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

quantifying lateral heterogeneities in fluvio deltaic sediments using three dimensional reflection seismic data offshore gulf of mexico scale invariant statistics and strong anisotropy in rock properties are documented from well log and three dimensional seismic data in pleistocene fluvial and deltaic deposits in the eugene island 330 field gulf of mexico systematic quantification of lateral lithologic heterogeneity within a stratigraphic framework using reflection seismic data reveals that fluvial and deltaic depositional systems exhibit statistical behavior related to stratigraphic fabric well log and seismic data profiles show a decay in power spectra with wavenumber k according to k with between 1 and 2 3 vertical and horizontal well log data exhibit power law scaling behavior with between 1 and 2 horizontal seismic horizon slices were extracted from within fluvial and deltaic deposits seismic data from fluvial and deltaic deposits exhibit distinct differences in variance and each depositional system reveals directional anisotropy in one dimensional seismic data profiles from the fluvial deposit reveal anisotropy along depositional strike 1 1 and dip 2 2 the higher correlation observed in the direction of stratigraphic dip for the fluvial deposit may reflect the depositional fabric associated with channel systems correlation parameters obtained in specific depositional environments can potentially be used to quantify rock fabric and provide constraints in the modeling of sedimentary processes

tsunami history of an oregon coastal lake reveals a 4600 yr record of great earthquakes on the cascadia subduction zone bradley lake on the southern oregon coastal plain records local tsunamis and seismic shaking on the cascadia subduction zone over the last 7000 yr thirteen marine incursions delivered landward thinning sheets of sand to the lake from nearshore beach and dune environments to the west following each incursion a slug of marine water near the bottom of the freshwater lake instigated a few year to several decade period of a brackish 4 salinity lake four additional disturbances without marine incursions destabilized sideslopes and bottom sediment producing a suspension deposit that blanketed the lake bottom considering the magnitude and duration of the disturbances necessary to produce bradley lake s marine incursions a local tsunami generated by a great earthquake on the cascadia subduction zone is the only accountable mechanism extreme ocean levels must have been at least 5 8 m above sea level and the cumulative duration of each marine incursion must have been at least 10 min disturbances without marine incursions require seismic shaking as well over the 4600 yr period when bradley lake was an optimum tsunami recorder tsunamis from cascadia plate boundary earthquakes came in clusters between 4600 and 2800 cal yr b p tsunamis occurred at the average frequency of 3 4 every 1000 yr then starting 2800 cal yr b p there was a 930 1260 yr interval with no tsunamis that gap was followed by a 1000 yr period with 4 tsunamis in the last millennium a 670 750 yr gap preceded the a d 1700 earthquake and tsunami the a d 1700 earthquake may be the fi rst of a new cluster of plate boundary earthquakes and accompanying tsunamis local tsunamis entered bradley lake an average of every 390 yr whereas the portion of the cascadia plate boundary that underlies bradley lake ruptured in a great earthquake less frequently about once every 500 yr therefore the entire length of the subduction zone does not rupture in every earthquake and bradley lake has recorded earthquakes caused by rupture along the entire length of the cascadia plate boundary as well as earthquakes caused by rupture of shorter segments of the boundary the tsunami record from bradley lake indicates that at times most recently 1700 yr b p overlapping or adjoining segments of the cascadia plate boundary ruptured within decades of each other

theory connecting nonlocal sediment transport earth surface roughness and the sadler effect earth surface evolution like many natural phenomena typified by fluctuations on a wide range of scales and deterministic smoothing results in a statistically rough surface we present theory demonstrating that scaling exponents of topographic and stratigraphic statistics arise from long time averaging of noisy surface evolution rather than specific landscape evolution processes this is demonstrated through use of elastic langevin equations that generically describe disturbance from a flat earth surface using a noise term that is smoothed deterministically via sediment transport when smoothing due to transport is a local process the geologic record self organizes such that a specific sadler effect and topographic power spectral density psd emerges variations in psd slope reflect the presence or absence and character of nonlocality of sediment transport the range of observed stratigraphic sadler slopes captures the same smoothing feature combined with the presence of long range spatial correlation in topographic disturbance

reintensification of the anomalous western north pacific anticyclone during the el nino modoki decaying summer relative importance of tropical atlantic and pacific sst anomalies abstractthe el nino modoki induced anomalous western north pacific anticyclone wnpac undergoes an interesting reintensification process in the el nino modoki decaying summer the period when el n

el nino phase dependent high frequency variability in western equatorial pacific the intensities of high frequency hf variability with period less than 90 days at different phases of el nino events were investigated through observational data analysis a large asymmetry in the hf variability intensity between the developing phase and decaying phase i e pre peak stage versus post peak stage of eastern pacific ep el nino is revealed while the amplitude and spatial pattern of the sea surface temperature anomaly during these two stages are almost same the diagnosis shows that the asymmetry is significant not only on intraseasonal time scale 20 90 days but also on synoptic time scale less than 20 days the anatomy analysis further unveils that the asymmetric synoptic variability between the two episodes arises from the asymmetric intensities of the equatorial rossby and mixed rossby gravity mrg waves we suggest that the stronger vertical easterly wind shear in the pre peak stage than that in the post peak stage plays a vital role in causing the stronger synoptic equatorial rossby and mrg waves in the pre peak stage meanwhile the drier atmosphere and more descending motion in the post peak stage contribute to the weakened intraseasonal and synoptic variabilities in that stage the aforementioned weakened easterly wind shear drier atmosphere and more descending motion in the post peak stage can be traced back to the occurrence of the anomalous anticyclone circulation over the western north pacific since the decaying phase of el nino the essential role of large scale environmental conditions in modulating the hf variability during the two episodes is further confirmed by modeling experiments

morphological analysis of the lake lahontan shoreline and beachfront fault scarps pershing county nevada abstract with the diffusion equation representation of landform evolution providing reference calculations quantitative comparisons between profiles of the high stand of lake lahontan presented here and profiles of the lake bonneville shoreline scarps analyzed elsewhere reveal that the two sets of scarps are nearly identical morphologically when care is exercised in the selection of profiles the lahontan high stand scarps are remarkably reproducible from one profile to the next highly suggestive evidence that the processes that have shaped and changed the shape of these landforms are correspondingly regular slope angle differences of only 2 are both discernible and interpretable features of these late quaternary landforms cut in weakly consolidated alluvium at a level of uncertainty of no more than 50 per cent the mass diffusivity of the lahontan high stand is the same as the lake bonneville shoreline 1 1 gkg 1 gkg 1 m 2 ka this result suggests that much can be learned about the ages of late quaternary fault scarps cut in weakly consolidated alluvium throughout the basin and range province from their morphology alone the beachfront fault scarps themselves truncated by lake lahontan in our study area are morphologically only slightly older 15 to 18 ka bp than the lahontan high stand 12 ka bp

