role of topography in forcing low level jets in the central united states during the 1993 flood altered terrain simulations regional model sensitivity simulations in which the height of elevated terrain was reduced to explore simulated changes in features of the low level jet llj are presented such an approach has not been reported and it provides complementary insight to the previous llj studies the simulations were carried out for a 45 day period during the 1993 summer flood in the central united states when strong lljs were frequent the simulations illustrate directly the significance of topographical blocking leeside cyclogenesis and terrain thermal effects exerted by the rocky mountains in support of llj formation in particular it is shown that in the absence of topography the ridging from the bermuda high extended considerably westward with weaker southerly flow over the high plains thus diminishing the potential for llj development the slope induced nocturnal horizontal thermal gradient was indicated to have a significant role in the formation of the llj

el nino evolution during the holocene revealed by a biomarker rain gauge in the galapagos islands abstract the el nino southern oscillation enso represents the largest perturbation to the climate system on an inter annual time scale but its evolution since the end of the last ice age remains debated due to the lack of unambiguous enso records lasting longer than a few centuries changes in the concentration and hydrogen isotope ratio of lipids produced by the green alga botryococcus braunii which blooms during el nino rains in the galapagos islands indicate that the early holocene 9200 5600 yr bp was characterized by alternating extremes in the intensity and or frequency of el nino events that lasted a century or more our data from the core of the enso region thus calls into question earlier studies that reported a lack of el nino activity in the early holocene in agreement with other proxy evidence from the tropical pacific the mid holocene 5600 3500 yr bp was a time of consistently weak el nino activity as were the early middle ages 1000 1500 yr bp el nino activity was moderate to high during the remainder of the last 3500 years periods of strong or frequent el nino tended to occur during peaks in solar activity and during extended droughts in the united states great plains linked to la nina these changing modes of enso activity at millennial and multi centennial timescales may have been caused by variations in the seasonal receipts of solar radiation associated with the precession of the equinoxes and or changes in solar activity respectively

impacts of el nino and la nina on the u s climate during northern summer the impacts of el nino and la nina on the u s climate during northern summer are analyzed separately composite analyses reveal that a continental scale anomalous high dominates over most of north america during la nina events and leads to hot and dry summers over the central united states however the impacts of el nino over north america are weaker and more variable a linear barotropic model is used to explore the maintenance of the anomalous patterns various forcing terms derived from observations via a single level vorticity budget analysis are used to drive the model when the barotropic model is driven by the total forcing rossby wave source plus transient eddy forcing plus nonlinear interactions the model simulations resemble the observed patterns and a strong and extensive anticyclone is reproduced in the la nina simulation the model responses to the individual forcing terms suggested that the vorticity stretching term fd and the transient eddy forcing contribute most to the responses over north america the stretching term fd excites a low in the el nino simulation and a high in the la nina simulation over north america however the transient eddy forcing favors an anomalous high over north america in both el nino and la nina simulations such that it weakens the el nino pattern and strengthens the la nina pattern

separating natural and anthropogenic vertical movements in fast subsiding areas the po plain n italy case the geological and the anthropogenic components of vertical movement act on different time scales millions to thousands years and hundreds to tens of years respectively this peculiarity has been used in order to separate the factors controlling sea level changes in the po plain area the component due to long term geological processes is calculated from stratigraphic data commercial wells and seismic lines adding to this long term component the contribution of pleistocene deglaciation obtained from analytical models an estimate of the total natural component of vertical velocities is obtained the validity of these values is confirmed by comparison with velocities obtained from archaeological data and detailed palynological and paleontological analyses the anthropogenic components can be inferred by comparison between the total natural vertical velocities we calculate and vertical velocities obtained from other data sets two applications are proposed using tide gauge records and geodetic data respectively

multiscale diagnosis of the north american monsoon system using a variable resolution gcm abstract the onset and evolution of the north american monsoon system during the summer of 1993 were examined from regional to large scales using the national aeronautics and space administration nasa goddard earth observing system geos stretched grid gcm the model s grid spacing for the dynamical core ranges from 0 4 0 5 in latitude longitude over the united states to about 2 5 3 5 at the antipode and the physical package is solved on an intermediate 1 1 uniform grid a diagnostic analysis of the monsoon s onset reveals the development of a positive potential temperature anomaly at the surface that favors a lower level cyclonic circulation while a negative potential vorticity pv anomaly below the tropopause induces an upper level anticyclonic circulation ignoring diabatic effects this pattern is consistent with the superimposition of idealized pv and anomalies as previously discussed in the literature the inclusion of the smaller scale features of the core monsoon in the mod

