modification and preservation of environmental signals in speleothems speleothems are primarily studied in order to generate archives of climatic change and results have led to significant advances in identifying and dating major shifts in the climate system however the climatological meaning of many speleothem records cannot be interpreted unequivocally this is particularly so for more subtle shifts and shorter time periods but the use of multiple proxies and improving understanding of formation mechanisms offers a clear way forward

diffusion kinetics of fe2 and mg in aluminous spinel experimental determination and applications the diffusion coefficients of fe2 and mg in aluminous spinel at 20 kb 950 to 1325 c and at 30 kb 1125 c have been determined via diffusion couple experiments and numerical modeling of the induced diffusion profiles the oxygen fugacity fo2 was constrained by graphite encapsulating materials the retrieved self diffusion coefficients of fe2 and mg at 20 kb 950 to 1325 c fit well the arrhenian relation d d0exp q rt where q is the activation energy with d0 fe 1 8 2 8 10 5 d0 mg 1 9 1 4 10 5 cm2 s q fe 198 19 and q mg 202 8 kj mol comparison with the data at 30 kb suggests an activation volume of 5 cm3 mol from analysis of compositional zoning in natural olivine spinel assemblages in ultramafic rocks previous reports concluded that d fe mg in spinel with cr cr al 0 5 is 10 times that in olivine the diffusion data in spinel and olivine have been applied to the problems of preservation of mg isotopic inhomogeneity in spinel within the plagioclase olivine inclusions in allende meteorite and cooling rates of terrestrial ultramafic rocks

dynamic crystallization of chondrule melts of porphyritic and radial pyroxene composition abstract dynamic crystallization experiments in which heterogeneous nucleation is an important variable have been completed on four melts of chondrule composition compositions were chosen to best represent chondrules with porphyritic pyroxene and radial pyroxene textures experimental results show that heterogeneous nucleation is essential for the formation of porphyritic textures without preexisting nuclei too much supercooling is established before crystallization is initiated and the textures are more likely to be dendritic or radial in the near total absence of nuclei radial textures can form at cooling rates as slow as 5 c hr in this study by varying the heterogeneous nucleation conditions and having a melt in which the appropriate phases are stable or metastable analogs to most of the recognized chondrule textures can be produced in a single melt composition olivine inclusions in pyroxene can form readily during an experiment from a starting material which did not initially contain olivine crystals thus care must be taken in the assumption that olivine inclusions in pyroxene represent preexisting crystals

the stable isotopic composition of modern soil carbonate and its relationship to climate the oxygen isotopic composition of modern soil carbonate is well correlated with the isotopic composition of local meteoric water the carbon isotopic cycle for co 2 in soils can be described in terms of the proportion of biomass using the c 4 photosynthetic pathway and the co 2 respiration rate of the soil at low soil respiration rates significant atmospheric co 2 mixing can occur in general the carbon isotopic composition of soil carbonate is related to the proportion of c 4 biomass present in soil but soils that freeze to the depth of carbonate formation often have a significant atmospheric component this suggests that freezing of the soil solution should be considered as another important mechanism for soil carbonate formation because of these relationships the isotopic composition of soil carbonate may be a paleoclimatic and paleoecologic indicator in cases in which diagenetic alteration has not occurred

origin of zoned metal grains in the que94411 chondrite laser ablation inductively coupled plasma mass spectrometry la icp ms was used to measure distributions of the siderophile elements p v cr fe co ni mo ru rh pd w re os ir and pt in metal grains in the metal rich chondrite que94411 with a spatial resolution of similar to 30 mum the platinum group elements pges except pd exhibit radial zoning in these grains that mimics that previously observed in ni and co the concentrations of these elements decreases from the cores to the rims of the grains the pge distributions support a condensation origin for the enhanced refractory element abundances in the zoned grains the lack of zoning in pd refutes an origin by a redox controlled process and none of the pge ni relationships support an origin by fractional crystallization from a metallic melt several models of grain formation were explored including equilibrium fractional condensation which failed to yield the correct radial zoning the zoning may be the product of a nonequilibrium fractional condensation process in which the refractory siderophiles remained supersaturated in the cooling solar nebula or of diffusion between refractory enhanced fe ni cores and other fe ni metal that may have been deposited later from the solar nebula copyright c 2001 elsevier science ltd

formation of metal in the ch chondrites alh 85085 and pca 91467 abstract siderophile element distributions within individual metal grains in two ch chondrites allan hills 85085 and pecora escarpment 91467 were measured by laser ablation inductively coupled plasma mass spectrometry those metal grains that are zoned in ni were also found to be zoned in other refractory siderophile elements such as ru but not in pd which is not refractory but is highly siderophile this pattern is consistent with an origin by condensation from a gas of approximately solar composition but not with an origin by redox processes or fractional crystallization the unzoned metal grains in ch chondrites were found to be frequently depleted in ru but not in pd consistent with later stage condensation from a solar gas after removal of the zoned metal gold is inversely correlated with ni in the unzoned metal grains and mean au abundances in zoned metal are always low both zoned and unzoned metal in ch chondrites could plausibly be produced from a thermostatically regulated nebula followed by rapid removal of the zoned metal and slower removal of the unzoned metal both at temperatures near or above the condensation temperature of au 1250 k this is also consistent with the isolation temperatures inferred from silicate grains in ch chondrites by previous workers based on their volatile element inventories the volatile siderophile cu is enriched in the rims relative to the interiors of both zoned and unzoned grains and is interpreted as the product of diffusion during low grade thermal processing the similarity of cu distributions and degree of kamacite taenite exsolution between zoned and unzoned metal in ch chondrites suggests that the two populations of metal experienced modest thermal metamorphism after they were brought together in the same environment probably on the ch parent body fragmentation and size sorting of the metal must have post dated the cu zoning and may have occurred in a regolith on the ch parent body the compositions of ch metal like that of metal from que 94411 and hh 237 are consistent with a nebular origin and may be the most primitive nebular materials as distinct from presolar grains sampled by chondrites

climate and vegetation history of the midcontinent from 75 to 25 ka a speleothem record from crevice cave missouri usa four missouri stalagmites yield consistent overlapping records of oxygen and carbon isotopic changes and provide a climate and vegetation history with submillennial resolution from 75 to 25 thousand years ago ka the thorium 230 dated records reveal that between 75 and 55 ka the midcontinental climate oscillated on millennial time scales between cold and warm and vegetation alternated among forest savanna and prairie temperatures were highest and prairie vegetation peaked between 59 and 55 ka climate cooled and forest replaced grassland at 55 ka when global ice sheets began to build during the early part of marine oxygen isotope stage 3

seasonal variations in sr mg and p in modern speleothems grotta di ernesto italy sub annual variations in trace element chemistry and luminescence have recently been demonstrated from speleothems and offer the potential of high resolution palaeoclimatic proxies however no studies have yet examined microscopic trace element variations in relation to modern cave conditions in this study the spatial variations in trace element sr mg and p concentrations in speleothems a stalagmite and a soda straw stalactite from the alpine ernesto cave temperature 6 6 0 1 c in a forested catchment in ne italy have been studied using secondary ion mass spectrometry sims and compared with environmental parameters and waters in the modern cave an annual lamination exists in the stalagmite and soda straw stalactite in the form of clear calcite with narrow visible layers which are uv fluorescent and interpreted to contain soil derived humic fulvic acids washed into the cave during autumn rains microanalyses were undertaken of seven annual laminae probably deposited during the 1960s in the stalagmite and seven laminae in the 1990s for the stalactite the analysis results show that sr consistently has a trough and p a peak centred on the inclusion rich layer mg shows mainly a negative covariation with sr in laminae formed in the 1990s but a positive covariation in the stalagmite formed in 1960s the spatial scale of the main geochemical variations is the same as that of annual laminae of inclusion poor and inclusion rich couplets mass balance arguments are used to show that the p is inorganic in form and presumably occurs as individual phosphate ions within the calcite most drip waters show limited chemical variations but a summer peak in trace elements in 1995 and a decrease in mg ca in the following winter are notable more pronounced covariations in mg ca and sr ca are shown by a site with highly variable drip rates where ratios increase at slow drip rates the strongest seasonal variations are found in pool waters where ratios increase reflecting significant ca removal from the water into the calcite during the winter in response to seasonal pco2 variations in cave air thus the cave waters compositions tend to reflect climate conditions such that mg ca and sr ca are tentatively interpreted to be higher when climate conditions are dry combining results from the speleothems and cave water along with the behaviour of each trace species mg ca variations in the speleothems are considered to reflect their variation in the cave waters whereas sr incorporation is also dependent on precipitation rate in this case mainly controlled by temporal variations in pco2 in the cave and conceivably also by inhibitors such as phosphate p adsorption a fraction of which is subsequently incorporated within calcite depends on aqueous phosphate concentration and water flux both of which should increase during the autumn therefore multiple trace element profiles in speleothems reflect multiple aspects of environment seasonality and conditions and hence a calibration against weather records is desirable to establish their palaeoclimatological meaning the strong annual variation of trace elements and particularly p can provide chronological markers for high resolution studies of other climate proxies such as stable isotopes

large intensity changes in tropical cyclones a case study of supertyphoon flo during tcm 90 abstract a unique dataset recorded during the rapid intensification and rapid decay of typhoon flo is analyzed to isolate associated environmental conditions and key physical processes this case occurred during the tropical cyclone motion tcm 90 field experiment with enhanced observations especially in the upper troposphere beyond about 300 km these data have been analyzed with a four dimensional data assimilation technique and a multiquadric interpolation technique while both the ocean thermal structure and vertical wind shear are favorable they do not explain the rapid intensification or the rapid decay a preconditioning phase is defined in which several interrelated factors combine to create favorable conditions i a cyclonic wind burst occurs at 200 mb ii vertical wind shear between 300 and 150 mb decreases 35 iii the warm core is displaced upward and iv 200 mb outflow becomes larger in the 400 1200 km radial band while a layer of inflow develops below this outflow these condit

