interdecadal change in typhoon genesis condition over the western north pacific the interdecadal changes in typhoon categories 1 3 frequency and its genesis condition over the western north pacific during the period of 1979 2011 are investigated with consideration for discrepancies among best track datasets to tide over data uncertainty a detection produced dataset is utilized as a homogeneous dataset with five available best track datasets typhoon experienced interdecadal changes around the mid 1990s and the mid 2000s in their genesis conditions even under the oceanic warm state typhoon frequency has decreased since the mid 1990s showing a northwestward movement of its genesis location over the main formation region the eastward gradient of vertical wind shear is the most significant factor for the change in typhoon genesis condition in recent decades the vertical wind shear behavior is strongly linked with zonal asymmetry of local sst we demonstrate that a westward gradient of local sst is the most important modulator of the recent typhoon behavior through the movement of favorable genesis location the present results indicate that the horizontal distribution not magnitude of local sst can be a key factor for prediction of future typhoon activity thus contributing to natural disaster mitigation and climate change adaptation strategies

carbon isotopes and light element abundances in carbonaceous chondrites stepped combustions of whole rock samples of orgueil ci murchison cold bokkeveld and murray cm renazzo cr allende and mokoia c3v carbonaceous chondrites were carried out between 200 and 1200 c at each step co2 was collected for carbon isotope measurement and so2 and h2o yields were measured nitrogen was combined for several steps all samples released most of their carbon between 200 and 400 c due to combustion of the organic matter bulk carbon concentration and isotopic composition of each meteorite are therefore closely similar to those of this predominant reservoir between 400 and 700 c carbonates decomposed in all meteorites but the c3vs carbon isotopes in these carbonates matched previously published values in renazzo the carbonates have a 13c close to 42 pdb similar to those of cm meteorites above 700 c all meteorites but the c3vs show one or two occurrences of very13c rich carbon carbon concentration decreases from 350 to 30 ppb c as temperature increases between 700 and 885 c 13c reaches 240 4 in orgueil 73 9 in murchison 130 9 in cold bokkeveld and 125 5 in murray and then decreases between 950 and 1060 c 13c reaches 177 8 in renazzo 335 1 in cold bokkeveld and 384 6 in murchison finally murray yielded 3 ppm of carbon with a 13c of 1164 in the 1125 1210 c combustion step a qualitative inverse correlation among the c2 meteorites between the carbon concentration and 13c above 700 c suggests that these distinct heavy carbon releases could be actually due to a single heavy carbon component

iron isotope differences between earth moon mars and vesta as possible records of contrasted accretion mechanisms the iron isotope compositions of shergotty nakhla chassigny snc meteorites thought to come from mars eucrites and diogenites assumed to sample asteroid 4 vesta and rocks from the moon and earth have been measured using high precision plasma source mass spectrometry the means of eight samples from mars and nine samples from vesta are within error identical despite a range of rock types they are lighter by 0 1 in 57fe 54fe compared to the average of 13 terrestrial mantle derived rocks the latter value is identical within uncertainty with a previously published mean of 46 igneous rocks from the earth the average for 14 lunar basalts and highland plutonic rocks covering a broad spectrum of major element composition is heavier by 0 1 in 57fe 54fe relative to our estimate for the earth s mantle and therefore 0 2 heavier than the eucrites diogenites and snc meteorites however the data scatter somewhat and the apollo 15 green glass and apollo 17 orange glass are identical to samples from mars and vesta there is no clear relationship between petrological characteristics and fe isotope composition despite a wide spectrum of samples instead contrasted planetary isotopic signatures are clearly resolved statistically after evaluating alternative scenario it appears that the most plausible explanation for the heavier fe in the earth and moon is that both objects grew via processes that involved partial vaporisation leading to kinetic iron isotope fractionation followed by minor loss this is consistent with the theory in which the moon is thought to have originated from a giant impact between the proto earth and another planet combined with numerical simulations fe isotope data can offer the potential to provide constraints on the processes that occurred in planetary accretion

decadal changes in tropical cyclone activity over the western north pacific in the late 1990s a pronounced decadal change in tropical cyclone tc activity over the western north pacific wnp in the late 1990s was identified based on a comparison of the two epochs that occurred before and after the late 1990s the tc genesis number exhibited an evident decrease over the southern wnp s wnp 5 20 n 105 170 e and an increase over the northern wnp n wnp 20 25 n 115 155 e which partly corresponded to a significant northward migration in the seasonal mean latitudinal location of tc genesis i e from 17 2 n to 18 7 n after the late 1990s the northwestward moving track became the most dominant track mode accompanied by the weakening of both the westward moving track and the northeastward recurving track meanwhile the tc occurrence frequency tcf experienced evident increases over southeastern china and the okinawa islands while prominent decreases occurred over the south china sea the philippine sea japan and east of japan changes in the tcf were determined by tc genesis changes tc track shifts and variations in regional tc durations which were all ascribed to the decadal change in tropical indo pacific sea surface temperature the full picture on the decadal changes in the wnp tc activity revealed in this study may provide useful guidance for regional tc seasonal forecasts and future projections

