on temperature inversions and the mesospheric surf zone 1 mesospheric thermal inversions are investigated in a numerical simulation with the whole atmosphere community climate model an upward extension of the national center for atmospheric research s community climate model the seasonal character spatial extent and magnitude of the inversion layers are realistic during winter in the model the occurrence of wintertime inversions is a direct consequence of the rapid decay with height of vertically propagating planetary waves which induces large temperature perturbations in the upper mesosphere to maintain hydrostatic equilibrium the magnitude of the inversions is highly correlated with planetary wave amplitude so that large inversions develop during episodes of planetary wave amplification gravity waves do not play a major direct role in the formation of the inversions because the largest thermal tendencies associated with gravity wave breaking occur well above the range of altitudes where inversions are found however gravity waves play an essential indirect role because they set up a critical line in the upper mesosphere where rossby waves break in the mesospheric surf zone

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

first simultaneous and common volume observations of noctilucent clouds and polar mesosphere summer echoes by lidar and radar we present the results of first simultaneous and common volume observations of noctilucent clouds nlc and polar mesosphere summer echoes pmse by two ground based lidars and one vhf radar the measurements were performed at the alomar facility 69 n 16 e during the time period july 23 through august 18 1994 throughout this period nlc layers were observed by the lidars on four occasions during each of these four lidar observed nlc events pmse layers were also observed overhead by the radar these joint nlc pmse events divide into two distinct types 1 tightly coupled and 2 loosely coupled nlc and pmse layers in one of the events the pmse layer developed into a well defined double layer with only 0 8 km vertical separation while the lidar observed nlc layer matched closely in time and space the lower pmse sublayer within all four nlc pmse layers the wind speed increased sharply with increasing altitude with wind shears amounting to 0 03 s 1 and larger current theories can explain some of the observed layer features

the co diagenesis of sulfur and iron in acid lake sediments of southwestern quebec reduced inorganic sulfur species constitute the major fraction of total sulfur in the recent sediments of eight acid lakes of southwestern quebec nearly all of the anthropogenically derived excess s present in the sediments has accumulated as reduced inorganic forms showing that organic s formation plays a very minor role in long term anthropogenic s retention in these lakes these results appear different from most other published studies on s fixation in acid lake sediments respectively 74 and 76 of the variance in total s and reduced inorganic s burden in the recent sediments can be explained by their fe content alone indicating that the reduced s is associated with iron and that the capacity of the sediments to retain s may be limited by available fe supply when indexes of organic c supply winter o2 deficit and sediment c are included with fe in a multiple regression analysis respectively 97 and 98 of the variance in total s and reduced inorganic s accumulation can be explained the origin of the pronounced subsurface fe maximum observed in most cores is attributed to the reduction and recent burial as iron sulfides of a surficial diagenetic fe oh 3 reserve in some sediments this fe iii reserve presently appears to be nearly or completely exhausted and the lakes may have lost their capacity to generate permanent alkalinity via so2 4 reduction the present rate of alkalinity production due to so2 4 reduction and fixation of reduced s in the sediments of one lake were estimated from several 210pb dated s profiles and averaged to 163 eq m 2 d 1 this value is comparable to those reported for other acid lakes

polar mesospheric clouds observed by an iron boltzmann lidar at rothera 67 5 s 68 0 w antarctica from 2002 to 2005 properties and implications 1 lidar observations of polar mesospheric clouds pmc were made at rothera antarctica from december 2002 to march 2005 overall 128 hours of pmc were detected among the 459 hours of observations giving a mean occurrence frequency of 27 9 the mean pmc centroid altitude is 84 12 0 12 km the mean pmc total backscatter coefficient is 2 34 0 11 10 6 sr 1 and the mean layer rms width is 0 93 0 03 km the distribution of pmc centroid altitudes over all observations is symmetric nearly gaussian with the most probable altitude 84 km near the center of the distribution the distribution of pmc brightness is non gaussian and is dominated by weak pmc the observed pmc altitudes at rothera support the earlier lidar findings that southern hemispheric pmc are on average 1 km higher than corresponding northern hemispheric pmc and higher pmc occur at higher latitudes significant interannual and diurnal variations are observed in pmc centroid altitude and brightness mean pmc altitude varies more than 1 km from one year to another in addition 24 hour 12 hour and 8 hour oscillations are clearly shown in pmc centroid altitude and brightness the altitude distribution of pmc brightness peaks at a nearly constant altitude of 84 km with weaker pmc found on either side of this altitude the mean pmc altitudes averaged in brightness bins are anticorrelated with the pmc brightness where weaker pmc occur at higher altitude and the pmc altitudes are proportional to the logarithm of the pmc brightness

hybrid rossby shelf modes in a laboratory ocean idealized laboratory experiments reveal the existence of forced dissipative hybrid rossby shelf modes the laboratory ocean consists of a deeper ocean accommodating basin scale rossby modes and a coastal step shelf accommodating trapped shelf modes planetary rossby modes are mimicked in the laboratory via a uniform topographic slope in the north south direction hybrid modes are found as linear modes in numerical calculations and similar streamfunction patterns exist in streak photography of the rotating tank experiments these numerical calculations are based on depth averaged potential vorticity dynamics with ekman forcing and damping preliminary nonlinear calculations explore the deficiencies observed between reality and the linear solutions the aim of the work is twofold to show that idealized hybrid rossby shelf modes exist in laboratory experiments and to contribute in a general sense to the discussion on the coupling and energy exchange associated with hybrid modes between shallow coastal seas and deep ocean basins

asymmetry of free circulations in closed ocean gyres steady flows in regions of closed geostrophic contours such as in ocean basins or over seamounts are examined by calculating solutions to the nonlinear quasigeostrophic and shallow water equations with topography for oceanically realistic choices of parameters the solutions are asymmetric in that those with cyclonic circulation resemble the topography while those with anticyclonic circulation exhibit small scale structure and cross isobath flow these small scale structures reflect topographic wave modes which are stationary with the anticyclonic circulation the implication of the asymmetry is that random wind forcing is much more likely to excite persistent cyclonic than anticyclonic flow this may explain why the circulation in the norwegian and greenland gyres is most often cyclonic

