the response of the southwest western australian wave climate to indian ocean climate variability knowledge of regional wave climates is critical for coastal planning management and protection in order to develop a regional wave climate it is important to understand the atmospheric systems responsible for wave generation this study examines the variability of the southwest western australian swwa shelf and nearshore wind wave climate and its relationship to southern hemisphere climate variability represented by various atmospheric indices the southern oscillation index soi the southern annular mode sam the indian ocean dipole mode index dmi the indian ocean subtropical dipole iosd the latitudinal position of the subtropical high pressure ridge strp and the corresponding intensity of the subtropical ridge stri a 21 year wave hindcast 1994 2014 of the swwa continental shelf was created using the third generation wave model simulating waves nearshore swan to analyse the seasonal and inter annual wave climate variability and its relationship to the atmospheric regime strong relationships between wave heights and the strp and the stri a moderate correlation between the wave climate and the sam and no significant correlation between soi dmi and iosd and the wave climate were found strong spatial seasonal and inter annual variability as well as seasonal longer term trends in the mean wave climate were studied and linked to the latitudinal changes in the subtropical high pressure ridge and the southern ocean storm belt as the southern ocean storm belt and the subtropical high pressure ridge shifted southward northward wave heights on the swwa shelf region decreased increased the wave height anomalies appear to be driven by the same atmospheric conditions that influence rainfall variability in swwa

the resolving power of cross borehole tomography the data collected in a cross borehole tomography problem is inherently incomplete since the boreholes do not completely surround the media under study the ability of the experiment to resolve structure is therefore limited by poor experimental geometry we use the method of backus and gilbert to investigate the ability of this technique to resolve variations in acoustic velocity and attenuation between the two boreholes both integrals that appear in the backus gilbert formulation can be performed analytically thus expediting the calculations the resolving kernels have significant horizontal width demonstrating that the horizontal position of structures can be only poorly resolved

global climatic anomalies associated with extremes in the southern oscillation abstract composite temperature and precipitation anomalies during various stages of an event in the southern oscillation so have been computed for several hundred stations across the globe large regions of coherent significant signals are shown to exist for both extremes of the so with warm event signals generally opposite to those during cold events in addition during the year preceding the development of an event in the so year 1 climatic anomalies tend to be opposite to those during the following year year 0 this confirms that the biennial tendency of the so over the pacific indian ocean sectors is also present in more remote regions with climatic signals related to the so many of the signals are consistent enough from event to event to be useful for extended range forecasting purposes

reconstruction of seasonal and water year precipitation anomalies from tree ring records of the southwestern united states abstract the annual cycle of precipitation in the southwestern united states is characterized by a bimodal distribution el nino southern oscillation enso episodes influence cool season precipitation while the north american monsoon nam brings warm season rainfall to the region because the covariability of the two seasons may result in both wet and dry water year anomalies we evaluated the long term contribution of cool and warm season precipitation to water year totals using newly collected and or updated tree ring chronologies precipitation reconstructions back to the late 17th century from 1663 to 2015 were produced using a total of 183 stem increment cores collected from seven ponderosa pine pinus ponderosa stands located along the southern edge of the colorado plateau in arizona and new mexico latewood chronologies were most correlated with july august rainfall brought by the north american monsoon while earlywood chronologies were related to november february precipitation also matching the time series variability of the southern oscillation index total ring width chronologies reflected water year precipitation and were used to account for precipitation falling outside of either the cool or the warm season while seasonal variability of precipitation was the main driver of regional climatic extremes the amount of precipitation falling outside the cool and warm seasons did not play a consistent role in determining frequency and severity of droughts and pluvials this study highlights how intra annual paleoclimatic reconstructions help with understanding the contribution of seasonal climate to wet and dry episodes influenced by large scale climatic modes

oceanic and atmospheric transport of multiyear el nino southern oscillation enso signatures to the polar regions 1 using monte carlo singular spectrum analysis mc ssa and wavelet transform wt we separate statistically significant components from time series and demonstrate significant co variance and consistent phase differences between ice conditions and the arctic oscillation and southern oscillation indices ao and soi at 2 2 3 5 5 7 and 13 9 year periods the 2 2 3 5 and 5 7 year signals detected in the arctic are generated about three months earlier in the tropical pacific ocean in contrast we show that the 13 9 year signal propagates eastward from the western pacificasequatorialcoupledwaves ecw 0 13 0 15ms 1 and then as fast boundary waves 1 3 ms 1 along the western margins of the americas with a phase difference of about 1 8 2 1 years by the time they reach the arctic our results provide evidence of dynamical connections between high latitude surface conditions tropical ocean sea surface temperatures mediated by tropical wave propagation the wintertime polar vortex and the ao index terms 1620 global change climate dynamics 3309 3309 meteorology and atmospheric dynamics climatology 1620 0312 atmospheric composition andstructure air seaconstituent fluxes 3339 4504 4504 oceanography physical air sea interactions 0312 4522 oceanography physical el nino citation jevrejeva s j c moore and a grinsted 2004 oceanic and atmospheric transport

anomalous north pacific atmospheric circulation and large winter floods in the southwestern united states abstract specific anomalous atmospheric circulation conditions over the north pacific are conducive to the occurrence of the largest winter floods 10 yr return period on rivers in six hydroclimatic subregions of arizona and southern utah nevada and california composite maps of anomalies in daily 700 mb heights indicate that floods in all of the subregions are associated with a low pressure anomaly off the california coast and a high pressure anomaly in the vicinity of either alaska or the aleutian islands of these two major circulation features the presence of the low is the controlling factor in determining whether large floods will occur shifts in the locations of the low and high pressure anomalies over the north pacific appear to control which subregions experience floods with high elevation topographic features and proximity to air masses forming a major influence over the specific atmospheric circulation conditions that generate large floods in each hydroclimatic region concerning the int

zonal asymmetry of the antarctic oscillation 1 in this research the zonal asymmetry of the southern annular mode or the antarctic oscillation aao is studied it is indicated that apparent zonal asymmetry exists in the normalized sea level pressure differences between the middle and high latitudes during the boreal summer among different longitudes especially between the western and eastern hemispheres results show that the southern oscillation so is responsible for part of the zonal asymmetry in aao the western hemisphere and the eastern hemisphere parts of aao are correlated at 0 23 and 0 52 respectively for the period of 1959 1998 before and after the linear regressions on the southern oscillation index soi have been removed from the time series the paper also discusses the relationship between the precipitation in the east asia and the aao before and after removing the linear regressions on so index soi indicating the stable relationship between the east asian precipitation and the zonal symmetric component of aao

