automated analysis of the temporal behavior of the double intertropical convergence zone over the east pacific this paper presents new methods for an automated analysis of the double intertropical convergence zone ditcz phenomena on a daily time scale over the east pacific long term geostationary operational environmental satellite goes visible and infrared data are used to spatially identify and segment the convection zones over the east pacific basin on both sides of the equator and to track the temporal variability of the itcz specifically to identify cases of ditczs northern or southern itcz or non presence events for the segmentation approach image processing techniques are developed to extract information about the spatial features of the itcz in both hemispheres for each satellite image these features serve as input to a temporal classification algorithm that is based on a combination of hidden semi markov model hsmm and support vector machine svm methods the performance of the proposed method is competitive with human experts and the methodology can thus be used to conduct an in depth analysis of the ditcz such an analysis could provide precise information for refining existing weather and climate models over the sparsely observed east pacific where the ditcz is greatly over represented in most models

dependence of sonic velocity on effective stress in north sea mesozoic mudstones abstract overpressure estimation methods that use sonic velocity as a proxy for porosity only account for excess pressure due to undercompaction so the influence of unloading processes in generating overpressure is ignored we have used wireline log data and pore pressure measurements in mudstones of the cromer knoll group and the heather formation in the north sea to investigate whether velocity is sensitive to the contribution of unloading processes to observed overpressures our approach was to fit the data by four alternative linear relationships with sonic velocity as the dependent variable the independent variables necessarily included porosity and vertical effective stress and optionally the natural log response and depth our preferred results are v p 3746 3744 11 1 v 4 7 in the cromer knoll mudstones and v p 4035 4269 8 6 v 5 5 in the heather mudstones for vertical effective stress over the range 10 30 mpa the sensitivity of sonic velocity to vertical effective stress is therefore around 10 m s 1 mpa 1 this sensitivity should be sufficient to improve estimates of pore pressure while drilling by using sonic density and natural logs in combination to make use of this sensitivity for pore pressure estimation robust empirical relationships with vertical effective stress as the dependent variable would have to be established for the formations of interest

a two dimensional model of overpressure development and gas accumulation in venture field eastern canada 1 we used a basin scale model to reconstruct the development of overpressures in a sedimentary basin the area of application is the venture gas field nova scotia canada it is in an overpressured zone in which sedimentation rates have been relatively low since 90 ma and where large horizontal stresses have been evidenced we investigated the importance of overpressure mechanisms using the institut francais du petrole temispack model which integrates compaction hydraulic fracturing fluid flow heat transfer and the formation and migration of hydrocarbons we first constructed a reference model using geological geochemical and physical data second we studied sensitivity of the model to several input parameters and from this deduced additional constraints the modeled permeability along faults and of shaly beds interlayered in the reservoirs must be very low to enable both the local and regional distributions of overpressure and gas to be reproduced several runs of the reference model studying the relative importance of possible overpressuring mechanisms and the relative contribution of plausible source rocks to gas accumulations showed that gas generation and accumulation and lateral compression contribute little to overpressuring which is mainly accounted for by compaction disequilibrium in spite of low sedimentation rates faults and shaly beds play an important role in maintaining the overpressure gas generation in the reservoir units or close to them does not contribute significantly to the field gas accumulations gas sources are likely to be found in the underlying formations

global climatic anomalies associated with extremes in the southern oscillation abstract composite temperature and precipitation anomalies during various stages of an event in the southern oscillation so have been computed for several hundred stations across the globe large regions of coherent significant signals are shown to exist for both extremes of the so with warm event signals generally opposite to those during cold events in addition during the year preceding the development of an event in the so year 1 climatic anomalies tend to be opposite to those during the following year year 0 this confirms that the biennial tendency of the so over the pacific indian ocean sectors is also present in more remote regions with climatic signals related to the so many of the signals are consistent enough from event to event to be useful for extended range forecasting purposes

observations of earthquake waves by the vertical earth potential difference method abstract it is still not clear what relationship exists between earthquake phenomena and electromagnetic ones the earth self potential difference has been observed with high time resolution for continuously monitoring earthquakes at sendai where artificial leakage current sources always exist a simple method to reduce the unnecessary signals induced by artificial and natural earth current sources is proposed with this method the potentil difference is measured through two electrodes buried at different vertical positions under the ground for all earthquakes with seismic intensities of more than 1 at sendai we have observed clear variations in the potential difference signal the observed electric p and s wave arrival times agree exactly with seismic data obtained by the japan meteorological agency jma

on the evolution of the southern oscillation abstract the evolution of the southern oscillation so is examined in the time domain by computing lagged cross correlations between sea level pressures at darwin and sea level or surface pressures at selected stations also in the northern hemisphere the historical and u s navy sea level pressure analyses are used all monthly time series are low pass filtered to retain periodicities greater than 20 months in order to highlight the interannual fluctuations which are primarily associated with the so a detailed analysis of the post 1941 period results in plotted maps of the phase lead or lag and magnitude of the maximum cross correlations with darwin in a manner analogous to a broadband coherence and phase spectrum the relationships within the so are further examined where possible back to 1882 using time series of running decadal cross covariances the dominant pattern reveals the two poles of the traditional standing oscillation or seesaw of the so with centers of opposite sign over indonesia

geology and diagenetic history of overpressured sandstone reservoirs venture gas field offshore nova scotia canada deep exploratory wells in the scotian basin offshore nova scotia canada have encountered overpressured formations with pressures 1 9 x the normal hydrostatic gradient the overpressures occur over an area of approximately 10 000 sq km in the venture field the abnormal pressures are confined below a depth of 4500 m and are associated with upper jurassic lower cretaceous gas and condensate bearing sandstone reservoirs the overpressures occur within normally compacted shales containing numerous overpressured sandstone reservoir beds the development of overpressures seals and secondary reservoirs are all diagenetically driven the volumetric increase achieved by kerogen to petroleum gas conversion and hydrocarbon expulsion are believed to be the main driving forces or venture overpressures three secondary porosity depth levels which top at 2500 m 65 degrees c 3700 m 95 degrees c and 4600 m 130 degrees c correlate with major steps in the organic matter maturation in the basin secondary porosity is initially achieved by alumosilicate dissolution with ferroan sparry calcite cement dissolution dominating below 4000 m porosity enhancement and preservation is not the result of a single diagenetic event but instead the result of a series of diagenetic events that overlapped in time formation of dynamic diagenetic barriers within the zone of peak gas generation helps retard the diffusive migration of hydrocarbons and other fluids expelled during shale diagenesis resulting in pressure build up the preservation of up to 32 percent porosity under 500 1000 atm of pressure could not be achieved without simultaneous pressuring of developing voids thus the expansion of secondary reservoirs in the overpressured zone also had to be late 50 ma or younger and about synchronous with pressurizing of the reservoirs significant for hydrocarbon exploration is that venture type diagenetic overpressures are not associated with undercompacted sediments and hence they cannot be predicted from compaction trends during drilling petrographic diagenetic and lithofacies studies can be instrumental in predicting potential areas of deep subsurface secondary reservoirs development

