rate of dune reddening in a humid tropical climate the formation of red beds has long interested geologists and pedologists1 3 it has been suggested that the nature and degree of reddening in dune sands can be a useful indicator of the relative age and environmental history of the sands several authors have concluded that dune sands undergo progressive reddening with time4 7 and james and stanley8 considered that coastal dunes might actually be mapped on the basis of colour however quantitative data regarding the rate of reddening in different environmental conditions are generally lacking i present here radiocarbon evidence from north east australia which suggests that red weathering profiles have developed in stabilized dunes of holocene age in humid tropical conditions within the past 7 500 yr

combination of precise leveling and insar data to constrain source parameters of the mw 6 5 26 december 2003 bam earthquake we used new precise leveling data acquired 40 days after the bam earthquake in combination with radar interferometry observations from both ascending and descending orbits to investigate static deformation associated with the 2003 bam earthquake we invert this geodetic data set to gain insight into the fault geometry and slip distribution of the rupture the best fitting dislocation model is a steeply east dipping right lateral strike slip fault that has a size of 11 by 8 km and strikes n2 w we find that such smooth geometry fits available geodetic data better than previously proposed models for this earthquake our distributed slip model indicates a maximum strike slip of 3 m occurring about 3 to 5 km deep the slip magnitude and depth of faulting taper to the north where the fault approaches the bam city inclusion of crustal layering increases the amount of maximum slip inferred at depth by about 4

the structure and annual variation of antisymmetric fluctuations of tropical convection and their association with rossby gravity waves abstract the signature of 4 5 day period rossby gravity waves is searched for in the tropical convection field across the indian pacific oceans the convergence divergence field of these waves in the lower troposphere is anticipated to produce an antisymmetric fluctuation in tropical convection antisymmetric fluctuations of tropical convection are shown to exhibit a pronounced spectral peak at a 4 5 day period only during boreal fall and only within about 30 longitude of the date line the peak amplitude occurs around 7 5 latitude these fluctuations propagate westward at 15 20 m s 1 with zonal wavelength of about 7000 9000 km the fluctuations of convection are coherent and out of phase with the equatorial meridional wind which also exhibits a pronounced spectral peak at a 4 5 day period in the lower troposphere near the date line the antisymmetric zonal wind also is strongly coherent with the antisymmetric convective fluctuations in this region the horizontal distributions of the 4 5 day power an

observations of rossby waves linked to convection over the eastern tropical pacific rossby wave activity propagating into the eastern tropical pacific from the midlatitudes during northern winter is examined in some detail these waves are associated with the intrusion of high potential vorticity air into low latitudes and they modulate cloudiness stability and vertical motion in the vicinity of the itcz in the upper troposphere and lower stratosphere the horizontal phase and group propagation of the wave activity are qualitatively like those of a nondivergent barotropic rossby wave as the waves move equatorward they become more shallow and propagate upward into the stratosphere the horizontal and vertical propagation is consistent with the tilts of the waves the large scale three dimensional background flow and with the signatures of momentum and heat fluxes associated with the wave activity in the lower troposphere paired cyclonic anomalies on either side of the equator accompany the upper level wave activity to the west of the itcz cloudiness signal these waves amplify following the peak in the itcz cloudiness and propagate westward along the equator this suggests that the upper level wave activity and possibly the associated convective heating can trigger the excitation of the equatorially trapped rossby modes the transient wave activity appears to be a crucial component of the momentum balance of the eastern tropical pacific circulation there is substantial interannual variability in the wave activity consistent with observed changes in the large scale basic state associated with the southern oscillation

slip distribution of the 1997 umbria marche earthquake sequence joint inversion of gps and synthetic aperture radar interferometry data 1 in september october 1997 a seismic sequence struck the southern part of the umbria marche region in central italy the three largest earthquakes took place on 26 september 0033 ut mw 5 7 09 40 gu mw 6 0 near colfiorito and on 14 october mw 5 6 near sellano we present a slip model for the main sequence over two separate fault planes we use previously published global positioning system gps and differential interferometric synthetic aperture radar dinsar data as well as new dinsar data covering the sellano event as input to a simulated annealing solution for the distribution of fault slip the combination of both types of geodetic data as well as the combination of sar interferograms from both ascending and descending satellite tracks allows us to make a more complete geodetically based assessment of the fault slip for these earthquakes for the solutions presented here we required the slip distribution to match the observed surface displacements while maintaining a total scalar seismic moment approximately equal to the seismologically inferred moments for this sequence we find the slip was concentrated in a zone at 4 5 5 km depth with a shallower tail extending to near the surface at the northern end of the colfiorito sequence for both the second colfiorito event and the sellano event individual patches were calculated with maximum slip of 2 m implying stress drops as high as 20 mpa coulomb stress calculations show that the coseismic slip distribution for the colfiorito events facilitated slip of the adjacent sellano earthquake

decorrelation in interferometric radar echoes a radar interferometric technique for topographic mapping of surfaces implemented utilizing a single synthetic aperture radar sar system in a nearly repeating orbit is discussed the authors characterize the various sources contributing to the echo correlation statistics and isolate the term which most closely describes surficial change they then examine the application of this approach to topographic mapping of vegetated surfaces which may be expected to possess varying backscatter over time it is found that there is decorrelation increasing with time but that digital terrain model generation remains feasible the authors present such a map of a forested area in oregon which also includes some nearly unvegetated lava flows such a technique could provide a global digital terrain map

coupled magma chamber inflation and sector collapse slip observed with synthetic aperture radar interferometry on mt etna volcano 1 volcanoes deform dynamically due to changes in both their magmatic system and instability of their edifice mt etna features vigorous and almost continuous eruptive activity from its summit craters and periodic flank eruptions even though its shape is that of a large stratovolcano its structure features two rift systems and a flank collapse structure similar to hawaiian shield volcanoes we analyze european remote sensing ers satellite differential interferometric synthetic aperture radar insar data 1993 1996 for mt etna spanning its quiescence from 1993 through the initiation of renewed eruptive activity in late 1995 we use synthetic aperture radar sar data from both ascending and descending ers satellite tracks comparison of independent interferograms covering the first 2 years of the inflationary period shows a pattern consistent with inflation of the volcano calculation of the tropospheric path delay based on meteorological data does not change this interpretation interferograms from late summer 1995 1996 show no significant deformation joint inversion of interferograms from ascending and descending satellite tracks require both inflation from a spheroidal magmatic source located beneath the summit at 5 km below sea level and displacement of the east flank of etna along a basal decollement both sources of deformation were contemporaneous within the resolution of our data and suggest that inflation of the central magma chamber acted to trigger slip of etna s eastern flank these results demonstrate that flank instability and recharge of a volcano s magma system must both be considered toward understanding how volcanoes work and in their hazard evaluation

circulation anomalies associated with tropical convection during northern winter abstract lagged cross correlations between outgoing longwave radiation olr and national meteorological center global analyses are utilized to isolate the preferred upper level and surface circulation anomalies associated with tropical convection during northern winter three intraseasonal time scales are studied 30 70 14 30 and 6 14 days in the 30 70 day band the upper level circulation signals are zonally elongated with zonal wavenumbers 0 2 dominant higher frequency signals are dominated by zonal wavenumbers 5 and 6 in the 14 30 day band convection over the eastern hemisphere is associated with upper level anticyclones in the subtropics and appears to be linked in some cases to midlatitude wave trains the strongest signals are for convection over africa australia and the eastern indian ocean only weak signals are seen for convection over indonesia in these regions of upper level easterlies olr anomalies peak prior to the maximum anomalies in wind suggesting forcing of the circulation b

estimation of seismic and aseismic deformation in mexicali valley baja california mexico in the 2006 2009 period using precise leveling dinsar geotechnical instruments data and modeling ground deformation and seismicity in mexicali valley baja california mexico the southern part of the mexicali imperial valley are influenced by active tectonics and human activity in this study data from two successive leveling surveys in 2006 and 2009 2010 are used to estimate the total deformation occurred in mexicali valley during 2006 2009 the leveling data span more than 3 5 years and include deformation from several natural and anthropogenic sources that acted at different temporal and spatial scales during the analyzed period because of its large magnitude the aseismic anthropogenic deformation caused by fluid extraction in the cerro prieto geothermal field obscures the deformation caused by other mechanisms and sources the method of differential interferograms stacking was used to estimate the aseismic interseismic tectonic and anthropogenic components of the observed displacement using sar images taken in 2007 during a period when no significant seismicity occurred in the study area after removing the estimated aseismic signal from the leveling data residual vertical displacement remained and to identify possible sources and mechanisms of this displacement a detailed analysis of records from tiltmeters and creepmeters was performed the results of this analysis suggest that the residual displacement is mainly caused by moderate sized seismicity in the area of study modeling of the vertical ground deformation caused by the coseismic slip on source fault primary mechanism of the two most important earthquakes may 24 2006 mw 5 4 and december 30 2009 mw 5 8 was performed the modeling results together with the analysis of geotechnical instruments data suggests that this moderate sized seismicity influences the deformation in the study area by coseismic slip on the source fault triggered slip on secondary faults and soft sediments deformation

