analyses and simulations of the upper ocean s response to hurricane felix at the bermuda testbed mooring site 13 23 august 1995 causedalargeincreaseinkineticenergyatnear inertialfrequencies internalgravitywavesin the thermocline and inertial pumping mixed layer deepening and significant vertical redistribution of heat with cooling of the upper 30 m and warming at depths of 30 70 m the temperature evolution was simulated using four one dimensional mixed layer models price weller pinkel pwp k profile parameterization kpp mellor yamada 2 5 my and a modified version of my2 5 my2 the primary differences in the model results were in their simulations of temperature evolution in particular when forced using a drag coefficient thathadalinear dependenceonwindspeed the kppmodelpredicted seasurface cooling mixed layer currents and the maximum depth of cooling closer to the observations than any of the other models this was shown to be partly because of a special parameterization for gradient richardson number rgkpp shear instability mixing in responsetoresolvedshearintheinterior themy2modelpredictedmoreseasurfacecooling and greater depth penetration of kinetic energy than the my model in the my2 model the dissipation rate of turbulent kinetic energy is parameterized as a function of a locally defined richardson number rgmy2 allowing for a reduction in dissipation rate for stable richardsonnumbers rgmy2 wheninternalgravitywavesarelikelytobepresent sensitivity simulations with the pwp model which has specifically defined mixing procedures show that most of the heat lost from the upper layer was due to entrainment parameterized as a function of bulk richardson number rbpwp with the remainder due to local richardson number rgpwp instabilities with the exception of the my model the models predicted reasonable estimates of the north and east current components during and after the hurricane passage at 25 and 45 m although the results emphasize differences between the modeled responsestoagivenwindstress currentcontroversyovertheformulationofwindstressfrom wind speed measurements including possible sea state and wave age and sheltering effects cautions against using our results for assessing model skill in particular sensitivity studies show that my2 simulations of the temperature evolution are excellent when the wind stress is increased albeit with currents that are larger than observed sensitivity experiments also indicate that preexisting inertial motion modulated the amplitude of poststormcurrents butthattherewasprobablynotasignificantresonantresponsebecauseof clockwise wind rotation for our study site index terms 4504 oceanography physical air sea interactions 0312 4572 oceanography physical upper ocean processes 4255 oceanography general numericalmodeling 4544oceanography physical internalandinertialwaves keywords hurricane tropical cyclone mixed layer modeling upper ocean processes inertial currents ocean storms

removal of wavelet dispersion from ground penetrating radar data wavelet dispersion caused by frequency dependent attenuation is a common occurrence in ground penetrating radar gpr data and is displayed in the radar image as a characteristic blurriness that increases with depth correcting for wavelet dispersion is an important step that should be performed before gpr data are used for either qualitative interpretation or the quantitative determination of subsurface electrical properties over the bandwidth of a gpr wavelet the attenuation of electromagnetic waves in many geological materials is approximately linear with frequency as a result the change in shape of a radar pulse as it propagates through these materials can be well described using one parameter q related to the slope of the linear region assuming that all subsurface materials can be characterized by some q value the problem of estimating and correcting for wavelet dispersion becomes one of determining q in the subsurface and deconvolving its effects using an inverse q filter we present a

winds waves and turbulence on a shallow continental shelf during passage of a tropical storm abstractmeasurements of collocated fields of atmospheric forcing surface waves and mean and turbulent velocities associated with passage of tropical storm ts barry over the u s navy tower r2 o

cold wake of hurricane frances 1 an array of instruments air deployed ahead of hurricane frances measured the three dimensional time dependent response of the ocean to this strong 60 ms 1 storm sea surface temperature cooled by up to 2 2 c with the greatest cooling occurring in a 50 km wide band centered 60 85 km to the right of the track the cooling was almost entirely due to vertical mixing not air sea heat fluxes currents of up to 1 6 ms 1 and thermocline displacements of up to 50 m dispersed as near inertial internal waves the heat in excess of 26 c decreased behind the storm due primarily to horizontal advection of heat away from the storm track with a small contribution from mixing across the 26 c isotherm sst cooling under the storm core 0 4 c produced a 16 decrease in air sea heat flux implying an approximately 5 ms 1 reduction in peak winds