annual trace element variations in a holocene speleothem high resolution secondary ionization mass spectrometry sims analysis along the growth axis of a holocene speleothem from northern scotland reveals high frequency oscillations and longer term trends in mg ca sr ca and ba ca at the scale of the high frequency oscillations mg ca and sr ca display a well defined anticorrelation while sr ca and ba ca are positively correlated imaging of elemental ratios in two dimensions reveals that the high frequency signal is well preserved and laterally continuous across the sample tims 230th ages and annual ultraviolet luminescence banding provide chronological control and demonstrate that the high frequency cyclicity is annual trace element variations in speleothem calcite are a reflection of hydrochemical processes in the unsaturated zone overlying the cave supply effects and partitioning at the water calcite interface mg partitioning between water and calcite is temperature dependent calculations suggest that the annual mg ca oscillations may be caused by seasonal temperature changes however the longer timescale variations in mg ca are too great to be explained by this mechanism seasonal variations in water residence time in the unsaturated zone which reflect effective precipitation provide a more probable explanation for the observed annual oscillations and also explain the inverse relationship between mg ca and sr ca this record suggests that trace elements in speleothems have the potential to provide the high resolution insights into interannual palaeoclimatic variability required for assessment of general circulation models

anthropogenic impact records of nature for past hundred years extracted from stalagmites in caves found in the nanatsugama sandstone formation saikai southwestern japan abstract in the nanatsugama area saikai city nagasaki prefecture japan covered by paleogene calcareous sandstone the environmental change information for the past hundred years was extracted from growing stalagmites in two limestone caves their annual microbanding information was used for dating from the shimizu do cave stalagmites the vegetation change from forest to grassland during 1500 to 1700 could be read using the carbon isotope and mg ca ratios of the stalagmites before 1500 the stable carbon isotope ratios ranged from 9 to 10 which are characteristic of forest vegetation from 1600 to 1700 the stable carbon isotope ratio increased 13 c 2 suggesting a drastic change to grassland vegetation probably for the purpose of collecting grasses for agricultural use the increase in mg ca due to the reduction in the biomass from 1500 to 1700 also showed the vegetation change from forest to grassland a ryuo do cave stalagmite recorded the change in the so 4 2 concentration several times during the period from 1600 to 1900 in addition to the sulfate of sea salt origin the higher concentration and smaller 34 s of sulfate in the ryuo do cave drip water compared to those in the shimizu do cave drip water may be due to the oxidation of biogenic pyrite in the marine kamashikiyama tuff formation which covers the calcareous sandstone of the nanatsugama sandstone formation the oxidation of pyrite is promoted by the biological activity of sulfur oxidizing bacteria under oxic conditions indicating that the surface cover was repeatedly changed into non paddy fields the change in the so 4 2 concentration could then be related to the changes in the amount of the nagasaki prefecture coal production in the early 20th century and the china fossil fuel consumption in the late 20th century transported a long distance by a monsoon from the china continent thus the combination of annual microbanding information and the mg 2 and so 4 2 concentrations and c and s stable isotope ratios of the stalagmites made it possible to extract local and or global anthropogenic environmental changes in nature the records extracted in this way were in good agreement with those partially extracted from ancient documents ancient picture maps and topographical maps

episodes of late holocene aridity recorded by stalagmites from devil s icebox cave central missouri usa two stalagmites from devil s icebox cave central missouri display similar 13 c and 18 o values and trends during the late holocene positive 13 c excursions at 3 5 2 6 ka and 1 2 0 9 ka are interpreted to reflect drier conditions these elevated stalagmite 13 c values could have plausibly been driven by increasing c4 plant abundances over the cave or an increased contribution of bedrock carbon both of which could reflect decreased effective moisture a lack of corresponding oxygen isotopic anomalies during these intervals suggests that neither mean annual temperature nor the seasonality of precipitation changed concomitantly with dryness both of the 13 c excursions identified in our stalagmite record are roughly

prediction and diagnosis of the motion and rapid intensification of typhoon sinlaku during tropical cyclone structure experiment 2008 tcs08 abstractthe impact of initial structure on storm evolution is examined for the case of a tropical storm entering rapid intensification at the onset of rapid intensification satellite cloud signatures suggest that the structural organization of typhoon sinlaku 2008 was dominated by a primary band of convection present at outer radii the development of the eyewall subsequently occurred within this band of deep convection numerical forecasts of sinlaku are initialized at 15 and 5 km resolution using a broad range of vortex scales at a time when the storm was still weak and its structure not clearly defined evidence is presented that beta propagation played a key role in changing the storm s motion under weak environmental steering it is found that the track forecast improves over the period when beta propagation is prominent if the vortex is initialized with a large radius of maximum wind rmw corresponding with the primary outer cloud band the initial vortex structure is also suggested to play a

heavily hydrated lithic clasts in ch chondrites and the related metal rich chondrites queen alexandra range 94411 and hammadah al hamra 237 fine grained heavily hydrated lithic clasts in the metal rich cb chondrites queen alexandra range que 94411 and hammadah al hamra 237 and ch chondrites such as patuxent range pat 91546 and allan hills alh 85085 are mineralogically similar suggesting genetic relationship between these meteorites these clasts contain no anhydrous silicates and consist of framboidal and platelet magnetite prismatic sulfides pentlandite and pyrrhotite and fe mn mg bearing ca carbonates set in a phyllosilicate rich matrix two types of phyllosilicates were identified serpentine with basal spacing of similar to0 73 nm and saponite with basal spacings of about 1 1 1 2 nm chondrules and feni metal grains in cb and ch chondrites are believed to have formed at high temperature 1300 k by condensation in a solar nebula region that experienced complete vaporization the absence of aqueous alteration of chondrules and metal grains in cb and ch chondrites indicates that the clasts experienced hydration in an asteroidal setting prior to incorporation into the ch and cb parent bodies the hydrated clasts were either incorporated during regolith gardening or accreted together with chondrules and feni metal gains after these high temperature components had been transported from their hot formation region to a much colder region of the solar nebula

refractory calcium aluminum rich inclusions and aluminum diopside rich chondrules in the metal rich chondrites hammadah al hamra 237 and queen alexandra range 94411 the metal rich chondrites hammadah al hamra hh 237 and queen alexandra range que 94411 paired with que 94627 contain relatively rare 1 vol calcium aluminum rich inclusions cais and al diopside rich chondrules forty cais and cai fragments and seven al diopside rich chondrules were identified in hh 237 and que 94411 94627 the cais 50 400 mum in apparent diameter include a 22 56 pyroxene spinel melilite forsterite rim b 11 28 forsterite bearing pyroxene spinel melilite anorthite forsterite rim c 2 5 grossite rich spinel melilite pyroxene rim d 2 5 hibonite melilite spinel pyroxene forsterite rim e 1 2 hibonite bearing spinel perovskite melilite pyroxene rim f 1 2 spinel melilite pyroxene anorthite and g 1 2 amoeboid olivine aggregate each type of cai is known to exist in other chondrite groups but the high abundance of pyroxene spinel melilite cais with igneous textures and surrounded by a forsterite rim are unique features of hh 237 and que 94411 94627 additionally oxygen isotopes consistently show relatively heavy compositions with delta o 17 ranging from 6 parts per thousand to 10 parts per thousand 1 sigma 1 3 parts per thousand for all analyzed cai minerals grossite hibonite melilite pyroxene spinel this suggests that the cais formed in a reservoir isotopically distinct from the reservoir s where normal o 16 rich delta o 17 20 cais in most other chondritic meteorites formed

formation of unequilibrated r chondrite chondrules and opaque phases abstract sulfide assemblages are commonly found in chondritic meteorites as small inclusions in the matrix or in association with chondrules these assemblages are widely hypothesized to form through pre accretionary corrosion of metal by h2s gas or through parent body processes we report here on two unequilibrated r chondrite samples that contain large chondrule sized sulfide nodules in the matrix both samples are from mount prestrud pre 95404 chemical maps and spot and broad beam electron microprobe analyses empa were used to assess the distribution stoichiometry and bulk composition of sulfide nodules and silicate chondrules in the clasts oxygen isotope data were collected via secondary ion mass spectrometry sims to assess the relationship of chondrules to other chondrite groups scanning electron microscopy sem focused ion beam fib and transmission electron microscopy tem analyses were used to assess fine scale features and identify crystal structures in sulfide assemblages thermodynamic models were used to assess the temperature sulfur fugacity fs2 total pressure dust to gas ratio and oxygen fugacity fo2 conditions during sulfide nodule and chondrule formation the unequilibrated clasts include a mixture of type i and type ii chondrules as well as non porphyritic chondrules chondrule oxygen isotopes overlap with ordinary chondrite chondrules sulfide nodules average 200 m in diameter have rounded shapes and are primarily composed of pyrrhotite pentlandite and magnetite some are deformed around chondrules in a petrologic relationship similar in appearance to compound chondrules both nodules and sulfides in chondrules include phosphate inclusions and cu rich lamellae which suggests a genetic relationship between sulfides in chondrules and in the matrix ni co ratios for matrix and chondrule sulfides are solar while fe and ni are non solar and inversely related we hypothesize that sulfide nodules formed via pre accretionary melt processes during chondrule formation precursors composed of a mixture of silicate and sulfide material were heated to form immiscible melt droplets which separated and cooled to form si rich chondrules and s rich nodules sulfide melt was stabilized by a high total pressure 1 atm in a dust or ice enriched environment heating of this material contributed to a high fs2 2 10 3 atm at 1138 c and high fo2 iw 1 to iw 4 in an environment with peak temperatures between 1539 c and 1750 c oxygen isotopic compositions in this region were similar to those recorded by the ll chondrite chondrules