pine island glacier antarctica a study of the catchment using interferometric synthetic aperture radar measurements and radar altimetry we have mapped the catchment region of pine island glacier antarctica using ers 1 and ers 2 radar altimetry and synthetic aperture radar sar interferometry the radar altimeter data were converted to a digital elevation model dem using an algorithm we developed that corrects for slopes and grids the surface elevation estimates in a single step we used the dem and precise postprocessed orbital ephemerides to generate terrain corrected and geolocated complex radar imagery interferometric pairs on both ascending and descending orbits corrected by means of the dem yielded components of ice surface motion in the radar look direction where possible we combined velocity components from ascending and descending tracks to produce vector velocities elsewhere the velocity was calculated by assuming the direction of motion is down the surface slope the velocity map reveals a system of tributaries that channel ice from the basin like catchment area into the fast flowing downstream trunk of pine island glacier none of the tributaries shows a clear onset region instead the ice speed gradually increases along with a gradual decrease in driving stress along each tributary we combined the velocity data with sparse information on ice thicknesses and snow accumulation rates to calculate an approximate mass balance we find that the region is in balance within an uncertainty of 30 of the total mass throughput

cross equatorial response to middle latitude forcing in a zonally varying basic state abstract a nonlinear model based on the shallow water equations is used to study cross equatorial propagation of forced waves in the presence of a longitudinally varying time mean basic state zonal wind field it is found that global scale planetary waves are unable to propagate past a critical latitude where the mean zonal wind speed vanishes however if the longitudinally asymmetric basic state includes a duet in which the zonal winds are westerly waves of zonal scale less than the zonal scale of the westerly duct may propagate from one hemisphere to the other even though the zonally symmetric mean zonal wind remains easterly in the equatorial region the amplitude of the response in one hemisphere to forcing in the opposite hemisphere increases strongly with the magnitude of the westerlies in the equatorial duct the existence and annual variations of a westerly duct region in the upper troposphere in the eastern pacific appear to account for some features of the low frequency variability in the no

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

insar assessment of surface deformations in urban coastal terrains associated with groundwater dynamics monitoring ground deformations arising from groundwater dynamics in dense urban coastal terrains is crucial for the sustainable development of infrastructures in these highly populated areas the city of montreal which is located in the saint laurent plain in eastern canada with its fast growing populations is a unique case study for other similar cities in coastal terrains the city undergoes high level house foundation damages with densities reaching up to 89 repairs km2 resulting from time dependent ground deformations that are correlated to groundwater dynamics and evapotranspiration using radarsat 2 c band synthetic aperture radar interferometry we observe 3 to 5 mm ground line of sight displacement variations temporally outphased by few months relative to the 2 m subartesian aquifer hydraulic head variations the deformations are observed over a 60 km2 area located in the central part of the montreal island in canada from 2008 to 2010 we observe displacements of 1 mm year uplift in the areas covered by 15 m thick clay layer these displacements are well correlated to the number of house repairs we also observe 2 mm year subsidence on elevated terrains associated with evapotranspiration the amplitudes of the displacements observed during this two year study are significant when integrated over the average lifetime of urban structures we conclude that the observed ground deformations are related to the seasonal variation of hydraulic head in most of the areas of montreal moreover wetter climate forecasts over upcoming decades for this area will accentuate groundwater level fluctuations thus more ground deformations are foreseen and have to be considered in future infrastructure design standards

connections between potential vorticity intrusions and convection in the eastern tropical pacific abstract the connections between intrusions of stratospheric air into the upper troposphere and deep convection in the tropical eastern pacific are examined using a combination of data analysis potential vorticity pv inversion and numerical simulations analysis of ncep ncar reanalyses and satellite measurements of outgoing longwave radiation during intrusion events shows increased cloudiness lower static stability upward motion and a buildup of convective available potential energy cape at the leading edge of the intruding tongue of high pv potential inversion inversion calculations show that the upper level pv makes the dominant contribution to the changes in the quantities that characterize convection this supports the hypothesis that upper level pv anomalies initiate and support convection by destabilizing the lower troposphere and causing upward motion ahead on the pv tongue the dominant role of the upper level pv is confirmed by simulations using the fifth generation pennsylvania state u

holocene development of an episodic transgressive dune barrier ramsay bay north queensland australia abstract an investigation of the stratigraphy and sedimentological properties of a tombolo barrier at ramsay bay north queensland has indicated that the barrier consists largely of aeolian sands which in places extend more than 30 m below present sea level two major episodes of dune activity are recognized on morphological and pedogenic criteria radiocarbon dating of organic muds associated with the barrier sands suggests the older dunes were partly drowned during the early holocene marine transgression 9500 6000 c 14 yrs b p the later generation of dunes formed in the late holocene probably within the last 900 c 14 yrs the ultimate causes of the aeolian episodes are not certain but appear to be related to periods of rapid shoreface erosion

the tropical extratropical interaction between high frequency transients and the madden julian oscillation abstract the interaction between high frequency transient disturbances and convection and the madden julian oscillation mjo is investigated using ncep ncar reanalysis and satellite outgoing longwave radiation data for 15 northern winters during the phase of the mjo with enhanced convection over the east indian ocean and indonesia and suppressed convection over the south pacific convergence zone both the asian pacific jet and the region of upper tropospheric tropical easterlies over the warm pool are displaced westward these changes in the basic state lead to a weaker or leakier waveguide in the asian pacific jet with a westward displaced forbidden region of tropical easterlies such that high frequency transient waves propagate equatorward into the deep tropics over the central pacific near the date line as these waves induce convection in the region of ascent and reduced static stability ahead of the upper level cyclonic disturbances there is an enhancement of high frequency convective var

quantification of everest region glacier velocities between 1992 and 2002 using satellite radar interferometry and feature tracking quincey d j luckman a benn d 2009 quantification of everest region glacier velocities between 1992 and 2002 using satellite radar interferometry and feature tracking journal of glaciology 55 192 596 606 sponsorship knowledge transfer project no 3742

strain accumulation in southern california 1973 1980 frequent surveys of seven trilateration networks in southern california over the interval 1973 1980 suggest that a regional increment in strain may have occurred in 1978 1979 prior to 1978 and after late 1979 the strain accumulation has been predominantly a uniaxial north south compression this secular trend was interrupted sometime in 1978 1979 by an increment in both north south and east west extension in five of the seven networks the onset of this change appears to have occurred first in the networks farthest south the changes occurred without any unusual seismicity within the networks but the overall seismicity in southern california was unusually low prior to and has been unusually high since the occurrence the average principal strain rates for the seven networks in the 1973 1980 interval are 0 17 mu strain yr north south contraction and 0 08 mu strain yr east west extension although the observed increment in strain could be related to unidentifed systematic error in the measuring system a careful review of the measurements and comparison with three other measuring systems reveal no appreciable cumulative systematic error

permanent scatterers analysis for atmospheric correction in ground based sar interferometry ground based synthetic aperture radar gb sar interferometry has already been recognized as a powerful tool complementary or alternative to spaceborne sar interferometry for terrain monitoring and for detecting structural changes in buildings it has been noted that in spite of the very short range compared with the satellite configuration in gb sar measurement the disturbances due to atmospheric effects cannot be neglected either the analysis of the interferometric phases of very coherent points called permanent scatterers pss allows the evaluation of the atmospheric disturbance and the possibility of removing it in this paper the ps analysis is carried out both on a test site facility and on a real campaign citrin valley italy that provided data with a temporal baseline of about ten months

early detection and in depth analysis of deformation phenomena by radar interferometry the spaceborne differential interferometric sar dinsar technique may play an important role in the measurement of land deformation phenomena especially in urban suburban and industrial areas in order to fully exploit its capabilities and increase its operational use this paper proposes two complementary levels of analysis the first one is a comprehensive low cost screening in order to detect unknown subsidence phenomena over large areas this analysis which provides a first estimation of deformations has to be performed using a limited set of sar images the second level includes an in depth quantitative analysis based on large image stacks which requires more image acquisition and data processing resources this type of analysis can be typically used to study deformation phenomena of special relevance where an effective support to the decision makers requires a fully quantitative estimation of deformations the two levels of analysis were proved over a test area of about 2100 km2 located in catalonia spain without any a priori information seven deformation phenomena were detected using a reduced set of interferograms furthermore the quantitative analysis of a subsidence of small spatial extent which was based on ascending and descending datasets confirmed the capability of dinsar to quantitatively assess deformation phenomena

