a climatology of rossby wave generation in the middle atmosphere of the southern hemisphere from merra reanalysis a climatological characterization of rossby wave generation events in the middle atmosphere of the southern hemisphere is conducted using 20 years of modern era retrospective analysis for research and applications merra reanalysis an automatic detection technique of wave generation events is developed and applied to merra reanalysis the rossby wave generation events with wave period of 1 25 to 5 5 days and zonal wave number from one to three dominate the eliassen palm flux divergence around the stratopause at high latitudes in the examined 20 year period these produce an eastward forcing of the general circulation between may and mid august in that region afterward from mid august to the final warming date rossby wave generation events are still present but the eliassen palm flux divergence in the polar stratopause is dominated by low frequency rossby waves that propagate from the troposphere the rossby wave generation events are associated with potential vorticity gradient inversion and so they are a manifestation of the dominant barotropic baroclinic unstable modes that grow at the cost of smearing the negative meridional gradient of potential vorticity the most likely region of wave generation is found between 60 and 80 s and at a height of 0 7 hpa but events were detected from 40 hpa to 0 3 hpa which is the top of the examined region the mean number of events per year is 24 and its mean duration is 3 35 days the event duration follows an exponential distribution

the climatology of zonal wave numbers 1 and 2 planetary wave structure in the mlt using a chain of northern hemisphere superdarn radars the zonal wave components 1 and 2 were extracted from the meridional wind along the latitude band of 51 66 n for the years 2000 2008 using eight super dual auroral radar network superdarn radars spanning longitudes from 25 e to 150 w each extracted zonal component represents the superposition of all temporal periods with that zonal structure and indicates the total planetary wave energy available with that wave number the hovmoller diagrams show stationary as well as eastward and westward traveling planetary waves propagating in the background wind the method used to detect the zonal planetary wave components in the superdarn data are detailed and validated using uk meteorological office data which allows the evolution of s1 and s2 planetary wave energy between the stratosphere and mesosphere to be assessed the climatology of zonal wave number 1 and 2 planetary wave activity in the mesosphere lower thermosphere mlt is presented and compared to the activity in the stratosphere the mlt climatology of the mean wind anomalies shows stronger planetary wave activity during winter and weaker activity during summer with enhancement around midsummer and autumn equinox the climatology of the mean wind displays similar amplitudes apart from very strong s1 planetary wave amplitudes during summer in addition planetary wave activity during winters with major and minor stratospheric warming events are examined and contrasted

climatology of mesopause region temperature zonal wind and meridional wind over fort collins colorado 41 n 105 w and comparison with model simulations 1 between may 2002 and april 2006 many continuous observations of mesopause region temperature and horizontal wind each lasting longer than 24 h termed full diurnal cycle observations were completed at the colorado state university na lidar facility in fort collins colorado 41 n 105 w the combined data set consists of 120 full diurnal cycle observations binned on a monthly basis with a minimum of 7 cycles in april and a maximum of 18 cycles in august each monthly data set was analyzed to deduce mean values and tidal period perturbations after removal of tidal signals monthly mean values are used for the study of seasonal variations in mesopause region temperature zonal and meridional winds the results are in qualitative agreement with our current understanding of mean temperature and wind structures in the midlatitude mesopause region with an observed summer mesopause of 167 k at 84 km summer peak eastward zonal wind of 48 m s at 94 km winter zonal wind reversal at 95 km and peak summer pole to winter pole meridional flow of 17 m s at 86 km the observed mean state in temperature zonal and meridional winds are compared with the predictions of three current general circulation models i e the whole atmosphere community climate model version 3 waccm3 with two different simulations of gravity wavefields the hamburg model of the neutral and ionized atmosphere hammonia and the 2003 simulation of the thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm while general agreement is found between observation and model predictions there exist discrepancies between model prediction and observation as well as among predictions from different models specifically the predicted summer mesopause altitude is lower by 3 km 8 km 3 km and 1 km for waccm3 the two waccm runs hammonia and time gcm respectively and the corresponding temperatures are 169 k 170 k 158 k and 161 k the model predicted summer eastward zonal wind peaks to 71 m s at 102 km to 48 m s at 84 km to 75 m s at 93 km and to 29 m s at 94 km in the same order the altitude of the winter zonal wind reversal and seasonal asymmetry of the pole to pole meridional flow are also compared and the importance of full diurnal cycle observations for the determination of mean states is discussed

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

instability at the winter stratopause a mechanism for the 4 day wave abstract studies using climatological fields in a three dimensional stability model show unstable modes near the polar winter stratopause with periods neat 4 days the calculated modes exhibit equatorward momentum and heat fluxes near the stratopause similar to characteristics of observed 4 day wave events demonstrating that both baroclinic and barotropic processes are important for this instability the baroclinic and baratropic components are considered separately by selectively removing either horizontal or vertical shear from the background flow although both situations reveal instability growth rates are very slow realistic growth rates occur only for climatological flows including both horizontal and vertical shears similar unstable fast moving waves are found near the polar stratopause for several winter months in both hemispheres

momentum flux spectrum of convectively forced internal gravity waves and its application to gravity wave drag parameterization part ii impacts in a gcm waccm abstract impacts of a spectral parameterization of gravity wave drag gwd induced by cumulus convection gwdc in the ncar whole atmosphere community climate model waccm1b are investigated in the spectral gwdc parameterization reference wave momentum flux spectrum is launched at cloud top and analytically calculated based on the physical properties of convection and the large scale flow the cloud top wave momentum flux is strong mainly in the tropics and midlatitude storm track regions and exhibits anisotropy and spatiotemporal variability the anisotropy and variability are determined by the distributions and variations of convective activities the moving speed of convection and horizontal wind and stability in convection regions zonal mean zonal gwdc has a maximum of 13 27 37 50 m s 1 day 1 in the mesosphere in january july impacts of gwdc on zonal wind appear mainly in the low to midlatitudes of the upper stratosphere and mesosphere in these regions biases of zonal wind with respect to

the 4 day wave in the antarctic mesosphere a zonal wave number one eastward propagating planetary wave observed in the high latitude winter stratosphere with a period near 4 days has been studied by a number of previous authors radar observations coupled with stratospheric analyses are here used to demonstrate that this wave known as the 4 day wave extends into the antarctic upper mesosphere previous workers have asserted that the wave is a manifestation of the observation of warm pools rotating in the polar vortex and that the pool seems to behave in a quasi nondispersive manner the observation of the 4 day wave in the upper mesosophere presented here appears to validate previous claims that the warm pools are being maintained by wavelike dynamics rather than simple advection