southern oscillation extremes reconstructed from tree rings of the sierra madre occidental and southern great plains abstract the el ninio southern oscillation enso is correlated with climate and tree growth over northern mexico and the southern great plains of the usa warm events favor moist cool conditions from october through march event years 0 and 1 and subsequent tree growth year 1 in the region tends to be above average the opposite climate and tree growth conditions prevail with less consistency during cold events enso sensitive tree ring chronologies from this region were selected to develop two reconstructions of the southern oscillation index soi back to 1699 for the first reconstruction a multiple regression based calibration equation between prewhitened and regionally averaged tree ring data from mexico and oklahoma and a prewhitened winter djf so index during the period 1900 71 were used to estimate the winter soi for each year from 1699 to 1971 the tree ring predictors account for 41 of the winter soi variance from 1900 to 1971 and the reconstructed so indices are significantly correl

removal of the detector ground coupling effect in the vertical seismic profiling environment in a controlled experiment with the gulf vsp tool the detector ground coupling was measured and removed from the recorded signal using the washburn wiley algorithm repeat measurements were made at a common detector depth with two coupling configurations the first to permit the true ground motion to be recorded and the second to ensure that a coupling resonance existed within the seismic frequency band the algorithm removed the distortion of the body wave portion of the seismogram caused by the coupling resonance for the second configuration and recovered true ground motion however lowering the coupling resonance into the seismic band also caused the tool to become sensitive to tube waves this observation is helpful in evaluating current vsp tools it implies that any vsp tool that is sensitive to tube waves has a coupling resonance within the seismic frequency band and that the signal recorded with such a tool does not measure true ground motion this test also showed that a detector used to mon

a doubling in snow accumulation in the western antarctic peninsula since 1850 1 we present results from a new medium depth 136 metres ice core drilled in a high accumulation site 73 59 s 70 36 w on the south western antarctic peninsula during 2007 the gomez record reveals a doubling of accumulation since the 1850s from a decadal average of 0 49 mweq y 1 in 1855 1864 to 1 10 mweq y 1 in 1997 2006 with acceleration in recent decades comparison with published accumulation records indicates that this rapid increase is the largest observed across the region evaluation of the relationships between gomez accumulation and the primary modes of atmospheric circulation variability reveals a strong temporally stable and positive relationship with the southern annular mode sam furthermore the sam is demonstrated to be a primary factor in governing decadal variability of accumulation at the core site r 0 66 the association between gomez accumulation and enso is complex while sometimes statistically significant the relationship is not temporally stable thus at decadal scales we can utilise the gomez accumulation as a suitable proxy for sam variability but not for enso

the antarctic circumpolar wave its presence and interdecadal changes during the last 142 years abstractthe southern ocean so is the region of the world ocean bordering on antarctica over which significant exchanges between the atmosphere the ocean and the sea ice take place here the strong and nearly unhindered eastward flow of the antarctic circumpolar current plays an important role in mean global climate as it transmits climate anomalies around the hemisphere features of interannual variability have been observed to propagate eastward around the so with the circumpolar flow in the form of a system of coupled anomalies known as the antarctic circumpolar wave acw in the present study the 142 yr series of the twentieth century reanalysis version 2 dataset 850 hpa geopotential height sea level pressure sea surface temperature surface meridional wind and surface air temperature spanning from 1871 to 2012 is used to investigate the presence and variability of acws this examination shows for the first time the presence of the acw before the mid 1950s and interdecadal changes in i

oscillatory climate modes in the eastern mediterranean and their synchronization with the north atlantic oscillation abstract oscillatory climatic modes over the north atlantic ethiopian plateau and eastern mediterranean were examined in instrumental and proxy records from these regions aside from the well known north atlantic oscillation nao index and the nile river water level records the authors study for the first time an instrumental rainfall record from jerusalem and a tree ring record from the golan heights the teleconnections between the regions were studied in terms of synchronization of chaotic oscillators standard methods for studying synchronization among such oscillators are modified by combining them with advanced spectral methods including singular spectrum analysis the resulting cross spectral analysis quantifies the strength of the coupling together with the degree of synchronization a prominent oscillatory mode with a 7 8 yr period is present in all the climatic indices studied here and is completely synchronized with the north atlantic oscillation an energy analysis of the synchronization

changes in el nino southern oscillation enso conditions during the greenland stadial 1 gs 1 chronozone revealed by new zealand tree rings the warming trend at the end of the last glacial was disrupted by rapid cooling clearly identified in greenland greenland stadial 1 or gs 1 and europe younger dryas stadial or yd this reversal to glacial like conditions is one of the best known examples of abrupt change but the exact timing and global spatial extent remain uncertain whilst the wider atlantic region has a network of high resolution proxy records spanning gs 1 the pacific ocean suffers from a scarcity of sub decadally resolved sequences here we report the results from an investigation into a tree ring chronology from northern new zealand aimed at addressing the paucity of data the conifer tree species kauri agathis australis is known from contemporary studies to be sensitive to regional climate changes an analysis of a historic 452 year kauri chronology confirms a tropical pacific teleconnection via the el nino southern oscillation enso we then focus our study on a 1010 year sub fossil kauri chronology that has been precisely dated by comprehensive radiocarbon dating and contains a striking ring width downturn between 12 500 and 12 380 cal bp within gs 1 wavelet analysis shows a marked increase in enso like periodicities occurring after the downturn event comparison to low and mid latitude pacific records suggests a coherency with enso and southern hemisphere atmospheric circulation change during this period the driver s for this climate event remain unclear but may be related to solar changes that subsequently led to establishment and or increased expression of enso across the mid latitudes of the pacific seemingly independent of the atlantic and polar regions

the modal evolution of the southern oscillation abstract the implementation of a progressive fourier transform applied to time series representative of the el nino southern oscillation enso provides a visual review of the frequency modes that have dominated throughout the available time series record the modal evolution maps constructed from the progressive fourier transform demonstrate that the enso is largely composed of a discrete number of low frequency modes and that these dominant modes demonstrate a localized influence in a temporal sense persisting for periods of years before showing deviations in characteristic frequency in support of other research significant energy is maintained in the quasi biennial and quasi quadrennial period modes throughout the length of available southern oscillation index soi record evident through the most recent record of both the soi and nino region sea surface temperature sst time series is the emergence of energy in the quasi decadal period modes the presence of a quasi decadal mode has also bee

reconstructing el nino southern oscillation using data from ships logbooks 1815 1854 part i methodology and evaluation the meteorological information found within ships logbooks is a unique and fascinating source of data for historical climatology this study uses wind observations from logbooks covering the period 1815 to 1854 to reconstruct an index of el nino southern oscillation enso for boreal winter djf statistically based reconstructions of the southern oscillation index soi are obtained using two methods principal component regression pcr and composite plus scale cps calibration and validation are carried out over the modern period 1979 2014 assessing the relationship between re gridded seasonal era interim reanalysis wind data and the instrumental soi the reconstruction skill of both the pcr and cps methods is found to be high with reduction of error skill scores of 0 80 and 0 75 respectively the relationships derived during the fitting period are then applied to the logbook wind data to reconstruct the historical soi we develop a new method to assess the sensitivity of the reconstructions to using a limited number of observations per season and find that the cps method performs better than pcr with a limited number of observations a difference in the distribution of wind force terms used by british and dutch ships is found and its impact on the reconstruction assessed the logbook reconstructions agree well with a previous soi reconstructed from jakarta rain day counts 1830 1850 adding robustness to our reconstructions comparisons to additional documentary and proxy data sources are provided in a companion paper

