joint correction of ionosphere noise and orbital error in l band sar interferometry of interseismic deformation in southern california the accuracy of l band synthetic aperture radar sar differential interferometry insar on crustal deformation studies is largely compromised by ionosphere path delays on the radar signals the ionosphere effects cause severe ionospheric distortion such as azimuth streaking and long wavelength phase distortion similar to orbital ramp error effective detection and correction of ionospheric phase distortion from l band insar images are necessary to measure and accurately interpret surface displacement in this paper we investigate the performance improvement of l band insar interseismic deformation measurements in southern california through the joint correction of both ionosphere noise and orbital error our results show that this method can effectively remove orbit and ionosphere phase distortions in comparison with in situ gps measurements the achieved insar measurement accuracy is improved from 30 mm to 10 mm by the proposed joint correction method we show that after the joint correction the remaining atmosphere noise can be further mitigated through stacking leading to an rms error of 4 7 mm year in resultant line of sight velocity as compared with 11 3 mm year before the correction our results demonstrate that the proposed joint correction technique provides a promising way to jointly correct orbital and ionospheric artifacts in l band insar studies of crustal deformation

redistribution of energy available for ocean mixing by long range propagation of internal waves ocean mixing which affects pollutant dispersal marine productivity and global climate1 largely results from the breaking of internal gravity waves disturbances propagating along the ocean s internal stratification a global map of internal wave dissipation would be useful in improving climate models but would require knowledge of the sources of internal gravity waves and their propagation towards this goal i present here computations of horizontal internal wave propagation from 60 historical moorings and relate them to the source terms of internal waves as computed previously2 3 analysis of the two most energetic frequency ranges near inertial frequencies and semidiurnal tidal frequencies reveals that the fluxes in both frequency bands are of the order of 1 kw m 1 that is 15 50 of the energy input and are directed away from their respective source regions however the energy flux due to near inertial waves is stronger in winter whereas the tidal fluxes are uniform throughout the year both varieties of internal waves can thus significantly affect the space time distribution of energy available for global mixing

insar bias and uncertainty due to the systematic and stochastic tropospheric delay we quantify the bias and uncertainty of interferometric synthetic aperture radar insar displacement time series and their derivatives the displacement velocities by analyzing the systematic and stochastic components of the temporal variation of the tropospheric delay the biases due to the systematic seasonal delay depend on the sar acquisition times whereas the uncertainties depend on the standard deviation of the random delay the number of acquisitions the total time span covered and the covariance of the time series of the stochastic delay between a pixel and the reference we study the contribution of the wet delay to the insar observations along the western india plate boundary using i moderate resolution imaging spectroradiometer precipitable water vapor ii stratified tropospheric delay estimated from the era i global atmospheric model and iii seven envisat insar swaths our analysis indicates that the amplitudes of the annual delay vary by up to 10 cm in this region equivalent to a maximum displacement bias of 24 cm in insar line of sight direction between two epochs assuming envisat is6 beam mode the stratified tropospheric delay correction mitigates this bias and reduces the scatter due to the stochastic delay for 7 years of envisat acquisitions along the western india plate boundary the uncertainty of the insar velocity field due to the residual stochastic wet delay after stratified tropospheric delay correction using the era i model is in the order of 2 mm yr over 100 km and 4 mm yr over 400 km we discuss the implication of the derived uncertainties on the full variance covariance matrix of the insar data

simulation of the supersar multi azimuth synthetic aperture radar imaging system for precise measurement of three dimensional earth surface displacement the supersar imaging system a novel multi azimuth synthetic aperture radar sar system capable of detecting earth surface deformation in three dimensions from a single satellite platform has recently been proposed in this paper we investigate the feasibility of detecting precise 3 d surface displacement measurements with the supersar imaging system using a point target simulation from this simulation we establish both a relationship between the interferometric sar phase and the across track displacement and a relationship between the multiple aperture interferometry phase and the along track displacement based on the supersar imaging geometry the theoretical uncertainties of the supersar measurement are analyzed in the across and along track directions and the theoretical accuracy of the 3 d displacement measurement from the supersar system is also investigated according to both the decorrelation and the squint and look angles in the case that the interferometric coherence is about 0 8 and that five effective looks are employed the theoretical 2 d measurement precision values are about 3 67 and 6 35 mm in the across and along track directions respectively and the theoretical 3 d measurement precision values for 3 d displacement are about 4 05 4 56 and 3 45 mm in the east north and up directions respectively the result of this study demonstrates that the supersar imaging system is capable of measuring the 3 d surface displacement in all directions with subcentimeter precision

new altimetric estimates of mode 1 m2 internal tides in the central north pacific ocean abstract new estimates of mode 1 m2 internal tide energy flux are computed from an extended ocean topography experiment topex poseidon t p altimeter dataset that includes both the original and tandem tracks improving spatial resolution over previous estimates from o 500 km to o 250 km additionally a new technique is developed that allows separate resolution of northward and southward components half wavelength features previously seen in unseparated estimates are shown to be due to the superposition of northward and southward wave trains the new technique and higher spatial resolution afford a new view of mode 1 m2 internal tides in the central north pacific ocean as with all altimetric estimates only the coherent or phase locked signals are detectable owing to the long repeat period of the tracks emanating from specific generation sites consistent with predictions from numerical models internal tidal beams 1 are as narrow as 200 km and 2 propagate a longer distance than previously observ

