a meteorological analysis of the 2013 alberta flood antecedent large scale flow pattern and synoptic dynamic characteristics abstractthe 19 21 june 2013 alberta flood was the costliest cad 6 billion natural disaster in canadian history the flood was caused by a combination of above normal spring snowmelt in the canadian rockies large antecedent precipitation and an extreme rainfall event on 19 21 june that produced rainfall totals of 76 mm in calgary and 91 mm in the foothills as is typical of flash floods along the front range of the rocky mountains rapidly rising streamflow proceeded to move downhill eastward into calgary a meteorological analysis traces an antecedent rossby wave train across the north pacific ocean starting with intense baroclinic development over east asia on 11 june subsequently downstream rossby wave development occurred across the north pacific a 1032 hpa subtropical anticyclone located northeast of hawaii initiated a southerly atmospheric river into alaska which contributed to the development of a cutoff anticyclone over alaska and a rex block ridge to the north cyclone to the south in

new constraint on the division of cambrian time a u pb zircon age of 530 7 0 9 ma for a volcanic ash in the lower placentian series of the avalonian terrane in southern new brunswick provides a precise point for calibration of early cambrian biologic evolution the ash is from the middle rusophycus avalonensis zone in saint john new brunswick this date is on subtrilobitic lower cambrian strata that may be approximately correlative with the sub tommotian manykaian stage of siberia and the lowest meishucunian stage of the south china platform this age when combined with published geochronologic data from the cambrian suggests that the manykaian stage may have lasted approximately 13 m y and that the tommotian may have been considerably shorter

climatology of anticyclonic and cyclonic rossby wave breaking on the dynamical tropopause in the southern hemisphere abstract the characteristics of the climatological distribution of the anticyclonic lc1 and cyclonic lc2 rossby wave breaking rwb in the southern hemisphere sh are investigated by calculating the occurrence frequency of the lc1 and lc2 like stratospheric potential vorticity pv streamers in the sh during the austral summer december february djf and wintertime june august jja on several isentropic surfaces by using the 40 yr european centre for medium range weather forecasts ecmwf re analysis era 40 daily dataset the results show that 1 on the equatorward flank of the climatological midlatitude jet mlj the lc1 like pv streamers are frequently found over the central oceanic regions whereas the lc2 like pv streamers are almost absent on the poleward flank of the climatological mlj both types of pv streamers are frequently observed and the lc2 like pv streamers predominate 2 the regions where the occurrences of the pv streamers are frequent overlap the weak zonal wind regions

far upstream precursors of heavy precipitation events on the alpine south side this study examines the upper level flow pattern that foreshadows the comparatively frequent co occurrence of heavy precipitation events on the alpine south side together with potential vorticity pv streamers aloft over western europe it is hypothesized that each streamer is itself preceded by a dynamically distinctive and a thermodynamically active flow associated with the space time development and the ultimate breaking over europe of synoptic scale rossby waves the ecmwf european centre for medium range weather forecasts era 40 dataset is used to examine the nature of a streamer s coherent precursor pattern by deriving seasonal composites of refined hovmoller diagrams the upper level pattern of the pv and its gradient and mid tropospheric diabatic heating for the autumn and winter seasons the composites reveal a significant and coherent wave packet precursor signal in the pv field that can be traced back 1 week to the central and eastern pacific contemporaneously the coherent signatures in the composite pv gradient field and diabatic heating fields are conducive to triggering and or supporting the wave signal and also contribute to subsequent downstream wave breaking in spring the composite precursor pv signal appears over and propagates eastward from the atlantic basin and its limited zonal extent is attributed to the lack of a coherent pv waveguide in summer the signal appears essentially in situ in the hovmoller analysis but extends across the atlantic basin in the pv composite results an indication is also provided of the extent to which the composite characteristics are evident in two individual events and note is made of the study s implications for medium range forecasting copyright 2008 royal meteorological society

three new upper cambrian stages for north america the existing upper cambrian stages for north america are obsolete three new stratotype defined stages are equivalent to and replace three successive biomeres marjuman stage replaces marjumiid biomere lower boundary at base ptychagnostus atavis zone steptoean stage replaces pterocephaliid biomere lower boundary at base aphelaspis zone sunwaptan stage replaces ptychaspid biomere lower boundary at base irvingella major subzone the base of the overlying ibexian series is placed at the base of the eurekia apopsis subzone

the morphology of northern hemisphere blocking abstract the morphology of regional blocking in the northern hemisphere is discussed using the 40 yr ecmwf re analysis era 40 dataset and a measure of blocking based on the reversal at storm track latitudes of meridional contrasts on a potential vorticity pv surface representative of the tropopause the focus is on cyclonic and anticyclonic rossby wave breaking that is inherent to the blocking development and the extent to which this is determined by the climatological jet position and the ambient shears more generally the importance of the climatological planetary scale is discussed the approach is mainly through composite behavior but informed by consideration of many individual events a diversity of behavior is found with longitude in both winter and summer and there is a striking reversal of the sense of the wave breaking between the two seasons that is generally consistent with the difference in the jet locations preferred behaviors are found in various regions and seasons and retrogre

