convectively forced internal gravity waves results from two dimensional numerical experiments two dimensional numerical simulations were performed to investigate the nature of tropospheric internal gravity waves of the type which are observed to occur above active thermal convection over an unstable boundary layer these gravity waves are believed to be excited by a combination of pure thermal forcing and by the boundary layer eddies and cumulus clouds acting as obstacles to the flow in the presence of mean environmental wind shear large amplitude internal gravity waves were obtained in the simulations with amplitudes and horizontal scales similar to the 12 june 1984 aircraft observations over western nebraska this was a day with strong wind shear in the lowest 3 km above the ground and with scattered cumulus clouds topping the boundary layer the simulations show that there is significant difference between the early time solutions as might be predicted by linear theory and late time solutions for the boundary layer eddy structure a layer interaction occurs in which gravity waves of the stable layer are excited by the boundary layer convection there is evidence to suggest that this layer interaction occurs both with and without shear but that it is stronger in the presence of low level shear results indicate that shear or the obstacle effect is a more efficient generator of gravity waves than is the pure thermal forcing the simulations show that the gravity waves initially forced by the boundary layer eddies lead to a feedback mechanism that acts to organize the boundary layer eddies and the cumulus convection the solutions suggest that the character of fair weather convection moist or dry is a non local problem involving at times the full depth of the troposphere the clouds produced in the simulations have very little influence on the wave field or boundary layer eddy structure as they are relatively small cumuli on the other hand the clouds are strongly influenced by the interactions between the wave and eddy fields upshear growth of cumulus clouds similar to that which is frequently observed in nature is reproduced in the simulations the development of feeder feeder is used here in a dynamical sense only clouds on typically the upshear side of the cloud is found to be a result of the interaction between the gravity wave field and the dry and moist convection the relative phase velocity between the gravity waves and the cloud plays a crucial role in determining the character of the cumulus cloud growth in the present simulations these simulations suggest that the dynamics both internal and external to the boundary of a cumulus cloud is a complicated mix between wave dynamics and the usually considered convection dynamics a brief discussion of the implications of the present results to cloud boundary baroclinic instability dynamics is also presented

heat flow along the nantroseize transect results from iodp expeditions 315 and 316 offshore the kii peninsula japan mal conductivity varies between about 1 0 w m 1 k 1 near the seafloor to 1 6 w m 1 k 1 at a depth of 1 km thermal conductivity generally increases with depth and correlates with variations in porosity and lithology thermal gradients along the transect are characterized by 48 sediment temperature measurements from 6 sites thermal corrections for the effects of bathymetric relief and sedimentation improve the confidence with which the heat flow values can be interpreted heat flow generally decreases with landward distance from the deformation front and varies from 70 mw m 2 just landward of the deformation front to 54 mw m 2 at sites characterizing the outer fore arc high and to 57 mw m 2 at the kumano basin site iodp heat flow measurements are significantly lower than nearby seafloor heat flow measurements this difference is most likely due to variations in bottom water temperature that have a large effect on values of seafloor heat flow thus the heat flow of the nankai accretionary prism is lower than previously thought we present thermal models of subduction along this transect and explore the impact of the initial geotherm conductive plate cooling based on the age of subducting seafloor 20 myr under predicts the observed heat flow we find a good fit to the data using a geotherm appropriate for 10 myr seafloor the extra heat is interpreted in terms of back arc thermal environments

heat flow and age of the gulf of oman we present the results of twenty heat flow stations in the gulf of oman which are used to infer the first reliable age estimates for the basin a mean surface heat flux of 42 6 3 6 mw m 2 exhibits no significant regional variation after correction for thick and rapidly deposited sediments this yields an age of 70 to 100 ma according to oceanic thermal models this age is also consistent with the sediment corrected basement depths of 5 5 6 0 km and with formation during the cretaceous quiet zone the latter can explain the absence of magnetic sea floor spreading lineations heat flow measurements are also used to confirm the presence of gas hyrdate layers the measured thermal gradient yields a depth for the solid to free gas phase transition which is the same as that deduced from bright spots seen on seismic reflection profiles

the vertical chloride ion profile at the iodp site c0002 kumano basin off coast of japan abstract the vertical profiles of chloride ion cl concentration and oxygen and hydrogen isotopic ratios in pore fluids of basin fill sediments in the southern kumano basin were examined a model has been proposed to explain those profiles in conjunction with published data by invoking diffusion and advection of freshwater from methane hydrate dissolution the model requires a low initial cl concentration in the old accretionary prism below the basin before the basin began to fill with sediments it also requires little or no methane hydrate formation in the old accretionary prism given these requirements an upward fluid advection rate of 1 10 12 m s has been estimated which is very low compared to other accretionary prisms our data suggests that the tectonic compaction of the basin filling sediments and fault activity under the basin sediments have not been that active recently in the kumano basin

thermal diffusivity measurements of porous methane hydrate and hydrate sediment mixtures 1 an experiment has been constructed to measure thermal diffusivity of methane hydrate and methane hydrate sand sediment mixtures thermal diffusivities of porous methane hydrate 40 pore space filled with methane gas and mixtures of methane hydrate with platte valley sand and blake ridge sediment have been measured between the temperature range 265 k and 281 k at pressures between 4 35 and 7 65 mpa thermal diffusivities of porous methane hydrate ranged between 3 1 10 7 and 3 3 10 7 m2 s thermal diffusivity of 0 4 porosity methane hydrate was found to have inverse dependence on temperature whereas the thermal diffusivity of methane hydrate sediment sand mixtures has positive temperature dependence thermal diffusivity of methane hydrate sand sediment mixtures increased with increasing hydrate volume fraction to a maximum between about 30 and 35 vol in sand and between about 20 and 40 vol in sediment after the maxima the thermal diffusivities decreased with increasing hydrate volume fraction

the marine atmospheric boundary layer during semaphore i mean vertical structure and non axisymmetry of turbulence this paper describes the vertical structure of the marine atmospheric boundary layer analysed using aircraft measurements in the azores region during semaphore structure des echanges mer atmosphere proprietes des heterogeneites oceaniques recherche experimentale the flights were performed in the middle of the solar day during near anticyclonic conditions with weak to moderate winds and weak surface sensible heat flux over a homogeneous oceanic area the boundary layer was characterized by a mixed layer driven by surface fluxes which was not coupled to the overlying broken stratocumulus layer this decoupling is demonstrated by the shape of the continuous profile of the dissipation rate of turbulent kinetic energy computed from the continuous slant profiles performed by the aircraft this method makes it possible to determine the thickness of the mixed layer which is a relevant scale for the parametrization of the profiles the turbulence field is analysed through the wavelength of the spectrum peak of the vertical velocity computed on 392 runs more or less parallel or perpendicular to the mean wind it demonstrates a stretching of the most energetic eddies along the mean wind the consequences of this non axisymmetric behaviour of the turbulent field on the flux estimates from aircraft data are discussed

india national gas hydrate program expedition 02 operational and technical summary abstract the india national gas hydrate program is being steered by the government of india s ministry of petroleum and natural gas mopng with participation of directorate general of hydrocarbons dgh oil and natural gas corporation limited ongc and the national oil companies and research institutes of india the india national gas hydrate program expedition 01 nghp 01 established the presence of gas hydrate in the krishna godavari kg and mahanadi basins and in the offshore area of the andaman sea basin however the gas hydrates discovered during nghp 01 were mainly distributed as fracture filling material in fine grained clay rich sediments the india national gas hydrate program expedition 02 nghp 02 was carried out with an objective to discover gas hydrate in sand rich sediment along the eastern offshore margin of india ongc planned and executed nghp 02 on the behalf of the mopng nghp 02 started on march 3 2015 and was completed on july 28 2015 total 147 days using the japanese scientific drilling vessel chikyu d v chikyu during nghp 02 42 holes at 25 sites were drilled cored and or surveyed with downhole logging tools these sites were located in four areas along the eastern margin of india and formally named area a mahanadi basin three sites area b northern part of the kg basin twelve sites area c central part of the kg basin six sites and area e southern part to the kg basin four sites all 25 sites established during nghp 02 were first drilled and logged with logging while drilling lwd tools and an additional 17 holes were then drilled and or cored with conventional coring tools hpcs escs or pressure coring tools pctb wireline logging was conducted in 10 holes and formation tests using a dual packer modular formation dynamics tester mdt tool were carried out in two holes the onboard science team used the laboratory facilities on the d v chikyu to examine and analyse the physical properties geochemistry and sedimentology of all the cores collected during the expedition core samples were also analysed in additional post expedition shore based studies conducted in numerous domestic and international gas hydrate research laboratories the nghp 02 sediment cores were archived at the national gas hydrate core repository in mumbai india which is associated with the ongc gas hydrate research and technology centre ghrtc the necessary data for characterizing the occurrence of gas hydrate such as interstitial water chlorinities core derived gas chemistry physical and sedimentological properties thermal images of the recovered cores pressure core and downhole measured logging data lwd and or conventional wireline log data were obtained from most of the drill sites established during nghp 02 almost all the drill sites yielded evidence for the occurrence of gas hydrate however the inferred in situ concentration of gas hydrate varied substantially from site to site for the most part the interpretation of downhole logging data core thermal images interstitial water analyses and pressure core images from the sites established during nghp 02 indicate that the occurrence of concentrated gas hydrate is mostly associated with coarser grained sand rich sediments this paper presents the operational and technical summary of nghp 02

