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

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

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

observed connection between stratospheric sudden warmings and the madden julian oscillation 1 the effect of the madden julian oscillation mjo on the northern hemisphere wintertime stratospheric polar vortex and major mid winter stratospheric sudden warmings ssws is evaluated using a meteorological reanalysis dataset the mjo influences the region in the tropospheric north pacific sector that is most strongly associated with a ssw consistent with this ssws in the reanalysis record have tended to follow certain mjo phases the magnitude of the influence of the mjo on the vortex is comparable to that associated with the quasi biennial oscillation and el nino the mjo could be used to improve intra seasonal projections of the northern hemisphere high latitude circulation and in particular of the tropospheric northern annular mode at lags exceeding one month

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

on the maintenance and initiation of the intraseasonal oscillation in the ncep ncar reanalysis and in the gla and ukmo amip simulations in this study satellite derived outgoing longwave radiation olr and the reanalysis from the national centers for environmental prediction national center for atmospheric research are used as verification data in a study of intraseasonal variability in the goddard laboratory for atmospheres gla and the united kingdom meteorological office ukmo atmospheric general circulation models these models simulated the most realistic intraseasonal oscillations io of the 15 atmospheric model intercomparison project models previously analyzed during the active phase of the intraseasonal oscillation convection is observed to migrate from the indian ocean to the western central pacific ocean and into the south pacific convergence zone spcz the simulated convection particularly in the gla model is most realistic over the western central pacific ocean and the spcz in the reanalysis the baroclinic structure of the io is evident in the eddy stream function and eastward migration of the anticyclone cyclone pairs occurs in conjunction with the eastward development of convection both the gla and ukmo models exhibit a baroclinic structure on intraseasonal time scales the gla model is more realistic than the ukmo model at simulating the eastward migration of the anticyclone cyclone pairs when the convection is active over the western central pacific in the ukmo model the main heating is located off the equator which contributes to the irregular structures seen in this model on intraseasonal time scales the maintenance and initiation of the intraseasonal oscillation has also been investigated analysis of the latent heat flux indicates that evaporative wind feedback is not the dominant mechanism for promoting the eastward propagation of the intraseasonal oscillation since evaporation to the west of the convection dominants the data suggest a wave cisk conditional instability of the secondkind type mechanism although the contribution by frictional convergence is not apparent in the gla model enhanced evaporation tends to develop in place over the west pacific warm pool while in the ukmo simulation westward propagation of enhanced evaporation is evident it is suggested that lack of an interactive ocean may be associated with the models systematic failure to simulate the eastward transition of convection from the indian ocean into the western pacific ocean this hypothesis is based upon the examination of observed sea surface temperature sst and its relationship to the active phase of the intraseasonal oscillation which indicates that the io may evolve as a coupled ocean atmosphere mode the eastward propagation of convection appears to be related to the gradient of sst with above normal sst to the east of the convection maintaining the eastward evolution and decreasing sst near the western portion of the convective envelope being associated with the cessation of convection

evolution of photoautotrophy and early atmospheric oxygen levels abstract current photochemical models suggest that oxygen levels in the prebiological atmosphere were extremely low most probably remaining in the range 10 8 10 14 pal present atmospheric level it is therefore reasonable to assume that only life processes were able to overwhelm these minor o2 pressures with free oxygen resulting from the reduction of carbon dioxide to the carbohydrate level during photoautotrophic carbon fixation using water as an electron donor 2 h 2 o co 2 rarr h ch 2 o h 2 o o 2 it is by now well established that reduced organic carbon is a common constituent of sedimentary rocks from the very start of the geological record 3 8 ga ago both direct assays and inferences derived from a carbon isotope mass balance suggest that the corg content of archaean sediments was not basically different from that of geologically younger rocks this poses the problem of the existence 3 5 ga ago of an oxidation equivalent of such a formidable ancient corg reservoir which depending on the model adopted for the growth of the sedimentary mass through time might have amounted to between 20 and 100 of the present one low atmospheric oxygen pressures in the early precambrian that are inferred from retarded oxidation reactions notably in the ancient continental weathering cycle are likely therefore to indicate extremely rapid processes of oxygen consumption in other parts of the system e g hydrosphere rather than the general absence of photosynthetic oxidation equivalents during this time

precambrian sulfur isotopes and a possible role for sulfite in the evolution of biological sulfate reduction this paper examines how and when the biochemical process of dissimilatory sulfate reduction evolved during sulfate reduction by modern sulfate reducing bacteria the sulfide produced is enriched in 32s compared to the starting sulfate this phenomenon is used to interpret the origin of sulfide in both modern and ancient environments the isotopic compositions of precambrian sulfide and sulfate minerals suggests that until ca 2 0 ga before present b p sulfide was the major s component in sediments and the hydrosphere and was formed mainly by volcanogenic processes after ca 2 0 ga b p when free oxygen was maintained in the atmosphere by the biological photolysis of water sulfate became the major sulfur component of the seas and was the main sulfur source for both biological and abiological sulfide formation dissimilatory sulfate reduction then became widespread the extent of 34s enrichment of a minor proportion of archaean and lower proterozoic volcanogenic sulfides indicates their formation by reduction of an oxidised sulfur source this source was not sulfate which formed the archaean deposits 34s so42 2 2 but most probably so2 so32 or hso3 introduced into the hydrosphere in exhalations in which h2s so2 and where isotopic equilibria favour 34s enrichment in the more oxidised sulfur compound it is suggested that 1 1 in the anoxic environments of the primitive earth sulfite was the most readily available and persistent s source to evolving procaryotes 2 2 the biochemical evolution of sulfite reduction occurred early among procaryotes and was the initial event leading to the evolution of dissimilatory sulfate reduction 3 3 dissimilatory and assimilatory sulfate reduction evolved when sulfate became the predominant sulfur compound available to the evolving procaryotes around 2 0 ga b p