a quantitative fluorescence technique for evaluating thermal maturity instrumentation and examples abstract fluorescence microscopy is useful not only for identifying most of the oil prone organic matter macerals in sedimentary rocks and coals but also for assessing their thermal maturities ranks this report introduces a violet light excitation system which induces more than one order of magnitude stronger fluorescence intensity that the commonly used uv light excitation system the red green quotient from violet light excited fluorescence q v of sporinite can be easily measured using this system several examples using coal and cuttings samples are presented to demonstrate the use of this technique for evaluating the thermal maturities of coals and sedimentary rocks from the results of our studies we conclude that 1 1 violet light excited fluorescence from sporinites can be routinely measured to assess thermal maturity 2 2 spectral quantitative fluorescence technique is useful for evaluating thermal maturity when samples are poorly polished or deficient in vitrinite 3 3 visual strew mounted kerogen slides can not be used for fluorescence measurements unless a non fluorescent mounting medium is used

coherent synoptic disturbances in the australian monsoon abstractcoherent synoptic scale weather systems within the australian monsoon are identified and tracked in the isentropic potential vorticity pv field from the ecmwf interim reanalysis era interim dataset during the southern hemisphere summer the resulting dataset is then used to compile statistics and synoptic composites of australian monsoon disturbances on average a synoptic system is found in the region every 2 5 days however the time interval between consecutive events is highly variable meaning that the synoptic activity in the australian monsoon is not well represented by commonly employed spectral techniques the analysis reveals that most synoptic systems originate within the australian monsoon but at the 315 k level approximately 700 hpa a significant proportion of systems are first detected near the east coast of the continent where extratropical rossby waves are observed to frequently break the average australian monsoon weather system propagates from east to west at approximatel

connections between potential vorticity intrusions and convection in the eastern tropical pacific abstract the connections between intrusions of stratospheric air into the upper troposphere and deep convection in the tropical eastern pacific are examined using a combination of data analysis potential vorticity pv inversion and numerical simulations analysis of ncep ncar reanalyses and satellite measurements of outgoing longwave radiation during intrusion events shows increased cloudiness lower static stability upward motion and a buildup of convective available potential energy cape at the leading edge of the intruding tongue of high pv potential inversion inversion calculations show that the upper level pv makes the dominant contribution to the changes in the quantities that characterize convection this supports the hypothesis that upper level pv anomalies initiate and support convection by destabilizing the lower troposphere and causing upward motion ahead on the pv tongue the dominant role of the upper level pv is confirmed by simulations using the fifth generation pennsylvania state u

long lived rossby wave trains as precursors to strong winter cyclones over europe the statistical connection between strong surface cyclones over europe and long lived upper tropospheric rossby wave trains is examined for the northern hemisphere winter season using 45 years of reanalysis data dates are selected for which the surface pressure anomaly over central europe is below a threshold yielding the 5 of lowest values composites of upper tropospheric meridional wind for these dates including a lead or lag in time display clear signs of a wave train the composite wave train lives for over two weeks and propagates eastward over more than 360 longitude the phase speed of individual lows and highs by contrast is close to zero and the same is true for the composite surface low there is a pronounced northward shift of the wave train as it propagates over the north american east coast although this composite wave train is statistically highly significant there is large scatter about the mean an index is defined that quantifies the similarity of the upper tropospheric meridional wind pattern for an arbitrary date with the composite wave train for a certain lead or lag given large positive values of the index there is an enhanced probability of a strong surface cyclone over central europe a few days later comparison with a previous study focusing on pacific cyclones shows noteworthy differences

two paradigms of baroclinic wave life cycle behaviour two idealized baroclinic wave 6 life cycles examined here suggest a framework of opposite extremes a in which to view the behaviour of real synoptic scale disturbances in middle latitudes and b in which to interrelate the synoptic and wave theoretic viewpoints using the saturation propagation saturation sps picture of wave 6 life cycle behaviour the two life cycles dented by lc1 and lc2 are higher resolution versions of the simmons hoskins basic and anomalous cases showing strong and weak late decay of eddy kinetic energy eke they illustrate in varying degrees two extreme types of behaviour here disignated anticyclonic and cyclonic and epitomized by strongly contrasting upper air trough behaviour anticyclonic behaviour dominates the late stages of lc1 and is characterized by backward tilted thinning troughs being advected anticyclonically and equatorward as in the commoner cases of planetary scale mid stratospheric rossby wave breaking cyclonic behaviour dominates lc2 and is characterized by forward tilted broadening troughs wrapping themselves up cyclonically and poleward producing major cut off cyclones in high latitudes these morphologies are visualized by upper air maps of potential temperature on the nominal tropopause defined as a constant potential vorticity surface some atmospheric mid latitude disturbances examined here using the same visualization applied to operational analyses show the same two extreme types of trough behaviour together with intermediate cases the sps picture is re examined using eliassen palm and refractive index cross sections it is shown in particular by reference to a wave activity theorem of haynes that the late stages of lc2 can be looked upon as a remarkably clear and morphologically novel large amplitude counterpart of the nonlinear reflection scenario of rossby wave critical layer theory the late stages of lc1 by constrast look more akin to an nonlinear critical layer absorption scenario lc2 exhibits region of largely undular pv contours adjacent to a nonlinear of irreversiby deformen pv contous in the latter region pv rearrangement and hence absorption of rossby wave activity has largely ceased this accounts for the more persistent ekee in the lc2 case