on the signature of the quasi 3 day wave in the thermosphere during the january 2010 ursi world day campaign 1 ultra fast kelvin waves with periods of 3 5 days are important in the coupling of the lower atmosphere to the thermosphere and ionosphere here we focus on the observations and effects of a 3 day wave during january 2010 as this time period coincides with a stratospheric warming event a coordinated set of observations with incoherent scatter radars are available while there is no evidence that the occurrence of this 3 day wave is connected with this event these observations offer an unprecedented glimpse of the thermospheric conditions during this period including the first ever detection of a 3 day wave with an incoherent scatter radar using a combination of ground and space based observations we identify an eastward moving zonal wave number one 3 day equatorial wave that is comprised of a kelvin wave at the lowest latitudes and a rossby gravity wave at higher latitudes in the equatorial region the vertical wavelength is 40 km and the wave peaks in amplitude around 95 100 km altitude the wave observed here is only seen to propagate to around 105 km altitude evidence of an interaction between this wave and the diurnal tide is seen between 82 88 km the resultant 3 day periodicity in the diurnal tide is seen to propagate up to altitudes of 150 km this could have a significant impact on the ionosphere via modulation of the e region dynamo thus carrying the 3 day periodicity to higher altitudes

oblique propagation of monsoon gravity waves during the northern hemisphere 2007 summer we present a combination of satellite observation and high resolution model output to understand monsoon convection as a source of high latitude mesospheric gravity waves gws the gws generated over the northern hemisphere nh monsoon region during the 2007 summer and the role of the winds in focusing these gws toward the high latitude middle atmosphere are analyzed using the saber timed satellite temperature data and the high resolution nogaps alpha model results in the nh above the stratosphere the monsoon gw momentum flux gwmf exhibits a poleward tilt that follows the slanted structure of the easterly jet the correlation coefficients 0 5 between the time series of nh tropical stratospheric gwmf and the global winds also have a slanted structure that coincide with the easterly jet confirming the modeling theory that stratospheric monsoon gws are refracted into the summer easterly jet and can reach the high latitude mesosphere since polar mesospheric clouds pmcs are sensitive indicators of changes in the polar summer mesosphere we compared the time series of tropical stratospheric gwmf to the pmc occurrence frequency of obtained from the cips aim satellite data to assess the influence of this wave focusing in the mesosphere there is a significant positive correlation between the high latitude pmc of and the tropical stratospheric gwmf suggesting a definite influence of monsoon gws on the high latitude mesosphere the disagreement in correlation at the end of the pmc season is attributed to the enhancement of the quasi 5 day planetary wave dominating over the influence of monsoon gws on pmcs

non steady state diagenesis of organic and inorganic sulfur in lake sediments abstract sulfur controls the fate of many geochemical elements in lake sediments including iron phosphorus and environmentally important trace elements we measured the speciation of pore water and sediment bound sulfur aqueous sulfate and sulfides elemental sulfur iron monosulfide pyrite organic sulfur and supporting geochemical variables carbon oxygen iron in the sediments of a perennially oxygenated and a seasonally anoxic basin of an oligotrophic lake in quebec using a combination of pore water analyses sequential extractions and x ray absorption near edge structure a non steady state early diagenetic model was developed and calibrated against this extensive dataset to help unravel the pathways and quantify the rates of s transformations results suggest that the main source of s to the sediments is the settling of organic ester sulfate r o so3 h hydrolysis of these compounds provides an additional source of sulfate for anaerobic microbial oxidation of sedimentary organic matter releasing sulfide to the pore water reduced solid bound s species accumulate as thiols r sh and iron sulfides in the perennially oxygenated and seasonally anoxic basin respectively the model estimated rate constant for r sh formation is lower than previously estimated for this particular lacustrine site but similar to that proposed for marine shelf sediments the solid sediment s profiles however carry the imprint of the time dependent sulfate input to the lake iron sulfide enrichments formed during past decades of elevated atmospheric so4 deposition are presently dissolving in the sediments of the perennially oxygenated basin this reaction hampers the build up of fe iii oxy hydroxide near the sediment water interface

a gravity wave climatology for antarctica compiled from challenging minisatellite payload global positioning system champ gps radio occultations 1 the seasonal geographical and altitudinal dependence of gravity wave activity in the lower stratosphere over antarctica is presented gravity wave activity is estimated by calculating potential energy ep from radio occultation profiles obtained by the challenging minisatellite payload global positioning system champ gps experiment significant seasonal variation of wave activity is observed smaller wave activity in summer is attributed to waves with small phase velocities experiencing critical level filtering at other times of the year when wave activity is large less filtering occurs and the strong background wind is likely to cause doppler shifting of waves to longer vertical wavelengths which can reach larger amplitudes before saturating relationships between gravity wave activity and geographic location indicate that topography is a strong source for wave activity especially over the antarctic peninsula however wind rotation in this area was found to reduce the wave energy in summer at certain altitudes a strong enhancement of wave energy is observed at the edge of the polar vortex again reduced critical level filtering and doppler shifting in the area of the jet are likely to be major causes for this finding possible limitations to this study due to observational filtering are discussed

time gcm results for the quasi two day wave to understand how the quasi two day wave qtdw interacts with the mean flow and migrating tides we perturbed the lower boundary of the national center for atmospheric research thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm to excite the qtdw results from our initial model runs computed for a perpetual january 15th show wave amplitudes in wind and temperature that are in qualitative agreement with previous model results and observations the wave period and amplitude change over the duration of the model run and it is expected that this results from changes in the zonal mean zonal winds evidence supporting nonlinear interactions between the qtdw and the migrating tides is presented

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

lidar observations of stratospheric gravity waves from 2011 to 2015 at mcmurdo 77 84 s 166 69 e antarctica 1 vertical wavelengths periods and frequency and vertical wave number spectra five years of atmospheric temperature data collected with an fe boltzmann lidar by the university of colorado group from 2011 to 2015 at arrival heights are used to characterize the vertical wavelengths periods vertical phase speeds frequency spectra and vertical wave number spectra of stratospheric gravity waves from 30 to 50 km altitudes over 1000 dominant gravity wave events are identified from the data the seasonal spectral distributions of vertical wavelengths periods and vertical phase speeds in summer winter and spring fall are found obeying a lognormal distribution both the downward and upward phase progression gravity waves are observed by the lidar and the fractions of gravity waves with downward phase progression increase from summer 59 to winter 70