ground deformation monitoring by using the permanent scatterers technique the example of the oltrepo pavese lombardia italy abstract the applicability of the permanent scatterers synthetic aperture radar interferometry psinsar technique for detecting and monitoring ground displacements was tested in the oltrepo pavese territory northern italy southern lombardia which could be representative of similar geological contexts in the italian apennines the study area which extends for almost 1100 km 2 is characterized by a complex geological and structural setting and the presence of clay rich sedimentary formations these characteristics make the oltrepo pavese particularly prone to several geological hazards shallow and deep landslides subsidence and swelling shrinkage of the clayey soils the psinsar technique used in this study overcomes most of the limitations of conventional interferometric approaches by identifying within the area of interest a set of radar benchmarks ps where very precise displacement measurements can be carried out more than 90 000 ps were identified by processing synthetic aperture radar sar images acquired from 1992 to 2001 by the european remote sensing satellites ers the psinsar application at a sub regional scale detected slow ground deformations ranging from 5 to 16 mm year and resulting from various processes landslides swelling shrinkage of clay soils and water pumping the ps displacements were analysed by collecting data obtained through geological geomorphologic field surveys geotechnical analysis of the soils and the information was integrated within a landslide inventory and the damaged building inventory despite the limited number of landslide bodies with ps 7 of the inventoried landslides the ps data helped to revise the state of activity of several landslides furthermore some previously unknown unstable slopes were detected two areas of uplift and two areas of subsidence were identified

late quaternary evolution of coastal sand barriers port stephens myall lakes area central new south wales australia abstract the geomorphic and stratigraphic history of six coastal embayments has been studied in the vicinity of newcastle new south wales n s w australia in order to determine modes of deposition and the degree to which marine and estuarine deposits can be correlated and dated each embayment possesses its own distinctive suite of landforms ranging from those dominated by coastal dunes to those in which beach ridges occur in four of the bays dual sand barriers comprising an inner barrier and an outer barrier provide the framework for correlation between embayments six stages are recognized in the deposition of late quaternary sediments in this area i pre last interglacial involving accumulation of separate composite units consisting of estuarine clays and transgressive dune complexes ii last interglacial stage during which inner barriers were formed iii last glacial reworking of barrier and dune sands by westerly winds iv postglacial marine transgression during which the outer barriers were initiated v mid holocene stage following cessation of sea level rise ca 6000 6500 yr b p on this coast and involving progradation of outer barriers in some embayments and vi late holocene episodic eolian reworking of dune complexes and outer barriers the relatively high wave and wind energy as well as the tectonic setting of the central n s w coast results in somewhat different geomorphic histories from barrier island coasts in north america and europe

landslide activity as a geoindicator in italy significance and new perspectives from remote sensing landslide activity responds to rapid environmental changes and represents a relevant geoindicator in mountainous or hilly areas this paper discusses the socio economic relevance of landslide hazard in italy and the problems encountered in establishing relationships between landslide frequency climate and vegetation changes at different time scales landslides blocking a river channel have been carefully taken into account because they are usually characterized by high intensities with regard to the involved masses and movement velocities and their occurrences are often datable via radiocarbon dating this is due to the recovery of organic matter in the landslide dammed lakes for these reasons they can be considered important geoindicators in the wider category of slope failures the marked effects of the anthropogenic activity on slope instability processes in the last 50 years are discussed with reference to two case histories the chianti hills in tuscany and the cinque terre national park in liguria finally two novel techniques of remote sensing are proposed as tools for a systematic monitoring of slope instability at different time and spatial scales both techniques are based on the interferometric synthetic aperture radar sar technology and differ on the type of platform satellite and ground based used to acquire data

phase gradient approach to stacking interferograms the phase gradient approach is used to construct averages and differences of interferograms without phase unwrapping our objectives for change detection are to increase fringe clarity and decrease errors due to tropospheric and ionospheric delay by averaging many interferograms the standard approach requires phase unwrapping scaling the phase according to the ratio of the perpendicular baseline and finally forming the average or difference however unique phase unwrapping is usually not possible since the phase gradient due to topography is proportional to the perpendicular baseline phase unwrapping is unnecessary prior to averaging or differencing phase unwrapping may be needed to interpret the results but it is delayed until all of the largest topographic signals are removed we demonstrate the method by averaging and differencing six interferograms having a suite of perpendicular baselines ranging from 18 to 406 m cross spectral analysis of the difference between two tandem interferograms provides estimates of spatial resolution which are used to design prestack filters a wide range of perpendicular baselines provides the best topographic recovery in terms of accuracy and coverage outside of mountainous areas the topography has a relative accuracy of better than 2 m residual interferograms single interferogram minus stack have tilts across the unwrapped phase that are typically 50 mm in both range and azimuth reflecting both orbit error and atmospheric delay smaller scale waves with amplitudes of 15 mm are interpreted as atmospheric lee waves a few global positioning system gps control points within a frame could increase the precision to 20 mm for a single interferogram further improvements may be achieved by stacking residual interferograms

ice velocity determined using conventional and multiple aperture insar abstract we combine conventional interferometric synthetic aperture radar insar and multiple aperture insar mai to determine the ice surface velocity on the langjokull and hofsjokull ice caps in iceland in 1994 this approach allows the velocity of the 20 principal ice cap outlet glaciers to be fully resolved we show that mai leads to displacement estimates of finer resolution 15 versus 150 m and superior precision 5 versus 15 cm to those afforded by the alternative technique of speckle tracking using sar data acquired in ascending and descending orbits we show that ice flows within 15 of the direction of maximum surface slope across 66 of the ice caps it is therefore possible to determine ice displacement over the majority of the ice caps using a single sar image pair thereby reducing errors associated with temporal fluctuations in ice flow

horizontal structure of 500 mb height fluctuations with long intermediate and short time scales abstract maps of standard deviations and one point correlation maps based on twice daily data subjected to a variety of temporal filters are presented in order to document the horizontal structure of 500 mb height fluctuations with different time scales the filters have been chosen to isolate fluctuations with long time scales periods much longer than 30 days intermediate time scales 10 30 day periods and short time scales 2 5 6 day periods the one point correlation maps for long time scales resemble the teleconnection patterns described by wallace and cutzler these patterns are strongly regionally dependent with meridionally oriented dipole structures in the jet exit regions over the oceans indicative of strong fluctuations in the zonal wind for intermediate time scales the dominant patterns consist of more zonally oriented wave trains which originate in the jet entrance regions and cross the jet streams as they curve southeastward into the tropics another important distinction between th

integrated satellite interferometry tropospheric noise gps estimates and implications for interferometric synthetic aperture radar products interferometric synthetic aperture radar insar like other astronomic and space geodetic techniques is limited by the spatially and temporally variable delay of electromagnetic waves propagating through the neutral atmosphere statistical analysis of these variations from a wide variety of instruments reveals a power law dependence on frequency that is characteristic of elementary kolmogorov turbulence a statistical model for a major component of the delay fluctuations the wet component has previously been developed by treuhaft and lanyi 1987 for very long baseline interferometry a continuous global positioning system gps network is now in place in southern california that allows estimation of along with geodetic parameters the total delay due to the atmosphere above each site on a subhourly basis these measurements are shown to conform to the treuhaft and lanyi tl statistical model both temporally and spatially the tl statistical model is applied to the problem of insar and used to produce the covariance between two points separated in time and or space the error due to the atmospheric variations for sar products such as topography and surface deformation is calculated via propagation of errors there are two methods commonly cited to reduce the effect of atmospheric distortion in products from sar interferometry stacking and calibration stacking involves averaging independent interferograms to reduce the noise calibration involves removing part or all of the delay using data from an independent source such as total zenith delay estimates from continuous gps networks despite the relatively poor spatial density of surface measurements calibration can be used to reduce noise if the measurements are sufficiently accurate reduction in tropospheric noise increases with increasing number of measurement points and increasing accuracy up to a maximum of n where n is the number of points stacking and calibration are shown to be complementary and can be used simultaneously to reduce the noise to below that achievable by either method alone

analysis of ground deformation detected using the sbas dinsar technique in umbria central italy ground deformation affecting the umbria region central italy in the 9 year period from 1992 to 2000 was investigated through multi temporal differential synthetic aperture radar interferometry dinsar for the purpose the small baseline subset sbas technique was adopted which allows studying the temporal evolution of the detected deformation at two spatial scales a low resolution regional scale and a full resolution local scale for the analysis sar data acquired by the european remote sensing ers 1 2 satellites along ascending and descending orbits were used the detected deformation was analysed to investigate its relevance to geophysical geomorphologic and human induced processes that may result in hazardous conditions to the population of umbria low resolution deformation data were used to i determine the amount of displacement caused by the umbria marche earthquake sequence from september 1997 to april 1998 in the foligno area ii determine the number and percentage of the known landslides that can be monitored by the dinsar technology in the investigated area and iii identify and measure subsidence induced by exploitation of a confined aquifer in the valle umbra results indicate that earthquakes moved through the foligno area westwards up to 3 9 cm and with an uplift reaching 1 7 cm intersection in a gis of the low resolution deformation maps with a detailed landslide inventory map allowed the determination that the portion of landslides that can be monitored by the sbas dinsar technique in umbria ranges from 2 7 to 3 4 and the percentage of the total landslide area ranges from 10 4 to 12 8 in the valle umbra a dependency was found between the time and the amount of detected ground deformation and the record of water withdrawal the full resolution deformation data were used to investigate the movement of the ivancich landslide in the assisi municipality joint analysis of the spatial and the temporal characteristics of the ground displacement allowed the formulation of a hypothesis on the landslide geometry and deformation pattern