photometric methods for measuring the thermal maturity on strew mounted kerogen slides abstract the optical examination of strew mounted kerogen slides is essential for evaluating the source quality and thermal maturity of potential source rocks the methods currently used to assess thermal maturity on kerogen slide should be improved because the data currently obtained are qualitative and operator dependent the use of two photometric methods to measure the thermal maturity of kerogen on strew mounted slides are introduced the kerogen analyst can measure the transmittance of spore pollen and the reflectance of vitrinite on a kerogen slide and convert the data to a calibrated thermal maturity scale tai thermal alteration index the advantages of using the photometrically measured transmittance and reflectance to assess the thermal maturity of a sample are 1 the method is semi quantitative 2 the parameters measured are physically defined and are easy for interlaboratory comparison of the data 3 the parameters measured supplement each other and 4 this method is applicable at all levels of maturity major limitations of this photometric methods are 1 the vitrinite reflectance is less reliable when measured from the kerogen slides of immature samples and 2 the palynomorph transmittance is thickness dependent

convective destabilization by upper level troughs the approach of an upper level trough is accompanied by a local ascent of the isentropic surfaces in the troposphere the associated cooling and moistening destabilizes the atmosphere to convection in this paper we attempt to quantify the maximum amount of destabilization as a function of the amplitude and horizontal scale of the trough the trough is represented by an elongated potential temperature perturbation on the tropopause its structure including the isentrope displacement it produces is calculated from the balanced shear line solutions of juckes these solutions are used to estimate the amount by which mid and lower tropospheric air masses are lifted when an upper tropospheric trough passes overhead on the assumption that isentropic potential vorticity anomalies are localized in the upper troposphere the amount of destabilization is characterized by the maximum change in convective available potential energy cape and convective inhibition cin brought about by the passage of the trough the calculations seek to isolate one aspect of the interaction between an upper level trough and a tropical cyclone we show that the changes in cape are significant in the tropics up to 83 for the soundings examined and even more so in the middle latitudes up to 130 and that the cin may be completely removed

testing patterns and causes of faunal stability in the fossil record with an example from the pliocene lusso beds of zaire abstract two central issues emerge from recent discussions of coordinated stasis in the fossil record testing pattern and testing causality testing the generality of brett and baird s observations of faunal stability in the paleozoic appalachian foreland basin is important to determine whether such clustering of evolutionary and ecological change into relatively brief intervals of time is a general phenomenon in the fossil record or a quirk of that particular time and place methods for assessing the linkage between paleoecological and evolutionary change are discussed using examples drawn from the molluscan faunas of the pliocene edward mobutu basin of zaire and uganda in the late pliocene lusso beds of eastern zaire an interval of paleoecological and morphological stability appears to be terminated by an episode of coordinated change this paper illustrates a quantitative approach to simultaneously testing for the presence of coordinated change in paleoecological composition and species morphology with due attention to taphonomic and stratigraphic controls testing for the generality of faunal stability in the fossil record is a relatively straightforward exercise causality however is a thornier issue three broad classes of explanation for the presence of coordinated faunal change in the fossil record can be identified in the literature these span a continuum from the purely evolutionary through combined evolutionary ecological to purely ecological explanations i argue here that the critical test to distinguish between different causal hypotheses for coordinated faunal stability and turnover is an examination of correlation between environmental change and biotic change in the fossil record

the influence of tropical cyclones on heat waves in southeastern australia 1 heat waves in southeastern australia in summer are commonly associated with slow moving surface high pressure systems which result in warm northerly flow from the continental interior the underlying dynamical pattern of heat waves in this region is associated with propagating rossby waves which grow in amplitude and eventually overturn forming an upper level anticyclonic potential vorticity anomaly the influence of tropical cyclones on the development of these anomalies is investigated here tropical cyclones may affect heat waves in this region indirectly as the divergent outflow at upper levels perturbs the rossby wave guide leading to downstream development however the effect may also be direct through the advection of anomalously anticyclonic potential vorticity from regions of deep convection in the vicinity of tropical cyclones into the upper level anticyclone our research shows that this direct reinforcement of the anticyclone is likely to be more important in the formation of severe heat waves in southeastern australia