petrology chemistry and origin of apollo 15 regolith breccias abstract variations in modal petrology mineral compositions and bulk compositions were determined for ten apollo 15 regolith breccias for comparison with local soils and assessment of the intrasite petrologic variability of the apollo 15 regolith based on the above criteria the breccias are of local origin and mimic the soils from the corresponding sampling stations with the exception of station 2 breccia 15205 this sample formed from an anomalous regolith and although not considered exotic to the site is not representative of the soil at the site kreep basalt and green glass components vary from trace amounts to dominant in the breccias evidence that these materials entered the regolith prior to formation of the breccias breccias from the edge of hadley rille are modally richer in highland fragments than the soils whereas at the base of hadley delta the reverse is true this is explained by the loss of material into the rille to be replaced by basalt derived material making the soils more basalt rich at the base of hadley delta highland material is accumulating and the soils are becoming more highland rich over billions of years these processes have developed differences between the present day evolving soils and fossil non evolving soils represented by the regolith breccias this shows that there has been little change in the geology and the morphology of the apollo 15 site probably since the eruption of mare basalts at the site 3 3 b y

volcanic degassing of argon and helium and the history of crustal production on venus we develop a new methodology linking 40ar and 4he degassing to crustal production on venus in order to examine two different scenarios for the history of magmatism on that planet both consistent with recent analyses of the cratering record of the venus surface the first scenario includes episodic global resurfacing events and modest levels of magmatism between such events while the second scenario invokes different rates of steady magmatism before and after a given transition time our degassing models include distinct mantle crustal and atmospheric reservoirs diffusive transfer of 40ar and 4he from the crust to the atmosphere is also taken into account the 40ar abundance in the present atmosphere reflects the integrated degassing and magmatism over most of planetary history in contrast helium escapes from the planetary atmosphere within a characteristic residence time of 200 myr to 1 8 gyr so the present atmospheric 4he abundance is relevant to the volume of magma produced during the last global resurfacing event and the rate of the magmatism subsequent to that event under the first scenario and to the two steady rates of magmatism and the transition time under the second unfortunately large uncertainties in mineral partition coefficients and in the ar and he mixing ratios in the lower atmosphere of venus presently prevent the use of our degassing models to distinguish among crustal formation history models we therefore explore the influence of these uncertain parameters on the degassing history in order to identify those new laboratory and in situ measurements that will most strongly constrain crustal production history as an important step in the development of the ar degassing model the k budget in the bulk silicate fraction of venus is re examined on the basis of venera and vega ray measurements of k u and th concentrations in surface materials for u and th concentrations in the bulk silicate planet of 18 29 ppb and 64 94 ppb respectively the degree of mantle melting that formed the surface materials at the venera 9 and 10 and vega 1 and 2 landing sites is calculated to lie between 0 02 and 0 16 the degree of melting calculated for materials at each landing site is combined with measurements of surface k concentration to estimate the k concentration in the bulk silicate portion of the planet at between 100 and 300 ppm these results suggest that venus and earth have similar heat production

westward shift of western north pacific tropical cyclogenesis tropical cyclones tcs in the western north pacific or typhoons account for one third of all tcs in the world and the change of the mean tc genesis location can affect billions of people in pacific islands and asian countries the annual mean tc genesis longitude is generally controlled by the east west shift of the tropical upper tropospheric trough tutt a pronounced westward shift in the tutt is found in all of the available reanalysis data sets during 1979 2012 suppressing tc genesis in the eastern portion east of 145 e of the western north pacific basin due to the enhanced vertical wind shear associated with the tutt shift as a result the annual mean tc genesis longitude has significantly shifted westward since 1979 the westward shifting trends in the tutt and tc genesis are associated with the enhanced tropical tropospheric warming which is consistent with the response of the tropospheric temperature to global warming

decadal interactions between the western tropical pacific and the north atlantic oscillation the relationship between interdecadal variations of tropical sea surface temperature sst in the last 120 years and circulation anomalies related to the north atlantic oscillation nao is investigated in this study using an atmospheric general circulation model agcm we confirm observational evidence that variations in the sst gradient in the western tropical pacific are related to the nao anomalies on decadal timescale and may be contributing to the shift towards the positive nao phase observed in the late 20th century the role played by the indian ocean nao teleconnection advocated in recent studies focused on the last 50 years is also assessed in the context of the 120 year long record it is suggested that a positive feedback between the pacific sst and the hemispheric circulation pattern embedding the decadal nao signal may act to enhance the internal variability of the coupled ocean atmosphere system and justify the stronger teleconnection found in observational data than in sst forced agcm experiments

