the role of tropical atlantic sst anomalies in modulating western north pacific tropical cyclone genesis the connection between north tropical atlantic nta sea surface temperature sst anomalies and tropical cyclone tc genesis over the western north pacific wnp and associated physical mechanisms are investigated in this study we demonstrate a remarkable negative correlation of wnp tc genesis frequency with the preceding boreal spring nta sst anomalies our analysis suggests that major factors for tc genesis including distributions of large scale vorticity and midtropospheric humidity are rendered unfavorable by remote teleconnections while barotropic energy conversion from the large scale flow is suppressed as shown in recent studies the remote teleconnection from the atlantic is sustained and enhanced throughout the typhoon season through local air sea interactions these results suggest that boreal spring nta sst anomaly could be a new predictor for the seasonal wnp tc activity

modulation of boreal summer intraseasonal oscillations over the western north pacific by enso abstractthe authors investigate the effects of el nino and la nina on the intraseasonal oscillation iso in the boreal summer may october over the western north pacific wnp it is found that during el nino summers the iso is dominated by a higher frequency oscillation with a period of around 20 40 days whereas during la nina summers the iso is dominated by a lower frequency period of around 40 70 days the former is characterized by northwestward propagating convection anomalies in the wnp and the latter is characterized by northward and eastward propagating convective signals over the tropical indian ocean maritime continent the possible mechanisms through which el nino southern oscillation enso induced background mean state changes influence the iso behavior are examined through idealized numerical experiments it is found that enhanced weakened mean moisture and easterly westerly vertical wind shear in the wnp during el nino la nina are the main causes of the strengthened weakened 2

the pacific meridional mode and the occurrence of tropical cyclones in the western north pacific abstractthis study investigates the association between the pacific meridional mode pmm and tropical cyclone tc activity in the western north pacific wnp it is found that the positive pmm phase favors the occurrence of tcs in the wnp while the negative pmm phase inhibits the occurrence of tcs there observed relationships are consistent with those from a long term preindustrial control experiment 1000 yr of a high resolution tc resolving geophysical fluid dynamics laboratory gfdl forecast oriented low ocean resolution flor coupled climate model the diagnostic relationship between the pmm and tcs in observations and the model is further supported by sensitivity experiments with flor the modulation of tc genesis by the pmm is primarily through the anomalous zonal vertical wind shear zvws changes in the wnp especially in the southeastern wnp the anomalous zvws can be attributed to the responses of the atmosphere to the anomalous warming in the northwestern part of the pmm pattern during th

climatic and tectonic controls on carbonate deposition in syn rift siliciclastic fluvial systems a case of microbialites and associated facies in the late jurassic this work provides new insights to assess the factors controlling carbonate deposition in the siliciclastic fluvial systems of rift basins sedimentological and stable isotope data of microbialites and associated carbonate facies along with regional geological information are shown to reveal the influence of climate and tectonics on the occurrence and attributes of carbonate deposits in these settings the vega formation a 150 m thick lower kimmeridgian siliciclastic fluvial sequence in asturias province northern spain constitutes a candidate for this approach this unit includes varied facies stromatolites rudstones packstones and wackestones containing oncoids intraclasts charophytes and shell bioclasts marlstones and polygenic calcareous conglomerates that formed in a low gradient fluvial lacustrine system consisting of shallow low sinuosity oncoid bearing channels and pools within marshy areas with sporadic coarse alluvial deposition the sedimentological attributes indicate common erosion by channel overflow and rapid lateral changes of subenvironments caused by water discharge variations the carbonate fluvial lacustrine system developed near uplifted marine jurassic rocks the occurrence of the system was conditioned by normal faults active during the deposition of the unit that favoured i springs of hco3 ca rich water from a rhaetian sinemurian carbonate rock aquifer and ii carbonate deposition in areas partially isolated from the adjacent siliciclastic fluvial system the microbialite 13c and 18o values support deposition in a hydrologically open system fed by ambient temperature meteoric water with riparian vegetation three types of lamination in the stromatolites and oncoids reflect distinct morphological types of cyanobacterial communities the textural pattern of lamination parallels 13c and 18o changes suggesting short term cycles of precipitation and temperature a moderately to strongly contrasted seasonal and or pluriannual precipitation regime is inferred from the cyclic 13c pattern of the lamination and from the discontinuous and asymmetrical growth of oncoids thus the isotopic and sedimentological attributes of the carbonate deposits were linked to short term climate changes associated with semi arid conditions consistent with the studied climatic zone

