high resolution sar interferometry estimation of local frequencies in the context of alpine glaciers synthetic aperture radar sar interferometric data offer the opportunity to measure temperate glacier surface topography and displacement the increase of the resolution provided by the most recent sar systems has some critical implications for instance a reliable estimate of the phase gradient can only be achieved by using interferogram local frequencies in this paper an original two step method for estimating local frequencies is proposed the 2 d phase signal is considered to have two deterministic components corresponding to low resolution lr fringes and high resolution hr patterns due to the local microrelief respectively the first step of the proposed algorithm consists in the lr phase flattening in the second step the local hr frequencies are estimated from the phase 2 d autocorrelation function computed on adaptive neighborhoods this neighborhood is the set of connected pixels belonging to the same hr spatial feature and respecting the ldquolocal stationarityrdquo hypothesis results with both simulated terrasar x interferograms and real airborne e sar images are presented to illustrate the potential of the proposed method

possible roles of atlantic circulations on the weakening indian monsoon rainfall enso relationship abstract since the 1970s the inverse relationship between the indian monsoon rainfall and the el nino southern oscillation enso has weakened considerably the cause for this breakdown is shown to be most likely the strengthening and poleward shift of the jet stream over the north atlantic these changes have led to the recent development of a significant correlation between wintertime western european surface air temperatures and the ensuing monsoon rainfall this western europe winter signal extended eastward over most of northern eurasia and remained evident in spring such that the effect of the resulting meridional temperature contrast was able to disrupt the influence of enso on the monsoon

combining airborne photographs and spaceborne sar data to monitor temperate glaciers potentials and limits monitoring temperate glacier activity has become more and more necessary for economical and security reasons and as an indicator of the local effects of global climate change remote sensing data provide useful information on such complex geophysical objects but they require specific processing techniques to cope with the difficult context of moving and changing features in high relief areas this paper presents the first results of a project involving four laboratories developing and combining specific methods to extract information from optical and synthetic aperture radar sar data two different information sources are processed namely 1 airborne photography and 2 spaceborne c band sar interferometry the difficulties and limitations of their processing in the context of alpine glaciers are discussed and illustrated on two glaciers located in the mont blanc area the results obtained by aerial triangulation techniques provide digital terrain models with an accuracy that is better than 30 cm which is compatible with the computation of volume balance and useful for precise georeferencing and slope measurement updating the results obtained by sar differential interferometry using european remote sensing satellite images show that it is possible to measure temperate glacier surface velocity fields from october to april in one day interferograms with approximately 20 m ground sampling this allows to derive ice surface strain rate fields required to model the glacier flow these different measurements are complementary to results obtained during the summer from satellite optical data and ground measurements that are available only in few accessible points

interactions of synoptic and planetary waves scale dependent forcing of a gcm abstract in order to better understand planetary wave synoptic wave interactions in the atmosphere and to develop a tool for further studies the authors have applied a wavenumber dependent external forcing to a general circulation model gcm the forcing constrains various length scales of the gcm to be close to those in the evolving analyses of the european centre for medium range weather forecasts and the national centers for environmental prediction the forcing acts either on the planetary waves pw defined as zonal wavenumbers 0 5 the synoptic waves sw defined as zonal wavenumbers 6 20 the synoptic waves plus the zonal mean sw0 or the synoptic waves plus the zonal mean and wavenumber 1 sw01 the form of the forcing is a linear relaxation to the evolving analyses with a time constant of 8 h this forcing is applied only to the temperature and vorticity equations of the gcm which has a spectral truncation of t42 control integrations of length 30 days have been run starting on 15 dece

role of north tropical atlantic sst on the enso simulated using cmip3 and cmip5 models in this study role of north tropical atlantic nta sst on the enso variability is examined with cmip3 and cmip5 simulations it is found that most climate models involved in cmip3 and cmip5 successfully simulate the inverse relationship between nta sst during the boreal spring and the enso during the subsequent boreal winter the multi model ensemble mme results show the observed westward propagating signals related to nta sst from the atlantic to the pacific along the off equatorial pacific itcz however different from the observational argument the main mechanism for the nta to induce the enso is likely to be different in the mme while the observational result exhibits the nta induced off equatorial rossby waves play a more dominant role in leading the pacific signal the equatorial wind over the western pacific related to the nta induced kelvin wave is likely to be more crucial to lead the pacific variability in addition the amplitude of nta sst induced enso in the mme tends to be systematically weaker and the preference for the central pacific sst anomaly is also weak these weak signals are distinctly improved in a model that simulates two types of el nino events independently that the strength of the nta effect to the pacific can be affected by the seasonal distribution of climatological precipitation is also discussed additionally the strength of the nta effect tends to be stronger when the model simulates phase locking of enso reasonably

tropical extratropical geopotential height teleconnections during the northern hemisphere winter abstract simultaneous and lagged correlation statistics have been calculated between time series of seasonal height anomalies at selected stations and extratropical grid point anomalies in both hemispheres the tropical stations in two major tropical precipitation zones the indo china maritime continent and africa are well correlated with each other these stations are also correlated with stations in the north pacific and australia but the coefficients are smaller the correlations between height anomalies at any of these stations and northern hemisphere height anomalies show a well defined global pattern depending upon the location of the stations the pattern is either a pacific north american pna a tropical northern hemisphere tnh pattern or a mixed pattern having both elements all three patterns pna tnh and wpo western pacific oscillation have been linked to tropical variations the correlations between height anomalies at these well correlated stations and the southern hemisphere heig

satellite radar interferometry for monitoring ice sheet motion application to an antarctic ice stream satellite radar interferometry sri provides a sensitive means of monitoring the flow velocities and grounding line positions of ice streams which are indicators of response of the ice sheets to climatic change or internal instability the detection limit is about 1 5 millimeters for vertical motions and about 4 millimeters for horizontal motions in the radar beam direction the grounding line detected by tidal motions where the ice goes afloat can be mapped at a resolution of 0 5 kilometer the sri velocities and grounding line of the rutford ice stream antarctica agree fairly well with earlier ground based data the combined use of sri and other satellite methods is expected to provide data that will enhance the understanding of ice stream mechanics and help make possible the prediction of ice sheet behavior

equatorial atlantic variability and its relation to mean state biases in cmip5 coupled general circulation model gcm simulations participating in the coupled model intercomparison project phase 5 cmip5 are analyzed with respect to their performance in the equatorial atlantic in terms of the mean state 29 out of 33 models examined continue to suffer from serious biases including an annual mean zonal equatorial sst gradient whose sign is opposite to observations westerly surface wind biases in boreal spring play an important role in the reversed sst gradient by deepening the thermocline in the eastern equatorial atlantic and thus reducing upwelling efficiency and sst cooling in the following months both magnitude and seasonal evolution of the biases are very similar to what was found previously for cmip3 models indicating that improvements have only been modest the weaker than observed equatorial easterlies are also simulated by atmospheric gcms forced with observed sst they are related to both continental convection and the latitudinal position of the intertropical convergence zone itcz particularly the latter has a strong influence on equatorial zonal winds in both the seasonal cycle and interannual variability the dependence of equatorial easterlies on itcz latitude shows a marked asymmetry from the equator to 15 n the equatorial easterlies intensify approximately linearly with itcz latitude when the itcz is south of the equator on the other hand the equatorial easterlies are uniformly weak despite serious mean state biases several models are able to capture some aspects of the equatorial mode of interannual sst variability including amplitude pattern phase locking to boreal summer and duration of events the latitudinal position of the boreal spring itcz through its influence on equatorial surface winds appears to play an important role in initiating warm events

