurements made with a partial reflection drift radar located nearby at yamagawa we propose that the occurrence of qp echoes is affected both by a contribution of the wind to the dynamo electric field and by the direction of the neutral wind we argue that because the wind vector of the planetary wave is elliptically polarized at midlatitudes a preferred wind direction conducive to the generation of qp echoes occurs once every 5 days on the other hand this wave is linearly polarized and directed zonally over the geographic equator the fact that qp echoes are most fully developed at midlatitudes and less so at lower latitudes suggests that zonal flow is not particularly favorable for qp echo production

temporal modulations of the longitudinal structure in f2 peak height in the equatorial ionosphere as observed by cosmic 1 this study investigates the temporal variability of longitudinal structure in f2 layer peak height hmf2 in the equatorial ionosphere for this study electron density profiles retrieved from the radio occultation measurements by the constellation observing system for meteorology ionosphere and climate cosmic are fitted with a two layer chapman function to determine hmf2 the hmf2 values in the magnetic equatorial region display a four peaked longitudinal structure that has been identified in other ionospheric observations the four peaked structure is likely the signature of the forcing by the eastward propagating nonmigrating diurnal tide with zonal wave number 3 de3 further analysis for the period of prominent four peaked structure over august september 2008 finds that this structure exhibits a 5 day periodicity coincidentally the all sky interferometric meteor radar s wind measurements at thumba 8 5 n 77 e in india for the mesosphere and lower thermosphere indicate strong 5 day planetary waves within that time period the observed temporal periodicity of the four peaked longitudinal structure in hmf2 could thus be attributed to the interaction of de3 with a 5 day planetary wave

rock magnetism and compositional investigation of brown tuffs deposits at lipari and vulcano aeolian islands italy abstract a rock magnetic investigation was carried out on the nonwelded ash deposits of the brown tuffs aeolian islands southern tyrrhenian sea to improve the stratigraphic correlation between the deposits cropping out on lipari and vulcano islands and locate their source area the study was supplemented by petrographical and geochemical analyses on selected strata with the intent to compare the brown tuffs to other rocks emplaced at vulcano in the same time span more than 30 levels were sampled in the intermediate 56 4 ka ibt 21 22 ka and upper 21 22 ka ubt parts of the brown tuffs sequences on the two islands their characteristic remanent magnetization chrm directions were derived from stepwise thermal demagnetization and the magnetic fabric from measurements of the anisotropy of magnetic susceptibility the levels with indistinguishable chrm directions were regarded as coeval and to form an individual stratigraphic unit the units were referred to the brown tuffs sequence of lucchi et al 2008 on the grounds of their emplacement age provided by comparison of their mean paleomagnetic direction with the paleosecular variation curves of the southern tyrrhenian region as well as the field constraints the closer correlation between the sequences of lipari and vulcano contributes to a better understanding of the volcanic activity that produced the brown tuffs and shows that most of the ibt and the oldest ubt levels were emplaced in a short time span between 24 and 20 17 ka the magnetic fabric is typically well developed but at most sites the magnetic foliation is very close to horizontal and no imbrication is defined the source area of the brown tuffs parent pyroclastic flows as constrained from the intersection of the magnetic lineations falls in the northeastern part of la fossa caldera structure although limited to major elements compositional data provide further indication about the parent plumbing system and its behaviour magma batch es involved in the ibt eruptions have homogeneous features and underwent frequent refilling and tapping processes conversely those involved in the early ubt eruptions are compositionally more variable this suggests more complex evolution and plumbing system activity the ubt eruptions represent either residual mafic magmas from the previous eruptions or the arrival of new fresh shoshonitic magma in the system

quasi biennial variation of the 5 day wave in the stratosphere 1 interannual variability of the 5 day wave in the stratosphere is examined by the use of national center for environmental prediction reanalysis data quasi biennial variation of the 5 day wave amplitude is clearly seen in the stratosphere this quasi biennial variation is closely related to the zonal wind variation associated with the equatorial quasi biennial oscillation in the stratosphere we give a short description of the mechanism bringing about the relationship

a case study of the mesospheric 6 5 day wave observed by radar systems 1 in this paper analysis of wind data detected by six ground based radar systems located in equatorial and midlatitude belts shows that a strong mesospheric 6 5 day wave event occurred during april may 2003 we compared the global distribution of the observed 6 5 day wave event with the theoretical wave structure rossby normal mode s n 1 2 additionally we investigated several important wave characteristics to understand the mesospheric 6 5 day wave event i e wave period vertical structure relationship with background wind propagating direction and the zonal wave number our results are summarized into three points 1 the latitudinal structure of the mesospheric 6 5 day wave during april may 2003 is basically in agreement with the theoretical rossby mode s n 1 2 although the wave amplitude of zonal wind peaked at the subequatorial latitude of northern hemisphere but not at the theoretical place equatorial region 2 the main wave periods and the altitude distribution of large amplitude of this wave event varied with latitude 3 the downward propagating wave phases indicated that this wave event originated in the lower atmosphere and propagated upward to the upper region

five day mesospheric waves observed in solar mesosphere explorer ozone solar mesosphere explorer sme ozone data were analyzed for short term periodic oscillations in the altitude region from 50 to 90 km a 5 day oscillation was found to be a dominant feature at high southern latitudes near the december solstice in the altitude range from 50 to 80 km the wave feature appears to travel westward with a speed consistent with that of a wave number one planetary scale oscillation circling the globe in 5 days the amplitude also appears to be consistent with the temperature oscillations predicted by geisler and dickinson 1976 this oscillation was not found to be a dominant feature in sme ozone during northern hemisphere summer

a 6 5 day westward propagating planetary wave origin and characteristics a large 10 30 m s 1 6 7 day period westward propagating planetary wave was seen in both ground radar and satellite data within the 80 100 km height regime during august and september 1993 previous analyses of these data argue that it was most likely a manifestation of the 1 2 rossby planetary wave commonly referred to as the 5 day wave perhaps shifted to longer periods by interaction with the mean zonal winds in this study the global scale wave model gswm hagan et al 1993 is used to analyze the characteristics of this westward propagating wave we propose that the observed wave is not a doppler shifted 5 day wave but rather an unstable mode drawing energy from unstable regions in the upper mesosphere whose realization is global in scale the concept of atmospheric instability is used to determine a likely source region and the model is used determine the characteristic period growth rate and perturbation fields of the instability driven wave