mapping ground surface deformation using temporarily coherent point sar interferometry application to los angeles basin abstract multi temporal interferometric synthetic aperture radar insar is an effective tool to detect long term seismotectonic motions by reducing the atmospheric artifacts thereby providing more precise deformation signal the commonly used approaches such as persistent scatterer insar psinsar and small baseline subset sbas algorithms need to resolve the phase ambiguities in interferogram stacks either by searching a predefined solution space or by sparse phase unwrapping methods however the efficiency and the success of phase unwrapping cannot be guaranteed we present here an alternative approach temporarily coherent point tcp insar tcpinsar to estimate the long term deformation rate without the need of phase unwrapping the proposed approach has a series of innovations including tcp identification tcp network and tcp least squares estimator we apply the proposed method to the los angeles basin in southern california where structurally active faults are believed capable of generating damaging earthquakes the analysis is based on 55 interferograms from 32 ers 1 2 images acquired during oct 1995 and dec 2000 to evaluate the performance of tcpinsar on a small set of observations a test with half of interferometric pairs is also performed the retrieved tcpinsar measurements have been validated by a comparison with gps observations from southern california integrated gps network our result presents a similar deformation pattern as shown in past insar studies but with a smaller average standard deviation 4 6 mm compared with gps observations indicating that tcpinsar is a promising alternative for efficiently mapping ground deformation even from a relatively smaller set of interferograms

three dimensional deformation retrieval in geosynchronous sar by multiple aperture interferometry processing theory and performance analysis the 3 d deformation retrieval is significant for the accurate evaluation of geologic disasters e g earthquakes and landslides multiple aperture interferometry mai is an effective method to obtain 3 d deformation combined with the cross heading tracks synthetic aperture radar sar data however because of the limitations of the low earth orbit sar a long satellite revisit time small common areas of the cross heading tracks data and the unsatisfied along track deformation measurement accuracy usually exist in the traditional mai 3 d deformation retrieval geosynchronous sar geo sar runs in the geosynchronous orbit which has the advantages of a large observation area and a short revisit time this paper focuses on 3 d deformation retrieval by geo sar mai processing aiming at the high orbit and the squint looking of geo sar the accurate expressions of the along track deformation 3 d deformation and the errors in geo sar mai processing are given the distortions and their correction in the mai interferogram brought by the geometrical difference between the forward and backward looking interferograms and the multicycles flat earth and topographic phases are given moreover an optimal subaperture selection method based on minimum position dilution of precision is proposed finally the effectiveness of the proposed method is validated by simulations and the experiment of beidou 2 inclined geosynchronous orbit navigation satellite the theoretical analysis and the experimental results suggest centimeter level and even millimeter level deformation measurement accuracy could be obtained in 3 d by geo sar mai processing

energetics of m2 barotropic to baroclinic tidal conversion at the hawaiian islands abstract a high resolution primitive equation model simulation is used to form an energy budget for the principal semidiurnal tide m2 over a region of the hawaiian ridge from niihau to maui this region includes the kaena ridge one of the three main internal tide generation sites along the hawaiian ridge and the main study site of the hawaii ocean mixing experiment the 0 01 horizontal resolution simulation has a high level of skill when compared to satellite and in situ sea level observations moored adcp currents and notably reasonable agreement with microstructure data barotropic and baroclinic energy equations are derived from the model s sigma coordinate governing equations and are evaluated from the model simulation to form an energy budget the m2 barotropic tide loses 2 7 gw of energy over the study region of this 163 mw 6 is dissipated by bottom friction and 2 3 gw 85 is converted into internal tides internal tide generation primarily occurs along the flanks of the kaena ridge and

surface manifestation of internal tides in the deep ocean observations from altimetry and island gauges the sea surface height signatures of internal tides in the deep ocean amounting to a few centimeters or less are studied using two complementary measurement types satellite altimetry and island tide gauges altimetry can detect internal tides that maintain coherence with the astronomical forcing island gauges can monitor temporal variability which in some circumstances is due to internal tides varying in response to changes in the oceanic medium this latter mechanism is at work at hilo and other stations on the northern coasts of the hawaiian islands by detecting spatially coherent low frequency internal tide modulations the tide gauges along with inverted echo sounders at sea suggest that the mean internal tide is also spatially coherent satellite altimetry confirms this at hawaii and in many other places topex poseidon altimetry detects mean surface waves spatially coherent and propagating great distances 1000 km before decaying below background noise when temporal variability is small the altimetry plus information on ocean density sets useful constraints on energy fluxes into internal tides at the hawaiian ridge 15 gw of tidal power is being converted from barotropic to first mode baroclinic motion examples elsewhere warn that a simplistic interpretation of the altimetry without regard to variability noise or in situ information may be highly misleading with such uncertainties extension of the hawaiian results into a usefully realistic estimate of the global internal tide energy balance appears premature at this time