a study of the relationship between stratospheric gravity waves and polar mesospheric clouds at davis antarctica 1 we used a rayleigh lidar located at davis station east antarctica to compare polar mesospheric cloud pmc and stratospheric gravity wave gw strengths in the austral summer 2005 2006 earlier similar studies from greenland noted that intervals of large stratospheric gw activity appeared to coincide with reduced pmc strengths we measure the stratospheric gw strength in the 30 45 km altitude range for waves of vertical wavelength between 2 and 10 km and of periods greater than 1 h we find little consistency with the greenland studies as the occurrence of pmc over davis appear to have little relationship to observed stratospheric gravity wave activity hemispheric differences in both pmc strength and occurrence and in gravity wave strength may have a role in explaining our results our data suggest that a significant controller of occurrence of pmc over davis is related to diurnal tidal movement we also investigate the potential influence of sampling biases in our data set

zonal wave numbers of the summertime 2 day planetary wave observed in the mesosphere by eos aura microwave limb sounder 1 recent observations and theoretical work suggest that the 2 day planetary wave in the summertime mesosphere is composed of multiple superposed zonal wave numbers here we use eos aura microwave limb sounder mls temperature data to determine the component zonal wave numbers of the 2 day wave in the mesosphere at latitudes of 70 s to 70 n from 2004 to 2009 we consider the effect of aliasing between different wave numbers and note that significant aliasing can occur and result in spurious signals particularly at high latitudes in winter the seasonal evolution of the different wave numbers is investigated and found to be very different between the northern and southern hemispheres in both hemispheres the wave is dominated by westward traveling waves of zonal wave number 3 and 4 w3 and w4 however in the southern hemisphere the wave is dominated by the w3 component but in the northern hemisphere the w3 component is smaller and the w4 component is often of similar or larger amplitude a small amplitude westward traveling zonal wave number 2 w2 wave is also evident in both hemispheres in the northern hemisphere the w2 amplitudes never exceed 3 k the w3 amplitudes can reach 3 5 k and the w4 can be the largest component reaching amplitudes of 4 k in the southern hemisphere the w2 amplitudes can reach up to 3 5 k the w3 amplitudes can be much larger reaching 12 k and the w4 amplitudes are smaller than in the northern hemisphere in 4 out of 5 years not exceeding 3 k the northern hemisphere w4 can reach large amplitudes in august when the w3 is small which means that the late summer northern hemisphere quasi 2 day wave is usually a w4 oscillation rather than the familiar w3 in contrast in the southern hemisphere the w3 is often larger than the w4 around the summer solstice and there are no episodes observed where the wave becomes dominated by the w4 for an extended period of time a high degree of interannual variability is evident particularly in the southern hemisphere where the w3 peak amplitudes vary from 12 k in january 2006 to 3 k in january 2009 the height latitude structure of the w4 suggests that this wave is a 4 0 rossby gravity wave

a model for sulfur accumulation in soft water lake sediments a geochemical model for sulfur in soft water lake sediments of the adirondack mountains new york is developed to gain insight into the timing and magnitude of historical changes in sulfur loading surficial sulfur concentrations range from 3500 to 10 000 mu g g minus sup 1 increase to 6000 to 20 000 mu g g minus sup 1 at a depth of 2 6 cm and then decrease downcore to background levels of 2500 7500 mu g g minus sup 1 sulfate concentrations are about 50 80 mu m in the overlying water and decrease rapidly below the sediment water interface a mathematical model is constructed assuming sulfur is incorporated into sediments by burial of detrital organic matter and by diffusion of dissolved sulfate from the overlying water with subsequent fixation into the sediment solids several scenarios of historical sulfate deposition were examined as model boundary conditions the observed sediment sulfur profiles are best modeled using boundary conditions showing loading increases of about a factor of 8 since about 1940 assuming as much as a decade of retention of sulfate within the terrestrial portion of the ecosystem this suggests that significant increases in sulfate deposition rates began sometime about 1930 in this area 34 refs 7 figs 2 tabs

global observations of 2 day wave coupling to the diurnal tide in a high altitude forecast assimilation system we examine wave components in a high altitude forecast assimilation system that arise from nonlinear interaction between the diurnal tide and the westward traveling quasi 2 day wave the process yields a westward traveling sum wave with zonal wavenumber 4 and a period of 16 hours and an eastward traveling difference wave with zonal wavenumber 2 and a period of 2 days while the eastward 2 day wave has been reported in satellite temperatures the westward 16 hour wave lies outside the nyquist limits of resolution of twice daily local time satellite sampling hourly output from a high altitude forecast assimilation model is used to diagnose the nonlinear quadriad a steady state primitive equation model forced by tide 2 day wave advection is used to intepret the nonlinear wave products the westward 16 hour wave maximizes in the midlatitude winter mesosphere and behaves like an inertia gravity wave the nonlinearly generated component of the eastward 2 day wave maximizes at high latitudes in the lower thermosphere and only weakly penetrates to low latitudes the 16 hour and the eastward 2 day waves are of comparable amplitude and alias to the same apparent frequency when viewed from a satellite perspective

polar mesosphere and lower thermosphere dynamics 1 mean wind and gravity wave climatologies 1 mean wind and gravity wave climatologies are presented for the polar mesosphere and lower thermosphere mlt the data were derived using mf radars at davis 69 s 78 e and syowa 69 s 40 e in the antarctic and poker flat 65 n 147 w and andenes 69 n 16 e in the arctic the dynamics of the antarctic mlt are found to be significantly different from the arctic mlt summer maxima in both the westward and equatorward winds occur closer to the solstice in the antarctic than in the arctic the greater symmetry around the solstice suggests radiative effects may play a greater role in controlling the state of the antarctic mlt than in the arctic where dynamical effects appear to be more important gravity wave observations also suggest that wave drag may be greater in the arctic than in the antarctic the equatorward flow near the mesopause persists later in summer in the arctic than in the antarctic as do observations of polar mesospheric clouds and polar mesospheric summer echoes all three phenomena begin at about the same time in each hemisphere but end later in the arctic than in the antarctic it is proposed that the magnitude of the meridional winds can be used as a proxy for gravity wave driving and the consequent adiabatic cooling in the mlt seasonal variations in gravity wave activity are predominately combinations of annual and semiannual components significant hemispheric differences are observed for both the timing and magnitude of these seasonal variations