identifying dynamically induced variability in glacier mass balance records abstractglacier mass balance provides a direct indicator of a glacier s relationship with local climate but internally generated variability in atmospheric circulation adds a significant degree of noise to mass balance time series making it difficult to correctly identify and interpret trends this study applies dynamical adjustment to seasonal mass balance records to identify and remove the component of variance in these time series that is associated with large scale circulation fluctuations dynamical adjustment refers here to a statistical method and not a glacier s dynamical response to climate mass balance records are investigated for three glaciers wolverine and gulkana in alaska and south cascade in washington north pacific sea level pressure and sea surface temperature fields perform comparably as predictors each explaining 50 60 of variance in winter balance and 25 35 in summer balance for south cascade and wolverine glaciers gulkana glacier located farther inland is less closely

on the linkage of mesospheric planetary waves with those of the lower atmosphere and ionosphere a case study from indian low latitudes 1 in this paper we study the planetary scale wave features using concurrent observations of mesospheric wind and temperature ionospherich f and tropospheric wind from tirunelveli gadanki and kolhapur all located in the indian low latitudes made during february 2009 our investigations reveal that 3 to 5 day periodicity characterized as ultrafast kelvin ufk waves was persistent throughout the atmosphere during this period these waves show clear signatures of upward wave propagation from troposphere to the upper mesosphere linking the ionosphere through a clear correlation between mesospheric winds and h f variations we also note that the amplitude of this wave decreased as we moved away from the equator these results are the first of their kind from indian sector portraying the vertical as well as latitudinal characteristics of the 3 to 5 day ufk waves simultaneously from the troposphere to the ionosphere

transient response of idealized glaciers to climate variations the transient response of glaciers to climate variations is investigated with a novel low order model of an idealized glacier resting on uniformly inclined bedrock the model consists of two volumes representing the accumulation and ablation areas which are joined by a flux gate controlling mass flow according to the shallow ice approximation under the assumption of a constant vertical mass balance gradient a volume length scaling relation is derived which depends explicitly on mass balance gradient and bedrock slope analytic expressions for the volume and area timescales are given which are inversely proportional to the mass balance gradient and a geometric factor which is the ratio between the vertical extent of the ablation area and the ice thickness at the equilibrium line from the low order model a dynamical system in length and volume is obtained results from this system are in good agreement with solutions obtained from a transient finite element model solving the full force balance and mass conservation equations under periodic forcing there are significant deviations of the length response which show that the usual relaxation type parameterization of length change is not well suited for short term reactions switching on and off periodic climate forcing the model glaciers show surprisingly large initial and final transient responses that have not been investigated before these results are of significance for the interpretation of length and thickness changes observed on glaciers

eastward propagating planetary waves with periods of 1 5 days in the winter antarctic stratosphere as revealed by merra and lidar 1 this study presents the first report of planetary wave pw influences on significant temperature perturbations 10 20 k within a course of one day detected by an fe lidar from 35 to 51 km in the austral winter of 2011 at mcmurdo 77 8 s 166 7 e antarctica such large temperature perturbations are captured in the modern era retrospective analysis for research and applications merra data and correspond to various phases of eastward propagating pws with periods of 1 5 days as revealed in merra the strongest pw dominating the temperature perturbations has a period of 4 5 days with wavenumber 1 a 2 day wave with wavenumber 2 and a 1 25 day wave with wavenumber 3 also have significant influences we find that these eastward propagating pws are highly confined to winter high latitudes likely because negative refractive indices equatorward of 45 s result in evanescent wave characteristics and prevent the pws from propagating to lower latitudes the eliassen palm flux divergence and instability analyses suggest that barotropic baroclinic instability at 50 s 60 s induced by the stratospheric polar night jet and or the double jet structure is the most likely wave source such instability in the region poleward of 70 s is a complementary source for the 4 day wave where we find that the heat flux of the 4 day wave is large and transported from 70 s toward the pole above 40 km this transport direction is likely linked to the meridional gradient of background temperature the migrating diurnal tide near 78 s in the upper stratosphere is discernable but significantly smaller than that of the dominant 4 day wave

observations of intermediate scale diurnal waves in the equatorial mesosphere and lower thermosphere 1 the purpose of this study is to seek observational evidence for diurnal vertically propagating inertia gravity waves igws in the mesosphere and lower thermosphere mlt numerical modeling studies indicate that vertically propagating igws excited by tropical heating provide a significant source of momentum for the semiannual oscillation sao in the equatorial zonal mean winds the power spectrum of these waves has a strong diurnal component we analyze global patterns of ascending and descending node differences in mlt satellite temperatures which are assumed in this study to be proxies for waves of diurnal period juxtaposed upon the planetary scale features are localized variations with longitudinal wavelengths ranging from 25 to 50 and with vertical wavelengths between 13 and 25 km these intermediate scale variations are spatially coherent and persist for several weeks their amplitudes generally increase with altitude while their phase structures suggest both eastward and westward propagation the variance of wave numbers 9 17 in the mlt is examined in relation to the underlying stratospheric zonal mean zonal gradient winds stronger variances generally coincide with periods where the underlying zonal mean winds are relatively light or unidirectional the weak inverse association between variance strength and zonal wind magnitude is suggestive of a wave filtering mechanism