large scale variabilities of wintertime wind stress curl field in the north pacific and their relation to atmospheric teleconnection patterns 1 wintertime wind stress curl wsc field in the north pacific is investigated to reveal large scale variabilities and their relation to atmospheric teleconnection patterns it is found that the leading empirical orthogonal function eof and the next three rotated eof modes of wintertime wsc anomalies well correspond to those of atmospheric teleconnection patterns i e pacific north american pna western pacific wp tropical northern hemisphere tnh and eastern pacific ep teleconnection patterns respectively time coefficient of the first eof mode well correlates with the north pacific index and does with the pacific decadal oscillation index to some degree it is also found that sverdrup transports in the two zonal bands of 25 n 30 n and 42 5 n 47 5 n have highly negative correlation and these variations can be represented by the forcing field of the first eof mode the pna forcing makes both subtropical and subpolar gyres spin up spin down simultaneously

assessment of seasonal prediction of south pacific convergence zone using apcc multi model ensembles we have quantified and examined the south pacific convergence zone spcz characteristics for the purpose of its seasonal prediction by defining two orientation indices strength and area the multi model ensemble mme tends to simulate the enso associated shift of spcz orientation especially for the 1 month forecast lead the migration of the spcz orientation indices associated with enso phases is clear in the observation and the mme the variation of the spcz strength and area associated with enso phases is not as clear as in the spcz orientation in spite of marginal changes in the spcz strength and area related to enso phases the spcz strength becomes a bit stronger during el nino and weaker during la nina which is represented in individual models and mme the performance of the mme in simulating the variability of the spcz orientation strength and area is also examined we found that the mme reasonably predicts the observed interannual variability of the western portion of the spcz with systematic and marginal shift southward compared to the western part of the spcz the mme seems to have a limitation in predicting the variability of the eastern part in comparison to the spcz orientation the mme is not capable of predicting the strength and area of the spcz the interannual variability of the spcz strength in the mme is systematically weaker compared to that in the analysis by comparison with spcz orientation and strength the spcz area is not resolved in the mme the spcz is a main source of precipitation in the south pacific and the spcz predictability also influences high impact weather prediction such as tropical cyclones therefore skillful predictions of seasonal variability of the spcz could benefit users who utilize the seasonal forecasting information for their decision making in many applicable sectors

daily states of the march april east pacific itcz in three decades of high resolution satellite data abstractzonally elongated areas of cloudiness that make up the east pacific intertropical convergence zone itcz can take on several configurations in instantaneous observations a novel statistical model is used to automatically assess the daily state of the east pacific itcz using infrared satellite images from 1980 to 2012 four itcz states are defined based on itcz location relative to the equator north nitcz and south sitcz of the equator simultaneously north and south of the equator ditcz for double itcz and over the equator eitcz a fifth itcz state is used to classify days when no zonally elongated area of cloudiness is present aitcz for absent itcz the itcz states can occur throughout the year except for the eitcz which is not present during june october with the nitcz state dominating in terms of frequency of occurrence interannual variability of the state distribution is large the most striking variability in itcz states is observed in spring during march april the ditcz

processes controlling the mean tropical pacific precipitation pattern part ii the spcz and the southeast pacific dry zone the nature of the south pacific convergence zone spcz is addressed by focusing on the dry and cool zone bounded by it and the coast of south america through numerical experiments as shown in a companion paper this dry zone is due to a large extent to orographically forced subsidence here it is shown that the northwestward expansion of this dry zone can be explained by advection of low moist static energy by the trade winds these results provide an explanation of the geometry of the western edge of the dry zone and therefore of the eastern edge of the adjacent spcz sea surface temperature underneath the spcz is enhanced by relatively high near surface humidity through evaporative processes which feeds back into its organization however in this model this feedback is not critical for the existence of the spcz the subsidence associated with the itcz in the north hemisphere negatively affects the precipitation rate in the spcz it was also found that the sensitivity of the forced response is largest for peak orographic heights below 3000 m which indicates that the exact representation of the andes in numerical models might not be as critical as that of lower orography such as that in southern africa

interannual variability of the south pacific convergence zone and implications for tropical cyclone genesis the interannual variability of the south pacific convergence zone spcz and its influence on tropical cyclone tc genesis in the south pacific are investigated using observations and era40 reanalysis over the 1979 2002 period in austral summer the spcz displays four typical structures at interannual timescales the first three are characterized by a diagonal orientation of the spcz and account for 85 of the summer seasons one is close to climatology and the other two exhibit a 3 northward or southward departure from the spcz climatological position in contrast the fourth one that only encompasses three austral summer seasons the extreme 1982 1983 and 1997 1998 el nino events and the moderate 1991 1992 el nino event displays very peculiar behaviour where the spcz largely departs from its climatological position and is zonally oriented variability of the western central pacific equatorial sea surface temperature sst is shown to modulate moisture transport south of the equator thereby strongly constraining the location of the spcz the spcz location is also shown to strongly modulate the atmospheric circulation variability in the south pacific with specific patterns for each class however independently of its wide year to year excursions the spcz is always collocated with the zero relative vorticity at low levels while the maximum vorticity axis lies 6 to the south of the spcz position this coherent atmospheric organisation in the spcz region is shown to constrain tropical cyclogenesis to occur preferentially within 10 south of the spcz location as this region combines all the large scale atmospheric conditions that favour the breeding of tcs this analysis also reveals that cyclogenesis in the central pacific in the vicinity of french polynesia only occurs when the spcz displays a zonal orientation while this observation was previously attributed to el nino years in general different characteristics of el nino southern oscillation enso related pacific equatorial warming are shown to impact differently on the spcz position suggesting that for regional scales such as the south pacific the spcz classification is more appropriate than a simple enso index to characterize tc interannual variability these findings suggest that forecasting the strength of el nino through sst variations in the eastern pacific may not be sufficient to accurately predict cyclogenesis in the south pacific especially east of the dateline

detecting the itcz in instantaneous satellite data using spatiotemporal statistical modeling itcz climatology in the east pacific abstract a markov random field mrf statistical model is introduced developed and validated for detecting the east pacific intertropical convergence zone in instantaneous satellite data from may through october the mrf statistical model uses satellite data at a given location as well as information from its neighboring points in time and space to decide whether the given point is classified as itcz or non itcz two different labels of itcz occurrence are produced ir only labels result from running the model with 3 hourly infrared data available for a 30 yr period 1980 2009 all data labels result from running the model with additional satellite data visible and total precipitable water available from 1995 to 2008 ir only labels detect less area of itcz than all data labels especially where the itcz is shallower yet qualitatively the results for the two sets of labels are similar the seasonal distribution of the itcz through the summer half year is presented showing typical location and e

