the interaction of the madden julian oscillation with the maritime continent in a gcm previous studies using the hadley centre coupled model hadcm3 have shown that the islands of the maritime continent act as an unrealistic block to the eastward propagation of the madden julian oscillation mjo this blocking effect is investigated using a simplified aqua planet version of this gcm with various idealized configurations of the maritime continent islands placed on the equator and an mjo like convective signal forced by a propagating sea surface temperature anomaly dipole results suggest that it is the orography of the islands rather than the presence of the islands themselves which results in the blocking of the mjo although the peak elevation of the orography in the gcm is very much lower than in reality it appears to act as effective block to the eastward propagation of the low level kelvin wave signal which accompanies the mjo in particular the representation of sumatra in the gcm as a north south oriented ridge straddling the equator seems to be particularly effective at blocking the kelvin wave signal which in a full gcm would result in the weakening or complete extinction of the mjo signal to the east of the maritime continent

propagation and the vertical structure of the madden julian oscillation abstract the madden julian oscillation mjo dominates tropical variability on time scales of 30 70 days during the boreal winter spring it is manifested as an eastward propagating disturbance with a strong convective signature over the eastern hemisphere the space time structure of the mjo is described using the national centers for environmental prediction national center for atmospheric research reanalysis advanced very high resolution radiometer outgoing longwave radiation observed sea surface temperature and the climate prediction center merged analysis of precipitation empirical orthogonal function analysis is used to identify the convective signature of the mjo and regression is used to identify key relationships with the convection compared to analyzing successive years of data the selection of years of strong mjo activity results in a more robust lead lag structure and an increase in explained variance the mjo exhibits a rich vertical structure with low level moisture convergence bein

rectification of the madden julian oscillation into the enso cycle an ocean general circulation model forced with idealized purely oscillating wind stresses over the western equatorial pacific similar to those observed during the madden julian oscillation mjo developed rectified low frequency anomalies in sst and zonal currents compared to a run in which the forcing was climatological the rectification in sst resulted from increased evaporation under stronger than normal winds of either sign from correlated intraseasonal oscillations in both vertical temperature gradient and upwelling speed forced by the winds and from zonal advection due to nonlinearly generated equatorial currents the net rectified signature produced by the mjo like wind stresses was sst cooling about 0 48c in the west pacific and warming about 0 18c in the central pacific tending to flatten the background zonal sst gradient it is hypothesized that in a coupled system such a pattern of sst anomalies would spawn additional westerly wind anomalies as a result of sst induced changes in the low level zonal pressure gradient this was tested in an intermediate coupled

barrier effect on mjo propagation by the maritime continent in the mjo task force gewex atmospheric system study models abstractthe simulated madden julian oscillation mjo events in 27 general circulation models gcms are identified using an mjo tracking method the results suggest that the occurrence frequencies

why is the bay of bengal less productive during summer monsoon compared to the arabian sea 1 the bay of bengal is traditionally considered to be a less productive basin compared to the arabian sea we explore the reasons for this in the central bay during summer copious rainfall and river water freshen the upper layers of the bay by 3 7 psu during summer and sst was warmer by 1 5 2 c than in the central arabian sea this leads to a strongly stratified surface layer the weaker winds over the bay are unable to erode the strongly stratified surface layer thereby restricting the turbulent wind driven vertical mixing to a shallow depth of 20 m this inhibits introduction of nutrients from below situated close to the mixed layer bottom into the upper layers while advection of nutrients rich water into the euphotic zone makes the arabian sea highly productive this process is unlikely in the bay of bengal

three different downstream fates of the boreal summer mjos on their passages over the maritime continent the boreal summer mjos exhibit three distinctive downstream evolutions on their passages over the maritime continent mc i smoothly transitioning from indian ocean io to western pacific type i ii rapidly decayed over the mc type ii and iii significantly intensified over the mc type iii during the life cycles of type i and iii mjos basin wide overturning circulations connect the convective dipoles between western and eastern north pacific for type ii mjo regional overturning circulations connect the convective dipoles between the io and western north pacific wnp for type i and iii mjos the associated convection over eastern io is able to generate strong kevin wave responses and significant positive sst anomalies over the mc and western pacific on the other hand for type ii mjo in the io a persistent convection lingers around the wnp it intensifies westerly monsoon flows thus preventing the generation of coherent positive sst anomalies ahead of the io mjo convection it also blocks the formation of a robust kelvin wave response over the mc and western pacific by delaying the northeastward migrations of the dry phase the convection of type i and iii mjos at eastern io is able to generate positive boundary layer moisture anomalies along with positive column integrated moisture tendencies over the mc and western pacific thus allowing them to propagate eastward smoothly on the other hand the type ii mjo convection in eastern io is associated with a very dry troposphere and negative column integrated moisture tendency over western pacific which result in the rapid decay of convection over the mc these results emphasize the important roles of robust kelvin wave responses and positive sst anomalies on the eastward propagation of boreal summer mjos over the mc through moistening the troposphere ahead of the convection

qbo mjo connection activities of the madden julian oscillation mjo in boreal winter has recently been found to be stronger in easterly phases of the stratospheric quasi biennial oscillation qbo than its westerly phases this qbo mjo connection was investigated in this study using a method that identifies individual mjo events by tracking their eastward propagating signals in precipitation stronger mjo activities in qbo easterly phases are a consequence of more mjo days not larger amplitudes of individual mjo events as previously thought more mjo days come from more mjo events initiated over the indian ocean and their longer duration because of a weaker barrier effect of the maritime continent on mjo propagation zonal heterogeneity exists in the connection between qbo mjo and tropical total precipitation in general this poses a challenge to our current understanding of the mjo dynamics which has yet to fully include upper tropospheric and stratospheric processes

