climatic fluctuations reflected in the evolution of fluvial systems of central eastern europe 60 8 ka cal bp abstract in general the evolution of fluvial systems in central eastern europe reflects the main phases of climatic changes during the period of 60 8 ka cal bp registered in greenland ice cores and their isotopic 18 o curves the greenland isotope curve shows many more wiggles and stages than the fluvial record of the same time especially during the interpleniglacial phase in central eastern europe we observe several deviations from those climatic trends connected with different factors among which are the long distance of the region from the atlantic ocean and an increase in continentality at times this region was occupied by permafrost although the coexisting warm summers during a part of the studied period enabled the presence of a forest cover these factors together controlled the specific features of the fluvial regime and sediment load reflected in alternating trends to erosion or aggradation and from meandering to braiding the permafrost influenced snowmelt floods and tendency to braiding the dense vegetation with trees reduced the supply of sediments and stabilized the meandering channels very distinct changes occurred in the river valleys that drain the mountains where ceaseless fluctuations of vegetation vertical zones were present especially during the unstable interpleniglacial when the supply of load from the higher vegetation zones was increased this system controlled by the climate and plant vegetation was modified by other factors including tectonics wind activity during dry periods blocking of valleys by ice sheets meltwater supply and sea level fluctuations of two reservoirs

chemical and boron isotopic compositions of tourmaline from the paleoproterozoic houxianyu borate deposit ne china implications for the origin of borate deposit abstract the houxianyu borate deposit in northeastern china is one of the largest boron sources of china hosted mainly in the paleoproterozoic meta volcanic and sedimentary rocks known as the liaohe group that are characterized by high boron concentrations the borate ore body has intimate spatial relationship with the mg rich carbonates silicates of the group with fine grained gneisses meta felsic volcanic rocks as main country rocks the presence of abundant tourmalinites and tourmaline rich quartz veins in the borate orebody provides an opportunity to study the origin of boron the nature of ore forming fluids and possible mineralization mechanism we report the chemical and boron isotopic compositions of tourmalines from the tourmaline rich rocks in the borate deposit and from the tourmaline bearing fine grained gneisses tourmalines from the fine grained gneisses are chemically homogeneous showing relatively high fe and na and low mg with 11b values in a narrow range from 1 22 to 2 63 tourmalines from the tourmaline rich rocks however commonly show compositional zoning with an irregular detrital core and a euhedral overgrowth and have significantly higher mg ree and more pronounced positive eu anomalies v 229 1852 ppm and sr 208 1191 ppm than those from the fine grained gneisses they show varied b isotope values ranging from 4 51 to 12 43 which plot intermediate between those of the terrigenous sediments and arc rocks with low boron isotope values as represented by the 11b 1 22 to 2 63 of the fine grained gneisses of this study and those of marine carbonates and evaporates with high boron isotope values in addition the rim of the zoned tourmaline shows notably higher mg ti v sn and pb and ree particularly lrees but lower fe co cr ni zn mn and lower 11b values than the core these data suggest that 1 the sources of boron of the borate ore body are mainly the paleoproterozoic meta volcanic and sedimentary rocks and 2 the ore forming fluids should be the high temperature metamorphic fluids related to the amphibolite facies metamorphism of the paleoproterozoic foldbelt which leach boron from the boron rich meta volcanic and sedimentary rocks of the liaohe group and the boron rich metamorphic fluids subsequently interacted with the marine mg rich carbonates and evaporates forming borate deposit the tourmaline overgrowth in the rim and the tourmaline rich rocks

intraseasonal modulation of south american summer precipitation intraseasonal variation of convection over south america is examined using singular spectrum analysis ssa the dipole convection pattern with centers of action over the sacz and the subtropical plains is modulated by modes of different timescales both oscillatory modes with periods of 36 40 days mode 40 and 22 28 days mode 22 influence convection over the sacz with the faster mode mode 22 leading the variability over the subtropical plains mode 40 is related to the madden julian oscillation outgoing longwave radiation anomalies olra propagate eastward from the western pacific to the central pacific with a period of 40 48 days the 200 hpa streamfunction composites show a wavenumber 1 structure in the tropics and a wave train propagating downstream from the convective area in the tropical pacific the development of the dipole pattern is also contributed by mode 22 which features the meridional propagation of olra over south america from midlatitudes to the tropics the streamfunction composites for mode 22 show a wave train extending from the central pacific eastward to about 608s and curving toward the northeast over south america when the sacz is enhanced these two modes become meridionally aligned locally such episodes are characterized by a wave train propagating northeastward from southern south america toward the tropics composites based on the ssa decomposition indicate that the dominant periods of variability 22 and 40 days cancel out over the pacific region and reinforce each other over the sacz for times close to onset of the enhanced sacz episodes

fluvial responses to tectonics and climate change during the late weichselian in the eastern part of the pannonian basin hungary abstract fine grained sandy silty channel belt and floodplain deposits of the berettyo koros rivers a main eastern transverse tributary system of the modern tisza river in the eastern part of the pannonian basin were deposited during the late pleistocene under net subsiding conditions the palaeo drainage network pattern of a 2500 km 2 large part of the alluvial plain was reconstructed based on interpretation of airborne photographs and analysis of 18th century topographic maps which show the natural river patterns that predate the introduction of river regulation schemes the investigation showed that a large meandering river system with two main channel belts surrounding a floodbasin entered the alluvial plain from the northeast and a braided river entered the alluvial plain from the southeast detailed sedimentary logs of seven continuous corings and several sand and clay pit sections were used to characterize different alluvial units optical luminescence dating osl of 25 quartz samples and four 14 c datings showed that the sediments are of late pleniglacial to late glacial age transport directions inferred from heavy mineral analyses combined with the osl ages strongly suggest that the large meandering system represents the palaeo tisza river which supposedly flowed along the northeast southwest striking ermellek depression during the late pleniglacial the braided river can be regarded as a precursor to the fekete and feher koros rivers which entered the alluvial plain from the southeast during the late glacial the interpretation of seismic profiles field measurements of neotectonic activity and variations in thickness of sediments along the studied profile revealed that river development was largely controlled by subsidence along the ermellek depression until 14 to 16 ky and by uplift of the southeastern part of the catchment area the studied fluvial successions also document the response of the palaeo tisza and koros system to the climate changes of the weichselian late pleniglacial late glacial period much of the sand from the meandering zones was deposited during the bolling allerod and sagvar lascaux interstadials whereas some dated sand units from the braided zone represent the older and younger dryas the error ranges of osl dates which often exceed the duration of weichselian substages and subdivisions prevented an unambiguous correlation of the studied sections with the millennial scale climate changes of the last 25 ky meandering and braided river activity coexisted under different climate conditions whereas locations of the main channel belts are related to subsidence anomalies the results of our study thus clearly indicate that tectonics was the primary control on river development

boundary layer control on convective available potential energy implications for cumulus parameterization 1 convective available potential energy cape frequently regarded as an indicator of the potential intensity of deep convection is strongly controlled by the properties of the planetary boundary layer bl variations in cape observed during field experiments in midcontinent north america the tropical east atlantic and the tropical west pacific can be accounted for mostly by changes in the temperature and humidity in the bl the coupling between cape and the bl holds for both convective and nonconvective conditions the coupling under conditions of deep convection implies a constraint on the intensity of deep convection which can be used as a closure for cumulus parameterization this constraint requires equilibrium in the environment of the parcel used as a basis for calculating cape over many cases parcel environment equilibrium is observed to hold more robustly than equilibrium of cape itself when observational uncertainties are considered it is uncertain whether quasi equilibrium in which the rate of change of cape is substantially less than the rate at which mean advection and bl fluxes change cape holds at subdiurnal timescales in the eastern atlantic and the western pacific quasi equilibrium is a poor approximation at subdiurnal timescales in midcontinent north america at timescales approaching diurnal quasi equilibrium holds in all cases cumulus parameterizations based on quasi equilibrium may be limited in their ability to model diurnal cycles as a result cape fluctuations related to large subdiurnal variations in surface fluxes are much sharper than cape fluctuations related to changes in mean advection above the bl especially over land the strong bl control on cape indicates that deep convection does not equilibrate rapid high amplitude variations in cape originating there less

an analysis of moisture fluxes into the gulf of california this study examines the nature of episodes of enhanced warm season moisture flux into the gulf of california both spatial structure and primary time scales of the fluxes are examined using the 40 yr ecmwf re analysis data for the period 1980 2001 the analysis approach consists of a compositing technique that is keyed on the low level moisture fluxes into the gulf of california the results show that the fluxes have a rich spectrum of temporal variability with periods of enhanced transport over the gulf linked to african easterly waves on subweekly 3 8 day time scales the madden julian oscillation mjo at intraseasonal time scales 20 90 day and intermediate 10 15 day time scale disturbances that appear to originate primarily in the caribbean sea western atlantic ocean in the case of the mjo enhanced low level westerlies and large scale rising motion provide an environment that favors large scale cyclonic development near the west coast of central america that over the course of about 2 weeks expands northward along the coast eventually reaching the mouth of the gulf of california where it acts to enhance the southerly moisture flux in that region on a larger scale the development includes a northward shift in the eastern pacific itcz enhanced precipitation over much of mexico and the southwestern united states and enhanced southerly southeasterly fluxes from the gulf of mexico into mexico and the southwestern and central united states in the case of the easterly waves the systems that reach mexico appear to redevelop reorganize on the pacific coast and then move rapidly to the northwest to contribute to the moisture flux into the gulf of california the most intense fluxes into the gulf on these time scales appear to be synchronized with a midlatitude short wave trough over the u s west coast and enhanced low level southerly fluxes over the u s great plains the intermediate 10 15 day time scale systems have zonal wavelengths roughly twice that of the easterly waves and their initiation appears to be linked to an extratropical u s east coast ridge and associated northeasterly winds that extend well into the caribbean sea during their development phase the short 3 8 day and to a lesser extent the intermediate 10 15 day time scale fluxes tend to be enhanced when the convectively active phase of the mjo is situated over the americas

northward propagation of the subseasonal variability over the eastern pacific warm pool 1 previous studies suggest that easterly vertical shear of summer mean flow could be a key factor in the northward propagation of the subseasonal variability ssv over the asian monsoon region e g jiang et al 2004 analysis indicates that this same mechanism may also be dictating propagation features over the eastern pacific epac consistent with the presence of local easterly vertical wind shear northward propagation of the ssv is also evident over the epac with a phase speed of about 0 6 deg day 1 moreover similar to its counterpart in the indian ocean the northward propagating ssv over this region is also characterized by positive anomalies of equivalent barotropic vorticity and lower tropospheric specific humidity and planetary boundary layer pbl convergence to the north of the convection center thus the present study provides another independent example of the essential role that easterly vertical wind shear may be playing in regulating the meridional migration of the ssv

