similarities among the plio pleistocene terrestrial aeolian dust deposits in the world and in hungary abstract the widely distributed plio pleistocene aeolian dust deposits are one of the most important terrestrial archives of past climate and environmental changes the alternation of loess and palaeosol layers is regarded as evidence of the cyclic nature of pleistocene climate changes the loess succession is underlain by aeolian red clay which has been formed under warm humid climates according to the studies of red clay loess palaeosol sequences from china central asia alaska south america and central europe the mineral dust deposition has shown similar patterns since the pliocene the typical loess of the last one million years reflects glacial interglacial conditions whereas the old loess palaeosol sequences could be the product of shorter arid humid climate cycles the similarity of the sedimentary structures could be caused by the similar global climate conditions controlled by orbital forcing the investigated sections from hungary central europe have been affected by local and regional geomorphological and climate factors even so they can be correlated fairly well with the major global climate changes the hungarian aeolian dust deposits consist of three main groups of sedimentary formations 1 pliocene early pleistocene aeolian red clays 2 the oldest loess palaeosol sequences formed from the almost continuous early pleistocene dustfall and 3 the typical glacial interglacial loess deposits of the last one million years without remarkable dust deposition in the warmer periods

propagating diurnal disturbances embedded in the madden julian oscillation 1 fine structure of large scale intraseasonal disturbance associated with the madden julian oscillation mjo was analyzed using the 3 hourly 3b42 trmm rainfall data over the maritime continent diurnal cycle becomes pronounced during the passage of mjo and the eastward propagating diurnal disturbances pdds dominate as an internal structure of large scale convection system of mjo importantly fast pdds that penetrate through the islands are observed within the slowly propagating mjo system this eastward penetration of pdds through the islands result in a sudden shift of the convection center from the western part of the islands to the east causing an overall propagation of the mjo from the indian ocean to the pacific our results demonstrate that the diurnal cycle of convection over and around the major islands thus plays an active role in the propagation of the mjo over the maritime continent

the madden julian oscillation recorded in early observations from the tropical rainfall measuring mission trmm a satellite data analysis is performed to explore the madden julian oscillation mjo focusing on the potential roles of the equatorial rossby er and kelvin waves measurements from the tropical rainfall measuring mission trmm precipitation radar pr and visible infrared scanner virs are analyzed in the frequency wavenumber domain to identify and ultimately filter primary low frequency modes in the tropics the space time spectrum of deep storm fraction estimated by pr and virs exhibits notable kelvin wave signals at wavenumbers 5 8 a distinct mjo peak at wavenumbers 1 7 and periods of about 40 days and a signal corresponding to the er wave these modes are separately filtered to study the individual modes and possible relationship among them in the time longitude space in 10 cases analyzed here an mjo event is often collocated with a group of consecutive kelvin waves as well as an intruding er wave accompanied with the occasional onset of a stationary convective phase the spatial and temporal relationship between the mjo and kelvin wave is clearly visible in a lag composite diagram while the ubiquity of the er wave leads to a less pronounced relation between the mjo and er wave a case study based on the geostationary meteorological satellite gms imagery together with associated dynamic field captures the substructure of the planetary scale waves a cross correlation analysis confirms the mjo related cycle that involves surface and atmospheric parameters such as sea surface temperature water vapor low clouds shallow convection and near surface wind as proposed in past studies the findings suggest the possibility that a sequence of convective events coupled with the linear waves may play a critical role in mjo propagation an intraseasonal radiative hydrological cycle inherent in the local thermodynamic conditions could be also a potential factor responsible for the mjo by loosely modulating the envelope of the entire propagation system

loess paleosol formation on the russian plain abstract the east european loess province is the largest one not only in the northern hemisphere but also on the earth the chronostratigraphic scheme for this province was worked out on the basis of data obtained by different research methods accumulation of loess like deposits began at the end of the pliocene in the post akchagilian time deposition of silt material and loess formation began in the second half of the eopleistocene during this period up to the holocene about 1 ma 6 interglacial soil complexes can be identified according to paleomagnetic data the brunhes matuyama boundary occurs within the don loess which corresponds to maximum don glaciation of eastern europe the composition of the loess paleosol complex of the middle pleistocene is much more complicated there are 3 interglacial soil horizons overlain by the middle pleistocene moraine of the dnieper glaciation a well developed interstadial soil horizon bryansk soil can be distinguished within the late pleistocene formation 32 26 ka bp the structure of the loess paleosol complex varies over different regions of the east european loess province these differences can be shown on a new type of map that of loess paleosol chronocomplexes

the matuyama brunhes boundary in loess sections in the south of the east european plain and their correlation on the basis of palaeomagnetic and palaeopedologic data abstract the matuyama brunhes boundary mbb in loess sections of the east european plain one of the greatest areas of global loess distribution is a highly debatable issue the ambiguity of the mbb position here results from the complexity of loess soil magnetization processes and an apparent delay in loess remanence acquisition and from the uncertainties of pedostratigraphic interpretations in the don glaciation area the mbb is unanimously placed below the don moraine although the exact position is still controversial in the sites of the northern azov sea the mbb is however placed in the loess horizon considered to be the equivalent of the don moraine in the north the inconsistency of this interpretation is demonstrated by detailed magnetostratigraphic and pedostratigraphic studies in the western sites of zaporozh e dnieper basin novaya etuliya lower danube basin and roxolany lower dniester basin in all these sites albeit with certain minor discrepancies the mbb is found two or three interglacial palaeosols below the don loess which is overlain by the good stratigraphic marker of the vorona pedocomplex a thick polygenetic red brown palaeosol formed supposedly in a mediterranean climate here the mbb is placed in a quadruple soil unit termed roxolany loess soil suite which consists of four closely spaced strongly calcareous soils occupying an interval between the don loess on top and the earlier well developed bobrov loess with reversed matuyama magnetization the roxolany suite can possibly be correlated with the three palaeosols of the pre don ilyinka unit of the russian unified stratigraphic scheme and thus confirms the interpretation of the mbb in the central areas of the east european plain as to the interval between the ternovka second pre don palaeosol and the troitsk third pre don palaeosol

