comparison of covalently bound aliphatic biomarkers released via hydropyrolysis with their solvent extractable counterparts for a suite of kimmeridge clays abstract fixed bed hydropyrolysis at pressures greater than 10 mpa has the unique ability to maximise the yields of covalently bound alkanes without adversely affecting their stereochemistries in order to compare the yields and compositions of the solvent extractable and kerogen bound hopanes and steranes for source rocks of varying maturity six kimmeridge clay samples jurassic type ii kerogen have been subjected to successive dichloromethane extraction and hydropyrolysis the ratios of free to kerogen bound aliphatic biomarkers increase markedly at relatively low vitrinite reflectance ca 0 45 0 50 with large reductions occurring in the concentrations of bound hopanes and steranes however the fact that the total concentrations of observable hopanes and steranes i e free plus kerogen bound do not decrease until the vitrinite reflectance is greater than ca 0 50 provides evidence that neither oil migration nor aromatisation has begun to occur to a significant extent below this maturity level to the authors knowledge this represents the first study to observe a systematic change in epimer ratios with increasing maturity for hopanes and steranes covalently bound in kerogens indeed the kerogen bound hopanes and steranes undergo the same epimerisation reaction pathways as their free counterparts in the bitumen but they are generally less mature in terms of isomerisation at both ring and side chain chiral centres indeed the range of the moretane hopane index for the hydropyrolysis oils is much larger than that for the bitumens ca 5 times indicating a much greater sensitivity to relatively small changes in maturity the covalently bound hopanes and steranes released via hydropyrolysis have enabled the maturity of a contaminated core from the north sea central graben maturity to be assessed and have showed that it is compatible with the kimmeridge formation

the 1997 and 2001 lahars of popocatepetl volcano central mexico textural and sedimentological constraints on their origin and hazards abstract popocatepetl volcano is the most active volcano in central mexico and represents a high risk for more than 40 million people including mexico city in 1994 volcanic activity at popocatepetl renewed with the formation of ash rich plumes up to 7 km high in april 1996 lava emissions filled the crater and were accompanied by a series of explosions that produced eruptive columns up to 8 km high associated with explosive events in 1997 and 2001 two major lahars events occurred leaving debris flow deposits along huiloac gorge for as far as 15 km to the town of santiago xalitzinta the 1997 debris flow deposit originated after a prolonged emission of ash which caused glacier melt and a rapid release of water 1 107 m3 the amount of melting water was sufficient to gradually erode the river bed causing a flood that gradually transformed from a debris flow to a hyperconcentrated flow in contrast the 2001 debris flow that originated from a post depositional remobilization of a pumice flow deposit did not experience any flow transformation and carried 25 water at maximum the different behavior of these two lahars has important hazard implications both lahars reached xalitzintla town but at that point the 1997 lahar had already transformed into a sediment loaded stream flow the 2001 lahar by contrast maintained the characteristics of a debris flow being more competent and with greater destructive power what happened with these lahars demonstrates how important it is to take into consideration secondary volcanic phenomena even though they were not large flows they were capable of threatening populated areas even during periods of volcanic quiescence or reduced magmatic activity

a geochemical reconstruction of oil generation in the barrow sub basin of western australia abstract a suite of crude oils and petroleum source rock extracts from the barrow sub basin of western australia have been analysed for biological marker compounds by capillary gc ms and for volatile hydrocarbons by whole oil capillary gc these analyses were used to calculate values for twenty three biomarker parameters in order to assess aspects of source type maturity migration and biodegradation of the hydrocarbons the crude oils had a source in the upper jurassic dingo claystone formation these hydrocarbons accumulated in the reservoir sands and in some cases were biodegraded several accumulation and biodegradation episodes have been recognised while the basin continued to subside which resulted in a suite of oils showing marked differences in composition

directional response of wind waves to a large wind shift abstract the directional response of a fully arisen sea to a 90 wind shift is studied using a combination of airborne radar and in situ directional wave observations the observations were made in february 1991 as a part of the surface wave dynamics experiment radar and buoy mean wave directions in several frequency bands are polynomial smoothed in fetch and duration coordinates and analyzed for the directional relaxation parameter b by using finite differences of the gridded smoothed data in a one dimensional advection equation for the mean wave direction the analysis is carried out using several different sets of buoy wind and wave data in an event window of 40 h in duration by 200 km in fetch 100 300 km offshore for the most well populated and reliable inverse wave age class in the study 1 2 u c 1 6 the authors find b 3 3 0 1 10 5 the data do not support any inference as to possible wave age dependence other than perhaps the null hypothesis b const u c frequencies near the

azimuthal and radial variation of wind generated surface waves inside tropical cyclones abstractfor wind generated waves the wind wave triplets reference wind speed significant wave height and spectral peak wave period are intimately connected through the fetch or duration limited wave growth functions the full set of the triplets can be obtained knowing only one of the three together with the input of fetch duration information using the pair of fetch limited duration limited wave growth functions the air sea energy and momentum exchanges are functions of the wind wave triplets and they can be quantified with the wind wave growth functions previous studies have shown that the wave development inside hurricanes follows essentially the same growth functions established for steady wind forcing conditions this paper presents the analysis of wind wave triplets collected inside hurricane bonnie 1998 at category 2 stage along 10 transects radiating from the hurricane center a fetch model is formulated for any location inside the hurricane applying the fetch model to the 2d hurric

