first measurements of thermospheric winds in antarctica by an optical ground based method the installation of a fabry perot interferometer at halley 75 5 s 26 8 w l 4 2 antarctica has now allowed the first comparison to be made between southern hemisphere ground based thermospheric wind measurements and the predictions of a three dimensional time dependent thermospheric global circulation model because some terms of the thermospheric momentum equation are more dependent on geomagnetic than geographic latitude the large separation of these that exists at halley provides a distinct contrast to the dynamic behaviour observed in the more frequently studied northern polar thermosphere although the initial results from the experiment are in general agreement with the model some consistent and significant differences between the observed wind field and that predicted are evident in the morning sector these may be related to uncertainties in mapping magnetospheric boundaries to ionospheric heights in the southern hemisphere

dependence of thermospheric zonal winds on solar flux geomagnetic activity and hemisphere as measured by champ the thermospheric zonal winds measured by the champ satellite are used to statistically determine climatology under quiet and active geomagnetic conditions by collectively analyzing the bin averaged wind trend with f10 7 and the solar induced difference in wind structures the solar flux dependence of global thermosphere zonal wind is determined the increase of solar flux enhances the eastward winds at low latitudes from 18 06 mlt the increased ion drag reduces the night time eastward wind in the subauroral latitudes and the daytime westward winds from 06 08 mlt at all latitudes decrease with increasing solar flux zonal winds show coupled seasonal extreme ultraviolet euv dependency the equatorial zonal winds from 18 04 mlt indicate weaker eastward winds during the june solstice at high solar flux levels quiet time eastward winds at subauroral latitudes from 16 20 mlt are further decreased in the winter hemisphere influenced by asymmetries in solar illumination and the magnetic field zonal winds show hemispheric asymmetries quiet daytime winds are additionally influenced by solar illumination effects and the westward winds at the middle and subauroral latitudes are always stronger in the summer the night time eastward winds are higher in the winter hemisphere during the solstices as in the southern hemisphere during equinoxes with the winter summer asymmetry lessened or receding at the solar maxima storm induced subauroral westward disturbance winds are higher in the summer hemisphere and in the northern hemisphere during equinoxes at a high level of solar flux the westward disturbance winds are comparable in the two hemispheres during december solstice geomagnetic disturbance wind observations from champ agree well with the empirical geomagnetic disturbance wind model dwm07 except for stronger subauroral westward jets westward winds during the afternoon may be enhanced in the auroral latitudes before the initial time of a storm main phase

a comparison of mesospheric and low thermospheric winds measured by fabry perot interferometer and meteor radar over central china wind data observed by a fabry perot interferometer fpi and a meteor radar mr deployed in two stations which are 430 km apart in ground distance are used to study wind climatology in mlt over central china and compare between the measurements a general morphologic similarity of the fpi winds and mr winds is identified with four years data since november 2011 at 87 km the wind vector plots show the fpi and mr winds agree with each other very well in all months the zonal winds of both instruments have an apparent semi annual variation with a maximal strength of 20 m s at around 18 ut in equinoctial months and the meridional winds from both instruments have an apparent annual variation with a maximal strength of 40 m s at around 15 ut in summer months the correlation coefficients between the measurements of the two instruments are about 0 95 for meridional wind and 0 90 for zonal wind at 97 km the wind vector plots show that fpi and mr winds agree with each other from may to october and are obviously different in the rest months there are very weak semi annual variation at around 18 ut for both zonal winds and pronounced annual variation at around 13 ut for both meridional winds the correlation coefficients between the fpi and mr winds are 0 73 for zonal wind and 0 86 for meridional wind which are overall smaller than that at 87 km a gaussian distribution of airglow profile is used to investigate the deviations associated with peak height and full width half maximum fwhm of airglow layer it is found that the variation of peak height could lead to about 20 variation of correlation coefficients between measurements at the height of 87 km and about 14 8 at the height of 97 km on average the variation of fwhm could lead to a correlation coefficient variation of about 2 4 and 3 5 at the height of 87 km and 97 km respectively some other reasons such as the influence of geomagnetic field on meteor trail the propagation of gravity waves could also contribute to these differences between measurements

late quaternary climates of the australian arid zone a review abstract aridity in australia has generally been associated with glacial intervals of the last few glacial cycles the causes and nature of aridity varied from north to south over the continent in northern and central australia reduced monsoon rain in global cold stages caused lakes and rivers to dry vegetation to become more sparse sand dunes to become active and dust advection to increase while the monsoon is correlated with warmer global temperatures and high sea levels overall the exact timing of the greatest development of the monsoon in stage 5 remains uncertain in southeastern australia the proxy records give a less clear picture while vegetation seems to have been more sparse in cold stages and sand dune activity and dust flux consequently greater records of runoff in rivers and lakes have mixed or opposite behaviour to northern or central australia the nature of aridity in southeastern australia is not analogous to conditions anywhere on the continent today greatly reduced temperatures over the central and southern interior greater influence of snow and periglaciation on runoff high groundwater tables lower rainfall and reduced atmospheric carbon dioxide levels may all have contributed to and interacted to produce the reconstructed picture of a cold sparsely vegetated arid landscape with large rivers and perennial lakes the largest changes in circulation patterns over the glacial cycle probably occurred in the location and or intensity of summer tropical convergence in northern australia over southern australia changes to the temperature and humidity of the westerly circulation have been more significant than the small fluctuations in latitude of the sub tropical high pressure ridge

climatology of the nighttime equatorial thermospheric winds and temperatures over brazil near solar minimum 1 we report on the climatology of equatorial thermospheric winds and temperatures based on fabry perot interferometer measurements of doppler shifts and doppler broadenings of the 630 0 nm spectral emission from the cajazeiras observatory located in the northeastern part of brazil 6 89 s 38 56 w these results apply to the lower thermosphere region near 240 km and were obtained during a period of weak solar activity with the solar flux typically within the range of 72 and 82 solar flux units examination of the monthly averaged meridional thermospheric winds for 1 year of measurement from october 2009 to september 2010 found the wind direction to be equatorward during summer months throughout the early evening hours with maximum speeds reaching 65 ms 1 during winter months the early evening meridional wind direction reversed to poleward with similar speeds this result is attributed to the cross hemispheric flow from the summer to winter hemisphere superimposed upon this wintertime meridional wind flow was an equatorward surge shortly before midnight this surge shifted to earlier local times in the transition from the vernal equinox to summer and to later local times between the summer solstice and the autumnal equinox this flow feature is attributed to tidal wave forcing the temperature observations exhibited the expected behavior with the midnight temperature maximum showing a greater amplitude 120 k in the vernal equinox with somewhat weaker amplitudes 75 k seen at earlier local times during the summer also observed was a phase lag of 60 to 90 min between the appearance of the equatorward meridional wind flow and occurrence of the midnight temperature maximum peak

climatology and latitudinal gradients of quiet time thermospheric neutral winds over millstone hill from fabry perot interferometer measurements 1 midlatitude nighttime thermospheric neutral winds are strongly dependent on season solar activity and latitude we use an extensive database of wind measurements made during 1989 2001 by the millstone hill fabry perot interferometer to study the detailed climatology of quiet time neutral winds near an altitude of 250 km to facilitate the analysis of these data we develop a local time day of year solar flux and latitude dependent empirical model with the latitude dependence obtained by considering north looking and south looking observations separately our results show that the zonal winds are predominantly eastward after dusk and westward before dawn with the strongest eastward winds occurring in the winter and with an east to west transition that occurs earliest in the summer the zonal winds exhibit weak to moderate latitudinal gradients with more westward values to the north the zonal wind magnitudes decrease with increasing solar flux the strongest trends occur during winter the meridional winds are predominantly equatorward in all cases and exhibit strong latitudinal gradients with larger values to the north the maximum nighttime equatorward winds decrease with increasing solar flux except during summer when there is no significant solar activity variation they are largest during the summer except at solar minimum when a semiannual variation is observed and the peak winds occur during the equinoxes earlier studies of midlatitude wind measurements are generally consistent with our data with our results providing a considerably more detailed description of the nighttime wind climatology at midlatitudes

trajectories of thermospheric air parcels flowing over alaska reconstructed from ground based wind measurements it is widely presumed that the convective stability and enormous kinematic viscosity of earth s upper thermosphere hinders development of both horizontal and vertical wind shears and other gradients any strong local structure over scale sizes of several hundreds of kilometers that might somehow form would be expected to dissipate rapidly air flow in such an atmosphere should be relatively simple and transport effects only slowly disperse and mix air masses however our observations show that wind fields in earth s thermosphere have much more local scale structure than usually predicated by current modeling techniques at least at auroral latitudes they complicate air parcel trajectories enormously relative to typical expectations for tracing air parcels we used wind measurements of an all sky scanning doppler fabry perot interferometer and reconstructed time resolved two dimensional maps of the horizontal vector wind field to infer forward and backward air parcel trajectories over time this is the first comprehensive study to visualize the complex motions of thermospheric air parcels carried through the actual observed local scale structures in the high latitude winds results show that thermospheric air parcel transport is a very difficult observational problem because the trajectories followed are very sensitive to the detailed features of the driving wind field to reconstruct the actual motion of a given air parcel requires wind measurements everywhere along the trajectory followed with spatial resolutions of 100 km or less and temporal resolutions of a few minutes or better understanding such transport is important for example in predicting the global scale impacts of aurorally generated composition perturbations

