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

bitumen as a hafting material on middle palaeolithic artefacts a scraper and a levallois flake discovered in the mousterian levels dated around 40 000 bc of the umm el tlel site in syria were submitted to an organic geochemieal study to identify a black substance occurring on their surface the shape of this black substance suggests that the organic traces are remnants of a hafting material used by middle palaeolithic people to glue handles onto their tools gas chromatography mass spectro metry gc ms analyses of both c15 alkanes and c15 aromatics confirm that the black substance is a highly weathered bitumen the source of which remains unknown according to some diagnostic molecular information for example the occurrence of fluoranthene and pyrene it seems that the raw bitumen used has been subjected to extreme temperature the scraper and the levallois flake described here are to the best of our knowledge the first reported examples of middle palaeolithic artefacts hutted with bitumen to handles

on the effectiveness of 2d electrical inversion results an agricultural case study electrical resistivity tomography was used in beauce france to assess the water extraction by corn plants evapotranspiration the acquired pseudosections show conductive anomalies under the plants a 2d inversion of measurements led us to identify clear resistive features associated with the water losses under the corn plant rows new models have been calculated with two different 3d algorithms finite difference and moment method to take into account 3d structure of the ground and to confirm that periodic resistive features may generate shifted apparent resistivity anomalies

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

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

an experimental study of crude oil alteration in reservoir rocks by water washing abstract the objective of this research was to establish the effect of water washing on the physical and chemical properties of crude oils to simulate water washing under reservoir conditions crude oil was washed in sandstone and limestone cores by as much as 240 liters of a degassed bacteria free water over a period of up to 149 days at 90 c 194 f under a confining pressure of 138 bars 2000 psi in a flow through core holder unit the water washed oils were recovered by soxhlet extraction compared to the original oils water washed oils show lower api gravities lower concentrations of light aromatic compounds such as phenanthrene and dibenzothiophene lower metal and sulfur content lower light paraffins with respect to heavy paraffins and isoprenoids more negative stable carbon isotopic ratios for the nso fraction lower diterpane content relative to triterpane content lower c 27 steranes relative to c 30 hopane and 4 methyl sterane and altered bicyclic alkane and aromatic steroid biomarkers oils washed in limestone cores show a more severe reduction in api gravity and loss of aromatics than those in sandstone cores these changes can be used to discern the effects of water washing from those caused by biodegradation deasphalting and maturation of related crude oils diterpane triterpane and sterane biomarkers are little affected by water washing and therefore can be used to correlate water washed oils with related unaltered oils and source rocks and to assess the depositional environments of the source rocks for the water washed oils although these experiments did not produce tarmat tarmat formation by water washing over geological time cannot be ruled out the api gravity sulfur and metal content of oils may be reduced by water injection

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

formation of immature asphalt from organic rich carbonate rocks i geochemical correlation abstract the formation of low maturity asphaltic oils immature asphalts from carbonate source rocks was investigated the senonian bituminous rocks sbr in israel are organic rich carbonate rocks that were deposited in a high productivity environment and they are part of a sedimentary sequence that also contains cherts and phosphorites the sbr were studied in different basins and the samples are from outcrops and three deep drillholes the bitumen contents of the rocks are exceptionally high up to 700 mg g c org and immature asphalts are found to be associated with them geochemical analysis indicates that the bitumens are indigenous to the host sbr and the associated asphalts are bitumens that have migrated a short distance with negligible chemical fractionation the high heteroatom content of the kerogens up to 30 in the sbr is suggested as a possible cause of the generation of asphaltic oils in an early stage of maturation