geopressured jurassic reservoirs in the viking graben modelling and geological significance abstract formation pressure data from jurassic and triassic reservoirs of 192 wells 68 in the norwegian sector 124 in the uk sector in the viking graben have been analysed several different pressure regimes are distinguished an open system consists of hydropressured reservoirs adjacent to the east shetland platform in the west and the horda platform in the east a restricted system consists of moderately geopressured reservoirs overpressure typically lower than 1500 psi located at greater distance from the platforms and is interpreted to be in partial pressure communication with the open system through lateral or vertical pressure drainage a closed system consists of geopressured reservoirs practically isolated from the open system in this system formation pressure is assumed to be representative of the various overpressuring mechanisms active locally pressure data analysis suggests that pore pressure is mainly controlled by rapid loading aquathermal pressuring oil generation and possibly by shale dewatering above the depth for the onset of gas generation formation overpressure typically in the range 1500 2500 psi gas generation is interpreted to constitute a major overpressuring mechanism below that depth formation overpressure higher than 2500 3000 psi in the former case a pore pressure gradient approximately 50 higher than the hydrostatic gradient is estimated in the latter case a much more drastic overpressure increase with depth is suggested this model also applies to the norwegian central graben where only a limited number of wells tested jurassic reservoirs despite unavoidable simplification and approximation this model is believed to provide a better understanding of the areal distribution of geopressured jurassic reservoirs in the viking and central grabens it may be used to impose constraints on hydrocarbon migration models and for prediction of porosity preservation in relation to reservoir overpressuring

relative influences of the interdecadal pacific oscillation and enso on the south pacific convergence zone 1 the south pacific convergence zone spcz one of the most extensive features of the global atmospheric circulation is shown to vary its location according to both the polarity of the el nino southern oscillation enso and of the interdecadal pacific oscillation ipo we first demonstrate that the ipo can be regarded as the quasi symmetric pacific wide manifestation of the pacific decadal oscillation that has been described for the north pacific shifts in the position of the spcz related to enso on interannual time scales and to the ipo on decadal time scales appear to be of similar magnitude and are largely linearly independent a station pressure based index of variations in spcz latitude is shown to be significantly related to the polarity of the ipo when enso influences are accounted for movements of this sensitive section of the spcz have occurred in phase with those of the ipo since the 1890s

development of convection along the spcz within a madden julian oscillation a subtropical rossby wave propagation mechanism is proposed to account for the poleward and eastward progression of intraseasonal convective anomalies along the south pacific convergence zone spcz that is observed in a significant proportion of madden julian oscillations mjos large scale convection associated with an mjo is assumed to be already established over the indonesian region the latent heating associated with this convection forces an equatorial rossby wave response with an upper tropospheric anticyclone centred over or slightly to the west of the convection large potential vorticity pv gradients associated with the subtropical jet and the tropopause lie just poleward of the anticyclone and large magnitude pv air is advected equatorwards on the eastern side of the anticyclone this high pv air or upper tropospheric trough is far enough off the equator that it has associated strong horizontal temperature gradients and it induces deep ascent on its eastern side at a latitude of about 15 30 if this deep ascent is over a region susceptible to deep convection such as the spcz then convection may be forced or triggered hence convection develops along the spcz as a forced response to convection over indonesia the response mechanism is essentially one of subtropical rossby wave propagation this hypothesis is based on a case study of a particularly strong mjo in early 1988 and is tested by idealized modelling studies the mechanism may also be relevant to the existence of the mean spcz as a forced response to mean indonesian convection

venture gas field offshore nova scotia case study of overpressuring in region of low sedimentation rate the venture gas field is a deep overpressured gas reservoir on the scotian shelf off eastern canada overpressuring occurs at depths below 4 5 km and is associated with significant quantities of gaseous hydrocarbons the overpressured zone is composed of high porosity sandstones interbedded with low porosity low permeability shales which have nearly normal levels of compaction pore pressures in this zone show a step wise increase with depth where pressure jumps correlate with low permeability 10 20m2 where 10 12m2 1 01 d shale beds petrophysical and lithological data for sandstones and shales in the overpressured zone are used to constrain a one dimensional single phase model of pore pressure development the con ersion of kerogen to hydrocarbons is simulated by simple kinetic reaction theory estimates of the effects on overpressuring of sediment compaction temperature changes and hydrocarbon generation were obtained from this model using the above data 2 disequilibrium compaction apparently is responsible for much of the overpressuring in the venture gas field in our simple single phase model the contribution of hydrocarbon generation to overpressuring was slight

diurnal cycle of the south pacific convergence zone in 30 years of satellite images 2015 american geophysical union a data set of three hourly south pacific convergence zone spcz location and extent from which ir temperature within the spcz may be obtained for 1980 2012 november april is used to examine the diurnal cycle of the spcz maximum spcz area occurs at 15 00 18 00 local standard time lst two minima in mean ir temperature are evident one at 13 00 16 00 lst nearly coinciding with the maximum in area and the second in the early morning hours at 05 00 07 00 lst when area is at a minimum the morning minimum in mean ir temperature is associated with a peak in deep convection while the afternoon minimum is associated with a peak in midlevel clouds on average the morning minimum in ir temperature dominates in the tropical regions of the spcz while the afternoon ir temperature minimum dominates in the subtropical regions of the spcz the relative strength of the two ir temperature minima is affected by the seasonal cycle intraseasonal variability associated with active madden julian oscillation events and interannual variability due to the el nino southern oscillation the morning ir temperature minimum becomes more dominant when the spcz is more frequently present or when the spcz is shifted toward the equator in terms of cloud height midlevel clouds dominate at all times in all regions of the spcz and peak in abundance between 15 00 18 00 lst low level clouds peak near midnight and then transition to high level clouds which peak between 03 00 06 00 lst just before sunrise

application of clustering algorithms to trmm precipitation over the tropical and south pacific ocean abstractunderstanding multiscale rainfall variability in the south pacific convergence zone spcz a southeastward oriented band of precipitating deep convection in the south pacific is critical

reconstructing the south pacific convergence zone position during the presatellite era a la nina case study abstractsixty four southwest pacific island meteorological stations were used to develop enso related austral warm season november april rainfall climatologies for 1961 90 historical data for the same station set were then examined for 1955 56 one of the strongest la ninas of the twentieth century the pattern for that event was typical of a well coupled protracted la nina with above normal rainfall 150 observed for 17 stations in the case study tropical cyclone tracks were also used to illustrate the proximal effects of historical storms on station rainfall several stations that were located along the northern edge of the tropical cyclone swarm but south of a region of anomalously low rainfall were selected as possible candidates having been close to the mean south pacific convergence zone spcz location linear interpolations between those stations highlighted a likely spcz position for the 1955 56 event the reconstructed spcz location indicated a position southwest of normal consistent wi