topographic rossby waves in a polar basin approximate analytical expressions for the eigenfrequencies of freely propagating divergent barotropic topographic rossby waves over a step shelf are derived the amplitude equation that incorporates axisymmetric topography while retaining full spherical geometry is analysed by standard asymptotic methods based on the limited latitudinal extent of the polar basin as the natural small parameter the magnitude of the planetary potential vorticity field pi p increases poleward in the deep basin and over the shelf however everywhere over the shelf pi p exceeds its deep basin value consequently the polar basin waveguide supports two families of vorticity waves here our concern is restricted to the study of topographic rossby shelf waves the leading order eigenfrequencies and cross basin eigenfunctions of these modes are derived moreover the spherical geometry allows an infinite number of azimuthally propagating modes we also discuss the corrections to these leading order eigenfrequencies it is noted that these corrections can be associated with planetary waves that can propagate in the opposite direction to the shelf waves for parameter values typical of the arctic ocean planetary wave modes have periods of tens of days significantly longer than the shelf wave periods of one to five days we suggest that observations of vorticity waves in the beaufort gyre with periods of tens of days reported in the refereed literature could be associated with planetary rather than topographic rossby waves

hydraulically drained flows in rotating basins part i method abstract an asymptotic method for coupling circulations in basins to hydraulically controlled overflows is introduced the method is applicable when the forcing dissipation and coupling with the overflow are weak in which case the lowest order solution for the homogeneous or 1 layer model consists of the natural basin modes including gravity inertia gravity potential vorticity helmholtz and steady geostrophic modes at the next order of approximation the mode amplitudes are found to vary slowly with time as the result of forcing dissipation interior nonlinear mode interactions and most importantly coupling with the overflow even when the latter are absent the overflow dynamics generally introduce nonlinearity although the basin dynamics are assumed linear to lowest order the overflow is intrinsically nonlinear to couple the two systems the overflow model must be adapted to serve as a nonlinear boundary condition on the basin flow to do so a rotating channel model introduced by whiteh

noctilucent clouds and wave dynamics observations at sondrestrom greenland rayleigh lidar measurements of the arctic summer stratosphere and mesosphere have been conducted routinely since 1994 at the sondrestrom atmospheric research facility near kangerlussuaq greenland 67 0n 50 9w between 1994 and 1996 seventeen separate events of noctilucent clouds nlcs as well as corresponding stratospheric wave structure have been observed we present in this study two main results 1 the occurrence of persistent quasi monochromatic wave structure in the stratosphere having observed vertical wavelengths of 8 to 12 km and observed temporal periods of approximately 2 3 hours and 2 evidence that the strength of such lower altitude waves may be associated with the overall strength of the observed nlc volume backscatter coefficient

the quasi 2 day wave activities during 2007 austral summer period as revealed by whole atmosphere community climate model the quasi 2 day wave qtdw observed during 2007 austral summer period is well reproduced in an reanalysis produced by the data assimilation version of the whole atmosphere community climate model waccm data assimilation research testbed developed at national center for atmospheric research ncar it is found that the qtdw peaked 3 times from january to february but with different zonal wave numbers diagnostic analysis shows that the mean flow instabilities refractive index and critical layers of qtdws are fundamental for their propagation and amplification and thus the temporal variations of the background wind are responsible for the different wave number structures at different times the westward propagating wave number 2 mode w2 grew and maximized in the first half of january when the mean flow instabilities related to the summer easterly jet were enclosed by the critical layers of the westward propagating wave number 3 w3 and wave number 4 w4 modes this prevented w3 and w4 from approaching and extracting energy from the unstable region the w2 decayed rapidly thereafter due to the recession of critical layer and thus the lack of additional amplification by the mean flow instability the w3 peaked in late january when the instabilities were still encircled by the critical layer of w4 the attenuation of w3 afterward was also due to the disappearance of critical layer and thus the lack of overreflection finally the w4 peaked in late february when both the instability and critical layer were appropriate

solar tides as revealed by measurements of mesosphere temperature by the mls experiment on uars abstract temperatures between 25 and 86 km measured by the microwave limb sounder mls experiment on the upper atmosphere research satellite uars are analyzed to delineate diurnal semidiurnal and terdiurnal tidal structures and stationary planetary waves these fourier components are determined from temperatures averaged in bins covering 5 latitude 30 longitude and 1 h in local time this study confirms the presence of diurnal nonmigrating tides with zonal wavenumbers s 0 2 3 s 0 s 0 implying westward eastward propagation and semidiurnal tides with s 1 and 3 and some components of lesser importance that were previously determined from uars wind measurements near 95 km the seasonal latitudinal and height structures of these components are now revealed and utilized to aid in interpreting their behaviors and ascertaining their origins new discoveries include the terdiurnal s 2 and s 4 components and trapped nonmigrating diurnal tides with s 0 and s 2 the former are like

first lidar observations of polar mesospheric clouds and fe temperatures at mcmurdo 77 8 s 166 7 e antarctica 1 we report the first lidar observations of polar mesospheric clouds pmcs and temperatures made with an fe boltzmann lidar at mcmurdo antarctica in summer 2010 2011 eighty five hours of pmcs were observed between 21 dec 2010 and 15 feb 2011 giving an overall occurrence frequency of 29 9 the mean pmc centroid altitude is 84 59 0 17 km confirming previous reports that clouds in the southern hemisphere are 1 km higher than in the north by combining the mcmurdo 77 8 s observations with those obtained at the south pole 90 s and rothera 67 5 s we find that the mean pmc altitude increases with increasing latitude with a statistically significant ascending rate of 40 3 m deg a negative correlation is found between the daily mean temperatures at 90 km and pmc brightness the observations provide direct evidence that the cold phase of wave induced temperature oscillations facilitates pmc formation and fe depletion supporting previous modeling results

anthropogenic inventories and historical and present accumulation rates of copper in great lakes sediments abstract sediment cores were collected from depositional basins in lakes michigan ontario and superior to assess spatial and temporal variations in cu accumulation rates and inventories sediment chronologies were determined via 210 pb dating and 210 pb inventories were used to correct for the effects of sediment focusing among the lakes studied cu loading histories generally decrease to the present signifying a regional reduction in the anthropogenic release of cu to the environment focusing corrected cu accumulation rates in surficial sediments vary significantly within lakes michigan and ontario suggesting that recent inputs of cu to these 2 lakes may have been dominated by localized sources variations in cu accumulation rates within lake superior are interpreted to be insignificant suggesting either that lake superior is well mixed with respect to copper inputs or that the lake is dominated by a single source for cu recent measurements of atmospheric fluxes of cu within the great lakes region generally indicate that the atmosphere accounts for less than 50 of the cu accumulating in surficial sediments historical cu accumulation rates from lake superior are poorly correlated with cu production associated with local smelters but favorably agree with national production rates trends in historical cu accumulation rates within all 3 lakes may indicate that recent declines in cu loading can be attributed to the enactment of stricter environmental regulations as well as changes in the use of cu focusing corrected cu inventories in lakes michigan ontario and superior are generally invariant within a given lake indicating that historically these lakes have been dominated either by a single source or were well mixed with respect to cu inputs the disparity between the results from recent accumulation rates and historical inventories may reflect differences in how the great lakes respond to contaminant loading on short e g years versus long e g decades timescales

