interactions of synoptic and planetary waves scale dependent forcing of a gcm abstract in order to better understand planetary wave synoptic wave interactions in the atmosphere and to develop a tool for further studies the authors have applied a wavenumber dependent external forcing to a general circulation model gcm the forcing constrains various length scales of the gcm to be close to those in the evolving analyses of the european centre for medium range weather forecasts and the national centers for environmental prediction the forcing acts either on the planetary waves pw defined as zonal wavenumbers 0 5 the synoptic waves sw defined as zonal wavenumbers 6 20 the synoptic waves plus the zonal mean sw0 or the synoptic waves plus the zonal mean and wavenumber 1 sw01 the form of the forcing is a linear relaxation to the evolving analyses with a time constant of 8 h this forcing is applied only to the temperature and vorticity equations of the gcm which has a spectral truncation of t42 control integrations of length 30 days have been run starting on 15 dece

spatial variation in solutional denudation and soil moisture over a hillslope hollow a spatial pattern of relative solutional denudation is described for a hillslope hollow and adjacent spurs at bicknoller combe somerset the pattern was obtained from a network of micro weight loss rock tablets emplaced in the soil the results show that the hollow is the main locus of solutional denudation the soil moisture distribution over the hollow indicates that it is a transmission zone for acid soil water percolating from the adjacent spurs to the saturated wedge at the base of the hollow the wetter acid soils in the hollow are responsible for the relatively higher solutional denudation taking place in the hollow

subsoil carbonate dissolution rates and their determining factors in a karst drainage basin sw china subsoil carbonate dissolution is the drives of atmosphere co2 consumption underground water alkalinity and karst landform specifically the determining factors and corresponding dissolution models for subsoil carbonate dissolution rate text r text carb remain under researched in various seasons and soil profiles in situ with standard limestone tablets they are the results of both ecosystem dynamics and hydrological processes thus this study aimed to explore text r text carb under different seasons soil depths and water drainage conditions in a karst drainage basin and reveal the factors determining them six hundred eighty four standard limestone tablets were exposed to fields in the subsoil of 10 cm 20 cm 30 cm and 40 cm deep sixteen plots five sites over every 3 to 4 months in a total of 423 days in the basin of the miaoguang underground river in southwest china the determining factors including soil co2 concentration moisture content temperature and ph were monitored at the same time the results are summarized in the following statements text r text carb ranged from 0 39 to 18 15 mg cm 2 a 1 were in a clear seasonal pattern principal component analysis pca of the observed soil factors revealed the mechanisms that in hot and rainy summer high text r text carb occurred in an open system with continuously supplemented co2 period i and decreased with rainfall amount period iv low text r text carb occurred in a closed system with inactive biological co2 production under cold weather period ii and iii hence as soil temperature decreased text r text carb increased text r text carb increased with soil depths as the elevated soil co2 temperature and available acid water dissolution occurred in an open system on an annual average scale and a well fitting equation of text r text carb and soil factors were given local water drainage was critical in carbonate chemical dissolving with implications of formations of local karst landform due to no or less groundwater drain and spring seepage text r text carb measured in site b a flat saddle with underlying dolomite bedrock was nearly zero conversely with water retention text r text carb was higher in gentle limestone hillslope or depression than in steep hillside because of longer water rock interaction duration in general in karst drainage basin areas text r text carb was determined by multiple factors about seasons soil depths and water drainage

five year measurements of rock tablet weathering on a forested hillslope in a humid temperate region in order to elucidate the effects of rock type and geomorphic setting on weathering rates field experiments using microweight loss techniques were carried out rock tablets for eight kinds of rock types granite granodiorite gabbro limestone andesite rhyolite crystalline schist and tuff with a diameter of 3 5 cm and a thickness of about 1 cm were enclosed in a nylon mesh bag and placed in the four corners of a soil bedrock interface on a granodiorite hillslope of central japan for over 5 years the results show that 1 the saturated grus layer is the main locus of solutional denudation 2 the 18 and 11 weight losses of limestone and tuff under a saturated soil layer were clearly the largest of all the rock types examined and 3 the weight loss is smaller for granite gabbro crystalline schist and andesite while it is larger for tuff and rhyolite at every location these results suggest that weathering rates are influenced by both lithology and environmental conditions

deterministic and statistical properties of the westerlies a brief description is presented of the classical theory of middle latitude atmospheric circulation which is essentially based on the analysis of zonally averaged stationary flows and their stability properties the structure and the statistical properties of observed circulation are discussed in some detail particular emphasis is placed upon the long lasting anomalies usually associated with the meteorological phenomenon of blocking anomalies raise several physical interpretations that may be keys to understanding the statistical properties of the atmospheric system and therefore of climate

rates of chemical weathering of porous rhyolites 5 year measurements using the weight loss method abstract to examine the rate of chemical weathering field experiments using microweight loss techniques were carried out two kinds of porous rhyolite forming lava domes in kozu shima island were selected 1 a younger rock weathering period is 2 6 ka and 2 an older rock 20 ka both rocks seem to have been very similar in their initial composition and structure they have however different properties in the present depending on the difference in weathering period rock tablets of these rhyolites with a diameter of 3 5 cm and a thickness of about 1 cm were enclosed in a nylon mesh bag and placed in a soil bedrock interface on a hillslope of central japan for over 5 years the younger rock has a lower weight loss by about 0 5 and the older rock has a higher weight loss of 3 to 5 these results show that older rock has a higher rate of chemical weathering than in younger rock this supports oguchi et al s oguchi t c hatta t matsukura y 1994 changes in rock properties of porous rhyolite through 40 000 years in kozu shima island japan geogr rev jpn 67a 775 793 in japanese with english abstr oguchi t c hatta t matsukura y 1999 weathering rates over 40 000 years based on changes in rock properties of porous rhyolite phys chem earth a 24 861 870 finding that the rate of change in chemical properties appears to accelerate with weathering time

trilobite associations taphonomy lithofacies and environments of the silurian reefs of north greenland abstract llandovery silurian reefs in north greenland have yielded extensive collections of remarkably well preserved trilobites dominated by scutelluids these collections provide a unique opportunity to analyse the reefs and their trilobite faunas in a palaeoenvironmental context and the study highlights the importance of pre existing collections to which further scientific value can be added counts of trilobite sclerites from thirteen reef localities are analysed using cluster and correspondence analyses to identify trilobite associations and taphonomic signatures lithofacies analysis allows these to be understood in a detailed palaeoenvironmental context seven trilobite associations are identified scutelluid illaenimorph scutelluid scutelluid cheirurid scutelluid harpetid proetid encrinurid and illaenimorph the number of associations highlights the variable distribution of taxa within the reefs which is partly a reflection of intense hydrodynamic sorting in reef environments trilobites are predominantly associated with a cement rich microbial lithofacies it is apparent that microbial processes were the principal contributors to the production of carbonate mud and played a significant role in the development of the greenland reefs the observed associations comprise time averaged event beds in an otherwise low energy and slow sedimentation regime and possibly result from storm activity remobilising sclerites and depositing them within depressions and cavity fills within the reef surface correspondence analysis reveals two distinct taphonomic signatures within the reef and transport distance is the primary influence on these the proetid association is readily separated from the others by its taphonomic attributes representing the least amount of transport and suggesting the taxa involved took advantage of the more sheltered niches within the reef this is the first study of reef dwelling trilobites to take advantage of multivariate techniques to identify associations and describe their taphonomic attributes in particular the effectiveness of correspondence analysis in recognising taphonomic signatures is demonstrated

scale issues in weathering studies a review of the major scale issues in weathering studies reveals concerns over the fundamental spatio temporal distributions of weathering phenomena as well as issues of upscaling microscope based observations and linking different scales of observations in explanations of landform development various strategies are proposed which can be used to tackle these issues many rooted in non linear dynamical systems ideas as an initial step spatio temporal scale distributions are estimated here for weathering processes landforms and controls based on a range of empirical data two case studies of phytokarst in grand cayman and blistering and scaling of building stones are presented to illustrate the types of data that might be used to establish more convincing scale linkages in weathering investigations

ten year remeasurement of chemical denudation on a magnesian limestone hillslope results from the measurement of microweight loss of magnesian limestone rock tablets placed at the soil bedrock interface on a hillslope over 10 years 1982 1992 gave the same relative pattern of upslope increase in weight loss as did short term measurements 1979 1981 but the absolute values were an order of magnitude lower 0 01 0 03 per cent per year long term and 0 1 0 6 per cent per year short term microweighed rock tablets may therefore give unreliable absolute rates and can only be used to indicate relative spatial differences rather than to give reliable data on temporal changes

multiple flow regimes in the northern hemisphere winter part i methodology and hemispheric regimes abstract recurrent and persistent flow patterns are identified by examining multivariate probability density functions pdfs in the phase space of large scale atmospheric motions this idea is pursued systematically here in the hope of clarifying the extent to which intraseasonal variability can be described and understood in terms of multiple flow regimes bivariate pdfs of the northern hemisphere nh wintertime anomaly heights at 700 mb are examined in the present paper using a 37 year dataset the two dimensional phase plane is defined by the two leading empirical orthogonal functions eofs of the anomaly fields pdfs on this plane exhibit synoptically intriguing and statistically significant inhomogeneities on the periphery of the distribution it is shown that these inhomogeneities are due to the existence of persistent and recurrent anomaly patterns well known as dominant teleconnection patterns that is the pacific north american pna pattern its reverse and zonal and blocked phases of the