intraseasonal teleconnection between north american and western north pacific monsoons with 20 day time scale abstract based on a recently released high resolution reanalysis dataset for the north american region the intraseasonal variability isv with a time scale of about 20 days of the north american monsoon nam is examined the rainfall signals associated with this phenomenon first emerge near the gulf of mexico and eastern pacific at about 20 n they subsequently migrate to the southwestern united states along the slope of the sierra madre occidental the rainfall quickly dissipates upon arrival at the desert region of arizona and new mexico aznm the enhanced rainfall over aznm is accompanied by strong southeasterly low level flow along the gulf of california this pattern bears strong resemblance to the circulation related to gulf surge events as documented by many studies the southeasterly flow is associated with an anomalous low vortex over the subtropical eastern pacific ocean off california and a midlatitude anticyclone over the central united states in the lower troposphere this flow pat

tracking and mean structure of easterly waves over the intra americas sea abstract easterly waves ews are prominent features of the intertropical convergence zone itcz found in both the atlantic and pacific during the northern hemisphere summer and fall where they commonly serve as precursors to hurricanes over both basins a large proportion of atlantic ews are known to form over africa but the origin of ews over the caribbean and east pacific in particular has not been established in detail in this study reanalyses are used to examine the coherence of the large scale wave signatures and to obtain track statistics and energy conversion terms for ews across this region regression analysis demonstrates that some ew kinematic structures readily propagate between the atlantic and east pacific with the highest correlations observed across costa rica and panama track statistics are consistent with this analysis and suggest that some individual waves are maintained as they pass from the atlantic into the east pacific whereas others are generated locally in the caribbean a

investigation of a large scale mode of ocean atmosphere variability and its relation to tropical pacific sea surface temperature anomalies abstract by examining the linearly coupled atmospheric and oceanic signals related to interannual variability in sea surface temperatures and upper air wind fields a hemispheric scale ocean atmosphere teleconnection mode is isolated that is significantly correlated with equatorial pacific ssts 12 months later the interannual component of this teleconnection mode is related to a basin scale dipole in the upper air wind fields stretching across the extratropical pacific with additional anomalies extending from the eastern tropical pacific over north america and into the atlantic basin in addition it is related to variability in the sst field with warm anomalies found over the tropical subtropical western pacific as well as the equatorial eastern pacific also there are related cold anomalies over the extratropical central north pacific that extend down into the central subtropical tropical pacific diagnostic studies investigating the ocean atmosphere structure for this mode of variability indicate th

long term fluvial archives in hungary response of the danube and tisza rivers to tectonic movements and climatic changes during the quaternary a review and new synthesis abstract the paper discusses the quaternary evolution of the danube and tisza rivers and their main tributaries in the context of evolution of the entire pannonian basin which is europe s largest intramontane basin within the alp carpathian orogen the palaeo drainage reconstruction of the pannonian basin for the pre quaternary period is outlined in connection with the gradual regression of lake pannon since the late miocene deltas of rivers that entered the basin from the northwest and northeast were gradually transformed into extended alluvial plains thus the earliest possible ancestor of the danube coming southeastwards from the alps could be as old as late miocene by the pliocene the whole lake pannon was infilled the former extensional basin formation was replaced by a compresional stress field which resulted in an uplift of the marginal flanks and late stage subsidence anomalies the increasing relief led to the formation of the quaternary drainage pattern the actively subsiding young basins were filled by fluvial sediments transported by the danube and tisza river systems from the uplifting mountains between the subsiding regions of the little and great plains the danube has formed an antecedent valley with terrace staircases between the uplifting sections of the transdanubian range and the north midmountains the formation of the terraces is attributed to periodic climate changes during the pleistocene combined with differences in the uplift rate the paper gives a complex overview of the classical chronology of the six terraces based on various data sources mostly dating of loess paleosol sequences travertines aeolian sand and tephra strata overlying the fluvial sediments complemented by scattered vertebrate faunal data and archaeological evidence directly from the terrace sediments the quaternary drainage pattern evolution of the great plain with a strong tectonic control is discussed in detail rivers originating from the uplifting marginal areas were drawn towards the subsiding depressions which served as local base level changes in subsidence rates in space and time throughout the quaternary resulted in the evolution of a complex drainage pattern a special emphasis is placed on the late pleistocene holocene development of the middle tisza region and the koros basin where the berettyo koros rivers form an eastern tributary system of the tisza river a comparative evaluation of these two areas is especially relevant as they provide insights into large scale late pleistocene avulsion of the tisza river osl dating complemented with inferred transport directions determined from heavy mineral analysis of fluvial sediments in the koros basin has revealed an ancient large meandering river system that can be identified with the palaeo tisza which was flowing along a tectonically controlled depression during the late pleniglacial successions in the middle tisza region have allowed differentiation between the older channels of the palaeo bodrog river and the sajo hernad alluvial fan and the younger meander belts of the new course of the tisza in the tisza system changes in river style braided to various scales of meandering show correspondence to millennial scale climate changes of the last 25 ka while in the koros basin the effects of tectonics are overprinted onto the regional climatic signals

estimation of water conductivity of the natural flood channels on the tisza flood plain the great hungarian plain abstract the rapidly subsiding central part of the pannonian basin the flood plain system of the tisza river is analyzed natural flood conducting channels that were functioning prior to the construction of the water control measures of the 19th century have been identified and mapped by now these channels have mostly disappeared only small traces of them can be found on modern maps the identification of these channels was achieved by studying historical maps of the region and by geomorphologic studies drawing the outline of the channels and the estimation of their initial meander size was supported by elevation models and satellite imagery eight flood breakout points and five independent channel systems were identified the flood conveying capacity of each channel was also estimated based on meander wavelengths the reliability of this estimation is discussed the channels functioned as anabranches conducting the floods of the tisza to its tributary the koros river the efficiency of the flood control system could be increased by regeneration of these natural channels the summarized water conveying capacity of the abandoned channels is estimated as 1000 m 3 s a value that is slightly under a half of the flood discharge of the tisza river

genesis of giant early proterozoic magnesite and related talc deposits in the mafeng area liaoning province ne china abstract this study aims to understand the origin of giant magnesite and talc deposits in the liaohe group liaoning province ne china magnesite stromatolites and the composition of fluid inclusions suggest that magnesite or high mg calcite precipitated directly from strongly restricted seawater pools with meteoric influx a primary evaporitic origin is also indicated for parts of the investigated dolomites by comparably heavy 18o values later intense metasomatic activity led to the formation of a magnesite dolomite succession with irregular contacts and a lighter isotopic signature of oxygen a slight shift in 18o to more positive values was observed for talc hosting magnesite which can be explained by the incorporation of isotopically light oxygen into talc this highlights that the hydrothermal processes that led to talc formation influenced the hosting carbonates as well which is also documented by a tendency to smaller crystal sizes a higher whiteness and lower trace element concentrations in samples from locations nearby large talc bodies although 13c is suggested to be less sensitive to hydrothermal activity comparably light 13c values were determined for magnesite sinters as well as for remobilized magnesites in general the 13c signature of the investigated magnesites is lighter than expected for proterozoic carbonates a single stage generation of the giant talc deposit in the study area is suggested based on elemental and isotopic data later deformation led to a iso chemical re location of talc at least once during this process irregularly distributed cloudy massive talc bodies acted as weak zones and were incorporated into shear bands up to several meters in thickness which form the actually present structurally controlled deposit the original ore type is preserved only in areas with minor deformation lamprophyre dykes prove jurassic volcanism and are clearly younger than the main phase of talc generation a younger post jurassic intense tectonic event is indicated by strongly tectonized dyke material that is re worked into strike slip faults and shows siliceous contact zones to the surrounding magnesite these faults occasionally cross cut the older deposit forming talc shear bands indicating that the event that led to the deformation of lamprophyre dykes was younger than the main phase of talc re location however this younger event did not lead to a second phase of major talc generation or affect the quality of the initial deposit to a large extent

characteristics of the dominant modes of atmospheric quasi biweekly oscillation over tropical subtropical americas abstractduring the boreal summer june august vigorous convection appears over the eastern pacific southern mexico and northern south america and oscillates on a distinct time scale of 10 20 days extended empirical orthogonal function eeof analysis shows that the quasi biweekly oscillation qbwo of the convection has two major modes a west east orientated mode wem and a north south orientated mode nsm the wem which is explained by the first two eeof modes originates over the eastern atlantic propagates westward along 15 n and enhances over the caribbean sea before disappearing over the central pacific the nsm explained by the third and fourth eeof modes originates over the western pacific moves eastward and strengthens over the eastern pacific it shifts northward after arriving over the caribbean sea both modes have notable seasonal dependence with the wem more active in july and august and the nsm more active in june or earlier the two distinct qbwo modes are linked to differen

the palaeoproterozoic boron deposits in eastern liaoning china a metamorphosed evaporite abstract we have carried out a field study of the palaeoproterozoic borate deposits of eastern liaoning province china the borates are hosted within mg silicate and mg carbonate rocks and have previously been interpreted as either skarns or metamorphosed volcanogenic exhalative deposits the deposits contain textures that are compatible with a sedimentary origin of the borates and there is a lack of the associated mineralization that is characteristic of magnesian skarns in addition preliminary boron isotope data indicate that the boron within the borates was not derived from the footwall rocks that have been proposed as the source of the skarn fluids a purely exhalative model can be dismissed on the basis of geochemical arguments and comparison with modern environments which show that borates are too soluble to precipitate directly from hydrothermal fluids the geology and field relationships show a number of similarities with recent non marine evaporite settings and young continental rifts in arid environments we conclude therefore that the liaoning deposits are metamorphosed evaporites in which the boron was originally present as primary evaporite borate minerals this model places the liaoning borates in the same category as the majority of other economic borate deposits in the world

is enso a cycle or a series of events 1 after early ideas that saw el ninos as isolated events the advent of coupled models brought the conception of enso as a cycle in which each phase led to the next in a self sustained oscillation twenty two years of observations that represent the el nino and la nina peaks east pacific sst and the memory of the system zonal mean warm water volume suggest a distinct break in the cycle in which the coupled system is able to remain in a weak la nina state for up to two years so that memory of previous influences would be lost similarly while the amplitude of anomalies persists from the onset of a warm event through its termination there is no such persistence across the la nina break these observations suggest that el ninos are in fact event like disturbances to a stable basic state requiring an initiating impulse not contained in the dynamics of the cycle itself

holocene sediment dynamics in the environs of the fortification enclosure of cornesti iarcuri in the romanian banat abstract the presented study combines data from geomorphological geochemical sedimentological chronometric and archaeological records providing first insights into the holocene landscape development in the environs of the late bronze age fortification enclosure cornesti iarcuri this large scale archaeological site is located in a loess covered undulating landscape at the eastern edge of the great hungarian plain in western romania sediment archives from geomorphologically different locations closely related to the copper age to late bronze age settlements are presented mainly stable geomorphic conditions throughout the holocene occurred on the high plains of the vinga plain as indicated by chemical alteration of the loss deposits and soil formation processes exceeding 2 m in contrast two cores from an alluvial fan of a minor drainage system in direct vicinity of the archaeological site document varying morphodynamics throughout the holocene phases of geomorphic activity and stability are indicated by the formation of fan deposits and paleosols developed in these sediments 14 c dates from charcoal extracted from the fan sediments show maximum deposition ages between c 4400 cal bp and c 2900 cal bp thus the formation of the charcoal coincides with the copper age to late bronze age development of the settlement sites daub pieces incorporated into these reworked soil sediments provide evidence for human activities in the catchment this in turn may indicate that the erosion processes that led to the fan formation are linked to those activities however reworking and redeposition of the charcoal and daub bearing sediments due to retrogressive erosion during the last millennia cannot be excluded