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

the archean proterozoic boundary in the kaapvaal province of southern africa abstract the kaapvaal province has long been considered unusual in that archean cover sequences developed over granite greenstone gneiss terranes 3060 25 ga whereas in other provinces the oldest cover sequences are generally 2500 ga however two unconformity bounded sequences 2 5 ga and of greater inter regional extent than the unconformably underlying archean sequences can now be recognized in the kaapvaal province the two basal unconformities of these sequences are candidates for the temporally defined 2 5 ga archean proterozoic boundary the older but geologically more discordant unconformity occurs at the base of the uppermost group of the ventersdorp supergroup the pniel group and in at least five other erosional remnants in central transvaal and adjacent botswana these other remnants include parts of the buffelsfontein and wolkberg groups which heretofore have been considered to be conformable protobasinal phases of the younger transvaal succession the pniel and the other remnants are truncated by the locally well known unconformity at the base of the transvaal succession on a world wide basis cratonization and the evolution of mineralogically mature cover sequences were and continue to be diachronous the kaapvaal province is unusual only in that it also contains archean cover sequences however with major conformities at about 2 5 ga and the presence of proterozoic unconformity bounded sequences the kaapvaal province seems little different than most other provinces that contain the archean proterozoic boundary

systematic decomposition of the madden julian oscillation into balanced and inertio gravity components we present a new method for the three dimensional multivariate decomposition of the mjo into balanced and inertio gravity ig components the method analyzes global fields with no filtering involved and it provides a quantitative comparison between the contribution of the rossby kelvin and other balanced and ig modes to the mjo circulation and its teleconnections results based on the era interim reanalysis data and the multivariate mjo index show that the rossby mode with the lowest meridional index is the largest contributor to the mjo circulation over the pacific a smaller role of the kelvin mode is diagnosed over the indian ocean and the maritime continent the mjo teleconnections in the polar stratosphere appear associated with the leading balanced vertical modes the presented method shows new ways of evaluating the mjo structure and its global impacts in weather and climate models

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

role of maritime continent land convection on the mean state and mjo propagation abstractthe maritime continent mc region is known as a barrier in the life cycle of the madden julian oscillation mjo during boreal winter the mjo detours the equatorial mc land region sout

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

dynamics oriented diagnostics for the madden julian oscillation abstractrealistic simulations of the madden julian oscillation mjo by global climate models gcms remain a great challenge to evaluate gcm simulations of the mjo the u s clivar mjo working group developed a standardized set of diagnostics providing a comprehensive assessment of statistical properties of the mjo here a suite of complementary diagnostics has been developed that provides discrimination and assessment of mjo simulations based on the perception that the mjo propagation has characteristic dynamic and thermodynamic structures the new dynamics oriented diagnostics help to evaluate whether a model produces eastward propagating mjos for the right reasons the diagnostics include 1 the horizontal structure of boundary layer moisture convergence blmc that moistens the lower troposphere to the east of a convection center 2 the preluding eastward propagation of blmc that leads the propagation of mjo precipitation by about 5 days 3 the horizontal structure of 850 hpa zonal wind and its

trace element and upb isotope compositions of pyrite types in the proterozoic black reef transvaal sequence south africa implications on genesis and age abstract the proterozoic black reef is in most cases indistinguishable from the gold uranium and pyrite bearing archaean witwatersrand reefs however the prevailing opinion that the black reef gold mineralization was largely derived from reworking of the underlying kimberley reef is not supported by the morphology trace element geochemistry and u pb isotope data on detrital pyrite in these reefs the grade of metamorphism recorded in the black reef quartzite formation is significantly lower than the 300 400 c that has been proposed for the sediments of the witwatersrand supergroup the u pb isotope and trace element geochemical signatures in pyrite have therefore been preserved in the black reef the morphological and compositional differences retained by the detrital and synsedimentary pyrite types both occurring together in the black reef imply that they were formed by different processes and in contrasting geochemical environments in the black reef the data for the detrital pyrite are consistent with their derivation from a 3000 2800 ma granitic probably hydrothermally altered source region by contrast the geochemical and pb isotopic composition of the concretionary pyrite is interpreted to reflect its synsedimentary formation in a lagoonal or tidal flat environment prior to 2500 ma the morphology primary mineral inclusions and the unradiogenic pb isotopic compositions preserved in the black reef detrital pyrite are irreconcilable with models proposed for the formation of witwatersrand pyrite by a process of pyritization of fe bearing detrital minerals fluids present in the black reef depositional diagenetic environment were anomalously enriched in radiogenic pb and any transformation process would not be able to escape acquiring this enriched pb isotopic signature

a possible meteor shower on the moon over the 3 day period from 12 to 14 october 1990 the sodium abundance in the lunar atmosphere at 80 south increased by 60 while interspersed measurements at the equator showed no substantial change the source is suggested to be an unknown meteor shower with a radiant near the south ecliptic pole a low relative velocity of 20 km sec combined with small particle masses would keep the shower below the detectability threshold of radar the stream could evolve from a reasonable asteroidal or cometary orbit with perihelion somewhat greater than 1 astronomical unit au and a major axis of a few au the short residence time of lunar sodium makes it much more favorable than the terrestrial sodium layer for detection of such an event

oxygen and ozone in the early earth s atmosphere abstract the precise amount of o2 and o3 in the earth s prebiological paleoatmosphere has been a topic of considerable discussion in the past since the photolysis of h2o and co2 the prebiological mechanisms to produce o2 depends on the ultraviolet uv flux from the sun a reliable quantification of the problem requires detailed knowledge of such flux using the most recent astronomical observation of young stars from the international ultraviolet explorer as well as a detailed photochemical model of the paleoatmosphere we find that the amount of o2 in the prebiological paleoatmosphere may have been as much as 106 times greater than previously estimated some of the implications of this new value are discussed