an observational study of tropical midlatitude interaction on intraseasonal time scales during winter abstract eight northern hemisphere winters of five and ten day average midlatitude 500 mb heights and tropical outgoing ir are used in a correlative study of tropical midlatitude interaction the seasonal cycle and interannual variability are removed so that only intraseasonal variability remains results indicate that energy predominantly propagates from midlatitudes to the tropics for both five and ten day averaged data although the propagation is more apparent in five day averaged data this is evidenced by the fact that the largest tropical ir patterns are southeastward of the 500 mb point with which the ir field is correlated the result is interpreted in terms of a quasi stationary rossby wave which has an eastward component of group velocity the southwest northeast tilt of the 500 mb height correlation patterns indicating poleward momentum transport or equatorward wave propagation also supports the hypothesis that midlatitude flow drives the tropics lead and lag correlations show that when 5

phase speed spectra of transient eddy fluxes and critical layer absorption abstract tropospheric zonal mean eddy fluxes of heat and momentum and the divergence of the eliassen palm flux are decomposed into contributions from different zonal phase speeds data analyzed are ecmwf operational global analyses covering 1980 87 eastward moving medium scale waves zonal waves 4 7 dominate the spectra of lower tropospheric heat fluxes in both hemispheres and all seasons upper tropospheric wave flux spectra are similar to the low level spectra in midlatitudes but shift to slower zonal phase speeds as low latitudes are approached the cause of this shift is the selective absorption of faster moving components in midlatitudes as the waves propagate meridionally latitude phase speed distributions of eddy fluxes are constructed and compared to the zonal mean wind structure these results demonstrate that upper tropospheric eddies break and decelerate the zonal mean flow approximately 10 20 in latitude away from their critical line where phase speed equals zonal wind speed compari

global teleconnections in the 250 mb streamfunction field during the northern hemisphere winter abstract teleconnections of the streamfunction in the global domain based on ecmwf 250 mb winds for the 11 northern winters from 1978 79 through 1988 89 are documented in this study a zonal structure with a node near the equator indicating an out of phase relationship between the streamfunctions in the northern and southern hemisphere appears to mask the fluctuations of the asymmetric components of streamfunction after removing zonal means a global pattern emerges as the dominant structure in the low frequency band this pattern consists of several dipoles straddling either the exit region of midlatitude jets or the equator indicating the existence of teleconnections not only between the midlatitudes and the tropics but also between the northern and southern hemispheres teleconnection patterns in the intermediate frequency band are predominantly wavelike seven waveguides are identified based on the one point lag correlation maps for base points near the maximum teleconnectivity among them are thr

upper tropospheric equatorial waves in ecmwf analyses tropical wind fields from the european centre for medium range weather forecasts operational analyses are analysed to search for equatorially trapped waves in the upper troposphere data are studied for 1980 87 zonal wind spectra show a predominance of power at low zonal wave numbers and low frequencies these data do not show distinct spectral peaks corresponding to eastward propagating kelvin waves or westward propagating equatorially trapped rossby waves the zonal wind spectra do show episodic evidence for westward propagating 5 day zonal wave 1 features with maxima over the equator these are likely related to rossby normal mode oscillations previously reported meridional wind spectra show a predominance of westward propagating power in the 6 to 10 day period range primarily concentrated in zonal waves 4 7 enhanced meridional wind activity at the equator occurs episodically in time with events persisting for one to several months duration wave packets are longitudinally localized with preferred occurrence over the eastern pacific ocean most cases show evidence of meridional wind maxima in the tropics suggesting a degree of equatorial trapping the horizontal structure of these oscillations is that of mixed rossby gravity waves although they are not necessarily centred directly over the equator these waves have largest amplitudes in the upper troposphere showing weak coherence with the surface they appear to be fundamentally distinct from fast 4 to 5 day rossby gravity waves observed in the western pacific a detailed study of a group of intense rossby gravity waves observed over the eastern pacific during august september 1985 is presented the reality of these features is confirmed in direct rawinsonde observations correlations are found between bursts of equatorial wave activity and enhanced meridional momentum fluxes from the subtropics suggesting extratropical forcing as at least one mechanism for their generation the waves are also strongly coupled to the upper tropospheric zonal wind field which likely accounts for their longitudinal and temporal confinement

accuracy of topographic maps derived from ers 1 interferometric radar an interferometric radar technique for topographic mapping of surfaces promises a high resolution approach to the generation of digital elevation models the authors present analyses of data collected by the synthetic aperture radar instrument on board the ers 1 satellite on successive orbits use of a single satellite in a nearly repeating orbit is attractive for reducing cost and spaceborne hardware complexity also it permits inference of changes in the surface from the correlation properties of the radar echoes the data have been reduced to correlation maps and digital elevation models the correlation maps show that temporal correlation decreases significantly with time but not necessarily at a constant well defined rate likely depending on environmental factors when correlation among passes remains high however it is possible to form digital elevation models analyses of noise expected in ers 1 interferometric data collected over alaska and the southwestern united states indicate that maps with relative errors less than 5 m rms are possible in some regions however orbit uncertainties imply that tie points are required in order to reduce absolute height errors to a similar magnitude the authors find that about 6 tie points per 40 spl times 40 km scene with 5 m rms or better height accuracy are needed to keep systematic map height errors below 5 m rms the performance of the ers 1 radar system for topographic applications though useful for a variety of regional and local discipline studies may be improved with respect to temporal decorrelation errors and absolute height acuity by modifying the orbit repeat period and incorporating precise orbit determination techniques the resulting implementation will meet many but not all objectives of a global mapping mission

interferometric radar measurement of ocean surface currents we describe a new method of measuring surface currents using an interferometric synthetic aperture radar an airborne implementation has been tested over the san francisco bay near the time of maximum tidal flow resulting in a map of the east west component of the current only the line of sight component of velocity is measured by this technique where the signal to noise ratio was strongest statistical fluctuations of less than 4 cm s 1 were observed for ocean patches of 60 60 m

an observational study of medium scale wave dynamics in the southern hemisphere summer part i wave structure and energetics abstract medium scale waves zonal wavenumbers 4 7 frequently dominate southern hemisphere sh summer midlatitude circulation patterns this work is an observational study that focuses on their temporal and spatial characteristics along with detailing the forcing mechanisms responsible for their formation medium scale wave characteristics for three sh summers 1978 79 through 1980 81 are discussed it is shown that the time mean medium scale wave structure is consistent with the basic state linear wave propagation characteristics the energetics of the medium scale waves are studied using the transformed eulerian mean formalism of plumb it is found that wave zonal mean exchange is a valid concept for describing the sh summer atmospheric circulation and that the flow vacillates between periods of highly perturbed and zonally symmetric states with a time wale on the order of 10 20 days these vacillations result from nonlinear baroclinic instabilities and the medium scale waves exhibit well defined

the lowest place on earth is subsiding an insar interferometric synthetic aperture radar perspective since the early 1990s sinkholes and wide shallow subsidence features wssfs have become major problems along the dead sea shores in israel and jordan sinkholes are readily observed in the field but their locations and timing are unpredictable wssfs are often difficult to observe in the field however once identified they delineate zones of instability and increasing hazard in this study we identify characterize and measure rates of subsidence along the dead sea shores by the interferometric synthetic aperture radar insar technique we analyze 16 sar scenes acquired during the years 1992 to 1999 by the european remote sensing ers 1 and ers 2 satellites the interferograms span periods of between 2 and 71 months wssfs are observed in the lisan peninsula and along the dead sea shores in a variety of appearances including circular and elongate coastal depressions a few hundred meters to a few kilometers in length depressions in ancient alluvial fans and depressions along salt diapir margins phase differences measured in our interferograms correspond to subsidence rates generally in the range of 0 20 mm yr within the studied period with exceptional high rates that exceed 60 mm yr in two specific regions during the study period the level of the dead sea and of the associated ground water has dropped by 6 m this water level drop within an aquifer overlying fine grained marly layers would be expected to have caused aquifer system consolidation resulting in gradual subsidence comparison of our insar observations with calculations of the expected consolidation shows that in areas where marl layers are known to compose part of the upper 30 m of the profile estimated consolidation settlements are of the order of the measured subsidence our observations also show that in certain locations subsidence appears to be structurally controlled by faults seaward landslides and salt domes gradual subsidence is unlikely to be directly related to the sinkholes excluding the use of the wssfs features as predictable precursors to sinkhole formation