luminescence dating of periods of sand movement from the godollő hills hungary abstract a sand dune intercalated by soil horizons was investigated using luminescence and radiocarbon dating methods to determine the time of aeolian activity and soil formation in the north eastern part of the godoll hills in hungary optically stimulated luminescence osl dating and infrared stimulated luminescence irsl dating of sand sized 100 200 m grains of quartz and feldspar respectively were tested in the present study the luminescence properties of quartz were not suitable for osl dating hence irsl dating of feldspar grains was applied to all samples with subsequent correction for anomalous fading two periods of increased aeolian activity were identified in the sediment succession at tura the sediments of the lower part of the profile accumulated during the end of the late pleniglacial and through the late glacial when climatic variations caused the alternation of sand and soil horizons in the region the sand and soil layers of the upper part of the sediment succession were deposited and formed during the subatlantic phase of the holocene when sand mobility was probably mainly triggered by human activities

towards a mechanical model for the formation of the pannonian basin abstract new maps showing crustal and lithospheric thickness variations in the pannonian basin and the surrounding east alpine carpathian and dinaric mountains have been prepared on the basis of recent seismic seismologic and electromagnetic data a map presenting miocene faults of regional significance has been also constructed for the same region by using a wealth of recently available national and or more local studies it is suggested that observed crustal and lithospheric structural contrasts have been controlled primarily by neogene kinematic history of the region kinematic history is characterized by the following main patterns 1 1 indentation by adria and large scale backthrusting in the southern alps 2 2 eastward escape and extension of the eastern alps 3 3 extensional collapse in the pannonian basin area 4 4 formation of broad wrench fault systems along strike in the dinarides and southern carpathians and the western carpathians with dextral and sinistral shear respectively 5 5 compression and accretion of the external thrust and fold belt in the eastern carpathians these kinematic patterns are thought to be interrelated and all are manifestations of the late stage evolution of an overthickened orogenic wedge in order to arrive at a better understanding of the mechanism of extension which formed the pannonian basin deep crustal seismic profiles hydrocarbon exploration reflection lines and borehole data have been analyzed in the little hungarian plain this plain represents the transition zone between the alps and the pannonian lowlands and the results are illustrated by eight interpreted cross sections one result of regional importance is the clear recognition that the transdanubian central range at the southeastern flank of the little hungarian plain is composed of alpine pre senonian thrust sheets this finding marks the end of a century of debate the allochthony of the substrata of the pannonian basin can be now considered proven another result of more general interest is that these cross sections document the mode of lithospheric extension preexisting compressional detachment planes reactivate as low angle normal faults and lead to tectonic unroofing of deeply buried metamorphic terranes characterized by ductile flow along subhorizontal lineation

the impact of convection on enso from a delayed oscillator to a series of events abstract the ncar community climate system model version 3 ccsm3 exhibits persistent errors in its simulation of the el nino southern oscillation enso mode of coupled variability the amplitude of the oscillation is too strong the dominant 2 yr period too regular and the width of the sea surface temperature response in the pacific too narrow with positive anomalies extending too far into the western pacific two changes in the parameterization of deep convection result in a significant improvement to many aspects of the enso simulation the inclusion of convective momentum transport cmt and a dilution approximation for the calculation of convective available potential energy cape are used in development integrations and a striking improvement in enso characteristics is seen an increase in the periodicity of enso is achieved by a reduction in the strength of the existing short circuited delayed oscillator mode the off equatorial response is weaker and less tropically confined largely as a

simulation of the intraseasonal variability over the eastern pacific itcz in climate models during boreal summer convective activity over the eastern pacific epac inter tropical convergence zone itcz exhibits vigorous intraseasonal variability isv previous observational studies identified two dominant isv modes over the epac i e a 40 day mode and a quasi biweekly mode qbm the 40 day isv mode is generally considered a local expression of the madden julian oscillation however in addition to the eastward propagation northward propagation of the 40 day mode is also evident the qbm mode bears a smaller spatial scale than the 40 day mode and is largely characterized by northward propagation while the isv over the epac exerts significant influences on regional climate weather systems investigation of contemporary model capabilities in representing these isv modes over the epac is limited in this study the model fidelity in representing these two dominant isv modes over the epac is assessed by analyzing six atmospheric and three coupled general circulation models gcms including one super parameterized gcm spcam and one recently developed high resolution gcm gfdl hiram with horizontal resolution of about 50 km while it remains challenging for gcms to faithfully represent these two isv modes including their amplitude evolution patterns and periodicities encouraging simulations are also noted in general spcam and hiram exhibit relatively superior skill in representing the two isv modes over the epac while the advantage of spcam is achieved through explicit representation of the cumulus process by the embedded 2 d cloud resolving models the improved representation in hiram could be ascribed to the employment of a strongly entraining plume cumulus scheme which inhibits the deep convection and thus effectively enhances the stratiform rainfall the sensitivity tests based on hiram also suggest that fine horizontal resolution could also be conducive to realistically capture the isv over the epac particularly for the qbm mode further analysis illustrates that the observed 40 day isv mode over the epac is closely linked to the eastward propagating isv signals from the indian ocean western pacific which is in agreement with the general impression that the 40 day isv mode over the epac could be a local expression of the global madden julian oscillation mjo in contrast the convective signals associated with the 40 day mode over the epac in most of the gcm simulations tend to originate between 150 e and 150 w suggesting the 40 day isv mode over the epac might be sustained without the forcing by the eastward propagating mjo further investigation is warranted towards improved understanding of the origin of the isv over the epac

the 10 20 day mode of the 1979 indian monsoon its relation with the time variation of monsoon rainfall abstract the synoptic structure of the 10 20 day monsoon mode and this intraseasonal monsoon mode s relationship with the indian monsoon rainfall are examined with the 1979 summer first garp global experiment iiib data of the european centre for medium range weather forecasts and the daily 1 1 rainfall estimates retrieved from the satellite data by the goddard laboratory for atmospheres the major findings of this study are as follows 1 the 10 20 day monsoon mode exhibits a double cell either double high or double low structure one cell is centered at about 15 20 n and the other at the equator 2 both cells of the 10 20 day monsoon mode propagate coherently westward along the indian monsoon trough and along the equator respectively 3 based upon the zonal wind and local hadley circulation the vertical structure of the 10 20 day monsoon mode does not exhibit a phase change 4 a significant rainfall occurs around low centers of the 10 20 day monsoon mode through the modulation of this monsoon

paleogeographic evolution of the late miocene lake pannon in central europe abstract the paleogeographic evolution of lake pannon within the pannonian basin is reconstructed with eight maps ranging from the middle miocene to the early pliocene the maps are based on the distribution of selected biozones and specific fossils and on complementary sedimentological and seismic information our reconstruction shows that the history of lake pannon can be divided into three distinct intervals an initial stage with low water level which resulted in isolation from the sea at about 12 ma and might have led to temporary fragmentation of the lake an interval of gradual transgression lasting until ca 9 5 ma and a long late interval of shrinkage and infilling of sediments that persisted into the early pliocene the deep subbasins of the lake formed during the transgressive interval in more basinward locations than the deep basins of the preceding sarmatian age the southern shoreline running parallel with the sava and danube rivers along the northern foot of the dinarides changed very little during the lifetime of the lake while the northern shoreline underwent profound changes

an advective reflective conceptual model for the oscillatory nature of the enso recent findings about zonal displacements of the pacific warm pool required a notable modification of the delayed action oscillator theory the current leading theory for the el nino southern oscillation enso simulations with a linearized coupled ocean atmosphere model resulted in 3 to 6 year enso like oscillations with many of the variable model parameters found to be very close to their observed values this simple model suggests that ocean processes that are ignored or underestimated in the delayed action oscillator theory such as zonal current convergence zonal advection of sea surface temperature and equatorial wave reflection from the eastern ocean boundary are fundamental to the development of the enso in particular to its manifestations in the central equatorial pacific

recent vertical surface movements in the carpathian basin abstract within the framework of the co operation of the academies of sciences and geodetic services of european socialist countries intensive and repeated geodetic investigations have been carried out with the purpose of revealing characteristic features of recent vertical movements of the area between the urals and eastern europe during the first period of investigations the second half of the 1960s the then available data from repeated levellings were used later geodetic surveys established a new levelling network of outstanding accuracy by means of this net the reliability of deduced velocities could be improved until now maps of recent vertical movements were compiled twice at a scale of 1 1 000 000 due to the above mentioned investigations recent vertical movements of the carpathian basin can be accurately described this paper presents results for the main geologic and geographic units of the area

local and remote atmospheric response to tropical instability waves a global view from space a la nina took place in the equatorial pacific in 1999 and strong tropical instability waves tiws developed causing large meanders of a sea surface temperature sst front between the equator and 3 n high resolution satellite measurements are used to describe the variability of sst surface wind velocity column integrated water vapor cloud liquid water and precipitation associated with these strong tiws in 1999 coherent ocean atmosphere patterns emerge in both the pacific and atlantic revealing rich regional characteristics in the far eastern pacific southeasterly trades strengthen weaken over positive negative sst anomalies apparently due to enhanced reduced mixing with high speed winds aloft in the central pacific we find evidence that sst induced sea level pressure changes also contribute substantially to wind fluctuations similar sst wind covariability also exists in the southern hemisphere along 2 s but the wind variability induced by unit sst anomaly is much larger than that north of the equator in the central pacific where the equatorial front is broad the northern sst pattern has a large meridional scale and reaches as far north as 6 n further to the north in the intertropical convergence zone itcz where local sst anomalies are small significant variability is found in clouds and precipitation which is further correlated with surface wind convergence in the atlantic tiw signals in sst are strongly trapped near the equator but they induce significant remote response in the itcz which takes a more southern position than its pacific counterpart and thus more susceptible to tiw influence

holocene aeolian sand mobilization vegetation history and human impact on the stabilized sand dune area of the southern nyirseg hungary abstract almost 20 of the territory of hungary is covered by stabilized dunes formed during the pleistocene with the climate amelioration during the early holocene the aeolian activity ceased however various environmental and anthropogenic factors could have reactivated the aeolian processes today there is an increasing climatic stress on the dune fields of the carpathian basin which is coupled with inadequate land use it is therefore necessary to determine the timing and circumstances of sand mobilization during the holocene the site of the present study is located in a dune interdune system on the southern part of the nyirseg alluvial fan where periods of holocene aeolian activity and environmental change were investigated using palynological and sedimentological methods optically stimulated luminescence and radiocarbon dating the data achieved show climate driven boreal aeolian activity at approximately 8 2 ka and also demonstrate for the first time that during the atlantic phase 6 4 and 5 3 ka in spite of the relatively humid climate and dense vegetation aeolian activity has taken place induced probably by agricultural practices following subboreal morphological stability aeolian activity occurred several times in the subatlantic phase 2 4 2 2 1 2 0 8 and 0 4 0 1 ka as a result of vegetation changes and human activity