measuring sea surface mean square slope with a 36 ghz scanning radar altimeter values of sea surface mean square slope mss computed from the backscattered power falloff with incidence angle measured by an airborne 36 ghz scanning radar altimeter are presented when the mss values are plotted against the 10 m wind speed extrapolated from the 46 to 110 m aircraft height for wind speeds up to 7 m s 1 the values scatter about a curve which is scaled from that obtained by wu 1990 by a factor of 0 85 wu s result was a reanalysis of the optical measurements of cox and munk 1954 the offset between the microwave and optical curves is reasonable because one would expect the surface to appear smoother to the microwave wavelength than to the optical this is unlike the mss values inferred from absolute power measurements at nadir by 14 ghz satellite altimeters which indicate a higher mss under light wind conditions than the optical measurements indicate for wind speeds below 7 m s 1 the peak of the backscattered power distribution is observed at nadir but for higher speeds the peak shifts off nadir in the downwind direction

propagation directions of ocean surface waves inside tropical cyclones abstractsurface wave propagation inside tropical cyclones tcs is complicated and multiple wave systems are frequently observed the directional wave spectra acquired by hurricane hunters are analyzed to quantify its azimuthal and radial variations referenced to the hurricane heading the dominate feature in the front half of the tc coverage area is single wave systems propagating toward left and left front multiple wave systems are generally observed in the back and right quarters outside the radius of maximum wind rmw the directional differences and locations of occurrences of multisystem spectra are gaussian distributed the directional differences of the secondary and tertiary wave systems from the primary system are centered around 60 70 the minor systems are more likely on the left hand side of the primary system than on the right hand side by a 3 to 1 ratio the most likely azimuthal location of multisystem spectra is about 210 counterclockwise from the heading in the right front quarter

airborne measurements of surface wind and slope statistics over the ocean abstractas reported in 1954 more than a half century ago c cox and w munk developed an empirical model of the slope distribution of ocean surface waves that has been widely used ever since to m

hurricane directional wave spectrum spatial variation in the open ocean abstract the sea surface directional wave spectrum was measured for the first time in all quadrants of a hurricane s inner core over open water the nasa airborne scanning radar altimeter sra carried aboard one of the noaa wp 3d hurricane research aircraft at 1 5 km height acquired the open ocean data on 24 august 1998 when bonnie a large hurricane with 1 min sustained surface winds of nearly 50 m s 1 was about 400 km east of abaco island bahamas the noaa aircraft spent more than five hours within 180 km of the eye and made five eye penetrations grayscale coded images of hurricane bonnie wave topography include individual waves as high as 19 m peak to trough the dominant waves generally propagated at significant angles to the downwind direction at some positions three different wave fields of comparable energy crossed each other partitioning the sra directional wave spectra enabled determination of the characteristics of the various components of the hurricane wave field and mapping of their sp

geochemical and biological marker assessment of depositional environments using brazilian offshore oils abstract a combined geochemical and molecular characterization of a wide selection of oils from the major brazilian offshore basins has been undertaken the elemental sulphur nickel and vanadium and bulk oapi and 13c properties of each sample been considered together with its molecular composition determined using liquid and gas chromatography and quantitative biological marker investigations using gas chromatography mass spectrometry for alkanes the results reveal significant differences in the chemical features of the various oils which enable them to be divided into five groups the distinction of the groups appears to reflect differences in the depositional environment of the source rocks of the oils each group is correlated tentatively with source rocks laid down in a specific depositional regime namely lacustrine freshwater lacustrine saline water marine evaporitic marine carbonate or marine deltaic the diagnostic features that allow this classification are the relative abundance and carbon number distributions of n alkanes pristane phytane ratios sulphur nickel and vanadium contents carbon isotope data the absolute concentrations of hopanes and steranes and their abundance relative to 4 methylsteranes and also the occurrence and abundance of several specific biological markers including 18 h oleanane gammacerane carotane tricyclic terpanes higher acyclic isoprenoids 28 30 bisnorhopane and 25 28 30 trisnorhopane this investigation shows the value of a combined geochemical and molecular approach in the assessment of the palaeoenvironment of deposition of the source rocks which gave rise to the oils

families of miocene monterey crude oil seep and tarball samples coastal california biomarker and stable carbon isotope ratios were used to infer the age lithology organic matter input and depositional environment of the source rocks for 388 samples of produced crude oil seep oil and tarballs to better assess their origins and distributions in coastal california these samples were used to construct a chemometric multivariate statistical decision tree to classify 288 additional samples the results identify three tribes of 13c rich oil samples inferred to originate from thermally mature equivalents of the clayey siliceous carbonaceous marl and lower calcareous siliceous members of the monterey formation at naples beach near santa barbara an attempt to correlate these families to rock extracts from these members in the nearby cost continental offshore stratigraphic test ocs cal 78 164 well failed at least in part because the rocks are thermally immature geochemical similarities among the oil tribes and their widespread distribution support the prograding margin model or the banktop slope basin model instead of the ridge and basin model for the deposition of the monterey formation tribe 1 contains four oil families having geochemical traits of clay rich marine shale source rock deposited under suboxic conditions with substantial higher plant input tribe 2 contains four oil families with traits intermediate between tribes 1 and 3 except for abundant 28 30 bisnorhopane indicating suboxic to anoxic marine marl source rock with hemipelagic input tribe 3 contains five oil families with traits of distal marine carbonate source rock deposited under anoxic conditions with pelagic but little or no higher plant input tribes 1 and 2 occur mainly south of point conception in paleogeographic settings where deep burial of the monterey source rock favored petroleum generation from all three members or their equivalents in this area oil from the clayey siliceous and carbonaceous marl members tribes 1 and 2 may overwhelm that from the lower calcareous siliceous member tribe 3 because the latter is thinner and less oil prone than the overlying members tribe 3 occurs mainly north of point conception where shallow burial caused preferential generation from the underlying lower calcareous siliceous member or another unit with similar characteristics in a test of the decision tree 10 tarball samples collected from beaches in monterey and san mateo counties in early 2007 were found to originate from natural seeps representing different organofacies of monterey formation source rock instead from one anthropogenic pollution event the seeps apparently became more active because of increased storm activity

