remote trigger of deep convection by cold outflow over the taiwan strait in the mei yu season a modeling study of the 8 june 2007 case abstractin this study the heavy rainfall event over central taiwan during the mei yu season on 8 june 2007 is investigated with an emphasis on the triggering mechanism for the deep convection that produced the rain observations indicate that there existed two lines of forcing with convection prior to the rain one over the northern taiwan strait along the mei yu front and the other over the southern taiwan strait yet the convection in question developed over the central strait between these two lines in an unstable environment with strong westerly vertical wind shear this motivated the authors to carry out the present study the cloud resolving storm simulation cress of nagoya university was used and the event was reproduced at a horizontal grid size of 2 km including the initiation of new convection over the central strait at the correct location and time the model results suggest a crucial role played by the series of active persistent and propagating storms in the southern strait along the

on the movement and low level structure of cold fronts abstract this paper presents a review of theoretical and observational studies relating to the low level structure of cold fronts and explores the factors that are pertinent to frontal motion observational studies have shown that in some cases surface cold fronts move at speeds faster than the normal component of the wind at all levels in the lower troposphere and therefore propagate other case studies have shown that the low level flow immediately behind the front and normal to it is faster than the front and that the front has the local structure of a gravity current its speed of movement being well determined by the gravity current speed equation them different types of behavior are related to results of recent theoretical studies and the mechanism by which fronts can propagate is elucidated it is shown that a necessary requirement for propagation is the existence of an alongfront temperature gradient we question the relevance of the gravity current speed equation in general despite its appar

dating young zircon a case study from southeast asian megacrysts abstract u pb geochronology of quaternary zircon crystals is challenging due to their low levels of radiogenic pb the importance of accurate common pb correction and the potential need for secular disequilibrium correction u th he dating offers an independent benchmark for the quality of u pb data and their reduction including the various corrections as the closure temperature of the he system in zircon is 900 c hence u pb ages must predate u th he ages or at least be equal to them in the case of rapid cooling analyses of southeast asian mantle derived zircon megacrysts from tram poung tr tok phrom to bang kacha ba and pailin pa provide new information about their pre eruptive and eruptive history sims u pb zircon ages of 6 7 3 4 ma tr 2 45 0 23 ma to 1 44 0 13 ma ba and 0 97 0 41 ma pa correspond to u th he ages of 5 30 0 52 ma tr 2 42 0 10 ma to 1 05 0 05 ma ba and 0 91 0 02 ma pa respectively the youngest of these u pb ages pa is corroborated by la icpms mapping of a grain that yields an age of 1 017 0 067 ma the grain mapping reveals no evidence for pb diffusion and the calculated pb diffusion temperatures for these megacrysts of 1110 1250 c are significantly greater than ti in zircon apparent temperatures of 659 c these observations may imply that the u pb ages reflect magmatic crystallization and hence the close similarity of the u pb and u th he dates observed in all samples documents high zircon megacryst growth rates of 1 10 12 to to 2 10 14 cm s tr

regional scale flows in mountainous terrain part i a numerical and observational comparison abstract this study uses observed data and a numerical simulation to examine the generation of thermally driven flows across the colorado mountain barrier on meso to meso scales the observations were collected from remote surface observing systems at exposed mountaintop locations throughout the state of colorado over the summers of 1984 88 as part of the rocky mountain peaks experiment rompex the data show the development of a recurrent circulation system across the colorado mountain barrier operating on a diurnal timescale from the observations the basic structure of the flow system appears as a daytime inflow toward the highest terrain and a nocturnal outflow away from it however when examined in detail the flow system exhibits more unusual behavior especially west of the barrier crest here winds in the early evening are occasionally observed to onset abruptly from an easterly direction generally counter to the upper level winds observations from rompex for 26 august 1985 are used

a numerical study of the evolving convective boundary layer and orographic circulation around the santa catalina mountains in arizona part i circulation without deep convection abstract the daytime evolution of the thermally forced boundary layer bl circulation over an isolated mountain about 30 km in diameter and 2 km high is examined by means of numerical simulations validated with data collected in the cumulus photogrammetric in situ and doppler observations cupido field campaign two cases are presented one remains cloud free in the simulations and the second produces orographic convection just deep enough to yield a trace of precipitation the weather research and forecasting version 3 simulations at a resolution of 1 km compare well with cupido observations the simulations reveal a solenoidal circulation mostly contained within the convective bl but this circulation and especially its upper level return flow branch are not immediately apparent since they are overwhelmed by bl thermals a warm anomaly forms over the high terrain during the day but it is rather shallow and does not extend over the depth of the convective bl which bulges over the mountain low

geochemistry and geochronology of late cenozoic basalts of southeast asia summary geological maps of southeast asia asia 1971 vietnam 1971 thailand 1969 show numerous occurrences of basalt which are considered to be late cenozoic in age occurrences in thailand and western kampuchea are generally small and scattered those in eastern kampuchea southern laos and vietnam are larger and more extensive fig 1 basalt bodies of similar age also occur in malaysia and southern china fig 1 these basalts form a late cenozoic continental volcanic province comparable to those in eastern australia irving and green 1976 and the western united states christiansen and lipman 1972 leeman and rogers 1970 basalts in southeast asia are especially intriguing as they are a major source of gem quality ruby sapphire and zircon fontaine and workman 1978 berrange and jobbins 1976 the purpose of this paper is to describe the distribution geochemistry and age of basalts in southeast asia available geochemical and age data are compiled and combined with new data from previously unstudied areas this is the first known regional synthesis that has been attempted for this large but relatively undocumented basaltic province