evidences linking enso and coral growth in the southwestern south atlantic physical and biological changes in the marine environment induced by oceanic atmospheric processes can be imprinted in massive coral skeletons herein we present an evidence of potential el nino impacts at the southwestern south atlantic ocean swsa inferred from the sclerochronology of the reef coral favia leptophylla the application of spectral analysis wavelet decomposition and the iterative regression to coral growth length and to meteorological oceanographic parameters air temperature sea surface temperature and precipitation as well as to southern oscillation index soi and solar irradiation indicated a major significant inverse relationship between soi and coral growth length at the 4 8 years frequency band we propose here that coral growth length from the swsa could be affected by el nino southern oscillation enso events through an atmospheric bridge in contrast to its direct effect at the pacific ocean related to the increase in sea surface temperature

the changing relationship between enso variability and moisture balance in the continental united states the el nino southern oscillation enso system orchestrates a well documented suite of climate anomalies worldwide the details of enso s extratropical influence vary among events but this variability has not been described or diagnosed beyond the past few decades and previous descriptions have looked at inter event differences rather than decadal patterns we use a new tree ring based drought reconstruction for the continental u s and instrumental enso indices to document systematic decadal changes in the u s drought enso relationship since the late 19th century significant enso drought correlation occurs consistently in the southwest u s but the strength of penetration of moisture anomalies into the continent varies substantially the most striking change over the past 130 years is the initiation of a bipolar enso drought signature around 1920 producing opposite sign moisture anomalies in the southwest and mid atlantic states shifts in teleconnection patterns coincide with variations in the strength of enso and in a north pacific mode

the moon and el nino regional climates around the world display cycles corresponding to the 18 61 year maximum lunar declination mld periodicity we suggest that these cycles are created by a relationship between mld and el nino southern oscillation enso both equatorial pacific sea surface temperature and south pacific atmospheric pressure significantly correlate with maximum lunar declination low mlds are associated with warmer equatorial pacific sea surface temperatures and negative values of the southern oscillation index a lunar influenced change in the pacific gyre circulation presents a viable physical mechanism for explaining these relationships we suggest that the gyre is enhanced by tidal forces under high mlds inducing cold water advection into the equatorial region but is restricted by the weak tidal forcing of low mlds thereby favoring el nino episodes an astronomical model utilizing this relationship produces a forecast of increased non el nino either la nina or neutral activity for the early part of this decade

a parametric study of borehole influence in resolving seismic velocity in well to well tomograms the data collected in a well to well tomography experiment is inherently incomplete even when augmented by vsp data the nature of the experiment suggests a geometric limitation to the resolution of any central structure a parametric model has now been developed which examines the effect on reconstructed velocity due to the borehole size transducer standoff altered annulus and the degree of velocity attenuation of the altered annulus using a range of host velocities and hole separations it was found that there are significant velocity variations caused by perturbations in borehole size these errors are particularly significant for boreholes with large diameters and small transducer offsets for an altered annulus errors in both the dimensions and the degree of velocity alteration gave significant velocity variation in reconstructed velocity particularly with large boreholes in all cases it is observed that the variation and alteration in reconstructed velocities increased as hole separation is decreased

discontinuous ephemeral streams abstract many ephemeral streams in western north america flowed over smooth valley floors before transformation from shallow discontinuous channels into deep arroyos these inherently unstable streams of semiarid regions are sensitive to short term climatic changes and to human impacts because hillslopes supply abundant sediment to infrequent large streamflow events discontinuous ephemeral streams appear to be constantly changing as they alternate between two primary modes of operation either aggradation or degradation may become dominant attainment of equilibrium conditions is brief disequilibrium is promoted by channel entrenchment that causes the fall of local base level and by deposition of channel fans that causes the rise of local base level these opposing base level processes in adjacent reaches are maintained by self enhancing feedback mechanisms the threshold between erosion and deposition is crossed when aggradational or degradational reaches shift upstream or downstream extension of entrenched reaches into channel fans tends to create continuous arroyos upvalley migration of fan apexes tends to create depositional valley floors with few stream channels less than 100 years is required for arroyo cutting but more than 500 years is required for complete aggradation of entrenched stream channels and valley floors discontinuous ephemeral streams have a repetitive sequence of streamflow characteristics that is as distinctive as sequences of meander bends or braided gravel bars in perennial rivers the sequence changes from degradation to aggradation headcuts concentrate sheetflow a single trunk channel conveys flow to the apex of a channel fan braided distributary channels end in an area of diverging sheetflow and converging sheetflow drains to headcuts the sequence is repeated at intervals ranging from 15 m for small streams to more than 10 km for large streams lithologic controls on the response of discontinuous ephemeral streams include 1 amount and size of sediment yielded from hillslopes 2 infiltration capacity of valley floor alluvium that influences both the unit stream power available for upstream headcut migration and the attenuation of flashy streamflow events by riparian vegetation in sheetflow reaches and 3 cohesiveness of alluvium which affects headcut and streambank morphology and rates of arroyo extension downcutting and widening initiation of arroyo cutting may be too complex to be attributed to a single cause such as change in mean annual precipitation or grazing by livestock but is most likely associated with a decrease in density of protective plant cover on hillsides and along valley floors relatively larger unit stream power makes downstream reaches more susceptible to initial entrenchment during floods than headwaters reaches and favors persistent arroyos entrenchment continues until an equilibrium longitudinal profile is briefly attained then channel widening occurs streambanks are undercut and aggradation begins

basin wavelength equatorial deep jet signals across three oceans equatorial deep jets edjs are equatorially trapped stacked zonal currents that reverse direction every few hundred meters in depth throughout much of the water column this study evaluates their structure observationally in all three oceans using new high vertical resolution argo float conductivity temperature depth ctd instrument profiles from 2010 to 2014 augmented with historical shipboard ctd data from 1972 to 2014 and lower vertical resolution argo float profiles from 2007 to 2014 the vertical strain of density is calculated from the profiles and analyzed in a stretched vertical coordinate system determined from the mean vertical density structure the power spectra of vertical strain in each basin are analyzed using wavelet decomposition in the indian and pacific oceans there are two distinct peaks in the power spectra one kelvin wave like and the other entirely consistent with the dispersion relation of a linear first meridional mode equatorial rossby wave in the atlantic ocean the first meridional mode rossby wave signature is very strong and dominates in all three ocean basins rossby wave like signatures are coherent across the basin width and appear to have wavelengths the scale of the basin width with periods of about 5 yr in the indian and atlantic oceans and about 12 yr in the pacific ocean their observed meridional scales are about 1 5 times the linear theoretical values their phase propagation is downward with time implying upward energy propagation if linear wave dynamics hold