tropical snowline depression at the last glacial maximum comparison with proxy records using a single cell tropical climate model 1 the substantial lowering of tropical snowlines at the last glacial maximum lgm circa 21 kya is examined using a modified version of the single cell tropical climate model of betts and ridgway 1989 these authors concluded that it was difficult to reconcile the large depression of snowlines at the lgm with the small reduction in mean tropical sea surface temperature sst of the climate long range investigation mapping and prediction climap reconstruction here climatic implications of the snowline depression are compared not with climap but with temperature proxies 18o and sr ca ratios in corals noble gas concentrations in aquifers alkenone and mg ca ratios in deep sea sediments and recent faunal reconstructions whose lgm values have been interpreted as implying lower surface temperatures in the tropics it proves difficult in the framework of this model to reconcile the coldest of the indicated paleotemperatures with the observed snowline depression which by itself is found to be consistent with an sst reduction of 3 k a cooling of this magnitude corresponds most closely to recent warm pool lgm sea surface temperature estimates based on mg ca paleothermometry discordance among the various proxy reconstructions may result at least in part from regional variations in surface temperature change at the lgm

simulated global mean sea level changes over the last half millennium simulations of the last 500 yr carried out using the third hadley centre coupled ocean atmosphere gcm hadcm3 with anthropogenic and natural solar and volcanic forcings have been analyzed globalmean surface temperature change during the twentieth century is well reproduced simulated contributions to global mean sea level rise during recent decades due to thermal expansion the largest term and to mass loss from glaciers and ice caps agree within uncertainties with observational estimates of these terms but their sum falls short of the observed rate of sea level rise this discrepancy has been discussed by previous authors a completely satisfactory explanation of twentieth century sea level rise is lacking the model suggests that the apparent onset of sea level rise and glacier retreat during the first part of the nineteenth century was due to natural forcing the rate of sea level rise was larger during the twentieth century than during the previous centuries because of anthropogenic forcing but decreasing natural forcing during the second half of the twentieth century tended to offset the anthropogenic acceleration in the rate volcanic eruptions cause rapid falls in sea level followed by recovery over several decades the model shows substantially less decadal variability in sea level and its thermal expansion component than twentiethcentury observations indicate either because it does not generate sufficient ocean internal variability or because the observational analyses overestimate the variability

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

the seasonal cycle of planetary waves in the winter stratosphere a simple mechanistic model with time independent planetary wave forcing at the lower boundary is used to investigate the observed differences between the northern hemisphere nh and southern hemisphere sh stratospheric evolution considered here are differences in both the zonal mean and the zonal wavenumber 1 structure of the winter vortex throughout its seasonal evolution in particular for small and intermediate forcing values the model robustly produces the midwinter minimum in geopotential wavenumber 1 amplitudes observed in the sh lower and middle stratosphere this feature is considered from the different viewpoints of transitions between stable equilibria wave transmission properties of the mean flow and resonant type interactions with the lower boundary wave forcing to assess the extent to which these viewpoints previously studied in the context of models representing variation with height only are relevant to a more complicated model representing variation in both height and latitude results show that resonance with the lower boundary forcing in early and late winter leading to early and late winter wave maxima and hence to an associated midwinter minimum is the dominant mechanism in the model considered for large forcing amplitudes more typical of the nh two possible winter and late winter evolutions are found to exist for the same forcing amplitudes which of these is selected depends on the details of the forcing in early winter note that there is no constant value of wave forcing amplitude that produces both a sh like undisturbed winter evolution as well a strong final warming suggesting that time varying lower boundary wave forcing is necessary to simulate these aspects of the sh evolution

climatological features of mesosphere and lower thermosphere stationary planetary waves within 40 latitude 1 zonal and meridional wind measurements from the high resolution doppler imager hrdi and wind imaging interferometer windii instruments on the upper atmosphere research satellite uars are used to construct monthly average stationary planetary wave spw structures from 15 km to 110 km over the period december 1991 to september 1994 because of viewing constraints of the instruments intercomparisons between northern hemisphere nh and southern hemisphere sh structures and seasonal evolutions are mainly confined to 40 latitude the largest zonal wave number s 1 amplitudes 10 25 m s 1 in the stratosphere and mesosphere at 40 exist in the zonal wind fields and occur during september january in the nh and july october in the sh spw s 2 structures are much less prevalent especially above 80 km because of more restrictive filtering effects due to the mean winds above about 70 km s 1 wave amplitudes 5 10 m s 1 are more uniform extending over all nonsummer months in both hemispheres up to 80 90 km with similar amplitudes existing throughout the year at higher altitudes our interpretation is that the spw above about 80 90 km during summer owe their existence to ducting from the winter hemisphere in agreement with numerical simulations by pogoreltsev and sukhanova 1993 the origin of spw above about 80 km during winter at midlatitudes is not possible to determine unambiguously phase structures undergo a transition from vertical propagation with long vertical wavelengths hundreds of kilometers below 80 km to either evanescent behavior or an extreme shortening of vertical scale at higher altitudes this change in phase behavior may be connected with negative values in refractive index q for quasi geostrophic wave propagation which occur over a narrow height region near 80 km during almost every month this interruption of normal phase progression makes it impossible to distinguish the origin of the planetary wave oscillations from 1 those that tunnel through the q 0 region and 2 those that might be excited in situ by zonally asymmetric momentum deposition from gravity waves which have undergone filtering by the stratospheric planetary wave wind field in addition quantitative estimates of aliasing due to the diurnal tide indicate that it may be of sufficient magnitude to contaminate retrieved spw structures between 80 90 km and 100 110 km where local time coverages are incomplete comparisons are made between the observed spw structure and those from the horizontal wind model hedin et al 1993 1996 this model is found to provide a reasonable approximation to nh winter spw s 1 structures below 80 km but severely underestimates the amplitudes of spw in the sh