mm5 modeling of the madden julian oscillation in the indian and west pacific oceans model description and control run results abstract a new methodology to study the madden julian oscillation mjo is introduced while previous mjo studies typically have involved highly simplified mathematical models or general circulation models this new approach seeks to reproduce the mjo by using a regional model with prescribed boundary conditions this paper reports initial control run results for this methodology using the fifth generation pennsylvania state university psu national center for atmospheric research ncar mesoscale model mm5 for a domain extending from the western indian ocean to the date line the control run boundaries are forced using the ncep ncar reanalysis nra dataset for a 24 month time period the climatology for the 24 month period is examined to establish the robustness of mm5 for this region results indicate good agreement in the mean winds between the model and the forcing dataset the primary differences are an easterly bias at 850 hpa and altered flow patterns in the indian monsoon region mean outgoing

a numerical investigation of the phytoplankton bloom in the bay of bengal during northeast monsoon 1 a 4 5 layer model of the indian ocean coupled to a four component npzd ecosystem model is used to study the phytoplankton bloom in the bay of bengal during the northeast monsoon of 1996 the model realistically simulates the surface chlorophyll bloom observed by satellite derived ocean color images in the western bay of bengal during that time it also reproduces the subsurface chlorophyll maximum present earlier in the fall the terms in the phytoplankton equation for the model s mixed layer show that the surface bloom is caused by the entrainment not only of subsurface nutrients but also of phytoplankton from the subsurface maximum to our knowledge this study is the first to report enrichment of surface chlorophyll by entrainment of the subsurface maximum upwelling caused by ekman pumping and mixed layer entrainment occurring over an already shallow thermocline drives the vertical fluxes an intense wind event from 26 november to 5 december also generated favorable conditions for the formation of a phytoplankton bloom

active fluid flow in the eugene island area offshore louisiana a sedimentary basin is a thermochemical reactor i e a complex dynamically interrelated system that is deformed and faulted by tectonic forces modified by sedimentation and erosion influenced by geopressuring and chemical reaction and subjected to constantly changing temperature pressure and fluid composition and movement we understand little about the coupling among these processes that comprise basin thermochemical reactors despite many recent advances in basin science and technology however we are certain that these processes are coupled so strongly that changes in one can completely alter the operation of all the others in a basin

propagation mechanisms for the madden julian oscillation the madden julian oscillation mjo is examined using 20 years of outgoing long wave radiation and national centers for environmental prediction national center for atmospheric research re analysis data two mechanisms for the eastward propagation and regeneration of the convective anomalies are suggested the first is a local mechanism operating over the warm pool region at the phase of the mjo with a dipole structure to the convection anomalies there is enhanced tropical convection over the eastern indian ocean and reduced convection over the western pacific over the equatorial western indian ocean the equatorial rossby wave response to the west of the enhanced convection includes a region of anomalous surface divergence associated with the anomalous surface westerlies and pressure ridge this lends to suppress ascent in the boundary layer and shuts off the deep convection eventually leading to a convective anomaly of the opposite sign over the indonesian sector the equatorial kelvin wave response to the east of the enhanced convection includes a region of anomalous surface convergence into the anomalous equatorial surface easterlies and pressure trough which will tend to favour convection in this region the indonesian sector is also influenced by an equatorial rossby wave response of opposite sign to the west of die reduced convection over the western pacific which also has a region of anomalous surface convergence associated with its anomalous equatorial surface easterlies and pressure trough hence convective anomalies of either sign tend to erode themselves from the west and initiate a convective anomaly of opposite sign via their equatorial rossby wave response and expand to the east via their equatorial kelvin wave response the second mechanism is global involving an anomaly completing a circuit of the equator enhanced convection over the tropical western pacific excites a negative mean sea level pressure m s l p anomaly which radiates rapidly eastward as a dry equatorial kelvin wave at approximately 35 m s 1 over the eastern pacific it is blocked by the orographic barrier of the andes and central america for several days before propagating through the gap at panama after rapidly propagating as a dry equatorial kelvin wave over the atlantic the m s l p anomaly is delayed further by the east african highlands before it reaches the indian ocean and coincides with the development of enhanced convection at the start of the next mjo cycle

a systematic comparison of tropical waves over northern africa part i influence on rainfall abstractlow latitude rainfall variability on the daily to intraseasonal time scale is often related to tropical waves including convectively coupled equatorial waves the madden julian oscillation

effects of surface orography and land sea contrast on the madden julian oscillation in the maritime continent a numerical study using echam5 sit abstractthis study uses the atmospheric general circulation model agcm echam5 coupled with the newly developed snow ice thermocline model echam5 sit to examine the effects of orography and land sea contrast on the madden julian oscillation mjo in the maritime continent mc during boreal winter the echam5 sit is one of the few agcms that realistically simulate the major characteristics of the mjo three experiments are conducted with realistic topography without orography and with oceans only in the mc region to evaluate the relative effects of orography and land sea contrast orography and land sea contrast have the following effects on the mjo in the mc 1 a larger amplitude 2 a smaller zonal scale 3 more realistic periodicity and stronger eastward propagating signals 4 a stronger southward detour during the eastward propagation 5 a distorted coupled kelvin rossby wave structure and 6 larger low level moisture convergence the existence of mountainous islands also enhances the mean w