possible impacts of mega el nino southern oscillation and atlantic multidecadal oscillation on eurasian heatwave frequency variability identifying predictability sources of heatwave variations is a scientific challenge and of practical importance this study investigates the summertime heatwave frequency hwf over eurasia for 1950 2014 the eurasian hwf is dominated by two distinct modes the interdecadal id mode featured by an increasing pattern overall centred around eastern europe central asia and mongolia southwestern china and the interannual ia mode resembling a tripole anomaly pattern with three centres over western northern europe northeastern asia and east asia the id mode is found to be influenced by mega el nino southern oscillation mega enso and the atlantic multidecadal oscillation amo and the latter has far more effect whereas the ia mode is connected with mega enso further analysis suggests that mega enso variations can incite a gill type response spreading to eurasia while the amo changes cause eastward propagating rossby wave trains toward eurasia these two teleconnection patterns together contribute to the large scale circulation anomalies of the id mode and those related to the ia mode arise from the teleconnection pattern excited by mega enso a strong mega enso triggers subsidence with high pressure anomalies warms the surface and increases the hwf significantly over northeastern asia particularly likewise the warm amo induced circulation anomalies engender surface radiative heating and hwf growth in most of the eurasian continent except some localized siberian and asian regions the situation is opposite for a weak mega enso and amo those models from phase 5 of the coupled model intercomparison project cmip5 which realistically capture the features of the id mode can reproduce the amo like sea surface temperature anomalies sstas while signals resembling mega enso are found in those with favourable capability of simulating the ia mode on the contrary these relevant sstas linked to the respective modes vanish in the models with little skills thus mega enso and the amo might provide two critical predictability sources for heat waves over eurasia

relationship between atmospheric blocking and warm season thunderstorms over western and central europe a statistically significant link is presented between atmospheric blocking located over the eastern north atlantic and northern europe and warm season thunderstorm activity over western and central europe lightning data from 2001 to 2014 were used to identify thunderstorm days and blocking events were extracted from the era interim reanalysis using an objective identification algorithm the statistical link between the two phenomena is established through odds ratio analysis two areas one over the eastern part of the north atlantic and one over the baltic sea were identified as locations where blocking influences the occurrence of deep moist convection in parts of western and central europe based on the mean ambient conditions on days with blocking in these two areas well known dynamic and thermodynamic mechanisms supporting or suppressing the development of thunderstorms were confirmed the anticyclonic circulation of a block over the eastern part of the north atlantic leads to a northerly to northwesterly advection of dry and stable air masses into europe on the eastern flank of the block in addition these environmental conditions are on average associated with large scale subsidence of air masses convection inhibiting conditions in contrast the southerly to southwesterly advection of warm moist and unstable air masses on the western flank of a block over the baltic sea results in convection favouring conditions over western and central europe both blocking situations are on average associated with weak wind speeds at mid tropospheric levels and with weak wind shear as a consequence thunderstorms related to atmospheric blocking over the baltic sea tend to be on average less organised

a multiscale analysis of the extreme weather events over western russia and northern pakistan during july 2010 abstractthis manuscript presents a detailed multiscale analysis using observations model analyses and ensemble forecasts of the extreme heat wave over russia and historic floods over pakistan during late july 2010 with an emphasis on the floods over northern pakistan the results show that recirculation of air and dynamically driven subsidence occurring with the intensification of the blocking anticyclone in late july 2010 were key factors for producing the exceptionally warm temperatures over western russia downstream energy dispersion from the blocking region led to trough deepening northwest of pakistan and ridge building over the tibetan plateau thereby providing the linkage between the russian heat wave and pakistan flood events on the large scale in agreement with previous studies the extratropical downstream energy dispersion and enhanced convective outflow on the large scale associated with the active phase of the madden julian oscillation facilitated the formation of an intense upper level