using motionally induced electric signals to indirectly measure ocean velocity instrumental and theoretical developments abstract the motion of conductive sea water through the earth s magnetic field generates electromagnetic em fields through a process called motional induction direct measurements of oceanic electric fields can be easily converted to water velocities by application of a first order theory this technique has been shown to obtain high quality velocities through instrumental advances and an accumulation of experience during the past decades em instruments have unique operational considerations and observe for instance vertically averaged horizontal velocity from stationary sensors or vertical profiles of horizontal velocity from expendable probes or autonomous profiling floats the first order theory describes the dominant electromagnetic response in which vertically averaged and vertically varying horizontal velocities are proportional to electric fields and electric currents respectively after discussions of the first order theory and deployment practices operational capabilities are shown through recently published projects that describe stream coordinate velocity structure of the antarctic circumpolar current quickly evolving overflow events in the denmark strait and time development of momentum input into the ocean from a hurricane a detailed analysis of the gulf stream at its separation point from the continental slope serves as a case study for interpreting em measurements including the incorporation of geophysical knowledge of the sediment in addition the first order approximation is tested by the many features at this location that contradict the approximation s underlying assumptions sharp horizontal velocity gradients steep topography and thick and inhomogeneous sediments numerical modeling of this location shows that the first order assumption is accurate to a few percent a few cm s 1 in almost all cases the errors in depth varying velocity are 1 are substantiated by the direct observations and can be corrected by iterative methods though errors in the depth uniform velocity are 1 1 or less in almost all regions of the ocean an error similar to the instrumental accuracy of em instruments

the bay of bengal upper ocean response to tropical cyclone forcing during 1999 1 the regional upper ocean dynamical and thermodynamical responses to two consecutive strong tropical cyclones tcs 04b 15 19 october and 05b 25 october to 3 november in 1999 hereafter tc1 and tc2 in the bay of bengal bob and the associated oceanic processes are investigated using an eddy permitting hybrid coordinate ocean model the tc winds induce positive sea surface height anomalies ssha along the northern bob coastline and andaman sea due to onshore convergence and negative ssha along the tc tracks due to ekman divergence which in turn induce geostrophic flow the tc associated radiation and precipitation have negligible effects on the northwestern bob top 30 m averaged temperature t0 30 m while the strong tc winds significantly enhance turbulent heat flux causing t0 30 m decrease due to the existence of the barrier layer and subsurface warm advection in the northwestern bob vertical mixing may induce near surface warming by entraining warm water from below as a result the proportion of the t0 30 m cooling caused by turbulent heat flux is likely elevated in the 6 6 footprints of the tcs both tc wind induced vertical mixing and upwelling significantly cool t0 30 m in tc1 s wake while upwelling dominates the maximum cooling region in tc2 s wake likely due to the preceding deepening of the mixed layer by tc1 the near surface cooling for both tcs has rightward bias because of the higher winds and the resonant response on the right and ekman divergence extends the cooling areas outward tc1 and tc2 s sizes and prestorm oceanic conditions are found to be the most influential factors for near surface cooling

forced stage response to a moving hurricane abstract the upper ocean s response to three hurricanes norbert 1984 josephine 1984 and gloria 1985 is examined using field observations and a numerical ocean model our goal is to describe the physical processes that determine the structure and amplitude of hurricane driven upper ocean currents all three of these northern hemisphere hurricanes produced a rightward biased response of the mixed layer current and transport this asymmetry arises because the wind stress vector rotates clockwise on the right side of the track and remains nearly parallel with the inertially rotating mixed layer current during most of the hurricane passage the maximum observed mixed layer current varied from 0 8 m s 1 in response to josephine which was a large but comparatively weak hurricane to 1 7 m s 1 in response to gloria which was very large and also intense these cases have been simulated with a three dimensional numerical model that includes a treatment of wind driven vertical mixing within the primitive