sea surface temperature in the north tropical atlantic as a trigger for el nino southern oscillation events the el nino southern oscillation in the pacific ocean influences temperature in other tropical ocean basins reanalysis data and model simulations suggest that temperature anomalies in the north tropical atlantic may also influence the development of la nina events

depositional facies and aqueous solid geochemistry of travertine depositing hot springs angel terrace mammoth hot springs yellowstone national park u s a petrographic and geochemical analyses of travertine de positing hot springs at angel terrace mammoth hot springs yellow stone national park have been used to define five depositional facies along the spring drainage system spring waters are expelled in the vent facies at 71 to 73 8c and precipitate mounded travertine composed of aragonite needle botryoids the apron and channel facies 43 728c is floored by hollow tubes composed of aragonite needle botryoids that encrust sulfide oxidizing aquificales bacteria the travertine of the pond facies 30 62 8c varies in composition from aragonite needle shrubs formed at higher temperatures to ridged networks of calcite and aragonite at lower temperatures calcite ice sheets calcified bubbles and aggregates of aragonite needles fuzzy dumbbells pre cipitate at the air water interface and settle to pond floors the prox imal slope facies 28 54 8c which forms the margins of terracette pools is composed of arcuate aragonite needle shrubs that create small microterracettes on the steep slope face finally the distal slope facies 28 30 8c is composed of calcite spherules and calcite feather crys tals despite the presence of abundant microbial mat communities and their observed role in providing substrates for mineralization the com positions of spring water and travertine predominantly reflect abiotic physical and chemical processes vigorous co 2 degassing causes a 12 unit increase in spring water ph as well as rayleigh type covariations between the concentration of dissolved inorganic carbon and corre sponding d 13 c travertine d 13 c and d 18 o are nearly equivalent to aragonite and calcite equilibrium values calculated from spring water in the higher temperature 50 738c depositional facies conversely

impacts of tropical north atlantic sst on western north pacific landfalling tropical cyclones abstractthis study examines the impacts of tropical north atlantic tna sea surface temperature anomaly ssta on western north pacific wnp landfalling tropical cyclones tcs the authors find that tna ssta has significant negative correlations with the frequency of tcs making landfall in china vietnam the korean peninsula and japan and the entirety of east asia tna ssta influences the frequency of tc landfalls in these regions by regulating tc genesis location and frequency associated with modulated environmental conditions during cold tna sst years larger low level relative vorticity and weaker vertical wind shear lead to more tc formations over the south china sea scs and western philippine sea wps and larger low level relative vorticity higher midlevel relative humidity and weaker vertical wind shear result in more tc formations over the eastern part of wnp ewnp more tcs forming over different regions are important for more tc landfalls in vietnam mainly forming over the scs and w

cyanobacterial tufa calcification in two freshwater streams ambient environment chemical thresholds and biological processes abstract calcareous freshwater streams near bad urach southwest germany were studied to determine the environmental limits to cyanobacterial calcification daily variations in temperature ph calcium concentration and alkalinity were measured at seasonal intervals from september 1993 to january 1995 in two small woodland streams with lengths of 1 0 and 1 5 km the principal cause of supersaturation in these fast flowing streams is inorganic carbon dioxide outgassing from resurging groundwater locally enhanced by turbulence at waterfalls and cascades photosynthetic uptake of carbon dioxide and temperature effects are negligible nonetheless organic substrates particularly cyanobacteria dominated microbial mats and biofilm significantly localize precipitation by providing suitable nucleation sites precipitation rates on artificial substrates up to 2 2 mm yr on limestone correlate with high saturation index values copper substrates inhibited microbial colonization and received negligible encrustation tufa formation and external calcium carbonate encrustation of cyanobacteria are conspicuous where the annual wateq4f saturation index exceeds 0 8 and are slightly below 0 7 calcium carbonate impregnation of cyanobacterial sheaths has not been observed we infer that in these fast flowing streams cyanobacteria utilize co2 in photosynthesis whereas elsewhere in sluggish freshwater cyanobacteria utilize hco3 leading to sheath impregnation by calcium carbonate even where saturation index is only 0 2 0 3 thus photosynthetic influence on cyanobacterial calcification appears to be negligible in fast flowing co2 rich streams and cyanobacterial calcification takes the form of external encrustation in slow flowing co2 poor streams and lakes cyanobacteria preferentially utilize bicarbonate and sheath impregnation can result modern tropical marine carbonate shelves have saturation indices commonly in the range 0 62 0 82 and cyanobacterial calcification is negligible extrapolation suggests that cyanobacterial calcification could occur in present day seas if saturation index exceeded 0 8 this level corresponding with heavy calcification in the freshwater streams studied may have been widespread in marine environments in the geological past at times when calcified cyanobacteria and environmentally influenced non skeletal calcium carbonate precipitates were abundant