applications of algebraic reconstruction techniques to crosshole seismic data tomographic imaging techniques were applied to two crosshole data sets to determine the velocity structures and the reliability and resolution of the algorithms on real data the experiments were carried out at the retsoff salt mine in new york and at the underground radioactive waste study site at the stripa mine facility in sweden the traveltimes at restoff were high quality and were obtained over raypaths of up to 500 m in length the structure was quite complicated with velocity contrasts up to 50 percent the stripa site was in granitic rock with velocity contrasts of only a few percent the dimensions of the experiment were small with maximum ray lengths of just over 10 m the data at this site were collected with very high accuracy source and receiver locations were measured to better than 1 0 mm and traveltimes were read to 0 001 ms a number of algorithms similar to the algebraic reconstruction techniques art used in medical imaging have been applied to the data some modifications of the algorithms such as the application of weighting schemes damping parameters and curved raypaths were performed the resulting velocity fields were compared to the known fields and with each other to determine an optimal method the algorithms were found to be a rapid reliable means of reconstructing the slowness field of real data low velocity zones were recovered with accuracy in location and value it was also found that great care was necessary in application of the techniques to ensure that proper damping parameters are used and the proper number of iterations taken otherwise poor reconstructions will result

reconstruction of monthly sst in the tropical pacific ocean during 1868 1993using adaptive climate basis functions abstract an eof based reconstruction of monthly sst anomaly fields is calculated for the years 1868 1993 in the tropical pacific ocean the eofs are computed from optimally interpolated sst anomaly fields from november 1981 to october 1995 from the same region these are used as a functional basis set for projecting sst anomalies from the comprehensive ocean atmosphere data set coads to produce a smooth spatially complete reconstruction the optimal number of eof modes for each month s reconstruction is chosen using large scale error analysis a modern subset of the coads sst is subsampled according to the distribution of observations in the historical month being reconstructed forming a testbed on which to evaluate the reconstruction based on a variable number of modes the test bed is least squares fit to the basis eofs the difference fields between the reconstruction and a smoothed version of the test bed is found the total variance of difference fields residual is minimized with respect to the

antarctic sea ice relationships with indices of the atmospheric circulation of the southern hemisphere a link between the antarctic sea ice extent and low frequency atmospheric variations particularly enso has been suggested by recent modeling and empirical studies this question is examined here using a high resolution by week by region data base of antarctic sea ice extent for the 1973 1982 period although of relatively short duration by northern hemisphere standards such a data base offers an opportunity rare in southern hemisphere climate studies the seaice variations are examined in the context of longer term indices of the large scale atmospheric circulation these are a southern oscillation index soi and an index of sea level pressure slp wavenumber one in the southern hemisphere extratropics the indices are updated through 1982 and their associations with regional scale pressure indices in the australia new zealand sector are also examined the 1973 1982 period is anomalous when compared with the period 1951 1972 correlation analysis of the monthly sea ice and circulation index values reveals that much of the apparent link between the ice and the soi suggested in previous studies arises from autocorrelations present in both data sets and the strong annual cycle of sea ice extent removing these effects from the data and re running the correlations reveals that most of the resulting significant associations between the ice and one or other of the circulation indices can probably be explained on the basis of chance in order to reconcile these findings with previous studies that show some strong ice circulation interactions on regional scales only those months in which significant correlations occur between both largescale circulation indices and the sea ice are examined further these occur preferentially in the ross and weddell sectors which constitute the regions contributing most to the variability of antarctic sea ice the analysis suggests that the sea ice extent changes lag the soi by several months but may precede changes in extratropical slp wavenumber one confirmation of these tentative regional ice extent circulation teleconnections necessarily awaits the forward extension of the high resolution sea ice data base beyond the 10 years available here

surface temperature patterns associated with the southern oscillation abstract the typical global and large scale regional temperature patterns associated with the low warm and high cold phases of the southern oscillation so are investigated a total of 12 separate regions were found to have consistent temperature patterns associated with low phase of the so while 11 areas were found to have temperature patterns associated with the high phase of these areas 9 have expected temperature patterns during both phases of the so in the tropics temperature anomalies are of the same sign as the so related sea surface temperature sst anomaly in all land regions except for one area in the west pacific three extratropical responses to the low phase of the so are found over north america and one is found in japan high so temperature patterns were found in the extratropies for japan western europe and northwestern north america the identified temperature responses are more consistent in tropical regions than in the extratropies the so can influence the estimation of

influence of the arctic oscillation and el nino southern oscillation enso on ice conditions in the baltic sea the wavelet approach 1 variability in time series of ice conditions in the baltic sea is examined within the context of atmospheric circulation represented by the north atlantic oscillation nao and arctic oscillation ao winter indices using the wavelet approach we develop methods of assessing statistical significance and confidence intervals of cross wavelet phase and wavelet coherence cross wavelet power for the time series indicates that the times of largest variance in ice conditions are in excellent agreement with significant power in the ao at 2 2 3 5 5 7 7 8 and 12 20 year periods similar patterns are also seen with the southern oscillation index soi and nino3 sea surface temperature nino3 series wavelet coherence shows in phase linkages between the 2 2 7 8 and 12 20 year period signals in both tropical and arctic atmospheric circulation and also with ice conditions in the baltic sea these results are consistent with gcm simulations showing dynamical connections between high latitude surface conditions tropical sea surface temperatures mediated by tropical wave propagation the wintertime polar vortex and the ao and with models of sea ice and oceanic feedbacks at decadal periods

accumulation variability in the antarctic peninsula the role of large scale atmospheric oscillations and their interactions abstracta new ice core drilled in 2010 to bedrock from the bruce plateau bp on the antarctic peninsula ap provides a high temporal resolution record of environmental conditions in this region the extremely high annual accumulation rate at this site facilitates analysis of the relationships between annual net accumulation an on the bp and large scale atmospheric oscillations over the last 45 years an on the bp has been positively correlated with both the southern annular mode sam and southern oscillation index soi extending this analysis back to 1900 reveals that these relationships are not temporally stable and they exhibit major shifts in the late 1940s and the mid 1970s that are contemporaneous with phase changes in the pacific decadal oscillation pdo these varying multidecadal characteristics of the an oscillation relationships are not apparent when only data from the post 1970s era are employed analysis of the longer ice core record reveals that the influence of the sam on an depends