synoptic scale disturbances near the equator abstract a spectral analysis of winds analyzed and initialized at the european centre for medium range weather forecasts reveals an abundance of power in the 850 mb meridional wind along the equator with periods near four days the power is mostly in the westward propagating component using high pass filtered data it is shown that the waves have westward phase and eastward group propagation relative to the mean wind the longest wavelengths are found over the pacific ocean while the shortest are found over the convectively variable regions of indonesia south america and africa mean phase speeds at 850 mb are positively correlated with the mean wind on the equator at 500 mb and below and negatively correlated with the mean wind above that level the effective advecting zonal wind of the disturbances seems to be the density weighted average of the lower troposphere the structure of the disturbances bears resemblance to the expected structure of an equatorially trapped mixed rossby gravity wave over t

synoptic scale waves in sheared background flow over the western north pacific abstracttropical depression td type waves are the dominant mode of synoptic scale fluctuations over the western north pacific by applying spatiotemporal filters to the observed olr data and the ncep doe amip ii reanalysis data for 1979 2013 this study reveals the characteristics and energetics of convectively coupled td type waves under the effects of different circulation patterns in association with vertical wind shear results exhibit that different ambient sheared flows significantly affect the vertical structure of westward propagating td type waves with a lower tropospheric mode in an easterly sheared background and an upper tropospheric mode in a westerly sheared background energetic diagnoses demonstrate that when the disturbance is trapped in the lower upper level by easterly westerly shear the horizontal mean flow in the lower upper level favors wave growth by converting energy from the shear of the zonal mean flow from the convergence of the meridional mean flow during the penet

modification of wave cut and faulting controlled landforms from a casual observation that the form of degraded fault scarps resembles the error function this investigation proceeds through an elementary diffusion equation representation of landform evolution to the application of the resulting equations to the modern topography of scarplike landforms the morphologic observations can be analyzed either in the form of one or more cross strike elevation profiles or in the form of the slope offset plot a point plot of maximum scarp slope versus scarp offset working with either or both of these data representations for nine geologic structures which range in age from 3 to 400 ka b p and in offset from 1 to 50 m we apply analytical solutions for the vertical initial value scarp the vertical continuous offset scarp and the finite slope initial value scarp the model calculations are intrinsically ambiguous yielding as the final answer only the product t in the case of the initial value problem or the product a 1 in the case of the repeated faulting problem here t is the age of a single scarp forming event 2a is the vertical slip rate and is the mass diffusivity a single profile across three sea cliffs along the santa cruz california coast is analyzed as three separate initial value problems a reasonably constrained age for the sea cliff standing above the highway 1 platform returns 11 gkg 1 gkg 1 m2 ka with this we can date the two older sea cliffs in fact we do the converse age estimates for these two older sea cliffs based on a uniform rate of uplift both yield the same as for the lower sea cliff we treat a single profile of the raymond fault in pasadena san marino in terms of the repeated faulting problem for it the uplift rate of r crook and others yields 16 gkg the very substantial preexisting offset across the raymond fault must have been buried leveled some 230 ka b p when the modern topography began to form our analysis of the lake bonneville shoreline scarps reveals a dependence of t on 2a suggestive of nonlinear modification processes this appearance is treated with the finite slope initial value scarp model to determine 1 1 gkg for the lake bonneville shoreline scarps the suggestion of m n machette that approximately 100 000 year old meter high scarps are unobservable in weakly consolidated alluvial terranes of the basin and range and rio grande rift valley provinces can be formulated as 1 gkg the coincidence between this inequality and the lake bonneville shoreline is striking and it suggests that the value of 1 gkg may be generally applicable as a good first approximation to the modification of alluvial terranes within the semiarid regions of the western united states the lake bonneville shoreline is the basis for dating four sets of fault scarps in west central utah the drum mountains fault scarps can be modeled in several different circumstances but the most likely interpretation is that these fault scarps formed as the result of a single episode of normal faulting 3 6 to 5 7 ka b p the younger age is associated with quite low initial slope angles 25 the other three sets of fault scarps show no evidence for finite initial value slopes fault scarps along the eastern base of the fish springs range are very young 3 ka b p we estimate the age of fault scarps along the western flank of the oquirrh mountains to be 32 ka b p which meets the weak geologic constraint that they be older than the lake bonneville shoreline fault scarps along the northeastern margin of the sheeprock mountains are even older 53 ka b p an intriguing consequence of our single event analysis of these scarps is that an 11 5 m offset occurred in a single earthquake

an observational study of easterly waves over the eastern pacific in the northern summer using fgge data abstract fgge revel iii b data provided by the european centre for medium range weather forecasts and the outgoing longwave radiation data measured by satellites are used to investigate observationally relationships between deep cloud activity and large scale meteorological fields during the northern hemisphere summer may september of 1979 over the eastern pacific aside from the summer monsoon area over southern and eastern asia the eastern pacific is the area where strong deep convection frequently develops in the northern summer this is also one of the tropical ocean areas that have been least explored meteorologically a power spectral analysis using the maximum entropy method is made for the meridional wind component at 850 mb at various grid points in the analysis domain for each mouth from may through september the waves with a period of 4 6 days are not only stronger in july and august than those of other months but active in the regions of 100 130 w in the eastern pacific and 130 160 e i

synthetic stratigraphy with a stochastic diffusion model of fluvial sedimentation abstract models of stratigraphic completeness and bed formation in fluvial depositional environments have most often assumed that successive depositional and erosional events deposit or erode amounts of sediment independently this results in a random walk model for the total amount of deposited sediment locally as a function of time we consider an extension of the random walk model of sedimentation in an alluvial plain in which deposition or erosion is concentrated in randomly avulsing channels and sediment transport is modeled by the diffusion equation culling s model in contrast to the random walk model this model results in an anticorrelated sequence locally as a function of time i e after an area has aggraded it has a higher elevation and a lower rate of future aggradation in a p evious paper we analyzed the topography generated by the model and argued that porosity variations could be associated with topographic variations the power spectrum s the square of the coefficients in a fourier series of one dimensional transects of topography and porosity horizontally and vertically in this model have a power law dependence on wave number k s k k s with values of s close to those observed in this paper we show that the model deposits sediment with a rate depending on time interval as a power law with exponent 3 4 more consistent with observations than the random walk model the model produces an exponential bed thickness distribution with a skew depen ent on the sedimentation rate of the basin in accordance with observations we also examine the persistence in the series of bed thicknesses as a function of depth for the stochastic diffusion model of sedimentation no persistence is observed if the model fully characterizes the autocyclic dynamics in fluvial sedimentary basins the lack of persistence in the synthetic bed sequences suggests that observed persistence and cyclicity in real bed thickness sequences must be the result of allocyclic processes