tropical and extratropical forcing of the large scale circulation a diagnostic study abstract seasonal anomalies in the large scale circulation are studied in relation to seasonal mean tropical forcing and extratropical transient eddy forcing using nine years of tropical wind and outgoing longwave radiation olr data the olr is used as a proxy for tropical conviction and the transient eddy forcing is estimated from the extended eliassen palm flux or e vector formulation hoskins et al results show that in the interannual time scale extreme swings in anomalous convection over the maritime continent of indonesia borneo and the equatorial central pacific an linked respectively by an east west seesaw or a dipole pattern identified with major fluctuations of the pacific walker circulation it is found that extratropical circulation anomalies are related to the fluctuation of this dipole beat source the overall extratropical circulation seems to be more responsive to the dipole heating with enhanced convection over the maritime continent while the characteristics of the transient ed

the displacement field of the landers earthquake mapped by radar interferometry geodetic data obtained by ground or space based techniques can be used to infer the distribution of slip on a fault that has ruptured in an earthquake although most geodetic techniques require a surveyed network to be in place before the earthquake1 3 satellite images when collected at regular intervals can capture co seismic displacements without advance knowledge of the earthquake s location synthetic aperture radar sar interferometry first introduced4 in 1974 for topographic mapping5 8 can also be used to detect changes in the ground surface by removing the signal from the topography9 10 here we use sar interferometry to capture the movements produced by the 1992 earthquake in landers california11 we construct an interferogram by combining topographic information with sar images obtained by the ers 1 satellite before and after the earthquake the observed changes in range from the ground surface to the satellite agree well with the slip measured in the field with the displacements measured by surveying and with the results of an elastic dislocation model as a geodetic tool the sar interferogram provides a denser spatial sampling 100 m per pixel than surveying methods1 3 and a better precision 3 cm than previous space imaging techniques12 13

teleconnections in the geopotential height field during the northern hemisphere winter abstract contemporaneous correlations between geopotential heights on a given pressure surface at widely separated points on earth referred to as teleconnections in this paper are studied in an attempt to identify and document recurrent spatial patterns which might be indicative of standing oscillations in the planetary waves during the northern hemisphere winter with time scales on the order of a month or longer a review of existing literature on the subject reveals the existence of at least four such patterns the north atlantic and north pacific oscillations identified by walker and bliss 1932 a zonally symmetric seesaw between sea level pressures in polar and temperature latitudes first noted by lorenz 1951 and what we will refer to as the pacific north american pattern which has been known to operational long range forecasters in this country since the 1950 s a data set consisting of nmc monthly mean sea level pressure and 500 mb height analyses for a 15 year period is used as a basis fo

synoptic analysis of the pacific north american teleconnection pattern in this study we use various diagnostic techniques to investigate the synoptic evolution of the pacific north american teleconnection pattern pna national center for environment prediction national center for atmospheric research reanalysis data are used these data cover the years 1948 2008 for the months of november march it is found that the positive pna is initiated by enhanced convection over the western tropical pacific and weakened convection over the tropical indian ocean the excitation of the negative pna exhibits opposite features for both phases the response to tropical convection excites a small amplitude pna about 8 12 days prior to the pattern attaining its maximum amplitude this is followed by slow steady growth for about 5 days after which driving by synoptic scale waves via their eddy vorticity flux together with stationary eddy advection lead to much more rapid growth and the establishment of the full pna for the positive pna the synoptic scale waves propagate eastward into the midlatitude northeastern pacific where they are observed to undergo cyclonic wave breaking for the negative pna the synoptic scale waves first amplify over the midlatitude northeastern pacific and then propagate equatorward into the subtropics where they undergo anticyclonic wave breaking once established for both phases the pna appears to be maintained through a positive feedback that involves a succession of wave breakings these results suggest that preconditioning may play an important role in the formation of the pna for the positive pna in its early development the strengthening and eastward extension of the subtropical jet result in an increase in the cyclonic shear and a decrease in the meridional potential vorticity gradient features that are known to favour cyclonic wave breaking for the negative pna opposite changes were observed for the background flow which favour equatorward wave propagation and anticyclonic wave breaking the role of optimal growth is also discussed our results also suggest that the pna is potentially predictable 1 2 weeks in advance copyright 2011 royal meteorological society

classification seasonality and persistence of low frequency atmospheric circulation patterns abstract orthogonally rotated principle component analysis rpca of northern hemisphere 1 month mean 700 mb heights is used to identify and describe the seasonality and persistence of the major modes of interannual variability the analysis is detailed and comprehensive in that 1 a high resolution approximately equal area 358 point grid is used for the virtually maximum possible 35 year period of record 2 a positive bias in the nmc data base in the early 1950s in the subtropics is largely eliminated for the first time and 3 homogeneous separate analyses of each month of the year are carried out detailing the mouth to month changes in the dominant circulation patterns winter results are similar to those of other recent rpca and teleconnection studies except that some less obvious patterns are identified and further detail of the better known patterns is provided two north south dipole patterns are found over the pacific ocean west pacific oscillation and east pacific pattern and over the atla

measuring snow and glacier ice properties from satellite satellite remote sensing is a convenient tool for studying snow and glacier ice allowing us to conduct research over large and otherwise inaccessible areas this paper reviews various methods for measuring snow and glacier ice properties with satellite remote sensing these methods have been improving with the use of new satellite sensors like the synthetic aperture radar sar during the last decade leading to the development of new and powerful methods such as sar interferometry for glacier velocity digital elevation model generation of ice sheets or snow cover mapping some methods still try to overcome the limitations of present sensors but future satellites will have much increased capability for example the ability to measure the whole optical spectrum or sar sensors with multiple polarization or frequencies among the methods presented are the satellite derived determination of surface albedo snow extent snow volume snow grain size surface temperature glacier facies glacier velocities glacier extent and ice sheet topography in this review emphasis is put on the principles and theory of each satellite remote sensing method an extensive list of references with an emphasis on studies from the 1990s allows the reader to delve into specific topics

measurement of ice sheet topography using satellite radar interferometry detailed digital elevation models dems do not exist for much of the greenland and antarctic ice sheets radar altimetry is at present the primary in many cases the only source of topographic data over the ice sheets but the horizontal resolution of such data is coarse satellite radar interferometry uses the phase difference between pairs of synthetic aperture radar sar images to measure both ice sheet topography and surface displacement we have applied this technique using ers 1 sar data to make detailed i e 80 m horizontal resolution maps of surface topography in a 100 km by 300 km strip in west greenland extending northward from just above jakobshavns isbrae comparison with a 76 km long line of airborne laser altimeter data shows that we have achieved a relative accuracy of 2 5m along the profile these observations provide a detailed view of dynamically supported topography near the margin of an ice sheet in the final section we compare our estimate of topography with phase contours due to motion and confirm our earlier analysis concerning vertical ice sheet motion and complexity in ers 1 sar interferograms

surface motion of mountain glaciers derived from satellite optical imagery a complete and detailed map of the ice velocity field on mountain glaciers is obtained by cross correlating spot5 optical images this approach offers an alternative to sar interferometry because no present or planned radar satellite mission provides data with a temporal separation short enough to derive the displacements of glaciers the methodology presented in this study does not require ground control points gcps the key step is a precise relative orientation of the two images obtained by adjusting the stereo model of one slave image assuming that the other master image is well georeferenced it is performed with numerous precisely located homologous points extracted automatically the strong ablation occurring during summer time on the glaciers requires a correction to obtain unbiased displacements the accuracy of our measurement is assessed based on a comparison with nearly simultaneous differential gps surveys performed on two glaciers of the mont blanc area alps if the images have similar incidence angles and correlate well the accuracy is on the order of 0 5 m or 1 5 of the pixel size similar results are also obtained without gcps an acceleration event observed in early august for the mer de glace glacier is interpreted in term of an increase in basal sliding our methodology applied to spot5 images can potentially be used to derive the displacements of the earth s surface caused by landslides earthquakes and volcanoes