investigation of magnesium isotope fractionation during basalt differentiation implications for a chondritic composition of the terrestrial mantle to investigate whether magnesium isotopes are fractionated during basalt differentiation we have performed high precision mg isotopic analyses by multi collector inductively coupled plasma mass spectrometry mc icp ms on a set of well characterized samples from kilauea iki lava lake hawaii usa samples from the kilauea iki lava lake produced by closed system crystal melt fractionation range from olivine rich cumulates to highly differentiated basalts with mgo content ranging from 2 37 to 26 87 wt our results demonstrate that although these basalts have diverse chemical compositions mineralogies crystallization temperatures and degrees of differentiation their mg isotopic compositions display no measurable variation within the limits of our external precision average 26 mg 0 36 0 10 and 25 mg 0 20 0 07 uncertainties are 2sd this indicates that mg isotopic fractionation during crystal melt fractionation at temperatures of 1055 c is undetectable at the level of precision of the current investigation calculations based on our data suggest that at near magmatic temperatures the maximum fractionation in the 26 mg 24 mg ratio between olivine and melt is 0 07 two additional oceanic basalts two continental basalts bcr 1 and bcr 2 and two primitive carbonaceous chondrites allende and murchison analyzed in this study have mg isotopic compositions similar to the kilauea iki lava lake samples in contrast to a recent report u wiechert a n halliday non chondritic magnesium and the origins of the inner terrestrial planets earth and planetary science letters 256 2007 360 371 the results presented here suggest that the bulk silicate earth has a chondritic mg isotopic composition 2007 published by elsevier b v

interdecadal variation of tropical cyclone genesis and its relationship to the convective activities over the central pacific using the outgoing longwave radiation olr data from the national oceanic and atmospheric administration archives this paper analyzes the interdecadal variation of convective activities over the central pacific cp from july to october of 1979 2013 and its impact on tropical cyclone tc genesis in the western north pacific wnp concurrent with the interdecadal decrease of tc genesis the tropical convection underwent a significant interdecadal change in the late 1990s overall the first leading empirical orthogonal function mode of the tropical olr during july october turned from a zonal dipole pattern during 1979 1997 to a tripole pattern during 1998 2013 concomitant to this change the boreal part of the walker circulation shrank westward with its downdraft branch located over the cp the downward motion anomalies over the cp increased after the late 1990s as did the trade easterlies consistent with the cp convective activity anomalies the negative low level relative vorticity anomalies and upper level divergence anomalies positive vertical wind shear anomalies and anomalous abundant water vapor can be observed over the southeastern part of the wnp additionally the tropical depression td type waves associated with the cp convective activities are significantly different before and after the late 1990s before the late 1990s the off equatorial td type waves could be distinctly observed with clear transitions located along the wnp monsoon trough however these transitions were vague after the late 1990s therefore the convective activities over the cp may have played an important role in affecting the interdecadal change of tc genesis by affecting the genesis of td type waves

grain size evolution and fractionation trends in an experimental regolith the comminution of blocky planetary surfaces into fine grained regoliths was simulated by impacting a fragmental gabbro target 200 times with stainless steel projectiles diameter 6 35 mm mass 1 2g vi 1 35 km s initially the target fragments were 2 32 mm in size with a mean diameter of 15 2 mm which was reduced to 0 4 mm after 200 shots for the first 60 shots comminution was linear with cumulative kinetic energy and thus essentially linear with time the comminution efficiency however decreased at later stages this could be due to a change in fracture mechanism from predominantly intergranular to predominantly intragranular and or due to a change in partitioning of the projectile s kinetic energy from collisional fragmentation or large fragments at early times to cratering in a progressively finer grained medium at later stages mineral specific preferential comminution is abundantly observed in the modal make up of various grain size fractions plagioclase comminutes more readily than pyroxenes plagioclase initially present at 54 vol comprises typically 65 70 of the 125 250 m fraction pyroxenes initially at 33 are depleted to 20 25 this fractionation occurs in the earliest samples analyzed and is not a time dependent phenomenon bulk chemical analyses reveal a corresponding increase in al2o3 cao and na2o and a decrease in feo and mgo the finest grain sizes are generally the most severely affected by differential comminution similar if not exactly identical trends are abundantly documented for lunar soil samples these experimental findings illustrate that differential comminution is capable of producing fractionation in the finest grain sizes they diminish the need for prominent lateral and vertical transport of components otherwise foreign to a lunar soil sampling site as postulated by some workers on the basis of multivariate chemical mixing models