september 2019 antarctic sudden stratospheric warming quasi 6 day wave burst and ionospheric effects an exceptionally strong stationary planetary wave with zonal wavenumber 1 led to a sudden stratospheric warming ssw in the southern hemisphere in september 2019 ionospheric data from esa s swarm

seasonal interannual and short term variability of planetary waves in met office stratospheric assimilated fields met office stratospheric assimilated data have been used to study the variability of travelling planetary waves in the upper stratosphere during the last decade 1992 2001 to distinguish the various travelling and quasi standing waves a new space time filtering method has been developed the results of this analysis show that longer period planetary waves 10 t 20 days have significant amplitudes mainly during winter in both hemispheres westward propagating waves are dominant in the northern hemisphere but in the southern hemisphere eastward and westward propagating waves have comparable amplitudes and sometimes eastward propagating waves are dominant it is suggested that the main forcing of longer period travelling waves is an internal variability of the quasi stationary planetary waves in the tropo stratosphere and that the substantial activity of eastward propagating waves in the southern hemisphere is associated with seasonal changes of the general circulation of the middle atmosphere in the shorter period part of the wavelet spectra t 10 days westward propagating waves are dominant and the observed maxima in amplitude spectra can be identified with the first symmetric normal atmospheric modes the so called 5 and 4 day waves these waves present in the stratosphere during most of the year increase in amplitude during seasonal transitions analysis of the behaviour of wavelet amplitudes at different pressure levels shows that these normal mode waves propagate upward from the lower atmosphere and their amplitudes increase with altitude there exists also a substantial long period modulation of the 5 day wave amplitude with quasi period of about 30 days copyright 2004 royal meteorological society

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

the new remote sensing derived swiss glacier inventory ii first results complete swiss glacier inventories are available for 1850 reconstructed and 1973 from aerial photography connected to the global land ice measurements from space project a new swiss glacier inventory for approximately the year 2000 sgi 2000 is compiled mainly based on satellite imagery the developed and applied remotesensing and geographical information system gis methods are described in part i of the contribution in part ii the inventory design first result analyses and comparisons with former glacial conditions are presented as basic entries sgi 2000 contains the individual glacier identification planimetric glacier boundaries as derived from image analysis digitized central flowlines and polygonal glacier basin maps all other parameters are automatically deduced from the above entries and a digital elevation model within a gis here we analyze a set of small bernese and valais glaciers of area 2 these glaciers lost about 21 of area from 1973 to 1998 in addition to about 80 during 1850 1973 both with respect to the 1973 area in order to track the latest trend in more detail anintermediate glacier condition has been compiled from satellite imagery of 1985 this analysis gave an increasing speed of area loss 19 for 1985 98

precursory effects in the subionospheric vlf signals for the kobe earthquake abstract the subionospheric vlf omega signal transmitted from tsushima japan geographic coordinates 34 37 n 129 27 e was continuously received at inubo 35 42 n 140 52 e this data was analyzed during an 8 month period centered on the great hyogo ken nambu kobe earthquake m g 7 2 on 17 january 1995 the epicenter located inside of fresnel zone of the vlf path to clarify the possible effect we developed the special tt terminator time method of data processing which was useful for our short vlf path distance 1000 km we discovered a statistically significant change of tt characteristics which began a few days before the main shock and probably continued a few weeks after it as a transient oscillation with period 10 days by simple modelling it was shown that tt changes could be caused by the decrease of the vlf reflection height by 2 km the possible underlying mechanisms of the effect are not defined however an increase of the regular electric field due to radon exhalation before the earthquake or an intensification of planetary waves by seismically influenced atmospheric turbulence might be considered

response time of glaciers as a function of size and mass balance 1 theory a simple interpretation of the traditional definitions of glacier and ice sheet response time e g thickness divided by mass balance rate h b suggests that larger glaciers respond more slowly than small glaciers to a perturbation in climate however with reasonable choices for mass balance behavior a scaling analysis shows that the response time of valley glaciers decreases as a function of increasing size when other variables are held constant in essence this is because larger valley glaciers push further into the ablation zone and ablation increases more rapidly than the thickness so that h b gets smaller ice sheets have different mass balance regimes than valley glaciers and as they grow larger the ablation does not increase faster than the thickness therefore as ice sheets grow in surface area the response time increases for both ice sheets and valley glaciers the response time also depends on a mass balance index which is defined as the slope of the balance curve as a function of horizontal distance along the glacier surface rather than elevation the response time decreases as the balance index increases so for valley glaciers an increase in the balance index and an increase in glacier size have opposite effects on the response time the balance index is typically larger for smaller valley glaciers therefore a small glacier will typically respond faster than a large glacier but this quicker response is because of mass balance considerations and not because of the dynamic characteristics of the glacier arising from its small size as often assumed

planetary waves and midlatitude sporadic e layers strong experimental evidence for a close relationship 1 a large amplitude 7 day period westward propagating s 1 planetary wave has been reported from ground radar and satellite wind measurements in the mesosphere lower thermosphere mlt during the second half of august and well into september 1993 following recent suggestions that planetary waves might play a role in the formation of midlatitude sporadic e layers es we have obtained and analyzed for the period from august 1 to september 30 1993 the sporadic e critical frequency foes time series from eight midlatitude ionosonde stations covering a large longitudinal zone from 58 e to 157 w the analysis revealed that all eight station foes data showed a strong 7 day periodicity occurring concurrently with the 7 day planetary wave reported elsewhere using independent methods for the analysis of the foes time series we computed identical estimates for the propagation direction zonal wave number and phase velocity of the 7 day wave which are in agreement with those reported from radar and satellite neutral wind mlt measurements the present findings provide the first direct evidence proving that planetary waves play an important role in the physics of midlatitude sporadic e region layers in addition our results include an important implication that the es parameters measured routinely and rather reliably with a dense global network of digital ionosondes as well as the enormous ionogram databases existing in world data centers may be used as an alternative means of studying large scale neutral atmospheric dynamics in the mlt region