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

response of marine terminating glaciers to forcing time scales sensitivities instabilities and stochastic dynamics recent observations indicate that many marine terminating glaciers in greenland and antarctica are currently retreating and thinning potentially due to long term trends in climate forcing in this study we describe a simple two stage model that accurately emulates the response to external forcing of marine terminating glaciers simulated in a spatially extended model the simplicity of the model permits derivation of analytical expressions describing the marine terminating glacier response to forcing we find that there are two time scales that characterize the stable glacier response to external forcing a fast time scale of decades to centuries and a slow time scale of millennia these two time scales become unstable at different thresholds of bed slope indicating that there are distinct slow and fast forms of the marine ice sheet instability we derive simple expressions for the approximate magnitude and transient evolution of the stable glacier response to external forcing which depend on the equilibrium glacier state and the strength of nonlinearity in forcing processes the slow response rate of marine terminating glaciers indicates that current changes at some glaciers are set to continue and accelerate in coming centuries in response to past climate forcing and that the current extent of change at these glaciers is likely a small fraction of the future committed change caused by past climate forcing finally we find that changing the amplitude of natural fluctuations in some nonlinear forcing processes such as ice shelf calving changes the equilibrium glacier state

the response of glaciers to intrinsic climate variability observations and models of late holocene variations in the pacific northwest discriminating between glacier variations due to natural climate variability and those due to true climate change is crucial for the interpretation and attribution of past glacier changes and for the expectations of future changes we explore this issue for the well documented glaciers of mount baker in the cascades mountains of washington state usa using glacier histories glacier modeling weather data and numerical weather model output we find that natural variability alone is capable of producing kilometer scale excursions in glacier length on multi decadal and centennial timescales such changes are similar in magnitude to those attributed to a global little ice age the null hypothesis that no climate change is required to explain the glacier fluctuations in this setting cannot be rejected these results for mount baker glaciers are also consistent with an earlier study analyzing individual glaciers in scandinavia and the alps the principle that long timescale fluctuations of glacier length can be driven by short timescale fluctuations in climate reflects a robust and fundamental property of stochastically forced physical systems with memory it is very likely that this principle also applies to other alpine glaciers and that it therefore complicates interpretations of the relationship between glacier and climate history however the amplitude and timescale of the length fluctuations depends on the details of the particular glacier geometry and climatic setting and this remains largely unevaluated for most glaciers

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

simulation of the eastward 4 day wave in the antarctic winter mesosphere using a gravity wave resolving general circulation model 1 the eastward moving 4 day wave in the antarctic winter mesosphere is investigated using a high resolution middle atmosphere general circulation model that directly simulates the spontaneous generation propagation and dissipation of gravity waves the results are also compared with the simulated seasonal march of the meridional structures of the westerly jet streams in the southern hemisphere upper stratosphere and mesosphere in order to investigate baroclinic barotropic instability as a possible excitation mechanism for the 4 day wave the model successfully reproduces the dynamically unstable double jet structure of the mesospheric westerly winds the simulated 4 day wave develops in association with the baroclinic and barotropic instability of the mesospheric mean flows and has similar characteristics to those observed at 50 60 s near the stratopause the 4 day wave has strong equatorward heat flux associated with strong baroclinicity in the antarctic winter mesosphere mainly attributable to poleward overturning circulation driven by gravity wave forcing eastward forcing due to the 4 day wave occurs within the double jet structure and offsets part of the westward forcing due to gravity waves such an effect partially acts to stabilize the unstable mean flow structure in the antarctic winter mesosphere

comment on gribenski n et al 2016 complex patterns of glacier advances during the late glacial in the chagan uzun valley russian altai quaternary science reviews 149 288 305

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

recent glacier retreat exceeds internal variability glacier fluctuations exclusively due to internal variations in the climate system are simulated using downscaled integrations of the echam4 opyc coupled general circulation model gcm a process based modeling approach using a mass balance model of intermediate complexity and a dynamic ice flow model considering simple shearing flow and sliding are applied multimillennia records of glacier length fluctuations for nigardsbreen norway and rhonegletscher switzerland are simulated using autoregressive processes determined by statistically downscaled gcm experiments return periods and probabilities of specific glacier length changes using gcm integrations excluding external forcings such as solar irradiation changes volcanic or anthropogenic effects are analyzed and compared to historical glacier length records preindustrial fluctuations of the glaciers as far as observed or reconstructed including their advance during the little ice age can be explained by internal variability in the climate system as represented by a gcm however fluctuations comparable to the present day glacier retreat exceed any variation simulated by the gcm control experiments and must be caused by external forcing with anthropogenic forcing being a likely candidate

quasi biennial oscillation of short period planetary waves and polar night jet in winter antarctica observed in saber and merra 2 and mechanism study with a quasi geostrophic model

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

on estimating length fluctuations of glaciers caused by changes in climatic forcing the reaction of alpine glaciers to shifts in the equilibrium line altitude ela is calculated by using a two dimensional numerical model to solve the full equations for the velocity and stress fields full system model in the absence of basal motion rates of advance and retreat of the snout of typically sized alpine glaciers are found to be insensitive to the details of the flow at the snout even when the glaciers are far from steady state a comparison of results obtained with a full system model and a shallow ice approximation sia model yields no significant differences in advance or retreat rates this assumption has been implicitly made in numerous previous climatic studies and is here shown to be well justified using a realistic mass balance altitude feedback only slight model dependent changes in steady state lengths are found the relative importance of mass balance and glacier dynamics for the transient response of alpine glaciers to changes in the ela is given a precise meaning by determining the model dependent additional shifts in ela needed for the sia and the full system models to produce identical changes in length for alpine glaciers these additional shifts in ela are on the order of 10 m which is within the error range of ela estimates it follows that at least in the absence of significant basal motion there is no need to include the effects of horizontal stresses when calculating the reaction of alpine glaciers to climatic changes attention should focus on accurate determination of the mass balance distribution and model tuning to give realistic ice thickness distributions

glacier change in northern sweden from ad 500 a simple geometric model of storglaciaren a simple geometric model of glacier volume is derived the model is based on the assumption that the net mass balance averaged over the glacier surface is related to the summer temperature and winter accumulation at a representative height on the glacier this height varies with time as climate changes in ways that are determined by the geometry of the glacier surface expressions are derived for the equilibrium glacier volume v eq as a function of summer temperature and winter accumulation and for the glacier response time as a function of volume the model is used to reconstruct the volume of storglaciaren over the period ad 500 1992 measured net mass balance data for storglaciren 1946 92 are used to estimate the model parameters for the summer temperature forcing the long treering based temperature reconstruction for northern fennoscandia is used to extend a temperature record near the glacier back to ad 500 for the past accumulation forcing a range of assumptions is tested the results show that the prime cause of the decrease in volume of storglaciaren between 1946 and 1992 was relatively low accumulation over 1946 89 as opposed to warm temperatures as previously supposed reconstructed volume changes agree well with geomorphological evidence where differences occur deductions can be made about past accumulation for example the maximum reconstructed glacier volume is associated with the cold period from 1580 to 1740 but relatively low accumulation probably limited the volume to values not much larger than that achieved around 1916