surface fluxes and ocean coupling in the tropical intraseasonal oscillation abstract sensitivity of tropical intraseasonal variability to mixed layer depth is examined in the modified national center for atmospheric research community atmosphere model 2 0 1 cam with relaxed arakawa schubert convection coupled to a slab ocean model som whose mixed layer depth is fixed and geographically uniform but varies from one experiment to the next intraseasonal west pacific precipitation variations during boreal winter are enhanced relative to a fixed sst infinite mixed layer depth simulation for mixed layer depths from 5 to 50 m with a maximum at 20 m interestingly near the observed value in the regions where the madden julian oscillation mjo is active but are strongly diminished in the 2 m depth simulation this nonmonotonicity of intraseasonal precipitation variance with respect to mixed layer depth was predicted by sobel and gildor using a highly idealized model further experiments with the same idealized model help to interpret results derived from the modified ncar c

fluid accumulation and channeling along the northern barbados ridge decollement thrust a volume of three dimensional seismic reflection data acquired in 1992 imaged the decollement beneath the northern barbados ridge accretionary prism revealing reflection amplitude and waveform variations attributed to fluid accumulations along the plate boundary fault we model the seismic reflection by inversion for seismic impedance the product of velocity and density throughout the 5 x 25 km survey area and thus map physical property variations in 1997 ocean drilling program leg 171a penetrated the protodecollement and decollement at five sites with a logging while drilling lwd tool to log density and other physical properties of the decollement we construct a regional map of density and inferred porosity within the decollement from seismic models calibrated with lwd density data in the sediments out in front of the trench the protodecollement forms in a radiolarian rich miocene mudstone with an anomalously high porosity 70 75 that appears as a pervasive inherent characteristic of this interval seaward of the deformation front in the decollement beneath the wedge a consolidation trend of decreasing porosity runs perpendicular to the deformation front with porosity decreasing from 70 at the wedge toe to 50 4 km from the wedge toe a second distinct trend also forms along a 10 km long 1 to 2 km wide ne sw zone in which porosity is 70 as high as it is in the protodecollement this zone can be explained as an area of the decollement where fluid accumulations develop by maintaining high fluid content we postulate that high fluid content is maintained by continuous recharge flowing into and along this channel this porosity distribution within the decollement also strongly influences fluid migration into the overlying accretionary wedge and is directly associated with fluid charging of ramps and out of sequence thrusts above the decollement

the role of topographically induced vortices in tropical cyclone formation over the indian ocean abstractthe role of sumatra and adjacent topographic features in tropical cyclone tc formation over the indian ocean io is investigated sumatra as well as the malay peninsula and java have mountainous terrain that partially blocks low level flow under typical environmental stratification for easterly low level flow these terrain features often produce lee vortices some of which subsequently shed and move westward from the northern and southern tips of sumatra and thence downstream over the io since sumatra straddles the equator extending in a northwest southeast direction from approximately 6 n to 6 s the lee vortices while counter rotating are both cyclonic hence they can serve as initial disturbances that eventually contribute to tc formation over the io in addition low level equatorial westerly flow impinging on sumatra is also typically blocked and diverges at times contributing to cyclonic circulations over the io primarily near the southern end of the island data from two recen

geophysics a moving fluid pulse in a fault zone evidence from the south eugene island block 330 oil and gas field in the gulf of mexico off louisiana suggests that the fault zones there have acted as conduits for fluids rising from deep in the earth s crust and now one of these fault burps has been observed directly seismic reflection imaging revealed the rapid ascent of a pulse of fluid rising vertically up the fault by 1 km between 1985 and 1992 burps like this may be important factors in subsurface hydrocarbon migration in the gulf of mexico fault zones are linked with a complex and dynamic system of plumbing in the earth s subsurface here we use time lapse seismic reflection imaging to reveal a pulse of fluid ascending rapidly inside one of these fault zones such intermittent fault burping is likely to be an important factor in the migration of subsurface hydrocarbons

effects of the mean walker circulations on the zonal variability of tropical cisk waves abstract an idealized zonally asymmetric mean state in the tropics is used to investigate the effects of atmospheric mean walker circulations and sea surface temperatures on the zonal variability of tropical waves with positive only wave cisk heating first the effects of the zonally symmetric vertical and meridional shears of the mean zonal flow are investigated with different vertical profiles of convective heating and temperature lapse rate with the observed vertical profile of temperature lapse rate in the tropics the effect of the vertical shear of the mean zonal flow on the fast waves period about 2 weeks associated with a maximum heating in the upper troposphere is found to be opposite to that on the slow waves period about 4 weeks with a maximum heating in the middle troposphere while the vertical shear effects with an idealized constant lapse rate are quite similar the meridional shear of the mean zonal flow acts only to reduce the effects of the vertical shear of the mean zonal flow s

an air sea coupled skeleton model for the madden julian oscillation this work is an extension and improvement of the minimal madden julian oscillation mjo skeleton model developed by majda and stechmann which can capture some important features of the mjo slow eastward propagation quadrupole vortex structure and independence of frequency on wavelength but is unable to produce unstable growth and selection of eastward propagating planetary waves with the addition of planetary boundary layer frictional moisture convergence these deficiencies can be remedied the frictional boundary layer selects the planetary scale eastward propagation as the most unstable mode but the dynamics remains confined to atmospheric processes only here the authors study the role of air sea interaction by implementing an oceanic mixed layer ml model of wang and xie into the mjo skeleton model in this new air sea coupled skeleton model the features of the original skeleton model remain additionally the air sea interaction under mean westerly winds is shown to produce a strong instability that selectively destabilizes the eastward propagating planetary scale waves although the cloud shortwave radiation seasurfacetemperature crs feedbackdestabilizesbotheastwardand westward modes theair sea feedback associated with the evaporation and oceanic entrainment favors planetary scale eastward modes over the western hemisphere where easterly background winds prevail the evaporation and entrainment feedbacks yield damped modes indicating that longitudinal variation of the mean surface winds plays an important role in regulation of the mjo intensity in addition to the longitudinal variation of the mean sea surface temperature or mean moist static stability this theoretical analysis suggests that accurate simulation of the climatological mean state is critical for capturing the realistic air sea interaction and thus the mjo