universal time variation of high latitude thermospheric disturbance wind in response to a substorm the temporal and spatial variation in thermospheric winds are studied at 400 km altitude in response to substorms that start at different universal time ut using a global ionosphere and thermosphere model the substorm induced disturbance winds at high latitudes are mainly in the poleward westward and upward directions in the dusk sector and in the equatorward westward and upward directions in the nighttime the daytime perturbation is due to ion drag driven by variations in interplanetary magnetic field imf bz whereas the nighttime perturbation is due to both the bz and hemispheric power input the nightside disturbed winds respond somewhat later than the dayside owing to low background ion density ion drag is the dominant driving force in the daytime for both meridional and zonal disturbed winds whereas joule heating is the dominant factor for the vertical winds the nighttime meridional and zonal winds are driven by a combination of ion drag joule heating and heating of the auroral belt whereas the vertical winds are mainly caused by auroral belt heating the viscous force acts to resist the ion drag whereas the coriolis force is negligible the disturbed winds exhibit large variations with ut during equinox and local winter conditions with more solar illumination stronger disturbed winds can be generated weak or even opposite variations with ut in the disturbed winds are found in local summer which is due to a smaller ut variation of the daytime ion density and a larger contribution from auroral heating than from ion drag

the distribution of apparent dose as determined by optically stimulated luminescence in small aliquots of fluvial quartz implications for dating young sediments abstract we noted recently murray et al 1995 that quartz samples taken from in channel fluvial deposits have apparent doses ranging over several orders of magnitude we suggested that these dose distributions are best explained by a mixture of a small number of poorly bleached grains and a larger number of well bleached grains in this paper we examine the distribution of apparent dose in small aliquots each composed of 2000 grains of different particle size fractions 63 90 m 90 125 m 125 180 m 180 212 m 212 250 m diameter from two samples collected from the murrumbidgee river new south wales australia the samples are of known burial age the first being 70 years old and the second being its modern equivalent 0 2 gy the difference in the lowest apparent dose in the two samples is considered to be the result of their different burial times we suggest a method for dating recently deposited

observations from millstone hill during the geomagnetic disturbances of march and april 1990 the incoherent scatter radars at millstone hill operated continuously during the periods march 16 23 and april 6 12 1990 providing observations of large scale ionospheric structure and dynamics over a large portion of eastern north america major geomagnetic storms occurred during each of these periods with deep nighttime ionospheric troughs and large magnetospheric convection electric fields observed equatorward of millstone the millstone observations provide a comprehensive data set detailing storm induced ionospheric effects over a 35 span of latitude during both of these intervals at the latitude of millstone the ionospheric peak height hmf2 rose above 600 km in the trough on march 22 and 23 and reached 500 km at night on april 11 and 12 increased recombination apparently due to the strong electric fields the temperature dependent recombination rate coefficient and neutral composition changes greatly depleted the f2 region over a wide latitude range during the day on april 10 1990 this resulted in an ionosphere dominated by molecular ions with ionospheric peak heights below 200 km on this day a number of frictional heating events during the disturbed periods are seen from comparison of ion temperature and velocity measurements the most intense event took place near 1200 ut 0715 lmt on april 10 1990 when kp reached 8 at 0110 ut on march 21 line of sight ion velocities in excess of 500 m s 1 were observed at the extreme southern limit of the millstone steerable radar s field of view 40 apex magnetic latitude at an altitude of 700 km these could be due to penetration of magnetospheric electric fields or electric fields associated with ring current shielding in the storm time outer plasmasphere about an hour later ion outflow was observed just equatorward of millstone this is most likely due to heating from a latitudinally confined region of intense westward convection neutral meridional winds above millstone were obtained by three different techniques employing radar and fabry perot measurements the latitude variation of the winds was also estimated from radar measurements of hmf2 and electric fields using the servo model method strong equatorward nighttime neutral wind surges were found during both the march and april disturbances which reached the equatorward limit of the observations at f peak heights

thermospheric dynamics at the south pole a self aligning fabry perot spectrometer has been installed at amundsen scott station antarctica geographic south pole and has been used to determine neutral upper thermosphere winds and temperatures obtained from the measurement of the doppler shift and doppler width of the line profiles of the oi 15 867 k 630 nm line emission during the austral winter of 1989 april 1989 to september 1989 these first ground based measurements of f region neutral dynamics at the south pole show a rich variety of dynamic phenomena and strong couplings with the ionospheric plasma data for two contrasting days in april 1989 are presented here the data of april 23 ut illustrate the diurnal variations of winds and temperatures during geomagnetic quiet to moderate conditions while the data of april 27 ut illustrate diurnal variations during geomagnetically disturbed periods these data are compared with the average pattern obtained at a similar geomagnetic latitude and conditions but in the northern hemisphere longyearbyen spitsbergen and with predictions of the average dynamics in the south pole region made by the ncar thermosphere ionosphere general circulation model tigcm the measured winds at the south pole have a stronger prevailing westward component in its diurnal cycle than is either observed at longyearbyen in the northern hemisphere or predicted at south pole by the tigcm

structural evolution of shale diapirs from reactive rise to mud volcanism 3d seismic data from the baram delta offshore brunei darussalam two areas of shale diapirism in a deltaic setting were examined using 3d seismic data from offshore brunei to determine the origin evolution and geometry of shale diapirs the study areas cover parts of the egret and ampa fields within the baram delta province the ampa diapir consists of a small bulge of the mobile setap shale around which lies a zone of chaotically disrupted country rock reflections at the crest of this chaotic zone vertical cylindrical shale pipes arise that end in a wider head the diapir heads wear halos of high amplitude reflections probably due to the presence of methane gas the egret data show the same features except that the bulge of the source layer is not detected due to low reflectivity and chaotic reflections at the base of the overburden the bulging of the setap shale on the ampa data is interpreted as modified reactive diapirism in response to differential loading the initial reactive diapir shape was modified by lateral or oblique upward migration of fluidized shales into the hanging wall of the fault controlling the reactive diapir this probably occurred as a network of dykes and sills the presence of some preserved bedding is indicated by weak but coherent reflectivity from the area initially defined as chaotic shale the spreading of overpressure and the injection of shale into the overburden is thought to be a late phenomenon possibly late pliocene or early pleistocene and the mobility of the shale is attributed to overpressure increase due to gas generation within the setap shale and maybe the lower part of the overburden gas migration perhaps ahead of the diapir intrusion probably facilitated the mud injection the ampa and egret diapirs formed in two diapiric phases an early reactive diapirism and a later active diapirism but the phases have little in common they are seperated by about 9 million years of inactivity and differ in process and probably differ in degree of overpressure in overpressure generating mechanism and in properties of the diapiric mud

an empirical model of the earth s horizontal wind fields hwm07 1 the new horizontal wind model hwm07 provides a statistical representation of the horizontal wind fields of the earth s atmosphere from the ground to the exosphere 0 500 km it represents over 50 years of satellite rocket and ground based wind measurements via a compact fortran 90 subroutine the computer model is a function of geographic location altitude day of the year solar local time and geomagnetic activity it includes representations of the zonal mean circulation stationary planetary waves migrating tides and the seasonal modulation thereof hwm07 is composed of two components a quiet time component for the background state described in this paper and a geomagnetic storm time component dwm07 described in a companion paper

seasonal variations in the equatorial thermospheric wind measured at arequipa peru studies have been carried out at arequipa peru of the seasonal variations in the thermospheric winds at moderate solar flux levels and low geomagnetic activity fabry perot interferometer measurements of the doppler shifts in the 630 0 nm nightglow emission line from march to august 1983 and from april to october 1988 have yielded monthly average meridional winds that are nearly zero 50 m s and possibly fluctuating in direction through much of the night but develop a southward flow at 50 100 m s in the early and the late night from may onward the average zonal winds are eastward throughout the night reaching peak velocities before local midnight and then decreasing the peak velocities increase to a maximum around the june solstice the winds are generally stronger in 1988 than in 1983 even though the solar euv fluxes are comparable for both years comparison of the present results with earlier satellite measurements as embodied in the horizontal wind model of hedin et al reveals generally satisfactory agreement at the equinox and june solstice except for the june 1988 period killeen et al s vector spherical harmonic form of the ncar thermospheric general circulation model calculated for similar solar flux levels yields meridional and zonal wind variations which exhibit the same temporal behaviors but generally smaller values than the present measurements the present wind patterns are also compared with those measured during the same years at arecibo puerto rico one finds oppositely directed meridional flows and similar eastward zonal flows at the two locations as expected from a consideration of solar euv heating as the principal driving force

optical dating of an aeolian deposit on the murrumbidgee floodplain abstract optical dating of quartz grains from an aeolian deposit using multiple aliquot additive dose and regenerative dose growth curves combined using the australian slide method produced ages slightly exceeding the 14 c 2 age range of 3470 4230 yr from charcoal fragments from the same horizon a slightly greater degree of scatter was observed about the additive dose growth curve than about the regenerative dose growth curve raising the possibility that the sample might have been composed of grains containing different palaeodose p as a result of incomplete predepositional bleaching this possibility was first investigated using small aliquots 10 grains and a single aliquot regenerative dose sar protocol asymmetric p distributions were observed initially interpreted as supporting the presence of a partially bleached population single grains of quartz were then examined to determine if several discrete p populations could be resolved thereby providing information on reworking events and larger aliquots were then measured in an attempt to reconcile the australian slide findings with the small aliquot and single grain results

direct observational evidence for the merging of equatorial plasma bubbles in this work we present direct ground based observational evidence for the merging of individual epbs obtained through the imaging of oi 630 0 nm airglow three potential mechanisms have been identified 1 one of the epbs tilts and reaches location of the adjacent growing epb finally merging with it 2 some of the branches of an epb arising from secondary instabilities reaches out to adjacent epb and merge with it 3 the eastward zonal drift of the epb on the eastern side slows down while the adjacent epb on the western side drifts relatively faster and catches up in one of the cases a branch of an epb was observed to get interchanged with another epb as a result of merging and consequent pinching off from the parent epb

