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

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

uhp metamorphism and exhumation of the dabie orogen china evidence from shrimp dating of zircon and monazite from a uhp granitic gneiss cobble from the hefei basin a shrimp u pb study of zircons separated from an ultrahigh pressure uhp granitic gneiss cobble sample ds12 from the upper jurassic fenghuangtai formation of the hefei basin north of the dabie orogen has identified three different domains 1 cores some of which show straight boundaries and strong oscillatory zoning with th u ratios of 0 12 0 70 and an imprecise upper intercept age of 777 220 ma mswd 2 4 2 mantles variable in shape and cathodoluminescence cl intensity and containing many uhp mineral inclusions including coesite and omphacite and with th u ratios of 0 02 0 26 and a weighted mean 206pb 238u age of 244 5 ma mswd 4 7 and 3 rims which are more homogeneous and luminescent in cl than the mantles and contain fewer uhp mineral inclusions with th u ratios of 0 01 0 05 and a weighted mean 206pb 238u age of 226 2 ma mswd 0 65 monazites from the same sample do not contain coesite and omphacite inclusions but they do show sector zones and are composed of two contrasting domains the light domains in backscattered electron bse images have a th u ratio of 7 3 18 9 and a weighted mean 206pb 238u age of 221 2 ma mswd 0 94 the dark domains in bse have a th u ratio of 2 8 7 2 and have a weighted mean 206pb 238u age of 218 2 ma mswd 0 96 based on these data and a review of the literature it can be concluded that 1 the protolith of gneiss sample ds12 is a granitoid of neoproterozoic age 2 the ages of 244 and 226 ma for the mantle and rim domains of the zircons are time records of two discrete stages in the uhp evolution of dabieshan 3 the ages of 221 and 218 ma for the light and dark gray domains respectively of the monazites record the times of two stages of retrogressive metamorphism during exhumation of the uhp granitic gneiss to a higher crustal level 4 the exhumation rate of the gneiss is estimated to be 6 km ma and 5 the uhp metamorphic blocks of the dabie orogen provided significant detritus to the hefei basin in the jurassic

comment on paleozoic ages and excess 40ar in garnets from the bixiling eclogite in dabieshan china new insights from 40ar 39ar dating by stepwise crushing by hua ning qiu and j r wijbrans abstract in a recent study qiu and wijbrans 2006 qiu h n and wijbrans j r 2006 paleozoic ages and excess 40ar in garnets from the bixiling eclogite in dabieshan china new insights from 40ar 39ar dating by stepwise crushing geochimica et cosmochimica acta 70 2354 2370 analyzed ar isotopes extracted by crushing garnets from the dabie shan bixiling eclogite and claimed to have constrained a pre triassic 450 ma episode of uhp metamorphism from primary fluid inclusions however in the absence of careful sample characterization and stepped heating analyses the reported ages are more easily explained as experimental artifacts related to ar extracted from either mineral inclusions or the interface sites between mineral inclusions and the garnet matrix dabie shan garnets commonly contain mineral impurities such as k rich omphacite and or k feldspar if dabie shan uhp metamorphism is of the generally accepted triassic age 210 240 ma the apparent age of a phengite sample in equilibrium with the garnet can be explained by the presence of an extraneous 40ar component with mean 40ar 36ar value of 5000 this value is similar to the composition of extraneous 40ar in other eclogite facies terrane

zonal and vertical structure of the madden julian oscillation abstract a statistical study of the three dimensional structure of the madden julian oscillation mjo is carried out by projecting dynamical fields from reanalysis and radiosonde data onto space time filtered outgoing longwave radiation olr data mjo convection is generally preceded by low level convergence and upward motion in the lower troposphere while subsidence cooling and drying prevail aloft this leads to moistening of the boundary layer and the development of shallow convection followed by a gradual and then more rapid lofting of moisture into the middle troposphere at the onset of deep convection after the passage of the heaviest rainfall a westerly wind burst region is accompanied by stratiform precipitation where lower tropospheric subsidence and drying coincide with continuing upper tropospheric upward motion the evolution of the heating field leads to a temperature structure that favors the growth of the mjo the analysis also reveals distinct differences in the vertical structure