wave cloud lines over northwest australia the frequency of occurrence and formation mechanisms of wave cloud lines off the northwest coast of australia are investigated prior to the present study little was known about these wave cloud lines apart from being spectacular atmospheric phenomenon in their own right these wave clouds can have a role in the secondary initiation of convection and can be a hazard to low flying aircraft a climatology of wave clouds produced from visible satellite imagery suggests two main types of cloud lines form over northwest australia the first are bore like waves similar in structure to the morning glory of northeast australia and occur at least 2 to 3 times per month throughout the entire year the second type are convectively generated cloud lines which are more circular in shape appear to originate from convective storms and occur at least 0 5 to 1 5 times per month during the wet season high resolution nested simulations are performed with the met office unified model for case studies of each type of wave the bore like waves occurred in the presence of synoptic scale low level southeasterly flow and a heat low along the northwest coast of australia at night the offshore southeasterlies accelerate into the heat low and collide with the onshore sea breeze the southeasterlies override the sea breeze and the wave cloud lines form at the leading edge of this front the convectively generated waves radiate outwards from the convective storms producing compensating subsidence and adiabatic warming these waves take the form of n 2 mode wave fronts which span the entire depth of the troposphere and are similar in structure to waves produced by deep convection which are described in previous studies

a study of mesoscale gravity waves over the north atlantic with satellite observations and a mesoscale model satellite microwave data are used to study gravity wave properties and variabilities over the northeastern united states and the north atlantic in the december january periods the gravity waves in this region found in many winters can reach the stratopause with growing amplitude the advanced microwave sounding unit a amsu a observations show that the wave occurrences are correlated well with the intensity and location of the tropospheric baroclinic jet front systems to further investigate the cause s and properties of the north atlantic gravity waves we focus on a series of wave events during 19 21 january 2003 and compare amsu a observations to simulations from a mesoscale model mm5 the simulated gravity waves compare qualitatively well with the satellite observations in terms of wave structures timing and overall morphology excitation mechanisms of these large amplitude waves in the troposphere are complex and subject to further investigations

the timing of marid metasomatism in the kaapvaal mantle an ion probe study of zircons from marid xenoliths abstract the precise timing of metasomatic events in the kaapvaal craton lithospheric mantle is poorly constrained and therefore it has proven difficult to relate mantle metasomatism in the source to igneous activity at the surface a suite of mica amphibole rutile ilmenite diopside bearing xenoliths marid represents the product of such metasomatic fluids or melts in this paper we report results of a shrimp and cathodoluminescence study on zircons from four marid samples from the kimberley cluster of pipes textures combined with experimental evidence suggest that zircons are late crystallizing phases in marids that form close to the solidus where the major precipitating phases are phlogopite and k richterite cathodoluminescence patterns reveal a complex growth history of the zircons involving strong deformation repeated events of crystallization resorption and or modification of the zircon composition possibly over several millions of years many of the u pb ages are significantly older than the intrusion age of the group i kimberlites of the kimberley cluster zircon ages in a marid xenolith from the wesselton kimberlite vary in the range 113 3 ma to 142 3 ma compared with a pipe age of 84 3 ma in two samples from the de beers bultfontein or dutoitspan pipes ages range from 85 5 to 119 2 ma in one and 80 4 to 90 2 ma in the other the ages obtained for the latter are indistinguishable from the pipe age of kimberlites belonging to the younger group i kimberlite event ca 80 95 ma zircons in this sample as well as the younger ages in the other may reflect real ages but most likely have lost radiogenic pb as a result of deformation and fluid or melt interaction the presence of pre group i ages in two of the samples demonstrates unambiguously that the metasomatism that yielded the older crystallization ages cannot be related to the group i kimberlite event instead minimum ages for the marid zircons coincide with the period of group ii kimberlite magmatism in the central to southeastern kaapvaal craton this coincidence in ages would be consistent with the contention based on experimental evidence that marid type rocks can be derived from group ii precursor magmas by olivine fractionation and exsolution of a carbonatitic component an alternative possibility not excluded by the zircon minimum ages is a genetic relation between marid metasomatism and karoo magmatism

zircon from the mantle a new way to date old diamonds we report the first successful dating by the shrimp u pb method of a tiny single zircon inclusion in a natural diamond from a kimberlite at mbuji mayi zaire the mbuji mayi diamonds are a composite suite of contrasting composition probable age and origins which includes diamonds of the typical ultramafic and eclogitic parageneses as well as many diamonds featuring a fibrous coating that formed in equilibrium with a volatile rich fluid phase the zircon diamond pair is believed to be cogenetic and the 628 pm 12 ma age obtained from the inclusion is the youngest yet recorded for a diamond originating in the earth s upper mantle though still much older than the cretaceous eruption age of the kimberlite host from which it was recovered significantly the age does not appear to correspond to any known geological event affecting the congo craton or adjacent areas as recorded in the currently exposed rocks unlike zircon megacrysts from mbuji mayi and elsewhere the inclusion is u rich up to 650 p

numerical study of an observed orogenic mesoscale convective system part 2 analysis of governing dynamics abstract a detailed analysis of the dynamics and thermodynamics responsible for the structure growth and propagation of an orogenic mesoscale convective system simulated in two dimensions is made the process of scale interaction is addressed through fourier analysis and reynolds averaging analysis of representative predicted variables diabatic forcing and momentum acceleration terms additional dynamical analysis is accomplished through sensitivity experiments in which coriolis diabatic heating and ambient airflow are varied the general conclusion is that the simulated orogenic development is a geostrophic adjustment process to convective heating which is itself modulated and maintained by orographically induced flow systems the heating scales range over a nearly continuous spectrum ranging from 10 250 km the heating occurs in response to primary advective gravity modes the larger scale gravity wave disturbances modulate the smaller scales by organizing mean upward vertical motion patterns the la