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

identifying goethite and hematite from rock magnetic measurements of soils and sediments we describe a sequence of experiments involving the acquisition of isothermal remanent magnetization irm in high 2 t fields followed by orthogonal demagnetization and the cooling and heating of remanent magnetization mr over the temperature range 196 c to 680 c the main aim of these experiments is to improve the basis for identifying the imperfect antiferromagnetic minerals contributing to the magnetic properties of natural soil and sediment samples which often contain complex mineral mixtures the procedures developed are first applied to a series of ore and synthetic samples of hematite and goethite each characterized by x ray diffraction xrd spectra and second to controlled mixtures of the two minerals the results confirm the mineral diagnostic nature of the experiments used they are subsequently used to identify goethite and hematite contributions to the rock magnetic properties of a variety of soils and recent sediments goethite can be unambiguously identified often accompanied by hematite in the majority of the samples studied despite indications from the synthetic mixtures that the ratio of goethite to hematite may have to exceed an order of magnitude before the goethite signatures are readily recognizable the rock magnetic tests are a much more sensitive basis for recognizing the presence of goethite in natural samples than are xrd analyses the results suggest that goethite s contribution to the rock magnetic properties of soil and sediment samples may often have been underestimated

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

the origin and dispersion characteristics of the observed tropical summertime synoptic scale waves over the western pacific abstract the origin initiation and dispersion behavior of the observed summertime synoptic scale disturbances in the tropical western pacific are studied these westward propagating disturbances have the strongest growth rate over the region of 130 160 e off the equator the three dimensional wave activity flux associated with a wave packet in the vicinity of this region is computed in general wave activity is directed westward there is accumulation of activity flux which gives rise to the amplification of waves in the low levels such accumulation can be attributed to the convergence of both the mean flow and the intrinsic group velocity diabatic forcing also contributes to the growth of disturbances and is most important in the 500 600 hpa layer along the east west oriented storm tracks of the synoptic scale disturbances there are two different dynamical regimes west of 150 e enhanced convection is associated with increased specific humidity at the top of the planetary boundary layer an

gaussian scaling noise model of seismic reflection sequences evidence from well logs a simple model for reflection series is desirable for two reasons first to have a means of generating model reflection sequences on which to test geophysical data processing techniques specifically methods of predictive deconvolution and second to suggest a way of parameterizing real reflection sequences for classification and further geologic study in this note we wish to discuss a model suggested by hosken 1980 our discussion is founded upon the powerful ideas of self similarity and scaling developed by mandelbrot 1983 and on the paucity of typical lengths in geology typical lengths are common in physics problems for example the length of an organ pipe governs the wavelengths of the notes played when taking photographs geologists include some manmade object to give scale to the photo otherwise it is very hard to tell if say folds are of centimeter size or form whole mountains

interaction between the mjo and high frequency waves over the maritime continent in boreal winter abstractthe two way interaction between madden julian oscillation mjo and higher frequency waves hfw over the maritime continent mc during boreal winter of 1984 2005 is investigated it is no

fayetteville green lake new york u s a viii mass balance for 137cs in water varved and non varved sediments abstract a mass balance for 137 cs was done in fayetteville green lake 43 of total 137 cs input was found in shallow water 0 18 m sediments 16 was found in deep water varved sediments 9 was found in the water column and 32 remained to be carried away by lake outflow shallow water sedimentary 137 cs must be resuspended and or dissolved to maintain current levels of 137 cs in the water column and current fluxes of 137 cs to deep water varved sediments 137 cs activities in individual varve year samples from 1946 to 1976 followed closely the pattern of published bomb fallout records but the varves contained only 28 34 of cumulative unit area fallout for this area in order to preserve the yearly record of 137 cs sedimentation the pore water diffusion coefficient for 137 cs must be 11 cm 2 s 1 bioturbation and physical mixing of these sediments does not occur some of the cores of shallow water sediments accumulated 137 cs in amounts greater than was supplied by fallout to the lake surface area this may be due to 1 horizontal transport of surface water 137 cs to shallow water sediments for direct absorption 2 bioconcentration by benthic algae and mosses or 3 localized funnelling of sediments

analytic models for orogenic collapse abstract orogenic plateaus and collisional mountain belts are formed by tectonic driving forces such as those associated with a continental collision and magmatism when the horizontal driving forces are removed e g at the conclusion of an orogeny the elevation of the plateau or collisional orogen will relax by one or both of two processes the first of these is erosion which removes the near surface rocks and allows uplift the second is the gravitational collapse of elevated topography in this paper we consider a simplified analysis in order to quantify the relative importance of erosion and gravitational collapse in the removal of topography we treat the erosion problem using the culling diffusion equation approach the basic assumption is that the material transport down slope is proportional to the slope with the equivalent coefficient of diffusion k the constant of proportionality the parameter k quantifies the rate of erosion it is applicable whether or not the topography is compensated for the gravitational collapse problem we use the thin viscous sheet approximation and assume a linear viscous rheology to simplify the analysis we assume the thickness of the continental crust approximates the thickness of the highly viscous lithosphere and that the crust overlies a much lower viscosity mantle we also assume the topography is harmonic with a wavelength the viscosity quantifies the thinning of the crust due to the buoyancy driven lateral flow our results indicate an exponential decay of topography with time and show that the relative role of erosion versus gravitational collapse for compensated topography is controlled by the value of the non dimensional collapse number c gh o 2 c 16 k 2 where g is the acceleration due to gravity h o is a reference thickness of the crust c is the density of the crust and k and are as defined above if c is large compared with unity gravitational collapse dominates if c is small compared with unity erosion dominates

low frequency equatorial waves in vertically sheared zonal flow part i stable waves abstract the mechanism by which a vertically sheared zonal flow affects large scale low frequency equatorial waves is investigated with two level equatorial plane and spherical coordinates models vertical shears couple barolinic and barotropic components of equatorial wave motion affecting significantly the rossby wave and westward propagating yanai wave but not the kelvin wave this difference results from the fact that the barotropic component is a modified rossby mode and can be resonantly excited only by westward propagating internal waves the barotropic components emanate poleward into the extratropics with a pronounced amplitude while the baroclinic components remain equatorially trapped a westerly vertical shear favors the trapping of rossby and yanai waves in the upper troposphere whereas an easterly shear tends to confine them in the lower troposphere as such their westward propagation is slowed down by both westerly and easterly shears when the strength of the vertical shear varies w