upb zircon geochronology of late archaean metamorphic rocks in the taihangshan wutaishan area north china abstract a geochronological study has been made in the taihangshan wutaishan area shanxi province on a sequence of precambrian supracrustal rocks and stratigraphically related intrusives these constitute part of the north china basement block the oldest rocks of the fuping group consist predominantly of mafic granulites paragneisses quartzites and amphibolites this group was always considered archaean and early k ar measurements yielded some minimum ages as old as 2300 ma and others as young as 1500 1900 ma the unconformably overlying wutai group is considered as the base of the proterozoic succession and consists of amphibolite grade paragneisses carbonates and amphibolites in its lower part and greenschist grade clastic sediments and volcanics in its upper part it has given apparent k ar mineral ages between 1500 and 2000 ma present investigations have employed the u pb zircon approach on selected parts of the sequences to provide direct depositional ages or age constraints for the fuping and wutai groups and to find the age s of subsequent metamorphic processes a minimum age for the fuping group and maximum age for the wutai group has been derived from zircon age measurements on the lanzhishan granite 2560 9 ma which intrudes the fuping group and is unconformably overlain by the wutai group this late archaean result can be interpreted as the age of an igneous crystallization event and therefore a maximum for the depositional age of the wutai group the above result is well substantiated by zircon dating of the wutai group itself zircons from a low grade metamorphosed keratophyric lava in the upper part of the group give a volcanic crystallization age of 2520 17 ma this provides close constraints for the age of deposition of the wutai group at between 2560 and 2520 ma ago if the wutai group is indeed basal proterozoic the archaean proterozoic boundary in this part of china is also dated at between 2560 and 2520 ma further evidence as to the antiquity of the wutai group comes from a u pb zircon age of 2520 30 ma for the ekou granite which intrudes the wutai group sequence the age of the underlying late archaean rocks in the tainhangshan wutaishan area the fuping group could not be directly determined because of the paucity of volcanic markers and the higher grade of metamorphism its minimum age is 2560 ma see above but only an approximate maximum age can be gleaned from the zircon systematics in granulite and amphibolite grade paragneiss samples these data indicate a degree of pb inheritance which combined with metamorphic disturbance and more recent pb loss inhibit any further interpretation other than that they indicate an approximate maximum age of around 2800 ma several of the paragneisses and one amphibolitic schist contain zircon systems which are interpreted as having completely responded to a well defined amphibolite facies metamorphic event at 2500 ma ago a younger but less well defined metamorphism caused complete pb loss from zircon and recrystallization in the amphibolite and granulite facies terrains at between 2000 and 1800 ma ago rocks which show evidence of this younger metamorphic event were not recognized from the field or structural data base but from the distribution of the few such samples analyzed it seems possible that this younger terrain may now be interpretable as a cross cutting proterozoic mobile belt this proterozoic metamorphic province is also reflected by k ar mica ages between 1600 and 2000 ma and some preliminary rb sr total rock ages at 1700 ma on nearby paragneisses whose u pb zircon age is 2500 ma

b_na rich palaeoproterozoic aravalli metasediments of evaporitic association nw india a new repository of gold mineralization we report field observations and preliminary petrochemical and stable isotopic compositions of the host rock and sulfide minerals for a recently discovered sulfide hosted gold deposit from the palaeoproterozoic aravalli rocks in northwestern india gold occurs associated with feascu co sulfides in lithofacies of diverse mineralogical composition dominated by amphibole bearing dolomitic marble and albite rich quartzo feldspathic rocks qfr the presence of vugs believed to be after dissolution of halite patches coupled with the development of scapolite bearing assemblages in dolomite marble occurrence of tourmaline rich mineralized rocks and very high na content of carbonates and qfr indicate hypersaline depositional environment for the host rock a narrow spread of 34 scdt values from 10 5 to 12 8 for stratiform arsenopyrite and remobilized pyrrhotite corroborates hypersaline to evaporitic depositional environment the 13 c values for gold bearing carbonates show bimodal distribution one population mean 0 4 v pdb is close to the sea water carbonate values while the other 3 l indicates probable mantle affinity the 18 o values for carbonates mean 18 4 v smow are not discriminative as they appear to have been modified by subsequent metamorphism and hydrothermal activity interpretation of mantellic source for carbon is borne out from the absence of biogenic activity and incompatibility of significantly negative 13 c values in the evaporitic setting of deposition of bhukia rocks we suggest that nab rich fluids channeled through rift related faults were responsible for creating hypersaline conditions that eventually evolved into an evaporitic environment mantle carbon through some still deeper faults was probably responsible for the gold transport and its subsequent deposition in an otherwise uncommon evaporitic repository of carbonates and qfr 2002 elsevier science b v all rights reserved

the west african monsoon dynamics part i documentation of intraseasonal variability intraseasonal variability in the west african monsoon is documented by using daily gridded datasets of rainfall and convection and reanalyzed atmospheric fields over the period 1968 90 rainfall and convection over west africa are significantly modulated at two intraseasonal timescales 10 25 and 25 60 day leading to variations of more than 30 of the seasonal signal a composite analysis based on the dates of the maximum minimum of a regional rainfall index in wet dry sequences shows that these sequences last on average 9 days and belong to a main quasiperiodic signal of about 15 days a secondary periodicity of 38 days is present but leads to a weaker modulation during a wet dry sequence convection in the itcz is enhanced weakened and its northern boundary moves to the north south while the speed of the african easterly jet decreases increases the speed of the tropical easterly jet increases decreases and the monsoon flow becomes stronger weaker all these features being similar to the ones associated with interannual variability characterizing wet and dry years this modulation of convection at intraseasonal timescales is not limited to west africa but corresponds to a westward propagating signal from eastern africa to the western tropical atlantic an enhanced monsoon phase is associated with stronger cyclonic activity in the low levels over the sahel associated with stronger moisture advection over west africa five days before the full development of the wet phase a stronger cyclonic circulation at 20 e induces enhanced southerly winds along 25 e where convection enhances while another westwardpropagating cyclonic circulation is located at 0 this atmospheric pattern is linked to the enhancement of the subsiding branch of the northern hadley cell at 35 n northerly advection of drier air over west africa and to increased dry convection in the heat low at 20 n it propagates westward leading to a zonally extended area of enhanced monsoon winds over west africa consistent with the occurrence of the wet phase

geochemistry and boron isotopic compositions of tourmaline from the paleoproterozoic amphibolites ne china implications for the origin of borate deposit abstract the paleoproterozoic metasediments and metavolcanics in the jiao liao ji belt northeastern china host a large number of borate deposits to trace the source of boron in these borate deposits we carried out in situ chemical and boron isotopic studies on tourmalines of amphibolites from the lieryu formation of the liaohe group in the jiao liao ji belt the petrology and the chemical compositions of tourmalines of amphibolites show that these tourmalines formed by influx of b rich fluids during different stages of metamorphism the 11b values of tourmaline continue to decline during the successive metamorphism tourmalines that formed during the prograde metamorphism show higher 11b values 9 52 10 18 than those formed during the peak metamorphism of amphibolite facies 7 22 9 43 subsequently tourmalines with lower 11b values formed during the retrograde metamorphism of greenschist facies which have slightly different boron isotopic compositions in cores 4 18 5 50 and rims 2 66 4 66 mainly due to the temperature effect the boron isotopic variations of tourmalines of amphibolites match well with our modeling study of boron isotope the results suggest that tourmalines may be precipitated from fluids released from dehydration of marine sediments with relative high 11b values 9 during prograde metamorphism in the same way the borate deposits formed from the liberated b rich fluids that interacted with the mg rich carbonates and or silicates

shallow meridional circulation in the tropical eastern pacific abstract based on four independent datasets this study presents observational evidence of a shallow meridional circulation cell in the eastern tropical pacific in this shallow meridional circulation cell the northerly cross equatorial return flow from the itcz into the southern hemisphere is found immediately above the atmospheric boundary layer in contrast to the classic concept of the hadley type deep meridional circulation whose northerly return flow resides in the upper troposphere the strength and depth of this shallow meridional circulation undergo a distinct annual cycle possible causes and climatic implications of this shallow meridional circulation are discussed

tertiary evolution of the intra carpathian area a model abstract the outer carpathian flysch nappes encircle an intra carpathian domain which can be divided into two megatectonic units north pannonian and tisza mostly on the basis of contrasting mesozoic and palaeogene facies development we see two major kinematic problems to be solved 1 1 the present distribution of the mesozoic and palaeogene facies is mosaic like and some belts form exotic bodies within realms of austroalpine affinity 2 2 late eocene palinspastic reconstruction of the outer carpathian flysch nappes suggest that the entire intra carpathian area must have been located several hundreds of kilometres to the south and to the west of its present position neogene extension can account for shortening in the external carpathian nappes but is unable to explain mesozoic facies anomalies and offsets of palaeogene formations we suggest that evolution of the intra carpathian area involved first late palaeogene early miocene juxtaposition of the north pannonian and tisza megatectonic units accompanied by the closure of the external carpathian flysch troughs thereafter extension of this amalgamated unit occurred which was compensated by thrusting of flysch nappes onto the european foreland and formation of molasse foredeeps eastward escape of the north pannonian unit from the alpine collisional belt involved left lateral shear along the pieniny klippen belt and right lateral shear along the mid hungarian zone parts of the late palaeogene basin and an early miocene volcanic edifice were dissected offset and elongated by several 100 kms the driving mechanism of the eastward escape of the intra carpathian area can be related to the collision of apulia and europe and the subduction of the external carpathian crust under the pannonian units the escape ceased gradually in the early miocene when oblique collision between the north pannonian unit and european continent occurred neogene extension of the pannonian region was an areal deformation the extension at locally variable rate resulted in the break up of the heterogenous floor of the neogene basin the driving mechanism of basin extension and contemporaneous compressional deformation of the external carpathians is thought to be related to ongoing subduction involving the marginal part of the attenuated european continental crust tectonic activity in the carpathians and basin subsidence and volcanism shifted in time and in unison from the west toward the east southeast

mjo and tropical cyclogenesis in the gulf of mexico and eastern pacific case study and idealized numerical modeling the role of the madden julian oscillation mjo in modulating the frequency and location of tropical cyclogenesis over the eastern pacific and the gulf of mexico during august september 1998 is examined during the nonconvective phase of the mjo convection and low level cyclonic vorticity occurred primarily in conjunction with the intertropical convergence zone itcz during the convective phase convection low level cyclonic vorticity and convergence expanded into the northeastern pacific and the gulf of mexico this was accompanied by enhanced eddy kinetic energy and barotropic energy conversions as compared to the nonconvective phase consistent with previous research during the nonconvective phase of the mjo vertical shear was relatively weaker but tropical cyclones tended to form mainly within the itcz on the contrary during the convective phase vertical wind shear exceeded 10 m s 1 over much of this region and tropical cyclone development occurred north of the itcz near the mexican pacific coast and the gulf of mexico idealized numerical experiments are conducted using a barotropic model with time invariant basic states representative of the nonconvective and convective phases of the mjo the simulations indicate that the propagation paths as well as the amplification of the eddies differ substantially between the two phases during the nonconvective phase the waves tend to propagate westward into the eastern pacific during the convective phase stronger southerlies steer the waves into the gulf of mexico the mjo related modulation of tropical cyclogenesis in the eastern pacific and gulf of mexico thus appears to involve anomalous convergence cyclonic vorticity vertical wind shear and differing tracks of easterly waves