west pacific teleconnection pattern in dynamical seasonal predictions how is it connected to the atlantic atmospheric mean bias this study examines the west pacific wp pattern one of the primary modes of low frequency variability during boreal winter isolated in 11 global climate model seasonal hindcasts wp mode separation are verified using three metrics selected mode number explained variance and pattern correlation coefficient of the loading vector when it comes to the pattern reproducibility it turns out that the wp is tightly linked to the atlantic jet and stationary wave to diagnose details of mean biases in terms of wp reproducibility atmospheric mean fields are composited for two groups one group replicates well the key feature a north south dipole pattern while the other manifests considerable displacements and magnitude disparities the group with a lower pattern correspondence to the observation shows noticeable biases with the southeastward shifted atlantic dipole of the stationary wave and downstream expanded atlantic jet which is attributed to the increase in meridional gradient of near surface temperature and resultant enhanced local baroclinicity magnified jet tail in the eastern north atlantic na can intensify the barotropic energy conversion thereby the wave energy actively passes toward both east and west the excessive wave energy over the arabian peninsula and the central north pacific can be favorable for the formation of a ridge therefore it possibly leads to disorganized wp patterns at both ends of na basin a series of analysis suggests the importance of a realistic winter climatology simulation over na for better wp representation through the interaction between different scales as well as different basins

the dynamics of large scale cyclogenesis over the north pacific ocean abstract earlier studies of persistent large scale flow anomalies have been extended with the aim of identifying the primary mechanisms for persistent anomaly development in this study the focus is on wintertime cases of persistent cyclonic flow anomalies over the north pacific these cases are typically manifested by an abnormally intense cyclonic circulation extending over the north pacific basin an unusually strong and eastward extended east asian jet and a well defined pacific north american teleconnection pattern we have conducted extensive diagnostic analyses in order to determine the mechanisms responsible for development in particular these diagnostics examine the processes influencing the time evolution of eddy potential enstrophy and potential vorticity anomalies the cases are preceded by a buildup of anomalously high potential vorticity air at upper levels over eastern asia this high potential vorticity air is initially advected eastward in association with synoptic scale cyclogenesis

using multiple radarsat insar pairs to estimate a full three dimensional solution for glacial ice movement 1 multiple sar interferograms are used to solve for the full 3 dimensional displacement of the surface of the henrietta nesmith glacier in northern ellesmere island canada the approach exploits the incidence angle flexibility of different ascending and descending beam modes and the azimuth angle diversity which occurs when different incidence angles are used at high latitudes line of sight displacements are estimated in 3 different orientations from the terrain corrected unwrapped differential phase and used to solve for the displacements in a local east north up frame uncertainty in the absolute line of sight displacements limits the absolute accuracy for vertical displacement however the relative solution coupled with knowledge of the surface slope allows spaceborne mapping of relative glacier thickening or thinning with unprecedented spatial resolution and with an accuracy of order a millimeter per day

toward understanding the response of the tropical atmosphere ocean system to increased co2 using equilibrium asynchronous coupling we investigate the response of the tropical pacific climate system to a tripling of co2 in a coupled atmosphere ocean model equilibrium asynchronous coupling eac is used to diagnose the climatic forcing mechanisms our results corroborate those from most other coupled gcms which generally simulate an el nino like mean climate state under increased co2 this pattern is characterized by enhanced warming of the ocean surface in the equatorial pacific in conjunction with a reduction in the zonal sst gradient stronger atmospheric convection and precipitation in the central equatorial pacific a stronger subtropical westerly jet and a deepened wintertime aleutian low in association with a pna like geopotential pattern aloft we show that these climate changes are triggered by a weakening of the tropical walker circulation which leads to weaker surface easterly winds along the equator and therefore less oceanic upwelling furthermore the main el nino like atmospheric anomalies do not depend critically on the existence of an east west equatorial gradient either in the simulated modern ssts or in the sst anomalies under increased co2 regardless of the details of the sst boundary conditions the atmosphere seems to respond similarly to a co2 warming perturbation and in a manner that favors the evolution of the climate system toward an el nino like state an enhanced meridional atmospheric circulation in the pacific is linked to increased convection along the itcz coinciding with subtropical anomalies of higher surface pressure and stronger subsidence aloft this anomalous surface pressure pattern is much more pronounced in the northern hemisphere presumably due to a pna like atmospheric teleconnection these surface pressure anomalies produce a stronger meridional outflow of wind toward the equator and weaker easterly winds along the equator the weaker equatorial easterlies reduce oceanic upwelling in the central and eastern equatorial pacific thereby promoting a reduced east west sst gradient and a maximum warming in the central equatorial pacific around 140 170 w

validation of alpine glacier velocity measurements using ers tandem mission sar data five ascending and four descending ers 1 2 tandem mode synthetic aperture radar sar interferometry insar data pairs with useful scene coherence are used to measure the surface flow field of an alpine glacier in the canadian rocky mountains the topographic component of the interferogram phase is calculated by using a digital elevation model dem of the terrain and precise orbit data to reconstruct the ers insar imaging geometry the dem is derived from the canada centre for remote sensing ccrs convair 580 airborne sar interferometer as dual line of sight los measurements are not sufficient to completely resolve the three dimensional 3d surface flow field several different assumptions for determining the missing variables are considered and the 3d surface flow field is estimated by using single and dual los measurements the insar results agree with historic and coincident displacement measurements made using traditional point surveying techniques

tidal motion ice velocity and melt rate of petermann gletscher greenland measured from radar interferometry over a floating glacier ice tongue or an ice shelf the glacier motion measured by a single repeat pass radar interferogram is difficult to analyze because the long term steady motion of the ice is intermixed with its cyclic downward motion induced by tidal forcing multiple interferograms and a quadruple difference technique are necessary to separate the tidal signal from the long term steady motion of the ice an example of application of this technique is given here using ers 1 radar images of petermann gletscher a major outlet glacier of northern greenland tidal displacements are measured with 5 mm statistical noise the long term ice velocity is measured with a precision of 1 m a 1 the inferred tidal displacements agree well with model predictions from a fixed elastic beam with an elastic damping factor of 0 47 0 01 km 1 the hinge line is mapped with a precision of 20 80 m combining the interferometric ice velocities with ice thickness data the glacier ice discharge is calculated at and below the hinge line at the hinge line the ice flux is 12 1 1 km3 a 1 at the ice front calf ice production is only 0 59 km3 a 1 meaning that 95 of the ice that crosses the grounding line melts before it reaches the calving front assuming steady state conditions the melt rate of the glacier tongue averages 12 1 m a 1 with peak values exceeding 20 m a 1 near the hinge line this high melt rate cannot be accommodated by surface ablation alone only about 2 3 m a 1 and is attributed to pronounced basal melting of the ice tongue basal melting often assumed to be negligible in greenland is the dominant process of mass release from the floating section of petermann gletscher

low frequency variability in the midlatitude atmosphere induced by an oceanic thermal front abstract this study examines the flow induced in a highly idealized atmospheric model by an east west oriented oceanic thermal front the model has a linear marine boundary layer coupled to a quasigeostrophic equivalent barotropic free atmosphere the vertical velocity at the top of the boundary layer drives the flow in the free atmosphere and produces an eastward jet parallel to the oceanic front s isotherms a large gyre develops on either side of this jet cyclonic to the north and anticyclonic to the south of it as the jet intensifies during spinup from rest it becomes unstable the most unstable wave has a length of about 500 km it evolves into a meander and eddies detach from the eastern edge of each gyre the dependence of the atmospheric dynamics on the strength t of the oceanic front is studied the gulf stream and kuroshio fronts correspond roughly in the scaling used here to t 7 c for weak fronts t 4 c the circulation is steady and exhibits two large antisymmetric gyres sepa