a line of convection embedded in a stratocumulus topped boundary layer during the southern ocean cloud experiment a line of convection embedded in an otherwise homogeneous stratocumulus layer was sampled at four levels by means of an instrumented aircraft at the lower levels there was an abrupt change in microphysical and thermodynamic properties from the updraught region to the environment at the upper level the change was more gradual and extended over a larger region indicating the spreading out of the convective region underneath the strong inversion capping the boundary layer precipitation was observed at all levels even in the convective region except near its centre core vertical velocity fluctuations in the convective region near the inversion were indistinguishable from the surroundings at these high levels the horizontal wind in the convective region was from the same direction as the air close to the surface but was at an angle of up to 60 with the horizontal wind from the surroundings the convective region was characterized by cloud droplet concentrations that were often more than double those recorded in the surrounding cloud this indicates that the modifications to the cloud droplet spectra associated with the onset of precipitation starts in the convective region and is enhanced in the stratiform region

generalization of gas hydrate distribution and saturation in marine sediments by scaling of thermodynamic and transport processes gas hydrates dominated by methane naturally occur in deep marine sediment along continental margins these compounds form in pore space between the seafloor and a sub bottom depth where appropriate stability conditions prevail however the amount and distribution of gas hydrate within this zone and free gas below can vary significantly at different locations to understand this variability we develop a one dimensional numerical model that simulates the accumulation of gas hydrates in marine sediments due to upward and downward fluxes of methane over time the model contains rigorous thermodynamic and component mass balance equations that are solved using expressions for fluid flow in compacting sediments the effect of salinity on gas hydrate distribution is also included the simulations delineate basic modes of gas hydrate distribution in marine sediment including systems with no gas hydrate gas hydrate without underlying free gas and gas hydrate with underlying free gas below the gas hydrate stability zone for various methane sources the results are scaled using combinations of dimensionless variables particularly the peclet number and damkohler number such that the dependence of average hydrate saturation on numerous parameters can be summa rized using two contour maps one for a biogenic source and one for upward flux from a deeper source simulations also predict that for systems at steady state large differences in parameters like seafloor depth seafloor temperature and geothermal gradient cause only small differences in average hydrate saturation when examined with scaled variables although important caveats exist our model presents a unified picture of hydrate accumulations that can be used to understand well characterized gas hydrate systems or to predict steady state average hydrate saturation and distribution at locations for which seismic or core data are not available

anomalous temperatures in central scotia sea sediments bottom water variation or pore water circulation in old ocean crust we report low temperature gradients from 60 to 12 of geothermal and extrapolated temperatures offset from modern bottom water temperatures in sediments from the central scotia sea we examine possible causes bearing in mind similar anomalous measurements 18 years previously attributed at the time to instrumental error small temperature offsets 0 1 c may reflect short term bottom temperature variation within eddies of the antarctic circumpolar current low sediment temperature gradients may be caused by horizontal advection of cold water within the upper oceanic basaltic layer documented in younger ocean floor elsewhere or by northward encroachment of colder bottom waters from the antarctic peninsula shelf or weddell sea for several years prior to measurement

a comparison of broadband and narrow band modal inversions for bottom geoacoustic properties at a site near corpus christi texas detailed comparison between narrow band and broadband techniques used in a series of acoustic experiments are presented with emphasis on a comparisons of the pressure field versus range predicted b comparisons of the bottom compressional wave speed model generated c the variance of the bottom model estimated and d the resolution of the bottom model generated the range dependence of the bottom medium and the seasonal dependence of the near surface sediment sound speed profile are observed and discussed

heat flow in the balearic and tyrrhenian basins western mediterranean we present the results of three detailed heat flow surveys which are used to investigate the variations of heat flow and age of the balearic and tyrrhenian basins in the western mediterranean analysis of 12 measurements within a 10 km radius from 40 01 4 55 e in the balearic abyssal plain shows a mean heat flow of 92 10 mw m 2 after correction for the effects of sedimentation this value agrees well with the predictions of plate cooling and high extension stretching models for crust of the late oligocene age proposed for the basin a similar survey with 18 measurements around 40 16 n 11 19 e in the western tyrrhenian gives a flux of 134 8 mw m 2 while the third survey of 26 measurements in the southern tyrrhenian abyssal plain at 37 17 n 12 58 e yields a slightly higher heat flow of 151 10 mw m 2 these values are within the range predicted by simple plate cooling models for the late miocene ages of the deep tyrrhenian basin thus our observations suggest that although the mode of crustal formation of these deep marginal basins is less well defined than that of the major ocean basins the thermal signature is similar also the trend of increasing heat flow from west to east through the balearic and tyrrhenian basins is in agreement with models of the formation of the western mediterranean behind an eastwardly migrating trench system in all three areas the measured flux shows significant local variability in the two westernmost surveys this can be attributed to the presence of buried high conductivity salt structures but in the third area se tyrrhenian the magnitude of the variations is several times greater than can be attributed to steady state thermal refraction alone instead evidence exists for localized hydrothermal activity linked to the small topographical relief within the survey area

multi measurement approach for establishing the base of gas hydrate occurrence in the krishna godavari basin for sites cored during expedition nghp 02 in the offshore of india abstract the 2015 national gas hydrate program of india s second expedition nghp 02 acquired logging and coring datasets for constraining the base of the gas hydrate occurrence zone deepest gh and the theoretical base of gas hydrate stability zone bghs these data are used here for two primary goals to constrain the deepest occurrence of gas hydrate relative to predicted stability limits and the observed bsr and to characterize the nature of the contact between gas hydrate bearing sediment and the underlying gas hydrate free sediment a consensus depth for the deepest gh is derived for each nghp 02 coring site from downhole indicators of gas hydrate occurrence obtained from well log electrical resistivity and acoustic data pressure core compressional wave velocity measurements and conventional core measurements of anomalously low temperatures to establish the theoretical bghs models of gas hydrate phase stability with depth are compared with downhole temperature profiles derived from 1 assuming a constant geothermal gradient consistent with downhole temperature measurements and 2 assuming constant heat flow using a geotherm through the downhole temperature measurements and incorporating thermal conductivity calculated from borehole logging data although the deepest nghp 02 gh occurrences are controlled at several sites by a lithologic boundary most sites have deepest gh occurrences within a single coarse grained lithology cutoffs within a single coarse grained lithology which occur for the primary nghp 02 area b gas hydrate reservoir will inhibit pore pressure drawdowns used to extract methane from gas hydrate as an energy resource

evolution of heat flow hydrothermal circulation and permeability on the young southern flank of the costa rica rift we analyze 67 new conductive heat flow measurements on the southern flank of the costa rica rift crr heat flow measurements cover five sites ranging in oceanic crustal age between approximately 1 6 and 5 7 ma and are co located with a high resolution multi channel seismic line that extends from slightly north of the first heat flow site 1 6 ma to beyond odp hole 504b in 6 9 ma crust for the five heat flow sites the mean observed conductive heat flow is 85 mwm 2 this value is approximately 30 per cent of the mean lithospheric heat flux expected from a half space conductive cooling model indicating that hydrothermal processes account for about 70 per cent of the heat loss the advective heat loss fraction varies from site to site and is explained by a combination of outcrop to outcrop circulation through exposed basement outcrops and discharge through faults super critical convection in layer 2a extrusives occurs between 1 6 and 3 5 ma and flow through a thinly sedimented basement high occurs at 4 6 ma advective heat loss diminishes rapidly between 4 5 and 5 7 ma which contrasts with plate cooling reference models that predict a significant deficit in conductive heat flow up to ages 65 10 ma at 5 7 ma the crr topography is buried under sediment with an average thickness 150 m and hydrothermal circulation in the basement becomes sub critical or perhaps marginally critical the absence of significant advective heat loss at 5 7 ma at the crr is thus a function of both burial of basement exposure under the sediment load and a reduction in basement permeability that possibly occurs as result of mineral precipitation and original permeability at the time of formation permeability is a non monotonic function of age along the southern flank of the crr in general agreement with seismic velocity tomography interpretations that reflect variations in the degree of ridge axis magma supply and tectonic extension hydrothermal circulation in the young oceanic crust at southern flank of crr is affected by the interplay and complex interconnectedness of variations in permeability sediment thickness topographical structure and tectonic and magmatic activities with age

geophysical inversion using approximate equality constraints current inversion methods estimating a physical property on a grid use two kinds of constraints 1 absolute constraints requiring that the solution vector be close to a prespecified vector as for example proximity to the null vector in the ridge regression and 2 relative constraints requiring that the elements of the solution vector be close to each other as for example smoothness imposed by methods requiring that spatial derivatives of the physical property be continuous using just absolute constraints may produce a biased solution conflicting with some true geological attributes of the source on the other hand using just relative constraints may be insufficient to stabilize the inversion we present a stable inversion method incorporating absolute constraints only at points where the physical property is known as for example outcroppings and boreholes elsewhere relative constraints are introduced according to a linear relationship for the spatial distribution of the physical property the proposed method is analogous to an interpolation method applied to the physical property distribution the interpolating function must satisfy some property like continuity and pass through the data the proposed method is versatile in incorporating not only factual but also indirect information such as continuity symmetry and trends in addition it may be applied both to linear and nonlinear problems the relevant results obtained from applying the method to synthetic potential field data were 1 ability to produce reliable mappings of the basement relief of a sedimentary basin from gravity data and of an areal distribution of magnetization using only smoothness constraints and restricted surface and borehole information 2 operational simplicity because of the solution insensitivity to the damping parameter the method is also applied to the bouguer anomaly over san jacinto graben california producing results consistent with previous interpretations