strong modulation of the pacific meridional mode on the occurrence of intense tropical cyclones over the western north pacific abstractthis study finds a significant positive correlation between the pacific meridional mode pmm index and the frequency of intense tropical cyclones tcs over the western north pacific wnp

a geochemical evaluation of perennial spring activity and associated mineral precipitates at expedition fjord axel heiberg island canadian high arctic abstract two groups of perennial springs are observed in the canadian high arctic at expedition fjord on axel heiberg island at colour peak and gypsum hill saline discharge 1 3 2 5 molal nacl produces a variety of calcite travertine and gypsum rich precipitates saturation index calculations of the spring waters at colour peak suggest co 2 degassing from the waters causes calcite precipitation gypsum precipitation dominates at gypsum hill where spring waters have lower alkalinity and higher so 4 concentrations mineral accumulations form both channel and rimstone pool morphologies as a result of varying slope conditions at colour peak confined flow in steep slope areas develop massive structures in contrast to more friable porous accumulations in areas where waters fan out on shallower slopes these morphological variations lead to corresponding varying apparent rates of mineral precipitation mineral precipitation at gypsum hill is far less notable as a result of lower discharge rates and annual degradation by icing formation microscopic observations and geochemical analyses of the channel precipitates at colour peak reveal alternating light calcite spar and dark anhedral microcrystalline calcite combined with organic matter and non carbonate minerals laminae rimstone pools forming in lower sections of spring discharge are composed of accumulations of large euhedral calcite crystals interbedded with allochthonous inputs high concentration of dissolved solids is responsible for slow travertine precipitation rates which occurs during winter this precipitation is further retarded during summer months by the introduction of crystal growth inhibitors such as fe 3 and deposition of organic matter and soil sediments

origin of annual laminations in tufa deposits southwest japan abstract laminated tufas and a tufa depositing stream in sw japan shirokawa ehime prefecture were studied monthly over a 3 yr period a series of samples from the tufa clearly reveals the pattern of annual laminations the annual layering pattern was primarily controlled by changes in the rate of calcite precipitation as calculated from water chemistry the concentration of dissolved caco 3 which correlates with the precipitation rate was high in summer autumn and low in winter spring owing to changes in the partial pressure of co 2 in underground air regular seasonal changes in underground pco 2 probably resulted from two temperature dependent processes the diffusion of soil co 2 and the ventilation of underground air these changes in addition to water temperature changes altered the precipitation rate which has a clear seasonal pattern especially in the lower stream the seasonal precipitation rate was high in summer autumn and low in winter spring which is consistent with the seasonal lamination pattern seen in the tufas the textures of collected samples show that the laminations consist of densely calcified summer autumn june october laminae and lightly calcified winter spring november may laminae we infer that the increased precipitation rate stimulated thick calcite encrustation on cyanobacterial filaments to produce the dense textures this interpretation is supported by the lowered organic inorganic carbon production ratio in summer autumn seasonal variations in cyanobacterial assemblages are present but do not reflect the seasonal lamination pattern because the relevant processes are temperature dependent the seasonal lamination pattern at shirokawa is thought to generally apply to other laminated tufas deposited in temperate climates however a reversed pattern can result from local and climatic circumstances dense laminae were deposited in winter near the source of the spring at shirokawa because calcite precipitation was high owing to low underground pco 2 in winter reversed patterns reported from northwestern europe were probably influenced by seasonal rainfall which is reflected in hydrological conditions

the chemical evolution of a travertine depositing stream geochemical processes and mass transfer reactions this field study focuses on quantitatively defining the chemical changes occurring in falling spring creek a travertine depositing stream located in alleghany county virginia the processes of co sub 2 outgassing and calcite precipitation or dissolution control the chemical evolution of the stream the observed chemical composition of the water was used with the computerized geochemical model wateqf to calculate aqueous speciation saturation indices and co sub 2 partial pressure values mass balance calculations were performed to obtain mass transfers of co sub 2 and calcite reaction times estimated from stream discharge were used with the mass transfer results to calculate rates of co sub 2 outgassing and calcite precipitation between consecutive sampling points the stream which is fed by a carbonate spring is supersaturated with respect to co sub 2 along the entire 5 2 km flow path outgassing of co sub 2 drives the solution to high degrees of supersaturation with respect to calcite metabolic uptake of co sub 2 by photosynthetic plants is insignificant because the high supply rate of dissolved carbon dioxide and the extreme agitation of the stream at waterfalls and rapids causes a much greater amount of inorganic co sub 2 outgassing to occur calcite precipitation is kinetically inhibited until near the crest of amore 20 m vertical waterfall calcite precipitation rates then reach a maximum at the waterfall where greater water turbulence allows the most rapid escape of co sub 2 physical evidence for calcite precipitation exists in the travertine deposits which are first observed immediately above the waterfall and extend for at least 1 0 km below the falls net calcite precipitation occurs at all times of the year but is greatest during low flow conditions in the summer and early fall less