remote sensing of ocean waves the surface wave process program experiment an airborne synthetic aperture radar sar has been used as an interferometer to obtain direct calibrated measurements of the ocean wind wave directional spectrum flights over the same area from three different directions produced reasonably consistent results the sar derived wave data agree well with simultaneous observations by a conventional wave measuring system and with a novel in situ acoustic doppler system

a comparison of sir b directional ocean wave spectra with aircraft scanning radar spectra directional ocean wave spectra derived from shuttle imaging radar b sir b l band imagery collected off the coast of southern chile on 11 and 12 october 1984 were compared with independent spectral estimates from two airborne scanning radars in sea states with significant wave heights ranging from 3 to 5 meters the sir b derived spectra at 18 and 25 off nadir yielded reasonable estimates of wavelengths directions and spectral shapes for all wave systems encountered including a purely azimuth traveling system a sir b image intensity variance spectrum containing predominantly range traveling waves closely resembles an independent aircraft estimate of the slope variance spectrum the prediction of a u s navy global spectral ocean wave model on 11 october 1984 exhibited no significant bias in dominant wave number but contained a directional bias of about 30 espect to the mean of the aircraft and spacecraft estimates

organic geochemistry of dsdp site 467 offshore california middle miocene to lower pliocene strata abstract results of the analyses of twenty three samples from the middle miocene to lower pliocene strata from dsdp site 467 offshore california are presented the analyses were performed with the aim of determining the origin of the organic matter the stratigraphic section s hydrocarbon generation potential and extent of organic diagenesis organic carbon contents are an order of magnitude greater than those typically found in deep sea sediments suggesting an anoxic depositional environment and elevated levels of primary productivity hydrocarbon generation potentials are above average for most samples the results of elemental analyses indicate that the kerogens are primarily composed of type ii organic matter and are thermally immature analysis of the bitumen fractions confirms that the samples are immature in cores from 541 to 614 meters the gas chromatograms of the c 15 non aromatic hydrocarbon fractions are dominated by a single peak which was identified as 17 h 18 h 21 h 28 30 bisnorhopane this interval is the same area in which the highest degrees of anoxia are observed as reflected by the lowest pristane phytane ratios this correlation may have some implications with regard to the origin of the bisnorhopane and its possible use as an indicator of anoxic depositional conditions within thermally immature sediments

directional ocean wave measurements in a coastal setting using a focused array imaging radar a unique focused array imaging doppler radar was used to measure directional spectra of ocean surface waves in a nearshore experiment performed on the north carolina outer banks radar images of the ocean surface s doppler velocity were used to generate two dimensional spectra of the radial component of the ocean surface velocity field these are compared to simultaneous in situ measurements made by a nearby array of submerged pressure sensors analysis of the resulting two dimensional spectra include comparisons of dominant wave lengths wave directions and wave energy accounting for relative differences in water depth at the measurement locations limited estimates of the two dimensional surface displacement spectrum are derived from the radar data the radar measurements are analagous to those of interferometric synthetic aperture radars insar and the equivalent insar parameters are shown the agreement between the remote and in situ measurements suggests that an imaging doppler radar is effective for these wave measurements at near grazing incidence angles

ocean wave imaging by synthetic aperture radar results from the sir b experiment in the n e atlantic waveheight spectra were extracted from synthetic aperture radar sar images close to a number of wave measuring buoys and the results of radar and in situ measurements were compared as a test of wave imaging theory sar and buoy spectra of waves traveling close to the radar range direction were in good quantitative agreement with any discrepancies probably attributable to the processing technique however sar estimates of the amplitude of azimuth traveling waves were very much lower than buoy derived values this cannot be accounted for by appealing to nonlinear imaging by the velocity bunching mechanism or by velocity smearing calculating the scene coherence time from the available buoy data rather the scene coherent time must be reduced by a factor of about two to within the range 0 022 0 027 s this result highlights a lack of knowledge of scatterer motions and lifetimes on the sea surface

airborne lidar measurements of wave energy dissipation in a coral reef lagoon system 1 quantification of the turbulent kinetic energy dissipation rate in the water column e is very important for assessing nutrient uptake rates of corals and therefore the health of coral reef lagoon systems however the availability of such data is limited recently at lady elliot island lei australia we showed that there was a strong correlation between in situ measurements of surface wave energy dissipation and e previously reineman et al 2009 we showed that a small airborne scanning lidar system could measure the surface wavefield remotely here we present measurements demonstrating the use of the same airborne lidar to remotely measure surface wave energy fluxes and dissipation and thereby estimate e in the lei reef lagoon system the wave energy flux and wave dissipation rate across the fore reef and into the lagoon are determined from the airborne measurements of the wavefield using these techniques observed spatial profiles of energy flux and wave energy dissipation rates over the lei reef lagoon system are presented the results show that the high lidar backscatter intensity and point density coming from the high reflectivity of the foam from depth limited breaking waves coincides with the high wave energy dissipation rates good correlations between the airborne measurements and in situ observations demonstrate that it is feasible to apply airborne lidar systems for large scale long term studies in monitoring important physical processes in coral reef environments when added to other airborne techniques the opportunities for efficient monitoring of large reef systems may be expanded significantly