the relative effects of sound speed variability in the water column versus the seabed on normal mode propagation in shallow water normal mode propagation in shallow water is influenced by variations in the acoustic properties of both the water column and the seabed specifically the sound speed in the water may fluctuate due to the passage of an internal wave while the sound speed in the bottom may change due to variable geological features assessing the relative effects of the water column versus the seabed on the characteristics of modal propagation is critical to the understanding of both the forward and inverse problems in shallow water acoustics in this paper perturbation theory is combined with a pekeris waveguide model to provide an analytic formalism for evaluating the delicate interplay between the water column and the seabed in shallow water propagation in particular the relative contributions of sound speed fluctuations in the water and the bottom to variations in the modal eigenvalues are determined the results are affected by both the strengths of the fluctuations and the magnitudes of the background modal eigen

tomographic inversion for sediment parameters in shallow water this article discusses inversions for bottom geoacoustic properties using broadband acoustic signals obtained from explosive sources the experimental data used for the inversions are sus charge explosions acquired on a vertical hydrophone array during the shelf break primer experiment conducted south of new england in the middle atlantic bight in august 1996 the sus signals were analyzed for their time frequency behavior using wavelets the group speed dispersion curves were obtained from the wavelet scalogram of the sus signals a genetic algorithm ga was used for the inversion of sound speeds in the water column and compressional wave speeds in the sediment layers the variations in the sound speeds in the water column were represented using empirical orthogonal functions eofs a range independent normal mode routine was used to construct the replica fields corresponding to the parameters comparison of group speeds for modes 1 to 9 and for a range of frequencies 8 to 200 hz was used to arrive at the best parameter fit an efficient hybrid optimization scheme using the ga and a levenberg marquardt algorithm is presented linear perturbation methods were also used to fine tune the inversions and to obtain resolution and variance estimates analysis was also done to compute the degree of convergence of each of the parameters by explicitly calculating the hessian matrices numerically a posteriori estimation of mean and covariance was also done to obtain error estimates group speeds for the inverted sound speed fields provide an excellent match to the experimental data the inverted sediment compressional speed profile compares well with in situ measurements

the impact of water column variability on horizontal wave number estimation and mode based geoacoustic inversion results the influence of water column variability on low frequency shallow water geoacoustic inversion results is considered the data are estimates of modal eigenvalues obtained from measurements of a point source acoustic field using a horizontal aperture array in the water column the inversion algorithm is based on perturbations to a background waveguide model with seabed properties consistent with the measured eigenvalues water column properties in the background model are assumed to be known as would be obtained from conductivity temperature and depth measurements the scope of this work in addressing the impact of water column variability on inversion is twofold range dependent propagation effects as they pertain to eigenvalue estimation are first considered it is shown that mode coupling is important even for weak internal waves and can enhance modal eigenvalue estimates second the effect of the choice of background sound speed profile in the water column is considered for its impact on the estim

interrelation between surface and basement heat flow in sedimentary basins petroleum system models psm result critically depend on the computed evolution of the temperature field as psm typically only resolve the sedimentary basin and not the entire lithosphere it is necessary to apply a basement heat flow boundary condition inferred from well data surface heat flow measurements and an assumed tectonic scenario the purpose of this paper is to assess the use of surface heat flow measurements to calibrate basin models we show that a simple relationship between surface and basement heat flow only exists in thermal steady state and that transient processes such as rifting and sediment deposition will lead to a decoupling we study this relationship in extensional sedimentary basins with a 1d lithosphere scale finite element model the numerical model was built to capture the large scale dynamic evolution of the lithosphere and simultaneously solve for transient thermal processes in basin evolution such as sedimentation compaction driven fluid flow and seafloor temperature variations our analysis shows that several corrections need to be applied when using surface heat flow information for the calibration of basement heat flow in psm not doing so can lead to significant errors of up to 30 50 c at typical petroleum reservoir and source rock depths we further show that resolving sediment blanketing effects in basin modeling is crucial with the thermal impact of sediment deposition being at least as important as rifting induced basement heat flow variations

the structure of gradually transforming marine stratocumulus during the astex first lagrangian experiment summary an analysis of the mean and turbulent structure of the planetary boundary layer is presented using aircraft data obtained during the atlantic stratocumulus transition experiment e rst lagrangian experiment the analysis of the mean vertical structure relies mostly on slant proe le data however part of the analysis also uses socalled porpoise runs in the vicinity of the cloud top the analysis of the turbulence structure utilizes all of the data horizontal eight legs as well as slant proe les and presents both scaled turbulence statistics and a spectral analysis the purpose is to investigate details in the temporal development of the e rst lagrangian experiment and to study the turbulent structure in order to e nd scale relations that can be utilized in improved modelling of the stratocumulus capped boundary layer the hypothesis is that so called cloud decoupling has a signie cant impact on the turbulence scaling the measured cloud water is corrected to become consistent between the two participating aircraft the corrected maximum cloud water is more constant in time than in previous studies of the erst lagrangian it is suggested that previously analysed temporal variability may be an artefact of using two different instruments to measure cloud water the cloud top jump in equivalent potential temperature is positive in the erst three eights sufe ciently large for a stable cloud top but decreases and becomes negative for the last two eights in line with the breaking up of the cloud eeld the upper part of the boundary layer warms and dries more rapidly than the lower suggesting entrainment to be a dominant factor in the development of the cloud the analysis of the porpoise e ight legs illustrates how sharp features at the cloud top inversion are smoothed out while analysing several proe les eight legs or even entire eights rather than normalizing each proe le with the height to the local cloud top scaling of the turbulent e uxes and the velocity variances shows that the cloud layer is decoupled throughout almost the entire erst lagrangian it is also shown that while surface layer scaling is appropriate for the marine atmospheric boundary layer mabl the cloud layer turbulence scales with convective scaling the lowfrequency spectrum has no spectral gap with the exception of the vertical velocity and continues to increase with decreasing frequency with only a change in slope this indicates the presence of mesoscale motions the cospectra of the turbulent euxes are very noisy throughout when averaging several spectra into height intervals the scales of the turbulence as indicated by the peak in the averaged spectra appear to vary with height above the surface in the mabl but to be height independent in the cloud layer an attempt to calculate a dissipation length scale shows scatter but is consistent with a dissipation length scale increasing linearly with height in the mabl but being roughly constant or possibly parabolic with height in the cloud layer

on the relationship among cloud turbulence droplet formation and drizzle as viewed by doppler radar microwave radiometer and lidar cloud radar microwave radiometer and lidar remote sensing data acquired during the atlantic stratocumulus transition experiment astex are analyzed to address the relationship between 1 drop number concentration and cloud turbulence as represented by vertical velocity and vertical velocity variance and 2 drizzle formation and cloud turbulence six cases each of about 12 hours duration are examined three of these cases are characteristic of nondrizzling boundary layers and three of drizzling boundary layers in all cases microphysical retrievals are only performed when drizzle is negligible radar reflectivity 0 5 between radar reflectivity and in cloud vertical velocity variance although one of the boundary layers that experienced drizzle exhibited a negative correlation between these parameters however in the subcloud region all boundary layers that experienced drizzle exhibit a negative correlation between radar reflectivity and vertical velocity variance

variations in heat flow across the ocean continent transition in the iberia abyssal plain abstract new heat flow observations have been made in the iberia abyssal plain off the galicia margin along the transect of ocean drilling program leg 149 drill sites in order to investigate the nature of this unusually wide and deep continent ocean transition region our results indicate the presence of three separate zones average values of 47 5 3 mw m 2 in the westernmost zone iii agree with predictions of standard oceanic lithospheric models for its estimated age of 126 ma in contrast the heat flow within zone ii is 5 15 mw m 2 higher than predicted assuming that the mantle heat flow remains constant across the basin this region of high values is coincident with the location of a major intra crustal s type reflector east of odp site 900 and the anomaly is consistent with the presence of 2 3 km of primarily upper continental crust above the reflector with concentrations of radiogenic components similar to those from granodiorite samples dredged off galicia bank it is not however consistent with the low values of heat production measured on gabbroic samples from its western end at odp site 900 in zone i detailed measurements across the tilted fault block south of odp site 901 show consistent variations which closely match predictions due to the effects of basement structure and sediment deposition there is no evidence for variations due to vertical convective transport along the dipping basement fault block once corrected for these variations measurements in zone 1 yield average values that agree quite well with previous measurements across galicia bank indicating no systematic landward increase in heat flow with decreasing amounts of continental extension

heat flow and depth versus age for the mesozoic northwest atlantic ocean results from the sohm abyssal plain and implications for the bermuda rise abstract heat flow in the sohm abyssal plain is measured to be 53 mw m 2 at an age of 163 ma this is 25 higher than predicted by conductive cooling models even though the sediment corrected basement depth of 6 5 km at this location is normal for its age an analysis of existing heat flow depth and geoid anomalies in the northwest atlantic shows that there is little correlation between heat flow and depth throughout the entire region depth and geoid are clearly related to the bermuda swell while the associated heat flow anomaly once adjusted for variations with age is limited to 5 mw m 2 and only decays to the south this means that the bermuda swell is probably not caused by extensive thermal reheating within the lithosphere but instead by dynamic uplift at its lower boundary due to the convective upwelling of a mantle plume the regionally high heat flow in the northwest atlantic may be a thermal remanent of previous plumes which passed beneath this region early in its history therefore depth and heat flow anomalies from this region cannot be used to provide constraints on steady state parameters of the lithosphere such as the presence or absence of a long term boundary layer at its base

geoacoustic inversion on the new jersey margin along and across the shelf this paper presents results of a range independent perturbative inverse approach applied to data from the shallow water experiment 2006 the inversion technique is based on a linearized relationship between sound speed in the sediment and modal eigenvalues horizontal wave numbers were estimated from data collected from two distinct source receiver tracks oriented along and across the shelf the specific inversion algorithm used is based on qualitative regularization and uses known information about the environment to constrain the solution locations of the r reflector and other layering information are used as a priori information for the inversion to emphasize the layered structure of the sediment