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

observed temperature two day wave and its relatives near the stratopause the two day wave is observed in the upper atmosphere research satellitemicrowave limb sounder temperature data around 40 58 km between december 1991 and september 1994 the two day wave temperature signature is most significant after each solstice when the derived easterly winds near the stratopause extend across the equator to at least 208 latitude in the winter hemisphere and the zonal mean winds near the equator are inertially unstable with observed inertial instability disturbances the observed two day wave consists of a 2 0 day period zonal wavenumber 3 and a 1 8 day period zonal wavenumber 4 component named 3 2 0 and 4 1 8 respectively the 3 2 0 component is dominant during two of the three available austral summers but its amplitude is much weaker than the 4 1 8 component during the two observed boreal summers during the austral summers correspondence between amplification of the two day wave temperature signatures regions of reversed potential vorticity gradient due to meridional curvature of the zonal mean flow and the critical lines for the 3 2 0 and 4 1 8 modes suggest barotropic instability as a source of both wave components momentum redistribution by observed inertial instability appears to barotropically destabilize the equatorward flank of the easterly jet where the wave components subsequently grow during the boreal summers the 4 1 8 component appears to be excited by instability that is associated with vertical shear and curvature of the flow seated above the observational domain the boreal 3 2 0 mode appears unrelated to the zonal flow instability within the observational domain and may reflect a normal mode like response during these periods

intraseasonal and interannual variability of the quasi 2 day wave in the northern hemisphere summer mesosphere this study uses global synoptic meteorological fields from a high altitude data assimilation system to investigate the quasi 2 day wave q2dw and migrating diurnal tide during the northern hemisphere nh summers of 2007 2009 by applying a two dimensional fast fourier transform to meridional wind and temperature fields we identify q2dw source regions and diagnose propagation of q2dw activity into the upper mesosphere and lower thermosphere we find that the q2dw in nh summer is composed primarily of westward propagating zonal wave number 3 and wave number 4 components that originate within baroclinically unstable regions along the equatorward flank of the summer midlatitude easterly jet the amplitude of the wave number 3 q2dw tends to peak in july while the amplitude of the wave number 4 q2dw tends to peak in late june and again in early august the seasonal mean q2dw amplitudes are largest in 2009 when the amplitude of the migrating diurnal tide in the upper mesosphere near 30 n was relatively weak however there is no evidence of rapid amplification of the q2dw via nonlinear interaction with the diurnal tide instead variations of q2dw amplitudes during nh summer appear to be linked to variations in the strength and location of the mesospheric easterly jet from one summer to the next with a stronger jet producing larger q2dw amplitudes linear instability model calculations based on the assimilated wind fields indicate that the fastest growing modes are zonal wave numbers 3 and 4 with periods near 2 days that originate in the vicinity of the easterly jet

observations of the 5 day wave in the stratosphere and mesosphere abstract observations from the nimbus 6 pressure modulator radiometer pmr are presented showing evidence of a westward traveling wave of period 5 to 6 days the wave is observed throughout the 20 month time span of the dataset the amplitude ranges from 0 5 k at 45 km altitude to about 1 0 k at 85 km the horizontal structure resembles that of the gravest symmetric wavenumber 1 free rossby wave and the vertical structure is similar to that of a lamb wave there is no evidence of a vertically trapped wave in the summer mesosphere although some asymmetry is noticeable the pmr data have been supplemented by using data from the nimbus 5 selective chopper radiometer scr to investigate vertical structure and seasonal modulation of wave period the results show that the wave amplitude grows with height but decreases at 62 km the period is closer to 6 days in the spring and autumn and about 5 2 days in winter and summer

high frequency holocene glacier fluctuations in the himalayan tibetan orogen abstract holocene glacial chronostratigraphies in glaciated valleys spread throughout the himalayan tibetan orogen including the himalaya tibet pamir and tian shan are developed using a landsystems approach detailed geomorphic mapping and new and published 10be surface exposure dating new studies in the kulti valley of lahul and the parkachik valley of the nun kun massif of the himalaya of northern india define three glacier advances at 14 7 12 2 0 5 ka in addition to one historically dated late 19th century advance in the kulti valley and one late holocene advance at 0 2 ka in the parkachik valley three major climatic groups subdivided into five climatic zones are defined across the orogen using cluster analysis ca and principal component analysis pca to identify glaciated regions with comparable climatic characteristics to evaluate the timing and extent of holocene glacier advances across these regions our regional analyses across the himalayan tibetan orogen suggest at least one lateglacial 15 3 11 8 ka and five himalayan tibetan holocene glacial stages hths at 11 5 9 5 8 8 7 7 7 0 3 2 2 3 1 0 and

constraints on southern hemisphere tropical climate change during the little ice age and younger dryas based on glacier modeling of the quelccaya ice cap peru 2015 the authors improving the late quaternary paleoclimate record through climate interpretations of low latitude glacier length changes advances our understanding of past climate change events and the mechanisms for past present and future climate change paleotemperature reconstructions at low latitude glaciers are uniquely fruitful because they can provide both site specific information and enhanced understanding of regional scale variations due to the structure of the tropical atmosphere we produce little ice age lia and younger dryas yd paleoclimate reconstructions for the huancane outlet glacier of the quelccaya ice cap qic and low latitude southern hemisphere regional sea surface temperatures ssts using a coupled ice flow and energy balance model we also model the effects of long term changes in the summit temperature and precipitiation rate and the effects of interannual climate variability on the huancane glacier length we find temperature to be the dominant climate driver of glacier length change also we find that interannual climate variability cannot adequately explain glacier advances inferred from the geomorphic record necessitating that these features were formed during past colder climates to constrain our lia reconstruction we incorporate the qic ice core record finding a lia air temperature cooling at the ice cap of between 0 7 c and 1 1 c and 0 4 c and regional ssts cooling of 0 6 c for the yd paleoclimate reconstructions we propose two limits on the precipitation rate since the ice core record does not extend into the pleistocene 1 the precipitation rate scales with the clausius clapeyron relationship upper limit on cooling and 2 the precipitation rate increases by 40 lower limit on cooling which is an increase about twice as great as the regional increases realized in gcm simulations for the period the first limit requires 1 6 c cooling in ice cap air temperatures and 0 9 c cooling in ssts and the second limit requires 1 0 c cooling in ice cap air temperatures and 0 5 c cooling in ssts our temperature reconstructions are in good agreement with the magnitude and trend of gcm simulations that incorporate the forcing mechanisms hypothesized to have caused these climate change events