a case study of wave current interaction near an oceanic front high resolution directional wave spectrum data were obtained from two nasa airborne radars during the frontal air sea interaction experiment fasinex in february 1986 the observations show a significant change in the wave number spectrum across the front on the basis of surveys from a towed sensor and on satellite imagery the front location and current field are estimated a numerical model is developed for the wave current interaction and is used to model the wave refraction across the frontal current a parametric study is performed to demonstrate the effects of current meandering the main consequence of meandering is the formation of caustics and shadow zone regions in which the wave energy is significantly enhanced or reduced spectral simulation along the aircraft track reveals a reduction of more than 60 in wave energy in the shadow zone this is consistent with the observations

spatial variations of ocean wave directional spectra from the seasat synthetic aperture radar seasat synthetic aperture radar ocean wave spectra for a 900 km pass are analyzed and interpreted in the context of both their probable generation sources and their surface current and bathymetric modifiers systematic vector wavenumber variations of several times the standard error of determination 1 5 in magnitude and 0 9 in direction occur along the entire 900 km pass the large scale spatial variation of a 200 m swell system can be accurately accounted for as a result of dispersion from a distant storm the more local variations are qualitatively well correlated in position with known currents and bathymetry but show systematic biases that appear partly due to an environmentally dependent instrument transfer function in the regions of high current and highest sea state there is also substantial evidence that a large angular deviation in the center of the pass is the result of a mesoscale eddy just to the east

compound specific isotope analysis as a tool for characterizing mixed oils an example from the west of shetlands area abstract the origin of an oil accumulation can be difficult to establish when the oil is a mixture from multiple sources or when multiple episodes of charging are involved in this study oils from the clair field west of shetland islands which are mixtures of nonbiodegraded oil added to biodegraded oil are characterized by comparing the carbon isotope ratios of the gasoline range hydrocarbons grh of the oil to the grh released from the pyrolysis of the asphaltenes in the oil this comparison allows characterization of the source of the first versus the second pulse of oil into the reservoir information useful in assessing the source potential of the basin

reworked triterpenoid and steroid hydrocarbons in a recent sediment abstract the distributions of steranes pentacyclic triterpanes and aromatic steroid hydrocarbons in core sections of a recent intertidal sediment bridgwater bay severn estuary u k have been examined by gas chromatography mass spectrometry depending on sample depth the distributions are explicable in terms of 1 i a reworked origin for these compounds from a geological source probably as a result of erosion of nearby organic rich sediments of lower liassic age or 2 ii a dual origin from both i and a more mature source probably an anthropogenic input of petroleum origin these results show that not all of these steroid and triterpenoid hydrocarbons in surface sediments necessarily result from fossil fuel pollution they indicate also that attention should be paid to the possibility of contributions from reworked components when using the distributions of these compounds in geochemical studies of sediments that are low in extractable organic matter

airborne scanning lidar measurement of ocean waves abstract a scanning lidar system provides high resolution three dimensional measurements of ocean wave displacement the airborne operation further enhances the speed of data acquisition these properties allow rapid characterization of the ocean wave environment in addition to active ranging the scanning optics can obtain passive measurements of surface emissivity yielding a digital image of surface brightness in real time processed into a binary image these measurements can provide information on the average statistics and the spatial distribution of breaking waves technical specifications of the system and examples of application are presented published by elsevier science inc

spatial statistics of the sea surface in fetch limited conditions abstractan analysis of airborne wave observations collected in the gulf of tehuantepec is presented the data include lidar measurements of the surface displacement as a function of two horizontal dimensions in fetch limited conditions with fetches between 20 and 500 km and winds between 10 and 20 m s 1 the spatial data have an advantage over the commonly used single point time series measurements allowing direct estimates of the wavelength and wave slope including spatial information such as the lengths of crests exceeding various thresholds this study presents an analysis of several statistical wind wave parameters including the joint probability distribution function pdf of wave amplitudes and wavelengths the pdf of wave heights wavenumber vectors and wave slopes as well as the statistics of the lengths of crests exceeding threshold wave heights and slopes the empirical findings from the lidar data are compared against analytical theories in the literature including some that had not been

fetch and duration limited nature of surface wave growth inside tropical cyclones with applications to air sea exchange and remote sensing abstractthe 2d wavenumber spectra collected by an airborne scanning radar altimeter in hurricane hunter missions are used to investigate the fetch and duration limited nature of wave growth inside hurricanes despite the much more complex wind forcing conditions the dimensionless growth curves obtained with the wind wave triplets reference wind velocity significant wave height and dominant wave period inside hurricanes except near the eye region are comparable to the reference similarity counterparts constructed with the wind wave triplets collected in field experiments conducted under ideal quasi steady fetch limited conditions in dimensionless terms the youngest waves are in the back quarter of the hurricane in the northern hemisphere the dimensionless frequency decreases systematically counterclockwise ccw and the most mature waves are in the left hand sector except for those waves near the eye region the dominant wave phase speeds are about 0 32 to 0 71 times of the local wind speed