the use of rock hard sodium sulphate tablets for quickly determining preferential water flow routes in soils subsurface water flow routes have been inferred from gypsum sphere weight loss with minimal disturbance to soil structure or flow nets crabtree and trudgill 1984 this technique is limited by the relatively slow fixed dissolution of gypsum a solution is to use tablets consisting of durham s rock hard water putty and sodium sulphate laboratory tests indicate that tablet dissolution is controlled by the ratio of rock hard to sodium sulphate and is proportional to net throughflow yet independent of throughflow ph between 3 0 and 9 0 and throughflow rate at rates 0 04 1 hr 1 the tablets are also mechanically stable economical and environmentally safe field study results using the rock hard sodium sulphate tablets are consistent with both the laboratory findings and the results of previous investigators

effects of aspect on weathering anomalous behaviour of sandstone gravestones in southeast england rocks in the humid temperate zone tend to weather more severely on faces exposed to the prevailing winds than on their more sheltered leeward faces in southeast england however gravestones composed of a non local quartz rich sandstone exhibit a reverse weathering pattern the east facing lee sides exhibit a much greater depth and areal extent of weathering than the west sides which face the westerly wind and rain possible reasons for the asymmetric pattern of weathering are discussed copyright 2000 john wiley sons ltd

north atlantic blocking during january 1979 linear theory the second half of january 1979 was a time of persistent and large scale blocking in the north atlantic region in this study we examine the instability properties of the flow during this period and relate the growing modes to the development that occurs we have analysed the growth rates phase frequencies and structures of the ten fastest growing modes within a five level quasi geostrophic model incorporating spherical geometry on each day for the period between 10 and 30 january 1979 large scale equivalent barotropic dipole or multipole instability modes are prevalent in the north atlantic during the second half of january these modes are stationary or slowly propagating and grow rapidly with efolding times as short as 1 7 days in some cases we find that there is a close connection between these modes and the dynamical developments observed subsequently a few days later associated with the early stages of block formation there are large scale eastward propagating westward tilting onset of blocking wave train modes the onset of blocking modes also appear to be associated with rapid cyclogenesis off the east coast of north america the formation of the north atlantic blocking system and diffluent flow also produces corresponding changes in the storm tracks during the early parts of this period the fastest growing monopole cyciogenesis instability modes have regions of preferential development in the climatological storm tracks over the pacific atlantic and siberian regions subsequently however the atlantic cyclogenesis modes split into wave trains poleward and equatorward of the block in the developments during this period we also examine the roles of the adjoint eigenmodes and of optimal perturbations which produce the largest initial tendency of the l2 norm squared of the streamfunction

the planetary and synoptic scale interactions in a southeast pacific blocking episode using pv diagnostics abstract the synoptic and planetary scale forcing in two blocking anticyclones occurring over the southeast pacific ocean was examined using potential vorticity diagnostics while many studies have examined the dynamic and thermodynamic forcing associated with blocking events in the northern hemisphere nh very few studies have examined blocking in the southern hemisphere sh climatological analysis suggests sh blocking events in the pacific region have similar characteristics to their nh counterparts however the occurrence of blocking is rare elsewhere in the sh and these events are relatively short lived some studies of nh blocking dynamics have also shown that the extent to which the planetary and synoptic scale and planetary synoptic scale interaction forcing that contribute to the genesis and maintenance of pacific and atlantic region events can be different thus a study of the relevant atmospheric dynamics associated with blocking events in the sh was carried out in order to determine wh

sub aerial weathering of chalk shore platforms during harsh winters in southeast england abstract chalk shore platforms are a common feature of the intertidal zone of parts of southeast england cracking and spalling of platform surfaces was widespread during exceptionally harsh winter weather in january 1985 and february 1986 damage was mostly confined to the upper reaches of the platforms and to surficial boulders laboratory simulations indicate that destructive freezing occurs only when the internal rock temperature drops below 4 5 c under the minimum air temperatures recorded during the winters of 1985 6 this will be several hours after rock surfaces are exposed to the air although temperatures as persistently low as those recorded in the winters of 1985 6 are relatively rare in southeast england temperatures sufficiently low to induce destructive freezing are encountered quite regularly and it is suggested that frost weathering of the platforms occurs during many winters although on a lesser scale than in 1985 6 frost weathering tends to remove surface irregularities and wear back the platform steps

storm tracks in the southern hemisphere subtropical oceans ocean storm tracks have previously been associated with the midlatitude western boundary currents wbcs and the antarctic circumpolar current acc here we identify and examine large scale baroclinically unstable waves occurring within waveguides associated with potential density gradients in the subtropical regions of the southern hemisphere sh oceans where the trade winds and westerlies meet and at depths associated with mode water formation in contrast to the northern hemisphere subtropics the sh pathways are more extensive allowing large scale coherent disturbances to communicate information westward from the midlatitudes to the subtropics south pacific ocean and from the subtropics to the tropics indian ocean particular consideration is given to the subtropical south pacific ocean as this is a region where resonant interactions between large scale rossby waves and significant topographic features have been reported to occur using an ocean general circulation model and a simple potential energy transfer diagnostic we identify the relevant nonlinearly modified structures comparing their propagation characteristics to planetary rossby waves calculated using a shallow water model although at first appearance baroclinic disturbances resemble planetary rossby waves we show they are inherently nonlinear multiscale and are amplified where topography occurs the location of the disturbances coincides with regions of high variability in sea surface height observed in satellite altimetry and their speeds closely match the large scale coherent westward propagating structures described in the observational literature our study provides evidence that in addition to the midlatitude wbcs and the acc significant ocean storm tracks are also manifest in the sh subtropics

study of block onset using sensitivity perturbations in climatological flows this work describes the dynamics of adjoint sensitivity perturbations that excite block onsets over the pacific and atlantic oceans appropriate functions are derived for the blocking indices for these two regions and the model basic flow is constructed from northern hemisphere climatological data the concepts of sensitivity analysis are extended to forced problems this tool is used to investigate block onset due to atmospheric forcing such as that resulting from tropical sea surface temperature anomalies these linear studies are carried out in a hemispherical primitive equations u coordinate two layer model results show that wind sensitivity perturbations less than 10 m s 21 and sensitivity forcing of vorticity sources of the order of 1 5 3 10210 s22 are sufficient to excite block onset both for the pacific and atlantic blocking sensitivity perturbations and forcing perturbations when expressed in terms of vertical vorticity display a rossby wave train structure mainly found on the southward flanks of the pacific and atlantic jets that is near the philippines and the caribbean regions from inferences based on the flow evolution of these sensitivity perturbations and with the help of potential vorticity analyses on the two constant potential temperature surfaces in this model a dynamical framework that may explain pacific and atlantic block onsets is proposed the nonuniform potential vorticity distribution in the jets in particular the concentration of these gradients on potential vorticity waveguides and the lagrangian advection of potential vorticity by the eddies making up the stationary rossby wave train and their energy propagation and convergence all conspire to play a key role in the growth of the synoptic scale eddies supported by baroclinic as well as barotropic processes it is proposed that the structural modification of the eddies in the wave train leads to the planetary structures that become associated with block onset more specifically the wave train in the pacific evolves into a blocking dipole while the atlantic block is found at the leading edge of the rossby wave train across the atlantic furthermore this study shows that at the initial time the pacific block displays a clear baroclinic structure while the wave train associated with the atlantic block has a much more barotropic structure the significance of these results and their potential applications to predictions of blocking are discussed

behavioural asymmetry in devonian trilobites abstract the cephalon of the trilobite phacopidae was usually separated from the thorax during moulting and abandoned near the trunk we statistically evaluated the distribution pattern of the cephala of omegops cornelius and found that near 70 of the total cephala were displaced on the right side from the upper devonian deposits of the western junggar in northwest china omegops cornelius might have actively pushed the cephalon to the right of its body during moulting indicating their preference to move counterclockwise this preferred movement direction manifested the behavioural asymmetry in trilobites a different type of asymmetry has been observed in phacopidae plagiolaria nandanensis from the lower devonian of guangxi in south china where about 67 of the cephala were found on the left side of the trilobite trunks so the behavioural asymmetry may be diverse or opposite in different species of trilobites and the reasons for the asymmetric moulting and movement patterns of the above two trilobites are likely related to their body structures or their living environments these new materials provide evidence for studying the origin and evolution of behavioural asymmetry

teleconnections in the geopotential height field during the northern hemisphere winter abstract contemporaneous correlations between geopotential heights on a given pressure surface at widely separated points on earth referred to as teleconnections in this paper are studied in an attempt to identify and document recurrent spatial patterns which might be indicative of standing oscillations in the planetary waves during the northern hemisphere winter with time scales on the order of a month or longer a review of existing literature on the subject reveals the existence of at least four such patterns the north atlantic and north pacific oscillations identified by walker and bliss 1932 a zonally symmetric seesaw between sea level pressures in polar and temperature latitudes first noted by lorenz 1951 and what we will refer to as the pacific north american pattern which has been known to operational long range forecasters in this country since the 1950 s a data set consisting of nmc monthly mean sea level pressure and 500 mb height analyses for a 15 year period is used as a basis fo