first palmer and millstone hill midlatitude conjugate observation of thermospheric winds the first midlatitude conjugate thermospheric wind observations in the american sector showed various degrees of conjugacy between palmer 64 s 64 w magnetic latitude mlat 50 s and millstone hill 42 82 n 71 5 w mlat 53 n under three different geomagnetic conditions recovery after a substorm moderately active and quiet the agreement with the national center for atmospheric research s thermosphere ionosphere electrodynamics general circulation model tiegcm simulations also varies with the geomagnetic activity level during substorm recovery the observations at palmer pa and millstone hill mh both showed strong westward zonal winds which the standard tiegcm greatly underestimated inadequate ion convection pattern size and lack of effect from subauroral polarization streams saps may be the cause of the large discrepancy the tiegcm with a saps model produced stronger westward zonal winds near pa but did not change the zonal wind near mh the empirical saps model needs further refinements in general there is better conjugacy with moderate geomagnetic activity levels the tiegcm also agrees better with the observations under geomagnetically quiet conditions the meridional winds appear to be less conjugate the agreement between the observations and model is reasonable optical conjugate observations are severely limited by the seasons and weather conditions in the two hemispheres yet they are necessary to understanding the thermospheric dynamics in the subauroral region and its relationship with geomagnetic activity levels the comparisons with tiegcm are necessary for future model improvements

seismic reflection study of upheaval dome canyonlands national park utah the origin of upheaval dome in canyonlands national park of southeastern utah has been a topic of controversy among geologists and planetary scientists the structure has long been thought to have been created by salt diapirism from the underlying paradox formation recent studies have suggested that impact could have formed the dome to test the various hypotheses we acquired processed and interpreted seismic reflection data within and adjacent to the structure both conventionally stacked and prestack migrated images show 100 m relief in the paradox formation contrary to salt diapirism hypotheses further we have identified features within the images typical of impact structures such as listric normal faults having displacements toward the center of the dome deformation occurs in two depth ranges with the faulting that created the central uplift appearing only above the hermosa formation in the upper 800 m of the structure the images also suggest limited fracturing of the hermosa and salt flow in the paradox formation perhaps due to gravitational relaxation of the crater form our image of a nearly flat top of the paradox salt strongly favors an impact origin for upheaval dome

optical and radiocarbon dating at jinmium rock shelter in northern australia the jinmium rock shelter is located in the kimberley region of northern australia claims for ancient rock art and an early human presence at this site1 were based on thermoluminescence ages of 50 75 thousand years kyr for quartz sands associated with buried circular engravings pecked cupules and on thermoluminescence ages of 116 176 kyr for the underlying artefact bearing deposits here we report substantially younger optical ages for quartz sand and ages based on measurements of radioactive carbon in charcoal fragments from the occupation deposit using conventional multiple grain optical dating methods we estimate that the base of the deposit is 22 kyr however dating of individual grains shows that some have been buried more recently the single grain optical ages indicate that the jinmium deposit is younger than 10 kyr this result is in agreement with the late holocene ages obtained for the upper two thirds of the deposit from radiocarbon measurements we suggest that some grains have older optical ages because they receivedinsufficient exposure to sunlight before burial the presence of such grains in a sample will cause age overestimates using multiple grain methods whether using thermoluminescence or optical dating

a climatology of middle and upper atmosphere radar observations of thermospheric winds shigaraki middle and upper atmosphere mu radar observations of horizontal thermospheric winds in the magnetic meridian plane over the period september 1986 to september 1996 are reported as climatological averages in the form of time of day variations for several combinations of seasonal and solar activity conditions and are compared with winds predicted by the horizontal wind model hwm and with winds measured at saint santin and millstone hill the dominant feature of the mu wind behavior is its mean diurnal variation of northward flow by day and southward flow by night with the nighttime wind smoothly approaching and receding from a midnight maximum while the daytime wind tends to show two peaks a strong one in the early daylight hours and a weak one in the afternoon evening hwm shows the same unimodal nighttime and bimodal daytime behavior but the hwm pattern is shifted about 2 hours later in time the amplitude of the diurnal harmonic decreases from 78 m s at solar minimum to 45 m s at solar maximum while hwm shows a corresponding increase from 53 to 62 m s the diurnal amplitude is remarkably stable with season but is superposed on a steady wind of 41 m s southward in summer 15 m s northward in winter and midway between these limits at the equinoxes hwm shows a symmetric pattern of 30 m s southward in summer and 30 m s northward in winter ion drag appears to be the main regulator of wind speed and the seasonal wind patterns have a profound effect on the seasonal behavior of the ionosphere

optical observations of thermospheric dynamics at arecibo observations of thermospheric neutral winds have been made at arecibo puerto rico by using a fabry perot interferometer to measure the doppler shift of the nighttime o d 630 nm emission we have developed a scheme of making observations at eight equally spaced azimuth positions with a constant zenith angle this technique allows us to determine the mean neutral wind velocities in the meridional and zonal directions as well as any horizontal gradients in the wind field it also provides a good means of simultaneously monitoring any spatial variations in neutral temperature and the intensity of the o d emission in general the highest equatorward wind velocity is observed at about 2100 lst the meridional wind velocity usually lessens as midnight approaches and sometimes but by no means always reverses after midnight the magnitude of the equatorward velocity is greater in summer than in winter months for winter and spring months the zonal wind blows eastward throughout the night with the velocity tending to decrease in a fairly regular fashion from about 125 m s 1 at 2100 lst towards zero by 0400 lst in summer the pattern is similar but the eastward flow usually reverses earlier and a westward velocity of some 50 m s 1 may be attained by 0400 lst significant horizontal wind gradients are often observed in the meridional direction but not in the zonal direction near midnight especially during both the equinox and summer months the equatorward wind is often greater to the north of arecibo than to the south we interpret this as being an effect of the passage of the midnight equatorial pressure maximum to the south of the station measurements of neutral temperature with the interferometer do indeed show that between 0100 0200 lst the neutral temperature to the south of arecibo is enhanced by some 40 k over that to the north

mesozoic dissolution tectonics on the west central shelf uk central north sea abstract 3 d seismic mapping of the upper jurassic kimmeridge clay formation on the west central shelf in the central north sea reveals a complex fault array which is constrained by seismic interpretation and well control to be of late jurassic early cretaceous age fault shapes in plan view range from linear to circular linear fault lengths are 200 300 m to 5 km the strongly curved and circular faults range in diameter from 100 1000 m fault trends are apparently random and display no correlation in location or trend with basement sub zechstein structures there is however a strong link between this fault pattern and the structure of the top zechstein top salt surface linear faults occur at the edges of elongate salt walls and the circular faults lie directly above structures which have been interpreted here as tall steep sided salt chimneys the salt chimneys are present only in the thick elongate minibasins of triassic sediment which lie between the salt walls it is argued that salt dissolution controls the timing location orientation and shape of the late jurassic early cretaceous faults a model is provided to account for the development of both salt walls and chimneys we suggest that early triassic karstification of the zechstein evaporites led to development of an array of circular collapse features during the ensuing episode of triassic halokinesis which led to minibasin subsidence and salt wall growth salt passively intruded the circular collapse features within the subsiding minibasins to form narrow salt chimneys the resulting array of salt walls and chimneys was subject to dissolution during subsequent subaerial exposure and the late jurassic marine transgression of the basin creating the observed fault array prior to sealing of the salt from circulating groundwater by compaction of the upper jurassic and lower cretaceous shales which blanket the area

seasonal dependence of northern high latitude upper thermospheric winds a quiet time climatological study based on ground based and space based measurements this paper investigates the large scale seasonal dependence of geomagnetically quiet time northern high latitude f region thermospheric winds by combining extensive observations from eight ground based optical remote sensing and three space based optical remote sensing and in situ instruments to provide a comprehensive picture of the wind morphology data are assimilated into a seasonal empirical vector wind model as a function of season latitude and local time in magnetic coordinates the model accurately represents the behavior of the constituent data sets there is good general agreement among the various data sets but there are some major offsets between goce and the other data sets especially on the duskside the assimilated wind patterns exhibit a strong and large duskside anticyclonic circulation cell sharp latitudinal gradients in the duskside auroral zone strong antisunward winds in the polar cap and a weaker tendency toward a dawnside cyclonic circulation cell the high latitude wind system shows a progressive intensification of wind patterns from winter to equinox to summer the latitudinal extent of the duskside circulation cell does not depend strongly on season zonal winds show a mainly diurnal variation two extrema around polar and middle latitudes and semidiurnal variation four extrema at auroral latitudes meridional winds are primarily diurnal at all high latitudes the strength of zonal winds channeling through the auroral zone on the duskside is strongest in the summer season the vorticity of the wind pattern increases from winter to summer whereas divergence is maximum in equinox in all three seasons divergence is weaker than vorticity