observations of the cold wake of typhoon fanapi 2010 1 several tens of thousands of temperature profiles are used to investigate the thermal evolution of the cold wake of typhoon fanapi 2010 typhoon fanapi formed a cold wake in the western north pacific ocean on 18 september characterized by a mixed layer that was 2 5 c cooler than the surrounding water and extending to 80 m twice as deep as the preexisting mixed layer the initial cold wake became capped after 4 days as a warm thin surface layer formed the thickness of the capped wake defined as the 26 c 27 c layer decreased approaching the background thickness of this layer with an e folding time of 23 days almost twice the e folding lifetime of the sea surface temperature sst cold wake 12 days the wake was advected several hundreds of kilometers from the storm track by a preexisting mesoscale eddy the observations reveal new intricacies of cold wake evolution and demonstrate the challenges of describing the thermal structure of the upper ocean using sea surface information alone

wave glider observations of surface winds and currents in the core of typhoon danas simultaneous monitoring of surface winds and currents is essential to understand oceanic responses to tropical cyclones we used a new platform a wave glider liquid robotics to observe air sea processes during a typhoon equivalent to a category 4 hurricane at peak strength near okinawa japan surface winds showed strong asymmetry in both speed and direction faster fore than aft rotations of surface winds and currents were not coupled currents rotated clockwise in the wake of the typhoon eye after passage of rapid wind rotations wind work was mostly done ahead of the eye amplifying prior inertial motions with a phase shift wind induced energy was nearly balanced with an increase in estimated kinetic energy of the upper ocean current relative to prior inertial oscillations this study provides a newer more complete view of actual atmosphere ocean interactions in a typhoon

effect of typhoon kalmaegi 2014 on northern south china sea explored using muti platform satellite and buoy observations data abstract based on observational data from a buoy mooring array and satellite remote sensing data for sea surface winds temperature and height during the passage of typhoon kalmaegi 2014 a systematic analysis is performed on the atmospheric and oceanic variables of winds sea level air pressure surface air temperature sensible and latent heat fluxes rainfall water temperature salinity and ocean currents kalmaegi passed through the south china sea scs with a mean non dimensional speed of 2 87 typical of a fast moving storm with a predominantly baroclinic oceanic response in addition to some well documented response features such as rightward biased intensifications in sea surface cooling and currents a much deeper mixed layer to the right side of the storm and a strong near inertial oscillation in the thermocline we here identify several new features as follows 1 the current velocity to the right side of the track decays faster than that to the left side 2 on the right side of the track the typhoon induced water temperature anomaly exhibits a three layered cooling warming cooling structure in the vertical with salinity and density anomaly profiles sharing a similar pattern 3 on the left side of the track the whole upper ocean is cooled whereas salinity shows no variation in the uppermost 20 m layer with a negative anomaly for water at depths from 20 to 50 m and a positive anomaly below 50 m the associated mechanisms are discussed in the text 4 the storm induced maximum cooling is not unique to kalmaegi 2014 in fact storms with tracks similar to that of kalmaegi 2014 may induce similar maximum cooling in the northern scs which may be useful in predictions of where such storms would induce the maximum cooling

effect of planetary rotation on oceanic surface boundary layer turbulence abstracta large eddy simulation les model is configured to investigate the effect of the horizontal northward component of earth s rotation on upper ocean turbulence the focus is on the variab