isometamorphic variations in the reflectance and fluorescence of vitrinite a key to depositional environment abstract petrographic investigations of serial ply samples from five high to medium volatile bituminous coal seams from australia 4 and canada 1 reveal substantial in seam variations in the reflectance and monochromatic microfluorescence intensities of the maceral subgroup telovitrinite the variations consist of one case of reflectance enhancement and fluorescence suppression and four cases of reflectance suppression and fluorescence enhancement the single case of reflectance enhancement and fluorescence suppression is due to the oxidation of the vitrinite nuclei at the sequence boundary between the bayswater and upper wynn seams in new south wales the four cases of reflectance suppression and fluorescence enhancement result from the syn and epigenetic absorption by the vitrinite nuclei of hydrogen donated by presumably anaerobic bacteria generated lipids two of the coals are marine influenced the liskeard seam from the bowen basin by combined syngenetic and epigenetic effects and the greta seam from the sydney basin mainly by epigenetic contact with sea water for both coals the results are strong vitrinite reflectance suppression and fluorescence enhancement the remaining two coals the bulli seam from the sydney basin and a coal seam from the gates formation in british columbia show moderate epigenetic effects on the optical properties of telovitrinite by fresh water in the bulli seam which was studied in two adjacent localities the reflectance suppression and fluorescence enhancement of telovitrinite are stronger under sandstone roof than under shale roof in some cases the epigenetic effects are superimposed on syngenetic telovitrinite reflectance and fluorescence variations resulting from the cogeneration and mixing of different telovitrinite precursors for example autochthonous roots and hypautochthonous or allochthonous shoots a measure of the degree of dispersal and mixing is the coefficient of variation of telovitrinite reflectance and or fluorescence this coefficient correlates well with detrital minerals and dispersed macerals e g inertodetrinite and to a lesser extent sporinite some comments are made on slitted so called pseudovitrinite which is regarded as a telovitrinite that was subjected to very weak post coalification desiccation and possibly oxidation without losing much of its thermoplastic properties

northern hemisphere rossby wave initiation events on the extratropical jet a climatological analysis abstracta climatology of rossby wave initiation rwi events on the northern hemisphere mid latitude jet is compiled by applying an objective rwi identification algorithm to the era interim re analysis dataset in winter rwi events occur most frequently over the northwestern pacific and less often over the north atlantic in summer the total number of rwi events is lower than in winter and the north pacific rwi region shifts towards the tibetan plateau composite analysis of the large scale flow prior to during and after winter north pacific rwi events shows an upstream wave train propagating across asia on the arctic waveguide prior to rwi the composite wave forms on a relatively weak zonal jet streak exhibits a baroclinic structure and is strongly amplified by latent heat release in the warm conveyor belt of a deepening surface cyclone moreover the wave forms in a region of large scale upper level deformation upstream of a pre existing ridge further active tropical convection affects the longit

the impact of wave packets propagating across asia on pacific cyclone development abstract in this paper ecmwf 40 yr reanalysis data have been examined to study the influence of upper level wave packets propagating across asia into the pacific on surface cyclone development over the pacific previous studies have shown that in winter wave packets propagate across asia over two branches a northern branch over siberia and a southern branch along the subtropical jet across southern asia results presented here show that subsequent to the presence of wave packets on either branch the frequency of occurrence of deep cyclones defined as cyclones with central pressure below 960 hpa as well as explosively deepening cyclones those with a deepening rate of 1 bergeron or more are significantly enhanced this enhancement also clearly follows the wave packet eastward as it propagates across the pacific wave packets from the two branches are found to interfere with each other such that if wave packets of the appropriate configuration are present on both the northern and southern branch s

the structure and evolution of heat waves in southeastern australia abstractthe underlying large scale dynamical processes responsible for the development of heat waves in victoria southeastern australia in summer are presented here heat waves are defined as periods of at least three days and two nights for which daily maximum and minimum temperatures exceed the 90th percentile for a particular location and month using a station daily temperature dataset composites of upper level potential vorticity anomalies from the interim ecmwf re analysis era interim reveal that heat waves in southeastern australia are associated with propagating rossby waves which grow in amplitude and eventually overturn the process of overturning generates an upper level anticyclone over southern australia and an upper level trough to the northeast with maximum amplitudes near the tropopause the northerly flow associated with the circulation around the surface anticyclone advects hot air from the continental interior over the southeast of australia leading to extreme surface temperatur

rossby wave packets on the midlatitude waveguide a review abstractrossby wave packets rwps are rossby waves for which the amplitude has a local maximum and decays to smaller values at larger distances this review focuses on upper tropospheric transient rwps along the midlatitude jet stream their central characteristic is the propagation in the zonal direction as well as the transfer of wave energy from one individual trough or ridge to its downstream neighbor a process called downstream development these rwps sometimes act as long range precursors to extreme weather and presumably have an influence on the predictability of midlatitude weather systems the paper reviews research progress in this area with an emphasis on developments during the last 15 years the current state of knowledge is summarized including a discussion of the rwp life cycle as well as rossby waveguides recent progress in the dynamical understanding of rwps has been based in part on the development of diagnostic methods these methods include algorithms to identify and track rwps

