quantification of holocene asian monsoon rainfall from spatially separated cave records abstract a reconstruction of holocene rainfall is presented for southwest china an area prone to drought and flooding due to variability in the east asian monsoon the reconstruction is derived by comparing a new high resolution stalagmite 18 o record with an existing record from the same moisture transport pathway the new record is from heshang cave 30 27 n 110 25 e 294 m and shows no sign of kinetic or evaporative effects so can be reliably interpreted as a record of local rainfall composition and temperature heshang lies 600 km downwind from dongge cave which has a published high resolution 18 o record wang y j cheng h edwards r l he y q kong x g an z s wu j y kelly m j dykoski c a li x d 2005 the holocene asian monsoon links to solar changes and north atlantic climate science 308 854 857 by differencing co eval 18 o values for the two caves secondary controls on 18 o e g moisture source moisture transport non local rainfall temperature are circumvented and the resulting 18 o signal is controlled directly by the amount of rain falling between the two sites this is confirmed by comparison with rainfall data from the instrumental record which also allows a calibration of the 18 o proxy the calibrated 18 o record provides a quantitative history of rainfall in southwest china which demonstrates that rainfall was 8 higher than today during the holocene climatic optimum 6 ka but only 3 higher during the early holocene significant multi centennial variability also occurred with notable dry periods at 8 2 ka 4 8 4 1 ka 3 7 3 1 ka 1 4 1 0 ka and during the little ice age this holocene rainfall record provides a good target with which to test climate models the approach used here of combining stalagmite records from more than one location will also allow quantification of rainfall patterns for past times in other regions

evaluation of infrasound signals from the shuttle atlantis using a large seismic network inclement weather in florida forced the space shuttle atlantis to land at edwards air force base in southern california on june 22 2007 passing near three infrasound stations and several hundred seismic stations in northern mexico southern california and nevada the high signal to noise ratio broad receiver coverage and atlantis positional information allow for the testing of infrasound propagation modeling capabilities through the atmosphere to regional distances shadow zones and arrival times are predicted by tracing rays that are launched at right angles to the conical shock front surrounding the shuttle through a standard climatological model as well as a global ground to space model the predictions and observations compare favorably over much of the study area for both atmospheric specifications to the east of the shuttle trajectory there were no detections beyond the primary acoustic carpet infrasound energy was detected hundreds of kilometers to the west and northwest nw of the shuttle trajectory consistent with the predictions of ducting due to the westward summer time stratospheric jet both atmospheric models predict alternating regions of high and low ensonifications to the nw however infrasound energy was detected tens of kilometers beyond the predicted zones of ensonification possibly due to uncertainties in stratospheric wind speeds

the detection of low magnitude seismic events using array based waveform correlation summary it has long been accepted that occurrences of a known signal are most effectively detected by cross correlating the incoming data stream with a waveform template such matched signal detectors have received very little attention in the field of detection seismology because there are relatively few instances in which the form of an anticipated seismic signal is known a priori repeating events in highly confined geographical regions have been observed to produce very similar waveforms and good signals from events at a given site can be exploited to detect subsequent co located events at lower magnitudes than would be possible using traditional power detectors even greater improvement in signal detectability can be achieved using seismic arrays running correlation coefficients from single sensors can be stacked over an array or network to result in a network correlation coefficient displaying a significant array gain if two events are co located the time separating the corresponding patterns in the wave train as indicated by the cross correlation function is identical for all seismic stations and this property means that the correlation coefficient traces are coherent even when the waveforms are not we illustrate the power of array based waveform correlation using the 1997 august 16 kara sea event the weak event that occurred 4 hr after the main event was barely detected using an sta lta detector on the spits array but is readily detected by signal matching on a single channel the main event was also recorded by the far more distant norsar array but no conventional detection can be made for the second event a clear detection is however made when the correlation coefficient traces are beamformed over all sensors of the array we estimate the reduction in detection threshold of a test signal on a regional seismic array using waveform correlation by scaling down a master signal and immersing it into seismic noise we show that for this case waveform correlation using a single channel detects signals of approximately 0 7 orders of magnitude lower than is possible using an sta lta detector on the array beam waveform matching on the full array provides an additional improvement of approximately 0 4 magnitude units we describe a case study in which small seismic events at the barentsburg coal mine on spitsbergen were detected using the signals from a major rockburst as master waveforms many spurious triggers occurred in this study whereby short sections of signal exhibited coincidental similarity with unrelated incoming wave fronts we demonstrate how such false alarms can almost always be identified and screened out automatically by performing frequency wavenumber analysis upon the set of individual correlation coefficient traces

seasonal and interannual variability of the mid holocene east asian monsoon in coral δ18o records from the south china sea understanding the full range of past monsoon variability with reference to specific monsoon seasons is essential to test coupled climate models and improve their predictive capabilities we present a 54 year long high resolution skeletal oxygen isotope 6180 record extracted from a well preserved massive porites sp coral at hainan island south china sea to investigate east asian monsoon variability during summer and winter similar to 4400 calendar yr ago analysis of modem coral 6180 confirms that porites from hainan island are well positioned to record winter monsoon forcing of sea surface temperature sst as well as the influence of summer monsoon rainfall on sea surface salinity sss the coral record for similar to 4400 yr ago shows similar to 9 amplification of the annual cycle of 6 delta o 18 in good agreement with coupled ocean atmosphere models showing higher summer rainfall lower coral 618 0 and cooler winter ssts higher coral delta o 18 in response to greater northern hemisphere insolation seasonality during the middle holocene mean ssts in the south china sea during the mid holocene were within 0 5 degrees c of modem values yet the mean 6 180 for the fossil coral is similar to 0 6 parts per thousand higher than that for the modem coral suggesting that the 6 180 of surface seawater was higher by at least similar to 0 5 parts per thousand relative to modem values the o 18 enrichment is likely to be driven by greater advection of moisture towards the asian landmass enhanced monsoon wind induced evaporation and vertical mixing and or invigorated advection of saltier o 18 enriched pacific water into the relatively fresh south china sea the o 18 enrichment of the northern south china sea similar to 4400 yr ago contributes to mounting evidence for recent freshening of the tropical western pacific today winter sst and summer sss variability in the south china sea reflect the interannual influence of enso and the biennial variability inherent to monsoon precipitation spectral analysis of winter ssts similar to 4400 yr ago reveals a strong enso cycle at 6 7 y which is significantly longer than the average 3 6 y cycle observed since 1970 the results suggest that the influence of enso on winter ssts in the south china sea was well established by similar to 4400 yr ago however spectral analysis of summer sss similar to 4400 yr ago shows no significant enso cycle suggesting that teleconnections between enso and summer monsoon rainfall were restricted taken together the results indicate marked differences in enso monsoon interactions during the winter and summer monsoon seasons in the past the fossil coral delta o 18 record also shows that the amplitude of interannual sst and sss variability was stronger similar to 4400 yr ago despite enso variability being significantly weaker in the pacific region thus it appears that the strengthened mid holocene monsoon was sensitive to forces other than enso that acted as alternative drivers of interannual monsoon variability if this is the case greater interannual climate variability could accompany the strengthening of the asian monsoon predicted to occur during the 21st century as transient greenhouse warming preferentially warms eurasia even if enso perturbations remain relatively stable c 2005 elsevier b v all rights reserved

lateral fluid flow in a compacting sand shale sequence south caspian basin the article lateral fluid flow in a compacting sand shale sequence south caspian basin by john d bredehoeft rashid d djevanshir and kenneth r belitz aapg bulletin v 72 no 4 april 1988 p 416 424 needs the following corrections there are several typographical errors that were the author s error equation 2 should be equation 2 equation 3 should be equation 3 although the equations were incorrect in the article the associated discussion and equations 4 and 5 are based upon the correct expressions as shown above table 3 the calculated regional sand permeabilities is also incorrect the hydraulic conductivity which in our case has the units of meters per second was incorrectly converted to millidarcys values in meters per second were multiplied by the standard conversion 1 m sec equals 1 04 108 md in retrospect this conversion was a conceptual error table 3 should read table 3 calculated regional sand permeabilities acknowledgment we appreciate the comments of stan lohman who brought our attention to these errors end of article last page 1525