mapping small elevation changes over large areas differential radar interferometry a technique that uses synthetic aperture radar sar images to measure very small 1 cm or less surface motions with good resolution 10 m over large swaths 50 km is presented along with experimental results the method could be used for accurate measurements of many geophysical phenomena including swelling and buckling in fault zones residual displacements from seismic events and prevolcanic swelling the method is based on sar interferometry where two images are made of a scene by simultaneously flying two physically separated antennas then the phases of corresponding pixels are differenced and altitude formation is deduced from some simple computation and image rectification it is also possible to use one antenna flown twice over the same scene then if the second flight exactly duplicates the track of the first an interesting possibility occurs there would be no phase changes between the images at all unless there was a physical change in the scene such as ground swelling that would alter the distance from some resolution element to the antenna since the phase changes all occur at the short carrier wavelength the basic limitation on sensitivity is only the phase noise in the system when the two imaging passes are made from flight tracks that are separated which is the case with the seasat images used here it is no longer possible to distinguish surface changes from the parallax caused by topography however with some additional computation a third image made at some other baseline may be used to remove the topography and leave only the surface changes this method was applied using seasat data to an imaging site in imperial valley california where motion effects were observed that were ascribed to the expansion of water absorbing clays phase change images of this area are shown along with associated ground truth about the presence of water problems with the technique are explored along with a discussion of future experimental possibilities on upcoming sar missions like earth observing system eos earth resources satellite ers 1 sir c and the venus imaging radar magellan

horizontal structure and seasonality of large scale circulations associated with submonthly tropical convection the relationship between deep tropical convection and large scale atmospheric circulation in the 6 30 day period range is examined regression relationships between filtered outgoing longwave radiation at various locations in the tropics and 200 and 850 mb circulation are mapped for the standard seasons and the spatial structure and seasonal dependence of the results are interpreted in view of the basic state circulation in regions where the convection is embedded in upper level easterlies anomalous equatorial easterly flow is typically present at 200 mb within and to the west of the convective signal along with patterns of meridional outflow into subtropical anticyclonic perturbations lagged relationships suggest that the convection is forcing the circulation in many of these cases the outflow and subtropical circulations are strongest into the winter hemisphere during the solstitial seasons with more symmetric signals about the equator seen in the equinoctial seasons the longitudinal positioning of the subtropical features with respect to the convection varies but is generally located due poleward or just to the east of the convection there tends to be a first baroclinic mode vertical structure to these circulations such that equatorial westerlies are present at 850 mb within the convection with closed circulations on either side of the equator resembling equatorial rossby modes especially common over the atlantic and pacific sectors as a contrast in regions located within upper level westerlies or along the margin of influence of upper westerly disturbances convection appears to be forced by upper level wave energy propagating into the deep tropics with the heating located in the upward motion region ahead of upper level troughs this occurs over the atlantic and eastern pacific sectors during northern winter and spring and over australia the south pacific and south america during southern summer when upper westerlies are at relatively low latitudes where they can interact with deep tropical convection the results confirm theoretical and modeling ideas that suggest that rossby wave energy is able to propagate into the deep tropics in regions where upper level westerlies exist in the tropics

flow dynamics and iceberg calving rates of devon ice cap nunavut canada the surface velocity field of devon ice cap nunavut canada was mapped using interferometric synthetic aperture radar insar ascending european remote sensing satellite 1 and 2 ers 1 2 tandem mode data were used for the western and southeast sectors and 3 day repeat pass ers 1 imagery for the northeast sector speckle tracking procedures were used with radarsat 1 imagery to obtain surface velocities over the terminus of belcher glacier a major calving front where decorrelation between ers data occurred the insar data highlight a significant contrast in ice flow dynamics between the east and west sides of the ice cap ice movement west of the main north south divide is dominated by relatively uniform sheet flow but three fast flowing outlet glaciers that extend 14 23 km beyond the ice cap margin also drain this region several outlet glaciers that extend up to 60km inland from the eastern margin drain the eastern side of the ice cap the dominant ice flow regimes were classified based on the relationship between the driving stress averaged over a length scale often ice thicknesses and the ratio of surface velocity to ice thickness the mapped distribution of flow regimes appears to depict the spatial extent of basal sliding across the ice cap this is supported by a close relationship between the occurrence of flow stripes on the ice surface and flow regimes where basal sliding was found to be an important component of the glacier motion iceberg calving rates were computed using measured surface velocities and ice thicknesses derived from airborne radio echo sounding the volume of ice calved between 1960 and 1999 was estimated to be 20 5 4 7 km 3 or 0 57km 3 a 1 approximately 89 of this loss occurred along the eastern margin the largest single source is belcher glacier which accounts for 50 of the total amount of ice calved

rossby wave propagation into the tropics in two gfdl general circulation models during the northern winter the eastern pacific is characterized by upper level westerly flow extending from the equator into the midlatitudes of both hemispheres theoretical and simple modeling studies suggest that such a region should favor the penetration of rossby waves into the tropics from higher latitudes observational results by kiladis and weickmann using 200 mb data indicate that rossby waves do indeed propagate freely into the tropical eastern pacific during the northern winter from the asian jet exit region they also confirmed that cross equatorial dispersion of energy from the northern into the southern hemisphere occurs frequently the present study examines these interactions in climatological runs of two gfdl gcms the northern wintertime mean states of these models are characterized by a rather realistically simulated upper level westerly regime in the tropical pacific despite the relative weakness of the asian jet and wave activity with respect to observations propagation of rossby waves into the tropics is present in both models and these waves are strongly positively tilted as seen in the observations a momentum budget of the zonal wind and e vector diagnostics over the tropical pacific indicate that these transients are an important component of the momentum balance of the equatorial westerlies in both the observations and in the models

horizontal energy propagation in a barotropic atmosphere with meridional and zonal structure abstract to investigate how the propagation of energy away from steady sources may be influenced by the horizontal structure of the time averaged flow in the troposphere solutions to a barotropic model are displayed and interpreted the model is steady and linearized about a basic state which varies in latitude and longitude emphasis is placed on cases where the longitudinal variations are gradual many of the results can be analyzed by locally applying tools developed for zonally symmetric basic states e g ray tracing and refractive indices simple background flows are constructed which have longitudinally confined critical lines reflective surfaces wave guides and regions conducive to propagation an example is given in which longitudinal derivatives of the basic state are significant the theory of ray tracing in a two dimensional wind must be employed as an interpretive tool in this case it is concluded that zonal variations tend to enhance poleward equatorward propagation in large scale tr

three pattern decomposition of global atmospheric circulation part ii dynamical equations of horizontal meridional and zonal circulations the three pattern decomposition of global atmospheric circulation tpdgac partitions three dimensional 3d atmospheric circulation into horizontal meridional and zonal components to study the 3d structures of global atmospheric circulation this paper incorporates the three pattern decomposition model tpdm into primitive equations of atmospheric dynamics and establishes a new set of dynamical equations of the horizontal meridional and zonal circulations in which the operator properties are studied and energy conservation laws are preserved as in the primitive equations the physical significance of the newly established equations is demonstrated our findings reveal that the new equations are essentially the 3d vorticity equations of atmosphere and that the time evolution rules of the horizontal meridional and zonal circulations can be described from the perspective of 3d vorticity evolution the new set of dynamical equations includes decomposed expressions that can be used to explore the source terms of large scale atmospheric circulation variations a simplified model is presented to demonstrate the potential applications of the new equations for studying the dynamics of the rossby hadley and walker circulations the model shows that the horizontal air temperature anomaly gradient atag induces changes in meridional and zonal circulations and promotes the baroclinic evolution of the horizontal circulation the simplified model also indicates that the absolute vorticity of the horizontal circulation is not conserved and its changes can be described by changes in the vertical vorticities of the meridional and zonal circulations moreover the thermodynamic equation shows that the induced meridional and zonal circulations and advection transport by the horizontal circulation in turn cause a redistribution of the air temperature the simplified model reveals the fundamental rules between the evolution of the air temperature and the horizontal meridional and zonal components of global atmospheric circulation

geodetic airborne laser altimetry of breidamerkurjokull and skeidararjokull iceland and jakobshavns isbrae west greenland

