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

dynamical linkage of tropical and subtropical weather systems to the intraseasonal oscillations of the indian summer monsoon rainfall part i observations the indian summer monsoon rainfall ismr over the western ghats wg and the bay of bengal bob is marked by the intraseasonal oscillations isos with preferred 10 20 day and 30 50 day bands on the basis of pentad climate prediction center merged analysis precipitation and daily sea level pressure and winds at 850 hpa derived from european center for medium range weather forecast reanalysis we present the structure and evolution of the isos linked to the ismr variations over the wg and the bob and the associated anomalies of the atmospheric circulation using the approaches of wavelet analysis bandpass filtering and composite analysis this study reveals that the activities of both the intertropical convergence zone itcz and the western pacific subtropical high wpsh contribute strongly to the structure and propagation of the isos on intraseasonal time scales northward development and propagation of the itcz plays a critical role in the northward propagating isos but not in the westward propagating bob 10 20 day isos the latter isos may be linked instead to the activity of synoptic scale weather systems to the east over the western tropical pacific the enhanced itcz in the tropical indian ocean plays a strong role in the sudden strengthening of the wpsh during the transition from the break to active phase of the 30 50 day isos we find that the strong wpsh in the asian summer monsoon season with generally northward advance and eastward withdrawal promotes the formation of a northwest to southeast tilted anomalous rainfall belt over the east asian tropical summer monsoon region and the western tropical pacific in the 30 50 day low frequency band positive negative elongated rainfall anomalies with an unbroken northwest southeast tilt strong easterly westerly anomalies in the tropical pacific and northward advance and eastward movement of strong weak wpsh are favorable for maintaining the eastward propagation of the 30 50 day isos in the pacific daily high resolution sea surface temperature obtained from the national oceanic and atmospheric administration is used to explain the propagation features of the 10 20 day isos in the indian ocean

velocity structure around the baikal rift zone from teleseismic and local earthquake traveltimes and geodynamic implications abstract we present new results on the velocity structure of the baikal rift zone asia deduced from a comparative teleseismic and local tomography analysis the aim of this paper is to better identify the role of deep mantle processes versus that of far field tectonic effects on the occurrence of extensional tectonics within a continental plate we use 36000 traveltimes of p refracted waves from the isc catalogues and pg and pn traveltimes of 578 earthquakes recorded by the russian regional network to determine a velocity model by the use of local and teleseismic inversion procedures the models show that some velocity patterns are continuous from the surface down to at least 400 km among them a narrow negative anomaly goes through mongolia and follows the southern and eastern margins of the siberian craton this structure is interpreted as a thin mantle plume rising beneath the rift axis however our results do not evidence any wide asthenospheric upwarp at this place other velocity anomalies observed near the surface are not deeply rooted in particular a negative anomaly is observed at shallow levels 48 km beneath the northern third of lake baikal which is disconnected from deeper structures it may be explained by the existence of underplated magmatic material at the bottom of the crust by comparing the geometry of deep rooted anomalies to the present day stress field patterns we conclude that the sub lithospheric mantle dynamics is not the main factor controlling extensional processes in the baikal rift however it does contribute to a thermal weakening of the lithosphere along a mechanical discontinuity bounding the siberian shield we finally conclude that three favourable conditions are gathered in the baikal area to generate extension far field extensional stress field mechanical inherited lithospheric weakness and heat supply further studies should help to precise the genetic link between these three factors

mechanisms of northward propagating intraseasonal oscillation over the south china sea during the pre monsoon period abstractin the present study the spatiotemporal structures of the northward propagating intraseasonal oscillation iso over the south china sea scs in the premonsoon period are analyzed by usin

the relationship between convection and sea surface temperature on intraseasonal timescales abstract the relationship between tropical convection surface fluxes and sea surface temperature sst on intraseasonal timescales has been examined as part of an investigation of the possibility that the intraseasonal oscillation is a coupled atmosphere ocean phenomenon the unique feature of this study is that 15 yr of data and the whole region from the indian ocean to the pacific ocean have been analyzed using lag correlation analysis and compositing techniques a coherent relationship between convection surface fluxes and sst has been found on intraseasonal timescales in the indian ocean maritime continent and west pacific regions of the tropics prior to the maximum in convection there are positive shortwave and latent heat flux anomalies into the surface followed by warm sst anomalies about 10 days before the convective maximum coincident with the convective maximum there is a minimum in the shortwave flux followed by a cooling due to increased evaporation associated with enhanced westerl

mechanisms of northward propagating intraseasonal oscillation a comparison between the indian ocean and the western north pacific abstract mechanisms of northward propagating intraseasonal oscillations isos over the indian ocean io and the western north pacific wnp are examined for the possibility of their existence in observations they include the following 1 the vorticity advection effect which is associated with the advection of anomalous baroclinic vorticity by mean baroclinic meridional winds 2 the vertical wind shear effect which is the vertical advection associated with the meridional gradient of baroclinic divergence and mean easterly vertical wind shear 3 the moisture advection effect induced by mean flow and 4 the air sea interaction via surface latent heat flux because of differences in mean state the influence of each mechanism on the northward propagating isos is different between the io and the wnp the vorticity advection effect is consistently found over both the io and the wnp while the air sea interaction has different impacts on the northward propagating isos over the io and the wnp the vertic

seismic velocity variations beneath central mongolia evidence for upper mantle plumes abstract central mongolia is marked by wide spread recent volcanism as well as significant topographic relief even though it is far from any plate tectonic boundaries the cause of the recent magmatism and topography remains uncertain partially because little is known of the underlying mantle seismic structure due to the lack of seismic instrumentation in the region from august 2011 through august 2013 69 broadband seismic stations were deployed in central mongolia teleseismic traveltime residuals were measured using waveform correlation and were inverted to image upper mantle p and s velocity variations significant lateral variations in seismic velocity are imaged in the deep upper mantle 100 to 800 km depth most significant are two continuous slow anomalies from the deep upper mantle to near the surface one slow feature has been imaged previously and may be a zone of deep upwelling bringing warm mantle to beneath the hangay dome resulting in uplift and magmatism including the active khanuy gol and middle gobi volcanoes the second deep low velocity anomaly is seen in the east from 800 to 150 km depth the anomaly ends beneath the gobi desert that is found to have fast shallow mantle indicating a relatively thick lithosphere we interpret the second deep slow anomaly as a mantle upwelling that is deflected by the thick gobi desert lithosphere to surrounding regions such as the hentay mountains to the north the upwellings are a means of feeding warmer than normal asthenospheric mantle over a widely distributed region beneath mongolia resulting in distributed volcanic activity and uplift there is no indication that the upwellings are rooted in the deep lower mantle i e classic plumes we speculate the upwellings may be related to deep subduction of the pacific and indian plates and are thus plumes anchored in the upper mantle

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

development and life cycle of the indian monsoon effect of the 30 50 day oscillation abstract the velocity potential fields generated from the fgge iii b horizontal winds of the european centre for medium range weather forecasts were subjected to an empirical orthogonal function eof analysis to extract the annual cycle and the 30 50 day mode of the divergent circulations we found that the indian monsoon circulation is portrayed by the annual cycle of the divergent circulation and develops as a classical giant sea breeze model on the other hand this monsoon system is modulated by the planetary scale 30 50 day low frequency mode to establish an onset active break revival retreat life cycle this modulation is accomplished through the following interaction process the northeastward propagation of the planetary scale 30 50 day mode over the indian monsoon region induces transient local hadley circulation through this type of circulation the planetary scale 30 50 day mode couples with and steers northward the low level 30 50 day monsoon troughs and ridges that originated around the e