the amplification of east pacific madden julian oscillation convection and wind anomalies during june november abstract madden julian oscillation mjo wind and convection anomalies are locally amplified over the northeast pacific warm pool during june november composite analysis using ncep reanalysis data indicates that perturbation available potential energy pape production through the positive correlation of intraseasonal temperature and convective diabatic heating anomalies supports the local intensification of mjo related east pacific warm pool wind anomalies pape production is maximum during periods of strong mjo convection and low level westerly wind perturbations pape is converted to perturbation kinetic energy through positive correlations between intraseasonal temperature and vertical velocity microwave sounding unit msu temperature and noaa outgoing longwave radiation data support the energy budget results derived from ncep reanalysis the amplified east pacific circulation enhances surface convergence and latent heat flux anomalies during mjo convective periods the surface convergence anomalie

permafrost or seasonal frost a review of paleoclimate proxies of the last glacial cycle in the east central european lowlands abstract our critical revision of the sedimentological characteristics and genetic interpretation of relict periglacial soil deformation features cryoturbations and sand wedges suggests that the continuous permafrost zone did not necessarily reached the lowland areas of the pannonian basin as suggested by previous studies the discontinuous permafrost zone most probably penetrated the north western part of the study area for a certain period but most of the lowlands might have been affected only by sporadic isolated permafrost and or deep seasonal frost the re evaluated climate conditions implied by the periglacial soil structures and other proxies for a periglacial environment of the area do not constrain such a narrow zone of extremely low mean annual air temperature maat and mean annual precipitation map the compilation of the climate thresholds suggested by the observed and revised interpretation cryoturbation features and thermal contraction cracks with other paleoclimate proxies converge on 0 2 c maat and 300 490 mm map on the lowland areas of the pannonian basin during the coldest phase of the last glacial these values indicate a temperature drop of 10 2 c and a precipitation decrease of 30 50 relative to modern conditions

early proterozoic tectonic styles and associated mineral deposits of the north china platform abstract the remarkable change in tectonic style from archean granite greenstone belts and high grade terrains to linear sedimentary basins marks the beginning of the early proterozoic in china the different evolutionary histories of and accumulations in the early proterozoic basins result in different archean early proterozoic boundaries two time limits 2 8 and 2 5 ga are significant for the boundary in eastern china early proterozoic basins displaying different tectonic styles contain different mineral deposits the liaodong peninsula type of early proterozoic basin contains the most abundant mineral resources and deposit types including stratabound b fe and pb zn deposits in the eugeosynclinal facies of the liaojitite suite and pyrite p and magnesite deposits in miogeosynclinal facies rocks the magnesite deposits in liaodong peninsula are the largest in the world and were formed in a unique geological setting

modulation of eastern north pacific hurricanes by the madden julian oscillation abstract hurricane and tropical storm statistics verify the modulation of eastern pacific tropical systems by the madden julian oscillation mjo as hypothesized by maloney and hartmann over twice as many named tropical systems hurricanes and tropical storms accompany equatorial 850 mb westerly anomalies than accompany equatorial easterly anomalies and the systems that do exist are stronger hurricanes are over four times more numerous during westerly phases of the mjo than during easterly phases the current study constructs a composite life cycle of the mjo during may november 1979 95 using an index based on the 850 mb equatorial zonal wind equatorial kelvin waves propagating eastward from convective regions of the western pacific ocean alter dynamical conditions over the eastern pacific ocean westerly easterly equatorial 850 mb wind anomalies are accompanied by enhanced suppressed convection over the eastern pacific hurricane region convection locally amplifies the wind anomalies over the ea

the full glacial forests of central and southeastern europe the presence of trees in central and southern europe during the last full glaciation has long been a matter of debate a low but persistent presence of fossil tree pollen in central and southern european full glacial paleoecological sequences has been interpreted either as representing long distance pollen transport from southerly refuges or as representing in situ refugial populations here we present macroscopic charcoal results from 31 sequences located throughout hungary that provide unequivocal evidence for the presence of at least seven different tree types between approximately 32 500 and 16 500 14c yr b p this evidence is presented in conjunction with molluscan and pollen analyses to indicate that during the last full glaciation trees grew as far north as hungary probably in microenvironmentally favorable sites these areas provided an important cold stage refugium for the european flora and fauna

chemical and stable isotopic compositions of proterozoic metamorphosed evaporites and associated tourmalines from the houxianyu borate deposit eastern liaoning china an integrated major element trace and rare earth element and stable isotope b si o and s study has been carried out on the houxianyu borate deposit eastern liaoning china the present day mineralogy of the deposit is closely similar to that of magnesian skarn deposits and the borates are underlain by granite however the geochemical and isotopic evidence does not favour a skarn type origin in particular the boron isotopic compositions of the borate minerals and associated tourmalines preclude their origin from fluids derived from the granite rather the data are compatible with the borate deposit being a metamorphosed evaporite the mineralogy and chemistry of the deposit are most compatible with a non marineorigin although the high 34s and 11b values suggest that there may have been some marine components to the evaporitic brines overall the premetamorphic origin of the houxianyu borate deposit is similar to that of the tertiary non marine evaporite borate deposits of western turkey there are also similarities with other proterozoic early rifting environments e g the upper proterozoic damaran orogen of south africa that have implications for the structural evolution and mineral potential of the region

the role of cross equatorial tropical cyclone pairs in the southern oscillation abstract the locations and frequencies of cross equatorial tropical cyclone pairs over the pacific ocean are compared between years of contrasting equatorial pacific sea surface temperature sst and atmospheric circulation anomalies i e high versus low southern oscillation so indices during the period 1971 79 weak southeast trade winds associated with low so indices allow warm 29 c surface water in the equatorial 0 5 s zone to extend eastward across the dateline encouraging formation of cyclone pairs near the dateline the cyclone pairs in turn provide the linkage between warm water and equatorial convection as indicated by canton island rainfall during southern summer in general the occurrences of cyclone pairs vary in longitude with the eastward excursions of warm equatorial water furthermore cyclone pairs appear to provide a positive feedback by advancing the eastward warm water extent in 1974 75 when no cyclone pairs developed near the dateline in spite of sufficiently high sst

a new greenland ice core chronology for the last glacial termination 1 we present a new common stratigraphic timescale for the north greenland ice core project ngrip and grip ice cores the timescale covers the period 7 9 14 8 kyr before present and includes the bolling allerod younger dryas and early holocene periods we use a combination of new and previously published data the most prominent being new high resolution continuous flow analysis cfa impurity records from the ngrip ice core several investigators have identified and counted annual layers using a multiparameter approach and the maximum counting error is estimated to be up to 2 in the holocene part and about 3 for the older parts these counting error estimates reflect the number of annual layers that were hard to interpret but not a possible bias in the set of rules used for annual layer identification as the grip and ngrip ice cores are not optimal for annual layer counting in the middle and late holocene the timescale is tied to a prominent volcanic event inside the 8 2 kyr cold event recently dated in the dye 3 ice core to 8236 years before a d 2000 b2k with a maximum counting error of 47 years the new timescale dates the younger dryas preboreal transition to 11 703 b2k which is 100 150 years older than according to the present grip and ngrip timescales the age of the transition matches the gisp2 timescale within a few years but viewed over the entire 7 9 14 8 kyr section there are significant differences between the new timescale and the gisp2 timescale the transition from the glacial into the bolling interstadial is dated to 14 692 b2k the presented timescale is a part of a new greenland ice core chronology common to the dye 3 grip and ngrip ice cores named the greenland ice core chronology 2005 gicc05 the annual layer thicknesses are observed to be log normally distributed with good approximation and compared to the early holocene the mean accumulation rates in the younger dryas and bolling periods are found to be 47 2 and 88 2 respectively

variability in the southerly flow into the eastern pacific itcz abstract during boreal summer and fall there is a strong southerly boundary layer flow across the equator into the east pacific intertropical convergence zone itcz the modulation of this flow on synoptic to seasonal time scales is studied using an index of meridional pressure difference between the equator and the itcz along 95 w two complementary datasets from the east pacific investigation of climate epic are used to study eastern pacific variability daily measurements of sea level pressure slp from tropical atmosphere ocean toa array buoys from may to november 2001 provide temporal coverage and eight flights by a c 130 aircraft during september to october 2001 document the associated modulation of lower tropospheric vertical structure the principal mode of variability of the perturbation slp along 95 w from 1 s to 12 n derived by principal component analysis from either the eight flights pc1c 130 or from daily tao buoy observations pc1 explains 77 of the meridional pressure gradien

structures and mechanisms of the northward propagating boreal summer intraseasonal oscillation abstract the spatial and temporal structures of the northward propagating boreal summer intraseasonal oscillation bsiso are revealed based on the analysis of both the echam4 model simulation and the ncep ncar reanalysis the bsiso structure and evolution characteristics simulated by the model bear many similarities to those derived from the ncep ncar reanalysis the most notable features are the remarkable meridional asymmetries relative to the bsiso convection in the vorticity and specific humidity fields a positive vorticity perturbation with an equivalent barotropic structure appears a few latitude degrees north of the convection center the maximum specific humidity also shows a clear northward shift in the lower troposphere two internal atmospheric dynamics mechanisms are proposed to understand the cause of the northward propagation of the bsiso the first is the vertical shear mechanism the key process associated with this mechanism is the generation of barotropic vorticity due to the couplin

genesis of a giant paleoproterozoic strata bound magnesite deposit constraints from mg isotopes abstract giant strata bound magnesite deposits are absent in modern and most phanerozoic sedimentary environments but occur predominantly in precambrian strata these deposits may have formed directly through precipitation of evolved mg rich seawater in an evaporative shallow marine setting or alternatively by epigenetic hydrothermal replacement of the mg rich carbonate precursor to test these hypotheses we obtained the first mg isotope data from the world s largest strata bound magnesite deposit belt hosted by the ca 2 1 ga dashiqiao formation in northeast china the mg isotope compositions 26 mg of most magnesite ores in the huaziyu deposit are heavier 0 75 0 26 than most proterozoic sedimentary dolostones the mg isotope compositions and major and trace element data indicate that the magnesites are probably not of hydrothermal origin instead a mg rich carbonate precursor precipitated from evaporating seawater in a semi closed system diagenetic brines altered the mg rich carbonate precursor to magnesite subsequently recrystallization during regional metamorphism produced coarsely crystalline and saddle magnesite these interpretations are consistent with the geological features and other geochemical data element concentrations and c and o isotopes for the magnesite ores hence we interpret the formation of the huaziyu magnesite deposit to be dominated by evaporative sedimentation and brine diagenesis