quaternary stratigraphy and optical dating of loess from the east european plain russia abstract optical dating of silt sized potassium feldspar grains was found to be suitable for dating the formation of key loess units at two sites on the central east european plain loess bracketing the bryansk palaeosol yielded optical ages in agreement with the well dated radiocarbon chronology when corrected for anomalous fading optical ages from loess bracketing a significant pedogenic unit below the bryansk palaeosol support our lithostratigraphic interpretation that it is the mezin palaeosol complex and its formation during the last interglaciation oxygen isotope stage ois 5 optical ages from a stratigraphically older loess unit directly underlying a significant 10 m thick till unit in conjunction with its regional stratigraphic context suggest that the loess and the till were deposited during the dnieper glaciation which probably occurred during ois 6

pedosedimentary division rock magnetism and chronology of the loess palaeosol sequence at roxolany ukraine abstract the loess mantle of the viii dniestre terrace at roxolany in the black sea area of ukraine is subdivided into six units which encompass the following palaeosol taxons pedocomplexes pk with evidence for several soil forming and sedimentary episodes incipient monogenetic palaeosols and horizons of carbonate concretions these cyclical loess palaeosol units provide a depositional record from the end of the matuyama chron through the holocene the detailed pedosedimentary subdivision of loesses at roxolany is generally consistent with magnetic susceptibility depth functions and seems to reflect global climatic variations earlier chronologies guidebook of the international geological congress xxvii session 1984 are re estimated on the basis of a revised position of the matuyama brunhes boundary and by detailed rock magnetic and micromorphological studies the strongly developed chernosem of pk 4 at approximately 22 m depth showing features of rubefication and the highest magnetic susceptibility value is viewed as a good stratigraphic marker of the late cromerian and seems to represent the climatic optimum of the brunhes chron oxygen isotope stage 13 the uppermost pk 2 is represented in the lower part by a chernosem analogous to surface soils of the area and is argued to be no younger than the last interglacial oxygen isotope stage 5e the poor preservation of pk 2 seems to result from processes of soil degradation and deflation at the time of interglacial glacial transition the closely spaced palaeosols between pk 2 and pk 4 seem to relate to three independent interglacials highest resolution of the palaeoclimatic record is found at the final matuyama chron from pk 9 to pk 8 and in incipient soils that contain either humic horizons with enhanced magnetic susceptibility or only horizons of large carbonate concretions

a lock in model for the complex matuyama brunhes boundary record of the loess palaeosol sequence at lingtai central chinese loess plateau summary in most marine sedimentary records the matuyama brunhes boundary mbb has been found in interglacial oxygen isotope stage 19 in the magnetostratigraphic records of most chinese loess palaeosol profiles the mbb is located in loess layer l8 which was deposited during a glacial period the mbb at lingtai central chinese loess plateau also occurs in l8 and is characterized by multiple polarity flips the natural remanent magnetization is mainly carried by two coexisting components the higher coercivity harder component dominates in loess layers and is thought to be of detrital origin the lower coercivity softer component prevails in palaeosols and was most probably formed in situ by bio chemical processes a lock in model for the lingtai mbb record has been developed by extending the lithologically controlled pdrm model of bleil von dobeneck 1999 it assumes two lock in zones the nrm of the magnetically harder component is physically locked by consolidation shortly after loess deposition whereas the softer component is formed at greater depth by pedogenesis and acquires a chemical remanent magnetization of younger age at polarity boundaries grains carrying reversed and normal directions may therefore occur together within a single horizon the model uses arm coercivity spectra to estimate the relative contributions of the two components it is able to explain the observed rapid multiple polarity flips and low magnetization intensities as well as the stratigraphic shift of the lingtai mbb with respect to the marine records

sarykul paleosol in southern urals sediments russia abstract sarykul paleosols in the southern urals russia with a stable position in geological sediments are considered the brunhes matuyama boundary was found in these paleosols and they were used as a source of information on the environment data were obtained during the study of the sarykul paleosols in four sections located in the mountain part of the southern urals on the miass river erosion accumulation terrace and at the eastern edge on the trans uralian peneplain saykul paleosols have a relatively thick and compact humic horizon with a tongued lower boundary the paleosols are dark grey with high toc content that is not usual for the early pleistocene paleosols the materials showed that sarykul paleosols formed on different parent rocks may have various characteristics of the mineral part texture ph magnetic susceptibility carbonate content ratio of exchangeable cations while their humic substances characteristics humic and fulvic acid ratio humic acid characteristics of elemental composition and structure are very similar climate conditions during sarykul paleosol formation changed from relatively warm and humid to less warm and more humid the study of southern urals sarykul paleosols has shown that they can serve as a reliable marker of the final early pleistocene due to their specific characteristics not analogous to the modern soils

orientation analysis of localized shear deformation in quartz fibres at the brittle ductile transition abstract the crystallographic preferred orientation of fibrous quartz veins deformed under subgreenschist facies conditions along a temperature gradient from 270 to 370 c has been investigated to explore the active mechanism during deformation of the quartz fibres the complete crystallographic orientation of individual recrystallized grains and subgrains was determined by using a combination of cip computer integrated polarization microscopy ebsd electron back scatter diffraction and additional specially developed image analysis techniques it was found that the quartz fibres deformed along crystallographically controlled shear bands from inverse pole figures of normals to the shear band boundaries it is evident that these bands occur along the positive and negative rhomb planes of quartz it is suggested that they are initiated as fractures along these planes inside the shear bands small grains broken off from the host grain show passive rotation of the lattice consistent with the shear sense of the shear bands continued deformation and increasing temperature lead to different recrystallization microstructures inside and outside the shear bands and to a partial obliteration of the sharp orientation relationships