quasi periodic oscillations in a symmetric general circulation model abstract long lime integrations with a symmetric version of the clas climate model with hydrology have shown that the hadley circulation has well defined strong and weak episodes this oscillation of the hadley circulation seems to occur in two dominant range of periodicities one with periods between 10 and 15 days and another with periods between 20 and 40 days this quasi periodic behavior of the hadley circulation is seen only when the moist convective heating is determined by dynamics if the latent beating in the atmosphere is prescribed and kept artificially fixed this oscillation of the hadley circulation disappears thus this oscillation of the hadley circulation appears as a result of interactions between moist convective and dynamical processes a wave phenomenon is seen in the lower atmosphere that propagates toward the position of maximum radiative beating this wave perturbation has a length scale of about 15 20 degrees latitude in the north south direction this phenomenon has large ampli

large scale mantle convection and the history of subduction a large scale pattern of mantle convention is evident in the shape of the earth s gravity field1 lateral variations in seismic velocity2 3 the distribution of hotspots4 and long wavelength bathv metric anomalies5 paradoxically these signals of mantle convection bear little resemblance to present day plate motions1 4 although they seem to be related to past subduction zone configurations6 here we quantify this relationship by correlating a time integrated history of subduction calculated in the hotspot reference frame for the past 180 myr with regions of the deep mantle inferred from other geophysical observations to be colder than average our results support suggestions6 9 that a direct relationship exists between large scale thermal heterogeneity in the lower mantle and subduction during the cenozoic and mesozoic

resolving the upper ocean warm layer improves the simulation of the madden julian oscillation here we show that coupling a high resolution one column ocean model to an atmospheric general circulation model dramatically improves simulation of the madden julian oscillation mjo to have realistic strength period and propagation speed the mechanism for the simulated mjo involves both frictional wave convective conditional instability of the second kind frictional wave cisk and air sea convective intraseasonal interaction ascii in particular better resolving the fine structure of upper ocean temperature especially the warm layer produces more vigorous atmosphere ocean interaction and strengthens intraseasonal variations in both sst and atmospheric circulation this helps organize and strengthen deep convection inducing a stronger kelvin wave like perturbation and frictional near surface convergence to the east in addition the warmer sst ahead of the mjo also acts to destabilize the boundary layer and enhance frictional convergence these lead to a more realistic eastward propagating mjo a suite of sensitivity experiments were performed to show the robustness of the mechanisms and to demonstrate 1 that mean state differences are not the main contributors to the improved simulation of our coupled model 2 the role of sst variability in enhancing frictional convergence and intraseasonal variations in precipitation and 3 that the simulation is significantly degraded when the first ocean model layer is thicker than 10 m our coupled model results are consistent with observations and demonstrate a simple but effective means to significantly improve mjo simulation and potentially also forecasts

contrast of 10 20 day and 30 60 day intraseasonal sst propagation during summer and winter over the south china sea and western north pacific this study documents the structure and propagation of intraseasonal sea surface temperature sst variations and relative contribution of surface latent heat flux and shortwave radiation to the sst propagation in the south china sea scs and western north pacific wnp regions the emphasis is on the contrast of intraseasonal sst propagation between summer and winter and between 10 20 day and 30 60 day time scales the dominant sst pattern during summer displays a tilted southwest northeast band from the scs to the subtropical wnp on both time scales but with a larger value in the subtropical wnp on the 10 20 day time scale and in the scs on the 30 60 day time scale the dominant sst pattern during winter resembles that during summer but with a larger value in the scs in summer the sst anomalies show obvious northwestward and northward propagations in the scs wnp region on the 10 20 day and 30 60 day time scales respectively the cloud radiation effect is a dominant factor for the sst propagation on both time scales in the scs wnp region with a supplementary effect from the wind evaporation effect on the 10 20 day time scale in winter the sst anomalies show southward propagation on both time scales in the scs while the southward propagation in the wnp is weak and confined to the subtropics on the 10 20 day time scale the wind evaporation effect makes a larger contribution to the sst propagation than the cloud radiation effect on both time scales in the scs wnp region

teleconnections associated with northern hemisphere summer monsoon intraseasonal oscillation the boreal summer intraseasonal oscillation bsiso has strong convective activity centers in indian i western north pacific wnp and north american na summer monsoon sm regions the present study attempts to reveal bsiso teleconnection patterns associated with these dominant intraseasonal variability centers during the active phase of ism a zonally elongated band of enhanced convection extends from india via the bay of bengal and philippine sea to tropical central pacific with suppressed convection over the eastern pacific near mexico the corresponding extratropical circulation anomalies occur along the waveguides generated by the north african asian jet and north atlantic north european jet when the tropical convection strengthens over the wnpsm sector a distinct great circle like rossby wave train emanates from the wnp to the western coast of united states us with an eastward shift of enhanced meridional circulation in the active phase of nasm large anticyclonic anomalies anchor over the western coast of us and eastern canada and the global teleconnection pattern is similar to that during a break phase of the ism examination of the evolution of the bsiso teleconnection reveals quasi stationary patterns with preferred centers of teleconnection located at europe russia central asia east asia western us and eastern us and canada respectively most centers are embedded in the waveguide along the westerly jet stream but the centers at europe and russia occur to the north of the jet induced waveguide eastward propagation of the iso teleconnection is evident over the pacific north america sector the rainfall anomalies over the elongated band near the monsoon domain over the indo western pacific sector have an opposite tendency with that over the central and southern china mexico and southern us providing a source of intraseasonal predictability to extratropical regions the bsiso teleconnection along and to the north of the subtropical jet provides a good indication of the surface sir temperature anomalies in the nh extratropics

pb isotopic compositions of archean komatiites and sulfides abstract pb isotopic compositions were measured in komatiites and other volcanic rocks from several archean greenstone belts and in magmatic and exhalative sulfides associated with these volcanics thin komatiite flows generally yielded pb pb isochron ages consistent with other geochronological or geological information but thicker basaltic flows gave ages that are too young these results suggest that the thin komatiite flows were hydrothermally altered during eruption and that this event is recorded by the pb pb age thicker basaltic flows resisted alteration during eruption but were affected by later events their pb pb ages probably correspond to the time of metamorphism and not to the time of emplacement magmatic and exhalative sulfides from the abitibi belt in canada fall on the same trend in the 207 pb 204 pb 206 pb 204 pb diagram as komatiites basalts sedimentary rocks and k feldspars from granites the calculated 1 value is 7 8 0 1 a similar suite of rocks and minerals from the kambalda area in australia has distinctly higher 207 pb 204 pb and a higher 1 of 8 3 nd isotopic data demonstrate that some kambalda rocks are highly contaminated with older continental crust the differences in initial pb isotopic compositions are attributed to the presence or absence and the age of underlying granitoid basement kambalda greenstones are underlain and contaminated by old 3 0 ga granitoid crust but significantly older granitoid basement appears absent from the abitibi belt the pb isotopic compositions of kambalda greenstones are dominated by the crustal component and do not represent the composition of the mantle source of these rocks the abitibi greenstones are not highly influenced by crustal contamination and their pb isotopic compositions may reflect those of archean mantle

mesozoic crust mantle interaction beneath the north china craton a consequence of the dispersal of gondwanaland and accretion of asia we present evidence from zircons entrained within lower crustal xenoliths in the cenozoic hannuoba basalt of multiple melting events beneath the north china craton in the late mesozoic peak activity was between 180 and 80 ma the upper crustal signature of which was the generation of voluminous granitoids and related volcanic rocks emplacement of dioritic and lamprophyric dikes and widespread gold mineralization the process involved partial loss of mantle lithosphere accompanied by wholesale rising of asthenospheric mantle beneath eastern china we correlate these events with lithospheric thinning resulting from the breakup and dispersal of gondwanaland accompanied by a major mantle overturn fueled by the destruction of oceanic lithosphere and triggered by its sinking into the lower mantle during the subsequent accretion of asia