monsoon tropical ocean interaction in a network of coral records spanning the 20th century abstract the 20th century evolution of basin wide gradients in surface ocean properties provides one essential test for recent models of the interaction between the asian monsoon and the tropical ocean because various feedback mechanisms should result in characteristic regional patterns of variability although the instrumental record of climate variability in the tropics is essentially limited to the last few decades the stable isotopic composition of living corals provides an effective means for extending the instrumental observations here we present two coral isotopic records from the indonesian maritime continent and we use these records with other previously published records to describe i the relationship between western pacific and central pacific climate variability over the past century with special emphasis on the biennial band and ii the strength of the west east indian ocean dipole we find that the amplitude of the biennial cycle in the pacific did not vary inversely with the strength of enso el nino southern oscillation as might be expected from some models of monsoonal feedback on the central pacific instead the biennial variability was modulated on decadal timescales throughout much of the pacific we also show that the zonal oxygen isotopic gradient in the indian ocean coral records was significantly correlated with central pacific sea surface temperature on a variety of timescales thus it is likely that this coral dipole was a product of strong enso like teleconnections over the indian ocean as opposed to being the result of unique indian ocean or monsoonal dynamics

modulation of north pacific tropical cyclone activity by three phases of enso abstract tropical pacific ocean warming has been separated into two modes based on the spatial distribution of the maximum sea surface temperature sst anomaly an east pacific warming epw and a central pacific warming cpw when combined with east pacific cooling epc these three regimes are shown to have different impacts on tropical cyclone tc activity over the north pacific by differential modulation of both local thermodynamic factors and large scale circulation patterns in epw years the genesis and the track density of tcs tend to be enhanced over the southeastern part and suppressed in the northwestern part of the western pacific by strong westerly wind shear the extension of the monsoon trough and the weak wind shear over the central pacific increases the likelihood of tc activity to the east of the climatological mean tc genesis location in cpw years the tc activity is shifted to the west and is extended through the northwestern part of the western pacific the westward shifting of c

dynamics of the intertropical convergence zone over the western pacific during the little ice age precipitation patterns in the western pacific changed at the onset of the little ice age a synthesis of precipitation reconstructions suggests that this change resulted from a contraction of the intertropical convergence zone

seismic investigation of the 26 march 2010 sinking of the south korean naval vessel cheonanham a south korean naval vessel sank on 26 march 2010 a seismic event with magnitude ml of 1 5 was observed at the time of vessel sinking seismic waveforms were collected from three local stations the event origin time is refined based on the p and s arrival times at the stations the calculated event location and time are close to the reported vessel sinking location and time suggesting that the observed seismic event is associated with the vessel sinking the amplitudes of s waves are comparable to those of p waves seismic waves coupled from acoustic waves are observed providing additional constraints of epicentral distance and source type the coupled acoustic waves have a dominant frequency of 32 hz the acoustic waves and high p s amplitude ratios suggest an underwater explosion the body wave magnitude based on pn is determined to be 1 46 which is consistent with the reported ml p energy is dominant at around 8 5 hz with multiple frequencies of 17 7 and 34 6 hz the primary frequency suggests the water column thickness in the source region to be 44 m which agrees with the reported value

infrasound detection of large mining blasts in kazakstan we describe infrasonic observations recorded since october 1997 at the kurchatov observatory in kazakstan from large mining blasts in kazakstan and siberia seismic signals are regularly recorded on a 21 element cross array from events located at the ekibastuz mine 250 km nw of kurchatov however associated infrasonic detections are infrequent and appear to be seasonal with maximum numbers of detections occurring during november to january raytracing through model atmosphere temperature and wind profiles predicts enhanced infrasound reception during the winter months when the prevailing stratospheric winds blow towards kurchatov in addition raytracing confirms that the first infrasound arrivals at kurchatov propagate through the troposphere and are followed some 50 70 s later by a stratospheric arrival

atmospheric wind and temperature profiles inversion using infrasound an ensemble model context this paper presents an inversion methodology where acoustic observations of infrasound waves are used to update an atmospheric model this paper sought a flexible parameterization that permits to incorporate physical and numerical constraints without the need to reformulate the inversion on the other hand the optimization conveys an explicit search over the solution space making the solver computationally expensive nevertheless through a parallel implementation and the use of tight constraints this study demonstrates that the methodology is computationally tractable constraints to the solution space are derived from the spread variance of era5 ensemble reanalysis members which summarize the best current knowledge of the atmosphere from assimilated measurements and physical models similarly the initial model temperature and winds for the inversion are chosen to be the average of these parameters in the ensemble members the performance of the inversion is demonstrated with the application to infrasound observations from an explosion generated by the destruction of ammunition at hukkakero finland the acoustic signals are recorded at an array station located at 178 km range which is within the classical shadow zone distance the observed returns are assumed to come from stratospheric reflections thus the reflection altitude is also an inverted parameter

lessons learned from oxygen isotopes in modern precipitation applied to interpretation of speleothem records of paleoclimate from eastern asia abstract variability in oxygen isotope ratios collected from speleothems in chinese caves is often interpreted as a proxy for variability of precipitation summer precipitation seasonality of precipitation and or the proportion of 18o to 16o of annual total rainfall that is related to a strengthening or weakening of the east asian monsoon and in some cases to the indian monsoon we use modern reanalysis and station data to test whether precipitation and temperature variability over china can be related to changes in climate in these distant locales we find that annual and rainy season precipitation totals in each of central china south china and east india have correlation length scales of 500 km shorter than the distance between many speleothem records that share similar long term time variations in 18o values thus the short distances of correlation do not support though by themselves cannot refute the idea that apparently synchronous variations in 18o values at widely spaced 500 km caves in china are due to variations in annual precipitation amounts we also evaluate connections between climate variables and 18o values using available instrumental measurements of 18o values in precipitation these data from stations in the global network of isotopes in precipitation gnip show that monthly 18o values generally do not correlate well with either local precipitation amount or local temperature and the degree to which monthly 18o values do correlate with them varies from station to station for the few locations that do show significant correlations between 18o values and precipitation amount we estimate the differences in precipitation amount that would be required to account for peak to peak differences in 18o values in the speleothems from hulu and dongge caves assuming that 18o scales with the monthly amount of precipitation or with seasonal differences in precipitation insofar as the present day relationship between 18o values and monthly precipitation amounts can be applied to past conditions differences of at least 50 in mean annual precipitation would be required to explain the 18o variations on orbital time scales which are implausibly large and inconsistent with published gcm results similarly plausible amplitudes of seasonal cycles in amounts or in seasonal variations in 18o values can account for less than half of the 4 5 difference between glacial and interglacial 18o values from speleothems in china if seasonal cycles in precipitation account for the amplitudes of 18o values on paleoclimate timescales they might do so by extending or contracting the durations of seasons a frequency modulation of the annual cycle but not by simply varying the amplitudes of the monthly rainfall amounts or monthly average 18o values amplitude modulation allowing that several processes can affect seasonal variability in isotopic content we explore the possibility that one or more of the following processes contribute to variations in 18o values in chinese cave speleothems different source regions of the precipitation which bring different values of 18o in vapor different pathways between the moisture source and the paleorecord site along which exchange of 18o between vapor surface water and condensate might differ a different mix of processes involving condensation and evaporation within the atmosphere or different types of precipitation each may account for part of the range of 18o values revealed by speleothems and each might contribute to seasonal differences between past and present that do not scale with monthly or even seasonal precipitation amounts