ecogeomorphic feedbacks in regrowth of travertine step pool morphology after dam decommissioning fossil creek arizona abstract the linkages between fluvial geomorphology and aquatic ecosystems are commonly conceptualized as a one way causal chain in which geomorphic processes create the physical template for ecological dynamics in streams with a travertine step pool morphology however biotic processes strongly influence the formation and growth of travertine dams creating the potential for numerous feedbacks here we take advantage of the decommissioning of a hydroelectric project on fossil creek arizona where restoration of caco 3 rich baseflow has triggered rapid regrowth of travertine dams to explore the interactions between biotic and abiotic factors in travertine morphodynamics we consider three conceptual frameworks where biotic factors independently modulate the rate of physical and chemical processes that produce travertine dams combine with abiotic factors in a set of feedback loops and work in opposition to abiotic processes such that the travertine step pool morphology reflects a dynamic balance between dominantly biotic constructive processes and dominantly abiotic destructive processes we consider separately three phases of an idealized life cycle of travertine dams dam formation growth and destruction by erosive floods dam formation is catalyzed by abiotic factors e g channel constrictions and bedrock steps and biotic factors e g woody debris and emergent vegetation from measurements of changes over time in travertine thickness on a bedrock step we find evidence for a positive feedback between flow hydraulics and travertine accrual measurements of organic content in travertine samples from this step show that algal growth contributes substantially to travertine accumulation and suggest that growth is most rapid during seasonal algal blooms to document vertical growth of travertine dams we embedded 252 magnets into nascent travertine dams along a 10 km stretch of river growth rates are calculated from changes over time in the magnetic field intensity at the dam surface at each magnet we record a range of hydraulic and travertine composition variables to characterize the dominant mechanism of growth abiotic precipitation algal growth trapping of organic material or in situ plant growth we find 1 rapid growth of travertine dams following flow restoration averaging more than 2 cm year 2 growth rates decline downstream consistent with loss of dissolved constituents because of upstream travertine deposition but also parallel to a decline in organic content in dam surface material and a downstream shift in dominant biotic mechanism 3 biotic mechanisms are associated with faster growth rates and 4 correlations between hydraulic attributes and growth rates are more consistent with biotic than abiotic controls we conclude that the strong influence of living organisms on rates of travertine growth coupled with the beneficial effects of travertine on ecosystem dynamics demonstrate a positive feedback between biology and geomorphology during our two year study period erosive flood flows occurred causing widespread removal of travertine the temporal distribution of travertine growth and erosion over the study period is consistent with a bimodal magnitude frequency relation in which growth dominates except when large infrequent storms occur this model may be useful in other systems where biology exerts strong controls on geomorphic processes

tropical cyclone movement and surrounding flow relationships abstract this paper presents results of a comprehensive study of the relationship between the movement of tropical cyclones and the large scale circulation which surrounds them cyclones have been stratified by direction and speed of movement latitude intensity change and size as determined by the radius of the outermost closed surface isobar in three ocean basins the northwest pacific the west atlantic and the australian south pacific region twenty one different stratifications are available in the northwest pacific 13 in the west atlantic and 6 in the australian south pacific area cyclone movement and surrounding flow relationships were studied at different pressure levels and a variety of radii pressure weighted layer averages were also analyzed in search of such relationships results show an important relationship between surrounding large scale flow and tropical cyclone movement for all stratifications the winds in the mid troposphere 500 700 mb at 5 7 latitude radius from the cyclone