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

a unified moisture mode framework for seasonality of the madden julian oscillation abstractthe madden julian oscillation mjo exhibits pronounced seasonality while it is largely characterized by equatorially eastward propagation during the boreal winter mjo convection undergoes marked poleward movement over the asian monsoon region during summer producing a significant modulation of monsoon rainfall in classical mjo theories that seek to interpret the distinct seasonality in mjo propagation features the role of equatorial wave dynamics has been emphasized for its eastward propagation whereas coupling between mjo convection and the mean monsoon flow is considered essential for its northward propagation in this study a unified physical framework based on the moisture mode theory is offered to explain the seasonality in mjo propagation moistening and drying caused by horizontal advection of the lower tropospheric mean moisture by mjo winds which was recently found to be critical for the eastward propagation of the winter mjo is also shown to play a dominant role in operating t

field relations and strontium isotope systematics of the marginal rocks of the eastern bushveld complex the well exposed basal contact of the eastern bushveld complex was mapped at scales of 1 10 000 and 1 20 000 along 130 km of strike and through a 9 km vertical section field relations petrography and geochemistry of the marginal rocks and associated sills have aided their subdivision into two main groups a broadly pyroxenitic group rims the complex from its base to the top of the pyroxenitic subzone of the critical zone a gabbroic group occurs above this level each group consists of a number of closely related rock types most of which have sill analogs rocks of the first group b1 include pyroxenites norites and peridotites all of which may have quench textures all contain orthopyroxene en 78 plagioclase an 65 and chromite with subordinate clinopyroxene and biotite rare earth element patterns are mostly strongly fractionated ce n yb n approximately 10 and have 40x chondritic abundances at ce their initial strontium isotope ratios at 2 05 b y fall in the range 0 7032 to 0 7057 and rb sr ratios approximate 0 2 the gabbroic group consists of microcrystalline two pyroxene gabbros b2n and b3n and their coarser grained equivalents b2 and b3 that border the upper critical and main zones respectively mineral assemblages are dominated by plagioclase approximately an 55 clinopyroxene and orthopyroxene approximately en 63 with abundant magnetite and traces of ilmenite and biotite their rare earth element patterns are less fractionated than b1 rocks the b2n and b2 family have ce n yb n approximately 6 and 30x chondritic abundances at ce the b3n and b3 rocks have ce n yb n approximately 3 6x chondritic abundances at ce and pronounced positive eu anomalies strontium isotope initial ratios at 2 05 b y fall in the range 0 706 to 0 708 and the rb sr ratios are approximately 0 02 whole rock and sr isotope compositions of the peridotitc sills can be successfully simulated by a model involving olivine fractionation from a liquid with an initial sr isotope ratio r 0 similar to that of the transition zone 0 7056 a fraction of such liquid enriched in cumulus olivine crystals when mixed with up to 30 percent of a pyroxenitic liquid with low r 0 0 7034 yields a product having the isotopic and compositional characteristics of the peridotite sills a continuum exists in the initial sr ratios through the pyroxenitic and gabbroic marginal rocks suggesting that these represent mixtures of at least two sources with distinct initial sr isotope ratio characteristics it is argued that neither magma aging nor crustal contamination adequately accounts for the sr isotope characteristics of the marginal rocks or their derived cumulates the unusual chemistry of the pyroxenitic early liquids sio 2 approximately 55 mgo approximately 13 coupled with high concentrations of incompatible elements should be considered primary

a diagnostic study of the evolution of the mjo from indian ocean to maritime continent wave dynamics versus advective moistening processes abstractthe evolution processes for propagating madden julian oscillations with strong magnitude over the indian ocean io and maritime continent mc are investigated through a diagnosis of ecmwf reanalysis data for november april 1982 2011 a scale separated lower tropospheric 1000 700 hpa moisture budget is analyzed for four stages of composite life cycle suppressed cloud developing convective and decaying overall the budgets in the io and mc are dominated by wave induced boundary layer convergence in the anomalous easterlies wc and advection starting from the suppressed stage in the central io moistening by wc and advection by easterly anomalies contributes to an initiation of the mjo convection in the western io while surface evaporation and or shallow convection moistens the central io in the following cloud developing and convective stage in the central io moistening by wc and advection by the downstream kelvin rossby wave east of central io lead to eastward propagation of deep conve

magnetospheric influence on the moon s exosphere 1 atoms in the thin lunar exosphere are liberated from the moon s regolith by some combination of sunlight plasma and meteorite impact we have observed exospheric sodium a useful tracer species on five nights of full moon in order to test the effect of shielding the lunar surface from the solar wind plasma by the earth s magnetosphere these observations conducted under the dark sky conditions of lunar eclipses have turned out to be tests of the differential effects of energetic particle populations that strike the moon s surface when it is in the magnetotail we find that the brightness of the lunar sodium exosphere at full moon is correlated with the moon s passage through the earth s magnetotail plasma sheet this suggests that omnipresent exospheric sources sunlight or micrometeors are augmented by variable plasma impact sources in the solar wind and earth s magnetotail

convectively forced diurnal gravity waves in the maritime continent abstractlong lived zonally propagating diurnal rainfall disturbances are a highly pronounced and common feature in the maritime continent mc a recent study argues that these disturbances can be

evidence for the transition to an oxygen rich atmosphere during the evolution of red beds in the lower proterozoic sequences of southern africa abstract strata 2 5 to 1 8 ga in southern africa appear to span the transition from a non oxidizing atmosphere to one characterized by free oxygen red beds in 2 3 to 2 1 ga unconformity bounded sequences have matrices of stained clay minerals and are spatially associated with volcanic rocks ironstones or banded iron formations which evidently were sources of iron for the matrices however red beds in 1 9 ga unconformity bounded sequences not only matrix staining but also hematitic coatings on grains these beds also have far fewer interstratified ferruginous lithologies because red beds with stained clay matrices banded iron formations pyritic witwatersrand type conglomerates and iron depleted paleosols all occur in the 2 2 ga pretoria group formation of these lithologies may not have been time dependent until atmospheric oxygen approached 10 2 atm by 1 9 ga atmospheric oxygen was 10 2 atm causing lateritic weathering and red beds with hematitic coatings on grains

