large scale patterns associated with tropical cyclogenesis in the western pacific abstract five characteristic low level large scale dynamical patterns associated with tropical cyclogenesis in the western north pacific basin are examined along with their capacity to generate the type of mesoscale convective systems that precede genesis an 8 yr analysis set for the region is used to identify and create composites for the five characteristic patterns of monsoon shear line monsoon confluence region monsoon gyre easterly waves and rossby energy dispersion this brings out the common processes that contribute to tropical cyclogenesis within that pattern which are described in detail a 3 yr set of satellite data is then used to analyze the mesoscale convective system activity for all cases of genesis in that period and to stratify based on the above large scale patterns it is found that mesoscale convective systems develop in all cases of genesis except one seventy percent of cases developed mesoscale convective systems at more than one time during the genesis period and 44 of

sources and accumulation of sediment and particulate organic carbon in a subarctic fjard estuary 210pb 137cs and δ13c records from lake melville labrador the sources and distribution of sediment and particulate organic carbon oc to lake melville labrador were characterized to better understand impacts from climate and hydrological changes to the system mass accumulation rates mars across the lake melville system lms were established from 15 sediment cores collected in 2013 and 2014 by fitting excess 210pb 210pbex profiles to a two layer advection diffusion model mars validated using 137cs varied between 0 04 and 0 41 g cm 2 a 1 and overall decreased with increasing distance from the churchill river which drains into goose bay a western extension of lake melville the churchill river is the greatest source of sediment to the system but surprisingly mars were greatest in western lake melville rather than goose bay reflecting the contribution of fine material carried eastward in the churchill river plume and inputs from nearby tributaries a comparison of 137cs and 210pbex inventories to expected atmospheric fallout 1 5 and 23 6 disintegr

patterns of suspended particle distribution and transport in a large fjordlike estuary seasonal and spatial patterns of the distribution and transport of suspended particles in puget sound a large fjordlike estuary are a product of the interaction of the subtidal circulation with surface and bottom particle sources the particle distribution differs from the distribution of hydrographic properties and is characterized by four persistant features 1 a thin 10 m high turbidity surface layer 2 a thick 50 m low turbidity zone centered around the level of no net motion between net seaward and landward flow 3 horizontal particle fronts at the sill entrances and 4 a bottom nepheloid layer maintained by local resuspension removal of particles from the surface waters by advective downwelling at the seaward sill and gravitational settling throughout the basin make puget sound an efficient particle trap particles sedimented on the basin floor are transported preferentially landward by the action of erosion deposition cycles enhanced by fortnightly intrusions of new marine water

eruption of soufriere hills 1995 2009 from an offshore perspective insights from repeated swath bathymetry surveys this contribution provides an analysis of the 1995 2009 eruptive period of soufriere hills volcano montserrat from a unique offshore perspective the methodology is based on five repeated swath bathymetric surveys the difference between the 2009 and 1999 bathymetry suggests that at least 395 mm3 of material has entered the sea this proximal deposit reaches 95 m thick and extends 7km from shore however the difference map does not include either the finer distal part of the submarine deposit or the submarine part of the delta close to the shoreline we took both contributions into account by using additional information such as that from marine sediment cores by march 2009 at least 65 of the material erupted throughout the eruption has been deposited into the sea this work provides an excellent basis for assessing the future activity of the soufriere hills volcano including potential collapse and other volcanoes on small islands

analytical and numerical studies of the beta effect in tropical cyclone motion part i zero mean flow abstract the effect on tropical cyclone motion is studied using an analytical as well as a numerical model in a nondivergent barotropic framework the analytical model and the linear version of the numerical model give essentially the same result the linear effect causes a westward stretching of the model vortex but no significant movement of the vortex center an east west asymmetry in the meridional wind field is also created it is the inclusion of the nonlinear term that produces the northwestward movement of the vortex previously found by other investigators e g kitade 1981 this northwestward movement increases with both the maximum wind speed and the radius of maximum wind in a constant shape vortex a wind maximum is also found to the northeast of the vortex which appears to be consistent with the observational findings of shea and gray this asymmetry plays an important role in the vortex motion

multifaceted re analysis of the enigmatic kitimat slide complex canada abstract repeat submarine landslides are challenging to study due to the tendency of subsequent slides to destroy previous deposits repeat slides are common in fjord head deltas where high amounts of sediment are focused in narrow valleys this study examines a well known slide deposit associated with the kitimat delta on canada s west coast that has been linked to tsunamigenic landslides in 1974 and 1975 for the first time we incorporate multibeam bathymetry to a multifaceted dataset including new high resolution acoustic data and sediment cores to examine the history of submarine slides at the kitimat delta based on morphological analysis and age modelling using 210pb and 14c data we determine that the complex surface morphology of the slide lobe consists of at least two large slide deposits that reach 5 km from the delta the known event that occurred in 1975 and an older event that occurred at 623 83 cal bp 95 confidence interval we demonstrate that slide deposits can be differentiated based on surface morphology and acoustic character this is confirmed by age modelling the 1975 slide resulted in a flow that ploughed through the seabed creating compression and translation along a basal shear plane resulting in deep deformation and a surface characterized by pressure ridges the 623 83 cal bp event resulted in a large amount of blocky slide material that overran the former seafloor and was transported 5 km from the delta front several buried events are observed at depth one of which occurred at 2592 84 cal bp and appears to be on the same order of magnitude as the 1975 event and showing very similar acoustic characteristics as for hazard implications we show submarine landslides of varying sizes have naturally occurred on this delta throughout the past several thousand years

environmental factors contributing to tropical cyclone genesis over the western north pacific abstractthe flow environment associated with tropical cyclone genesis tcg over the western north pacific was assessed via categorization into five flow patterns monsoon shear line sl monsoon confluence region cr monsoon gyre gy easterly wave ew and preexisting tropical cyclone ptc using reanalysis data and an objective algorithm the authors defined contribution scores for the five flow patterns each score represents the contribution to tcg from each flow pattern and scores were calculated for 908 tcg cases from 1979 to 2008 30 yr of the major contribution flow patterns sl accounted for 42 of tcgs ew for 18 cr for 16 ptc for 11 and gy for 6 seasonal variations in the occurrence frequency of these five patterns were clear but interannual variations were not as apparent tropical cyclones often appear to be generated in conditions with multiple flow patterns thus relationships between multiple flow patterns were investigated by comparing contribution scores the sl and

morphology and sedimentology of deltas in fjord and fjord valley lakes abstract sediment supply depositional processes and the associated morphology and sedimentology of deltas in a fjord and several fjord lakes have been studied two deltas in lakes in eastern norway receive sediments from fluvial erosion of quaternary glacial deposits and are only to a slight extent influenced by modern glaciers the other deltas are situated in western norway in the drainage area of the jostedalsbreen ice cap the meltwater rivers draining this glacier are characterized by a high rate of sediment transport in a wide range of grain sizes the main modes of the grain size distribution curves occur in the silt sand and cobble fractions the sediment transport and the water discharge of the rivers have been measured during the same periods the sedimentation rate of different grain fractions and their downstream variation in the frontal area of the deltas were determined by sediment traps the morphology of the deltas have been investigated with echo sounding differences in downstream sedimentation rates of the various deltas are related to dynamic and geometrical properties of the systems the effect of different factors on delta morphology and sedimentology is discussed

