the corresponding tropospheric environments during downward extending and nondownward extending events of stratospheric northern annular mode anomalies abstractusing the ncep ncar reanalysis dataset this study classifies stratospheric northern annular mode nam anomalies during the negative or positive phase into two categories anomalies extendi

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

precipitation regime of dronning maud land antarctica derived from antarctic mesoscale prediction system amps archive data 1 the precipitation regime of dronning maud land dml antarctica was studied using antarctic mesoscale prediction system amps archive data precipitation is the most important component of the mass balance of the antarctic ice sheet precipitation studies of dml are particularly important because two deep ice core drilling sites kohnen station and dome fuji are located in this region for the correct interpretation of the ice core properties a thorough understanding of the precipitation regime is necessary we used the high resolution amps archive data for the years 2001 2006 to investigate the temporal and spatial distribution of precipitation the results were compared to a recently published mass balance map derived from glaciological data of western dml the mass balance map and the amps mean annual precipitation field show fairly similar patterns which are mostly related to topography and prevailing wind systems precipitation is found to generally decrease from the coast to the inland plateau along the escarpment between the low altitude coastal areas and the interior plateau local minima and maxima in precipitation correspond to the leeward and windward sides of topographical ridges interannual variability of monthly sums of precipitation is fairly high owing to the influence of cyclone activity on precipitation which affects not only the coastal regions but also the interior of the continent more than previously thought

middle to late holocene relative sea level rise climate variability and environmental change along the colombian caribbean coast we analyzed diatoms lithology and stable isotopes in a sediment core from the cienaga grande de santa marta lagoon to reveal the history of late holocene relative sea level rise and the ontogeny of the lagoon on the caribbean coast of colombia at 5300 cal yr bp the area was characterized by shallow freshwater ponds that were prone to seasonal flooding from 4250 to 2060 cal yr bp these ponds became brackish as relative sea level began to rise and since 2060 cal yr bp marine conditions have prevailed in addition to tracking relative sea level rise we also investigated periods of greater and lesser precipitation during times of brackish and marine conditions respectively as indicated by diatom inferred changes in water salinity and shifts in the source of sediment organic matter comparisons with other regional paleoenvironmental records suggest that humid climate conditions prevailed in the caribbean until about 4000 cal yr bp after that time climate became more variable with drier conditions registered from 4000 to 2000 cal yr bp wetter conditions returned after 2000 cal yr bp

evidence for warmer interglacials in east antarctic ice cores reconstructions of temperature variations from antarctic ice cores rely on the assumption that the relationship between hydrogen and oxygen isotopic ratios and temperature are stable in space and time sime et al analyse three 340 000 year old ice cores from east antarctica and use an isotope enabled general circulation model to show that instead the relationship is nonlinear during warm periods the ratios are less sensitive to temperature so previous estimates of interglacial temperatures are likely to be about 3 c too low this is consistent with peak antarctic interglacial temperatures at least 6 c higher than today this work suggests that there are serious deficiencies in our understanding of climates that are warmer than today s reconstructions of temperature variations from antarctic ice cores rely on the assumption that the relationship between hydrogen and oxygen isotope ratios and temperature are stable in space and time three east antarctic ice core records are now analysed alongside input from general circulation models to reveal that during warmer interglacial periods the isotope ratios are less sensitive to temperature than during colder interglacials consequently previous estimates of interglacial temperatures are probably too cold stable isotope ratios of oxygen and hydrogen in the antarctic ice core record have revolutionized our understanding of pleistocene climate variations and have allowed reconstructions of antarctic temperature over the past 800 000 years 800 kyr refs 1 2 the relationship between the d h ratio of mean annual precipitation and mean annual surface air temperature is said to be uniform 10 over east antarctica3 and constant with time 20 refs 3 5 in the absence of strong independent temperature proxy evidence allowing us to calibrate individual ice cores prior general circulation model gcm studies have supported the assumption of constant uniform conversion for climates cooler than that of the present day3 5 here we analyse the three available 340 kyr east antarctic ice core records alongside input from gcm modelling we show that for warmer interglacial periods the relationship between temperature and the isotopic signature varies among ice core sites and that therefore the conversions must be nonlinear for at least some sites model results indicate that the isotopic composition of east antarctic ice is less sensitive to temperature changes during warmer climates we conclude that previous temperature estimates from interglacial climates are likely to be too low the available evidence is consistent with a peak antarctic interglacial temperature that was at least 6 k higher than that of the present day approximately double the widely quoted 3 1 5 k refs 5 6

zonal mean dynamics of extended recoveries from stratospheric sudden warmings abstractthe recovery of the arctic polar vortex following stratospheric sudden warmings is found to take upward of 3 months in a particular subset of cases termed here polar night jet oscillation pjo events the anomalous zonal mean circulation above the pole during this recovery is characterized by a persistently warm lower stratosphere and above this a cold midstratosphere and anomalously high stratopause which descends as the event unfolds composites of these events in the canadian middle atmosphere model show the persistence of the lower stratospheric anomaly is a result of strongly suppressed wave driving and weak radiative cooling at these heights the upper stratospheric and lower mesospheric anomalies are driven immediately following the warming by anomalous planetary scale eddies following which anomalous parameterized nonorographic and orographic gravity waves play an important role these details are found to be robust for pjo events as opposed to sudden warmings in general in that ma

the life cycle of the northern hemisphere sudden stratospheric warmings motivated by recent evidence of strong stratospheric tropospheric coupling during the northern hemisphere winter this study examines the evolution of the atmospheric flow and wave fluxes at levels throughout the stratosphere and troposphere during the composite life cycle of a sudden stratospheric warming the composite comprises 39 major and minor warming events using 44 years of ncep ncar reanalysis data the incipient stage of the life cycle is characterized by preconditioning of the stratospheric zonal flow and anomalous quasistationary wavenumber 1 forcing in both the stratosphere and troposphere as the life cycle intensifies planetary wave driving gives rise to weakening of the stratospheric polar vortex and downward propagation of the attendant easterly wind and positive temperature anomalies when these anomalies reach the tropopause the life cycle is marked by momentum flux and mean meridional circulation anomalies at tropospheric levels that are consistent with the negative phase of the northern hemisphere annular mode the anomalous momentum fluxes are largest over the atlantic half of the hemisphere and are associated primarily with waves of wavenumber 3 and higher

planetary wave coupling from the stratosphere to the thermosphere during the 2002 southern hemisphere pre stratwarm period 1 temperature observations between 20 and 120 km from the saber instrument on the timed spacecraft are used to investigate the nature of planetary wave activity during the 60 days prior to the midwinter stratospheric warming that commenced on 26 september 2002 in the southern hemisphere the primary wave components consist of eastward propagating quasi 10 day waves with zonal wave numbers s 1 and s 2 and a stationary planetary wave with s 1 the waves are found to extend from the lower stratosphere to the 100 120 km height region with surprisingly little amplitude attenuation although wave amplitudes oscillate with altitude like a standing wave pattern time evolution of the waves is also addressed with emphasis on 86 km altitude where temperature observations from three antarctic stations at davis 69 s 78 w rothera 68 s 68 w and syowa 69 s 40 e are available during the same period we demonstrate that the temporal evolution of temperature obtained by superposition of the waves derived from saber measurements accounts for nearly all the temperature variability observed at the longitudes of the three antarctic stations

a numerical study of the interaction between stationary rossby waves and eastward traveling waves in the southern hemisphere stratosphere abstract quasi stationary rossby waves with a wavenumber 1 component wave 1 and eastward traveling waves with a wavenumber 2 component wave 2 whose period lies in 10 20 days have been frequently observed during the late winter and early spring in the stratosphere of the southern hemisphere temporal variations of these amplitudes are remarkably enhanced during this period the interaction among wave 1 wave 2 and the zonal mean flow was simulated using a low order truncated semispectral model it was assumed that both the stationary wave 1 and eastward traveling wave 2 are forced at the tropopause when the wavenumbers from 1 to 3 or 4 were included in the model with use of a reasonable forcing amplitude and the observed monthly mean zonal wind the following results were obtained 1 the amplitude of wave 1 reaches a maximum value when the ridge of wave 2 overlaps that of wave 1 2 the amplitude of wave 2 is negatively correlated with wave 1 3 in many cases the large amplification of wave 1 occu

holocene climate change and sea level oscillations in the pacific coast of mexico abstract a 2 75 m long core was recovered from la joya lagoon at the southern pacific coast of mexico the base of the core gave an age of ca 5600 a bp the ams 14c dating results indicate a continuously depositional history over the past 5600 years with varied sedimentation rates of 0 022 0 08 cm yr sediment samples were analyzed for pollen diatoms loss on ignition loi magnetic susceptibility and elemental analysis to study the environmental and marine changes ocurred during the holocene in the study site of the pacific coast our data provided indications of the paleoenviromental changes in the study site from the south pacific coast of mexico a complete marine environment from ca 5600 to ca 3200 a bp a transitional lagoon from ca 3200 to 1100 a bp and followed by a shift toward a close lagoon with fresh water during the last 1100 years the pollen data the presence of pollen from cucurbitaceae and secondary taxa related to disturbed vegetation of la joya record show evidence of agricultural activities and human occupation in the study area might exist 5000 a bp