potassium isotopic compositions of international geological reference materials abstract there is a renewed interest in k isotope geochemistry driven by the advances in analytical precision and it is emerging as a useful tracer in a variety of disciplines ranging from earth sciences to biology however high quality k isotopic data for reference materials are still limited but highly needed here we report high precision stable k isotopic compositions 41k for 23 commercially available international reference materials including igneous sedimentary and metamorphic rocks as well as an in house seawater standard potassium in digested samples was separated by cation exchange chromatography with bio rad ag50w x8 200 400 mesh resin in 0 5 n hno3 media potassium isotopes were measured on a nu plasma ii high resolution mc icpms the reproducibility of k isotopic analysis based on over one year of measurements of pure k solutions and rock standards was 0 06 95 confidence interval synthetic solutions made by mixing single element standards to represent various rock matrices confirmed the accuracy of our methods the 23 reference materials have 41k values ranging from 0 562 to 0 253 and the seawater standard has a much higher 41k value of 0 143 the comprehensive dataset presented here provides a reference for quality control and inter laboratory comparison of high precision k isotopic analyses for future studies

origin of interplanetary southward magnetic fields responsible for major magnetic storms near solar maximum 1978 1979 the origins of the interplanetary southward bz which cause the 10 major dst 100 nt magnetic storms detected during the 500 days of study august 16 1978 to december 28 1979 of the gonzalez and tsurutani 1987 work are examined in detail a full complement of isee 3 plasma and field data an 11 station ae index and the near equatorial dst index are used in this analysis it is found that the origins of the interplanetary southward bz events are quite varied if it is defined that the bz event which leads to dst 100 nt is the cause of the storm then one of the storm intensifications is caused by shock compression of preexisting southward interplanetary magnetic fields four or five are related to driver gas magnetic fields one or two are caused by shocked kinky heliospheric current sheets two or three by turbulence or waves behind interplanetary shocks and one possibly by draped fields associated with a noncompressive density enhancement event without a shock or a high speed stream in simplistic terms four or five storms are caused by driver gas fields four by shocked sheath fields and one possibly by high intensity draped fields in actuality many of the interplanetary southward bz and corresponding magnetic storm dst structures are more complex than stated above at least four of the interplanetary events have both major sheath and driver gas southward bz events in two storms sheath southward bz features led to dst reaching levels of 90 nt prior to driver gas southward bz features the following driver gas fields then caused dst to exceed our storm criteria of 100 nt in two other cases sheath bz features led to magnetic storm onsets dst 100 nt the following driver gas southward bz features cause further storm intensifications the above magnetic storms therefore displayed two stage development characteristics the results of this study indicate the equal importance of both sheath fields or draped fields and driver gas fields for the generation of major geomagnetic storms because of the importance of the sheath fields the intensity and duration of geomagnetic storms cannot be predicted by solar observations of active regions alone tang et al 1988 will address this topic in detail

influence of climate regime shift on the interdecadal change in tropical cyclone activity over the pacific basin during the middle to late 1990s in this study a new interpretation is proposed for the abrupt decrease in tropical cyclone tc activity in the western north pacific wnp after the late 1990s we hypothesize that this abrupt change constitutes a part of the phenomenon of interdecadal change in tc activity in the pacific basin including the wnp western south pacific wsp and eastern north pacific our analysis revealed that the climate regime shift crs in the pacific during the middle to late 1990s resulted in a la nina like mean state which was responsible for the interdecadal change in tc activity in the late 1990s analyses of the tc genesis potential index and numerical experiments revealed that the decline in tc activity in both the wnp and wsp was primarily attributable to the increase of vertical wind shear in the central pacific due to the la nina like associated cold sea surface temperature sst conversely the la nina like associated warm sst in the western pacific produced anomalous vertical transport of water vapor increasing moisture levels in the mid troposphere and tc activity in the western wnp furthermore the crs modified the mean tc genesis position and shifted the steering flow to the west resulting in the increased frequency of tc landfalls in taiwan southeastern china and northern australia after the late 1990s

systematic variation of summertime tropical cyclone activity in the western north pacific in relation to the madden julian oscillation abstract the variability of observed tropical cyclone tc activity i e genesis track and landfall in the western north pacific wnp is examined in relation to the various categories of the madden julian oscillation mjo during summer june september for the period 1979 2004 the mjo categories are defined based on the empirical orthogonal function analysis of outgoing longwave radiation data the number of tcs increases when the mjo related convection center is located in the wnp the axis of a preferable genesis region systematically shifts like a seesaw in response to changes in the large scale environments associated with both the eastward and northward propagation of the mjo and the intraseasonal variability of the wnp subtropical high furthermore the authors show that the density of tc tracks in each mjo category depends on the systematic shift in the main genesis regions at first order also the shift is affected by the prevailing large scale steering flows in each mjo category when th