the 6 5 day wave and its seasonal variability in the middle and upper atmosphere 1 the zonal wave number 1 planetary wave of period near 6 5 days is a robust feature in the mesosphere and lower thermosphere mlt region with prominent seasonal variability as revealed by ground based and satellite observations this wave and its seasonal variability are well reproduced in a recent one model year run of the national center for atmospheric research thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm with its lower boundary specified according to the national centers for environmental prediction analysis year 1993 wavelet analysis of the model output shows that in the mlt region the wave maximizes before and after the equinoxes and minimizes at solstices the wave amplitudes at the equinoxes are smaller than the peaks before and after but are still larger than the wave amplitudes at solstices however at the lower boundary near 30 km the wave peaks are predominantly between fall and the following spring by examining the episodes of maximum and minimum wave amplitude and by conducting additional control experiments using the time gcm the structure of this planetary wave and the factors determining the wave characteristics and seasonal variability are studied in detail it is found that the wave source mean wind structure instability and the critical layers of the wave can all affect the wave response in the mlt region and can have a strong seasonal dependence before and after equinox the wave follows the waveguide and propagates from the stratosphere to the summer mesosphere mesopause where it may amplify due to baroclinic barotropic instability such instability is usually absent from the equinoctial atmosphere so that there is no wave amplification at equinox at solstice the wave decays significantly when propagating away from its winter source due to the strong eastward winter stratospheric jet in the summer side the westward jet is also strong and the meridional and vertical extension of the critical layer of the wave is large enough to enclose the instability in the summer mesosphere mesopause at middle to high latitudes the wave is thus reflected away and prevented from reaching and amplifying at the unstable region the seasonal variation of the quasi two day wave which has zonal phase speed similar to the 6 5 day wave is also studied using similar diagnostics it is further shown that within certain seasonal window periods the variability in the mlt especially the summer mlt may closely track the lower atmospheric variability associated with these waves

holocene glacier fluctuations in the canadian cordillera alberta and british columbia abstract although the record of holocene glacier fluctuations in british columbia and alberta is still very fragmentary much recent progress has been made in their study dating of end moraines has been supplemented by studies of lateral moraine stratigraphy and dating of glacially overridden organic matter upstream of end moraines dates from sites close to contemporary glaciers indicate that ice had retreated to about its present limits before 10 ka bp prior to deposition of mazama tephra a minor pre hypsithermal readvance the crowfoot advance left deposits in the rockies and the interior of british columbia the earliest known neoglacial advances occurred 5 6 ka bp in the coast mountains and shortly after 4 ka bp in the rockies an advance culminating ca 4 3 ka bp has been reported from bugaboo glacier while evidence of another advance culminating in the period ca 2 5 1 8 ka bp the tiedemann advance is reported from more than one site following a recession the little ice age expansion the cavell advance began shortly after 900 bp this advance culminated in most cases in the 18th or 19th centuries the crowfoot tiedemann and little ice age advances were apparently of roughly the same magnitude the latter was most extensive in most cases but at several sites crowfoot moraines lie slightly farther downvalley than little ice age moraines during the present century ice fronts have generally retreated particularly rapidly in the period 1920 1950 a d although rates of retreat have decreased in the last three decades and some glaciers have readvanced slightly

quantifying the effects of climate and surface change on glacier mass balance when a mass balance is computed using an outdated map that computation does not reveal the actual mass change but older maps often must be used for practical reasons we present a method by which with a few additional measurements each year a mass balance computed with an outdated map can be transformed into an actual mass change this is done by taking into account the influence of changes in areal extent and changes in the surface elevation of the glacier since the map was made this method is applied to south cascade glacier washington u s a as an example the computed cumulative mass balance from 1970 to 1997 would have been 16 too negative if the 1970 map had not been updated while the actual volume change of a glacier is relevant to hydrological studies the change that would have occurred on a constant or static surface is more relevant to certain glacier dynamics problems and most climate problems we term this the reference surface balance and propose that such a balance which deliberately omits the influence of changes in area and surface elevation is better correlated to climatic variations than the conventional one which incorporates those influences

paleomagnetic secular variation at vulcano aeolian islands during the last 135 kyr abstract paleosecular variation psv of the earth s magnetic field during the last 135 kyr has been investigated in lavas scoriae and pyroclastic rocks of vulcano aeolian islands about 1000 samples have been collected at 77 sites from 25 distinct volcanic units whose age is either known from published isotopical data or constrained on the grounds of statigraphical relationships magnetic mineralogy investigation shows that ti magnetite is the main ferromagnetic mineral at most sites secondary magnetization components are either absent or easily removed by stepwise thermal or alternating field demagnetization the mean site direction of the characteristic remanent magnetization is usually well defined since the semi angle of confidence is greater than 5 at only four sites the mean paleomagnetic direction over the last 135 kyr d 9 4 i 53 2 95 3 5 differs from the geocentric axial dipole gad at vulcano d 0 i 57 8 and might be interpreted as the effect of a long term non axial dipolar component the psv record from vulcano agrees well with those from the lacustrine sediments of lago grande di monticchio 100 kyr bp and lago di mezzano 30 kyr bp located in the italian peninsula brandt et al quat sci rev 18 1999 961 976 the inclination anomaly i found at vulcano corresponds to about half of the shallowing observed in the sediments of the two lakes and the declination anomaly d may be used to tie the declination values derived from azimuthally unoriented cores to the geographical reference system in order to find the optimum site to be used as reference for psv studies in italy the angular values of the earth s magnetic field measured at the 113 repeat stations of the italian geomagnetic network coticchia et al boll geod sci aff 40 2001 277 291 have been analyzed with the relocation via pole method noel and batt geophys j int 102 1990 753 756 the viterbo station lat 42 27 n long 12 02 e proved the best since the mean error is 0 3 for both declination and inclination wherever the original psv site is located in italy a preliminary composite psv curve for the last 30 kyr bp is thus proposed merging and relocating to viterbo the data from vulcano and the curve from lago di mezzano corrected for the gad deviation found at vulcano