a madden julian oscillation event realistically simulated by a global cloud resolving model a madden julian oscillation mjo is a massive weather event consisting of deep convection coupled with atmospheric circulation moving slowly eastward over the indian and pacific oceans despite its enormous influence on many weather and climate systems worldwide it has proven very difficult to simulate an mjo because of assumptions about cumulus clouds in global meteorological models using a model that allows direct coupling of the atmospheric circulation and clouds we successfully simulated the slow eastward migration of an mjo event topography the zonal sea surface temperature gradient and interplay between eastward and westward propagating signals controlled the timing of the eastward transition of the convective center our results demonstrate the potential making of month long mjo predictions when global cloud resolving models with realistic initial conditions are used

misleading positions of geomagnetic reversal boundaries in eurasian loess and implications for correlation between continental and marine sedimentary sequences abstract the matuyama brunhes boundary mbb where the earth s magnetic field changed to its present orientation is one of the most frequently used time markers in continental quaternary stratigraphy although magnetic signals have been successfully recovered from loess deposits and an apparently coherent magnetostratigraphy seems to be in place a close examination of the published loess records from northern mid latitudes reveals significant uncertainty and variability for the position of the mbb in asia and part of central europe the mbb has been found in loess a glacial deposit this is in contrast to the well established palaeomagnetic records in deep sea sediments where the mbb is located in the interglacial oxygen isotope stage 19 this discrepancy has caused serious confusion in stratigraphic correlation between loess and marine sequences here we examine the causes of the discrepancy between the two sedimentary environments in their records of the mbb our approach includes a comparison of the mbb in loess and other continental records and an evaluation of the stratigraphic significance of the microtektites found around the mbb based on the occurrence of the mbb in an interglacial stage in lake and continental margin sequences and the correlative stratigraphic positions of the microtektites in marine sediments and loess we demonstrate that the measured positions of the mbb in loess are erroneous and misleading and its true occurrence was during the time of formation of the palaeosol corresponding to oxygen isotope stage 19 the most plausible cause for the apparent offset i e the mbb being found in the underlying loess instead is that the acquisition of remanent magnetisation in loess occurs at a certain depth substantially below the land surface the degree of such displacement is dependent on the lithology and structure of the deposits formed prior to the reversal and the time delay is estimated to be in the order of 103 104 years we show that other geomagnetic boundaries such as those of jaramillo and cobb mountain in loess have been similarly displaced though to a varying extent we suggest that the remanence acquisition in loess is closely related to the post depositional evolution in the structure of loessic materials which is in part influenced by regional climate conditions our conclusions on the displaced remanence acquisition have implications for loess chronology magnetostratigraphy as well as the geomagnetic interpretation of detailed magnetic signatures from loess

a tem investigation of shock metamorphism in quartz from the sudbury impact structure canada abstract the sudbury basin in canada is an elliptical feature approx 60 27 km in size that is now widely believed to be part of a large approx 200 km diameter meteorite impact structure which formed about 1 85 ga ago and was subsequently deformed and metamorphosed despite prolonged debate over the origin and original size of the sudbury structure strong evidence for meteorite impact has been provided by the discovery in its rocks of a wide range of shock metamorphic features especially the optically observable traces fluid inclusion arrays of former planar deformation features pdfs in quartz parallel to 10 1 3 planes in this new examination of sudbury samples no preserved original pdfs glassy lamellae were observed optically in quartz grains from basement rock fragments in the onaping formation a unit interpreted as a fallback breccia deposited within the original crater however tem revealed other thin lamellar features preserved in the quartz these are identified as brazil twin lamellae parallel to the basal plane 0001 these lamellae are 15 200 nm thick show a typical spacing of 30 nm to several microns apart and are occasionally decorated with fluid inclusions 0 5 m in size which probably formed during post shock alteration and annealing numerous subgrain boundaries sgbs were also detected many of them oriented roughly parallel to the basal plane 0001 the sgbs apparently formed during post shock recrystallization leading to the local disappearance of brazil twin lamellae experimental evidence suggests that such basal brazil twins are the unique product of high pressure shock waves the features in the sudbury samples are identical to those observed in the vredefort structure south africa which is also widely accepted as an ancient impact structure about 2 0 ga old the recognition of basal brazil twins in quartz at sudbury provides additional evidence for meteorite impact origin and also emphasizes the high value of these durable shock features for identifying old and tectonically metamorphosed impact structures

tropical oceanic rainfall and sea surface temperature structure parsing causation from correlation in the mjo abstractbased upon on the findings of y li and r e carbone the association of tropical rainfall with sst structure is further explored with emphasis on the mjo passband analyses include the tropical indian ocean maritime continent and tropical western pacific regions the authors examine the anomalies of and correlations between sst structure the frequency of rainfall events and rainfall amount based on detailed examination of a 49 month time series all findings are statistical inferences and interpretations consistent with established theory the statistical inferences are broadly consistent with a pivotal role played by the convergent laplacian of sst together with an expected but somewhat indirect role of sst itself the main role of sst in the mjo passband appears limited to production of moist static energy which is highly correlated with cumulative precipitation yet bears a decidedly conditional relationship to the occurrence of rainfall if rain occurs then more rain is likely over

the madden julian oscillation observed during the toga coare iop global view abstract during the toga coare intensive observing period november 1992 february 1993 two pronounced madden julian oscillation mjo events associated with super cloud clusters and westerly wind bursts were observed this paper presents a global view of the mjos including the origin of the super clusters in the indian ocean their migration into the maritime continent and the toga coare large scale soundings array lsa in the western equatorial pacific and their rapid decay over cold water of the eastern pacific the structure and evolution of the mjo are examined with emphasis on the coupling between large scale motion and convection because of differences in propagation speeds the positions of maximum zonal wind perturbations relative to deep convection undergo systematic changes during the travel of the mjo however the centers of deep convection always coincide with those of large scale ascent the super cloud cluster accompanies a wide area of warm air in the upper troposphere over the warm