calcite supersaturation and precipitation kinetics in the lower colorado river all american canal and east highline canal in situ ph determinations and analysis of major ions in solution indicated that the lower colorado river is supersaturated with respect to calcite throughout the entire daily cycle in both winter and summer although the ion activity product was 4 to 6 times greater than the calcite solubility product there was no detectable precipitation chemical analyses of water samples taken along 350 km of the river and canals from parker dam to the salton sea also revealed no evidence of calcium carbonate precipitation despite the inflow of saline and highly supersaturated irrigation return flows laboratory kinetic studies indicated that calcite crystal growth rates with colorado river water are about 30 of the rate for pure ca hco3 waters and about 70 of that for synthetic colorado river water calcite precipitation by crystal growth in the river is limited by the combination of short residence times and unavailability of reactive calcite critical supersaturation levels necessary for heterogeneous nucleation do not occur a high suspended load limits algal photosynthesis and thus prevents large decreases in daytime h2co3 levels

stable isotopic and elemental characteristics of recent tufa from a karstic krka river south east slovenia useful environmental proxies tufa samples from 16 consecutive barrages along a 13 km section of a groundwater fed krka river slovenia were analysed for their petrographical mineralogical elemental and stable carbon 13c and oxygen 18o isotope composition to establish their relation to current climatic and hydrological conditions waters constantly oversaturated with calcite and the steep morphology of the krka riverbed stimulate rapid co2 degassing and subsequent tufa precipitation the carbon isotope fractionation 13c between dic and tufa in the krka river evolves toward isotopic equilibrium being controlled by continuous co2 degassing and tufa precipitation rate downstream the 13c increased from 1 9 to 2 5 vienna peedee belemnite however since tufa precipitation rates remain similar downstream the major controlling factor of carbon isotope exchange is most probably related to the continuous 12co2 degassing downstream leaving the carbon pool enriched in 13c in the case of oxygen the isotope fractionation was found to be from 1 0 to 2 3 smaller than reported in the literature the observed discrepancies are due to different precipitation rates of calcite deposits as krka tufas on cascades grow relatively faster compared to slowly precipitated calcite deposits in cave or stream pools due to non equilibrium oxygen isotope exchange between krka tufa and water the 18o proxy showed from 1 2 to 8 2 c higher calculated water temperatures compared to measured water temperatures demonstrating that 18o proxy based temperature equations are not reliable for water temperature calculations of fast growing tufa on cascades because mg is bound to the terrigenous dolomite fraction in the krka tufa samples the mg ca was also found to be an unreliable temperature proxy yielding over up to 20 c higher calculated water temperatures this article is protected by copyright all rights reserved

simulated impacts of two types of enso events on tropical cyclone activity in the western north pacific large scale atmospheric response the present paper uses an atmospheric general circulation model to explore large scale atmospheric response to various el nino southern oscillation events associated with tropical cyclone tc activity in the western north pacific the simulated response is basically consistent with and confirms the observed results for eastern pacific warm epw event anomalously wet ascent occurs over the tropical central eastern pacific and dry descent is over the western pacific this walker circulation is associated with anomalous low level convergence reduced vertical wind shear vws and enhanced genesis potential index gpi in the southeast sub region these are consistent with the observed increase of the tc formation in the southeast sub region but decrease in the northwest sub region during july september jas and the increase in the southwest and northwest sub regions during october december ond in addition the strong westerly anomalies of the tc steering flow prevail in the east asian coast suppressing the tc northwestward or westward tracks for eastern pacific cold epc event all of the simulated variables show almost a mirror image of epw for central pacific warm event the anomalous walker circulation shifts westward because of the westward shift of the maximum sst anomaly forcing the anomalous subsidence associated with the western branch of the walker circulation during ond shifts northward to the south china seas resulting in a decrease of the tc genesis there the tc steering flow patterns during jas are favorable for tcs to make landfall over japan and korea compared with epc the descending motion in the central eastern pacific is much stronger for central pacific cold cpc event accompanied by more enhanced vws and reduced gpi in the southeast sub region therefore cpc provides a more adverse environment to the tc formation there during jas and ond consistent with the observed decrease of tc formation there moreover the easterly anomalies of the tc steering flow dominate the tropics during jas enhancing tc activity in the east coast of china additionally the convection over the western pacific moves to the south china sea during ond favoring the tc genesis there