the ti al molar ratio as a new proxy for tracing sediment transportation processes and its application in aeolian events and sea level change in east asia abstract ti al molar ratios of sediments in various sedimentary environments are used to explain sediment transportation from source regions to sink areas samples were collected from outcrops soils fluvial lake and marine sediment environments initial ti al molar ratios of sediments are controlled by those of parent soils or rocks these ratios tend to decline gradually as a result of heavy mineral gravity fractionation during transportation sedimentary ti al molar ratios in sink areas such as lakes and pelagic environments are lower than those in source regions in this study for the changjiang river huanghe river and kaoping river ti al molar ratios decline considerably from downstream to estuary environments additionally well sorted aeolian sands have extremely low ti al molar ratios in northern china the ti al molar ratios of aerosol particles found in taiwan and the east china sea show reduced ratios as a result of asia dust storm episodes furthermore lower ti al molar ratios in deep ocean sediments were discovered by tracing the distribution of sedimentary ti al molar ratios in the south china sea when sea levels dropped during glacial periods the river estuary was closer to deep marine areas and carried more terrestrial sediments into deep marine environments the closer estuary with relatively higher ti al ratio would lead increase of ti al molar ratios in deep sea sediments in this study ti al molar ratio is promoted as a new proxy to help with understanding changes in sedimentary environments

modulations in the planetary wave field induced by upward propagating rossby wave packets prior to stratospheric sudden warming events a case study a diagnostic framework is introduced in which anomalous zonally averaged rossby wave activity injection into the stratosphere is decomposed into a contribution solely from zonally confined upward propagating rossby wave packets and another from interaction of the wave packets with the climatological planetary waves to pinpoint the tropospheric sources of the wave packets a particular form of wave activity flux is evaluated for the associated circulation anomalies the framework is applied to reanalysis data for the period prior to a stratospheric sudden warming ssw event in january 2006 which was associated with two successive events of above normal wave activity injection from the troposphere in the earlier event a pair of wave packets that emanated from tropospheric anomalies over the north pacific and over europe enhanced the upward wave activity injection which was augmented further by their interaction with the climatological planetary wave in contrast in the later period a wave packet that emanated from an anticyclonic anomaly over the north atlantic is found to be the primary contributor to the enhanced planetary wave activity injection while its interaction with the climatological planetary wave contributed negatively the predominant importance of the sole contribution from a single wave packet is also found in a major ssw event observed over antarctica in september 2002 these results indicate that the diagnostic framework presented in this study is a useful tool for understanding the interaction between anomalies associated with zonally confined wave packets and climatological mean planetary waves in the study of stratosphere troposphere dynamical coupling copyright 2009 royal meteorological society

climate dependent contrast in surface mass balance in east antarctica over the past 216 ka documenting past changes in the east antarctic surface mass balance is important to improve ice core chronologies and to constrain the ice sheet contribution to global mean sea level change here we reconstruct past changes in the ratio of surface mass balance smb ratio between the epica dome c edc and dome fuji df east antarctica ice core sites based on a precise volcanic synchronization of the two ice cores and on corrections for the vertical thinning of layers during the past 216 000 a this smb ratio denoted smb edc smb df varied between 0 7 and 1 1 being small during cold periods and large during warm periods our results therefore reveal larger amplitudes of changes in smb at edc compared with df consistent with previous results showing larger amplitudes of changes in water stable isotopes and estimated surface temperature at edc compared with df within the last glacial inception marine isotope stages mis 5c and mis 5d the smb ratio deviates by up to 0 2 from what is expected based on differences in water stable isotope records moreover the smb ratio is constant throughout the late parts of the current and last interglacial periods despite contrasting isotopic trends

137cs and 210pb transport and geochronologies in urbanized reservoirs with rapidly increasing sedimentation rates sedimentation rates have been measured in three reservoirs in northeastern ohio u s a by means of 137cs and 210pb geochronologies volumetric surveys and varve counting these various methods while only partially overlapping for each reservoir show dramatic three fold increases in rates of sediment accumulation in each system between about 1940 and 1977 mass sedimentation rates are very nearly proportional to the size of the population in the region and possess a doubling time of roughly 19 yr in these systems with changing sedimentation rates the preferred model for use with 210pb geochronologies is one which assumes a constant activity of material added to surface sediments in systems possessing large watershed reservoir area ratios increasing erosion is evidently accompanied by a proportionate increase in the erosion of excess 210pb high near surface activities of 137cs are due to system integration effects with time constants the order of 10 yr to a few decades total accumulation of fallout 137cs and excess 210pb far exceed direct atmospheric loadings thus indicating the importance of watershed contributions and implying annual retention of the radionuclides in the reservoirs of between 15 and 80 in lake rockwell sedimentary fluxes of zn pb and cu have increased with time the flux of cu in particular has increased very markedly since 1970 and concentrations are high in surface materials due in large part to addition of cuso4 an algicide to the water because of increased rates of sedimentation the remaining useful life of lake rockwell has decreased from 203 to 67 yr while the remaining useful life of mayfair lake is now less than 5 yr

geographical dependence observed in blocking high influence on the stratospheric variability through enhancement and suppression of upward planetary wave propagation abstractprevious studies have suggested the importance of blocking high bh development for the occurrence of stratospheric sudden warming ssw while there is a recent study that failed to identify their statistical linkage through composite analysis applied to high amplitude anticyclonic anomaly events observed around every grid point over the extratropical northern hemisphere the present study reveals a distinct geographical dependence of bh influence on the upward propagation of planetary waves pws into the stratosphere tropospheric bhs that develop over the euro atlantic sector tend to enhance upward pw propagation leading to the warming in the polar stratosphere and in some cases to major ssw events in contrast the upward pw propagation tends to be suppressed by bhs developing over the western pacific and the far east resulting in the polar stratospheric cooling this dependence is found to arise mainly from the sensitivity of the interference between the climatological pws and upward p

seasonal variations in the southern hemisphere storm tracks and jet streams as revealed in a reanalysis dataset abstract regional characteristics of the climatological seasonal variations in southern hemisphere sh storm tracks are examined based on a reanalysis dataset when differences in vertical structure between the subpolar and subtropical jet streams spj and stj respectively are considered the regional characteristics can be interpreted reasonably well from a potential vorticity perspective of baroclinic eddy growth and downstream development of a baroclinic wave packet eddy activity in the upper and lower tropospheres is strongest in the core region of the spj over the eastern south atlantic and indian ocean throughout the year even in austral winter when the intense stj forms over the indian ocean and south pacific showing its eddy driven nature the spj accompanies the strong surface westerlies along a well defined baroclinic zone above an intense oceanic frontal zone in this core region of the storm track low level eddy activity is strongly correlated with the local near surface baroclinicity

transport and mixing in the extratropical tropopause region in a high vertical resolution gcm part i potential vorticity and heat budget analysis abstract a high vertical resolution general circulation model gcm output has been analyzed to clarify transport and mixing processes in the extratropical tropopause region the high resolution gcm with a vertical resolution of about 300 m above the extratropical upper troposphere allows simulation of fine atmospheric structures near the tropopause such as the extratropical tropopause transition layer extl and the tropopause inversion layer til the high resolution gcm realistically simulates fine thermal and dynamic structures in the extratropical tropopause region the thickness and maximum stability of the simulated til are consistent with observations the high resolution output was analyzed using a zonal mean potential vorticity pv equation to identify dominant transport processes in the extratropical tropopause region in the northern hemisphere extratropics during winter mean downward advection sharpens the pv gradient between the tropopause and 20 k below it whereas latitudinal variati

recent deposition of 210pb on the greenland ice sheet variations in space and time detailed 210pb profiles were determined for four chernobyl dated snowpits sampled during a wide ranging survey of the greenland ice sheet during the 1988 season the profiles from widely separated pits show little or no coherence even for two pits only 40 km apart the profiles differ in detail there does not appear to have been any seasonality in the deposition of 210pb onto the ice sheet in the two years since the chernobyl accident the total d eposition of 210pb during this period 10 20 bq m 2 was about 20 times less than has been observed at mid latitude sites in the eastern united states the three pits west of th e ice sheet divide recorded very similar depositional f1uxe s while the one eastern pit had only two thirds the a verage of the others suggesting a west to east gradient in the d eposition of 210pb and perhaps other continentall y derived s ubmicron aerosols onto the greenland ice sheet