potassium isotope fractionation during continental weathering and implications for global k isotopic balance abstract potassium isotopic compositions of profiles through saprolites developed on a diabase in south carolina u s a and on a granite in guangdong china allow characterization of the behavior of k isotopes during continental weathering saprolites from the diabase profile are heavily weathered with chemical index of alteration cia values up to 95 however their k isotopic variation is limited with 41k ranging from 0 475 0 028 in the unweathered diabase to 0 407 0 021 for the saprolites the lack of significant k isotope fractionation mainly reflects the conservative behavior of k in the diabase weathering profile with 50 of the original k remaining in the saprolites by contrast k isotopes are fractionated during granite weathering and correlate with sample depth cia and kaolinite abundance with 41k decreasing from 0 493 0 030 in the unweathered granites at the bottom to 0 628 0 021 in the most weathered saprolite close to the surface these observations suggest the preference of light k isotopes in saprolites relative to fluids which is further supported by the overall isotopically heavy nearby stream water samples 41k 0 709 0 017 to 0 339 0 018 these results demonstrate that continental weathering plays an important role in the global k isotopic budget through the formation of isotopically heterogeneous rivers and weathered regolith recycling of k rich crustal materials with distinct k isotopic signatures may produce distinct mantle k isotopic end members

isotopic composition of zinc copper and iron in lunar samples abstract we determined by icp ms the concentrations and isotopic ratios of fe cu and zn in the ti rich lunar basalt 74275 in the lunar orange glass 74220 and in up to 10 lunar soils namely 14163 15231 64501 66041 68841 69941 70011 72501 75081 and 76501 two analyses of zinc in lunar basalt 74275 give 66 zn 0 17 and 0 75 values within the range of those measured in terrestrial basalts copper in lunar basalt 74275 has 65 cu 1 4 which is isotopically heavier than values observed in terrestrial basalts in the orange glass we measured 56 fe 0 24 65 cu 0 42 and 66 zn 3 6 these values of are more negative than those obtained for 74275 and for typical lunar basalts but for cu comparable to those observed in terrestrial sulfides and meteorites in lunar soils we found 0 11 56 fe 0 51 2 6 65 cu 4 5 and 2 2 66 zn 6 4 insofar as we can generalize from a small sample set s fe cu zn and cd show similar trends in isotopic fractionation on the moon lunar basalts have nearly terrestrial isotopic ratios relative to the lunar basalt 74275 the pyroclastic glass 74220 is enriched in the lighter isotopes of fe cu and zn and the soils are enriched in the heavier isotopes of fe cu and zn the patterns in the basalts are likely inherited from the source material the light isotope enrichments seen in the orange glass originated during lava fountaining or less probably during partial condensation of vapor and the heavy isotope enrichments in the lunar soils were likely created by a combination of processes that included micrometeorite vaporization and sputtering in the orange glass the light isotope enrichments relative to lunar basalts of zn are larger than those of cu if these enrichments reflect accurately the isotopic composition of the gas they suggest that cu is more volatile than zn in the liquid from which the gas derived a simple model built on the known flux of micrometeorites to the lunar surface and a published estimate that micrometeorites generate 10 times their own mass of vapor predicts heavy isotope enrichments comparable to those observed in soils but only if the regolith gardening rate is set at about one twentieth of the generally accepted value of 1 cm my this discrepancy may reflect the difference in the time constants for micrometeorite milling and decimeter scale gardening or the importance of sputtering

an experimental investigation of agglutinate melting mechanisms shocked mixtures of sodium and potassium feldspars we report the results of an experiment designed to test the validity of the model for agglutinate formation involving fusion of the finest fraction or f3 papike et al 1981 impact glasses were formed from various mixes of orthoclase and albite powders which were used as analogs for soils with chemically contrasting coarse and fine fractions shock pressures ranged from 31 8 gpa to 78 0 gpa 318 780 kbar results show that the composition of the finest soil fraction is the dominant factor in displacing the composition of the impact melt agglutinate glass from that of the bulk other factors are degree of shock amount of melt and volatile loss a soil with no fine fraction displays only the effects of volatile loss whereas in other runs the glasses are compositionally displaced away from the bulk and toward the finest fraction as predicted by the model the lower pressure melts are the most fractionated higher pressure is accompanied by increased melting causing glass compositions to approach the bulk in general the systematics predicted by the model are observed and it appears that the fusion of the finest fraction model is valid