role of the boundary layer moisture asymmetry in causing the eastward propagation of the madden julian oscillation the moisture budget associated with the eastward propagating madden julian oscillation mjo was diagnosed using 1979 2001 40 yr ecmwf re analysis era 40 data a marked zonal asymmetry of the moisture relative to the mjo convection appears in the planetary boundary layer pbl below 700 hpa creatingapotentiallymoreunstablestratificationtotheeastofthemjoconvectionandfavoringtheeastward propagation of mjo the pbl integrated moisture budget diagnosis indicates that the vertical advection of moisture dominates the low level moistening ahead of the convection a further diagnosis indicates that the leading term in the vertical moisture advection is the advection of the background moisture by the mjo ascending flow associated with pbl convergence the cause of the zonally asymmetric pbl convergence is further examined it is found that heating induced free atmospheric wave dynamics account for 75 90 of the total pbl convergence while the warm sst anomaly induced by air sea interaction contributes 10 25 of the total pbl convergence the horizontal moisture advection also plays a role in contributing to the pbl moistening ahead of the mjo convection the leadingterm in the moistureadvectionis the advectionacross the backgroundmoisture gradient by the mjo flow in the western indian ocean maritime continent and western pacific the meridional moisture advection by the mjo northerly flow dominates while in the eastern indian ocean the zonal moisture advection is greater the contribution of the moisture advection by synoptic eddies is in generalsmall ithas a negativeeffect overthetropicalindianoceanand westernpacificandbecomespositive in the maritime continent region

the origin of ch4 rich fluids in reduced porphyry skarn cu mo au systems abstract although most of the methane on earth is of biogenic origin significant abiogenic methane has been identified in a variety of geological environments moreover the presence of methane has been reported recently in fluid inclusions from a number of reduced porphyry deposits the genesis of this methane however remains poorly understood here we present results of a study of magma exsolved ch4 rich aqueous fluid inclusions in the seleteguole reduced porphyry skarn cu mo au deposit nw china four types of fluid inclusions namely intermediate density two phase aqueous inclusions low density vapor inclusions brine inclusions and aqueous liquid inclusions have been distinguished on the basis of the phases present at room temperature the intermediate density inclusions were trapped as a single phase and contain 3 8 10 4 mol kg ch4 corresponding to an oxygen fugacity between fmq 1 and fmq 0 5 this attests to the remarkably reduced nature of the fluid the 13c value of the ch4 hosted fluid inclusions ranges from 29 4 to 19 1 pdb which distinguishes this methane from biogenic methane indeed the high homogenization temperature of the ch4 rich inclusions 400 c implies that the ch4 was exsolved directly from the magma given the environment in which the magma was likely generated i e at or immediately above a subducting plate we propose that the methane was produced by reactions involving organic matter bearing carbonate rocks in the subduction zone although cu mo and au in most porphyry systems are interpreted to have been transported under oxidizing conditions our results indicate that reduced aqueous liquids and vapors are also capable of transporting appreciable concentrations of these metals

propagating and nonpropagating mjo events over maritime continent abstractthe observed outgoing longwave radiation olr and era interim data during 1979 2008 from november to april were analyzed to reveal fundamental differences between eastward propagating ep and nonpropagating np mjo events across the maritime continent mc it was found that when the maximum mjo convection arrives near 120 e a positive moisture tendency lies in a longitudinal zone 10 s 10 n 130 170 e for the ep cases whereas a negative tendency appears in the same region for the np cases in the latter cases there are clearly detectable westward propagating rossby wave type dry signals over the equatorial central western pacific the dry rossby wave signal may hinder the development of new convection to the east of the mjo convective center preventing the eastward propagation of the mjo a moisture budget analysis shows that the positive tendency of specific humidity in the ep composite is mainly attributed to the advection of the mean moisture by an intraseasonal ascending motion ano

evolution of the madden julian oscillation in two types of el nino abstractevolution characteristics of the madden julian oscillation mjo during the eastern pacific ep and central pacific cp types of el nino have been investigated mjo activities are strengthened over the western pacific during the predeveloping and developing phases of ep el nino but suppressed during the mature and decaying phases in contrast mjo activities do not show a clear relationship with cp el nino before their occurrence over the western pacific but they increase over the central pacific during the mature and decaying phases of cp el nino lag correlation analyses further confirm that mjo activities over the western pacific in boreal spring and early summer are closely related to ep el nino up to 2 11 months later but not for cp el nino ep el nino tends to weaken the mjo and lead to a much shorter range of its eastward propagation anomalous descending motions over the maritime continent and western pacific related to el nino can suppress convection and moisture flux convergence the