the role of upper level dynamics and surface processes for the pakistan flood of july 2010 in july and august 2010 floods of unprecedented impact afflicted pakistan the floods resulted from a series of intense multi day precipitation events in july and early august at the same time a series of blocking anticyclones dominated the upper level flow over western russia and breaking waves i e equatorward extrusions of stratospheric high potential vorticity pv air formed along the downstream flank of the blocks previous studies suggested that these extratropical upper level breaking waves were crucial for instigating the precipitation events in pakistan here a detailed analysis is provided of the extratropical forcing of the precipitation piecewise pv inversion is used to quantify the extratropical upper level forcing associated with the wave breaking and trajectories are calculated to study the pathways and source regions of the moisture that precipitated over pakistan limited area model simulations are carried out to complement the lagrangian analysis the precipitation events over pakistan resulted from a combination of favourable boundary conditions with strong extratropical and monsoonal forcing factors above normal sea surface temperatures in the indian ocean led to an elevated lower tropospheric moisture content surface monsoonal depressions ensured the transport of moist air from the ocean towards northeastern pakistan along this pathway the air parcel humidity increased substantially 60 90 of precipitated moisture via evapotranspiration from the land surface extratropical breaking waves influenced the surface wind field substantially by enhancing the wind component directed towards the mountains which reinforced the precipitation

identifying rossby wave trains and quantifying their properties a novel method is introduced to automatically identify upper level rossby wave trains and to objectively diagnose their properties based on the envelope of the upper tropospheric meridional wind represented in a hovmoller diagram the algorithm identifies individual rossby wave trains as objects these depend to some extent on user defined parameters the utility of the method is demonstrated in two areas of application first the skill of a particular numerical weather prediction model is analysed for a specific case of a long lived rossby wave train for this purpose a novel diagnostic is designed based on a hovmoller diagram of the rossby wave train objects that contains forecast data with the same lead time throughout the diagram automatically calculated properties of the different forecast rossby wave trains are compared second the climatological behaviour of rossby wave train objects is investigated in long time series from reanalysis data there are preferred regions for the generation and the decay of rossby wave trains and these regions show significant differences for rossby wave trains of different minimum lifetimes in addition there are substantial differences between the seasons

representation of the scandinavia greenland pattern and its relationship with the polar vortex in s2s forecast models the strength of the stratospheric polar vortex is a key contributor to subseasonal prediction during boreal winter anomalously weak polar vortex events can be induced by enhanced vertically propagating rossby waves from the troposphere driven by blocking and wave breaking here we analyse a tropospheric pattern the scandinavia greenland s g pattern associated with both processes the s g pattern is defined as the second empirical orthogonal function eof of mean sea level pressure in the northeast atlantic the first eof is a zonal pattern resembling the north atlantic oscillation we show that the s g pattern is associated with a transient amplification of planetary wavenumber2 and meridional eddy heat flux followed by the onset of a weakened polar vortex which persists for the next 2 months we then analyse 10 different models from the s2s database finding that while all models represent the structure of the s g pattern well some models have a zonal bias with more than the observed variability in their first eof and accordingly less in their second eof this bias is largest in models with the lowest resolution skill in predicting the s g pattern is not high beyond week 2 in any model in contrast to the zonal pattern we find that the relationship between the s g pattern and enhanced eddy heat flux and a weakened polar vortex is initially well represented but significantly decays with lead time in most s2s models our results motivate improved representation of the s g pattern and its stratospheric response at longer lead times for improved subseasonal prediction of the stratospheric polar vortex

the dynamics of euro atlantic blocking onsets the mechanisms leading to euro atlantic blocking are investigated using 31 winters of 500 hpa geopotential height from nmc and ecmwf daily analyses and a 30 000 day perpetual winter run from a simple 3 level quasi geostropic model a composite analysis of the atmospheric flow during days preceding blocking events is carried out it indicates that euro atlantic blocking events have two simultaneous main precursors a high latitude retrograding wave number 1 pattern at planetary scale and an enhanced baroclinic wavetrain travelling across the north atlantic at synoptic scale these phenomena are identified both in observed and in simulated data the nonlinear interactions between small scale large scale and the mean flow during the establishment of the blocking anomaly are examined by a budget analysis of the quasi geostrophic potential vorticity equation these diagnostics demonstrate that wave wave interactions contribute to about 50 of the local amplification of the blocking anomaly while wave mean flow interactions contribute to propagation of the large and small scale anomalies and their phase locking finally the question is addressed as to whether the two precursors are necessary and sufficient conditions for blocking onsets by performing various sets of initial value experiments performed with the quasi geostrophic model these experiments show that the two precursors occur simultaneously but only the synoptic scale baroclinic wavetrain is necessary to trigger euro atlantic blocking

facies anatomy of an upper cambrian grand cycle bison creek and mistaya formations southern alberta the bison creek and mistaya formations form the youngest cambrian sedimentary grand cycle exposed in banff and jasper national parks the shaly half cycle of the bison creek formation records the displacement of a carbonate bank during a major rise in sea level that can be identified in other parts of north america lithofacies of the bison creek formation fall into three recurrent associations that represent sedimentation in shallow subtidal storm dominated shelf settings the mistaya formation records the reestablishment of carbonate bank deposition probably due to a decrease in the rate of sea level rise and includes two facies associations that represent a mosaic of shallow subtidal to supratidal environments the grand cycle was terminated by a sea level rise possibly eustatic in nature that drowned the carbonate platform the overlying shales mudstones packstones grainstones and rudstones of the survey peak formation mark a return to subtidal storm dominated shelf conditions