a mechanistic model of the northern annular mode 1 the northern annular mode nam is the leading mode of variability in the northern hemisphere the nam consists of a meridional dipole of the zonal mean zonal wind that extends into the stratosphere during the winter season during the high index state of the nam high latitude westerly winds are stronger than normal leading to a stronger and colder polar vortex over the past few decades observations show a trend toward higher nam index values to investigate whether this trend is a result of natural variability or is related to greenhouse warming a mechanistic model is developed that provides a simple analogue of the nam the model represents the interaction between the zonally symmetric flow and planetary waves for two meridional modes of variation greenhouse warming is specified in the model by varying the radiative equilibrium meridional temperature gradient variations in the second meridional mode qualitatively resemble those of the observed nam model runs that correspond to larger greenhouse gas concentrations yield on average higher nam index values

greenland ice core signal characteristics an expanded view of climate change the last millenium of earth history is of particular interest because it documents the environmental complexities of both natural variability and anthropogenic activity we have analyzed the major ions contained in the greenland ice sheet project 2 gisp 2 ice core from the present to 674 a d to yield an environmental reconstruction for this period that includes a description of nitrogen and sulfur cycling volcanic emissions sea salt and terrestrial influences we have adapted and extended mathematical procedures for extracting sporadic e g volcanic events secular trends and periodicities found in the data sets finally by not assuming that periodic components signals were stationary and by utilizing evolutionary spectral analysis we were able to reveal periodic processes in the climate system which change in frequency turn on and turn off with other climate transitions such as that between the little ice age and the medieval warm period

blocking in the southern hemisphere abstract the focus of this paper is on the frequency and spatial distributions of blocking and persistent anomalies of geopotential height over the southern hemisphere the analysis is based upon daily height fields at 1000 and 500 mb for both summer and winter histogram frequency distributions of height anomalies and maps of the skewness and kurtosis have been computed blocking events are objectively defined by requiring a large positive anomaly to exist for 5 days or more composite flow and anomaly fields for several cases are presented and examined in detail the geographical distribution of the frequency of lame amplitude 150 gpm anomalies at 500 mb that persist for only 1 3 days is very similar to that of the high frequency band 2 8 day period variances that identity the storm tracks in the southern hemisphere the primary location for blocking in the southern hemisphere is in the new zealand sector and blocking occurs through a local enhancement of the climatological split in the mean westerli

upward and downward injection of rossby wave activity across the tropopause a new aspect of the troposphere stratosphere dynamical linkage propagation of zonally confined rossby wave activity between the troposphere and lower stratosphere of the southern hemisphere during austral winter and spring of 1997 is studied by using a wave activity flux and refractive index both defined for stationary rossby waves on a zonally asymmetric time mean flow a particular event of large scale quasi stationary cyclogenesis in the troposphere is discussed to which downward wave activity injection from anticyclonic anomalies upstream that had developed in the exit region of the lower stratospheric polar night jet pnj contributed substantially consistent with that downward injection phase lines of observed stream function anomalies exhibited a distinct eastward tilt with height the development of the anticyclonic anomalies occurred at the leading edge of a quasi stationary rossby wave train propagating along the pnj that had originated from a tropospheric blocking ridge farther upstream though less common than upward wave activity injection across the tropopause similar events of downward wave activity injection occurred several times during that season primarily in the regions south of australia and over the central south pacific over each of which the pnj exit overlapped with a tropospheric subpolar jet to form a vertical waveguide locally it is argued that the downward wave activity propagation is essentially due to refraction in the vertically sheared westerlies and the zonal asymmetries in the time mean flow are a likely factor for the observed geographical preference of the downward wave activity injection copyright 2005 royal meteorological society

mechanisms determining the winter atmospheric response to the atlantic overturning circulation abstractin climate models an intensification of the atlantic meridional overturning circulation amoc precedes a warming in the north atlantic subpolar basin by a few years in the ipsl cm5a lr model this warming may explain the atmospheric response to the amoc observed in winter which resembles a negative phase of the north atlantic oscillation nao to firmly establish the causality links between the ocean and the atmosphere and illustrate the underlying mechanisms in this model ensembles of atmosphere only simulations are conducted prescribing the sst and sea ice anomalies that follow an amoc intensification in late winter the north atlantic sst and sea ice anomalies drive atmospheric circulation anomalies similar to those found in the coupled model simulations only driven by the sst anomalies related to the amoc show that the largest oceanic influence is due to the warm subpolar sst anomaly which enhances the oceanic heat release and decreases the lower tropospheric baroclinicity in the reg

tropical sst preconditioning of the sh polar vortex during winter 2002 the response of the southern hemisphere sh polar atmosphere to the tropical sea surface temperature sst during the 2002 winter spring season is investigated by using a general circulation model gcm the sh stratospheric winter of 2002 was particularly unusual characterized by a weaker than normal polar vortex during the whole season it also registered at the end of september the first major warming yet observed in the sh this event is unexpected in the sh and it is supposed to be induced by a preconditioning of the polar vortex starting at the beginning of the winter atmospheric gcm experiments with prescribed sst boundary conditions are performed the sensitivity of the antarctic dynamics to the tropical sst of 2002 a year characterized by an el nino event of moderate intensity is studied and the uniqueness of the 2002 tropical oceanic condition is investigated through the comparison of the simulated response of the climatic system to 2002 and 1997 tropical sst 1997 being a year with a strong el nino event model results highlight a primary role played by the tropical sst of 2002 in the development of the peculiar characteristics of the antarctic dynamics during the winter months that appears to be a necessary condition for the generation of the anomalous destabilization of the polar vortex during the following spring results for june 2002 show a strong generation of vertically propagating waves resulting from the tropical sst that through the perturbation of the westerly jet at middle latitudes produces a preconditioning of the polar vortex by affecting the wave refraction index the particular structure of the tropical sst anomalies during the winter of 2002 is thought to have influenced the subsequent preconditioning of the stratospheric vortex

210pb dating of cold alpine firn ice cores from colle gnifetti switzerland datation 210 pb 210 po d une carotte de glacier froid le taux d accumulation corrige est de 39 cm an pour une carotte de 1977 65 m

energy enhancements of gravity waves in the antarctic lower stratosphere associated with variations in the polar vortex and tropospheric disturbances 1 gravity waves in the antarctic lower stratosphere are examined using original operational radiosonde data obtained at syowa station 69 0 s 39 6 e with fine vertical resolution in the lower stratosphere the temporal variation in gravity wave energy depends on height in the height region of 13 15 km just above the tropopause the seasonal variation in gravity wave energy is not evident the wave energy is rather enhanced when the absolute value of potential vorticity in the upper troposphere becomes small over syowa station this fact implies that tropospheric disturbances affect the dynamical processes of gravity waves there however the gravity wave energy in the height region of 15 25 km shows clear seasonal variation having a maximum in spring the time variation in gravity wave energy is examined in detail in terms of the polar vortex by using the equivalent latitude coordinate energy enhancements occur when the edge of the polar vortex approaches syowa station and the enhancements are especially large when the polar vortex breaks down in spring these results suggest that height variation in the background atmosphere leads to the difference of wave characteristics between the two height regions the enhancements of wave energy are partly explained as modification of the wave structure by the background wind speed and the static stability but it is also likely that enhancements of wave activity contribute to the energy enhancement at the edge of the polar vortex in spring

propagation of planetary waves between the troposphere and stratosphere abstract the propagation of planetary waves between the troposphere and stratosphere is investigated using a linear time dependent primitive equation model it is found that the tropopause acts like a valve for the propagation of planetary waves the key parameters controlling the valve are the vertical gradient of buoyancy frequency and the vertical shear of the zonal winds at the tropopause for a given wind profile smaller gradient of buoyancy frequency enhances the propagation of planetary waves for a given profile of buoyancy frequency the larger the shear the more the wave activity is trapped in the troposphere and therefore there is less left to propagate into the stratosphere the transmission across the tropopause is however not sensitive to zonal winds in the upper stratosphere the propagation of planetary waves is very sensitive to transience more transient waves propagate more vertically within the troposphere and for more transient waves more wave activity is transferred into the

ice sheets and sea level of the last glacial maximum this paper outlines the general issues regarding ice sheets and sea level of the last glacial maximum lgm which formed the basis of an epilog project workshop papers in this special issue of quaternary science reviews provide a comprehensive assessment of these issues from the perspective of geological reconstructions of ice sheet extent records of sea level change ice sheet modelling geophysical models of glacial isostatic adjustment and geochemical proxies of ice volume this new assessment has substantially narrowed the uncertainties in the total changes in ice sheets and sea level and their proxies suggesting a net decrease in eustatic sea level at the lgm ranging from 120 to 135 m r 2001 elsevier science ltd all rights reserved