an improvement of the performance of multiple aperture sar interferometry mai multiple aperture synthetic aperture radar sar interferometry mai enables the measurement of along track surface deformations by means of split beam sar processing this paper examines the effects of flat earth and topographic phases on the mai phase and derives formulas to correct them detailed mai processing steps are introduced and discussed with particular consideration given to coherence improvement as well as to computational efficiency forward and backward looking mai pairs have different perpendicular baselines which play a key role in phase distortion consequently an orbital deviation of only a few centimeters could result in a significant flat earth phase a second order polynomial model was used to estimate the perpendicular baseline difference european remote sensing 2 satellite sar data sets of the hector mine earthquake event in 1999 were used for performance evaluation the proposed processing with the flat earth and topographic phase corrections achieved precision of along track deformation ranging from 10 2 to 13 1 cm two coseismic pairs were compared and the standard deviation of the difference between the two independent measurements was 7 0 cm with a mean difference of 0 24 cm thus the measurement accuracy of mai was improved using flat earth correction and coherence enhancement

potential and limits of insar to characterize interseismic deformation independently of gps data application to the southern san andreas fault system the evaluation of long wavelength deformation associated with interseismic strain accumulation traditionally relies on spatially sparse gps measurements or on high spatial resolution insar velocity fields aligned to a gps based model in this approach the insar contributes only short wavelength deformation and the two data sets are dependent thereby challenging the evaluation of the insar uncertainties and the justification of atmospheric corrections here we present an analysis using 7 years of envisat insar data to characterize interseismic deformation along the southern san andreas fault saf and the san jacinto fault sjf in southern california where the saf bifurcates onto the mission creek mcf and the banning bf fault strands we outline the processing steps for using insar alone to characterize both the short and long wavelength deformation and evaluate the velocity field uncertainties with independent continuous gps data insar line of sight los and continuous gps velocities agree within 1 2 mm yr in the study area suggesting that multiyear insar time series can be used to characterize interseismic deformation with a higher spatial resolution than gps we investigate with dislocation models the ability of this mean los velocity field to constrain fault slip rates and show that a single viewing geometry can help distinguish between different slip rate scenarios on the saf and sjf 35 km apart but multiple viewing geometries are needed to differentiate slip on the mcf and bf 12 km apart our results demonstrate that interseismic models of strain accumulation used for seismic hazards assessment would benefit from the consideration of insar mean velocity maps

assessments of land subsidence in the gippsland basin of australia using alos palsar data abstract in this paper the land deformation in the gippsland basin victoria australia has been mapped using the interferometric synthetic aperture radar insar time series analysis with the alos l band sar data land subsidence in the basin resulting from mining activities has already been known over the past few decades there has been ongoing concern that irrigation and off shore oil and natural gas extraction has significantly lowered groundwater levels on shore and that this may lead to further subsidence therefore it is important to map the land surface change in the basin in order to understand the actual impact of these activities the total area of gippsland basin is approximately 46 000 km2 where approximately one third of the basin is located onshore because of the large area of the basin alos palsar data from 4 different paths were used to map the land displacement over the basin the insar result suggests that the land displacement at 98 of the measurement points in the basin was between 10 mm year and 10 mm year the insar result has been compared to the ground survey data in several areas collected with gps and total station surveys the comparison of results suggested that the insar measurement and the ground survey measurement agree with each other in general the standard deviation of difference between the insar results and the ground survey data is approximately 4 mm year near the coastal area and 15 mm year near the mining sites several rapidly deforming areas have been identified at the mining sites and the surrounding areas deformation rate at up to 82 9 mm year is observed in these areas the deformation at the mining sites and the surrounding areas are expected to be resulted from mining activities and associated mine dewatering moreover several minor displacement zones have been observed and investigated in the area between the loy yang mines and the gippsland coast as well as the area between yanakie and wilsons promontory

global patterns of low mode internal wave propagation part i energy and energy flux abstract extending an earlier attempt to understand long range propagation of the global internal wave field the energy e and horizontal energy flux f are computed for the two gravest baroclinic modes at 80 historical moorings around the globe with bandpass filtering the calculation is performed for the semidiurnal band emphasizing m2 internal tides generated by flow over sloping topography and for the near inertial band emphasizing wind generated waves near the coriolis frequency the time dependence of semidiurnal e and f is first examined at six locations north of the hawaiian ridge e and f typically rise and fall together and can vary by over an order of magnitude at each site this variability typically has a strong spring neap component in addition to longer time scales the observed spring tides at sites northwest of the hawaiian ridge are coherent with barotropic forcing at the ridge but lagged by times consistent with travel at the theoretical mode 1 group speed from the ridge phase c

transient strain accumulation and fault interaction in the eastern california shear zone satellite synthetic aperture radar interferometry reveals transient strain accumulation along the blackwater little lake fault system within the eastern california shear zone the surface strain map obtained by averaging eight years 1992 2000 of earth resource satellite ers radar data shows a 120 km long 20 kmwide zone of concentrated shear between the southern end of the 1872 owens valley earthquake surface break and the northern end of the 1992 landers earthquake surface break the observed shear zone is continuous through the garlock fault which does not show any evidence of left lateral slip during the same time period a dislocation model of the observed shear indicates right lateral slip at 7 6 3 mm yr on a vertical fault below 5 km depth a rate that is two to three times greater than the geologic rates estimated on northwest trending faults in the eastern mojave area this transient slip rate and the absence of resolvable slip on the garlock fault may be the manifestation of an oscillatory strain pattern between interacting conjugate fault systems