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

fluids in deeply subducted continental crust petrology mineral chemistry and fluid inclusion of uhp metamorphic veins from the sulu orogen eastern china abstract the complex vein associations hosted in southern sulu ultrahigh pressure uhp eclogites contain quartz omphacite or jadeite kyanite allanite zoisite rutile garnet these minerals have chemical compositions similar to those of host eclogites inclusions of polycrystalline quartz pseudomorphs after coesite were identified in vein allanite and garnet and coesite inclusions were found in vein zircon these facts suggest that the veins together with host eclogites have been subjected to synchronous uhp metamorphism the vein minerals contain relatively high concentrations of rare earth elements ree high field strength elements hfse and transition metal elements tme a kyanite quartz vein has a whole rock composition similar to adjacent uhp metamorphic granitic gneisses abundant primary multi solid fluid inclusions trapped within uhp vein minerals contain complex daughter minerals of muscovite calcite anhydrite magnetite pyrite apatite celestite and liquid and gas phase of h 2 o with solids up to 30 70 of the inclusion volume the presence of daughter minerals anhydrite and magnetite indicates the subduction fluids were oxidizing and provides a possible interpretation for the high oxygen fugacity of subduction zone magmas these characteristics imply that the uhp vein minerals were crystallized from supercritical silicate rich aqueous fluids that were in equilibrium with peak uhp minerals and that the fluids in deeply subducted continental crust may contain very high concentrations of silicate as well as hree hfse and tme such fluids might have resulted in major fractionation between nb and ta i e the uhp fluids have subchondritic nb ta values whereas the host eclogites after extraction of the fluids have suprachondritic nb ta values therefore voluminous residual eclogites with high nb ta ratios may be the complementary suprachondritic reservoir capable of balancing the subchondritic depleted mantle and continental crust reservoirs

effect of vertical moist static energy advection on mjo eastward propagation sensitivity to analysis domain previous studies have shown great uncertainty in assessing the effect of vertical moist static energy mse advection term to the zonal asymmetry of mse tendency this study addresses this issue by qualitatively assess the fractional contribution of the vertical mse advection to the zonal asymmetric pattern of the mse tendency field and how its contribution depends on the choice of the analysis domain based on both observational and numerical simulation results it is shown that the vertical mse advection indeed plays a critical role in generating the zonal asymmetry of mse tendency accounting for 60 of the total mse tendency field in observation and even more in aqua planet simulations it is indicated that the underestimated contribution from vertical mse advection by some previous studies is attributed to the unphysical selection of analysis domain for the zonal asymmetric mse tendency pattern

moisture asymmetry and mjo eastward propagation in an aquaplanet general circulation model abstractthe role of zonal moisture asymmetry in the eastward propagation of the madden julian oscillation mjo is investigated through a set of aquaplanet atmospheric general circulation model agcm experiments with a zonally symmetric sea surface temperature distribution in the control experiment the model produces eastward propagating mjo like perturbations with a dominant period of 30 90 days the model mjo exhibits a clear zonal asymmetry in the lower tropospheric specific humidity field with a positive negative anomaly appearing to the east west of the mjo convection a diagnosis of the lower tropospheric moisture budget indicates that the asymmetry primarily arises from vertical moisture advection associated with boundary layer convergence while horizontal moisture advection has the opposite effect in a sensitivity experiment the lower tropospheric specific humidity field is relaxed toward a zonal mean basic state derived from the control simulation in this case the model s mean state r

fundamental causes of propagating and nonpropagating mjos in mjotf gass models abstractthis study investigates the fundamental causes of differences in the madden julian oscillation mjo eastward propagation among models that participated in a recent model intercomparison project these models are categorized into good and poor groups characterized by prominent eastward propagation and nonpropagation respectively column integrated moist static energy mse budgets are diagnosed for the good and the poor models it is found that a zonal asymmetry in the mse tendency characteristic of eastward mjo propagation occurs in the good group whereas such an asymmetry does not exist in the poor group the difference arises mainly from anomalous vertical and horizontal mse advection the former is attributed to the zonal asymmetry of upper midtropospheric vertical velocity anomalies acting on background mse vertical gradient the latter is mainly attributed to the asymmetric zonal distribution of low tropospheric meridional wind anomalies advecting background mse and moisture fields base