mass balance of glaciers and ice caps consensus estimates for 1961 2004 1 working with comprehensive collections of directly measured data on the annual mass balance of glaciers other than the two ice sheets we combine independent analyses to show that there is broad agreement on the evolution of global mass balance since 1960 mass balance was slightly below zero around 1970 and has been growing more negative since then excluding peripheral ice bodies in greenland and antarctica global average specific balance for 1961 1990 was 219 112 kg m 2 a 1 representing 0 33 0 17 mm sle sea level equivalent a 1 for 2001 2004 the figures are 510 101 kg m 2 a 1 and 0 77 0 15 mm sle a 1 including the smaller greenland and antarctic glaciers global total balance becomes 0 38 0 19 mm sle a 1 for 1961 1990 and 0 98 0 19 mm sle a 1 for 2001 2004 for 1991 2004 the glacier contribution 0 77 0 26 mm sle a 1 is 20 30 of a recent estimate of 3 2 0 4 mm a 1 of total sea level rise for 1993 2005 while our error estimates are not rigorous we believe them to be liberal as far as they go but we also discuss several unquantified biases of which any may prove to be significant

planetary wave mean flow interaction in the stratosphere a comparison between northern and southern hemispheres by the use of stratospheric height and temperature field data obtained from the tiros satellite dynamical interaction between planetary waves and mean zonal winds in the stratosphere is investigated special attention is paid to differences between northern and southern hemispheres an analysis is made for pressure levels from 70 to 0 4 mb during the period from june 1981 to may 1982 eliassen palm e p flux diagnostics are used as a powerful and useful tool to investigate the wave mean flow interaction from winter to summer the seasonal marches of wave activity measured by the e p flux and of mean zonal wind are different between the two hemispheres in the nh wave activity varies intermittently with a characteristic timescale of about two weeks once the core of the stratospheric westerly jet shifts poleward due to a minor warming the subsequent wave activity breaks the westerlies dramatically to replace them by the easterlies in association with the sudden warming whilst in the sh wave activity in mid winter is quiet corresponding to small time variations of the maximum westerly speed in late winter the core of the stratospheric westerly jet suddenly shifts poleward and downward due to a wavenumber 2 minor warming after the shifting of the westerly jet the wave activity of wavenumber 1 is enhanced and continues until early summer on the basis of this observational evidence we discuss i the seasonal evolutions of wave activity and the mean zonal wind ii the interannual variability of the stratospheric circulations and iii the time variation of wave activity

subionospheric vlf signal perturbations possibly related to earthquakes a likely vlf subionospheric signal effect related to seismic activity was first reported by hayakawa et al 1996a b in association with the great kobe earthquake we have analyzed similar data during periods around 10 other great earthquakes magnitude m 6 in order to understand the main features of such an effect the following characteristics emerged from our analysis the effect appears as a transient oscillation with a 5 to 10 day period which is initiated a few days before a large earthquake and decays over a few days to weeks after it it is mainly related to crustal earthquakes it appears when resonant atmospheric oscillations with periods in a range of 5 11 days exist before the earthquake the seismic influence on the vlf signal is probably explained by the generation of long period gravity waves during the earthquake process and their intensification at heights of 70 90 km

intercomparison of planetary scale diagnostics derived from separate satellite and radiosonde time mean temperature fields the planetary scale components of the extratropical northern hemisphere troposphere stratosphere 1973 74 winter circulation are diagnosed using separate time mean temperature fields based on radiosonde and satellite observations meridional cross sections of zonal wind together with for zonal wavenumbers 1 2 and 3 the streamfunction amplitude phase and eliassen palm flux are displayed with the relative accuracy of the satellite derived diagnostics assessed through comparison with the ground truth radiosonde information the satellite and radiosonde diagnostics compare most favourably in terms of zonal wind speed and shear direction of wave propagation and meridional wave structure all of which are closely related to the differential properties of the atmospheric temperature field the intensity of the satellite derived patterns of tropospheric wave propagation is underestimated due to the effects of spatial smoothing and residual cloud contamination present in the satellite radiance measurements

some comparisons between the middle atmosphere dynamics of the southern and northern hemispheres comparisons are drawn between certain middle atmosphere dynamical processes in the southern hemisphere and the northern hemisphere attention is focused on the zonal mean climatological state stationary waves transient waves of various types stratospheric sudden warmings and polar ozone minima observations of the similarities and differences between the hemispheres are mentioned and ways in which these comparisons may be used to enhance our dynamical knowledge of the whole middle atmosphere are discussed

the new remote sensing derived swiss glacier inventory i methods a new swiss glacier inventory is to be compiled from satellite data for the year 2000 the study presented here describes two major tasks 1 an accuracy assessment of different methods for glacier classification with landsat thematic mapper tm data and a digital elevation model dem 2 the geographical information system gis based methods for automatic extraction of individual glaciers from classified satellite data and the computation of three dimensional glacier parameters such as minimum maximum and median elevation or slope and orientation by fusion with a dem first results obtained by these methods are presented in part ii of this paper kaab and others 2002 thresholding of a ratio image from tm4 and tm5 reveals the best suited glacier map the computation of glacier parameters in a gis environment is efficient and suitable for worldwide application the methods developed contribute to the u s geological survey led global land ice measurements from space glims project which is currently compiling a global inventory of land ice masses within the framework of global glacier monitoring haeberli and others 2000

observations of the 5 day wave in the mesosphere and lower thermosphere the 5 day planetary wave has been detected in the winds measured by the high resolution doppler imager hrdi on the upper atmosphere research satellite uars in the mesosphere and lower thermosphere 50 110 kin the appearances of the 5 day wave are transient with a lifetime of 10 20 days in the two year data set the structures of selected 5 day wave events are in generally good agreement with the 1 1 rossby normal mode for both zonal and meridional components a climatology of the 5 day wave is presented for an altitude of 95 km and latitudes mainly between 40os and 40on