the response of glaciers to climatic persistence 1 attribution of past glacier fluctuations to changes in the climate requires character2 izing glacier mass balance variability the available observational records which are 3 relatively short are consistent with random fluctuations uncorrelated in time plus 4 an anthropogenic trend however longer records of other climate variables suggest 5 that in fact there is a degree of temporal persistence associated with internal that 6 is unforced climate variability and that it varies with location and climate variable 7 therefore it is likely that climatic persistence does exist for mass balance but that 8 records are too short to confirm its presence or establish its magnitude with conven9 tional statistical tests extending previous work we explore the impact of potential 10 climatic persistence on glacier length fluctuations we use a numerical model and a 11 newly developed analytical model to establish that even a degree of persistence so 12

a link between variability of the semidiurnal tide and planetary waves in the opposite hemisphere 1 horizontal wind observations over four years from the meteor radar at esrange 68 n 21 e are analyzed to determine the variability of the semidiurnal tide simultaneous global observations of temperature and geopotential from the saber satellite instrument are used to construct time series of planetary wave amplitudes and geostrophic mean zonal wind during northern hemisphere summer and fall the temporal variability of the semidiurnal tide at esrange is found to be well correlated with the amplitude of planetary wavenumber 1 in the stratosphere in high southern latitudes i e in the opposite hemisphere the correlations indicate that a significant part of the tidal variation at esrange is due to dynamical interactions in the southern hemisphere a corresponding robust correlation pattern for the esrange tides is not apparent at other times of the multiple years analyzed

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

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

a macroscopic approach to glacier dynamics a simple approach to glacier dynamics is explored in which there is postulated to be a relationship between area and volume with three parameters the time for area to respond to changes in volume a thickness scale and an area characterizing the condition of the initial stale this approach gives a good fit to the measurements of cumulative balance and area on south cascade glacier from 1970 97 the area time scale is roughly 8 years the thickness scale about 123 m and the 1970 area roughly 4 larger than required for adjustment with volume combining this relationship with a version of mass continuity expressed in terms of area and volume produces a theory of glacier area and volume response to climate in which another time constant the volume time scale appears area and volume both respond like a damped spring and mass system the damping of the south cascade response is approximately critical and the volume time scale is roughly 48 vexes six times the area time scale the critically damped spring and mass analogy reproduces the time dependence predicted by the more complicated traditional theory of nyc

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

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

reconstructing climate from glaciers glaciers offer the potential to reconstruct past climate over timescales from decades to millennia they are found on nearly every continent and at the last glacial maximum glaciers were larger in all regions on earth the physics of glacier climate interaction are relatively well understood and glacier models can be used to reconstruct past climate from geological evidence of past glacier extent this can lead to significant insights regarding past present and future climate for example glacier modeling has demonstrated that the near ubiquitous global pattern of glacier retreat during the last few centuries resulted from a global scale climate warming of 1 c consistent with instrumental data and climate proxy records climate reconstructions from glaciers have also demonstrated that the tropics were colder at the last glacial maximum than was originally inferred from sea surface temperature reconstructions future efforts to reconstruct climate from glaciers may provide new constraints on climat

how do glaciers surge a review the quasi periodic oscillations between normal and fast motion exhibited by surge type glaciers provide the best observational opportunity to determine limiting conditions that allow fast motion the measurements from variegated glacier prove that its surge motion is caused by rapid sliding induced by high water pressure this arises from a major restructuring of the basal hydraulic system which impedes water discharge prior to and during surge although the evolving glacier geometry and stress distribution play a principal enabling role the seasonal timing of two distinct surge pulses each initiated in winter and terminated in summer indicates a major influence from variable external water inputs this influence is not considered in existing surge models and should promote caution in the use of data from temperate and subpolar surge type glaciers to deduce surge potential in polar ice masses the spatial spreading of surge motion from a zone of local initiation occurs by stress redistribution which may spread the surging zone rapidly upglacier or downglacier inside a region of active ice and by mass redistribution with compressional thickening at the surge front which enables down glacier propagation into less active ice the data from other surge type glaciers including the extensive data from medvezhiy glacier are not inconsistent with the above processes but are inadequate to establish whether completely different mechanisms operate in some surges the way by which water accumulates and produces fast sliding is not established in detail for any surge type glacier and may be different on different glaciers depending for example on the presence or absence of unconsolidated debris between the ice and rock

nonmigrating diurnal tides in the equatorial middle atmosphere abstract data from the nimbus 7 limb infrared monitor of the stratosphere lims are used to extend the analysis of diurnal tides in the middle atmosphere to include the zonally symmetric and eastward propagating components these modes show vertical and meridional structures that are generally consistent with the predictions of linear tidal theory the zonal and meridional wind fields are calculated from the tidal temperatures diurnal perturbations in lims temperature and derived winds agree well with equinoctial model calculations comparisons with day night differences of radiosonde temperature and rocket winds show qualitative agreement in vertical structure and amplitude the zonally symmetric and eastward migrating tidal components show a higher degree of temporal variability than the sun synchronous component these modes at times contribute substantially to the diurnal signal in wind and temperature with combined amplitudes equal to or in excess of the amplitude of the main migrating diurnal tid

late glacial mountain glacier culmination in arctic norway prior to the younger dryas abstract climate changes during the late glacial period lg 15 11 ka as recorded in greenland and antarctic ice cores show a bipolar pattern between 14 5 ka and 13 ka ago the northern latitudes experienced the bolling allerod ba warm period while southern records feature the antarctic cold reversal acr between 12 9 ka and 11 7 ka ago the north was under the younger dryas yd cold spell while southern latitude temperature rose in parallel to atmospheric co2 concentrations while the southern hemisphere pattern is well documented in mountain glacier moraine records from new zealand and patagonia in northern mid latitudes and the arctic the lg glacier culmination has been connected to the yd stadial apparently confirming the bipolar pattern we present a geomorphic map of mountain glaciers in arctic norway a cosmogenic nuclide chronology from 71 moraine boulders from the lg and the holocene and first order glacier modeling experiments the model and dating results show that the studied mountain glaciers are most sensitive to summer temperature change that their response to those changes is highly correlated to a wider region and that these mountain glaciers in arctic norway reached their maximum lg extent about 14 ka ago prior to the yd following considerable retreat through the first part of the yd glaciers re stabilized in the mid yd and showed slower oscillatory retreat through the latter part of the yd we compare this glacier pattern to updated earlier glacier records in the wider arctic and north atlantic region and propose a pattern of coherent glacier response to climate changes during this interval the lg results from arctic glaciers show consistency to the glacier record from new zealand and patagonia this first order interhemispheric coherency of lg mountain glacier fluctuations driven mainly by summer temperature would support the view that the bipolar seesaw was primarily a northern winter phenomenon during the lg period and the yd in particular more similar experiments need to be performed to further test this scenario