on the fundamental difference between coal rank and coal type abstract this article addresses the fundamental difference between coal rank and coal type while theoretically settled long ago as being different aspects of coal systems science the two concepts are still often confounded in recent years this has resulted in the publication of several works stating that coal type changes with coal rank coal type refers solely to coals depositional origin and the maceral mineral admixture resulting from that origin coal types typically fall in to two categories humic coals developed from peat and sapropelic coals developed from organic mud either type may be allocthonous or autochthonous and within types further refinement of depositional environment can be made coal rank refers to the changes in geochemistry and resultant changes in reflectance caused by increasing thermal maturity of the coal thus it provides an overprint of maturity on existing coal types with proper techniques such as use of crossed polars and etching maceral forms can be differentiated even at high ranks and the original coal type determined

physical processes involved in the 1988 drought and 1993 floods in north america abstract an analysis of the spring summer 1988 drought and 1993 floods over north america reveals a reversal in the sign of anomalies in several fields large sea surface temperature anomalies of opposite signs existed in the tropical pacific with strong la nina conditions in 1988 and a mature el nino in 1993 the distribution of tropical convection in the convergence zones and associated latent heating of the atmosphere were correspondingly altered implying a large scale switch in the anomalous tropical heating and forcing of extratropical quasi stationary waves in the atmosphere influencing the subtropical jet stream over the north pacific and across north america in 1988 the jet stream and the closely related storm track of high frequency disturbances in the upper troposphere were displaced into canada well north of the normal location the farthest north of any year from 1979 to 1993 in 1993 a broader jet stream and the storm track were displaced well south of normal to a more springlike location a

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

towards a mechanical model for the formation of the pannonian basin abstract new maps showing crustal and lithospheric thickness variations in the pannonian basin and the surrounding east alpine carpathian and dinaric mountains have been prepared on the basis of recent seismic seismologic and electromagnetic data a map presenting miocene faults of regional significance has been also constructed for the same region by using a wealth of recently available national and or more local studies it is suggested that observed crustal and lithospheric structural contrasts have been controlled primarily by neogene kinematic history of the region kinematic history is characterized by the following main patterns 1 1 indentation by adria and large scale backthrusting in the southern alps 2 2 eastward escape and extension of the eastern alps 3 3 extensional collapse in the pannonian basin area 4 4 formation of broad wrench fault systems along strike in the dinarides and southern carpathians and the western carpathians with dextral and sinistral shear respectively 5 5 compression and accretion of the external thrust and fold belt in the eastern carpathians these kinematic patterns are thought to be interrelated and all are manifestations of the late stage evolution of an overthickened orogenic wedge in order to arrive at a better understanding of the mechanism of extension which formed the pannonian basin deep crustal seismic profiles hydrocarbon exploration reflection lines and borehole data have been analyzed in the little hungarian plain this plain represents the transition zone between the alps and the pannonian lowlands and the results are illustrated by eight interpreted cross sections one result of regional importance is the clear recognition that the transdanubian central range at the southeastern flank of the little hungarian plain is composed of alpine pre senonian thrust sheets this finding marks the end of a century of debate the allochthony of the substrata of the pannonian basin can be now considered proven another result of more general interest is that these cross sections document the mode of lithospheric extension preexisting compressional detachment planes reactivate as low angle normal faults and lead to tectonic unroofing of deeply buried metamorphic terranes characterized by ductile flow along subhorizontal lineation

a 10 000 year record of dune activity dust storms and severe drought in the central great plains dune fi elds and loess deposits of the great plains of north america contain stratigraphic records of eolian activity that can be used to extend the short observational record of drought we present a 10 000 yr reconstruction of dune activity and dust production in the central great plains region based on 95 optically stimulated luminescence ages the integration of data from both eolian sand and loess is an important new aspect of this record clusters of ages defi ne episodes of extensive eolian activity which we interpret as a response to frequent severe drought at 1 0 0 7 ka and 2 3 4 5 ka with peaks centered on 2 5 and 3 8 ka sustained eolian activity occurred from 9 6 to 6 5 ka parts of this record may be consistent with hypotheses linking holocene drought to sea surface temperature anomalies in the pacifi c or atlantic oceans or to the el nino southern oscillation phenomenon but the record as a whole is diffi cult to reconcile with any of these hypotheses

