carbonate crusts of paleolake zhuyeze tengeri desert china formation mechanism and paleoenvironmental implications abstract carbonate crusts with unusual morphologies are scattered on the holocene sand surface i e dunes which cover the paleolake zhuyeze bed in the tengeri desert china two types of the crusts were identified the first type contained fossilized wrinkles of plant root cortex while the second type consisted of hollow chambers without the wrinkle features optical microscopy scanning electron microscopy and cathodoluminescence analyses were performed to investigate the mineralogy and geochemistry of the crusts fossilized cortex texture imprints on the first type of crusts suggested that the crusts formed around the deceased rhizomes of reeds phragmites communis as the nuclei of encrustation weakly oxidizing soil sediment with rhizome was a prerequisite which was favorable for rhizome decomposition to produce sufficient co2 and hco3 and generate carbonate minerals of encrustation on rhizome surfaces with lake water as the main ca2 supply a conceptual formation mechanism of the encrustation was conjectured similar to the formation mechanism of the first type another type of crusts with chambers and without fossilized imprints of the cortex textures formed around the spherical rhizomes of scirpus maritimus the crust characteristics and other evidence suggested that the lake water was fresh water plants such as p communis and s maritimus and snails previously inhabited the water and encrustation reflected a stable slow oxidizing soil sediment environment these desert crusts provided insights to study paleoecology paleohydrology and water soil sediment interface environment in the paleolake

planetary scale selection of the madden julian oscillation in an air sea coupled dynamic moisture model the authors present an air sea coupled dynamic moisture asdm model to explore the mechanism of preferred planetary scale of the madden julian oscillation mjo this asdm model extended from the original frictionally coupled dynamic moisture model and a mixed layer model can present a good simulation of planetary scale characteristics of the mjo including a slow eastward propagation of 5 m s 1 coupled rossby kelvin wave like structure and phase leading of convective center by warm sea surface temperature sst it is interesting that the planetary scale selection in terms of instability is only found in the nonlinear asdm model with the assumption of positive only heating such a scale selection however cannot be found in the asdm model with linear heating or in an uncoupled atmosphere model the essential mechanism for the scale selection is nonlinear positive only heating and the air sea interaction primarily provides an instability source to support this scale selection this scale selection is attributed to different phase speeds of coupled moist rossby kelvin waves and dry kelvin waves from short wave initial perturbations the easterly wind anomalies of eastward propagating dry kelvin waves from a stronger wave component will catch up with other weaker moist components and suppress their westerly wind anomalies resulting in weak sst gradient as well as reduced moisture convergence and precipitation for these suppressed components as a result the wavenumber one structure is selected the warm pool like mean state will select the stronger component among the initial short wave perturbations and accelerate this scale selection process these results provide new insight into mjo mechanism in terms of air sea interaction

the sensitivity of subannual and intraseasonal tropical variability to model ocean mixed layer depth 1 the influence of air sea interaction on subannual and intraseasonal tropical variability is explored through analysis of three long simulations of the commonwealth scientific and industrial research organisation atmospheric general circulation model gcm with differing ocean specifications a coupled ocean gcm a simple 50 m mixed layer model or climatological sea surface temperatures sst together with 50 year simulations with mixed layer depths of 10 m and 20 m the analysis focuses initially on a signal similar to a madden julian oscillation mjo contained in the first two empirical orthogonal functions eof of monthly anomalies of tropical 807 hpa winds in january in the coupled model time lag regression is used to demonstrate that these patterns propagate eastward although at only half the speed of the mjo and induce perturbations to the australian monsoon the specified sst model shows no such propagation similar results are then obtained using daily data filtered to retain subannual periods the eastward propagation speed is faster in the shallower mixed layer cases with the 10 m case producing speeds close to observations in the interactive models surface energy fluxes force sst anomalies propagating ahead of the eof convergence these fluxes are largely consistent with evaporation perturbed by wind anomalies to the monsoon westerlies augmented by solar radiation the sst anomalies then further perturb the winds as is confirmed by a separate sst perturbation experiment from the examination of other seasons it is seen that air sea interaction generally enhances the amplitude of the mjo like patterns it also enhances their eastward propagation along westerly wind bands analysis of zonal wave number one winds confirms the strong sensitivity to mixed layer depth in the amplitude and period of the eastward propagating component particularly during september through february the results suggest that air sea interaction may be important to the mjo provided that the ssts are sufficiently responsive to the atmospheric patterns