systematic model forecast error in rossby wave structure diabatic processes can alter rossby wave structure consequently errors arising from model processes propagate downstream however the chaotic spread of forecasts from initial condition uncertainty renders it difficult to trace back from root mean square forecast errors to model errors here diagnostics unaffected by phase errors are used enabling investigation of systematic errors in rossby waves in winter season forecasts from three operational centers tropopause sharpness adjacent to ridges decreases with forecast lead time it depends strongly on model resolution even though models are examined on a common grid rossby wave amplitude reduces with lead 5 days consistent with underrepresentation of diabatic modification and transport of air from the lower troposphere into upper tropospheric ridges and with too weak humidity gradients across the tropopause however amplitude also decreases when resolution is decreased further work is necessary to isolate the contribution from errors in the representation of diabatic processes

oxygen isotope trends and seawater temperature changes across the late cambrian steptoean positive carbon isotope excursion spice event the globally recognized late cambrian steptoean positive c isotope excursion spice is characterized by a 3 5 positive 13 c shift spanning org and pyrite we analyzed 18 o values of apatitic inarticulate brachiopods from three upper cambrian successions across laurentia to evaluate paleotemperatures during the spice 18 o values range from 12 5 to 16 5 estimated seawater temperatures associated with the spice are unreasonably warm suggesting that the brachiopod 18 o values were altered during early diagenesis despite this all three localities show similar trends with respect to the spice 13 c curve suggesting that the brachiopod apatite preserves a record of relative 18 o and temperature changes the trends include relatively high 18 o values at the onset of the spice decreasing and lowest values during the main event and an increase in values at the end of the event the higher 18 o values during the global extinction at the onset of the spice suggests seawater cooling and supports earlier hypotheses of upwelling of cool waters onto the shallow shelf decreasing and low 18 o values coincident with the rising limb of the spice support the hypothesis that seawater warming and associated reduced thermohaline circulation rates contributed to decreased dissolved o 2 concentrations which enhanced the preservation burial of c org causing the positive 13 c shift

a study of frontal dynamics with application to the australian summertime cool change abstract the dynamics of frontal evolution is investigated in the context of the australian summertime cool change using a two dimensional numerical model the model is essentially the same as that used by reeder and smith but with different initial conditions and with an open rather than periodic flow domain the initial conditions are an idealization of cross sections through a typical preexisting finite amplitude disturbance prior to its amplification to an intense front trough system basically they consist of a warm prefrontal northerly airstream embedded in a zonal shear flow in thermal wind balance the model develops a quasi steady surface cold front during the 24 hours real time of integration and this front is shown to have many features in common with a kinematic model of the australian summertime cool change the latter model was synthesized from observational data on surface cold fronts obtained during the phase i and ii field experiments of the australian cold fronts research program

a climatology of anticyclones and blocking for the southern hemisphere abstract an automated procedure for locating and tracking high pressure centers is applied to 10 years of twice daily ecmwf analyses during 1980 89 to survey the behavior of anticyclones in the southern hemisphere anticyclones are concentrated in the 25 45 s band with preferred regions consistent with previous studies except in the new zealand nz south pacific sector where a double occurrence maximum noted in earlier studies was only weakly evident marked interannual variability was found in this region with the poleward branch of maximum occurrence south of 50 s present in only 3 out of 10 years mean central pressure maximized about 10 south of the time averaged ridge with highest values in winter anticyclones poleward of 50 s involve an anomalous breakdown of the westerlies with mean central pressures there 20 30 hpa higher than climatology highs tend to form and intensify in western regions of ocean basins and weaken and dissipate in the east of these oceans regions southeast of australi

influence of upstream diabatic heating upon an alpine event of heavy precipitation abstract narrow extended troughs associated with elongated streamers of potential vorticity pv are a frequent feature of upper tropospheric flow and they can instigate or modify surface weather systems in this study consideration is given to the generation of one particular pv streamer that was itself a dynamical precursor of a heavy precipitation event in the alpine region it is shown that the streamer s parturition over the eastern north atlantic is linked to a prior event of cyclo and frontogenesis upstream over the western north atlantic diagnostic trajectory analysis and heuristic simulations with a limited area nwp model suggest that the streamer s origin is influenced crucially by the following chain of physical processes cloud diabatic heating associated with the upstream cyclogenesis enhances a downstream negative pv anomaly in the upper troposphere and the flow associated with this anomaly subsequently helps transform a farther downstream preexisting broad positive pv anomaly into an elo