archean sulfide inclusions in paleozoic zircon megacrysts from the mir kimberlite yakutia implications for the dating of diamonds zircon megacrysts from the mir kimberlite yakutia contain inclusions of chromite chrome diopside magnesian olivine ni rich monosulfide solid solution and phlogopite the mineral chemistry of the inclusion suite suggests that the zircons grew in a metasomatized peridotite matrix twenty three zircons were chosen for u pb dating hf isotope and trace element determinations the trace element data are typical of kimberlitic zircons worldwide lam icpms u pb dating yields a weighted mean 206pb 236u age of 353 6 2 5 ma hf isotope measurements by lam mc icpms yield hf values of 3 0 9 2 and model ages tdm of 600 800 ma these data constrain the crystallization of the zircons to between 350 and 600 ma however lam mc icpms microanalysis of os isotopes in sulfides included in three zircons yields trd model ages of 2 37 2 92 ga tma 2 39 3 19 ga to explain the discordance between the ages of the zircons and their sulfide inclusions we suggest that these zircons grew in a metasomatized peridotite which contained sulfides that were residual from ancient melting events these sulfides together with other peridotite phases were trapped in the metasomatic zircon with little modification of their elemental or isotopic composition this model has important implications for the interpretation of re os model ages of sulfide inclusions in diamonds diamonds also could capture and preserve older sulfides during their growth or regrowth in mantle rocks and the inclusions therefore do not necessarily date the formation of the diamond

a case study of the interaction of a mesoscale gravity wave with a mesoscale convective system abstractthis study documents the high amplitude mesoscale gravity wave mgw event of 7 march 2008 in which two mgws strongly impacted the sensible weather over a large portion of the southeast united states these mgws exhibited starkly contrasting character despite propagating within similar environments the primary i e long lived mgw was manifest by a solitary wave of depression associated with rapid sinking motion and adiabatic warming while the secondary short lived mgw was manifest by a solitary wave of elevation mgwel dominated by rising motion and moist adiabatic cooling genesis of the primary mgw occurred as a strong cold front arrived at the foot of mexico s high terrain and perturbed the appreciable overriding flow the resulting gravity wave became ducted in the presence of a low level frontal stable layer and caused surface pressure falls up to 4 hpa the mgw later amplified as it became coupled with a stratiform precipitation system which led to its evolution into an intense

a mesoscale gravity wave event observed during ccope iii wave environment and probable source mechanisms abstract synoptic and special mesoscale observations taken during the cooperative convective precipitation experiment ccope are used to describe the multiscale environment of a gravity wave event understand the wave environment interactions that led to the development of severe thunderstorms and asses possible wave generation mechanisms the storms formed sequentially as a packet of gravity waves propagated across a stationary thunderstorm outflow boundary convection developed most rapidly in that part of the mesonetwork in which existed the combination of relatively high parcel buoyant energy weak restraining inversion strong storm downdraft potential and substantial vertical wind shear associated with a mesoscale jet streak synoptic scale analysis reveals that the waves were excited north of a stationary front and within the right exit region of the jet streak as it approached a stationary ridge in the 300 mb height field strong indications of unbalanced flow were diagnosed within the gravit

topographic effects on the tropical land and sea breeze abstractthe effect of an inland plateau on the tropical sea breeze is considered in terms of idealized numerical experiments with a particular emphasis on offshore effects the sea breeze is modeled as the response to an oscillating interior heat source over land the parameter space for the calculations is defined by a nondimensional wind speed a scaled plateau height and the nondimensional heating amplitude the experiments show that the inland plateau tends to significantly strengthen the land breeze part of the circulation as compared to the case without terrain the strengthening of the land breeze is tied to blocking of the sea breeze density current during the warm phase of the cycle the blocked sea breeze produces a pool of relatively cold stagnant air at the base of the plateau which in turn produces a stronger land breeze density current the following morning experiments show that the strength of the land breeze increases with the terrain height at least for moderate values of the height

chemical abrasion of zircon and ilmenite megacrysts in the monastery kimberlite implications for the composition of kimberlite melts abstract ilmenite and zircon megacrysts among other minerals representing the subcontinental lithospheric mantle are exclusively delivered to the surface by kimberlite magmas the intimate association of ilmenite and zircon with their transporting kimberlite melts still remains perplexing as these minerals do not belong to the kimberlite liquidus assemblage at crustal pressures the ilmenite and zircon megacrysts from the monastery kimberlite south africa represent a textbook example of the megacryst suite the megacrysts show substantial chemical modification along contacts with the host kimberlite fine grained reaction assemblages comprising minerals rich in zr baddeleyite and sodium zirconium silicates and ti ti fe oxides perovskite sphene kassite are present around zircon and ilmenite respectively at the zircon ilmenite contact chemical contributions from both minerals are recorded in zr ti rich phases such as calzirtite and zirkelite the megacrysts contain crystallised melt pools and secondary melt inclusions in healed fractures their mineral assemblage is dominated by alkali bearing phases including silicates nepheline kalsilite sodalite phlogopite tetraferriphlogopite titanates priderite freudenbergite zirconium silicates khibinskite parakeldyshite carbonates zemkorite eitelite phosphates apatite bradleyite nahpoite sulfates aphthitalite and chlorides halite sylvite these inclusions and melt pools are interpreted to be produced by reaction between the megacrysts and the transporting kimberlite melt which infiltrated fractures in the megacrysts most secondary minerals at contacts with kimberlite require a supply of ca which is readily available in the carbonatite component of the kimberlite magma the enrichment of the encapsulated mineral assemblages in alkali and volatile elements na k s cl also appears to originate from the kimberlite melt the similar u pb ages and identical hf isotope compositions of the megacryst assemblage 89 2 2 8 ma ehf 0 4 to 1 3 the reaction assemblage 98 7 ma and the host kimberlite 90 4 ma ehf 0 6 to 1 7 imply their close genetic affinity although the megacrysts and kimberlite magma originated from the same source at the same time the chemical disequilibrium recorded in the alteration of megacrysts precludes a simple parental melt cognate crystal relationships this apparent paradox can be resolved by considering the unmixing of a protokimberlite melt into silicate oxide and carbonate liquids at mantle conditions