synoptic analysis of the pacific north american teleconnection pattern in this study we use various diagnostic techniques to investigate the synoptic evolution of the pacific north american teleconnection pattern pna national center for environment prediction national center for atmospheric research reanalysis data are used these data cover the years 1948 2008 for the months of november march it is found that the positive pna is initiated by enhanced convection over the western tropical pacific and weakened convection over the tropical indian ocean the excitation of the negative pna exhibits opposite features for both phases the response to tropical convection excites a small amplitude pna about 8 12 days prior to the pattern attaining its maximum amplitude this is followed by slow steady growth for about 5 days after which driving by synoptic scale waves via their eddy vorticity flux together with stationary eddy advection lead to much more rapid growth and the establishment of the full pna for the positive pna the synoptic scale waves propagate eastward into the midlatitude northeastern pacific where they are observed to undergo cyclonic wave breaking for the negative pna the synoptic scale waves first amplify over the midlatitude northeastern pacific and then propagate equatorward into the subtropics where they undergo anticyclonic wave breaking once established for both phases the pna appears to be maintained through a positive feedback that involves a succession of wave breakings these results suggest that preconditioning may play an important role in the formation of the pna for the positive pna in its early development the strengthening and eastward extension of the subtropical jet result in an increase in the cyclonic shear and a decrease in the meridional potential vorticity gradient features that are known to favour cyclonic wave breaking for the negative pna opposite changes were observed for the background flow which favour equatorward wave propagation and anticyclonic wave breaking the role of optimal growth is also discussed our results also suggest that the pna is potentially predictable 1 2 weeks in advance copyright 2011 royal meteorological society

the use of gypsum spheres for identifying water flow routes in soils gypsum plaster of paris has been cast into spheres and placed in soils weight loss has been used to identify relative water flow routes theoretical considerations and laboratory experimentation show that solutional weight loss of the material used increases with increasing water flow but is independent of ph above ph 4 results for gypsum sphere weight loss are presented for soils where moisture conditions have been measured independently using tensiometers the data suggest that the weight loss method provides a viable time integrated demonstration of relative water flow routes

on the dynamics of austral heat waves this work examines summer heat wave events in four different regions of australia southwest central southeast and northeast to assess similarities and differences in the circulations that precede accompany and follow the heat wave events a series of circulation composites are constructed for days from 10 days prior to 5 days following onset of each heat wave event the composites of geopotential height anomalies and wave activity flux vectors show that heat waves in southwest and southeast australia are preceded by coherent wave train structures in the indian ocean region accompanied by blocking in the australian region as an amplified node of the wave train structure and followed by coherent responses of wave train patterns in the pacific and south america regions the heat wave blocking high is maintained by convergence of wave activity in a well defined wave channel the concentration of wave activity in the block is aided by the formation of a subtropical jet branch and wave barrier on the equatorward side of the block heat waves in central and northeast australia show similar wave train life cycle responses but with a proximate ridge in the midtroposphere and a trough in the nearby waveguide region heat waves in australia can be viewed as an element of successive expression of the planetary waveguide modes in the southern hemisphere and serve as signifiers of organized active phases of these modes

metastability of northern hemisphere teleconnection modes abstractthis study applies a finite element bounded variation vector autoregressive method to assess midtropospheric flow regimes characterized by regime switches between metastable states the flow is assessed in reanalysis data from three different reanalysis sets assimilating surface data only surface and upper air data and ocean surface and upper air data results are generally consistent across the reanalyses and confirm the utility of surface only reanalyses for capturing midtropospheric variability the method is applied to a set of regional domains in the northern hemisphere and for the full hemispheric domain composites of the metastable states for each region yield structures that are consistent with the well documented teleconnection modes the north atlantic oscillation in the atlantic ocean the pacific north america pattern pna in the pacific ocean and scandinavian blocking over eurasia the pna mode includes a clear waveguide structure in midlatitudes the northern hemisphere doma

wind as a cooling agent substrate temperatures are responsible for variable lithobiont induced weathering patterns on west and east facing limestone bedrock of the negev spatial variability in lithobiont induced weathering patterns on desert rocks is aspect dependent while differences between the northern and southern aspects have been extensively studied little is known concerning the differences between east facing ef and west facing wf aspects in deserts including the negev desert whereas cobbles on both slopes are inhabited by endolithic lichens epilithic lichens which render the bedrock a smooth appearance and free living cyanobacteria which give the bedrock a rugged microrelief predominate on wf and ef bedrock respectively following previous research that regarded dew as the principal factor that determines lithobiont distribution measurements of radiation temperature wind and dew were carried out during 2008 2009 in the negev desert the data indicated that albeit slightly higher midday surface temperatures that characterize wf surfaces cobbles and bedrock nocturnal temperatures on these surfaces were significantly lower therefore facilitating higher dew condensation high amounts of dew result from the relatively rapid drop in temperatures 14 00 20 00 due to the afternoon northwesterly sea breeze wind with a cooling rate of the wf bedrock being 52 9 higher than on ef bedrock 2 6 c h 1 in comparison to only 1 7 c h 1 and facilitate the growth of high chlorophyll dew fed and rain fed epilithic lichens which may act as bio protectors on wf bedrock lack of condensation on ef bedrock results in turn in the growth of rain fed free living cyanobacteria responsible for high rock dissolution and subsequently for a rugged microrelief by affecting the nocturnal bedrock temperatures wind acts as a cooling agent impacting in turn the amount of dew and subsequently lithobiont composition and weathering patterns in the negev desert copyright 2016 john wiley sons ltd copyright 2016 john wiley sons ltd

a diagnosis of two blocking events that occurred simultaneously in the midlatitude northern hemisphere using the goddard laboratory for atmospheres goddard earth observing system 1 analyses the horizontal distribution of atmospheric forcing processes involved in the growth maintenance and decay of two northern hemisphere midlatitude blocking anticyclones that occurred simultaneously were examined with the goal of determining whether there was a dynamic connection between the two cases the complete form of the zwack okossi equation which is a generalization of the petterssen sutcliffe development equation was used as the primary diagnostic tool the basic analyses were partitioned into their planetary scale and synoptic scale components noninteraction 500 hpa height tendencies as well as scale interaction 500 hpa height tendencies based on the results of this diagnosis there was no dynamic connection between these blocking anticyclones this result agrees with findings of other studies based on a statistical analysis of simultaneous blocking these results also imply that blocking may be a local phenomenon the diagnostic results from these blocking events were in many respects similar to those of previous studies however some key differences were found for example it was found here that for both mode 2 blocking events temperature advection was an important mechanism in block formation earlier results showed vorticity advection as the primary atmospheric forcing process in block formation for a mode 1 block also the scalepartitioned results show that upstream cyclones contributed to block formation and intensification in these events directly through the synoptic scale component often with the support of the interaction component of the total forcing earlier scale partitioned results showed that the interaction component of the total forcing was most important in the formation of a mode 1 block

variability of the observed midlatitude storm tracks in relation to low frequency changes in the circulation pattern abstract the principal modes of month to month variability of the wintertime storm tracks over the north pacific and north atlantic are identified by empirical orthogonal function analysis of the root mean square statistics of bandpass 2 5 6 day filtered geopotential height data for 19 yr one of the two leading modes depicts fluctuations in the level of synoptic scale activity without any noticeable spatial displacement of the storm track axes whereas the other mode is associated with meridional shifts of the storm tracks from their time averaged positions higher order modes are indicative of diversion or truncation of cyclone tracks in particular geographical regions it is demonstrated that the leading storm track modes are linked to some of the best known monthly averaged teleconnection patterns the dipolar western pacific and western atlantic patterns for the monthly mean flow are seen to be accompanied by marked changes in the intensity of the storm tracks over the western oceans whereas the m

field and laboratory experiments on weathering rates of granodiorite separation of chemical and physical processes to study the rate and mechanism of granitic rock weathering field weathering experiments using granodiorite tablets diameter 3 5 cm height 1 1 cm weight 30 g were conducted at a catchment over 10 yr the tablets were exposed at three positions having different weathering conditions ground surface above aquifer and in aquifer the weight of the tablets decreased linearly with time 0 022 wt yr 1 for the ground surface 0 013 wt yr 1 above the aquifer and 0 42 wt yr 1 in the aquifer only minor changes of the tablet surface were observed after 10 yr of weathering at the ground surface and above the aquifer in contrast the tablets in the aquifer were remarkably weathered and weathering of biotite was particularly noticeable whereas that of plagioclase k feldspar quartz and hornblende was minor or moderate the weathering of granodiorite is inferred to proceed by initial dissolution of mineral grain boundary chemical process and subsequent detachment of the mineral grain physical process to evaluate the amount of weathering caused only by the chemical process a laboratory dissolution experiment was conducted on the granodiorite tablet using a flow through reactor at 20 c and ph 6 7 the obtained rates 0 0078 0 010 wt yr 1 were 50 times slower than the field rate in the aquifer this result shows that the contribution of the physical process to granodiorite weathering in the aquifer is very large compared to that of the chemical process and the relative intensities of the two processes during the 10 yr weathering are estimated to be chemical physical 1 50

investigation of systematic errors by relaxation experiments the systematic errors of the ecmwf forecast model have been investigated by relaxing forecasts towards analyses in selected regions this method proved to be a useful tool to study the initial error growth in a certain region and the subsequent error propagation the forecast fields in the tropics were relaxed towards the analysis by adding a contribution proportional to the current forecast error to the tendencies of temperature and momentum from the comparison of control forecasts with tropically relaxed forecasts it was possible to separate large errors generated in the extra tropics from comparatively small errors penetrating from the tropics into the extra tropics relaxation in the major mountain regions showed different results for the rocky mountains and the himalayas the errors originating from the rocky mountains are substantial contributors to errors of both transient eddies and stationary eddies the baroclinic waves in the atlantic storm track are weakened and the stationary eddies develop a wave train like error pattern which is typical for many operational forecasts in the winter season the errors in the pacific are much less dependent on errors from the mountainous region the error structure of the transient and stationary eddies as revealed from experiments in which the asian mountains are excluded or included from the relaxation shows little similarity to operational forecast errors