late cambrian middle furongian shallow marine dysoxic mudstone with calcrete and brachiopod olenid lotagnostus faunas in avalonian cape breton island nova scotia the common belief that organic rich mudstones formed in quiescent distal settings is further weakened by study of an upper cambrian leptoplastus lower peltura superzones succession in the chesley drive group in avalonian cape breton island that is comparable to alum shale successions in baltica dramatic sea level likely eustatic changes are now recognized by punctuation of deposition of shallow wave influenced black mudstone with brachiopod orusia lenticularis and olenid trilobite bearing limestones by offlap and formation of a subaerially cemented calcrete clast conglomerate subaerial exposure was followed by transgression and accumulation of clastic pyrite sand and phosphatic granules with leptoplastus superzone l ovatus zone trilobite sclerites dynamic processes are shown by wave ripples in the mudstone and limestone sorting and winnowing of fossil rudstones and pre compactional fracture of the conglomerate and rudstones orusia rudstones in the succession below the conglomerate are regarded as analogues of eoorthis and billingsella rudstones in the biomere extinction intervals of the laurentian basal sunwaptan the lowest orusia rich beds are no older than the p spinulosa zone but as elsewhere in avalonia they range into the higher leptoplastus cape breton and even the peltura britain new brunswick superzones rare agnostoid sclerites in lower peltura superzone ctenopyge tumida zone olenid rudstone resemble those traditionally assigned to lotagnostus trisectus in avalonian britain and sweden and are distinct from laurentian l americanus an l americanus zone cannot be identified in avalonia or baltica and the first appearance datum fad of purported l americanus is not suitable as a standard for the base of the highest cambrian stage

temporal persistence and stability of cambrian biofacies sunwaptan upper cambrian trilobite faunas of north america abstract during the upper cambrian sunwaptan stage ptychaspid biomere trilobite faunas diversified following a mass extinction at the base of the unit during and immediately after the extinction interval a small number of low diversity trilobite biofacies were spread widely over the shelf turnover at all taxonomic levels was brisk and in all facies there was a sequence of rapid biofacies replacements by the end of the sunwaptan a well developed spectrum of environmentally circumscribed trilobite biofacies was developed in carbonate depositional systems and tracking of lithofacies by biofacies can be demonstrated however rapid turnover still took place at the species level so persistence and stability of biofacies was expressed at the clade level a preliminary assessment of other sunwaptan faunal elements including articulate and inarticulate brachiopods suggests that they were characterized by more persistent stable assemblages even at the species level the pattern of stability of cambrian trilobite biofacies stands in marked contrast to the species level coordinated stasis documented for the articulate brachiopod rich biofacies of the devonian of new york state the difference in behavior of these biofacies may simply be an expression of differences in the extinction and speciation rates of component taxa biofacies assembled from volatile taxa such as cambrian trilobites will inevitably display rapid turnover whereas coordinated stasis is likely to be characteristic of less volatile groups such as articulate brachiopods or bivalves the extent of biofacies stability will therefore be controlled ultimately by factors influencing evolutionary rates such as behavioral complexity niche breadth population size and dispersal ability

a paired apatite and calcite clumped isotope thermometry approach to estimating cambro ordovician seawater temperatures and isotopic composition the secular increase in 18 o values of both calcitic and phosphatic marine fossils through early phanerozoic time suggests either that 1 early paleozoic surface temperatures were high in excess of 40 c tropical mat 2 the 18 o value of seawater has increased by 7 8 vsmow through paleozoic time or 3 diagenesis has altered secular trends in early paleozoic samples carbonate clumped isotope analysis in combination with petrographic and elemental analysis can deconvolve fluid composition from temperature effects and therefore determine which of these hypotheses best explain the secular 18 o increase clumped isotope measurements of a suite of calcitic and phosphatic marine fossils from late cambrian to middle late ordovician aged strata the first paired fossil study of its kind document tropical sea surface temperatures near modern temperatures 26 38 c and seawater oxygen isotope ratios similar to today s ratios

blocking and rossby wave breaking on the dynamical tropopause in the southern hemisphere abstract rossby wave breaking on the dynamical tropopause in the southern hemisphere the 2 pvu surface is investigated using the era 40 dataset the indication of wave breaking is based on reversal in the meridional gradient of potential temperature and persistent large scale wave breaking is taken as a strong indication that blocking may be present blocking in the midlatitudes is found to occur predominantly during wintertime in the pacific and is most vigorous in the east pacific while during summertime the frequency of blocking weakens and its extent becomes confined to the west pacific the interannual variability of blocking is found to be high wave breaking occurs most frequently on the poleward side of the polar jet and has some but not all of the signatures of blocking so it is referred to as high latitude blocking in general cyclonic wave breaking occurs on the poleward side of the polar jet otherwise anticyclonic breaking occurs however at least in wintertime wave breaking in th