shock melts in que 94411 hammadah al hamra 237 and bencubbin remains of the missing matrix we have studied the cb carbonaceous chondrites queen alexandra range que 94411 hammadah al hamra hh 237 and bencubbin with an emphasis on the petrographical and mineralogical effects of the shock processing that these meteorite assemblages have undergone iron nickel metal and chondrule silicates are the main components in these meteorites these high temperature components are held together by shock melts consisting of droplets of dendritically intergrown fe ni metal sulfide embedded in silicate glass which is substantially more feo rich 3040 wt than the chondrule silicates feo 5 wt fine grained matrix material which is a major component in most other chondrite classes is extremely scarce in que 94411 and hh 237 and has not been observed in bencubbin this material occurs as rare hydrated matrix lumps with major and minor element abundances roughly similar to the ferrous silicate shock melts and cl we infer that hydrated fine grained material compositionally similar to these matrix lumps was originally present between the fe ni metal grains and chondrules but was preferentially shock melted other shock related features in que 94411 hh 237 and bencubbin include an alignment and occasionally strong plastic deformation of metal and chondrule fragments

external influences on hurricane intensity part iii potential vorticity structure abstract the interaction of hurricane elena 1985 with a baroclinic wave was reexamined using both potential vorticity pv and a formulation for eliassen palm fluxes in cylindrical coordinates the hurricane began to deepen rapidly as a narrow upper level positive pv anomaly became nearly superposed over the low level center the intensification appeared to represent an evaporation wind feedback activated by constructive interference of the pv anomalies enhanced convection associated with this process eroded the upper pv anomaly and prevented it from crossing the hurricane and reversing the intensification the eliassen palm flux divergence showed that maximum eddy activity remained in the upper troposphere prior to the reintensification this activity was produced in part because the action of the outflow anticyclone of the hurricane contributed to synoptic scale wave breaking the upper level pv anomaly that approached the center was much narrower in extent than the original synoptic scale trough th

some aspects of hurricane inner core dynamics and energetics abstract the energy cycle of the mature hurricane resides in the secondary circulation that passes through the storm s eyewall by equating the generation of energy in this cycle to boundary layer dissipation an upper bound on wind speed is derived this bound depends on the degree of thermodynamic disequilibrium between the tropical ocean and atmosphere on the difference between sea surface and outflow absolute temperatures and also on the ratio between the enthalpy exchange and surface drag coefficients such a bound proves to be an excellent predictor of maximum wind speeds in two different axisymmetric numerical models and does not appear to depend on the existence of the hurricane eye but further consideration of the detailed dynamics of the eye and eyewall show that the intensification of hurricanes is accelerated by feedbacks associated with a component of eye subsidence forced by radial turbulent diffusion of momentum this radial momentum diffusion is an inevitable by product of the strong fr

the effect of relative flow on the asymmetric structure in the interior of hurricanes abstract asymmetric structure of tropical cyclones simulated by the geophysical fluid dynamics laboratory high resolution triply nested movable mesh hurricane model was analyzed emphasis was placed on the quasi steady component of the asymmetric structure in the region of the eyewall it was found that the asymmetry was primarily caused by the relative wind that is the flow entering and leaving the storm region relative to the moving storm a set of idealized numerical experiments was first performed both with a constant and a variable coriolis parameter f and the addition of basic flows that were either constant or sheared with height analysis was then made for one case of hurricane gilbert 1988 to demonstrate that the quasi steady asymmetric structure analyzed in the idealized studies could be identified in this real data case vorticity analysis in the variable f experiment indicated that quasi steady asymmetries resulted in the eyewall region through the effect of vorticity advection due to

variations in atmospheric sulphate recorded in stalagmites by synchrotron micro xrf and xanes analyses abstract we report here the first speleothem time series of the variability of sulphate a species whose abundance in catchments is strongly influenced by atmospheric anthropogenic and volcanic sources annually resolved archives of s mg si and p were generated by applying synchrotron radiation micro x ray fluorescence xrf to two speleothems from different sites in northern italy x ray absorption edge spectrometry proves that the s is in the form of sulphate and xrf mapping demonstrates that s is within calcite and enriched zones are predominantly as layers a post 1850 a d record from the ernesto cave shows a substantial rise in sulphate interpreted as reflecting the largely anthropogenically forced variation of sulphate of the atmospheric boundary layer moderated by some ecosystem storage analysis of the circa 5 2 to circa 5 0 ka interval of a speleothem from savi cave where ecosystem retention of s is likely to have been minimal shows a spiky sulphate record resembling that of ice cores a series of sulphate peaks suggest that multiple volcanic sulphate aerosol emissions at that time this probably enhanced summer temperature cooling thus favouring the preservation of the human mummy of neolithic copper age the iceman on the watershed between italy and austria both examples illustrate the power of speleothems to record atmospheric sulphate variability

the effect of vertical shear on tropical cyclone intensity change abstract the effect of vertical shear on tropical cyclone intensity change is usually explained in terms of ventilation where heat and moisture at upper levels are advected away from the low level circulation which inhibits development a simple two layer diagnostic balance model is used to provide an alternate explanation of the effect of shear when the upper layer wind in the vortex environment differs from that in the lower layer the potential vorticity pv pattern associated with the vortex circulation becomes tilted in the vertical the balanced mass field associated with the tilted pv pattern requires an increased midlevel temperature perturbation near the vortex center it is hypothesized that this midlevel warming reduces the convective activity and inhibits the storm development previous studies have shown that diabatic heating near the storm center acts to reduce the vertical tilt of the vortex circulation these studies have also shown that there is an adiabatic process that acts to redu

geochemical and stable isotope studies on natural water in the taroko gorge karst area taiwan chemical weathering of carbonate rocks by deep source co2 and sulfuric acid the geochemical cycle of co2 and the hydrological cycle in the taroko gorge karst area taiwan are discussed using chemical composition data of the natural water together with stable isotope ratios of carbon and oxygen of the water and soil co2 the soil co2 concentration at a depth of 1 m showed seasonal variations with a maximum of 5 2 v v and the minimum of 0 6 v v at three different altitudes ranging from 50 to 2000 m asl the soil temperature is the most important factor controlling the soil co2 concentration in this area the solubility of carbonates in groundwater can be explained by evolution under closed system conditions depending on the soil co2 concentration measured unexpectedly high 13c values of hco3 in groundwater were observed at some springs there was also an equivalent relationship between the sum of the concentration of mg2 and ca2 ions and that of hco3 and so42 ions in their waters these two facts suggest that some deep source co2 and sulfuric acid derived from weathering of pyrite may take part in the chemical weathering of carbonate rocks mainly calcareous schist as well as the soil co2 after the correction for the contribution of sulfuric acid the 13c values of hco3 of groundwater issuing from some springs were still high suggesting the presence of a deep source co2 flux altitude isotope effects were observed for surface water and rainwater in this area and could be expressed as 18o 0 0024h 3 67 h altitude m asl the estimated altitudes of catchment basins of springs using this equation were over 1000 2000 m higher than those of springs the rain falling high in the mountains is supplied with soil co2 dissolves carbonate rocks under closed system conditions penetrates deep underground and comes out again from springs together with the deep source co2 along fault crushing belts

two mathematical models of mg and sr partitioning into solution during incongruent calcite dissolution implications for dripwater and speleothem studies abstract positive correlation between sr ca and mg ca in cave dripwaters and speleothem is often attributed to prior calcite precipitation pcp where exclusion of mg and sr from calcite precipitated upstream of the dripwater speleothem site results in enrichment in the mg ca and sr ca ratios of residual effluent modelling predicts that pcp will produce a straight line correlation in graphs of ln sr ca vs ln mg ca with a theoretical slope that is given by kd sr 1 kd mg 1 calculated to be 0 88 0 13 regardless of rock or absolute dripwater composition sinclair et al submitted for publication while this makes the correlation slope potentially diagnostic for pcp mg and sr are also preferentially released from calcite during incongruent calcite dissolution icd and it is possible that icd produces a similar correlation between ln sr ca and ln mg ca to examine this possibility mathematical formulations for two different mechanisms of icd are presented model 1 simulates net dissolution as a dynamic kinetic process where forward and reverse reactions compete dissolution is congruent but ions are fractionated by a simultaneous reverse reaction where new calcite forms with sr ca and mg ca ratios that are determined by the solution composition and kd sr and kd mg model 2 simulates leaching of mg and sr from a fresh calcite surface by tracking the dissolution of a thin layer where high ion mobility allows the calcite to maintain a homogenous composition controlled by kd sr and kd mg in both models generalised kinetic equations are used in the derivations meaning that the results are not specific to a particular kinetic model in both models of icd the mathematics predict that under conditions that may prevail during dissolution of limestone the correlation between ln sr ca and ln mg ca is approximately linear with a slope given by kd sr 1 kd mg 1 thus this property is not specific to just pcp however for both pcp and icd this slope is universal expected to occur regardless of kinetics and the absolute composition of solution or host rock a correlation slope of 0 88 in either karst waters or speleothem is therefore diagnostic for calcite water interaction

on hurricane outflow structure abstract flow fields from the model of wu and emanuel are presented it is demonstrated that the interaction of background shear with a uniform source of low potential vorticity air at the storm top can produce many of the observed characteristics of hurricane outflow including outflow jets our model is compared to other extant models of hurricane outflow