simulation of the madden julian oscillation in a coupled general circulation model part ii the role of the basic state abstract in part i of this study it was shown that air sea coupling had a positive impact on some aspects of the simulation of the madden julian oscillation mjo by a gcm however errors in the basic state climate of that gcm appeared to be preventing the mjo related convection from propagating into the west pacific in this paper the actual impact of these errors will be addressed an integration of a flux adjusted version of the coupled model has been performed which has reduced basic state errors in the west pacific in this version of the coupled gcm the mjo does propagate into the west pacific the simulation of the mjo by a coupled model with the same atmospheric component but a different ocean gcm is also analyzed this coupled gcm has similar systematic errors in low level zonal wind and precipitation to the model studied in part i but with warmer ssts results from this experiment together with the other available evidence suggest that it is the errors in the low level zonal wind component

the organization of tropical convection by intraseasonal sea surface temperature anomalies the organization of convection by intraseasonal sea surface temperature sst anomalies is investigated to examine the role that atmosphere ocean coupling may play in the maintenance of the madden julian oscillation an atmospheric general circulation model with an ocean covered surface is used to investigate the response of tropical convection to idealized imposed intraseasonal sst anomalies and the sensitivity of this response to their propagation speed the convection is found to be organized on the spatial and temporal scales of the imposed sst anomalies and the location of the maximum in precipitation relative to the sst anomaly is in good agreement with observations and different from that for a stationary sst anomaly the magnitude of the precipitation anomalies increases with decreasing propagation speed of the sst anomalies the role of the free tropospheric humidity is crucial for determining the location and magnitude of the precipitation response

on the eastward shift of winter surface chlorophyll a bloom peak in the bay of bengal analysis of satellite derived surface layer phytoplankton chlorophyll a concentration chl a in the bay of bengal revealed an eastward shift of peak of chl a bloom during northeast monsoon period november march from western to the eastern bay the winter chl a bloom in the western bay is shorter duration 1 2 months while that in the eastern bay is longer duration 3 4 months unlike other oceans the eastward bloom peak shift found in the bay of bengal is opposite to the direction of propagation of rossby wave and seasonal mean zonal currents during winter sufficient light is available in the bay of bengal for phytoplankton growth herein we studied the processes controlling the eastward winter bloom peak shift and the zonal depiction of bloom duration in the bay of bengal there is no single dominant process that drives the eastward bloom peak shift everywhere in the bay of bengal rather different physical processes operate in different regions the physical mechanisms governing the eastward winter chl a bloom peak shift reported here include open ocean ekman pumping coastal upwelling upwelling driven by rossby wave wind induced vertical mixing nutrients supply from river input and westward advection through prevailing zonal currents

boreal winter links between the madden julian oscillation and the arctic oscillation abstract there is increasing evidence that the madden julian oscillation mjo modifies the mid to high latitude circulation and in particular appears to have a relationship to the leading mode of extratropical variability the arctic oscillation ao in this study new insights into the observed similarities between the mjo and the ao are explored it is shown that the eastward progression of the convectively active phase of the mjo is associated with a corresponding shift in the tendency and sign of the ao index moreover the ao and the mjo share several analogous features not only in the global circulation but also in surface temperature fields also the ao is linked to a pattern of eastward propagating mjo like variability in the tropics that is partially reproduced in free runs of the ncep climate forecast system cfs model finally it is shown that the structure of the ao as defined by the leading mode in the 1000 hpa geopotential height field is significantly altered based on the phase o

northern hemisphere mid winter vortex displacement and vortex split stratospheric sudden warmings influence of the madden julian oscillation and quasi biennial oscillation we investigate the connection between the equatorial madden julian oscillation mjo and different types of the northern hemisphere mid winter major stratospheric sudden warmings ssws i e vortex displacement and vortex split ssws the mjo ssw relationship for vortex split ssws is stronger than that for vortex displacement ssws as a result of the stronger and more coherent eastward propagating mjos before vortex split ssws than those before vortex displacement ssws composite analysis indicates that both the intensity and propagation features of mjo may influence the mjo related circulation pattern at high latitudes and the type of ssws a pronounced quasi biennial oscillation qbo dependence is found for vortex displacement and vortex split ssws with vortex displacement split ssws occurring preferentially in easterly westerly qbo phases the lagged composites suggest that the mjo related anomalies in the arctic are very likely initiated when the mjo related convection is active over the equatorial indian ocean around the mjo phase 3 further analysis suggests that the qbo may modulate the mjo related wave disturbances via its influence on the upper tropospheric subtropical jet as a result the mjo related circulation pattern in the arctic tends to be wave number one wave number two 25 30 days following phase 3 i e approximately phases 7 8 when the mjo related convection is active over the western pacific during easterly westerly qbo phases which resembles the circulation pattern associated with vortex displacement vortex split ssws

a new mechanism of the slow eastward propagation of unstable disturbances with convection in the tropics implications for the mjo abstractto understand the slow eastward propagation of the madden julian oscillation mjo the authors propose a new mechanism of slow eastward propagation of an unstable disturbance slow eastward propagating disturbance sed in the tropics assuming a simplified instability source two conditions are necessary over the convective region associated with the sed for this mechanism i moderately negative gross moist stability gms and ii strong stretching in the lower layer the instability due to i needs to be moderate for causing a propagating convective disturbance under the structure of twin cyclonic vortices to the west and convection to the east stretching of planetary vorticity associated with the convection produces cyclonic vorticity which results in eastward propagation of the vortices equatorial plane dynamics explain the positional relation between the twin vortices and convection coherently strong equatorial low level westerly winds accompanying the vortices induce convergence