origin of zircon megacrysts from cenozoic basalts in northeastern cambodia evidence from u pb age hf o isotopes and inclusions abstractzircon megacrysts found in basalts may provide a window into metasomatic processes and element transport in the upper mantle however little is known about the formation conditions of these zircons here we report u pb ages hf o isotope compositions trace element data and mineral inclusion analyses for six large fragments of zircon megacrysts from the gem village in northeastern cambodia the zircons have low contents of u th y p and rare earth elements rees 130 288 ppm the normalized ree pattern is characterized by a steeply rising slope from light rees to heavy rees and positive ce anomalies secondary ion mass spectrometer isotopic analyses on the zircon megacrysts yield a mean u pb age of 0 98 0 04 ma 2 and homogeneous oxygen isotopic composition with a mean 18o value of 5 0 0 18 2 identical to the 18o mantle value the 176hf 177hf values range from 0 282970 0 000024 2 to 0 283040 0 000016 2 with ehf 0 98 ma values of 6 6 9 0 obtained by the laser ablati

daytime boundary layer evolution over mountainous terrain part 1 observations of the dry circulations abstract this paper presents the boundary layer structure which accompanies the development of daytime local wind systems in a broad mountain valley as revealed by cross sections of potential temperature it describes how this structure leads to the occurrence of a region of convergence to the downwind side of mountains previous studies based primarily on one dimensional sounding of potential temperature and horizontal winds have shown that profiles of static stability and the presence of winds aloft have an important effect on the manner in which daytime thermally forced wind systems develop in the present study two dimensional cross sections obtained from aircraft data vertical soundings and surface mesonet data show several relevant features in mid to late morning near the surface for example upslope winds form in a shallow mixed layer at the underside of the nocturnal inversion layer cold pool at elevations above the top of this cold pool convectively mixed surface winds exist the spat

measurement of thermal properties of select intact and weathered granulites and their relationship to rock properties abstractunderstanding the thermal properties of granulites a group of high grade metamorphic rocks representing composition of lower crust of the earth is necessary to arrive at effective crustal heat flow modeling however the thermal conductivity and diffusivity of intact and weathered granulites and parameters that influence them are poorly known the above properties for a few felsic mafic and intermediate granulites and associated soils from the southern granulite terrain india were investigated using a cost effective self fabricated setup the results generated by this technique were precise reproducible and comparable with other published procedures and values because the samples analyzed were of intact in situ specimens the thermal conductivity and diffusivity could be directly used in practical applications among several parameters it was observed that sio2 mgo fe2o3 ratio grain size and bulk density were the principal factors to influence the conductivity and diffusivity of fresh

zircons from kimberlite new insights from oxygen isotopes trace elements and ti in zircon thermometry zircons found in mantle sourced kimberlite provide probes into the isotopic chemistry of the asthenosphere and subcontinental lithospheric mantle however little is known about the conditions of formation of these zircons a suite of 88 zircons found in kimberlites from africa siberia brazil and the united states have been analyzed for their ti concentration and selected zircons were analyzed for their rare earth element ree concentrations by ion microprobe in addition precise and accurate laser fluorination oxygen isotope data were obtained for zircons from brazil 5 1 0 3 1sd and the midwest united states 5 3 0 3 yielding mantle like d 18 o values similar to published data for africa 5 2 0 3 and siberia 5 3 0 2 most megacrysts in this study preserve fine scale oscillatory zoning in cl and are generally homogenous in oxygen isotopic composition consistent with preservation of primary compositions a few zircons from brazil show some evidence of chemical zoning due to recrystallization the ti content of mantle zircon is in general low with average compositions from each locality of 13 8 4 ppm 1sd kaapvaal craton 12 8 7 ppm siberian platform 18 11 ppm brazil and 4 8 4 3 ppm united states the recently calibrated ti in zircon thermometer yields an average temperature of 744 62 c 1sd for the average of 13 9 ppm ti with no correction for pressure atio2 o rasio2 the ti content of zircons found within rutile nodules from the orapa kimberlite kaapvaal craton is almost indistinguishable from those with no constraint on atio2 suggesting that reduced atio2 is not responsible for lower than expected mantle temperatures the average temperature in this study corresponds to 3 gpa on a 40 mw m 2 cratonic geotherm if correct this would suggest that zircon megacrysts from all four cratons formed in the shallow lithospheric mantle however there are several possibly confounding effects to this thermometer including a pressure correction and disequilibrium zircon growth zircons from rutile nodules have ree contents that span the range of mantle zircon ree and are similar to both zircon megacrysts and zircons from metasomatic assemblages 2007 elsevier ltd all rights reserved

numerical simulations of a gravity wave event over ccope part iii the role of a mountain plains solenoid in the generation of the second wave episode abstract mesoscale model simulations have been performed of the second episode of gravity waves observed in great detail in previous studies on 11 12 july 1981 during the cooperative convective precipitation experiment the dominant wave simulated by the model was mechanically forced by the strong updraft associated with a mountain plains solenoid mps as this updraft impinged upon a stratified shear layer above the deep well mixed boundary layer that developed due to strong sensible heating over the absaroka mountains the gravity wave was created this wave rapidly weakened as it propagated eastward however explosive convection developed directly over the remnant gravity wave as an eastward propagating density current produced by a rainband generated within the mps leeside convergence zone merged with a westward propagating density current in eastern montana the greatly strengthened cool pool resulting from this new convection then generated a bore wave that appeared to be continuous with the move

numerical simulations of a gravity wave event over ccope part ii waves generated by an orographic density current a mesoscale numerical model and detailed observations are used to investigate the generation and maintenance of a mesoscale gravity wave event observed in eastern montana on 11 july 1981 during the cooperative convective precipitation experiment ccope it is shown that the interaction between an orographic density current and a mountain barrier leads to the generation of the gravity waves the simulation results suggest the following four stage conceptual model during stage i shortly after sunset the remnant up branch of a thermally driven upslope flow east of the rockies was driven back toward the mountain by the pressure gradient force associated with a cool pool over north dakota the nocturnal stable layer over eastern montana was strengthened during passage of this density current during the 1 2 h transition period of stage ii the advancing density current became blocked as it encountered the higher terrain an isentropic ridge developed above the original warm lee trough due to strong adiabatic cooling caused by the sustained upward motion in the presence of orographic blocking during stage iii an even stronger upward motion center formed to the east of the density current head updraft in response to an eastward horizontal pressure gradient force produced by the isentropic ridge in stage iv as the density current head collapsed and downward motion developed to the west of the original updraft in quadrature phase with the isentropic perturbation a gravity wave was generated this wave propagated eastward with the mean wind opposite to the motion of the earlier density current and was maintained by the strong wave duct established earlier by the density current thus the mountain plains circulation may at times generate mesoscale gravity waves and deep convection hours after diurnal heating has ended