downsag and extension at calderas new perspectives on collapse geometries from ice melt mining and volcanic subsidence structures at calderas may form as a result of precursory tumescence subsidence due withdrawal of magmatic support resurgence and regional tectonism structural reactivation and overprinting are common to explore which types of structures may derive directly from subsidence without other factors evidence is reviewed from pits caused by the melting of buried ice blocks mining subsidence scaled subsidence models and from over 50 calderas this review suggests that complex patterns of peripheral deformation with multiple ring and arcuate fractures both inside and outside caldera rims topographic embayments arcuate graben and concentric zones of extension and compression may form as a direct result of subsidence and do not require a complex subsidence and inflation history downsag is a feature of many calderas and it does not indicate subsidence on an inward dipping ring fault as has been inferred previously where magmatic inflation is absent or slight initial arcuate faults formed during collapse are likely to be multiple and dip outwards to vertical associated downsag causes the peripheries of calderas undergo radial centripetal extension and this accounts for some of the complex peripheral fractures arcuate crevasses graben and some topographic moats the structural boundary of a caldera defined here as the outermost limits of subsidence and related deformation including downsag commonly lies outside ring faults and outside the embayed topographic wall it is likely to be funnel shaped i e inward dipping even though ring and arcuate fractures within it may dip outward inward dipping arcuate normal faults at shallow levels and steep inward dipping contacts between a caldera s fill and walls may both occur at a caldera that has initially subsided on outward dipping ring faults they arise due to peripheral surficial extension gravitational spreading and scarp collapse topographic enlargement at some calderas and the formation of embayments may reflect general progressive downsag and localized downsag respectively these processes may occur in addition to surficial degradation of oversteep ring fault scarps

combined optical and radar wind measurements in the f region over millstone hill a fabry perot interferometer has been gathering f region wind data at millstone hill routinely since mid 1988 a total of 27 nights of optical data have been collected with simultaneous incoherent scatter radar data data for 22 nights of which 10 were geomagnetically quiet and 12 were unsettled have been used to evaluate the o o collision frequency our data show that the collision frequency based on dalgarno s adjusted theoretical value dalgarno 1964 that was used at millstone hill observatory before 1988 should be increased by a factor of 1 9 0 15

equatorial f region neutral winds and shears near sunset measured with chemical release techniques the period near sunset is a dynamic and critical time for the daily development of the equatorial nighttime ionosphere and the instabilities that occur there it is during these hours that the pre conditions necessary for the later development of equatorial spread f esf plasma instabilities occur the neutral dynamics of the sunset ionosphere are also of critical importance to the generation of currents and electric fields however the behavior of the neutrals is experimentally understood primarily through very limited single altitude measurements or measurements that provide weighted altitude means of the winds as a function of time to date there have been very few vertically resolved neutral wind measurements in the f region at sunset we present two sets of sounding rocket chemical release measurements one from a launch in the marshall islands on kwajalein atoll and one from alcantara brazil analysis of the release motions has yielded vertically resolved neutral wind profiles that show both the mean horizontal winds and the vertical shears in the winds in both experiments we observe significant vertical gradients in the zonal wind that are unexpected by classical assumptions about the behavior of the neutral wind at these altitudes at sunset near the geomagnetic equator

observations on the origins and ascent mechanisms of granitic magmas this review presents a summary of most current beliefs about the origins of granitic magmas together with calculations of some important properties of granitic melts and magmas turning attention to magma ascent mechanisms diapirism and dyking represent two competing end member models the differences in processes and products between the two are fundamental and the implications of the differences are profound for the evolution of the continental crust the weight of evidence favours dyke ascent for the majority of granitic magmas and modelling shows that dyke ascent is both rapid and thermally effcient furthermore the structural and petrological features expected in crust through which granitic diapirs have passed have not been discovered in nature granites in the upper crust commonly have forms and structures indicating that diapirism could not have been the emplacement mechanism in contrast granitic dykes are common suggesting that it is reasonable to consider the ascent of granitic magmas through fracture systems many granitic batholiths are tabular and some have been fed by large dykes the rate limit in granitic plutonism is not magma ascent but either the rate of melting and segregation near the magma source or the rate of deformation at the emplacement site

optical dating of holocene sediments from a variety of geomorphic settings using single grains of quartz this paper presents an improved method for the optical dating of holocene sediments from a variety of geomorphic settings we have measured the equivalent dose de in individual grains of quartz using green laser light for optical stimulation and have simulated the de distributions for multiple grain synthetic aliquots using the single grain data for 12 samples of known independent age we show that application of a minimum age model to the single grain and small 10 grain aliquot de data provides the most accurate estimate of the burial dose for nine of the samples examined 3 aeolian 5 fluvial and 1 marine the weighted mean de as obtained using the central age model gives rise to burial age overestimates of up to a factor of 10 for these nine samples whether single grains small aliquots or large 100 grain aliquots are used for the other three samples two aeolian and one fluvial application of either the minimum age model or the central age model to the single grain small aliquot and large aliquot de data yields burial ages in accord with the independent age control we infer that these three samples were well bleached at the time of deposition these results show that heterogeneous bleaching of the optical dating signal is commonplace in nature and that aeolian transport offers no guarantee that the sample will be well bleached at the time of deposition we also show that grains sensitive to infrared ir stimulation can give rise to low de values which will result in significant underestimation of the burial dose and hence of the age of deposition we demonstrate that use of a modified single aliquot regenerative dose protocol incorporating ir stimulation prior to green light stimulation deals effectively with contamination by ir sensitive grains we conclude that application of the modified protocol to single grains or small aliquots of quartz using the lowest de population to estimate the burial dose is the best means of obtaining reliable ages for holocene sediments from a wide range of depositional environments d 2003 elsevier b v all rights reserved

wolfe creek crater a continuous sediment fill in the australian arid zone records changes in monsoon strength through the late quaternary abstract a bolide that impacted nw australia during the late quaternary left a circular depression more than 100 m deep and nearly a kilometer in diameter with a crater rim 30 m above the regional terrain the resultant crater is a window into the regional water table the surface of the contemporary central pan is 25 m below the adjacent terrain coincident with the late holocene regional water table modified by local evaporative processes shielded from aeolian deflation by the crater rim the central depression has slowly filled with dust sand and chemical precipitates estimated to be 20 100 m thick based on geophysical surveys one of the few continuous depocenters in the australian arid zone the nature of the crater s sediment fill is controlled by interactions between the water table primarily in response to changes in summer monsoon rain changes in the delivery of sand and dust to the crater by the prevailing easterly winds and the level of the sedimentary fill surface optically stimulated luminescence osl and 14c dates constrain an age model indicating the upper 10 m of sediment fill recovered from the central pan span the past 60 ka the lowest 3 m consist of clayey sand deposited in perennial water during marine isotope stage mis 3 the water table subsequently dropped rapidly 35 ka and remained more than 7 m below the late holocene level through most of mis 2 during which 2 m of sandy clay was deposited on a dry crater floor confirming a dry and dusty last glacial maximum lgm climate by 14 ka a rising water table intersected the crater surface modifying the upper 50 cm of lgm sediment and syndepositionally modifying another 60 cm of subsequent sandy clay deposition aeolian sediment delivery effectively ceased 13 ka and the upper 4 8 m is a gypsum dominated precipitate which initially accumulated rapidly before equilibrating with the late holocene water table shortly after 6 ka lacustrine carbonate encrustations on rocks at the base of the crater wall and 4 m above the central pan with 14c ages 40 ka document a time when regional groundwater maintained a water body in the crater 3 5 4 5 m above the modern groundwater level the crater wall deflected the prevailing easterly winds creating a horseshoe dune extending westerly on both sides of the crater with an extension rate of 35 m ka 1 an augered hole through the northern dune revealed 10 m of sediment overlying ferricrete the lowest meter is a mixture of broken ferricrete and sand that we interpret to be debris from the bolide impact three osl dates through the dune project an age for the debris dune contact of 120 10 ka changes in physical properties and bulk sediment 13c through the 9 m of aeolian sediment indicate the lowest 1 8 m was deposited during mis 5 120 85 ka under a uniformly wetter climate than present the overlying 4 3 m of sediment was deposited between 85 and 14 ka mis 4 3 2 and exhibits transitional characteristics between the lower unit and the upper 3 8 of sand which was deposited primarily during the holocene large changes in the regional water table occurred over the past 60 ka including an lgm water table persistently 7 m lower than late holocene levels and 3 5 4 5 m higher prior to 40 ka plausibly in mis 5 indicative of a stronger australian summer monsoon than at any time subsequently age models and sediment properties from the two sedimentary records indicate the crater was formed 60 ka and most likely 120 ka more recently than previous estimates

airglow observations of nighttime medium scale traveling ionospheric disturbances from yonaguni statistical characteristics and low latitude limit the characteristics of nighttime medium scale traveling ionospheric disturbance mstid features observed over yonaguni 24 5 n 123 0 e 19 3 n dip latitude japan are studied using all sky imaging of oi 630 0 nm airglow emission the uniqueness of these observations is that the area observed by the imager covers the transition region between low to middle latitudes in the ionosphere typical low latitude limit of midlatitude type nighttime mstids possessing phase front alignments along the northwest to the southeast occurs in this region these mstid features are rarely sighted at dip latitudes below 15 we selected 2 year period for analysis in which 1 year corresponded to the solar minimum conditions and another year to the solar maximum conditions the mstids were observed to extend to farther lower latitudes during the solar minimum conditions than during the solar maximum periods their observed range of wavelengths phase velocities phase front alignment and propagation directions are similar to those observed at typical midlatitude sites however on many occasions the phase fronts of the observed mstids did not extend over the whole field of view of the imager indicating that some process inhibits their extension to further lower latitudes detailed investigation suggests that the poleward propagating enhancement of airglow intensity probably associated with the midnight pressure bulge causes the mstid features to disappear when they reach lower latitudes later in the night when the mstids reach lower latitudes well before midnight they are found to be inhibited by the equatorial ionization anomaly crest region

the age of the palaeodunefield of the northern murray basin in south australia preliminary results abstract a vast field of old desert dunes extends from northwestern eyre peninsula across yorke peninsula and the northern adelaide plains into the murray basin and northwestern victoria there are patches of parabolic forms but the sand ridges under review are of seif linear or longitudinal type they trend nw se in the west and west east in the east here we record luminescence dates for three dune sites in the waikerie district of the northwestern murray basin they range from respectively 151 25 3 ka 157 33 3 ka and a basal age of 59 6 ka with sand movement also indicated around 1906 and 1933 ce apart from the last named no unconformities are discernible in the sampled sections