prediction of the madden julian oscillation a review abstractthere has been an accelerating interest in forecasting the weather and climate within the subseasonal time range the madden julian oscillation mjo an organized envelope of tropical conv

role of topography on the mjo in the maritime continent a numerical case study the role of topography on a madden julian oscillation mjo event in the maritime continent mc is explored using a regional model four simulations are conducted lower resolution 12 km simulations using cumulus parameterization in the presence lr and absence lr flat of topography and higher resolution 4 km simulations without cumulus parameterization in the presence hr and absence hr flat of topography in the lr simulation the mjo remains unorganized with no clear eastward propagation while the lr flat simulation captures the mjo and its eastward propagation across the mc in the absence of cumulus parameterization both hr and hr flat capture the mjo and show several similarities and differences compared to the lr and lr flat simulations to better understand these differences a moisture budget analysis is conducted during the passage of the mjo in the lr flat simulation vertical advection of moisture is increased to the east of the islands leading to continuity in mjo associated convection continuity that was not present in the lr simulation the increase in vertical advection in the absence of topography is due to an increase in the mean moisture advection by the anomalous vertical winds in the middle of the mc horizontal advection seems to be the most important for an uninterrupted eastward propagation of the mjo the increase in the horizontal advection in the absence of topography is primarily due to an increase in the anomalous moisture advection by the mean zonal winds to what extent the mjo was influenced by the upstream effect from the new guinea topography was also explored these results indicate that the important physical processes for mjo associated convection may be different in different parts of the mc further implications of these results in the context of other recent studies on mjo propagation across the mc are discussed

fluid evolution in the dabei gas field of the kuqa depression tarim basin nw china implications for fault related fluid flow abstract a series of fault related folds developed in the dabei gas field of the kuqa depression western china form major traps for hydrocarbon accumulation the bashijiqike k 1 bs sandstone reservoirs in the different fault related folds of the dabei gas field display similar excess fluid pressure formation water type and salinity and as well as light oil and gas properties the light oil and gas in the k 1 bs sandstone reservoir of the traps share the same source and were generated at a thermal maturity level of 1 4 1 6 r o and 1 7 2 3 r o respectively to investigate the fluid evolution in the fault related fold traps an integrated fluid inclusion analysis was performed including petrography fluorescence spectroscopy microthermometry laser raman spectroscopy and thermodynamic modeling the fluid evolution recorded by the fluid inclusions in the different fault related folds indicates that the formation fluid was characterized by low salinity at normal hydrostatic pressure from approximately 9 5 ma from 5 to 3 ma the formation water salinity and fluid pressure increased rapidly the formation water attained the highest salinity at approximately 3 ma to present while the pore fluid overpressure decreased with time in the reservoir two episodes of oil and one episode of gas charge were identified in the k 1 bs sandstone reservoir with the second episode of oil charge occurring around 5 4 ma while the gas charge occurred around 3 2 ma the injection of new fluids associated with oil and gas charge caused changes of the formation water salinity in the different fault related fold traps within the gas field the fluid evolution in the dabei gas field can be used to indicate fault related fluid flow as the thrust faults are suggested to be the primly pathways for fluid migration and the fluid flow was controlled by the reactivation of these thrust faults the similarity of the oil and gas charge histories formation water salinity and fluid pressure evolution in the k 1 bs sandstone reservoirs among the different fault related traps in the dabei gas field implies that the fault related fluid flow process and activation of the thrust faults were concomitant since approximately 9 ma

episodic fluid expulsion from geopressured sediments numerical simulation of fluid explusion from geopressured sediments using a one dimensional finite difference model shows that large volumes of fluid can be transported through a fractured seal during short lived 100 year expulsion events in this model abnormal fluid pressures are maintained by an impermeable seal when the fluid pressure exceeds 85 of the lithostatic pressure a vertical fracture opens in the seal providing a permeable pathway from the geopressured sediments into the overlying section fluid pressure in the seal decreases as fluid flows through the fracture closing the fracture as sediments in the seal compact once the fracture closes the seal remains impermeable until fluid flowing from deeper in the section increases fluid pressure to the fracture criteria a process that takes 10 000 500 000 years fractures emplaced in relatively incompressible seals such as compacted and or cemented sediments remain open for 20 50 years fluid fluxes through the seal integrated over the life of these events are 1 5 107 kg m2 and temperatures in the overlying sediments are increased by 5 20 c these temperature anomalies decay to less than half their original value in 300 years suggesting that the thermal anomalies observed in wells that are attributed to fluid expulsion formed in response to a very recent or currently active event

aspects of interannual and intraseasonal variability of the tropopause and lower stratosphere radiosonde and national centers for environmental prediction national center for atmospheric research reanalysis data are utilized to consider aspects of large scale variability in tropopause height temperature and pressure this variability is related to coherent dynamical fluctuations in the troposphere and lower stratosphere through the use of linear correlation and regression on interannual time scales significant global scale tropopause fluctuations are tied to variability in sea surface temperature sst associated with the el ni o southern oscillation phenomenon when sst is anomalously high in the central tropical pacific tropopause height pressure is high low throughout the tropics with largest perturbation amplitudes in the subtropical pacific at the same time the tropopause is cold over the tropical and subtropical pacific sector but warm elsewhere in the tropics over the extratropics wave like perturbations in the tropopause are seen with anomalous cyclonic flow corresponding to a lower tropopause height and higher tropopause temperature and pressure and vice versa the sign of the temperature anomalies in the lower stratosphere tends to match that at the tropopause over much of the globe with opposite signed anomalies in the upper troposphere the vertical structure of these perturbations is consistent with the expected potential vorticity anomalies induced by quasi stationary rossby waves and vertically propagating gravity waves forced by displacements of tropical convection similar relationships are associated with the eastward propprotion of tropical convection due to the madden julian oscillation on intraseasonal time scales