the synoptic setting and possible energy sources for mesoscale wave disturbances abstract thirteen case studies of mesoscale wave disturbances characterized by either a singular wave of depression or wave packets with periods of 1 4 h horizontal wavelengths of 50 500 km and surface pressure perturbation amplitudes of 0 2 7 0 mb are reviewed to isolate common synoptic features for these cases and to shed light on possible energy sources for the waves a strong thermal inversion in the lower troposphere north of a frontal boundary and a jet streak propagating toward a ridge axis in the upper troposphere are commonly observed in all the cases in general the area of wave activity is bounded by the jet axis to the west or northwest a surface front to the southeast an inflection axis between the trough and ridge axes to the southwest and the ridge axis to the northeast the conditions specified by lindzen and tung as being necessary to form a wave duct which include the existence of the lower tropospheric inversion seem to be met in many of these cases this suggests that a du

a transient method of measuring the thermal properties of rocks the aim of the paper is to describe a new rapid transient method for the determination of thermal diffusivity and thermal conductivity of rocks the present transient method is based on the application of a constant heat flux to the top surface of a block of rock that is insulated on all other surfaces results of a sensitivity analysis of the method indicate that thermal diffusivity can be measured to a best accuracy of about 3 percent and thermal conductivity of saturated rocks can be determined to a best accuracy of about 8 percent the method provides estimates of thermal conductivity that are consistent with estimates made using the steady state divided bar apparatus the method is applied to determine the thermal conductivity of a suite of rocks from western australian sedimentary basins

diurnal variations of warm season precipitation over northern china abstract this study examines the diurnal variations of the warm season precipitation over northern china using the high resolution precipitation products obtained from the climate prediction center s morphing technique cmorph during may august of 2003 09 the areas of focus are the yanshan taihangshan mountain ranges along the east peripheries of the loess and inner mongolian plateaus and the adjacent north china plains it is found that the averaged peak in local precipitation begins early in the afternoon near the top of the mountain ranges and propagates downslope and southeastward at a speed of 13 m s 1 the peak reaches the central north china plains around midnight and the early morning hours resulting in a broad area of nocturnal precipitation maxima over the plains the diurnal precipitation peak minimum is closely collocated with the upward downward branch of a mountain plains solenoid mps circulation both the mps and a low level southwesterly nocturnal jet are likely to be jointly resp

wave cloud lines over the arabian sea meteosat visible satellite images between 2006 and 2011 show wave cloud lines over the arabian sea in all months outside the summer monsoon june september these lines are most frequent between january and may 2 3 per month in a given year all wave cloud lines in the region propagate offshore as these wave cloud lines are associated with coherent convergence lines the objective technique described by berry and reeder is applied to the era interim reanalysis and a climatology of convergence lines at 850 hpa developed despite the coarse resolution of the era interim reanalysis the statistical properties of these lines are broadly constant with those deduced from the meteosat visible satellite images the generation mechanism is investigated in a simulation with the met office unified model of a particular wave cloud line 12 march 2011 the process appears to be similar to that over northwestern australia which has been documented previously during the day a synoptic scale northeasterly flow opposes the inland advection of the sea breeze on the west coast of india however as the daytime turbulence decays and the boundary layer stabilizes the northeasterly flow accelerates pushing offshore the leading edge of the sea breeze during the late evening and early hours of the morning a wave is generated as the northeasterlies penetrate the marine boundary layer and this wave propagates westward producing cloud at its leading edge where there is strong ascent

a mesoscale gravity wave event observed during ccope part ii interactions between mesoscale convective systems and the antecedent waves abstract this paper presents the results of a very detailed investigation into the effects of preexisting gravity waves upon convective systems as well as the feedback effects of convection of varying intensity upon the waves the analysis is based on the synthesis of synoptic surface and barograph data with high resolution surface mesonetwork radar and satellite data collected during a gravity wave event described by koch and golus in part i of this series of papers use is also made of the synoptic barograph data and satellite imagery to trace the waves beyond the mesonetwork and thus determine their apparent source region just upstream of the mesonetwork it is shown that two of the gravity waves modulated convection within a weak squall line as they propagated across the line the other six waves remained closely linked with convective systems that they appeared to trigger however it is shown that the waves were not excited by convection furthermore the waves retained their signatures in the su

petrophysical laboratory measurements for basin and reservoir evaluation the quality of computer modelling in basin and reservoir studies critically depends on the quality of input data core measurements may directly provide such data cores also help establish correlations between log measured parameters and parameters required in basin or reservoir evaluation correlations may also permit simple index measurements to be used for data assessment instead of more tedious laboratory procedures this paper summarizes different petrophysical laboratory techniques that can be utilized for these purposes the importance of performing laboratory measurements under representative conditions and to account for core damage effects is underlined

impacts of mountain plains solenoid on diurnal variations of rainfalls along the mei yu front over the east china plains abstractconvection permitting numerical experiments using the weather research and forecasting wrf model are performed to examine the impact of a thermally driven mountain plains solenoid mps on the diurnal variations of precipitation and mesoscale convective vortices along the mei yu front over the east china plains during 1 10 july 2007 the focus of the analyses is a 10 day simulation that used the 10 day average of the global analysis at 0000 utc as the initial condition and the 10 day averages every 6 h as lateral boundary conditions with diurnal variations only despite differences in the rainfall intensity and location this idealized experiment successfully simulated the observed diurnal variation and eastward propagation of rainfall and mesoscale convective vortices along the mei yu front it was found that the upward branch of the mps along with the attendant nocturnal low level jet is primarily responsible for the midnight to early morning rainfall enhancement along the mei yu front th