controls on trace element sr mg compositions of carbonate cave waters implications for speleothem climatic records abstract at two caves clamouse s france and ernesto ne italy cave drip and pool waters were collected and sampled at intervals over a 2 3 year period mg ca and sr ca concentration ratios corrected for marine aerosols are compared with those of bedrocks and in some cases aqueous leachates of soils and weathered bedrocks cave waters do not lie along mixing lines between calcite and dolomite of bedrock carbonate but typically show enhanced and covarying mg ca and sr ca four factors are considered as controlling processes 1 the much faster dissolution rate of calcite than dolomite allows for the possibility of increase of mg ca if water rock contact times are increased during drier conditions a theoretical model is shown to be comparable to experimental leachates 2 prior calcite precipitation along a flow path is a powerful mechanism for generating enhanced and covarying mg ca and sr ca ratios this mechanism requires the solution to lose co 2 into pores or caverns 3 incongruent dolomite dissolution has only limited potential and is best regarded as two separate processes of dolomite dissolution and calcite precipitation 4 selective leaching of mg and sr with respect to ca is shown to be important in leachates from ernesto where it appears to be a phenomenon of calcite dissolution in general selective leaching can occur whenever ca is sequestered into precipitates due to freezing or drying of soils or if there is derivation of excess sr and mg from non carbonate species the ernesto cave has abundant water supply which in the main chamber is derived from a reservoir with year round constant p co 2 of around 10 2 4 and no evidence of calcite precipitation in the karst above the cave two distinct but overlying trends of enhanced and covarying mg ca and sr ca away from the locus of bedrock compositions are due to calcite precipitation within the cave and at a variable drip site due to enhanced selective leaching at slow drip rates mg enhancement in the first chamber is due to a more dolomitic bedrock and longer residence times the clamouse site has a less abundant water supply and presents geochemical evidence of prior calcite precipitation both in the cave and in overlying porous dolomite dedolomitized limestone bedrock initial p co 2 values as high as 10 1 are inferred experimental incubations of clamouse soils which generated enhanced p co 2 and precipitated caco 3 had compositions similar to the karst waters calcite precipitation is inferred to be enhanced in drier conditions hydrological controls on cave water chemistry imply that the trace element chemistry of speleothems may be interpretable in palaeohydrological terms drier conditions tends to promote not only longer mean residence times enhancing dolomite dissolution and hence mg ca but also enhances degassing and calcite precipitation leading to increased mg ca and sr ca

evolution of the upper tropospheric outflow in hurricanes iselle and julio 2014 in the navy global environmental model navgem analyses and in satellite and dropsonde observations upper tropospheric outflow was examined during the life cycles of two hurricanes in the eastern and central pacific ocean the outflow from hurricanes iselle and julio was evaluated using analyses from the navy global environmental model navgem which were very highly correlated with satellite atmospheric motion vector amv and noaa g iv dropsonde observations a synoptic overview provided the environmental context for the lifecycles of both tropical cyclones tcs then the outflow magnitude and direction within 6 radial degrees of each tc center were analyzed in relation to tc intensity the synoptic environment and inertial stability with the following results in both iselle and julio the azimuthally averaged outflow magnitude was maximized initially more than 4 radial degrees from the center and that maximum moved steadily inward during a 4 day intensification period and reached a position radially inward of 2 degrees within 6 h of the time of maximum surface winds furthermore the direction of the outflow in both tcs was related to the evolution of the large scale upper tropospheric flow pattern particularly the phasing of subtropical jet ridges and troughs moving eastward north of both tcs finally outflow channels were consistently bounded by regions of lowest highest values of inertial stability counterclockwise clockwise from the maximum outflow azimuth a pattern that persisted throughout the life cycles of both storms regardless of intensity environmental flow and the number and direction of outflow channels present

the cr chondrite clan implications for early solar system processes in this paper we review the mineralogy and chemistry of calcium aluminum rich inclusions cais chondrules feni metal and fine grained materials of the cr chondrite clan including cr ch and the metal rich cb chondrites queen alexandra range 94411 hammadah al hamra 237 bencubbin gujba and weatherford the members of the cr chondrite clan are among the most pristine early solar system materials which largely escaped thermal processing in an asteroidal setting bencubbin weatherford and gujba may be exceptions and provide important constraints on the solar nebula models these constraints include 1 multiplicity of cai formation 2 formation of cals and chondrules in spatially separated nebular regions 3 formation of cais in gaseous reservoir s having o 16 rich isotopic compositions chondrules appear to have formed in the presence of o 16 poor nebular gas 4 isolation of cais and chondrules from nebular gas at various ambient temperatures 5 heterogeneous distribution of al 26 in the solar nebula and 6 absence of matrix material in the regions of cai and chondrule formation

shock features in iron nickel metal and troilite of l group ordinary chondrites shock metamorphic features in opaque minerals feni metal and troilite of 22 l chondrites have been studied petrographically and geochemically in an attempt to establish a connection between the present silicate based shock classification scheme stoffler et al 1991 and the peak shock and postshock thermal history recorded in these minerals unshocked to weakly shocked s1 s3 l chondrites contain feni metal and troilite that display textures related to normal slow cooling they may also contain rare disequilibrium shock features which suggest localized departures from equilibrium shock conditions above shock stage s3 selected melting of feni metal and troilite produces melt droplets whose composition and abundance correspond to the maximum equilibrium shock state achieved by the sample at these higher shock levels the abundance of other shock induced features such as polycrystalline kamacite sheared and fizzed troilite coarse grained pearlitic plessite polycrystalline troilite and polymineralic melt veins serve as textural criteria that can be used to establish peak shock conditions minimum postshock temperatures obtained from analyses of plessite components show a systematic increase in temperature with an increase in shock stage thereby providing additional information about the postshock thermal histories of l chondrites at the highest shock levels recorded in l chondrites s6 and above melting and chemical homogenization of feni metal produces flattened ni profiles that may partially to completely obscure any evidence for an earlier slow cooling history all of these features serve as aids for shock classifying l chondrites as well as for quantifying minimum peak temperatures that resulted during shock metamorphism

a composite study of the interactions between tropical cyclones and upper tropospheric troughs abstract the objective of this study is to understand how interactions with upper tropospheric troughs affect the intensity of tropical cyclones the study includes all named atlantic tropical cyclones between 1985 and 1996 to minimize other factors affecting intensity change times when storms are over subcritical sea surface temperatures 26 c or near landfall are removed from the sample a trough interaction is defined to occur when the eddy momentum flux convergence calculated over a 300 600 km radial range is greater than 10 m s 1 day 1 the trough interaction cases are separated into four composites i favorable superposition tropical cyclone intensifies with an upper tropospheric potential vorticity pv maximum within 400 km of the tropical cyclone center ii unfavorable superposition iii favorable distant interaction upper pv maximum between 400 and 1000 km from the tropical cyclone center and iv unfavorable distant interaction for comparison two additional composites are cre

luminescent microbanding in speleothems high resolution chronology and paleoclimate when illuminated by ultraviolet light many calcite speleothems stalagmites stalactites flowstones display luminescence caused by the presence of organic humic substances occluded in the calcite the amplitude of luminescence varies in a banded pattern parallel to growth layering through 14 c and thermal ionization mass spectrometry uranium series dating we show that cyclical oscillations in the luminescence have periodicities ranging from a few days to 10 5 yr a well defined annual cycle is present in many vadose zone speleothems and can be used to define the chronology of short term events this cycle is probably a response to hydrological events in the recharge to the cave longer term oscillations are inferred to be controlled by climate through its effect on organic activity in the overlying soil

temperature and altitudinal influence on karst dripwater chemistry implications for regional scale palaeoclimate reconstructions from speleothems abstract the reconstruction of robust past climate records from speleothems requires a prior understanding of the environmental and hydrological conditions that lead to speleothem formation and the chemical signals encoded within them on regional scales there has been little quantification of the dependency of cave dripwater geochemistry on meteorology net infiltration temperature environmental and geographical factors elevation latitude soil activity vegetation cover atmospheric aerosol composition and geological properties of the aquifer lithology porosity and thickness in the present study we analysed over 200 karst waters collected in 11 caves of the trentino region ne italy the caves span sub humid mediterranean to cold humid temperate climates and infiltration elevations zinf ranging from 355 to 2400 m a s l corresponding to infiltration mean annual temperatures matinf between 12 and 0 c since all the caves developed in pure carbonate rocks soil pco2 is found to be the main factor controlling the carbonate dissolution for this reason the parameters controlling the carbonate carbonic acid system and calcite saturation state sicc are directly correlated with the matinf which influences the vegetation zones and eventually the production of co2 in the soil sicc linearly depends on matinf sicc 0 09 matinf 0 4 and sicc 0 is reached at zinf 1 66 km a s l corresponding to a matinf 4 4 c this point identifies the speleothem limit defined here as the elevation or corresponding matinf above which no sparitic speleothem precipitation usually occurs we demonstrate that due to temperature forced changes in the soil and vegetation and subsequently sicc the speleothem limit shifts to higher altitudes during maximum interglacial conditions speleothems from high altitude caves 1 5 2 5 km a s l thus can identify optimum interglacial periods by contrast speleothems formed at lower altitudes are better suited as archives of hydrological proxies at altitudes below 1 2 km a s l prior calcite precipitation pcp modifies percolating waters particularly during periods of reduced infiltration we introduce the use of the sio2 ca and so4 ca ratios in cave waters to complement mg ca and sr ca ratios as markers of pcp so4 and sio2 are derived from atmospheric deposition and siliciclastic minerals in the soil zone rather than carbonate host rocks as in the case of mg and sr by combing shifts to higher mg ca sio2 ca and so4 ca ratios along their characteristics pcp lines we improve the robustness of the interpretation that this resulted from increasing pcp rather than incongruent calcite dissolution icd our method permits the quantification of pcp between 0 and 40 for low elevation cave waters this novel approach has important implications for speleothem based paleoclimate studies where the distinction between pcp and icd can be ambiguous and in combination with mg ca and sr ca ratios permits the quantification of net infiltration and or rainfall amount from speleothem records

tropical storm formation in a baroclinic environment abstract an analysis is presented of the large scale conditions associated with the initial development of tropical storm diana september 1984 in a baroclinic environment ordinary extratropical wave cyclogenesis began along an old frontal boundary east of florida after 0000 utc 7 september and culminated in tropical cyclogenesis 48 h later water vapor satellite imagery showed that the initial cyclogenesis and incipient tropical storm formation was nearly indistinguishable from a classical midlatitude development cyclogenesis occurred in three stages a large scale cold trough and associated frontal system crossed the atlantic coast while a small potential vorticity maximum aloft fractured off the main trough and stalled over central florida in the first stage as the main trough sheared off eastward cyclogenesis began along the southwestern end of the stalled frontal zone east of florida anticyclogenesis to the north in the wake of the shearing trough allowed a surge of cooler and drier air to flo