satellite data analysis and numerical simulation of tropical cyclone formation 1 forecast of tropical cyclone tc formation has long been a great challenge owing to lack of reliable observations over vast open oceans recent satellite products provide a unique opportunity to reveal detailed atmospheric wave structures prior to tc formation using the quikscat surface wind and the tropical rainfall measurement mission microwave image data we document temporal and spatial structures of rossby wave trains induced by energy dispersion from a pre existing tc and easterly wave propagation characteristics prior to cyclogenesis in the western north pacific using a baroclinic model we further simulate cyclogenesis processes associated with the tc energy dispersion and easterly waves

observational analysis of sudden tropical cyclone track changes in the vicinity of the east china sea abstractan observational analysis of observed sudden typhoon track changes is conducted with a focus on the underlying mechanism and the possible role of slowly varying low frequency flows four typhoons that took a generally northwestward track prior to sharply turning northeastward in the vicinity of the east china sea are investigated it is found that the sudden track changes occurred near the center of the madden julian oscillation mjo scale cyclonic circulation or at the bifurcation point of the steering flows at 700 hpa and they were all associated with a well developed quasi biweekly oscillation qbw scale gyre calculation of vorticity advection suggests that the peripheral ridging resulting from the interaction between the typhoons and the flows on the mjo and qbw scales can compress the typhoon circulation leading to an area of high winds to the east or south of the typhoon center the enhanced synoptic scale winds shifted the typhoons northward and placed them in a northeastward orbit unde

propagation and maintenance mechanism of the tc submonthly wave pattern and tc feedback in the western north pacific abstractpropagation and maintenance mechanisms of the tropical cyclone submonthly wave pattern in the western north pacific are explored the wave pattern exhibited an equivalent barotropic structure with maximum vorticity and kinetic energy in the lower troposphere and propagated northwestward in the philippine sea in the intraseasonal oscillation iso westerly phase and north northeastward near the east asian coast in the easterly phase the mean flow advection played a dominant role in the propagation in both phases barotropic energy conversion is the dominant process in maintaining the kinetic energy of the pattern the wave pattern tended to occur in the confluent zone between the monsoon trough and the anticyclonic ridge where the kinetic energy could be efficiently extracted from the westerly mean flow associated with the monsoon trough the individual circulation circuit embedded in the pattern was oriented northeast southwest east west to have optimal growth and propagation during the iso wes

how significant are low level flow patterns in tropical cyclone genesis over the western north pacific abstractthe low level flow pattern characteristics of the tropical cyclone genesis tcg environment over the western north pacific wnp were investigated not only for the periods during which tcg

physical processes controlling earlier and later onset of a typhoon season in the western north pacific the interannual variability of typhoon onset date in western north pacific wnp during 1979 2015 is investigated the average date in the earlier later onset group is early april late july a diagnosis of the genesis potential index shows that the key factor affecting the earlier and later onset lies in the background moisture field according to their evolution feature the earlier onset cases are further divided into two sub groups in the first sub group positive specific humidity anomalies were confined in the western wnp and caused primarily by circulation anomalies associated with a la nina in the equatorial eastern pacific in the second sub group positive specific humidity anomalies were confined in the eastern wnp and caused by anomalous convection associated with the pacific meridional mode pmm in the tropical and subtropical eastern pacific in the later onset composite negative specific humidity anomalies appear in the wnp and were accompanied by an anomalous anticyclone in situ and a v shape negative ssta pattern in the western pacific in addition the change of background vertical wind shear vws also influences the tc onset date a decrease increase in the vws magnitude and an easterly westerly shear anomaly occur in the earlier later onset composite physically it is argued that both the magnitude of the vws and the sign of anomalous zonal wind shear may affect tc formation in the wnp

the interaction of easterly waves orography and the intertropical convergence zone in the genesis of eastern pacific tropical cyclones the interaction of an idealized easterly wave with an orographic feature representing the sierra madre of mexico and a large scale meridionally sheared zonal flow representing the itcz in the eastern north pacific is examined through numerical integration of the shallow water equations on an equatorial beta plane channel the model simulations show that as a wave approaches the orography from the east the relative vorticity in the lee increases due to the wave being modified by the orography this relative vorticity maximum increases the northward advection of the itcz in the lee of the mountain that occurs due to the influence of the mountain anticyclone the result of this interaction is the development of a localized region of enhanced cyclonic vorticity that moves parallel to the contours of the model orography there is a minimal increase in the amplitude of the vorticity occuring during interactions between the wave and orography itcz and orography and wave and itcz the position of the incident wave upstream of the orography at the time that the disturbance in the lee begins to develop and the subsequent motion of the leeside vorticity maximum are in agreement with an observed case of eastern pacific tropical cyclogenesis which is also presented

submarine deposits from pumiceous pyroclastic density currents traveling over water an outstanding example from offshore montserrat iodp 340 pyroclastic density currents have been observed to both enter the sea and to travel over water for tens of kilometers here we identified a 1 2 m thick stratified pumice lapilli ash cored at site u1396 offshore montserrat integrated ocean drilling program iodp expedition 340 as being the first deposit to provide evidence that it was formed by submarine deposition from pumice rich pyroclastic density currents that traveled above the water surface the age of the submarine deposit is ca 4 ma and its magma source is similar to those for much younger soufriere hills deposits indicating that the island experienced large magnitude subaerial caldera forming explosive eruptions much earlier than recorded in land deposits the deposit s combined sedimentological characteristics are incompatible with deposition from a submarine eruption pyroclastic fall over water or a submarine seafloor hugging turbidity current derived from a subaerial pyroclastic density current that entered water at the shoreline the stratified pumice lapilli ash unit can be subdivided into at least three depositional units with the lowermost one being clast supported the unit contains grains in five separate size modes and has a 12 phi range particles are chiefly subrounded pumice clasts lithic clasts crystal fragments and glass shards pumice clasts are very poorly segregated from other particle types and lithic clasts occur throughout the deposit fine particles are weakly density graded we interpret the unit to record multiple closely spaced 2 d hot pyroclastic density currents that flowed over the ocean releasing pyroclasts onto the water surface and settling of the various pyroclasts into the water column our settling and hot and cold flotation experiments show that waterlogging of pumice clasts at the water surface would have been immediate the overall poor hydraulic sorting of the deposit resulted from mixing of particles from multiple pulses of vertical settling in the water column attesting to complex sedimentation slow settling particles were deposited on the seafloor together with faster descending particles that were delivered at the water surface by subsequent pyroclastic flows the final sediment pulses were eventually deflected upon their arrival on the seafloor and were deposited in laterally continuous facies this study emphasizes the interaction between products of explosive volcanism and the ocean and discusses sedimentological complexities and hydrodynamics associated with particle delivery to water