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

strong influence of water vapor source dynamics on stable isotopes in precipitation observed in southern meghalaya ne india to calibrate 18o time series from speleothems in the eastern indian summer monsoon ism region of india and to understand the moisture regime over the northern bay of bengal bob we analyze the 18o and d of rainwater collected in 2007 and 2008 near cherrapunji india d values range from 18 5 to 144 4 while 18o varies between 0 8 and 18 8 the local meteoric water line lmwl is found to be indistinguishable from the global meteoric water line gmwl late ism september october rainfall exhibits lowest 18o and d values with little relationship to the local precipitation amount there is a trend to lighter isotope values over the course of the ism but it does not correlate with the patterns of temperature and rainfall amount 18o and d time series have to be interpreted with caution in terms of the amount effect in this subtropical region we find that the temporal trend in 18o reflects increasing transport distance during the ism isotopic changes in the northern bob surface waters during late ism and vapor re equilibration with rain droplets using an isotope box model for surface ocean waters we quantify the potential influence of river runoff on the isotopic composition of the seasonal freshwater plume in the northern bob temporal variations in this source can contribute up to 25 of the observed changes in stable isotopes of precipitation in ne india to delineate other moisture sources we use backward trajectory computations and find a strong correlation between source region and isotopic composition palaeoclimatic stable isotope time series from northeast indian speleothems likely reflect changes in moisture source and transport pathway as well as the isotopic composition of the bob surface water all of which in turn reflect ism strength stalagmite records from the region can therefore be interpreted as integrated measures of the ism strength

southward movement of the pacific intertropical convergence zone ad 1400 1850 tropical rainfall patterns control the subsistence lifestyle of more than one billion people seasonal changes in these rainfall patterns are associated with changes in the position of the intertropical convergence zone which is characterized by deep convection causing heavy rainfall near 10 n in boreal summer and 3 n in boreal winter dynamic controls on the position of the intertropical convergence zone are debated but palaeoclimatic evidence from continental asia africa and the americas suggests that it has shifted substantially during the past millennium reaching its southernmost position some time during the little ice age ad1400 1850 however without records from the meteorological core of the intertropical convergence zone in the pacific ocean quantitative constraints on its position are lacking here we report microbiological molecular and hydrogen isotopic evidence from lake sediments in the northern line islands galapagos and palau indicating that the pacific intertropical convergence zone was south of its modern position for most of the past millennium by as much as 500km during the little ice age a colder northern hemisphere at that time possibly resulting from lower solar irradiance may have driven the intertropical convergence zone south we conclude that small changes in earth s radiation budget may profoundly affect tropical rainfall

increased effective moisture in northern vietnam during the little ice age abstract we present a 650 yr record of hydroclimate inferred from 18o values of lacustrine carbonate from ao tien fairy pond in northern vietnam ao tien occupies a collapsed karst basin that formed during the worst drought of the last millennium i e the angkor i drought which marks a dry transitional period between the medieval climate anomaly and the little ice age a multi centennial trend of increasing effective moisture spans the little ice age ending with aridity in the late 18th century that accompanied great societal turmoil across southeast asia after 1850 ce the ao tien record exhibits a drying trend that continues to the present over the last 650 years the 18o inferred hydroclimate is significantly correlated with the reconstructed southern oscillation index of precipitation soipr suggesting that a prolonged la nina like state existed during the little ice age generating overall wetter conditions in vietnam decadal scale droughts and pluvials from the ao tien record agree with a robust tree ring hydroclimate reconstruction from southern vietnam that identified the angkor i and ii droughts of the late 13th early 14th centuries and significant droughts during the early and late 17th century and latter half of the 18th century the decrease in effective moisture during the last 30 years is also evident in the tree rings and is consistent with a documented weakening of the pacific walker circulation major pluvials are indicated for the period between the two angkor droughts and the wettest period of the record is during the early 18th century comparison of the ao tien data with records from indonesia to china indicates regionally coherent climate during the little ice age however the overall wet conditions in easterly sites are difficult to ascribe to shifts in the itcz rather the pattern suggests that pacific walker circulation may have been the overriding control on precipitation

free thermohaline convection in sediments surrounding a salt column complex groundwater convection patterns are possible near salt domes because groundwater is subject to both lateral heat and salinity gradients in order to assess the mechanisms responsible for driving convection near salt domes we use dimensional analysis and numerical simulations to investigate coupled heat and salt transport in homogeneous sediments surrounding a cylindrical salt column the dimensional analysis does not require the boussinesq assumption the coupled heat solute and groundwater transport equations are controlled by three dimensionless parameters the rayleigh number the lewis number and the buoyancy ratio the buoyancy ratio is the ratio of salinity to temperature effects on groundwater density and it directly affects the groundwater flow equation a finite difference numerical multigridding algorithm is used to iteratively solve the coupled transport equations the multigridding technique was about 3 times faster than a point wise successive overrelaxation solution boundary conditions for the numerical simulations were adjusted to represent different contrasts in the thermal gradient between the salt and the overlying sediments the contrast in thermal gradient is parameterized by the thermal conductivity ratio and is responsible for isotherms being elevated near the salt the analysis suggests that a wide range of convective flow patterns are possible with flow occurring either up or down along the salt flank the sense of convection is dependent mainly on the value of the buoyancy ratio and how sharply isotherms are pulled up near the salt these factors in turn depend on the regional salinity variation the time since diapirism and the thermal conductivity of water saturated sediments while this analysis provides useful insight into the mechanisms driving free convection near salt domes the assumptions about medium and fluid properties may limit the applicability of dimensional analysis in simulating flow in specific geologic settings

summer monsoon precipitation variations in central china over the past 750 years derived from a high resolution absolute dated stalagmite abstract a 2 3 year resolution record of stalagmite oxygen isotope variations from the south flank of the qinling mountains central china has revealed the asian summer monsoon asm precipitation variations in the investigated area over the past 750 years the summer monsoon precipitation gradually increased since 1249 ad reaching its highest values in the period 1535 1685 ad and then decreased with substantial decadal to centennial scale fluctuations the monsoon precipitation increased again between 1920 and 1970 ad three intervals of high monsoon precipitation were identified 1535 1685 ad 1755 1835 ad and 1920 1970 ad three intervals of low precipitation were inferred in 1249 1325 ad 1390 1420 ad and 1890 1915 ad the 18 o composition and lithological features of the stalagmite coincidently indicate a wetter climate during the little ice age lia which is also confirmed by climate records from chinese historical documents within this area a comparison with other high resolution speleothem records indicates regional differences in monsoon precipitation variability from the south to the north of central china in the last 750 years on decadal to centennial scale power spectrum analysis of the 18 o record shows significant 117 8 34 6 14 10 3 and 6 year periodicities these periodicities are widely observed in the climate records from asm controlled areas of china and are consistent with the gleissburg periodicity br ckner periodicity sunspot periodicity of solar activity and el nino southern oscillation enso periodicity these correlations suggest that both solar activity and enso periodicity may have had important influences on asm precipitation in china over the past 750 years

a satellite derived climatology of the itcz abstract this paper presents fundamental climatological characteristics of the intertropical convergence zone itcz in a simple concise manner using the highly reflective cloud hrc dataset this satellite derived dataset uses both visible and infrared observations to measure the frequency of occurrence of large scale convective systems over the global tropics at a 1 spatial resolution these dataset characteristics make the hrc particularly well suited for climatological analysis of the itcz because the dataset is based on estimates of organized deep convective cloud systems rather than observations of clouds as a whole and it provides the spatial resolution needed to identify thew large wale convective structures furthermore the dataset covers a time period extending nearly two decades which provides for a fairly robust climatology and the opportunity to examine seasonal and interannual variability of both the convection and the latitude of the itcz