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

secular variation in phanerozoic marine biocalcification and the original mineralogy and mode of calcification of receptaculitids a reply

impact of air sea coupling on the madden julian oscillation in a general circulation model abstract the impact of air sea coupling on the dynamics of the tropical madden julian oscillation mjo is investigated with an atmospheric general circulation model gcm coupled to an ocean mixed layer model in the uncoupled gcm where climatological sea surface temperature sst is specified realistic space time spectra of near equatorial zonal wind and precipitation are produced with power concentrated at eastward wavenumbers 1 3 with periods of 35 90 days however the simulated mjo is roughly 50 stronger than observed largely resulting from enormous activity during northern summer furthermore during southern summer when the observed mjo is most dominant across the indian and western pacific oceans intraseasonal variance in the uncoupled model is overly concentrated to the north and east of australia with little activity extending into the equatorial indian ocean contrary to other recent modeling studies coupling did not alleviate either of these problems nor did it have any other apprecia

coupling between northward propagating intraseasonal oscillations and sea surface temperature in the indian ocean using a hybrid atmosphere ocean coupled model it is shown that during the boreal summer northwardpropagating intraseasonal oscillations npisos are strongly coupled to the underlying sea surface temperature sst in the indian ocean sector on the one hand the intraseasonal atmospheric convection changes the sst through solar radiation latent heat flux and mixed layer entrainment on the other the induced sst fluctuations feed back to affect the intraseasonal convection the preferential northward rather than southward propagation of boreal summer isos in the indian ocean is partially explained by an interaction among the summer mean climate state the atmospheric disturbances and the ocean surface temperature a solution to an atmosphere only model forced with daily sst produces much stronger npisos than a similar solution forced with monthly mean sst amip type run the atmosphere only model however even when it is forced by daily sst from the coupled model with a small amount of noise in the initial and or boundary conditions is unable to reproduce the npisos in the coupled case in the coupled system intraseasonal sst anomalies are forced by intraseasonal atmospheric convection and hence are in quadrature with the convection in the stand alone atmospheric model however sst acts only as a boundary forcing and the resultant atmospheric convection has almost the same phase with the underlying sst one consequence is that the intensity of the sst forced intraseasonal convection in the stand alone atmospheric model is considerably weaker than in the coupled model finally solutions indicate that the northward movement of the off equatorial convection in the northern indian ocean is more closely related to local intraseasonal sst anomalies than to the equatorial eastward moving madden julian oscillation positive negative sst anomalies in the northern indian ocean lead the active break phases of the intraseasonal convection by about 2 pentads 10 days therefore intraseasonal sst anomalies in the northern indian ocean are potentially a useful index to forecast active break spells of the south asian summer monsoon

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

an mjo simulated by the nicam at 14 and 7 km resolutions this study discloses detailed madden julian oscillation mjo characteristics in the two 30 day integrations of the global cloud system resolving nonhydrostatic icosahedral atmospheric model nicam using the allseason real time multivariate mjo index of wheeler and hendon the model anomaly is derived by excluding the observed climatology because the simulation is sufficiently realistic results show that the mjo has a realistic evolution in amplitude pattern geographical locations eastward propagation and baroclinic and westwardtilted structures in the central indian ocean convection develops with the low level easterly wind anomaly then matures where the low level easterly and westerly anomalies meet anomalous moisture tilts slightly with height in contrast over the western pacific the convection grows with a low level westerly anomaly moisture fluctuations leading convection in eastward propagation tilt clearly westward with height the frictional moisture convergence mechanism operates to maintain the mjo such success can be attributed to the explicit representation of the interactions between convection and large scale circulations the simulated event however grows faster in phases 2 and 3 and peaks with 30 higher amplitude than that observed although the 7 km version shows slight improvement the fast growth phases are induced by the fast growing low level convergence in the indian ocean and the strongly biased itcz in the west pacific when the model undergoes a spinup the simulated olr has a substantial bias in the tropics possible solutions to the deficiencies are discussed

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

distinctive roles of air sea coupling on different mjo events a new perspective revealed from the dynamo cindy field campaign abstractprevious observational analysis and modeling studies indicate that air sea coupling plays an essential role in improving mjo simulations and extending mjo forecasting skills however whether the sst feedback plays an indispensable role for the existence of the mjo remains controversial and the precise physical processes through which the sst feedback may lead to better mjo simulations and forecasts remain elusive the dynamo cooperative indian ocean experiment on intraseasonal variability in the year 2011 cindy field campaign recently completed over the indian ocean reveals a new perspective and provides better data to improve understanding of the mjo it is found that among the five mjo events that occurred during the dynamo cindy field campaign only two mjo events the november and march ones have robust sst anomalies associated with them for the other three mjo events the october december and january ones no coherent sst anomalies are observed this observational scenario suggests th