dynamic cyrstallization of chondrule melts of porphyritic olivine composition textures experimental and natural abstract melts of the same composition as has been defined for porphyritic olivine chondrules have been crystallized under controlled cooling conditions dynamic crystallization the full range of textures observed in such chondrules has been duplicated in the experimentally produced analogs the primary controlling factor in producing this range of textuures is the heterogeneous nucleation behavior in general if nuclei are present when cooling begins growth starts immediately at low degrees of supercooling and porphyritic textures result the shapes of the phenocyrsts depend on the growth rate which in turn depends on the cooling rate with high nucleation densities and modest to low cooling rates the textures are microporphyritic with generally equant euhedral phenocrysts as the nucleatio density decreases the phenocrysts become larger and as the cooling rate increases they become increasingly skeletal if nuclei are not present when cooling begins growth is delayed until subcritical sized embryos graduate to supercritical nuclei growth usually begins at some significant degree of supercooling depending on the cooling rate and how long it takes the embryos to become nuclei the shapes of the crystals depend on the degree of supercooling when growth is initiated and on the subsequent cooling rate the resulting textures vary from plate dendrites barred olivine chondrules to randomly oriented elongated skeletal crystals as the degree of supercooling and cooling rates decreases the results of a matrix of experiments set limits on the maximum melting temperatures of chondrule forming materials and the subsequent cooling rates based primarily on crystal shape the porphyritic textures develop best for this composition at melting temperatures less than 1590 c and cooling rates near 100 c hr and definitely less than 1000 c hr at cooling rates significantly less than 100 c hr the phenocrysts are generally larger than observed in chondrules and as cooling rates approach 1000 c hr they become more skeletal barred olivine chondrule textures form best from materials melted at higher temperatures and cooling rates in the range 1000 to 3000 c hr

the role of synoptic scale flow during tropical cyclogenesis over the north atlantic ocean abstract the synoptic scale flow during tropical cyclogenesis and cyclolysis over the north atlantic ocean is investigated using compositing methods genesis and lysis are defined using the national hurricane center nhc now known as the tropical prediction center best track data genesis lysis occurs when nhc first last identifies and tracks a tropical depression in the final best track dataset storm centered composites are created with the analysis of the tropical oceanic lower level atoll 900 hpa and 200 hpa winds for june november produced by nhc for the years 1975 93 results show that significant regional differences exist in 200 hpa flow during genesis across the atlantic basin composites of genesis in the western part of the basin show a 200 hpa trough ridge located to the west east of the atoll disturbance in the eastern half of the basin composites of genesis show a sprawling 200 hpa ridge centered northeast of the atoll disturbance the major axis of this elliptically shaped 20

postshock annealing and postannealing shock in equilibrated ordinary chondrites implications for the thermal and shock histories of chondritic asteroids abstract in addition to shock effects in olivine plagioclase orthopyroxene and ca pyroxene petrographic shock indicators in equilibrated ordinary chondrites oc include chromite veinlets chromite plagioclase assemblages polycrystalline troilite metallic cu irregularly shaped troilite grains within metallic fe ni rapidly solidified metal sulfide intergrowths martensite and various types of plessite metal sulfide veins large metal and or sulfide nodules silicate melt veins silicate darkening low ca clinopyroxene silicate melt pockets and large regions of silicate melt the presence of some of these indicators in every petrologic type 4 to 6 ordinary chondrite demonstrates that collisional events caused all equilibrated oc to reach shock stages s3 s6 those type 4 to 6 oc that are classified as shock stage s1 on the basis of sharp optical extinction in olivine underwent postshock annealing due to burial beneath materials heated by the impact event those type 4 to 6 oc that are classified s2 on the basis of undulose extinction and lack of planar fractures in olivine were shocked to stage s3 s6 annealed to stage s1 and then shocked again to stage s2 some oc were probably shocked to stage s3 after annealing it seems likely that many oc experienced multiple episodes of shock and annealing because 40ar 39ar chronological data indicate that mil 99301 ll6 s1 was annealed 4 26 ga ago presumably as a consequence of a major impact it seems reasonable to suggest that other equilibrated s1 and s2 oc which contain relict shock features were also annealed by impacts because some type 6 s1 oc e g guarena kernouve portales valley all of which contain relict shock features were annealed 4 44 4 45 ga ago during a period when impacts were prevalent and most oc were thermally metamorphosed it follows that impact induced annealing could have contributed significantly to oc thermal metamorphism

deep source co2 in natural waters and its role in extensive tufa deposition in the huanglong ravines sichuan china abstract the aqueous geochemistry of huanglong ravine sichuan china where tufa is being deposited extensively is discussed using chemical composition data together with the carbon and oxygen stable isotope ratios the water quality of tufa depositing surface streams in this area is basically controlled by the mixing of two source waters fault bounded spring water and snow and or glacier melt water the spring water contains high concentrations of co 2 supplied via faults the resulting high concentration of dissolved co 2 gives rise to much greater dissolution of carbonate rocks than is usual in karst springs and also to the dissolution of silicate rocks upstream spring waters in the ravine are close to equilibrium with respect to calcite concentrations of dissolved inorganic carbon dic and their 13 c values result from the interaction of about 0 02 mol l 1 co 2 aq of 13 c 3 with carbonate rocks of 13 c 3 under closed system conditions about 70 of the co 2 is estimated to be supplied from the upper mantle the data for all the springs fall in the kaolinite stability field in agreement with observed dissolutional aggressiveness towards na and ca feldspar and that the dissolution rates of these minerals are too slow to move the composition of these waters into the feldspar stability field the dic species in the surface streams are in isotopic equilibrium variations in 13 c dic found at different sites are mainly due to differences in the degree of co 2 degassing from the water there is a linear relationship between 18 o values and the altitude at which samples were collected the oxygen isotope composition of surface stream water in this area is controlled by evaporation water chemistry in daytime and nighttime and daily change of ph in the surface water flowing on the tufa deposition indicate that biological activities contribute to the carbonate precipitation although their extent is not great the daily precipitation rate in this area is estimated to be 4300 kg as caco 3 day 1 over a surface area of 0 9 km 2 i e 0 1 cm year 1

external influences on hurricane intensity part i outflow layer eddy angular momentum fluxes abstract outflow layer winds were objectively analyzed every 12 h for 6 days during the life cycle of hurricane elena 1985 a high correlation was found between angular momentum fluxes by azimuthal eddies at large radii and central pressure changes in the storm 27 33 h later momentum flux by eddies exceeded that by the azimuthal mean outside the 800 km radius while vortex spinup by the eddies reached instantaneous magnitudes as large as 25 m s 1 day outflow maxima and minima repeatedly appeared more than 1000 km from the hurricane center and tracked inward with time the results provide evidence of significant environmental control on the behavior of the storm after reaching hurricane strength elena experienced a major secondary intensification associated with a large inward cyclonic eddy momentum flux produced by the passage of a middle latitude trough north of the hurricane an outflow maximum appeared radially inside of the eddy momentum source consistent with balanced vortex theory and tracke

sulphate concentration in cave dripwater and speleothems long term trends and overview of its significance as proxy for environmental processes and climate changes sulphate concentrations in speleothems identify major volcanic eruptions provide useful information on soil and aquifer dynamics and in similar fashion to the 14c bomb peak its anthropocene peak can be used to date recent cave formations however the transmission of s from the atmosphere to cave dripwater and its incorporation in speleothems is subjected to biogeochemical cycling and accurate studies of each cave site are needed in order to assess how the s atmospheric signal is modified and eventually encoded in speleothems this study investigates the role of biogeochemical cycling and aquifer hydrology by utilising published and new dripwater and speleothem data from grotta di ernesto er in northern italy here we provide the first long term record of sulphate concentration in cave dripwater based on over 20 years of measurements fast drip site st er1 is characterised by a continuous decrease in so4 concentration from a high of 7 5 0 8 mg l in 1993 1994 to a low of 2 2 0 2 mg l in 2013 2014 and replicates with a delay of 15 years the decline in the atmospheric so2 emissions the s series of slow flow er78 site is further delayed by 4 5 years in relation to the s retention in the aquifer matrix the dripwater data are used to extend the previously published s record 1810 1998 ad of stalagmite er78 and reconstruct the anthropogenic s peak this displays a delay of 20 years with respect to the atmospheric s emission peak due to biogeochemical cycling and aquifer storage however sulphur recycling above the cave did not operate with the same degree of efficiency through time which resulted in a variable time delay between s deposition and incorporation into the stalagmite in the pre anthropocene era and in particular during the cold little ice age biogeochemical cycling was far less efficient than today and the fast transmission of the atmospheric signal allowed capture of s released during major volcanic eruptions by stalagmites

chondrules as products of dust collisions with totally molten droplets within a dust rich nebular environment an experimental investigation abstract chondrules are usually interpreted as the products of incomplete melting of mineral aggregates in the solar nebula and have textures controlled by the number of residual nuclei present after melting if barred olivine bo chondrules formed by nearly total melting at their respective liquidi i e over a wide temperature range it is surprising that there are so few totally glassy chondrules the occurrence of fine grained accretionary rims on chondrules suggests mineral dust in the chondrule forming environment which might have collided with totally molten droplets to produce chondrule textures we have therefore conducted experiments in which mineral dusts encounter molten droplets during their cooling at 500 c h and cause nucleation our experiments reproduce the majority of common chondrule textures the production of textures in our experiments is a function of the temperature at which dust is encountered the number of dust grains encountered and to a lesser extent the mineralogy of the encountered mineral grains crystal growth rates increase with lower dust encounter temperatures giving a textural range with increasingly skeletal or elongated crystals for lower temperature encounters we have produced some less commonly discussed types of chondrule textures e g barred olivine porphyritic olivine pyroxene bo pop by dust seeding that have not been reproduced by the incomplete melting of starting materials the reproduction of bo pop and excentroradial textures by dust collisions and the scarcity of natural totally glassy chondrules suggest that formation by seeding of total melts was common for chondrules with the lowest liquidus temperatures e g feo rich chondrules from these seeding experiments we suggest that the maximum melting temperature chondrules experienced is limited only to the temperature at which evaporation of chondrule liquid occurs however we have reproduced the very fine grained microporphyritic textures characteristic of type ia chondrules only by incomplete melting such chondrules could not have reached average internal temperatures above their liquidus temperatures the conclusion that at least some chondrules formed from total melts that collided with mineral dust during cooling indicates that chondrule formation occurred within a region of the nebula rich in mineral dust