day to day migrating and nonmigrating tidal variability due to the six day planetary wave 1 to investigate day to day variability in the mesosphere and lower thermosphere mlt an idealized simulation of a six day westward propagating zonal wave number 1 planetary wave is performed using the national center for atmospheric research ncar thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm the six day planetary wave introduces a six day periodicity in the zonal mean atmosphere migrating and nonmigrating tides as well as in secondary waves that are produced by nonlinear planetary wave tide interactions we have further used the linear global scale wave model gswm to isolate the effect of how the day to day changes in zonal mean zonal winds may influence tides in the mlt the most significant changes are observed in the migrating diurnal tide dw1 eastward propagating nonmigrating tides with zonal wave numbers 2 and 3 de2 and de3 and a 20 hr eastward propagating wave with zonal wave number 2 20e2 because we have included the lower atmospheric source of nonmigrating tides de2 and de3 are present with relatively large amplitudes in the mlt even in the absence of planetary wave forcing the 20e2 wave is produced by the nonlinear interaction between the de3 and the six day planetary wave and its large amplitude indicates the importance of including the realistic spectra of nonmigrating tides in numerical simulations of planetary waves the gswm simulations reveal that the dw1 is not significantly influenced by the changes in the zonal mean winds we thus conclude that the dw1 changes are driven by a combination of changes due to nonlinear interaction with the six day planetary wave as well as changes due to zonal asymmetries that result from the six day planetary wave the six day planetary wave induced changes in zonal mean zonal winds lead to a general reduction in the amplitude of de2 and de3 and introduce a slight periodic behavior in these tides the effect of changing zonal mean zonal winds appears to be the primary driver of the changes in the de2 however for de3 although the changes that can be attributed to zonal mean zonal wind variability are not insignificant the primary driver of the de3 perturbations appears to be the nonlinear interaction with the six day planetary wave last we demonstrate that the day to day changes in the de3 introduce similar day to day changes in the daytime wave number 4 longitude structure in the low latitude ionosphere these results indicate that short term variability in the low latitude ionosphere is likely to be driven by similar short term variability in nonmigrating tides in the mlt

departures from the local inverse barometer model at periods of 5 days in the central south atlantic tide gauge data from ascension and st helena in the central south atlantic supplemented by altimeter data from the topex poseidon mission suggest that the local inverse barometer lib model for the forcing of sea level variability by means of air pressure changes is not applicable within a narrow band of the variability spectrum with periods of approximately 5 days this is in contrast to other sections of the wider frequency band spanning approximately 0 05 to 0 5 cycles d wherein the data are either consistent with approximate lib response or at least suggest no departures from the lib model of similar magnitude these results have similarities to findings from pacific gauges obtained over a decade ago but so far no comparisons have been to data from other ocean areas they are also qualitatively similar to predictions for the region from a recent global barotropic numerical model the anomalous part of the spectrum coincides in frequency with the madden and julian 1972 1973 5 day pressure wave in the atmosphere if that global scale forcing is responsible for both the atlantic and pacific departures from the lib model around 5 days then similar features should be observable in tide gauge data from other tropical areas

interannual variability of the vertical descent rate in the antarctic polar vortex to investigate a descent rate in the antarctic polar vortex we analyzed the long lived trace gas data derived from the halogen occultation experiment on board the upper atmosphere research satellite during the 6 year period from 1992 to 1997 by comparing the antarctic fall february and march and spring september and october methane profiles we estimated the middle stratospheric descent for each of the six winters large year to year variations are seen 1 2 1 8 km month 1 at 0 6 ppmv which consist of a biennial oscillation and a decreasing trend for the period analyzed the descent rate is larger in the even years 1992 1994 and 1996 than in the odd years 1993 1995 and 1997 dynamical fields for the 6 years are also analyzed using the united kingdom meteorological office assimilation data the differences between the even and odd years are clear in the midwinter in the even years the downward and poleward movement of the westerly jet occurs earlier the thermal wind relation infers that this event is associated with the development of a warm pool around the antarctic stratopause resulting from adiabatic heating due to the downward motion of air planetary wave activity over the winter season is more vigorous in the even years than in the odd years suggesting a close relationship between the mean flow and planetary waves

global variability of mesospheric temperature planetary scale perturbations at equatorial and tropical latitudes 1 the study examines the source of a cold temperature perturbation observed in the wind imaging interferometer windii daytime daily zonal mean temperatures at 87 km height during march april 1993 also seen to some extent in 1995 and 1997 over the latitude range 25 s to 25 n the perturbation appears centered at 10 s as a departure of 10k to 35k below the semiannual climatological mean which peaks at equinox after accounting for tidal contributions to the observations by adopting tidal parameters determined from the microwave limb sounder mls temperature observations the cold temperature signature still remained in the residual data the perturbation is a global phenomenon immediately following march equinox and lasts over a period of 2 weeks the period is marked by the presence of mesospheric temperature inversions over the altitude range of 70 90 km harmonic analysis reveals the presence of planetary waves of wave number 1 with periods of 3 days 4 5 days and 7 days a cross section of the temperature monthly zonal mean data and month of the year over the period from january 1992 to december 1995 revealed a distinct msao modulated by a qbo with strong cold anomalies in march april 1993 1995 and 1997 in excellent agreement with the msao easterly phase of correlative mf radar wind observations at tirunelveli 8 7 n 77 8 e it is shown that the observed temperature anomalies can be produced by the residual circulation associated with the wave driving of the msao itself

climatology of the quasi 6 day wave in the mesopause region and its modulations on total electron content during 2003 2017

large scale rossby normal modes during some recent northern hemisphere winters abstractlarge scale rossby normal modes are studied for the northern hemisphere winters of 2005 2006 2008 and 2009 using global observational meteorological analyses spanning the 0 92 km altitude range spectral analysis of geopotential height fields shows pronounced peaks at westward propagating zonal wavenumber 1 near the theoretical locations of the free rossby waves at 25 16 10 and 5 days that in some cases have amplitudes significantly larger than the estimated background spectrum evidence is also found for a wavenumber 2 free mode near 4 days a coherence analysis is used to extract the amplitude and phase of the waves and to isolate those regions of the latitude altitude plane where the signals are statistically significant although the spectral location temporal evolution and vertical structure of several of these waves are suggestive of the presence of rossby normal modes this study shows that in the real atmosphere the waves only occasionally have the global properties of classical