observed patterns of month to month storm track variability and their relationship to the background flow month to month storm track variability is investigated via eof analyses performed on era 40 monthlyaveraged high pass filtered daily 850 hpa meridional heat flux and the variances of 300 hpa meridional wind and 500 hpa height the analysis is performed both in hemispheric and sectoral domains of the northern and southern hemispheres patterns characterized as pulsing and latitudinal shifting of the climatologicalmean storm tracks emerge as the leading sectoral patterns of variability based on the analysis presented storm track variability on the spatial scale of the two northern hemisphere sectors appears to be largely but perhaps not completely independent pulsing and latitudinally shifting storm tracks are accompanied by zonal wind anomalies consistent with eddy forced accelerations and geopotential height anomalies that project strongly on the dominant patterns of geopotential height variability the north atlantic oscillation nao northern hemisphere annular mode nam is associated with a pulsing of the atlantic storm track and a meridional displacement of the upper tropospheric jet exit region whereas the eastern atlantic ea pattern is associated with a latitudinally shifting storm track and an extension or retraction of the upper tropospheric jet analogous patterns of stormtrack and upper tropospheric jet variability are associated with the western pacific wp and pacific north america pna patterns wave mean flow relationships shown here are more clearly defined than in previous studies and are shown to extend through the depth of the troposphere the southern hemisphere annular mode sam is associated with a latitudinally shifting storm track over the south atlantic and indian oceans and a pulsing south pacific storm track the patterns of storm track variability are shown to be related to simple distortions of the climatological mean upper tropospheric jet

is there a single surge mechanism contrasts in dynamics between glacier surges in svalbard and other regions 1 during the 1990s monacobreen a 40 km long tidewater glacier in svalbard underwent a major surge we mapped the surge dynamics using ers synthetic aperture radar images differential dual azimuth interferometry and intensity correlation tracking a series of 11 three dimensional 3 d velocity maps covering the period 1991 1997 show a months long initiation and years long termination to the surge with no indication of a surge front travelling downglacier during the surge the front of the glacier advanced 2 km the velocity and derived strain rate increased by more than an order of magnitude and maximum ice flow rates measured during 1994 were 5 m d 1 the spatial pattern of both velocity and strain rate was remarkably consistent and must therefore be controlled by spatially fixed processes operating at the glacier bed we combine these results with those published in the literature to construct a typical svalbard glacier surge cycle and compare this to surge dynamics of glaciers from other cluster regions especially those of variegated glacier in alaska the strong contrast in dynamics suggests that there exist at least two distinct surge mechanisms

northern winter stationary waves theory and modeling a review is provided of stationary wave theory the theory for the deviations from zonal symmetry of the climate to help focus the discussion the authors concentrate exclusively on northern winter several theoretical issues including the external rossby wave dispersion relation and vertical structure critical latitude absorption the nonlinear response to orography and the interaction of forced wave trains with preexisting zonal asymmetries are chosen for discussion while simultaneously presenting a decomposition of the wintertime stationary wave field using a nonlinear steady state model

investigating mountain glacier motion with the method of sar intensity tracking removal of topographic effects and analysis of the dynamic patterns abstract accurate knowledge of glacier motion variations can provide critical information for assessing glacier mass balance changes for fast flowing high mountain glaciers sar intensity tracking may be the most appropriate technique to measure their motions however due to the slant range imaging mode topographic relief can give rise to pixel disalignments in sar image and then bring errors to sar intensity tracking as a result the application of sar intensity tracking has been limited to sar pairs with short baselines because the use of image pairs with long baselines would suffer significant topographic effects over mountainous regions this paper presents an improvement to sar intensity tracking by adding an explicit procedure of topographic correction such correction will not only significantly increase the accuracy of the sar pairs with shorter baselines but also allow the image pairs with longer baselines to be taken advantage of instead of letting them to be dismissed otherwise using the improved sar intensity tracking technique we derive the highly precise motion variation patterns of 11 giant glaciers in tuomuer khan tengri mountain ranges one of the largest glacial centers in tien shan the results manifest that most glaciers there saw flow deceleration during the observation interval 6 january 2007 4 march 2011 except the northern and southern inylchek glacier regarding the glacier motion mechanism ice thermal character and climate features there we deduce that the flow acceleration and deceleration should be the sign of glacier mass gain and loss respectively and the sharp and slight flow decelerations should correspond to remarkable and mild mass loss respectively we confirm these deductions by exploring the close link between the long term motion variations and the dynamic patterns of these glaciers the obvious diversities of the dynamic patterns among the studied glaciers are ascribed to the discrepancies of the glaciers location and scale longer observations are still needed to confirm or redefine these findings in the future though provided that the precipitation keeps increasing whether the glaciers in tuomuer khan tengri mountain ranges will regain mass or not has not been determined yet

global view of the intraseasonal oscillation during northern winter abstract in this study svd analysis is applied to a normalized 200 mb streamfunction olr covariance matrix to extract the most recurrent coupled pattern in the northern winter after the removal of the climatological seasonal cycle and seasonal means for each winter the first two singular vectors are on an intraseasonal timescale and the combination of the two forms an oscillation it is characterized by eastward propagation in the indian ocean and the western pacific standing oscillations in both the tropics and the extratropics and the poleward propagation of a zonally symmetric structure although there exists an eastwardly propagating pattern the phase relationship between geopotential wind and streamfunction fields is inconsistent with that of equatorial kelvin waves eastward propagation is most evident in the tropics of the southern hemisphere while the signals in the northern hemisphere are characterized by standing oscillations the distinct characteristics of the northern and southern he

dynamical relationship between the phase of north atlantic oscillations and the meridional excursion of a preexisting jet an analytical study abstract in this paper it is shown from an analytical solution that in the presence of a preexisting jet the interaction between the zonal jet and the topography of the land sea contrast lsc in the northern hemisphere nh tends to induce a dipole component that depends crucially upon whether this zonal jet exhibits a north south excursion this phenomenon cannot be observed if the zonal jet has no north south shift when the preexisting jet is located more northward southward the induced dipole can have a low over high high over low structure and thus can make the center of the stationary wave anomaly shift southward northward which can be regarded as an initial state or embryo of a positive negative phase north atlantic oscillation nao this dipole component can be amplified into a typical nao event under the forcing of synoptic scale eddies to some extent this result provides an explanation for why the positive negative phase of the nao can be controlled by the northward southward

seasonal and interannual ice velocity changes of polar record glacier east antarctica we present a study of seasonal and interannual ice velocity changes at polar record glacier east antarctica using ers 1 2 envisat and palsar data with d insar and intensity tracking ice flow showed seasonal variations at the front of the glacier tongue velocities in winter were 19 less than velocities during summer no significant interannual changes were detected ice velocities in the grounding zone and grounded glacier did not show clear seasonal or interannual changes the distribution of the seasonal variations suggests that the cause for the changes should be localized possible causes are seasonal sea ice changes and iceberg blocking satellite images show that the sea ice surrounding polar record glacier undergoes seasonal changes frozen sea ice in winter slowed the huge iceberg and provided increased resistance to the glacier flow the interaction between the glacier tongue iceberg and sea ice significantly influences their flow pattern