the extratropical transition of tropical cyclones part i cyclone evolution and direct impacts abstractextratropical transition et is the process by which a tropical cyclone upon encountering a baroclinic environment and reduced sea surface temperature at higher latitudes transforms into an extratropical cyclone this process is influenced by and influences phenomena from the tropics to the midlatitudes and from the meso to the planetary scales to extents that vary between individual events motivated in part by recent high impact and or extensively observed events such as north atlantic hurricane sandy in 2012 and western north pacific typhoon sinlaku in 2008 this review details advances in understanding and predicting et since the publication of an earlier review in 2003 methods for diagnosing et in reanalysis observational and model forecast datasets are discussed new climatologies for the eastern north pacific and southwest indian oceans are presented alongside updates to western north pacific and north atlantic ocean climatologies advances in understanding and in some cases mode

subtropical cyclones over the southwestern south atlantic climatological aspects and case study abstracthurricane catarina 2004 and subtropical storm anita 2010 called attention to the development of subtropical cyclones scs over the south atlantic basin besides strong and organized storms a large number of weaker shallower cyclones with both extratropical and tropical characteristics form in the region impacting the south american coast the main focus of this study is to simulate a climatology of subtropical cyclones and their synoptic pattern over the south atlantic proposing a broader definition of these systems in addition a case study is presented to discuss the main characteristics of one weak sc the interim ecmwf re analysis era interim and ncep ncar reanalysis are used to construct the 33 yr 1979 2011 climatology and a comparison between them is established both reanalyses show good agreement in the scs intensity geographical distribution and seasonal variability but the interannual variability is poorly correlated anomaly composites for austral summer show that sub

a new metal rich chondrite grouplet abstract a new grouplet of primitive metal rich chondrites here called the cb c carbonaceous b bencubbinite chondrites has been recognized it includes bencubbin weatherford hammadah a1 hamra hh 237 and queen alexandra range que 94411 paired with que 94627 their mineral compositions as well as their oxygen and nitrogen isotopic compositions indicate that they are closely related to the cr and ch chondrites all of which are members of the more inclusive cr clan cb chondrites have much greater metal silicate ratios than any other chondrite group widely increasing the range of metal silicate fractionation recorded in solar nebular processes they also have the greatest moderately volatile lithophile element depletions of any chondritic materials metal has compositional trends and zoning patterns that suggest a primitive condensation origin in contrast with metal from other chondrite groups cb chondrites as well as other cr clan chondrites have much heavier nitrogen higher 15n 14n than that in other chondrite groups the primitive characteristics of the cb chondrites suggest that they contain one of the best records of early nebular processes another chondrite grosvenor mountains 9555 1 is petrographically similar to the cb chondrites but its mineral and oxygen and nitrogen isotope compositions indicate that it formed from a different nebular reservoir

stable isotopes and trace elements of drip waters at desoto caverns during rainfall contrasting years abstract a monitoring study at desoto caverns during two years 2012 2013 of rainfall contrasting variability presents the opportunity to test the response of the hydroclimate proxies in drips and active speleothems to forcing factors on intrannual and interannual time scales the weighted monthly mean rainwater 18o and 2h range from 1 2 to 6 4 v smow and 4 to 41 6 v smow respectively and show modest interannual variation d excess values exhibit a large intrannual contrast suggesting a primary control by sub cloud evaporation processes coeval drip water 18o and 2h vary from 3 1 to 5 3 v smow and 9 9 to 30 5 v smow respectively and exhibit interannual negative trends from the 2012 dry warm year to the 2013 relatively wet cool year substantial attenuation of drip water isotope amplitudes relative to its rainwater source is likely caused by mixing of fresh with residual evaporated water in the epikarst zone drip water ca mg sr and mg ca and sr ca ratios exhibit an inverse relation with respect to the contrasting hydroclimate years such that lower values and higher ratios occur during the dry warm year and higher values and lower ratios occur during the wet cool year we assert that interannual rainfall variability exerts a dominant control on the elemental concentrations and their ratios of the drips through changes of biomass productivity in the soils overlying the cave and prior aragonite precipitation in the epikarst the distribution coefficients of mg dmg 3 49 10 3 1 06 10 3 and sr dsr 1 12 0 041 between drips and aragonite speleothems estimated in this study are in broad agreement with aragonite solute experimental values coeval changes of trace elements and 18o in response to interannual rainfall variability confirm their usefulness to better constrain the controlling hydroclimate drivers

synoptic and frontal scale influences on tropical transition events in the atlantic basin part i a six case survey abstract the process by which a baroclinic vertically sheared extratropical cyclone is transformed into a warm core vertically stacked tropical cyclone is known as tropical transition six recent tropical transitions of strong extratropical precursors in the subtropical north atlantic are compared to better understand the manner by which some of the canonical structures and dynamical processes of extratropical cyclones serve to precondition the cyclone for transition all six transitions resulted from the interaction between a surface baroclinic zone and an upper level trough during the extratropical cyclogenesis of each storm a period of intense near surface frontogenesis along a bent back warm front occurred to the northwest of each sea level pressure minimum within the resultant circulation diabatic redistribution of potential vorticity pv promoted the growth of a low level pv maximum near the western end of the warm front concurrently the upper level pv anomaly associated with each trough w

a detailed 31 000 year record of climate and vegetation change from the isotope geochemistry of two new zealand speleothems abstract uranium series dating and stable isotope analyses of two speleothems from northwest nelson new zealand record changes in regional climate and local forest extent over the past 31 000 years oxygen isotope variation in these speleothems primarily represents changes in the meteoric waters falling above the caves possibly responding to latitudinal changes in the position of the subtropical front in the tasman sea seven positive excursions can be identified in the oxygen isotope record which coincide with periods of glacier advance known to be sensitive to northward movement of the subtropical front four glacier advances occurred during oxygen isotope stage 2 with the most extreme glacial conditions centered on 19 000 cal yr b p 2 an excursion in the oxygen isotope record from 13 800 to 11 700 cal yr b p provides support for a previously identified new zealand glacier advance at the time of the younger dryas stade but suggests it began slightly before the younger dryas as recorded in greenland ice cores carbon isotope variations in the speleothems record changes in forest productivity closely matching existing paleovegetation records on the basis of vegetation changes stage 2 glacial climate conditions terminated abruptly in central new zealand from 15 700 to 14 200 cal yr b p evidence of continuous speleothem growth at one site suggests that depression of the local treeline was limited to 600 700 m below its present altitude throughout the last 31 000 years

synoptic scale disturbances with circular symmetry abstract ate balanced flow structure of various classic synopitc scale disturbances is reviewed using the invertibility principle for isentropic potential vorticity ipv distributions complete solutions are shown for cold and warm core structures of various types the basic model imagines the tropopause to be the interface between the lower potential vorticity of the troposphere and the approximately six fold larger value typical of the lower stratosphere the sensitivity of the structure of the potential temperature variation along the tropopause and at the surface is described results are presented in diagrammatic form to allow easy diagnosis of the vortex structure from synoptic data available at perhaps only a few levels the point is made that upper air ipv and surface potential temperature distributions are often the most crucial in accounting for the balanced flow structure

a technique for diagnosing three dimensional ageostrophic circulations in baroclinic disturbances on limited area domains abstract the methodology developed by keyser et al for representing and diagnosing three dimensional vertical circulations in baroclinic disturbances using a two dimensional vector streamfunction referred to as the psi vector is restricted to f plane channel model geometry the vertical circulation described by the psi vector consists of the irrotational or divergent part of the ageostrophic wind and the vertical velocity a key property of the psi vector is that its projections onto arbitrarily oriented orthogonal vertical planes yield independent vertical circulations allowing separation of a three dimensional vertical circulation into two two dimensional components and thus objective assessment of the extent to which a three dimensional vertical circulation is oriented in a preferred direction here the methodology for determining the psi vector is modified to be suitable for real data applications the modifications consists of reformulating the diagnostic equations to apply to conformal map pr

compositions of unzoned and zoned metal in the cbb chondrites hammadah al hamra 237 and queen alexandra range 94627 the cbb chondrites are rare primitive metal rich meteorites that contain several features including zoned metal that have previously been interpreted as evidence for origins in the solar nebula we have measured concentrations of ni cu ga ru pd ir and au within both zoned and unzoned metal grains in the cbb chondrites hammadah al hamra hah 237 and queen alexandra range que 94627 using laser ablation inductively coupled plasma mass spectrometry the refractory elements ni ru and ir are enriched in the grain cores relative to the rims in the zoned metal all refractory elements are uniform across the unzoned metal grains at concentrations that are highly variable between grains the volatile elements cu ga and au are usually depleted relative to chondritic abundances and are most often uniform within the grains but are sometimes slightly elevated at the outermost rim the pd abundances are nearly uniform at close to chondritic abundances in all of the metal grains a condensation origin is inferred for both types of metal the data support a model in which the zoned metal formed at high temperatures in a relatively rapidly cooling nebular gas and the unzoned metal formed at lower temperatures and at a lower cooling rate the cbb metal appears to have formed by a process very similar to that of the ch chondrites but the cbb meteorite components experienced even less thermal alteration following their formation and are among the most primitive materials known to have formed in the solar nebula