evidence of enhanced double diffusive convection below the main stream of the kuroshio extension in this study a navis microrider microstructure float and an em apex float were deployed along the kuroshio extension front the observations deeper than 150 m reveal widespread interleaving thermohaline structures for at least 900 km along the front presumably generated through mesoscale stirring and near inertial oscillations in these interleaving structures microscale thermal dissipation rates are very high o 10 7 k2s 1 while turbulent kinetic energy dissipation rates are relatively low o 10 10 10 9 wkg 1 with effective thermal diffusivity k of o 10 3 m2s 1 consistent with the previous parameterizations for double diffusion and k is two orders of magnitude larger than the turbulent eddy diffusivity for density k the average observed dissipation ratio in salt finger and diffusive convection favorable conditions are 1 2 and 4 0 respectively and are larger than that for turbulence our results suggest that mesoscale subduction obduction and near inertial motions could catalyze double diffusive favorable conditions and thereby enhancing the diapycnal tracer fluxes below the kuroshio extension front

observation of tropical cyclone induced shallow water currents in taiwan strait the data from three stations equipped with acoustic doppler current profilers adcps deployed in the shallow water of the taiwan strait tws were used to study the shallow coastal ocean response to five quasi continuous tropical cyclone tc events in the late summer 2006 we revealed that in the forced stage when the large and strong tc bilis transited the geostrophic currents were formed which dominated the whole event while the strong but relatively small one saomai or the weak one bopha primarily leaded to the generation of ekman currents in the relaxation stage the barotropic subinertial waves and or the baroclinic near inertial oscillations nios were triggered typically during the transit of the saomai subinertial waves were induced which demonstrated a period of 2 8 4 1 days and a mean alongshore phase velocity of 14 9 3 2 m s in the form of free barotropic continental shelf waves however the nios are only notable in the area in which the water column is stably stratified and also where the wind stress is dominated by the clockwise component and accompanied by high frequency near inertial variations we also demonstrated that due to the damping effects the nonlinear wave wave interaction e g between nio and semidiurnal tide in our case together with the well known bottom friction led to the rapid decay of the observed tc induced near inertial currents giving a typical e folding time scale of 1 3 inertial periods moreover such nonlinear wave wave interaction was even found to play a major role during the spring tide in tws

comparing induced polarization responses from airborne inductive and galvanic ground systems tasmania abstractwe have first analyzed the ability of polarizable and superparamagnetic thin sheets in the near surface to fit airborne electromagnetic aem data using data from western tasmania then we analyzed the results of such fitting in the context of geologic mapping and available ground induced polarization ip data small to large ip effects were found to considerably improve the fit to the observed aem data and the overall fitted ip parameters were spatially consistent however the locations of anomalous ip parameters were quite distinct from anomalies in other geophysical data the airborne chargeability highs were adjacent to or surrounded the ground chargeability highs in the five cases analyzed from tasmanian data modeling using the established cole cole physical property values for sulfides predicts that an inductive airborne system is insensitive to many conventional ip targets unless the mineral grain size is substantially less than 1 mm in the cases in which airborne ip responses were ad

nonbreaking wave induced mixing in upper ocean during tropical cyclones using coupled hurricane ocean wave modeling the effects of turbulence generated by nonbreaking waves have been investigated by testing and evaluating a new nonbreaking wave parameterization in a coupled hurricane ocean wave model the mpi version of the princeton ocean model pom with hurricane forcing is coupled with the wavewatch iii ww3 surface wave model hurricane ivan is chosen as the test case due to its extreme intensity and availability of field data during its passage the model results are validated against field observations of wave heights and sea surface temperatures ssts from the national data buoy centre ndbc during hurricane ivan and against limited in situ current and bottom temperature data a series of numerical experiments is set up to examine the influence of the nonbreaking wave parameterization on the mixing of upper ocean the sst response from the modeling experiments indicates that the nonbreaking wave induced mixing leads to significant cooling of the sst and deepening of the mixed layer it was found that the nondimensional constant b1 in the nonbreaking wave parameterization has different impacts on the weak and the strong sides of the storm track a constant value of b1 leads to improved predictions on the strong side of the storm while a steepness dependent b1 provides a better agreement with in situ observations on the weak side a separate simulation of the intense tropical cyclone olwyn in north west australia revealed the same trend for b1 on the strong side of the tropical cyclone