stratigraphy and significance of brown tuffs on the aeolian islands southern italy abstract brown tuffs bt are volcaniclastic ash deposits prominently represented in the stratigraphic profiles of all the aeolian islands and capo milazzo on the northern coast of sicily detailed stratigraphy and tephrochronology together with available radiometric ages suggest that they were emplaced over a long time interval spanning from the end of the last interglacial period ca 80 ka bp up to 4 5 ka bp age of the overlying punte nere pyroclastic products on vulcano the most complete bt succession is documented on lipari where 14 distinct and successive units are subdivided by the interbedding of widespread tephra layers local volcanic products paleosols and epiclastic deposits and the occurrence of local erosive surfaces inter island occurrence of ischia tephra a widely known tephra layer in the aeolian archipelago dated at 56 ka bp and monte guardia pyroclastics from lipari dated at 22 20 ka bp subdivides the bt succession in upper ubt intermediate ibt and lower bt units lbt which can be correlated at regional level the lbt was emplaced between 80 and 56 ka bp the ibt between 56 and 22 ka bp and the ubt between 20 and 4 5 ka bp on the basis of stratigraphy similarity in lithology and textural features morphology of glass fragments composition and consistency of thickness and grain size variations ubt units correlate with piano grotte dei rossi tuffs on vulcano island they were generated by pulsating hydromagmatic explosive activity giving rise to pyroclastic density currents spreading laterally from a source located inside the la fossa caldera on vulcano island composition is in agreement with this hypothesis since ubt compositional features match those of vulcano magmas erupted in that period the effect of co ignimbrite ash clouds or associated fallout processes from sustained eruptive columns is seen to explain the presence of ubt in areas further away from the suggested source e g salina and lipari islands and capo milazzo the origin of ubt exposed on panarea island is still a matter of debate due to contrasting compositional data due to large uniformity of lithological textural and componentry characters with respect to the ubt the lower portions of the bt succession lbt ibt are considered to be the result of recurrent large scale hydromagmatic eruptions of similar type moreover for the ibt units the correlation with monte molineddo 3 pyroclastics of vulcano island on the basis of lithological compositional and stratigraphic matching again suggests source s related to the vulcano plumbing system and located within the la fossa caldera

is the decline of ice on kilimanjaro unprecedented in the holocene glaciers on kilimanjaro s highest peak kibo are currently regarded as a persistent feature of the holocene here we synthesize all available measurements observations and our understanding of current processes on kibo gained from intensive research over the past decade to formulate an alternative hypothesis about the age of these ice fields this suggests a shorter discontinuous history of the tabular shaped glaciers on kibo s plateau where typical life cycles of the ice may last only a few hundred years if life cycles overlap they are likely the cause of the observed steps in the plateau glaciers thus it is likely that ice has come and gone repeatedly on kibo s summit plateau throughout the holocene such a cyclicity is supported by lake derived proxy records

a study of tidal and planetary wave periodicities present in midlatitude sporadic e layers the diurnal and semidiurnal atmospheric tides are known to be of fundamental importance in the formation of midlatitude sporadic e layers acting through their vertical windshear forcing of the long living metallic ions in the lower thermosphere also recent studies suggested that planetary waves play a role on sporadic e generation as well a fact that went unnoticed in the long going research of sporadic layers in this paper a methodology is employed to investigate the tidal and planetary wave periodicities imprinted onto sporadic e critical frequencies foes in this approach standard analysis techniques used in neutral atmospheric dynamics are applied on foes time series obtained during summertime when sporadic e occurrence is nearly continuous it is shown that besides the dominant and known 24 hour and 12 hour tidal periodicities in foes there is often a weaker terdiurnal 8 hour oscillation present as well in addition there are planetary wave periodicites in foes with periods near the normal rossby modes that is 2 5 10 and 16 days it is also found that the tidal oscillations in foes undergo a strong amplitude modulation with periods comparable to the dominant planetary wave periodicities present in the data our results are in line with recent findings based on a single event study which suggested that sporadic e layers are affected indirectly by planetary waves through their nonlinear interaction and modulation of the atmospheric tides at lower altitudes the close relationship between neutral wave dynamics and midlatitude sporadic e periodicities suggests that the ionosonde data can be used as an alternative means of studying tidal and planetary wave characteristics and their climatology in the lower thermosphere

composite detrital and thermal remanent magnetization in tuffs from aeolian islands southern tyrrhenian sea revealed by magnetic anisotropy this paper reports on the complex relation between rock emplacement and remanence acquisition in tuffs deposited by pyroclastic density currents disclosed by systematic measurements of the anisotropy of magnetic susceptibility and natural remanent magnetization nrm thermal demagnetization shows that the nrm consists of two components with different blocking temperature spectra the direction of the low temperature component is consistent with the geocentric axial dipole value whereas the high temperature component has dispersed directions the magnetic fabric is oblate the magnetic foliation is close to the bedding and the lineations are generally dispersed along a girdle within the foliation plane the directions of the magnetic lineation and the high temperature remanence component of individual specimens are close to each other this correspondence suggests that the high blocking temperature grains acquired a remanence aligned to their long dimension before deposition while cooling within the explosive cloud and the moving pyroclastic current thereafter during deposition the traction processes at the base of the current oriented the grains along the flow direction and affected both fabric and high temperature remanence this nrm component results from mechanical orientation of previously magnetized grains and is thus detrital in origin a second thermal component was then acquired during the cooling of the low blocking temperature grains after deposition these results show that nrm in fine grained pyroclastic rocks is affected by the earth s magnetic field as well as the emplacement processes and that magnetic fabric data are essential to unravel its complex nature