properties of the quasi 16 day wave derived from eos mls observations 1 this paper describes the use of eos microwave limb sounder mls data to observe the field of traveling planetary waves with quasi 16 day periods this study utilizes mls v2 2 temperature and geopotential data between 1 january 2005 and 31 december 2008 in the range 316 hpa to 0 001 hpa approximately 8 to 97 km to examine these waves analysis demonstrates that the quasi 16 day wavefield is made up of a number of components with westward and eastward propagating s 1 and s 2 waves generally dominant in the northern hemisphere the westward and eastward propagating s 1 waves have similar magnitudes and are larger than the other modes while in the southern hemisphere the eastward propagating s 1 and s 2 waves are larger than the westward propagating wave modes all of the modes examined display strong seasonal patterns in the temperature amplitude significant variability in the wave activity from year to year and the presence of strong pulse like patterns in the activity all of the modes also display large median temperature amplitudes poleward of 40 degrees in both hemispheres our analysis also demonstrates that the variability in winter from year to year is larger in the northern hemisphere than the southern hemisphere detailed study also suggests that the exclusion of waves from regions of negative refractive index squared likely forms much of the seasonal pattern observed thus regions of strong westward wind speeds effectively exclude vertically propagating waves as expected from theory the reflection and absorption of waves associated with critical lines is also likely to explain the frequent occurrence of standing wave patterns in the eos mls temperature observations this study highlights the potential of mls observations for observing waves from the upper troposphere to the lower mesosphere

observed interannual oscillations of planetary wave forcing in the northern hemisphere winter 1 using ncep ncar reanalysis data from 1958 to 1998 two interannual oscillations in the eddy forcing due to planetary waves wavenumbers 1 3 are found in the northern hemisphere winter called as the stratospheric interannual oscillation sio and the tropospheric interannual oscillation tio the temporal evolutions are different between the sio and the tio suggesting different dynamic mechanisms the planetary waves tend to be bent equatorward in the troposphere during a positive tio phase and in the mid and upper stratosphere during a positive sio phase the result also suggests that upward propagation of planetary waves into the polar waveguide across the tropopause is closely associated with the tio further regression and correlation analyses suggest that the tio is closely linked to the northern annular mode nam whereas the sio is closely associated with the el nino southern oscillation enso

extraordinary features of the planetary wave propagation during the boreal winter 2013 2014 and the zonal wave number two predominance observational features of the winter 2013 2014 are investigated using of the japanese 55 year reanalysis jra 55 data this winter can be characterized by the continuous predominance of planetary waves of zonal wavenumber two wn2 that did not cause major sudden stratospheric warming ssw events it is found that the vertical component of the eliassen palm flux of wn2 for the winter 2013 2014 is almost equal to the highest value of the winter 2008 2009 the longitudinal distribution of vertical components of plumb wave activity flux wafz for this winter shows marked downward propagation around 100 w and upward propagation around 60 e both of which are the strongest of their type among the 56 winters since 1958 1959 the convergence of wave packets propagating from around 60 e contributes to the development and continuance of the quasi barotropic aleutian high which is associated with the extension of negative extended refractive index ks region the extension of negative ks region is related to the convergence or reflection of the wave packets emanating from tropospheric blocking highs developing in the north pacific ocean the development and continuance of the quasi barotropic aleutian high is considered to be one of plausible reasons for the lack of major ssws in the winter 2013 2014 in addition to these results we revealed the significant contribution of smaller scale waves with a zonal wavenumber of three or more to the structure of localized wave packet propagation in the stratosphere

extreme wave deposits on the pacific coast of mexico tsunamis or storms a multi proxy approach abstract historical and instrumental data show that the pacific coast of mexico has been exposed to destructive tsunamis over at least the past 500 years this coast is also affected by hurricanes generated in the eastern pacific the great 1985 mexico earthquake and its aftershock generated tsunamis that affected the ixtapa zihuatanejo and michoacan coast the purpose of our study was two fold a to determine whether storm and tsunami deposits could be distinguished and b whether tsunami deposits from historical events are preserved in the tropical environments of the ixtapa zihuatanejo coast two anomalous sand units in the ixtapa estuary are interpreted to be the result of high energy marine inundation events that occurred in the last century several lines of evidence using a multi proxy approach historical studies interviews with local witnesses geomorphological and geological surveys coring and trenching laboratory analyses including grain size micropaleontology geochemistry magnetic susceptibility and radiometric dating and numerical modeling indicate the occurrence of two tsunamis that we link to local events the 21st september 1985 mexico and possibly the 14th march 1979 petatlan earthquakes we thereby provide the first onshore geological evidence of historical tsunamis on the pacific coast of mexico

winter warming over dome fuji east antarctica and semiannual oscillation in the atmospheric circulation an abrupt warming was observed in the winter around dome fuji 3810 m above sea level asl in east antarctica the air temperature increased from 73 c to 36 c in two days from june 13 to 14 1994 warming occurred first in the coastal region near the lambert glacier east antarctica then progressed inland to dome fuji during the warming a blocking high was observed in the middle troposphere and it persisted for several weeks this circulation pattern brought warm air inland a blocking high over east antarctica also appeared in the upper troposphere this high pressure area corresponded to a ridge of stratospheric circulation this condition occurred after a displacement of the polar vortex from east antarctica to west antarctica warming at the surface of the ice sheet occurred suddenly however in the stratosphere the circulation pattern began to change on a seasonal scale prior to the warming as part of the first phase of the semiannual oscillation

a new deep ice core from akademii nauk ice cap severnaya zemlya eurasian arctic first results the paper presents first results from the upper 54m of a 723 91m ice core drilled on akademii nauk ice cap severnaya zemlya eurasian arctic in 1999 2001 supplemented by data from shallow ice cores the glacier s peculiarity is the infiltration and refreezing of meltwater which changes the original isotopic and chemical signals therefore stratigraphical observations in these ice cores are more difficult than in those from central greenland or antarctica however the 1963 maximum of artificial radioactivity from atmospheric nuclear tests is clearly detectable in the deep ice core and the 18 o profile of a 12 82 m shallow core shows annual variations consequently at least for the upper part of the main core an almost seasonal time resolution of palaeoclimate record could be expected the chernobyl layer is detected by increased 137 cs activity at depths of 11 81 12 51m related to the ad 2000 surface the resulting mean annual net mass balance is 53 2 g cm 2 a 1 data from dielectric profiling of the main core show considerable peaks in conductivity one of them is interpreted as a volcano event according to the resulting chronology this part of the core represents approximately the last 100 years

tropospheric influence on the diminished antarctic ozone hole in september 2002 in late september of 2002 the first recorded major sudden stratospheric warming occurred over antarctica lead ing to sudden breakdown of the cold polar vortex and the col lapse of the ozone hole our diagnosis reveals that the warming was associated with propagation of a rossby wavepacket from a prominent tropospheric blocking ridge over the south atlan tic into the stratospheric polar night jet that had already weak ened unusually the blocking developed from anomalies that had formed as a component of another rossby wavetrain that appeared to be forced in mid september by anomalous deep cumulus convection in the south pacific convergence zone

the role of atmospheric rivers in anomalous snow accumulation in east antarctica recent heavy snow accumulation events over dronning maud land dml east antarctica contributed significantly to the antarctic ice sheet surface mass balance smb here we combine in situ accumulation measurements and radar derived snowfall rates from princess elisabeth station pe located in the dml escarpment zone along with the european centre for medium range weather forecasts interim reanalysis to investigate moisture transport patterns responsible for these events in particular two high accumulation events in may 2009 and february 2011 showed an atmospheric river ar signature with enhanced integrated water vapor iwv concentrated in narrow long bands stretching from subtropical latitudes to the east antarctic coast adapting iwv based ar threshold criteria for antarctica by accounting for the much colder and drier environment we find that it was four and five ars reaching the coastal dml that contributed 74 80 of the outstanding smb during 2009 and 2011 at pe therefore accounting for ars is crucial for understanding east antarctic smb

a major stratospheric sudden warming event in january 2009 abstract the major stratospheric sudden warming ssw event of january 2009 is analyzed using the japan meteorological agency jma climate data assimilation system jcdas this ssw event is characterized by the extraordinary predominance of the planetary scale wave of zonal wavenumber 2 wave 2 the total amount of the upward eliassen palm ep flux for wave 2 was the strongest since the winter of 1978 79 it is found that the remarkable development of the upper troposphere ridge over alaska played important roles in the ssw in january 2009 during the first development stage the ridge excited wave packets upward as well as eastward over around alaska the eastward propagating packets intensified a trough over eastern siberia which led to the development of the planetary wave over eastern siberia during the second development stage the results of this study indicate that the pronounced wave 2 pattern observed in the stratosphere was brought about by accumulative effects of rather localized propagati