hillslope hydrochemistry and stream response on a wooded permeable bedrock the role of stemflow abstract the hillslope hydrochemical processes operating on a permeable carbonate bedrock can be linked to the hydrochemical response which a slope foot stream shows to rainfall events solute sources hydrochemical inputs and outputs and storm responses have been evaluated for a wooded hillslope section the data could not be interpreted in terms of a throughflow soil water movement mechanism storm events produced a rapid input of solute rich water to the stream by vertical percolation in the bedrock and subsequent lateral movement at depth the solute rich nature of the response implies that a displacement mechanism operates the rapid response from the hillslope may be initiated by stemflow which produces large concentrated point source inputs to the soil by passing the soil matrix baseflow runoff is produced by throughfall percolating through the soil matrix stemflow may be used to explain the different hydrochemical responses of the wooded hillslope and the non wooded upper portion of the catchment

gondwana derived microcontinents the constituents of the variscan and alpine collisional orogens abstract the european variscan and alpine mountain chains are collisional orogens and are built up of pre variscan building blocks which in most cases originated at the gondwana margin such pre variscan elements were part of a pre ordovician archipelago like continental ribbon in the former eastern prolongation of avalonia and their present day distribution resulted from juxtaposition through variscan and or alpine tectonic evolution the well known nomenclatures applied to these mountain chains are the mirror of variscan resp alpine organization it is the aim of this paper to present a terminology taking into account their pre variscan evolution at the gondwana margin they may contain relics of volcanic islands with pieces of cadomian crust relics of volcanic arc settings and accretionary wedges which were separated from gondwana by initial stages of rheic ocean opening after a short lived ordovician orogenic event and amalgamation of these elements at the gondwanan margin the still continuing gondwana directed subduction triggered the formation of ordovician al rich granitoids and the latest ordovician opening of palaeo tethys an example from the alps external massifs illustrates the gradual reworking of gondwana derived pre variscan elements during the variscan and alpine tertiary orogenic cycles

the seasonally varying effect of the tibetan plateau on northern hemispheric blocking frequency and amplitude the northern hemisphere atmospheric blocking is a primary weather and climate system that accompanies extreme cold spells and heat waves this study assesses effects of the tibetan plateau tp the largest continental mountain belt on the blocking frequency bf and amplitude ba with progressive tp uplift experiments from 0 to 100 using a coupled atmosphere ocean general circulation model the tp uplift increases the annual mean bf by 3 and 21 over the pacific and atlantic basins respectively a particular focus is placed on the seasonally distinct mechanism in the effects of tp uplift on the boreal winter and summer blockings during winter the tp uplift increases the bf over the active centers of both ocean basins via amplifying the eddy kinetic energy of stationary waves on the other hand in summer the tp uplift tends to shift the location of bf northward due to notable poleward displacement of the jet stream and transient eddy activities particularly over the atlantic compared to the considerable bf increase in both seasons the amplification of ba due to the tp uplift is much stronger in winter than in summer reaffirming the seasonally varying tp effect on the blocking further analyses reveal that in summer the tp uplift modulates more effectively the jet displacement than its strength leading more linear northward shift of jet and bf especially over the atlantic this study will contribute to advances in simulation and prediction of atmospheric blocking events

on the source of midlatitude low frequency variability part ii nonlinear equilibration of weather regimes abstract we present a new statistical dynamical approach to the concept of weather regimes including the effect of tralisients without any assumption other than scale separation the method is applied to a quasi geostrophic channel model without topography and forced by a local baroclinic jet baroclinic perturbations grow and decay along a storm track which is linked with a maximum of low frequency variability towards its exit in agreement with the observations the weather regimes are searched within the subspace spanned by the large scales only they are identified through the resolution of a stationary problem in which the feedback of the transients is included as an ensemble average over analogs of the large scale flow in this way the feedback is a continuous function of the large scale flow only and the system of equations is closed taking into account the whole coupling the solution is obtained using a nonlinear optimization technique several regimes are identified corresponding to zonal a

persistent anomalies blocking and variations in atmospheric predictability abstract we consider regimes of low frequency variability in large scale atmospheric dynamics the model used for the study of these regimes is the fully nonlinear equivalent barotropic vorticity equation on the sphere with simplified forcing dissipation and topography twenty five modes are retained in a spherical harmonics expansion of the streamfunction solutions are studied as a function of the nondimensional intensity of the forcing and dissipation multiple stationary solutions are obtained as a result of nonlinear interaction between waves mean flow and orography the number of modes retained in the analysis permits these multiple equilibria to appear for realistic values of the forcing the equilibria exhibit blocked and zonal flow patterns bearing a marked resemblance to synoptically defined zonal and blocked northern hemisphere midlatitude flows wave wave interactions influence strongly the stability properties of the equilibria and the time evolution of nonequilibrium solutions time depe

daily scale planetary wave patterns and the modulation of cold season weather in the northern extratropics tropospheric planetary waves often linked to asymmetries in lower boundary forcing significantly modulate atmospheric blocking and storm track structures that are in turn linked to extreme surface weather events day to day variability in the planetary scale circulation taken as wavenumbers 1 to 5 in the daily 500 hpa geopotential heights and the associated impact on storm tracks and regional weather are studied for the period 1950 2005 six boreal cold season distinct planetary wave patterns are identified via hierarchical cluster analysis the first second and sixth patterns feature a prominent zonal wavenumber 1 structure while the fourth and fifth patterns resemble the negative and positive phases of northern annular mode respectively the second pattern represents an amplification of the climatological mean wave structure while the third pattern resembles the zonal wavenumber 3 pattern a multi taper spectral analysis of the daily projection indices indicates that the planetary wave patterns are primarily intraseasonal in nature the first sixth pattern combines the positive negative phase of the pacific north american teleconnection pattern and negative positive phase of the north atlantic oscillation inducing poleward equatorward shifts in the pacific storm track and a weakened strengthened atlantic storm track in contrast the fourth fifth pattern results in a simultaneous equatorward poleward displacement of both storm tracks extreme cold waves over the continental united states us are favored during occurrences of the fourth and sixth patterns during episodes of the first pattern increased rainfall prevails over much of the us while precipitation anomalies induced by the other patterns are more regional in nature

interactions between the tropical iso and midlatitude low frequency flow in this study we investigate the interaction between the tropical intraseasonal oscillation iso and midlatitude atmospheric low frequency variability using observational data and numerical models with a special emphasis on the role of the synoptic eddy feedback a statistical closure for the synoptic eddy to low frequency flow feedback is constructed based on a singular value decomposition svd method with observational data applying this statistical closure to a barotropic model and a baroclinic 2 layer model we study the role of the synoptic eddy feedback in the midlatitude response to the tropical iso forcing both observational and modeling studies show that the strongest synoptic eddy forcing appears at the pacific and atlantic storm track regions and the synoptic eddy exerts a positive feedback to the midlatitude low frequency flow induced by tropical iso forcing our numerical experiments demonstrate the possible role of midlatitude disturbance forcing in the iso initiation at the equator the signal of the midlatitude perturbations propagates southeastward in the form of a rossby wave package it may reach the equator within several days under either easterly or westerly basic flow regimes the response at the equator has observed iso like structure and eastward propagation characteristics

relationship between ural siberian blocking and the east asian winter monsoon in relation to the arctic oscillation and the el nino southern oscillation this study attempts to assess the possible linkage between ural siberian blocking and the east asian winter monsoon eawm during the boreal winter the dominance of blocking thermally enhances cold advection downstream the frequent occurrence of ural siberian blocking potentially promotes a cold eawm and vice versa the seasonal blocking activity can be regarded as the combined effect of the arctic oscillation ao and the el nino southern oscillation enso weakened strengthened meridional flow in the positive negative phase of the ao is unfavorable favorable for the formation of blocking highs because the ao shows a close relationship with the north atlantic oscillation nao its teleconnection with ural siberian blocking may exist in the form of an eastward propagating wave train be that as it may the wave train signal across east asia may be disturbed by the external effect of a strong enso event which probably enhances weakens the westerlies near siberia in its warm cold phase consequently the blocking eawm relationship is stronger weaker when the ao and enso are in phase out of phase if both ao and enso attain the positive negative phase the siberian high tends to be weaker stronger and the temperature tends to be higher lower in east asia with less more ural siberian blocking on the other hand if they are out of phase they are not strongly linked to the intensity of the siberian high and the blocking activity over ural siberia is unclear

barotropic wave propagation and instability and atmospheric teleconnection patterns abstract a global barotropic model linearized about the 300 mb climatological mean january flow is perturbed by applying a series of localized forcings distributed throughout the tropics and subtropics structures which resemble the observed pacific north american and east atlantic teleconnection patterns noted by wallace and gutzler 1981 tend to recur in the responses similar patterns are found to result from the dispersion of isolated initial perturbations placed at a variety of locations in the tropics and midlatitudes it is shown that these structures are related to the most rapidly growing mode associated with barotropic instability of the zonally varying climatological basic state in the absence of damping this mode has an e folding time of about a week and a period close to 50 days in localized regions the instantaneous growth rates can be competitive with those of baroclinic instability these episodes of rapid local barotropic growth are interspersed with intervals in which the local