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

annular modes in a multiple migrating zonal jet regime the authors investigate the dynamics of zonal jets in a semihemisphere zonally reentrant ocean model the forcings imposed in the model are an idealized atmospheric wind stress and relaxation to a latitudinal temperature profile held constant in time while there are striking similarities to the observed atmospheric annular modes where the leading mode of variability is associated with the primary zonal jet s meridional undulation secondary weaker jets emerge and systematically migrate equatorward the model output suggests the following mechanism for the equatorward migration while the eddy momentum fluxes sustain the jets the eddy heat fluxes have a poleward bias causing an anomalous residual circulation with poleward equatorward flow on the poleward equatorward flanks by conservation of mass there must be a rising residual flow at the jet from the thermodynamics equation the greatest cooling occurs at the jet core thus creating a tendency to reduce the baroclinicity on the poleward flank while enhancing it on the equatorward flank consequently the baroclinic zone shifts perpetuating the jet migration

seasonal evolution of the qbo induced wave forcing and circulation anomalies in the northern winter stratosphere diagnostics of wave mean flow and wave wave interactions in isentropic coordinates are analysed regarding the mechanisms that govern the holton tan effect hte whereby the tropical quasi biennial oscillation qbo modulates the northern winter stratospheric polar vortex we find a clear seasonal evolution of a qbo modulation of rossby waves and linear and nonlinear wave interactions along with multiple mechanisms at work in early winter when the lower stratospheric qbo is easterly there is enhanced upward stationary planetary wave activity in the subtropical to midlatitude lower stratosphere these upward propagating waves are first refracted towards the zero wind line approximately one month later poleward propagating wave anomalies appear at midlatitudes as a result of nonlinear wave interactions the enhanced upward wave propagation appears to be due to a combination of the qbo influence on the latitudinal location of the zero wind line and the increased midlatitude baroclinicity associated with the qbo induced meridional circulation this is further aided by a gradual poleward shift over the winter of the middle stratospheric waveguide refracting waves poleward the associated wave breaking weakens the polar vortex and drives a stronger meridional circulation throughout the lower to middle stratosphere contributing to the high latitude warming it is additionally found that in late winter the modified high latitude waveguide associated with the weaker polar vortex consequently reduces upward propagating transient planetary waves at high latitudes whilst simultaneously enhancing upward propagating synoptic waves at midlatitudes this highlights the need to view the hte and its mechanisms as an evolving phenomenon throughout the winter

modulation of northern hemisphere wintertime stationary planetary wave activity east asian climate relationships by the quasi biennial oscillation 1 the modulation of the relationship between the tropospheric stationary planetary wave activity and the east asian winter climate by the tropical quasi biennial oscillation qbo wind in the stratosphere is investigated in the qbo easterly phase a significant warming appears in northeastern asia in the presence of high wave activities this corresponds to a weakened east asian trough at 500 hpa which determines the extent to which cold waves penetrate into east asia however in the qbo westerly phase both the surface warming and the weakening of the east asian trough become insignificant in response to high wave activities the possible mechanism for this qbo modulation on the tropospheric wave activities may be attributed to the indirect influence of the qbo induced polar and extratropical stratospheric circulation changes under the qbo easterly phase conditions the tropospheric wave activity flux divergence in the higher latitude region is enhanced due to enhanced upward eliassen palm ep flux into the stratosphere while the wave flux convergence in the subtropical troposphere is increased due to the decrease in the equatorward flux this leads to an enhanced wave activity difference and thus the associated east asian climate anomalies become larger and robust an opposite effect i e reduced wave activity difference appears in the qbo westerly phase further analyses reveal that the qbo significantly modulates both the zonal wave number 1 and 2 in the sea level pressure field but not for wave number 3 the combination of wave number 1 and 2 patterns leads to the strongest surface temperature anomalies in northern asia

the statistical connection between tropospheric and stratospheric circulation of the northern hemisphere in winter abstract the associated anomaly patterns of the stratospheric geopotential height field and the tropospheric geopetential and temperature height fields of the northern hemisphere are determined applying the canonical correlation analysis with this linear multivariate technique the coupled modes of variability of lime series of two fields are isolated in the space of empirical orthogonal functions the one dataset is the 50 hpa geopotential height field the other set consists of different height fields of the tropospheric pressure levels 200 500 700 and 850 hpa and the temperature of the 850 hpa pressure level for the winter months december january february two natural coupled modes a barotropic and a baroclinic one of linear relationship between stratospheric and tropospheric circulation are found the baroclinic mode describes a connection between the strength of the stratospheric cyclonic winter vortex and the tropospheric circulation over the north atlantic the corresponding temperature