hurricane directional wave spectrum spatial variation at landfall abstract the nasa scanning radar altimeter sra flew aboard one of the noaa wp 3d hurricane research aircraft to document the sea surface directional wave spectrum in the region between charleston south carolina and cape hatteras north carolina as hurricane bonnie was making landfall near wilmington north carolina on 26 august 1998 two days earlier the sra had documented the hurricane wave field spatial variation in open water when bonnie was 400 km east of abaco island bahamas bonnie was similar in size during the two flights the maximum wind speed was lower during the landfall flight 39 m s 1 than it had been during the first flight 46 m s 1 also bonnie was moving faster prior to landfall 9 5 m s 1 than when it was encountered in the open ocean 5 m s 1 the open ocean wave height spatial variation indicated that hurricane bonnie would have produced waves of 10 m height on the shore northeast of wilmington had it not been for the continental shelf the gradual shoaling distributed t

estimation of sea surface wave spectra using acoustic tomography ocean acoustic tomography signals that interact with the ocean surface suffer travel time perturbations which have information on the frequency direction spectrum of that surface in this paper a technique for tomographically estimating spatially varying frequency direction spectra is introduced to demonstrate this technique synthetic signal spectra data were generated using an empirical model for a fetch limited sea the synthetic data were then inverted using linear inverse techniques to produce an estimate of the original sea surface spectra inverse solutions for both noise free and noisy experiments are presented and discussed

the southern ocean waves experiment part i overview and mean results the southern ocean waves experiment sowex was an international collaborative air sea interaction experiment in which a specially instrumented meteorological research aircraft simultaneously gathered atmospheric turbulence data in the marine boundary layer and sea surface topography data over the southern ocean for a wide range of wind speeds the aim was to increase present knowledge of severe sea state air sea interaction this first paper presents an overview of the experiment and a detailed discussion of the methodology and mean results a companion paper describes the findings on variability of the wind speed and wind stress and their relationship to variations in the underlying sea surface roughness

airborne observations of fetch limited waves in the gulf of tehuantepec abstract the authors present airborne observations of fetch limited waves during strong offshore winds in the gulf of tehuantepec the measurements collected over a wide range of fetches include one and two dimensional surface wavenumber spectra and turbulent fluxes in winds up to 25 m s 1 the evolution of the wave spectra is in good agreement with the fetch relationships from previous observations the tails of the observed one dimensional k1 spectra in the dominant wave direction exhibit a power law over a wide range of wavenumbers the authors present the first quantification of the transition between the equilibrium and saturation ranges for the omnidirectional spectrum in the wavenumber domain the energy density within the equilibrium range shows a dependence on the wave age at wavenumbers higher than the spectral peak the width of the spectrum in the direction orthogonal to the dominant waves is nearly independent of the wave age however in the azimuthal direction the spreading of the sp

comparison of shuttle imaging radar b ocean wave image spectra with linear model predictions based on aircraft measurements during october 1984 coincident shuttle imaging radar b synthetic aperture radar sar imagery and wave measurements from airborne instrumentation were acquired the two dimensional wave spectrum was measured by both a radar ocean wave spectrometer and a surface contour radar aboard the aircraft in this paper we compare two dimensional sar image intensity variance spectra with these independent measures of ocean wave spectra to verify previously proposed models of the relationship between such sar image spectra and ocean wave spectra the results illustrate both the functional relationship between sar image spectra and ocean wave spectra and the limitations imposed on the imaging of short wavelength azimuth traveling waves

airborne measurements of the wavenumber spectra of ocean surface waves part i spectral slope and dimensionless spectral coefficient an airborne scanning lidar system acquires 3d spatial topography of ocean surface waves from the spatial data wavenumber spectra are computed directly the spectral analyses of two distinctively different wave fields are presented the first one is a quasi steady wave field under active wind generation and the second one is a decaying wave field following a slackening of the wind field subtle differences in different representations of the one dimensional spectrum omnidirectional marginal and traverse are illustrated the spectral properties in terms of the dimensionless spectral coefficient and spectral slope in the equilibrium range are investigated using the wavenumber spectra directly computed from the 3d topography of the ocean surface the results are in excellent agreement with existing data the rapid data acquisition afforded by an airborne system provides an enhanced capability for studying the spatial variation of a wave field with minimal temporal changes in the environmental forcing conditions the data of the 3d surface topography are also ideal for the quantitative investigation of the directional properties of a random wave field

on the estimation of wave slope and height varnance spectra from sar imagery a procedure is described for using synthetic aperture radar sar imagery to estimate two dimensional ocean wave slope and height variance spectra the logic underpinning the procedure is based both on the results of the numerical simulation of sar wave imagery and analytic descriptions of the sar imaging process the procedure when applied to sar imagery of waves acquired during the recent shuttle imaging radar mission sir b is shown to produce spectra that agree with independent measures of both the two dimensional slope and height variance spectra the implications of these results for future sar missions aimed at measuring ocean waves are considered