polar mesospheric cloud structures observed from the cloud imaging and particle size experiment on the aeronomy of ice in the mesosphere spacecraft atmospheric gravity waves as drivers for longitudinal variability in polar mesospheric cloud occurrence patterns and structures in polar mesospheric clouds pmcs around the summertime mesopause region which are qualitatively similar to structures seen in noctilucent clouds nlcs from ground based photographs the structures in pmc are generally considered to be manifestations ofupward propagating atmospheric gravity waves agws variability of agw effects on pmc reported at several lidar sites has led to the notion of longitudinal differences in this relationship this studycompares thelongitudinal variability in thecips observed wave occurrence frequency with cips measured pmc occurrence frequency and albedo along with mesospheric temperatures measured by the sounding of the atmosphere using broadband emission radiometry instrument on board the thermosphere ionosphere mesosphere energetics and dynamics spacecraft our results for the latitude ranges between 70 and 80 show a distinct anticorrelation of wave structures with cloud occurrence frequency and correlations with temperature perturbations for at least two of the four seasons analyzed supporting the idea of gravity wave induced cloud sublimation the locations of the observed wave events show regions of high wave activity in both hemispheres in the northern hemisphere while the longitudinal variability in observed wave structures show changes from the 2007 2008 seasons there exist regions of both low and high wave activities common to the two seasons these persistent features may explain some of the observed differences in pmc activity reported by ground based lidar instruments distributed at different longitudes the statistical distribution of horizontal scales increases with wavelength up to at least 250 km we also discuss the possibility of atmospheric tides especially the nonmigrating semidiurnal tide aliasing our observations and affecting the results presented in this analysis

large scale waves in the mesosphere and lower thermosphere observed by saber observations made by the sounding of the atmosphere using broadband emission radiometry saber instrument on board nasa s thermosphere ionosphere mesosphere energetics and dynamics timed satellite have been processed using salby s fast fourier synoptic mapping ffsm algorithm the mapped data provide a first synoptic look at the mean structure and traveling waves of the mesosphere and lower thermosphere mlt since the launch of the timed satellite in december 2001 the results show the presence of various wave modes in the mlt which reach largest amplitude above the mesopause and include kelvin and rossby gravity waves eastward propagating diurnal oscillations non sunsynchronous tides and a set of quasi normal modes associated with the so called 2 day wave the latter exhibits marked seasonal variability attaining large amplitudes during the solstices and all but disappearing at the equinoxes saber data also show a strong quasi stationary rossby wave signal throughout the middle atmosphere of the winter hemisphere the signal extends into the tropics and even into the summer hemisphere in the mlt suggesting ducting by westerly background zonal winds at certain times of the year the 5 day rossby normal mode and the 4 day wave associated with instability of the polar night jet are also prominent in saber data

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

an eastward propagating two day wave evidence for nonlinear planetary wave and tidal coupling in the mesosphere and lower thermosphere 1 temperature observations from the saber instrument on the timed spacecraft are used to investigate the structure and evolution of an eastward propagating zonal wavenumber 2 disturbance with a period near two days this oscillation obtains a maximum amplitude of nearly 10 k in the southern hemisphere mid latitudes during late january the timing and location of this planetary wave is coincident with the regular quasi two day wave intensification that occurs annually in late january the period wavenumber and spatial structure of the eastward propagating two day wave are consistent with a wave that results from a nonlinear interaction between the quasi two day wave and the migrating diurnal tide the existence of an eastward propagating wave with a period near two days coincident with the westward propagating two day wave will have an impact on the interpretation of ground based observations analysis of the saber temperature observations are utilized to determine the structure and evolution of both this eastward propagating two day wave and the classic westward propagating zonal wavenumber 3 quasi two day wave during january 2005

observations of the quasi two day wave in the middle and lower atmosphere over christmas island we present analyses of data collected at christmas island in the mesosphere and lower thermosphere using a meteor echo detection and collection system medac in addition to data collected in the troposphere and lower stratosphere using a clear air stratosphere troposphere st radar these data which provide 5 years of semicontinuous horizontal wind velocity estimates are analyzed to determine the temporal structure of the quasi two day wave in the middle and lower atmosphere our results show the presence of strong wave activity in the middle atmosphere during late january and early february as well as a secondary maxima in june august for each of the years we have data however the magnitude and duration of the wave events observed in late january and early february exhibit interannual variability

gravity waves and mesospheric clouds in the summer middle atmosphere a comparison of lidar measurements and ray modeling of gravity waves over sondrestrom greenland 1 we conducted gravity wave ray tracing experiments within an atmospheric region centered near the arclite lidar system at sondrestrom greenland 67 n 310 e in efforts to understand lidar observations of both upper stratospheric gravity wave activity and mesospheric clouds during august 1996 and the summer of 2001 the ray model was used to trace gravity waves through realistic three dimensional daily varying background atmospheres in the region based on forecasts and analyses in the troposphere and stratosphere and climatologies higher up reverse ray tracing based on upper stratospheric lidar observations at sondrestrom was also used to try to objectively identify wave source regions in the troposphere a source spectrum specified by reverse ray tracing experiments in early august 1996 when atmospheric flow patterns produced enhanced transmission of waves into the upper stratosphere yielded model results throughout the remainder of august 1996 that agreed best with the lidar observations the model also simulated increased vertical group propagation of waves between 40 km and 80 km due to intensifying mean easterlies which allowed many of the gravity waves observed at 40 km over sondrestrom to propagate quasi vertically from 40 80 km and then interact with any mesospheric clouds at 80 km near sondrestrom supporting earlier experimentally inferred correlations between upper stratospheric gravity wave activity and mesospheric cloud backscatter from sondrestrom lidar observations a pilot experiment of real time runs with the model in 2001 using weather forecast data as a low level background produced less agreement with lidar observations we believe this is due to limitations in our specified tropospheric source spectrum the use of climatological winds and temperatures in the upper stratosphere and mesosphere and missing lidar data from important time periods