moisture dynamics of the northward and eastward propagating boreal summer intraseasonal oscillations possible role of tropical indo west pacific sst and circulation boreal summer intraseasonal oscillation bsiso has complex spatial structure due to the co existence of equatorial eastward and off equatorial northward propagation in the equatorial indian ocean as a result equatorial indian ocean convection has simultaneous northward and eastward ne northward only n only and eastward only e only propagations it is well established that the convection propagates in the direction of increasing moist static energy mse the moisture and mse budget analysis reveals that the horizontal advection of anomalous mse contributes to positive mse tendency which is in agreement with the horizontal advection of column integrated moisture anomaly northward movement of warm sst and the anomalous moisture advected by zonal wind are the major initiative for the northward propagation of convection from the equatorial indian ocean in both ne and n only category at the same time warm sst anomaly in the equatorial west pacific along with moisture advection caused by anomalous meridional wind is important for the equatorial eastward branch of ne propagation as these anomalies in the west pacific moves northward equatorial indian ocean convection establishes over the equatorial west pacific the absence of these processes confines the bsiso in northward direction for n only category in the case of e only movement warm sst anomaly and moisture advection by zonal component of wind causes the eastward propagation of convection boundary layer moisture convergence always remains east of convection center in e only propagation while it coincides with convection centre in other two categories thus the present study concludes that the difference in underlying sst and atmospheric circulation in tropical indo west pacific oceanic regions encourage the differential propagation of bsiso convection through moisture dynamics

northwestward propagation of the intraseasonal oscillation in the western north pacific during the boreal summer structure and mechanism abstract the convection of the intraseasonal timescale in the western north pacific during the boreal summer tends to propagate northwestward in the philippine sea to near 20 n and then continues propagating westward the formation of enhanced convection in the western north pacific is a result of the merging of a convective system moving eastward along the equator and a westward propagating low level convergence anomaly which is located to the east of a vortex in the subtropics a positive feedback between the anomalous circulation and convection leads to a rapid enhancement of the system the strengthened southwesterly associated with the vortex enhances evaporation over the oceans e g the eastern indian ocean the bay of bengal and the south china sea and transports moisture northeastward the moisture converges at the northwestern corner of the convection and results in a potentially unstable atmosphere the result is the northwestward propagation of the coupled circulation convection system in

identification of groundwater contamination zones and its sources by using multivariate statistical approach in thirumanimuthar sub basin tamil nadu india hydrogeochemical studies have been made in the study area by using multivariate statistical analysis which is mainly helpful for interpretation of complex data matrices to better understand the geochemical evolution of the area and it allows identifying the possible factors sources that influence water systems the spatial distribu tion of electrical conductivity reveals that an untreated industrial effluents landfill and anthropogenic activities affecting their groundwater quality in its vicinity and the surrounding area the dominance of ions was in the order of na ca 2 mg 2 k cl hco3 so4 2 no3 and ca 2 mg 2 na k hco3 cl no3 so4 2 during pre monsoon prm and post monsoon pom respectively the statistical results reveals that the groundwater chemistry gets altered by silicate weathering ion exchange leaching anthropogenic input from agricultural return flow and longer distance of migrating groundwater the hydrogeochemical regimes are distributed along the upstream side northwestern western and eastern parts of the study area the study highlights the descriptive capabilities of conventional and multivariate techniques as effective tools in groundwater evaluation

the baikal rift zone the effect of mantle plumes on older structure abstract the main chain of sw ne striking cenozoic half grabens of the baikal rift zone brz follows the frontal parts of early paleozoic thrusts which have northwestern and northern vergency most of the large rift half grabens are bounded by normal faults at the northwestern and northern sides we suggest that the rift basins were formed as a result of transformation of ancient thrusts into normal listric faults during cenozoic extension seismic velocities in the uppermost mantle beneath the whole rift zone are less than those in the mantle beneath the platform this suggests thinning of the lithosphere under the rift zone by asthenosphere upwarp the geometry of this upwarp and the southeastward spread of its material control the crustal extension in the rift zone this nw se extension cannot be blocked by sw ne compression generated by pressure from the indian lithospheric block against central asia the geochemical and isotopic data from late cenozoic volcanics suggest that the hot material in the asthenospheric upwarp is probably provided by mantle plumes to distinguish and locate these plumes we use regional isostatic gravity anomalies calculated under the assumption that topography is only partially compensated by moho depth variations variations of the lithosphere asthenosphere discontinuity depth play a significant role in isostatic compensation we construct three dimensional gravity models of the plume tails the results of this analysis of the gravity field are in agreement with the seismic data the group velocities of long period rayleigh waves are reduced in the areas where most of the recognized plumes are located and azimuthal seismic anisotropy shows that these plumes influence the flow directions in the mantle above their tails the baikal rift formation like the kenya rio grande and rhine continental rifts achauer u granet m 1997 complexity of continental rifts as revealed by seismic tomography and gravity modeling in jacob a w b delvaux d khan m a eds lithosphere structure evolution and sedimentation in continental rifts proceedings of the igcp 400 meeting dublin march 20 22 1997 institute of advanced studies dublin pp 161 171 is controlled by the three following factors i mantle plumes ii older prerift linear lithosphere structures favorably positioned relative to the plumes and iii favorable orientation of the far field forces

mongolian plateau evidence for a late cenozoic mantle plume under central asia the 2500 x 700 km mongolian plateau average elevation 2000 m is situated between the altai orogen and the siberian craton and occupies much of mongolia and transbaikalia in russia the plateau is characterized by 1 basin and range topography and two major domes hentai 600 x 300 km and hangai 800 x 550 km where altitudes reach 3905 m 2 lithosphere that is thinner than adjacent areas minimum 50 km 3 elevated heat flow up to 120 mw m2 4 dominantly alkaline basaltic volcanism in the form of cones lava fields and volcanic plateaus mostly of miocene quaternary age and 5 rifts including baikal main evolution in the pliocene quaternary tunka oligocene early miocene and hobsogol pliocene quaternary existing models explain these features in terms of diapiric upwelling of a mantle asthenolith below the main rifts and or as a long distance effect of the india asia collision we propose that the late cenozoic uplift of the whole mongolian plateau and associated rifting magmatism high heat flow and lithospherec thinning are not externally driven by the india asia collision but are the expression of the interaction of a mantle plume with overlying lithosphere some rifts link and interact with major strike slip faults such as the bolnai such faults may be the major expression of the india asia collision in this region

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

quasi biweekly oscillation over the tibetan plateau and its link with the asian summer monsoon abstract intraseasonal variation isv is especially prominent and unique in the asian summer monsoon region in this work the dominant isv mode over the tibetan plateau tp in the summer monsoon season june august together with its structure and evolution is identified using station observations global precipitation climatology project precipitation data and era interim during 1979 2011 results indicate that quasi biweekly oscillation qbwo is the dominant mode of isv over the tp and is significant in terms of the circulation precipitation and diabatic heating fields in particular the qbwo is closely related to the onset and active break phases of the tp summer monsoon in most cases the qbwo originates from the equatorial western pacific and first propagates northwestward to the bay of bengal and northern india then northward to the southeastern tp and finally eastward to the east asian area showing a clockwise propagation pathway two main mechanisms are responsible for the northward

low frequency equatorial waves in vertically sheared zonal flow part i stable waves abstract the mechanism by which a vertically sheared zonal flow affects large scale low frequency equatorial waves is investigated with two level equatorial plane and spherical coordinates models vertical shears couple barolinic and barotropic components of equatorial wave motion affecting significantly the rossby wave and westward propagating yanai wave but not the kelvin wave this difference results from the fact that the barotropic component is a modified rossby mode and can be resonantly excited only by westward propagating internal waves the barotropic components emanate poleward into the extratropics with a pronounced amplitude while the baroclinic components remain equatorially trapped a westerly vertical shear favors the trapping of rossby and yanai waves in the upper troposphere whereas an easterly shear tends to confine them in the lower troposphere as such their westward propagation is slowed down by both westerly and easterly shears when the strength of the vertical shear varies w