ocean surface wave spectra inside tropical cyclones abstractdirectional wave spectra acquired in hurricane reconnaissance missions are compared with wind wave spectral models the comparison result is quantified with two indices of model measurement spectral agreement in the main region of hurricane coverage the indices vary sinusoidally with the azimuth angle referenced to the hurricane heading while showing a weak dependence on the radial distance from the hurricane center the measured spectra agree well with three models evaluated in the back and right quarters and they are underdeveloped in the front and left quarters the local wind and wave directions also show a weak radial dependence and sinusoidal variation along the azimuth the wind and wave vectors are almost collinear in the back and right quarters they diverge azimuthally and become almost perpendicular in the left quarter the azimuthally cyclical correlation between the indices of spectral agreement and the wind wave directional difference is well described by the sinusoidal variations

airborne remote sensing of ocean wave directional wavenumber spectra in the marginal ice zone interactions between surface waves and sea ice are thought to be an important but poorly understood physical process in the atmosphere ice ocean system in this work airborne scanning lidar was used to observe ocean waves propagating into the marginal ice zone miz these represent the first direct spatial measurements of the surface wave field in the polar miz data were compared against two attenuation models one based on viscous dissipation and one based on scattering both models were capable of reproducing the measured wave energy the observed wavenumber dependence of attenuation was found to be consistent with viscous processes while the spectral spreading of higher wavenumbers suggested a scattering mechanism both models reproduced a change in peak direction due to preferential directional filtering floe sizes were recorded using co located visible imagery and their distribution was found to be consistent with ice breakup by the wave field

directional wave spectra measured with the surface contour radar abstract the surface contour radar is a 36 ghz computer controlled airborne radar which generates a false color coded elevation map of the sea surface below the aircraft in real time and can routinely produce ocean directional wave spectra with post flight data processing which has much higher angular resolution than pitch and roll buoys when compared with waveriders and the xerb and edeco pitch and roll buoys there is good agreement among the nondirectional spectra there is also good agreement among the angles associated with a1 b1 and a2 b2 fourier coefficients of the spreading function for xerb endeco and the surface contour radar there are indications that the pitch and roll buoys in this study may have calibration problems with the magnitudes of the fourier coefficients of the spreading function and that the radar system determines the fourier coefficients with significantly less noise and bias the high spatial resolution and rapid mapping capability over extensive areas make the surface

dependence of the microwave radar cross section on ocean surface variables comparison of measurements and theory using data from the frontal air sea interaction experiment the purpose of this investigation was to study the ability of theoretical radar cross section rcs models to predict the absolute magnitude of the ocean radar cross section under a wide variety of sea and atmospheric conditions the dependence of the rcs on wind stress as opposed to wind speed was also studied an extensive amount of experimental data was acquired during the frontal air sea interaction experiment fasinex this consisted of rcs data from the nasa jet propulsion laboratory ku band scatterometer mounted on a c130 aircraft 10 separate flights as well as a wide variety of atmospheric measurements including stress and sea conditions measurements across an ocean front demonstrated that the vertical polarization v pol and horizontal polarization h pol radar cross section were more strongly dependent on wind stress than on wind magnitude current theoretical models for the rcs based on stress were tested with this data in situations where the bragg scattering theory does not agree with the measured radar cross section magnitude and angle dependence revisions are hypothesized and evaluated for example the v pol theory worked well in most cases studied while the h pol theory was usually too low by about a factor of 2 at incidence angles of 50 and 60

estimating aircraft sar response characteristics and ocean wave spectra in the labrador sea extreme waves experiment the labrador extreme waves experiment lewex was an international effort to assess methods of measuring and modeling the directional aspects of wind generated ocean waves especially their evolution in the presence of rapidly turning winds the author describes data processing methods that have been developed to derive estimates of two dimensional wave height variance spectra from the ocean imagery obtained in lewex by a c band synthetic aperture radar sar system aboard a canadian cv 580 aircraft sar spectra at altitudes of 20000 and 12000 ft are compared for both large approximately 50 degrees and small approximately 25 degrees radar look angles independence spectral estimates from both a surface contour radar and a radar ocean wave spectrometer aboard a nasa aircraft are used to verify the surface wave spectrum

the occurrence of bisnorhopane trisnorhopane and 25 norhopanes as free hydrocarbons in some australian shales abstract the triterpenoid hydrocarbons of some west australian shales have been examined by gc ms in addition to the common 17 h 21 h hopanes 17 h 21 h hopanes and 17 h 21 h moretanes 28 30 bisnorhopane 25 28 30 trisnorhopane and 25 norhopanes were identified in the organic extracts in contrast pyrolysates of the solvent extracted sediments contained only the common hopane and moretane series indicating that 28 30 bisnorhopane 25 28 30 trisnorhopane and 25 norhopanes are not bonded to kerogen but rather are present in the sediments as free hydrocarbons

observation of sea ice using the 36 ghz surface contour radar in january 1984 a 36 ghz scanning pencil beam radar was used at 175 m altitude over ice in the greenland sea to produce high spatial resolution 3 m by 5 m topographic and backscattered power maps incidence angles from nadir to approximately 300 offnadir were included in the data set when the radar maps were compared with the ice topography indicated by simultaneous photography and an analysis of the shadows of the ridges cast by the low sun angle 3 5 it was found that the backscattered power data sharply delineated many of the features observed in the photography the elevation data were less impressive but still consistent with the general variation of the topography