eastward propagating mjo during boreal summer and indian monsoon droughts improved understanding of underlying mechanism responsible for indian summer monsoon ism droughts is important due to their profound socio economic impact over the region while some droughts are associated with external forcing such as the el nino and southern oscillation enso many ism droughts are not related to any known external forcing here we unravel a fundamental dynamic process responsible for droughts arising not only from external forcing but also those associated with internal dynamics we show that most ism droughts are associated with at least one very long break vlb breaks with duration of more than 10 days and that the processes responsible for vlbs may also be the mechanism responsible for ism droughts our analysis also reveals that all extended monsoon breaks whether co occurred with el nino or not are associated with an eastward propagating madden julian oscillation mjo in the equatorial indian ocean and western pacific extending to the dateline and westward propagating rossby waves between 10 and 25 n the divergent rossby wave associated with the dry phase of equatorial convection propagates westward towards indian land couple with the northward propagating dry phase and leads to the sustenance of breaks thus the propensity of eastward propagating mjo during boreal summer is largely the cause of monsoon droughts while short breaks are not accompanied by westerly wind events wwe over equatorial western pacific favorable for initiating air sea interaction all vlbs are accompanied by sustained wwe the wwes associated with all vlb during 1975 2005 initiate air sea interaction on intraseasonal time scale extend the warm pool eastward allowing the convectively coupled mjo to propagate further eastward and thereby sustaining the divergent circulation over india and the monsoon break the ocean atmosphere coupling on interannual time scale such as el nino can also produce vlb but not necessary

fluid flow in the south eugene island area offshore louisiana results of numerical simulations abstract numerical simulations of heat and fluid transport in the south eugene island sei area offshore louisiana suggest fluids migrate from deep abnormally pressured sediments along fault zones and into overlying oil and gas reservoirs in the simulations fluid flow along the fault produces a narrow thermal anomaly around the fault a negative thermal anomaly forms adjacent to the thermal maximum when permeable sediments dip away from the fault zone in the simulations this negative thermal anomaly dissipates 100 200 years after it forms the presence of a similar negative thermal anomaly in the sei area suggests that fluid movement in the area is a recent event the observation that the thermal maximum in the study area is not centered about the fault zone further suggests that the primary vertical conduit for fluid flow in the sei area is not a major fault but minor splay faults in the hanging wall

evaluation of solitary waves as a mechanism for oil transport in poroelastic media a case study of the south eugene island field gulf of mexico basin abstract hydrocarbons in shallow reservoirs of the eugene island 330 field in the gulf of mexico basin are thought to have migrated rapidly along low permeability sediments of the red fault zone as discrete pressure pulses from source rocks at depths of about 4 5 km the aim of this research was to evaluate the hypothesis that these pressure pulses represent solitary waves by investigating the mechanics of solitary wave formation and motion and wave oil transport capability a two dimensional numerical model of eugene island minibasin formation predicted overpressures at the hydrocarbon source depth to increase at an average rate of 30 pa yr reaching 52 mpa by the present day and oil velocities of 10 12 m yr far too low for kilometer scale oil transport to fill shallow plio pleistocene reservoirs within the 3 6 million year minibasin history calculations from a separate one dimensional model that used the pressure generation rate from the two dimensional model showed that solitary waves could only form and migrate within sediments that have very low permeabilities between 10 25 and 10 24 m 2 and that are highly overpressured to 91 93 of lithostatic pressure solitary waves were found to have a maximum pore volume of 10 5 m 3 to travel a maximum distance of 1 2 km and to have a maximum velocity of 10 3 m yr based on these results solitary waves are unlikely to have transported oil to the shallowest reservoirs in the eugene island field in a poroelastic fault gouge rheology at the pressure generation rates likely to have been caused by disequilibrium compaction and hydrocarbon generation however solitary waves could perhaps be important agents for oil transport in other locations where reservoirs are closer to the source rocks where the pore space is occupied by more than one fluid or where sudden fracturing of overpressured hydrocarbon source sediments would allow the solitary waves to propagate as shock waves

organization of tropical convection in a gcm with varying vertical resolution implications for the simulation of the madden julian oscillation experiments using a gcm with two different vertical resolutions show differences in the amount of variability in the tropical upper tropospheric zonal wind component associated with the madden julian oscillation mjo the gcm with lower vertical resolution shows very little variability in this quantity whereas when the vertical resolution is doubled in the free troposphere the gcm produces variability which is of the same strength as observations however the eastward propagation of an enhanced convective region from the indian ocean into the west pacific is not well represented in either simulation of this atmospheric gcm a water covered or aqua planet version of the same gcm is used to investigate the behaviour of tropical convection when the vertical resolution is doubled when the vertical resolution is increased the spectrum of tropical cloud types changes from a bimodal distribution with peaks representing shallow cumulus and deep cumulonimbus clouds to a trimodal distribution with a third peak in mid troposphere near the melting level associated with periods when these mid level congestus clouds are dominant the detrainment from these clouds significantly moistens the mid troposphere the appearance of these congestus clouds is shown to be partly due to improved resolution of the freezing level and the convective processes occurring at this level however due to the way in which convective detrainment is parametrized in this model the vertical profile becomes rather noisy and this too contributes to the change in the nature of the convective clouds the resulting cloud distribution more closely resembles observations particularly during the suppressed phase of the mjo when cumulus congestus is the dominant cloud type