photochemistry of methane in the earth s early atmosphere abstract a detailed model is presented of methane photochemistry in the primitive terrestrial atmosphere along with speculation about its interpretation steady state ch 4 mixing ratios of 10 6 10 4 could have been maintained by a methane source of about 10 11 cm 2 s 1 which is comparable to the modern biogenic methane production rate in the absence of a source methane would have disappeared in 4 years being either oxidized or polymerized into more complex hydrocarbons the source strength needed to maintain a steady ch 4 mixing ratio and the degree to which methane could have polymerized to form higher hydrocarbons depend upon the amount of co 2 present in the early atmosphere the dependence on h 2 is much weaker infrared absorption by methane and especially by other hydrocarbon species may have supplemented the greenhouse warming due to carbon dioxide a radiative model is needed to establish this effect quantitatively the destruction of the methane greenhouse early in the proterozoic may have triggered the huronian glaciation these calculations also suggest that atmospheres rich in both co 2 and ch 4 may be photochemically unstable with respect to conversion to co

primitive earth environments organic syntheses and the origin and early evolution of life abstract the precambrian is the longest and least understood period in the history of our planet there is no direct evidence which bears on the primitive earth environment the synthesis of organic compounds and the origin of life on our planet since the geological record only goes back to 3 8 ga ago to overcome this deficiency it is necessary to extrapolate backwards from 3 8 ga ago to the time when the earth was formed 4 6 ga ago and also make use of additional scientific approaches these include models of the solar nebula and planet formation comparative observations with other cosmic environments and experimental simulation studies under plausible primitive earth conditions particularly in regard to the prebiological synthesis of organic compounds a large number of interstellar organic molecules have been detected by radioastronomy in the interstellar medium particularly in places where other solar systems may be in the process of formation it is remarkable that 10 of these molecules are known to be the precursors of the most important biochemical monomers furthermore some of these monomers e g amino acids purines and pyrimidines have also been detected in carbonaceous chondrites which were presumably synthesized on the parent bodies of the meteorites or possibly in the solar nebula comparative studies on the terrestrial planets indicate that their primitive atmospheres resulted primarily from outgassing of co2 and other partially oxidized co n2 and reduced h2 ch4 nh3 h2s volatiles furthermore comets and meteorites are thought to have made a significant contribution to the reduced carbon precursors for the prebiological synthesis of biochemical compounds a brief review of the experiments carried out in the laboratory under possible primitive earth conditions shows that amino acids purines pyrimidines monosaccharides fatty acids and other compounds are readily obtained using different energy sources however the formation of oligopeptides oligonucleotides and phospholipids requires more restrictive conditions they have been synthesized by means of condensing agents such as cyanamide as well as by heating under relatively dry conditions of less than 100 c experiments have been carried out on the formation of liposomes from prebiotically synthesized phospholipids also using 2 methylimidazolide derivatives of nucleotides the template directed synthesis of polynucleotides has been demonstrated in the latter experiments a high fidelity of complementary base pairing has been observed which if further improved would approach that of enzyme catalyzed replication however it is not known how the prebiologically synthesized polymers became organized into a self replicating system at any rate the first living systems were probably very rudimentary heterotrophic micro organisms which used organic compounds from the environment for both cell components and energy they were probably followed by fermenters and eventually by autotrophic co2 reducing micro organisms similar to the methanogenic and photosynthetic bacteria

evidence for the transition to an oxygen rich atmosphere in the rooiberg group south africa a note abstract the rooiberg felsite group is a rare example of a conformable succession that apparently spans the period of evolution of an oxygen rich atmosphere this conclusion is reached indirectly from a review of the proterozoic stratigraphy of south africa and directly from a consideration of the rooiberg itself the atmospheric transition coincides with the stratigraphic interval between the dark silicic lavas and associated grey volcaniclastics of the damwal formation and the overlying red rhyodacites and intercalated red bed sedimentary rocks of the selonsrivier formation radiometric age measurements indicate that this transition occurred after 2224 21 ma but before 2090 40 ma

interaction between the mjo and high frequency waves over the maritime continent in boreal winter abstractthe two way interaction between madden julian oscillation mjo and higher frequency waves hfw over the maritime continent mc during boreal winter of 1984 2005 is investigated it is no

circulation factors determining the propagation speed of the madden julian oscillation abstractthe eastward propagating madden julian oscillation mjo events exhibit various speeds ranging from 1 to 9 m s 1 but what controls the propagation speed remains elusive this study attempt

propagating versus nonpropagating madden julian oscillation events abstractbasinwide convective anomalies over the indian ocean io associated with the madden julian oscillation mjo sometimes propagate eastward and reach the west pacific wp but sometimes do not long term observations and reanalysis products are used to investigate the difference between the propagating and nonpropagating mjo events io convection onset events associated with the mjo are grouped into three categories based on the strengths of the simultaneous dry anomalies over the eastern maritime continent and wp the io convection anomaly preferentially makes eastward propagation and reaches the wp when the dry anomaly is stronger analysis of the column integrated moist static energy mse budget shows that horizontal advection moistens the atmosphere to the east of the positive mse anomaly associated with the active convection over the io and is of sufficient magnitude to explain the eastward propagation of the positive mse anomaly interpretation is complicated however by lack of closure in