optical observations of thermospheric neutral winds at arecibo between 1980 and 1987 since 1980 optical observations of nighttime thermospheric winds have been made using a fabry perot interferometer at the arecibo observatory puerto rico high resolution spectra of the o sup 1 d airglow emission at 630 0 nm are obtained by observing at eight equally spaced azimuth positions and a fixed zenith angle of 60 degree the neutral wind field is inferred by assuming that each component of the wind velocity vector may be expanded in a linear taylor expansion about a point directly above the observatory both the zonal and meridional components of the thermospheric wind field are observed to have well defined seasonal and nocturnal variations for each year between 1980 and 1987 eastward flow was observed in the evening hours with an average peak velocity of about 100 m s sup minus 1 near 2 200 ast in the winter months the zonal wind generally remains eastward throughout the night however in summer a reversal to westward flow is usually observed after local midnight in the meridional direction the largest equatorward velocities are observed in summer a reduction or reversal in the meridional wind velocity is most often observed after midnight in the summer and equinoctial months the authors find that the nocturnal and seasonal variations in themore neutral wind field at arecibo are remarkably unaffected by changes in the solar cycle less

the shape of drumlins their distribution in drumlin fields and the nature of the sub ice shaping forces this paper examines attempts to define and interpret drumlin shape in particular the chorley lemniscate and the reed galvin miller ellipsoid it also considers the koenderink approach to describing shape which ignores statistically defined shapes and concentrates on arbitrary smooth lumps of three dimensional space the basic shape of a drumlin at first sight appears to offer no clue to the rightness of any of the hypotheses or conjectures about drumlin formation the shape suggests that a flowing fluid erodes the parts of landscape which have a lower shear strength than the adjacent parts however by considering whether the fluid is ice very viscous or water less viscous it is suggested that it is possible to distinguish between a drumlin formed by deformation and a drumlin formed by basal water erosion by identifying subtle shape differences produced by different flow regimes we find little indication either from drumlin shape or disposition of drumlins in fields that the basal water erosion mechanism causes the formation of drumlins observations of the growth and break up of bubbles rising through a fluid may serve as an appropriate analogy for describing drumlin growth and eventual break up this bubble model is useful in suggesting an accretion model for drumlin growth and predicting that the form of a drumlin before break up is similar to a spherical cap or parabolic drumlin the bubble model and observation of flow past obstacles at very low reynolds numbers suggest that a minimum resistance shape is not always a lemniscate the variation of the critical stress and strength parameters across a drumlin field essentially perpendicular to the ice flow direction suggests that the distribution could be zonal that across a drumlin field a change in drumlin density should occur considering the drumlins as a whole field phenomenon the dimpled surface of the drumlin swarm may actually reduce drag

thermospheric dynamics above saint santin statistical study of the data set the meridional neutral winds at 300 km altitude have been calculated from the data obtained during 15 years of measurements by the incoherent scatter facility at saint santin france the analysis is based on the classical technique the meridional neutral wind is given by the difference between the measured ion velocity and the computed diffusion velocity this relies on knowledge of the o o collision frequency which is still the subject of some controversy a simple but reasonable expression is given and has been agreed upon with workers at millstone hill so that comparisons may be made this expression gives values consistent with the equations used elsewhere which are more complicated but no more reliable the whole set of data gives 223 twenty four hour periods of measurements from which the average meridional winds are computed for a range of conditions a statistical analysis shows how the diurnal variations depend on season solar flux and geomagnetic activity it is shown that these variations are well represented by four harmonic components of which amplitudes and phases are given

volcanic geomorphology an overview abstract the review examines the role of geomorphology in analyzing the volcanoes on earth five objectives are stressed first classifications of volcanic landforms should be improved to take care of the complexity in volcanic landform generation as magmatic systems style of eruption and the erupted material all influence the morphology second geomorphology should contribute to the science of volcanology through its capability in reconstructing growth stages in complex volcanoes and also in analyzing the structural factors which contribute to the catastrophic collapse of volcanoes third geomorphology can contribute to physical volcanology by assessing the effects of topography on transport erosion and deposition of volcanogenic flows and identifying the sources and climatic tectonic conditions which govern the emplacement of volcaniclastic deposits fourth volcanic geomorphology a identifies sedimentary facies associations b constructs facies models for dynamic volcano delivery systems and c analyzes the characteristics of sediment gravity flows in order to determine relevant parameters for modelling their behaviour fifth process oriented geomorphology is critical in developing accurate methods for measuring rates of geomorphic processes that shape ephemeral volcanic constructs and for evaluating and comparing geomorphic impacts on disturbed catchments and the related hydrologic response before during and after eruptions this should help to refine parameters for the exponential decay model finally volcanic geomorphology is essential for risk assessment through geomorphic hazard zonation and composite risk zonation such treatments are necessary in order to face the enhanced challenge posed by the combination of natural hazards and the increasing number of people who are at risk around volcanoes

mud volcanoes in deepwater nigeria abstract detailed study of 3d seismic data from deepwater nigeria has revealed the presence of features interpreted to be mud volcanoes they occur in an upper slope environment seen as 1 2 km circular features at the seabed seabed cores from the mud volcanoes contain oil gas and sand shale clast content richer than the seabed background pliocene fossils have been identified in the cores demonstrating transport of material from depth the features show a high seabed seismic amplitude above a chimney of chaotic seismic reflections and data wipe out the mud volcanoes in the study area shows two distinct clusters located over deeper structural culminations four active mud volcanoes area 1 are located above a rollover anticline in the central part of the area cuspate listric faults reach the seabed on the up slope side of these mud volcanoes four abandoned mud volcanoes have also been identified with progressively older ages towards the crest of the underlying structure these abandoned features are associated with an extremely chaotic seismic signature a combination of over pressured carrier beds and low integrity top seals are believed to be responsible for the formation of these mud volcanoes it is further believed that gas expansion subsequent to seal failure was the main driving force for what must have been violent eruptions the long lived mud volcano activity over the deep structural closure suggests a plumbing system that focuses on escaping compaction water and hydrocarbons through time in the south west of the study area another cluster of five mud volcanoes is located above a shale diapir the seabed expression of the members of this cluster is more varied some show a positive relief at the seabed while others show circular depressions the largest feature represents an assemblage of many smaller mud volcanoes with a common root system their seismic expression is also different from that of area 1 with a well defined sediment wedge at surface and a shallower root system these features are believed to represent a less violent type of mud volcano characterised by ductile flow tectonic stress due to growth of the underlying diapir is thought to have played an important role during eruption in addition to focused methane escape and the low mechanical strength of the overburden

phreatomagmatism and its relevance abstract phreatomagmatic explosive volcanism results from the interaction of magma with external water groundwater or surface water close to or at the earth s surface magma of any composition acid to ultrabasic may be involved in this type of explosive activity at present the relevance of phreatomagmatism is realized increasingly because it takes place in many diverse environments and affects not only small monogenetic volcanoes but also large volcanoes at some volcanoes as for example at lake taupo new zealand a volume of several tens of km 3 of magma may have been mixed with several km 3 of external water phreatomagmatism has thus become an important aspect in volcanic hazard assessments other fields involving the interaction of water with a melt are the study of nuclear and other industrial safety hazards of magma mixing of diamond carrying volcanism and of hydrothermal ore deposits as well as geothermal and groundwater reservoirs experiments on the dynamics of magma water interactions provide increasing insight into the principles and hazards of phreatomagmatic explosions this type of research will become a new field in experimental petrology

overburden deformation patterns and mechanisms of salt diapir penetration in the central graben north sea abstract active and passive diapirism control the deformation and geometry of hydrocarbon traps in the overburden and a more detailed understanding of this process will help reservoir prediction and hydrocarbon recovery cores studies of seven central graben diapirs indicate zechstein salt penetrated late cretaceous chalk by extreme tectonic thinning with high angle 70 to bedding normal faulting tensile fracturing and pressure solution attenuation of the chalk significantly weakens the overburden allowing buoyancy forces to dome up the overburden doming created enough topography for downslope sliding of chalk slabs on slip planes parallel to bedding or in the case of the kyle diapir for chaotic debris flows of lithified chalk significant extensional bedding parallel faults and slump folds are developed within palaeocene shale on the diapiric flanks inter granular slip in unconsolidated clastic material was probably the dominant deformation mechanism diapirs have penetrated the palaeocene clastic sediments by maintaining topographic relief so that unlithified sediment continually slid off the crest producing translated intact rafts up to several tens of metres in thickness

geometry and growth kinematics of salt pillows in the southern north sea abstract low amplitude salt pillow structures can potentially reveal important details of the physical behaviour of salt and overburden from their growth histories this is because the initial characteristic wavelengths are likely to be preserved beds are more easily traceable across the tops of the structures and original salt thicknesses can be accurately estimated for these reasons a detailed analysis of depth converted seismic data was undertaken to gain insight into the formation growth and spatial distribution of salt pillows in the southern north sea basin around quadrant 44 this area contains a permian zechstein salt interval which has undergone widespread halokinesis to the pillow stage since triassic times but with the main movement during the tertiary perhaps due to inversion the wavelength of the pillows decreases northwards from over 24 to 1 km and estimated original salt thickness also decreases northwards from 1300 to 800 m and there is a strong positive relationship between salt thickness and pillow wavelength pillows appear to be spaced at a characteristic wavelength as they are not directly related to faults and the wavelength varies smoothly through the area however there is a strong alignment of some pillows parallel with the underlying nw se fault trend suggesting that their axis of elongation was controlled by faulting average vertical growth rates of the pillows vary from 40 m ma in the north to less than 10 m ma in the central part of the area measured over vertical distances up to 1250 m most of the growth occurred in the tertiary although a few pillows initiated in the triassic in the north of the area the northern pillows appear to have slowed or even stopped growing during the jurassic and cretaceous and then restarted in the tertiary assuming rayleigh taylor instability controlled the initial pillow wavelengths and using the calculated original salt overburden thicknesses ratios the viscosity ratio between the overburden and the salt can be estimated across the area and was found to vary from 6000 to less than 100 the pillows which moved earliest had the lowest inferred viscosity ratios which is probably because the sediments were less lithified at the time of movement