dislocation generation slip systems and dynamic recrystallization in experimentally deformed plagioclase single crystals abstract three samples of gem quality plagioclase crystals of an60 were experimentally deformed at 900 c 1 gpa confining pressure and strain rates of 7 5 8 7 10 7 s 1 the starting material is effectively dislocation free so that all observed defects were introduced during the experiments two samples were shortened normal to one of the principal slip planes 010 corresponding to a hard orientation and one sample was deformed with a schmid factor of 0 45 for the principal slip system 001 010 corresponding to a soft orientation several slip systems were activated in the soft sample dislocations of the 001 010 and 110 001 system are about equally abundant whereas 110 111 and 101 in 131 to 242 are less common in the soft sample plastic deformation is pervasive and deformation bands are abundant in the hard samples the plastic deformation is concentrated in rims along the sample boundaries deformation bands and shear fractures are common twinning occurs in close association with fracturing and the processes are clearly interrelated glissile dislocations of all observed slip systems are associated with fractures and deformation bands indicating that deformation bands and fractures are important sites of dislocation generation grain boundaries of tiny defect free grains in healed fracture zones have migrated subsequent to fracturing these grains represent former fragments of the fracture process and may act as nuclei for new grains during dynamic recrystallization nucleation via small fragments can explain a non host controlled orientation of recrystallized grains in plagioclase and possibly in other silicate materials which have been plastically deformed near the semi brittle to plastic transition

mjo like coherent structures sensitivity simulations using the cloud resolving convection parameterization crcp abstract interaction between equatorially trapped disturbances and tropical convection is investigated using a nonhydrostatic global model that applies the cloud resolving convection parameterization crcp the crcp represents subgrid scales of the global model by embedding a 2d cloud resolving model in each column of the global model the modeling setup is a constant sst aquaplanet with the size and rotation of earth in radiative convective quasi equilibrium the global atmosphere is assumed to be initially at rest no large scale organization of convection is present outside the equatorial waveguide inside the waveguide on the other hand the model simulates spontaneous formation of coherent structures with deep convection on the leading edge and strong surface westerly winds to the west the westerly wind bursts these coherent structures resemble the madden julian oscillation mjo observed in the terrestrial tropics and are present in simulations applying prescribed and interactive radiation an

the onset of convection in the madden julian oscillation abstract an observational study of the onset of convection in the madden julian oscillation mjo was performed composites of radiosonde data from the comprehensive aerological reference data set were constructed for an ensemble of tropical stations located in the indian ocean maritime continent and western pacific ocean the composites suggest that for the off equatorial stations used in this study the mjo period may be set by the buildup and discharge of the low level moist static energy this result supports the discharge recharge hypothesis of blade and hartmann mjo events appear to begin when the off equatorial atmosphere has been destabilized through a combination of low level moist static energy buildup and concurrent drying of the middle troposphere by subsidence in the wake of the previous cycle of mjo convection the low level moist static energy buildup is controlled by a corresponding increase in low level moisture the increase in low level moisture is not caused by the 1000 mb convergen

a climatology of waves in the equatorial region abstract propagating anomalies of moisture and moist deep convection in the tropics are organized into a variety of large scale modes these include but are not limited to the so called intraseasonal oscillations convectively coupled waves similar to those predicted by shallow water theory on the equatorial beta plane and tropical depression type disturbances along with the annual and diurnal cycles these modes act and interact to control much of the variance of tropical convection analyses of 10 yr of outgoing longwave radiation olr and precipitable water pw data are carried out to develop comparative climatologies of these wavelike modes the analysis relaxes the commonly used cross equatorial symmetry constraints which allows study of the portions of the wavelike processes that are asymmetric across the equator mean background states are found for olr and for pw as functions of day of the year examination of anomalies together with the background reveals much about how the waves are affec

on large scale circulations in convecting atmospheres the dominant thinking about the interaction between large scale atmospheric circulations and moist convection holds that convection acts as a heat source for the large scale circulations while the latter supply water vapour to the convection we show that this idea has led to fundamental misconceptions about this interaction and offer an alternative paradigm based on the idea that convection is nearly in statistical equilibrium with its environment according to the alternative paradigm the vertical temperature profile itself rather than the heating is controlled by the convection which ties the temperature directly to the subcloud layer entropy the understanding of large scale circulations in convecting atmospheres can therefore be regarded as a problem of understanding the distribution in space and time of the subcloud layer entropy we show that the subcloud layer entropy is controlled by the sea surface temperature the surface wind speed and the large scale vertical velocity in the convecting layer and demonstrate how the recognition of this control leads to a simple physically consistent view of large scale flows ranging from the hadley and walker circulations to the 30 50 day oscillation in particular we argue that the direct effect of convection on large scale circulations is to reduce by roughly an order of magnitude the effective static stability felt by such circulations and to damp all of them

the influence of grain boundary fluids on the microstructure of quartz feldspar mylonites quartz rich domains in pre alpine water deficient amphibolite facies 510 580 c 250 450 mpa pegmatite mylonites from mont mary mm western alps preserve a fine dynamically recrystallized grain size without significant annealing despite the high synkinematic temperatures and subsequent static greenschist facies alpine overprint the microstructure is dramatically different from more typical water rich amphibolite facies mylonites such as from the simplon fault zone in the central alps where the recrystallized grain size is on the millimetre scale the difference reflects the dominant strain induced recrystallization mechanism 1 progressive subgrain rotation and grain boundary bulging for the dry mm examples and 2 fast grain boundary migration for the wet simplon examples the grain boundary microstructure imaged with sem is also very different with most grain boundaries in the dry mm samples lacking porosity whereas grain boundaries in the wet samples are decorated by a multitude of pores quartz grain boundaries from both wet and dry samples are locally coated by thin 100 s of nanometres possibly amorphous silica films despite the differences in microstructure the crystallographic preferred orientations cpos of quartz rich domains from both areas are very similar water deficient conditions hinder grain boundary mobility and thereby modify the dominant recrystallization mechanism s but apparently have little influence on the intracrystalline slip systems as reflected in the cpos strong c axis y maxima in mm mylonites both k feldspar and plagioclase an33 38 dynamically recrystallize consistent with the inferred metamorphic conditions under water deficient conditions mid to lower crustal rocks can deform heterogeneously under transitional ductile brittle conditions at high differential stress for mm ca 300 500 mpa as estimated for dry mohr coulomb failure and preserve this high stress microstructure because of the low mobility of dry grain boundaries