roles of barotropic convective momentum transport in the intraseasonal oscillation both observational data analysis and model simulations suggest that convective momentum transport cmt by cumulus convection may play a significant role in the intraseasonal oscillations iso by redistributing atmospheric momentum vertically through fast convective mixing process the authors present a simple theoretical model for the iso by parameterizing the cumulus momentum transport process in which the cmt tends to produce barotropic wind anomalies that will affect the frictional planetary boundary layer pbl in the model with equatorial easterly vertical wind shear vws it is found that the barotropic cmt tends to select most unstable planetary scale waves because cmt suppresses the equatorial ekman pumping of short waves which reduces the shortwave instability from the pbl moisture convergence and accelerates the shortwave propagation the model with subtropical easterly vws has behavior that can be qualitatively different from the model with equatorial easterly vws and has robust northward propagation the basic mechanism of this northward propagation is that the cmt accelerates the barotropic cyclonic wind to the north of iso which will enhance the precipitation by pbl ekman pumping and favor the northward propagation the simulated northward propagation is sensitive to the strength and location of the seasonal mean easterly vws these results suggest that accurate simulation of the climatological mean state is critical for reproducing the realistic iso in general circulation models

tropical 45 day oscillations during the 1979 northern hemisphere summer abstract based on fgge 1 cvel iiib data the structural features of 45 day perturbations over a tropical belt 15 n 15 s during the 1979 summer are detailed at the equator 45 day perturbations which are primarily associated with the zonal wind components of wavenumber 1 propagate eastward 8 of longitude per day and upward 0 7 km per day probably indicating downward energy flux in the southern hemisphere tropics 0 15 s the 45 day zonal mean wind perturbations propagate downward with an approximate phase speed of 0 8 km per day in the northern hemisphere tropics they are largely of standing character with the maximum amplitude 3 m s 1 near 200 mb at 15 n there exists a strong association between monsoon activity over south asia and changes in the intensity of the equatorial walker circulation when active monsoons occur over south asia the walker circulation becomes stronger than usual with prominent 850 mb easterlies 200 mb easterlies over the eastern pacific east of the date line an

interaction between the summer monsoons in east asia and the south china sea intraseasonal monsoon modes abstract the summer monsoons in east and southeast asia are characterized respectively by the mei yu in eastern china baiu in japan front mbf and by the monsoon trough stretching from northern indochina to the philippine sea these two major monsoon elements are separated by the north pacific anticyclone as indicated by the 850 mb zonal wind and cumulus convection over some key areas a distinct opposite phase intraseasonal variation exists between the two monsoon elements two approaches are adopted to explore the cause of this opposite phase variation which reflects the coupling between the two monsoon components 1 the correlation coefficient patterns between the 850 mb zonal wind monsoon index and the 850 mb streamfunction field and 2 the composite 850 mb streamline charts and the 120 e zonal wind cross sections it is shown that the opposite phase variation between the two monsoon elements is caused by the anomalous circulation associated with the northward migrating 30 60 day monsoon tr

pliocene to quaternary deformation in south east sayan siberia initiation of the tertiary compressive phase in the southern termination of the baikal rift system the south east sayan area wof the lake baikal is subjected to a very complex tectonic setting where the extensional stress field of the baikal rift system meets the compressional stress field generated by the india asia collision further south using satellite images aerial photographs srtm dem field mapping of geomorphological structures and published neotectonics and geological data we show that most of the relief in the se sayan initiated during late pliocene pleistocene through compressive reactivation of inherited structures by late quaternary clockwise rotation of the compressive field generated strike slip faulting and local secondary extension still within a general compressional stress field we demonstrate that the formation of the small scale extensional basins within the east sayan range is not linked to general the extension in the baikal rift system nor to a possible asthenospheric plume acting at the base of the crust but rather to the rotation of small rigid tectonic blocks driven by the compression

global view of the intraseasonal oscillation during northern winter abstract in this study svd analysis is applied to a normalized 200 mb streamfunction olr covariance matrix to extract the most recurrent coupled pattern in the northern winter after the removal of the climatological seasonal cycle and seasonal means for each winter the first two singular vectors are on an intraseasonal timescale and the combination of the two forms an oscillation it is characterized by eastward propagation in the indian ocean and the western pacific standing oscillations in both the tropics and the extratropics and the poleward propagation of a zonally symmetric structure although there exists an eastwardly propagating pattern the phase relationship between geopotential wind and streamfunction fields is inconsistent with that of equatorial kelvin waves eastward propagation is most evident in the tropics of the southern hemisphere while the signals in the northern hemisphere are characterized by standing oscillations the distinct characteristics of the northern and southern he

contrasting characteristics between the northward and eastward propagation of the intraseasonal oscillation during the boreal summer abstract this study investigates the structural and evolutionary characteristics of the eastward and northward propagating intraseasonal oscillation iso in the indian ocean and western pacific during the boreal summer along the equator the near surface moisture convergence located to the east of the deep convection region appears to result in the eastward propagation of the iso consistent with the frictional wave cisk conditional instability of the second kind mechanism proposed in previous studies the eastward propagation is characterized by sequentially downstream development of deep convection occuring mainly in certain regions such as 60 95 120 and 145 e and the date line the northward propagation of deep convection can be attributed to the low level moisture convergence located to the north this convergence is a deep structure extending from the surface to the middle troposphere near surface convergence appears only after the systems approach the landmass in the north it is sugges

the most recent 682 792 ce volcanic eruption in the jombolok lava field east sayan central asia triggered exodus of mongolian pre chinggis khaan tribes 778 786 ce abstract this study presents new data on one of the most recent historical volcanic eruptions in central asia the jombolok lava field located in the east sayan mountains southern siberia was formed during late pleistocene and holocene times at least four phases of volcanic activity have been identified and evidences associated with the last phase have been found in the upper reaches of the khi gol valley and in the oka jombolok basin the volcanic activity is represented by young basaltic lava located among older lavas live and dead trees have been sampled in the young lava field nine fragments of wood have been found embedded in lavas of the latest eruption dendrochronological analysis radiocarbon dating and the analysis of historical chronicles have shown that the latest eruption occurred during the period 682 792 ce the volcanic activity possibly triggered the migration of mongolian tribes out of the locality known in historical chronicles as ergune kun towards the onon river which 400 years later became the place of birth and rise of chinggis khaan

influence of sea surface temperature on the intraseasonal variability of the south china sea summer monsoon the objective of this study is to examine based on recently available high resolution satellite and observational data the evolution and role of sea surface temperature sst in influencing the intraseasonal variability of the south china sea scs summer monsoon sm the study focuses on the 30 60 day timescale when the northward propagating anomalies are dominant over the scs composite analysis of the sst maximum events during scs sm shows that increased sst anomalies over the scs are significantly influenced by the downward shortwave radiation flux anomalies with the suppressed surface latent heat flux anomalies supplementing to it a thermal damping of the positive sst anomalies induces positive upward heat fluxes which then destabilize the lower atmosphere between 1 000 and 700 hpa the positive sst anomalies lead the positive precipitation anomalies over the scs by 10 days with a significant correlation r 0 44 between the sst precipitation anomalies the new findings here indicate an ocean to atmosphere effect over the scs where underlying sst anomalies tend to form a favorable condition for convective activity and sustain enhanced precipitation during the scs sm it is also argued based on our observations that the negative sea level pressure anomalies induced by the positive sst anomalies play a role in enhancing the northward propagation of the intraseasonal anomalies over the scs

helium isotopes provide no evidence for deep mantle involvement in widespread cenozoic volcanism across central asia abstract small volume alkali basaltic volcanism has occurred intermittently for the past 30 my across a vast area of thick continental crust from southern siberia through mongolia to northeast china with a lack of evidence for basin and range type crustal extension or rifting models to explain the widely dispersed yet long lived volcanism tend to favour involvement of one or more mantle plume s we examine the range of 3he 4he isotope values in olivine phenocrysts from basalts and their entrained mantle xenoliths from hamar daban in southern siberia and hangai in central mongolia in order to examine whether upwelling lower mantle appears to be present beneath central asia and thus test the validity of the plume model for this region our results show that the maximum 3he 4he value for the siberian basalts is 8 12 0 2ra and the maximum value for mongolian basalts is 9 5 0 5ra these values suggest that there is no significant contribution from a high 3he 4he primordial component that would strongly argue a lower mantle source overlap with commonly reported values for morb leads us to propose that the source of the magmatism derives from the shallow asthenosphere alternative models to a deeply sourced mantle plume that may be able to explain the magmatism include a shallow thermal anomaly confined to the upper mantle but either fed laterally or caused by thermal blanketing of the large asian landmass replacement or delamination of the lowermost lithosphere in response to tectonic stresses or large scale mantle disturbance or overturn caused by a protracted history of subduction beneath central asia that ended regionally with the jurassic closure of the mongol okhotsk ocean but continues further afield with the present indo asia collision