first u s china joint ground based fabry perot interferometer observations of longitudinal variations in the thermospheric winds for the first time three fabry perot interferometers from the u s boulder 40 degrees n 105 degrees w 49 degrees n magnetic latitude mlat and china xinglong 40 degrees n 115 degrees e 34 degrees n mlat kelan 39 degrees n 112 degrees e 33 degrees n mlat were used to examine the longitudinal variations in the thermospheric winds due to the geomagnetic latitude differences between the american and asian sectors during a case of quiet geomagnetic condition the meridional winds were very similar at the u s and chinese stations the meridional winds at boulder reached most equatorward winds after midnight whereas in china the largest equatorward winds were found near midnight the boulder zonal winds turned westward earlier in the morning hours and had larger diurnal variations because of its higher magnetic latitude during the case of low geomagnetic activity kp similar to 2 the meridional winds were still similar in the u s and in china boulder zonal winds had much larger diurnal variation compared to the quiet condition kp similar to 1 thermosphere ionosphere electrodynamics general circulation model simulations show a very good agreement with observation for the meridional winds the simulated zonal winds exhibit noticeable differences with observations but the general tendencies in longitudinal variations with a larger diurnal variation near the auroral oval are correct simulations showed that the ion drift is not directly responsible for the longitudinal variations in the winds the pressure gradient had more direct effect on the longitudinal changes in the winds the simulation results also showed larger diurnal variations at higher geomagnetic latitudes due to the auroral oval heating nonmigrating tides were not observed in the two cases in october 2012

late quaternary palaeoenvironmental change in the australian drylands in this paper we synthesise existing palaeoenvironmental data from the arid and semi arid interior of the australian continent for the period 40 0 ka moisture is the predominant variable controlli

using incoherent scatter radar to investigate the neutral wind long term trend over arecibo 1 thermospheric neutral winds can be the most important driver when modeling ionospheric densities and temperatures several papers in this special edition show interesting features of the neutral winds behavior during the last 30 years at the arecibo observatory 18 3 n 66 75 w 28 25 dip latitude using fabry perot interferometer fpi data a neutral wind vector that changes its direction becoming more dominantly eastward over the years and a meridional neutral wind component that decreases in magnitude were found the main goal of this work is to look for similar evidence of long term trends in the radar derived winds that might support these recent discoveries and explore the associated ionospheric parameter measurements to look for the effects of these changing winds on the ionosphere with this purpose in mind incoherent scatter radar isr measurements of the f region vector drifts are used to derive the corresponding meridional thermospheric neutral wind along the magnetic field over arecibo during 20 years major findings include a decreasing long term trend lowering of the height where the f2 layer peak density occurs hmf2 which could be related with a more increased downward flux of the ionosphere a slight decrease in the peak density of the f2 layer nmf2 after local midnight also was found during the period studied the meridional wind along the magnetic field derived from isr data also revealed a long term trend becoming more northward during the period studied with a maximum variation between 02 30ut and 05 30ut

altitude dependence of middle and low latitude daytime thermospheric disturbance winds measured by windii 1 thermospheric neutral winds exhibit strong altitudinal and latitudinal variation during geomagnetically quiet and active times we use daytime middle and low latitude neutral winds measured by the wind imaging interferometer windii instrument on board the upper atmosphere research satellite uars over the 90 275 km height range to study the altitude and season dependent climatology of disturbance winds i e with quiet time patterns removed in magnetic coordinates the daytime perturbations winds are generally equatorward and westward and decrease toward the magnetic equator both the zonal and meridional components decrease sharply below 120 km and are essentially insignificant below 100 km the seasonal dependence of the disturbance winds is strongest in the early morning sector the zonal disturbance winds are predominantly westward with largest magnitudes near 150 km at late afternoon upper midlatitudes magnetic latitudes 50 60 and near 120 km in the early morning winter between 25 and 45 at upper midlatitudes in the early morning sector the zonal perturbation winds are eastward above 120 km in the summer hemisphere and between 120 and 180 km in the winter hemisphere eastward perturbations are also observed near the magnetic equator with largest values near noon at 250 km the meridional perturbation winds are mostly equatorward and nearly height independent above 150 km with the largest magnitudes occurring in the early morning winter hemisphere in the late afternoon sector the upper midlatitude meridional disturbance winds are poleward and there is a small winter to summer flow at lower latitudes in general the storm time dependence of the disturbance winds is quite complex the perturbation winds begin to develop after 0 9 hours and tend to saturate 12 24 hours after storm onset the development does not change much with altitude and the seasonal dependence is generally important only at storm times greater than 6 12 hours

a study of the weddell sea anomaly observed by formosat 3 cosmic 1 more than two years of cosmic electron density profiles at low solar activities are collected to study the evolution of the weddell sea anomaly wsa which appears as an evening enhancement in electron density during local summer observations show that the change in nmf2 the f2 peak electron density is associated with the change in hmf2 the f2 peak height while the latter is correlated closely with the components of the geomagnetic field we find that 1 in the afternoon hmf2 is more liable to rise drastically in regions with a larger jsin 2i j value which would occur early at certain declinations eastward in the southern hemisphere and westward in the northern hemisphere 2 subsequently a larger increment of hmf2 is coincidentally followed by a stronger enhancement of nmf2 and the enhancement ends just around the local sunset and 3 in midlatitudes the evolution pattern of hmf2 in the evening of equinoxes and winter is similar to that in summer albeit without a lasting nmf2 enhancement as that in summer these features suggest that the nmf2 enhancement and the hmf2 increase could arise from the thermospheric wind effect and solar photoionization plays a crucial role in the enhancement as well the general midlatitude f2 layer enhancement in local summer evening is consistent with the wsa on the above features indicating that the wsa is a manifestation with a particular geometry of the magnetic field of the evening enhancement induced by the winds

brightening of 630 0 nm equatorial spread f airglow depletions 1 observations from the boston university all sky imaging system at arecibo puerto rico 18 3 n 66 7 w 28 n mag show an unusual behavior of nighttime 630 0 nm airglow depletions associated with equatorial spread f esf these structures move eastward before reversing their motion and become airglow enhancements few other cases have been found all during december solstices for the case study presented here data from the arecibo incoherent scatter radar and the republic of china scientific satellite rocsat 1 provide supporting information the radar shows that around local midnight the background zonal and meridional plasma motions reverse to westward and southward respectively rocsat 1 shows enhanced ion density i e a low latitude plasma blob above the bright feature recorded by the all sky imager indicating a possible connection between both phenomena drifts parallel to the magnetic field are observed only in the region where the enhancement occurs one possible interpretation of this change in the brightness of the depleted structure involves the influence of northward meridional winds and a reversal in the zonal drift motion most likely caused by a zonal wind reversal

how do longitudinal dunes respond to climate forcing insights from 25 years of luminescence dating of the australian desert dunefields abstract this paper presents a meta analysis of 689 luminescence age estimates of australian desert sand dunes this analysis had two aims to examine the hypothesis that quaternary climate changes have forced dune accumulation and to understand longitudinal dune behaviour from the age architecture of sand dunes for which stratigraphic information is often absent or poorly known a novel approach to the analysis of probability density curves of dune age frequency shows that in the mallee dunefield of southeastern australia only the period leading up to and including the last glacial maximum lgm 18 34 ka experienced marked dune growth which cannot be explained by random stochastic activity during the lgm most but not all mallee longitudinal dunes were accumulating more rapidly than before and after in the strzelecki dunefield source bordering sbd longitudinal dune tl n 61 and osl n 40 ages are more frequent at the pleistocene holocene transition but nearby non sbd longitudinal dunes n 21 ages were only active above background levels during the lgm however the strzelecki dune age data set suffers from being drawn from a small number of individual dunes 10 sbd dated using tl 12 sbd dated by osl 7 non sbd dated by osl with a marked bias away from surficial young and basal old depths even during the lgm many dunes do not record active growth and the dunefield was most likely a mosaic of stable dune surfaces and bare mobile patches supported by the scant pollen data from the arid zone hyper aridity has not been experienced in these dunefields these vegetated dunes exhibit conservative behaviour with limited response to the range of climate forcing experienced in the late pleistocene a more complete understanding of dunefield response to quaternary climates would require an intensive and structured dating program to overcome the noise from stochastic processes leading to small scale activity in these dunes and the simultaneous removal of parts of the sedimentary record

optical dating of river terrace sediments from kanto plains japan abstract optical dating of river terrace sediments has been carried out in a test of the methodology for luminescence age determination of river terrace formation over the last 100 ka in this study samples were collected at river terraces whose ages were estimated by marker tephra geochronology and from a recent riverbed in the kanto plain japan samples from the recent riverbed show a weak osl signal only and gave young ages samples of river terrace sediments for optical dating were collected systematically from the section of about 8 m at the wall of a gravel quarry the optical ages found corresponded well with those estimated by the age of the marker tephras for samples deeper than 2 5 m however the samples from the ground surface to 2 5 m exhibited considerable scatter in the growth curves and gave a wide range of ages all significantly exceeding expectation this was attributed to the mixing of different age sediments by inundation and or human activities analyses of osl from single grains of quartz confirmed that these sediments were composed of grains having a wide range of palaeodoses consistent with such mixing