late quaternary paleodrainage reconstruction of the maros river alluvial fan abstract the surface of the extensive maros alluvial fan is densely 0 78 km km 2 covered by paleochannels the aim of the present study is to reconstruct the final late quaternary stage of the alluvial fan development by identifying paleodrainage directions and determining morphology and pattern of the paleochannels and the age of their activity on the surface of the alluvial fan 18 meandering braided anastomosing or misfit paleochannel zones were identified the existence of these channels indicates that the main process of the fan development was avulsion rather than lateral channel shift and the overbank floodplain accumulation played a minor role as the paleochannels were not buried the oldest paleodrainages a c shifted towards north from the east west axis of the alluvial fan draining water to the koros basin the similar age 18 7 2 3 ka 14 2 1 4 ka of the paleochannel zones indicates rapid avulsions or the coexistence of paleodrainages in the northern half of the alluvial fan the last large d paleodrainage change occurred 12 4 2 1 ka when the channel turned westward a large meandering channel functioned for a period 12 4 2 1 ka 9 6 1 3 ka and with the coexisting misfit channels these channels drained a considerable amount of water q b 2500 m 3 s in the next development phase e paleodrainages the maros flowed north but after a sharp bend it turned toward the south and it started to form the southern lobe of the alluvial fan these channels existed between 8 5 0 9 ka and 3 5 0 4 ka and had a bankfull discharge of 1000 2000 m 3 s the last f paleodrainage of the maros river existed for a short time 1 9 0 3 ka 1 6 0 3 ka and indicated decreasing discharge q b 1400 m 3 s in the final phase of the alluvial fan evolution the present day course of the river was developed and its discharge decreased further 680 m 3 s

stress induced late stage subsidence anomalies in the pannonian basin abstract subsidence sedimentation and tectonic quiescence of the pannonian basin was interrupted a few million years ago by tectonic reactivation this recent activity has manifested itself in uplift of the western and eastern flanks and continuing subsidence of the central part of the pannonian basin low to medium magnitude earthquakes of the carpathian pannonian region are generated mostly in the upper crust by reverse and wrench fault mechanisms there is no evidence for earthquakes of extensional origin 2 d model calculation of the subsidence history shows that a recent increase in magnitude of horizontal compressional intraplate stress can explain fairly well the observed quaternary uplift and subsidence pattern we propose that this stress increase is caused by the overall europe africa convergence in late pliocene consumption of subductible lithosphere at the eastern margin of the pannonian basin was completed and the lithosphere underlying the pannonian basin became locked in a stable continental frame consequently extensional basin formation has come to an end and compressional inversion of the pannonian basin is in progress

on the termination of el nino a feature of the end phase of recent el nino periods is thermocline shallowing to normal depths in the central and eastern equatorial pacific before sea surface temperature sst returns to normal also characteristic of el nino periods is a late in the year shift of the el nino equatorial westerly wind anomalies from symmetric about the equator to centered south of the equator we show that the directly forced ocean response to this shift produces thermocline shallowing like that observed the wind shift may result from the normal seasonal evolution of pacific waters warmer than 28 c these shift from being relatively symmetric about the equator in october november to concentrated south of the equator in december january thus the seasonal cycle may be a central part of the mechanism of el nino termination

links between tropical cyclone activity and madden julian oscillation phase in the north atlantic and northeast pacific basins abstract the leading intraseasonal mode of atmospheric and oceanic variability the madden julian oscillation mjo influences tropical and extratropical sea level pressure temperature divergent and rotational wind components moisture and deep convection as a 40 to 50 day oscillation the mjo is also known to influence tropical phenomena including tropical cyclone tc activity in various tc basins the links between the mjo and multiple measures of tc activity including genesis landfall and an integrative accumulated cyclone energy ace index were quantified for multiple tc formation basins across the western hemisphere including the north atlantic and northeast pacific ocean and subbasins for the period 1978 2006 using this relatively long 29 yr tc dataset and employing an upper tropospheric mjo diagnostic that is physically meaningful over the entire western hemisphere this study extends existing research on the relationships between the mjo and tcs the noaa climate prediction cente

the evolution of the great hungarian plain fluvial system fluvial processes in a subsiding area from the beginning of the weichselian abstract in the great hungarian plain ghp one of the most complex fluvial systems of europe developed through tectonic and climatic factors and vegetation change the aim of the present study is to summarise these controlling factors and to describe the evolution of the ghp special attention is paid to the latest results on late weichselian and holocene development in the tisza river and their effects on the river s largest tributary the maros river several tectonically active subsiding basins existing in the ghp have determined the direction of river courses and erosional accumulational fluvial processes as a result of uneven subsidence the river s flow routes have shifted frequently for example the danube and the tisza shifted 80 100 km abandoning their alluvial fans where extensive aeolian processes started upstream from the subsiding areas incision propagated headward which resulted in the development of floodplain levels and terraces though climate and vegetation changes also simultaneously influenced the rivers hydro morphology channel pattern changes were found just along the margin of the plain and only meandering paleo channels remained in the center of the ghp during dry and cold periods braided patterns appeared in the alluvial fans most likely the result of abundant sediment supply and due to the inability of sparse riparian vegetation to stabilise the banks effectively based on paleo discharge calculations by the end of the pleistocene the rivers of the ghp produced three to eight times more discharge than they do currently and discharge levels continuously decreased during the holocene however due to the long length of the rivers there is a considerable time lag between the response rates of the different river sections which makes creating paleo hydrological reconstructions even more difficult

from deposition to erosion spatial and temporal variability of sediment sources storage and transport in a small agricultural watershed article i nfo article history the spatial and temporal variability of sediment sources storage and transport were investigated in a small agricultural watershed draining the coast ranges and sacramento valley in central california results of field laboratory and historical data analysis in the willow slough fluvial system document changes that transformed a transport limited depositional system to an effective erosion and transport system despite a large sediment supply these changes were caused by a combination of factors i an increase in transport capacity and ii hydrologic alteration alteration of the riparian zone and drainage network pattern during the past 150 years included a twofold increase in straightened channel segments along with a baselevel change from excavation that increased slope and increased sediment transport capacity by 7 hydrologic alteration from irrigation water contributions also increased transport capacity by extending the period with potential for sediment transport and erosion by 6 months year field measurements document quaternary alluvium as a modern source of fine sediment with grain size distributions characterized by 5 to 40 fine material about 60 of an upland and 30 of a lowland study reach incised into this deposit exhibit bank erosion during this study the wet 2006 and relatively dry 2007 water years exhibited a range of total annual suspended sediment load spanning two orders of magnitude 108 500 kg km

the inner zone of the liaoji paleorift its early structural styles and structural evolution abstract a suite of eugeosynclinal formations together with common occurrence of extensional granitic rocks constitutes the major part of the inner zone of the liaoji paleorift in liaodong peninsula china two characteristic associations of deformation structures formed under different crustal conditions have been recognized in the liaoji paleorift zone from macro meso and micro structural studies and tectono thermal analyses magmatic core complex mcc a special structural style of extensional regime inherited from early rifting is constituted by the spatial temporal and genetic associations of magmatic cores bedding parallel ductile shear zones and extensional nappes such complexes are widely developed in the rift zone superposed on the mccs thrust nappes and thrusting related brittle ductile shear zones dominate a compressional event in the later evolution of the rift zone early structures were strongly deformed and transformed by later structures and meanwhile also exerted control on the latter e g the thrust nappes are often related to early folds and represented by fold nappes with extensive reactivation and reemplacement of granitic rocks in the cores a schematic evolutionary model for the early structural evolution of the early proterozoic in the inner zone is presented which indicates a different evolution of early rift zones from those of younger ones

extension of the stochastic mixing model to cumulonimbus clouds abstract the stochastic mixing model of cumulus clouds is extended to the case in which ice and precipitation form a simple cloud microphysical model is adopted in which ice crystals and aggregates are carried along with the updraft whereas raindrops graupel and hail are assumed to immediately fall out the model is then applied to the 2 august 1984 case study of convection over the magdalena mountains of central new mexico with excellent results the formation of ice and precipitation can explain the transition of this system from a cumulus congestus cloud to a thunderstorm

channel sinuosity of the koros river system hungary romania as possible indicator of the neotectonic activity abstract the koros river drainage basin is located in the eastern part of the great hungarian plain west of the apuseni mts in the middle of the pannonian basin the channels of the river and its tributaries are mostly meandering characterized by large loops and multiple bends in their pre regulation form the channel sinuosity of this river system is analyzed in order to draw conclusions on the neotectonic activity of the eastern region of the great hungarian plain the original pre regulation status of the river thalwegs was digitized from rectified historical maps sinuosities at different sample section lengths were computed in a gis software environment providing so called sinuosity spectra for each point of the analyzed channels high sinuosity sections were correlated to linear features identified in seismic survey sections indicating their neotectonic activity some low sinuosity sections former marshlands and a special river section having anastomosed planform suggest zones of rapid subsidence all of the above features cannot be verified by the topography as the relief in this area is below 10 m

the central american midsummer drought regional aspects and large scale forcing abstract the midsummer drought msd is a diminution in rainfall experienced during the middle of the rainy season in southern mexico and central america as well as in the adjacent caribbean gulf of mexico and eastern pacific seas the aim of this paper is to describe the regional characteristics of the msd and to propose some possible forcing mechanisms satellite and in situ data are used to form a composite of the evolution of a typical msd which highlights its coincidence with a low level anticyclone centered over the gulf of mexico and associated easterly flow across central america the diurnal cycle of precipitation over the region is reduced in amplitude during midsummer the msd is also coincident with heavy precipitation over the sierra madre occidental part of the north american monsoon reanalysis data are used to show that the divergence of the anomalous low level flow during the msd is the main factor governing the variations in precipitation a linear baroclinic model is used to show

modulation of hurricane activity in the gulf of mexico by the madden julian oscillation the madden julian oscillation mjo is a large scale episodic modulation of tropical winds and precipitation that travels eastward from asia to america with a characteristic repeat time of 30 to 60 days here it is shown that when mjo wind anomalies in the lower troposphere of the eastern pacific are westerly gulf of mexico and western caribbean hurricane genesis is four times more likely than when the mjo winds are easterly accurate predictions of the mjo may lead to improved long range forecasts of tropical cyclone activity

local versus remote wind forcing of the equatorial pacific surface temperature in july 2003 1 after the moderate el nino of 2002 the tropical pacific seemed poised to enter a la nina phase wind anomalies during may and june 2003 however led to a sudden termination of this event counter to earlier predictions forecasts from july 2003 correctly predicted normal conditions for the remainder of the year in this paper the causes of this abrupt turn of events are analyzed it is shown that wind anomalies in the eastern tropical pacific played a major role in terminating the incipient cold enso phase although westerly wind bursts in the western pacific explained most of the ocean subsurface behavior to the west of 110 w their impact on sst was confined to the central equatorial pacific