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

flow and structure in a dendritic glacier with bedrock steps sherpa romeo green journal open access article creative commons attribution 4 0 international cc by 4 0 applies

echinoderm skeletal preservation calcite aragonite seas and the mg ca ratio of phanerozoic oceans abstract the alternation between abiotic calcite and aragonite precipitation in shallow seawater and the oscillation of seawater mg ca ratio throughout the phanerozoic are both popular hypotheses echinoderms with well preserved stereom provide new empirical evidence that supports both these hypotheses analyses are reported from 29 specimens cambrian to eocene age containing ossicles preserved either as mg calcite 3 3 to 8 mole mgco3 or as mixed calcite and dolomite 5 to 12 5 mole mgco3 echinoderms with high mole mgco3 occur in the early cambrian and late carboniferous to triassic low values come from the silurian and jurassic to cretaceous the average composition of echinoderms with preserved stereom does not fall below 3 5 mol mgco3 during the phanerozoic and reaches its highest mean value of 16 0 mol mgco3 today an empirical partition coefficient of 0 03182 for modern tropical echinoids is used to indicate the mg ca ratio of ancient seawater from the mg ca ratio of fossil stereom some assumptions are involved and a likely error is calculated from the mg2 variation of modern echinoids high mean seawater mg ca ratios are calculated for early cambrian 3 3 and the late carboniferous to triassic 2 3 but never reached today s value of 5 2 low mg ca ratios 1 1 are indicated from jurassic to cretaceous echinoderms the 29 echinoderm samples plot close to first order mg ca seawater oscillations derived from geochemical models and mg ca ratios determined from fluid inclusions but considerable discrepancies exist when shorter 106 myr time intervals are considered further data and improved understanding of mg partitioning is required before accurate secular variation in the mg ca of seawater can be determined from echinoderms however they are an underused resource in this context and provide an excellent seawater archive

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

barotropic wave propagation and instability and atmospheric teleconnection patterns abstract a global barotropic model linearized about the 300 mb climatological mean january flow is perturbed by applying a series of localized forcings distributed throughout the tropics and subtropics structures which resemble the observed pacific north american and east atlantic teleconnection patterns noted by wallace and gutzler 1981 tend to recur in the responses similar patterns are found to result from the dispersion of isolated initial perturbations placed at a variety of locations in the tropics and midlatitudes it is shown that these structures are related to the most rapidly growing mode associated with barotropic instability of the zonally varying climatological basic state in the absence of damping this mode has an e folding time of about a week and a period close to 50 days in localized regions the instantaneous growth rates can be competitive with those of baroclinic instability these episodes of rapid local barotropic growth are interspersed with intervals in which the local

on the three dimensional propagation of stationary waves abstract a locally applicable nonzonally averaged conservation relation is derived for quasi geostrophic stationary waves on a zonal flow a generalization of the eliassen palm relation the flux which appears in this relation constitutes it is argued a useful diagnostic of the three dimensional propagation of stationary wave activity this is illustrated by application to a simple theoretical model of a forced rossby wave train and to a northern hemisphere winter climatology results of the latter procedure suggest that the major forcing of the stationary wave field derives from the orographic effects of the tibetan plateau and from nonorographic effects diabatic heating and or interaction with transient eddies in the western north atlantic and north pacific oceans and siberia no evidence is found in the data for wave trains of tropical origin forcing by the orographic effects of the rocky mountains seems to be of secondary importance

evaluation of remote sensing techniques to measure decadal scale changes of hofsjokull ice cap iceland dynamic surficial changes and changes in the position of the firn line and the areal extent of hofsjokull ice cap iceland were studied through analysis of a time series 1973 98 of synthetic aperture radar sar and landsat data a digital elevation model of hofsjokull which was constructed using sar interferometry was used to plot the sar backscatter coefficient vs elevation and air temperature along transects across the ice cap seasonal and daily patterns are caused by freezing or thawing of the ice cap surface and abrupt changes in are noted when the air temperature ranges from 5 to 0 c late summer 1997 sar and reflectance landsat boundaries agree and appear to be coincident with the firn line and a sar boundary that can be seen in the january 1998 sar image in january 1994 through 1998 the elevation of this boundary on the ice cap was quite stable ranging from 1000 to 1300 m while the equilibrium line altitude as measured on the ground varied considerably thus the equilibrium line may be obscured by firn from previous years techniques are established to measure long term changes in the elevation of the firn line and changes in the position of the ice margin

on the derivation of coseismic displacement fields using differential radar interferometry the landers earthquake we present a map of the coseismic displacement field resulting from the landers california june 28 1992 earthquake derived using data acquired from an orbiting high resolution radar system we achieve results more accurate than previous space studies and similar in accuracy to those obtained by conventional field survey techniques data from the ers 1 synthetic aperture radar instrument acquired in april july and august 1992 are used to generate a high resolution wide area map of the displacements the data represent the motion in the direction of the radar line of sight to centimeter level precision of each 30 m resolution element in a 113 km by 90 km image our coseismic displacement contour map gives a lobed pattern consistent with theoretical models of the displacement field from the earthquake fine structure observed as displacement tiling in regions several kilometers from the fault appears to be the result of local surface fracturing comparison of these data with global positioning system and electronic distance measurement survey data yield a correlation of 0 96 thus the radar measurements are a means to extend the point measurements acquired by traditional techniques to an area map format the technique we use is 1 more automatic 2 more precise and 3 better validated than previous similar applications of differential radar interferometry since we require only remotely sensed satellite data with no additional requirements for ancillary information the technique is well suited for global seismic monitoring and analysis

teleconnections from tropics to northern extratropics through a southerly conveyor rossby wave propagation theory predicts that rossby waves in a tropical easterly flow cannot escape from the tropics to the extratropics here the authors show that a southerly flow component in the basic state a southerly conveyor may transfer a rossby wave source northward thus a forcing embedded in the deep tropical easterlies may excite a rossby wave response in the extratropical westerlies it is shown that the southerly conveyor determines the location of the effective rossby wave source and that the extratropical response is relatively insensitive to the location of the tropical forcing provided that the tropical response can reach the southerly conveyor a stronger southerly flow favors a stronger extratropical response and the spatial structure of the extratropical response is determined by the extratropical westerly basic flows

interferometric estimation of three dimensional ice flow using ascending and descending passes satellite radar interferometry sri provides an important new tool for determining ice flow velocity interferometric measurements made from a single track direction are sensitive only to a single component of the three component velocity vector observations from along three different track directions would allow the full velocity vector to be determined a north south looking synthetic aperture radar sar could provide these observations over large portions of the globe but not over large areas of the polar ice sheets the authors develop and demonstrate a technique that allows the three component velocity vector to be estimated from data acquired along two track directions ascending and descending under a surface parallel flow assumption this technique requires that there are accurate estimates of the surface slope which are also determined interferometrically to demonstrate the technique the authors estimate the three component velocity field for the ryder glacier greenland their results are promising although they do not have yet ground truth data with which to determine the accuracy of their estimates

the integration of jers 1 and ers sar in differential interferometry for measurement of complex glacier motion complex glacier motion in the grove mountains region antarctica is measured using four pass differential synthetic aperture radar sar interferometry insar the components of the motion vector field are resolved using a 44 day separation japanese earth resources satellite 1 jers 1 insar pair and a european remote sensing satellite 1 2 ers 1 2 tandem insar pair the 44 day temporal baseline provides the sensitivity required to observe the range of ice motion around 8 10 m a 1 and the 1 day short baseline provides the best choice for glacier digital elevation model reconstruction it is remarkable that the scattering field of the jers 1 pair remained coherent over the long time interval and the interferometric fringes are clear the overall ice flow is from east to west downslope and towards lambert glacier the regional flow is obstructed by nunataks extending north south with two wide gaps two narrow glaciers flow past the nunataks and rejoin each other at the downstream end regional morphology and the resolved flow in the grove mountains area suggests that ice flow is channeled throughout this eastern flank of lambert glacier