barotropic and baroclinic tides in the central north pacific ocean determined from long range reciprocal acoustic transmissions abstract travel times of reciprocal 1000 km range acoustic transmissions determined from the 1987 reciprocal tomography experiment are used to study barotropic tidal currents and a large scale coherent baroclinic tide in the central north pacific ocean the difference in reciprocal travel times determines the tidal currents while the sum of reciprocal travel times determines the baroclinic tide displacement of isotachs or equivalently isotherms the barotropic tidal current accounts for 90 of the observed differential travel time variance the measured harmonic constants of the eight major tidal constituents of the barotropic tide and the constants determined from current meter measurements agree well with the empirical numerical tidal models of schwiderski and cartwright et al the amplitudes and phases of the first mode baroclinic tide determined from sum travel times agree with those determined from moored thermistors and current meters the baroclinic tidal signals are consistent with a large

interseismic megathrust coupling beneath the nicoya peninsula costa rica from the joint inversion of insar and gps data the nicoya peninsula costa rica was struck by a long anticipated and gap filling mw 7 6 earthquake in 2012 to study interseismic strain accumulation on the megathrust beneath the nicoya peninsula we present an improved interseismic coupling model by integrating interferometric synthetic aperture radar insar and gps data our model reveals three strongly coupled patches the first strongly coupled patch locates beneath the nicoya peninsula and ruptured during the 2012 earthquake the second strongly coupled patch locates offshore the central nicoya peninsula and remained largely unbroken however this region is close to and possibly intermingled with shallow slow slip and tremor suggesting that accumulated strain in this region may be released both seismically and aseismically the third strongly coupled patch offshore of the southeastern end of nicoya overlaps part of the coseismic rupture of the 1990 mw 7 0 nicoya gulf earthquake indicating that significant strain has re accumulated since this event incorporating insar data provides a more refined interseismic coupling model than using gps alone and allows for a more reliable comparison with local seismic and aseismic activities this comparison indicates that strongly locked regions during the interseismic stage are the loci of coseismic slip and deep slow slip and low frequency earthquakes occur in regions of low coupling or transition zones from low to high coupling while shallow slow slip and tremor commingle with strongly coupled regions our study demonstrates that insar data can be used to recover small long wavelength deformation signals with refined resolution in challenging subduction zone environments when integrated with gps observations

reduced mixing from the breaking of internal waves in equatorial waters in the oceans heat salt and nutrients are redistributed much more easily within water masses of uniform density than across surfaces separating waters of different densities but the magnitude and distribution of mixing across density surfaces are also important for the earth s climate as well as the concentrations of organisms most of this mixing occurs where internal waves break overturning the density stratification of the ocean and creating patches of turbulence predictions of the rate at which internal waves dissipate were confirmed earlier at mid latitudes here we present observations of temperature and velocity fluctuations in the pacific and atlantic oceans between 42 degrees n and 2 degrees s to extend that result to equatorial regions we find a strong latitude dependence of dissipation in accordance with the predictions in our observations dissipation rates and accompanying mixing across density surfaces near the equator are less than 10 of those at mid latitudes for a similar background of internal waves reduced mixing close to the equator will have to be taken into account in numerical simulations of ocean dynamics for example in climate change experiments

mapping low mode internal tides near hawaii using topex poseidon altimeter data 1 objective maps of m2 internal tide variability are derived from topex poseidon altimeter data obtained near the hawaiian ridge an estimate of the wavenumber spectrum shows that the radiation is dominated by a few spectral peaks at wavenumbers consistent with the theoretically expected value for mode 1 internal tides the data are not always consistent with the traveling wave model because the spacing of the altimeter tracks is larger than the internal tide wavelength the objective map underestimates the energy between the altimeter tracks with this caveat the maps are used to determine that 2 6 gw of power is radiated from a 1700 km section of the hawaiian ridge time series of hydrographic data obtained at the hot site north of oahu hawaii show that changes in mode 1 phase speed caused by variations in stratification have only a small effect on the propagation of the mode 1 internal tides