rossby waves in zonally opposing mean flow behavior in northwest pacific summer monsoon abstract the interactions between monsoon circulations and tropical disturbances in the northwest pacific where the low level mean flow is westerly in the west and easterly in the east are studied with a barotropic model the authors model results suggest that the scale contraction by the confluent background flow the nonlinear dynamics the effect and the large scale convergence are important for the energy and enstrophy accumulation near the region where the zonal flow reverses the energy enstrophy accumulation can be maintained with a continuous rossby wave emanation upstream the largest accumulation occurs when the emanating zonal wavelength is around 2000 km longer rossby waves experience less scale contraction and nonlinear effects while shorter rossby waves cannot hold a coherent structure against dispersive effects the nonlinear energy enstrophy accumulation mechanism is significantly different from previous linear energy accumulation theories in the linear theories this is primarily a

genesis of hurricane julia 2010 within an african easterly wave low level vortices and upper level warming abstractwhile a robust theoretical framework for tropical cyclogenesis tcg within african easterly waves aews has recently been developed little work explores the development of low level meso scale vortices llvs and a meso scale surface low in relation to deep convection and upper tropospheric warming in this study the development of an llv into hurricane julia 2010 is shown through a high resolution model simulation with the finest grid size of 1 km the results presented expand upon the connections between llvs and the aew presented in previous studies while demonstrating the importance of upper tropospheric warming for tcg it is found that the significant intensification phase of hurricane julia is triggered by the pronounced upper tropospheric warming associated with organized deep convection the warming is able to intensify and expand during tcg owing to formation of a storm scale outflow beyond the rossby radius of deformation results confirm previous ideas by demonstrating that th

large scale influences on tropical cyclogenesis in the western north pacific abstract objectively analyzed data from the european centre for medium range weather forecasts are used to examine the large scale aspects of the formation of tropical cyclones it is hypothesized that tropical cyclogenesis occurs when external atmospheric forcing on the synoptic or larger scale provides uplift through a deep layer enhancing convection in a region with environmental conditions favorable for genesis emphasis is placed on the roles of upper level troughs low level wind surges preexisting tropical cyclones and propagating wave disturbances in triggering tropical cyclogenesis composites of the 200 hpa and 850 hpa flows reveal the presence of both upper level troughs and low level wind surges respectively prior to genesis in the composites the wind surges also appear to be related to the presence of a prior circulation located approximately 2000 km to the west of the genesis location an examination of the individual cases demonstrates that approximately 85 of all storms had either

downstream development in the southern hemisphere monsoon during fgge wmonex abstract evidence is presented of a downstream development mechanism operating across the entire longitudinal span of the 1978 79 southern hemisphere monsoon observationally it is seen as progressive cyclonic and anticyclonic vorticity increases that develop eastward in the monsoon trough at a speed of approximately 5 m s 1 the process results in many tropical cyclone and tropical depression formations over northern australia and the south pacific it is shown that the downstream development process is generally consistent with linearized barotropic dynamics and that the southern hemisphere monsoon because of an intrinsic westerly basic state is a particularly suitable region for downstream events it is also shown that some apparent contradictions in previous observational studies can be rationalized by the theory the interactions between the regional components of the monsoon indonesian australian and south pacific sectors can also he better understood we further suggest that the process has i

roles of the synoptic scale wave train the intraseasonal oscillation and high frequency eddies in the genesis of typhoon manyi 2001 abstractexperiments using the weather research and forecasting wrf model were conducted to investigate the effects of multiscale motions on the genesis of typhoon manyi 2001 in the western north pacific the precursor signal associated with this typhoon genesis was identified as a northwest southeast oriented synoptic scale wave train swt the model successfully simulated the genesis of the typhoon in the wake of the swt further experiments were conducted to isolate the effects of the swt the intraseasonal oscillation iso and high frequency shorter than 3 days eddies in the typhoon formation removing the swt in the initial and boundary conditions eliminates the typhoon genesis this points out the importance of the swt in the typhoon genesis it was noted that the swt strengthened the wake cyclone through southeastward energy dispersion the strengthening wake cyclone triggered multiple episodes of strong sustained convective updrafts leading to aggregation of vertical vorticity and formatio

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

a long square barrel gravity corer for sedimentological and geochemical investigation of fine grained sediments abstract large volume undisturbed sediment cores 3 m long are obtained using a modified gravity corer the corer is square in cross section 12 7 12 7 cm and is designed to facilitate acquisition and subsampling of fine grained sediments sedimentological and geochemical data demonstrate that the modified gravity corer obtains undisturbed cores and preserves the sediment water interface

a sediment budget for the choptank river estuary in maryland u s a abstract a sediment budget for the choptank river one of the three largest estuaries on the eastern shore of chesapeake bay was developed from measurements of sediment carried in upland runoff shore erosion sedimentation and levels of suspended sediments in estuarine waters shore erosion was the major source of sediment 340 106 kg y 1 contributing seven times more sediment than upland runoff low relief the rural character of the coastal plain drainage basin and the susceptibility of poorly consolidated shoreline materials to erosion contributed to the dominance of shore erosion over runoff as a sediment source box modelling indicated a net annual flux 14 44 106 kg y 1 of sediment from the choptank river to chesapeake bay a mass balance estimate of sedimentation calculated as the difference between total inputs and loss at the mouth of the estuary 350 106 kg y 1 agreed well with an estimate based on 210pb profiles 340 106 kg y 1 measured along the longitudinal axis of the estuary lead 210 sedimentation rates correspond to accumulation rates of 1 5 7 9 mm y 1

an assessment of the impact of transient eddies on the zonal flow during a blocking episode using localized eliassen palm flux diagnostics abstract the eliassen palm e p flux applied to zonal men flows is an indicator of both the flux of eddy activity and the eddy forcing of the zonal mean flow for time mean flows a localized e p flux is derived and used diagnostically to assess the impact of transient eddies on a major blocking episode that occurred over the south pacific during the southern hemisphere winter of 1979 in contrast to previous studies that have focused on the mean quasi geostrophic potential vorticity equation the focus here is on the mean momentum equations eddy transports and the associated induced meridional circulation and other internal adjustments necessary to maintain the thermal wind balance are gathered together allowing the residual circulation and the effects of the eddies to be determined the time mean equations of motion are thus transformed to consist of mean terms the residual circulation and the divergence of a localized e p flux vector the latter is a measure of the eddy forcing of the mean flow

mixed rossby gravity waves and western pacific tropical cyclogenesis part i synoptic evolution abstract a large amplitude mixed rossby gravity wave packet is identified in the western pacific using 6 10 day bandpass filtered winds individual disturbances of 2300 3000 km wavelength propagated westward as the packet moved slowly eastward the packet first appeared and subsequently amplified within a region of active convection associated with the madden julian oscillation mjo which was isolated by low pass filtered outgoing longwave radiation the packet lasted about 5 weeks then rapidly dispersed as the active mjo moved away from it to the east west of 150 e individual disturbances within the packet turned northwestward away from the equator indicating an apparent transition from mixed rossby gravity waves to off equatorial tropical depression td type disturbances cyclones filled with cloud and anticyclones cleared during the transition nevertheless convective structure consistent with mixed rossby gravity waves remained outside the circulation centers and three tropical cyclones for