vertical structure of wintertime teleconnection patterns abstract orthogonal rotated principal component analysis of the wintertime northern hemisphere 5 day mean sea level pressure field yielded five modes which are of some dynamical interest one can be identified with the well known north atlantic oscillation and another with the pacific north american pattern three of the other modes are highly baroclinic in the sense that their sea level pressure patterns and their associated 500 mb height patterns are different in shape and opposite in polarity over substantial areas these more baroclinic patterns attain their largest amplitudes in the vicinity of the himalayas and rockies their spatial patterns evolve very differently in the lower and middle troposphere the sea level pressure patterns exhibit a distinctive eastward and or equatorward phase propagation parallel to contours of surface elevation along the northern and or eastern side of the mountain ranges while the corresponding 500 mb patterns evolve in a manner consistent with the concept of ros

rock glacier dynamics in southern carpathian mountains from high resolution optical and multi temporal sar satellite imagery the dynamics of rock glaciers in marginal periglacial environments are poorly understood especially in eastern europe where the enhanced continentality produces a distinct pattern of periglacial phenomena multi temporal image analysis of high resolution optical and radar satellite imagery of the southern carpathian mountains romania revealed the small dynamic nature and a slow geomorphologic evolution of rock glaciers over a 46 yr period of record 1968 2014 nine rock glaciers located in glacial cirques and troughs within the central area of retezat mountain were included in this study overall the estimated displacement rates are extremely low i e a few cm year compared with other active rock glaciers from all over the world despite their relative attenuated activity it appears that judele valea rea and pietrele are still active rock glaciers but in an evident disequilibrium imbalance with the actual climate these findings document the lowest altitude and easternmost active rock glaciers at this latitude from europe quantitative investigations were concentrated on pietrele rock glacier subject of recent field campaigns optical data analysis indicated a slight acceleration of the horizontal velocities at the surface of pietrele rock glacier in recent years this acceleration appears to be caused by an increase in the temperature of permafrost resulting from an evident warming of external air temperature radar data analysis suggested seasonal variability of surface motion with higher deformation in autumn whereas in early summer or spring the deformation is negligible overall the results obtained with cross correlation analysis interferometric synthetic aperture radar insar coherence analysis and small baseline subset sbas multitemporal interferometry are consistent displaying similar deformation patterns with the highest creep rates located in the southern and western portions of the glacier these findings are supported by thermal and geophysical measurements which suggest the probable presence of permafrost within these areas the observed displacements were interpreted as permafrost creep and their very low velocity rates suggest the deforming frozen layers are very thin these results provide i baseline information and decadal scale trends and a ii strategy for future monitoring of the health and integrity of the rock glacier environment in the carpathian mountains

inconstant ancient seas and life s path seawater composition has changed over geological time geochemists now realize has biological evolution changed along with it a paper in this issue of science p 1222 suggests that oscillations in the chemical composition of the world ocean likely driven by the varying tempo of plate tectonics might have helped trigger a number of important evolutionary events

a new look at the midlatitude mjo teleconnection in the northern hemisphere winter the midlatitude to madden julian mjo teleconnection in the northern hemisphere wintertime was investigated using twenty years of outgoing long wave radiation and national center for atmospheric research national centers for environmental prediction re analysis data it is revealed through empirical orthogonal functions and regression analyses that the tropical upper level divergence convergence associated with enhanced reduced tropical convection has a subtropical counterpart of upper level convergence divergence as the convective region of mjo moves eastward from the indian ocean to the western pacific the divergent circulation connecting the tropics and subtropics moves eastward from an analysis of vertical motion diagnosed by the generalized omega equation it was revealed that the position of the subtropical rossby gyres of the mjo with respect to the asian pacific jet was the most important factor affecting the existence of the localized divergence convergence and associated lower level vertical motion in the subtropics as the subtropical rossby gyres pass by the longitudinal position of the asian pacific jet vertical motion occurs to meet the balance required by quasi geostrophic theory since this anomalous vertical motion is large enough to cause convection at that region the diabatic heating process reinforces the vertical motion furthermore other dynamical processes neglected in quasi geostrophic theory are activated and contribute to the vertical motion balancing the diabatic heating as a result of the vertical motion near the jet entrance region in the subtropics the vorticity advection by vertical wind and the tilting of vorticity become important since these two terms are similar in shape and magnitude they reinforce each other during the development phase of the midlatitude mjo teleconnection combining these two terms we define the baroclinic jet source bjs in order to evaluate the bjs as a source for the midlatitude mjo teleconnection a numerical experiment is carried out the linear barotropic model is forced by only two terms yet the model captured clearly the main feature of the midlatitude mjo teleconnection copyright 2006 royal meteorological society

piecewise tendency diagnosis of weather regime transitions abstract piecewise tendency diagnosis ptd is extended and employed to study the dynamics of weather regime transitions originally developed for adiabatic and inviscid quasigeostrophic flow on a beta plane ptd partitions local geopotential tendencies into a linear combination of dynamically meaningful source terms within a potential vorticity pv framework here ptd is amended to account for spherical geometry diabatic heating and ageostrophic processes and is then used to identify the primary mechanisms responsible for northern hemisphere weather regime transitions height tendency patterns obtained by summing the contributions of individual ptd forcing terms correspond very well to actual height tendencies composite ptd analyses reveal that linear pv advections provide the largest dynamical forcing for the weather regime development over the north pacific specifically linear baroclinic growth provides the primary forcing while barotropic deformation of pv anomalies provides a secondary contrib

repeat pass interferometry with airborne synthetic aperture radar it is shown that interference can be observed by coherently combining pairs of either x or c band airborne synthetic aperture radar sar images from separate passes over the same test site coherence between separate images is obtained only if the aircraft is flown and the data are processed in such a way that each resolution cell in the two images is viewed with very nearly the same geometry successful repeat pass interferometric results were obtained from those passes flown by the ccrs convair 580 aircraft with flight line offsets of less than a few tens of meters a summary of the experiment the phase correction of nonrectilinear aircraft motion and the subsequent data processing is provided

the north pacific oscillation west pacific teleconnection pattern mature phase structure and winter impacts abstract the north pacific oscillation npo in sea level pressure and its upper air geopotential height signature the west pacific wp teleconnection pattern constitute a prominent mode of winter midlatitude variability the npo wp its mature phase expression is identified from principal component analysis of monthly sea level pressure variability as the second leading mode just behind the pacific north american variability pattern npo wp variability primarily on subseasonal time scales is characterized by a large scale meridional dipole in slp and geopotential height over the pacific and is linked to meridional movements of the asian pacific jet and pacific storm track modulation the hemispheric height anomalies at upper levels resemble the climatological stationary wave pattern attributed to transient eddy forcing the npo wp divergent circulation is thermal wind restoring pointing to independent forcing of jet fluctuations intercomparison of sea level pressure geopotential height and zonal