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

quantitative methods for analyzing the roughness of the seafloor the bathymetry of the world ocean has been mapped using a variety of acoustic sounding instruments and traditional contouring methods prior to this study relatively few quantitative studies have been focused on the detailed morphology of the seafloor the work of most investigators has generally dealt with the analysis of seafloor relief without regard to spatial frequency or concern for obvious morphologic anisotropies a brief review of previous work is presented and is accompanied by an identification of the specific applications and limitations of those approaches the availability of more precise digital sounding data coupled with the development of higher resolution sonar mapping instruments e g deeptow seamarc now make it possible to investigate quantitatively many important aspects of seafloor relief and the geological processes responsible for its formation typical bathymetric contour maps represent a low frequency deterministic model of the seafloor to describe the higher frequency variability or roughness of the seafloor requires the development of an appropriate statistical method for generating a valid stochastic model new methods are developed herein which allow valid statistical models of the variability of oceanic depths to be derived from existing digital bathymetric soundings the smooth contoured surface often preserved as a geographic grid of depths when supplemented by such a roughness model can provide an essentially complete statistical description of the relief statistical models of seafloor roughness are also valuable tools for predicting acoustic scattering and bottom loss and in addition contain a wealth of information for more comprehensive interpretations of deep sea relief forming geological processes to allow the variability of depths to be described as a function of scale spatial frequency the amplitude spectrum is employed as the fundamental statistic underlying the model since the validity of the amplitude spectrum depends upon the assumption of a statistically stationary sample space a computer algorithm operating in the spatial domain was developed which delineates geographic provinces of limited statistical heterogeneity within each of these provinces a spectral model is derived by fitting the amplitude estimates with one or two two parameter power law functions using specialized regression techniques the distribution of resultant model parameters is examined for a large test area adjacent to the coast of oregon 42 45 n 130 124 w which includes several contrasting geologic environments the distribution of roughness corresponds generally with the various physiographic provinces observed in the region within some provinces additional complexities are apparent in the roughness model which cannot be inferred by simply studying the bathymetry these patterns are related to a variety of geological processes operating in the region such as the convergence of the continental margin and the presence of a propagating rift on the northern gorda rise in contrast a very large area of the continental margin off the east coast of the united states was found to have in common a single distinct amplitude spectrum this amplitude spectrum is almost identical to that found from the tufts abyssal plain region off the west coast of the united states spectra from both of these areas can be clearly separated into two straight line segments of different slope the two segments of these spectra are interpreted as reflecting two dominant relief forming processes the higher frequency band representing a sedimentary regime and the lower frequency band representing an underlying tectonic volcanogenic regime in many cases the calculated roughness statistics are not constant for data collected along different ship track directions this is due to the anisotropic nature of the seafloor relief a simple model is developed which describes the roughness statistics as a function of azimuth the parameters of this model quantify the anistropy of the seafloor allowing insight into the directionality of the corresponding relief forming processes and the physical meaning of the derived model statistical parameters finally the model is used to successfully predict the roughness of a surface at scales much smaller than those resolvable by surface sonar systems the model regression line derived from a hull mounted sonar is compared to data from deep towed sonars and bottom photographs the amplitude of roughness is predicted to within half an order of magnitude over five decades of spatial frequency and this prediction capability can probably be improved even further the stochastic models presented also demonstrate the potential for closely approximating the full two dimensional nature of some areas of the seafloor with only four statistical parameters these parameters can be estimated from random ship track data given a sufficient number of tracks and range of headings

impact of indian summer monsoon on the south asian high and its influence on summer rainfall over china by using the monthly era 40 reanalysis data and observed rainfall data we investigated the effect of the indian summer monsoon ism on the south asian high sah at 200 hpa and the role played by the sah in summer rainfall variation over china it is found that in the interannual timescale the east west shift is a prominent feature of the sah with its center either over the iranian plateau or over the tibetan plateau when the ism is stronger weaker than normal the sah shifts westward eastward to the iranian plateau tibetan plateau the east west position of sah has close relation to the summer rainfall over china a westward eastward location of sah corresponds to less more rainfall in the yangtze huai river valley and more less rainfall in north china and south china a possible physical process that the ism affects the summer rainfall over china via the sah is proposed a stronger weaker ism associated with more less rainfall over india corresponds to more less condensation heat release and anomalous heating cooling in the upper troposphere over the northern indian peninsula the anomalous heating cooling stimulates positive negative height anomalies to its northwest and negative positive height anomalies to its northeast in the upper troposphere causing a westward eastward shift of the sah with its center over the iranian plateau tibetan plateau as a result an anomalous cyclone anticyclone is formed over the eastern tibetan plateau and eastern china in the upper troposphere the anomalous vertical motions in association with the circulation anomalies are responsible for the rainfall anomalies over china our present study reveals that the sah may play an important role in the effect of ism on the east asian summer monsoon