characteristics of precipitation cloud and latent heating associated with the madden julian oscillation abstract this study investigates the evolution of cloud and rainfall structures associated with madden julian oscillation mjo using tropical rainfall measuring mission trmm data two complementary indices are used to define mjo phases joint probability distribution functions pdfs of cloud top temperature and radar echo top height are constructed for each of the eight mjo phases the genesis stage of mjo convection over the western pacific phases 1 and 2 features a bottom heavy pdf characterized by abundant warm rain low clouds suppressed deep convection and higher sea surface temperature sst as mjo convection develops phases 3 and 4 a transition from the bottom heavy to top heavy pdf occurs the latter is associated with the development of mixed phase rain and middle to high clouds coupled with rapid sst cooling at the mjo convection peak phase 5 a top heavy pdf contributed by deep convection with mixed phase and ice phase rain and high echo top heights 5 km dominates the decay

effects of low frequency wave interactions on intraseasonal oscillations abstract intraseasonal oscillations isos control much of the large scale variability of convection in the tropics on time scales of about 15 100 days these disturbances are often thought to be dominated by eastward propagating modes especially during austral summer but disturbances that propagate westward are also important this work demonstrates by means of a multiple linear regression model and a brief case study that eastward and westward moving intraseasonal modes often cooperatively interact with one another to produce many of the characteristics of the observed southern hemisphere summer iso these interactions appear to be facilitated by topography and or by the convective anomalies that are cooperatively induced by the eastward and the westward moving components of the oscillations these interactions do not occur during every period of intraseasonal convective activity but they do commonly occur during periods of high amplitude convective anomalies this analysis shows that eastward and

palaeowind directions and sources of detrital material archived in the roxolany loess section southern ukraine abstract measurements of the anisotropy of whole rock magnetic susceptibility ams and u pb ages of detrital zircons have been combined to define the palaeowind directions and sources of wind blown dust in the loess palaeosol key section at roxolany southern ukraine zircon dating has also been used to determine the age and provenance of the interbedded roxolany tephra the distribution of ams axes in the loess indicates that the prevailing wind during its accumulation blew from the north west the same as the mean present day summer wind direction measured in the nerby city of odessa the u pb isotopic ages of the detrital zircons mostly range between 0 25 and 2 ga with clusters at 0 28 0 32 0 45 0 58 1 0 and 1 5 ga single neoarchean grains ca 2 7 ga were also found these ages indicate that material from carpathian and podolian sources formed the roxolany loess this material initially was transported by the dniester river then was wind blown form the dniester liman and the lower dniester valley located nw of roxolany most of the pyroclastic zircons from the roxolany tephra gave ages of 470 840 ka with a peak between 500 and 750 ka this age range is consistent with their being derived from the ciomadul volcano in romania

the roxolany tephra ukraine new evidence for an origin from ciomadul volcano east carpathians we present major element glass data and correlations for the roxolany tephra a so far geochemically unconstrained volcanic ash layer previously described in last glacial marine isotope stage 2 loess deposits of the roxolany loess palaeosol complex in south west ukraine this exceptionally well preserved 2 3 cm thick tephra layer is characterized by a rhyolitic glass composition that is comparable to that of proximal tephra units from ciomadul volcano in the east carpathians central romania the chemistry particularly matches that of the final latest st ana phreatomagmatic activity pyroclastic fall unit of st ana crater that is radiocarbon dated in the proximal mohos coring site moh 2 to 29 6 0 62 cal ka bp the age of the tephra correlative agrees with the newest radiocarbon and infrared optically stimulated luminescence age constraints from overlying palaeosols and tephra embedding loess of the roxolany sequence respectively which place the tephra between ca 33 and 24 cal ka bp and thus confirm the long debated chronostratigraphy of this important environmental archive the occurrence of a distal ciomadul tephra ca 350 km east of its source indicates great potential for further tephra and cryptotephra findings from this volcanic complex in the south eastern mediterranean and black sea region

attributing tropical cyclogenesis to equatorial waves in the western north pacific abstract tropical cyclogenesis is attributed to an equatorial wave when the filtered rainfall anomaly exceeds a threshold value at the genesis location it is argued that 0 mm day 1 simply requiring a positive anomaly is too small a threshold because unrelated noise can produce a positive anomaly a threshold of 6 mm day 1 is too large because two thirds of storms would have no precursor disturbance between these extremes consistent results are found for a range of thresholds from 2 to 4 mm day 1 roughly twice as many tropical cyclones are attributed to tropical depression td type disturbances as to equatorial rossby waves mixed rossby gravity waves or kelvin waves the influence of the madden julian oscillation mjo is even smaller the use of variables such as vorticity and vertical wind shear in other studies gives a larger contribution for the mjo it is suggested that its direct influence on the rainfall in forming tropical cyclones is less than for other variables the impacts of tropical

observed evolution of northward propagating intraseasonal variation over the western pacific a case study in boreal early summer abstractthis report describes the in situ observed evolution of the atmospheric profile during an event of the boreal summer intraseasonal variation bsisv in the tropical western pacific ocean the convectively active region of the bsisv proceeded northward over the sounding and radar network over the array the situation changed from a convectively inactive period to an active period inspection of the sounding data revealed the gradual moistening of the lower troposphere during the convectively inactive period the sounding derived heat and moisture budget analyses indicated that both the convective and large scale processes caused moistening of the lower and middle troposphere where the radar echo tops were observed most frequently this study is the first to identify such a preconditioning process for the bsisv in the western pacific using detailed in situ observational data during the preconditioning an increase in cape was observed as in previous studies of the mjo an increase of moisture

convectively coupled equatorial waves 1 convectively coupled equatorial waves ccews control a substantial fraction of tropical rainfall variability their horizontal structures and dispersion characteristics correspond to matsuno s 1966 solutions of the shallow water equations on an equatorial beta plane namely kelvin equatorial rossby mixed rossby gravity and inertio gravity waves because of moist processes the tilted vertical structures of ccews are complex and their scales do not correspond to that expected from the linear theory of dry waves the dynamical structures and cloud morphology of ccews display a large degree of self similarity over a surprisingly wide range of scales with shallow convection at their leading edge followed by deep convection and then stratiform precipitation mirroring that of individual mesoscale convective complexes ccews have broad impacts within the tropics and their simulation in general circulation models is still problematic although progress has been made using simpler models a complete understanding of ccews remains a challenge in tropical meteorology