winds in the high latitude lower thermosphere dependence on the interplanetary magnetic field 1 wind observations in the summertime lower thermosphere at high southern latitudes measured by the wind imaging interferometer windii on the upper atmosphere research satellite are statistically analyzed in magnetic coordinates and correlated with the interplanetary magnetic field imf to determine influences of imf dependent ionospheric convection on the winds effects are clearly detectable down to 105 km altitude above 125 km the wind patterns show considerable similarity with ionospheric convection patterns and the speed of the averaged neutral wind in the polar cap often exceeds 300 m s the correlation between the imf bz component and the diurnal harmonic of the winds is generally best when the imf is averaged over the preceding 1 4 5 hours the magnetic zonal mean zonal wind below 120 km correlates best with the imf by component when the latter is averaged over approximately the preceding 20 hours the wind has a significantly stronger rotational than divergent component around and above 120 km a dusk side anticyclonic wind vortex is prominent consistent with earlier findings around 140 km and higher the dusk side vortex intensifies for negative bz but around 120 km it is the dawn side cyclonic vortex that responds more strongly to bz variations the dependence of the wind on the imf is nonlinear especially with respect to imf bz for positive bz the difference winds are largely confined to the polar cap while for negative bz the difference winds extend to subauroral latitudes a significant correlation between the diurnal bz dependent neutral and convection velocity components exists above 108 km when the convection velocity is suitably rotated in magnetic local time mlt with respect to the wind the rotation that maximizes the correlation ranges from 1 5 hours at 130 km wind preceding convection to nearly 6 hours at 108 km wind lagging convection the rotated diurnal bz dependent wind pattern projects onto the diurnal bz dependent ionospheric convection pattern with about 60 the amplitude of the latter above 125 km decreasing to about 17 at 108 km on timescales of 20 hours a by dependent magnetic zonal mean zonal wind generally exists with maximum wind speeds at 80 magnetic latitude typically 10 m s at 105 km increasing to about 60 m s at 123 km and 80 m s at 200 km in the southern hemisphere the wind is cyclonic when the time averaged by is positive and anticyclonic when by is negative the wind direction is expected to be opposite in the northern hemisphere

how will we recognize buried impact craters in terrestrial sedimentary basins criteria that are deemed critical for recognition of terrestrial impact craters include features from hand specimens such as shock metamorphic structures although these criteria have been selected because they are unique physical products of bolide impact strict adherence to these criteria means that we cannot positively identify buried astroblemes that are tomographically imaged on three dimensional seismic data but are undrilled because many of earth9s deeply buried structures may never be drilled because of prohibitive cost and lack of commercial incentive a large proportion of as yet undiscovered terrestrial astroblemes including the best preserved examples may remain unclassified and be excluded from impact structure research a framework for the identification of impact structures imaged on three dimensional seismic data is proposed on the basis of geometrical criteria plus additional image quality and preservation criteria that assign a level of confidence to the assessment

the geomagnetic quiet nighttime thermospheric wind pattern over fritz peak observatory during solar cycle minimum and maximum nighttime thermospheric winds and temperatures at f region heights have been measured over fritz peak observatory colorado 39 9 n 105 5 w with a high resolution fabry perot spectrometer from about november 1972 to the present the winds and temperatures are obtained from the doppler shifts and line profiles of the o i 15 867 k 630 nm line emission the data obtained during geomagnetic quiet conditions ap 20 have been separated into two groups representing solar cycle minimum conditions 1972 1977 and solar cycle maximum conditions 1978 1979 the monthly variation of the nighttime zonal and meridional winds are presented for both groups the results show that during solar cycle minimum the zonal winds are predominantly eastward during the winter months at speeds of 50 75 m s 1 and westward during the summer months at speeds of 50 100 m s 1 the meridional winds measured to the north and south of fritz peak observatory are equatorward throughout most of the night at nearly the same speed the equatorward winds in the summer peak near midnight at about 100 150 m s 1 the equatorward winds in the winter also peak near midnight but with smaller speeds 50 75 m s 1 during solar cycle maximum the zonal winds are again predominantly eastward during the winter months reaching peak speeds of 60 75 m s 1 in the early evening hours and decreasing afterward in the summer the winds are eastward during the early evening hours shifting to westward near midnight and increasing to a maximum speed of 75 100 m s 1 in the early morning hours the meridional winds are poleward at 20 m s 1 in the early evening hours shifting to equatorward near 2100 lt and then increasing in magnitude with maximum speeds near or after midnight there is a considerable difference in the speed of the winds measured to the north and south of fritz peak observatory during the summer the equatorward winds measured to the north are 150 175 m s 1 whereas the equatorward winds measured to the south are 50 75 m s 1 during the winter the speeds are smaller 50 75 m s 1 and 25 30 m s 1 to the north and south of the station respectively calculations made with the national center for atmospheric research thermospheric general circulation model for different seasons are in reasonable agreement with the observations during both solar minimum and solar maximum during solar cycle maximum the observed and calculated meridional wind differences to the north and south of fritz peak observatory are attributed to enhanced auroral heating and ion drag associated with magnetospheric convection north of the observatory the equatorward driven winds slow south of fritz peak observatory owing to the diminishing influence of high latitude forcings

a study on the nighttime midlatitude ionospheric trough constellation observing system for meteorology ionosphere and climate cosmic electron density profiles are used to investigate the nighttime midlatitudeionospheric trough mit we find that at midnight the longitudinally deepest mit occursto the west of the geomagnetic pole in both the northern and southern hemispheres duringthe equinox seasons and local summer the deepest mit could be ascribable to theenhanced depletion caused by horizontal neutral wind in the early evening the eastwardneutral wind prevails in the midlatitude f region which blows the plasma downwardwhere the declination is eastward in the northern hemisphere but westward in thesouthern hemisphere both lying to the west of the geomagnetic pole the downward driftwould enhance the plasma depletion for more molecular composition at lower altitude in addition we find for the first time that the location of nighttime mit minimumoscillated with a periodicity of 9 days and an amplitude of about 1 1 5 geomagneticlatitude during 2007 2008 associated with the recurrent high speed solar wind ourresults shed new light on the empirical description and numerical simulation of mit

a 20 km diameter multi ringed impact structure in the north sea most craters found on earth are highly eroded poorly preserved and only exposed on land here we describe a multi ringed impact structure discovered in the north sea from the analysis of three dimensional seismic reflection data the structure is 20 km in diameter and has at least ten distinctive concentric rings located between 2 and 10 km from the crater centre the structure affects cretaceous chalk and jurassic shales and is well preserved below several hundred metres of post impact tertiary strata which constrains its age to be 60 65 myr old the formation of concentric ringed impact structures at this relatively small scale had not previously been thought possible especially on the terrestrial planets we have mapped the ring structures at a resolution of tens of metres both laterally and in depth and show that the rings are fault bounded graben structures similar to fault arrays formed in low strain rate detachment tectonic settings strata deeper than 500 m palaeodepth appear unfaulted and we infer that the concentric ring structures may have accommodated post impact extension towards the excavated crater through detachment on weak layers within the chalk

recognition of eroded astroblemes abstract the morphology of lunar craters degrades only slowly by the formation of new impacts and their ejecta it is not the same on earth because of weathering and tectonism generally the typical crater topography has disappeared and the term impact structure or astrobleme is applied on planetary surfaces as on the moon two classes of craters are recognized based on their depth to diameter ratio simple bowl shaped and complex readjusted flat bottomed craters with a sharp transition from simple to complex pike 1977 1980 on earth small simple craters retain some of their typical rimmed pit morphology because they are generally recent many are associated with meteorite fragments large impact structures or astroblemes in addition to their specific circular features are recognized as such only by the presence of shock metamorphism criteria such as dense minerals coesite stishovite diaplectic minerals and glass maskelynite planar deformation features in minerals principaly in quartz and feldspars and shattercones which are commonly used these criteria are abundant in allochthonous breccia particularly in fall back breccia among which there are glass fragments such as tectite or microtectite glass spherules shards droplets rods etc but on the floor of the astroblemes the criteria of shock metamorphism are restricted to the central part which is often covered or eroded using the measurements of nine astroblemes visited a scaling model is presented for two types of craters readjusted along listric slip surfaces a well readjusted model based on data from charlevoix and manicouagan canada and a partly readjusted model based on data from the ries germany both possess a central uplift and a ring graben there is also on the floor of the astrobleme a specific type of breccia mylolisthenite and pseudotachylite associated with the displacement along the autochthonous masses of rocks in very large impact structures the shock metamorphism is able to melt a part of the floor grieve and cintala 1992 the heat resulting from the superheated impact melt destroys a part of the shock metamorphism criteria