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

molecular archaeology export of dead sea asphalt to canaan and egypt in the chalcolithic early bronze age 4th 3rd millennium bc abstract nine archaeological bitumens from excavations in canaan sinai and egypt tel irani ein zik palmahim tel arad jerusalem ein besor site h sheik awad and maadi dated 3900 2200 bc and two natural asphalts of the dead sea area ein gedi floating blocks and nahal heimar have been compared using the following geochemical techniques chloroform extraction and gc and gc ms analyses of c15 alkanes and c15 aromatics isotopic analysis 13c and d on chloroform extracts and asphaltenes and rock eval pyrolysis of the insoluble organic residue all samples are genetically related and are different from other archaeological bitumens from syria and iraq tel irani archaeological bitumen was found to be identical to the floating block asphalts of the dead sea other archaeological bitumens were recognized as having been weathered and biodegraded to various degrees at archaeological sites in the course of the millennia they are regarded as counterparts of floating block asphalts altered by aging this study is the first evidence of the trade and export of raw bitumens from the dead sea area within canaan and to egyptian trading centers on the mainland route to egypt between 3900 and 2200 bc prior to the extensive utilization of bitumen for mummification in ancient egypt

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

asphalts oils and bituminous rocks from the dead sea area a geochemical correlation study oils and asphalts gilsonite from the dead sea area israel were characterized by bulk composition specific c15 hydrocarbons n alkanes isoprenoids steranes triterpanes and aromatics including sulfur compounds and light hydrocarbons c2 to c8 molecular range these indicators complemented by literature data sulfur content sulfur isotope composition and distribution of petroporphyrins define the oils and asphalts as belonging to a single geochemical province the geochemical characteristics suggest a source material of bacterially reworked algae and a source rock poor in clay minerals probably a calcareous rock calcareous bituminous rocks of the campanian maestrichtian ghareb formation are exposed on the margin of the dead sea graben on downwarped blocks and they probably extend under the thick graben fill the agreement of the geochemical indicators suggests that these bituminous rocks are a potential source of the asphalts and oils in the dead sea area differences between the various types of hydrocarbon occurrences are due to a combination of several effects such as variations in source material the thermal history of the different downwarped blocks water washing and biodegradation the distribution characteristics of hydrocarbons c6 to c35 and c2 to c8 is sensitive to biodegradation and or water washing the aromatic fractions except very soluble compounds like benzene toluene etc are less affected by these processes and record the variability due to source and possibly thermal history the interpretation of the triterpane and sterane distribution corroborates that of other hydrocarbons with respect to maturation and type of source rock differences in maturation are pronounced the bituminous rocks and asphalts are immature and the oils are derived from source rocks in an initial stage of petroleum generation

solar wind dynamic pressure effect on planetary wave propagation and synoptic scale rossby wave breaking we provide statistical evidence of the effect of the solar wind dynamic pressure psw on the northern winter and spring circulations we find that the vertical structure of the northern annular mode nam the zonal mean circulation and eliassen palm ep flux anomalies show a dynamically consistent pattern of downward propagation over a period of 45 days in response to positive psw anomalies when the solar irradiance is high the signature of psw is marked by a positive nam anomaly descending from the stratosphere to the surface during winter when the solar irradiance is low the psw signal has the opposite sign occurs in spring and is confined to the stratosphere the negative psw signal in the nam under low solar irradiance conditions is primarily governed by enhanced vertical ep flux divergence and a warmer polar region the winter psw signal under high solar irradiance conditions is associated with positive anomalies of the horizontal ep flux divergence at 55 n 75 n and negative anomalies at 25 n 45 n which corresponds to the positive nam anomaly the ep flux divergence anomalies occur 15 days ahead of the mean flow changes a significant equatorward shift of synoptic scale rossby wave breaking rwb near the tropopause is detected during january march corresponding to increased anticyclonic rwb and a decrease in cyclonic rwb we suggest that the barotropic instability associated with asymmetric ozone in the upper stratosphere and the baroclinic instability associated with the polar vortex in the middle and lower stratosphere play a critical role for the winter signal and its downward propagation