the madden julian oscillation in echam4 coupled and uncoupled general circulation models the madden julian oscillation mjo dominates tropical variability on timescales of 30 70 days during the boreal winter spring it is manifested as an eastward propagating disturbance with a strong convective signature over the eastern hemisphere the space time structure of the mjo is analyzed using simulations with the echam4 atmospheric general circulation model run with observed monthly mean sea surface temperatures ssts and coupled to three different ocean models the coherence of the eastward propagation of mjo convection is sensitive to the ocean model to which echam4 is coupled for echam4 opyc and echo g models for which 100 years of daily data is available monte carlo sampling indicates that their metrics of eastward propagation are different at the 1 significance level the flux adjusted coupled simulations echam4 opyc and echo g maintain a more realistic mean state and have a more realistic mjo simulation than the nonadjusted scale interaction experiment sintex coupled runs the sintex model exhibits a cold bias in indian ocean and tropical west pacific ocean sea surface temperature of 0 5 c this cold bias affects the distribution of time mean convection over the tropical eastern hemisphere furthermore the eastward propagation of mjo convection in this model is not as coherent as in the two models that used flux adjustment or when compared to an integration of echam4 with prescribed observed sst this result suggests that simulating a realistic basic state is at least as important as air sea interaction for organizing the mjo while all of the coupled models simulate the warm cold sst anomalies that precede succeed the mjo convection the interaction of the components of the net surface heat flux that lead to these anomalies are different over the indian ocean the echam4 opyc model in which the atmospheric model is run at a horizontal resolution of t42 has eastward propagating zonal wind anomalies and latent heat flux anomalies however the integrations with echo g and sintex which used t30 atmospheres produce westward propagation of the latent heat flux anomalies contrary to reanalysis it is suggested that the differing ability of the models to represent the near surface westerlies over the indian ocean is related to the different horizontal resolutions of the atmospheric model employed

planetary and synoptic scale influences on eastern pacific tropical cyclogenesis abstract the structure and evolution of lowpass filtered background flow and synoptic scale easterly waves were examined during the 1991 eastern pacific hurricane season active and inactive cyclogenesis periods conformed well to the sign of the near equatorial lowpass filtered 850 mb zonal wind anomaly consistent with the recent results of maloney and hartmann this behavior emphasizes the importance of westerly wind bursts associated with the madden julian oscillation mjo in creating an environment favorable for eastern pacific tropical cyclogenesis synoptic scale easterly waves reached the western caribbean and eastern pacific regularly from upstream usually from africa the amplitude of waves leaving africa had little correlation with the likelihood of a wave producing an eastern pacific storm rather easterly waves intensified and tropical depressions formed during the convectively active phase of the mjo in the western caribbean and eastern pacific wave growth measured by strengthening o

the march 1997 westerly wind event and the onset of the 1997 98 el nino understanding the role of the atmospheric response in a previous study the effect of the march 1997 westerly wind event wwe on the evolution of the tropical pacific ocean was studied using an ocean general circulation model gcm the response was characterized by i a cooling of the far western pacific 0 88c ii a rapid eastward displacement of the warm pool 2000 km in a month and iii a weak warming of the central eastern pacific along the path of the oceanic kelvin wave excited by the wwe 0 58c in this study the atmospheric response to these aspects of the sea surface temperature sst response are investigated using an atmospheric gcm forced with the sst anomalies from the ocean only experiments the results have demonstrated that the three aspects of the sst anomaly field generated by the wwe

patterns of alluvial rivers the pattern planform of a river can be considered at vastly different scales depending upon both the size of the river and the part of the fluvial system that is under consideration figure 1 for example in the broadest sense river patterns comprise a drainage network dendritic parallel trellis etc figure la the type of pattern is of interest to geomorphologists and geologists who interpret geologic conditions from aerial photographs at another scale a river reach which in figure lb is meandering is of interest to the geomorphologist who is interested in what that pattern reveals about river history and behavior and to the engineer who is charged with maintaining navigation and preventing major instability when a single meander is examined figure 1 c the hydraulics offtow the sediment transport and the potential for bank erosion are of concern in addition the sedimentologist is interested in the distribution of sediment within the bend bed forms within the channel figure ld and sedimentary structures figure ie which also establish a component of roughness for the hydraulic engineer finally the individual grains figure if provide geologic information on the sediment sources the nature of sediment loads and the feasibility of dredging for gravel there is an interaction of hydrology hydraulics geology and geomorphology at all scales which emphasizes the point that the fluvial system as a whole cannot be ignored even though only a component of the system is to be studied in this review only the patterns or planforms of alluvial rivers are discussed although it is apparent that the hydrologic and sediment yield characteristics of the drainage basin figure la as well as its geologic history cannot be ignored in the explanation of the pattern of any river

late quaternary dynamics of the tisza river evidence of climatic and tectonic controls abstract the focus of this study is to understand a dramatic avulsion event on the tisza river during the late pleistocene the river course switched by about 80 km from the east to west of the great hungarian plain ghp through the zahony bend to its present meander belt the aim of this study is to date this zahony avulsion based upon radiocarbon and pollen samples from six cores in the polgar study area situated in the west of the ghp at the middle course of the tisza river in addition a grain size composition and heavy mineral analysis has been performed the results of these analyses reveal a sequence of paleochannels and have been plotted on a high resolution digital elevation model illustrating the paleochannel form and age relationships the study suggests that the age of this major avulsion event is significantly older than it was previously supposed instead of 10 to 11 ka it is according to our new data 16 18 ka and definitely predates the last glacial maximum lgm the river cut into the previous contiguous surface and formed at least one climatic terrace then drifted gradually westward as a response to a tilt or the differential subsidence of tectonic origin

a new parameterization for shallow cumulus convection and its application to marine subtropical cloud topped boundary layers part i description and 1d results abstract a new parameterization of shallow cumulus convection is presented the parameterization consists of a mass flux scheme based on a buoyancy sorting entrainment detrainment plume model the mass flux scheme is coupled to a 1 5 order turbulence closure model with an entrainment closure for convective boundary layers model performance is verified using single column model simulations at relatively high vertical resolution of pure trade cumulus convection and a cumulus to stratocumulus transition mixing rates cloud cover and vertical flux profiles as deduced from previously published large eddy simulation studies are well reproduced by the parameterization the model is used to demonstrate that height variations of lateral mixing rates can be successfully captured by a simple implementation of a buoyancy sorting mechanism in the updraft cloud model a companion paper describes the implementation of the scheme in a mesoscale model

late pleistocene loess palaeosol sequences in the vojvodina region north serbia late pleistocene loess palaeosol sequences are widespread in the vojvodina region with thicknesses reaching a maximum of about 20 m our investigations include more than 40 of these loess sections geochronology of the last glacial loess palaeosol sequences based on lumines cence dating and amino acid racemisation provides correlations between upper pleistocene loess palaeosol sediments in vojvodina and comparable deposits at other european localities sedimentary logs of magnetic susceptibility grain size measurements and carbonate content combined with malacological evidence indicate two main relatively cold and arid phases during the last glacial period related to intensive accumulation of loess units l1l1 and l1l2 as well as many brief episodes of dry and windy climatic conditions suggesting a possible relationship with cold events recorded in the north atlantic region generally late pleistocene climate in the region was dry and relatively warm compared with glacial period sites in central europe and was characterised by sharp differences between glacial and interglacial modes new data and interpretations presented in this study emphasise the significance of loess palaeosol sequences in vojvodina for the reconstruction of the temporal and spatial evolution of late pleistocene palaeoclimate in this part of europe copyright 2007 john wiley sons ltd

triggering of el nino by westerly wind events in a coupled general circulation model two ten members ensemble experiments using a coupled ocean atmosphere general circulation model are performed to study the dynamical response to a strong westerly wind event wwe when the tropical pacific has initial conditions favourable to the development of a warm event in the reference ensemble cref no wind perturbation is introduced whereas a strong westerly wind event anomaly is introduced in boreal winter over the western pacific in the perturbed ensemble cwwe our results demonstrate that an intense wwe is capable of establishing the conditions under which a strong el nino event can occur first it generates a strong downwelling kelvin wave that generates a positive sea surface temperature sst anomaly in the central eastern pacific amplified through a coupled ocean atmosphere interaction this anomaly can be as large as 2 5 c 60 days after the wwe secondly this wwe also initiates an eastward displacement of the warm pool that promotes the occurrence of subsequent wwes in the following months these events reinforce the initial warming through the generation of additional kelvin waves and generate intense surface jets at the eastern edge of the warm pool that act to further shift warm waters eastward the use of a ten members ensemble however reveals substantial differences in the coupled response to a wwe whereas four members of cwwe ensemble develop into intense el nino warming as described above four others display a moderate warming and two remains in neutral conditions this diversity between the members appears to be due to the internal atmospheric variability during and following the inserted wwe in the four moderate warm cases the warm pool is initially shifted eastward following the inserted wwe but the subsequent weak wwe activity when compared to the strong warming cases prevents to further shift the warm pool eastwards the seasonal strengthening of trade winds in june july can therefore act to shift warm waters back into the western pacific reducing the central eastern pacific warming this strong sensitivity of the coupled response to wwes may therefore limit the predictability of el nino events as the high frequency wind variability over the warm pool region remains largely unpredictable even at short time lead

two late pleistocene climate driven incision aggradation rhythms in the middle dnieper river basin west central russian plain abstract in valleys of the river seim and its tributaries in the middle dnieper basin west central russian plain two low terraces t1 10 16 m and t0 5 7 m above the river and a floodplain 2 4 m with characteristic large and small palaeochannels exist a range of field and laboratory techniques was applied and 30 new numerical ages osl and 14c dates were obtained to establish a chronology of incision and aggradation events that resulted in the current valley morphology two full incision aggradation rhythms and one additional aggradation phase from the previous rhythm were recognized in the late pleistocene holocene climate cycle the following events were detected 1 late mis 5 early mis 4 aggradation of terrace t1 following the deep incision at the end of mis 6 2 late mis 4 40 30 ka incision into terrace t1 below the present day river formation of the main scarp in the bottom of the valley between terrace t1 and terrace t0 floodplain levels 3 mis 2 aggradation of terrace t0 lateral migrations of a shallow braided channel located few meters above the present day river since 25 ka through the lgm 4 18 13 ka incision into terrace t0 below the modern river multiple thread channels concentrated in a single flow that at some places formed large meanders in the period 15 13 ka high floods that rose above the present day floods left large levees and overbank loams on terrace t0 5 younger dryas holocene transition aggradation up to the modern channel level transformation of large late glacial to small holocene meanders the established incision aggradation rhythms are believed to be manifested over the central russian plain outside the influence of ice sheets in the north and base level changes in the south the two phase deepening of the valley occurred in the last quarter of the last glacial epoch but can not be attributed directly to the glacial interglacial transition both the detected incision events correspond to relatively warm climate phases late mis 3 post lgm warming including the bolling allerod interstadial anomalously large size of the preserved river palaeochannels prove that the post lgm incision phase was induced by a climatically forced large increase of water runoff considerable increase of water discharges is considered the most probably cause for the late mis 4 incision phase also therefore river incision seems to have been governed rather by changing water runoff that oscillated in phase shift with the thermal regime