three dimensional model of alluvial stratigraphy theory and applications abstract a three dimensional model of alluvial stratigraphy has been developed to simulate the spatial distribution proportion and connectedness of coarse grained channel belt deposits in alluvial strata as a function of channel belt width floodplain width bankfull channel depth channel belt and overbank sedimentation rates avulsion location and period compaction and tectonism tilting and faulting in this model a floodplain surface of variable width and length is occupied by a single channel belt changes in floodplain topography are produced by spatial and temporal variation of channel belt and floodplain deposition rates and by compaction and local or regional tectonism the location and timing of avulsions are determined by local changes in floodplain slope relative to channel b lt slope and by flood magnitude and frequency the diverted channel belt follows the locus of maximum floodplain slope at the end of each simulation architectural parameters are calculated including channel deposit proportion and connectedness and the dimensions of channel belt sandstone bodies three dimensional perspective diagrams mesh surfaces and two dimensional stratigraphic sections can be plotted to illustrate depositional surfaces time planes and the location and geometry of coarse grained channel belt deposits within finer grained overbank deposits the model predicts that channel belt proportion and connectedness and dimensions of sandstone bodies vary as a function of distance from avulsion points and cross section orientation upstream from avulsion points sandstone bodies have low width thickness ratios because of aggradation in a fixed channel belt immediately downstream from avulsion points channel belts tend to be connected resulting in sandstone bodies with high width thickness ratios avulsion sequences develop where points of avulsion shift up valley with a progressive decrease in avulsion period such sequences may produce successions in which channel belt proportion and connectedness vary vertically with a cyclic period of 103 to 105 years down valley increases in aggradation rate or down valley decreases in floodplain slope for example associated with a rise in base level may result in an increase in channel belt proportion and connectedness because of high avulsion frequencies in down valley regions of the floodplain down valley decreases in aggradation rate as in alluvial fans foreland basins and during base level fall may result in high avulsion frequencies in up valley parts of the floodplain tectonic tilting and faulting locally increase avulsion probabilities and channel belts generally shift toward areas of maximum subsidence under certain conditions however depositional topography may cause channels to shift away from areas of maximum subsidence channel deposit proportion and connectedness are gen rally high near downthrown areas of the floodplain but distribution clustering of channel belts may not be a reliable indicator of fault geometry or displacement models of alluvial architecture that consider only sediment accumulation rate as the main controlling factor are oversimplified the three dimensional model presented here predicts many of the features of channel behavior observed in modern rivers but there is a pressing need for better models and adequate natural data to test them

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 investigation of the spectral properties of primary reflection coefficients this paper investigates the form of the nonwhiteness found in the reflection coefficients from a wide variety of rock sequences around the world in all but one case densities are taken as constant due to the paucity of suitable density data the reflection sequences are pseudo white only above a corner frequency below which their power spectrum falls away according to a power law f where is between 0 5 and 1 5 this spectrum can be adequately modelled in practice very simply with an arma 1 1 process which acts on a white innovation sequence the corollary of this is that before wavelet estimation methods are applied all of which except those based on synthetic seismograms presuppose white reflection sequences or deconvolution filters estimated seismic traces should be filtered with the inverse of this process interestingly the estimated arma processes group themselves into two clearly differentiated categories having very different indices of predictability or strictly indices of linear determinism the two categories apparently correlate precisely with two kinds of sedimentation one which consists largely of sequences of rocks with repeating properties called repetitive in this paper but perhaps loosely describable as cyclic and the other which is randomly bedded with no apparent pattern of components the former has indices of predictability which are two to four times as great as those of the latter another probably related property is that for the repetitive sequences tends to be greater than that for non repetitive rock columns the observed power spectra are shown to be consistent with a simple model for the logarithm of acoustic impedance consisting of a mixture of processes where the distribution of time scale parameters is reciprocal detailed effects of block averaging and sampling the logs are shown to depend on the type of sequence under examination

mid proterozoic dolomitic varves and microcycles from the mcarthur basin northern australia abstract the middle proterozoic 1 75 ga wollogorang formation of the unmetamorphosed intracratonic mcarthur basin of northern australia contains a dolomitic black shale facies that has distinctive millimetre and sub millimetre scale bedding laminations and microcycles of alternating organic rich mudstone and organic poor dolostone the microcycles are between 1 and 20 mm thick and their internal laminations are arranged rhythmically into a lower subdivision of mainly dolostone with subordinate mudstone laminae and an upper subdivision of mainly mudstone with thin dolostone laminae the microcycles vary systematically in both thickness and character the thinnest laminations visible around 0 2 mm thick are interpreted as chemical varves the microcycles represent bundles of varves deposited over longer periods over these longer periods each microcycle shows a gradual upward decrease in the amount of dolomite precipitated and or preserved this is related in part to original climatic controls in the environment of deposition and also to a secondary but pre lithification process of dissolution similar to that invoked by trendall 1972 1973 for the formation of mesobands in the bif s of the hamersley basin western australia simple statistical calculations of varve thickness variations on about 100 microcycles from a 1 5 m long core indicate the presence of 7 to 11 year and 300 year periods these periods are comparable with those published by williams 1981 for glaciogenic varves from late proterozoic 680 ma rocks in south australia he relates the former to sunspot cycles and the later to longer term climate periods as evident from tree ring studies although nowhere near as conspicuous as the sunspot cycles described by williams 1981 or the double sunspot cycles of trendall 1972 from the latest and earliest proterozoic respectively these microcycles from the middle proterozoic may be due to similar sunspot related processes and therefore add support to their suggestions for long term stability of solar processes

structures and mechanisms of the northward propagating boreal summer intraseasonal oscillation abstract the spatial and temporal structures of the northward propagating boreal summer intraseasonal oscillation bsiso are revealed based on the analysis of both the echam4 model simulation and the ncep ncar reanalysis the bsiso structure and evolution characteristics simulated by the model bear many similarities to those derived from the ncep ncar reanalysis the most notable features are the remarkable meridional asymmetries relative to the bsiso convection in the vorticity and specific humidity fields a positive vorticity perturbation with an equivalent barotropic structure appears a few latitude degrees north of the convection center the maximum specific humidity also shows a clear northward shift in the lower troposphere two internal atmospheric dynamics mechanisms are proposed to understand the cause of the northward propagation of the bsiso the first is the vertical shear mechanism the key process associated with this mechanism is the generation of barotropic vorticity due to the couplin

tc permitting gcm simulations of hurricane frequency response to sea surface temperature anomalies projected for the late twenty first century abstracta tropical cyclone permitting global atmospheric model is used to explore the hurricane frequency response to sea surface temperature sst anomalies generated by coupled models for the late twenty first century results are presented for sst anomalies averaged over 18 models as well as from 8 individual models for each basin there exists large intermodel spread in the magnitude and even the sign of the frequency response among the different sst projections these sizable variations in response are explored to understand features of sst distributions that are important for the basin wide hurricane responses in the north atlantic the eastern pacific and the southern indian basins most 72 86 of the intermodel variance in storm frequency response can be explained by a simple relative sst index defined as a basin s storm development region sst minus the tropical mean sst the explained variance is significantly lower in the south pacific 48 and much lower in the western pacific basin 27