barrier effect of the indo pacific maritime continent on the mjo perspectives from tracking mjo precipitation abstractexplanations for the barrier effect of the indo pacific maritime continent mc on the mjo should satisfy two criteria first they should include specific features of the mc namely its intricate land sea distributions and elevated terrains second they should include mechanisms for both the barrier effect and its overcoming by some mjo events guided by these two criteria a precipitation tracking method is applied to identify mjo events that propagate across the mc mjo c and those that are blocked by the mc mjo b about a half of mjo events that form over the indian ocean propagate through the mc most of them 75 become weakened over the mc the barrier effect cannot be explained in terms of the strength horizontal scale or spatial distribution of mjo convection when it approaches the mc from the west a distinction between mjo b and mjo c is their precipitation over the sea versus land in the mc region mjo c events rain much more over the sea than over land whereas rainfall over

development characteristics and dynamic structure of tropical intraseasonal convection anomalies abstract the development and dynamical structure of intraseasonal low frequency convection anomalies in the equatorial region are investigated using 10 years 1975 85 of outgoing longwave radiation olr and 7 years 1979 85 of 200 and 850 mb wind data the composite olr anomalies for 36 cases show a four stage development process initiation over equatorial africa rapid intensification when passing through the indian ocean mature evolution characterized by a weakening in the maritime continent and redevelopment over the western pacific and dissipation near the date line in moderate events or emanation from the equator toward north america and southeastern pacific in strong events a noticeable feature in vertical structure is that the 850 mb convergence leads convection and midtropospheric upward motion by about 30 degrees longitude in both developing and mature phases equatorial upper lower level easterly westerly anomalies and associated twin anomalous anticyclonic cyclonic circulation an

a new look at the midlatitude mjo teleconnection in the northern hemisphere winter the midlatitude to madden julian mjo teleconnection in the northern hemisphere wintertime was investigated using twenty years of outgoing long wave radiation and national center for atmospheric research national centers for environmental prediction re analysis data it is revealed through empirical orthogonal functions and regression analyses that the tropical upper level divergence convergence associated with enhanced reduced tropical convection has a subtropical counterpart of upper level convergence divergence as the convective region of mjo moves eastward from the indian ocean to the western pacific the divergent circulation connecting the tropics and subtropics moves eastward from an analysis of vertical motion diagnosed by the generalized omega equation it was revealed that the position of the subtropical rossby gyres of the mjo with respect to the asian pacific jet was the most important factor affecting the existence of the localized divergence convergence and associated lower level vertical motion in the subtropics as the subtropical rossby gyres pass by the longitudinal position of the asian pacific jet vertical motion occurs to meet the balance required by quasi geostrophic theory since this anomalous vertical motion is large enough to cause convection at that region the diabatic heating process reinforces the vertical motion furthermore other dynamical processes neglected in quasi geostrophic theory are activated and contribute to the vertical motion balancing the diabatic heating as a result of the vertical motion near the jet entrance region in the subtropics the vorticity advection by vertical wind and the tilting of vorticity become important since these two terms are similar in shape and magnitude they reinforce each other during the development phase of the midlatitude mjo teleconnection combining these two terms we define the baroclinic jet source bjs in order to evaluate the bjs as a source for the midlatitude mjo teleconnection a numerical experiment is carried out the linear barotropic model is forced by only two terms yet the model captured clearly the main feature of the midlatitude mjo teleconnection copyright 2006 royal meteorological society

frictional moisture convergence in a composite life cycle of the madden julian oscillation abstract a composite life cycle of the madden julian oscillation mjo is constructed using an index based on the first two eofs of the bandpass filtered 20 80 days 850 mb zonal wind averaged from 5 n to 5 s every 2 5 around the equator precipitation 1000 mb convergence 850 mb wind and 200 mb wind are composited for the period 1979 95 water vapor integrated from the surface to 300 mb is composited for the period 1988 92 frictional moisture convergence at the equator is shown to play an important role in the life cycle of the madden julian oscillation mjo regions of boundary layer convergence foster growth of positive water vapor anomalies to the east of convection this convergence coincides with 850 mb easterly wind anomalies as is consistent with kelvin wave dynamics drying of the atmosphere occurs rapidly after the passage of convection with the onset of 850 mb westerly perturbations possible mechanisms for this drying include boundary layer divergence and subsidence or horizontal advect

topographic influence on the mjo in the maritime continent abstract this study demonstrates that during the passage of the mjo through the maritime continent in the boreal winter the corresponding deep convection and near surface wind anomalies tend to skirt around mountainous islands flow bifurcation around elongated mountainous islands such as new guinea is clearly seen topographic blocking generates distinctive vorticity and convergence distributions in this specific domain mountain wave like structures are also observed throughout the maritime continent with a clear spatial relationship with the high terrains in sumatra sulawesi and new guinea the existence of topography seems to create extra lifting and sinking within the large scale circulation and thus the convective system exhibits quasi stationary features near the major topography during the mjo passage through the maritime continent it is suggested that resolving the detailed topographic effects may play a key role in simulating realistic characteristics of the mjo in the maritime continent

why does the mjo detour the maritime continent during austral summer eastward propagation of the madden julian oscillation mjo detours the maritime continent mc region southward during austral summer exhibiting enhanced convective activity preferentially in the southern part of the mc area with much weaker anomalies in the central mc area column integrated moist static energy budget of the mjo is analyzed to understand the processes responsible for the mjo detouring results show that zonal and meridional moisture advection is the essential process to the mjo detouring causing the difference between the southern and central mc regions in the moisture recharge before and during the mjo onset further analysis reveals that moisture advection by mjo perturbation winds acting upon the background moisture gradient has the dominant contribution to the regional contrast between the central and southern mc areas the zonal moisture advection is greater in the southern mc region because the zonal gradient of the background moisture field is much steeper in the southern mc area than in the central mc area the onset of the australian monsoon in austral summer contributes to the establishment of the sharp zonal moisture gradient in the southern mc region the meridional moisture advection is weaker in the central mc area because meridional wind anomalies associated with the mjo vary regionally presumably through interactions with the topography and land sea contrast