inversion of needle probe data for sediment thermal properties of the eastern flank of the juan de fuca ridge 1 an estimation method is introduced for measuring thermal conductivity thermal diffusivity and heat capacity of sediment from temperatures using a needle probe this method is based on the continuous cylindrical heat source model thermal conductivity is estimated from needle probe temperature data using asymptotic approximation of the model heat capacity is then inverted from early time temperature data using a complete form of the model finally thermal diffusivity is calculated from the estimated thermal conductivity and heat capacity numerical experiments with synthetic temperature data indicate that the estimation error of the sediment s heat capacity is 12 the error of thermal diffusivity is thought to be greater than that of heat capacity we apply the method to needle probe temperature data obtained during integrated ocean drilling program expedition 301 carried out on the eastern flank of the juan de fuca ridge and estimate the sediments thermal properties the results indicate that thermal properties of sediments are strongly dependent on lithology and porosity examination results of the relations of heat capacity and thermal diffusivity to thermal conductivity show that these relations depend on the amount of quartz the empirical formulas for these relations are provided and they differ from those which are commonly used in thermal conductivity reduction schemes

convective cells in altocumulus observed with a high resolution radar abstractvery high resolution doppler radar observations are used together with aircraft measurements to document the dynamic and thermodynamic structure of a dissipating altocumulus cloud system associated with a deep virga layer the cloud layer circulation is shown to consist of shallow vertical velocity couplets near cloud top and a series of subkilometer scale rayleigh benard like cells that extend vertically through the depth of the cloud layer the subcloud layer was observed to contain a number of narrow virga fall streaks that developed below the more dominant rayleigh benard updraft circulations in the cloud layer these features were discovered to be associated with kilometer scale horizontally orientated rotor circulations that formed along the lateral flanks of the streaks collocated downdraft circulation the doppler analysis further reveals that a layer mean descent was present throughout both the cloud and subcloud layers this characteristic of the circulation is analyzed with regard to th

an evaluation of the accuracy of shallow water matched field inversion results in this article the accuracy of geo acoustic and geometric parameter estimates obtained through matched field inversion mfi was assessed multi frequency mfi was applied to multi tone data 200 600 hz received at a 2 km source receiver range the acoustic source was fixed and the signals were received at a vertical array simultaneously with the acoustic transmissions a ctd conductivity temperature and depth chain was towed along the acoustic track a genetic algorithm was used for the global optimization whereas a normal mode model was applied for the forward acoustic calculations acoustic data received at consecutive times were inverted and the stability of the inverted parameters was determined also the parameter estimates were compared with independent measurements such as multi channel seismic surveys for geo acoustic parameters the obtained uncertainty in the inversion results was assumed to have two distinct origins the first origin is the inversion method itself since each optimization will come up with some solution close to the exact optimum parameter coupling and the fact that some parameters hardly influence the acoustic propagation further contribute to this uncertainty the second is due to oceanographic variability both contributions were evaluated through simulation the contribution of oceanographic variability was evaluated through synthetic inversions that account for the actual sound speed variations as measured by the towed ctd chain

a new boundary layer mixing scheme part i scheme description and single column model tests a new boundary layer turbulent mixing scheme has been developed for use in the ukmo weather forecasting and climate prediction models this includes a representation of nonlocal mixing driven by both surface fluxes and cloud top processes in unstable layers either coupled to or decoupled from the surface and an explicit entrainment parameterization the scheme is formulated in moist conserved variables so that it can treat both dry and cloudy layers details of the scheme and examples of its performance in single column model tests are presented

on the evolution of rifted continental margins comparison of models and observations for the nova scotian margin summary a model for the formation and evolution of rifted continental margins based on lithospheric extension during rifting and its thermal and mechanical consequences is proposed model predictions are then compared with geological and geophysical observations from a transect of the 185 ma old rifted margin off nova scotia through the scotian basin three kinematic models of the rifting process are discussed these are 1 the uniform extension model in which the amount of extension is uniform with depth but varies with position across the margin 2 the uniform extension and melt segregation model which has similar properties but also provides an explanation for the properties of the extended continental crust and its transition to oceanic crust by postulating that basaltic melt segregates from the asthenosphere and migrates to the crust and 3 the depth dependent extension model in which the first order consequences of rapidly changing rheological properties with depth in the lithosphere are included by decoupling the lithosphere into two zones with depth each of which undergoes differing amounts of extension these rift models predict the form of crustal and lithospheric thinning subsidence and temperature change once the amount of extension has been determined this is estimated from seismic measurements of present crustal thickness on the assumption that the crust had a uniform thickness equal to that currently measured in the adjacent continental region before rifting occurred rifting is also considered to occur instantaneously a time stepping thermo mechanical model is used to predict the cooling of rifted margin additional thermal contraction subsidence and its amplification by water and sediment loading thermal aspects are calculated using a finite difference model of time dependent conductive heat transport whereas regional isostatic response to loading is calculated by a finite element model the models are coupled because the temperature distribution is used to define a rheological lithosphere an elastic region with thickness that varies in time and space as the model evolves for flexural calculations in the mechanical model secondary coupling occurs through perturbations to the temperature field by sedimentary thermal blanketing and advection of heat during isostatic adjustment the model predictions of 1 sedimentary basin stratigraphy 2 moho position 3 free air gravity anomaly 4 age depth relations for deep exploratory wells and 5 subsidence and temperature histories agree well with observations from the scotian basin additional effects due to sedimentary and crustal radiogenic heat production lateral heat transport and the possible existence of a near surface brittle listric faulted region created during rifting are also considered it is concluded that a model in which rifting occurred by depth dependent extension and which includes a finite thickness for the rheological lithosphere radiogenic heat production in the sediments and crust and a brittle listric faulted crustal layer affords an accurate description of the first order processes that occur during rifting and evolution of this margin

origin of low chloride fluid in sediments from the eastern continental margin of india results from the national gas hydrate program expedition 02 abstract national gas hydrate program expedition 02 was conducted in 2015 by d v chikyu in the western bay of bengal india analyses of interstitial water in sediment from four drilling sites along the eastern and western transect in the krishna godavari basin show that dissolved chloride cl concentrations decreased with depth from seawater values 550 mm near the sediment surface to 300 400 mm at 350 400 m below seafloor mbsf suggesting the upward advection of low cl fluid excursions of cl concentrations toward low values in gas hydrate zones were attributed to the presence of fresh water released by dissociation of gas hydrate during core recovery at sites in the western transect cl concentrations below the gas hydrate reservoir around 280 mbsf were ca 60 mm and ca 45 mm lower than those from above the reservoir and 18o and d values were 1 2 and 0 7 1 3 higher than those from above the reservoir respectively these results suggest that a fraction of migrating low cl fluid is trapped in the gas hydrate zone causing decreases of 18o and d in the residual water due to isotopic fractionation during gas hydrate formation from mass balance calculations we estimated that 10 20 of the advected fluid is trapped at the gas hydrate zone at all sites the 18o and d values below the gas hydrate zone representing relatively unaltered low cl fluid were 0 5 1 higher and ca 13 15 lower than those of seawater respectively this trend is consistent with water derived from the dehydration of clay minerals which generally occurs in deeply buried sediments the contribution of clay mineral dehydration is relatively large at the western transect compared to that in the eastern transect our results imply that fluid advection contributes to the accumulation of gas hydrate in the study area

observations of wind shear over the southern ocean 1 the thermodynamic structure of the lower troposphere over the southern ocean is analyzed by employing over 16 years of high resolution upper air soundings from macquarie island 54 62 s 158 85 e the soundings are analyzed to develop an understanding of the structure of the boundary layer and wind shear occurring through the lower levels over this region and to compare this to european centre for medium range weather forecasts ecmwf model level reanalysis data for the year of tropical convection yotc a multiple layered structure is commonly observed in the high resolution soundings and is also observed in yotc but with a lower frequency the climatological mean and variability of a number of variables are calculated for both data sets which reveals that yotc performs well but has weaknesses in modeling the observed moisture and wind fields particularly evident in wind shear profiles a distinction between a number of boundary layer types is made and the frequency with which they occur is quantified for both data sets this highlights important differences between the observations in the macquarie island soundings and the reanalysis product proxy cloud fields are constructed for the two data sets and these suggest that clouds are commonly observed in a region between the top of the boundary layer and a secondary temperature inversion i e a buffer layer in the words of russell et al 1998 the peak relative frequency of observing these clouds lies roughly around 912 5 hpa for both data sets an examination of the wind shear across the cloud boundaries finds wind shear over cloud base occurs more frequently than cloud top suggesting that the cloud fields are not embedded in a well mixed boundary layer

hydrogeology and mechanics of subduction zone forearcs fluid flow and pore pressure at subduction zones fluid flow pore pressure and tectonic processes are tightly interconnected excess pore pressure is driven by tectonic loading and fluids released by mineral dehydration and it has profound effects on fault and earthquake mechanics through its control on effective stress the egress of these overpressured fluids which is in part governed by the presence of permeable fault zones is a primary mechanism of volatile and solute transport to the oceans recent field measurements new constraints gained from laboratory studies and numerical modeling efforts have led to a greatly improved understanding of these coupled processes here we summarize the current state of knowledge of fluid flow and pore pressure in subduction forearcs and focus on recent advances that have quantified permeability architecture fluxes the nature and timing of transience and pressure distribution thus providing new insights into the connections between fluid metamorphic mechanical and fault slip proc