seasonal modulations of different impacts of two types of enso events on tropical cyclone activity in the western north pacific the paper examines different impacts of eastern pacific warm cold epw epc and central pacific warm cold cpw cpc events on tropical cyclones tcs in the western north pacific wnp by considering the early season of april june amj the peak season of july september jas and the late season of october december ond during amj epw epc is associated with a significant increase of the tc genesis number in the southeastern southwestern sub region of the wnp but no class of el nino southern oscillation enso events shows a significant change in the tc lifetime and intensity during jas epw corresponds to an increase decrease of the tc genesis number in the southeastern northwestern sub region but cpw shows no significant change epc increases the tc genesis in the northwestern and northeastern sub regions and decreases the genesis in the southwestern sub region whereas cpc suppresses the genesis in the southeastern sub region both the lifetime and intensity of tcs are increased in epw but only a shortened lifetime is seen for cpc during ond epw reduces the tc genesis in the southwestern and northwestern sub regions whereas cpw enhances the genesis in the southeastern sub region over the south china sea cpw and cpc show a significant decrease and increase of the tc genesis respectively the tc lifetime is significantly longer in both epw and cpw and shorter in epc and tcs tend to be more less intense in epw cpc all of these variations are consistent with the development of enso related sst anomalies during different seasons and are supported by distributions of the genesis potential index a combination of large scale oceanic and atmospheric factors that affect tc activity tcs in the wnp mainly take the straight westward northwestward and recurving tracks during amj of epw years the tc steering flow patterns favor the recurving track and suppress the straight westward and northwestward tracks during jas epw is associated with the steering flows that are unfavorable for tcs to move northwestward or westward whereas cpw favors the northwestward track and suppresses the straight westward track the steering flow patterns during ond are similar to those during jas except that epc may increase the possibility of the northwestward track

factors controlling present day tufa dynamics in the monasterio de piedra natural park iberian range spain depositional environmental settings sedimentation rates and hydrochemistry the tufa record and hydrochemical characteristics of the river piedra in the monasterio de piedra natural park ne spain were studied for 6 years the mean discharge of this river was 1 22 m3 s the water was supersaturated with calcium carbonate the hco3 ca2 and tdic concentrations decreased along the 0 5 km long studied stretch whereas the calcite si showed no systematic downstream or seasonal variation over the same stretch several sedimentary subenvironments exist in which four broad types of tufa facies form 1 dense laminated tufa stromatolites 2 dense to porous massive tufa 3 porous coarsely laminated tufa with bryophytes and algae and 4 dense hard laminated deposits in caves the half yearly period thickness and weight of sediment accumulated on 14 tablets installed in several subenvironments showed that the deposition rate was greater in fast flowing river areas and in stepped waterfalls and lower in slow flowing or standing river areas and in spray and splash areas mechanical co2 outgassing is the main factor controlling calcite precipitation on the river bed and in waterfalls but this process does not explain the seasonal changes in depositional rates the deposition rates showed a half yearly period pattern recorded in all fluvial subenvironments persistent over time 5 26 mm 0 86 g cm2 in warm periods 2 26 mm 0 13 g cm2 in cool periods mass balance calculations showed higher calcite mass values in warm 21 58 mg l than in cool 13 68 mg l periods this biannual variation is mainly attributed to the seasonal differences in temperature that caused changes in inorganic calcite precipitation rate and in biomass and the correlative photosynthetic activity tufa sedimentation was therefore controlled by both physicochemical and biological processes the results of this study may help test depositional rates and their environmental controls and thus assess the climatic and hydrological significance of ancient tufas in semi arid conditions in particular in the quaternary

tropical cyclone track characteristics as a function of large scale circulation anomalies abstract factors that contribute to intraseasonal variability in western north pacific tropical cyclone track types are investigated it is hypothesized that the 700 mb large scale circulation can affect tropical cyclone track characteristics by enhancing or excluding genesis in certain regions and concurrently prohibiting or favoring recurving versus straight tracks a track type climatology indicates that genesis location alone may explain some of the variability in track type although some genesis regions have no preference for straight moving or recurving tracks a formation north of 20 n or east of 150 e and north of 10 n favors a recurvature track these recurving storms are classified as recurving north and recurving storms that form in regions with nearly equal probability of straight or recurving tracks are classified as recurving south a compositing technique is used to define anomalous 700 mb large scale circulations that exist during the formation of tropical cyclones that subsequently fol

upper mantle beneath a young oceanic rift peridotites from the island of zabargad red sea information on the nature of the upper mantle in a young rift zone with lithosphere transitional from continental to oceanic was obtained from the island of zabargad probably an uplifted fragment of red sea lithosphere the island exposes exceptionally fresh mantle derived peridotite spinel iherzolite bodies the mineralogy and major element rare earth element and mineral chemistry of the spinel iherzolites suggest that they equilibrated last at depth 30 km in the mantle and that they have oceanic rather than continental affinity it is unlikely that the zabargad ultramafics are part of a late precambrian early paleozoic ophiolite as found elsewhere in circum red sea regions rather they were uplifted probably in connection with the development of the red sea rift the zabargad peridotites are in tectonic contact with continental metamorphic basement rocks it appears therefore that regions of an embryonic rift such as the red sea can be covered with continental type crust but be underlain by an upper mantle having already oceanic affinities