an automatic seismic event processing for detection and location the p m c c method we present a new method for automatic detection and location of seismic events recorded on a network it is based on a progressive study of the interstation correlation functions which leads to a consistent set of time delays when a seismic phase is present three different examples are processed on networks of different sizes

seismic detection of sonic booms the pressure signals from a sonic boom will produce a small but detectable ground motion the extensive seismic network in southern california consisting of over 200 sites covering over 50 000 square kilometers is used to map primary and secondary sonic boom carpets data from the network is used to analyze three supersonic overflights in the western united states the results are compared to ray tracing computations using a realistic model of the stratified atmospheric at the time of the measurements the results show sonic boom ground exposure under the real atmosphere is much larger than previously expected or predicted by ray tracing alone finally seismic observations are used to draw some inferences on the origin of a set of mystery booms recorded in 1992 1993 in southern california

the influence of the interdecadal pacific oscillation on temperature and precipitation over the globe the interdecadal pacific oscillation ipo is a 40 60 year quasi oscillation seen mostly in the pacific basin but its impacts on surface temperature t and precipitation p have been found over australia the southwest u s and other regions here a global analysis of ipo s impacts on t and p and its modulation of enso s influence on t and p over the globe is performed using observational and reanalysis data and model simulations since 1920 there are two warm 1924 1944 and 1977 1998 and two cold 1945 1976 and 1999 present ipo phases whose change is associated with abrupt shifts in north pacific sea level pressure slp and contrasting anomaly patterns in t and p and atmospheric circulation over the eastern and western pacific the ipo explains more than half of the interdecadal variations in t and p over many regions such as northeastern australia western canada and northern india significant correlations between the ipo and local p are observed over eastern australia southern africa and the southwest u s the ipo also modulates enso s influence on local t and p over most of these regions t over northern india is positively correlated with nino3 4 enso index during cold ipo phases but the correlation turns negative or insignificant during ipo warm phases over northeastern australia the t versus enso and p versus enso correlations are stronger during the ipo cold phases than during the warm phases the p versus enso correlation over southern africa tends to be negative during ipo warm phases but becomes weaker or insignificant during ipo cold phases the ipo induced p anomalies can be explained by the associated anomaly circulation which is characterized by a high slp center and anti cyclonic flows over the north pacific and negative slp anomalies and increased wind convergence over the indonesia and western pacific region during ipo cold phases these observed influences of the ipo on regional t and p are generally reproduced by an atmospheric model forced by observed sea surface temperatures

east asian monsoon variability since the mid holocene recorded in a high resolution absolute dated aragonite speleothem from eastern china abstract paleoclimatic conditions associated with the east asian monsoon are reconstructed for the mid to late holocene using 18o values 819 measurements from a precisely dated 10 230th dates aragonite stalagmite from lianhua cave hunan province china 18o values 1 6 to 7 0 are interpreted to reflect the precipitation amount effect related to the strength of summer monsoonal circulation throughout this period the intensity of east asian summer monsoonal circulation declined in response to changes in insolation and a southward shift in the intertropical convergence zone itcz punctuating this first order trend are abrupt millennial to decadal scale fluctuations the most prominent of which occurred around 3337 5 yr bp and records a dramatic weakening in summer monsoonal circulation that coincides with the beginning of neoglacial conditions comparisons between the 18o values of stalagmite a1 and previously published data from stalagmite hs 4 from heshang cave and stalagmites d4 and da from dongge cave china demonstrate a similar regional response to changes in east asian monsoonal circulation several spectral analysis techniques and wavelet analysis were applied to these stalagmite records to evaluate the nature and character of cyclicity in the east asian monsoon during the holocene multi taper method mtm lomb scargle and single spectrum analysis ssa results reveal common periodicities that are unlikely to be artifacts of any single technique the periodicities expressed in the stalagmite 18o records occur at both solar and non solar frequencies and support previous interpretations that variability in monsoonal circulation responds to both solar forcing and internal climatic mechanisms wavelet analysis demonstrates that some of these frequencies are intermittent and recur at semi regular intervals which may indicate long term cyclicity that is unconstrained by the chronology of the record

groundwater upwelling near bay st elaine salt dome in southeastern louisiana as inferred from fluid property variations fluid pressures temperatures and salinities derived from 62 well logs were mapped in three vertical cross sections across the bay st elaine salt dome in southeastern louisiana to qualitatively determine groundwater flow patterns around the dome near hydrostatic conditions prevail in the sand rich shallow section from depths of 0 to 2 5 km however fully enclosed within the hydropressured section are lenses of slightly overpressured sediments which slope up toward the dome hydraulic heads may be as much as 500 m above ground level within these enclosed lenses in some strongly overpressured sediments deeper than 2 5 km hydraulic heads are as much as 2500 m above ground level pore water salinities increase with depth within the hydrostatically pressured section fr m 0 wt at the surface to maximum values of 10 12 wt at the top of the overpressured section within the overpressured section salinities decrease to as little as 6 wt with increasing depth immediately adjacent to the northeastern flank of the dome is a steeply dipping lobe of relatively fresh waters 6 wt sodium chloride that separates the flank of the dome from saltier 8 10 wt waters away from the dome this low salinity water mass appears to be connected to similar low salinity waters in the overpressured section and is postulated to be due to pore water upwelling from a depth of 4 km to a depth of about 1 5 km

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

stable isotopes of oxygen and hydrogen in the truckee river pyramid lake surface water system 3 source of water vapor overlying pyramid lake during 1988 and 1989 a series of water vapor extractions were conducted in the pyramid lake basin to determine the source of moisture that overlies the lake calculations of the isotopic and water vapor balances were made from isotopic and meteorological data from the pyramid lake and reno nevada areas the results indicate that in the warm season most of the moisture that overlies the lake is derived from evaporation as opposed to advected moisture isotopic fluxes at the lake surface can be approximated by climatic data from the lake site which simplifies the calculation of this input in numerical simulations of the isotopic evolution of the lake the stable isotopic composition of a lake is a function of the volume weighted isotopic values of each component of the lake s hydrologic balance researchers have used the stable isotope history of a lake together with the volume weighted isotopic composition of easily measured components of the hydrologic balance to estimate the stable isotope values or amounts of less easily measured components of the hydrologic balance see iaea 1970 1979 it is usually relatively simple to quantify the amounts and isotopic compositions of components of the surface water system and the isotopic composition of groundwater it is often more difficult to quantify the amount and direction of groundwater transport across the sediment water interface and the amount and isotopic composition of lake surface evaporation the isotopic value of water evaporated from a lake is highly dependent on the isotopic value acknowledgments we express our appreciation to those who assisted in sampling including jim davis dan mosley and nancy vucinich special thanks to irving friedman who loaned us the copper traps used for water vapor extraction to carol kendall and tyler coplen who oversaw the isotopic analyses to james ashby who maintained the weather stations and to steve hostetler who extracted the meteorological data from the weather station database and stratified the wind data for the sutcliffc and northshore sites we also thank zell peterman steve hostetler and pieter tans for reviews of earlier versions of this manuscript

the framework of hydrocarbon generation and migration gulf of mexico continental slope abstract the occurrence of large volumes of crude oil and thermogenic gas in plio pleistocene reservoirs and holocene seeps of the gulf of mexico slope argues that the process of hydrocarbon generation and migration continues at the present time calculated thermal maturity models based on deep seismic stratigraphy indicate that cretaceous and possibly early tertiary sediments are presently within the thermal maturity range for generation and expulsion of crude oil the cretaceous and early tertiary sediments are suggested as possible source rocks because younger sediments are thermally immature for crude oil generation and older sediments are thermally overmature for crude oil preservation the calculated thermal maturity profile for the slope indicates that some generation of crude oil could occur as shallow as 6 km and that liquid hydrocarbons could be preserved as deep as 9 km thermogenic gas is stable at even greater depths migration with a strong vertical component must be invoked to explain thermogenic hydrocarbons in shallow reservoirs and seeps of the slope the great depth at which liquid hydrocarbons and dry gas can be preserved in reservoirs of the gulf of mexico salt basin indicates that huge volumes of prospective section remain essentially unexplored