the role of equatorial waves forced by convection in the tropical semiannual oscillation abstract recent satellite observations suggest that convection over the tropical continents is capable of exciting wave motions over a wide range of spatial and temporal scales an equatorial beta plane model was used to investigate the forcing by convective heating of equatorial waves with zonal wavenumbers from 1 to 15 and a wide range of periods including diurnal oscillations also studied are the propagation of these waves in the equatorial middle atmosphere and their role in driving the tropical semiannual oscillation sao specification of the heating distribution used to force the model is guided by observations and analyses of tropical convection it was found that intermediate scale kelvin and inertia gravity waves provide between 25 and 50 of the forcing necessary to drive the westerly phase of the sao near the stratopause while the remainder is supplied by planetary scale kelvin waves in the mesosphere intermediate scale waves account for an even larger fraction of the force required to

extracting a climate signal from 169 glacier records i constructed a temperature history for different parts of the world from 169 glacier length records using a first order theory of glacier dynamics i related changes in glacier length to changes in temperature the derived temperature histories are fully independent of proxy and instrumental data used in earlier reconstructions moderate global warming started in the middle of the 19th century the reconstructed warming in the first half of the 20th century is 0 5 kelvin this warming was notably coherent over the globe the warming signals from glaciers at low and high elevations appear to be very similar

what do glaciers tell us about climate variability and climate change glaciers respond to long term climate changes and also to the year to year fluctuations inherent in a constant climate differentiating between these factors is critical for the correct interpretation of past glacier fluctuations and for the correct attribution of current changes previous work has established that century scale kilometre scale fluctuations can occur in a constant climate this study asks two further questions of practical significance how likely is an excursion of a given magnitude in a given amount of time and how large a trend in length is statistically significant a linear model permits analytical answers wherein the dependencies on glacier geometry and climate setting can be clearly understood the expressions are validated with a flowline glacier model the likelihood of glacier excursions is well characterized by extreme value statistics although probabilities are acutely sensitive to some poorly known glacier properties conventional statistical tests can be used for establishing the significance of an observed glacier trend however it is important to determine the independent information in the observations which can be effectively estimated from the glacier geometry finally the retreat of glaciers around mount baker washington state usa is consistent with but not independent proof of the regional climate warming that is established from the instrumental record

evidence for equatorial kelvin modes in nimbus 7 lims abstract eastward propagating disturbances over the equator are diagnosed in two independent nimbus 7 lims limb infrared monitor of the stratosphere data sets they are evident consistently at several pressure levels throughout the stratosphere and account for much of the temperature variance in the tropics the disturbances which can be seen in wavenumbers 1 3 are in phase and symmetric about the equator latitudinally evanescent and have short moderate vertical phase structure 10 40 km which progresses downward wavenumber 1 has spectral components which propagate eastward at periods of 6 7 8 6 days 54 69 m s 1 and 3 5 4 0 days 115 135 m s 1 wavenumber 2 exhibits eastward propagating variance at periods of 6 0 7 5 days 31 39 m s 1 and 3 8 4 3 days 55 62 m s 1 the faster waves appear principally in the upper stratosphere these features are in reasonable agreement with the structure and dispersion characteristics of simple quasi separable kelvin modes with the exception of the slower w

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

the role of the cryosphere in source to sink systems abstract glacial erosion and sediment production are of interest to diverse scientific communities concerned with the interaction of climatic tectonic and surface processes that influence the evolution of orogens and with the climatic signals archived in glacigenic strata we review the current state of knowledge on the generation transfer and accumulation of glacigenic sediment from land to sea we draw from geomorphology marine geology geochronology numerical modeling of surface processes and landscape evolution and experimental and field observations of glacier erosion and deposition and the interaction of ice with its bed and the ocean boundary our primary goal is to examine glacial systems using a holistic source to sink approach with a focus on describing a how glacial motion produces sediment b how the sediments sink record the dynamic nature of glacial systems under different climatic thermal regimes c the challenges in using the sedimentary record to interpret these dynamics in space and time and d the approaches still needed to further our understanding of how ice and associated sediment fluxes respond to climatic and other perturbations the dynamic state of ice i e the ice flux and ice extent is defined differently between the source and sink communities reflecting the challenges of establishing a stratigraphic signal that volumetrically constrains glacigenic sediment production as a function of the ice response to climate advances in marine geophysics have greatly assisted our understanding of mass transfer pathways and of former ice extents as a measure of ice dynamics and have identified the primary depocenters and key lithofacies of glacial sinks sediment fluxes associated with the dynamic state of the ice are best constrained where sediment volumes derived from key lithofacies and seismic reflection isopachs can be temporally partitioned of which there are few examples rather than from discrete point measures of sediment flux that are subject to sediment transfer biases forward numerical modeling of sediment fluxes as a function of ice dynamics agree with observational data at the continental margin scale but finer time space scale ice dynamic models do not yet recreate observed ice extent or flowpaths future source to sink work in glaciated systems should focus on refining empirical relationships between ice velocity and sediment production and expand the application of existing methods to develop sediment volumes and fluxes in known depocenters of former and modern ice streams

the effects of interannual climate variability on the moraine record valley glacier moraines are commonly used to infer past mean annual precipitation and mean melt season temperature however recent research has demonstrated that even in steady climates multi decadal kilometer scale fluctuations in glacier length occur in response to stochastic year to year variability in mass balance when interpreting moraine sequences it is important to include the effect of interannual weather variability on glacier length moraines record advances that are forced either by interannual variability or by a combination of climate change and interannual variability we address this issue for the last glacial maximum lgm glaciers of the colorado front range united states using a linear glacier model that allows thorough exploration of parameter uncertainties supplemented by a shallow ice flowline model our analyses suggest that 1 glacial standstills longer than 50 years were unlikely 2 mean glacier lengths are 10 15 up valley from maximum glacier lengths and 3 individual lgm terminal moraines were formed by a combination of a climate change and interannual variability forced advances