poroelastic rebound along the landers 1992 earthquake surface rupture maps of surface displacement following the 1992 landers california earthquake generated by interferometric processing of ers 1 synthetic aperture radar sar images reveal effects of various postseismic deformation processes along the 1992 surface rupture the large scale pattern of the postseismic displacement field includes large lobes mostly visible on the west side of the fault comparable in shape with the lobes observed in the coseismic displacement field this pattern and the steep displacement gradient observed near the emerson camp rock fault cannot be simply explained by afterslip on deep sections of the 1992 rupture models show that horizontal slip occurring on a buried dislocation in a poisson s material produces a characteristic quadripole pattern in the surface displacement field with several centimeters of vertical motion at distances of 10 20 km from the fault yet this pattern is not observed in the postseismic interferograms as previously proposed to explain local strain in the fault step overs peltzer et al 1996b we argue that poroelastic rebound caused by pore fluid flow may also occur over greater distances from the fault compensating the vertical ground shift produced by fault afterslip such a rebound is explained by the gradual change of the crustal rocks poisson s ratio value from undrained coseismic to drained postseismic conditions as pore pressure gradients produced by the earthquake dissipate using the poisson s ratio values of 0 27 and 0 31 for the drained and undrained crustal rocks respectively elastic dislocation models show that the combined contributions of afterslip on deep sections of the fault and poroelastic rebound can account for the range change observed in the sar data and the horizontal displacement measured at global positioning system gps sites along a 60 km long transect across the emerson fault savage and svarc 1997 using a detailed surface slip distribution on the homestead valley kickapoo and johnson valley faults we modeled the poroelastic rebound in the homestead valley pull apart a poisson s ratio value of 0 35 for the undrained gouge rocks in the fault zone is required to account for the observed surface uplift in the 3 5 years following the earthquake this large value implies a seismic velocity ratio vp vs of 2 1 consistent with the observed low vs values of fault zone guided waves at shallow depth li et al 1997 the sar data also reveal postseismic creep along shallow patches of the eureka peak and burnt mountain faults with a characteristic decay time of 0 8 years coseismic dilatant hardening locking process followed by post seismic pore pressure controlled fault creep provide a plausible mechanism to account for the decay time of the observed slip rate along this section of the fault

change detection on alaska s north slope using repeat pass ers 1 sar images measurements of the c band wavelength 5 cm radar cross section of an area in the brooks range foothills on the north slope of alaska using images from the ers 1 satellite that show significant temporal changes occur these changes are strongly correlated with elevation and hill slope orientation and are greatest on some of the elevated areas and weaker in river drainages by constructing difference images using various image pairs and by analyzing climatological and hydrological data from the site it is concluded that the radar backscatter changes are largely due to changes in soil and vegetation liquid water content induced by freeze thaw events the correlation with topography in the difference images arises from the dependence of vegetation organic layer thickness and volumetric water content on hill slope position and orientation these results demonstrate the viability of radar backscatter intensity comparisons using repeat pass images as a means of change detection

a diagnostic study of recurrent meteorological anomalies appearing in a 15 year simulation with a gfdl general circulation model abstract the spatial structure and temporal characteristics of prominent anomalies occurring in a 15 year simulation with a gfdl spectral general circulation model are examined using empirical orthogonal functions teleconnection patterns composite charts lagged correlation functions and frequency spectra despite the absence of any nonseasonal perturbation in the prescribed forcing such as sea surface temperature insolation and cloud cover the simulated circulation exhibits an appreciable degree of temporal variability on monthly time scales the standing oscillation in the northern hemisphere winter which accounts for the largest fraction of this variance has a coherent three dimensional structure in the middle and upper troposphere this preferred mode of oscillation is characterized by a wavelike pattern with multiple centers of action the corresponding anomaly pattern at the sea level is dominated by north south pressure seesaws over the north atlantic and north pacific the flow patterns assoc

time variation of 500 mb height fluctuations with long intermediate and short time scales as deduced from lag correlation statistics abstract the time variation of northern hemisphere wintertime 500 mb height fluctuations with short intermediate and long time scales is investigated using lag correlation patterns derived from time filtered data fluctuations with short 2 5 6 day periods time scales propagate eastward at a rate consistent with the notion of a steering level around 700 mb which supports an interpretation in terms of baroclinic waves the mobile teleconnection patterns associated with the intermediate 10 30 day periods time scales exhibit a pattern of time variation suggestive a rossby wave dispersion with a predominance of southward dispersion from middle latitudes into the tropics the geographically fixed teleconnection patterns characteristic of the longer time scales do not show a well defined pattern of time variation but their horizontal structure resembles that of the fastest growing normal mode associated with barotropic instability of the climatological mean wintertime flow

spatial analysis of surface deformation distribution detected by persistent scatterer interferometry in lanzhou region china persistent scatterer synthetic aperture radar interferometry ps insar is a remote sensing method that can be used to detect surface deformation which is an indicator of potential geohazards by capturing such deformations over time it is possible to obtain valuable information regarding geohazards such as landslides this study focused on the use of ps insar to investigate the distribution and causes of surface deformation in the lanzhou region of gansu province in china between 2003 and 2010 41 advanced synthetic aperture radar images were captured by the envisat satellite and analyzed using ps insar and the correlation between the observed surface deformation and topographic geologic and anthropogenic factors was derived based on a geographic information system platform it was found that the largest number and highest density of surface deformations occurred at elevations of 1486 1686 m it was also established that slope ranges of 25 30 and 35 40 are threshold values at which surface deformation changes abruptly and that slopes with north and northwest aspects are most prone to surface deformation the lithologies most susceptible to surface deformation are clay sandy soil and loess the normalized difference vegetation index indicated that surface deformation occurred most often in areas with sparse vegetation anthropogenic activities e g construction and wastewater discharge could be inferred as causal mechanisms of surface deformation comparison of the distributions of geohazards and surface deformation showed considerable consistency which proves surface deformation can induce geohazards these results could help governments improve urban planning and geohazard mitigation

deformation time series generation in areas characterized by large displacement dynamics the sar amplitude pixel offset sbas technique we exploit the amplitude information of a sequence of synthetic aperture radar sar images acquired at different times in order to generate displacement time series in areas characterized by large and or rapid deformation the size of which is on the order of the image s pixel dimensions we follow the same rationale of the small baseline subset sbas differential sar interferometry dinsar approach by coupling the available sar images into pairs characterized by a small separation between the acquisition orbits we exploit the amplitudes of the selected image pairs in order to calculate the relative across track range and along track azimuth pixel offsets po finally we apply the sbas inversion strategy to retrieve the range and azimuth displacement time series this approach referred to as pixel offset po sbas technique has been applied to a set of 25 envisat sar observations of the sierra negra caldera galapagos islands spanning the 2003 2007 time interval the retrieved deformation time series show the capability of the technique to detect and measure the large displacements affecting the inner part of the caldera that in correspondence to the october 2005 eruption reached several meters moreover by comparing the po sbas results to continuous gps measurements we estimate that the accuracy of the po sbas time series is on the order of 1 30th of a pixel for both range and azimuth directions

a model of rossby waves linked to submonthly convection over the eastern tropical pacific equatorward propagating wave trains in the upper troposphere are observed to be associated with deep convection over the eastern tropical pacific on the submonthly timescale during northern winter the convection occurs in the regions of ascent and reduced static stability ahead of cyclonic anomalies in the wave train in this study an atmospheric primitive equation model is used to examine the roles of the dry wave dynamics and the diabatic heating associated with the convection many features of a dry integration initialized with a localized wave train in the african asian jet on a threedimensional climatological basic state quantitatively agree with the observations including the zonal wavenumber 6 7 scale of the waves the time period of approximately 12 days and the cross equatorial rossby wave propagation over the eastern pacific there is ascent and reduced static stability ahead of the cyclonic anomalies consistent with the interpretation that the waves force the convection the spatial scale of the waves appears to be set by the basic state baroclinic growth upstream in the asian jet favors waves with zonal wavenumber 6 on reaching the pacific sector lower wavenumber components of the wave train are not refracted so strongly equatorward while higher wavenumber components are advected quickly along the pacific jet before they can propagate equatorward once over the pacific the wave train approximately obeys barotropic rossby wave dynamics the observed lower tropospheric anomalies include an equatorial rossby wave that propagates westward from the region of cross equatorial wave propagation and tropical convection however this equatorial rossby wave is not forced directly by the dry equatorward propagating wave train but appears in a separate integration as a forced response to the observed diabatic heating associated with the tropical convection

change detection for thematic mapping by means of airborne multitemporal polarimetric sar imagery the paper addresses the detection of changes in multitemporal polarimetric radar images focusing on small objects and narrow linear features the images were acquired at c and l band by the airborne emisar system it is found that the radar intensities are better suited for change detection than the correlation coefficient and the phase difference between the co polarized channels in the case of linear features there is no obvious difference between the c and l bands and slight variations of the flight tracks are acceptable at look angles larger than 35 degrees theoretical detection thresholds are evaluated from the statistical distribution of the intensity ratio due to speckle for the linear features and for urban environments the observed thresholds are larger than the theoretical predictions this is interpreted as an effect of radar intensity variations on length scales smaller than the spatial image resolution the signature of urban areas is very sensitive to deviations between the flight tracks and the sensitivity is larger at c band than at l band on the other hand the intensity contrast between buildings and the urban background is smaller at l band and larger at c band for change detection thresholds may have to be chosen separately for each object class because the intensity ratios of different object classes vary differently as a function of time