rossby wave energy dispersion from tropical cyclone in zonal basic flows this study investigates tropical cyclone energy dispersion under horizontally sheared flows using a nonlinear barotropic model in addition to common patterns unusual features of rossby wave trains are also found in flows with constant vorticity and vorticity gradients in terms of the direction of the energy dispersion the wave train can rotate clockwise and elongate southwestward under anticyclonic circulation ash which contributes to the reenhancement of the tropical cyclone tc the wave train even splits into two obvious wavelike trains in flows with a southward vorticity gradient wsh energy dispersed from tcs varies over time and variations in the intensity of the wave train components typically occur in two stages wave activity flux diagnosis and ray tracing calculations are extended to the frame that moves along with the tc to reveal the concrete progress of wave propagation the direction of the wave activity flux is primarily determined by the combination of the basic flow and the tc velocity along the flux the distribution of pseudomomentum effectively illustrates the development of wave trains particularly the rotation and split of wave propagation ray tracing involves the quantitative tracing of wave features along rays which effectively coincide with the wave train regimes flows of a constant shear parabolic meridional variation produce linear nonlinear wave number variations for the split wave trains the real and complex wave number waves move along divergent trajectories and are responsible for different energy dispersion ducts

are multiple tropical cyclone events similar among basins abstractthe present study intercompares multiple tropical cyclone event mtce characteristics among each global tropical cyclone tc basin using best track data specific focus is placed on examining the number of mtces and tcs during mtces the zonal distance between tcs during mtces and the spatiotemporal separation between genesis events during mtces the results suggest that the ratio of mtces relative to single tcs is substantially higher in the eastern north pacific enp western north pacific wnp and south indian ocean si basins compared to the north atlantic na and south pacific sp the prolific nature of enp wnp and si mtce activity results in approximately half of tcs occurring during mtces during new tc genesis the majority of preexisting tcs are generally located westward at a consistent zonal distance from new tc genesis for mtces within each basin with median values between 1620 and 1961 km tc induced rossby wave dispersion may set this zonal length scale as implied by it

high resolution seismic reflection imaging of growth folding and shallow faults beneath the southern puget lowland washington state abstract marine seismic reflection data from southern puget sound washington were collected to investigate the nature of shallow structures associated with the tacoma fault zone and the olympia structure growth folding and probable holocene surface deformation were imaged within the tacoma fault zone beneath case and carr inlets shallow faults near potential field anomalies associated with the olympia structure were imaged beneath budd and eld inlets beneath case inlet the tacoma fault zone includes an 350 m wide section of south dipping strata forming the upper part of a fold kink band coincident with the southern edge of an uplifted shoreline terrace an 2 m change in the depth of the water bottom onlapping postglacial sediments and increasing stratal dips with increasing depth are consistent with late pleistocene to holocene postglacial growth folding above a blind fault geologic data across a topographic lineament on nearby land indicate recent uplift of late holocene age profiles acquired in carr inlet 10 km to the east of case inlet showed late pleistocene or holocene faulting at one location with 3 to 4 m of vertical displacement south side up north of this fault the data show several other disruptions and reflector terminations that could mark faults within the broad tacoma fault zone seismic reflection profiles across part of the olympia structure beneath southern puget sound show two apparent faults about 160 m apart having 1 to 2 m of displacement of subhorizontal bedding directly beneath one of these faults a dipping reflector that may mark the base of a glacial channel shows the opposite sense of throw suggesting strike slip motion deeper seismic reflection profiles show disrupted strata beneath these faults but little apparent vertical offset consistent with strike slip faulting these faults and folds indicate that the tacoma fault and olympia structure include active structures with probable postglacial motion

210pb derived sediment accumulation and mixing rates for the greater puget sound region abstract recent sediment accumulation rates of 46 1200 mg cm2 yr are calculated from excess 210pb activity profiles in 44 sediment cores from 27 sites in the greater puget sound region rates calculated for nine stations in the deeper waters of central puget sound average 480 mg cm2 yr and are greatest between seattle and tacoma near the southern end of this region the standard error of this mean is 113 mg cm 2 yr magnitudes and geographic trends of 210pb derived accumulation rates agree with limited data on sediment inputs and transport paths their accuracy is further supported by several independent approaches including comparison with particle fluxes collected in year long series of sediment trap deployments at two sites accumulation rates are calculated assuming no mixing beneath surface mixed layers of 2 22 cm sediment mixing coefficients in these surface layers average at least 43 cm2 yr four times greater than those reported in open washington coast sediments the difference is attributed to the greater benthic biomass in puget sound sediments particle residence times in surface mixed layers vary from 1 5 to 68 years and introduce corresponding uncertainties in ages of horizons beneath the mixed layers for most of this region these residence times will cause a 20 30 year time lag in achieving an equivalent response of surface sediment chemical concentrations to changes in concentrations in freshly depositing particles for constituents whose stability and phase associations resemble those of 210pb these time lags limit the ability of sediment chemistry monitoring programs to recognize recent changes in composition and fluxes of chemicals to sediments recent fluxes calculated from the product of surface sediment chemical concentration and accumulation rates will be inaccurate for chemicals if their input concentrations have changed in the last 20 30 years

influence of equatorial waves on the genesis of super typhoon haiyan 2013 abstractthe influence of equatorial wave disturbances on the genesis of super typhoon haiyan 2013 is investigated through spectral composite and ensemble sensitivity analysis of various observational datasets in combination with predictions from an operational ensemble under the favorable large scale environmental conditions of the asian monsoon combined with the madden julian oscillation mjo the incipient haiyan develops from a cyclonic disturbance that originates from a train of westward propagating mixed rossby gravity mrg waves haiyan eventually develops in the monsoon trough region at the leading edge of the moist mjo phase that has strong low level convergence high moisture content and weak shear along with high sea surface temperature these favorable environmental conditions promote the intensification of deep moist convection that facilitates the development of the cyclonic disturbance from an mrg wave into a tropical depression which later intensifies rapidly into super typhoon ha

where will tropical cyclogenesis occur around a preexisting tropical cyclone an observational study focusing on the locations of tropical cyclogenesis induced by tropical cyclone energy dispersion tced in the western north pacific is conducted statistical results indicate that the cyclogenesis cases associated with tced widely occur around preexisting tropical cyclones tcs in addition to the typical scenario of cyclogenesis to the southeast of a preexisting tc new tcs can even form in the east or southwest directions at distances ranging from 1000 km to 3500 km further analyses reveal that the locations of cyclogenesis are mainly governed by large scale environments via regulating the patterns of rossby wave trains the observational relationships between wave train regimes and the structures of environmental flows are revealed which are broadly consistent with previous idealized numerical simulations the results in this study provide a valuable reference for the prediction of cyclogenesis considering the tced mechanism