hydrogeochemical characteristics of surface water sw and groundwater gw of the chinnaeru river basin northern part of nalgonda district andhra pradesh india groundwater and surface water samples from 47 locations 28 groundwater 10 tanks and 9 stream channel were collected during the pre monsoon may june and post monsoon season november from chinnaeru river basin chinnaeru river basin is situated 30 km east of hyderabad city and its area covers 250 km2 and falls in the survey of india toposheet no 56 k 15 the extensive agricultural industrial and urbanization activities resulted in the contamination of the aquifer to study the contamination of groundwater water samples were collected from an area and analyzed for major cations and anions various widely accepted methods such as salinity sodium absorption ratio kelly s ratio residual sodium carbonate soluble sodium percentage permeability index and water quality index are used to classify groundwater and surface water tank and stream for drinking as well as irrigation purposes besides this piper trilinear diagram wilcox diagram doneen s classification and gibb s plot were studied for geochemical controls and hydrogeochemistry of groundwater and surface water samples were studied

the 1985 86 intraseasonal oscillation and the role of the extratropics abstract an intraseasonal oscillation that occurred in the 1985 86 northern winter is documented in this study the tropical convection of this event is dominated by the mixture of a standing oscillation over the maritime continent and an eastward moving feature from the indian ocean into the central pacific the time evolution of the upper tropospheric circulation patterns instead of propagating eastward along the equator as suggested in the existing composites of the intraseasonal oscillation is characterized by a series of wave patterns in the northern hemisphere and does not complete the cycle around the globe the familiar moist kelvin wave explanation for the intraseasonal oscillation receives little support from diagnosis of this event using zonal wind height field streamfunction and potential vorticity only in the lower troposphere near the date line is the convincing evidence for its existence found a scenario for the intraseasonal oscillation which is suggested by the analysis includes

topographic effects on the eastward propagation and initiation of the madden julian oscillation abstract this study investigates the relationship between deep convection and heating anomaly in the madden julian oscillation mjo and the tropical topography the eastward propagation of the deep heating anomalies is confined to two regions the indian ocean and the western pacific warm pool superimposed on the eastward propagation is a series of quasi stationary deep heating anomalies that occur sequentially and discretely downstream in a leapfrog manner in the central indian ocean the maritime continent tropical south america and tropical africa the deep heating anomaly usually preceded by near surface moisture convergence and shallow heating anomalies tends to occur on the windward side of the tropical topography in these regions except the central indian ocean under the prevailing surface easterly anomaly of the mjo it is suggested that the lifting and frictional effects of the tropical topography and landmass induce the near surface moisture convergence anomaly which in turn triggers

cenozoic tectonic evolution of asia a preliminary synthesis abstract asia has been a major testing ground for various competing models of continental deformation due to its relatively well understood plate boundary conditions in the cenozoic exceptional exposure of active structures and strain distribution and widespread syn collisional igneous activity as a proxy for the thermal state of the mantle and crust two cenozoic orogens dominate the continent the himalayan tibetan orogen in the east induced by the india asia collision and the turkish iranian caucasus orogen in the west induced by the arabia asia collision the development of the two orogens was accomplished by shortening in the early stage followed by strike slip faulting and extension in the late stage in the himalayan tibetan orogen shortening across two discrete thrust belts at 55 30 ma in southern and northern tibet created a large intracontinental basin the paleo qaidam basin in between subsequent crustal thickening and a possible thermal event in the mantle e g convective removal of central tibetan mantle lithosphere may have raised the elevation of this early intra plateau basin up to 2 3 km to its current height collision between india and asia also caused lateral extrusion of southeast asia between 32 ma and 17 ma the latest stage of the india asia collision was expressed by north trending rifting and the development of trench facing v shaped conjugate strike slip faults in central mongolia central tibet eastern afghanistan and southeast asia in the turkish iranian caucasus orogen early crustal thickening in the orogenic interior began at or prior to 30 20 ma this style of deformation was replaced by strike slip faulting at 15 5 ma associated with further northward penetration of arabia into asia westward extrusion of the anatolia turkey block and rapid extension across the sea of crete and sea of aegean the late stage extension in both orogens was locally related to extensional core complex development the continental margin extension of east asia was developed in two stages initially in a widely distributed zone that has an east west width of 500 800 km during 65 35 ma which was followed by localized extension and opening of back arc basins associated with the development of spreading centers at 32 17 ma e g japan sea or east korea sea bohai bay and south china sea opening of the back arc basins could be induced by 1 rapid eastward migration of the western pacific trench system or 2 oblique subduction of pacific plate beneath asia that had produced a series of en echelon right slip primary shear zones linking with back arc spreading centers oriented obliquely to the strike of the nearby trench since 15 ma the eastern margin of asia became contractional in the east west direction as indicated by the collapse of back arc basins in the western pacific and the development of fold thrust belts along the eastern continental margin coeval with the contraction is widespread east west extension in siberia north china and the tibetan plateau the above observations can be explained by a change in boundary condition along the eastern margin of asia that allowed the thickened asian continent to spread eastward causing east west extension in its trailing edge and east west compression in its leading edge in west asia continental margin extension started at about 25 20 ma in the aegean and cretan regions which was associated with a rapid southward retreat of the hellenic arc the complex evolution of cenozoic deformation in asia may be explained by a combined effect of temporal changes in plate boundary conditions thermal evolution of the upper mantle perturbed by collisional tectonics and the built up of gravitational energy through crustal thickening and thermal heating although the past research in asia has treated the india asia and arabia asia convergence as separate collisional processes their interaction may have controlled the far field cenozoic deformation in asia the most pronounced result of this interaction is the creation of a northeast trending 300 400 km wide and 1500 km long zone of northwest striking right slip faults which extends from the zagros thrust belt in the south to western mongolia in the north and links with the active tian shan and altai shan intracontinental orogens cenozoic deformation and coeval igneous activity spatially overlap with one another in the himalayan tibetan and turkish iranian caucasus orogens a large cenozoic magmatic gap exists between tibet in the south and mongolia in the north where cenozoic deformation has not been associated with any coeval igneous activity finally cenozoic igneous activity is always associated with jurassic cretaceous magmatic arcs suggesting a causal relationship between the early arc magmatism and later syn collisional magmatism

intracontinental porphyry and porphyry skarn mineral systems in eastern china scrutiny of a special case made in china in this contribution we discuss a series of porphyry and porphyry skarn mineral systems which constitute important metallogenic belts along major lithospheric breaks and or collision zones that form the margins of the north china craton and the yangtze craton we describe a selection of porphyry and porphyry skarn deposits in the great xing an range in northeast china the yanshan liaoning xilamulum belts along the northern margin of the north china craton the qinling orogen and the middle lower yangtze river valley along the bonudaries between the north china and the yangtze cratons the occurrence of platform carbonate successions may have played some role in the evolution of ore fluids that resulted in the formation of porphyry skarn deposits the porphyry deposits of eastern china although sharing some common features with classic porphyry systems that are related to convergent margins do exhibit unusual features particularly in terms of ore fluid compositions the common presence of fluorite hydrothermal alteration assemblages which tend to be less hydrous than the porphyry at convergent margins on the other hand the porphyry mineral systems of eastern china have some similarities with the climax type porphyry a major tectonothermal event yanshanian which took place in the jurassic cretaceous affected eastern china and most of the eastern margin of asia this yanshanian event was responsible for the magmatism and associated mineral systems in the region the granitoid intrusions and accompanying porphyry and porphyry skarn deposits were developed along orogenic belts and major structural discontinuities mostly along the tectonic boundaries between the north china and yangtze cratons and between the northern margin of the north china craton and the mongolia siberia plate the porphyry and porphyry skarn deposits herein described include chalukou in the great xing an range orogen jiguanshan in the xilamulun metallogenic belt xiaojiayingzi lanjiagou chehugou yuanbaoshan in the yanshan liaoning belt nanninhu yuchiling jinduicheng lemeingou in the east qinling orogen tongchakoou shaxi from the middle lower yangtze river valley the role of mantle lithosphere dynamics in eastern china which led to the formation of these porphyry and porphyry skarn mineral systems is discussed and reviewed