a mesoscale gravity wave event observed during ccope i multiscale statistical analysis of wave characteristics abstract this paper is the first in a series of three papers concerning a gravity wave event that occurred over the north central united states on 11 12 july 1981 the event is analyzed with superb detail resulting from the availability of digitized radar surface mesonetwork and other special data from the cooperative convective precipitation experiment ccope in montana the subject matter of this paper consists of 1 a statistical determination of the wave characteristics 2 a demonstration that the observed phenomena display a nature consistent with that of gravity waves and 3 a discussion of the principles and limitations of statistical methods for detecting and tracking mesoscale gravity waves two distinct wave episodes of 8 h duration within a longer 33 h period of wave activity are studied in detail both episodes contain strongly coherent bimodal wave activity the primary secondary wave mode isolated from autospectral and perturbation map analyses displays mean periods of 2 5 0 9 h

structure of an internal bore and dissipating gravity current as revealed by raman lidar abstract detailed moisture observations from a ground based raman lidar and special radiosonde data of two disturbances associated with a dissipating gust front are presented a synthesis of the lidar data with conventional meteorological data in conjunction with theoretical calculations and comparison to laboratory studies leads to the conclusion that the disturbances seen in both the lidar and accompanying barograph data represent a weak gravity current and an associated undular bore the disturbances display excellent coherence over hundreds of kilometers upstream of the lidar site bore formation occurs at the leading edge of the gust front coincidentally with the rapid weakening of the gravity current analysis suggests that the bore was generated by the collapse of the gravity current into a stable nocturnal inversion layer and subsequently propagated along this wave guide at nearly twice the speed of the gravity current the raman lidar provided detailed measurements of the vertical structure o

determination of matrix thermal conductivity from dry drill cuttings this paper reports experimental data relating the observed dry bulk thermal conductivities of powdered minerals to the porosities of the powdered aggregates the mineral samples were obtained by crushing quartz calcite and feldspar crystals experiments also were conducted on clays from various sources the experimental data suggest an exponential relationship between the dry bulk thermal conductivity and the aggregate porosity the thermal conductivities of the original quartz calcite and feldspar crystals were determined in a dry state to estimate their matrix thermal conductivities an empirical relationship was determined among dry bulk thermal conductivity aggregate porosity and matrix thermal conductivity this empirical relationship provided estimates of matrix thermal conductivity that were consistent with theoretical mix formulae for 50 50 mixtures of combinations of the minerals quartz calcite and feldspar and also a sample of flag sandstone from the north west shelf australia the method was used to estimate heat flows at the sites of two australian north west shelf wells dampier 1 and tryal rocks 1 which are 47 4 mw m2 and 79 7 mw m2 respectively these values are less than sea floor estimates of heat flow in the same region and suggest nonconductive heat transfer processes within the north west shelf sedimentary section

generation of mesoscale gravity waves in upper tropospheric jet front systems abstract multiply nested mesoscale numerical simulations with horizontal resolution up to 3 3 km are performed to study the generation of mesoscale gravity waves during the life cycle of idealized baroclinic jet front systems long lived vertically propagating mesoscale gravity waves with horizontal wavelengths 100 200 km are simulated originating from the exit region of the upper tropospheric jet streak in a manner consistent with past observational studies the residual of the nonlinear balance equation is found to be a useful index in diagnosing flow imbalance and predicting wave generation the imbalance diagnosis and model simulations suggest that balance adjustment as a generalization of geostrophic adjustment is likely responsible for generating these mesoscale gravity waves it is hypothesized that through balance adjustment the continuous generation of flow imbalance from the developing baroclinic wave will lead to the continuous radiation of gravity waves

sensitivity of mesoscale gravity waves to the baroclinicity of jet front systems abstract this study investigates the sensitivity of mesoscale gravity waves to the baroclinicity of the background jet front systems by simulating different life cycles of baroclinic waves with a high resolution mesoscale model four simulations are made starting from two dimensional baroclinic jets having different static stability and wind shear in order to obtain baroclinic waves with significantly different growth rates in all experiments vertically propagating mesoscale gravity waves are simulated in the exit region of upper tropospheric jet streaks a two dimensional spectral analysis demonstrates that these gravity waves have multiple components with different wave characteristics the short scale wave components that are preserved by a high pass filter with a cutoff wavelength of 200 km have horizontal wavelengths of 85 161 km and intrinsic frequencies of 3 11 times the coriolis parameter the medium scale waves that are preserved by a bandpass filter with 200 and 600 km cutoff wavelengths ha

daytime boundary layer evolution over mountainous terrain part ii numerical studies of upslope flow duration abstract numerical simulators of upslope flow forming on the lee side of a heated mountain ridge showed this flow to be a transient phenomenon in agreement with observations the simulations performed with a two dimensional dry version of the cloud model of tripoli and cotton included a nocturnal inversion layer cold pool and ridgetop winds cross sections of potential temperature and vertical profiles of potential temperature and horizontal winds reproduced observations well runs with and without the inversion layer showed that this layer was important in the formation of upslope winds near the ground when ridgetop level winds were present the runs without an inversion layer never developed upslope flow on the lee slopes runs in which the upper level winds were varied showed that the duration of the upslope flow on the lee slope bore an inverse relationship to upper level wind speed runs with stronger winds had shorter lived upslope flow a set of observations from south park colorado supporte