the variability of se2 tide extracted from timed saber observations based on the temperature observations of the timed saber in mlt region 70 110 km altitudes and at the low and mid latitudes 45 s 45 n from 2002 to 2012 the variability of the non migrating tide se2 with one day resolution is analyzed using the method from li et al 2015 it is found that the climatological features large scale variability of the se2 tide are similar with the results from the previous researches the se2 tide manifests mainly at the low mid latitudes around 30 the northern hemisphere tidal amplitudes below 110 km are larger than the southern hemisphere tide at the same time its peaks below 110 km mainly present between 100 and 110 km altitude the tidal amplitudes below 110 km occur a north south asymmetry about the equator in the annual variation in the southern hemisphere se2 occurs with an obvious annual variation with a maximum of tidal amplitudes in december while in the northern one the semi annual variations with maximum at the equinoxes herein owing to the high resolution tidal data we could research the short term day to day variations of se2 we found that the day to day variations manifests mainly at between 100 and 110 km altitudes it increases gradually with latitudes and it is stronger at the low mid latitudes it is relatively slightly stronger around solstices than equinoxes it does not present a remarkably inter annual variation the se2 day to day variations may be composed by the absolute amplitudes variance and the impact of the wave phases and the latter ones are more important

an exercise in glacier length modeling interannual climatic variability alone cannot explain holocene glacier fluctuations in new zealand abstract recent model studies suggest that interannual climatic variability could be confounding the interpretation of glacier fluctuations as climate signals paleoclimate interpretations of moraine positions and associated cosmogenic exposure ages may have large uncertainties if the glacier in question was sensitive to interannual variability here we address the potential for interannual temperature and precipitation variability to cause large shifts in glacier length during the holocene using a coupled ice flow and mass balance model we simulate the response of cameron glacier a small mountain glacier in new zealand s southern alps to two types of climate forcing equilibrium climate and variable climate our equilibrium results suggest a net warming trend from the early holocene 10 69 0 41 ka 2 7 c cooler than present to the late holocene ce 1864 1 3 c cooler than present interannual climatic variability cannot account for the holocene glacier fluctuations in this valley future studies should consider local environmental characteristics such as a glacier s climatic setting and topography to determine the magnitude of glacier length changes caused by interannual variability

first observations of short period eastward propagating planetary waves from the stratosphere to the lower thermosphere 110 km in winter antarctica unique fe lidar observations in may 2014 at mcmurdo combined with aura microwave limb sounder mls measurements lead to a new discovery that the amplitudes of 4 day and 2 5 day planetary waves pws grow rapidly from 1 2 k at 100 km to over 10 k at 110 km this report is also the first observation of short period 1 5 days eastward propagating pws from 30 km all the way to 110 km the specified dynamics whole atmosphere community climate model reproduces the observed three dominant peaks of amplitudes in temperature and coherent vertical phase structures the data model comparison indicates a possible mechanism after pws originated from the stratosphere dissipate along the critical level the surviving waves are amplified by in situ instability in the mesosphere and lower thermosphere resulting in the second third peak in geopotential temperature this third peak in temperature explains the pw amplitude growth from 100 to 110 km

a global morphology of gravity wave activity in the stratosphere revealed by the 8 year saber timed data 1 from 8 years saber timed temperature profiles between january 2002 and december 2009 we studied the activity of gravity waves in the stratosphere globally global distribution of stratospheric gravity wave potential energy was calculated from the temperature perturbations seasonal comparison of gravity wave potential energy ep shows an annual variation in middle and high latitudes and a semiannual variation in the tropics around the equator gravity wave interannual enhancements are identified just below the zonal wind zero u 0 contours corresponding to descending eastward shear phase of the qbo furthermore we provide observation evidence to support the conclusion that the deep convection is a major source for the observed tropical gravity wave activity the considerable longitude variations of largest potential energy around the equator are related not only to the specific topography and tropical convections but also to many other factors we can infer that topography and tropical deep convection are the important sources of the gravity waves in the stratosphere but the observed gravity waves in the tropical subtropical stratosphere are strongly affected by winds with different qbo phases

a geometric glacier model for sea level change calculations towards accounting for the dynamic response of glaciers and ice caps in the estimation of their contribution to sea level rise due to global warming a mass balance degree day model is coupled to a geometric glacier model the ice dynamics are treated implicitly in the geometric model by using scaling parameters that have been extensively investigated in the literature the model is tested by presenting a case study of the glacier hintereisferner austrian alps the results are compatible with geomorphological data and other modelling studies an estimate is made of the volume decrease due to initial disequilibrium an extensive sensitivity study using generalized glacier shapes and sizes allows a comparison of results with dynamic theory according to the geometric model glaciers with a narrowing channel change more with a change in mass balance than glaciers with a widening channel due to their shape and the way in which that shape changes with a changing climate also their response time is longer as time progresses after a mass balance perturbation the longer response time for continental glaciers compared to glaciers with a larger mass turnover offsets the effect of their smaller static sensitivity thus although for the next century we may expect greater changes in volume from alpine glaciers the equilibrium or committed change is greater for the continental glaciers

geodynamics of continental plate collision during late tertiary foreland basin evolution in the timor sea constraints from foreland sequences elastic flexure and normal faulting abstract tectonic subsidence of the australian lithosphere during the late tertiary propagates from the southwest to the northeast in the timor sea as a consequence of the oblique collision between the eurasian and australian plates we reconstruct the asynchronous nature of deflection of the australian plate created during the plate convergence by best matching the geometry of de compacted foreland strata against the predictions of simple bending elastic beam models we infer a maximum subsidence of 3500 m and a maximum width for the basin of 470 km the effective elastic thickness of the australian lithosphere 80 to 100 km does not change significantly during basin evolution the low curvature imposed on the plate 5 1 10 8 m 1 during bending is too small to weaken the plate yet abundant but small slip normal faulting related to bending implies some degree of inelastic yielding the polarity of fault propagation supports the oblique nature of the collision flexural models indicate that at least 570 km of australian plate mostly areas of stretched continental crust was flexed primarily by the tectonic loading of the timor island and that the total amount of subducted plate was at least 100 km during basin evolution