a tree ring based reconstruction of the atlantic multidecadal oscillation since 1567 a d 1 we present a tree ring based reconstruction of the atlantic multidecadal oscillation amo which demonstrates that strong low frequency 60 100 yr variability in basin wide 0 70 n sea surface temperatures ssts has been a consistent feature of north atlantic climate for the past five centuries intervention analysis of reconstructed amo indicates that 20th century modes were similar to those in the preceding 350 yr and wavelet spectra show robust multidecadal oscillations throughout the reconstruction though the exact relationships between low frequency sst modes higher frequency 7 25 yr atmospheric modes e g north atlantic oscillation arctic oscillation and terrestrial climates must still be resolved our results confirm that the amo should be considered in assessments of past and future northern hemisphere climates

comparison of the structure of the itcz in the west pacific during the boreal summers of 1989 93 using amip simulations and ecmwf reanalysis the dynamic structure and interannual variability of the itcz in the western north pacific and east asia during the boreal summers of 1989 93 are investigated european centre for medium range weather forecasts ecmwf reanalyses are used to characterize the dynamical structure of the itcz the itcz structure in the national center for atmospheric research ncar community climate model 3 ccm3 6 and the national aeronautics and space administration nasa goddard institute of space studies giss si2000 gcm is also explored the itcz axis can be partitioned into three sections in the western north pacific and east asia the continental monsoon trough cmt in india the bay of bengal and indo china the oceanic monsoon trough omt in the pacific warm pool and the trade wind trough twt in the central pacific the confluence point cp is defined as an area where the broad cyclonic flow in omt changes to the easterly trades of the twt east of the cp both gcms simulate a weaker easterly trade wind regime with a broader itcz due to the dislocation of the pacific high to the west of the cp both gcms simulate a weaker cross equatorial flow and omt both models show skill in simulating the interannual variability of the location of the cp however for the peak enso warm phase years 1992 93 the spread among ensemble members of the cp longitude is comparable to the shift of ensemble mean cp location relative to 1989 that is the internal variability of each gcm is on the same order as the simulated interannual variability in this region

detection and analysis of near surface explosions on the kola peninsula seismic and infrasonic observations of signals from a sequence of near surface explosions at a site on the kola peninsula have been analyzed norsar s automatic network processing of these events shows a significant scatter in the location estimates and to improve the automatic classification of the events we have performed full waveform cross correlation on the data set although the signals from the different events share many characteristics the waveforms do not exhibit a ripple for ripple correspondence and cross correlation does not result in the classic delta function indicative of repeating signals using recordings from the arces seismic array 250 km w of the events we find that a correlation detector on a single channel or three component station would not be able to detect subsequent events from this source without an unacceptable false alarm rate however performing the correlation on each channel of the full arces array and stacking the resulting traces generates a correlation detection statistic with a suppressed background level which is exceeded by many times its standard deviation on only very few occasions performing f k analysis on the individual correlation coefficient traces and rejecting detections indicating a non zero slowness vector results in a detection list with essentially no false alarms applying the algorithm to 8 years of continuous arces data identified over 350 events which we confidently assign to this sequence the large event population provides additional confidence in relative travel time estimates and this together with the occurrence of many events between 2002 and 2004 when a temporary network was deployed in the region reduces the variability in location estimates the best seismic location estimate incorporating phase information for many hundreds of events is consistent with backazimuth measurements for infrasound arrivals at several stations at regional distances at lycksele 800 km sw of the events as well as at arces infrasound is detected for most of the events in the summer and for few in the winter at apatity some 230 km s of the estimated source location infrasound is detected for most events as a first step to providing a ground truth database for this useful source of infrasound we provide the times of explosions for over 50 events spanning 1 year

ephemeral thermal and solute plumes formed by upwelling groundwaters near salt domes geochemical observations made by previous workers indicate that rapid upward advection of hot water has occurred along the flanks of some salt domes in the northern gulf of mexico basin and in the danish central trough the observations are based on pore fluid chemistry and on high temperatures of formation of metal sulfides and other diagenetic minerals near the crests of salt domes some of the diagenetic minerals formed at 40 c to 80 c above the ambient temperature of the host rocks numerical simulations of coupled heat and dissolved salt transport show that thermal perturbations in excess of 60 c can be repeatedly produced near the crest of a salt dome by focused dewatering of a thick strongly overpressured sedimentary interval around the dome in our simulations dewatering was triggered and stopped by cyclically changing the permeability at the salt sediment interface the thermal plumes dissipated within 100 kyr after dewatering ceased stratigraphically shallow brine plumes were also formed by dewatering and these gravitationally unstable plumes dissipated more slowly by sinking within 1 m y simulations showed that free thermohaline convection can also generate thermal perturbations near the crest of a dome in this mode of upwelling thermal perturbations reached 30 c when the vertical permeability of the hydrostatically pressured interval was 10 14 m2 10 mdarcy because such permeabilities seem large for the hydrostatically pressured interval as a whole in the northern gulf of mexico basin the formation of high temperature metal sulfide deposits near the crests of salt domes seems more likely to be due to dewatering of the overpressured interval with very strong focusing of expelled waters along the flanks of salt domes

a record of the southern oscillation index for the past 2 000 years from precipitation proxies the el nino southern oscillation enso is a coupled ocean atmosphere climate phenomenon in the tropical pacific ocean the interannual climate variations have been shown to modify both the hadley and walker meridional and zonal atmospheric circulations with strong impacts on global climate 1 3 proxy based reconstructions of the southern oscillation index on a multi decadal scale have shown that the strength and frequency of el nino occurrences have varied over the past millennium 4 7 here we compile reconstructions of precipitation 8 15 from regions that experience substantial enso variability to extend the multidecadal scale southern oscillation index to include the past 2 000 years we find that the medieval warm period similar to ad 800 1300 was characterized by a negative index which indicates more el nino dominated conditions whereas during the little ice age similar to ad 1400 1850 more la nina dominated conditions prevailed the southern oscillation index we derive is significantly correlated with reconstructions of solar irradiance and mean northern hemisphere temperature fluctuations

a 400 year record of hydroclimate variability and local enso history in northern southeast asia inferred from tree ring δ18o abstract we present here a chronology of tree ring cellulose 18 o for the period 1588 2002 based on individual measurements of seven fokienia hodginsii trees growing in northern laos response function analysis of meteorological data revealed that this oxygen isotope chronology has a significant negative correlation with monsoon season precipitation the water level of the mekong river and the palmer drought severity index pdsi our reconstructed monsoon season pdsi which accounts for 41 5 of pdsi variance showed that wetter phases occurred during the periods ad 1660 1695 and ad 1705 1790 that the main drier periods were ad 1630 1660 ad 1900 1940 and ad 1954 2002 and that there has been a trend of decreasing moisture during the monsoon season over the last 200 years a reduction in monsoon activity can also be seen in various tree ring oxygen isotope records from the himalaya tibet plateau and southeast asia rising sea surface temperatures over the tropical pacific and indian ocean could be responsible for this reduction in the asian summer monsoon by combining proxies sensitive to the el nino southern oscillation enso in northern laos and vietnam we were able to reconstruct the annual multivariate enso index mei and local enso event history and so improve our understanding of long term variations in enso and its influences on southeast asia