formation of paleoproterozoic eclogitic mantle slave province canada insights from in situ hf and u pb isotopic analyses of mantle zircons abstract in situ hf isotope analyses and u pb dates were obtained by laser ablation mc icp ms for a zircon bearing mantle eclogite xenolith from the diamondiferous jericho kimberlite located within the archean slave province nunavut canada the u pb zircon results yield a wide range of ages 2 0 to 0 8 ga indicating a complex geological history of importance one zircon yields a u pb upper intercept date of 1989 67 ma providing a new minimum age constraint for zircon crystallization and eclogite formation in contrast hf isotope systematics for the same zircons display an intriguing uniformity and corresponding hf depleted mantle model ages range between 2 1 0 1 and 2 3 0 1 ga the youngest hf model age is within error to the oldest u pb date the jericho eclogites have previously been interpreted as representing remnants of metamorphosed oceanic crust and their formation related to paleoproterozoic subduction regimes along the western margin of the archean slave craton during the wopmay orogeny hf isotope compositions and u pb results for the jericho zircons reported here are in good agreement with a paleoproterozoic subduction model suggesting that generation of oceanic crust and eclogite formation occurred between 2 0 and 2 1 ga the slightly older hf depleted mantle model ages 2 1 to 2 3 ga may be reconciled with this model by invoking mixing between crustal derived hf from sediments and more radiogenic hf associated with the oceanic crust during the 2 ga subduction event this results in intermediate hf isotope compositions for the jericho zircons that yield fictitiously older hf model ages

origin evolution and finescale structure of the st valentine s day mesoscale gravity wave observed during storm fest part iii gravity wave genesis and the role of evaporation abstract on 14 february 1992 a long lived moderate amplitude mesoscale gravity wave formed in kansas during the storm scale operational and research meteorology fronts experiment systems test storm fest wave formation was evident in correlated surface pressure and wind fields the wave of depression accompanied by a weak rainband tracked across the state a wealth of data was collected on the mature wave as it passed over the storm fest dual doppler domain however the mechanism of genesis remained difficult to ascertain since wave formation occurred in a region of less comprehensive observations the genesis of the storm fest gravity wave is successfully simulated using the fifth generation pennsylvania state university national center for atmospheric research penn state ncar mesoscale model mm5 which was run at 6 km grid spacing in the innermost domain the lee cyclone movement dry airmass development and gravity wave formation over kansas were successfully captured by the model results

detection of geothermal anomalies using advanced spaceborne thermal emission and reflection radiometer aster thermal infrared images at bradys hot springs nevada usa abstract surface temperature anomalies associated with geothermal activity at bradys hot springs churchill county nevada were mapped using advanced spaceborne thermal emission and reflection radiometer aster thermal infrared tir image data in order to highlight subsurface contributions of geothermal heat the aster images were processed to minimize temperature variations caused by the diurnal heating effects of the sun surface temperature variations caused by changes in albedo were corrected with visible and near infrared aster bands and a 10 meter smoothed digital elevation model dem was used to correct for topographic slope effects field measurements of ground surface temperatures made over 24 hour periods were used to design a thermal inertia correction incorporating day and night thermal infrared images in the resulting processed image background temperature variations were reduced 30 50 without reducing the intensity of geothermal anomalies thus making it easier to distinguish geothermal activity from false anomalies caused by non thermal springs topographic effects and variable rock soil and vegetation compositions

zircon inclusions in corundum megacrysts i trace element geochemistry and clues to the origin of corundum megacrysts in alkali basalts abstract zircons enclosed in corundum megacrysts from basalts have a short prismatic habit with the prism slightly more developed than the pyramidal faces the 110 prism is dominant compared with 100 indicating crystallisation from alkaline peralkaline environments rare zircon decomposition reactions suggest the possible presence of a primary sio 2 phase in the source paragenesis for corundum megacrysts the zircon inclusions are geochemically distinctive high y up to 1 2 u uo 2 up to 1 7 wt th tho 2 up to more than 2 wt hf up to 3 4 wt and ree ree up to 5000 ppm they form a cogenetic group that is characterised by extreme ree fractionation with preference for the hree varying from 30 100 chondritic sm to 5000 20000 chondritic lu ree partitioning between zircon and silicate liquid is evaluated the parental melts calculated for the zircon inclusions and other corundum related zircons using zircon melt partition coefficients derived in the present paper show concave down ree patterns with a maximum sm concentration close to 100 chondritic sm abundance such ree patterns represent highly evolved melts after extensive fractionation of low ca feldspar prior to and throughout the crystallisation of zircon the characteristics of zircon inclusions provide evidence that corundum megacrysts must have crystallised from alkaline and highly evolved melts under very reducing conditions implying that the corundum is unlikely to have formed as high pressure phenocrysts in the host mafic magmas

processes leading to the formation of mesoscale waves in the midwest cyclone of 15 december 1987 abstract on 15 december 1987 several long lived large amplitude mesoscale wave disturbances accompanied a rapidly developing extratropical cyclone in the midwest united states previous observational and modeling studies have suggested that the disturbances had large amplitudes and long lifetimes as a result of a wave cisk type instability occurring within an imperfect wave duct and were initiated by convection however infrared ir satellite imagery and radar echoes shortly before the wave disturbances formed suggest that convection was not the primary feature in the wave genesis region at that time instead a meso scale comma shaped cloud was present and appeared to evolve into the wave disturbances the origins of the comma cloud can be traced back to a cloud streak and precipitation maximum in the left exit region of an approaching jet streak over northern mexico 15 h earlier in this study satellite observations are examined in conjunction with numerical simulations of the case to explore a n

rainy season precipitation over the sichuan basin and adjacent regions in southwestern china abstractthe spatial variability and diurnal propagation of mean precipitation in the summer rainy seasons from 2003 to 2010 over the sichuan basin scb and adjacent mountainous regions are examined using high spatiotemporal resolution satellite derived precipitation estimates the scb is located just east of the tibetan plateau tp and is prone to heavy precipitation that often peaks over nighttime and early morning the large scale environment over the scb during the rainy season is characterized by weak low to midtropospheric convergence in the lee of the tp and by the upper tropospheric jet stream to the north under this flow configuration the study links the unique diurnal variations in the precipitation pattern and propagation to the unique topography in this region it is found that during the rainy season the local diurnal precipitation maximum moves primarily downslope and southeastward from over the tp in the daytime to scb at night a secondary maximum moves northeastward downslope of t