the role of high and low frequency dynamics in blocking formation time evolutions of prominent blocking flow configurations over the north pacific and europe are compared based upon composites for the 30 strongest events observed during 27 recent winter seasons fluctuations associated with synoptic scale migratory eddies have been filtered out before the compositing a quasi stationary wave train across the atlantic is evident during the blocking amplification over europe while no counterpart is found to the west of the amplifying blocking over the north pacific correlation between the tropopause level potential vorticity pv and meridional wind velocity associated with the amplifying blocking is found to be negative over europe in association with the anticyclonic evolution of the low pv center but it is almost zero over the north pacific feedback from the synoptic scale eddies as evaluated in the form of 250 mb geopotential height tendency due to the eddy vorticity flux convergence accounts for more than 75 of the observed amplification for the pacific blocking and less than 45 for the european blocking this difference is highlighted in two types of contour advection with surgery experiments in one of them pv contours observed four days before the peak blocking time were advected by composite time series of the low pass filtered observational wind and in the other experiment they were advected by the low pass filtered wind from which the transient eddy feedback evaluated as above had been removed at every time step hence the latter data should be dominated by low frequency dynamics for the european blocking both experiments can reproduce the anticyclonic evolution of low pv air within a blocking ridge as observed for the pacific blocking in contrast the observed intrusion of low pv air into the higher latitudes cannot be reproduced without the transient feedback furthermore in a barotropic model initialized with the composite 250 mb flow observed three days before the peak time a simulated blocking development over the north pacific is more sensitive to the insertion of the observed transient feedback than that over europe these results suggest that the incoming wave activity flux associated with a quasi stationary rossby wave train is of primary importance in the blocking formation over europe whereas the forcing by the synoptic scale transients is indispensable to that over the north pacific

influences of enso on stratospheric variability and the descent of stratospheric perturbations into the lower troposphere abstractthe linkage between el nino southern oscillation enso and north atlantic oscillation nao through the stratospheric pathway is examined using a global coupled climate model gfdl climate model version 3 cm3 with increased vertical resolution and extent in the stratosphere as compared to an earlier model gfdl climate model version 2 cm2 it is demonstrated that the relationship between enso and nao is stronger in cm3 than in cm2 it is found that enso plays an important role in modulating the frequency of occurrence of the stratospheric polar vortex anomalies through enhancement attenuation of the amplitudes of zonal wavenumbers 1 and 2 especially in late winter a higher frequency of weak strong stratospheric vortex events is simulated in cm3 during el nino la nina episodes the weak vortex events during el nino winters are preceded by enhancement of the zonal wave 1 pattern and weakening of zonal wave 2 pattern these modified tropospheric planetary waves propagate upward and then w

a 200 year 210pb record from greenland a continuous profile of 210pb activity extending back to 1766 has been developed for a firn ice core collected at site d in central greenland in 1984 unexpectedly high activities of 210pb were found at the base of this core 0 032 pci kg 1 in samples more than 200 years old calling into question the common assumption that supported 210pb can be neglected when constructing chronologies in glacial snow and ice it is problematic to assert that all of the 210pb measured at depth should be attributed to the supported fraction given previous estimates of dust loading in greenland ice cores however even if an estimated constant value of 0 032 pci supported 210pb kg 1 is subtracted from the measured values to estimate excess 210pb the 210pb chronology for site d yields ages that are significantly younger mean accumulation rate too high than an independent depth age scale based on annual layer counting it is apparent that the flux of excess and or supported 210pb to this site must have decreased over the past 2 centuries with decreasing trends in both fractions most likely previously published 210pb profiles for cores from summit and dye 3 greenland show similar trends which had been interpreted as decreasing fluxes of excess 210pb only for all three sites it is not possible to separate variations in the fluxes of the excess and supported fractions of 210pb but variations in the total 210pb flux will impact 210pb based chronologies generally if these variations have not been restricted to the greenland ice sheet

the seasonal evolution of planetary waves in the southern hemisphere stratosphere and troposphere seasonality in planetary wave structure in the southern hemisphere stratosphere and troposphere 1000 1 mb is studied based on eight years 1979 1986 of daily geopotential data emphasis is placed on the distinctive seasonality in the stratosphere along with tracing the stratospheric fluctuations into the troposphere time filtering is used to separate stationary and transient components maximum geopotential height variance is observed in the middle to upper stratosphere in late winter spring with a distinct secondary smaller maximum in late fall early winter these maxima sandwich the strongest mid winter zonal winds this sequence occurs approximately one month earlier in the upper stratosphere two corresponding peaks are observed in stratospheric zonal mean wind and temperature fluctuations the two maxima in stratospheric wave variance are not in agreement with observed seasonal changes in quasi geostrophic refractive index of the zonal mean flow the stratospheric geopotential variance maxima result from nearly equal amounts of stationary and transient zonal wave 1 fluctuations with transient wave 2 also contributing during late winter stationary wave 1 shows intriguing seasonal evolution the early winter maximum is predominantly equivalent barotropic whereas that of late winter spring is highly baroclinic in the stratosphere stratospheric poleward fluxes of heat and momentum both exhibit pronounced maxima during september october these result primarily from the stationary wave 1 contributions and the transients assume a secondary role although not as pronounced as the stationary wave seasonality seasonal differences in transient wave behaviour are also documented including three dimensional propagation characteristics and wave mean flow interaction diagnostics

a precipitation seesaw mode between northeast asia and siberia in summer caused by rossby waves over the eurasian continent abstract there is a dominant seesaw pattern in summertime precipitation between northeast asia and siberia examined here is a mechanism of the seesaw mode focusing on quasi stationary rossby waves propagating on two upper tropospheric waveguides along the asian jet and over northern eurasia empirical orthogonal function eof analysis to the low frequency 10 day low pass filtered variation during summer reveals wave propagation patterns on both of the waveguides the time evolution of the two composite fields constructed using the obtained eof modes for each phase of the seesaw mode was investigated by the wave activity flux in both composite fields eastward propagating rossby waves originating from the north atlantic european sector branch off around eastern europe onto the two waveguides which become out of phase toward the east because of the difference in longitudinal wavelengths along them this results in opposite phase anomalies of meridional winds over northeast asia and siberia budget

glaciological investigations in the crete area central greenland a search for a new deep drilling site the results of the 1984 85 post gisp campaigns in central greenland are presented eight ice cores were obtained some spanning up to 360 years we present i geographical positions and elevations at the drill sites

pitfalls of normalization of marine geochemical data using a common divisor abstract normalization of trace element contents of sediment through division by the content of an immobile element usually aluminum is common practice in marine geochemical studies this might appear to be a simple way of correcting for dilution by sedimentary phases barren of a particular trace element for instance carbonates or silica and for comparison with its content in a standard clay or shale the purpose of this paper is to revive the awareness of the pitfalls of this practice by giving numerical examples of the often unexpected results of normalization taking a statistical perspective it is first shown that uncorrelated variables acquire spurious correlations when normalized but normalization can also increase decrease change sign of or even blur the correlations between unmodified variables next a number of realistic scenarios are worked out to show that the correlations between normalized element contents still suffer from the closure effect only in a few simple cases it is possible to extract from the normalized data realistic estimates of trace element contents in distinct sedimentary phases such as organic matter this is ascertained from data on copper contents in sediment from the black sea and arabian sea when the coefficient of variation i e standard deviation divided by the mean of the aluminum data is relatively low and much lower than for the original values of the trace elements comparisons of correlations can equally well or even better be made on the basis of the unmodified values then the comparison of trace element data with their values for standard shales is discussed the inherent problem is that the composition of the commonly used standard shale and consequently the reference values of normalized elements are not necessarily representative of the local or regional sediments in the study area also this method falls short of identifying the processes responsible for enrichment or diminution in trace element contents finally consideration is given to some aspects of a proper use of al normalization

synoptic behavior of baroclinic eddies during the blocking onset abstract synoptic behavior of individual baroclinic eddies in the course of their interactions with amplifying blocking anticyclones is examined based upon a 30 year record of the tropospheric circulation in the northern hemisphere winter high pass filtered as well as unfiltered fields of geopotential height and potential vorticity were composited relative to the onset of the five different types of blocking patterns before the compositing the entire sequence of the fields was slightly shifted in time and space in such a way that the strongest baroclinic eddy during the onset of each blocking event occupies a prescribed position in the upstream storm track when it reaches its maximum intensity since this shifting considerably reduces the cancellation between the individual high frequency migratory eddies this type of compositing can present a more synoptically oriented view of those interactions than conventional compositing in our composite results one or two pairs of cyclonic and anticyclonic

the 1500m south pole ice core recovering a 40 ka environmental record supported by the us national science foundation a new 1500 m approximately 40 ka old ice core will be recovered from south pole during the 2014 15 and 2015 16 austral summer seasons using the new us intermediate depth drill the combination of low temperatures relatively high accumulation rates and low impurity concentrations at south pole will yield detailed records of ice chemistry and trace atmospheric gases the south pole ice core will provide a climate history record of a unique area of the east antarctic plateau that is partly influenced by weather systems that cross the west antarctic ice sheet the ice at south pole flows at approximately 10m a exp 1 and the south pole ice core site is a significant distance from an ice divide therefore ice recovered at depth originated progressively farther upstream of the coring site new ground penetrating radar collected over the drill site location shows no anthropogenic influence over the past approximately 50 years or upper 15 m depth age scale modeling results show consistent and plausible annual layer thicknesses and accumulation rate histories indicating that no significant stratigraphic disturbances exist in the upper 1500m near the ice core drill site