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

intraseasonal periodicities in indian rainfall abstract spectral analysis of a 70 year 1901 70 record of daily precipitation from 3700 stations in the country of india is carried out to search for periodicities on subseasonal time scales during the summer monsoon two statistically significant spectral peaks are found a 40 50 day spectral peak corresponding to the madden julian oscillation is found over most of the portion of india south of 23 n the phase of the oscillation is such that the precipitation maximum appears first over the relatively dry southeastern portion of the peninsula ten to 12 days later the precipitation peaks simultaneously all along the coast west of the western ghats and along a line running across india between 20 and 25 n the precipitation maximum then spreads slowly northward and loses significance cross spectral analysis shows strong coherence between the precipitation patterns and wind oscillations the zonal wind oscillations at 850 and 200 mb am about 180 degrees out of phase equatorward of about 20 n but in pha

circulation response to fast and slow mjo episodes abstractfast and slow madden julian oscillation mjo episodes have been identified from 850 and 200 hpa zonal wind and outgoing longwave radiation olr for 32 winters 16 october 17 march 1980 81 2011 12 for 26 fast cases the olr took no more than 10 days to propagate from phase 3 convection over the indian ocean to phase 6 convection over the western pacific for 8 slow cases the propagation took at least 20 days fast episode composite anomalies of 500 hpa height z500 show a developing rossby wave in the mid pacific with downstream propagation through mjo phases 2 4 changes in the frequency of occurrence of the nao weather regime are modest this rossby wave is forced by anomalous cooling over the maritime continent during phases 2 and 3 seen in phase independent wave activity flux the upper level anticyclonic response to phase 3 heating is a secondary source of wave activity the z500 slow episode composite response to mjo phases 1 and 2 is an enhanced aleutian low followed by a north a

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

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

mjo propagation shaped by zonal asymmetric structures results from 24 gcm simulations abstracteastward propagation is an essential characteristic of the madden julian oscillation mjo yet simulation of mjo propagation in general circulation models gcms remains a major challenge and understanding the causes of propagation remains controversial the present study explores why the gcms have diverse performances in mjo simulation by diagnosis of 24 gcm simulations an intrinsic linkage is found between mjo propagation and the zonal structural asymmetry with respect to the mjo convective center the observed and realistically simulated mjo eastward propagations are characterized by stronger kelvin easterly waves than rossby westerly waves in the lower troposphere which is opposite to the gill pattern where rossby westerly waves are 2 times stronger than kelvin easterly waves the gcms simulating stronger rossby westerly waves tend to show a stationary mjo mjo propagation performances are robustly correlated with the quality of simulated zonal asymmetries in the 850 hpa equatorial zonal w

voluminous acid volcanism in the busheveld complex a review of the rooiberg felsite the 2 1 b y old rooiberg felsite roofs and is intruded by the mafic layered rocks and granites of the bushveld complex the felsite unit which locally exceeds 5 km in thickness and may represent an originally erupted volume of more than 300 000 km3 is dominated by rhyolitic to dacitic lavas with minor pyroclastic and sedimentary rock types volcanic rocks of more mafic composition occur towards the base of the sequence the rooiberg episode essentially terminated the volcanic activity in the transvaal basin and heralded the emplacement of the bushveld complex

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

origin and distribution of gold in the huronian supergroup canada the case for witwatersrand type paleoplacers abstract field observations and experimental results show that gold is mobile under a wide range of natural conditions in the surficial environment however the extent to which and the form s in which gold was mobile in ancient placers remains speculative rather more convincing is the extent to which diagenetic and metamorphic processes have been active in redistributing the gold huronian paleoplacer gold deposits span a critical transition in earth history namely the oxyatmoversion evidence for which exists in the upper gowganda formation dated at 2 288 ga prior to this transition deposition of gold occurred under reducing atmospheric conditions with transportation of the more finely divided material possibly as organic protected colloids as has been suggested for the witwatersrand following the oxyatmoversion gold deposition will have been subject to secondary enrichment like many phanerozoic placer gold occurrences for this reason and on purely sedimentological grounds upper huronian strata ought to have as much potential for hosting economic deposits of gold as the basal units a total of 121 au and au u occurrences including several past and presently producing mines from the huronian supergroup are examined these are classified according to whether mineralization is in or adjacent to diabase dikes 11 cases in quartz quartz carbonate veins 85 cases stratiform 25 cases of the non diabase hosted occurrences 41 3 occur in the cobalt group 15 7 in the quirke lake group 24 9 in the hough lake group and 9 in the elliott lake group frequency of occurrence can be related to transgressive sedimentary cycles with deposits concentrated in the matinenda mississagi and gowganda formations which immediately overlie the archean huronian unconformity most of the deposits occur in the gowganda formation although none of these is stratiform in terms of au content there is a large overlap in class intervals of stratiform vein deposits vein deposits are in general richer than stratiform by a factor of 10 selected stratiform deposits in the matinenda mississagi and serpent formations are examined in light of available geological and geochemical data in these deposits anomalous gold values in dominantly quartzitic metasediments are accompanied by fine grained pyrite and other heavy minerals including uranium which occurs in most but not all cases metamorphic grade ranges from upper greenschist to lower amphibolite facies a few of the stratiform occurrences are accompanied by accumulations of carbonaceous material an association reminiscent of the witwatersrand goldfields results of electron microprobe study indicate that much of the gold in the huronian metasediments occurs as low level concentrations in pyrite of morphologically different types in arsenopyrite chalcopyrite and in pyrrhotite variously altered to marcasite it is clear that huronian paleoplacer gold deposits exist but only in conditions much modified by diagenetic and metamorphic processes

effects of enhanced front walker cell on the eastward propagation of the mjo abstractwell organized eastward propagation of the madden julian oscillation mjo is found to be accompanied by the leading suppressed convection lsc over the maritime continent mc and the wes