global and hemispheric temperature reconstruction from glacier length fluctuations temperature reconstructions for recent centuries provide a historical context for the warming over the twentieth century we reconstruct annual averaged surface temperatures of the past 400 years on hemispherical and global scale from glacier length fluctuations we use the glacier length records of 308 glaciers the reconstruction is a temperature proxy with decadal resolution that is completely independent of other temperature records temperatures are derived from glacier length changes using a linear response equation and an analytical glacier model that is calibrated on numerical model results the global and hemispherical temperatures reconstructed from glacier length fluctuations are in good agreement with the instrumental record of the last century furthermore our results agree with existing multi proxy reconstructions of temperature in the pre instrumental period the temperature record obtained from glacier fluctuations confirms the pronounced warming of the twentieth century giving a global cumulative warming of 0 94 0 31 k over the period 1830 2000 and a cumulative warming of 0 84 0 35 k over the period 1600 2000

committed retreat controls on glacier disequilibrium in a warming climate the widespread retreat of mountain glaciers is a striking emblem of recent climate change yet mass balance observations indicate that many glaciers are out of equilibrium with current climate meaning that observed retreats do not show the full response to warming this is a fundamental consequence of glacier dynamics mountain glaciers typically have multidecadal response timescales and so their response lags centennial scale climate trends a substantial difference between transient and equilibrium glacier length persists throughout the warming period we refer to this length difference as disequilibrium forcing idealized glacier geometries with gradual warming shows that the glacier response timescale fundamentally governs the evolution of disequilibrium comparing a hierarchy of different glacier models suggests that accurate estimates of ice thickness and climatology which control the timescale are more important than higher order ice dynamics for capturing disequilibrium current glacier disequilibrium has previously been estimated for a selection of individual glaciers our idealized modeling shows that sustained disequilibrium is a fundamental response of glacier dynamics and is robust across a range of glacier geometries this implies that many mountain glaciers are committed to additional kilometer scale retreats even without further warming disequilibrium must also be addressed when calibrating glacier models used for climate reconstructions and projections of retreat in response to future warming

amplification of the quasi two day wave through nonlinear interaction with the migrating diurnal tide 1 we present a case study of the non linear interaction between the quasi two day wave q2dw and the migrating diurnal tide based on global synoptic meridional wind fields for january 2006 and january 2008 from a high altitude data assimilation forecast system we find large quasi two day wave amplitudes small diurnal tide amplitudes and phase locking of the q2dw with the diurnal cycle during january 2006 in january 2008 the amplitudes of the q2dw were much smaller with no evidence of phase locking while the tidal amplitudes were larger than in the 2006 case space time spectral analysis reveals an enhancement in a diurnal zonal wavenumber 6 feature in the january 2006 case which can be attributed to a non linear interaction between the q2dw and migrating diurnal tide the relatively strong summer easterly jet in the extratropical upper mesosphere during early january 2006 appears to have created conditions favoring this interaction

late pleistocene glaciation and deglaciation in the crestone peaks area colorado sangre de cristo mountains usa chronology and paleoclimate abstract cosmogenic 10be surface exposure dating and numerical glacier modeling are used to reconstruct glacial chronology and climate in the colorado sangre de cristo mountains during the local last glacial maximum llgm and the subsequent deglaciation twenty two surface exposure ages on moraine boulders and polished bedrock outcrops in the willow creek valley and ten in two adjacent valleys indicate that glaciers were at or near their maxima from 21 ka until 17 16 ka and then retreated rapidly nearly deglaciating the willow creek valley entirely by 14 ka coupled energy mass balance and flow modeling of two of the glaciers indicates that if changing ice extent was driven only by temperature and insolation changes temperature depressions of 5 0 and 5 1 c from modern conditions with an uncertainty of approximately 1 5 1 0 c would have sustained the glaciers in mass balance equilibrium at their llgm extents doubling or halving of modern precipitation during the llgm would have been associated with 2 7 3 0 c and 6 9 7 0 c temperature depression respectively approximately half of the subsequent llgm to modern climate change was accomplished by 14 ka if the rapid main phase of deglaciation between about 16 ka and 14 ka was driven solely by temperature and insolation changes it would have been associated with a temperature rise of about 2 5 c at a mean rate of approximately 1 1 c ky this new chronology of the last glaciation is generally consistent with others developed recently in the colorado rocky mountains the numerical modeling however suggests a lesser llgm temperature depression from modern conditions than have most previous studies in colorado

time scale for adjustment of glaciers to changes in mass balance the length of time tm over which a glacier responds to a prior change in climate is investigated with reference to the linearized theory of kinematic waves and to results from numerical models we show the following tm may in general be estimated by a volume time scale describing the time required for a step change in mass balance to supply the volume difference between the initial and final steady states the factor f in the classical estimate of m l u where i is glacier length and u is terminus velocity has a simple geometrical interpretation ft is the ratio of thickness change averaged over the full length i to the change at the terminus although both u and f relate to dynamic processes local to the terminus zone the ratio f u and therefore tm are insensitive to details of the terminus dynamics in contrast to conclusions derived from some simplified kinematic wave models a more robust estimate of tm independent of terminus dynamics is given by tm h b where h is a thickness scale for the glacier and b is the mass balance rate negative at the terminus we suggest that tm for mountain glaciers can be substantially less than the 1o2 103 years commonly considered to be theoretically expected

the excitation of equatorial waves by deep convection in the ncar community climate model ccm3 the forcing of equatorial waves by convective heating in the national center for atmospheric research community climate model ccm3 is investigated and compared with the forcing deduced from observations of convective clouds the analysis is performed on two different simulations wherein convection is represented by the zhang mcfarlane and the hack parameterization schemes respectively spectra of equatorial waves excited by convective heating rossby kelvin and gravity waves are obtained by projecting the heating field onto hough modes the dynamical response to the heating is then calculated in terms of the vertical component of the eliassen palm flux fz focusing on waves that are able to propagate into the middle atmosphere the same analysis is repeated using observations of outgoing longwave radiation as a proxy for tropical convection comparison of ccm3 results with those derived from observations indicates that high frequency heating variability is underestimated in both ccm3 simulations despite the fact that time mean values of convective heating are well represented moreover the two convective parameterization schemes differ substantially from each other compared to observations fz is severely underestimated at most frequencies when ccm3 is run with the zhang mcfarlane scheme when the hack scheme is used fz at frequencies v 0 5 cycles per day is comparable to the observations but it is underestimated at higher frequencies misrepresentation of the variability of convective heating is likely to have important consequences for the dynamical simulation of the middle atmosphere and even the troposphere

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