precise determination of the isotopic composition of potassium application to terrestrial rocks and lunar soils we detail a method for the precise and accurate determination of isotopic variations in the 41k39k ratio with a precision of 0 5 2 m purified potassium is chemically extracted from rocks soils minerals or solutions by ion exchange chromatography complete chemical yields 99 8 are achieved in order to avoid laboratory induced isotopic fractionations the purified potassium is converted to a glass by melting with barium borate flux and the resultant bead is mounted for ion probe analysis the sims method utilized by the ion probe produces extremely stable k ion beams with no measurable temporal variability in the isotope ratio the instrumental fractionation is steady at about 4 and is corrected for by measurement of a standard the measurement of gravimetrically prepared isotopic standards indicates that the method is accurate at the stated level of precision and free of egregious errors analysis of terrestrial samples including peridotite basalts granites carbonatite biotite schists and seawater indicate the complete absence of isotopic variations in 41 1k among terrestrial materials at the 0 5 o level application to lunar soils and a regolith breccia confirms previously observed large isotopic fractionation effects garner et al 1975a church et al 1976 some lunar soils e g 14163 are shown to have large sample heterogeneity 7 o while others e g soils and a regolith breccia at several apollo 15 sites station 79 are homogeneous at the level of analytical precision the presence of potassium isotopic effects in bulk soils up to 12 7 in this study with magnitudes comparable to the rayleigh fractionation factor 25 indicates that volatility during micrometeorite impact melting played a large role in lunar regolith formation as much as 15 of the regolith potassium has been lost from the moon through the tenuous lunar atmosphere

solar and interplanetary sources of major geomagnetic storms dst 100 nt during 1996 2005 1 we present the results of an investigation of the sequence of events from the sun to the earth that ultimately led to the 88 major geomagnetic storms defined by minimum dst 100 nt that occurred during 1996 2005 the results are achieved through cooperative efforts that originated at the living with a star lws coordinated dataanalysis workshop cdaw held at george mason university in march 2005 on the basis of careful examination of the complete array of solar and in situ solar wind observations we have identified and characterized for each major geomagnetic storm the overall solar interplanetary solar ip source type the time velocity and angular width of the source coronal mass ejection cme the type and heliographic location of the solar source region the structure of the transient solar wind flow with the storm driving component specified the arrival time of shock disturbance and the start and ending times of the corresponding ip cme icme the storm driving component which possesses a prolonged and enhanced southward magnetic field bs may be an icme the sheath of shocked plasma sh upstream of an icme a corotating interaction region cir or a combination of these structures we classify the solar ip sources into three broad types 1 s type in which the storm is associated with a single icme and a single cme at the sun 2 m type in which the storm is associated with a complex solar wind flow produced by multiple interacting icmes arising from multiple halo cmes launched from the sun in a short period 3 c type in which the storm is associated with a cir formed at the leading edge of a high speed stream originating from a solar coronal hole ch for the 88 major storms the s type m type and c type events number 53 60 24 27 and 11 13 respectively for the 85 events for which the surface source regions could be investigated 54 63 of the storms originated in solar active regions 11 13 in quiet sun regions associated with quiescent filaments or filament channels and 11 13 were associated with coronal holes remarkably nine 11 cme driven events showed no sign of eruptive features on the surface or in the low corona e g no flare no coronal dimming and no loop arcade etc even though all the available solar observations in a suitable time period were carefully examined thus while it is generally true that a major geomagnetic storm is more likely to be driven by a frontside fast halo cme associated with a major flare our study indicates a broad distribution of source properties the implications of the results for space weather forecasting are briefly discussed

two step development of geomagnetic storms using the dst index more than 1200 geomagnetic storms from weak to intense spanning over three solar cycles have been examined statistically interplanetary magnetic field imf and solar wind data have also been used in the study it is found that for more than 50 of intense magnetic storms the main phase undergoes a two step growth in the ring current that is before the ring current has decayed significantly to the prestorm level anew major particle injection occurs leading to a further development of the ring current and making dst decrease a second time thus intense magnetic storms may often be the result of two closely spaced moderate storms the corresponding signature in the interplanetary medium is the arrival of double structured southward imf at the magnetosphere