remnants of premetamorphic fluid and oxygen isotopic signatures in eclogites and garnet clinopyroxenite from the dabie sulu terranes eastern china a combined oxygen isotope and fluid inclusion study has been carried out on high and ultrahigh pressure metamorphic hp uhpm eclogites and garnet clinopyroxenite from the dabie sulu terranes in eastern china coesite bearing eclogites garnet clinopyroxenite and quartz eclogites have a wide range in whole rock 18ovsmow from 0 to 11 the high t oxygen isotope fractionations preserved between quartz and garnet preclude significant retrograde isotope exchange during exhumation and the wide range in whole rock oxygen isotope composition is thought to be a presubduction signature of the precursors aqueous fluids with variable salinities and gas species n2 co2 or ch4 rich are trapped as primary inclusions in garnet omphacite and epidote and in quartz blebs enclosed within eclogitic minerals in high 18o hp uhpm rocks from hujialin and shima high salinity brine and or n2 inclusions occur in garnet porphyroblasts which also contain inclusions of coesite cl rich blue amphibole and dolomite in contrast in low 18o eclogites from qinglongshan and huangzhen the cl concentrations in amphibole are very low 0 2 wt and low salinity aqueous inclusions occur in quartz inclusions in epidote porphyroblasts and in epidote cores these low salinity fluid inclusions are believed to be remnants of meteoric water although the fluid composition was modified during pre and syn peak hp uhpm eclogites at houshuichegou and hetang contain ch4 rich fluid inclusions coexisting with high salinity brine inclusions methane was probably formed under the influence of co2 rich aqueous fluids during serpentinisation of mantle derived peridotites prior to or during plate subduction remnants of premetamorphic low to high salinity aqueous fluid with minor n2 and or other gas species preserved in the dabie sulu hp uhpm eclogites and garnet clinopyroxenite indicate a great diversity of initial fluid composition in the precursors implying very limited fluid rock interaction during syn and post peak hp uhpm

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

impact of rossby and kelvin wave components on mjo eastward propagation abstractthere are contrasting views concerning the impact of rossby wave component of mjo flow on its eastward propagation one view called drag effect argues that because rossby waves propagat

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

the influence of sea surface temperature on the tropical intraseasonal oscillation a numerical study abstract the development and movement of the tropical intraseasonal system tis exhibit remarkable annual variations it was hypothesized that spatial and temporal variation in sea surface temperature sst is one of the primary climatic factors that are responsible for the annual variation of tiss this paper examines possible influences of sst on the tis through numerical experiments with a 2 5 layer atmospheric model on an equatorial plane in which sst affects atmospheric heating via control of the horizontal distribution of moist static energy and the degree of convective instability the gradient of the antisymmetric with respect to the equator component of sst causes a southward propagation of the model tis toward northern australia in boreal winter and a northward propagation over the indian and western pacific oceans in boreal summer the phase speed of the meridional propagation increases with the magnitude of antisymmetric sst gradients the poleward propagation of the equatorial disturba

seamount subduction at the north ecuadorian convergent margin effects on structures inter seismic coupling and seismogenesis at the north ecuadorian convergent margin 1 s 1 5 n the subduction of the rough nazca oceanic plate leads to tectonic erosion of the upper plate and complex seismogenic behavior of the megathrust we used three selected pre stack depth migrated multi channel seismic reflection lines collected during the sisteur cruise to investigate the margin structure and decipher the impact of the subducted atacames seamounts on tectonic erosion interseismic coupling and seismogenesis in the region of the 1942 mw7 8 earthquake this dataset highlights a subducted 30 40 km 30 40 km double peak seamount that belongs to the atacames seamount chain and that is associated with a deep morphologic re entrant containing mass transport deposits the seamount subduction uplifted the margin basement by 1 6 km and pervasively broke the margin by deep and intense reverse faulting ahead of the seamount a process that is likely to weaken considerably the margin in the seamount wake the basement reverse fault system rotated counter clockwise this faulted basement is overlain with slope sediment sliding along listric normal faults that sole out onto the bsr this superposition of deep tectonic contraction within the basement and shallow gravitational extension deformation within the sediment highlights the key role of gas hydrate on outer slope erosion in addition to long term regional basal erosion the margin basement has thinned locally by an extra 0 8 1 km in response to the subduction of the atacames seamount chain and hydrofracturing by overpressured fluids at the margin toe this pervasively and deeply fractured margin segment is associated with a seismically quiet and gps modeled low interseismic coupling corridor that terminates downdip near the 1942 epicenter and locked zone we suggest that the deeply buried double peak atacames seamount triggered the 1942 earthquake ahead of its leading flank this result supports previous studies proposing that subducted seamounts provide unfavorable conditions for locking the updip segment of the plate boundary limiting the updip extent of seismogenic zones but may favor large subduction earthquakes at greater depths