interaction of langmuir turbulence and inertial currents in the ocean surface boundary layer under tropical cyclones abstractbased on a large eddy simulation approach this study investigates the response of the ocean surface boundary layer osbl and langmuir turbulence lt to extreme wind and complex wave forc

observed upper ocean response to typhoon megi 2010 in the northern south china sea typhoon megi passed between two subsurface moorings in the northern south china sea in october 2010 and the upper ocean thermal and dynamical response with strong internal tides present was examined in detail the entire observed water column 60 360 m was cooled due to strong ekman pumped upwelling up to 50 m in the thermocline by megi with maximum cooling of 4 2 c occurring in thermocline a relatively weak maximum amplitude of 0 4 m s 1 and quickly damped e folding time scale of 2 inertial periods near inertial oscillation nio was observed in the mixed layer power spectrum and wavelet analyses both indicated an energy peak appearing at exactly the sum frequency fd1 with maximum amplitude up to 0 2 m s 1 of nio f and diurnal tide d1 indicating enhanced nonlinear wave wave interaction between f and d1 during and after typhoon numerical experiments suggested that energy transfer from nio to fd1 via nonlinear interaction between f and d1 may have limited the growth and accelerated the damping of mixed layer nio generated by megi the occurrence of fd1 had a high correlation with nio the vertical nonlinear momentum term associated with the vertical shear of nio and vertical velocity of d1 or vertical shear of d1 and vertical velocity of nio was more than 10 times larger than the horizontal terms and was responsible for forcing fd1 after megi surface layer diurnal energy was enhanced by up to 100 attributed to the combined effect of the increased surface layer stratification and additional megi forced diurnal current

comparing induced polarization responses from airborne inductive and galvanic ground systems lewis ponds new south wales we have evaluated the mapping of polarizable material using a cole cole model to fit second order effects in concentric loop airborne electromagnetic system responses at lewis ponds in new south wales an inverted ground dipole dipole array data has accurately imaged in 3d disseminated sulfide extending above and around ore grade massive sulfides the polarizable zone is present in the near surface where from modeling airborne systems may have sensitivity to the small inductive induced polarization effects although the inverted chargeability measured from galvanic current injection into the ground was spatially coincident with the mineralized target the estimated chargeabilities from induced polarization effects in an airborne versatile time domain electromagnetic survey were substantially displaced to the east the airborne induced polarization response may be associated with finer grained mineralization in the hanging wall of the sulfide deposits or have a quite different source such as clays associated with faulting

observed near surface flows under all tropical cyclone intensity levels using drifters in the northwestern pacific 1 data from drifters of the surface velocity program and tropical cyclones tcs of the joint typhoon warning center during 1985 2009 were analyzed to demonstrate strong currents under various storm intensities such as category 4 to 5 category 2 to 3 and tropical storm to category 1 tcs in the northwestern pacific current speeds over 2 0 m s 1 are observed under major tcs with the strongest mean currents to the right of the storm track this study provides the characterization of the near surface velocity response to all recorded tcs and agrees roughly with geisler s theory 1970 our observations also verify earlier modeling results of price 1983

vertically averaged velocities in the north atlantic current from field trials of a lagrangian electric field float abstract a subsurface lagrangian float that utilizes motional induction to calculate vertically averaged velocities was tested in the north atlantic current nac taking advantage of existing cruises and infrastructure the electric field float eff is a rafos float with horizontal electrodes that measures its own velocity by rafos tracking and calculates vertically averaged velocities when merged with the electrode system the observations showed depth averaged velocities that were fast in the core of the nac 0 6 0 9 m s 1 and moderate in adjacent recirculations and eddies 0 3 0 4 m s 1 a float at 850 dbar moved at close to the depth averaged velocity while shallower floats followed surface intensified flow on top of the depth averaged motion integral time scales of depth averaged velocity 1 3 1 6 0 4 d are slightly shorter than time scales of float velocity 1 6 2 0 0 3 d while integral length scales of depth averaged water velocity 35 10 km for u 18 6 km for v are slightly shorter than length scales of float motion 53 12 km for u 28 6 km for v velocity spectra of depth averaged velocity show significant variance at inertial periods quantitative and qualitative validation with multiple independent data sets confirms the accuracy of the instrument and sampling strategy in the nac advancing the limited observational knowledge of depth averaged circulation in subpolar regions