magnetosphere preconditioning under northward imf evidence from the study of coronal mass ejection and corotating interaction region geoeffectiveness 1 motivated by recent observations and simulations of the formation of a cold and dense plasma sheet in the tail of the magnetosphere under northward interplanetary magnetic field imf and of the direct influence of the plasma sheet density on the ring current strength this paper aims at 1 highlighting how the coupling of these effects may lead to a preconditioning of the magnetosphere under northward imf and 2 performing first tests of the validity of this hypothesis we have analyzed superposed epoch time series of various parameters to investigate the response of the magnetosphere as indicated by the dst index to the passage of coronal mass ejections cmes and corotating interaction regions cirs we first focused on the difference between the measured dst signature and that predicted by a semiempirical dst model for both cme and cir driven storms the superposed epoch results show that the model dst predictions tend to underestimate the actual storm strength by up to 10 30 for events that are preceded by a substantial interval of northward imf as opposed to those with no such preceding northward imf we also analyzed los alamos geosynchronous spacecraft data for these events the average density and temperature measured at storm onset are substantially higher and slightly lower respectively for the cases with preceding northward imf intervals these results suggest that solar wind structures may be more geoeffective if preceded by a northward imf interval and they are consistent with the hypothesis of a preconditioning by a cold dense plasma sheet a colder and denser plasma sheet may lead to a stronger ring current when that plasma is convected inward during the main phase of an ensuing storm

a nonmagmatic origin of group iie iron meteorites abstract new neutron activation data on 10 elements in 12 iie and iie related irons lead to a reclassification of several irons seymchan and lonaconing are removed from iie and leshan added four iie members are designated iie an to call attention to some anomalous properties the eight normal iie members define element ni trends generally similar to those in the nonmagmatic group iab the small negative slopes on w ni and ir ni diagrams are strongly indicative of a nonmagmatic origin of the iie irons we propose that iie irons like iab irons originated as individual pools of impact produced melt in the near surface region of a chondritic parent body the positive as ni and au ni trends are the only evidence suggesting fractional crystallization but their slopes are lower than those in magmatic group iiiab and only slightly higher than those of cu and sb in iab we suggest that the s and c contents of the iie precursor materials were much lower than those of the iab precursors thus higher temperatures were required to generate enough metallic melt to segregate into pools these higher temperatures are also reflected in the nonchondritic compositions of the silicate inclusions

el nino modoki and its possible teleconnection 1 using observed data sets mainly for the period 1979 2005 we find that anomalous warming events different from conventional el nino events occur in the central equatorial pacific this unique warming in the central equatorial pacific associated with a horseshoe pattern is flanked by a colder sea surface temperature anomaly ssta on both sides along the equator empirical orthogonal function eof analysis of monthly tropical pacific ssta shows that these events are represented by the second mode that explains 12 of the variance since a majority of such events are not part of el nino evolution the phenomenon is named as el nino modoki pseudo el nino modoki is a classical japanese word which means a similar but different thing the el nino modoki involves ocean atmosphere coupled processes which include a unique tripolar sea level pressure pattern during the evolution analogous to the southern oscillation in the case of el nino hence the total entity is named as el nino southern oscillation enso modoki the enso modoki events significantly influence the temperature and precipitation over many parts of the globe depending on the season the impacts over regions such as the far east including japan new zealand western coast of united states etc are opposite to those of the conventional enso the difference maps between the two periods of 1979 2004 and 1958 1978 for various oceanic atmospheric variables suggest that the recent weakening of equatorial easterlies related to weakened zonal sea surface temperature gradient led to more flattening of the thermocline this appears to be a cause of more frequent and persistent occurrence of the enso modoki event during recent decades

cluster analysis of tropical cyclone tracks in the southern hemisphere a probabilistic clustering method is used to describe various aspects of tropical cyclone tc tracks in the southern hemisphere for the period 1969 2008 a total of 7 clusters are examined three in the south indian ocean three in the australian region and one in the south pacific ocean large scale environmental variables related to tc genesis in each cluster are explored including sea surface temperature low level relative vorticity deep layer vertical wind shear outgoing longwave radiation el nino southern oscillation enso and the madden julian oscillation mjo composite maps constructed 2 days prior to genesis show some of these to be significant precursors to tc formation most prominently westerly wind anomalies equatorward of the main development regions clusters are also evaluated with respect to their genesis location seasonality mean peak intensity track duration landfall location and intensity at landfall enso is found to play a significant role in modulating annual frequency and mean genesis location in three of the seven clusters two in the south indian ocean and one in the pacific the enso modulating effect on genesis frequency is caused primarily by changes in low level zonal flow between the equator and 10 s and associated relative vorticity changes in the main development regions enso also has a significant effect on mean genesis location in three clusters with tcs forming further equatorward poleward during el nino la nina in addition to large shifts in mean longitude the mjo has a strong influence on tc genesis in all clusters though the amount modulation is found to be sensitive to the definition of the mjo