short term variability in the migrating diurnal tide caused by interactions with the quasi 2 day wave 1 the migrating diurnal tide is one of the dominant dynamical features in the low latitudes of the earth s mesosphere and lower thermosphere mlt region representing the atmospheric response to the largest component of solar forcing ground based observations of the tide have resolved short term variations attributed to nonlinear interactions between the tide and planetary waves that are also in the region using the ncar thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm we simulate a quasi 2 day wave qtdw event under late january conditions in this case sideband sum and difference child waves are resolved indicating that a nonlinear interaction is occurring between the qtdw and the tide the migrating diurnal tide in the mlt displays local amplitude decreases of 20 40 as well as a shortening of vertical wavelength by roughly 4 km examining the physical mechanisms driving the interaction nonlinear advection is found to result in amplification of the tide in some regions and damping in others manifesting as increased smoothing of the tidal structure when the qtdw is present in the mlt additionally the qtdw also enhances the easterly summer mean wind jet that can also account for changes in tidal amplitude and vertical wavelength we find that qtdw induced background atmosphere changes in time gcm can drive tidal variability at levels greater than nonlinear advection a possibility not previously considered

gravity wave momentum flux in the mesosphere measured by vhf radar at davis antarctica polar mesospheric summer echoes observed in vhf mst radar measurements at davis antarctica 68 5 s 78 0 e are used to measure high frequency gravity wave momentum flux in the vicinity of the mesopause during the southern hemisphere summer of 2014 15 the momentum flux spectrum is generally isotropic with a slight bias in the seasonal mean towards the southeast zonal and meridional components of the seasonal mean momentum flux are an order of magnitude smaller than the absolute momentum flux diurnal and semidiurnal modulation of the momentum flux correspond to perturbations of the seasonal mean winds by atmospheric tides quantitative measures of gravity wave intermittency yield high values and increase with altitude through the mesopause region these intermittency characteristics are attributed to the increase with altitude of wind variability through the mesopause region as a result of the tides

hybrid coastal and interior modes for two dimensional flow in a cylindrical ocean flows on coastal shelves and in the deep interior ocean are often considered separately but transport of fluid between these two regions can have important biologial or environmental consequences this paper considers a linear coupled coastal and deep interior ocean model in the idealized context of a homogeneous two dimensional cylindrical ocean with a rigid lid and axisymmetric step shelf topography both a semianalytical mode matching approach and brute force finite element numerics have been used to analyze the linear dynamics it is shown that hybrid planetary plane rossby and topographic shelf modes emerge the structure of these inviscid modes is clarified by considering their frequency dependence on shelf break radius by contrasting the evolution of hybrid modes to the evolution of pure shelf and pure plane rossby modes considering streamfunction fields and particle paths and by showing solutions of the initial value problem both ocean and laboratory parameter values are considered hybrid modes exchange information between the deep ocean and coastal shelves especially at the intermediate frequencies where the separate planetary rossby mode and topographic shelf mode dispersion curves overlap the role of these modes is particularly clear in an initial value problem wherein a localized initial condition on the southern shelf later leads to large scale interior ocean circulation forced dissipative calculations reveal the sensitivity of resonantly generated hybrid rossby shelf modes to the strength of ekman damping for typical oceanic and laboratory parameter values hybrid modes are altered by increasing ekman damping but do not disappear

low latitude 2 day planetary wave impact on austral polar mesopause temperatures revealed by a january diminution in pmse above davis antarctica 1 a new characteristic of the austral summer polar mesopause as revealed by ground based radar and satellite temperature measurements is reported that is linked to inter annual variability of the low latitude easterly wind jet four consecutive seasons of polar mesosphere summer echoes pmse and mesosphere temperature observations above davis antarctica 68 6 s show a mid january diminution in pmse occurrence rate that coincides with a minor mesopause warming of several degrees spectral analyses of pmse aura microwave limb sounder mls temperatures and radar meridional winds show the presence of 4 5 day planetary waves pws throughout the austral summer in the polar upper mesosphere together with enhanced 2 day pw activity from mid january to mid february analysis of mls temperatures show that the 2 day pws have zonal wavenumbers s with both westward s 2 3 and eastward s 2 3 components although displaying some inter annual variation in the peak onset time the mid january mesopause warming coincides with a weakening of the equatorward meridional wind above davis and enhancement of low latitude 2 day pw activity

persistent ice cloud in the midsummer upper mesosphere at high latitudes three dimensional modeling and cloud interactions with ambient water vapor 1 we infer from the observed occurrence frequency of polar mesosphere summer echoes and from the three dimensional 3 d modeling of conditions in the high latitude mesopause region that a persistent layer of icy particles exists in midsummer at all latitudes poleward of about 60 n at and a few kilometers below the mesopause all of these icy particles are transported equatorward by the climatological mean winds at the same time many of the larger icy particles possess a high enough sedimentation velocity to induce a net downward transport of water vapor both types of particle motions cause the mesopause region to become substantially dryer than without these transports of icy particles we follow the interactions between water vapor and icy particles by means of a 3 d dynamical and chemical model which includes a module for the formation growth and sublimation of icy particles for midsummer conditions and poleward of 67 n latitude the model predicts 1 a strongly dehydrated region typically above 84 km in which the water vapor mixing ratio can fall below 0 2 ppmv and 2 atmospheric regions with enhanced water vapor abundance near both the lower and the equatorward borders of the icy particle layer

diurnal variation of gravity wave momentum flux and its forcing on the diurnal tide 1 the diurnal variation of gravity wave gw momentum flux is derived from the 5 years of meteor radar wind measurements at maui hawaii the amplitude and phase relationships between the gw forcing and the diurnal tide are analyzed by calculating their equivalent rayleigh frictions the results show that the gw momentum flux is clearly modulated by the diurnal tide the forcing from the momentum flux convergence has strong effects on both the amplitude and phase of the diurnal tide they can reach 80 ms 1 day 1 for the amplitude and 15 h day 1 for the phase the gw forcing tends to increase the diurnal tide amplitude above 90 km but has a small damping effect below 90 km it tends to increase the phase of the diurnal tide throughout all altitudes seasonal variations of the gw forcing exist which result in differences in their effects on the diurnal tide the magnitudes of the forcing are in agreement with recent results from satellite observations but are much larger than values used in general circulation models this work also demonstrates that meteor radar measurements can provide a valuable data set for the study of gw tide interactions