concretion morphology classification and genesis abstract a discussion of the most relevant morphological features of concretionary bodies and the different classifications and the criteria involved in these classifications is presented together with suggestions for improvements to the various classification schemes the meaning of syngenetic diagenetic and epigenetic related to the relative timing and environment of growth of concretionary bodies is also reviewed and discussed the replacement of mixed morphogenetic classifications which lead to conflicting results by classification categories based on textural features is proposed because the identification of the genetic environment of a concretionary body tells little about its history i recommend defining growth patterns in which the successive steps associated with changes in composition and or texture and the development of new structures are recorded a new path is presented that accounts for the contradiction between textural and isotope features which suggests respectively syngenetic and diagenetic or even epigenetic signatures this new path is characterized by the preservation of large porosities over very long time spans and down to depths that are somewhat greater than expected due to the inhibition of normal compaction caused by early overpressuring this overpressuring is the result of the development of hydraulic seals since approximately the syngenetic phase times the concepts of force of crystallization and displacive growth are also reviewed it is being suggested to discard some controversial interpretations of their actual importance for true concretionary displacive growth under epigenetic conditions in accordance with other authors the conclusion is reached that displacive growth is only possible if the shear strength of the host is very low and the stress field within the host is almost hydrostatic a new model the symcompactional concretionary growth model is proposed which explains how a concretionary body generally a nodule can grow while its host thins down by compaction this overpressured undercompacted model will be useful for the interpretation of an assemblage of features such as injection dikes hydraulic breccias cone in cone structures among others that are thought to be representative of the former presence of overpressured horizons these overpressured horizons could serve as detachment planes in paleotectonically active basins seals that could have controlled the movement of brines and hydrocarbons during the diagenetic evolution of the basin can also be assessed this is relevant for the identification of maturation conditions the potential development of secondary fracture permeability due to hydraulic fracturing in buried areas of the basin can also be evaluated based on the identification of formerly overpressured horizons in outcrops the origin of concretions is generally a geological puzzle clifton 1957

links between the onset of modern walker circulation and the mid pleistocene climate transition sea surface temperatures ssts reconstructed from ocean drilling program sites 806 and 849 in the western and eastern equatorial pacific provide a history of the strength of the walker circulation between 1 5 and 0 5 ma a progressive cooling in the eastern equatorial pacific is paralleled by intensification of the equatorial zonal sst gradient that began 1 17 ma prior to the expansion of global ice volume associated with the mid pleistocene climate transition the ssts in the eastern equatorial pacific and the zonal gradient reached modern values by 0 9 ma we propose that this onset and intensification of the modern walker circulation reduced heat flux but increased moisture transport to high latitudes leading to the development of more extensive ice sheets and the shift toward the 100 ka world

variability of the intertropical convergence zone recorded in coral isotopic records from the central indian ocean chagos archipelago we have analyzed the stable oxygen isotopic composition of two porites corals from the chagos archipelago which is situated in the geographical center of the indian ocean coral 18o at this site reliably records temporal variations in precipitation associated with the intertropical convergence zone itcz precipitation maxima occur in boreal winter when the itcz forms a narrow band across the indian ocean the chagos then lies within the center of the itcz and rainfall is strongly depleted in 18o a 120 yr coral isotopic record indicates an alternation of wet and dry intervals lasting 15 to 20 yr the most recent 2 decades are dominated by interannual variability which is tightly coupled to the el nino southern oscillation enso this is unprecedented in the 120 yr of coral record as the itcz is governed by atmospheric dynamics this provides evidence of a major change in the coupled enso monsoon system

electromagnetic and acoustic emission associated with rock fracture abstract to understand the physical mechanism of the anomalous electromagnetic emissions observed before earthquakes we carried out some laboratory experiments on electromagnetic and acoustic emission from a rock granitic samples were loaded at a constant strain rate and electromagnetic and acoustic emission were simultaneously recorded during deformation of the sample ten to 20 of the acoustic emissions detected during the experiment are associated with electromagnetic emission the onset time of electromagnetic emission is found to coincide with the origin time of the acoustic emission this demonstrates that the emission of electromagnetic waves is truly associated with microcracking in the sample the efficiency of generating electromagnetic emission seems to be higher in tensile cracks than in shear cracks the frequency spectrum of the electromagnetic emission obtained with five coil antennae of different frequency responses indicates that the main power of the electromagnetic emission is in the frequency range 0 5 mhz a possible mechanism of electromagnetic emission is electrification of a fresh surface created by subcritical cracking in a rock if this interpretation is correct production of new cracks is a necessary condition for generation of electromagnetic emissions although we do not completely understand how a natural earthquake occurs it is generally considered to be a result of shear faulting that connects pre existing small cracks therefore it is reasonable to expect anomalous electromagnetic emission associated with small tensile cracks before an earthquake and to expect that the anomalous electromagnetic emission will be observed only before an earthquake but not at the main shock which may not be very efficient for creation of a fresh surface

el nino southern oscillation time scale covariation of sea surface salinity and freshwater flux in the western tropical and northern subtropical pacific we examined the covariation of sea surface salinity sss and freshwater flux in the western tropical and northern subtropical pacific on the el nino southern oscillation timescale using a canonical correlation analysis of monthly data between 2001 and 2013 the dominant covariation i e the first canonical mode has large positive and negative amplitudes in regions east of the philippines and new guinea respectively and reaches peaks in autumn to winter of el nino years the positive sss anomaly east of the philippines is advected to the kuroshio extension region we found that the second canonical mode is another coupled variation with localized amplitudes of sss under the atmospheric convergence zones in winter to spring of la nina years however the negative sss anomaly is annihilated possibly by the evaporation in the subtropical region

a late quaternary marine palynological record oxygen isotope stages 1 to 7 for the humid tropics of northeastern australia based on odp site 820 a late quaternary marine palynological record from the ocean drilling program odp site 820 adjacent to the humid tropics region of northeastern australia has demonstrated marked variation in orbital scale cyclicity and also trends associated with both climate and human impact however some uncertainties in interpretation have resulted from concerns about the records chronology and continuity here we present for the first time the complete palynological data from detailed analysis of the top 67 m of sediment and examine it in relation to the marine isotope sequence from the core it is proposed that the record is relatively continuous through the last 250 000 years although the latter part of oxygen isotope stage ois 5 as well ois 4 may be missing despite the variation on orbital scales most palynological changes are not in phase with those from the marine isotope record suggesting a lack of direct milankovitch forcing on vegetation this lack of correspondence combined with major trends towards more open and sclerophyllous vegetation in association with increased burning supports a previous proposal that major control is being exercised by el nino southern oscillation variability whose influence may have been initiated by changes in oceanic circulation in the region within the mid pleistocene the lack of impact on the distribution of complex rainforest suggests that increased climate variability did not involve an overall decrease in total precipitation c 2007 elsevier b v all rights reserved