a systematic relationship between the representations of convectively coupled equatorial wave activity and the madden julian oscillation in climate model simulations abstractthe relationship between a model s performance in simulating the madden julian oscillation mjo and convectively coupled equatorial wave ccew activity during wintertime is examined by analyzing precipitation from 26 general circulation models gcms participating in the mjo task force global energy and water cycle experiment gewex atmospheric system study gass mjo model intercomparison project as well as observations based on the tropical rainfall measuring mission trmm a model s performance in simulating the mjo is determined by how faithfully it reproduces the eastward propagation of the large scale intraseasonal variability isv compared to trmm observations results suggest that models that simulate a better mjo tend to 1 have higher fractional variances for various high frequency wave modes kelvin mixed rossby gravity and westward and eastward inertio gravity waves which are defined by the ratios of wave variances of specific wave modes to the total variance and 2 exhibit

equatorial waves including the madden julian oscillation in trmm rainfall and olr data four years of outgoing longwave radiation olr and rainfall data from the tropical rainfall measuring mission trmm are investigated to find the dominant large scale wave modes in the tropics by using space time cross section analysis and spectral analysis the longitudinal and latitudinal behaviors of the overall waves and the dominant waves are observed despite the noisy nature of precipitation data and the limited sampling by the trmm satellite pronounced peaks are found for kelvin waves n 5 1 equatorial rossby waves er and mixed rossby gravity waves mrg madden julian oscillation mjo and tropical depression td type disturbances are also detected the seasonal evolution of these waves is investigated an appendix includes a study of sampling and aliasing errors due to the peculiar space time sampling pattern of trmm it is shown that the waves detected in this study are not artifacts of these sampling features the results presented here are compared with previous studies consistency with their results gives confidence in the trmm data for wave studies the results from this study can be utilized for modeling and testing theories also it may be useful for the future users of the trmm data to understand the nature of the trmm satellite sampling

how systematic is organized tropical convection within the mjo 1 recent theories of the dynamics of the madden julian oscillation mjo have been building on its multiscale structure while it is observed that much of the convection within the mjo envelope is related to higher frequency equatorial waves it is not known to what extent this organization is systematic from one mjo event to another for instance it is of interest to know whether mjo favors waves of particular types and propagation direction and how this variability changes seasonally this work presents a wavenumber frequency spectral analysis of the mjo convective envelope which indicates that there is no strong preferred scale of high frequency organization that is ubiquitous to the mjo this null finding supports the use of convective parametrizations in modeling the mjo since while moist convection is likely critical to its initiation and maintenance the particular details of that organization may not be critical for its prediction and simulation

simulating coseismic deformation of quartz in the middle crust and fabric evolution during postseismic stress relaxation an experimental study abstract non steady state deformation and annealing experiments on vein quartz are designed to simulate earthquake driven episodic deformation in the middle crust three types of experiments were carried out using a modified griggs type solid medium deformation apparatus all three start with high stress deformation at a temperature of 400 c and a constant strain rate of 10 4 s 1 type a some are followed by annealing in the stability field of quartz for 14 15 h at zero nominal differential stress and temperatures of 800 1000 c type a b or by annealing for 15 h at 900 c and at a residual stress type a c the quartz samples reveal a very high strength 2 gpa at a few percent of permanent strain the microstructures after short term high stress deformation type a record localized brittle and plastic deformation statisc annealing type a b results in recrystallisation restricted to the highly damaged zones the new grains aligned in strings and without crystallographic preferred orientation indicate nucleation and growth annealing at non hydrostatic conditions type a c results in shear zones that also develop from deformation bands or cracks that formed during the preceding high stress deformation in this case however the recrystallised zone is several grain diameters wide the grains are elongate and a marked crystallographic preferred orientation indicates flow by dislocation creep with dynamic recrystallisation quartz microstructures identical to those produced in type a b experiments are observed in cores recovered from long valley exploratory well in the quaternary long valley caldera california with considerable seismic activity the experiments demonstrate the behaviour of quartz at coseismic loading type a and subsequent static annealing type a b or creep at decaying stress type a c in the middle crust the experimentally produced microfabrics allow to identify similar processes and conditions in exhumed rocks

abrupt termination of the 1997 98 el nino in response to a madden julian oscillation the role of the madden julian oscillation a global atmospheric wave in the tropics that is associated with convective activity and propagates eastwards with a period of about 30 60 days refs 1 2 in triggering el nino events has been discussed before3 4 5 6 7 8 but its possible connection with a termination of el nino has yet to be investigated despite the difficulty in explaining the timing of el nino terminations by the basic wind induced oceanic wave processes9 10 for the extreme 1997 98 event the mechanism of both onset and termination have been investigated3 but the reason for the abruptness of the termination has yet to be resolved here we present global data of precipitation sea surface temperatures and wind speeds that show a precipitation system associated with an exceptionally strong madden julian oscillation travelling around the equator in may 1998 the propagation of this atmospheric system was associated with an abrupt intensification of the easterly trade winds over the eastern equatorial pacific ocean combined with the already shallow equatorial thermocline in the central and eastern pacific ocean at that time3 these strong winds provided the triggering mechanism for the observed accelerated ending of the 1997 98 el nino event

prism and basal plane parallel subgrain boundaries in quartz a microstructural geothermobarometer empirical data on quartz subgrain patterns from various metamorphic rocks show that at least up to 10 kbar in the stability field of low quartz prismatic subgrain boundaries are dominant whereas basal subgrain boundaries are not developed in the high quartz stability field both prismatic and basal subgrain boundaries occur and form typical rectangular chessboard patterns the likely reason behind the different occurrence of these subgrain patterns is that in high quartz prismatic glide becomes as easy as or probably even easier than basal glide the two types of subgrain patterns can be clearly distinguished by optical microscopy consequently the occurrence of chessboard subgrain patterns in quartz represents a practicable geothermobarometer the possibilities of its application are far reaching and include the specification of deformation conditions at high grade metamorphism the recognition of syntectonic intrusions and the distinction between pluton emplacement at lower and at higher crustal levels