global baroclinic tides an approximate estimate of the energy in the first mode m2 baroclinic tide has been made from satellite observations results based on topex poseidon t p precision altimetry indicate that the internal tide patterns are similar to those expected from mid ocean topographic features in the global oceans both the orthotide and harmonic analyses indicate that the total energy in global m2 baroclinic tide is approximately 50 pj for a variety of reasons m2 is the only component that can be obtained reliably from altimetric measurements even then the energy value may be an underestimate and the energy flux the dissipation rate cannot be deduced from altimetry since it is the tidal currents flowing over mid ocean topographic features that are responsible for generating internal tides a model calibrated by m2 observations is a plausible alternative currents from a high resolution 15 barotropic tidal model have therefore been used to obtain an estimate of both the energy and the dissipation rate in m2 s2 and k1 baroclinic tides a simple model of baroclinic tide generation has been used and the unknown constant in this model has been selected to yield a total energy of 50 pj in the first mode m2 baroclinic tide based on this calibration the total energy is 8 pj in s2 first mode baroclinic tide and 15 pj in k1 the total in all first mode baroclinic tides is 90 pj about 16 of the total energy 580 pj in barotropic tides the model results also suggest that about 360 gw of tidal energy are dissipated in m2 baroclinic tides alone and 520 gw are dissipated in all first mode baroclinic tides the latter value is approximately 15 of the power input into barotropic ocean tides 3490 gw by the lunisolar tidal forces we have preferred to be conservative and hence these are likely to be underestimates especially since the altimetric tracks do not often intersect mid ocean topographic features at optimum angles while these values are very much within the range of earlier estimates in literature they should be regarded as still uncertain to perhaps a factor of two the dissipation rate could be anywhere from 400 gw to 800 gw the most likely value being about 600 gw the small signal to noise ratio involved in altimetric measurements of the surface manifestation of internal tides and potential contamination by mesoscale signals are serious problems in situ measurements at least a few locations underneath altimetric tracks are essential for confirmation and or refinement of these preliminary estimates hopefully these very first estimates of the energy and dissipation rate in global baroclinic tides though rather crude will serve as a catalyst for a better estimation in the future since internal tides are likely to be a prominent source of mixing in the deep oceans and important to thermocline maintenance

calibrating interferometric synthetic aperture radar insar images with regional gps network atmosphere models summary interferometric synthetic aperture radar insar technology provides a valuable tool for obtaining earth surface deformation and topography at high spatial resolution for crustal deformation studies similar to global positioning system gps insar measurements are affected by the earth s ionospheric and tropospheric layers as the electromagnetic signals significantly refract while propagating through the different layers while gps signals propagating through the neutral atmosphere are affected primarily by the distribution pressure and temperature of atmospheric gases including water vapour the propagation through the ionosphere is mainly affectedbythenumberoffreeelectronsalongthesignalpath here wepresenttheuseofdense regional gps networks for extracting tropospheric zenith delays and ionospheric total electron content tec maps in order to reduce the noise levels in insar images the results show significant reduction in the root mean square rms values when simultaneously combining the two corrections both at short time periods where no surface deformation is expected and at longer periods where imaging of localized subsidence and fault creep is enhanced

a unified analysis of crustal motion in southern california 1970 2004 the scec crustal motion map 1 to determine crustal motions in and around southern california we have processed and combined trilateration data collected from 1970 to 1992 vlbi data from 1979 to 1992 and gps data from 1986 to 2004 a long temporal coverage required in part by the occurrence of several large earthquakes in this region from a series of solutions for station positions we have estimated interseismic velocities coseismic displacements and postseismic motions within the region from 31 n to 38 n and east to 114 w the final product includes estimated horizontal velocities for 1009 gps 190 trilateration and 16 vlbi points with ties between some of these used to stabilize the solution all motions are relative to the stable north american reference frame snarf as realized through the velocities of 20 gps stations this provides a relatively dense set of horizontal velocity estimates with well tested errors for the past quarter century over the plate boundary from 31 n to 36 5 n these velocities agree well with those from the plate boundary observatory which apply to a later time period we also estimated vertical velocities 533 of which have errors below 2 mm yr most of these velocities are less than 1 mm yr but they show 2 4 mm yr subsidence in the ventura and los angeles basins and in the salton trough our analysis also included estimates of coseismic and postseismic motions related to the 1992 landers 1994 northridge 1999 hector mine and 2003 san simeon earthquakes postseismic motions increase logarithmically over time with a time constant of about 10 days and generally mimic the direction and relative amplitude of the coseismic offsets

model estimates of m2 internal tide energetics at the hawaiian ridge 1 a primitive equation model is used to examine the structure and energetics of m 2 internal tides generated at the hawaiian ridge recent estimates based on altimeter data suggest that 20 gw of barotropic tidal dissipation occurs at the ridge with conversion to internal tides believed to be the dominant dissipation mechanism the model simulates an internal tide that accounts for 9 7 gw of radiated energy away from the ridge in the northeast and southwest directions the strongest generation occurs at three sites where enhanced barotropic currents flow across elongated topographic features the depth integrated baroclinic energy flux and energy densities at these sites are on the order of 10 4 w m 1 and 10 4 j m 2 respectively a modal decomposition indicates that 62 of the outgoing energy flux is accounted for by the first internal mode 15 is accounted for by the second mode and less than 5 is accounted for by each subsequent higher mode the tidal dissipation due to bottom friction along the ridge is estimated to be 0 1 gw the level of turbulent dissipation near the ridge owing to tidal energy conversion remains to be determined to assess fully the barotropic baroclinic energy budget