present day stress field and deformation in eastern austria we analysed fault plane solutions and borehole breakouts in the eastern part of the eastern alps and found a heterogeneous stress field which we interpret as a transition zone of three different stress provinces the western european stress province with nw to nnw sh orientation and mainly strike slip faulting regime the adriatic stress province with a radial stress pattern and thrust faulting to strike slip faulting regime and the dinaric pannonian stress province with ne sh orientation and strike slip faulting regime the western pannonian basin seems to be a part of the transition zone with wnw to nw sh orientation a stress regime stimulating strike slip faulting prevails in the eastern alps the south bohemian basement spur as a major tectonic structure with a high rheological contrast to surrounding units has a strong influence on the stress field and exhibits the highest seismicity at its tip due to stress concentration from a constructed vertical stress orientation profile we found stress decoupling of the northern calcareous alps from the underlying european foreland both the molasse and the flysch helvetic zone are considered as candidates for decoupling horizons due to stress orientation observations and due to their rheological behaviour from seismological and rheological data we suggest a horizontal stress decoupling across the eastern alps caused by a weakened central alpine lithosphere

tropical extratropical teleconnections in boreal summer observed interannual variability abstractmaximum covariance analysis is performed on the fields of boreal summer tropical rainfall and northern hemisphere nh 200 hpa height for the 62 yr period of record of 1948 2009 the leading mode which appears preferentially in summers preceding the peak phases of the el nino southern oscillation enso cycle involves a circumglobal teleconnection cgt pattern in the nh extratropical 200 hpa height field observed in association with indian monsoon rainfall anomalies the second mode which tends to occur in summers following enso peak phases involves a western pacific north america wpna teleconnection pattern in the height field observed in association with western north pacific summer monsoon rainfall anomalies the cgt pattern is primarily a zonally oriented wave train along the westerly waveguide while the wpna pattern is a wave train emanating from the western pacific monsoon trough and following a great circle the cgt is accompanied by a pronounced tropical extratropical seesaw in t

centennial eolian cyclicity in the great plains usa a dominant climate pattern of wind transport over the past 4000 years proxy evidence at decadal resolution from late holocene sediments from pickerel lake northeastern south dakota shows distinct centennial cycles 400e700 years in magnetic susceptibility contents of carbonate organic carbon and major elements abundance in ostracodes and d 18 o and d 13 c values in calcite proxies indicate cyclic changes in eolian input productivity and temperature maxima in magnetic susceptibility are accompanied by maxima in aluminum and iron mass accumulation rates mars and in abundances of the ostracode fabaeformiscandona rawsoni this indicates variable windy and dry conditions with westerly wind dominance including during the medieval climate anomaly maxima in carbonates organic carbon phosphorous and high d 13 c values of endogenic calcite indicate moister and less windy periods with increased lake productivity including during the little ice age and alternate with maxima of eolian transport times of the maunder sporer and wolf sunspot minima are characterized by maxima in d 18 o values and aluminum mars and minima in d 13 c values and organic carbon content we interpret these lake conditions during sunspot minima to indicate decreases in lake surface water temperatures of up to 4e5 c associated with decreases in epilimnetic productivity during

an extended pacific north american index from upper air historical data back to 1922 abstract this paper presents a reconstruction of a pacific north america pna index from historical upper level data for the period 1922 47 the data have been compiled from a number of sources and cover the pacific north american sector relatively well over this time period temperature and geopotential height profiles from aircraft kite and radiosonde ascents back to 1922 have been digitized and validated wind speed and direction from pilot balloon data back to the early 1920s provided by ncar have also been used a statistical regression approach is used for the reconstruction and calibrated in the post 1948 period using ncep ncar reanalysis data split sample validation experiments were performed within the ncep ncar period and sensitivity experiments with different subsets of predictors were performed similar reconstructions and validation experiments were carried out using a 540 yr control run from the community climate system model version 3 ccsm3 the reconstructed index series together