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

energetics of the western hemisphere circulation pattern abstractthe western hemisphere wh circulation pattern identified by self organizing maps cluster analysis is a low frequency atmospheric regime that influences the fluctuations of large scale c

relationship between the tibetan plateau heating and east asian summer monsoon rainfall 1 this study reveals the close correspondence between the interannual variability of the dominant east asian summer rainfall pattern and the diabatic heating over the tibetan plateau in both spring and summer the heating fluctuation over the tibetan plateau is associated with two wave like circulation patterns which bear the characteristics of forced rossby wave emanating away from the deep heating the wave like pattern in turn affects the east asian summer rainfall because of the persistent heating over the tibetan plateau from spring to summer and its possible effect on the surrounding areas the heating index defined in this study can be used as a good predictor for the jja heating and precipitation distributions evidences shown suggest that external conditions other than the sst anomaly must be considered to understand the interannual variability of the east asian summer rainfall

glaciological advances made with interferometric synthetic aperture radar spaceborne interferometric synthetic aperture radar insar techniques for measuring ice flow velocity and topography have developed rapidly over the last decade and a half revolutionizing the study of ice dynamics spaceborne interferometry has contributed to major progress in many areas of glaciological study by providing the first comprehensive measurements of ice stream flow velocity over the major outlets of greenland and antarctica revealing that ice stream and outlet glacier flow can change rapidly months to years improving understanding of several ice sheet and ice shelf processes providing velocity for flux gate based mass balance assessment mapping flow of mountain glaciers and capturing the geomorphic traces of past ice flow we review the basic technique development the measurement characteristics and the extensive set of results yielded by these measurements

evolution of tethyan phosphogenesis along the northern edges of the arabian african shield during the cretaceous eocene as deduced from temporal variations of ca and nd isotopes and rates of p accumulation abstract the evolution of tethyan phosphogenesis during the cretaceous eocene is examined to try to explain fluctuations of phosphogenesis through time and whether or not they reflect long term changes in ocean circulation or in continental weathering twenty seven time stratigraphic phosphate levels in various tethyan sites covering a time span of about 90 myr from the hauterivian to the eocene were analyzed for 44 ca 42 ca and 143 nd 144 nd in their carbonate fluorapatite cfa fraction p and ca accumulation rates and bulk sedimentation rates were quantified throughout the cretaceous eocene negev sequence to examine how changes in 44 ca 42 ca and 143 nd 144 nd are reflected in the intensity of phosphogenesis a clear cut change occurs in e nd t and 44 ca and in the rates of p and ca accumulation and bulk sedimentation through the time analyzed e nd t is much lower in the hauterivian lower cenomanian 12 8 to 10 9 than in the upper cenomanian eocene 7 8 to 5 9 much lower 44 ca values occur in the hauterivian turonian 0 22 to 0 02 than in the coniacian eocene 0 23 to 0 40 p accumulation rates in the negev steeply increase from 2 k yr 1 in the albian coniacian to 1500 mol cm 2 k yr 1 in the campanian whereas a strong decrease is concomitantly recorded in the rates of ca accumulation and bulk sedimentation in addition distinct e nd t values are shown by the phosphorites of the negev 6 7 to 6 4 and egypt 9 1 to 7 6 during the campanian and by those of the negev 7 8 to 6 3 and north africa 10 1 to 8 9 during the maastrichtian eocene the culmination of p accumulation rates in the negev during the campanian occurring with a high in e nd t and 44 ca and a low in sedimentation rates indicates that paleoceanographic and paleogeographical factors mostly governed phosphorite accumulation in this area the abrupt e nd t rise after the cenomanian is attributed to increased incursion of pacific radiogenic water masses into the tethys driven by the late cretaceous global sea level rise the connection between north and south atlantic the global post santonian cooling and the progressive widening of the caribbean threshold all acting in combination to significantly intensify the tethyan circumglobal current tcc it also reflects a weakening of the continental nd signal due to a reduction of exposed landmasses caused by increased flooding of continental shelves high 44 ca values at those times also point to a decrease in weathering ca 2 fluxes and expansion of carbonate sedimentation in shelves both enriching seawater with isotopically heavy ca 2 deep ocean circulation intensified by the post santonian cooling of high latitudes increased p inventory in the tethys basin whereas the strengthened tcc and the folded shelf likely resulted in coastal and topographically induced upwelling supplying p rich intermediate waters to southeastern tethys shelves only in the paleocene eocene following major changes in global circulation produced by narrowing of tethys and widening of the atlantic did phosphogenesis shifts its locus of high intensity to the western atlantic tethys and west african atlantic coasts this change in paleocirculation is expressed by distinctly differing e nd t in the middle east and the north and west african phosphorites suggesting different oceanic p sources and current systems for these two major groups of phosphorites our nd isotope results further suggest a weaker tcc during the mid cretaceous becoming more intense in late cretaceous times they also point to the north pacific ocean as major source of deep water formation for the intermediate deep waters in the tethys basin during the late cretaceous

diabatic and orographic forcing of northern winter stationary waves and storm tracks abstract in this study a dry global circulation model is used to examine the contributions made by orographic and diabatic forcings in shaping the zonal asymmetries in the earth s northern hemisphere nh winter climate by design the model mean flow is forced to bear a close resemblance to the observed zonal mean and stationary waves the model also provides a decent simulation of the storm tracks in particular the maxima over the pacific and atlantic and minima over asia and north america are fairly well simulated the model also successfully simulates the observation that the atlantic storm track is stronger than the pacific storm track despite stronger baroclinicity over the pacific sensitivity experiments are performed by imposing and removing various parts of the total forcings in terms of the nh winter stationary waves in the upper troposphere results of this study are largely consistent with previous studies diabatic forcings explain most of the modeled stationary waves with orographic

origins of the 1988 north american drought the 1988 summer drought in the united states was the most extensive in many years because the drought developed in different places at different times not all regional effects can be traced to the same cause along the west coast and in the northwestern united states drought conditions developed during 1987 in association with the 1986 to 1987 el nino in the tropical pacific ocean record low rainfalls from april to june 1988 led to rapid development of drought in the north central united states strong anticyclonic conditions and a northward displaced jet stream in the upper atmosphere over north america throughout this period were only part of pronounced and distinctive wavetrain of anomalies in the atmospheric circulation that appeared to emanate from the tropical pacific below average sea surface temperatures along the equator in the pacific in the northern spring of 1988 combined with warmer than normal water from 10 degrees to 20 degrees n led to a northward displaced but still active intertropical convergence zone itcz southeast of hawaii results from a steady state planetarywave atmospheric model indicate that the atmospheric heating anomalies associated with the displaced itcz can force an anomalous wavetrain across north america similar to that observed land surface processes probably contributed to the severity and persistence of the drought however the large scale atmospheric circulation perturbations associated with natural variations in the coupled atmosphere ocean system in the tropical pacific were most likely the primary cause

the arctic oscillation signature in the wintertime geopotential height and temperature fields the leading empirical orthogonal function of the wintertime sea level pressure field is more strongly coupled to surface air temperature fluctuations over the eurasian continent than the north atlantic oscillation nao it resembles the nao in many respects but its primary center of action covers more of the arctic giving it a more zonally symmetric appearance coupled to strong fluctuations at the 50 hpa level on the intraseasonal interannual and interdecadal time scales this arctic oscillation ao can be interpreted as the surface signature of modulations in the strength of the polar vortex aloft it is proposed that the zonally asymmetric surface air temperature and mid tropospheric circulation anomalies observed in association with the ao may be secondary baroclinic features induced by the land sea contrasts the same modal structure is mirrored in the pronounced trends in winter and springtime surface air temperature sea level pressure and 50 hpa height over the past 30 years parts of eurasia have warmed by as much as several k sea level pressure over parts of the arctic has fallen by 4 hpa and the core of the lower stratospheric polar vortex has cooled by several k these trends can be interpreted as the development of a systematic bias in one of the atmosphere s dominant naturally occurring modes of variability

horizontal structure and energetics of northern hemisphere wintertime teleconnection patterns abstract the horizontal structure and dynamical properties of the teleconnection patterns in the interannual variability of the northern hemisphere wintertime 500 mb height field are investigated regression maps based on indices for the eastern atlantic ea pacific north american pna western atlantic wa western pacific wp and eurasian eu patterns defined by wallace and gutzler are used to define the geographically fixed patterns space spectrum analysis including a spherical harmonic decomposition is applied to these maps anomalous geostrophic wind fields derived from these regression maps are used to estimate the kinetic energy conversion between the climatological mean state and the wave structures associated with the teleconnection patterns the teleconnection patterns comprise seesaw and or wavelike structures in general the kinetic energy of the teleconnection patterns is concentrated in total wavenumber n 5 and 6 components with zonal wavenumbers m 0 1 and 2 which correspond