gc ms characterisation of c27 and c28 triterpanes in sediments and petroleum abstract earlier studies have shown that an unusual c 27 triterpane is abundant in sediments from the norwegian continental shelf and the north sea this compound was assigned the tentative structures 24 28 30 trisnormoretane or 25 28 30 trisnormoretane but we have now shown from detailed retention time measurements and a reinterpretation of the mass spectral data that its correct structure is 17 h 18 h 21 h 25 28 30 trisnorhopane two other triterpanes 25 28 30 trisnormoretane and 28 30 bisnormoretane have also been identified as minor constituents of extracts of sediments from the north sea possible origins for these compounds are discussed

airborne remote sensing applications to coastal wave research airborne sensors provide effective coverage of a broad region and are suitable for large scale experiments in this paper two scanning sensors that use the direct ranging technique to measure surface wave displacement are described on a nasa p 3 aircraft the sensors can complete one run across a 100 km continental shelf in 17 min a case study is presented using radar measured two dimensional surface topography to derive wave damping due to bottom friction the results are in good agreement with an analytical model based on a quadratic formulation of bottom shear stress this study demonstrates that remote sensing measurements can be used for rapid characterization of surface waves on the continental shelf and in coastal regions examples illustrated in this paper include the derivation of wavenumber spectra and estimation of the dissipation rate of shoaling ocean swell

a numerical study of the retrieval of sea surface height profiles from low grazing angle radar data a numerical study of the retrieval of sea surface height profiles from low grazing angle radar observations is described the study is based on a numerical method for electromagnetic scattering from 1 d rough sea profiles combined with the ldquoimproved linear representationrdquo of creamer for simulating weakly nonlinear sea surface hydrodynamics numerical computations are performed for frequencies from 2975 to 3025 mhz so that simulated radar pulse returns are achieved the geometry utilized models a radar with an antenna height of 14 m observing the sea surface at ranges from 520 to 1720 m the low grazing angles of this configuration produce significant shadowing of the sea surface and standard analytical theories of sea scattering are not directly applicable three approaches for retrieving sea height profile information are compared the first method uses a statistical relationship between the surface height and the computed radar cross sections versus range an incoherent measurement a second method uses the phase difference between scattering measurements in two vertically separated antennas ldquovertical interferometry in the retrieval the final technique retrieves height profiles from variations in the apparent doppler frequency coherent measurements versus range and requires that time stepped simulations be performed the relative advantages and disadvantages of each of the three approaches are examined and discussed

numerical simulation of sea surface directional wave spectra under hurricane wind forcing numerical simulation of sea surface directional wave spectra under hurricane wind forcing was carried out using a high resolution wave model the simulation was run for four days as hurricane bonnie 1998 approached the u s east coast the results are compared with buoy observations and nasa scanning radar altimeter sra data which were obtained on 24 august 1998 in the open ocean and on 26 august when the storm was approaching the shore the simulated significant wave height in the open ocean reached 14 m agreeing well with the sra and buoy observations it gradually decreased as the hurricane approached the shore in the open ocean the dominant wavelength and wave direction in all four quadrants relative to the storm center were simulated very accurately for the landfall case however the simulated dominant wavelength displays noticeable overestimation because the wave model cannot properly simulate shoaling processes direct comparison of the model and sra directional spectra in all four quadrants of the hurricane shows excellent agreement in general in some cases the model produces smoother spectra with narrower directional spreading than do the observations the spatial characteristics of the spectra depend on the relative position from the hurricane center the hurricane translation speed and bathymetry attempts are made to provide simple explanations for the misalignment between local wind and wave directions and for the effect of hurricane translation speed on wave spectra

chemical molecular and isotopic differentiation of organic facies in the tertiary lacustrine duaringa oil shale deposit queensland australia abstract total organic matter extractable organic matter bitumen and pyrolysates released on low temperature sealed tube pyrolysis of kerogen were analysed chemically and isotopically based on bulk bitumen and biomarker parameters the sediments are immature to a depth of approx 1300 m within the terrestrial and lacustrine depositional environments of the tertiary duaringa basin various organic facies have been classified according to inorganic input and maceral abundances of organic matter derived from land plant and algal sources the latter derived mainly from pediastrum and with a varying botryococcus content the lacustrine upper lamosite is chemically and isotopically distinct from the lower lamosite due to a changing algal community relative contributions from allochthonous land plants and for the lower lamosite a slightly more saline and restricted lake environment the lower lamosite is associated with the highest concentrations of c 28 c 30 4 methylsteranes and 13 c depletion in toc in the upper lamosite there is a strong positive correlation between botryococcus content and 13 c enrichment the organically lean claystones have sources nearly identical to the lamosites but the organic matter is diluted due to rapid influx of siliciclastics the terrestrial facies the cannel coal and carbonaceous shales are mainly distinguished from the lacustrine facies by higher relative proportions of c 29 steranes c 30 4 methylsteranes and 13 c values for the pyrolysed hydrocarbons intermediate between the two lamosite facies the carbonaceous oil shale has a composite geochemical signature intermediate between the two end members lamosite and cannel coal oleanane and ring a degraded triterpanes derived from lupane arborane and oleanane skeletons are distributed throughout all organic facies representing both autochthonous and allochthonous higher plant inputs higher concentrations of oleanane and des a lupane are associated with the terrestrial facies hopanes dominate over steranes in all organic facies and their concentration ranges are independent of facies for the lamosites the aliphatic biopolymer algaenan is implicated as the dominant source for n alkanes from analysis of their yields homologue abundances and individual 13 c values in the terrestrial facies resinites are paraffinic and are a major source for the n alkanes released on pyrolysis compound specific analysis of extractable and pyrolysate hydrocarbons allowed deconvolution of different source inputs to free lipids and kerogen for the lamosites low molecular weight n alkanes in the bitumen are derived mainly from a pediastrum source while botryococcus is associated with waxy n alkanes however the situation is reversed in the kerogen pediastrum algeanan has a longer average alkyl chain length than botryococcus algaenan the magnitude of the isotopic differences between single n alkanes released at different temperatures is useful in determining multiplicity of sources