anticorrelated intensity change of the quasi biweekly and 30 50 day oscillations over the south china sea 1 over the south china sea the year to year variations in the intensity of the quasi biweekly qbw and 30 50 day oscillations during june july are anti correlated an explanation is offered for the out of phase relationship we found during strong qbw years the june july mean convection and easterly vertical shear are enhanced over the equatorial western central pacific with corresponding low level cyclonic meridional shear to the northwest these conditions concurring with the equatorial eastern pacific warming are favorable for emanation of moist rossby waves from the equatorial western pacific on the other hand the 30 50 day becomes active when the mean convection is enhanced over the eastern indian ocean and maritime continent where this mode stems from and develops which often corresponds to cold western io one of these two large scale settings often occurs in the absence of the other so that when one mode is strong during june july the other mode tends to be weak

baikal rift zone structure and geodynamics abstract the cenozoic baikal rift zone is superimposed on the caledonian baikal fold belt representing the suture between the precambrian siberian craton and several microcontinents the baikal rift zone consists of a system of disconnected fault bounded basins and extensional and wrench faults that straddles a major arch having a topographic relief of 2 3 km rifting activity commenced during the oligocene and is still active as evident from high seismicity of the baikal rift zone across the baikal rift zone upper crustal extension is considerably smaller than would be expected from its crustal thickness which decreases by 8 11 km across the baikal basins as compared to the adjacent unextended areas the discrepancy between upper and lower crustal attenuation could be attributed to intrusion of a major diapir indeed geophysical data indicate that the sayan baikal dome coincides with such a diapir the top of which is located at the crust mantle boundary this intrusion is held responsible for oligocene and quaternary doming of the rift zone development of the intra continental baikal rift system is thought to be related to asthenospheric diapirism active rifting however intra plate stresses in conjunction with the himalayan collision may have played some role

revised cloud and convective parameterization in cfsv2 improve the underlying processes for northward propagation of intraseasonal oscillations as proposed by the observation based study the performance of revised climate forecast system version 2 cfsv2 are evaluated on the simulation of the underlying cloud and convective processes associated with the strong and weak boreal summer intraseasonal oscillations bsisos events the revised version of the cfsv2 consists of a six class weather research forecasting single moment wsm6 cloud microphysics scheme and the default version has zhao and carr zc cloud microphysics scheme both the version uses revised simplified arakawa schubert rsas convection scheme the study reveals that the revised version of cfsv2 rsas wsm is able to better simulate the northward propagation of bsisos and associated dynamical and thermodynamical mechanism put forward by earlier observation based studies it is found that the large scale organized northwest southeast tilted structure of rain band is better captured in rsas wsm simulation as compared to the default version of cfsv2 rsas zc during strong bsiso events further the reasonable large scale or stratiform rainfall associated with the northward propagating strong bsiso events is seen in rsas wsm while it is completely missing in rsas zc simulation the pressure latitude profiles of cloud liquid water clw and cloud ice cli show more realistic steady northward propagation in rsas wsm simulation consistent with the clw and cli distribution and their influence on the large scale heating structure the large scale condensation heating shows quasi periodic northward propagation in rsas wsm whereas such type of distribution is not captured in rsas zc simulation the realistic representation of cloud processes in wsm leads to simulate reasonable dynamical and thermodynamical processes associated with the strong bsiso events which follows the observation based hypothesis proposed by earlier studies

role of stratiform rainfall in modifying the northward propagation of monsoon intraseasonal oscillation 1 the stratiform and convective rain rate measurement from the tropical rainfall measuring mission trmm satellite data can give a realistic idea of the latent heating distribution in the tropics the vertical profile of diabatic heating related to the convective and the stratiform rain is known to modulate the dynamical response of atmosphere and also the vertical structure of madden julian oscillation in this study the contribution of the stratiform and convective rain rate to the total rain rate during different phases of the northward propagating boreal summer monsoon intraseasonal oscillation iso is examined using the trmm data two new insights have emerged from this analysis first unlike conventional wisdom the convective component shows weak northward propagation and grows and decays in situ during the evolution of active and break phases while the northward propagation of the monsoon iso is largely achieved by organized movement of the stratiform component second the trademark meridional dipole pattern of total rainfall between the monsoon trough zone and the southern equatorial indian ocean also arises largely from the contribution of stratiform anomalies as the northward propagation of the monsoon iso is known to be due to the anomalous response of the atmosphere to heating in the presence of mean easterly vertical shear modification of the vertical profile of heating due to a contribution from stratiform rain could influence the northward propagation of the monsoon iso this hypothesis is tested using a simple global atmospheric circulation model to study the response of the convective and stratiform heating profiles on the modification of the mean condition modification in the large scale response of the atmosphere as a result of proper specification of convective and stratiform heating anomalies indicates that the presence of stratiform heating favors the northward propagation of the heat source thereby facilitating the positive feedback leading to northward propagation of the monsoon iso these results underline the importance of simulating the partitioning of convective and stratiform rain by cumulus parameterization in climate models if they have to get the space time structure of the summer isos correct

jom bolok holocene volcanic field in the east sayan mts siberia russia structure style of eruptions magma compositions and radiocarbon dating jom bolok volcanic field is located in the east sayan mts of siberia russia a portion of the asian convergent zone it is located at the boundary of the riphean tuva mongolia massif which was probably reactivated because of the interplay between far field tectonic stress derived from the india asia collision zone and extension in the south western baikal rift system the volcanic field comprises a number of hawaiitic lava flows of various lengths which flowed down paleorivers flows were fed by fissure eruptions and the largest lava flow field was dated as 7 130 140 cal 14c years bp using a buried organic sample found inside the associated cinder cone this lava flow field is about 70 km long 100 km2 in area and 7 9 km3 in volume the area and volume of this flow field ranks this eruption highly in the global record of fissure fed effusive eruptions this lava flow field makes up 97 of the entire jom bolok volcanic field a fact which raises a puzzling question why and or how did a relatively small volume volcanic field produce such a large volume individual eruption a working hypothesis is that a pond of sublithospheric melt accumulated over a relatively prolonged period this was then rapidly drained in response of tectonic changes triggered by unloading of ice in the early holocene

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

hydrochemical assessment of groundwater in alluvial aquifer region jalandhar district punjab india hydrogeochemical investigations have been carried out in the jalandhar district punjab india to decipher hydrochemistry and groundwater quality for its suitability for drinking and irrigation purposes most of the irrigation practices depend on shallow or deeper tube wells as an alternative source to the surface water and consequently rapid decline of the groundwater levels based on sodium absorption ratio sodium chloro alkaline indices are cai i cai ii and permeability index results most of the groundwater samples collected in the study area were good for drinking and irrigation purposes the hydrochemical facies suggested that the fluids interacted with carbonate minerals and have not been significantly altered by cation exchange dissolution of evaporates and or mixing with more evolved waters the analysis of gibbs plot indicated the groundwater chemistry controlled by weathering process of silicate minerals the aim of the study was to assess the spatial distribution of hydrogeochemical parameters and to determine controlling factor of geochemical process of the water composition based on the major ion chemistry of 44 groundwater samples collected in the study area

multi scale interactions of equatorial waves associated with tropical cyclogenesis over the western north pacific the tropical cyclone tc centric approach developed in previous studies tends to overemphasize the direct impact of tropical waves and underestimates their large scale modulation of western north pacific wnp tropical cyclogenesis tcg to overcome these limitations this study proposes a new approach based on empirical orthogonal function analyses to re examine associations of multiple waves including the madden julian oscillation mjo quasi biweekly oscillation qbwo convective equatorial rossby er waves and synoptic scale waves ssws with wnp tcg events there is a close association between wnp tcg events total of 273 tcs in this study and ssws 64 mjo 68 qbwo 64 and er 65 waves these suggest that ssw is critical for many tcg events and all of these intra seasonal waves significantly modulate tcg events a majority of tcs 79 were found to be related to more than one wave type indicating an important role for a combination of dynamic and thermodynamic conditions associated with multiple waves in tcg events further analyses show that ssw activity is strongly modulated by the mjo and er waves while the qbwo has no significant impact on ssws during convectively active mjo and er phases stronger ssw trains with more distinct southeast northwestward aligned structures can be found compared to convectively inactive phases similar intra seasonal modulation of the transition from the mixed rossby gravity waves from the equatorial central pacific to the ssw trains over the wnp by the three waves is noted with such transitions largely favored during convectively active mjo and er phases