eastern margin variability of the south pacific convergence zone 1 the influence of low level inflow wind and its high frequency variability on the spatial characteristics of the eastern margin of the south pacific convergence zone spcz is examined compositing daily and 5 day mean low level wind precipitation and tropospheric moisture data reveals a clear relationship between high frequency zonal inflow variations and the eastern spcz margin with relaxation of trade wind intensity associated with increased moisture near the mean eastern spcz margin and an eastward displacement of the convection an idealized 2 dimensional model demonstrates that variations in dry air inflow cause tropospheric moisture and precipitation variations akin to those observed in this prototype factors affecting the extent of spcz variability are also important to the mean margin position spcz margin shifts under natural variability thus offer an observational target against which to evaluate simulated interactions of inflow air mass characteristics with convection

global patterns of enso induced precipitation although there have been many analyses of el nino southern oscillation enso induced precipitation anomalies global patterns from these analyses remain incomplete here we combine recent satellite estimates of oceanic precipitation and historical rain gauge records to derive a global climatology of enso induced precipitation anomalies using empirical orthogonal function eof analyses the patterns suggest that the re arrangement of convection centers of the walker circulation during enso events induces large precipitation anomalies in the tropics while associated changes in the monsoon systems through the hadley cell over the pacific indian and atlantic oceans and their interactions with midlatitude westerlies generate coherent anomaly patterns over the extratropics our results can be used to evaluate climate models and forecast enso induced precipitation anomalies

co seismic geoelectric potential changes observed in japan co seismic signals of geoelectric potential have been observed for several earthquakes eqs in japan it has been argued that if there are precursory changes stronger signals should be at the time of eq our results prove that co seismic signals do exist but they start with the arrival of seismic waves and not at the origin time of eqs their amplitude does not scale with the dipole length both facts indicate that the changes are local effects of passing seismic waves and not due to electric signals emitted from the seismic source observed changes contain two components oscillatory and offset decay ones the former is synchronized with seismic waves whereas the latter with a rise time of a few seconds and a decay time of 0 1 1 hour is suspected to be related to eq induced subsurface hydrological change in both cases the origin of electric potential variations may be electrokinetic

delayed enso impact on spring precipitation over north atlantic european region the delayed impact of winter sea surface temperature sst anomalies in tropical pacific on spring precipitation over the north atlantic european nae region is examined using both measured and modeled data for the period 1901 2002 in an amip type atmospheric general circulation model agcm ensemble the observed delayed spring precipitation response in europe to winter enso related sst anomalies is well reproduced a series of targeted agcm coupled gcm experiments are performed to further investigate the mechanisms for this delayed influence it is found that late winter enso sst anomalies lead to the well documented rossby wave train arching from the pacific into the atlantic region a positive negative enso event leads to a quasi barotropic trough ridge in the north atlantic region the resulting wind and cloud changes cause anomalies in the surface heat fluxes that result in negative positive sst anomalies in the central north atlantic and anomalies of the opposite sign further to the south the sst anomalies persist into spring and the atmospheric response to these anomalies is an extension of the enso induced trough ridge into the european region leading to enhanced reduced moisture flux and low level convergence divergence and thus positive negative precipitation anomalies although the signal is overall relatively weak correlation coefficients of european spring rainfall with winter enso ssts of about 0 3 a proper representation of the outlined mechanism in seasonal forecasting systems may lead to improved seasonal predictions

the influence of diabatic heating in the south pacific convergence zone on rossby wave propagation and the mean flow the south pacific convergence zone spcz is a northwest southeast oriented precipitation band over the south pacific ocean latent heat release from condensation leads to substantial diabatic heating which has potentially large impacts on local and global climate the influence of this diabatic heating within the spcz is investigated using the intermediate general circulation model igcm4 precipitation in the spcz has been shown to be triggered by transient rossby waves that originate in the australian subtropical jet and are refracted towards the equatorial eastern pacific a rossby wave triggers a spcz convective event with associated diabatic heat release and vortex stretching consequently the rossby wave is dissipated in the spcz region these features are simulated well in a control integration of igcm4 in an experiment convective heating is prescribed to its climatological value in the spcz region during the rossby wave events and dynamic forcing from rossby waves is decoupled from the usual thermodynamic response in this experiment rossby waves over the spcz region are not dissipated confirming the vortex stretching mechanism from previous studies furthermore the change in rossby wave propagation has an impact on momentum transport overall the effect of the rossby wave induced convection in the spcz is to decrease the strength of the pacific subtropical jet and the equatorial eastern pacific upper tropospheric westerlies by about 2 6 m s 1 following these changes to the basic state two potential feedbacks in the spcz and larger pacific climate system are suggested increased spcz convection due to the enhancement of negative zonal stretching deformation in the spcz region and decreased equatorward refraction of rossby waves into the westerly duct leading to less spcz events as the convective events in the spcz have a significant impact on pacific mean climate it is crucial that the spcz is represented correctly in climate models

a multiscale framework for the origin and variability of the south pacific convergence zone the diagonal south pacific convergence zone spcz is the major climatological precipitation feature over the pacific region during the northern hemisphere winter however the basic mechanisms that control its structure and variability are only partly understood here an analysis of the spcz is carried out in a multiscale framework this identifies two modes that dominate a westward shifted spcz and an enhanced spcz which occur independently of each other within both modes the primary mechanism for the initiation of precipitation is a transient synoptic wave propagating along the subtropical jet which is then refracted by the basic state toward the westerly duct over the central equatorial pacific individual vorticity centres in the wave become elongated with a diagonal northwest southeast tilt convection then occurs in a diagonal band in the poleward flow ahead of the cyclonic vorticity anomaly in the wave however latent heat release in the convection leads to upper tropospheric divergence and anticyclonic vorticity forcing which dissipates the wave shutting off the convective forcing and stopping the precipitation hence each individual wave or event only lasts a few days and contributes a discrete pulse of diagonally oriented precipitation to the region the sum of these events leads to the diagonal climatological spcz event occurrence is a stochastic process the probability of which is modified by lower frequency variability of the basic state including the madden julian oscillation mjo and el nino southern oscillation enso for example during periods of enhanced convection over the eastern indian ocean to western pacific mjo phases 3 6 and la nina the westerly duct expands westwards allowing synoptic waves to refract equatorwards earlier and increasing the probability of westward shifted spcz events hence both the existence and variability of the spcz depend fundamentally on scale interactions between dynamical processes on time scales ranging from daily to interannual copyright 2011 royal meteorological society