mapping surface currents and waves with interferometric synthetic aperture radar in coastal waters observations of wave breaking in swell dominant conditions airborne and spaceborne interferometric synthetic aperture radars insars produce surface velocity measurements at very high spatial resolutions over a large area the data allow construction of the velocity strain field for highlighting ocean surface processes such as wave breaking and rip currents also coherence between signals from two interferometric channels is a descriptor of the correlation condition of the surface roughness that scatters back the radar signals and it is an indication of the ocean surface turbulence wave breaking is a major turbulence source causing surface roughness decorrelation thus the coherence parameter serves as an independent means for detecting wave breaking the results of breaking detection using roughness decorrelation and critical local acceleration are comparable in this paper the breaking fraction in swell dominant mixed seas along a cross shore transect is compared with several steepness parameters characterizing different length scales of surface waves the highest correlation coefficient from 0 90 to 0 99 is between the breaking fraction and windsea mean square slope contributed primarily by short waves this result reinforces the previous field observations showing that the length scales of breaking waves are much shorter than the energetic components near the spectral peak although dominant waves and the associated wave group modulation are important in triggering the breaking process the large spatial coverage of airborne or spaceborne operation further offers the opportunity to investigate evolution of the surface wave spectrum in high spatial subkilometer resolution this capability is very useful for monitoring the coastal wave and current environment

upper ocean response to hurricane gilbert the evolving upper ocean response excited by the passage of hurricane gilbert september 14 19 1988 was investigated using current and temperature observations acquired from the deployment of 79 airborne expendable current profilers axcps and 51 airborne expendable bathythermographs from the national oceanic and atmospheric administration wp 3d aircraft in the western gulf of mexico the sea surface temperatures ssts mixed layer depths and bulk richardson numbers were objectively analyzed to examine the spatial variability of the upper ocean response to gilbert net decreases of the ssts of 3o 4oc were observed by the profilers as well as by the airborne infrared thermometer airt along the flight tracks and advanced very high resolution radiometer avhrr imagery the axcps indicated a marked cooling from 29oc to about 25 5oc on september 17 1988 which was about 1 2 inertial periods ip following storm passage this pool of cooler water 3 5 o was located further downstream in the hurricane wake by september 19 2 7 ip following the storm as a result of the near inertial currents in the mixed layer while there was a bias of about 0 6oc and 1 7oc between the in situ and avhrr derived ssts respectively both the avhrr images and the objectively analyzed fields indicated a rightward bias in the upper ocean cooling that extended from the storm track to about 4rmax where rmax the radius of maximum winds is equal to 50 km the larger sst offset of 1 7oc was due to the difference between the time of the avhrr image and the time of the aircraft experiment on september 19 the ssts derived from the avhrr images and the airt also indicated large gradients between the cold wake and the warm eddy in the central gulf of mexico the mixed layer deepened by about 30 35 m on the right side of the track during the storm and 1 2 ip later with little evidence of continued deepening afterward the mixed layer current vectors demonstrate that a strong near inertially rotating current was excited by the passage of gilbert with maxima of about 1 1 4 m s 1 the currents observed during and subsequent to 1 2 ip the storm diverged from the storm track whereas the mixed layer current vectors 2 7 ip after storm passage converged toward the track with relative maxima of 0 8 1 m s 1 this alternating pattern of convergence and divergence of the mixed layer current was associated with the upwelling and downwelling cycles of the baroclinic response considerable current shear existed between the mixed layer and the thermocline currents in the cool wake between the storm track and the 4rmax estimates of the bulk richardson numbers ranged between 0 2 and 1 0 during gilbert and at 1 2 ip which suggests that enhanced current shears were responsible for some of the mixed layer deepening

airborne remote sensing of wave propagation in the marginal ice zone airborne scanning lidar was used to measure the evolution of the surface wave field in the marginal ice zone miz during two separate wave events in the beaufort sea in october 2015 the lidar data consisted of a 2 d field of surface elevation with horizontal resolutions between 17 and 33 cm over a swath approximately 150 220 m wide centred on the ground track of the aircraft those data were used to compute directional wavenumber spectra of the surface wave field comparison with nearly collocated buoy data found the lidar and buoy measurements to be generally consistent during the first event waves traveling from open water into the ice were attenuated by the ice the low spectral spreading and k7 4 spectral dependence of the attenuation was consistent with dissipative models that treat sea ice as a highly viscous fluid floating on a less viscous ocean upper ocean eddy viscosities calculated using that model were found to be significantly lower than those from previous work the second event was in off ice winds and cold temperatures allowing measurement of the wave fetch relation in ice forming conditions the wave growth rate was found to be slightly higher than previous measurements under unstable atmospheric conditions without ice formation comparison with wavewatch iii model output highlighted the importance of accurate ice information and fine geographic computational resolution when making predictions near the ice edge finally the very short scales over which the wave field was observed to evolve in the miz are discussed