volcaniclastic resedimentation in distal fluvial basins induced by large volume explosive volcanism the ebisutoge fukuda tephra plio pleistocene boundary central japan the ebisutoge fukuda tephra plio pleistocene boundary central japan has a well recorded eruptive style history magnitude and resedimentation styles despite the absence of a correlative volcanic edifice this tephra was ejected by an extremely large magnitude and complex volcanic eruption producing more than 400 km 3 total volume of volcanic materials volcanic explosivity index 7 which extended more than 300 km away from the probable eruption centre remobilization of these ejecta occurred progressively after the completion of a series of eruptions resulting in thick resedimented volcaniclastic deposits in spatially separated fluvial basins more than 100 km from the source facies analysis of resedimented volcaniclastic deposits was carried out in distal fluvial basins the distal tephra 100 300 km from the source comprises two different lithofacies primary pyroclastic fall deposits and reworked volcaniclastic deposits the resedimented volcaniclastic succession shows five distinct sedimentary facies interpreted as debris flow deposits facies a hyperconcentrated flow deposits facies b channel fill deposits facies c floodplain deposits with abundant flood flow deposits facies d and floodplain deposits with rare flood deposits facies e resedimented volcaniclastic materials at distal locations originated from unconsolidated deposits of a climactic large ignimbrite forming eruption factors controlling inter and intrabasinal facies changes are 1 temporal change of introduced volcaniclastic materials into the basin 2 proximaldistal relationship and 3 distribution pattern of pyroclastic flow deposits relative to drainage basins thus studies of the ebisutoge fukuda tephra have led to a depositional model of volcaniclastic resedimentation in distal areas after extremely large magnitude eruptions an aspect of volcaniclastic deposits that has often been ignored or poorly understood

dynamics and deposits generated by the kos plateau tuff eruption controls of basal particle loss on pyroclastic flow transport the explosive eruption of voluminous silicic magmas often produces widespread and massive deposits formed from pyroclastic density currents while these punctuated events dramatically alter the landscape and have potential climate altering impact our understanding of the internal structure and transport dynamics of these eruptions is hampered by a lack of direct observations we utilize the natural boundary conditions encountered by the eruption of the kos plateau tuff to probe its internal structure as well as constrain the neotectonic activity in the region and eruption duration of this moderate to large 60 km3 event at the time of the eruption 161 ka the lower sea level in the mediterranean may have resulted in flows that traversed mostly land to the north of the eruptive vent while flows to the south may have encountered an expanse of water steep topography and overwater transport can impede the transport of the dense basal portions of the flow where particles make multiple or sustained contact with the bed we use an eulerian eulerian lagrangian computational approach coupled with overwater and overland boundary conditions including topography to determine the role of bed load versus suspended load in the transport of these flows we find that a ring vent structure and eruptive fluxes greater than 2 106 m3 s are required for the spatial distribution of the kpt the maximum grain size and deposit locations of the first voluminous ignimbrite unit d can be explained by suspended flow to the south consistent with overwater transport and bed load and suspended load transport to the north consistent with overland transport however the maximum lithic size for the largest and last ignimbrite unit e requires some bed load transport in all directions we propose that the boundary conditions were significantly altered during the course of the eruption through either the in filling of a shallow sea to the south or the development of a thick pumice raft to aid saltation on the basis of the inferred eruptive flux we estimate that the duration of the eruption climax in which most of the material was erupted likely only lasted from a few hours to a day

tropical cyclogenesis associated with rossby wave energy dispersion of a preexisting typhoon part i satellite data analyses abstract the structure and evolution characteristics of rossby wave trains induced by tropical cyclone tc energy dispersion are revealed based on the quick scatterometer quikscat and tropical rainfall measuring mission trmm microwave imager tmi data among 34 cyclogenesis cases analyzed in the western north pacific during 2000 01 typhoon seasons six cases are associated with the rossby wave energy dispersion of a preexisting tc the wave trains are oriented in a northwest southeast direction with alternating cyclonic and anticyclonic vorticity circulation a typical wavelength of the wave train is about 2500 km the tc genesis is observed in the cyclonic circulation region of the wave train possibly through a scale contraction process the satellite data analyses reveal that not all tcs have a rossby wave train in their wakes the occurrence of the rossby wave train depends to a certain extent on the tc intensity and the background flow whether or not a rossby wave train can finally lead to cy

an in situ erosion rate for a fine grained marine sediment near bottom current and particulate concentration data and a theoretical model of sediment resuspension together have led to inferences about the erosional response of a fine grained sediment to bottom stress tidal boundary layer observations made 5 m from the bottom in the main basin of puget sound washington show that currents with speeds exceeding 40 cm s cause an increase in concentration as much as sixfold from a background level of 1 mg 1 when the erosion rate e is given a power law dependence on bottom stress in accord with laboratory fine sediment entrainment measurements the field data and theoretical model together suggest that 4 0 and 1 7 10 6 g cm2 s uncertainty in these values stemming from a variety of factors is discussed the analysis also points to sediment resuspension of material with relatively large settling velocity ws 0 1 cm s taking place against a background of much finer particles and a depth of sediment reworking of approximately 0 3 mm under typical strong flow conditions comparison of this in situ erosion rate with previous laboratory rate estimates shows it to be comparable to rates measured for some freshwater sediments

explosive destruction of a pliocene hot lava dome underwater dogashima japan transition from effusive to explosive volcanism is common during subaerial eruptions and here we demonstrate that this behavior is also possible underwater the pyroclastic facies produced underwater are distinctive and can be used to distinguish subaqueous from subaerial eruptions and depositional settings the pliocene dogashima formation izu peninsula japan is a pumice rich succession originally deposited in an open marine below wave base setting jutzeler et al 2014a a thick clast supported gray andesite breccia composed of very coarse dense andesite clasts with quenched margins was sourced from disintegration of an active lava dome overall the gray andesite breccia is gradationally to sharply overlain by thick graded clast supported white pumice breccia chiefly composed of angular pumice clasts and free broken crystals regional setting and distinctive facies show that this succession was produced by a fully underwater magmatic volatile driven pumice forming explosive eruption the gradational contact between the two breccias compositional similarities rare mingled clasts and fluidal textures in the gray andesite clasts suggest that the explosive eruption destroyed a hot lava dome and generated an eruption fed high concentration density current in most places the coarsest hot lava dome fragments were deposited first followed by the lower density white pumice clasts the low amount of fine 2 mm components well developed hydraulically controlled grading and sorting clast angularity and very coarse dome derived clasts some including well defined quenched margins and common fluidal textures distinguish the products of subaqueous effusive to explosive eruptions from their subaerial counterparts

tropical cyclogenesis associated with rossby wave energy dispersion of a preexisting typhoon part ii numerical simulations abstract the cyclogenesis events associated with the tropical cyclone tc energy dispersion are simulated in a 3d model a new tc with realistic dynamic and thermodynamic structures forms in the wake of a preexisting tc when a large scale monsoon gyre or a monsoon shear line flow is present maximum vorticity generation appears in the planetary boundary layer pbl and the vorticity growth exhibits an oscillatory development this oscillatory growth is also seen in the observed rainfall and cloud top temperature fields the diagnosis of the model output shows that the oscillatory development is attributed to the discharge and recharge of the pbl moisture and its interaction with convection and circulation the moisture convection feedback regulates the tc development through controlling the atmospheric stratification raindrop induced evaporative cooling and downdraft pbl divergence and vorticity generation on one hand ascending motion associated with deep convection transports moisture upward and le