interdecadal pacific oscillation reconstructed from trans pacific tree rings 1350 2004 ce the interdecadal pacific oscillation ipo represents the decadal mode of the el nino southern oscillation phenomenon as such the ipo is one of the dominant modes of decadal climate variability on both sides of the pacific ocean basin for this paper we utilized a newly developed tree ring data network comprised of five multi centennial vietnamese cypress ring width chronologies that range from around 11 n 23 n latitude we combined these data with an average of tree ring derived drought indices from the north american drought atlas over the south central usa from a box that spans from 27 5 n 35 0 n 85 0 110 0 w and contains 55 gridpoints and more than 100 tree ring site chronologies these 2 locations exhibit rainfall variations that are strongly negatively correlated with each other and are representative of the influence of the ipo on terrestrial rainfall the final reconstruction model weighted most heavily on the three most southerly of the five vietnamese cypress records spans from 1350 to 2004 and explains nearly 57 of the variance in the original ipo data for the 5 month season of october february the reconstruction model passes all standard statistical tests using a split calibration verification scheme we reveal 15 positive and 15 negative phase shifts of the ipo prior to the period of instrumentation suggesting that the ipo has been active for at least the past seven centuries with varying degrees of intensity we compare our reconstruction with two related millennial records the macdonald and case geophys res lett 32 8 l08703 2005 tree ring derived reconstruction of the pacific decadal oscillation and an ice core derived reconstruction of the ipo from the law dome ice core in antarctica by vance et al geophys res lett 33 6 l06712 2015 while there is good general agreement with the latter record there are three key periods of the past where the two records are out of phase and we explore the reasons for this disparity direct comparison with the related tripole index tpi shows weaker correlation likely owing to the stronger relationship between our tree ring data and the equatorial pacific region relative to the north and south regions of the pacific that combine to comprise the tpi calculation

a predictability study of simulated north atlantic multidecadal variability the north atlantic is one of the few places on the globe where the atmosphere is linked to the deep ocean through air sea interaction while the internal variability of the atmosphere by itself is only predictable over a period of one to two weeks climate variations are potentially predictable for much longer periods of months or even years because of coupling with the ocean this work presents details from the first study to quantify the predictability for simulated multidecadal climate variability over the north atlantic the model used for this purpose is the gfdl coupled ocean atmosphere climate model used extensively for studies of global warming and natural climate variability this model contains fluctuations of the north atlantic and high latitude oceanic circulation with variability concentrated in the 40 60 year range oceanic predictability is quantified through analysis of the time dependent behavior of large scale empirical orthogonal function eof patterns for the meridional stream function dynamic topography 170 m temperature surface temperature and surface salinity the results indicate that predictability in the north atlantic depends on three main physical mechanisms the first involves the oceanic deep convection in the subpolar region which acts to integrate atmospheric fluctuations thus providing for a red noise oceanic response as elaborated by hasselmann the second involves the large scale dynamics of the thermohaline circulation which can cause the oceanic variations to have an oscillatory character on the multidecadal time scale the third involves nonlocal effects on the north atlantic arising from periodic anomalous fresh water transport advecting southward from the polar regions in the east greenland current when the multidecadal oscillatory variations of the thermohaline circulation are active the first and second eof patterns for the north atlantic dynamic topography have predictability time scales on the order of 10 20 y whereas eof 1 of sst has predictability time scales of 5 7 y when the thermohaline variability has weak multidecadal power the hasselmann mechanism is dominant and the predictability is reduced by at least a factor of two when the third mechanism is in an extreme phase the north atlantic dynamic topography patterns realize a 10 20 year predictability time scale additional analysis of sst in the greenland sea in a region associated with the southward propagating fresh water anomalies indicates the potential for decadal scale predictability for this high latitude region as well the model calculations also allow insight into regional variations of predictability which might be useful information for the design of a monitoring system for the north atlantic predictability appears to break down most rapidly in regions of active convection in the high latitude regions of the north atlantic

possible linkage between the monsoon trough variability and the tropical cyclone activity over the western north pacific abstractthe present study investigates the influence of the monsoon trough mt on the interannual variability of tropical cyclone tc activity over the western north pacific during july november for the period 1979 2007 it is shown that the tc activity is closely related to the mt location during the years when the mt extends eastward retreats westward more less tcs form within the southeastern quadrant of the western north pacific such a relationship can be explained by the changes in large scale environmental factors associated with the movement of the mt an eastward extension of the mt coincides with warmed ocean surface enhanced convection increased relative humidity in the lower and midtroposphere reduced vertical shear of zonal wind intensified upper level divergence and low level anomalous cyclonic vorticity over the southeast quadrant of the western north pacific these conditions associated with the eastern extension of the mt are favorable for tc genesis while those associated w

considerations in phase estimation and event location using small aperture regional seismic arrays the global monitoring of earthquakes and explosions at decreasing magnitudes necessitates the fully automatic detection location and classification of an ever increasing number of seismic events many seismic stations of the international monitoring system are small aperture arrays designed to optimize the detection and measurement of regional phases collaboration with operators of mines within regional distances of the arces array together with waveform correlation techniques has provided an unparalleled opportunity to assess the ability of a small aperture array to provide robust and accurate direction and slowness estimates for phase arrivals resulting from well constrained events at sites of repeating seismicity a significant reason for the inaccuracy of current fully automatic event location estimates is the use of f k slowness estimates measured in variable frequency bands the variability of slowness and azimuth measurements for a given phase from a given source region is reduced by the application of almost any constant frequency band however the frequency band resulting in the most stable estimates varies greatly from site to site situations are observed in which regional p arrivals from two sites far closer than the theoretical resolution of the array result in highly distinct populations in slowness space this means that the f k estimates even at relatively low frequencies can be sensitive to source and path specific characteristics of the wavefield and should be treated with caution when inferring a geographical backazimuth under the assumption of a planar wavefront arriving along the great circle path moreover different frequency bands are associated with different biases meaning that slowness and azimuth station corrections commonly denoted sascs cannot be calibrated and should not be used without reference to the frequency band employed we demonstrate an example where fully automatic locations based on a source region specific fixed parameter template are more stable than the corresponding analyst reviewed estimates the reason is that the analyst selects a frequency band and analysis window which appears optimal for each event in this case the frequency band which produces the most consistent direction estimates has neither the best snr or the greatest beam gain and is therefore unlikely to be chosen by an analyst without calibration data

joint seismic infrasonic processing of recordings from a repeating source of atmospheric explosions a database has been established of seismic and infrasonic recordings from more than 100 well constrained surface explosions conducted by the finnish military to destroy old ammunition the recorded seismic signals are essentially identical and indicate that the variation in source location and magnitude is negligible in contrast the infrasonic arrivals on both seismic and infrasound sensors exhibit significant variation both with regard to the number of detected phases phase travel times and phase amplitudes which would be attributable to atmospheric factors this data set provides an excellent database for studies in sound propagation infrasound array detection and direction estimation

cluster analysis of typhoon tracks part ii large scale circulation and enso abstract a new probabilistic clustering method based on a regression mixture model is used to describe tropical cyclone tc propagation in the western north pacific wnp seven clusters were obtained and described in part i of this two part study in part ii the present paper the large scale patterns of atmospheric circulation and sea surface temperature associated with each of the clusters are investigated as well as associations with the phase of the el nino southern oscillation enso composite wind field maps over the wnp provide a physically consistent picture of each tc type and of its seasonality anomalous vorticity and outgoing longwave radiation indicate changes in the monsoon trough associated with different types of tc genesis and trajectory the steering winds at 500 hpa are more zonal in the straight moving clusters with larger meridional components in the recurving ones higher values of vertical wind shear in the midlatitudes also accompany the straight moving tracks compared to