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

the boreal summer intraseasonal oscillation relationship between northward and eastward movement of convection the summertime intraseasonal oscillation iso is an important component of the south asian monsoon lagged regressions of intraseasonally filtered 25 80 days outgoing longwave radiation olr reveal that centers of convection move both northward and eastward from the central equatorial indian ocean subsequent to the initiation of an iso eastward movement of convection is also seen at indian subcontinent latitudes 10 8 208n based on the regression results the summertime iso convection signal appears as a band tilting northwestward with latitude and stretching from the equator to about 208n viewed along any meridian convection appears to propagate northward while equatorial convection propagates to the east to examine the robustness of the connection between eastward and northward movement individual isos are categorized and composited relative to the strength of the large scale eastward component of convection in the central equatorial indian ocean it is found that the majority of isos that exhibit northward movement onto the indian subcontinent 42 out of 54 isos or 78 also exhibit eastward movement into the western pacific ocean it is also found that when convection in the central indian ocean is not followed within 10 20 days by convection in the western pacific ocean 12 out of 54 isos or 22 the independent northward movement of convection in the indian ocean region is somewhat stunted the link between the eastward and northward movement of convection is consistent with an interpretation of the summertime iso in terms of propagating equatorial modes the northward moving portion of convection is forced by surface frictional convergence into the low pressure center of the rossby cell that is excited by equatorial iso convection a similar convergence pattern is seen for the northern winter iso but it does not generate poleward movement due to relatively cool ssts underlying the surface convergence

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

deep structure and mechanical behavior of the lithosphere in the hangai hovsgol region mongolia new constraints from gravity modeling we investigate the deep structure and mechanical behavior of the lithosphere beneath the hangai ho vsgo l region central mongolia asia in order to explain the origin and support of large scale doming in this deforming area we propose a gravity and topography based model which accounts for constraints provided by other independent results from xenolith and tomography studies deviations of the measured gravity from the theoretical airy compensation model are examined a long wavelength low gravity anomaly is spatially correlated with low pressure and shear velocity anomalies in the mantle and with the extent of cenozoic volcanic outcrops we interpret it as a deep seated low density asthenosphere and model its effect on the bouguer gravity signal using a 600 km wide light asthenospheric body density reduction 310 kg m 33 located between 100 and 200 km north and south of the hangai ho vsgo l dome short wavelength highs and lows in the bouguer gravity field are clearly correlated with fault activity they seem to reflect opposite senses of flexure of a rigid lithosphere across two major active faults the sayan and bogd transpressional systems and are modeled by moho deflections of 10 and 5 km respectively finally a shortwavelength 200 km high amplitude 350 mgal gravity residual remains beneath the highest part of the mountain bulge namely the hangai dome based on previously published xenolith analyses we interpret it as an anomalous low density body which may represent underplated cumulates or mafic granulites at the uppermost mantle we conclude that upper mantle dynamics necessarily play an important role in the origin and evolution of the hangai ho vsgo l dome but without requiring significant thinning of the lithosphere fl 2002 elsevier science b v all rights reserved

mechanisms of monsoon low frequency variability surface hydrological effects abstract observations indicate that monsoon systems are characterized by orderly large scale and low frequency variations with a time scale of two weeks and sometimes longer regions of ascending motion are observed to form to the north of the equator and propagate slowly northward across southeast asia the propagation appears to be associated with the active break sequence of the summer monsoon which acts as a modulator on the activity of the synoptic scale disturbances a zonally symmetric non linear two layer model containing an interactive ocean and a continent poleward of 18 n is used to investigate the mechanisms which produce the observed low frequency variability only when a full hydrology cycle is considered does the model product variations which resemble the observed structures mechanisms are traced to include the interaction of the components of the total heating function the sensible heat input in the boundary layer although considerably smaller than the other heating components de

imaging a mantle plume beneath the french massif central abstract teleseismic tomography is now widely recognised as a very powerful tool for studying the velocity structure of the lithosphere asthenosphere system on both local and regional scales a prime objective is to identify velocity perturbations and to constrain their location and intensity here we use the arrival times of p waves from teleseismic events recorded by a dense network of mobile and permanent stations within the french massif central to derive a 3d p velocity model for an area of 425 km 300 km combined with knowledge of the basement geology of the area and the timing and geochemical characteristics of tertiary quaternary volcanic activity we consider that the velocity model provides unequivocal evidence for the ascent of a thermally and chemically anomalous mantle plume beneath the massif central during tertiary times our model is consistent with regional bouger gravity anomalies documented patterns of neogene recent uplift and deformation fabrics within lithosphere derived mantle xenoliths exhumed by the volcanics

mechanism for northward propagation of boreal summer intraseasonal oscillation convective momentum transport 1 this study demonstrates that the momentum transport by cumulus convection plays a significant role in the organization and northward propagation of intraseasonal iso convection anomalies over the indian and western pacific regions during boreal summer a version of seoul national university s atmosphere ocean coupled general circulation model simulates northward propagation when convective momentum transport cmt is implemented the northward propagation disappears when cmt is disabled an axially symmetric shallowwatermodel withaparameterized cmtis used to understand the role of cmt in the northward propagation of iso the basic mechanism of northward propagation is the lower level convergence to the north of convection which is induced by the secondary meridional circulation associated with large momentum mixing by convection in the region of large mean vertical shear a large meanverticalshearexistsinsouthasianregionduringboreal summer citation kang i s d kim and j s kug 2010 mechanism for northward propagation of boreal summer intraseasonal oscillation convective momentum transport geophys res lett 37 l24804 doi 10 1029 2010gl045072

the 30 50 day mode at 850 mb during monex abstract the analyzed wind field at 850 mb during the summer monsoon experiment monex is subjected to a time series analysis to confirm the existence of a peak in the time range of 30 50 days having established that this study presents a mapping of the motion field for this time scale in this short paper we illustrate the steady meridional propagation of a train of troughs and ridges that seem to form near the equator and dissipate near the himalayas the meridional scale of this mode is around 300 km and its meridional speed of propagation is 0 75 latitude per day the amplitude of the wind for this mode is around 3 6 m s 1 the salient contributions here are the mapping and the demonstration of a very regular behavior of this mode its existence is here noted from a period well before the onset of monsoon i e from early may to late july three major storms during monex were noted to form within the trough line of this system and the period of major cessation of rains over the indian subconti