eruptive and emplacement mechanisms of widespread fine grained pyroclastic deposits on vulcano island italy tufi di grotte dei rossi inferiori are thick ash deposits representing the most voluminous stratigraphic unit on vulcano island the deposits are related to hydromagmatic eruption which occurred under shallow water inside a caldera depression grain size data and results of sem investigation allow the character of the transporting medium solid material concentration in the cloud during the lateral expansion and the nature and role of the fluids present at the time of deposition to be constrained we suggest that the eruption was characterized by closely timed hydromagmatic pulses giving rise to eruption clouds rich in water vapor and steam the coarser material was not significantly transported in the eruptive cloud and it probably deposited in the caldera depression area the finer material was extensively transported in the cloud creating turbulent flows which surmounted the caldera rim barrier and dispersed in a southward direction forming widespread deposits in the piano area lower concentrated flows produced laminated deposits of more limited dispersion whereas higher concentrated flows formed more dispersed thicker massive layers

a sudden warming in the middle atmosphere of the southern hemisphere this paper presents a case study of a wave mean flow interaction or minor warming near the southern hemisphere stratopause for 15 30 july 1974 the analysis is based mainly on data from the selective chopper radiometer carried by nimbus 5 a deceleration of the zonal mean wind of 70 m s 1 from 20 to 25 july is observed in middle latitudes at 0 5 mb with an acceleration further south the polar vortex is however not disrupted eliassen palm cross sections are presented for the event and a good correlation found between the e p flux convergence and the deceleration the channelling of the e p fluxes from the tropopause to the convergent region is in broad agreement with the distribution of refractive index but there is a region of e p flux divergence at high levels in polar latitudes suggesting a source of wave activity there the residual circulation is calculated both from the momentum budget and from an omega equation both methods diagnosing a region of modest equatorward flow near the region of e p flux divergence embedded in the stronger poleward flow elsewhere maps of potential vorticity on the isentropic surface of 0 1640 k are presented and the evolving pattern related to zonal mean and isobaric descriptions the event is shown to be associated with an incursion of low latitude air into middle latitudes with a corresponding irreversible mixing of potential vorticity reminiscent of the wave breaking in northern hemisphere events reported by mcintyre and palmer j at ter ph 46 825 but of much smaller amplitude

complex remanent magnetization in the kizilkaya ignimbrite central anatolia implication for paleomagnetic directions abstract pyroclastic flow deposits known as ash flow tuffs or ignimbrites are invaluable materials for paleomagnetic studies with many applications for geological and tectonic purposes however little attention has been paid to evaluating the consistency and reliability of the paleomagnetic data when results are obtained on a single volcanic unit with uneven magnetic mineralogy in this work we investigate this issue by concentrating on the kizilkaya ignimbrite the youngest large volume unit of the neogene ignimbrite sequence of the central anatolian volcanic province in turkey bringing evidence of significant magnetic heterogeneities in ignimbrite deposits magnetic mineralogy susceptibility magnetic remanence coercivity etc and emphasizing the importance of a stratigraphic sampling strategy for this type of volcanic rocks in order to obtain reliable paleomagnetic data six sections were sampled at different stratigraphic heights within the devitrified portion of the ignimbrite isothermal remanence measurements point to low ti titanomagnetite as the main magnetic carrier at all sites at some sites the occurrence of oxidized ti magnetite and hematite is disclosed the bulk susceptibility k m decreases vertically at two out of six sections its value for the topmost samples is commonly one order of magnitude lower than that of the samples at the base in most cases low k m values relate to high coercivity of remanence b cr values which range from 25 to 400 mt and to low s ratios measured at 0 3 t between 0 28 and 0 99 these data point to the occurrence of oxidized magnetic phases we therefore consider the k m parameter as a reliable proxy to check the ignimbrite oxidation stage and to detect the presence of oxidized ti magnetite and hematite within the deposit the characteristic remanent magnetization is determined after stepwise thermal and af demagnetization and clearly isolated by principal component analysis at most sites for these sites the site mean paleomagnetic direction is consistent with data from the literature at a few other sites the remanence is more complex the direction moves along a great circle during demagnetization and no stable end point is reached the occurrence of oxidized ti magnetite or hematite as well as two remanence components with overlapping coercivity and blocking temperature spectra suggest that the kizilkaya ignimbrite acquired first a thermal remanent magnetization and then during the final cooling or a short time later a secondary remanent magnetization component which is interpreted as a crm acquired during post emplacement devitrification processes notwithstanding the kizilkaya ignimbrite is a single cooling unit its magnetic properties suffered substantial variations laterally and vertically within the deposit the kizilkaya case shows that thick pyroclastic deposits should be sampled using a stratigraphic approach at different sites and different stratigraphic heights at each individual sampling location otherwise under sampling may significantly affect the paleomagnetic results when sampling is performed on a short duration or on very poorly preserved deposits we recommend drilling the lower central portion in the most strongly welded and devitrified facies such sampling strategy avoids complications arising from the potential presence of a pervasive secondary crm masking the original chrm

the 6 5 day wave in the tropical stratosphere and mesosphere 1 the 6 5 day wave is a westward propagating zonal wave number 1 s 1 planetary wave that is prominent near equinox the spatial temporal structure of the 6 5 day wave seen in the united kingdom meteorological office ukmo data in the stratosphere is found to be consistent with that obtained from upper atmosphere research satellite high resolution doppler imager hrdi measurements of horizontal winds and temperatures in the mesosphere lower thermosphere mlt two wave events are commonly observed before and after equinox at low latitudes in both ukmo and hrdi data this paper focuses on a pair of such events in late 1994 the amplitude growth and phase decrease with altitude of the zonal wind 6 5 day wave appear to be continuous between the two data sets for the period analyzed both wave events appear to grow from the stratosphere to the upper atmosphere at a rate consistent with the suggested vertical phase velocity such consistency between the two data sets establishes that the wave previously observed in the mlt is propagating from the stratosphere further analyses of the ukmo data shows the presence of the 10 day s 1 and 4 day s 2 waves that appear to be either nonlinearly coupled with the 6 5 day wave or related through a common sourcing mechanism