the switching between zonal and blocked mid latitude atmospheric circulation a dynamical system perspective atmospheric mid latitude circulation is dominated by a zonal westerly flow such a flow is generally symmetric but it can be occasionally broken up by blocking anticyclones the subsequent asymmetric flow can persist for several days in this paper we apply new mathematical tools based on the computation of an extremal index in order to reexamine the dynamical mechanisms responsible for the transitions between zonal and blocked flows we discard the claim that mid latitude circulation features two distinct stable equilibria or chaotic regimes in favor of a simpler mechanism that is well understood in dynamical systems theory we identify the blocked flow as an unstable fixed point or saddle point of a single basin chaotic attractor dominated by the westerlies regime we also analyze the north atlantic oscillation and the arctic oscillation atmospheric indices whose behavior is often associated with the transition between the two circulation regimes and investigate analogies and differences with the bidimensional blocking indices we find that the arctic oscillation index which can be thought as a proxy for a hemispheric average of the tibaldi molteni blocking index keeps track of the presence of unstable fixed points on the other hand the north atlantic oscillation representative only of local properties of the north atlantic blocking dynamics does not show any trace of the presence of unstable fixed points of the dynamics

kinematic wave approximation to the transport of escherichia coli in the vadose zone threshold values for macropore flow parameters that are thought to be critical in the transport of microbial suspensions through macroporous soils were established through the application of a kinematic wave approach to bacterial breakthrough curves according to the presented examples moisture content w and conductance b in the macropore systems of four different soils had simultaneously to exceed 0 015 m3 m3 and 0 1 m s respectively before substantial microbial breakthrough was observed at the bottom of undisturbed columns of macroporous soils with lengths ranging from 0 21 to 0 32 m the application of these thresholds in a modeling approach to large scale flow revealed that hardly any microbes can be transported deeper than 2 3 m in soils when durations and intensities of naturally occurring precipitation events were entered into the model it was also shown however that prolonged or intensified water input to the soil surface may efficiently carry microbes deeper than 100 m into the vadose zone

characteristics of southern hemisphere blocking as determined from a time series of observational data a time series of 500 mb geopotential heights has been used to assess characteristics of southern hemisphere blocking a zonal index similar to the index used in an analogous study of northern hemisphere blocking has been used characteristics of blocking situations have been computed with a simple algorithm which has been programmed and are presented as statistics we found one preferred region for blocking action the australian new zealand region two other regions where blocks occur are the atlantic east of south america and the indian ocean south east of south africa the number of days with blocked flow is considerably less over the atlantic and the indian ocean than in the australian new zealand region the annual variation shows two maxima one peak value of 19 in april and one extended maximum of c 20 during june august in the australian new zealand region there is no clear indication of a seasonal variation in the atlantic and the indian ocean region investigation of individual blocking episodes reveals that the majority of the blocks have a mean eastward velocity although the longer they last the more of them are westward moving longlasting episodes are almost exclusively found in the australian region

model experiments on the impact of pacific sea surface temperature anomalies on blocking frequency abstract sensitivity experiments with a perpetual january version of a low resolution general circulation model are conducted to investigate the influence of pacific sea surface temperature sst anomalies on blocking in the northern hemisphere six 1200 day integrations each of which contains a different specified sst anomaly superimposed upon a fixed climatological sst distribution are compared with a 1200 day control simulation to examine the impact of both equatorial pacific and midlatitude north pacific anomalous forcing an ensemble of eight independent 90 day realizations is extracted from each simulation distributions of the ensemble mean differences in the total number of blocking days from the control simulation are presented along with estimates of the statistic significance of these differences pacific sst anomalies do not strongly affect the total number of days in which a block is present anywhere over the north pacific basin but they apparently can affect the preferred regions over th

distribution patterns of upper devonian phacopid trilobites paleobiogeographical and paleoenvironmental significance phacopid trilobites are relatively widespread in devonian deposits after a maximum diversity in the middle devonian most phacopids were severely affected by repeated sea level eustatic changes especially in the frasnian and it was during that time that the main groups of reduced eye or blind phacopids arose the aim of this investigation was to evaluate the distribution patterns of upper devonian phacopids at a global level through a clustering analysis in a paleogeographical and paleoenvironmental framework in order to understand their fluctuations in time and space the phacopid biodiversity is represented in this study by 22 taxa from the frasnian to the late famennian additionally four main time intervals frasnian i famennian post i famennian ii iii and famennian iv vi have been explored to complete the clustering analysis two ordering methods i e a seriation routine and a detrended correspondence analysis have been performed respectively to reveal chronological sequences and to identify indirect paleoenvironmental gradients analyses enabled us to establish 1 bathymetrical gradients showing some taxa such as omegops restricted to shallower environments and other taxa such as ductina or dianops to deeper environments and 2 paleobiogeographical affinities showing exchanges along the margins of north gondwana and avalonia baltica and probable connections along the margin of north east gondwana after the major mid givetian taghanic transgression

the climatology of blocking anticyclones for the northern and southern hemispheres block intensity as a diagnostic abstract a 30 yr climatology of blocking events was compiled by stratifying the data into seasonal and three regional categories for both the northern and southern hemispheres using the ncep ncar reanalyses several characteristics of blocking anticyclones were included in the study and these were frequency of occurrence preferred formation regions duration blocking days and intensity the block intensity bi calculation was modified successfully from a previous study in order to automate the procedure for use with large datasets and it is applied for the first time to derive a long term observational record of this quantity this modification also makes bi suitable for use as a diagnostic tool blocking events in the northern southern hemisphere were the most persistent and strongest during the cold season and over the atlantic pacific region as found using bi to measure intensity the characteristics of blocking events derived in this study were compared to previous long term climatological s

northern hemisphere snow cover and atmospheric blocking variability 1 the interseasonal relationship between northern hemisphere nh snow cover and regional blocking patterns is explored for a 31 year data set it is found that snow cover exerts an important influence on regional atmospheric blocking which in turn modulates snow cover extent at subcontinental scales observational results provide strong evidence of two primary linkages in the seasonal snow cover blocking relationship that support an interannual persistence cycle the first one links winter blocking over the atlantic and the subsequent spring summer eurasian north american snow cover anomalies the second one implies that spring summer eurasian north american snow cover precedes an anomalous winter atlantic blocking activity we describe the temporal stages of the snow cover blocking relationship in the framework of a six step conceptual model according to that an enhanced atlantic blocking activity in winter favors a later spring snow disappearance through an enhanced cold advection toward western eurasia the resulting snow cover anomalies partially force an opposite sign blocking response over west and central pacific which is sustained through spring and early summer presumably because of the persistence of snow cover anomalies this anomalous pattern seems to play a role in the propagation of snow cover anomalies from eurasia in spring to the hudson s bay region of north america in summer the excessive snow cover over this region induces an asymmetrical temperature distribution which in turn favors blocking activity over europe and the west pacific the connection between autumn and winter climates is not clear but it could be related with the ability of autumn high atl blocking activity to determine an early snow cover appearance in october over western eurasia this linkage completes a snow cover blocking cycle of interactions which identifies snow cover as a candidate for the recently observed blocking trends and a contributor to the interannual persistence of winter climate

first occurrence of a phacopid trilobite faunule from the upper devonian of saoura valley algeria and biodiversity fluctuations phacopid trilobites are relatively widespread in devonian deposits of north gondwana and some have been collected from several sections of the saoura valley in sw algeria new occurrences of phacopids assigned to trimerocephalus dianops and phacops sensu lato are described from this area and comparisons are made with closely allied species from morocco and europe the trilobite assemblagesofthe argilesdemarhouma formationareconsideredtobefrasnian famennianinage thesenewoccurrenceshavebeenintegratedintoananalysisofupperdevonianphacopidbiodiversity diversity fluctuations reflect environmental changes bioevents and stratigraphic turnovers throughout the upper devonian peak diversity was attained after the post kellwasser event

formation mechanisms of the pacific north american teleconnection with and without its canonical tropical convection pattern abstractthe mechanisms that drive the pacific north american pna teleconnection pattern with and without its canonical tropical convection pattern are investigated with daily era interim and noaa olr data the former pattern is referred to as the convective pna and the latter pattern is referred to as the nonconvective pna both the convective and nonconvective positive pna are found to be preceded by wave activity fluxes associated with a eurasian wave train these wave activity fluxes enter the central subtropical pacific a location that is favorable for barotropic wave amplification just prior to the rapid growth of the pna the wave activity fluxes are stronger for the positive nonconvective pna suggesting that barotropic amplification plays a greater role in its development the negative convective pna is also preceded by a eurasian wave train whereas the negative nonconvective pna grows from the north pacific contribution to a circumglobal teleconnection pattern driving by high frequency ed