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

asthenospheric flow and origin of volcanism in the baikal rift area the origin of low volume hotspot like volcanism often observed in continental rift areas is debated as is the nature of the flow in the mantle beneath in this paper we assemble seismic constraints on the mantle flow below the baikal rift zone we combine new evidence from upper mantle tomography and from a radially anisotropic shear velocity profile measured beneath and se of the rift with published shear wave splitting constraints on azimuthal anisotropy fast directions of azimuthal anisotropy are perpendicular to the rift on both of its sides stable siberian platform lithosphere on the northern side extends down to 200 km on the southern side the lithosphere is only 60 70 km thick this asymmetry with the thick cratonic root forming a barrier to convective flow inhibits a mid ocean ridge like flow pattern the radially anisotropic profile yields evidence for horizontal flow in the upper asthenosphere 60 100 km se of the rift but no evidence for vertical flow these results are consistent with horizontal asthenospheric flow nw to se perpendicular to the rift from beneath the thick siberian towards the thin baikal mongolian lithosphere when asthenosphere ascends from the 200 km depth beneath the craton to shallower depths beneath the rift decompression melting of embedded veins of enriched rock can produce the hotspot like basaltic volcanism observed the occurrence of such veins of enriched mantle in sub cratonic asthenosphere has been predicted by geochemical mantle models we propose that sub horizontal asthenospheric flow from beneath cratons is a common cause for hotspot like volcanism in continental rift zones

he sr and nd isotopes of mantle derived xenoliths in volcanic rocks of ne china abstract abundances and isotopic ratios of he and isotopic ratios of sr and nd have been measured for 18 mantle derived xenoliths from three cenozoic volcanic provinces in ne china the xenoliths are characterized by low he concentrations 2 3 10 9 2 5 10 7 cm3 stp g 1 and large variations of 3he 4he ratios 1 6 10 7 15 8 10 6 or r ra 0 1 11 3he 4he 87sr 86sr and 143nd 144nd ratios in xenoliths from kuandian holocene volcanic provinces are consistent with those observed in mid oceanic ridge basalt morb indicating that the source of he sr nd in the lithospheric mantle is chemically and isotopically identical to that of morb reservoir however xenoliths in huinan pleisteocene holocene volcanic province are characterized by slightly low 3he 4he ratios r ra 4 3 6 5 and more radiogenic sr and nd the age corrected 3he 4he ratios suggest that their time integrated ratio of u th 3he is slightly elevated compared to the depleted upper mantle the hannuoba xenoliths in the miocene volcanic province show much lower and wider variable 3he 4he ratios which is most likely caused by in situ radiogenic 4he accumulation since it erupted on to the surface the he sr nd results suggest chemical and isotopical heterogeneity in the subcontinental mantle beneath ne china

horizontal and vertical structures of the northward propagating intraseasonal oscillation in the south asian monsoon region simulated by an intermediate model abstract the structures and mechanism of the northward propagating boreal summer intraseasonal oscillation bsiso in the southern asian monsoon region are simulated and investigated in a three dimensional intermediate model 3d model the horizontal structure of the intraseasonal variability in the 3d model depicts the kelvin rossby wave type disturbance which may or may not produce the northward propagating disturbance in the indian ocean depending on the seasonal mean background winds two experiments are conducted in order to identify what characteristic of seasonal mean background can induce the northwestward tilted band in the kelvin rossby wave whose overall eastward movement gives the impression of the northward propagation at a given longitude when the prescribed boreal summer mean winds are excluded in the first experiment the phase difference between the barotropic divergence tendency and convection disappears consequently the rossby wave type convection forms a zonally elongated band

a model for the boreal summer intraseasonal oscillation abstract the tropical intraseasonal oscillation iso exhibits pronounced seasonality the boreal summer iso is more complex than its winter counterpart due to the coexistence of equatorial eastward off equatorial westward and northward propagating low frequency modes and their interactions based on observational evidence and results obtained from numerical experiments a mechanism is proposed for the boreal summer iso in which the northern hemisphere summer monsoon nhsm circulation and moist static energy distribution play essential roles with a climatological july mean basic state the life cycle of model low frequency waves consists of four processes an equatorial eastward propagation of a coupled kelvin rossby wave packet an emanation of moist rossby waves in the western pacific a westward propagation and amplification of the rossby waves in south asian monsoon regions and a reinitiation of the equatorial disturbances over the central indian ocean the life cycle spans about one month and p

structure of the crust in the baikal rift zone and adjacent areas from deep seismic sounding data abstract 2 d p wave velocity models of the crust along dss profiles have been used together with 2 d seismic tomography for constructing maps of the moho topography and average p wave velocity in the crust in baikal rift zone brz and adjacent areas there are significant changes of moho depth between 35 and 50 km but there is no pronounced crustal thinning beneath the rift axis instead changes in crustal thickness appear to be related to accretion entities including the transition between the archean craton and the tectonic collage of the transbaikal fold belt taking into account the decrease in resolution of the deep seismic sounding dss method with depth it was found that the crust at a depth of approximately 20 km could be divided into two parts the interval velocities in the upper and lower parts of the crust are inversely correlated both within the craton and in the transbaikal belt locally this relationship does not hold and as such may be used to discriminate tectonic blocks velocity anomalies coincident with the position of the baikal rift zone are distinctly seen in the upper part of the crust only

the shift of convection from the indian ocean to the western pacific ocean during a 30 60 day oscillation abstract a strong 30 60 day oscillation during november december 1981 is studied using analyzed winds from the national meteorological center outgoing longwave radiation and satellite low level moisture data the outgoing longwave radiation and 150 mb velocity potential for five adjacent events are also examined consistent features include the slow 5 m s 1 propagation of convective energy over the indian ocean western pacific ocean and the fast 15 m s 1 propagation of 150 mb tropical velocity potential in regions remote from the oceanic warm pool the individual events have characteristics of the seasonal and anomalous base state within which they are embedded for the november december 1981 event we concentrate on the details of the shift of convection from the eastern indian ocean to the western pacific ocean an intense cold surge and accompanying convective increase near 110 e precede the shift cast by about 12 days the regional 150 mb circulation responds to the enhanced convection with an i

biweekly and 21 30 day variations of the subtropical summer monsoon rainfall over the lower reach of the yangtze river basin abstract the lower reach of the yangtze river basin lyrb is located at the central region of the mei yu and baiu front which represents the subtropical east asian ea summer monsoon based on the newly released daily rainfall data two dominant intraseasonal variation isv modes are identified over the lyrb during boreal summer may august with spectral peaks occurring on day 15 the biweekly mode and day 24 the 21 30 day mode these two modes have comparable intensities and together they account for above about 57 of the total intraseasonal variance both isv modes exhibit baroclinic structures over the lyrb at their extreme phases however the genesis and evolutions associated with the two modes are different considering the genesis of their extreme wet phases over the lyrb the biweekly mode is initiated by a midlatitude jet stream vorticity anomaly moving southeastward while the 21 30 day mode is primarily associated with a low level westward propagation of an anticyclonic anomaly from

volcanism in the baikal rift 40 years of active versus passive model discussion abstract in this review we focus on the volcanism that occurred in transbaikalia siberia after the closure of the mongolia okhotsk ocean the closure happened in the early jurassic after that time lithosphere in transbaikalia went through two phases of rifting in the early cretaceous and again in the late cretaceous until present the latter rifting event is known as the baikal rifting we consider the chronology of the volcanism and basin formation in the baikal rift and show that there has been a complex relationship between the two extension initiated in the central part of the rift system this area is now occupied by lake baikal sedimentary basins initially developed by deepening and widening of the central part of the rift system and then by bilateral propagation of basin formation outwards volcanism was generally offset from the axial rift considering along axis distribution of volcanism it initiated in the central part of the system and propagated bilaterally to the modern rift ends we argue that tectonic stress controlled localization of the eruptive centres extension and shearing probably caused melting at mantle depth suggestive of the passive model of volcanism however when considering the baikal rift and adjacent non rifted regions of mongolia in a wider context of tectonics and volcanism of central and east asia it is not possible to rule out that the volcanism may be associated with mantle transition zone diapirs thus the active model of volcanism may also apply the diapirs are located by regional isostatic gravity anomalies and considered as upwelling parts of the upper mantle convective cell controlled by the pacific subduction and slab stagnation in the mantle transition zone we do not see any geochemical geophysical and geochronological evidence for involvement of deeper mantle to explain volcanism in either baikal rift non rifted regions of mongolia or anywhere else within central and east asia