importance of the vertical resolution in simulating sst diurnal and intraseasonal variability in an oceanic general circulation model abstractin this paper the influence of high vertical resolution near the surface in an oceanic general circulation model in simulating the observed sea surface temperature sst variability is investigated in situ observations of vertical temperature profiles are first used to quantify temperature variability with depth near the ocean surface the analysis shows that there is a sharp vertical temperature gradient within the top 10 m of the ocean both diurnal and intraseasonal variabilities of the ocean temperatures are largest near the surface and decrease with the ocean depth numerical experiments with an oceanic general circulation model are next carried out with 1 and 10 m vertical resolutions for the upper ocean to study the dependence of the simulated sst and vertical temperature structure on the vertical resolution it is found that the simulated diurnal and intraseasonal variabilities as well as the associated vertical temperature gradient near the surface are strongly influenced by the ocea

mjo initiation in the real time multivariate mjo index abstractmadden julian oscillation mjo initiation in the real time multivariate mjo rmm index is explored through an analysis of observed case studies and composite events specific examples illustrate that both the dates of mjo initiation and the existence of the mjo itself can vary substantially among several well known mjo indices depending on whether the focus is on convection or circulation composites of primary mjo initiation events in which the rmm index rapidly increases in amplitude from a non mjo state to an mjo state are presented and are supplemented by two case studies from the 1985 86 winter season results illustrate that for primary mjo initiation events in the indian ocean rmm phase 1 slowly eastward propagating 850 hpa 200 hpa easterly westerly anomalies over the indian ocean precede the amplification of the rmm index by at least 10 days while suppressed convection over the western pacific ocean precedes the amplification by 5 days these local eastern hemispheric prede

a madden julian oscillation event realistically simulated by a global cloud resolving model a madden julian oscillation mjo is a massive weather event consisting of deep convection coupled with atmospheric circulation moving slowly eastward over the indian and pacific oceans despite its enormous influence on many weather and climate systems worldwide it has proven very difficult to simulate an mjo because of assumptions about cumulus clouds in global meteorological models using a model that allows direct coupling of the atmospheric circulation and clouds we successfully simulated the slow eastward migration of an mjo event topography the zonal sea surface temperature gradient and interplay between eastward and westward propagating signals controlled the timing of the eastward transition of the convective center our results demonstrate the potential making of month long mjo predictions when global cloud resolving models with realistic initial conditions are used

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

the madden julian oscillation observed during the toga coare iop global view abstract during the toga coare intensive observing period november 1992 february 1993 two pronounced madden julian oscillation mjo events associated with super cloud clusters and westerly wind bursts were observed this paper presents a global view of the mjos including the origin of the super clusters in the indian ocean their migration into the maritime continent and the toga coare large scale soundings array lsa in the western equatorial pacific and their rapid decay over cold water of the eastern pacific the structure and evolution of the mjo are examined with emphasis on the coupling between large scale motion and convection because of differences in propagation speeds the positions of maximum zonal wind perturbations relative to deep convection undergo systematic changes during the travel of the mjo however the centers of deep convection always coincide with those of large scale ascent the super cloud cluster accompanies a wide area of warm air in the upper troposphere over the warm

on the role of sea surface temperature gradients in forcing low level winds and convergence in the tropics abstract we examine the importance of pressure gradients due to surface temperature gradients to low level p 700 mb flow and convergence in the tropics over time scales 1 month the latter plays a crucial role in determining the distribution of cumulonimbus convection and rainfall our approach is to consider a simple one layer model of the trade cumulus boundary layer wherein surface temperature gradients are mixed vertically consistent with ecmwf analyzed data the top of the layer is taken at 700 mb the influence from higher levels is intentionally suppressed by setting horizontal pressure gradients and frictional stresses to zero at the top of the layer horizontal convergence within the layer is taken up by cumulonimbus mass flux however the development of the cumulonimbus mass flux is associated with a short relaxation time o hr roughly the development time for such convection during this short time horizontal convergence acts to redistribute mass so as to reduce horizontal pressur