heat flow in jane basin northwest weddell sea the jane basin is a marginal basin situated immediately to the east of the south orkney microcontinent in the northwest section of the weddell sea thirty five heat flow measurements made in the jane basin ranged in value from 67 5 4 3 to 92 1 3 0 mw m2 excluding values that were corrected for tilting or were on the very edge of the basin the remaining 28 values range between 75 0 8 0 and 84 6 9 1 mw m2 magnetostratigraphy on the recovered core from ocean drilling program hole 697 which was drilled in jane basin to a depth of 322 m allowed sedimentation rates to be calculated back to 4 5 ma single channel seismic reflection data from rss shackleton allowed estimations of total sediment thickness for the jane basin to be made we calculate that the measured heat flow is only 86 89 of the actual heat flow as a result of sedimentation heat generation in the sediments contributes 1 5 1 9 mw m2to the total heat flow the corrected heat flow gives an age for the jane basin of between 25 and 32 ma from age versus heat flow comparisons similar to the age determined from basement depth the scotia sea located to the north of jane basin and the south orkney microcontinent has been dated as anomaly 10 30 ma and younger our calculated age for the jane basin would indicate that it may have been created prior to the initiation of seafloor spreading in the scotia sea evidence from major plate motions indicate that antarctica began to rotate clockwise away from south america at about 65 ma such motion may have triggered subduction along the southeast side of jane bank and the opening of jane basin as a back arc basin subduction at jane bank ended at anomaly 6a time 22 ma as evidenced by the age of the identified magnetic anomalies on the antarctic plate found immediately to the east of jane bank we conclude that jane basin opened prior to the opening of the scotia sea and that the spreading center that opened jane basin may have jumped to the scotia sea and produced the seafloor spreading there

simulating the transition from drizzling marine stratocumulus to boundary layer cumulus with a mesoscale model a case of coastal california summer season boundary layer cloud has been simulated with the u s navy coupled ocean atmosphere mesoscale prediction system and the results analyzed in the context of consistency with conclusions derived from large eddy simulation based les studies results show a pronounced diurnal cycle and fair agreement with satellite derived observations of liquid water path when drizzle processes are included a significant degree of mesoscale organization emerges in the form of cloud bands accompanied by a transition from a well mixed boundary layer topped by unbroken stratocumulus cloud into a more potentially unstable convective boundary layer regime the transition and the subsequent development of mesoscale variability is analogous to the drizzle induced cloud breakup produced in large eddy simulation studies the dynamics of the pure stratocumulus cloud are dictated by the model s subgrid parameterization while the more convective regime exhibits appreciable vertical velocities characteristic of an ensemble of cumulus updrafts the existence of convective updrafts is tied to a weak drizzle induced decoupling of the cloud and subcloud layer after which air of higher equivalent potential temperature ue can pool at the surface some similarities to the propagation of deep convection are also noted

the impact of vertical resolution upon gcm simulations of marine stratocumulus the impact of increased vertical resolution in the hadley centre climate model upon the simulation of stratocumulus is investigated in experiments using single column scm and general circulation gcm model configurations a threefold enhancement of vertical resolution in the boundary layer leads to improvements in the vertical structure of the cloud topped boundary layer produced by the scm and gcm in both well mixed and decoupled situations however single and decoupled mixed layers in the marine stratocumulus subsidence regions are still too shallow and despite increasing layer cloud amounts remain generally too low moreover closer examination of gcm data and scm timeseries reveals an underlying sensitivity to vertical resolution in model interactions between boundary layer and convection processes which appears unrealistic stratocumulus simulation is thus unlikely to improve significantly as a result of enhanced resolution alone and further work is being undertaken to improve the hadley centre model s boundary layer scheme and in particular its interaction with the convection scheme nevertheless this study shows that the full benefit of an improved boundary layer scheme will not be realized if the boundary layer structure is constrained by the rather poor lower troposphere resolution of the standard 19 level climate model future hadley centre model versions will seek to combine the added flexibility of a better resolved structure with improvements to the subgrid boundary layer parametrizations

regional heat flow variations across the sedimented juan de fuca ridge eastern flank constraints on lithospheric cooling and lateral hydrothermal heat transport seafloor heat flow has been estimated continuously along a transect on the sedimented eastern flank of the juan de fuca ridge to provide constraints on the scale and rate of lateral heat and fluid transport in the upper igneous crust and on the total flux from the young lithosphere beneath the profile extends from 20 km east of the ridge axis where turbidite sediments lap onto the oceanic crust at an age of less than 1 ma and ends 110 km east of the axis over 3 6 ma crust estimated heat flow is derived from the combination of the depth to igneous basement determined from seismic reflection profiles and basement temperatures measured in nine ocean drilling program boreholes along the transect the strategy is based on the knowledge that in this young area upper basement temperatures are locally homogenized by vigorous hydrothermal circulation and hence vary smoothly between drilling sites at the young end of the transect near the region of extensive outcrop heat flow is only 15 of that predicted for lithosphere of this age heat flow increases systematically to the east reaching the full predicted level about 20 km from the point of sediment basement onlap the anomaly can be accounted for by mixing and or eastward flow of cool water in the upper igneous crust beneath the sediment at a darcian rate of the order of 1 m yr a geochemical signature of fresh seawater in basement is observed many tens of kilometers farther to the east although the thermal signature is no longer present along the remainder of the transect the heat flow conforms very well to that predicted by simple boundary layer cooling theory once the thermal effects of rapid sedimentation on this ridge flank are accounted for

age thermal evolution and history of the black sea basin based on heat flow and multichannel reflection data abstract multichannel reflection data tugolessov et al 1985 have revealed two deeps in the basement topography of the black sea which are filled with sediments from 12 to 15 km thick the deeps lack the granitic layer and are underlain by oceanic type crust which we assume to be generated by seafloor spreading processes the age of the deeps was interpreted previously in a highly controversial manner as being from the paleozoic early mesozoic to the recent in the paper age estimations were undertaken using surficial heat flow data assuming that they are related to deep seated age dependent heat flow generated by the cooling oceanic lithosphere but that they are strongly distorted by the heating of continuously accumulating sediments as well as by additional heat input from radiogenic production within sediments using reliable thermophysical parameters of compacting sediments the distorted heat flow in the sediments was evaluated numerically this allowed us to estimate the age of the black sea deeps floor the results show that the west black sea deep is 130 to 95 m y old and the east black sea deep is nearly 110 m y old these figures support an interpretation of the black sea deeps as remnants of a late mesozoic back arc basin that evolved behind the lesser caucasian pontide island arc the inferred middle cretaceous age of the deeps is the first estimate obtained quantitatively and corresponds well with available heat flow and multichannel reflection data

the mesoscale stability of entrainment into cloud topped mixed layers abstract the lilly type models for stratocumulus capped mixed layers are shown to allow for a mesoscale instability in which mesoscale fluctuations of buoyancy and humidity are reinforced in phase by entrainment in a model of an amtex mixed layer this mesoscale instability has a maximum growth rate of about 2 10 5s 1 at wavelengths 30 times the depth of the mixed layer the instability is able to account for the existence and broad scale of the stratiform cloud patterns known as mesoscale cellular convection

observations of the interaction between cumulus clouds and warm stratocumulus clouds in the marine boundary layer during astex abstract decoupling of the marine boundary layer beneath stratocumulus clouds and the formation of cumulus clouds at the top of a surface based mixed layer sml have frequently been observed and modeled when such cumulus clouds penetrate the overlying stratocumulus layer the cloud microphysics and hence the radiative properties of the cloud are altered locally observations made during a series of lagrangian experiments in the azores as part of the atlantic stratocumulus transition experiment astex june 1992 have been analyzed to ascertain how the properties of a stratocumulus layer with which cumulus clouds are interacting differ from those of an unaffected cloud layer the results suggest that in regions where cumulus clouds penetrate the cloud layer the stratocumulus is thickened as the cumuli spread out into its base transport of air from the sml into the cloud by convective updrafts is observed and the increase in available moisture within the penetrating cumulus clouds results in increased

thermal origin of the hawaiian swell heat flow evidence and thermal models the lithospheric reheating hypothesis for the origin of the hawaiian swell has been tested by heat flow measurements along the swell between hawaii and midway ninety five measurements at eight carefully selected sites show that the heat flux on the swell increases systematically from near normal values 52 2 mw m 2 near hawaii to values near midway 59 2 mw m 2 about 20 25 higher than normal for lithosphere of that age 110 m y this heat flow pattern is qualitatively consistent with a deep seated thermal anomaly created in a lithospheric plate moving across a fixed heat source modeling of the heat flow and bathymetry data on the hawaiian swell strongly suggest that the swell is caused by a rapid heating within 40 to 50 km depth of normal 90 m y old lithosphere over a relatively broad 500 1000 km region near hawaii this model is also consistent with gravity and geoid anomalies associated with the swell which require a low density region in the lower lithosphere and with flexure studies of seamounts in the hawaiian chain which indicate that the rigidity of the lithosphere is not significantly reduced by the reheating appendices a c are available with entire article on microfiche order from american geophysical union 2000 florida avenue n w washington d c 20009 document j82 005 1 00 payment must accompany order

mesoscale shallow convection in the atmosphere this paper is a review of the observational experimental theoretical and numerical studies of mesoscale shallow convection msc in the atmosphere typically msc is 1 to 2 km deep has a horizontal length scale of a few to a few tens of kilometers and takes distinctive planforms linear and hexagonal the former is called a cloud street roll or band while the latter is called mesoscale cellular convection mcc comprising three dimensional cells msc is characterized by its shape horizontal extent convective depth and aspect ratio the latter is the ratio of the horizontal extent to that in the vertical for cells the horizontal extent is their diameter whereas for rolls it is their spacing rolls usually align along or at angles of up to 10 from the mean horizontal wind of the convective layer with lengths from 20 to 200 km widths from 2 to 10 km and convective depths from 2 to 3 km the typical value of aspect ratio ranges from 2 to 20 rolls may occur over both water surface and land surfaces mesoscale convective cells may be divided into two types open and closed open cell circulation has downward motion and clear sky in the cell center surrounded by cloud associated with upward motion closed cells have the opposite circulation both types of cell have diameters ranging from 10 to 40 km and aspect ratios of 5 to 50 and both occur in a convective layer with a depth of about 1 to 3 km both the magnitude and direction of horizontal wind in the convective layer change little with height msc results from a complex and incompletely understood mix of processes these processes are outlined and their interplay is examined through a review of theoretical and laboratory analyses and numerical modeling of msc