contrasting the flavors of el nino southern oscillation using sea surface salinity observations 1 the recent detection of a central pacific type of el nino has added a new dimension to the el nino southern oscillation climatic puzzle sea surface salinity sss observations collected during 1977 2008 in the tropical pacific are used to contrast the three eastern pacific ep 1982 1983 1991 1992 1997 1998 and seven central pacific cp 1977 1978 1986 1988 1990 1991 1992 1995 2002 2003 2004 2005 2006 2007 types of el nino events as well as the six ep 1985 1986 1988 1989 1995 1996 1999 2001 2005 2006 2007 2008 and two cp 1983 1984 1998 1999 types of la nina events the ep el nino events result in large 30 longitude eastward displacements of the eastern edge of the low salinity warm pool waters in the equatorial band a resulting well marked sss freshening 1 near the dateline and a sss increase 1 below the mean position of the south pacific convergence zone spcz the cp el nino events are characterized by smaller 50 eastward displacements of the eastern edge a 15 longitude westward shift of the equatorial sss freshening and a comparatively reduced 50 sss increase in the spcz a qualitative analysis indicates that changes in zonal currents and precipitation can account for the observed contrasted signature in sss eastward current anomalies appear over most of the equatorial band during ep el nino events in contrast there is a tendency for zonal current convergence slightly west of the dateline during cp el nino events consistent with the confinement of the warm fresh pool in the western central equatorial basin the related quasi inexistent northeastward migration of the spcz and associated heavy precipitation regime

regional velocity depth anomalies north sea chalk a record of overpressure and neogene uplift and erosion a normal velocity depth trend for the upper cretaceous danian chalk group is determined by identifying interval velocity data that represent maximum burial in areas unaffected by overpressuring these data are derived from 845 wells throughout the north sea basin data from pelagic carbonate deposits on a stable plateau constrain the trend for shallow depths positive velocity anomalies relative to the trend are mapped along the western and eastern margins of the north sea basin and reflect regional neogene uplift and erosion of up to 1 km along the present day limit of the chalk a hiatus at the base of the quaternary increases in magnitude away from the basin center where a complete cenozoic succession is found this hiatus is consistent in size with the missing section estimated from chalk velocities when allowance is made for the quaternary reburial of the chalk negative velocity anomalies in the central and southern parts of the basin outline an area within which overpressures in the chalk exceed 10 mpa equivalent to a burial anomaly greater than 1 km relative to the normal trend the chalk pressure system is primarily dependent on overburden properties because retention of overpressure generated by the load of the upper overburden depends on the thickness and sealing quality of the lower overburden therefore the chalk is considered to represent a regional aquitard and the hydrodynamic model of long distance migration within the chalk is rejected the neogene uplift and erosion of the margins of the north sea basin and the rapid late cenozoic subsidence of its center fit into a pattern of late cenozoic vertical movements around the north atlantic

interannual signature in daily itcz states in the east pacific in boreal spring abstractthe intertropical convergence zone itcz in the east pacific is located north of the equator during most of the year in daily data it is most variable in march april when it may be located north of the equator nitcz on both sides of the equator ditcz or south of the equator sitcz or it may be absent when convection does not take on a zonally elongated form additionally in strong el nino years it is located on the equator during the boreal winter half year here the focus is on conditions when the itcz has a presence south of the equator ditcz sitcz and composites of various fields are compared to normal conditions i e when the itcz is north of the equator nitcz composites of sea surface temperature sst precipitation outgoing longwave radiation and the upper level circulation show very similar patterns for ditcz and sitcz days where the latter cases have almost double the amplitude of the former the sitcz state is viewed as an extreme case of the ditcz state both

emission of electromagnetic radiation preceding the ito seismic swarm of 1989 there have been several reports1 8 of electromagnetic radiation being detected in air and or underground before large earthquakes or volcanic eruptions unfortunately such measurements are often plagued by contamination from other sources of noise we have developed an electrode system that is effective at filtering out urban and atmospheric background noise here we report the detection of anomalous electromagnetic signals several hours before the occurrence of large earthquakes near ito city japan about 150 km from the location of the electrodes we have also detected anomalous signals about one day before an undersea volcanic eruption that constituted part of the same seismic swarm near ito although the mechanism responsible for such signals is still unclear these results indicate that their monitoring could be valuable for the prediction of seismic activity

subseasonal to interannual variability of rainfall over new caledonia sw pacific daily rainfall occurrence and amount at 55 stations over new caledonia nc 20 s 166 e are examined throughout the calendar year during 1980 2010 using a hidden markov model hmm daily rainfall variability is described in terms of six discrete rainfall states identified by the hmm three states are interpreted as trade wind regimes associated with persistent low level anticyclonic conditions and weak to strong easterlies the most prevalent state state 1 36 of days is dry everywhere and is characterized by an elongated anticyclone centered around australia nc is located on the eastern edge of this anticyclone this state is predominant from mid may to mid december and peaks in september the second most prevalent state state 2 27 of days and the last trade regime state 4 12 of days are most frequent in austral summer states 2 and 4 are associated with the subtropical anticyclone centered south of nc close to its climatological location in austral summer and light state 2 to moderate state 4 rainfall mostly along the windward coast a distinct state state 3 11 of days is mostly associated with wintertime extratropical eastward traveling troughs between new caledonia and new zealand inducing light rainfall over the sw of the main island of new caledonia the two last states 5 and 6 are infrequent 15 of days but account for almost 70 of total rainfall across the archipelago they occur mostly in austral summer with their frequency of occurrence peaking in late february early march these states are associated with synoptic wave traveling eastward from eastern australia leading to a strong influx of moisture from the equatorial latitudes when the associated cyclonic centre is located west of new caledonia the wettest state is also strongly modulated by intra seasonal 15 80 days variability these events contribute to intermittent southwestward shifts of the south pacific convergence zone from its mean location northeast of new caledonia on interannual timescales the occurrence of the rainfall states is modulated by el nino southern oscillation enso events the enso impact is strongest from mid august to march with more less frequent trade regimes 1 2 and less more frequent unstable trade regime 4 and states 5 6 during central pacific warm cold enso events stochastic simulations of daily rainfall occurrence and amount at the 55 stations are generated by using predictors based on nino 4 sea surface temperature index and a local intra seasonal 15 80 days olr index superimposed on a climatological annual cycle the cross validated skill peaks in september november

abnormal formation pressure and shale porosity an abnormally pressured jurassic shale from the north sea viking graben has a fluid pressure over burden ration close to 0 8 at a depth of more than 4 000 m and is associated with low porosity and high density the porosity and fluid pressure history of the shale involves three successive stages 1 normal gravitational compaction prevailed during the first few hundred meters of burial 2 the shale porosity was severely reduced by carbonate cementation in conjunction with a major break in sedimentation but the fluid pressure remained hydrostatic and finally 3 the porosity was further reduced by compaction and possibly cementation and the fluid pressure increased to above hydrostatic in response to renewed subsidence and the cretaceous and tertiary overburden lo d