influence of the size of supertyphoon megi 2010 on sst cooling abstractsupertyphoon megi 2010 left behind two very contrasting sst cold wake cooling patterns between the philippine sea 1 5 c and the south china sea 7 c based on various radii of radial winds we found that the size of megi doubles over the south china sea when it curving northwards on average the radius of maximum wind rmw increased from 18 8 km over the philippine sea to 43 1 km over the south china sea the radius of 64 kt typhoon force wind r64 increased from 52 6 km to 119 7 km the radius of 50 kt damaging force wind r50 increased from 91 8 km to 210 km and the radius of 34 kt gale force wind r34 increased from 162 3 km to 358 5 km to investigate the typhoon size effect we conduct a series of numerical experiments on megi induced sst cooling by keeping other factors unchanged i e typhoon translation speed and ocean subsurface thermal structure the results show that if it were not for megi s size increase over the south china sea the during megi sst cooling magnitude woul

detecting and characterizing ekman currents in the southern ocean abstractthis study presents a unique array of velocity profiles from electromagnetic autonomous profiling explorer em apex profiling floats in the antarctic circumpolar current acc north of kerguelen the authors use these profiles to examine the nature of ekman spirals formed by the action of the wind on the ocean s surface in light of ekman s classical linear theory and more recent enhancements vertical decay scales of the ekman spirals were estimated independently from current amplitude and rotation assuming a vertically uniform geostrophic current decay scales from the ekman current heading were twice as large as those from the current speed decay indicating a compressed spiral consistent with prior observations and violating the classical theory however if geostrophic shear is accurately removed the observed ekman spiral is as predicted by classical theory and decay scales estimated from amplitude decay and rotation converge toward a common value no statistically robust relationship is

frequency dependent attenuation analysis of ground penetrating radar data in the early 1990s it was established empirically that in many materials ground penetrating radar gpr attenuation is approximately linear with frequency over the bandwidth of a typical pulse further a frequency independent q parameter characterizes the slope of the band limited attenuation versus frequency curve here i derive the band limited q function from a first order taylor expansion of the attenuation coefficient this approach provides a basis for computing q from any arbitrary dielectric permittivity model for cole cole relaxation i find good correlation between the first order q approximation and q computed from linear fits to the attenuation coefficient curve over two octave bands the correlation holds over the primary relaxation frequency for some materials this relaxation occurs between 10 and 200 mhz a typical frequency range for many gpr applications frequency dependent losses caused by scattering and by the commonly overlooked problem of frequency dependent reflection

spatial and temporal characterization of sea surface temperature response to tropical cyclones abstractthe spatial structure and temporal evolution of the sea surface temperature sst anomaly ssta associated with the passage of tropical cyclones tcs as well as their sensitivity to tc characteristics including tc intensity and translation speed and oceanic climatological conditions represented here by latitude are thoroughly examined by means of composite analysis using satellite derived sst data the magnitude of the tc generated ssta is larger for more intense slower moving and higher latitude tcs and it occurs earlier in time for faster moving and higher latitude storms the location of maximum ssta is farther off the tc track for faster moving storms and it moves toward the track with time after the tc passage the spatial extension of the cold wake is greater for more intense and for slower moving storms but its shape is quite independent of tc characteristics consistent with previous studies the calculations show that the mean ssta over a tc centered box nearly linearly corre