patterns of extinction and recovery of phacopid trilobites during the frasnian famennian late devonian mass extinction event canning basin western australia a diverse fauna of phacopid trilobites is described from the late devonian middle frasnian to early famennian of the northern canning basin western australia one new genus and four species in two genera are described from zones 11 13a and 13b of the middle and late frasnian trimerocephaloides sinevisus gen nov and sp nov t linguiformis sp nov acuticryphops acuticeps kayser 1889 and a klapperi sp nov late frasnian phacopines are either blind as shown for the first time in trimerocephaloides sinevisus or show trends to decreasing eye size up to the frasnian famennian kellwasser mass extinction event this evolutionary trend in acuticryphops is demonstrated to have been global at this time one new genus and six species of early famennian phacopids are described from the upper triangularis crepida and rhomboidea zones houseops gen nov with the new taxa h canningensis sp nov h beckeri sp nov and h sp a babinops planiventer feist becker 1997 b minor sp nov trimerocephalus tardispinosus feist becker 1997 and t mimbi sp nov in contrast to european sections where exclusively blind phacopids are known in earliest famennian sites initial recovery following the mass extinction event in canning peri reefal environments is characterized by oculated forms these trilobites must have evolved from conservative ancestors with normal eyes that had succeeded in surviving the kellwasser biocrises in reef related shallow water niches thus the origin of post event phacopids from shallow water environments is demonstrated for the first time descendant lineages show increasing eye size increased cephalic vaulting and effacement during the early famennian of the five orders of trilobites that are present during the frasnian stage at the beginning of the late devonian only two the proetida and the phacopida survived into the famennian the presence of a conformable sequence of trilobite bearing fore reef limestones the virgin hills formation that form part of the late devonian reef system in the northern part of the canning basin in western australia allows the patterns of evolution and extinction of the late frasnian and early famennian trilobites to be assessed in these deposits the three orders that became extinct during the frasnian famennian biocrises were the corynexochida mcnamara feist 2006 the lichida feist mcnamara 2007 and the harpetida mcnamara feist ebach in press here we focus on one of the groups that survived this event the phacopida although with a single exception they are rare elements of the trilobite fauna in the canning basin the phacopids are generically the most diverse of the

stemflow influences on the formation of solution pipes in bermuda eolianite abstract soil filled pipes consisting of calcite casings were found in all of the eolianite formations of bermuda except the rocky bay formation the pipes are cylindrical in shape taper vertically downwards and occur in aggregated clusters they are most commonly exposed in areas of shoreline erosion in the form of soil filled cylindrical rims of calcite projecting up from the surrounding host eolianite in the early literature on the geology of bermuda it was suggested that these features were fossilized stumps of the bermuda palmetto tree sabal bermudiana in the study presented here this hypothesis is rejected on the basis of the morphology and stratigraphic position of these geomorphic features and their basal area and areal density compared with existing natural stands of s bermudiana the soil filled pipes of bermuda however cannot be simply explained as random solutional features that correspond to points where percolating soil water happened to converge and cause localized subsurface dissolution in situ measurements of stemflow from indigenous tree species suggest that the soil filled solution pipes of bermuda may be the product of stemflow drainage from particular tree species stemflow from s bermudiana was the most acidic with ph values as low as 4 29 compared to the gross rainfall in the open which had a ph of 5 58 the crowns of the bermuda cedar juniperus bermudiana and the subtropical tree species eugenia axillaris had the most significant funnelling effect stemflow volumes from individual trees representing these two species were 20 times greater than the volume of water that would have been collected in rain gauges with orifice areas equivalent to the trees trunk basal areas tree species capable of acidifying intercepted rainwater and funnelling large quantities down their trunks as stemflow may be the cause of subsurface dissolution loci extending vertically downward through bermuda s soluble eolianite formations stemflow from long lived trees representing these species could account for the diameters the cyclindrical shape the vertical orientation and the soil filled interiors of the pipes successive generations of these trees in preferred habitats could explain their clustered distribution and high areal densities 103 pipes ha

on the dynamics of persistent states and their secular trends in the waveguides of the southern hemisphere troposphere we identify the dynamical drivers of systematic changes in persistent quasi stationary states regimes of the southern hemisphere troposphere and their secular trends we apply a purely data driven approach whereby a multiscale approximation to nonstationary dynamical processes is achieved through optimal sequences of locally stationary fast vector autoregressive factor processes to examine a high resolution atmospheric reanalysis over the period encompassing 1958 2013 this approach identifies regimes and their secular trends in terms of the predictability of the flow and is granger causal a comprehensive set of diagnostics on both isentropic and isobaric surfaces is employed to examine teleconnections over the full hemisphere and for a set of regional domains composite states for the hemisphere obtained from nonstationary nonparametric cluster analysis reveal patterns consistent with a circumglobal wave 3 polar wave 5 subtropical pattern while regional composites reveal the pacific south american pattern and blocking modes the respective roles of potential vorticity sources stationary rossby waves and baroclinic instability on the dynamics of these circulation modes are shown to be reflected by the seasonal variations of the waveguides where rossby wave sources and baroclinic disturbances are largely contained within the waveguides and with little direct evidence of sustained remote tropical influences on persistent synoptic features warm surface temperature anomalies are strongly connected with regions of upper level divergence and anticyclonic rossby wave sources the persistent states identified reveal significant variability on interannual to decadal time scales with large secular trends identified in all sectors apart from a region close to south america

a unified three dimensional instability theory of the onset of blocking and cyclogenesis abstract the instability characteristics of three dimensional flow typical of the northern hemisphere average winter troposphere are examined in a two layer spherical quasigeostrophic model the properties of the four fastest growing small amplitude disturbances that develop on the basic state have been analyzed for three cases case 1 2a and 3 having increasingly larger static stability parameters for case 1 the fastest growing disturbance mode which is propagating eastward rather rapidly has a monopole cyclogenesis structure with maximum amplitudes slightly downstream of the jetstream maxima in the pacific ocean and off the cast coast of north america comparisons of streamfunctions squared and momentum and heat fluxes with bandpass filtered observations for transient eddies which pick out the developing storms are quite reasonable considering that a two layer model is used and the contributions from individual linear modes are considered for case 2a the fastest growing mode has large scale hi

stratigraphic paleoecology bathymetric signatures and sequence overprint of mollusk associations from upper quaternary sequences of the po plain italy upper quaternary sequences of the po plain italy were used to assess the informative strength and sequence stratigraphic overprint of quantitative paleoecological patterns three densely sampled cores 89 samples 98 genera 23 280 specimens dominated by extant mollusk species with known environmental distributions were analyzed with detrended correspondence analysis dca the dca scores calibrated using extant genera provided outstanding estimates of bathymetry 3 m and related environmental parameters depth related successions of mollusk associations delineated by using dca were consistent with independent sequence stratigraphic interpretations and yielded insights inaccessible via routine techniques e g depth estimates for maximum flooding surfaces the dca ordination demonstrates the severity of the sequence stratigraphic overprint samples are highly uniform taxonomically during late transgressive systems tracts and highly variable during the following highstand systems tracts when analyzed across comparable systems tracts similar species associations repeat during the last and current interglacial cycles suggesting that po plain mollusk associations have remained remarkably stable over the past 125 k y the results are consistent with the bathymetric interpretation of the dc axis 1 postulated previously for the paleozoic fossil record demonstrate the sequence stratigraphic overprint of paleoecological patterns predicted by computer modeling and illustrate the utility of quantitative paleoecological patterns in augmenting sequence stratigraphic interpretations

hydrochemical budgets for a magnesian limestone catchment in lowland england a solute budget study of a magnesian limestone catchment in lowland eastern england showed that 66 of the total solute output from the catchment was derived from chemical weather with 451 302 kg yr 1 778 1 kg ha 1 yr 1 removed in solution the major solutes species produced were ca2 mg2 and hco 3 derived mainly from chemical weathering by percolating acidic rain water catchment runoff was deduced to be comprised of combined piston flow in fissures to springs and matrix seepage each had an overlapping range of ca2 mg2 ratios suggesting a similar long residence time

a chronology of paleozoic sea level changes sea levels have been determined for most of the paleozoic era 542 to 251 million years ago but an integrated history of sea levels has remained unrealized we reconstructed a history of sea level fluctuations for the entire paleozoic by using stratigraphic sections from pericratonic and cratonic basins evaluation of the timing and amplitude of individual sea level events reveals that the magnitude of change is the most problematic to estimate accurately the long term sea level shows a gradual rise through the cambrian reaching a zenith in the late ordovician then a short lived but prominent withdrawal in response to hirnantian glaciation subsequent but decreasingly substantial eustatic highs occurred in the mid silurian near the middle late devonian boundary and in the latest carboniferous eustatic lows are recorded in the early devonian near the mississippian pennsylvanian boundary and in the late permian one hundred and seventy two eustatic events are documented for the paleozoic varying in magnitude from a few tens of meters to 125 meters

low frequency variability in a simplified atmospheric global circulation model storm track induced spatial resonance the interaction between two storm tracks is analysed by using idealized experiments with a simplified global circulation model a zonal distance of 180 between the storm tracks drives a retrograde travelling zonal wave number two wave with an amplitude modulation of about 50 days the stream function tendency equation demonstrates that the amplitude modulation is excited in the storm track regions by the high frequency periods between two and eight days eddy forcing spatial resonance of a retrograde propagating zonal wave number two rossby wave and high frequency eddy forcing are proposed as the amplifying mechanisms while friction and self interaction between the low frequency eddies ensure damping sensitivity experiments indicate that the pronounced modulation of 50 days vanishes with decreasing zonal distance between the storm tracks thereby enhancing the intensity and duration of blocking events