the south pacific convergence zone in three decades of satellite images interannual variability seasonal evolution and intraseasonal variability of the south pacific convergence zone spcz are quantified using a new data set of 3 hourly spcz labels available from 1980 to 2012 nov apr the spcz label is a binary field indicating presence 1 or absence 0 of the spcz at each grid point 1 2 longitude by 1 2 latitude as a function of time and is the output of a bayesian spatiotemporal statistical model that takes in instantaneous data from geostationary satellites the statistical model is designed to emulate the way human observers identify the spcz results show two distinct parts to the spcz the western tropical part and the eastern subtropical part at times the two parts do not connect when they do connect they are oriented quite differently such that the subtropical part has a steeper meridional slope the spcz is present 50 70 of the time in the tropics from jan to mar and is usually anchored to the warm sea surface temperature sst distribution of the equatorial west pacific the subtropical part does not have the same sensitivity to the underlying sst distribution and is present more often in nov dec and apr than in jan mar when the sst is highest interannual variability in spcz location is strongly associated with el nino southern oscillation enso however no change in overall spcz area is detected in association with enso on the intraseasonal time scale composite analysis shows the distinct spatial patterns in spcz presence associated with each phase of the madden julian oscillation key points developed a 30 year 3 hourly data set of spcz location and extent presents interannual and intraseasonal variability of spcz location presents seasonal evolution of spcz location and extent 2013 american geophysical union all rights reserved

short term earthquake prediction current status of seismo electromagnetics abstract loss of human lives as a result of earthquakes is caused overwhelmingly by the collapse of buildings within less than a few minutes of main shocks the most urgent countermeasure consists of two key elements one is strengthening of weak structures and the other is short term earthquake prediction short term prediction needs precursors although some promising precursors are reported the prevailing views in japan and elsewhere are overly pessimistic the pessimism largely roots in the fact that short term precursors are generally non seismic and tools developed for seismology are not designed to detect them nonetheless nationally funded large scale earthquake prediction programs always emphasize the need to reinforce seismometer networks they do not take into account the views of those in the science community who point to the importance of non seismic precursors while there are well founded causes to be skeptical the situation needs to be improved one reason for skepticism is that the observations of precursors have not yet been perfect enough and another is that some important fundamental aspects of non seismic precursors are still unresolved we review some of these problems

the ability of rock physics models to infer marine in situ pore pressure pore fluid pressure is an important parameter defining the mechanical strength of marine sediments obtaining high spatial resolution in situ pore pressure measurements in marine sediments however is a challenge and as a result only a handful of in situ pore pressure measurements exist at scientific drill sites integrating rock physics models with standard iodp odp measurements provides a potentially widely applicable approach for calculating in situ pore pressure here we use a rock physics approach to estimate in situ pore pressure at two scientific ocean drill sites where in situ pressure is well constrained odp site 1173 used as reference for normal hydrostatic fluid pressures and odp site 948 where previous studies infer high fluid pressures 0 45 0 95 where the pore pressure ratio is defined as the pore pressure above hydrostatic divided by the difference between the largest principal stress and hydrostatic stress our analysis indicates that the rock physics method provides an accurate low precision method for estimating in situ pore pressure at these drill sites and sensitivity analysis indicates this method can detect modestly high 0 6 pore pressure at the 95 confidence level this approach has broad applicability because it provides an inexpensive high resolution meter scale method for retrospectively detecting and quantifying high pore pressure at any drill site where quality wireline logs and ocean drilling data exist

a dynamical framework for the origin of the diagonal south pacific and south atlantic convergence zones the south pacific convergence zone spcz and south atlantic convergence zone sacz are diagonal bands of precipitation that extend from the equator southeastward into the southern hemisphere over the western pacific and atlantic oceans respectively with mean precipitation rates over 5 mm day 1 they are a major component of the tropical and global climate in austral summer however their basic formation mechanism is not fully understood here a conceptual framework for the diagonal convergence zones is developed based on calculations of the vorticity budget from reanalysis and rossby wave theory wave trains propagate eastward along the southern hemisphere subtropical jet with initially quasi circular vorticity centres in the zonally sheared environment on the equatorward flank of the jet these vorticity centres become elongated and develop a northwest southeast tilt ray tracing diagnostics in a non divergent barotropic rossby wave framework then explain the observed equatorward propagation of these diagonal vorticity structures toward the westerly ducts over the equatorial pacific and atlantic the baroclinic component of these circulations leads to destabilisation and ascent ahead of the cyclonic vorticity anomaly in the wave triggering deep convection because of the high sea surface temperatures in this region latent heat release then forces additional ascent and strong upper tropospheric divergence with an associated anticyclonic vorticity tendency a vorticity budget shows that this cancels out the advective cyclonic vorticity tendency in the wave train over the spcz and dissipates the wave within a day the mean spcz is consequently comprised of the sum of these pulses of diagonal bands of precipitation similar mechanisms also operate in the sacz however the vorticity anomalies in the wave trains are stronger and the precipitation and negative feedback from the divergence and anticyclonic vorticity tendency are weaker resulting in continued propagation of the wave and a more diffuse diagonal convergence zone

high frequency seismo electromagnetic effects abstract electromagnetic perturbations caused by natural geophysical activity such as earthquakes and volcanic eruptions have been studied since the great alaskan earthquake in 1964 in recent years interest has been increasing because when a precursor event occurs it normally does so less than a few hours before the shock this paper presents a review of the high frequency seismo electromagnetic phenomena already observed and occurring before as well as after the shock the term high frequency is to be taken in the seismic sense i e larger than a few hertz mechanisms that might produce these seismo electromagnetic emissions will be described it is shown that at the moment a causal relationship between electromagnetic signals and seismic activity still remains to be demonstrated theoretical as well as intensive experimental studies are necessary to understand the physical processes responsible for seismo or volcano electric variations electrical resistivity variations electromagnetic effects associated with dilatance as well as electromagnetic fields generated during laboratory experiments or ionospheric disturbances

interannual to decadal variability in the bifurcation of the north equatorial current off the philippines satellite altimeter sea surface height ssh data from the past 17 yr are used to investigate the interannualto decadal changes in the bifurcation of the north equatorial current nec along the philippine coast the nec bifurcation latitude migrated quasi decadally between 108 and 158n with northerly bifurcations observed in late 1992 1997 98 and 2003 04 and southerly bifurcations in 1999 2000 and 2008 09 the observed necbifurcationlatitudecanbeapproximatedwellbythesshanomaliesinthe128 148nand1278 1308ebox east of the mean nec bifurcation point using a 1 layer reduced gravity model forced by the ecmwf reanalysis wind stress data the authors find that the ssh anomalies in this box can be simulated favorably to serve as a proxy for the observed nec bifurcation with the availability of the long term reanalysis wind stress data this helps to lengthen the nec bifurcation time series back to 1962 although quasi decadal variability was prominent in the last two decades the nec bifurcation was dominated by changes with a 3 5 yr period during the 1980s and had low variance prior to the 1970s these interdecadalmodulationsin the characteristics of the nec bifurcation reflect similar interdecadal modulations in the wind forcing field over the western tropical north pacific ocean although the nec bifurcation on interannual and longer time