use of hydraulic head and hydraulic gradient to characterize geopressured sediments and direction of fluid migration in louisiana gulf coast abstract abstract the characterization of geopressured sediments in the gulf coast is commonly made on the basis of increases in pressure gradient or geostatic ratio that is in situ fluid pressure divided by total depth fluids and sediments having geostatic ratios in excess of 0 47 psi ft are usually considered geopressured those with geostatic ratios greater than 0 70 psi ft hard geopressured an alternative and more informative way of characterizing geopressured sediments is by use of the parameter hydraulic head hydraulic head can be used not only to distinguish between hydropressured and geopressured sediments but also to provide potentially quantitative information on the direction and rate of subsurface fluid flow hydraulic head h feet is defined as h z pg where z is depth below a reference datum p is measured or calculated fluid pressure g is acceleration due to gravity and is fluid density in the absence of osmotic effects the hydraulic gradient dh dl dimensionless where l is path length can be used in conjunction with hydraulic conductivity in darcy s law to predict the direction and rate of fluid migration variations in calculated hydraulic head have been correlated along several regional cross sections through the tertiary sedimentary sequence of south louisiana four distinct hydrodynamic zones can be distinguished with depth in the region studied near surface to 7000 feet in depth hydropressured fresh to saline waters having hydraulic heads near zero and vertical hydraulic gradients of 0 01 or less 7000 feet to 10 000 14 000 feet in depth a transition zone of weakly geopressured sediments with hydraulic heads ranging from 0 to 3000 feet above sea level hydraulic gradients range from 0 1 to 4 and show many reversals with depth many commerically important hydrocarbon plays occur within this zone 10 000 14 000 feet to 12 000 18 000 feet the hard geopressured zone in which hydraulic head progressively increases with depth from values of 3000 to 16 000 feet of head above sea level gradients of 4 to 5 are typical but locally can exceed 25 there are few reversals in gradient with depth depths below zone 3 suggestion based on sparse data that hydraulic gradients begin to decrease with depth in contrast to the hard geopressured zone where hydraulic flow appears to consist of a broad generally upward moving front hydraulic flow in the transition zone appears to be more strongly focused through preferred channel ways

the 12 december 2017 baumgarten gas hub explosion a case study on understanding the occurrence of a large infrasound azimuth residual and a lack of seismic observations the baumgarten explosion occurred on 12 december 2017 at a gas storage site about 30 km east of vienna austria acoustic arrivals from this accidental surface explosion were detected at dozens of stations of the alparray seismic network to distances up to 150 km mainly in easterly directions thus it was expected that the hungarian infrasound array pszi located about 230 km to the east southeast of baumgarten would detect this acoustic wave as well standard progressive multichannel correlation processing and frequency wavenumber analysis identified a signal emerging at 7 57 55 utc from an azimuth of 296 300 and with trace velocity 400 m s the extraordinarily high trace velocity and excessive backazimuth residual relative to the explosion site direction of 282 however cast strong doubts on the arrival s connection to the baumgarten event accounting for the effect of non planar geometry of the infrasound array results in a reduction of the azimuth residual by half additionally 2d and 3d raytracing methods are used including the european centre for medium range weather forecasts ecmwf atmospheric model to further explain the remaining azimuth residual as well as to elucidate the large trace velocity estimates the prevailing stratospheric winds in excess of 150 m s are identified as the underlying cause including both factors the initial azimuth residual of up to 18 decreases to 4 allowing to associate the infrasound signal at pszi with the baumgarten event finally the data from a seismic station at 30 km range is re investigated for magnitude estimation the local magnitude of ml 1 0 explains well the scarcity of seismic observations within 50 km range where three or four stations show signals mainly consisting of rg type surface waves but no body waves

structure and variances of equatorial zonal circulation in a multimodel ensemble the structure and variance of the equatorial zonal circulation as characterized by the atmospheric mass flux in the equatorial zonal plane is examined and inter compared in simulations from 9 cmip3 coupled climate models with multiple ensemble members and the ncep ncar and era 40 reanalyses the climate model simu lations analyzed here include twentieth century 20c3m and twenty first century sres a1b simulations we evaluate the 20c3m modeled zonal circulations by com paring them with those in the reanalyses we then examine the variability of the circulation its changes with global warming and the associated thermodynamic maintenance the tropical zonal circulation involves three major com ponents situated over the pacific indian and atlantic oceans the three cells are supported by the corresponding diabatic heating extending deeply throughout the tropo sphere with heating centers apparent in the mid tropo sphere seasonal features appear in the zonal circulation including variations in its intensity and longitudinal migration most models and hence the multi model mean represent the annual and seasonal features of the circulation and the associated heating reasonably well the multi model mean reproduces the observed climatology better than any individual model as indicated by the spatial pattern correlation and mean square difference of the mass flux and the diabatic heating compared to the reanalysis based values projected changes in the zonal circulation under a1b forcing are dominated by mass flux changes over the pacific and indian oceans an eastward shift of the pacific walker circulation is clearly evident with global warming with anomalous rising motion apparent over the equatorial central pacific and anomalous sinking motions in the west and east which favors an overall strengthening of the walker circulation the zonal circulation weakens and shifts westwards over the indian ocean under external forcing whereas it strengthens and shifts slightly west wards over the atlantic ocean the forced circulation changes are associated with broad sst and atmospheric diabatic heating changes in the tropics linear trends of these forced circulation changes as characterized by regional spatial maximum amplitudes of mass fluxes and their longitudes over the three oceans are statistically significant at the 5 level for 2000 2099 for the multi model mean however wide differences of the trends are apparent across the models because of both deficiencies in the simulation of the circulations in different models and the high internal variability of the circulations

geochemistry of dissolved inorganic carbon and carbonate weathering in a small typical karstic catchment of southwest china isotopic and chemical constraints abstract the sources of dissolved inorganic carbon dic and rock weathering processes were studied in the houzhai catchment a typical karstic catchment in the changjiang river basin southwest china the carbon isotopic compositions 13 c dic of dic in the samples collected from the catchment vary from 13 5 to 6 9 with a mean value of 9 8 the dic in the catchment is thereby considered to be mainly derived from soil co 2 and weathering of carbonate rocks the dic concentrations and the 13 c dic values show pronounced seasonal variations with the lowest values being observed during the high flow season from may to october the logpco 2 values in the waters were positively correlated with the dic contents and negatively correlated to the saturation index of calcite sic and 13 c dic values these observations indicate that co 2 derived from organic matter oxidation plays an important role in the dissolution of carbonate for this typical karstic environment based on a chemical mass balance the weathering rate of carbonate rocks in the houzhai catchment was estimated to be approximately 133 t km 2 year or 584 10 3 mol km 2 year in terms of co 2 consumption rate which is higher than the reported values for other rivers in southwest china

a high resolved record of the asian summer monsoon from dongge cave china for the past 1200 years abstract two annually laminated and 230th dated stalagmite oxygen isotope 18o records from dongge cave china provided a high resolution asian summer monsoon asm history for the past 1200 years a close similarity between annual band thickness and stable isotope analyses 13c and 18o suggests the calcite 18o is most likely a proxy associated with asm precipitation the two duplicated stalagmite 18o records show that the asm varies at a periodicity of 220 years concordant with a dominant cycle of solar activity a period of strong asm activity occurred during the sporer minimum 1450 1550 a d followed by a striking drop circa 1580 a d potentially consistent with the social unrest in the final decades of china s ming dynasty 1368 1644 a d centennial scale changes in asm precipitation over the last millennium match well with changes in tropical atlantic sea surface temperatures ssts and south american summer monsoon precipitation our findings suggest that variations in low latitude monsoon precipitation are probably driven by shifts in the mean position of the intertropical convergence zone itcz which is further mediated by solar activity and tropical ssts