an analysis of a relatively rare case of continental blocking planetary and synoptic scale analyses of a relatively rare continental blocking event that occurred over north america during the spring of 1980 are undertaken to determine whether or not this event was different from its counterparts which occur over oceanic regions the planetary scale analysis demonstrates that during the spring season a ridge was located further inland over the north american continent and amplified with respect to climatology the position of this ridge may have been linked to a broad region of colder than normal sea surface temperatures found over the north central pacific during the spring season and much of the previous winter simple sutcliffe type and thermodynamic analyses of the accompanying lower tropospheric warm anomaly associated with the ridging show that lower tropospheric temperature advection and subsidence associated with anticyclonic vorticity advection by the time mean thermal wind produced much of the anomalous warmth a simple synoptic scale analysis was performed using both the zwack okossi zo equation and potential vorticity pv thinking approaches these complementary analyses demonstrated that synoptic scale cyclones were instrumental in the formation and maintenance and or intensification of this blocking event the pv analysis demonstrated that low pv air was swept polewards and then was advected over the blocking region sustaining the broad region of low potential vorticity associated with the block over north america the zo analysis showed that the advection of anticyclonic vorticity was the most important mechanism forcing geopotential height rises at 500 hpa over the block centre the region of low pv and zo height rises could be associated with the anticyclonic shear side of an upstream jet maximum typically found in association with developing and or intensifying blocking events thus negative pv advection correlated significantly with calculated zo height rises finally it is suggested that a favourable phase relationship between the upstream cyclones and the large scale ridge is necessary for block development or intensification

the statistical properties of general atmospheric circulation observational evidence and a minimal theory of bimodality in this paper we address the problem of constructing a minimal model of atmospheric circulation able to describe the bulk of the statistical properties of the general circulation in middle latitudes after a brief reexamination of the charney devore theory of multiple equilibria we compare the statistical properties that can be deduced from it with those resulting from analysis of observations of the northern hemisphere middle latitude circulation at 500 mb while the prediction concerning the amplitude of the waves seems to be confirmed by the presence of a clear bimodality of the statistical distribution we find no trace of bimodality in the zonal wind we show how the theory can be brought into agreement with observations by introducing nonlinearity into the wave equation in such a way that the charney devore resonance curve is bent producing different states corresponding to the same value of the zonal wind we finally address ourselves to the question of what physical processes determine the observed unimodal statistics of zonal wind a subject of future work

soil development at snail s pace evidence from a 6 ma soil chronosequence on basalt in north queensland australia abstract in semi arid tropical australia basaltic lava flows with ages of 0 01 0 89 2 46 2 64 3 4 and 5 59 ma show a trend of progressive soil thickness increase of ca 0 30 m ma this rate is 10 to 1000 times slower than most soils on unconsolidated parent materials such as alluvium dune sand and glacial deposits reverse polarity magnetisation of pedogenic hematite in the lower b horizons of soils on the four oldest flows indicates acquisition of the remanence prior to the brunhes matuyama polarity transition at 0 78 ma preservation of such a reverse polarity implies that the remanence carrier pedogenic hematite has been unchanged by chemical weathering or physical disturbance by soil biota for at least 0 78 ma a conceptual model of soil development is presented which implies that prior to 0 78 ma soil weathering may have occurred to a greater depth because summer rainfall was significantly higher than present the extremely slow rate of soil formation implied from these basaltic soils in northern australia is a clear warning that agricultural use of such soils is unlikely to be sustainable against accelerated surface erosion

piecewise tendency diagnosis of weather regime transitions abstract piecewise tendency diagnosis ptd is extended and employed to study the dynamics of weather regime transitions originally developed for adiabatic and inviscid quasigeostrophic flow on a beta plane ptd partitions local geopotential tendencies into a linear combination of dynamically meaningful source terms within a potential vorticity pv framework here ptd is amended to account for spherical geometry diabatic heating and ageostrophic processes and is then used to identify the primary mechanisms responsible for northern hemisphere weather regime transitions height tendency patterns obtained by summing the contributions of individual ptd forcing terms correspond very well to actual height tendencies composite ptd analyses reveal that linear pv advections provide the largest dynamical forcing for the weather regime development over the north pacific specifically linear baroclinic growth provides the primary forcing while barotropic deformation of pv anomalies provides a secondary contrib

skewness of low frequency fluctuations in the tropospheric circulation during the northern hemisphere winter abstract departures of lowpass filtered 500 mb height and sea level pressure anomalies from a gaussian distribution have been examined based on northern hemisphere operational analyses for 30 winters at each gridpoint we evaluated several indices that are measures of the differences between the amplitudes and frequencies of the persistent anomalies with positive and negative polarities and differences in the temporal variability observed within extended periods of positive and negative anomalies the spatial patterns for these indices are all quite similar and they resemble the distribution of the moment coefficient of skewness documented by white positive skewness is observed to the north of the stormtrack latitudes and the negative to the south of them the skewness pattern in the sea level pressure field is weaker particularly at high latitudes and it exhibits a bias toward negative skewness anomalies with amplitudes larger than two standard deviations which occur about 5 of the time account

field and laboratory experiments on high dissolution rates of limestone in stream flow abstract field and laboratory experiments were performed to examine dissolution rates of limestone in stream flow field experiments were conducted in three stream sites a c with different lithological or hydrological settings around a limestone plateau in the abukuma mts japan sites a and b are allogenic streams which flow from non limestone sources into dolines and site c has a karst spring source tablets made of limestone from the same plateau with a diameter of 3 5 cm and a thickness of 1 cm were placed in the streams for 3 years 2008 2011 where alkalinity ph and major cation concentrations were measured periodically the saturation indices of calcite sic of stream water were 2 8 0 4 at site a 2 5 0 4 at site b and 0 5 0 4 at site c annual weight loss ratios for tablets were extremely high at site a 0 11 0 14 mg cm 2 d 1 high at site b 0 05 mg cm 2 d 1 and low at site c 0 005 mg cm 2 d 1 the contrasting rates of weight loss are mainly explained by chemical conditions of stream water in addition laboratory experiments for dissolution of limestone tablets using a flow through apparatus revealed that flow conditions around the limestone tablet is another important factor for dissolution in the stream environment these results revealed that limestone dissolves at a rapid rate where water unsaturated to calcite continuously flows such as in an allogenic stream

precursors to blocking anomalies the tangent linear and inverse problems abstract the development of perturbations or errors is considered during periods of observed northern hemisphere blocking the evolution of initial onset of blocking mode perturbations is studied using a two level tangent linear model with time dependent basic states taken from observations in the first half of november 1979 during this period a blocking high formed in the gulf of alaska between 5 and 12 november followed by decay and the subsequent development of a block in the north atlantic initial baroclinic wave train perturbations with large amplitudes stretching from east asia into the central pacific propagate eastward as they grow and become equivalent barotropic large amplitude large scale perturbations form over the gulf of alaska as the observed block amplifies subsequently downstream development occurs with rapid amplification of the perturbation near the east coast of north america followed by the formation of large scale tripole anomalies in the blocking region over the north atlanti

relationship between the tibetan plateau heating and east asian summer monsoon rainfall 1 this study reveals the close correspondence between the interannual variability of the dominant east asian summer rainfall pattern and the diabatic heating over the tibetan plateau in both spring and summer the heating fluctuation over the tibetan plateau is associated with two wave like circulation patterns which bear the characteristics of forced rossby wave emanating away from the deep heating the wave like pattern in turn affects the east asian summer rainfall because of the persistent heating over the tibetan plateau from spring to summer and its possible effect on the surrounding areas the heating index defined in this study can be used as a good predictor for the jja heating and precipitation distributions evidences shown suggest that external conditions other than the sst anomaly must be considered to understand the interannual variability of the east asian summer rainfall

weathering of igneous rocks during shallow burial in an upland peat environment observations from the bronze age copney stone circle complex northern ireland abstract the stone circle complex at copney county tyrone is a key bronze age site that forms part of the mid ulster stone circle complex this site was excavated in 1995 and since then deterioration of the archaeological stonework has been a serious problem deterioration is visible as splitting fracturing of stones the development of a bleached outer margin surface scaling and granular disintegration and in some cases complete disintegration of individual stones to sandy regolithic material environmental conditions at this site exacerbate the deleterious action of weathering processes with periodic waterlogging and sub zero temperatures during winter months the copney stones comprise two igneous lithologies quartz porphyry and porphyritic andesite both lower ordovician 470 ma in age both rock types show extensive alteration by hydrothermal processes resulting in weakened stone fabrics exploited by weathering processes during burial and subsequent exposure mineralogy of buried and exposed material indicates that approximately 2500 years of burial in a peat bog has produced secondary porosity comprising extensive microfracture networks and dissolution voids which permitted further ingress of moisture and acidic waters thus promoting chemical alteration of mineral constituents the occurrence of completely grussified stones and arenisation of boulder surfaces at copney indicates that the processes of grussification are not solely restricted to deep weathering environment but can be achieved by burial in a shallow aggressive environment over periods measured in thousands of years

storm track organization and variability in a simplified atmospheric global circulation model a storm track is simulated in a coarse resolution multilevel primitive equation model with linear surface friction and heating terms a restoration temperature distribution consisting of a dipole embedded in a zonally symmetric profile forces the model to simulate the surface heating three simulations each with a different dipole orientation are performed to test the sensitivity of storm track organization to the external forcing field the climatological time mean circulation and the transient disturbances of the reference simulation agree well with observations of northern hemisphere wintertime storm tracks local energetics show that baroclinic instability is responsible for the enhanced eddy kinetic energy downstream of the jet and the downstream end of the storm track results from the barotropic conversions of eddy kinetic energy to the time mean flow low frequency fluctuations with a period of about 50 days associated with a retrograding large scale wave pattern are identified by a complex empirical orthogonal function analysis of the vertically averaged stream function a composite life cycle of the low frequency variability reveals the growth and decay of a blocking anticyclone downstream of the storm track a cyclogenesis initiated by an eastward propagating wave train is observed a few days before the amplitude of the low frequency anomaly attains its peak the net forcing of the high frequency eddies contributes to the growth and decay of the blocking anticyclone the results suggest that the occurrence of the blocking like event is part of the storm track dynamics