global abyssal mixing inferred from lowered adcp shear and ctd strain profiles abstract internal wave wave interaction theories and observations support a parameterization for the turbulent dissipation rate e and eddy diffusivity k that depends on internal wave shear vz2 and strain z2 variances its latest incarnation is applied to about 3500 lowered adcp ctd profiles from the indian pacific north atlantic and southern oceans inferred diffusivities k are functions of latitude and depth ranging from 0 03 10 4 m2 s 1 within 2 of the equator to 0 4 0 5 10 4 m2 s 1 at 50 70 diffusivities k also increase with depth in tropical and subtropical waters diffusivities below 4500 m depth exhibit a peak of 0 7 10 4 m2 s 1 between 20 and 30 latitudes where semidiurnal parametric subharmonic instability is expected to be active turbulence is highly heterogeneous though the bulk of the vertically integrated dissipation e is contributed from the main pycnocline hotspots in e show some correlation with small scale bottom roughness and near bottom flow at sites where st

measuring azimuth deformation with l band alos 2 scansar interferometry we analyze the methods for measuring azimuth deformation with the l band advanced land observing satellite 2 alos 2 scanning synthetic aperture radar scansar interferometry to implement the methods we extract focused bursts from the alos 2 full aperture product which is the only product available for scansar interferometry at present the extracted bursts are properly processed to measure azimuth deformation using interferometric phase we apply the range split spectrum method to scansar to estimate the differential ionospheric phase of the interferogram and take the azimuth derivative of the differential ionospheric phase to mitigate the relative azimuth shift caused by ionosphere for the first time azimuth deformation of a large earthquake april 25 2015 nepal earthquake is nearly completely measured by the l band scansar interferometry with moderate precision the result is validated by the azimuth deformation measured by incoherent cross correlation using a pair of high resolution radarsat 2 images in addition to the final azimuth deformation we show the possibility of processing full aperture scansar product using a burst by burst approach to form regular interferograms we also show the recent strong large scale ionospheric effects on the l band alos 2 scansar interferograms other possible applications of this paper include measuring the movement of glaciers

vertical structure of the baroclinic tides in the central north pacific subtropical gyre abstract cruises are made monthly to the world ocean circulation experiment deep water station about 100 km north of oahu hawaii during these cruises the principal causes of variability in dynamic height are the internal tides having a range about 30 of the annual range in dynamic height the internal tides have peak to peak vertical displacements of up to 30 dbar but show little vertical coherence at the diurnal frequencies modal fits typically require 6 8 baroclinic modes to account for 90 of the variance suggesting that the diurnal tide should not be described in terms of dynamic modes the semidiurnal tide has about two to three times the amplitude of the diurnal tide and shows more vertical phase coherence but still requires three or four modes to describe it generally the dominant mode is the second or third mode

statistical testing for paleocommunity recurrence are similar fossil assemblages ever the same abstract observations of the recurrence of similar fossil assemblages through long intervals of geologic time punctuated by rapid changes in both the composition and structure of fossil assemblages has recently resulted in the concept of coordinated stasis to describe this pattern in the behavior of paleocommunities through time coordinated stasis may imply the existence of ecological mechanisms that actively maintain particular community structures and thus have a significant impact on the process of macroevolution however before such mechanisms can be invoked it must be shown that ecological stasis as observed in the fossil record is more significant than the persistence of similar community types due to the repeated reinvasion of recurring habitats from a persistent species pool the null hypothesis for paleocommunity recurrence analysis of the relationship between communities and paleocommunities and an expansion of the ecological hierarchy at the community paleocommunity level allows the creation of a rigorous definition of the entities composing the local paleocommunity the samples collected within a stratigraphic horizon at a single locality paleocommunity groups of samples shown to be statistically identical and paleocommunity type groups of samples that are similar but can be shown to be statistically different these definitions permit the development of the null model for paleocommunity recurrence and establish a base level of variability within a local paleocommunity that permits rigorous statistical comparisons to be made between paleoecological samples at larger temporal and geographic scales paleoecological samples from four marine tongues in the middle pennsylvanian breathitt formation are used to analyze species abundance variability at several spatial and temporal scales and to test for paleocommunity recurrence although recurrence of statistically identical local paleocommunities occurs at single localities and between localities within individual marine units it is usually not detectable between marine tongues suggesting that paleocommunity recurrence in the marine strata of the breathitt formation is the recurrence of paleocommunity types and does not falsify the null hypothesis

subtropical catastrophe significant loss of low mode tidal energy at 28 9 1 an idealized numerical study of a northward propagating internal tide reveals a dramatic loss of energy to small scale subharmonic instabilities near 28 9 n inspired by observations of the internal tide radiating northward from the hawaiian ridge a three dimensional numerical model is initialized with a northward baroclinic tidal flux of approximately 1 7 kw m after an initial spinup period energy is quickly transferred from the baroclinic tide to subharmonic motions with half the horizontal tidal wavenumber and small vertical scales through nonlinear advection of horizontal tidal velocity gradients potential oceanic implications are twofold first once a steady state has been reached the instability acts as a partial filter of northward tidal flux between 27 5 and 29 5 n in rough agreement with some altimetric tidal observations second elevated shear of the subharmonic motions suggests the potential for elevated near surface dissipation rates near the critical latitude that may be important for upper ocean mixing