addition of aeolian dusts to soils in southeastern australia red silty clay trapped in dunes bordering murrumbidgee river in the wagga wagga region in southeastern australia aeolian dust deposits are very common and have a significant influence on soil properties and soil landscapes however the characteristics of the pure dust materials and the rates of dust fall in the past are unclear because of the low overall rate of dust deposition and mixing with locally derived sediments in the wagga wagga region some dunes have functioned as dust traps thin 1 cm thick red clayey bands and thick up to 2 5 m red clayey layers within the dune sequences are likely to represent illuviated aeolian dust these dust materials are characterised by a bi modal particle size distribution one mode in the clay and another in the coarse medium silt the clay minerals are dominated by kaolinite illite and smectite both 14c and optical dating indicate the most recent period of dune formation was around 3 4 ka in an example of these young dunes there is a total of 2 cm equivalent thickness of dust materials giving a deposition rate of 0 5 0 7 cm ka 1 all three samples from an elevated dune are saturated with respect to environmental radiation dosage and give minimum optical ages in excess of 80 ka in this higher dune the total thickness of dust is 50 80 cm similar to that 50 100 cm of the yarabee parna the youngest aeolian dust deposit in the wagga wagga region this may have been deposited unevenly being more concentrated during the period 25 16 ka which has been identified as a major dust deposition period in the tasman sea if this variation occurred the dust deposition rate indicated by the 50 80 cm dust material in the dune could have been as high as 5 cm ka 1 for the period 25 16 ka

climatologies of nighttime upper thermospheric winds measured by ground based fabry perot interferometers during geomagnetically quiet conditions 2 high latitude circulation and interplanetary magnetic field dependence we analyze upper thermospheric 250 km nighttime horizontal neutral wind patterns during geomagnetically quiet kp 3 conditions over the following locations south pole 90 s halley 76 s 27 w millstone hill 43 n 72 w sondre stromfjord 67 n 51 w and thule 77 n 68 w we examine the wind patterns as a function of magnetic local time and latitude solar cycle day of year and the dawn dusk and north south components of the interplanetary magnetic field imf b y and b z in magnetic coordinates the quiet time high latitude wind patterns are dominated by antisunward flow over the polar cap with wind speeds that generally increase with increasing solar extreme ultraviolet euv irradiation the winds are generally stronger during equinox than during winter particularly over the south pole in the direction of eastern longitudes imf b y exerts a strong influence on the wind patterns particularly in the midnight sector during winter b y positive winds around midnight in the northern southern hemisphere are directed more toward the dusk dawn sector compared to corresponding b y negative winds this behavior is consistent with the b y dependence of statistical ionospheric convection patterns the strength of the wind response to b y tends to increase with increasing solar euv irradiation roughly in proportion to the increased wind speeds quiet time b y effects are detectable at latitudes as low as that of millstone hill magnetic latitude 53 n quiet time b z effects are negligible except over the magnetic polar cap station of thule

revised global model of thermosphere winds using satellite and ground based observations thermospheric wind data obtained from the atmosphere explorer e and dynamics explorer 2 satellites have been combined with wind data for the lower and upper thermosphere from ground based incoherent scatter radar and fabry perot optical interferometers to generate a revision hwm90 of the hwm87 empirical model and extend its applicability to 100 km comparison of the various data sets with the aid of the model shows in general remarkable agreement particularly at mid and low latitudes the ground based data allow modeling of seasonal diurnal variations which are most distinct at mid latitudes while solar activity variations are now included they are found to be small and not always very clearly delineated by the current data they are most obvious at the higher latitudes the model describes the transition from predominately diurnal variations in the upper thermosphere to semidiurnal variations in the lower thermosphere and a transition from summer to winter flow above 140 km to winter to summer flow below significant altitude gradients in the wind are found to extend to 300 km at some local times and pose complications for interpretation of fabry perot observations

dwm07 global empirical model of upper thermospheric storm induced disturbance winds 1 we present a global empirical disturbance wind model dwm07 that represents average geospace storm induced perturbations of upper thermospheric 200 600 km altitude neutral winds dwm07 depends on the following three parameters magnetic latitude magnetic local time and the 3 h kp geomagnetic activity index the latitude and local time dependences are represented by vector spherical harmonic functions up to degree 10 in latitude and order 3 in local time and the kp dependence is represented by quadratic b splines dwm07 is the storm time thermospheric component of the new horizontal wind model hwm07 which is described in a companion paper dwm07 is based on data from the wind imaging interferometer on board the upper atmosphere research satellite the wind and temperature spectrometer on board dynamics explorer 2 and seven ground based fabry perot interferometers the perturbation winds derived from the three data sets are in good mutual agreement under most conditions and the model captures most of the climatological variations evident in the data

climatologies of nighttime upper thermospheric winds measured by ground based fabry perot interferometers during geomagnetically quiet conditions 1 local time latitudinal seasonal and solar cycle dependence 1 we analyze ground based fabry perot interferometer observations of upper thermospheric 250 km horizontal neutral winds derived from doppler shifts in the 630 0 nm red line nightglow the winds were measured over the following locations south pole 90 s halley 76 s 27 w arequipa 17 s 72 w arecibo 18 n 67 w millstone hill 43 n 72 w sondre stromfjord 67 n 51 w and thule 77 n 68 w we derive climatological quiet time kp 150 the seasonal dependence of the winds is generally annual but there are isolated cases in which a semiannual variation is observed within the austral winter winds measured from the south pole show a substantial intraseasonal variation only along longitudes directed toward the magnetic pole imf effects are described in a companion paper

meridional winds derived from cosmic radio occultation measurements 1 meridional winds at the magnetic meridian in the upper thermosphere are derived from the peak height and density of the ionospheric f2 layer as retrieved by the constellation observing system for meteorology ionosphere and climate cosmic satellites for 4 months from november 2006 to february 2007 these winds referred to as cosmic winds are first validated by comparison at multiple locations with winds obtained from ground based incoherent scatter radar isr and fabry perot interferometer fpi measurements then longitudinal variations of these winds are investigated and compared with simulations by the national center for atmospheric research thermosphere ionosphere electrodynamics general circulation model ncar tie gcm the results show generally good agreement between cosmic winds ground based measurements and the simulations significant longitudinal variations are presented in the cosmic winds at 40 n local winter around midnight the cosmic winds exhibit stronger and longer duration equatorward velocities within 110 w 20 w large negative magnetic declination sector than those in other longitudes during late morning hours the poleward winds show similar longitudinal variations at 40 s local summer during the daytime the poleward winds are stronger within 120 e 110 w large positive magnetic declination sector than in 60 w 90 e large negative magnetic declination sector while during the nighttime the maximum equatorward winds shifts about 2 h later in 60 w 90 e than in 120 e 110 w analysis of the tie gcm simulations suggests that the longitudinal variation of meridional winds is mainly induced by magnetic declination due to the contribution of geographic zonal wind

climatology of nighttime upper thermospheric winds from fabry perot interferometer 2011 2019 measurements over kelan 38 7 n 111 6 e china local time seasonal solar cycle and geomagnetic activity dependence

optical dating of sediments a new method for dating sediments is proposed which determines the time since the sediment was last exposed to sunlight an argon ion laser is used to excite electrons from thermally stable light sensitive traps and the subsequent luminescence used as a measure of the past radiation dose two sample sequences spanning the periods 0 700 kyr and 0 6 kyr show steadily increasing luminescence with age an age of 62 8 kyr is obtained for a silt radiocarbon dated at 58 8 0 3 kyr problems were found with two much younger samples

ionospheric symmetry caused by geomagnetic declination over north america 1 we describe variations in total electron content tec in the north american sector exhibiting pronounced longitudinal progression and symmetry with respect to zero magnetic declination patterns were uncovered by applying an empirical orthogonal function eof decomposition procedure to a 12 year ground based american longitude sector gps tec data set the first eof mode describes overall average tec while the strong influence of geomagnetic declination on the midlatitude ionosphere is found in the second eof mode or the second most significant component we find a high degree of correlation between spatial variations in the second eof mode and vertical drifts driven by thermospheric zonal winds along with well organized temporal variation results strongly suggest a causative mechanism involving varying declination with longitude along with varying zonal wind climatology with local time season and solar cycle this study highlights the efficiency and key role played by the geomagnetic field effect in influencing mesoscale ionospheric structures over a broad midlatitude range

a preliminary study of thermosphere and mesosphere wind observed by fabry perot over kelan china a fabry perot interferometer fpi system was deployed in kelan 38 7 n 111 6 e center china in november 2011 which observes the airglows at wavelengths of 892 0 nm 557 7 nm and 630 0 nm from oh and oi emissions in the upper atmosphere to derive the wind and temperature at heights around 87 km 97 km and 250 km respectively from late 2011 through 2013 a series of more than 4500 measurements at each height are validated according to manufacture data quality criteria by using these data the morphology of wind in the mesosphere and thermosphere is investigated in this study preliminary results are as follows 1 as for the diurnal variation meridional and zonal winds at heights of 87 km and 97 km which are derived through 892 0 nm and 557 7 nm airglows usually range from 50 m s to 30 m s and 50 m s to 50 m s respectively with typical random errors of about 6 10 m s at 87 km and 2 3 m s at 97 km meridional winds usually are northward at dusk southward at middle night and back to northward at dawn and zonal winds usually are eastward at dusk westward at middle night and back to eastward at dawn the monthly mean winds are in good agreement with those of hwm93 results meridional and zonal winds at a height of 250 km which are derived through 630 0 nm nightglow range from 110 m s to 80 m s with typical random errors of about 8 10 m s meridional winds usually are northward at dusk southward at middle night and back to northward at dawn and zonal winds usually are eastward at dusk zero at middle night and westward at dawn and they are also well consistent with hwm93 results 2 as for the seasonal variation meridional winds at the heights of 87 km and 97 km have a visible annual variation at 12 17 lt and with a little semiannual variation at all other hours but the zonal winds at the heights of 87 km and 97 km have a semiannual variation all night the seasonal dependence of the winds both meridional and zonal winds at the height of 250 km is generally annual but isolated cases of semiannual variation are observed 3 the horizontal winds at 250 km evidently respond to the two storms of july 2012 apparent enhancement of the velocity of the southwestward wind but no other obvious storm effects can be found from the winds at 87 km and 97 km during the same period