principal modes of rainfall sst variability of the asian summer monsoon a reassessment of the monsoon enso relationship abstract using global rainfall and sea surface temperature sst data for the past two decades 1979 98 the covariability of the asian summer monsoon asm and el nino southern oscillation enso was investigated the findings suggest three recurring rainfall sst coupled modes characterized by a pronounced biennial variability the first mode is associated with generally depressed rainfall over the western pacific and the maritime continent stemming from the eastward shift of the walker circulation during the growth phase of el nino the associated sst pattern consists of an east west sst seesaw across the pacific and another seesaw with opposite polarity over the indian ocean the second mode is associated with a growing la nina comprising mixed regional and basin scale rainfall and sst variability with abnormally warm water in the vicinity of the maritime continent and western pacific it possesses a pronounced low level west pacific anticyclone wpa near the philippines and exhibits large sub

climate and hydrographic variability in the indo pacific warm pool during the last millennium planktonic foraminiferal mg ca and delta o 18 derived sea surface temperature and salinity records from the makassar strait indonesia show a long term cooling and freshening trend as well as considerable centennial scale variability during the last millennium the warmest temperatures and highest salinities occurred during the medieval warm period mwp while the coolest temperatures and lowest salinities occurred during the little ice age lia these changes in the western pacific along with observations from other high resolution records indicate a regionally coherent southern displacement of the inter tropical convergence zone during the lia with more arid conditions in the northern tropics and wetter conditions in the southern tropics

regional variations in physical and chemical properties of south louisiana oil field brines abstract knowledge of in situ physical and chemical properties of pore fluids in sedimentary basins is essential in understanding problems of fluid migration and diagenetic reaction we have completed a study of the regional variations in pore fluid temperature pressure and salinity for the entire tertiary section of south louisiana to depths of 4 to 6 km from this information it is possible to calculate values for hydraulic head and in situ pore fluid densities and viscosities parameters necessary in quantifying rates and directions of subsurface fluid migration it is also possible to determine such chemical properties as methane solubility maximum salinities typically in the range of 120 150 g 1 are found in the lower part of the hydropressured zone where salt is introduced by dissolution of salt diapirs hydraulic head increases from essentially zero in the hydropressured zone to values exceeding 3 km above mean sea level deep in the geopressured section fluid densities increase with depth to maximum values approaching 1 07 g cm at depths of approximately 2 km densities decrease with further depth as a result of increasing temperature and decreasing pore water salinity the entire lower portion of the pore fluid column is thus gravitationally unstable a factor favoring fluid overturn fluid viscosities systematically decrease from 1 cp at the surface to less than 0 2 cp at depth as a result of these variations in density and viscosity pore waters will flow five times more efficiently at depth methane solubility decreases upward from over 50 scf bbl in deep overpressured sediments to 10 scf bbl at the base of the hydropressured zone to less than 5 scf bbl at shallow depth significant exsolution of methane should thus occur as a result of upward migration of pore fluid or molecular diffusion of dissolved methane

post glacial evolution of the indo pacific warm pool and el nino southern oscillation recent research has revealed new insights into the temperature size and variability of the indo pacific warm pool ipwp and the nature of the el nino southern oscillation enso since the last glacial maximum lgm sea surface temperature sst reconstructions from foraminiferal mg ca alkenone and revised coral sr ca palaeothermometry agree that ssts in the ipwp during the lgm were similar to 3degreesc cooler than at present in the central portion of the ipwf the rapid post glacial rise in sst led the deglaciation by similar to 3000 years to produce near modern ssts by the early holocene in contrast further west and north post glacial shifts in ssts in the south china and sulu seas are synchronous with abrupt climate changes in the north atlantic new evidence for the nature of the little ice age in the tropics has been obtained from a 420 year record of coral sr ca and 6180 from the great barrier reef australia this indicates that ssts and salinity were higher in the 18th century than in the 20th century the results suggest that the tropical pacific played a role as a source region of water vapour during the global expansion of little ice age glaciers the onset of modern enso periodicities is identified by palaeo enso records throughout the tropical pacific region similar to 5000 years ago with an abrupt increase in enso magnitude similar to 3000 years ago individual enso events recorded by corals reveal that the precipitation response to el nino temperature anomalies was subdued in the mid holocene the apparent non linear onset of enso in the late holocene appears to reflect abruptly enhanced interaction between the southern oscillation and the pacific intertropical convergence zone comparisons of precipitation variability recorded by great barrier reef corals with enso indices for the last 350 years confirms that non stationarity of enso teleconnections is a natural characteristic of modern climate c 2003 elsevier ltd and inqua all rights reserved

analysis of local seismo acoustic events in the korean peninsula 1 in order to discriminate between man made explosions and earthquakes a preliminary seismo acoustic analysis was performed in the korean peninsula from august 1999 to december 2000 during this time 202 seismo acoustic events were identified as blasts these events were concentrated in specific regions a rock quarry an open pit mine and a construction site which were identified by field survey all of these events occurred within 200 km of a seismo acoustic array we applied ray tracing methods to the atmosphere using local meteorological observations to understand the short distance propagation characteristics of infrasonic signals calculated infrasonic traveltime using a local meteorological model fits well with observed traveltime from a quarry local winds make possible infrasonic wave ducts in the lower atmosphere and allow infrasonic wave arrival at short distances ray tracing using a local meteorological model has been used for the association between seismic and infrasonic signals

climate variability in central china over the last 1270 years revealed by high resolution stalagmite records oxygen and carbon isotopic variations in the upper section of a stalagmite sf 1 from buddha cave 33 40 n 109 05 e dated by 230th 234u 210pb and lamination counting to a time resolution as fine as 1 3 years have recorded climate changes in central china for the last 1270 years the changes include those corresponding to the medieval warm period little ice age and 20th century warming lending support to the global extent of these events the isotopic records also show cycles of 33 22 11 9 6 and 7 2 years the 33 year cycle could well represent the 35 year periodicity of climate fluctuations previously recognized in china and europe cycles of 22 11 and 9 6 years have often been associated with the sunspot or lunar orbit variations the 7 2 year cycle was recently identified also in tree ring records from an area close to buddha cave these cycles suggest that external forcing e g solar irradiance may affect the summer monsoon over eastern china the general consistency between the climate characteristics inferred from the stable isotope records of sf 1 and those from other proxy records underscores the value of stalagmites as recorders of paleoclimate

speleothem evidence for temporal spatial variation in the east asian summer monsoon since the medieval warm period published annual to decadal resolution stalagmite d 18 o records since ad 900 from six caves dongge furong heshang buddha shihua and wanxiang in china were analyzed to detect temporal and spatial variability of the east asian summer monsoon strength which strongly affects wet dry conditions in eastern china the empirical mode decomposition method was used to obtain trends of the six cave records after the base trend was determined d 18 o anomalies of each record were computed by subtracting the base trend mean d 18 o anomaly values of the detrended time series for each cave record were calculated for four periods i medieval warm period mwp ad 900 1250 ii little ice age phase 1 lia 1 ad 1250 1550 iii little ice age phase 2 lia 2 ad 1550 1850 and iv modern period md ad 1850 2000 from these anomalies the temporal and spatial variability of wet dry conditions has been identified positive values of the mean d 18 o anomalies indicating drier conditions appeared in the lower yangtze river drainage area and southeast coast area during md 1 lia 1 and mwp whereas negative values existed in north south and yangtze areas of eastern china during lia 2 the results agree with the dryness wetness index reconstructed by chinese historic records in general these results illustrate that wet and dry conditions in different regions of eastern china could be opposite under monsoon influence so that no single speleothem d 18 o record could represent the monsoonal climate in this vast region climatic patterns in the monsoonal region can be either a combination of warm wet and cold dry or a combination of cold wet and warm dry on annual to centennial scales a 128 year periodic cycle exists in all six cave records whereas 64 year possibly a harmonic of 128 year periodicity and 42 year periodicities appear in shihua heshang and dongge records these cycles may reflect the influence of solar activity on the east asian summer monsoon copyright 2012 john wiley sons ltd