time varying spectral characteristics of enso over the last millennium the characteristics of el nino southern oscillation enso spectra over the last millennium are examined to characterise variability over past centuries seven published palaeo enso reconstructions and nino3 4 from six coupled model intercomparison project phase 5 and paleoclimate modelling intercomparison project phase 3 cmip5 pmip3 last millennium simulations were analysed the corresponding historical and pre industrial control cmip5 pmip3 simulations were also considered the post 1850 spectrum of each modelled or reconstructed enso series captures aspects of the observed spectrum to varying degrees we note that no single model or enso reconstruction completely reproduces the instrumental spectral characteristics the spectral power across the 2 3 years near biennial 3 8 years classical enso and 8 25 years decadal periodicity bands was calculated in a sliding 50 year window revealing temporal variability in the spectra there was strong temporal variability in the spectral power of each periodicity band in observed nino3 4 and soi and for all reconstructions and simulations of enso significant peaks in spectral power such as observed in recent decades also occur in some of the reconstructed palaeo enso around 1600 the early 1700s and 1900 and modelled series around the major volcanic eruptions of 1258 and 1452 while the recent increase in spectral power might be in response to enhanced greenhouse gas levels the increase lies within the range of variability across the suite of enso reconstructions and simulations examined here this study demonstrates that the analysis of a suite of enso reconstructions and model simulations can build a broader understanding of the time varying nature of enso spectra and how the nature of the past spectra of enso is to some extent dependant on the climate model or palaeo enso reconstruction chosen

tropical variability and stratospheric equatorial waves in the ipslcm5 model the atmospheric variability in the equatorial regions is analysed in the earth system model pre industrial simulation done at ipsl in the framework of cmip5 we find that the model has an interannual variability of about the right amplitude and temporal scale when compared to the el nino southern oscillation enso but that is too confined to the western pacific at the intra seasonal periods the model variability lacks of large scale organisation and only produces one characteristic madden julian oscillation every 10 winters typically at shorter time scales and in the troposphere the model has rossby and kelvin convectively coupled equatorial waves ccews but underestimates the kelvin ccews signal on olr in the model stratosphere a composite analysis shows that the temperature and velocities fluctuations due to the kelvin waves are quite realistic in the model nevertheless the stratospheric waves are less related to the convection than in the observations suggesting that their forcing by the midlatitudes plays a larger role still in the model the kelvin waves are not predominantly occurring during the life cycle of the tropospheric kelvin ccews a behaviour that we find to be dominant in the observations the composite analysis is also used to illustrate how the waves modify the zonal mean flow and to show that the model kelvin waves are too weak in this respect this illustrates how a model can have a reasonable kelvin waves signal on the velocities and temperature but can at the same time underestimate their amplitude to modify the mean flow we also use this very long simulation to establish that in the model the stratospheric equatorial waves are significantly affected by enso hence supporting the idea that the enso can have an influence on the quasi biennial oscillation

bellingshausen sea ice extent recorded in an antarctic peninsula ice core annual net accumulation an from the bruce plateau bp ice core retrieved from the antarctic peninsula exhibits a notable relationship with sea ice extent sie in the bellingshausen sea over the satellite era both bp an and bellingshausen sie are influenced by large scale climatic factors such as the amundsen sea low southern annular mode and southern oscillation in addition to the direct response of bp an to bellingshausen sie e g more open water as a moisture source these large scale climate phenomena also link the bp and the bellingshausen sea indirectly such that they exhibit similar responses e g northerly wind anomalies advect warm moist air to the antarctic peninsula and neighboring bellingshausen sea which reduces sie and increases an comparison with a time series of fast ice at south orkney islands reveals a relationship between bp an and sea ice in the northern weddell sea that is relatively consistent over the twentieth century except when it is modulated by atmospheric wave patterns described by the trans polar index the trend of increasing accumulation on the bruce plateau since 1970 agrees with other climate records and reconstructions in the region and suggests that the current rate of sea ice loss in the bellingshausen sea is unrivaled in the twentieth century

recent advances in wavelet analyses part 2 amazon parana orinoco and congo discharges time scale variability this paper is devoted to illustrating new wavelet analysis methods in the field of hydrology new wavelet indicators are applied to long term hydrological and climatologic proxies they are first applied to four atlantic large river monthly discharges amazon parana orinoco and congo and then applied to two well known long term climatologic indexes the southern oscillation and the north atlantic oscillation this approach makes it possible to suggest physical explanations for time scale dependant relationships six month variability is present in all the rivers except in the parana in the congo river this signal is near stationary with strong entropy the strength of this scale coincides with higher discharge variability before 1920 and over the orinoco basin with higher discharge values between 1940 and 1955 an annual cycle is present in all the rivers but is much stronger along with the entropy in the rivers with a large tropical basin as in the amazon and the orinoco this annual signal is not permanent in the congo and much more intermittent in the parana where the annual recharge appears as very irregular a quasi biennial variability is apparent in all the equator ward rivers and a nearly permanent 2 year coherence is found between soi and the amazon discharge a 3 6 year oscillation typical of enso variability is observed in all the rivers it is intermittent observed before 1930 in all the rivers and after 1980 mostly in the amazon river these peaks of activity correspond to periods of major soi variability an 8 year variability is particularly strong in the parana river before 1940 and around 1970 and to a lesser extent in the orinoco river during the low nao index period between 1940 and 1970 the congo river exhibits that time scale around 1970 a 13 year variability common to soi nao and the south atlantic ocean circulation is observed in the parana and congo discharges in all the rivers the greatest entropy is observed at bi and multi decadal time scales with the greatest coherence with both nao and soi a near 20 year time scale is observed in most of the series around 1970 although it is strongest in amazon and parana discharges finally a 30 year time scale is observed between 1940 and 1970 it is to be noted that most of the time scale dominant activities in all the rivers may have been influenced by the interdecadal shifts that took place around 1940 and 1970 in the pacific and in the atlantic therefore in this contribution the application of new wavelet indicators combined continuous and multi resolution analysis wavelet entropy wavelet coherence wavelet cross correlation leads to several improvements in the analysis of these global hydrological signal fluctuations and of their mutual time varying relationships it is demonstrated that wavelets should be used more systematically in preference to the classical fourier analysis notably in hydrology

detection of a gravitational oscillation in length of day abstract a high resolution length of day data set spanning approximately the last 42 years is found to contain an oscillation with a period of 5 8 0 8 years this oscillation is interpreted to represent a normal mode of the earth that arises due to gravitational coupling between the mantle and inner core in order to match the observed period of the oscillation the strength of the gravitational coupling between the mantle and inner core must be 3 0 1020 n m this coupling constant depends on the heterogeneous density distribution of the mantle including flow induced deformation of the core mantle boundary the existence of this normal mode requires that the relaxation time of the inner core be sufficiently long on the order of a few years or more that a perturbation from equilibrium results predominantly in solid body rotation not viscous deformation of the inner core the inferred lower bound for the viscosity of the inner core is of the order of 1017 pa s