convectively coupled equatorial waves within the mjo during cindy dynamo slow kelvin waves as building blocks this study examines the relationship between the mjo and convectively coupled equatorial waves ccews during the cindy2011 dynamo field campaign using satellite borne infrared radiation data in order to better understand the interaction between convection and the large scale circulation the spatio temporal wavelet transform stwt enables us to document the convective signals within the mjo envelope in terms of ccews in great detail through localization of space time spectra at any given location and time three mjo events that occurred in october november and december 2011 are examined it is in general difficult to find universal relationships between the mjo and ccews implying that mjos are diverse in terms of the types of disturbances that make up its convective envelope however it is found in all mjo events that the major convective body of the mjo is made up mainly by slow convectively coupled kelvin waves these kelvin waves have relatively fast phase speeds of 10 13 m s 1 outside of and slow phase speeds of 8 9 m s 1 within the mjo sometimes even slower eastward propagating signals with 3 5 m s 1 phase speed show up within the mjo which as well as the slow kelvin waves appear to comprise major building blocks of the mjo it is also suggested that these eastward propagating waves often occur coincident with n 1 wig waves which is consistent with the schematic model from nakazawa in 1988 some practical aspects that facilitate use of the stwt are also elaborated upon and discussed

high resolution simulation of mean convection and its intraseasonal variability over the tropics in the mri jma 20 km mesh agcm abstract tropical mean convection and its organization on different spatiotemporal scales in a simulation using the meteorological research institute japan meteorological agency mri jma global atmospheric general circulation model agcm at 20 km resolution tl959l60 has been investigated comparison with two lower resolution simulations of 120 km tl159l40 and 180 km tl95l40 shows that convection climatological fields and moist stability over the indian ocean and south pacific convergence zone are better represented in tl959l60 than in lower resolution simulations however the simulated three dimensional structure of the walker and hadley cells and the vertical structure of convective heating do not show marked improvement relative to lower resolution simulations the amplitude and phase speed of convectively coupled equatorial waves show that although the kelvin waves the observed hierarchical structure of cloud clusters associated with the madden julian oscillation mjo convection and th

variability in the characteristics of precipitation systems in the tropical pacific part i spatial structure regional and temporal variability in the vertical and horizontal characteristics of tropical precipitating clouds are investigated using the precipitation radar pr and the visible and infrared scanner virs on board the tropical rainfall measuring mission trmm satellite the present study focuses on the three oceanic regions west central and east pacific together with two continental regions for comparison and the two separate time periods february 1998 and february 2000 under different phases of the el nino southern oscillation enso in order to examine regional and enso related variations the height spectrums of storms are investigated in terms of radar echo top height and infrared brightness temperature the variability in the spectrum clearly correlates with the large scale circulation and its enso related change on the basis of the height spectrum storm systems are classified into the four categories of shallow cumulus congestus deep stratiform and deep convective the deep stratiform and deep convective categories both of which have very cold cloud tops are differentiated by radar echo top heights so that deep convective systems are accompanied with an appreciable amount of large frozen particles aloft while shallow events are dominant in the probability of occurrence over relatively cold oceans deep convective systems take their place for warmer sea surface temperatures ssts the turnover occurs at the sst threshold of 28 29 c for all the oceanic regions and years investigated except the west pacific in 2000 for which deep convective systems prevail over the entire range of sst rain correlation scale length rcsl and cloud correlation scale length ccsl are introduced as statistical indicators of the horizontal scale of storms while the rcsl is 8 18 km for shallow and cumulus congestus type clouds without significant regional and temporal variations the rcsl and ccsl associated with deep stratiform and deep convective systems consistently exceed 100 km and exhibit a systematic variability the rcsl and ccsl in the central and east pacific particularly increase significantly in the el nino year

intraseasonal behavior of clouds temperature and motion in the tropics abstract the spectral character of tropical convection is investigated in an 11 yr record of outgoing longwave radiation from the advanced very high resolution radiometer to identify interaction with the tropical circulation along the equator in the eastern hemisphere the space time spectrum of convection possesses a broad peak at wave numbers 1 3 and eastward periods of 35 95 days significantly broader than the dynamical signal of the madden julian oscillation mjo this quasi discrete convective signal is associated with a large scale anomaly that propagates across and modulates time mean or climatological convection over the equatorial indian ocean and western pacific outside that region the convective signal is small even though under amplified conditions coherence can be found east of the date line and in the subtropics having a zonal scale of approximately wavenumber 2 anomalous convection propagates eastward at some 5 m s 1 and suppresses as well as reinforces climatological convection

kinematic and thermodynamic characteristics of the flow over the western pacific warm pool during toga coare abstract rawinsonde and satellite infrared radiation ir data from the tropical ocean global atmosphere toga coupled ocean atmosphere response experiment coare are used to investigate mean and transient behavior and horizontal variability of the atmosphere over the western pacific warm pool infrared data for the 4 mo intensive observing period iop and vertical motion fields indicate that the intensity of convection height of maximum upward motion and sst all increased from west 140 e to east across the coare domain iop mean ir data show a double itcz intertropical convergence zone structure north and south of the intensive flux array ifa centered at 2 s 156 e although marked variability in the patterns occurred on a month to month basis three prominent westerly wind bursts occurred over the ifa during the 4 mo iop in association with the intraseasonal oscillations isos strong upward motion usually occurred 1 3 weeks prior to the peak low level westerlies subsidence dominated when