a mechanism to explain the variations of tropopause and tropopause inversion layer in the arctic region during a sudden stratospheric warming in 2009 the mechanism to explain the variations of tropopause and tropopause inversion layer til in the arctic region during a sudden stratospheric warming ssw in 2009 was studied with the modern era retrospective analysis for research and applications reanalysis data and gps constellation observing system for meteorology ionosphere and climate cosmic temperature data during the prominent ssw in 2009 the cyclonic system changed to the anticyclonic system due to the planetary wave with wave number 2 wave2 the gps cosmic temperature data showed that during the ssw in 2009 the tropopause height in the arctic decreased accompanied with the tropopause temperature increase and the til enhancement the variations of the tropopause and til were larger in higher latitudes a static stability analysis showed that the variations of the tropopause and til were associated with the variations of the residual circulation and the static stability due to the ssw larger static stability appeared in the upper stratosphere and moved downward to the narrow region just above the tropopause the descent of strong downward flow was faster in higher latitudes the static stability tendency analysis showed that the strong downward residual flow induced the static stability change in the stratosphere and around the tropopause the strong downwelling in the stratosphere was mainly induced by wave2 which led to the tropopause height and temperature changes due to the adiabatic heating around the tropopause a pair of downwelling above the tropopause and upwelling below the tropopause due to wave2 contributed to the enhancement of static stability in the til immediately after the ssw

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

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

the tropospheric jet response to prescribed zonal forcing in an idealized atmospheric model abstract this paper explores the tropospheric jet shift to a prescribed zonal torque in an idealized dry atmospheric model with high stratospheric resolution the jet moves in opposite directions for torques on the jet s equatorward and poleward flanks in the troposphere this can be explained by considering how the critical latitudes for wave activity absorption change where the eastward propagation speed of eddies equals the background zonal mean zonal wind while the increased zonal winds in the subtropics allow the midlatitude eddies to propagate farther into the tropics and result in the equatorward shift in the critical latitudes the increased winds in the midlatitudes accelerate the eastward eddy phase speeds and lead to the poleward shift in the critical latitudes in contrast the jet moves poleward when a westerly torque is placed in the extratropical stratosphere irrespective of the forcing latitude the downward penetration of zonal winds to the troposphere displays a poleward slope for the

interannual relationship between the boreal spring arctic oscillation and the northern hemisphere hadley circulation extent abstractthis study investigates the interannual relationship and the dynamical linkage between the boreal spring arctic oscillation ao and the northern hemisphere hadley circulation extent hce

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

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

a model study of the dynamical connection between the arctic oscillation and stratospheric vacillations the dynamical connection between the stratosphere and the troposphere in the northern hemisphere winter is investigated with general circulation model gcm simulations under perpetual january conditions the variability in the stratosphere is strongly dominated by vacillations on a timescale of 100 days one point correlation maps of the zonal mean zonal wind reveal the characteristic downward propagation of the stratospheric disturbances the meridional structure of the stratospheric vacillations is well described by a few empirical orthogonal functions eofs of geopotential height the leading eof describes a standing oscillation of the stratosphere while the two next describe the vertical and horizontal propagation in the troposphere the leading eof of the surface pressure shows the characteristic circumpolar structure of the arctic oscillation the covariance between the leading eof of the surface pressure and the zonal mean zonal wind reveals a vertical structure similar to the observed below 10 hpa while the sign of the covariance changes above 10 hpa where observations are scarce the downward propagating stratospheric modes play a prominent role in the vertical coupling singular value decomposition of the cross covariance matrix between the stratospheric zonal mean zonal wind and the surface pressure shows that a significant part of the tropospheric variability can be related to the downward propagating anomalies the leading pattern of surface pressure anomalies found in this way closely resembles the pattern of the arctic oscillation and describes 20 30 of the total variance this result is confirmed by studying the covariance between the geopotential height fields and the stratospheric principal components