hf isotopic compositions of the standard zircons and baddeleyites used in u pb geochronology abstract zircon and baddeleyite u pb geochronological dating is widely used in solid earth sciences and the advent of rapid in situ methods of analysis such sims and icp ms has re emphasized the importance of having uniform standards recently it has been shown that hf isotopic data can provide important information on these minerals since they contain high concentrations of hf but have low lu hf ratios which results in negligible age correction however the complex internal structures that result from multiple thermal events such as inherited cores and metamorphic overgrowths require that the hf isotopic data be measured with high spatial resolution however the isobaric interferences of 176 yb and 176 lu on 176 hf hamper the precise determination of the 176 hf 177 hf ratio during in situ laser ablation mc icpms analysis it is shown here that mass biases of yb yb and hf hf change with time during analyses and behave differently for solutions and solid material therefore it is suggested that the mean yb value of the individual spot be used to obtain the precise isotopic composition for in situ zircon and baddeleyite hf isotopic analyses for low yb hf 176 yb 177 hf yb value have little effect on the accuracy of the hf isotopic composition however the appropriate yb isotopic abundance is necessary for high yb hf 176 yb 177 hf 0 001 zircons and baddeleyites since the interference of 176 yb on 176 hf is significant using the mean yb value of the individual spot and newly published yb isotopic abundance data six standard zircons and two standard baddeleyites have been investigated using a neptune mc icpms with 193 nm laser for zircons the obtained 176 hf 177 hf ratios are 0 282307 31 2sd for 91500 0 282680 31 2sd for temora 0 281729 21 2sd for cz3 282177 17 2sd for cn92 1 0 282983 17 2sd for fm0411 and 281234 11 2sd for phalaborwa the baddeleyites from phalaborwa and sk10 2 have 176 hf 177 hf ratios of 0 281238 12 and 0 282738 13 2sd these results agree well with the values obtained by the solution method and indicate that these standards have different hf isotopic compositions in which the extremely low 176 lu 177 hf and 176 yb 177 hf values of cz3 zircon and phalaborwa baddeleyite make them excellent standards for machine calibration during in situ zircon hf isotopic measurement with the other standards being more suitable for the development of the correction method

rare earth element selenochemistry of immiscible liquids and zircon at apollo 14 an ion probe study of evolved rocks on the moon abstract secondary ion mass spectrometry sims analyses of trace elements in two zircons from 14001 7003 are similar in most respects to one reported recently hinton and meyer 1991 hinton and upton 1991 the major difference being the lack of a positive ce anomaly in the zircon ree pattern reported here which obviates an oxidizing environment for lunar zircon using recently published ree partition coefficients all three lunar zircons indicate separation from a primitive magma with a large negative eu anomaly which is slightly lree enriched and contains rees 10 30 cl chondrites however this calculated liquid has a ree pattern which is unlike the host material or any lunar granite it is postulated that these lunar zircons were precipitated in the upper crust of the moon from late stage gabbroic to anorthositic magmas which have undergone extensive fractionation the exact nature of these evolved magmas remains uncertain evidence for suspected immiscible liquids has been found as glasses in fragments from sample 14001 7003 though the granitic complement to this immiscible pair is a viable immiscible liquid composition the mafic complement has likely undergone some post immiscibility modification however the original liquid liquid element partitioning has not been grossly affected by the post immiscibility modification analyses of the glasses by sims yields a set of partitioning data for the ree in actual rocks from the moon for the most part the partitioning of the rees between the glasses is consistent with that determined experimentally and indicates the importance of liquid immiscibility in late stage lunar igneous processes

heat flow measurements in late palaeoproterozoic to permian geological provinces in south and central norway and a new heat flow map of fennoscandia and the norwegian greenland sea abstract new heat flow determinations from 9 sites in south and central norway situated in late palaeoproterozoic to permian geological provinces show that topographically and palaeoclimatically corrected surface heat flow generally varies between 50 and 60 mw m 2 the palaeoclimatic corrections are significant typically constituting 10 20 of the final heat flow values higher heat flow was encountered at 3 sites however only at the fredrikstad site situated in the high heat producing iddefjord granite could this elevated heat flow be related to high heat production a compilation of new and previously published heat flow data from norway show that on the scale of major geological provinces heat flow varies significantly and is generally overlapping the lowest heat flow values ca 30 mw m 2 come from the early palaeoproterozoic karasjok kautokeino greenstone belt and the early neoproterozoic egersund anorthosite complex both of which are dominated by low heat producing rocks the highest heat flow values ca 60 80 mw m 2 come from early neoproterozoic high heat producing post orogenic granites in south norway these geological provinces display relatively little variation in lithology and heat production which allows such relationships to be made in general however significant lithological variation within geological provinces makes relationships between heat flow and geological factors such as tectonometamorphic age lithology and heat production on a country scale obscure at best in contrast a compilation of almost 1000 heat flow measurements from fennoscandia and the norwegian greenland sea shows a distinct correlation between heat flow and tectonic age the archaean provinces in ne fennoscandia karelia display low heat flow of ca 35 40 mw m 2 increasing gradually to ca 50 55 mw m 2 southwestwards in palaeoproterozoic and mesoproterozoic provinces the transscandinavian igneous belt which consists largely of relatively high heat producing granites breaks this trend with a heat flow of ca 60 65 mw m 2 on the norwegian continental margin the heat flow is rather constant at ca 60 mw m 2 and the oceanic crust shows an exponential increase in heat flow from ca 60 mw m 2 near the continent ocean boundary oceanic crust ca 55 million years old to 200 mw m 2 near the mid atlantic spreading ridge similar to heat flow determined from oceanic crust elsewhere as well as to theoretical models of oceanic heat flow although a number of factors may render individual heat flow measurements uncertain the abundance of available data obtained by different methods and the clear correlation between heat flow and geology provide confidence as to the significance of these heat flow values