co2 outgassing and calcite precipitation in falling spring creek virginia u s a abstract chemical and physical observations are presented to explain the evolution of stream water chemistry along the flow path in warm river cave and falling spring creek mixing of two chemically and thermally distinct waters in the cave defines the initial stream water chemistry all along the flow path the observed composition is influenced by outgassing of co2 the water is supersaturated with respect to co2 both in the subsurface and at the surface of the earth but outgassing is greatest in turbulent stretches of the stream above and at the waterfalls the loss of co2 drives the solution to high degrees of supersaturation with respect to calcite physical evidence for calcite precipitation exists in the rimstone dams observed inside the cave and in the travertine deposits above and below the falls along falling spring creek travertine precipitation in the streambed consumes ca2 and hco 3 with most of the precipitation occurring where the stream experiences the most rapid co2 loss the stream water maintains a significant level of supersaturation with respect to calcite over the entire length of the flow path studied

trigonal dendritic calcite crystals forming from hot spring waters at waikite north island new zealand amorphous silica and calcite form the deposits in the vent and on the discharge apron of waikite spring 100 ws 100 which is located in the waikite geothermal area on north island new zealand these precipitates formed from spring water that has a temperature of 90 c and a ph of 8 1 8 8 the opaline silica is restricted to areas around the vent where cooling and evaporation of the spring water triggered precipitation the calcite deposits in the spring vent and on the discharge apron are formed of large up to 15 cm long asymmetrical dendrite crystals that are characterized by multiple levels of branching branches grew preferentially from the downflow side of their parent branch all branches have a trigonal transverse cross section except in areas where competition for growth space induced merger of neighboring crystals the primary branches of the dendrite crystals are sub perpendicular to the substrate even in areas where the discharge apron slopes at a high angle up to 80 on the steeper parts of the discharge apron the plate like primary branches form the floors of the small terrace pools whereas their distal edges form the rims of the pools growth of these dendrite crystals is attributed to abiotic processes high levels of saturation with respect to calcite were caused by rapid co2 degassing of the sheets of spring water that flowed down the steep discharge apron calcite crystals with different crystal morphologies characterize other springs near this spring the variation in crystal morphologies from spring to spring is attributed to different levels of saturation that are related to the initial pco2 of the spring water upon discharge and the rate of co2 degassing at each spring

the sst gradient between the southwestern pacific and the western pacific warm pool a new factor controlling the northwestern pacific tropical cyclone genesis frequency abstractthe sea surface temperature gradient sstg between the southwestern pacific ocean 40 20 s 160 e 170 w and the western pacific warm pool 0 16 n 125 165 e in boreal spring has been identified as a new factor that controls the interannual variability of tropical cyclone tc frequency over the western north pacific ocean wnp this sstg can explain 53 of the total variance of the wnp tc genesis frequency during the typhoon season for the period 1980 2011 the positive sstg anomaly produces an anomalous cross equatorial pressure gradient and thus anomalies in low level southward cross equatorial flow and tropical easterlies over the central western pacific the anomalous easterlies further produce local equatorial upwelling and seasonal cooling in the central pacific which in turn maintains the easterly anomalies throughout the typhoon season these dynamical thermodynamical effects induced by the positive sstg anomaly lead to a reduced low level cyclonic shear increased vertical wind sh

remote forcing of the northern tropical atlantic sst anomalies on the western north pacific anomalous anticyclone this study uses both observations and numerical modeling experiments to investigate the lead lag relationship and the associated physical mechanism of the western north pacific anomalous anticyclone wnpac with sea surface temperature sst anomalies over the northern tropical atlantic nta the results show that the wnpac from late spring to the middle of autumn has a significant in phase relationship with the nta sst anomalies up to two seasons ahead this relationship reaches a peak when the nta sst leads by approximately 1 2 months and is nearly independent of the el nino southern oscillation variability diagnosis based on observations and numerical experiments using the community atmospheric model version 5 3 reveals that the nta warming favors intensified local convection activity during the spring autumn seasons causing enhanced low level convergence and upper level divergence i e ascending motion over the nta and opposite flow anomalies over the central tropical pacific the enhanced subsidence over the central tropical pacific in turn triggers an anomalous low level anticyclone over the western north pacific moreover the intensity of the anomalous local convection activity that is associated with the nta sst is closely related to the seasonal migration of the atlantic intertropical convergence zone itcz as the atlantic itcz migrates northward the nta sst induced local convection activity extends northward from a narrow band near the equator during early spring to nearly the entire nta region during the middle of summer leading to the strongest remote effect of the nta sst anomalies on the wnpac during late summer and early autumn