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

coronagraphic observations of the lunar sodium exosphere january june 2017 abstract in order to observe the lunar sodium exosphere out to one half degree around the moon we designed built and installed a small robotically controlled coronagraph at the winer observatory in sonoita arizona observations are obtained remotely every available clear night from our home base at goddard space flight center or from prescott arizona we employ an andover temperature controlled 1 5 a wide narrow band filter centered on the sodium d2 line and a similar 1 5 a filter centered blueward of the d2 line by 3 a for continuum observations our data encompass lunations in 2015 2016 and 2017 thus we have a long baseline of sodium exospheric calibrated images during the course of three years we have refined the observational sequence in many respects therefore this paper only presents the results of the spring 2017 observing season we present limb profiles from the south pole to the north pole for many lunar phases our data do not fit any power of cosine model as a function of lunar phase or with latitude the extended na exosphere has a characteristic temperature of about 2250 6750 k indicative of a partially escaping exosphere the hot escaping component may be indicative of a mixture of impact vaporization and a sputtered component

precambrian atmospheric oxygen and banded iron formations a delayed ocean model abstract evidence and arguments increasingly in favor of free oxygen in the earth s early atmosphere renew the constraints on the environmental significance of precambrian banded iron formations an early moist greenhouse atmosphere with a delay in and gradual growth of the world oceans offers a mechanism to provide a geochemically and mechanically segregated source of iron and silica for banded iron formation while simultaneously cannibalizing evidence for early archean red beds the model supports the high rates of weathering necessary to remove initially outgassed co2 quickly favors continuity in early biogenic evolution provides a mechanism for hydrogen and strontium isotope partitioning and is consistent with iron oxide facies that are devoid of organic carbon or stromatolites that are not encrusted by iron oxide

qbo influence on mjo amplitude over the maritime continent physical mechanisms and seasonality abstractthe quasi biennial oscillation qbo is stratified by stratospheric zonal wind direction and height into four phase pairs easterly midstratospheric winds qboem easterly lower stratosphe

variation of lunar sodium during passage of the moon through the earth s magnetotail we measured sodium emission above the lunar equator over a range of lunar altitudes from 100 to 4000 km the measurements were repeated approximately every 24 hours from june 7 to 16 1998 covering the period during which the moon passed through the earth s magnetotail sodium temperatures derived from the altitude dependence of emission intensity ranged from 1200 to 2900 k this result supports the view that photodesorption is a primary source of sodium in the exosphere since the most probable temperature of sodium from this source is in this range passage of the moon through the earth s magnetotail where solar wind is essentially absent affected the sodium density such that it was higher before the moon entered the earth s magnetotail than after the moon left it this suggests that the solar wind plays a role in production of lunar sodium we propose that its function is to mobilize sodium and bring it to the surface where photodesorption can eject it into the exosphere a two step process such as this could help to explain the latitude dependence of sodium density which varies as the second or higher power of cosine latitude

an overview of the geology of the transvaal sequence and bushveld complex south africa the late archaean early proterozoic transvaal sequence is preserved within the transvaal kanye and griqualand west basins with the 2050 ma bushveld complex intrusive into the upper portion of the succession within the transvaal basin both transvaal and bushveld rocks are extensively mineralized the former containing large deposits of iron manganese asbestos andalusite gold fluorine lead zinc and tin ores and the latter some of the world s major occurrences of pge chromium and vanadium ores transvaal sedimentation began with thin predominantly clastic sedimentary rocks black reef vryburg formations which grade up into a thick package of carbonate rocks and bif chuniespoort ghaap taupone groups these lithologies reflect a carbonate bif platform sequence which covered much of the kaapvaal craton in reaction to thermal subsidence above ventersdorp aged rift related fault systems an erosional hiatus was followed by deposition of the clastic sedimentary rocks and volcanics of the pretoria postmasburg segwagwa groups within the three basins under largely closed basin conditions an uppermost predominantly volcanic succession rooiberg group loskop formation is restricted to the transvaal basin a common continental rift setting is thought to have controlled pretoria group sedimentation rooiberg volcanism and the intrusion of the mafic rocks of the rustenburg layered suite of the bushveld complex the dipping sheets of the rustenburg magmas cut across the upper pretoria group stratigraphy and lifted up the rooiberg lithologies to form the roof to the complex subsequent granitic rocks of the lebowa and rashoop suites of the bushveld complex intruded both upper rustenburg rocks and the rooiberg felsites

the 30 50 day variation of convective activity over the western pacific ocean with emphasis on the northwestern region abstract coherent 30 50 day oscillations between regions north and south of 20 n were observed using the latitude time y t diagram of a convective index ic along 140 e over the entire 1979 summer may september the oscillation in the northern region exhibits a relatively regular north south movement of deep convective clouds while the oscillation in the southern region shows enhancement or suppression fluctuations of broad and intensive deep convective clouds with a period of 30 50 days the southward northward movement of the midlatitude oscillation coincides with the suppression enhancement of the tropical deep convective clouds the midlatitude deep convective clouds are usually maintained by the divergent circulation and are associated with fronts the empirical orthogonal function eof analysis of velocity potential at 200 mb shows that the north south 30 50 day oscillation of deep convective clouds over the northwestern pacific is a response of the regional weather system to the eastwar

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

diurnal forcing and phase locking of gravity waves in the maritime continent abstractan unfiltered zonal hovmoller depiction of rainfall in the maritime continent mc reveals remarkable spatiotemporal continuity of zonally propagating disturbances with a diurnal period wh