a numerical study of the outflow layer of tropical cyclones abstract the structure and dynamics of the outflow layer of tropical cyclones are studied using a three dimensional numerical model weak and strong tropical cyclones are produced by the numerical model when starting from idealized initial vortices embedded in mean hurricane soundings the quasi steady state outflow layers of both the weak and strong tropical cyclones have similar characteristics 1 the circulations are mainly anticyclonic except for a small region of cyclonic flow near the center and highly asymmetric about the center 2 the outflow layer is dominated by a narrow but elongated outflow jet which contributes up to 50 of the angular momentum transport and 3 the air particles in the outflow jet mostly originate from the lower level following in up and out trajectories we found that there are secondary circulations around the outflow jet very much like those associated with midlatitude westerly jet streaks in the jet entrance region the secondary circulation is thermally direct

high resolution sulphur isotope analysis of speleothem carbonate by secondary ionisation mass spectrometry sulphur emitted into the atmosphere from industrial activity is regarded as a key mechanism in forcing recent climate and has impacts upon the environment and human health at both local and regional scales trace amounts of sulphate present within speleothem carbonate can be used to provide an emissions inventory for regional sulphur loading to the atmosphere where sulphur isotopes can be extracted and used as a tool for provenance however speleothem sulphur concentrations are low and manual techniques for sulphur isotope analysis allow only low sampling resolution sims secondary ionisation mass spectrometry is used here to develop records of sulphur isotopic change in speleothems from the italian and austrian alps where annual laminae are less than 100 mu m thick analysis at annual resolution over the past 100 years demonstrates an excursion in sulphur isotopic composition from values close to the carbonate bedrock end member composition in the pre industrial era to values isotopically depleted in 34 s this trend is mirrored by increasing concentrations of sulphate and is suggested to reflect the increase in so2 emissions with industrial activity subsequent decline in speleothem sulphate concentrations in one of the stalagmites reflects the recent european decline in industrial atmospheric so2 content and is matched by a rebound in sulphur isotopic composition to values more enriched in 345 superimposed on this general secular trend are smaller annual variations in concentration reflecting cave environmental conditions high magnitude events of short duration potentially reflect volcanic inputs of so2 or the incorporation of dust particulates into the speleothem carbonate this is the first micro analysis of carbonate associated sulphate cas sulphur isotopes by sims sims analysis of delta s 34 so4 in speleothem carbonate reveals a high resolution archive depicting a regional sulphur emissions inventory for so2 loading to the atmosphere c 2010 elsevier b v all rights reserved

evolution and classification of acapulcoites and lodranites from a chemical point of view we examined 15 bulk samples of the acapulcoite lodranite clan for their major minor and trace element concentrations using inaa techniques among the analyzed meteorites are 2 new acapulcoites dhofar dho 290 thiel mountains til 99002 as well as an additional acapulcoite that has been described previously only in very brief form graves nunataks gra 98028 the petrographic attributes of these 3 samples are addressed thoroughly we also include petrographic information on 2 acapulcoites from africa northwest africa nwa 725 and nwa 1058 in general our study strongly supports the widely accepted idea that acapulcoites and lodranites evolved through partial melting and melt migration of metal sulfide phases and plagioclase furthermore we concur with previous researchers that the original bimodal classification scheme for acapulcoites and lodranites proves to be too simple based on our data set we introduce an alternative extended scheme with respect to their elemental distribution patterns we distinguish 5 subtypes comprising primitive typical transitional and enriched acapulcoites on one hand and lodranites on the other the chemical distinction between the primitive typical and transitional acapulcoites is rather subtle and gradual it stands in contrast to the clear modifications observed for the signatures of the enriched acapulcoites and the lodranites the definition of subcategories basically reflects the concentrations of 2 key elements k and se we note however that the assignment of subgroups may not be exclusively inferred from elemental abundances but should also consider additional petrographic information

upb systematics of phosphates from equilibrated ordinary chondrites u pb systematics were determined from fifteen phosphate separates from equilibrated ordinary chondrites and from small bulk fragments of the same meteorites the high 238u204pb ratios of thirteen of these phosphate separates lead to extremely radiogenic pb whose 206pb204pb ratios range from 250 up to 3500 the pb pb model ages for these phosphates range from 4 563 to 4 502 ga with an analytical precision of 106 y and the u pb system is apparently concordant the time interval observed 60 106 y reflects the thermal processing of the equilibrated chondrites and is consistent with that previously derived from the rb sr k ar and pu chronologies the pb pb ages of the phosphates from the seven h chondrites show a negative correlation versus their metamorphic grade this is the first clear relationship ever observed between a long lived chronometer and the intensity of metamorphism as reflected by metamorphic grade assuming that the pb pb age indicates the accurate u pb closure time in phosphates the pb pb chronology is compatible with the model of a layered h chondrite parent body however this interpretation of the u pb systematics is not unique it postulates a slow cooling of the equilibrated materials at high temperature in apparent conflict with petrological observations except for the h chondrites which agree rather well with pu systematics comparison of the pb pb chronology with published radiochronometric data does not reveal simple correlations in the present debate concerning the thermal history of chondrites the chronometric information derived from each isotope system is interpreted as the time of its thermal closure however this basic assumption may not be correct for all the radiochronologies and must be evaluated before the radiochronometric data can be applied as compelling time constraints for the period of 4 56 4 4 ga of proto planetary history

the fountain hills unique cb chondrite insights into thermal processes on the cb parent body we report the results of an extensive study of the fountain hills chondritic meteorite this meteorite is closely related to the cba class mineral compositions and o isotopic ratios are indistinguishable from other members of this group however many features of fountain hills are distinct from the other cb chondrites fountain hills contains 23 volume percent metal significantly lower than other members of this class in addition fountain hills contains porphyritic chondrules which are extremely rare in other cba chondrites fountain hills does not appear to have experienced the extensive shock seen in other cb chondrites the chondrule textures and lack of fine grained matrix suggests that fountain hills formed in a dust poor region of the early solar system by melting of solid precursors refractory siderophiles and lithophile elements are present in near ci abundances within a factor of two related to the enhancement of metal moderately volatile and highly volatile elements are significantly depleted in fountain hills the abundances of refractory siderophile trace elements in metal grains are consistent with condensation from a gas that is reduced relative to solar composition and at relatively high pressures 10 3 bars fountain hills experienced significant thermal metamorphism on its parent asteroid combining results from the chemical gradients in an isolated spinel grain with olivine spinel geothermometry suggests a peak temperature of metamorphism between 535 c and 878 c similar to type 4 ordinary chondrites

formation of metal in grosvenor mountains 95551 and comparison to ordinary chondrites abstract siderophile element abundances in individual metal grains in the ungrouped chondrite grosvenor mountains gro 95551 and in the ordinary chondrites tieschitz h3 6 soko banja ll4 and allegan h5 were measured with laser ablation inductively coupled plasma mass spectrometry matrix metal in gro 95551 falls into two distinct compositional groups a high ni group with 7 2 0 4 wt ni and a low ni group with 3 7 0 1 wt ni indicating that kamacite taenite equilibration at 1020 k was followed by rapid cooling the nonrefractory siderophile elements p co cu ga ge as pd and au also partition between the high ni and low ni metal in a manner consistent with kamacite taenite fractionation but the refractory siderophiles ru re os ir and pt show correlated variations that are unrelated to kamacite taenite partitioning and indicate that variations in refractory components of the metal were not completely erased during equilibration at 1020 k the ni normalized bulk metal composition of gro 95551 is refractory depleted and volatile rich relative to bencubbin and related metal rich chondrites but bears strong similarities to equilibrated ordinary chondrite metal gro 95551 represents a new chondrite type with chemical affinity to the ordinary chondrites individual metal grains in unequlibrated ordinary chondrites also have correlated variations in refractory siderophile contents that cannot be produced by redox processes alone these variations span three orders of magnitude and diminish with increasing metamorphic grade of the ordinary chondrites

the dynamics of the enso atlantic hurricane teleconnection enso related changes to the north african asian jet affect atlantic basin tropical cyclogenesis abstract the nature of the teleconnection linking enso variability with atlantic basin tropical storm formation is investigated solutions of the linearized barotropic vorticity equation forced with august october el nino event divergence produce upper tropospheric vorticity anomalies over the sahel and at the mouth of the north african asian naa jet over the tropical atlantic these responses are similar in magnitude and orientation to observed enso vorticity variability for this region further investigation reveals that the vorticity anomalies over the subtropical atlantic develop primarily in response to very low wavenumber westward propagating stationary rossby waves excited by el nino related convective activity over the equatorial pacific ocean however the dynamics of this teleconnection change as the atlantic basin hurricane season progresses in august and september the response is dominated by the westward propagating stationary rossby waves that alter vorticity within the naa jet and to it

quasi biweekly oscillations of the south asian monsoon and its co evolution in the upper and lower troposphere the upper tropospheric quasi biweekly oscillation uqbw of the south asian monsoon is studied using the potential vorticity field on the 370 k isentrope the uqbw is shown to be a common occurrence in the upper troposphere during the monsoon and its typical evolution is described we suggest that the uqbw is a phenomenon of both the middle and tropical latitudes owing its existence to the presence of the planetary scale upper tropospheric monsoon anticyclone the uqbw is first identified as rossby waves originating in the northern flank of the monsoon anticyclone these rossby waves break when reaching the pacific ocean and their associated cyclonic pv anomalies move southward to the east of asia and then westward across the indian ocean and africa advected by the monsoon anticyclone a strong correlation or co evolution between the uqbw and quasi biweekly oscillations in the lower troposphere qbw is also found in particular analysis of vertically integrated horizontal moisture transport 850 hpa geopotential and outgoing long wave radiation show that the uqbw is usually observed at the same time as and co evolves with the lower tropospheric qbw over south asia we discuss the nature of the uqbw and its possible physical link with the qbw