calcite precipitation rates in the field measurement and prediction for a travertine depositing stream abstract rates of calcite precipitation from a travertine depositing stream were determined from changes in stream composition between consecutive sampling points and were compared with rates predicted from a laboratory derived rate law plummer et al 1978 the agreement in rates was generally within an order of magnitude and routinely within a factor of 3 least agreement between measured and predicted rates was obtained for sections of flowpath where relatively little change in bulk chemical composition occurred which were the sections with the greatest mass transfer calculation error and for the stream segment including a waterfall which was the section with the greatest error in estimated surface area reaction rate obtained from the mass of calcite precipitated onto seed crystals placed in the stream significantly underestimated the mass transfer rate for the travertine depositing stream of warm river cave and falling spring creek virginia the coupling of equilibrium speciation models with mass balance calculations and simple field measurements allowed successful field based quantification of reaction rates

modulation of western north pacific tropical cyclone activity by the atlantic meridional mode this study examines the year to year modulation of the western north pacific wnp tropical cyclones tc activity by the atlantic meridional mode amm using both observations and the geophysical fluid dynamics laboratory forecast oriented low ocean resolution version of cm2 5 flor global coupled model 1 the positive negative amm phase suppresses enhances wnp tc activity in observations the anomalous occurrence of wnp tcs results mainly from changes in tc genesis in the southeastern part of the wnp 2 the observed responses of wnp tc activity to the amm are connected to the anomalous zonal vertical wind shear zvws caused by amm induced changes to the walker circulation during the positive amm phase the warming in the north atlantic induces strong descending flow in the tropical eastern and central pacific which intensifies the walker cell in the wnp the intensified walker cell is responsible for the suppressed enhanced tc genesis in the eastern western part of the wnp by strengthening weakening zvws 3 the observed wnptc amm linkage is examined by the long term control and idealized perturbations experiment with flor fa a suite of sensitivity experiments strongly corroborate the observed wnptc amm linkage and underlying physical mechanisms

effects of tropical north atlantic sst on tropical cyclone genesis in the western north pacific the tropical cyclone genesis number tcgn in july october jaso over the western north pacific wnp exhibits a robust interannual variation it shows a longitudinally tri pole pattern with a high in the eastern wnp and south china sea scs and a low in the western wnp which explain 42 2 and 23 4 of total tcgn variance in the eastern wnp and scs respectively the high low high pattern is similar to that derived from a tc genesis potential index gpi to understand the cause of the longitudinal distribution of the dominant interannual mode we examine the contributions of environmental parameters associated with gpi it is found that relative humidity and relative vorticity are important factors responsible for tc variability in the scs while vertical shear and relative vorticity are crucial in determining tc activity in eastern wnp a simultaneous correlation analysis shows that the wnp tcgn in jaso is significantly negatively correlated with a correlation coefficient of 0 5 with sea surface temperature anomalies ssta in the tropical north atlantic tna the longitudinal distribution of tc genesis frequency regressed onto tna ssta resembles that regressed upon the wnp tcgn series the spatial patterns of regressed environmental variables onto the ssta over the tna also resemble those onto tcgn in the wnp that is an increase of relative humidity in the scs and a weakening of vertical shear in the eastern wnp are all associated with cold ssta in the tna further analyses show that the cold ssta in the tna induce a negative heating in situ in response to this negative heating a low upper level anomalous aniti cyclonic cyclonic flows appear over the subtropical north atlantic and eastern north pacific and to east of the cold ssta anomalous low level westerlies appear in the tropical indian ocean given pronounced mean westerlies in northern indian ocean in boreal summer the anomalous westerly flows increase local surface wind speed and surface evaporation and cool the sst in situ cold ssta in northern indian ocean further suppress local convection inducing anomalous westerlies to its east leading to enhanced cyclonic vorticity and low surface pressure over the wnp monsoon trough region idealized numerical experiments further confirm this indian ocean relaying effect through which cold ssta in the tropical atlantic exert a remote impact to circulation in the wnp

western north pacific tropical cyclone tracks in cmip5 models statistical assessment using a model independent detection and tracking scheme abstractpast studies have shown that tropical cyclone tc projection results can be sensitive to different types of tc tracking schemes and that the relative adjustments of detection criteria to