cementation and blackening of holocene sands by peat derived humates a case study from the great dune of pilat landes des gascogne southwestern france abstract the base sand layers of the aeolian great dune of pilat which stretches along the coast of arcachon bay have been locally impregnated with a dark brown to black amorphous organic substance of humate composition the humate cemented sand forms a well indurated horizon 40 50 cm in thickness that developed immediately beneath the holocene peaty layer p1 paleosoil the humate identified by means of ft ir and raman micro spectroscopy acted both as a cementing agent and as a coloring agent it formed thin coats and meniscus cements between individual sandstone grains which in turn caused the dark asphaltic like appearance of the sandstone field observations combined with geochemical analyses and the presence of identical geochemical compounds recognized in the peat and sandstone humate cement suggest that the peat containing low coalified rr 0 2 fragments of higher submerged and floating plants and marine algae deposited in a saline and reducing environment served as an obvious source rock for the humate the humate derived from decaying organic remains that descended from the peat into the permeable sand where it indurated irreversibly over a period shorter than 3500 years the present day actions of waves and tides contribute to the erosion of the frontal parts of the humate impregnated sandstone horizon resulting in the formation of the dark rounded sandstone slabs and pebbles that are deposited on nearby beaches this process provides a fine example of recent black pebble formation that derived from pre existing organic matter impregnated source rocks in contrast to their tropical carbonate counterparts however the humate induced blackening of the sandstone pebbles appears to be relatively unstable as the impregnated fragments bleach when exposed to air and seawater for a few seasons

characteristics and significance of some humate cemented sands humicretes at cape flattery queensland australia humate cemented sands humicretes are exposed at several locations along the foreshore and in gullies near cape flattery north queensland australia three broad types of humate accumulation are recognized a pedogenetic b groundwater and c aquatic pedogenetic and groundwater humicretes usually have a grain supported fabric in which quartz represents 99 of the framework grains hand specimens of humicrete are brittle but disintegrate rapidly in 0 1 n naoh concentration of humate is considered to have occurred by vertically and laterally migrating groundwater while induration has probably been caused by irreversible drying of the humic substances during periods of seasonal water table lowering radiocarbon dating of an in situ root embedded in indurated humate near cape flattery has indicated a background age of 48000 c 14 years

topographic mapping from interferometric synthetic aperture radar observations interferometric synthetic aperture radar observations provide a means for obtaining high resolution topographic terrain maps from data acquired simultaneously at two slightly displaced antennas calculation of the three dimensional coordinates of all the points in a radar image can be made from the combination of along track slant range and interferometer fringe measurements thus the result compensates for the layover exhibited by conventional radar maps and removes the false targets generated by multiple signal paths to a given object in the scene we have derived a topographic map of a portion of the san francisco bay area utilizing data that were recorded by a radar system mounted on a nasa cv990 aircraft and processed by a general purpose digital computer this map displays the height above sea level of a region approximately 11 km by 10 km in size sampled on an 11 m pixel grid uncertainties in the estimated height result from imprecise knowledge of the observational geometry radar bandwidth limitations and finite signal to noise ratios for our system each factor contributed approximately 3 4 m to a relative rms error of about 6 m additional global errors of the order of 10 m can result from inaccurate monitoring of aircraft attitude the statistical variation of the height measurements from the ocean portion of the map which we can presume to be quite flat is 2 10 m rms which is consistent with the theoretical estimate comparison of our results with u s geological survey contour maps indicates a high degree of correlation between the two sets of altitude data

the structure and propagation of intraseasonal oscillations appearing in a gfdl general circulation model abstract the three dimensional structure and temporal evolution of quasi periodic planetary scale tropospheric oscillations simulated by a 15 wavenurnber gcm are investigated by applying cross spectral eigenvector composite and temporal correlation techniques to 12 years of model output evident from this diagnostic study is the presence in the model tropics of well defined eastward traveling features with spatial scales of zonal wavenumbers 1 and 2 and with temporal scales of 25 40 and 15 20 days respectively the flow pattern associated with the oscillations of both spatial scales is characterized by circulation cells oriented along the equatorial zonal plane with the zonal wind and geopotential height fluctuations near the sea level being negatively correlated with the corresponding fluctuations in the upper troposphere the movement of these zonal circulation cells along the equatorial bell is accompanied by systematic migration of the global scale horizontal divergence field and by dipole like

actively growing anticlines beneath catania from the distal motion of mount etna s decollement measured by sar interferometry and gps we used sar interferometry and gps to measure the rise of an anticline beneath the urban area of catania italy which originates from outward thrusting above the basal decollement of etna volcano the anticline grows at a rate of over 0 015 m a 1 of se thrusting and about 0 007 m a 1 of relative uplift by relating this growth to the simultaneous extension measured at the summit of the volcano we demonstrate the occurrence of active volcanic spreading this process may exert a control on eruptions earthquakes sector collapses and landslides

monitoring very slow slope movements by means of sar interferometry a case study from a mass waste above a reservoir in the otztal alps austria the application of radar interferometry to detect slope movements on the order of millimeters to centimeters per year is demonstrated the deformation field of a slope above a hydropower reservoir in the austrian alps was derived from sar interferometric pairs of the satellites ers 1 and ers 2 acquired between july 1992 and august 1998 above the treeline it was possible to map the motion from interferograms covering time spans up to three years whereas ground based geodetic measurements focussed on the movements of the lower slope section the interferometric analysis shows that the mass wasting processes affect the entire slope of 1000 m vertical extent significant interannual differences of the displacement rates became apparent which were found to be related to the pattern of summer rainfall

lithological heterogeneity in a back barrier sand island implications for modelling hydrogeological frameworks abstract sediment mineralogy quartz grain surface textures grain size analysis bore hole logging and ground penetrating radar are combined to develop a three dimensional stratigraphic model of a back barrier sand island in southeast queensland australia the island consists of an unconsolidated sedimentary pile above an erosional bounding surface at the top of the underlying bedrock the stratigraphy is complex recording the shift in depositional environments from fluvio deltaic to strandplain via estuarine stages of evolution the back barrier island deposits are correlated with the stratigraphy of the adjacent coastal plain to the west and the barrier island to the east extrapolation of optically stimulated luminescence dates obtained from the barrier island combined with direct dating of the back barrier island sediments is used to constrain the depositional age and chronology of the back barrier island stratigraphy the modern depositional environment evolved from a chenier plain into a barrier island system by the flooding of an interdune swale and development of a shore parallel back barrier tidal lagoon the lithological heterogeneity of the back barrier island succession was controlled by the presence of a bedrock incised palaeovalley and changes in relative sea level sedimentary facies associations constrain the spatial distribution of hydraulic properties controlled by lithological heterogeneity post depositional alteration horizons are integrated with the facies model to account for the effects of weathering and diagenesis on hydraulic behaviour the derived hydrostratigraphy describes a vertically stacked dual aquifer island groundwater system consisting of a semi confined palaeovalley aquifer overlain by an unconfined strand plain aquifer hydrostratigraphic analysis based on sedimentary facies associations integrated with post depositional alteration characteristics reveals great complexity of groundwater systems within small island settings the facies modelling approach employed in this study more accurately estimates the distribution of lithological heterogeneity and the associated variations in hydraulic properties in the sedimentary pile

formation of quartz silt during humid tropical weathering of dune sands abstract quartz dune sand grains in northeast australia break down in situ under humid tropical weathering conditions to form substantial amounts of silt fragmentation appears to occur primarily due to silica solution along microfractures and dislocation structures in grains which have experienced tectonic deformation prior to deposition the surface textures of quartz grains viewed with the sem exhibit a close dependency on crystallographic properties in the b and c horizons of some weathered late pleistocene dunes silt forms up to 10 of the bulk sediment local remobilisation of such deposits by wind allows selective removal of the silt which is later deposited as a thin surficial sheet in more sheltered areas downwind these observations provide further evidence that weathering processes provide a major mechanism of silt formation and are an important factor to be considered in relation to the origin of loess and siltstones

the shape propagation and mean flow interaction of large scale weather systems abstract for a zonal average operator the eliassen palm flux provides a diagnostic of both eddy behavior and the feedback of the eddies onto the mean flow this paper addresses the diagnosis problem for other averaging operators and in particular for time averaging which has proved in recent years such a powerful means of viewing the three dimensional tropospheric flow the horizontal velocity correlation tensor gives a measure of the characteristic horizontal eddy shape at a point it also implies the direction of the group velocity relative to the mean flow in cases where such a concept is valid however the major emphasis here is on the mean flow feedback of eddies in this respect the eddy vorticity flux is determined by derivatives of the components of the anisotropic part of the tensor making a reasonable approximation allows the eddy vorticity flux convergence to be written in terms of e v 2 u 2 u v a simple interpretation of the mean flow feedback of eddies is then possible a sligh