the very strong coastal el nino in 1925 in the far eastern pacific the 1925 el nino en event was the third strongest in the twentieth century according to its impacts in the far eastern pacific fep associated with severe rainfall and flooding in coastal northern peru and ecuador in february april 1925 in this study we gathered and synthesised a large diversity of in situ observations to provide a new assessment of this event from a modern perspective in contrast to the extreme 1982 1983 and 1997 1998 events this very strong coastal el nino in early 1925 was characterised by warm conditions in the fep but cool conditions elsewhere in the central pacific hydrographic and tide gauge data indicate that downwelling equatorial kelvin waves had little role in its initiation instead ship data indicate an abrupt onset of strong northerly winds across the equator and the strengthening weakening of the intertropical convergence zones itcz south north of the equator observations indicate lack of external atmospheric forcing by the panama gap jet and the south pacific anticyclone and suggest that the coupled ocean atmosphere feedback dynamics associated with the itczs northerly winds and the north south sst asymmetry in the fep lead to the enhancement of the seasonal cycle that produced this en event we propose that the cold conditions in the western central equatorial pacific through its teleconnection effects on the fep helped destabilize the itcz and enhanced the meridional ocean atmosphere feedback as well as helping produce the very strong coastal rainfall this is indicated by the nonlinear relation between the piura river record at 5 s and the sst difference between the fep and the western central equatorial pacific a stability proxy in summary there are two types of en events with very strong impacts in the fep both apparently associated with nonlinear convective feedbacks but with very different dynamics the very strong warm enso events like 1982 1983 and 1997 1998 and the very strong coastal en events like 1925

last century changes in ocean wind wave height from global visual wave data 1 centennial time series of visually observed wave height were derived from the international comprehensive ocean atmosphere data set along the major ship routes in the world ocean and homogenized they demonstrate positive trends in significant wave height over the north pacific with a maximum of 8 10 cm decade in the northeast pacific in the north atlantic and other basins significant upward changes up to 14 cm decade are observed only for the last 50 years and not for centennial records long term changes in wind wave height are closely associated with the north atlantic oscillation in the atlantic and with north pacific oscillation and el nino southern oscillation in the pacific

independent patterns of water mass anomalies over australia from satellite data and models the gravity recovery and climate experiment grace products allow the quantification of total water storage tws changes at global to regional scales however the quantity measured by grace represents mass signals integrated over vertical columns requiring their separation into their original sources such a separation is vital for australia for which grace estimates are affected by leakage from the surrounding oceans the independent component analysis ica method that uses higher order statistics is implemented here to separate grace derived water storage signals over the australian continent from its surrounding oceans covering from october 2002 to may 2011 the performance of ica applied to grace is then compared to the ica of watergap global hydrology model wghm and the ica of the australian water resources assessment awra system to study the influence of rainfall variability on the derived independent patterns use is made of tropical rainfall measuring mission trmm data set from january 2000 to may 2011 implementing ica on grace tws showed a remarkable improvement in separating the continental hydrological signals from the surrounding oceanic anomalies which was not achievable using a conventional principle component analysis reconstructing the continental tws changes using only those independent components of grace that were located over the continent showed a high correlation with wghm tws and awra tws mass concentrations over the oceans and particularly s2 semi diurnal aliased pattern were separated as independent modes correlation analysis between the independent components of grace and climate teleconnections showed that the mass anomalies over the northern ocean gulf of carpentaria and north eastern parts of australia were significantly correlated with the el nino southern oscillation while those over south and south eastern parts of australia were mainly linked to the indian ocean dipole

changes in the southwest monsoon mean daily rainfall intensity in sri lanka relationship to the el nino southern oscillation abstract daily rainfall data for 187 stations in sri lanka spanning the period 1960 1996 were analyzed to investigate the spatial and temporal characteristics of the mean rainfall intensity mri through this time interval with special focus on the southwest monsoon may september particular emphasis was laid on temporal changes in the mri series the mean and standard deviation sd of the mri data showed considerable spatial variation regression analysis expressing precipitation as a function of time at the various stations revealed distinct spatial trends the results point to high mri in lowland areas and low mri in mountain areas principal components analysis of the temporal relationships among a reduced set of stations located in an equal sized grid showed that the three dominant principal components pcs are characterized by the maximum and minimum mean and sd of the mri series together with the mean number of rainy days the first second and third pc modes show significant patterns of the mri data series over the northern half southern half and southwestern coastal belt of sri lanka respectively the time series pattern of the dominant pc modes revealed distinct changes in mri over time a noticeable higher value in mri was found from 1977 to 1996 this tendency is most pronounced for the first pc mode the time series of the southern oscillation index was found to be closely related to changes in the mri patterns associated with the first pc mode in addition el nino years coincide with low values of the first pc mode some la nina years show a positive response for the first and third pc modes while there is no clear response for the mri pattern identified by the second pc

a possible signal of the el nino southern oscillation in time series of the diurnal tide long time series of diurnal pressure variations s1 p at macao 22 n 113 e and batavia now djakarta 6 s 107 e are analysed and at both locations a correlation is found between s1 p and el nino southern oscillation enso some possible physical explanations for this correlation are given

the relationship between the east asian summer monsoon and el nino southern oscillation revealed by reconstructions and a control simulation for millennium abstract proxy based reconstructions of the asian summer monsoon exhibit variability over multiple scales from inter annual to centennial the relationship between east asia summer monsoon easm variability and the el nino southern oscillation enso over the last millennium remains unclear and a focus of current research this study investigates this relationship using observations reanalysis data proxy based reconstructions and a control simulation using the community earth system model cesm the results derived from both the observation reanalysis proxy based reconstruction and the simulation show consistently that the relationship between easm strength and nino3 4 sst is divergent the observation reanalysis data illustrate strong negative correlations between nino3 4 sst and easm strength at an annual scale in the 1920s 1930s and 1980s 1990s with weak correlations during other periods the proxy based reconstruction demonstrates strong negative correlations at inter decadal scales from the 1360s to the 1530s with either weak correlations or positive correlations during other periods moreover the simulations reveal positive correlations in some periods and negative or weak correlations in other periods the simulations demonstrate that the divergent relationship may be derived from multi decadal variations in pacific sst caused by internal variability in the climate system likely due to the inter decadal pacific oscillation ipo the easm variation is usually in out of phase with nino3 4 sst during the positive negative phase of the ipo in the positive phase of the ipo there is a tripolar pattern expressed in a cyclone anticyclone cyclone arrangement at pressure level of 850 hpa from the tropics to mid latitudes over the northwest pacific warming of the nino3 4 strengthens the tropical cyclone by weakening the trade winds and subsequently strengthening the subtropical anticyclone leading to a strong meiyu front which suggests a strong easm however in the negative phase of the ipo a huge cyclone occupies the northwest pacific warming of the nino3 4 strengthens the cyclone by weakening the trade winds which leads to a weak meiyu front which suggests a weak easm these results may be helpful in further understanding the mechanisms through which the enso and ipo impact the atmospheric circulations in the asian pacific especially regarding the long term variations in easm at inter annual to inter decadal scales