an extreme cold air outbreak over the labrador sea roll vortices and air sea interaction abstract observational data from two research aircraft flights are presented the flights were planned to investigate the air sea interaction during an extreme cold air outbreak associated with the passage of a synoptic scale low pressure system over the labrador sea during 8 february 1997 this is the first such aircraft based investigation in this remote region both high level dropsonde and low level flight level data were collected the objectives were twofold to map out the structure of the roll vortices that cause the ubiquitous cloud streets seen in satellite imagery and to estimate the sensible and latent heat fluxes between the ocean and atmosphere during the event the latter was achieved by a lagrangian analysis of the flight level data the flights were part of the labrador sea deep convection experiment investigating deep oceanic convection and were planned to overpass a research vessel in the area the aircraft observed roll vortices had a characteristic wavelength of 4 5 km particular

the impact of ocean sound speed variability on the uncertainty of geoacoustic parameter estimates this paper investigates the influence of water column variability on the estimates of geoacoustic model parameters obtained from matched field inversions the acoustic data were collected on the new jersey continental shelf during shallow water experiments in august 2006 the oceanographic variability was evident when the data were recorded to quantify the uncertainties of the geoacoustic parameter estimates in this environment bayesian matched field geoacoustic inversion was applied to multi tonal continuous wave data the spatially and temporally varying water column sound speed is parametrized in terms of empirical orthogonal functions and included in the inversion its impact on the geometric and geoacoustic parameter estimates is then analyzed by the inter parameter correlations two different approaches were used to obtain information about the variation of the water sound speed one used only the profiles collected along the experimental track during the experiment and the other also included observations collected over a larger area the geoacoustic estimates from both the large and small sample sets are consistent however due to the diversity of the oceanic sound speed more empirical orthogonal functions are needed in the inversion when more sound speed profile samples are used

a modeling case study of mixed phase clouds over the southern ocean and tasmania abstract the cloud structure associated with two frontal passages over the southern ocean and tasmania is investigated the first event during august 2006 is characterized by large quantities of supercooled liquid water and little ice the second case during october 2007 is more mixed phase the weather research and forecasting model wrfv2 2 1 is evaluated using remote sensed and in situ observations within the post frontal air mass the thompson microphysics module is used to describe in cloud processes where ice is initiated using the cooper parameterization at temperatures lower than 8 c or at ice supersaturations greater than 8 the evaluated cases are then used to numerically investigate the prevalence of supercooled and mixed phase clouds over tasmania and the ocean to the west the simulations produce marine stratocumulus like clouds with maximum heights of between 3 and 5 km these are capped by weak temperature and strong moisture inversions when the inversion is at temperatures warmer

inversion for sediment geoacoustic properties at the new england bight this article discusses inversions for bottom geoacoustic properties using broadband acoustic signals obtained from explosive sources two different inversion schemes for estimating the compressional wave speeds and attenuation are presented in this paper in addition to these sediment parameters source receiver range is also estimated using the arrival time data the experimental data used for the inversions are sus charge explosions acquired on a vertical hydrophone array during the shelf break primer experiment conducted south of new england in the middle atlantic bight in august 1996 the modal arrival times are extracted using a wavelet analysis in the first inversion scheme arrival times corresponding to various modes and frequencies from 10 to 200 hz are used for the inversion of compressional wave speeds a hybrid inversion scheme based on a genetic algorithm ga is used for the inversion in an earlier study potty et al j acoust soc am 108 3 973 986 2000 have used this hybrid scheme in a range independent environment in the present study results of range dependent inversions are presented the sound speeds in the water column and bathymetry are assumed range dependent whereas the sediment compressional wave speeds are assumed range independent the variations in the sound speeds in the water column are represented using empirical orthogonal functions eofs the replica fields corresponding to the unknown parameters were constructed using adiabatic theory in the second inversion scheme modal attenuation coefficients are calculated using modal amplitude ratios the ratios of the modal amplitudes are also calculated using time frequency diagrams a ga based inversion scheme is used for this search finally as a cross check the computed compressional wave speeds along with the modal arrival times were used to estimate the source receiver range the inverted sediment properties and ranges are seen to compare well with in situ measurements and historical data

mineralogy porosity and fluid control on thermal conductivity of sedimentary rocks summary estimates of thermal conductivity of the main non clay and clay sedimentary minerals are presented especially for the case of argillaceous ones these estimates are averaged estimates based on the interpretation of laboratory conductivity porosity and mineralogy measurements performed on small volumes of the order of 100cm3 of water saturated moist and air saturated samples the sampling is representative of the main sedimentary rocks sandstones carbonates evaporites and shales and it is composed of samples considered as structurally isotropic material first we experimentally verify the first order control of mineralogy porosity and fluid content on bulk conductivity and we demonstrate that such influences may be predicted accurately using a geometric mean model as long as isotropic samples are used then we interpret the data using an inverse method in order to estimate the average mineral conductivities of the main non clay and clay minerals which give the best fit to the individual laboratory measurements through the geometric mean model the analysis is based on measurements on 82 non clay samples and 29 clay samples taken on oil well cores or cuttings on outcrops and on artificially recompacted samples estimates of average mineral conductivities returned by the inversion process for the main non clay minerals are similar to generally admitted values 7 7 w m k for quartz 3 3 w m i k for calcite 5 3 w m l k for dolomite and 6 3 w m k for anhydrite values obtained for the clay minerals are systematically lower than those obtained for non clay ones they are of the order of 1 9 w m k for illite and smectite 2 6 w m k for kaolinite and 3 3 w m l k for chlorite these estimates combined with porosity and mineralogy data are used with the geometric mean model in order to verify its first order validity for predicting thermal conductivity of small volumes of porous isotropic sedimentary rocks the bulk conductivity is predicted with an accuracy of the order of f10 per cent for moist or water saturated samples and of the order of f20 per cent for air saturated samples

observed lagrangian transition of stratocumulus into cumulus during astex mean state and turbulence structure aircraft measurements made during the first lagrangian of the atlantic stratocumulus transition experiment astex between 12 and 14 june 1992 are presented during this lagrangian experiment an air mass was followed that was advected southward by the mean wind five aircraft flights were undertaken to observe the transition of a stratocumulus cloud deck to thin and broken stratocumulus clouds penetrated by cumulus from below from the horizontal aircraft legs the boundary layer mean structure microphysics turbulence structure and entrainment were analyzed the vertical profiles of the vertical velocity skewness are shown to illustrate the transition of a cloudy boundary layer predominantly driven by longwave radiative cooling at the cloud top to one driven mainly by convection due to an unstable surface stratification and cumulus clouds during the last flight before the stratocumulus deck was observed to be broken and replaced by cumuli the total water flux the virtual potential temperature flux and the vertical velocity variance in the stratocumulus cloud layer were found significantly larger compared with the previous flights to analyze the cloud top stability the mean jumps of conserved variables across the inversion were determined from porpoising runs through the cloud top these jumps were compared with cloud top entrainment instability criteria discussed in the literature it is suggested that enhanced entrainment of dry air is a key mechanism in the stratocumulus cumulus transition

shallow water waveguide characterization using the hankel transform a coherent processing technique is proposed for the characterization of shallow water channels for a horizontally stratified ocean and bottom the method consists of measuring the magnitude and phase versus range of the pressure due to a cw point source and hankel transforming this data to obtain the depth dependent green s function versus horizontal wave number the green s function contains all the information about the channel necessary to solve the forward problem including the nature of the discrete and continuous spectra and the plane wave reflection coefficient of the bottom characteristics of the green s function can also be used to infer acoustic properties of the bottom results for simple examples are presented using synthetic data and implications for the nonstratified case are discussed

heat flow through the sea bottom around the yucatan peninsula heat flow studies were conducted in january february 1987 off the atlantic coast of mexico on board the r v akademik nikolai strakhov two areas were surveyed one transecting the salt dome province and the campeche canyon in the gulf of mexico and the other on the eastern flank of the yucatan peninsula conductive heat flow through the bottom sediments was determined as the product of vertical temperature gradient and in situ thermal conductivity measured with a thermal probe using a multithermistor array and real time processing capabilities forward two dimensional modeling allows us to estimate heat flow variations at both sites from local disturbances and to obtain average heat flow values of 51 mw m2 for the transect within the gulf of mexico and 38 and 69 mw m2 for two basins within the yucatan area sea bottom relief has a predominant effect over other environmental factors in the scatter of heat flow determination in the gulf of mexico

the effects of sedimentation and compaction on oceanic heat flow summary the estimation of environmental effects forms an important part of the interpretation of oceanic heat flow measurements in particular the perturbations associated with sedimentation and surface temperature changes must be taken into account analytical solutions can be obtained only for individual simplified versions of these problems whereas any real example is complicated by the process of sediment compaction which changes the bulk thermal properties with depth a physical model is developed which uses sediment porosity trends to predict the thermal parameters and material advection rates for an evolving sediment basement system these values are then used in a numerical solution to the heat flow equation to give estimates of the perturbed surface heat flux through time in addition to variations in sedimentation rate sediment type radioactive heat production and surface temperature changes are considered heat flow corrections may vary by up to a factor of 2 according to sediment type while radioactive heat production can offset the effects of sedimentation by as much as 40 per cent the results also indicate that alterations determined from simple analytical models tend to over estimate the true perturbation to the flux