climate change and population history in the pacific lowlands of southern mesoamerica core man015 from pacific coastal guatemala contains sediments accumulated in a mangrove setting over the past 6500 yr chemical pollen and phytolith data which indicate conditions of estuarine deposition and terrigenous inputs from adjacent dry land document holocene climate variability that parallels the maya lowlands and other new world tropical locations human population history in this region may be driven partly by climate variation sedentary human populations spread rapidly through the estuarine zone of the lower coast during a dry and variable 4th millennium b p population growth and cultural florescence during a long relatively moist period 2800 1200 b p ended around 1200 b p a drying event that coincided with the classic maya collapse

a climatological analysis of high precipitation events in dronning maud land antarctica and associated large scale atmospheric conditions the link between high precipitation in dronning maud land dml antarctica and the large scale atmospheric circulation is investigated using era interim data for 1979 2009 high precipitation events are analyzed at halvfarryggen situated in the coastal region of dml and at kohnen station located in its interior this study further includes a comprehensive comparison of high precipitation in era interim with precipitation data from the antarctic mesoscale prediction system amps and snow accumulation measurements from automatic weather stations awss with the limitations of such a comparison being discussed the era interim and amps precipitation data agree very well however the correspondence between high precipitation in era interim and high snow accumulation at the awss is relatively weak high precipitation events at both halvfarryggen and kohnen are typically associated with amplified upper level waves this large scale atmospheric flow pattern is preceded by the downstream development of a rossby wave train from the eastern south pacific several days before the precipitation event at the surface a cyclone located over the weddell sea is the main synoptic ingredient for high precipitation both at halvfarryggen and at kohnen a blocking anticyclone downstream is not a requirement for high precipitation per se but a larger share of blocking occurrences during the highest precipitation days in dml suggests that these blocks strengthen the vertically integrated water vapor transport ivt into dml a strong link between high precipitation and the ivt perpendicular to the local orography suggests that ivt could be used as a proxy for high precipitation in particular over dml s interior

diagnostic case studies of the northern annular mode abstract recent observational studies of the northern annular mode nam indicate that significant case to case variability exists in the structural evolution of individual events in particular certain nam events remain confined to stratospheric altitudes whereas others readily penetrate downward into the troposphere we perform observational diagnostic analyses that are targeted at identifying the physical mechanisms behind this distinction our results thereby provide a test of the different existing theories regarding stratospheric influences upon tropospheric climate we contrast robust stratospheric nam events with differing tropospheric signals in order to identify the underlying dynamical reasons for the observed differences piecewise potential vorticity pv inversions and eliassen palm flux analyses are performed to study the roles of different forcing mechanisms during nam onset our results indicate that variations in the tropospheric response are readily explained on the basis of piecewise

wave maintained annular modes of climate variability abstract the leading modes of month to month variability in the northern and southern hemispheres are examined by comparing a 100 yr run of the geophysical fluid dynamics laboratory gcm with the ncep ncar reanalyses of observations the model simulation is a control experiment in which the ssts are fixed to the climatological annual cycle without any interannual variability the leading modes contain a strong zonally symmetric or annular component that describes an expansion and contraction of the polar vortex as the midlatitude jet shifts equatorward and poleward this fluctuation is strongest during the winter months the structure and amplitude of the simulated modes are very similar to those derived from observations indicating that these modes arise from the internal dynamics of the atmosphere dynamical diagnosis of both observations and model simulation indicates that variations in the zonally symmetric flow associated with the annular modes are forced by eddy fluxes in the free troposphere while

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

lower stratospheric rossby wave trains in the southern hemisphere a case study for late winter of 1997 behaviour of quasi stationary circulation anomalies observed in the lower stratosphere of the extratropical southern hemisphere during austral late winter of 1997 is studied the anomalies are defined as daily low pass filtered departures from the circulation varying slowly with the seasonal cycle a wave activity flux and refractive index for stationary rossby waves are utilized in the analysis each of which is defined locally for the zonally varying westerlies subseasonal fluctuations in the lower stratosphere were often associated with zonally confined wave trains emanating upward from localized quasi stationary anomalies in the troposphere including blocking ridges the three dimensional propagation of the waves was found sensitive to the structure of a local waveguide upward injection of rossby wave activity into the stratosphere tended to occur slightly upstream or just beneath of a lower stratospheric waveguide associated with the developed polar night jet pnj which led to the subsequent formation of a well defined wave train downstream along that jet the distribution of the lower stratospheric subseasonal variability thus exhibits significant zonal asymmetries reflecting those in the pnj structure and the distribution of tropospheric disturbances seasonal evolution of the pnj and that of the tropospheric intraseasonal variability substantially modulated the lower stratospheric activity of subseasonal fluctuations copyright 2004 royal meteorological society

the unusual southern hemisphere stratosphere winter of 2002 abstractthe southern hemisphere sh stratospheric winter of 2002 was the most unusual winter yet observed in the sh climate record temperatures near the edge of the antarctic polar vortex were considerably warmer than normal over the entire course of the winter the polar night jet was considerably weaker than normal and was displaced more poleward than has been observed in previous winters these record high temperatures and weak jet resulted from a series of wave events that took place over the course of the winter the propagation of these wave events from the troposphere is diagnosed from time series of eliassen palm flux vectors and autoregression time series strong levels of planetary waves were observed in the midlatitude lower troposphere the combinations of strong tropospheric waves with a low index of refraction at the tropopause resulted in the large stratospheric wave forcing the wave events tended to occur irregularly over the course of the winter and the cumulative effect of these wave

changing controls on oceanic radiocarbon new insights on shallow to deep ocean exchange and anthropogenic co2 uptake 1 the injection of radiocarbon 14c into the atmosphere by nuclear weapons testing in the 1950s and 1960s has provided a powerful tracer to investigate ocean physical and chemical processes while the oceanic uptake of bomb derived 14c was primarily controlled by air sea exchange in the early decades after the bomb spike we demonstrate that changes in oceanic 14c are now primarily controlled by shallow to deep ocean exchange i e the same mechanism that governs anthropogenic co2 uptake this is a result of accumulated bomb 14c uptake that has rapidly decreased the air sea gradient of 14c c 14c and shifted the main reservoir of bomb 14c from the atmosphere to the upper ocean the air sea 14c gradient reduced further by fossil fuel dilution is now weaker than before weapons testing in most regions oceanic 14c and particularly its temporal change can now be used to study the oceanic uptake of anthropogenic co2 we examine observed changes in oceanic 14c between the woce save 1988 1995 and the clivar 2001 2007 eras and simulations with two ocean general circulation models the community climate system model ccsm and the estimating the circulation and climate of the ocean model ecco observed oceanic 14c and its changes between the 1980s 90s and 2000s indicate that shallow to deep exchange is too efficient in ecco and too sluggish in ccsm these findings suggest that mean global oceanic uptake of anthropogenic co2 between 1990 and 2007 is bounded by the ecco based estimate of 2 3 pg c yr 1 and the ccsm based estimate of 1 7 pg c yr 1

record high temperatures in the antarctic a synoptic case study abstract during the period 23 29 december 1978 abnormally high temperatures were recorded at several antarctic stations new records were set at south pole memurdo and vostok and near record high temperatures were reached at coastal stations in east antarctica synoptic scale events accompanying these unprecedented high temperatures were investigated using surface satellite and radiosonde data the high temperatures were associated with two intrusions of warm air which penetrated the continent from the atlantic and indian ocean sectors warming at south pole occurred with the passage of a jet like feature and its accompanying baroclinic zone