effects of magnetic clouds on the occurrence of geomagnetic storms the first 4 years of wind 1 we investigate geomagnetic activity associated with magnetic clouds as well as some aspects of the clouds magnetic field structure e g magnetic field distributions of the clouds thirty four magnetic cloud events observed by wind over the years 1995 1998 are investigated in this study magnetic clouds are a principal source of strong long lasting interplanetary negative bz fields in solar magnetospheric coordinates and hence are a major source of geomagnetic activity dst 50 nt the region just upstream of a cloud may be a significant source of southward fields instead of or as well as the cloud itself we call this upstream region a sheath if it is bounded by a shock or a pressure pulse and the cloud this study helps to identify the major sources regions of southward bz following shock passages or within the magnetic clouds that are most dominant in the generation of geomagnetic storms it is found that a geomagnetic storm can be induced by 1 a sheath 2 the leading i e front part region of a cloud 3 the trailing part of a cloud and 4 both sheath and cloud regions because of this complexity a storm with a multistep main phase can occur the related occurrence percentages of storms were 17 6 six events 44 1 15 events 5 9 two events and 20 6 seven events and the averaged storm intensities minimum dst were 60 85 92 and 58 nt respectively for the remaining four events 11 8 there were no storms the occurrence timing of storm intensity is highly correlated with the occurrence timing of minimum bz maximum vbs or for a magnetic cloud with the field rotating from southward to northward

isotopic composition of silicon in meteorites abstract samples of bulk meteorites show only mass dependent fractionation of silicon isotopes no isotopic anomalies were found the variation of the ratios 29 si 28 si and 30 si 28 si over the meteorite classes is small 1 per mass unit difference the average si isotopic composition for each class of meteorites is identical within analytical uncertainties this is quite unlike o whose anomalous isotopic abundances in bulk samples differentiate among the classes of meteorites the overlapping abundance ranges of si isotopes among many classes of meteorites suggest closed system behavior for this element prior to meteorite accretion and allow calculation of an average solar system si isotope composition

an experimental investigation of agglutinate melting mechanisms shocked mixtures of apollo 11 and 16 soils mixtures of chemically contrasting lunar soils from a 11 and a 16 have been shocked at pressures ranging from 18 2 62 0 gpa 182 620 kb other than the generation of impact melts modal and textural changes caused by shock include destruction of pore space and fused soil clasts and conversion of plagioclase to maskelynite the loss of the fused soil component in these runs indicates that low agglutinate contents in shocked and or compacted regolith breccias cannot be considered by themselves to be evidence of formation from immature regolith from the petrographic and chemical data it appears that the impact glass formed mainly from the fine fraction and the fused soil component in the target with relatively minor contributions from the other coarse clasts the impact glasses exhibit the same chemical enrichments and depletions as their corresponding fine fractions and plot on or near a mixing line between the bulk and fine fraction of the soil in which they were formed from this as well as several other studies it appears that the fusion of the finest fraction f3 model is valid and that it accurately predicts the chemical systematics of impact glass formed from lunar soil in addition fusion of agglutinates present in the target soil is an important process

contribution of the interdecadal pacific oscillation to the recent abrupt decrease in tropical cyclone genesis frequency over the western north pacific since 1998 abstractprevious studies have documented an abrupt decrease of tropical cyclone tc genesis frequency over the western north pacific wnp since 1998 in this study results from an objective clus

role of scale interactions in the abrupt change of tropical cyclone in autumn over the western north pacific tropical cyclone tc activity in autumn september november over the western north pacific experienced an abrupt change in 1998 which can be detected by the bayesian change point analysis during the decade before the regime shift 1988 1997 the occurrence frequency of tc genesis increased significantly over the tropical western pacific where the seasonal cyclonic flow intraseasonal oscillation iso and synoptic scale eddy sse were all strengthened compared to those observed in the decade after 1998 1998 2007 the tc trajectories also exhibited spatial differences during the active decade the tcs had a higher probability to move westward into the philippine sea and the south china sea and recurved northeastward toward the east of japan meanwhile the northwestward propagating tcs approaching taiwan and southeastern coast of china were reduced to understand the role of mean flow iso sse interaction in the decadal changes of sse and associated tc activity we diagnosed a newly proposed sse kinetic energy ke equation that separates the contributions of seasonal mean circulation and iso to the sse the results show that during the active tc decade the sse obtained higher ke from both mean flow and iso through eddy barotropic energy conversion when the enhanced sse momentum flux interacted with the strengthened monsoon trough and vigorous iso cyclonic anomaly over the western tropical pacific the increased sse ke contributed positively to the increased tc genesis over the main genesis region 7 5 20 n 130 170 e it also benefited the growth of tcs over the philippine sea and the south china sea during the active decade the decadal change in tc frequency over the extratropics was related to the eddy baroclinic energy conversion instead of the barotropic conversion associated with scale interaction during the active tc decade sse gained more less ke from the sse available potential energy over the east of japan the east china sea favoring disfavoring the succeeding development of tcs in this region