a high resolution absolute dated late pleistocene monsoon record from hulu cave china oxygen isotope records of five stalagmites from hulu cave near nanjing bear a remarkable resemblance to oxygen isotope records from greenland ice cores suggesting that east asian monsoon intensity changed in concert with greenland temperature between 11 000 and 75 000 years before the present yr b p between 11 000 and 30 000 yr b p the timing of changes in the monsoon as established with 230th dates generally agrees with the timing of temperature changes from the greenland ice sheet project two gisp2 core which supports gisp2 s chronology in this interval our record links north atlantic climate with the meridional transport of heat and moisture from the warmest part of the ocean where the summer east asian monsoon originates

no fes layer in mercury evidence from ti al measured by messenger abstract in this study we investigate the likeliness of the existence of an iron sulfide layer fes matte at the core mantle boundary cmb of mercury by comparing new chemical surface data obtained by the x ray spectrometer onboard the messenger spacecraft with geochemical models supported by high pressure experiments under reducing conditions we present a new data set consisting of 233 ti si measurements which combined with al si data show that mercury s surface has a slightly subchondritic ti al ratio of 0 035 0 008 multiphase equilibria experiments show that at the conditions of mercury s core formation ti is chalcophile but not siderophile making ti a useful tracer of sulfide melt formation we parameterize and use our partitioning data in a model to calculate the relative depletion of ti in the bulk silicate fraction of mercury as a function of a putative fes layer thickness by comparing the model results and surface elemental data we show that mercury most likely does not have a fes layer and in case it would have one it would only be a few kilometers thick 13 km we also show that mercury s metallic fe si core cannot contain more than 1 5 wt sulfur and that the formation of this core under reducing conditions is responsible for the slightly subchondritic ti al ratio of mercury s surface

asymmetric distribution of convection associated with tropical cyclones making landfall along the south china coast this study examines the convection distribution associated with 18 tcs that made landfall along the south china coast during 1995 and 2005 cloud top temperatures from high resolution satellite imageries of the geosynchronous meteorological satellite 5 are used as proxy of strong convection it is found that convection tends to be enhanced on the western side of the tc as it makes landfall in 10 of the cases in agreement with the conclusion of some previous studies four cases have stronger convection on the eastern side this deviation from the general rule appears to be related to the tcs being more slow moving or their interaction of the tc with another land surface prior to its making landfall along the south china coast for the remaining cases in which no significant asymmetries in convection can be identified the vertical wind shear appears to enhance convection on the east side

evidence for oxidizing conditions in the solar nebula from mo and w depletions in refractory inclusions in carbonaceous chondrites abstract depletions of mo and w relative to other refractory metals of similar volatility re os ir ru pt are common in a suite of 16 ca al rich inclusions cais from 5 carbonaceous chondrites twelve of the 16 cais from allende grosnaja leoville and ornans show mo depletions six of these 12 inclusions also show w depletions the one cai analyzed from the essebi chondrite shows no depletions the mo and w depletions have a very characteristic pattern with mo always more depleted than w the same mo and w depletion pattern occurs in calculated refractory metal alloy compositions formed at oxygen fugacities 10 3 to 10 4 times greater than the canonical solar nebula oxygen fugacity we conclude that mo and w depletions are common in cais from carbonaceous chondrites and that the depletions result from high temperature oxidation the oxidation may have occurred during the evaporation of primitive dust into cais but is also consistent with condensation at high oxygen fugacities no potential alternative processes appear to be capable of producing the observed mo and w depletion patterns

petrology and geochemistry of the northwest africa 3368 eucrite analysis of the mineralogy isotopic and bulk compositions of the eucrite meteorites is imperative for understanding their origin on the asteroid 4 vesta the proposed parent body of the hed meteorites we present here the petrology mineral compositions and bulk chemistry of several lithic components of the new brecciated basaltic eucrite northwest africa nwa 3368 to determine if all the lithologies reflect formation from one rock type or many rock types the meteorite has three main lithologies coarse and fine grained clasts surrounded by a fine grained recrystallized silicate matrix silicate compositions are homogeneous and the average rare earth element pattern for nwa 3368 is approximately 10 ci chondrites with a slight negative eu anomaly major and trace element data place nwa 3368 with the main group nuevo laredo trend high ti chromites with ilmenite exsolution lamellae provide evidence of nwa 3368 s history of intense metamorphism we suggest that this meteorite underwent several episodes of brecciation and metamorphism similar to that proposed by metzler et al 1995 we conclude that nwa 3368 is a monomict basaltic eucrite breccia related to known eucrites in texture and in mineral bulk and oxygen isotopic composition

sulfide rich metallic impact melts from chondritic parent bodies sacramento wash 005 saw 005 meteorite hills 00428 met 00428 and mount howe 88403 how 88403 are s rich fe ni rich metal meteorites with fine metal structures and homogeneous troilite we compare them with the h metal meteorite lewis cliff 88432 phase diagram analyses suggest that saw 005 met 00428 and how 88403 were liquids at temperatures above 1350 c tridymite in how 88403 constrains formation to a high temperature and low pressure environment the morphology of their metal troilite structures may suggest that met 00428 cooled the slowest saw 005 cooled faster and how 88403 cooled the quickest saw 005 and met 00428 contain h chondrite like silicates and saw 005 contains a chondrule bearing inclusion that is texturally and compositionally similar to h4 chondrites the compositional and morphological similarities of saw 005 and met 00428 suggest that they are likely the result of impact processing on the h chondrite parent body saw 005 and met 00428 are the first recognized iron and sulfide rich meteorites which formed by impact on the h chondrite parent body which are distinct from the iie iron meteorite group the morphological and chemical differences of how 88403 suggest that it is not from the h chondrite body although it likely formed during an impact on a chondritic parent body

the 2002 2003 el nino recorded in australian cave drip waters implications for reconstructing rainfall histories using stalagmites 1 a 30 month study of drip hydrochemistry from kooringa cave eastern australia revealed a clear geochemical response to the 2002 2003 el nino through the drought drip discharge fell to base flow drip ca2 concentrations fell by half and drip mg ca and sr ca increased in a co varying pattern calcite mg ca and sr ca predicted from drip waters displayed a marked increase through and just beyond the period of greatest moisture deficit the results suggest that stalagmites from shallow caves in drought sensitive eastern australia potentially preserve a valuable record of el nino la nina history

formation of metal and silicate globules in gujba a new bencubbin like meteorite fall gujba is a coarse grained meteorite fall composed of 41 vol large kamacite globules 20 vol large light colored silicate globules with cryptocrystalline barred pyroxene and barred olivine textures 39 vol dark colored silicate rich matrix and rare refractory inclusions gujba resembles bencubbin and weatherford in texture oxygen isotopic composition and in having high bulk 15n values 685 the 3he cosmic ray exposure age of gujba 26 7 ma is essentially identical to that of bencubbin suggesting that they were both reduced to meter size fragments in the same parent body collision the gujba metal globules exhibit metal troilite quench textures and vary in their abundances of troilite and volatile siderophile elements we suggest that the metal globules formed as liquid droplets either via condensation in an impact generated vapor plume or by evaporation of preexisting metal particles in a plume the lower the abundance of volatile elements in the metal globules the higher the globule quench temperature we infer that the large silicate globules also formed from completely molten droplets their low volatile element abundances indicate that they also formed at high temperatures probably by processes analogous to those that formed the metal globules the coarse grained bencubbin weatherford gujba meteorites may represent a depositional component from the vapor cloud enriched in coarse and dense particles a second class of bencubbin like meteorites represented by hammadah al hamra 237 and que 94411 may be a finer fraction derived from the same vapor cloud

precise dating of dansgaard oeschger climate oscillations in western europe from stalagmite data the signature of dansgaard oeschger events millennial scale abrupt climate oscillations during the last glacial period is well established in ice cores and marine records but the effects of such events in continental settings are not as clear and their absolute chronology is uncertain beyond the limit of 14 c dating and annual layer counting for marine records and ice cores respectively here we present carbon and oxygen isotope records from a stalagmite collected in southwest france which have been precisely dated using 234u 230th ratios we find rapid climate oscillations coincident with the established dansgaard oeschger events between 83 000 and 32 000 years ago in both isotope records the oxygen isotope signature is similar to a record from soreq cave israel and deep sea records indicating the large spatial scale of the climate oscillations the signal in the carbon isotopes gives evidence of drastic and rapid vegetation changes in western europe an important site in human cultural evolution we also find evidence for a long phase of extremely cold climate in southwest france between 61 2 0 6 and 67 4 0 9 kyr ago

the convective evolution and rapid intensification of hurricane earl 2010 abstractthe relationship between an inner core r 100 km lightning outbreak and the subsequent rapid intensification ri of hurricane earl 2010 is examined using lightning strikes recorded by the world wide lightning location network wwlln and in situ observations from various aircraft missions moderate 8 4 m s 1 northeasterly deep layer 850 200 hpa vertical wind shear caused by outflow from hurricane danielle existed over earl at the beginning of a prolonged period of ri over 70 of the lightning strikes within a 500 km radius occurred downshear with a preference toward downshear right in the outer rainbands in agreement with previous studies the location of inner core strikes in earl differed markedly from previous studies the inner core lightning activity precessed from left of shear to upshear an extremely rare event beginning just prior to the onset of ri diagnosis of the vortex tilt midway through the lightning precession showed this convection was occurring downtilt in the ups

potential vorticity analysis of tropical cyclone intensification the interaction of marginal tropical storm danny 1985 with an upper tropospheric positive potential vorticity anomaly was examined the intensification mechanism proposed earlier for mature hurricane elena appears to be valid for danny as well despite significant differences in the synoptic scale environment and in the stage of the tropical cyclone prior to the interaction both storms experienced rapid pressure falls as a relatively smallscale positive upper potential vorticity anomaly began to superpose with the low level tropical cyclone center the interaction is described in terms of a complex interplay between vertical wind shear diabatic heating and mutual advection among vortices at and below the level of the outflow anticyclone despite this complexity the superposition principle appears to be conceptually useful to describe the intensification of tropical cyclones during such interactions