time lapse imaging of saline tracer transport in fractured rock using difference attenuation radar tomography 1 accurate characterization of fractured rock aquifer heterogeneity remains one of the most challenging and important problems in groundwater hydrology we demonstrate a promising strategy to identify preferential flow paths in fractured rock using a combination of geophysical monitoring and conventional hydrogeologic tests cross well differenceattenuation ground penetrating radar was used to monitor saline tracer migration in an experiment at the u s geological survey fractured rock hydrology research site in grafton county new hampshire radar data sets were collected every 10 min in three adjoining planes for 5 hours during each of 12 tracer tests an innovative inversion method accounts for data acquisition times and temporal changes in attenuation during data collection the inverse algorithm minimizes a combination of two functions the first is the sum of weighted squared data residuals second is a measure of solution complexity based on an a priori space time covariance function subject to constraints that limit radarattenuation changes to regions of the tomograms traversed by high difference attenuation ray paths the time series of tomograms indicate relative tracer concentrations and tracer arrival times in the image planes from these we infer the presence and location of a preferential flow path within a previously identified zone of transmissive fractures these results provide new insights into solute channeling and the nature of aquifer heterogeneity at the site index terms 0910 exploration geophysics data processing 0915 exploration geophysics downhole methods 1829 hydrology groundwater hydrology 1832 hydrology groundwater transport 1894 hydrology instruments and techniques keywords radar tomography fractured rock ground penetrating radar geophysics hydrogeophysics

detection and analysis of lnapl using the instantaneous amplitude and frequency of ground penetrating radar data this paper reports the results of using the ground penetrating radar gpr method to detect light non aqueous phase liquids lnapl floating on the water table in an area where the thickness of lnapl present ranges from a few centimetres to several decimetres to understand the gpr response in this context gpr theoretical models are calculated using information from the literature and hydrogeological field data the study revealed that in the case of lnapl floating on the water table in a static condition there is an increase in the reflection amplitude from the water table due to the decrease in the capillary fringe nevertheless the amplitude of reflection from the water table can discriminate the contaminated from the non contaminated zone apart from an analysis of the real traces the analysis of some attributes of the complex trace instantaneous amplitude phase and frequency are also good tools to detect hydrocarbons floating on the water table such attributes depending on both the signal frequency and the hydrocarbon thickness can also give information about the thickness of the hydrocarbon layer it is concluded that analysing the lateral variations in signal amplitude of the real trace and in the amplitude phase and instantaneous frequency of the complex signal permits the delimiting of the area polluted by the hydrocarbon

upper ocean response to hurricane frances 2004 observed by profiling em apex floats abstractthree autonomous profiling electromagnetic autonomous profiling explorer em apex floats were air deployed one day in advance of the passage of hurricane frances 2004 as part of the coupled boundary layer air sea transfer cblast high field experiment the floats were deliberately deployed at locations on the hurricane track 55 km to the right of the track and 110 km to the right of the track these floats provided profile measurements between 30 and 200 m of in situ temperature salinity and horizontal velocity every half hour during the hurricane passage and for several weeks afterward some aspects of the observed response were similar at the three locations the dominance of near inertial horizontal currents and the phase of these currents whereas other aspects were different the largest amplitude inertial currents were observed at the 55 km site where sst cooled the most by about 2 2 c as the surface mixed layer deepened by about 80 m based on the time depth evolution of the richar