modeling the occurrence of overpressures on the scotian shelf offshore eastern canada many wells on the scotian shelf offshore from nova scotia have drilled into overpressured zones in particular the wells comprising the venture gas field have all encountered overpressures at depths below 4 5 km the characteristics of the overpressure zones in the venture field vary in some important details from overpressured zones on the u s gulf coast in the venture field the shales in the overpressured zones are observed to be normally compacted and interbedded with layers of overpressured sandstones this is in contrast to the gulf coast where the shales in the overpressure zone are undercompacted resistivity logs sonic logs and bulk density logs all provide some indications of overpressures in the venture field but are not as unequivocal indicators of overpressure as they are on the gulf coast theoretical investigations of the causes of overpressures in an environment such as the venture field show that overpressures are unlikely to be caused by loading of sediments the most probable cause of overpressures is recent and continuing fluid generation which is related to the transformation of kerogen to hydrocarbons limits are placed on the average permeabilities and fluid generation rates which are required if overpressures are to be produced by fluid generation

physical properties of the variations of the electric field of the earth preceding earthquakes i abstract in an earlier paper we described the physical properties of the preseismic transient variations in the electrotelluric field the present letter clarifies a few points that were not properly emphasized in our previous publications furthermore recent results like that of the destructive kalamata earthquake on september 13 1986 indicate that the duration of a preseismic electric signal may reach considerably high values lasting up to several hours

evolution of petrophysical properties of oil shales during high temperature compaction tests implications for petroleum expulsion abstract the transport properties of permian to miocene oil shales torbanite posidonia messel himmetoglu and condor were studied using petrophysical and geochemical techniques the aims of this study were to assess permeability of oil shales evaluate the evolution of porosity specific surface area and intergranular permeability during high temperature compaction tests and to verify the suitability of intergranular permeability for petroleum expulsion measured permeability coefficients for two samples were 0 72 10 21 m for the eocene messel shale and 2 63 10 21 m for the lower jurassic posidonia shale from s germany respectively bet specific surface areas of the original samples ranged from 0 7 to 10 6 m g and decreased after compaction to values from 0 3 to 3 7 m g initial porosity values ranged from 7 6 to 20 1 for pre deformation and from 9 99 to 20 7 for post deformation samples porosity increased during the high temperature compaction experiments due to petroleum generation and expulsion permeability coefficients estimated using the kozeny carman equation varied from 6 97 10 24 m to 5 22 10 21 m for pre deformation and from 0 2 10 21 m to 4 8 10 21 m for post deformation samples reflecting the evolution of their porosity and bet specific surface areas measured and calculated permeability were similar for the messel shale whereas calculated permeability was two orders of magnitude lower for the posidonia shale from s germany petroleum expulsion efficiencies under the experimental conditions ranged from 38 6 for the torbanite to 96 2 for the posidonia shale from s germany they showed strong positive correlation with the petroleum generation index r 0 91 and poor correlations with porosity r 0 46 average pore throat diameters r 0 22 and compaction r 0 02 estimated minimum pore system saturations for petroleum expulsion during the experiments were 12 for the torbanite and 30 for the posidonia shale from n germany pore system saturation determines whether expulsion occurs mainly through matrix or fracture permeability for samples with saturation levels above 20 fracture permeability dominated during the experiments evidence based on the measured permeability coefficients expulsion flow rates consideration of capillary displacement during generation related pore invasion and the existence of transport porosity suggests that fracture permeability is the principal avenue of petroleum expulsion from source rocks this conclusion is supported by microscopic observations

why the south pacific convergence zone is diagonal during austral summer the majority of precipitation over the pacific ocean is concentrated in the south pacific convergence zone spcz the surface boundary conditions required to support the diagonally northwest southeast oriented spcz are determined through a series of experiments with an atmospheric general circulation model continental configuration and orography do not have a significant influence on spcz orientation and strength the key necessary boundary condition is the zonally asymmetric component of the sea surface temperature sst distribution this leads to a strong subtropical anticyclone over the southeast pacific that on its western flank transports warm moist air from the equator into the spcz region this moisture then intensifies diagonal bands of convection that are initiated by regions of ascent and reduced static stability ahead of the cyclonic vorticity in rossby waves that are refracted toward the westerly duct over the equatorial pacific the climatological spcz is comprised of the superposition of these diagonal bands of convection when the zonally asymmetric sst component is reduced or removed the subtropical anticyclone and its associated moisture source is weakened despite the presence of rossby waves significant moist convection is no longer triggered the spcz disappears the diagonal spcz is robust to large changes up to 6 c in absolute sst i e where the sst asymmetry is preserved extreme cooling change 6 c results in a weaker and more zonal spcz due to decreasing atmospheric temperature moisture content and convective available potential energy

the south pacific convergence zone spcz a review abstract the circulation features associated with the south pacific convergence zone spcz and its accompanying cloud band are reviewed and discussed the paper focuses on the following topics location structure and characteristics of the spcz theories and observations concerning its existence the significance and scope of the spcz in global scale circulation patterns quasi periodic changes in its location and strength and synoptic scale features within its regional influence e g cyclones subtropical jets it concludes with some challenging problems for the future

diagenesis and primary migration in upper jurassic claystone source rocks in north sea carbonate bands are common in central graben kimmeridgian upper jurassic claystone that is mature for oil generation x ray diffraction thermal analysis mossbauer spectroscopy thin section studies scanning microscopy and electron microprobe investigations showed that the bands are composed of claystone fragments coarse grains of dolomite quartz and siderite and diagenetic layer silicates all cemented to a certain degree by ankerite the diagenetic layer silicates are kaolinite being neoformed into muscovite in claystones adjacent to the carbonate bands ankerite fills pores about 50 m in diameter however claystone further away from the bands contains little ankerite gas adsorption with n2 kr and h2o together with microscopy showed porosity in the claystone is composed of a large amount of micropores and mesopores possibly with inlet constrictions and a few macropores with diameters of about 50 m in the carbonate bands microporosity and mesoporosity are probably located in the claystone fragments whereas several pores with diameters of about 50 m are present in the carbonate matrix the presence of claystone fragments fluid release structures and large amounts of diagenetic carbonates indicates that carbonate bands formed through fracturing possibly as a result of overpressuring porosity parameters indicate that fluid transport occurred by diffusion in the claystone matrix to claystone macropores and further through macropores in the carbonate bands out of the source rock the diagenesis of carbonates and clay minerals in the carbonate bands and in the claystone points to two migration stages an early migration of fresh neutral fluids and a later migration in connection with hydrocarbon migration of saline alkaline fluids