eastward propagating 2 to 15 day equatorial convection and its relation to the tropical intraseasonal oscillation anomalies of outgoing longwave radiation olr in 1980 1989 were examined in a narrow latitude band about the equator to elucidate the propagation and interaction of tropical intraseasonal oscillations tios and synoptic scale convective activity hovmoller diagrams of olr data reconstructed from two frequency bands corresponding to periods of 30 60 days and 2 15 days respectively revealed a clear distinction between the phase speed of eastward moving tios 3 7 m s 1 and that of eastward synoptic scale convection 10 13 m s 1 coherent propagation of tios from the indian to the western pacific oceans was often observed with temporary diminution of amplitude over the maritime continent propagation of high frequency anomalies was generally confined to an individual basin dominance of eastward propagating synoptic scale convection in the equatorial zone contrasts sharply with the westward propagation of off equatorial convergence zones interaction between the tio and high frequency activity resolved by daily olr was visible as a modest enhancement of eastward synoptic scale events and of high frequency activity in general during the convectively active phase of the tio

a joint satellite and global cloud resolving model analysis of a madden julian oscillation event model diagnosis 1 in this study a methodology to diagnose a global cloud resolving model gcrm is explored on the basis of a joint analysis with satellite measurements the madden julian oscillation experiment carried out with the nonhydrostatic icosahedral atmospheric model nicam is used as the test bed the nicam output is compared with tropical rainfall measuring mission trmm and cloudsat measurements in terms of composite analysis contoured frequency by altitude diagrams cfads and the joint histogram of cloud top and precipitation top heights it is found in the composite diagram that the gcrm reproduces a slow eastward migration of a convective envelope well comparable to the satellite measurement the gcrm cfad qualitatively reproduces trmm and cloudsat cfads except that the gcrm tends to overly produce snow in deep convection the joint histograms reveal that while the overproduction of snow is evident nicam simulated snow is incapable of producing 94 ghz radar echoes higher than 5 dbz this deficiency can be mitigated by a modification to microphysical parameterization in the way that a proportion of small particles is enhanced in the snow mass spectrum

a moist static energy budget analysis of quasi 2 day waves using satellite and reanalysis data a moist static energy mse budget analysis is applied to quasi 2 day waves to examine the effects of thermodynamic processes on the wave propagation mechanism the 2 day waves are defined as westward inertia gravity wig modes identified with filtered geostationary infrared measurements and the thermodynamic parameters and mse budget variables computed from reanalysis data are composited with respect to the wig peaks the composite horizontal and vertical mse structures are overall as theoretically expected from wig wave dynamics a prominent horizontal mse advection is found to exist although the wave dynamics is mainly regulated by vertical advection the vertical advection decreases mse around the times of the convective peak plausibly resulting from the first baroclinic mode associated with deep convection normalized gross moist stability ngms is used to examine the thermodynamic processes involving the large scale dynamics and convective heating ngms gradually decreases to zero before deep convection and reaches a maximum after the convection peak where low high ngms leads lags deep convection the decrease in ngms toward zero before the occurrence of active convection suggests an increasingly efficient conversion from convective heating to large scale dynamics as the wave comes in while the increase afterward signifies that this linkage swiftly dies out after the peak

microcracks in rocks a review abstract in the past decade the number of studies about microcracks in rocks has rapidly increased this review of recent work concentrates on microcracks in rock as separate entities emphasizing microcrack morphogenesis kinematics dynamics population statistics and observational techniques cracks are produced when the local stress exceeds the local strength the local stress may be augmented by twin lamellae interactions kink bands and deformation lamellae stress concentrations at grain boundary contacts and around intracrystalline cavities local strength may be reduced along cleavage planes along grain boundaries and along any internal surface as a result of corrosion by chemically active fluids dislocations appear not to be a significant factor for crack nucleation below about 500 c in silicates spatial and temporal changes in temperature can also induce microcracking as a result of differential thermal expansion between grains with different thermoelastic moduli and thermal conductivities the amount of quartz in the rock has a significant effect on thermally induced microcracks because of its large and variable thermal expansivity the application of hydrostatic pressure between 100 and 200 mpa effectively closes most cracks but the closure may not be uniform if crack wall asperities exist hydrostatic pressure appears to stabilize cracks and make crack growth more difficult the number and average size of mechanically induced microcracks is greater in rock deformed at higher pressures the application of a deviatoric stress field on the boundaries of a rock mass results on a microscopic scale in a very complex stress system which greatly affects nucleation and propagation paths the relative amount of intragranular and intergranular cracking appears to depend upon mineralogy rock type and stress state the vast majority of stress induced microcracks in rocks appear to be extensional statistically they are predominantly oriented within 30 of the macroscopic maximum stress direction crack densities increase as macroscopic deviatoric stress increases above a threshold level crack size distributions may be either lognormal or exponential fracture in rock under compressive boundary loads is a result of the coalescence of many microcracks not the growth of a single crack some crack configurations are more favorable for coalescence than others as deviatoric stress increases and rock failure is approached the microcrack population changes spatially from random to locally intense zones of cracking away from the fault the crack density dies off rapidly to the background level a few grains away under lesser deviatoric stresses slow subcritical microcrack growth can occur as a result of stress aided corrosion at the crack tip the rate governing mechanism may be either the chemical reaction rate or the rate at which water can get to the crack tip important details still remain to be worked out

low temperature intracrystalline deformation microstructures in quartz a review of numerous genetic interpretations of the individual low temperature intracrystalline deformation microstructures in quartz shows that there is no consensus concerning their formation mechanisms therefore we introduce a new purely descriptive terminology for the three categories of intracrystalline deformation microstructures formed in the low quartz stability field fine extinction bands feb wide extinction bands web and localised extinction bands leb the localised extinction bands are further subdivided into blocky bleb straight sleb and granular gleb morphological types a detailed polarised light microscopy study of vein quartz from the low grade metamorphic high ardenne slate belt belgium further reveals a series of particular geometric relationships between these newly defined intracrystalline deformation microstructures these geometric relationships are largely unrecognised or underemphasised in the literature and need to be taken into account in any future genetic interpretation based on our observations and a critical assessment of the current genetic models we argue that the interpretation of the pertinent microstructures in terms of ambient conditions and deformation history should be made with care as long as the genesis of these microstructures is not better confined