enso regulation of mjo teleconnection the extratropical teleconnections associated with madden julian oscillation mjo are shown to have an action center in the north pacific where the pressure anomalies have opposite polarities between the phase 3 convective indian ocean and phase 7 convective western pacific of the mjo the teleconnection in the same phase of mjo may induce opposite anomalies over east asia and north america between el nino and la nina years during mjo phase 3 a gigantic north pacific anticyclonic anomaly occurs during la nina making coastal northeast asia warmer wetter than normal but the west us colder drier whereas during el nino the anticyclonic anomaly is confined to the central north pacific hence the northwest us experiences warmer than normal weather under influence of a downstream cyclonic anomaly during phase 7 an extratropical cyclonic anomaly forms over the northwest pacific during la nina due to convective enhancement over the philippine sea causing bitter winter monsoon over japan whereas during el nino the corresponding cyclonic anomaly shifts to the northeast pacific due to enhanced convection over the equatorial central pacific which causes warm and wet conditions along the west coast of us and canada further the presence of enso induced seasonal anomalies can significantly modify mjo teleconnection but the aforementioned mjo teleconnection can still be well identified during phase 3 the mjo teleconnection pattern over north pacific will be counterbalanced enhanced by el nino la nina induced seasonal mean anomalies during phase 7 on the other hand the mjo teleconnection anomalies in the northeastern pacific will be enhanced during el nino but reduced during la nina thereby the impacts of mjo teleconnection on the north america is expected to be stronger during el nino than during la nina

intraseasonal teleconnection between the summer eurasian wave train and the indian monsoon this study investigated the most recurrent coupled pattern of intraseasonal variability between midlatitude circulation and the indian summer monsoon ism the leading singular vector decomposition svd pattern reveals a significant coupled intraseasonal variation between a rossby wave train across the eurasian continent and the summer monsoon convection in northwestern india and pakistan hereafter referred to as nism the wave train associated with an active phase of nism rainfall displays two high pressure anomalies one located over central asia and the other over northeastern asia they are accompanied by increased rainfall over the western siberia plain and northern china and decreased rainfall over the eastern mediterranean sea and southern japan the circulation of the wave train shows a barotropic structure everywhere except the anomalous central asian high located to the northwest of india where a heat induced baroclinic circulation structure dominates the time lagged svd analysis shows that the midlatitude wave train originates from the northeastern atlantic and traverses europe to central asia the wave train enhances the upper level high pressure and reinforces the convection over the nism region meanwhile it propagates farther toward east asia along the waveguide provided by the westerly jet after an outbreak of nism convection the anomalous central asian high retreats westward composite analysis suggests a coupling between the central asian high and the convective fluctuation in the nism the significance of the midlatitude ism interaction is also revealed by the close resemblance between the individual empirical orthogonal functions and the coupled svd modes of the midlatitude circulation and the ism it is hypothesized that the eastward and southward propagation of the wave train originating from the northeastern atlantic contributes to the intraseasonal variability in the nism by changing the intensity of the monsoonal easterly vertical shear and its associated moist dynamic instability on the other hand the rainfall variations over the nism reinforce the variations of the central asian high through the monsoon desert mechanism thus reenergizing the downstream propagation of the wave train the coupling between the eurasian wave train and nism may be instrumental for understanding their interaction and can provide a way to predict the intraseasonal variations of the indian summer monsoon and east asian summer monsoon

the continuum of north pacific sea level pressure patterns intraseasonal interannual and interdecadal variability this study combines k means cluster analysis with linear unidimensional scaling to illustrate the spatial and temporal variability of the wintertime north pacific sea level pressure slp field daily wintertime slp data derived from the ncep ncar reanalysis are used to produce 16 slp anomaly patterns that represent a discretized approximation of the continuum of north pacific slp patterns this study adopts the continuum perspective for teleconnection patterns which provides a much simpler framework for understanding north pacific variability than the more commonly used discrete modal approach the primary focus of this research is to show that variability in the north pacific on intraseasonal interannual and interdecadal time scales can be understood in terms of changes in the frequency distribution of the cluster patterns that compose the continuum each of which has a time scale of about 10 days this analysis reveals 5 6 pacific north american like pna like patterns for each phase as well as dipoles and wave trains a self organizing map som analysis of coupled slp and outgoing longwave radiation data shows that many of these patterns are associated with convection in the tropical indo pacific region on intraseasonal time scales the frequency distribution of these patterns in particular the pna like patterns is

the late fall extratropical response to enso sensitivity to coupling and convection in the tropical west pacific abstract the extratropical response to el nino in late fall departs considerably from the canonical el nino signal observational analysis suggests that this response is modulated by anomalous forcing in the tropical west pacific twp so that a strong fall el nino teleconnection is more likely when warm sst conditions and or enhanced convection prevail in the twp while these twp sst anomalies may arise from noise and or long term variability they may also be generated by differences between el nino events through variations in the tropical atmospheric bridge this bridge typically drives subsidence west of the date line and enhanced trade winds over the far twp which cool the ocean in late fall however some relatively weaker and or more eastward shifted el nino events produce a correspondingly weakened and displaced tropical bridge which results in no surface cooling and enhanced convection in the twp because the north pacific circulation is very sensitive to forcing from the twp at this time

the geometry and petrogenesis of dolomite hydrocarbon reservoirs the wide distribution of dolomite rocks in north american middle and far eastern hydrocarbon reservoirs is reason enough for their intensive study in this volume dolomite enthusiasts review progress and define the current boundaries of dolomite research related particularly to the importance of these rocks as reservoirs as might be expected reviews provide critical analyses of past ideas on origins and why many are no longer tenable discussions range between conceptual models and numerical simulations of the flow paths of dolomitizing fluids geochemical modelling and microbial mediation case studies from areas as diverse as north america the middle east se asia and australia provide a solid background but illustrate important differences in views on the origins of these enigmatic rocks

discovering anomalous dynamics and disintegrating behaviour in glaciers of chandra bhaga sub basins part of western himalaya using dinsar abstract glacier velocity is one of the important parameters to know about glacier dynamics its mass and health understanding glacier velocity also assists in the analysis of ice thickness ice flux and mass balance furthermore basin sub basin wise studies are helpful to understand the climate change over that region instead of monitoring individual glaciers in the current study the spatial distribution of glacier velocity is generated for the entire chandra and bhaga sub basins in the lahaul spiti district of himachal pradesh india using advanced land observing satellite 2 phased array type l band synthetic aperture radar 2 alos 2 palsar 2 differential interferometry pair images with a 14 days temporal gap the glaciers in chandra sub basin are found to have a high flow rate as compared to the glaciers in bhaga sub basin local slope and ice thickness which decrease towards the terminus in general control the movement of valley glaciers and lower movement rate is observed for most of glaciers towards the terminus frontal area however a few glaciers of bhaga sub basin demonstrate an accelerated movement in their frontal areas this irregular behaviour is also studied in this work and it is discovered that terrain slope and influx of melting water from adjacent glaciers are the major causes for such behaviour of these glaciers they are therefore prone to accelerated mass loss compared to other glaciers in the sub basin another key finding of the anomalous glacier dynamics study is the disintegrating behaviour of glaciers which is also identified by interpreting the responses of physical scattering mechanisms retrieved from glaciers using fully polarimetric alos 2 palsar 2 warming temperatures are expected to cause glacier retreat and separation of tributary glaciers from the main glacier body melt water from tributary glaciers can further accelerate glacier flow and ice melt in lower part of glacier trunk this can lead to formation of dead ice zones and disintegration of himalayan glaciers which are supported by numerous tributary glaciers therefore we expect that the loss in glacier area due to warming will be larger than the present prediction where mass loss is considered from conventional way