latitudinal distribution of mixing rate caused by the m2 internal tide abstract ten years of ocean topography experiment topex poseidon tidal data and an energy balance relation are used to estimate the mixing rate caused by m2 internal tides in the upper ocean the results indicate that latitudinal distribution of the mixing rate has a generally symmetrical structure with respect to the equator the maxima are distributed around 28 9 n and 28 9 s and can be as high as 3 8 10 5 m2 s 1 in the pacific 5 10 5 m2 s 1 in the atlantic and 3 7 10 5 m2 s 1 in the indian oceans the minimum which is only 10 of those at 28 9 is located near the equator the data imply that midlatitudes are the key regions for internal tide mixing

altimeter and current meter observations of internal tides do they agree abstract baroclinic tides can be observed both remotely from the ocean topography experiment topex poseidon t p altimeter and in situ using current meters however it is rare that current meter moorings have high vertical resolution and are located under t p ground tracks so that a direct comparison can be made between the two methods of observations here data from a current meter mooring directly under a t p ground track off the bounty plateau new zealand are used to obtain energy estimates of the first baroclinic mode these estimates are compared with those calculated from the t p surface elevation the two methods return estimates of the internal tide that are in agreement in phase and direction but have about a factor of 2 difference in amplitude and a factor of 4 difference in energy the flux estimates are 787 and 170 w m 1 respectively uncertainties in these estimates are relatively large and there is a low but not negligible probability that the differences are entirely due to measu

measurement of precise three dimensional volcanic deformations via terrasar x synthetic aperture radar interferometry abstract multiple aperture sar interferometry mai is an advanced technique that is used to retrieve actual surface motions by complementing missing components of insar measurements despite the wide use of the mai method in the geosciences x band sar has rarely been applied in mai based studies due to the relatively shorter decorrelation periods involved thus we need to evaluate the mai measurements from x band sar for the use in the geosciences in this paper an assessment of the mai performance for terrasar x system was carried out at the test site k lauea volcano hawaii focusing on the kamoamoa fissure eruption episode that occurred on march 6 10 2011 the root mean square rms errors of single mai interferograms were 3 26 1 32 cm and 2 95 0 77 cm for descending and ascending datasets respectively multi stacked mai interferograms showed reduced error levels of 1 77 and 2 04 cm for descending and ascending datasets respectively in addition empirical uncertainty models of the mai measurements were generated with respect to the interferometric coherence of single and multi stacked mai measurements and these regression models enabled us to confirm the difference between the theoretical and practical accuracies of the mai measurements moreover the mai based 3d model based on high accuracy 3d maps showed some possibilities of new findings and interpretations of the geologic sources

significant dissipation of tidal energy in the deep ocean inferred from satellite altimeter data how and where the ocean tides dissipate their energy are long standing questions1 that have consequences ranging from the history of the moon2 to the mixing of the oceans3 historically the principal sink of tidal energy has been thought to be bottom friction in shallow seas4 5 there has long been suggestive evidence6 7 however that tidal dissipation also occurs in the open ocean through the scattering by ocean bottom topography of surface tides into internal waves but estimates of the magnitude of this possible sink have varied widely3 8 9 10 11 here we use satellite altimeter data from topex poseidon to map empirically the tidal energy dissipation we show that approximately 1012 watts that is 1 tw representing 25 30 of the total dissipation occurs in the deep ocean generally near areas of rough topography of the estimated 2 tw of mixing energy required to maintain the large scale thermohaline circulation of the ocean12 one half could therefore be provided by the tides with the other half coming from action13 on the surface of the ocean

propagation of low mode internal waves through the ocean abstract the baroclinic tides play a significant role in the energy budget of the abyssal ocean although the basic principles of generation and propagation are known a clear understanding of these phenomena in the complex ocean environment is only now emerging to advance this effort a ray model is developed that quantifies the effects of spatially variable topography stratification and planetary vorticity on the horizontal propagation of internal gravity modes the objective is to identify baroclinic shoals where wave energy is spatially concentrated and enhanced dissipation might be expected the model is then extended to investigate the propagation of internal waves through a barotropic mesoscale current field the refraction of tidally generated internal waves at the hawaiian ridge is examined using an ensemble of mesoscale background realizations derived from weekly ocean topography experiment topex poseidon altimetric measurements the path of mode 1 is only slightly affected by typical cur

feasibility of along track displacement measurement from sentinel 1 interferometric wide swath mode the european space agency s sentinel 1 a c band imaging radar mission to be launched in mid 2013 will provide a continuity of radar data for monitoring the changing earth the azimuth resolution of sentinel 1 s background mode interferometric wide swath iw mode is four times lower than that of european remote sensing satellite ers and envisat systems therefore the measurement accuracy of along track displacement from sentinel 1 iw images presumably will be significantly reduced in this paper we test the feasibility of along track displacement measurement from sentinel 1 iw mode we simulate sentinel 1 iw synthetic aperture radar sar images from the ers raw data that captured the coseismic deformation of the 1999 hector mine earthquake in california along track displacement maps are generated using multiple aperture interferometric sar mai and intensity tracking techniques respectively and are compared with gps measurements the root mean square rms error between the synthetic sentinel 1 mai and gps measurements is about 9 6 cm which corresponds to only 0 5 of the azimuth resolution the rms error between the along track displacements from synthetic sentinel 1 offset tracking and gps is about 27 5 cm which is about 1 4 of the azimuth resolution these results suggest that the mai method will still be useful to measure along track displacements from sentinel 1 iw insar imagery and that it would be difficult to effectively measure the along track displacements by the sentinel 1 offset tracking method