propagating and standing components of the intraseasonal oscillation in tropical convection abstract two questions related to the intraseasonal variability of tropical convection and circulation remain controversial 1 to what degree is the convective component of the madden julian oscillation mjo a standing oscillation 2 is the eastward propagating circulation anomaly of the mjo coherent with a standing oscillation in convection in an attempt to settle these issues the authors undertake a series of statistical analyses of gridded outgoing longwave radiation and winds to quantify the magnitudes of the propagating and standing components of convection and their coherence with the propagating component of the circulation they demonstrate that no dominant standing oscillation in convection can be identified instead intraseasonal variability of convection is dominated by an eastward propagating mode which the authors interpret as the convective signal of the mjo this propagating component accounts for almost all of the convective variance that is coherent with the eastward propagating di

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

simulations of mjo propagation across the maritime continent impacts of sst feedback abstractthe observed madden julian oscillation mjo tends to propagate eastward across the maritime continent from the eastern equatorial indian ocean to the western pacific however numerical simulations present different levels of fidelity in representing the propagation especially for the tropical convection associated with the mjo this study conducts a series of coupled simulations using the ncep cfsv2 to explore the impacts of sst feedback and convection parameterization on the propagation simulations first two simulations differing in the model horizontal resolutions are conducted the mjo propagation in these two simulations is found generally insensitive to the resolution change further based on the cfsv2 with a lower resolution two additional experiments are performed with model ssts nudged to climatologies with different time scales representing different air sea coupling strength it is demonstrated that weakening the air sea coupling strength significantly degrades the mjo propagation

organic geochemical indicators of dynamic fluid flow processes in petroleum basins a variety of preliminary geophysical geochemical and geological observations anderson et al geophysics 12 17 april 1991a b anderson oil gas j 85 91 26 april 1993 along with well production data schumacher aapg ann conv abstr april 1993 have led to the hypothesis that fluid injection into eugene island block 330 ei 330 in the u s louisiana gulf coast may be a continuing episodic process with the most recent injections having occurred on short geologic time scales 10 000 yr or less organic geochemical evidence presented here suggests these processes may occur on very short time scales years a process called dynamic fluid injection was proposed to explain these observations and is envisioned as episodic pressure build up followed by rapid escape of gas and oil through geopressure and injection into overlying reservoirs

enso regulation of mjo teleconnection the extratropical teleconnections associated with madden julian oscillation mjo are shown to have an action center in the north pacific where the pressure anomalies have opposite polarities between the phase 3 convective indian ocean and phase 7 convective western pacific of the mjo the teleconnection in the same phase of mjo may induce opposite anomalies over east asia and north america between el nino and la nina years during mjo phase 3 a gigantic north pacific anticyclonic anomaly occurs during la nina making coastal northeast asia warmer wetter than normal but the west us colder drier whereas during el nino the anticyclonic anomaly is confined to the central north pacific hence the northwest us experiences warmer than normal weather under influence of a downstream cyclonic anomaly during phase 7 an extratropical cyclonic anomaly forms over the northwest pacific during la nina due to convective enhancement over the philippine sea causing bitter winter monsoon over japan whereas during el nino the corresponding cyclonic anomaly shifts to the northeast pacific due to enhanced convection over the equatorial central pacific which causes warm and wet conditions along the west coast of us and canada further the presence of enso induced seasonal anomalies can significantly modify mjo teleconnection but the aforementioned mjo teleconnection can still be well identified during phase 3 the mjo teleconnection pattern over north pacific will be counterbalanced enhanced by el nino la nina induced seasonal mean anomalies during phase 7 on the other hand the mjo teleconnection anomalies in the northeastern pacific will be enhanced during el nino but reduced during la nina thereby the impacts of mjo teleconnection on the north america is expected to be stronger during el nino than during la nina

barrier effect of the indo pacific maritime continent on mjo propagation in observations and cmip5 models abstractthis study explores possible mechanisms for the barrier effect of the indo pacific maritime continent mc on mjo propagation in particular this study examines whether similar mechanisms

convectively coupled kelvin wave propagation past sumatra a june case and corresponding composite analysis 1 the propagation of two sequential convectively coupled cc kelvin waves past sumatra in june 2006 is examined in reanalysis data and satellite observations rainfall data are presented that are consistent with a considerable damping of the first wave such damping is not unexpected however reanalysis data suggest that in some instances including the episode described here cc kelvin waves can condition the low level flow in a manner that promotes passage of subsequent waves past the island the mechanism involves a sustained northward shift in the low level equatorial westerly winds and the latitude of zero absolute vorticity generated as a cc kelvin wave passes for the june 2006 case kelvin wave filtered low level winds are presented which are consistent with the view that such conditioning associated with the first wave caused the second wave to be shifted northward assisting its eastward propagation a vorticity analysis points to the development of widespread low level divergence within a vortex to the west of sumatra and associated vortex expansion as key factors in the observed conditioning a composite analysis is presented for the region demonstrating recurring divergence events of this nature coupled with concomitant northward shifts in the dynamic equator it finds that such events often occur in association with cc kelvin waves though the climatological extent to which the propagation of successor waves is affected is not addressed possible causes of the observed divergence events including equatorial rossby waves and contributions from transitions to stratiform convection are investigated