origin of the summertime synoptic scale wave train in the western north pacific abstract the origin of the summertime synoptic wave train in the western north pacific is investigated with a multilevel nonlinear baroclinic model a realistic three dimensional summer mean state is specified and eigenvectors are calculated by introducing small perturbation initially to the model numerical experiments indicate that the origin of the synoptic wave train may arise from instability of the summer mean flow in the presence of a convection frictional convergence cfc feedback in the lack of the cfc feedback the summer mean flow supports only a least damped mode characterized by a northwest southeast oriented wave train pattern with a zonal wavelength of 2500 km in the presence of both the realistic summer mean flow and the cfc feedback the model reproduces a fast growing mode whose structure and propagation characters are similar to the observed sensitivity experiments with different initial perturbation patterns indicate that the model solution is not sensitive to initial conditions

on the westward turning of hurricane sandy 2012 effect of atmospheric intraseasonal oscillations abstracthurricane sandy 2012 experienced an unusual westward turning and made landfall in new jersey after its northward movement over the atlantic ocean the landfall caused severe casualties an

sill processes related to deep water renewal in a fjord observations of the gravitational circulation over the sill at the entrance to puget sound indicate a fortnightly modulation of the two layer flow with a corresponding variation in stratification gravitational circulation and stratification reach a maximum during neap tides and a minimum during spring tides the modulation appears to be a function of the turbulence generation by tidal flow over the sill which varies as a function of tidal amplitude the enhanced gravitational circulation during neap tides augments the flux of dense water across the sill region and episodes of bottom water renewal in puget sound result intrusions of dense water in the main basin of the sound show a fortnightly periodicity with a phase lag appropriate for the propagation of an internal bore from the sill region commencing at the neap tide observations indicate that the intrusions take the form of gravity currents propagating at approximately 20 cm s 1 down the main basin the detailed dynamics of the turbulent mixing processes that modulate the onset of inflow were not resolved in this study but the integrated effect of tidal mixing on the low frequency circulation is clearly demonstrated

enso phase dependent td and mrg wave activity in the western north pacific the three dimensional structure and evolution characteristics of tropical depression td and mixed rossby gravity wave mrg type disturbances in the tropical western north pacific during el nino and la nina summers are investigated based on observational and reanalysis data a clear mrg to td transition was observed during el nino summers while such a transition is unclear during la nina summers the vertical structure of the td mrg waves appears equivalent barotropic during el nino but becomes tilted eastward with height during la nina the diagnosis of barotropic energy conversion shows that both the rotational and divergent components of the background flow change associated with e1 nino southern oscillation enso are responsible for energy conversion from the mean flow to the td mrg perturbations a further examination of the pure mrg mode shows that its intensity does not vary between el nino and la nina while its phase speed does a faster slower westward propagation speed during la nina el nina is attributed to enhanced reduced mean easterlies in the western equatorial pacific the heating associated with the mrg wave appears more anti symmetric during la nina than during el nino in contrast to the mrg waves the amplitude of the td waves depends greatly on the enso phase the enhanced suppressed td disturbances during el nino la nina is attributed to greater less barotropic energy conversion associated with the background flow change the vertical structure of the td waves appears quasi barotropic in the geopotential height field but baroclinic in the divergence field

tropical cyclone energy dispersion under vertical shears 1 tropical cyclone rossby wave energy dispersion under easterly and westerly vertical shears is investigated in a baroclinic model in a resting environment the model simulates a rossby wave train that has a baroclinic structure with alternating cyclonic anticyclonic cyclonic anticyclonic cyclonic anticyclonic circulations in the lower upper troposphere a significant asymmetry appears in the wave train development under easterly and westerly vertical shears that is an easterly westerly shear confines the maximum amplitude of the wave train primarily to the lower upper level it is proposed that the vertical wind shear may impact the rossby wave train development through both the barotropic baroclinic mode coupling and the modulation of the group velocity by the mean flow through a doppler shift effect additional experiments with uniform westerly and easterly mean flows confirm the hypothesis the enhancement of the rossby wave train in the lower level by the easterly shear may have an important implication for understanding the tropical cyclogenesis and the origin of the synoptic wave trains in the western north pacific

an examination of the thermodynamic impacts of western north pacific tropical cyclones on their tropical tropospheric environment abstractthe present study examines the tropospheric thermodynamic anomalies induced by western north pacific tropical cyclone tc passage using storm relative composites negative moist static energy mse anomalies containing embedded westward propagating anomalies generally occur only following larger tcs for two months following tc passage in a region extending from the domain center to 3000 km to its west larger tcs force negative mse anomalies likely because of feedbacks from stronger broader tc induced negative sea surface temperature sst anomalies and the excitation of tc induced rossby waves to the southeast of the tc the negative mse anomalies are composed of lower and midtropospheric negative latent energy anomalies with smaller contributions from boundary layer and upper tropospheric negative sensible heat anomalies the lower and midtropospheric negative mse anomalies are forced by the tc whereas the upper tropospheric negative mse anomalies are forced by the madden julian oscillatio

some aspects of vortex structure related to tropical cyclone motion abstract some effect of tropical cyclone structure on the vortex motion are examined in a nondivergent barotropic numerical model with no basic current as suggested earlier by demaria the initial maximum wind speed has little effect on the track vortex translation associated with the beta effect depends sensitively on the strength of the flow between 300 and 1000 km from the center if the flow in this annulus is made more cyclonic the track will turn cyclonically and move more toward the west in the northern hemisphere the dynamics of this beta drift is studied via a decomposition into symmetric and asymmetric circulations the symmetric flow experiences a slight weakening of the maximum wind speed and an anticyclonic circulation is induced beyond 600 km the asymmetric circulation is dominated by an azimuthal wavenumber one circulation with an anticyclonic gyre east of the center a cyclonic gyre to the west and a nearly uniform broad scale ventilation flow between the gyres the vortex translati

holocene vs anthropocene sedimentary records in a human altered estuary the pasaia case northern spain abstract this work deals with the microfaunal benthic foraminifera and geochemical trace metals 14c 210pb 137cs and 239 240pu study of two boreholes 1200 and 1400 cm length and three subtidal sediment cores 38 58 cm length collected in the pasaia estuary northern spain foraminiferal assemblages in the holocene deposits depend on the paleogeographic setting while different species appear in the anthropocene sediments as a consequence of the physical transformation of the estuary into an estuarine port regarding the geochemical composition the impact of ancient mining activities probably of roman age can be recognized in the form of peaked values of pb and zn however older sediments exhibit relatively low contents of trace metals which are conditioned by hydrodynamic patterns and lithogenic inputs in the anthropocene record the influence of these factors is displaced by the decisive role of human activities as evidenced by the enhanced concentrations of trace metals and the occurrence of artificial radioisotopes and glass microspheres additionally this work provides information about trace metal contamination that may be of interest to corresponding authorities in order to set priorities of action and to take specific measures to prevent further degradation