detection of sedimentary cyclicity and stratigraphic completeness by wavelet analysis an application to late albian cyclostratigraphy of the western canada sedimentary basin abstract on the basis of the time frequency scaling property of the wavelet transform accumulation rates and stratigraphic completeness can be calculated for various observation time spans ot by using wavelet analysis wavelet analysis also allows automatic detection of high frequency sedimentary cyclicity and abrupt and gradual variations in sedimentation rate the preservation of different frequency cycles is strongly dependent on variations of the intensity to noise ratio of the original cycles and accumulation rate through time as demonstrated by computer models wavelet analysis was used to detect and correlate periodic cyclic successions of marine sediments in the western canada sedimentary basin in observation time spans ranging from 100 kyr to 3 8 myr cycles in gamma ray data are in accordance with sonic logging lithology and biotic change cyclic units embedded in the upper albian westgate and joli fou formations are almost periodic with 11 and 10 repetitions respectively accumulation rates at ot 100 kyr vary from 5 7 cm kyr in mudstone successions to 29 cm kyr in sandstone successions of the rocky mountains foothills these 100 kyr cycles are preserved from 30 in the manitoba escarpment to 100 in se alberta in the westgate formation these cycles can be correlated throughout facies belts of siliciclastic sedimentation in the entire basin in gamma ray logging the cyclicity is most pronounced in the foredeep succession and almost without fluctuations in the basin center cyclic changes from wet to dry climate probably forced by milankovitch cycles of 100 kyr eccentricity may have controlled the stable periodic sedimentary cyclicity

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

a fractal interpretation of topography and geoid spectra on the earth moon venus and mars global spectra are available for topography and geoid on the earth venus mars and the moon if the spectral energy density has a power law dependence on wave number a fractal is defined the topography spectrum for the earth is a well defined fractal with d 1 5 this corresponds to brown noise with the amplitude proportional to the wave length although there is more scatter for the other planetary bodies the data for mars and the moon correlate well with the data for the earth venus topography also exhibits a brown noise behavior but with a smaller amplitude the power law dependence of the earth s geoid is known as kaula s law we show that uncompensated brown topography gives a geoid with a power law dependence that is in quite good agreement with kaula s law however the required amplitude is only 8 of the observed topography a similar result is found for the other bodies with the ratio of the amplitude of topography required to explain the geoid to the observed topography increasing to 72 for the moon

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

characteristics of sedimentary varve chronologies a review abstract we constructed a varve data base vdb to study the worldwide distribution of varved sediment records and the fidelity of their varve chronologies clusters of lakes with varved sediments exist in central north america in the canadian arctic and in northern and central europe among the 108 sites included in the vdb varved records are typically 200 500 cm long and cover a period of 1000 2000 years their varve chronologies are often based on counting of annual layers from fresh sediment surfaces and photographs or from epoxy embedded sediment blocks and thin sections the vdb indicates that chronological errors associated with counting sedimentary varves fall generally between 1 and 3 but only 57 of published records are providing quantitative error estimations for their chronologies with a careful documentation of varves and by applying radiometric dating methods to surface sediments as well as using historical events as time markers there is the potential of having centennial long varved records with a very precise age depth control however it is unrealistic to expect errors significantly below 1 from several millennia long sections we found no indication that varve chronologies would have been substantially more accurate and precise in some parts of the world than in others or statistically dependent on varve thickness or temporal extension of a varved sequence according to the vdb close to 90 of the published varve chronologies have been cross checked with some independent dating methods

atmospheric dynamic and thermodynamic processes driving the western north pacific anomalous anticyclone during el nino part ii formation processes abstractin part i the authors showed that northerly anomalies associated with the rossby wave response to el nino heating anomalies in the equatorial central pacific lead to the southward advection of low moist enthalpy air forming the western north pacific anomalous anticyclone wnpac why does such a remote forcing not cause the formation of the anomalous anticyclone in el nino developing summer the physical mechanism responsible for the timing of the wnpac formation is investigated in part ii through both an observational analysis and idealized numerical model experiments the authors find that the onset timing of the wnpac relies on the following three factors the first is a sign change from positive to negative of the meridional gradient of background low level specific humidity over the key tropical western north pacific wnp region in november the second is a sign change from positive to negative of the meridional gradient of background relative vorticity which efficiently reduces the w

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

impact of interannually varying background circulation on summertime wave patterns and tropical cyclone tracks in the western north pacific this study analyzed summertime wave patterns in the western north pacific by separating them into those during el nino en and la nina ln years for 1979 2015 the background flow revealed that in the en years the subtropical high was weaker and the east asian summer monsoon trough was deeper and extended farther southeastward the composite results indicated that in the en years tropical cyclone tc tracks were more solid and stably associated with wave pattern propagation routes because the circulation anomalies were significantly stronger however in the ln years when the wave patterns were weak under the shorter and less organized monsoon trough due to the enhanced subtropical high the tc tracks and cyclonic anomalies were irregular and sporadic further background flow analyses indicated that the en circulation favored the development of the monsoon trough and east west expansion and contraction of the subtropical ridge whereas the stronger subtropical ridge dominated most western north pacific areas in the ln years therefore the monsoon trough was weaker in the ln years and induced recurving tcs to take more scattered routes near taiwan and china s east coast therefore taiwan experienced more rainfall during recurving tc periods in the ln years than in the en years for the straight moving tcs passing through taiwan rainfall was concentrated over southern taiwan in the en years but more evenly distributed in the ln years thus background flow changes strongly affect wave patterns and tcs

annually laminated lake sediments and the study of quaternary environmental changes a review abstract annually laminated lake sediments non glacial varves have in recent years been discovered in increasing abundance especially since the development of in situ freezer samplers so far the majority of examples have been found in three main areas eastern north america northern and central europe and east and central africa a much more widespread distribution seems highly probable however the formation of annual laminations in freshwater lakes is governed by a number of factors the most important of which appears to be morphometry seasonality of sediment supply which may be controlled by physical biological or even cultural processes in the lake or in its catchment is also clearly significant four main types of laminations here termed ferrogenic calcareous biogenic and clastic have so far been recorded although it is quite clear that others exist special field and laboratory techniques are needed in order that the particular properties of varved sediments may be fully exploited annually laminated sediments have so far been applied to the investigation of a number of aspects of the quaternary these include the study of a geochronology b climatic change c vegetation history especially the role of fire in forest ecosystems d the calculation of rates of sediment influx to lakes and of rates of erosion from their catchments and e the monitoring of processes in the modern environment such as heavy metal pollution eutrophication and acid rain annually laminated lake sediments combine an internal independent chronology with the preservation of discrete visible increments of seasonal and annual sedimentation given this unique property and the likelihood that many more examples will be discovered the prospects for further applications of studies of these sediments to the investigation of the quaternary seem very good indeed