a train observations of maritime midlatitude storm track cloud systems comparing the southern ocean against the north atlantic abstractcloud and precipitation properties of the midlatitude storm track regions over the southern ocean so and north atlantic na are explored using reanalysis datasets and a train observations from 2007 to 2011 in addition to the high level retrieval products lower level observed variables cloudsat radar reflectivity and cloud aerosol lidar and infrared pathfinder satellite observations calipso lidar attenuated backscatter are directly examined using both contoured frequency by altitude diagrams cfads and contoured frequency by temperature diagrams cftds to provide direct insight into thermodynamic phase properties while the wintertime temperature profiles are similar over the two regions the summertime environment is warmer over the na the na atmosphere is generally moister than the so while the so boundary layer is moister during winter the results herein suggest that although the two regions exhibit many similarities in the prevalence of boundary layer clouds blcs and frontal syste

a modified version of archie s law to estimate effective diffusion coefficients of radionuclides in argillaceous rocks and its application in safety analysis studies abstract because of the very low hydraulic conductivity of clay rocks molecular diffusion is the main process responsible for the transport of radionuclides released from the waste matrix into the host rock diffusion values are thus important input parameters in safety analyses because diffusion measurements are very time consuming it is impossible to measure diffusion coefficients for all radionuclides of interest it is therefore important to develop procedures for doing reliable estimates of diffusion coefficients diffusion data of mainly tritiated water hto and anions i cl measured in different sedimentary rocks were taken from the literature the effective diffusion coefficient could be related to the transport porosity by an extended version of archie s law e archie d e d w e m 1 b e m 2 the extended version deviates from the classical law at porosity values below ca 0 1 effective diffusion coefficients of hto 36cl and 22na were measured for a series of swiss clay rocks brauner dogger effingen member opalinus clay and helvetic marls and for one hungarian rock boda claystone formation and could be satisfactorily described by the extended version of archie s law bounded by an upper and a lower curve a method was developed based on e archie for estimating effective diffusion coefficients for a series of radionuclides important input parameters are the accessible porosity of the rock and the diffusion coefficient of the radionuclide in water in case of cations showing surface diffusion a correction term was introduced based on the work of gimmi and kosakowski 2011

inversion for range dependent water column sound speed profiles on the new jersey shelf using a linearized perturbative method the environment of the new jersey shelf is characterized by high spatial and temporal variability of water column properties caused by intrusions of warm salty water from the continental slope these intrusions cause fluctuations in the water column sound speed profile which can have significant effects on acoustic propagation in shallow water in this work a linearized perturbative inverse technique is applied to estimate range dependent water column sound speed profiles this method utilizes estimates of horizontal wave numbers to determine sound speed as a function of depth this technique is appropriate for the range dependent shallow water environment as horizontal wave numbers can be measured semilocally 1 2 km aperture and their values are a direct measurement of the local environmental parameters difficulty is encountered in application of the perturbative inverse technique because the wave number data are insensitive to some portions of the waveguide and as a result the solution can deviat

a mechanism for the formation of methane hydrate and seafloor bottom simulating reflectors by vertical fluid expulsion bottom simulating reflectors bsr are observed commonly at a depth of several hundred meters below the seafloor in continental margin sedimentary sections that have undergone recent tectonic consolidation or rapid accumulation they are believed to correspond to the deepest level at which methane hydrate clathrate is stable we present a model in which bsr hydrate layers are formed through the removal of methane from upward moving pore fluids as they pass into the hydrate stability field in this model most of the methane is generated below the level of hydrate stability but not at depths sufficient for significant thermogenic production the methane is primarily biogenic in origin the model requires either a mechanism to remove dissolved methane from the pore fluids or disseminated free gas carried upward with the pore fluid the model accounts for the evidence that the hydrate is concentrated in a layer at the base of the stability field for the source of the large amount of methane contained in the hydrate and for bsrs being common only in special environments strong upward fluid expulsion into the hydrate stability field does not occur in normal sediment depositional regimes so bsrs are uncommon upward fluid expulsion does occur as a result of tectonic thickening and loading in subduction zone accretionary wedges and in areas where rapid deposition results in initial undercconsolidation in these areas hydrate bsrs are common the most poorly quantified aspect of the model is the efficiency with which methane is removed and hydrate is formed as pore fluids pass into the hydrate stability field the critical boundary in the phase diagram between the fluid plus hydrate and fluid only fields is not well constrained however the amount of methane required to form the hydrate and limited data on methane concentrations in pore fluids from deep sea boreholes suggest very efficient removal of methane from rising fluid that may contain less than the amount required for free gas production in most fluid expulsion regimes the quantity of fluid moved upward to the seafloor is great enough to continually remove the excess chloride and the residue of isotope fractionation resulting from hydrate formation thus as observed in borehole data there are no large chloride or isotope anomalies remaining in the local pore fluids the differences in the concentration of methane and probably of co2 in the pore fluid above and below the base of the stability field may have a significant influence on early sediment diagenetic reactions

numerical study of convection observed during the winter monsoon experiment using a mesoscale two dimensional model abstract a two dimensional version of the pennsylvania state university mesoscale model has been applied to winter monsoon experiment data in order to simulate the diurnally occurring convection observed over the south china sea the domain includes a representation of part of borneo as well as the sea so that the model can simulate the initiation of convection also included in the model are parameterizations of mesoscale ice phase and moisture processes and longwave and shortwave radiation with a diurnal cycle this allows use of the model to test the relative importance of various heating mechanisms to the stratiform cloud deck which typically occupies several hundred kilometers of the domain frank and cohen s cumulus parameterization scheme is employed to represent vital unresolved vertical transports in the convective area the major conclusions are ice phase processes are important in determining the level of maximum large scale heating and vertical motion because there is a strong anvil componen

a constraint on the shear stress at the pacific australian plate boundary from heat flow and seismicity at the kermadec forearc new heat flow measurements and relocated hypocenters that constrain the subduction geometry of the pacific plate at the kermadec trench yield an estimate of shear stress on the thrust fault with the exception of a few relatively high values 60 mw m 2 on the upper forearc region near the active volcanic ridge most of the 64 heat flow values along two profiles across the forearc range from 20 to 40 mw m 2 corrections for bottom water temperature variations that caused nonuniform temperature gradients were required for most measurements the means of the most reliable values for the northern and southern profiles are 28 9 5 8 mw m 2 n 33 and 28 9 7 2 mw m 2 n 19 respectively and the measurements show no apparent systematic variation along the profiles over the range 50 to 150 km distance from the trench the means of the 10 values at each of two sites on the pacific plate seaward of the profiles are 57 2 6 3 and 60 2 6 6 mw m 2 redeterminations of focal depths and fault plane solutions of earthquakes in the vicinity of the heat flow profiles indicate thrust faulting on a plane dipping 17 2 calculated values of heat flow for a two dimensional analytical approximation to conduction through the upper plate diffusion into the downgoing slab and advection by that slab are consistent with either a uniform stress of 40 17 mpa along the thrust fault or stress increasing linearly at 0 5 0 2 mpa km 1 with distance from the trench axis the comparable scatter in the heat flow measurements about those calculated from these simple stress distributions does not show one to be a better approximation than the other

evidence for excess pore pressures in southwest indian ocean sediments brown clay cores from the madagascar and crozet basins show the following evidence of excess pore pressures large amounts of flow in increasing average sedimentation rate with age and nonlinear temperature gradients additionally many hilltops in these basins have no visible sediment cover the bare hilltops may result from periodic slumping caused by excess pore pressures calculated excess pore pressures which equal or exceed the overburden pressure were inferred from water fluxes predicted by nonlinear temperature gradients and laboratory permeability measurements by using darcy s law since pore pressures which exceed the overburden pressure are unreasonable we attribute this discrepancy to laboratory measures which underestimate the in situ permeability the widespread presence of overpressured sediments in areas of irregular topography provides a process for resuspension of clay sized particles this mechanism does not require high current velocities for the erosion of clay and therefore can be applied to many areas where no strong currents are evident carbonate rich sediments from the madagascar ridge the mozambique ridge and the agulhas plateau had almost no flow in and occurred in areas where all topography was thickly draped with sediment since the age and tectonic location of the ridges and plateaus preclude water circulation in the basement wemore attribute these differences between the brown clay and the carbonate rich material to an absence of significant excess pore pressures in the plateau and ridge sediments less

constraints on the fluid supply rate into and through gas hydrate reservoir systems as inferred from pore water chloride and in situ temperature profiles krishna godavari basin india abstract we estimate the rate of upward pore fluid flow and chlorinity cl concentrations at depth through a joint analysis of cl concentration and temperature versus depth profiles obtained from gas hydrate related test sites drilled and cored in the krishna godavari basin off the eastern coast of india cl measured on conventional core samples decreases with depth at all sites but some of the cl profiles show a prominent convex shape whereas in situ temperature profiles obtained by the advanced piston coring temperature probe are mostly linear at all sites established during the national gas hydrate program 02 expedition nghp 02 assuming a one dimensional time dependent model for the advection of pore fluid including the sedimentation effect and depth dependent diffusivity we estimate darcy velocity and the cl concentrations at depth the best fit darcy velocity of 1 2 1 6 10 11 m s was estimated for the sites along the crest of the regional anticlinal structure in the nghp 02 area b which was significantly faster than those on the flanks of the anticline because the thermal diffusion coefficient is much larger than the chloride ion diffusion coefficient estimated darcy velocities are not great enough to generate nonlinear temperature profiles with depth which is consistent with observed linear thermal profiles