a multicentury stable isotope record from a new caledonia coral interannual and decadal sea surface temperature variability in the southwest pacific since 1657 a d a 335 year stable isotope record from a new caledonia coral 22 s 166 e helps fill a large gap in historical climate reconstructions although the long term coral 18o based sea surface temperature sst trend is one of warming there are notable decadal fluctuations especially in the early 18th and early 19th centuries mean annual ssts between 1658 and 1900 are estimated to be 0 3 c lower than the 20th century average with interdecadal excursions of 0 5 0 8 c time series analyses of the coral isotope record reveals significant concentrations of variance in the el nino band an inderdecadal spectral peak is present but its robustness requires additional statistical evaluation a secular but irregular decrease in coral 13c values begins in the mid 1800s and may reflect the anthropogenic perturbation of the carbon reservoir these and other results indicate that the new caledonia coral isotope record is a valuable source of information on southwest pacific climate history

post younger dryas seasonality in the north american midcontinent region as recorded in lake huron varved sediments a sediment core from northwestern lake huron contains a sequence of red and gray layered sediments that are postglacial and early holocene glaciolacustrine varves two hundred and sixty four couple

theoretical far field radiation from a low frequency horizontal acoustic point force in a vertical borehole a subsurface point body force can be realized using a body force on the axis of a small radius borehole drilled perpendicular to the force this observation originally made by kitsunezaki 1980 is having a significant impact in shear wave logging and may potentially affect downhole seismic sources applying the principle of reciprocity to this finding a horizontal vibration sensor on the axis of a vertical hole will be unaffected by the existence of the hole at low frequencies numerical methods determine both the frequency below which and the offset beyond which borehole related effects are negligible if the shear wavelength is greater than ten times the diameter of the hole and if the measurement is made at least one shear wavelength from the point force then the borehole effects will be minimal

ice cores as an index of global volcanism from 1850 to the present to evaluate an important cause of past climate change climate researchers need reliable estimates of volcanic aerosol loading in the atmosphere previous indices the dust veil index volcanic explosivity index and those by mitchell 1970 sato et al 1993 and khmelevtsov et al unpublished manuscript 1993 all have drawbacks ice core acidity and sulfate records because they contain physical evidence of atmospheric loading are a promising source of information on past volcanic aerosols but these records contain large nonvolcanic signals as well we have compared northern hemisphere nh and southern hemisphere sh annual average versions of five indices with eight nh and six sh ice core records for the period 1850 to the present in an attempt to identify the volcanic signal common to all records the indices are all highly correlated with each other for the nh although the individual ice core records are in general not well correlated with each other or with any of the indices a composite derived from averaging the cores the ice core volcano index ivi shows promise as a new index of volcanic aerosol loading this new index correlates well with the existing non ice core volcanic indices and with high frequency temperature records for the sh the individual ice cores and indices are better correlated the shivi is again highly correlated with all indices and individual ice cores but not with high frequency temperature records for both hemispheres the southern oscillation index shows no significant correlation with the volcanic indices ice cores or the ivi thus providing no evidence for the impact of volcanic eruptions on el nino southern oscillation events

recharge to groundwater in the turi basin northern chile an evaluation based on tritium and chloride mass balance techniques summary the turi basin contains an unconfined phreatic aquifer within the toconce formation volcano sedimentary sequence that passes eastwards under the quaternary volcanic chain and outcrops in the altiplano the phreatic aquifer is floored by impermeable welded miocene ignimbrites precipitation captured by the volcanic edifices infiltrates through high permeability soils to recharge the phreatic aquifer the hydrochemistry of the groundwater in the phreatic aquifer shows little evidence of mixing with geothermal water and therefore approximates to a closed system tritium values demonstrate that recharge is occurring under current climatic conditions and takes around 40 years to pass 10 km from recharge areas on the slopes of the volcanoes and the altiplano to the center of the basin the chloride mass balance technique has been used to quantify precipitation recharge at 15 500 m3 d 1 this is significantly less than the flow through the phreatic aquifer 58 000 86 000 m3 d 1 calculated from its physical properties and the difference is interpreted to be due to subsurface inflow through the toconce formation from the altiplano the results of this study have wider application throughout the andean hydrological environment of northern chile

attenuation of acoustic modes due to viscous drag at the borehole wall white 1983 among others has shown that the propagation and attenuation of stoneley waves in a fluid filled borehole contain information on the porosity and permeability of the surrounding formation prior to extracting permeability from attenuation the correct viscous loss of stoneley waves in a borehole in a nonporous medium must be completely understood with this motivation in mind the purpose of this paper is to derive the viscous loss due to drag at the wall of a borehole from the exactly solvable case of a perfectly cylindrical borehole in an elastic nonporous formation filled with a fluid that is viscous in shear thus the fluid pressure and fluid motion in the small but critical region near the fluid solid interface can be calculated we have obtained dispersion and attenuation of trapped waves and tube waves but here we report only on tube waves

response of extreme floods in the southwestern united states to climatic variations in the late holocene a regional synthesis of paleoflood chronologies on rivers in arizona and southern utah reveals that the largest floods over the last 5000 years cluster into distinct time periods that are related to regional and global climatic fluctuations the flood chronologies were constructed using fine grained slackwater deposits that accumulate in protected areas along the margins of bedrock canyons and selectively preserve evidence of the largest events high magnitude floods were frequent on rivers throughout the region from 5000 to 360014c yrs bp dendrocalibrated age 3800 2200 bc and increased again after 2200 bp 400 bc with particularly prominent peaks in magnitude and frequency around 1100 900 bp ad 900 1100 and after 500 yrs bp ad 1400 in contrast the periods 3600 2200 bp 2200 400 bc and 800 600 yrs bp 1200 1400 ad are marked by sharp decreases in the occurrence of large floods on these rivers in the modern record storms that generate large floods 10 year in the region fall into three categories 1 winter north pacific frontal storms 2 late summer and fall storms that draw in moisture from recurved pacific tropical cyclones and 3 summer storms mainly convective thunderstorms winter storms and tropical cyclones are associated with the most severe floods on the rivers in this study and are the most probable causes of the paleofloods over the last 5000 years floods from both winter storms and tropical cyclones occur when deep mid latitude troughs steer storm systems into the region composite anomaly maps of daily 700 mbar heights indicate that these floods are associated with a low pressure anomaly off the california coast and a high pressure anomaly over the aleutians or gulf of alaska a strong connection exists between the negative phase of the southern oscillation index often associated with el nin o conditions and the large floods associated with winter storms and tropical cyclones the paleoflood records confirm the existence of centennial scale variations in the conditions conducive to the occurrence of extreme floods and flood generating storms in this region the episodes with an increased frequency of high magnitude floods coincide with periods of cool wet climate in the western u s whereas warm intervals such as the medieval warm period are times of dramatic decreases in the number of large floods a positive relationship between the paleofloods and long term variations in the frequency of el nin o events is evident over the last 1000 years this relationship continues over at least the last 3000 years with warm coastal sea surface temperatures indicative of el nin o like conditions