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

extratropical forcing of tropical pacific convection during northern winter abstract statistical evidence is presented to support the notion that tropical convection in the eastern pacific and atlantic intertropical convergence zone itcz during northern winter can be forced by disturbances originating in the extratropics the synoptic scale transients in these regions are characterized at upper levels by strong positive tilts in the horizontal and appear to induce vertical motions ahead of troughs as in midlatitude baroclinic systems two case studies of such interactions are examined one for the eastern north pacific itcz and another somewhat different type of interaction for the south pacific convergence zone spcz over the western south pacific both cases are associated with upper level troughs strong cold advection deep into the tropics and the formation of a frontal boundary at low levels the itcz case is characterized by the advection of anomalously high isentropic potential vorticity air southward a strong poleward flux of heat and westerly momentum and the devel

reconnaissance thermoluminescence dating of northern australian coastal dune systems abstract quaternary lithostratigraphic units in coastal dunes have been dated at three locations in northern australia cobourg peninsula shelburne bay and cape flattery by both radiocarbon dating of shell and organic carbon and thermoluminescence tl sediment dating both coarse fraction and fine fraction tl methods were used seventeen tl dates were measured none of the tl dates contradict the ages given by radiocarbon where multiple tl dates were taken from a unit they overlap within 2 standard deviation giving added confidence in the results a phase of dune emplacement during the late holocene ca 2700 1800 yr b p was identified in two of the dune fields an early holocene phase of dune emplacement ca 8600 7500 yr b p in two of the dune fields and a late pleistocene episode ca 24 000 17 000 yr b p in both the cape york dunefields three older units gave dates of about 29 000 81 000 and 171 000 yr b p but these must be treated with caution

deformation and seismicity in the coso geothermal area inyo county california observations and modeling using satellite radar interferometry interferometric synthetic aperture radar insar data collected in the coso geothermal area eastern california during 1993 1999 indicate ground subsidence over a 50 km 2 region that approximately coincides with the production area of the coso geothermal plant the maximum subsidence rate in the peak of the anomaly is 3 5 cm yr 1 and the average volumetric rate of subsidence is of the order of 10 6 m 3 yr 1 the radar interferograms reveal a complex deformation pattern with at least two irregular subsidence peaks in the northern part of the anomaly and a region of relative uplift on the south we invert the insar displacement data for the positions geometry and relative strengths of the deformation sources at depth using a nonlinear least squares minimization algorithm we use elastic solutions for a prolate uniformly pressurized spheroidal cavity in a semi infinite body as basis functions for our inversions source depths inferred from our simulations range from 1 to 3 km which corresponds to the production depths of the coso geothermal plant underpressures in the geothermal reservoir inferred from the inversion are of the order of 0 1 1 mpa except a few abnormally high underpressures that are apparently biased toward the small source dimensions analysis of the insar data covering consecutive time intervals indicates that the depths and or horizontal extent of the deformation sources may increase with time this increase presumably reflects increasing volumes of the subsurface reservoir affected by the geothermal exploitation we show that clusters of microearthquakes associated with the geothermal power operation may result from perturbations in the pore fluid pressure as well as normal and shear stresses caused by the deflation of the geothermal reservoir

estimation of ice sheet motion using satellite radar interferometry method and error analysis with application to humboldt glacier greenland satellite radar interferometry provides glaciologists with an important new tool for determining the motion and topography of large ice sheets we examine the sources of error in interferometrically derived ice motion measurements including those errors due to inaccurate estimates of the interferometric baseline several simulations are used to assess baseline accuracy in terms of tie point error and the number and distribution of tie points these results give insight into how best to select tie points and also demonstrate the level of accuracy that can be achieved examination of two representative cases likely to occur in mapping ice sheet motion leads to the conclusion that with adequate tie point information ice velocity can be measured accurately to within a few meters per year a method to correct horizontal velocity estimates for the effect of vertical displacement using surface slopes is also developed finally we estimate the single component velocity field for an area on humboldt glacier northern greenland using interferograms formed from ers i sar images we estimate that these velocity measurements are accurate to within 2 3 m year 1

coseismic and early post seismic slip associated with the 1999 izmit earthquake turkey from sar interferometry and tectonic field observations summary we use combined tectonic field observations and sar data to determine an improved model of the slip associated with the 1999 izmit earthquake which ruptured the north anatolian fault at the eastern end of the sea of marmara the leading goal is to understand the main features of the coseismic and post seismic deformation which are captured together in the sar data to achieve this we make a critical analysis of the ers1 2 sar data which allows atmospheric effects to be identified and removed we also use detailed field mapping and measurements of the earthquake surface rupture dislocations in elastic half space and a forward modelling strategy allow us to obtain a slip model by steps a trial and error approach is combined with conventional inversion techniques to determine the slip in the different regions of the fault the sar data are well explained with three main zones of high slip along the fault releasing a total moment of 2 3 10 20 nm mw 7 6 which is higher than the seismological estimates 1 7 2 0 10 20 n m the inhomogeneous slip distribution correlates with fault segments identified at the surface the izmit rupture appears to have extended 30 km west of the hersek peninsula into the sea of marmara with slip tapering fro m2mt ozero the western end of the rupture is located 40 km sse from istanbul we show that some features seen near to mudurnu and gevye and previously interpreted as slip on secondary faults are explained mostly as atmospheric effects correlated with the topography using our approach and the available gps data we obtain a slip model that represents the coseismic slip alone which suggests that the moment release during the main shock was 1 9 10 20 nm mw 7 5 consistent with the seismological estimates we conclude that the sar data include the effects of 2 m of fast after slip during the month following the main shock within a zone of the fault located 12 24 km below the epicentral region near the hypocentre at a depth of 18 km the fault appears to have experienced dynamic slip of 1 m associated with the main shock followed by 2 m of rapidly decelerating post seismic shear during the following month we suggest that the distribution of heterogeneous slip and loading along the different fault segments may be important factors controlling the propagation of large earthquake ruptures along the north anatolian fault

monitoring playa sedimentation using sequential radar images a series of ers 1 radar images of the chott el djerid playa in tunisia obtained at intervals of 35 days demonstrates the ability to monitor geological change from space the c band radar backscatter is shown from field measurements to be sensitive to changes in surface roughness at millimetric scale due to evaporative growth of halite and gypsum crystals backscatter increases gradually during the dry summer months and decreases rapidly in early winter as the rains begin episodic hydrogeological and sedimentological events including lake development channel flow and aeolian deposition can also be detected in addition to the seasonal pattern multitemporal spaceborne radar offers the prospect of being able to map the dynamics of evaporite sedimentation in continental playas

three pattern decomposition of global atmospheric circulation part i decomposition model and theorems in order to study the interactions between the atmospheric circulations at the middle high and low latitudes from the global perspective the authors proposed the mathematical definition of three pattern circulations i e horizontal meridional and zonal circulations with which the actual atmospheric circulation is expanded this novel decomposition method is proved to accurately describe the actual atmospheric circulation dynamics the authors used the ncep ncar reanalysis data to calculate the climate characteristics of those three pattern circulations and found that the decomposition model agreed with the observed results further dynamical analysis indicates that the decomposition model is more accurate to capture the major features of global three dimensional atmospheric motions compared to the traditional definitions of rossby wave hadley circulation and walker circulation the decomposition model for the first time realized the decomposition of global atmospheric circulation using three orthogonal circulations within the horizontal meridional and zonal planes offering new opportunities to study the large scale interactions between the middle high latitudes and low latitudes circulations

sar monitoring of progressive and seasonal ground deformation using the permanent scatterers technique spaceborne differential radar interferometry has proven a remarkable potential for mapping ground deformation phenomena e g urban subsidence volcano dynamics coseismic and postseismic displacements along faults as well as slope instability however a full operational capability has not been achieved yet due to atmospheric disturbances and phase decorrelation phenomena these drawbacks can often be at least partially overcome by carrying out measurements on a subset of image pixels corresponding to natural or artificial stable reflectors permanent scatterers ps and exploiting long temporal series of interferometric data this approach allows one to push the measurement precision very close to its theoretical limit in the order of spl sim 1 mm for c band european remote sensing ers like sensors in this paper the detection of both time uniform and seasonal deformation phenomena is addressed and a first assessment of the precision achievable by means of the ps technique is discussed results highlighting deformation phenomena occurring in two test sites in california are reported fremont in the southern bay area and san jose in the santa clara valley

novel three pattern decomposition of global atmospheric circulation generalization of traditional two dimensional decomposition this study investigates the differences and connections between the three pattern decomposition of global atmospheric circulation the representation of the horizontal vortex circulation in the middle high latitudes and the local partitioning of the overturning circulation in the tropics it concludes that the latter two methods are based on the traditional two dimensional 2d decomposition of the vortex and divergent circulations in the fluid dynamics and that the three pattern decomposition model is not a simple superposition of the two traditional methods but a new three dimensional 3d decomposition of global atmospheric circulation the three pattern decomposition model can decompose the vertical vorticity of atmosphere into three parts one part is caused by the horizontal circulation whereas the other two parts are induced by divergent motions which correspond to the zonal and meridional circulations the diagnostic results from the decomposed vertical vorticities accord well with the classic theory the atmospheric motion at 500 hpa is quasi horizontal and nondivergent and can represent the vertical mean state of the entire atmosphere the analysis of the climate characteristics shows that the vertical vorticities of the zonal and meridional circulations are the main cause of the differences between the three pattern circulations and traditional circulations the decomposition of the vertical vorticity by the three pattern decomposition model offers new opportunities to quantitatively study the interaction mechanisms of the rossby hadley and walker circulations using the vorticity equation