multi scale interactions of equatorial waves associated with tropical cyclogenesis over the western north pacific the tropical cyclone tc centric approach developed in previous studies tends to overemphasize the direct impact of tropical waves and underestimates their large scale modulation of western north pacific wnp tropical cyclogenesis tcg to overcome these limitations this study proposes a new approach based on empirical orthogonal function analyses to re examine associations of multiple waves including the madden julian oscillation mjo quasi biweekly oscillation qbwo convective equatorial rossby er waves and synoptic scale waves ssws with wnp tcg events there is a close association between wnp tcg events total of 273 tcs in this study and ssws 64 mjo 68 qbwo 64 and er 65 waves these suggest that ssw is critical for many tcg events and all of these intra seasonal waves significantly modulate tcg events a majority of tcs 79 were found to be related to more than one wave type indicating an important role for a combination of dynamic and thermodynamic conditions associated with multiple waves in tcg events further analyses show that ssw activity is strongly modulated by the mjo and er waves while the qbwo has no significant impact on ssws during convectively active mjo and er phases stronger ssw trains with more distinct southeast northwestward aligned structures can be found compared to convectively inactive phases similar intra seasonal modulation of the transition from the mixed rossby gravity waves from the equatorial central pacific to the ssw trains over the wnp by the three waves is noted with such transitions largely favored during convectively active mjo and er phases

iso modulation on the submonthly wave pattern and recurving tropical cyclones in the tropical western north pacific abstract this study demonstrates the multiscale nature from synoptic to intraseasonal time scales of the atmospheric flow in the tropical western north pacific the multiscale features include intraseasonal oscillations iso northwestward propagating submonthly wave patterns and recurving tropical cyclones tcs in the iso westerly phase the wave pattern was better organized and the tcs were clustered near the cyclonic circulation of the wave pattern during the genesis development and propagation on the other hand the wave pattern and tcs were weak and poorly organized in the iso easterly phase the distinct characteristics between the westerly and easterly phases could be attributed to the iso modulation on the monsoon trough and the subtropical anticyclonic ridge the iso in the westerly phase provided a favorable background e g enhanced monsoon trough and moisture confluent zone for the wave tc pattern development while the iso in the easterly phase provided a less favorable environment

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

monsoonal interactions leading to sudden tropical cyclone track changes abstract sudden poleward track changes of tropical cyclones embedded in monsoon gyres in the western north pacific are documented during these track changes which are generally not well forecast the cyclones are often accompanied by a separate comma shaped area of gale force winds and deep convection along the eastern periphery this monsoon surge is distinct from the tropical cyclone synoptic analyses often reveal a building anticyclone to the east or southeast of the monsoon gyre the hypothesis that the sudden track change is initiated by a binary interaction of the tropical cyclone and monsoon gyre is tested with a nondivergent barotropic model tropical cyclone scale vortices with initial positions within the eastern semicircle of a larger monsoon gyre scale vortex initially coalesce with the monsoon gyre and then exhibit sudden poleward track changes that are similar to the observations during the coalescence phase the large and relatively weak monsoon gyre undergoes a induced dispersion in

large scale vapor transport of remotely evaporated seawater by a rossby wave response to typhoon forcing during the baiu meiyu season as revealed by the jra 55 reanalysis the modulation of large scale moisture transport from the tropics into east asia in response to typhoon induced heating during the mature stage of the baiu meiyu season is investigated using the japanese 55 year reanalysis jra 55 aided by a rayleigh type global isotope circulation model icm we highlighted the typhoons that migrate northward along the western periphery of the north pacific subtropical high and approach the vicinity of japan anomalous anticyclonic circulations to the northeast and southeast of typhoons and cyclonic circulation to their west become evident as they migrate toward japan which could be interpreted as a rossby wave response to typhoon heating these resultant anomalous circulation patterns form moisture conveyor belt mcb stretching from the south asian monsoon region to east asia via the confluence region between the monsoon westerlies and central pacific easterlies the icm results confirm that the well defined nature of the mcb leads to penetration of the indian ocean south china sea philippine sea and pacific ocean water vapors into western japan the typhoons have the potential to accumulate large amounts of moisture from distant tropical oceans through the interaction of their rossby wave response with the background flow in the case of a typical typhoon the total precipitable water around the typhoon center as it approaches japan is maintained by the moisture supply from distant oceans rather than from the underlying ocean which indirectly leads to the occurrence of heavy rainfall over western japan

accumulation rates of recent sediments in puget sound washington abstract sixteen profiles of unsupported 210pb activity from long cores along the axis of the main basin of puget sound show that bottom sediments are accumulating at rates of 0 26 0 03 to 1 20 0 16 g cm 2 yr 1 these rates and seven others published earlier suggest that highest accumulation occurs nearly midway along the length of this tidal current dominated basin bioturbated surface layers of cores are as deep as 40 cm but biologic mixing rates are poorly determined individual 210pb accumulation rates along the axis of the main basin range from approximately one to five times greater than the predicted areal average accumulation rate based on estimates of recent sediment input from adjoining rivers and shorelines

origins and mechanisms of eastern pacific tropical cyclogenesis a case study the genesis of hurricane hernan 1996 in the eastern pacific was investigated using gridded analyses from the european centre for medium range weather forecasts and gridded outgoing longwave radiation hernan developed in association with a wave in the easterlies that could be tracked back to africa in longitude time plots of the filtered y component of the wind 2 6 day period at 700 mb the wave crossed central america near lake nicaragua with little change in its southwest northeast tilt but the most intense convection shifted from near the wave axis in the caribbean to west of the wave axis in the pacific the wave intensified as it moved through a barotropically unstable background state defined by a low pass filter with a 20 day cutoff in the western caribbean and eastern pacific a surge in the southwesterly monsoons and enhanced convection along 108n occurred to the west of the 700 mb wave in the pacific and traveled with the wave this had the effect of enhancing low level vorticity over a wide region ahead of the 700 mb wave available evidence suggests that additional low level vorticity was produced by enhanced flow from the north through the isthmus of tehuantepec as the 700 mb wave approached depression formation did not occur until 6 12 h after the 700mb wave reached this region of large low level vorticity in the gulf of tehuantepec eastern pacific sst and vertical wind shear magnitude are typically favorable for tropical cyclone development in northern hemisphere summer and early fall because the favorable mountain interaction and the surge in the low level monsoons appear to relate directly to the wave in the easterlies it is argued that the strength of such waves reaching central america from the east is the single most important factor in whether subsequent eastern pacific cyclogenesis occurs possible parallels with western pacific cyclogenesis are discussed

development of synoptic scale disturbances over the summertime tropical northwest pacific abstract this study addresses the origin of the synoptic scale disturbances that occur in the tropical western north pacific ocean wp region in northern hemisphere summer these have been called easterly waves and tropical depression type td disturbances this analysis uses the national center for environmental prediction national center for atmospheric research reanalysis dataset by performing a regression analysis on several terms in the vorticity equation at 850 hpa it is shown that the td disturbances propagate approximately as barotropic rossby waves at 850 hpa given this ray tracing calculations and the wave activity diagnostic introduced by plumb are used to show that wave accumulation is a promising candidate for the initial development mechanism of the td disturbances the expected local growth rate from this mechanism is simply the convergence of the group velocity which reaches values corresponding to a growth timescale of 3 days this convergence is dominated by but somewhat lar