uncertainty in regional temperatures inferred from sparse global observations application to a probabilistic classification of el nino instrumental records showing increases in surface temperature are some of the robust and iconic evidence of climate change but how much should we trust regional temperature estimates interpolated from sparse observations here we quantify the uncertainty in the instrumental record by applying multi resolution lattice kriging a recently developed interpolation technique that leverages the multiple spatial scales of temperature anomalies the probability of monthly anomalies across the globe is represented by an ensemble based on hadcrut4 morice et al 2012 and accounting for observational and coverage uncertainties to demonstrate the potential of this new data we investigate the area averaged temperature anomalies over the nino 3 4 region in the equatorial pacific having developed a definition of the el nino southern oscillation enso able to cope with probability distribution functions we classify the enso state for each year since 1851 we find that for many years it is ambiguous as to whether there was an el nino or not from the nino 3 4 region alone these years are mainly before 1920 but also just after world war ii

an enso signal in the north atlantic subtropical area precipitation in the canary islands is studied from a synoptic point of view for the 1955 1998 period using data from the ncep ncar reanalysis the use of automatic objective techniques allows the identification of five patterns leading to precipitation in the area the influence of intense el nino and la nina events on these patterns is then studied the results show that la nina conditions are characterized by more intense and frequent precipitation episodes as result of deeper and more frequent geopotential anomalies at the 500 hpa level

tree ring based reconstructions of northern patagonia precipitation since ad 1600 long term reconstructions 400 years of seasonal and annual precipitation variations were developed for northern patagonia east of the andes using a new set of 16 tree ring width chronologies from austrocedrus chilensis d don endl reconstructions which capture between 41 and 50 of the precipitation variance show that the twentieth century contains the most extreme long periods of wetness and dryness in the past 400 years since about ad 1910 the reconstructions are also characterized by an increase in interannual variability and one of the highest rates of extreme events within the last 400 years a prominent oscillation on the order of 2 2 1 years in length has been identified in the reconstructions using spectral analysis quasi biennial oscillations have been shown to be very marked in some circulation indices of the southern hemisphere although significant oscillations within the preferred frequency domain of el nino southern oscillation enso are present in the reconstructions no clear trod consistent responses to enso have been observed correlations of reconstructions with mean sea level pressure around south america for the interval ad 1912 1984 reveal the influence of subtropical and high latitude features of the atmospheric circulation on precipitation variations in northern patagonia droughts result from an intensification of the subtropical pacific anticyclone off the chilean coast and the deepness of the circum antarctic trough over the south orkney antarctic peninsula sector mean sea level pressure reconstructions for the south atlantic sector of the southern oceans were used to evaluate the temporal stability of the relationships between northern patagonia precipitation and high latitude climatic variations since ad 1750 the influence of high latitude circulation on precipitation appears to be more significant during the twentieth century which in turn may respond to an intensification of wavenumbers 3 on the mean planetary wave structure over the southern hemisphere recent increase of precipitation variability in northern patagonia may reflect stronger interactions between middle and high latitude atmospheric circulation in the southern hemisphere during the twentieth century

tree ring δ18o inferred spring drought variability over the past 200 years in the hengduan mountains southwest china abstract in this study we developed a tree ring 18o chronology of abies delavayi from diancangshan 25 41 n 100 06 e in the hengduan mountains of southwest china spanning 205 years 1810 2014 ce tree ring 18o from abies delavayi showed the highest negative correlation with relative humidity in the spring r 0 59 p

interannual variability of deep convection over the tropical warm pool satellite data show that the total amount of deep convection was nearly constant from year to year over the warm pool region of the tropical indian and pacific oceans but the spatial distribution varied in the 1986 1987 warm el nino southern oscillation event the maximum of deep convective activity was over the high sea surface temperature sst of the west central pacific with a local minimum over the eastern indian ocean in the 1988 1989 cold enso event the maximum convective activity switched to the eastern indian ocean with a minimum over the west central pacific the sst changed very little over the eastern indian ocean from year to year and the centers of convective activity were always collocated with the four month mean low level westerlies in each year the latitude of the cloudy region of the intraseasonal oscillation iso varied interannually the interannual differences in deep convective activity over the warm pool were accounted for almost exclusively by the occurrence or nonoccurrence of extremely large long lasting deep mesoscale cloud systems cloud tops 208 k with horizontal dimensions 300 700 km such cloud systems occurred more frequently than normal over the western pacific during the warm enso event and over the eastern indian ocean during the cold event they occurred more frequently over the tropical eastern indian and western pacific oceans than over the maritime continent thus accounting for the seesaw pattern of the observed cold cloudiness between the two oceanic regions on both interannual and intraseasonal timescales

role of atmospheric circulation with respect to the interannual variability in the date of snow cover disappearance over northern latitudes between 1988 and 2003 1 this paper analyzes the main spatial patterns in the dates of snow cover disappearance variability over northern latitudes between 1988 and 2003 the dates of snow cover disappearance were calculated using satellite passive microwave data from the special sensor microwave imager spatial and temporal patterns were obtained using principal components analysis in the s mode we identified eight components each representing a large region characterized by homogeneous interannual variability in the dates of snow cover disappearance we found that atmospheric circulation summarized by means of teleconnection indices had an important impact on the date of snow cover disappearance for most of these regions a role is played by the arctic oscillation in western siberia the spring east atlantic west russian pattern in central siberia and the pacific north

numerical modelling of thrust structures in unconsolidated sediments implications for glaciotectonic deformation abstract the mechanics of thrust faulting induced by a differential vertical load has been studied by application of a dynamic finite element model the modelled scenario is analogous to the glaciostatic load imposed onto an unconsolidated sedimentary substrate by a stationary ice sheet the objective is to evaluate whether large scale glaciotectonic deformation may be induced by gravity spreading in front of a stationary glacier or if a push from the rear is required the model is capable of handling large strains and rotations combined with visco elastic plastic rheologies model parameters are derived from a pleistocene large scale glaciotectonic thrust complex in the eastern danish north sea the plastic behaviour of the unconsolidated sediments is described by a time and pressure dependent drucker prager yield criterion combined with a non associated flow law the modelling results show that gravity spreading in front of a stationary ice sheet can form strain localisations and possibly cause thrust faults to nucleate in unconsolidated sediments several kilometres beyond the snout of the ice sheet provided a decollement surface is situated at a suitable depth relative to the effective load of the ice sheet hence it is concluded that large scale glaciotectonic thrusting may be formed by gravity spreading alone and a push from the rear is not generally required to explain the observed deformation