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

a mass flux scheme view of a high resolution simulation of a transition from shallow to deep cumulus convection in this paper an idealized high resolution simulation of a gradually forced transition from shallow nonprecipitating to deep precipitating cumulus convection is described how the cloud and transport statistics evolve as the convection deepens is explored and the collected statistics are used to evaluate assumptions in current cumulus schemes the statistical analysis methodologies that are used do not require tracing the history of individual clouds or air parcels instead they rely on probing the ensemble characteristics of cumulus convection in the large model dataset they appear to be an attractive way for analyzing outputs from cloud resolving numerical experiments throughout the simulation it is found that 1 the initial thermodynamic properties of the updrafts at the cloud base have rather tight distributions 2 contrary to the assumption made in many cumulus schemes nearly undiluted air parcels are too infrequent to be relevant to any stage of the simulated convection and 3 a simple model with a spectrum of entraining plumes appears to reproduce most features of the cloudy updrafts but significantly overpredicts the mass flux as the updrafts approach their levels of zero buoyancy a buoyancy sorting model was suggested as a potential remedy the organized circulations of cold pools seem to create clouds with larger sized bases and may correspondingly contribute to their smaller lateral entrainment rates our results do not support a mass flux closure based solely on convective available potential energy cape and are in general agreement with a convective inhibition cin based closure the general similarity in the ensemble characteristics of shallow and deep convection and the continuous evolution of the thermodynamic structure during the transition provide justification for developing a single unified cumulus parameterization that encompasses both shallow and deep convection

key processes for the eastward propagation of the madden julian oscillation based on multimodel simulations as a prominent climate variability mode with widespread influences on global weather extremes the madden julian oscillation mjo remains poorly represented in the latest generation of general circulation models gcms with a particular challenge in simulating its eastward propagating convective signals in this study by analyzing multi model simulations from a recent global mjo model evaluation project an effort is made to identify key processes for the eastward propagation of the mjo through analyses of moisture entropy me processes under a moisture mode framework for the mjo the column integrated horizontal me advection is found to play a critical role for the eastward propagation of the mjo in both observations and good mjo models with a primary contribution through advection of the lower tropospheric seasonal mean me by the mjo anomalous circulations by contrast the horizontal me advection effect for the eastward propagation is greatly underestimated in poor mjo gcms due to model deficiencies in simulating both the seasonal mean me pattern and mjo circulations leading to a largely stationary mjo mode in these gcms these results thus pinpoint an important guidance towards improved representation of the mjo in climate and weather forecast models while this study mainly focuses on fundamental physics for the mjo propagation over the indian ocean complex influences by the maritime continent on the mjo and also me processes associated with the mjo over the western pacific warrant further investigations

mjo initiation processes over the tropical indian ocean during dynamo cindy2011 abstracta multination joint field campaign called the dynamics of mjo cooperative indian ocean experiment on intraseasonal variability in year 2011 dynamo cindy2011 took place in the equatorial indian ocean io in late 2011 during the campaign period two strong mjo events occurred from the middle of october to the middle of december referred to as mjo i and mjo ii respectively both the events were initiated over the western equatorial indian ocean wio around 50 60 e using multiple observational data products era interim the ecmwf final analysis and nasa merra the authors unveil specific processes that triggered the mjo convection in the wio it is found that 10 days prior to mjo i initiation a marked large scale ascending motion anomaly appeared in the lower troposphere over the wio the cause of this intraseasonal vertical motion anomaly was attributed to anomalous warm advection by a cyclonic gyre anomaly over the northern io the mjo ii initiation was preceded by a low level specifi

geology and major and trace element chemistry of late archean weathering profiles in the fortescue group western australia implications for atmospheric po2 abstract we have identified two thick weathering profiles between flows of the mt roe basalt unit of the fortescue group in the pilbara area of western australia the age of weathering is constrained by u pb zircon dating to lie between 2765 and 2715 ma the profiles herein referred to as the mt roe 1 and 2 paleosols were mapped in detail for 1500 m and 760 m along strike respectively samples were collected along traverses across both profiles where they were well developed and well exposed the profiles which may be structurally offset parts of the same weathering horizon have well developed upper sericite zones 1 15 m thick these grade downward into chlorite rich zones which are chemically and physically heterogeneous the chlorite zones grade downward into unweathered basalts the mt roe 1 profile is overlain by 2 6 m of bedded probably lacustrine sediments these in turn are covered by succeeding lava flows evidence of a surficial origin for the paleosols includes mud cracks ripple marks and rip ups of the paleosol material in the post paleosol sediments soft sediment deformation and probable dewatering structures are present along the paleosol sediment contact the mt roe 2 profile is overlain directly by the succeeding lava flow with little or no intervening sediments some brecciation and pillowing is observed along the base of the overlying basalt flow in both cases probably due to emplacement of lava into a shallow lake or onto wet soil in the sericite zones of both profiles nearly all of the fe mn mg and zn and a substantial fraction of the ca pb na ni and si have been leached the chlorite zones have elevated fe pb ni and zn contents and appear to be repositories of elements lost from the sericite zone al ti zr and th were immobile in the mt roe 1 paleosol and are concentrated by factors of 2 5 2 6 over the unweathered basalt v u and cr were also nearly immobile major element and trace element data indicate that weathering took place under conditions of low atmospheric oxygen k is strongly enriched toward the upper contact of the sericite zone and was introduced during post weathering metasomatism together with rb and sr na and ca are also enriched near the top of each profile and small amounts of each may have been introduced during regional low grade metamorphism of the hamersley basin at 2168 10 ma

geochemical evolution of the rooiberg silicic lavas in the loskop dam area southeastern bushveld the rooiberg felsite is the voluminous volcanic precursor to the plutonic episodes of bushveld magmatism in the area north of the loskop dam a 3 520 m thickness of felsite is dominated by flows of dacitic and rhyodacitic lava occasional silicic andesites are developed near the base whereas true rhyolites become overwhelmingly dominant toward the top of the sequence nine major stratigraphic units of lava are present these are usually separated by and sometimes include volumetrically minor pyroclastic and sedimentary deposits whole rock chemical data on 165 lava samples embracing the entire stratigraphy suggest that nonuniform alteration processes have been most effective in the upper units nevertheless field petrographic and chemical criteria enable identification of three felsite magma types a high mg type mgo 1 7 containing low zr and y contents is present only within the lowermost 1 400 m of section a low mg type mgo 2 asymp 1 p 2 o 5 asymp 0 35 type which only occurs in the lower part of the succession the high mg lavas exhibit a systematic eruptive progression from more to less evolved compositions apparently reflecting continuous tapping of successively deeper levels of a normally zoned magma chamber during the early volcanism the low mg lavas were erupted intermittently with the high mg types probably from a separate and much larger chamber pronounced differentiation of this magma is only evident in the youngest volcanic units where several element profiles display conspicuous steplike variations across the prominent ash flow horizons the steps reflect upward enrichments in nb zr and y and corresponding incremental depletions in ti p and sc such trends imply the existence of a discontinuous but reversed compositional zonation in the evolved low mg chamber the high fe ti p lavas were also erupted from the low mg chamber this may indicate the development of an early type of chemical stratification that was markedly different from the compositional layering in the evolved system