weathering and durability of the goldsworthy chalk stones south downs west sussex england the goldsworthy chalk stones 14 roughly shaped balls of chalk each approximately 2 m in diameter were installed in june 2002 initial assessments by the artist andy goldsworthy and the strange partners commissioning team concluded that they would last for about 2 years the balls disintegration has been measured as part of an ongoing scientific monitoring programme designed to assess their durability and to study controls on rates of chalk weathering preliminary assessment of the first 3 years of data shows that 76 of the total mass loss occurred during year 1 19 during year 2 and 5 during year 3 this might reflect the fact that winter rainfall amounts decreased substantially over the period of study the west facing sides of the balls have tended to show greater mass loss than those facing east which might also be a function of exposure to rain judging from their present slow rates of weathering the balls will last for over 200 years but an exceptionally cold wet winter might cause sudden and massive breakdown three models of chalk mass weathering are presented the ongoing scientific monitoring programme will focus experimental work on four key research themes process lithology environment and stress history

space time spectral structure of a glas general circulation model and a comparison with observations abstract the wavenumber frequency spectra of geopotential height have been computed from a winter simulation of a glas general circulation model and are compared to the spectra obtained from 15 winters of observed analyses the variances in several broadly defined space time categories are presented and their distribution with latitude and height discussed the low frequency planetary waves wavenumbers 1 4 in the model have substantially less variance than is observed and their latitudinal structure also differs from observations the same is true for the medium frequency planetary waves the synoptic scale waves wavenumbers 5 10 with both low and medium frequencies are quite well reproduced by the model with the total variances and their latitude height structure comparing well to the observations the net propagation tendency is examined for low frequency planetary waves and the medium frequency synoptic scale waves the model results show too much tendency for eastward propagation the discrepan

chemical denudation on a magnesian limestone hillslope field evidence and implications for modelling the pattern of relative denudation at the soil bedrock interface over a wooded magnesian limestone hillslope was investigated using micro weight loss bedrock tablets the resulting pattern of weight loss after emplacement for one year indicated a consistent upslope increase in solutional denudation results from tablets emplaced for two years confirmed this dye tracing and gypsum sphere weight loss results showed that water movement over the slope was by vertical percolation and not by throughflow the pattern of solutional denudation was related to changes in soil type and associated changes in soil ph continued slope development by solutional denudation will ultimately lead to slope decline comparison with a similar study suggests that a general soil chemistry based model of hillslope solutional denudation can be proposed

zonal wavenumber characteristics of northern hemisphere transient eddies abstract eleven winters and twelve summers of twice daily national meteorological center nmc analyses of geopotential height and temperature at five levels for the extratropical northern hemisphere are partitioned into long wave fields with zonal wavenumbers m 5 and short wave fields with zonal wavenumbers m 6 the data are also bandpass filtered to investigate fluctuations of periods 2 5 10 days from these fields the standard deviation of 500 mb geopotential height and the poleward geostrophic transient eddy fluxes of sensible heat and zonal momentum are calculated and presented the results are compared with theoretical and numerical modeling studies of nonlinear baroclinic instability both the observations and modeling studies produce evidence that baroclinic eddies have a definite life cycle and that the strongest baroclinic eddies are of intermediate size zonal wavenumbers 6 8 some interesting differences between observations and modeling results also emerge

explosive cyclogenesis and large scale circulation changes implications for atmospheric blocking abstract large scale circulation changes attending explosive surface cyclogenesis are quantitatively examined in two cases selected from recent winter seasons both cases feature a rapidly deepening surface cyclone over the western atlantic ocean but changes in the 500 mb geopotential height field near the cyclone differ in each case one event during january 1977 is characterized by the retrogression of an anticyclonic vortex blocking high in the 500 mb height field downstream of the surface cyclone the second case in february 1978 is distinguished by the formation of a 500 mb cyclonic vortex cutoff low upstream of the surface cyclone but no downstream anticyclonic vortex is observed the retrogression of the january 1977 block over the atlantic ocean coincides with the migration of a 500 mb synoptic scale perturbation associated with the surface cyclone from a planetary scale trough over north america toward a planetary scale ridge over europe in the february 1978 case the blocking cyclo

acid rain damage to carbonate stone a quantitative assessment based on the aqueous geochemistry of rainfall runoff from stone an onsite experimental procedure was used to identify and quantify acid rain damage to carbonate stone based on the change in rain runoff chemical composition observed changes in runoff from stone are attributed to the interaction of acidic species present in the rain with the stone surface onsite data obtained during the summer and fall of 1984 at three locations in the northeastern united states indicate that carbonate stone surface recession is related to acid deposition although the study is continuing current data are not adequate to distinguish differences in the acid stone reaction between limestone and marble nor among the three study sites a single linear relation between carbonate stone surface recession the dependent variable and hydrogen ion loading to the stone surface the independent variable appears to describe the data set

experimental frost weathering of sandstone by various combinations of salts weathering experiments are reported combining frost and a range of salts that occur naturally on rock faces in western and central europe potassium and ammonium alums enhanced frost weathering quite considerably both singly and in combination though they were less potent than halite the destructiveness of which at sub zero temperatures was again confirmed by contrast alunogen and gypsum had little or no effect on rates of frost weathering either singly or in combination combining halite and gypsum produced breakdown that was intermediate between that of the two salts individually as did the combination of gypsum and potassium alum breakdown in solutions of ammonium alum and gypsum and in a combination of potassium and ammonium alum with gypsum caused greater breakdown over 25 cycles of freeze thaw than was recorded with the salts singly the results extend the range of salts known to enhance frost weathering and show that it is difficult to predict the aggressiveness of combinations of salts by experimenting with each salt separately copyright 2001 john wiley sons ltd

transient eddy forcing of the rotational flow during northern winter abstract the total direct transient eddy forcing of the vorticity balance in the upper troposphere during northern winter is examined using 11 years of 2 to 8 day bandpassed global analyses most examinations of the importance of high frequency eddy vorticity fluxes to the maintenance of either the climatological standing waves or low frequency anomalous flows have focused on only the horizontal blow or the rotational component of the horizontal transient flow the latter simplification has been shown to be questionable for planetary scales the vorticity flux by the transient divergent flow produces a forcing of the mean streamfunction that is of comparable magnitude with the equivalent rotational term however the streamfunction forcing by the sum of the transient vertical advection and twisting terms largely balances the fearing by the vorticity flux convergence associated with the divergent flow the result is that the convergence of the eddy vorticity flux by the total transient flow is not a good a

the continuum of north pacific sea level pressure patterns intraseasonal interannual and interdecadal variability this study combines k means cluster analysis with linear unidimensional scaling to illustrate the spatial and temporal variability of the wintertime north pacific sea level pressure slp field daily wintertime slp data derived from the ncep ncar reanalysis are used to produce 16 slp anomaly patterns that represent a discretized approximation of the continuum of north pacific slp patterns this study adopts the continuum perspective for teleconnection patterns which provides a much simpler framework for understanding north pacific variability than the more commonly used discrete modal approach the primary focus of this research is to show that variability in the north pacific on intraseasonal interannual and interdecadal time scales can be understood in terms of changes in the frequency distribution of the cluster patterns that compose the continuum each of which has a time scale of about 10 days this analysis reveals 5 6 pacific north american like pna like patterns for each phase as well as dipoles and wave trains a self organizing map som analysis of coupled slp and outgoing longwave radiation data shows that many of these patterns are associated with convection in the tropical indo pacific region on intraseasonal time scales the frequency distribution of these patterns in particular the pna like patterns is

the late fall extratropical response to enso sensitivity to coupling and convection in the tropical west pacific abstract the extratropical response to el nino in late fall departs considerably from the canonical el nino signal observational analysis suggests that this response is modulated by anomalous forcing in the tropical west pacific twp so that a strong fall el nino teleconnection is more likely when warm sst conditions and or enhanced convection prevail in the twp while these twp sst anomalies may arise from noise and or long term variability they may also be generated by differences between el nino events through variations in the tropical atmospheric bridge this bridge typically drives subsidence west of the date line and enhanced trade winds over the far twp which cool the ocean in late fall however some relatively weaker and or more eastward shifted el nino events produce a correspondingly weakened and displaced tropical bridge which results in no surface cooling and enhanced convection in the twp because the north pacific circulation is very sensitive to forcing from the twp at this time

a morphological study of greenschist weathering on dated coastal structures south devon uk three dated structures up to 450 years in age display the effects of coastal weathering of the greenschist of which they are constructed a variety of weathering forms is present the various topographic surfaces of the structures create variation in weathering environments and consequent weathering processes and rates weathering is enhanced by direct exposure to salt bearing spray and by humid conditions and apparently limited by direct exposure to solar radiation the maximum rates of weathering on the three surfaces approximate to 0 6 mm a 1 over this period consistent with measured contemporary weathering rates for a natural surface formed by this rock type in a nearby coastal location 1997 by john wiley sons ltd