westerly wind bursts enso s tail rather than the dog westerly wind bursts wwbs in the equatorial pacific occur during the development of most el nino events and are believed to be a major factor in enso s dynamics because of their short time scale wwbs are normally considered part of a stochastic forcing of enso completely external to the interannual enso variability recent observational studies however suggest that the occurrence and characteristics of wwbs may depend to some extent on the state of enso components implying that wwbs which force enso are modulated by enso itself satellite and in situ observations are used here to show that wwbs are significantly more likely to occur when the warm pool is extended eastward based on these observations wwbs are added to an intermediate complexity coupled ocean atmosphere enso model the representation of wwbs is idealized such that their occurrence is modulated by the warm pool extent the resulting model run is compared with a run in which the wwbs are stochastically applied the modulation of wwbs by enso results in an enhancement of the slow frequency component of the wwbs this causes the amplitude of enso events forced by modulated wwbs to be twice as large as the amplitude of enso events forced by stochastic wwbs with the same amplitude and average frequency based on this result it is suggested that the modulation of wwbs by the equatorial pacific sst is a critical element of enso s dynamics and that wwbs should not be regarded as purely stochastic forcing in the paradigm proposed here wwbs are still an important aspect of enso s dynamics but they are treated as being partially stochastic and partially affected by the large scale enso dynamics rather than being completely external to enso it is further shown that wwb modulation by the large scale equatorial sst field is roughly equivalent to an increase in the ocean atmosphere coupling strength making the coupled equatorial pacific effectively self sustained

air sea interaction over the eastern pacific warm pool gap winds thermocline dome and atmospheric convection high resolution satellite observations are used to investigate air sea interaction over the eastern pacific warm pool in winter strong wind jets develop over the gulfs of tehuantepec papagayo and panama accelerated by the pressure gradients between the atlantic and pacific across narrow passes of central american cordillera patches of cold sea surface temperatures ssts and high chlorophyll develop under these wind jets as a result of increased turbulent heat flux from the ocean and enhanced mixing across the base of the ocean mixed layer despite a large decrease in sst exceeding 38c in seasonal means the cold patches associated with the tehuantepec and papagayo jets do not have an obvious effect on local atmospheric convection in winter since the intertropical convergence zone itcz is located farther south the cold patch of the panama jet to the south on the other hand cuts through the winter itcz and breaks it into two parts a pronounced thermocline dome develops west of the gulf of papagayo with the 208c isotherm only 30 m deep throughout the year in summer when the panama jet disappears and the other two wind jets weaken sst is 0 58c lower over this costa rica dome than the background this cold spot reduces local precipitation by half punching a hole of 500 km in diameter in the summer itcz the dome underlies a patch of open ocean high chlorophyll this thermocline dome is an ocean dynamic response to the positive wind curls south of the papagayo jet which is optimally oriented to excite ocean rossby waves that remotely affect the ocean to the west the meridionally oriented tehuantepec and panama jets by contrast only influence the local thermocline depth with few remote effects on sst and the atmosphere the orographical triggered air sea interaction described here is a good benchmark for testing high resolution climate models now under development

the effect of the mjo on the north american monsoon abstract the effect of the madden julian oscillation mjo in the eastern pacific on the north american monsoon is documented using ncep ncar reanalysis and daily mean precipitation data from 1958 to 2003 it is found that positive zonal wind anomalies in the eastern tropical pacific lead to above normal precipitation in northwest mexico and arizona from several days to over a week later this connection between the tropical pacific and monsoon precipitation appears to be limited to regions influenced by moisture surges from the gulf of california as a similar connection does not exist for new mexico precipitation the evidence suggests that the mjo might affect monsoon precipitation by modulating the strength of low level easterly waves off the coast of mexico which in turn triggers the development of a gulf surge

ages of periods of sand movement in hungary determined through luminescence measurements abstract the late glacial and holocene climatic oscillations in hungary are manifested by changing fluvial and aeolian sand deposition as well as by intercalated soil formations the sand blown territories have special interest since the buried fossil soils provide detailed information about climate and environment changes during the past two decades the time of the sand moving periods was studied exclusively by radiocarbon age determination but by now thanks to the latest investigations these results have been controlled and completed by the thermoluminescence and infrared optically stimulated luminescence dating methods these techniques have been applied to provide a more detailed chronological framework for late pleistocene and holocene sand accumulation periods five aeolian sand accumulation periods can be recognized covering the late glacial and holocene time period at 14 0 2 3 12 0 1 9 9 2 1 7 6 0 0 5 and 0 6 0 07 ka the sand blown formations are intercalated by soil horizons the radiocarbon age estimates provide evidence for late glacial bolling allerod and lower atlantic soil forming periods

reconstruction of a pleistocene meandering river in east hungary by vhr seismic images and its climatic implications abstract the upper 20 30 m of the pleistocene alluvial sequence on the tisza river hungary is investigated by 200 km of vhr single channel seismic sections frequent internal configurations such as 1 bundles of inclined reflections 2 trough shaped converging and 3 horizontal parallel reflections are interpreted respectively as lateral accretion of point bars abandoned channel fills and floodplain deposits the series of 5 8 m thick inclined strata sets occurring at the same depth throughout the area suggest the presence of a meandering river dated to about 43 47 ka in the late pleistocene according to osl data newly recorded quasi 3d seismic profiles reveal that each 1 3 km long inclined series correlates with an individual point bar continuously migrating in the same direction small deviations in the direction of migration are caused by natural wandering of the meander bend morphometric parameters of point bars are used to calculate ancient channel parameters width and depth of 200 500 m and 5 8 m respectively values imply a channel forming discharge of q 400 900 m 3 s these results imply a greater amount of runoff and supply in the basin during mis3 compared to the present day long lasting meandering indicates the role of local factors and a different fluvial environment compared to the commonly anastomosing systems in nw europe our data support the thesis of the three axis drainage system for the basin new evidence is provided for the antecedent existence of a temporally active third trunk river in addition to the ancestors of danube and tisza rivers contrary to the present day two axis drainage pattern

a comprehensive mass flux scheme for cumulus parameterization in large scale models abstract observational studies indicate that a mass flux approach may provide a realistic framework for cumulus parameterization in large scale models but this approach through the introduction of a spectral cloud ensemble leads normally to rather complex schemes in this paper the question is addressed whether much simpler schemes can already provide realistic values of the thermal forcing by convection under various synoptic conditions this is done through verifying such a scheme first on data from field experiments for periods of tropical penetrative convection gate marshall islands tradewind cumuli atex bomex and extratropical organized convection sesame 79 and then in a nwp model the scheme considers a population of clouds where the cloud ensemble is described by a one dimensional bulk model as earlier applied by yanai et al in a diagnostic study of tropical convection cumulus scale downdrafts are included various types of convection are represented i e penetrative convection in c

a multi isotope approach towards constraining the origin of large scale paleoproterozoic b fe mineralization in ne china the final publication is available at elsevier via https doi org 10 1016 j precamres 2017 01 030 2017 this manuscript version is made available under the cc by nc nd 4 0 license http creativecommons org licenses by nc nd 4 0

the midsummer drought over mexico and central america abstract the annual cycle of precipitation over the southern part of mexico and central america exhibits a bimodal distribution with maxima during june and september october and a relative minimum during july and august known as the midsummer drought msd the msd is not associated with the meridional migration of the intertropical convergence zone itcz and its double crossing over central america but rather with fluctuations in the intensity and location of the eastern pacific itcz during the transition from intense to weak weak to intense convective activity the trade winds over the caribbean strengthen weaken such acceleration in the trade winds is part of the dynamic response of the low level atmosphere to the magnitude of the convective forcing in the itcz the intensification of the trade winds during july and august and the orographic forcing of the mountains over most of central america result in maximum precipitation along the caribbean coast and minimum precipitation along the pacific

milankovitch scale multi proxy records from fluvial sediments of the last 2 6 ma pannonian basin hungary abstract the continuous cores of two nearly 500 m deep boreholes cutting pleistocene fluvial sequences in the eastern part of the pannonian basin hungary have been studied magnetostratigraphy indicates that the sediment sequences span the last 2 6 ma without significant hiatuses comparison of systematic variations in magnetic susceptibility with changes in grain size distribution revealed milankovitch scale cyclicity in sedimentation of 40 and 100 kyr cyclicity which also shows a correspondence with the 18o variations of the odp 677 site comparison of pollen and gastropod paleoecological data with the magnetic susceptibility proxies suggests that climate was a major allogenic control on the cyclicity zones of high magnetic susceptibility correspond closely with sandy and coarse silty parts of the borehole successions which largely coincide with pollen and molluscs indicating a warm climate on the contrary zones with low magnetic susceptibility correspond to silts and clays and in most cases coincide with cold climate indicator pollen and molluscs heavy mineral and xrd studies revealed that magnetic susceptibility reflects the absolute amount of detrital fe oxide minerals mostly magnetite variations in the amount of magnetite are related to changes in heavy mineral content which arise primarily from changes in sediment supply to the basin by rivers the depositional model for the pleistocene fluvial sediments suggests that sediment flux increased towards the basin during interglacials due to the increased discharge and transport capacity of the rivers while a decreased sediment supply to the distal parts of the basin occurred during glacials a delay between erosion and storage of weathering products near to the source area and subsequent transportation and re deposition of sediments in the basin interior setting is an important cause of this effect

electrical resistivity imaging of anastomosing river subsurface stratigraphy and possible controls of fluvial style change in a graben like basin czech republic abstract subject to frequent channel avulsions due to the increased frequency of floods rise of base level and or sediment overloading anastomosing rivers are sensitive to external climatic or tectonic forcing in sedimentary basins the morava river czech republic shows a well developed holocene anastomosis confined to the pull apart type upper morava basin umb we studied the stratigraphy and aggradation rates of the umb using electrical resistivity tomography ert dipole electromagnetic profiling demp core data and radiocarbon ages with the aim of identifying factors triggering the anastomosis at the pleistocene holocene transition the ert and demp proved to be excellent tools to visualize the shape and thickness of floodplain depositional units abandoned meanders scroll bars etc the major geophysical surfaces identified are the base of the late weichselian braided stream deposits osl age 34 53 3 42 ka interpreted as a palaeo stream gradient of the morava river and their transition to holocene floodplain deposits in the late weichselian the river aggraded at an average rate of 0 2 mm yr the holocene oldest 14c age 7 066 0 072 ka short term aggradation rates reached up to 13 7 mm yr but the average long term rates 0 07 to 0 4 mm yr are comparable to the late weichselian the stratigraphy and sediment ages indicate that the onset of anastomosis was not likely associated with accelerated basin subsidence possible controls of the anastomosis include upstream control by numerous tributaries large wood debris in the floodplain forests and changes in land use the tectonic and geomorphic context of the umb pull apart basin probably favoured the development of the anastomosis