upper ocean response to typhoon kalmaegi 2014 typhoon kalmaegi passed over an array of buoys and moorings in the northern south china sea in september 2014 leaving a rare set of observations on typhoon induced dynamical and thermohaline responses in the upper ocean the dynamical response was characterized by strong near inertial currents with opposite phases in the surface mixed layer and in the thermocline indicating the dominance of the response by the excitation of the first baroclinic mode the thermohaline response showed considerable changes in the mean fields in addition to a near inertial oscillation in particular temperature and salinity anomalies generally exhibited a three layer vertical structure with the surface layer becoming cooler and saltier the subsurface layer warmer and fresher and the lower layer cooler and saltier again the response in the surface and subsurface layers was much stronger to the right of the typhoon track while that in the lower layer was stronger along the track and to the left these features of the upper ocean response were grossly reproduced by a three dimensional numerical model a model based heat budget analysis suggests that vertical mixing was mainly responsible for the surface cooling and subsurface warming while upwelling was the cause of cooling from below both observations and model results indicate that the whole upper ocean experienced an overall cooling in the wake of typhoon kalmaegi

response of upper ocean currents to typhoon fanapi the response of upper ocean currents to typhoon fanapi in fall 2010 was studied using an extensive air deployed drifter array separation of the observations into near inertial and sub inertial motions quantified the importance of strong advection by the sub inertial circulation for the evolution of the cold wake formed by typhoon fanapi the near inertial currents generated during the storm showed the expected rightward bias with peak magnitudes of up to 0 6 m s and an e folding time of about 4 days for the strong currents within the cold wake the shear of the near inertial currents is crucial for the storm induced cooling and deepening of the mixed layer and such instabilities were here directly observed across the base of the mixed layer in typhoon fanapi s cold wake during the recovery the diurnal cycle a dominant process for the wake warming was found to be noticeably reduced when the near inertial motions were strongest

highly resolved observations and simulations of the ocean response to a hurricane 1 an autonomous profiling float called em apex was developed to provide a quantitative and comprehensive description of the ocean side of hurricane ocean interaction em apex measures temperature salinity and pressure to ctd quality and relative horizontal velocity with an electric field sensor three prototype floats were air deployed into the upper ocean ahead of hurricane frances 2004 all worked properly and returned a highly resolved description of the upper ocean response to a category 4 hurricane at a float launched 55 km to the right of the track the hurricane generated large amplitude inertially rotating velocity in the upper 120 m of the water column coincident with the hurricane passage there was intense vertical mixing that cooled the near surface layer by about 2 2 c we find consistent model simulations of this event provided the wind stress is computed from the observed winds using a high wind speed saturated drag coefficient

inversion of induced polarization data we present an algorithm for inverting induced polarization ip data acquired in a 3 d environment the algorithm is based upon the linearized equation for the ip response and the inverse problem is solved by minimizing an objective function of the chargeability model subject to data and bound constraints the minimization is carried out using an interior point method in which the bounds are incorporated by using a logarithmic barrier and the solution of the linear equations is accelerated using wavelet transforms inversion of ip data requires knowledge of the background conductivity we study the effect of different approximations to the background conductivity by comparing ip inversions performed using different conductivity models including a uniform half space and conductivities recovered from one pass 3 d inversions composite 2 d inversions limited aim updates and full 3 d nonlinear inversions of the dc resistivity data we demonstrate that when the background conductivity is simple reasonable ip results are obtainable without using the best conductivity estimate derived from full 3 d inversion of the dc resistivity data as a final area of investigation we study the joint use of surface and borehole data to improve the resolution of the recovered chargeability models we demonstrate that the joint inversion of surface and crosshole data produces chargeability models superior to those obtained from inversions of individual data sets

subsurface radar propagation deconvolution the frequency dependence of attenuation is typically far greater for subsurface radar waves than for seismic waves since this frequency dependence causes the subsurface radar pulse shape to change as it propagates through the earth conventional wavelet deconvolution techniques are often inadequate to reconstruct the earth s reflectivity series the application of a time variant filter that undoes the effect of frequency dependent attenuation can substantially improve the resolution of subsurface radar data this filter is minimum phase with amplitude characteristics equal to the inverse of the attenuation function of the medium investigated preliminary tests on data from surveys over a water tank an underground mine stope and fractured granite suggest that good results can also be achieved by assuming attenuation is linearly proportional to frequency similar to a constant q model