quasi lagrangian superpressure balloon measurements of gravity wave momentum fluxes in the polar stratosphere of both hemispheres 1 superpressure balloons were flown in 2002 and 2005 in the winter polar vortices of both hemispheres the balloons can drift for months in the stratosphere acting as quasi lagrangian tracers of air parcel motions the meteorological datasets acquired are used to retrieve small scale internal atmospheric gravity wave parameters using wavelet techniques for the first time gravity wave momentum fluxes are estimated over wide geographical areas and the results will help constrain gravity wave parameterization schemes used in general circulation climate models the importance of mountain waves is confirmed with largest fluxes observed in the lee of greenland and the antarctic peninsula however significant momentum fluxes are also observed over the oceans showing the importance of other wave generation mechanisms

frictionally modified continental shelf waves and the subinertial response to wind and deep 0cean forcing abstract analytic solutions am obtained for the barotropic shelf circulation caused by wind and deep ocean forcing at subinertial frequencies an inclined beach model of the continental shelf is used and only situations in which bottom friction is important are considered three different alongshore forces are considered pressure gradients and currents maintained by the deep ocean at the shelf break and wind stress over the shelf in each case the model is formulated as a boundary value problem in which the boundary conditions are determined by the forcing mechanism in general a damped resonant response occurs when the forcing function has the same longshore velocity as an unforced continental shelf wave and is most significant for the fim mode in the case of forcing by an alongshore pressure gradient at the edge of the shelf this leads to the amplification of the pressure signal toward the coast the model frequencies and structures are determined for various frictional values when friction is s

two day wave traveling westward with wave number 1 during the sudden stratospheric warming in january 2017 quasi two day wave qtdw propagating westward with wavenumber number 1 w1 in january 2017 is studied using global temperature observed by saber and wind observed by a meteor radar at fuke china 19 0on 109 8oe the amplitude of w1 significantly enhances during january 2017 when two stratospheric warming events occur the temperature perturbation of w1 reaches maximum amplitude of more than 6k at latitude 15o around 84 km and 95 km the structure of temperature w1 is symmetric with regard to the equator the temporal variation of w1 is consistent with the stationary planetary wave with wavenumber 2 spw2 but contrary to the qtdw propagating westward with wavenumber 3 w3 when spw2 is large during two sudden stratospheric warming events energy transfers from w3 to w1 two bursts of the two day wave in meridional wind observed by the meteor radar are just corresponding to the local maxima of w3 and w1 respectively we conclude that during january 2017 w1 is generated by the nonlinear interaction between spw2 and w3 spw2 which is modulated by the quasi 16 day perturbation in the stratosphere plays a key role in the energy transmission from w3 to w1 and it is responsible for the 16 day variation of w1

global distribution and variability of quasi 2 day waves based on the nogaps alpha reanalysis model this study presents the analysis of 14 months january 2009 february 2010 of continuous hourly nogaps alpha reanalysis data used for examining the quasi 2 day wave otdw the global structure and seasonal variability of the eastward and westward traveling qtdws in all meteorological fields geopotential height zonal and meridional wind and temperature have been studied the use of hourly reanalysis data allows a comprehensive understanding of the global spatial temporal qtdw distribution by simultaneous separations of all tides and planetary waves the wave characteristics amplitudes and phases are presented in latitude range 80 and altitudes from 15 to 95 km two different types of eastward traveling waves are identified i waves at middle and high latitudes with zonal wave numbers 2 and 3 which are observed in the local winters and ii waves observed predominantly over the equator with zonal wave number 2 which do not have a well defined seasonal variability but show some enhancement between june and august while the first type waves are seen in all meteorological fields the second ones are not seen in the meridional wind and belong to the ultra fast kelvin waves two different types of westward traveling waves have been identified as well i waves at middle and high latitudes with zonal wave numbers 2 3 and 4 which are observed mainly in summer hemisphere and ii waves observed predominantly over the equator with zonal wave numbers 1 2 and 3 enhanced predominantly at both solstices but are seen in other seasons as well while the first type waves are seen in all meteorological fields the second ones are observed in the meridional wind and are rossby gravity normal modes

nondivergent planetary oscillations in midlatitude ocean basins with continental shelves abstract free oscillations in square midlatitude basins with continental shelves and planetary vorticity gradients are numerically computed using the nondivergent shallow water equations the topography may rend a planetary mode into a family of basinwide modes each comparable to the flat bottom counterpart in frequency and midbasin structure this phenomenon can be interpreted in terms of coupled planetary wave shelf wave oscillations the mechanism provides an alternative to strong dissipation in explaining broadbanded planetary wave signals signals observed in tide guage records

interstation correlation of high latitude lower stratosphere gravity wave activity evidence for planetary wave modulation of gravity waves over antarctica 1 four years of operational radiosonde balloon flights from three australian stations in eastern antarctica casey 66 3 s 110 0 e davis 68 6 s 78 0 e and mawson 67 6 s 62 9 e are analyzed to derive lower stratosphere 12 20 km altitude gravity wave information from perturbations in wind and temperature gravity wave activity and seasonal behavior was found to be similar to that seen in earlier studies from antarctica interstation comparisons of zonal wind and gravity wave activity showed very high correlations throughout the entire data set between mawson and davis stations 600 km distant with a lag near 0 5 days the correlations between casey and davis 1400 km apart were lower but still significant with a lag near 1 day there is no significant correlation between stratospheric gravity wave activity and surface winds our results suggest a pattern of winds and waves moving eastward over the stations with a speed near 15 m s 1 as this is comparable to planetary wave speeds we interpret our results as being evidence for a significant planetary wave induced modulation of the zonal wind and the gravity wave field although we are unable to identify the mechanism by which this operates our work suggests that the high latitude lower stratosphere gravity wave fields are relatively uniform on spatial scales of 500 1000 km and on timescales of around 0 5 1 days