210pb and 137cs in margin sediments of the arctic ocean controls on boundary scavenging 1 210pb and 137cs were measured in 25 sediment cores collected during the international polar year from a transect spanning the north american arctic margin from the north bering sea to baffin bay davis strait profiles and inventories of the radioisotopes were used to determine sediment mixing and accumulation at each site and to assess the intensity of scavenging and burial sediment accumulation rates derived from 210pb and validated using 137cs are between 0 04 and 0 23 g cm 2 yr 1 210pb cannot be used to derive sedimentation rates for vigorously biomixed sediments from the north bering chukchi shelf elevated 137cs activities and inventories in recently deposited sediments imply delayed inputs of particle associated 137cs to the sediments likely transported from the watershed to the coast and subsequently redistributed to shelf slope sediments inventories of 210pbex in all cores meet or exceed the estimated supply of 210pbex from atmospheric deposition and decay of 226ra in the water column this implies that in contrast to the deep arctic ocean basin there is a sufficient supply of suspended particulates along the north american arctic margin to scavenge the supply of 210pbex 210pbex inventories in sediments are up to 21 fold greater than the in situ supply at some sites large inventories of 210pbex in sediments along the north bering chukchi shelf result primarily from focusing while those along the north chukchi slope barrow canyon and in baffin bay davis strait reflect strong boundary scavenging likely supported by lateral exchanges with deep interior atlantic origin waters

rapid sea level rise and ice sheet response to 8 200 year climate event 1 the largest abrupt climatic reversal of the holocene interglacial the cooling event 8 6 8 2 thousand years ago ka was probably caused by catastrophic release of glacial lake agassiz ojibway which slowed atlantic meridional overturning circulation amoc and cooled global climate geophysical surveys and sediment cores from chesapeake bay reveal the pattern of sea level rise during this event sea level rose 14 m between 9 5 to 7 5 ka a pattern consistent with coral records and the ice 5g glacio isostatic adjustment model there were two distinct periods at 8 9 8 8 and 8 2 7 6 ka when chesapeake marshes were drown as sea level rose rapidly at least 12 mm yr 1 the latter event occurred after the 8 6 8 2 ka cooling event coincided with extreme warming and vigorous amoc centered on 7 9 ka and may have been due to antarctic ice sheet decay

stratospheric polar vortex splits and displacements in the high top cmip5 climate models sudden stratospheric warming ssw events can occur as either a split or a displacement of the stratospheric polar vortex recent observational studies have come to different conclusions about the relative impacts of these two types of ssw upon surface climate a clearer understanding of their tropospheric impact would be beneficial for medium range weather forecasts and could improve understanding of the physical mechanism for stratosphere troposphere coupling here we perform the first multimodel comparison of stratospheric polar vortex splits and displacements analyzing 13 stratosphere resolving models from the fifth coupled model intercomparison project cmip5 ensemble we find a wide range of biases among models in both the mean state of the vortex and the frequency of vortex splits and displacements although these biases are closely related consistent with observational results almost all models show vortex splits to occur barotropically throughout the depth of the stratosphere while vortex displacements are more baroclinic vortex splits show a slightly stronger north atlantic surface signal in the month following onset however the most significant difference in the surface response is that vortex displacements show stronger negative pressure anomalies over siberia this region is shown to be colocated with differences in tropopause height suggestive of a localized response to lower stratospheric potential vorticity anomalies

snowfall driven mass change on the east antarctic ice sheet 1 an improved understanding of processes dominating the sensitive balance between mass loss primarily due to glacial discharge and mass gain through precipitation is essential for determining the future behavior of the antarctic ice sheet and its contribution to sea level rise while satellite observations of antarctica indicate that west antarctica experiences dramatic mass loss along the antarctic peninsula and pine island glacier east antarctica has remained comparably stable in this study we describe the causes and magnitude of recent extreme precipitation events along the east antarctic coast that led to significant regional mass accumulations that partially compensate for some of the recent global ice mass losses that contribute to global sea level rise the gain of almost 350 gt from 2009 to 2011 is equivalent to a decrease in global mean sea level at a rate of 0 32 mm yr over this three year period

extra tropical synoptic cyclones and downward propagating anomalies in the northern annular mode 1 during most winters anomalies in the northern annular mode nam propagate downward from the stratosphere to the troposphere in this paper the relationship between extra tropical synoptic scale cyclones and downward propagating positive nam and negative nam anomalies is investigated both pacific and atlantic storm tracks are significantly influenced by the downward propagating nam anomalies while only the atlantic storm tracks are significantly influenced by the downward propagating nam anomalies the number of cyclones changes by up to 30 during both nam and nam within certain regions also fluctuations in the nam follow corresponding fluctuations in the storm activity with a lag of three days during nam and nam

does the arctic stratospheric polar vortex exhibit signs of preconditioning prior to sudden stratospheric warmings abstractcharacteristics of the arctic stratospheric polar vortex are examined using reanalysis data with dynamic time warping dtw and a clustering technique to determine whether the polar vortex

mangrove vegetation responses to holocene climate change along konkan coast of south western india abstract the pollen signatures preserved in the mangrove sediments provided records of species variation over a period of time with past climate and sea level changes the airoli profile has a late pleistocene sequence and all the other studied profiles and intervals cover the holocene only the absence of mangrove signatures during the late pleistocene interval is attributed to a relatively low sea level the ideal conditions for mangrove development along konkan prevailed during middle holocene when the first extensive mangrove swamps appeared in sindhudurg dhamapur hadi area particularly between 7220 and 4770 yrs bp this period coincides with the holocene climate optimum hco when monsoon asia witnessed much higher precipitation however the mangroves responded to environmental changes due to relative abundance of fresh water leading to change in species composition two different scenarios of mangrove response during the late holocene one in dhamapur and the other in palm beach are found to be significant the rhizophora sonneratia transition from early mid holocene to late holocene is considered to be the most distinctive feature the decline of mangroves since 3500 yrs bp and further degradation has been attributed to the prevailing arid climate and weakening trends of the monsoon until 1500 yrs bp however there seems to be a positive trend in emergence of mangroves in the least disturbed areas of south konkan attributed to strengthening of summer monsoon in the recent past

downward propagating temperature anomalies in the preconditioned polar stratosphere abstract dynamical links of the northern hemisphere stratosphere and troposphere are studied with an emphasis on whether stratospheric changes have a direct effect on tropospheric weather and climate in particular downward propagation of stratospheric anomalies of polar temperature in the winter spring season is examined based upon 22 years of ncep ncar reanalysis data it is found that the polar stratosphere is sometimes preconditioned which allows a warm anomaly to propagate from the upper stratosphere to the troposphere and sometimes it prohibits downward propagation the arctic oscillation ao is more clearly seen in the former case to understand what dynamical conditions dictate the stratospheric property of downward propagation the upper stratospheric warming episodes with very large anomalies such as stratospheric sudden warming are selected and divided into two categories according to their downward propagating features eliassen palm e p diagnostics and wave propagation theories are u

eastward travelling waves in the southern hemisphere stratosphere during the spring of 1983 this paper presents a case study of planetary waves in the southern hemisphere stratosphere during the spring of 1983 using the global temperature and geopotential height data provided by the united states national meteorological center nmc the eastward travelling wave of zonal wavenumber 2 with a period of 9 2 days persisted from mid september to early november it had a phase structure which showed only slight tilt with height and latitude while the quasi stationary wave 1 tilted westwards with increasing height and towards the equator during the vigorous period of the eastward travelling wave 2 the amplitude of the quasi stationary wave 1 varied with a period of about 10 days this variation was due to a coincidence between the phases of the stationary wave 1 and the eastward travelling wave 2 when the ridges of waves 1 and 2 overlap wave 1 amplitude reaches its maximum the active period of the travelling wave 2 is closely related to the seasonal change in the mean zonal winds in 1983 the eastward travelling wave 2 became vigorous after the zonal mean westerly jet moved rapidly poleward and downward compared with the other 5 years for which we have data the wind structure for the month of september 1983 was peculiar because of the stronger meridional curvature of the westerly jet

precipitation over the interior east antarctic ice sheet related to midlatitude blocking high activity abstract intermittent atmospheric blocking high activity in the south tasman sea is shown to play a key role in delivering substantial snowfall as far south as at least 75 s on the central east antarctic ice sheet plateau typically cyclones fail to penetrate this far 1000 km inland and accumulation was thought to be dominated by clear sky precipitation in east antarctica the meridional cloud bands delivering the moisture originate from as far north as 35 40 s and appear to preferentially pass over the east antarctic coast in a corridor from 120 to 160 e comparison of surface observations model and satellite data suggests that a few such episodes contribute a significant proportion of the low mean annual accumulation of the central east antarctic ice sheet e g an estimated 44 at dome c over 18 days in december 2001 january 2002 blocking high related incursions also cause abrupt increases in the surface wind speed snow redistribution and air temperature this has implications for th

intraseasonal dynamical evolution of the northern annular mode abstract the northern hemisphere annular mode nam accounts for a significant fraction of the extratropical wintertime atmospheric variability the dynamics of nam events have been studied on monthly time scales but little is known about the physical mechanisms that give rise to nam variability on shorter time scales composite diagnostic analyses based on daily nam indices are performed with a goal of identifying the dominant processes responsible for the growth and decay of large amplitude positive and negative nam events on short intraseasonal time scales transformed eulerian mean piecewise potential vorticity inversions and regional plumb flux diagnoses are employed to deduce the proximate forcings of the zonal mean wind tendency during maturing and declining nam stages a remarkable degree of reverse symmetry is observed between the zonal mean dynamical evolution of positive and negative nam events anomalous equatorward and downward poleward and upward eliassen palm fluxes are observed during