modulation of the convectively coupled kelvin waves over south america and the tropical atlantic ocean in association with the madden julian oscillation abstractin this study evidence of the strong modulation of the convectively coupled kelvin wave cckw activity by the madden julian oscillation mjo is presented with a particular focus over the south america and tropical atlantic region the mjo impacts on cckws over this region as noted in anomalous fields of rainfall as well as vertical profiles of wind moisture and temperature are primarily through the modulation of kelvin wave amplitude with secondary effects on vertical structure and little impact on wavenumber cckw activity is enhanced during mjo phases 8 1 and 2 and damped during mjo phases 4 5 and 6 further analyses reveal that the strong modulation of the mjo on the cckw activity could be largely through two factors namely the vertical zonal wind shear and the lower to middle tropospheric specific humidity the cckw activity tends to be enhanced during mjo phases when the easterly vertical wind shear and positive low to midtroposphere moisture anomalies are present and vice ve

geostatistical analysis of an experimental stratigraphy 1 a high resolution stratigraphic image of a flume generated deposit was scaled up to sedimentary basin dimensions where a natural log hydraulic conductivity ln k was assigned to each pixel on the basis of gray scale and conductivity end members the synthetic ln k map has mean variance and frequency distributions that are comparable to a natural alluvial fan deposit a geostatistical analysis was conducted on selected regions of this map containing fluvial fluvial floodplain shoreline turbidite and deepwater sedimentary facies experimental ln k variograms were computed along the major and minor statistical axes and horizontal and vertical coordinate axes exponential and power law variogram models were fit to obtain an integral scale and hausdorff measure respectively we conclude that the shape of the experimental variogram depends on the problem size in relation to the size of the local scale heterogeneity at a given problem scale multilevel correlation structure is a result of constructing variogram with data pairs of mixed facies types in multiscale sedimentary systems stationary correlation structure may occur at separate scales each corresponding to a particular hierarchy the integral scale fitted thus becomes dependent on the problem size the hausdorff measure obtained has a range comparable to natural geological deposits it increases from nonstratified to stratified deposits with an approximate cutoff of 0 15 it also increases as the number of facies incorporated in a problem increases this implies that fractal characteristic of sedimentary rocks is both depositional process dependent and problem scale dependent

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

fractals in petrology abstract a fractal power law distribution is the only statistical distribution applicable to a scale invariant process one of the major problems in petrology is the distribution of trace elements in the earth s crust extreme values of this distribution result in ore deposits there is accumulating observational evidence that tonnage grade statistics of ore deposits are often fractal power law rayleigh distillation and chromatographic models can explain power law fractal distributions for the extreme values of trace element concentrations an alternative fractal approach to problems in petrology is to use self affine fractals the standard approach is to take a fourier transform of a continuous signal an example would be the concentration of a mineral along a linear track if the fourier coefficients scale as a power law of the wavelength the distribution is a self affine fractal many well logs give this result multifractal analyses can also be applied to problems in petrology

annually laminated lake sediments and environmental changes in bashang plateau north china abstract angulinuo lake is the biggest lake on the bashang plateau north china and is 47 6 km2 in area and 2 6 m in depth a core from the inner part of angulinuo lake was sliced and the sediment was observed by scanning electronic microscope sem annual laminations characterized by variable color and grain size were found and interpreted as recording the cyclic deposition of lacustrine clay and aeolian dust the results of chemical analysis of coarse grains conducted by sem edax and grain size analysis of modern aeolian dust in the ice on angulinuo lake support an aeolian origin for the light coarse layers image analysis technique was used to calculate the size and number of coarse grains in each layer the coarse grains were fractionated into four classes 42 m 14 42 m 14 4 2 m and 1 4 4 2 m in general the abundance of the four classes shows similar temporal variation patterns around angulinuo lake the winter monsoon is strong and transports aeolian dust into the lake when the winter monsoon is strong the size and amount of coarse grains are expected to increase we infer that the winter monsoon was weaker during 8430 5440 year bp and was unstable in the later part of this period from 5440 year bp the winter monsoon became stronger and then weaker from 3250 to 2490 year bp during 2490 1170 year bp the winter monsoon was slightly stronger but since 1170 year bp it has become weaker again the changes of the winter monsoon intensity recorded in the annual laminations in angulinuo lake sediments correspond well to environmental changes in north china and to changes in sea level during the same period periods of weaker winter monsoon correspond to times of higher sea levels while the periods of stronger winter monsoon correspond to the neoglaciation stage in china and the periods of lower sea levels

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

upper crustal seismic velocity heterogeneity as derived from a variety of p wave sonic logs sonic log measurements provide detailed 1 d information on the distribution of elastic properties within the upper crystalline crust at scales from about one metre to several kilometres 10 p wave sonic logs from six upper crustal drill sites in europe and north america have been analysed for their second order statistics the penetrated lithological sequences comprise archean volcanic sequences proterozoic mafic layered intrusions and precambrian to phanerozoic gneisses and granites despite this variability in geological setting tectonic history and petrological composition there are notable similarities between the various data sets after removing a large scale deterministic component from the observed velocity depth function the residual velocity fluctuations of all data sets can be described by autocovariance functions corresponding to band limited self affine stochastic processes with quasi gaussian probability density functions depending on the maximum spatial wavelength present in the stochastic part of the data the deterministic trend can be approximated either by a low order polynomial best fit or by a moving average of the original sonic log data the choice of the trend has a significant impact on the correlation length and on the standard deviation of the residual stochastic component but does not affect the hurst number for trends defined by low order polynomial best fits correlation lengths were found to range from 60 to 160 m whereas for trends defined by a moving average the correlation lengths are dominated by the upper cut off wavenumber of the corresponding filter regardless of the trend removed the autocovariance functions of all data sets are characterised by low hurst numbers of around 0 1 0 2 or equivalently by power spectra decaying as 1 k a possible explanation of this statistical uniformity is that sonic log fluctuations are more sensitive to the physical state in particular to the distribution of cracks than to the petrological composition of the probed rocks