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

neoarchaean c 2 58 ga halite casts implications for palaeoceanic chemistry possibly the most extensive and best preserved archaean halite casts yet discovered occur in the c 2 58 ga upper black reef and basal oaktree formations transvaal supergroup in mpumalanga province south africa halite casts are isolated on bedding planes range in size from c 1 mm to 20 mm and have cubic dumbbell and triangular shapes as well as hopper like pyramidal hollows on cube faces some of the casts display distinct hopper shapes characteristic of halite crystals the halite cast bearing pavements are developed within silicified mudstone interbedded with siltstone or stromatolitic dolomite associated sedimentary structures pointing to subaerial exposure include adhesion ripples and warts desiccation and prism cracks rill marks and tepee structures halite cast bearing beds are interpreted as supratidal flat or sabkha deposits the presence of isolated casts and hopper shaped crystals suggests that halite resulted from displacive growth within the sediment from supersaturated residual brines after mudstone deposition absence of any indication of the former presence of gypsum or anhydrite supports previous contentions that the neoarchaean ocean was deficient in sulphate or contained a high bicarbonate to calcium ratio such that with progressive evaporation most calcium was consumed before the gypsum stability field was reached the association of halite and carbonate in the upper black reef and basal oaktree formations constrains the palaeolatitude of the transvaal basin at 2 58 ga to subequatorial 10 30

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

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

intraseasonal teleconnection between the summer eurasian wave train and the indian monsoon this study investigated the most recurrent coupled pattern of intraseasonal variability between midlatitude circulation and the indian summer monsoon ism the leading singular vector decomposition svd pattern reveals a significant coupled intraseasonal variation between a rossby wave train across the eurasian continent and the summer monsoon convection in northwestern india and pakistan hereafter referred to as nism the wave train associated with an active phase of nism rainfall displays two high pressure anomalies one located over central asia and the other over northeastern asia they are accompanied by increased rainfall over the western siberia plain and northern china and decreased rainfall over the eastern mediterranean sea and southern japan the circulation of the wave train shows a barotropic structure everywhere except the anomalous central asian high located to the northwest of india where a heat induced baroclinic circulation structure dominates the time lagged svd analysis shows that the midlatitude wave train originates from the northeastern atlantic and traverses europe to central asia the wave train enhances the upper level high pressure and reinforces the convection over the nism region meanwhile it propagates farther toward east asia along the waveguide provided by the westerly jet after an outbreak of nism convection the anomalous central asian high retreats westward composite analysis suggests a coupling between the central asian high and the convective fluctuation in the nism the significance of the midlatitude ism interaction is also revealed by the close resemblance between the individual empirical orthogonal functions and the coupled svd modes of the midlatitude circulation and the ism it is hypothesized that the eastward and southward propagation of the wave train originating from the northeastern atlantic contributes to the intraseasonal variability in the nism by changing the intensity of the monsoonal easterly vertical shear and its associated moist dynamic instability on the other hand the rainfall variations over the nism reinforce the variations of the central asian high through the monsoon desert mechanism thus reenergizing the downstream propagation of the wave train the coupling between the eurasian wave train and nism may be instrumental for understanding their interaction and can provide a way to predict the intraseasonal variations of the indian summer monsoon and east asian summer monsoon

primary and successive events in the madden julian oscillation conventional analyses of the mjo tend to produce a repeating cycle such that any particular feature cannot be unambiguously attributed to the current or previous event we take advantage of the sporadic nature of the mjo and classify each observed madden julian mj event as either primary with no immediately preceding mj event or successive which does immediately follow a preceding event 40 of mj events are primary events precursor features of the primary events can be unambiguously attributed to that event a suppressed convective anomaly grows and decays in situ over the indian ocean prior to the start of most primary mj events an associated mid tropospheric temperature anomaly destabilises the atmosphere leading to the generation of the active mj event hence primary mj events appear to be thermodynamically triggered by a previous dry period although stochastic forcing may also be important other theories predict that boundary layer convergence humidity propagation of dynamical structures around the equator sea surface temperatures and lateral forcing by extratropical transients may all be important in triggering an event although precursor signals from these mechanisms are diagnosed from reanalysis and satellite observational data in the successive mj events they are all absent in the primary mj events hence it appears that these apparent precursor signals are part of the mjo once it is established but do not play a role in the spontaneous generation of the mjo the most frequent starting location of the primary events is the indian ocean but over half of them start elsewhere from the maritime continent to the western pacific copyright 2008 royal meteorological society

crustal diffusion of gases out of mercury and the moon the author has calculated an upper limit to the rate of diffusion of sodium and potassium out of mercury and the moon and have compared the resulting flux to that required to maintain the known exospheres he finds that diffusion rates are inadequate by 12 orders of magnitude on the moon and 9 orders of magnitude on mercury for diffusion out of orthoclase minerals diffusion will be more rapid out of pure glass by 5 to 6 orders of magnitude and out of shocked basalt by an amount depending on the microstructure of the mineral the observed abundance and distribution of volatiles in small glass spherules on the moon indicates that diffusion is very inefficient after solidification and cooling at mercury the limitation on sodium flux to the atmosphere is shown to be the rate at which new regolith is created the discrepancy between the observed column abundance of sodium in the mercurean atmosphere and the known sources may indicate that either mercury s crust has a larger volatile content than the moon or that a recycling mechanism exists in the mercurean atmosphere which is not present for the moon