blocking over the south pacific and rossby wave propagation abstract atmospheric blocking events over the south pacific are investigated using a 39 yr record of 500 hpa height fields from the ncep ncar reanalysis dataset the analysis extends earlier work using a 16 yr record and confirms that the occurrence of blocking over the southeast pacific is strongly modulated by the enso cycle during austral spring and summer comparison of results at 500 hpa with the 300 hpa meridional wind component showed that blocking events are associated with large scale wave trains lying across the south pacific from the region of australia to southern south america similar wave trains are evident in both hemispheres in singular value decomposition analyses between 300 hpa meridional wind components and tropical pacific outgoing longwave radiation olr anomalies the hypothesis that the divergence associated with tropical olr anomalies forces an extratropical wave response that results in enhanced blocking over the southeast pacific was tested using a linearized barotropic vorti

midwinter warmings in the southern hemisphere stratosphere in 1988 an analysis was made of intense midwinter warmings which took place in the southern hemisphere stratosphere during august september 1988 by using the southern hemispheric data set up to the 1 mb level provided by the japan meteorological agency it is found that the 30mb temperature increase over eastern antarctica about 60 k for 10 days from 22 august to 1 september is associated with the amplification of a quasi stationary planetary wave of zonal wavenumber 1 the enhancement of wave 1 appears quasi periodically with a period of about 2 weeks during the midwinter of 1988 clear evidence is presented to show that the quasi periodic amplification of wave 1 is due to the wave wave interaction between the quasi stationary forced wave of wavenumber 1 and the eastward travelling wave of wavenumber 2 it is emphasized therefore that the mechanism of warming in this case is quite different from that of the transient vertical propagation of a planetary wave forced from below as observed in the northern hemisphere winter

permafrost heat flow and the geothermal regime at prudhoe bay alaska temperature measurements through permafrost in the oil field at prudhoe bay alaska combined with laboratory measurements of the thermal conductivity of drill cuttings permit an evaluation of in situ thermal properties and an understanding of the general factors that control the geothermal regime a sharp contrast in temperature gradient at approx 600 m represents a contrast in thermal conductivity caused by the downward change from interstitial ice to interstitial water at the base of permafrost under near steady state conditions interpretation of the gradient contrast in terms of a simple mode for the conductivity of an aggregate yields the mean ice content approx 39 and thermal conductivities for the frozen and thawed section 8 1 and 4 7 mcal cm s sup 0 c respectively these results yield a heat flow of approx 1 3 hfu which is similar to other values on the alaskan arctic coast the anomalously deep permafrost is a result of the anomalously high conductivity of the siliceous ice rich sediments curvature in the upper 160 m of the temperature profiles represents a warming of approx 1 8 sup 0 c of the mean surface temperature and a net accumulation of 5 6 kcal cm sup 2 by the solid earth surface during the last 100 years or so rising sea levelmore and thawing of ice rich sea cliffs probably caused the shoreline to advance tens of kilometers in the last 20 000 years inundating a portion of the continental shelf that is presently the target of intensive oil exploration a simple conduction model suggests that this recently inundated region is underlain by near melting ice rich permafrost to depths of 300 500 m its presence is important to seismic interpretations in oil exploration and to engineering considerations in oil production with confirmation of the permafrost configuration by offshore drilling heat conduction models can yield reliable new information on the chronology of arctic shorelines less

influence of large scale atmospheric circulation on marine air intrusion toward the east antarctic coast marine air intrusions into antarctica play a key role in high precipitation events here we use shipboard observations of water vapor isotopologues between australia and syowa on the east antarctic coast to elucidate the mechanism by which large scale circulation influences marine air intrusions the temporal isotopic variations at syowa reflect the meridional movement of a marine air front they are also associated with atmospheric circulation anomalies that enhance the southward movement of cyclones over the southern ocean the relationship between large scale circulation and the movement of the front is explained by northerly winds which in association with cyclones move toward the antarctic coast and push marine air with isotopically enriched moisture into the inland covered by glacial air with depleted isotopic values future changes in large scale circulation may have a significant impact on the frequency and intensity of marine air intrusion into antarctica

abrupt changes in meteorological conditions observed at an inland antarctic station in association with wintertime blocking time evolution of a prominent wintertime blocking event over east antarctica and the associated drastic changes in weather conditions observed at an inland station are documented a strong blocking ridge was formed at the leading edge of a quasi stationary rossby wavetrain where a wave activity flux emanating from the subtropics was convergent the ridge pumped up heat and moisture from lower latitudes into inland antarctica with a strong poleward flow along its upstream flank the station was situated under this flow just for two days during which the normal condition with cold and clear weather was markedly disturbed the flow climbing up the continental slope led to cloud formation above the inland station enhanced downward longwave radiation from the clouds and enhanced vertical mixing associated with the record setting wind speeds resulted in a sudden drastic increase in surface air temperature and the breakdown of the developed surface inversion layer

dynamical connection between the stratospheric arctic vortex and sea surface temperatures in the north atlantic we used two long term reanalysis datasets and time slice simulations to examine the decadal relationship between the stratospheric arctic vortex sav and sea surface temperature anomalies sstas in the north atlantic and the dynamic mechanisms involved in the linkage between the two our results show that there is a significant decadal linkage between sstas over the north atlantic and the sav where warmed cooled sstas over the north atlantic in association with its principal mode correspond to a weakened strengthened sav the warmed north atlantic sstas tend to result in a weakened sav via two dynamic processes 1 constructive interference at high latitudes with a ridge in the atlantic sector and a trough in the pacific accompanied by a negative north atlantic oscillation like pattern over the north atlantic and a weakened aleutian low over the north pacific and 2 more wavenumber 1 waves propagated into the arctic stratosphere by modifying the baroclinic term of the zonal mean background state and altering the propagating conditions around the tropopause over the arctic results from reanalysis and model simulations both suggest that a strengthening wave intensity in the high latitude troposphere and more upward propagation of the planetary wavenumber 1 wave in response to the warmed north atlantic sstas conjunctly contribute to the increased planetary wave flux in the arctic stratosphere facilitating a weakened sav these results provide a new understanding of what dynamic processes control the sav and will help to predict the stratosphere on decadal timescales

the role of synoptic scale features and advection in prolonged warming and generation of different forms of precipitation at dome fuji station antarctica following a prominent blocking event 1 a blocking event over the east antarctic ice sheet during june 1997 generated the highest surface air temperature which increased from around 70 c to around 30 c and pressure of that year at the dome fuji station 77 5 s 40 e following the blocking event the anomalously high air temperature around 50 c to 60 c and pressure were maintained at the surface for about 1 week this study investigates how these warm conditions were maintained and documents the sequential occurrence of two forms of synoptic scale high pressure systems with conditions that produced precipitation by different processes in each case in the first half of the warm period a solitary high pressure system the solitary high formed over the dome fuji station and traveled west over east antarctica after being cut off from the tip of the preceding blocking ridge during this phase tropospheric temperatures were higher and surface based temperature inversions were more intense than during the following period while a dry out developed in the troposphere below about 300 hpa the precipitation of ice crystals in the surface based temperature inversion layer was generated by deposition of moisture that had become trapped in the boundary layer after being transported onto the continent by the previous blocking ridge this mechanism has not been previously reported elsewhere during the second half of the warm period a ridge of high pressure the transcontinental ridge traversed east antarctica almost completely and its western section was amplified by the merging of the solitary high with a preceding quasi stationary rossby wave train propagating along the southern ocean this ridge allowed an intrusion of warm moist air from the weddell sea toward the station which generated precipitation throughout the whole troposphere by orographic uplift once again and ended the dry out this represents the typical mechanism of both moisture transportation and the generation of precipitation and this mechanism was the same as that associated with the preceding blocking ridge

a climatology of the northern hemisphere winter anticyclones 1 a climatology of the northern hemisphere winter anticyclonic activity is presented based on the european centre for medium range weather forecasts reanalysis data set for the 1957 2002 period era 40 and a system centered method of tracking diagnostics the method tracks the anticyclonic systems and monitors their evolution along their paths thus allowing documentation of aspects that have been previously overlooked due to the common perception of anticyclones as semi stationary relatively uniform slowly evolving structures the anticyclonic signal is examined in a wide range of meteorological fields and at multiple levels over the continental masses over the subtropical ocean basins and over the sectors where blocking highs tend to develop structural features thermal and vorticity properties and mobility characteristics of the corresponding anticyclones are highlighted over continental regions an association with low level pools of cold air is found to be prevalent for the eurasian anticyclones but less so for the north american anticyclones in the subtropical zone the anticyclonic signal in the regions affected by the winter monsoon including southeastern asia and the western pacific features prominently in the upper levels in the eastern sectors of the subtropical ocean basins the anticyclonic signal is less deep intense anticyclonic development at low levels is also identified over the western sectors of the subtropical continents where it appears associated to the effect of orography and of low level cooling the dominant type of anticyclone observed in the regions of blocking is characterized by 5 6 days timescales and considerable eastward mobility