radar interferogram filtering for geophysical applications the use of sar interferometry is often impeded by decorrelation from thermal noise temporal change and baseline geometry power spectra of interferograms are typically the sum of a narrow band component combined with broad band noise we describe a new adaptive filtering algorithm that dramatically lowers phase noise improving both measurement accuracy and phase unwrapping while demonstrating graceful degradation in regions of pure noise the performance of the filter is demonstrated with sar data from the ers satellites over the jakobshavns glacier of greenland

measuring two dimensional movements using a single insar pair 1 we present a new method to extract along track displacements from insar data based on split beam insar processing to create forward and backward looking interferograms the phase difference between the two modified interferograms provides the along track displacement component thus from each conventional insar pair we extract two components of the displacement vector one along the line of sight the other in the along track direction we analyze the precision of the new method by comparing our solution to gps and offset derived along track displacements in interferograms of the 1999 hector mine earthquake the rms error between gps displacements and our results ranges from 5 to 8 8cm our method is consistent with along track displacements derived by pixel offsets which are limited to 12 15cm precision the theoretical precision of the new method depends on snr and coherence for a signal to noise ratio of 30 the expected precisions are 3 11cm for coherence of 0 8 0 4 respectively

ionospheric correction of insar data for accurate ice velocity measurement at polar regions abstract interferometric synthetic aperture radar insar has become an essential tool for measuring ice sheet velocity in the polar regions at low radar frequencies e g l band 1 2 ghz but also at higher frequency e g c band 5 6 ghz the ionosphere has been documented to be an important source of noise in these data in this paper we employ a split spectrum technique and investigate its performance for correcting ionospheric effects in insar based ice velocity measurements in greenland and antarctica three case studies using alos palsar data are used to assess the performance of the split spectrum technique for ionosphere correction over a range of environmental parameters we employ several approaches to evaluate the results including visual inspection profile analysis comparison of experimental and theoretic errors comparison with reference data from other sources generation of double difference interferograms and analysis of time series of multi temporal data our experiments show that ionospheric distortions are observed regularly and in our analyzed greenland dataset and antarctic dataset the ionospheric noise reaches 14 m yr and 10 m yr respectively which exceeds the signal associated with ice motion our analysis using several different approaches demonstrates that the split spectrum technique provides an effective correction the split spectrum technique is also found to be superior to currently used approaches such as baseline fitting and multi temporal averaging the noise level is reduced by a factor of 70 in greenland test areas and 90 in antarctic test areas

internal tide scattering at the line islands ridge 1 scattering of the m2 mode one internal tide from the line islands ridge is examined with a primitive equation numerical model model runs with baroclinic and barotropic forcing are performed to distinguish scattered from locally generated internal tides tpxo 5 tidal model sea surface elevations provide barotropic forcing while for the run with baroclinic forcing a mode one m2 energy flux of 1000 w m 1 is used to represent energy fluxes emanating from the hawaiian ridge scattering redistributes more energy flux from mode one than is locally generated in mode one for the higher modes scattering and generation contribute equally in terms of the overall energy flux spatial and modal distributions of energy density and flux show internal tide scattering dominates at hutchinson seamount while higher modes are generated locally at sculpin ridge hutchinson seamount s slopes are steeper over a greater continuous area than sculpin ridge scattered energy is found downstream of the steepest topographies similar to simulations with idealized gaussian ridges at the line islands ridge 37 of the incident mode one energy flux is lost because of scattering into modes 2 5 19 dissipation by the model s turbulence parameterization 15 and nonlinear transfer to the m4 internal tide 3 two topex ground tracks pass through the model domain roughly normal to the ridge topography and confirm the general features of the modal and spatial distribution found in the model in the topographically rough western pacific internal tide scattering may be a significant source of energy for mixing away from topography

internal tide radiation from mendocino escarpment abstract strong semidiurnal internal tides are observed near mendocino escarpment in full depth profile time series of velocity temperature and salinity velocity and density profiles are combined to estimate the internal tide energy flux divergence of this flux demonstrates that its source is the barotropic tide interacting with the escarpment a baroclinic energy flux of 7 kw m 1 radiates from the escarpment corresponding to 3 of the 220 kw m 1 fluxing poleward in the surface tide energy and energy flux are concentrated in packets that emanate from the flanks of the ridge surmounting the escarpment and one site 90 km north of the escarpment coherent beamlike structure along semidiurnal ray paths remains identifiable until the first surface reflection beyond the first surface reflection north of the escarpment the energy flux drops by 2 kw m 1 and beams are no longer discernible turbulence as inferred from finescale parameterizations is elevated by over two orders of magnitude relative to th