first observations of southern hemisphere polar mesosphere winter echoes including conjugate occurrences at 69 s latitude 1 we present the first account of polar mesosphere winter echoes pmwe observed from the southern hemisphere sh using measurements from davis antarctica 68 6 s 78 0 e pmwe were observed by mesosphere stratosphere troposphere mst radar during solar proton events spes and auroral substorms we supplement the mst radar measurements with profiles of temperature and turbulent velocity from co located rayleigh lidar and medium frequency mf radar respectively as well as temperature data from the microwave limb sounder mls onboard the aura satellite we establish that sh pmwe exhibit similar characteristics to their well studied northern hemisphere counterpart significantly our observations reveal that these radar echoes in the lower mesosphere 50 80 km can occur year round and on occasions simultaneously in both hemispheres we report the seasonal occurrence distribution of sh pmwe is linked to the seasonal distribution of atmospheric turbulence in the lower mesosphere we hypothesise that given sufficient turbulent velocities in the neutral atmosphere and co located gradients in electron density pmwe can occur throughout the year however they are more likely in winter when turbulent velocities in the lower mesosphere maximise

lidar observations of polar mesospheric clouds at south pole diurnal variations polar mesospheric clouds pmcs were observed by a ground based fe boltzmann temperature lidar for 65 h on 17 19 and 24 26 january 2000 above the geographic south pole the mean pmc backscatter ratio volume backscatter coefficient total backscatter coefficient layer centroid altitude and layer rms width are 53 5 2 9 l0 9 m 1sr 1 4 3 10 6 sr 1 85 37 km and 0 78 km respectively strong semidiurnal and diurnal oscillations were observed in the pmc backscatter ratio volume backscatter coefficient total backscatter coefficient and centroid altitude the oscillations are all maximum around 0630 and 1900 ut the variations appear to be linked to vertical advection of the pmc scattering layers by a persistent oscillation in the vertical wind velocity scattering is strongest when the pmcs are highest which suggests that the colder temperatures at higher altitudes near the mesopause facilitate the formation of larger pmc particles

variability of the near surface eddy kinetic energy in the california current based on altimetric drifter and moored current data low pass filtered velocities obtained from world ocean circulation experiment woce surface drifters deployed in the california current off northern california during 1993 1995 have been compared with surface geostrophic velocity estimates made along subtracks of the topex poseidon altimeter and with moored acoustic doppler current profiler adcp data to obtain absolute geostrophic velocities a mean sea surface height ssh field was estimated using the mean drifter velocities and historical hydrographic data and was added to the altimetric ssh anomalies the correlation between collocated drifter and altimetric velocities is 0 73 significant at the 95 level the component of the drifter velocity which was uncorrelated with the altimetric velocity was correlated with the wind in the ekman transport sense monthly averages of eddy kinetic energy eke estimated using all drifter and altimeter data within the domain 124 132 w 33 40 5 n show energy levels for the drifters that are about 13 greater than those for the altimeter drifter altimeter and adcp measurements all exhibit similar seasonal cycles in eke with the altimeter data reaching maximum values of about 0 03 m 2 s 2 in late summer fall wavenumber spectra of the altimeter velocity indicate that the velocity fluctuations were dominated by features with wavelengths of 240 370 km while the adcp data suggest that the temporal scales of these fluctuations are at least several months between 36 and 40 5 n the region of monthly maximum eke migrates westward to about 128 w on a seasonal timescale this region of maximum eke coincides with the maximum zonal ssh gradient with increased eke associated with increased southward flow a simple model shows that much of the seasonal cycle of the ssh anomalies can be produced by linear processes forced by the curl of the wind stress although the model cannot explain the offshore movement of the front

first southern hemisphere common volume measurements of pmc and pmse 1 using rayleigh lidar and mesosphere stratosphere troposphere radar at davis antarctica 68 6 s during the 2005 2006 austral summer we obtained the first southern hemisphere common volume measurements of polar mesospheric clouds pmc and polar mesosphere summer echoes pmse pmc were observed with 6 probability during 349 hours of lidar observations pmse were simultaneously observed during 70 of the pmc events the mean centroid altitudes of simultaneous pmc and pmse were 83 97 0 10 km and 85 31 0 14 km respectively the altitude difference 1 3 km is comparable to earlier boreal common volume measurements both phenomena show clear diurnal variations in altitude and occurrence pmc had a unimodal local time occurrence distribution which peaked 4 6 hours after solar midnight pmse were most prevalent at this time but had a secondary occurrence peak 6 hours after solar noon when pmc were absent we explain the altitude time distributions of pmc and pmse in terms of the thermal structure of the mesopause region determined using measurements from the aura satellite

low frequency baroclinic waves off coastal boundaries abstract the behavior of low frequency baroclinic rossby wave motion in the vicinity of coastal boundaries is investigated using linearized modulated wave theory in a stratified constant depth equatorial plane ocean a primary objective is to obtain an equation that describes large scale low frequency pressure fluctuations along variable geometry ocean boundaries at all latitudes for use in the analysis of coastal sea level observations both eastern and western boundaries are considered and the effect of direct wind stress forcing at the coast is included but our major interest concerns the response along eastern ocean boundaries to incident baroclinic equatorial kelvin waves in that case for an incident wave at a fixed frequency a critical latitude with coriolis parameter f fc exists such that for f fc the waves are coastally trapped the magnitude of fc depends on and on the angle of the coastline

seasonal and latitudinal variation of noctilucent cloud altitudes 1 we present a summary of 1500 hours of lidar measurements of noctilucent cloud nlc altitudes at kuhlungsborn 54 n alomar 69 n and spitsbergen 78 n mean centroid altitudes zc are 82 75 km 83 33 km and 83 68 km respectively standard deviations representing geophysical variability are 0 7 1 6 km errors of mean heights zc are much smaller 60 340 m several processes which are not yet fully understood influence zc therefore is a better measure of uncertainties in zc compared to zc the increase of nlc heights with latitude is very small 43 65 m deg and statistically not significant at alomar zc varies with season by up to 1 1 5 km nlc heights accumulate around climatological temperatures of 145 k at 69 n and 78 n higher at 54 n the lima model nicely reproduces observations and indicates that non variation of nlc heights at polar latitudes is caused by temperature uniformity the 145 k isotherm varies in height by less than 250 m from the pole to 60 n

structure of the terdiurnal tide at 95 km satellite wind observations from the high resolution doppler interferometer hrdi instrument on the upper atmosphere research satellite uars are used to describe the latitudinal structure and seasonal variation of the terdiurnal 8 hour atmospheric tide at 95 km the amplitude of the annual average tide is 5 m s meridional and 15 m s zonal within the range observed 60 s to 60 n the maximum amplitudes are found during fall and winter at midlatitudes only weak temporal correlations with the diurnal and semidiurnal tides are seen on the monthly time scales resolved