a model for radionuclides in sediments influenced by mixing and compaction a model for the activity of radionuclides in sediments has been set up based on the one dimensional advection diffusion equation the model considers sedimentation mixing and compaction observed distributions of deposit feeding organisms and the nature of physical disturbances indicate that a gaussian diffusion coefficient may be appropriate two layer models with constant and gaussian mixing respectively in the upper layer are compared with measured pb 210 profiles for two cores from green bay lake michigan and it is found that the maximal diffusion coefficient d0 in the gaussian model is considerably greater than the constant d value e g d0 4 versus d 0 2 cm2 year if compaction effects are neglected the solution for the gaussian model is based on an approximate power series method compaction can be taken into account by using an exponential sedimentation rate or bulk sediment density by comparing with measured data for a lake ontario core it is seen that compaction alone can give an appreciable flattening of the activity curves near the top layers

northwestward propagating wave patterns over the tropical western north pacific during summer abstract the possible relationship between northwestward propagating wave disturbances and tropical cyclones over the tropical western north pacific during summer is studied using data assimilated by the navy s global model during may september 1989 91 a multiple set canonical correlation mcc analysis is applied to the 850 hpa meridional v component over a core domain covering the western pacific the analysis seeks the maximal geometrically averaged correlation between 12 consecutive twice daily fields two mcc components with a 90 phase difference and comparable variances that combine to nearly one third of the total variance describe the northwestward propagating pattern with a period near 8 9 days upstream of this steady northwestward propagating pattern there is a weaker westward propagation along 5 n that may be traced back to 170 e the surface pressure cell advancing east of the philippines is consistent with low level winds for a circulation in gradient wind balance it has a zonal wave

scale interactions during the formation of typhoon irving the development of typhoon irving is investigated using a variety of data including special research aircraft data from the tropical cyclone motion tcm 92 experiment objective analyses satellite data and traditional surface and sounding data the development process is treated as a dry adiabatic vortex dynamics problem and it is found that environmental and mesoscale dynamics mutually enhance each other in a cooperative interaction during cyclone formation synoptic scale interactions result in the evolution of the hostile environment toward more favorable conditions for storm development mesoscale interactions with the low level large scale circulations and with other midlevel mesoscale features result in development of vorticity in the midlevels and enhancement of the low level vorticity associated with the developing surface cyclone multiple developments of mesoscale convective systems after the storm reaches tropical depression strength suggests both an increase in low level confluence and a tendency toward recurrent development of associated mesoscale convective vortices this is observed in both aircraft data and satellite imagery where subsequent interactions including mergers with the low level tropical depression vortex are observed a contour dynamics experiment suggests that the movement of mesoscale convective systems in satellite imagery corresponds well to the movement of their associated midlevel vortices results from a simple baroclinic experiment show that the midlevel vortices affect the large scale low level circulation in two ways 1 initially interactions between midlevel vortices produce a combined vortex of greater depth 2 interaction between midlevel vortices and the low level circulation produces a development downward of the midlevel vorticity this strengthens the surface vortex and develops a more cohesive vortex that extends from the surface through the midtroposphere

evidence for carbonate platform failure during rapid sea level rise ca 14 000 year old bioclastic flow deposits in the lesser antilles bioclastic flow deposits offshore from the soufriere hills volcano on montserrat in the lesser antilles were deposited by the largest volume sediment flows near this active volcano in the last 26 kyr the volume of these deposits exceeds that of the largest historic volcanic dome collapse in the world which occurred on montserrat in 2003 these flows were most probably generated by a large submarine slope failure of the carbonate shelf comprising the south west flank of antigua or the east flank of redonda adjacent islands that are not volcanically active the bioclastic flow deposits are relatively coarse grained and either ungraded or poorly graded and were deposited by non cohesive debris flow and high density turbidity currents the bioclastic deposit often comprises multiple sub units that cannot be correlated between core sites some located just 2 km apart multiple sub units in the bioclastic deposit result from either flow reflection stacking of multiple debris flow lobes and or multi stage collapse of the initial landslide this study provides unusually precise constraints on the age of this mass flow event that occurred at ca 14 ka few large submarine landslides have been well dated but the slope failures that have been dated are commonly associated with periods of rapid sea level change

a numerical study on the combined effect of midlatitude and low latitude systems on the abrupt track deflection of typhoon megi 2010 abstractin 2010 supertyphoon megi experienced an abrupt track deflection in the south china sea scs after traversing luzon island to reveal the physical processes responsible for the timing and location of the sudden track deflection the potential vorticity pv diagnosis and numerical simulations with initial strength perturbations are applied to investigate the individual and combined effects of environmental systems on megi s motion based on the steering flow theory results indicate that megi s northward track deflection was mainly determined by the effect of the midlatitude circulation or rather the break of the high pressure belt joined by the continental high ch and the pacific subtropical high sh the retraction of ch played a particularly critical role in the break of the high pressure belt making it the most important feature of the midlatitude circulation to determine megi s deflection in addition a small low latitude anticyclone sa southeast of megi was crucial in affecting the

joint contribution of multiple equatorial waves to tropical cyclogenesis over the western north pacific abstracta composite study is performed to examine the differences in equatorial wave behaviors and large scale background patterns during tropical cyclone tc genesis after removing tc contamination madden julian oscillation mjo equatorial rossby er wave mixed rossby gravity mrg wave and tropical depression td type disturbance jointly referred to as the mt wave are quantified to evaluate the attribution of tc geneses given that tc geneses are attributed to a single wave or multiple waves the eight categories are specified based on the moderate thresholds the tc geneses related to multiple waves are roughly twice as many as those related to a single wave the mt wave alone accounts for a minor proportion of tc geneses without collaboration with other larger scale waves the mean tc genesis location related to er wave shifts to higher latitudes and the tc geneses attributed to both of mjo and mt waves are more concentrated at the west the single wave categories are characterized by a zo

western north pacific tropical cyclone characteristics stratified by genesis environment abstractthe characteristics of tropical cyclones tcs in the summer and autumn seasons over the western north pacific that are associated with different environmental factors that influence tc genesis tcg were studied we objectively categorized factors into the five tcg factors classified by ritchie and holland 1999 monsoon shear line sl monsoon confluence region cr monsoon gyre gy easterly wave ew and the rossby wave energy dispersion from a preexisting tc ptc the gy tcs tended to develop slowly and the highest rates of occurrence of rapid intensification ri were found for the cr tcs whereas the gy tcs rarely experienced ri the average storm size of the gy tcs at the time of formation was the largest of the averages of the other tc types while the ew and ptc tcs were smaller although these differences disappeared at the mature time there were no significant differences in the sea surface temperature sst beneath the tcs but the tropical cyclone heat potential tchp of t

barotropic aspects of itcz breakdown abstract in satellite images the itcz intertropical convergence zone is sometimes observed to undulate and break down into a series of tropical disturbances tropical cyclones may later develop within these disturbances and move into higher latitudes allowing the itcz to reform it has been proposed that itcz breakdown results from a convectively modified form of combined barotropic and baroclinic instability of the mean flow an unstable mean flow can be produced by itcz convection in just a couple of days in this sense the itcz produces favorable conditions for its own instability and breakdown in this study a nonlinear shallow water model on the sphere is used to simulate barotropic aspects of itcz breakdown in the shallow water model the itcz is simulated by a prescribed zonally elongated mass sink near the equator the mass sink produces a cyclonic potential vorticity pv anomaly that has a reversed meridional pv gradient on its poleward side according to the ripa theorem a flow that has a