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

regional simulation of the october and november mjo events observed during the cindy dynamo field campaign at gray zone resolution abstractthis study investigates the october and november mjo events observed during the cooperative indian ocean experiment on intraseasonal variability in the year 2011 cindy dynamics of the mjo dynamo field campaign through cloud permitting numerical simulations the simulations are compared to multiple observational datasets the control simulation at 9 km horizontal grid spacing captures the slow eastward progression of both the october and november mjo events in surface precipitation outgoing longwave radiation zonal wind humidity and large scale vertical motion the vertical motion shows weak ascent in the leading edge of the mjo envelope followed by deep ascent during the peak precipitation stage and trailed by a broad second baroclinic mode structure with ascent in the upper troposphere and descent in the lower troposphere both the simulation and the observations also show slow northward propagation components and tropical cyclone like vortices after the passage of the mjo active phase

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

simulations of the madden julian oscillation in four pairs of coupled and uncoupled global models the status of the numerical reproduction of the madden julian oscillation mjo by current global models was assessed through diagnoses of four pairs of coupled and uncoupled simulations slow eastward propagation of the mjo especially in low level zonal wind is realistic in all these simulations however the simulated mjo suffers from several common problems the mjo signal in precipitation is generally too weak and often eroded by an unrealistic split of an equatorial maximum of precipitation into a double itcz structure over the western pacific the mjo signal in low level zonal wind on the other hand is sometimes too strong over the eastern pacific but too weak over the indian ocean the observed phase relationship between pre cipitation and low level zonal wind associated with the mjo in the western pacific and their coherence in gen eral are not reproduced by the models the seasonal migration in latitude of mjo activity is missing in most simulations air sea coupling generally strengthens the simulated eastward propagating signal but its effects on the phase relationship and coherence between precipi tation and low level zonal wind and on their geographic distributions seasonal cycles and interannual variability are inconsistent among the simulations such inconsis tency cautions generalization of results from mjo sim ulations using a single model in comparison to observations biases in the simulated mjo appear to be related to biases in the background state of mean pre cipitation low level zonal wind and boundary layer moisture convergence this study concludes that while the realistic simulations of the eastward propagation of the mjo are encouraging reproducing other funda mental features of the mjo by current global models remains an unmet challenge

roles of deep and shallow convection and microphysics in the mjo simulated by the model for prediction across scales the november event of the madden julian oscillation mjo during the dynamo field campaign was simulated using the global compressible nonhydrostatic model for prediction across scales mpas with global coarse 60 and 15 km and regional the indian ocean cloud permitting 3 km meshes the purpose of this study is to compare roles of parameterized deep and shallow cumulus and microphysics in mjo simulations two cumulus schemes were used tiedtke and grell freitas the deep and shallow components of tiedtke scheme can be turned on and off individually the results reveal that microphysics alone without cumulus parameterization is able to produce strong signals of the mjo in precipitation with 3 km mesh and weak mjo signals with 15 km mesh a shallow scheme tiedtke along with microphysics strengthens the mjo signals but makes them less well organized on large scales a deep cumulus scheme can either improve the large scale organization of mjo precipitation produced by microphysics and shallow convection tiedtke or impair them grell freitas the deep scheme of tiedtke cannot reproduce the mjo well without its shallow counterpart the main role of shallow convection in the model is to transport moisture upward to the lower mid troposphere by doing so it removes dry biases in the lower mid troposphere a distinct feature in simulations with weak or no mjo signals and enhances total precipitation and diabatic heating produced by microphysics and deep cumulus schemes changing model grid spacing from 60 to 15 km makes a little difference in the model fidelity of reproducing the mjo all roles of shallow convection in 15 km simulations with parameterized deep convection cannot be reproduced in 3 km simulations without parameterized deep convection results from this study suggest that we should pay more attention to the treatment of shallow convection and its connection to other parameterized processes for improving mjo simulations in other words a holistic approach should be taken that consider parameterization of shallow cumulus microphysics boundary layer as well as deep cumulus as a whole for model improvement

the role of global circumnavigating mode in the mjo initiation and propagation a series of convection permitting regional model simulations are used to study the influences of intraseasonal forcings from the periphery of the tropical indian ocean on the october 2011 mjo event well observed during the dynamics of the madden julian oscillation dynamo field campaign these sensitivity experiments demonstrate the predominant role of a global circumnavigating mode in the initiation and propagation of this mjo event although the regional framework would not completely rule out influences from the extratropics through the western boundary of the model domain it is found that filtering out intraseasonal forcing leads to the absence of kelvin waves which may reduce moisture transport and weakened lower level convergence at the leading edge of the westerlies and further leads to diminishing mjo signatures in these sensitivity experiments meanwhile for the same regional domain initiated two weeks before the onset of the mjo convection there is little impact of whether or not the global mjo signals retained in the initial conditions on the other hand the removal of the global mjo signals from the lateral boundary conditions will not affect the propagation of the mjo after it has been initiated in the regional model domain

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

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