meridional displacement of the east asian trough and its response to the enso forcing this paper examined the underlying dynamic mechanisms associated with the meridional displacement of the east asian trough eat which is closely related to the temperature variability in the southern part of east asian winter monsoon eawm during the southward displacement of the eat the siberian high is stronger and the aleutian low is displaced southward this is due mainly to the anomalous cyclonic flow associated with seasonal eddies over the midlatitude central pacific which enhances the horizontal advection of cold warm air to the southern northern part of the eat in the lower troposphere the cold warm advection narrows thickens the height thickness and results in negative positive temperature anomalies in the southern northern part of the eat these anomalous circulation features can be reasonably explained by the phase of the el nino southern oscillation enso the results are also verified by the numerical experiments with prescribing enso like heat source anomalies over the tropical eastern and western pacific in an anomaly atmospheric general circulation model all of these results advance our understanding for the linkage between the enso and the eawm via its modulation of the eat

annual laminations in the sediments of loe pool cornwall annually laminated freshwater lacustrine sediments have been recorded at several sites in central europe1 5 north america6 13 and fennoscandia14 24 the presence of laminations may reflect either 1 regular changes within the lake ecosystem itself or 2 variation in the intensity of erosion and transport of material from the catchment particularly where instability in the lake watershed system has occurred as a result of human activities22 the principal cause of lamination is therefore seasonal variation of environmental conditions particularly climate lakes with laminated sediments tend to be physically deep exhibit a strong seasonal stratification and be situated in areas of continental climate we describe here what we believe to be the first reported instance of a long sequence of laminated lake sediments from great britain unlike most of the previous examples these have been formed in a shallow polymictic lake in an oceanic climate

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

scale invariant topography and porosity variations in fluvial sedimentary basins we consider a model offloodplain evolving with channelvulsion deposition nd erosion avulsion is modeled asrndom process in spce and time sediment transport is modeled by the diffusion equation culling s model the power spectrum of vritions in the topographic profiles predicted by the model s k is proportional to k 2 where k is the wvenumber this is the brown noise often observed in topography the power spectrum of wristions in the local elevation in time is proportional to f s where f is the frequency the model prediction of brown noise floodplain topography is roughly consistent with spectralnlyses of microtopography measured with lserltimetry we inferred brown noise pleotopogrphy by comparing the pir correlation function of showing wells in the denvernd powder river basins with a synthetic oil field bsed on caprock with brown noise topography topographic control of variations in the grain size of deposited sediment suggests that porosity vritions my exhibit the scale invrince predicted for the topographic profile to illustrate vertical scale invariance in porosity vritions we computed the power spectrum of vertical porosity well logs in 15 offshore wells in the gulf of mexico at spatial scales bove 3 m we find anverge power spectral exponent of 1 4 close to our model prediction of 1 5

fayetteville green lake new york u s a abstract a varve chronology extending back to 1900 with dated stratigraphic markers has been established for deep water sediment in the northern part neck of meromictic fayetteville green lake and correlated to a similar chronology established earlier in the deeper southern end of the lake main basin precise estimates of net annual varve sedimentation rates are given for each year between 1938 and 1977 for the neck these rates are 27 higher than those previously reported in the main basin and range between 454 and 1090 g m 2 yr 1 varve sedimentation rates have significantly increased throughout the lake during the last 30 years with no changes in the relative ratio of varve sedimentation rates in the neck and the main basin although there is considerable year to year variation in this ratio higher varve sedimentation rates occur in shallower portions of the permanently stratified water probably because resuspension is unlikely in this low energy environment because of basin morphometry and meromixis sediment focusing creates higher varve sedimentation rates in relatively shallow water near the upper limit of the permanently stratified water rather than in the deepest water

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

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

dynamical and thermodynamical coupling between the north atlantic subtropical high and the marine boundary layer clouds in boreal summer this study investigates dynamical and thermodynamical coupling between the north atlantic subtropical high nash marine boundary layer mbl clouds and the local sea surface temperatures ssts over the north atlantic in boreal summer for 1984 2009 using ncep doe reanalysis 2 dataset various cloud data and the hadley centre sea surface temperature on interannual timescales the summer mean subtropical mbl clouds to the southeast of the nash is actively coupled with the nash and local ssts a stronger weaker nash is often accompanied with an increase a decrease of mbl clouds and abnormally cooler warmer ssts along the southeast flank of the nash to understand the physical processes between the nash and the mbl clouds the authors conduct a data diagnostic analysis and implement a numerical modeling investigation using an idealized anomalous atmospheric general circulation model agcm results suggest that significant northeasterly anomalies in the southeast flank of the nash associated with an intensified nash tend to induce stronger cold advection and coastal upwelling in the mbl cloud region reducing the boundary surface temperature meanwhile warm advection associated with the easterly anomalies from the african continent leads to warming over the mbl cloud region at 700 hpa such warming and the surface cooling increase the atmospheric static stability favoring growth of the mbl clouds the anomalous diabatic cooling associated with the growth of the mbl clouds dynamically excites an anomalous anticyclone to its north and contributes to strengthening of the nash circulation in its southeast flank the dynamical and thermodynamical couplings and their associated variations in the nash mbl clouds and ssts constitute an important aspect of the summer climate variability over the north atlantic

the influence of sea surface temperature on the tropical intraseasonal oscillation a numerical study abstract the development and movement of the tropical intraseasonal system tis exhibit remarkable annual variations it was hypothesized that spatial and temporal variation in sea surface temperature sst is one of the primary climatic factors that are responsible for the annual variation of tiss this paper examines possible influences of sst on the tis through numerical experiments with a 2 5 layer atmospheric model on an equatorial plane in which sst affects atmospheric heating via control of the horizontal distribution of moist static energy and the degree of convective instability the gradient of the antisymmetric with respect to the equator component of sst causes a southward propagation of the model tis toward northern australia in boreal winter and a northward propagation over the indian and western pacific oceans in boreal summer the phase speed of the meridional propagation increases with the magnitude of antisymmetric sst gradients the poleward propagation of the equatorial disturba

scaling geology and seismic deconvolution the reflection seismic signal observed at the surface is the convolution of a wavelet with a reflection sequence representing the geology deconvolution of the observations without prior knowledge of the wavelet can be done by making assumptions about the statistics of the reflection sequence in particular the widely used prediction error filter is obtained by assuming that the power spectra of reflection sequences are white however evidence from well logs suggests that the power spectra are in fact proportional to a power of the frequency f that is to f with equal approximately to 1