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

the organic geochemistry of the hasbeya asphalt lebanon comparison with asphalts from the dead sea area and iraq abstract the hasbeya asphalt from lebanon and the mezar 1 asphalt from the golan heights were analyzed using current tools of petroleum geochemistry namely isotopic analyses d 13 c 34 s and molecular sterane and terpane parameters the geochemical properties of these asphalts were compared to several other asphalts from israel floating blocks of the dead sea massada nahal heimar iprg all the asphalts belong to the same genetic family e g high gammacerane and high steroid contents no diasteranes and originate from senonian upper cretaceous organic matter rich carbonate source rocks deposited in an anoxic or dysoxic perhaps hypersaline palaeoenvironment this family of asphalts is well differentiated from another famous asphalt from the near east the hit abu jir asphalt from iraq the hasbeya asphalt is slightly biodegraded whereas the mezar 1 asphalt was affected by more severe biodegradation occurrence of 25 nor hopanes isotopic ratios of asphaltenes were found to be useful in allowing differentiation of asphalts from the same genetic family this study completes the existing knowledge on dead sea asphalts by demonstrating that similar asphalts may be identified within a much larger geographic area including the golan heights and lebanon these results raise the question of whether some of the archaeological asphalts that are found in the southern fertile crescent egypt israel syria etc and which were assumed to be of dead sea origin may actually have come from hasbeya

asphalt in iron age excavations from the philistine tel miqne ekron city israel origin and trade routes asphalts found as pure lumps or coatings on potsherds were excavated at the philistine site of tel miqne ekron 12th to 7th century bc in the southern inner coastal plain of israel they were studied using the techniques of petroleum geochemistry and were compared to some natural asphalts from the area dead sea floating blocks israel wadi weida a asphalt jordan and hasbeya lebanon tel miqne ekron bitumens show evidence of weathering indicating biodegradation and oxidation they contain less aromatics and more asphaltenes than dead sea asphalt evaporation and biodegradation are recorded at a molecular level especially via the phenanthrenes and dibenzothiophenes however several isotopic and molecular parameters allowed us to correlate the tel miqne ekron asphalt with the dead sea asphalt from the floating blocks the asphalts of hasbeya and wadi weida a do not match the tel miqne ekron asphalt the latter in particular is much more biodegraded based on its steranes the study shows that the dead sea asphalt was imported to tel miqne ekron over a 500 year period this trade posed no problem in the 7th century bc when philistia israel and judah were at peace as part of the pax assyriaca of the assyrian empire however trade during the 12th century bc is puzzling since the asphalt had to be transported across israelite territory that was hostile to the philistines as indicated in the bible e g samson and delilah david and goliath consequently it seems that profitable commerce surpassed ethnic religious and political conflict as can also be observed in the contemporary world

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

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

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

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

eddy zonal flow feedback in the northern hemisphere winter abstract the variability of the zonal mean zonal wind in the northern hemisphere winter december march is studied using eof analysis and momentum budget diagnostics of ncep ncar reanalysis data 1976 2001 the leading eof of the zonal mean zonal wind is well separated from the remaining eofs and represents the north south movement of the midlatitude westerlies analysis of the momentum budget shows that a positive feedback between the zonal mean wind anomalies and the eddy momentum fluxes selects the leading eof of midlatitude variability like the southern hemisphere the baroclinic eddies reinforce the zonal wind anomalies while external rossby waves damp the wind anomalies in the northern hemisphere the quasi stationary eddies also reinforce the zonal wind anomalies but the baroclinic eddies are most important for the positive eddy zonal flow feedback the observations support the following feedback mechanisms 1 above normal baroclinic wave activity is generated in the region of enhanced wester