characterization of the sedimentary thermal regime along the corsair growth fault zone texas continental shelf using corrected bottomhole temperatures temperatures of deep 3 km 1 8 mi sediments along the corsair growth fault zone in the texas continental shelf are elevated relative to those off the fault zone this observation is based on a compilation of nearly 400 bottomhole temperatures bhts obtained from about 230 wells widely distributed across the continental shelf the bhts have been individually corrected for the thermal disturbance associated with drill fluid circulation the isotherm of 140 c 284 f derived from the corrected bhts shows more or less continuous peaks along the fault zone thermal gradients in the depth range of 3 to 5 km 1 8 to 3 1 mi shows higher values along the fault zone than off the fault zone these trends are similar to the previous observations made along the wilcox growth fault zone in the texas coastal plain previous studies suggest that the faults of the wilcox system serve as the conduits for hot fluids expelled from deep overpressured sediments a similar mechanism may explain the elevated temperatures along the corsair fault zone

parameter estimation using multifrequency range dependent acoustic data in shallow water the estimation of all forward model parameters geometric geoacoustic and ocean sound speed by the inversion of acoustic field observations is considered the data was taken at a mildly range dependent shallow water site in the mediterranean sea the inversion is based on data from a vertical array and carried out using information at multiple frequencies global optimization using a directed monte carlo search based on genetic algorithms and the bartlett objective function is used all geometric parameters are well determined a range dependent geoacoustic model is determined and the ocean sound speed is estimated comparisons of the observed pressure field as a function of depth and the predicted field show good agreement the use of observations at multiple frequencies provides considerable stability for the estimated parameters optimization of only geometric and geoacoustic parameters in a range independent environment is found to be satisfactory at the lower frequencies 165 175 hz but for the h

heat flow and the thermal origin of hot spot swells the hawaiian swell revisited we present 150 new heat flow measurements obtained at eight sites along a 1230 km long profile across the hawaiian swell about 700 km ese of midway island most of the measurements include in situ thermal conductivity determinations which helped to reduce the statistical uncertainties 95 confidence at all sites to 59 mw m 2 about 20 higher than the predicted heat flow for 100 ma seafloor based on simple lithospheric cooling models thus even though there is a small increase in heat flow with age along the swell when compared with the off swell heat flux the anomalous heat flow associated with the hawaiian swell is probably of the order of 5 10 mw m 2 and arguably may not exist at all a previous investigation von herzen et al 1982 may have overestimated the magnitude of the heat flow anomaly associated with the hawaiian swell by comparing heat flux measurements on the swell with values expected for simple lithospheric cooling models the heat flow anomalies associated with the bermuda rise and the cape verde rise may also be smaller than previously estimated given the uncertainties in the heat flux on the normal seafloor surrounding these swells the lack of a significant heat flow anomaly associated with the bathymetric expression of the hawaiian swell is inconsistent with simple models of lithospheric reheating dynamic support accompanied by modest temperature increases 80 ma oceanic lithosphere

aircraft observations of boundary layer rolls off the coast of california abstract large scale horizontal rolls can have a significant influence on turbulent transport across the atmospheric boundary layer the formation and maintenance of such rolls is dependent on the thermal and dynamic stability of the boundary layer bl the authors present aircraft observations of boundary layers both with and without roll circulations off the coast of california the contribution of the rolls to the turbulent fluxes of heat moisture and momentum and the variances of the three velocity components are determined for four cases the fractional roll contributions to the u and w variances and the sensible heat and along wind momentum fluxes show a near linear increase with altitude from less than 10 at 30 m to more than 70 at the top of the bl the variance in and crosswind momentum flux are more scattered although the variance shows a slight increase with altitude from about 40 to 60 the latent heat flux also shows a great deal of scatter especially in the lower third of th

strong impact of ion filtration on the isotopic composition of chlorine in young clay rich oceanic sediment pore fluids abstract a collection of 34 pore fluids from young clay rich sedimentary piles of the shikoku basin on the philippine oceanic plate at the front of the nankai subduction zone southeast of japan were analyzed for their chloride content and chlorine stable isotope composition 35cl and 37cl reported as 37cl these pore fluids are samples from iodp sites c0011 and c0012 which penetrate deeper than 500 meters below the seafloor at both sites the 37cl values display a regular decrease with depth from about 0 seawater value at the seafloor to 8 5 and 6 5 respectively in hydrogeologically isolated low permeability sediment levels at some depths local deviations of up to 6 in 37cl interrupt the overall decreasing trends they may be interpreted as the injection of external fluids into the sedimentary piles as a result of sedimentary levels with higher permeability at the bottom of the sedimentary piles the injected fluids probably originating from the altered oceanic crust systematically have 37cl values closer to seawater literature data indicate the display of downward trends of decreasing 37cl values of the pore fluids in many other young clay rich sedimentary piles nankai trough and the japan trench accretionary prisms black ridge and juan de fuca ridge flank here we use conservation equations to demonstrate that these 37cl depth profiles can be modeled using the effect of the compaction of growing clay rich sedimentary piles on the water and chlorides including 35cl and 37cl isotopes this modeling shows that a small isotope fractionation of chlorine isotopes 37cl 35clexpulsed fluid residual fluid in the range of 1 006 to 1 001 may explain the observed negative 37cl chlorides at the bottom of the sedimentary piles the complementary positive 37cl chlorides must accumulate at the top but are very likely erased by dilution with seawater chlorides across the seafloor interface this range of chlorine isotope fractionation values is in agreement with the theory of ion filtration of phillips and bentley 1987 in which the mobility of chlorides through semi permeable clay membrane is determined by ion repulsion based on this study we show that young pore fluids in clay rich sediments of the oceanic crust are 37cl depleted chloride reservoirs they might be the source of 37cl depleted chloride fluids advected at mud volcanoes on the seafloor but do not seem to contribute largely to subduction zone magmatic tectonic metamorphic products where no such 37cl depleted chlorine is documented this in turn is a strong argument to propose that most of the clay rich sediment s pore waters are released back into the ocean rather than subducted

the effects of environmental variability and spatial sampling on the three dimensional inversion problem the overall goal of this work is to quantify the effects of environmental variability and spatial sampling on the accuracy and uncertainty of estimates of the three dimensional ocean sound speed field in this work ocean sound speed estimates are obtained with acoustic data measured by a sparse autonomous observing system using a perturbative inversion scheme rajan lynch and frisk j acoust soc am 82 998 1017 1987 the vertical and horizontal resolution of the solution depends on the bandwidth of acoustic data and on the quantity of sources and receivers respectively thus for a simple range independent ocean sound speed profile a single source receiver pair is sufficient to estimate the water column sound speed field on the other hand an environment with significant variability may not be fully characterized by a large number of sources and receivers resulting in uncertainty in the solution this work explores the interrelated effects of environmental variability and spatial sampling o

heat flow and thermal models of the barbados ridge accretionary complex the pattern of heat flow from the barbados ridge accretionary complex has been derived from marine surveys with heat flow probes from measurements in drill holes and from the depths of bottom simulating seismic reflectors caused by gas hydrate the heat flow from the accretionary complex has been simulated using a finite difference model to investigate how heat flow responds to changes in the cross sectional shape of the complex and the rate of convergence and to variations in pore fluid pressure within the complex and along the decollement at its base in the south of the complex heat flow decreases westward from the toe of the wedge towards the island arc because the downward movement of subducting lithosphere beneath the wedge and the active thickening of the accreted sedimentary sequence reduce the geothermal gradient more rapidly than thermal diffusion can maintain it localised high anomalies attributed to the flow of warm fluids along fault zones are superimposed on the conductive heat flow pattern farther west heat flow increases arcward produced partly by thermal diffusion re establishing a steeper thermal gradient where the rate of thickening is decreased but mainly by the arcward increase of frictional heating along the base of the wedge caused by the increase of slip rate and increased normal stress arising from thickening of the wedge in the north of the complex around the odp leg 110 drill sites the conductive model cannot reproduce the anomalously high heat flow measurements which can only be explained by the advection of warm pore fluids

effect of ocean sound speed uncertainty on matched field geoacoustic inversion the effect of ocean sound speed uncertainty on matched field geoacoustic inversion is investigated using data from the sw06 experiment along a nearly range independent bathymetric track significant sound speed differences were observed at the source and receiving array and several environmental parameterizations were investigated for the inversion including representing the ocean sound speed at both source and receivers with empirical orthogonal function eof coefficients a genetic algorithm based global optimization method was applied to the candidate environmental models then a bayesian inversion technique was used to quantify uncertainty in the environmental parameters for the best environmental model which included an eof description of the ocean sound speed

estimates of the temporal and spatial variability of ocean sound speed on the new jersey shelf estimates of the spatial and temporal variability of ocean sound speed on the new jersey shelf were obtained using acoustic signals measured by a set of freely drifting buoys the range and time dependent inversion problem is computationally intensive and a linearized perturbative algorithm was applied to obtain results in an efficient manner the inversion algorithm uses estimates of modal travel time to determine sound speed as a function of range and depth in order to handle the high volume of data associated with the acoustic sensing network the modal travel time estimation process was automated using an adaptive time frequency signal processing method known as time warping time warping is a model based transform that converts the frequency dependent modal arrivals to monotones in the warped domain where they can be easily filtered the data analyzed in this paper were collected on 16 march 2011 on the new jersey shelf when the ocean was relatively well mixed while the observed sound speed variations are small both spatial and temporal trends are observed in the results furthermore the estimated sound speed profiles show good agreement with temporally and spatially collocated measurements