deep structure and kinematics of the northern calcareous alps transalp profile the northern calcareous alps nca of southern bavaria and northern tyrol constitute a carbonate dominated polyphase fold thrust wedge together with its grauwacken zone basement it is the northernmost part of the far travelled upper austroalpine thrust complex of the eastern alps the present geometry developed in several kinematic stages jurassic extensional faults that affected large parts of the nca and their basement originated when the main part of the nca was still located southeast of the central alpine otztal silvretta complex these faults and related facies transitions influenced the later style of detachment of the nca thrust sheets mid to late cretaceous detachment thrust sheet stacking and motion over the central alpine complex are registered in clastic deposits of syntectonic basins the latest cretaceous to cenozoic nne to n directed motion of the nca towards europe in front of the central alpine complex created another set of significant contraction structures which at depth overprinted all previous structures during cretaceous to cenozoic deformation the nca experienced about 80 km of shortening i e about 73 along the transalp profile the european basement and autochthonous mesozoic cover beneath the allochthonous nca thrust sheets and flysch complexes seem to have remained relatively undeformed

north american droughts of the mid to late nineteenth century a history simulation and implication for mediaeval drought unlike the major droughts of the twentieth century that are readily identified in the instrumental record similar events in the nineteenth century have to be identified using a combination of proxy data historical accounts and a sparse collection of early instrumental records in the usa three distinct periods of widespread and persistent drought stand out in these records for the latter half of the nineteenth century 1856 1865 1870 1877 and 1890 1896 each of these events is shown to coincide with the existence of an anomalously cool la nina like tropical pacific to examine the physical mechanisms behind these droughts two ensembles of simulations with an atmosphere general circulation model agcm were generated the first forces an agcm with the observed history of sea surface temperatures ssts everywhere from 1856 to 2001 the goga experiment the second forces the agcm only with tropical pacific ssts being coupled to a two layer entraining mixed layer ml ocean elsewhere the poga ml experiment owing to a sparsity of instrumental precipitation data at this time proxy evidence from tree rings is used as verification a comparison of modelled soil moisture with tree ring reconstructions of the palmer drought severity index pdsi a proxy for soil moisture from the north american drought atlas is made both the poga ml and goga ensemble means capture the three multi year droughts of the mid to late nineteenth century indicating that the droughts were sst forced the similarity of the poga ml and goga simulations implies that the component of each drought signal that is forced by the sst is driven ultimately by the la nina like tropical pacific the global atmosphere ocean context of each of the mid to late nineteenth century droughts reveals a zonally and hemispherically symmetric pattern consistent with forcing from the tropics in addition rossby wave propagation from the cooler equatorial pacific amplifies dry conditions over the usa finally using published coral data for the last millennium to reconstruct a nino 3 4 history the modern day relationship between nino 3 4 and north american drought is applied to recreate two of the severest mediaeval drought epochs in the western usa the large scale spatial similarity to the drought atlas data demonstrates the potential link between a colder eastern equatorial pacific and the persistent north american droughts of the mediaeval period

variations in north american summer precipitation driven by the atlantic multidecadal oscillation understanding the development and variation of the atmospheric circulation regimes driven by the atlantic multidecadaloscillation amo isessentialbecausethesecirculationsinteractwithotherforcingsondecadaland interannual time scales collectively they determine the summer june july and august precipitation variations for north america in this study a general circulation model gcm is used to obtain such understanding with a focus on physical processes connecting the amo and the summertime precipitation regime change in northamerica twoexperimentalrunsareconductedwithseasurfacetemperature sst anomaliesimposedin the north atlantic ocean that represent the warm and cold phases of the amo climatological ssts are used elsewhere in the oceans model results yield summertime precipitation anomalies in north america closely matching the observed anomaly patterns in north america suggesting that the amo provides a fundamental control on summertime precipitation in north america at decadal time scales the impacts of the amo are achieved by a chain of events arising from different circulation anomalies during warm and cold phases of the amo during the warm phase the north atlantic subtropical high pressure system nash weakens and the north american continent is much less influenced by it a massive body of warm air develops over the heated land in north america from june august associated with high temperature and low pressure anomalies in the lowertroposphereandhighpressureanomaliesintheuppertroposphere incontrast duringthecoldphaseofthe amo the north american continent particularly to the west is much more influenced by an enhanced nash cooler temperatures and high pressure anomalies prevail in the lower troposphere and a frontal zone forms in the upper troposphere these different circulation anomalies further induce a three cell circulation anomaly pattern over north america in the warm and cold phases of the amo in particular during the cold phase the three cell circulation anomaly pattern features a broad region of anomalous low level southerly flow from the gulf of mexico into the u s great plains superimposed with an upper troposphere front more frequent summertime storms develop and excess precipitation occurs over most of north america a nearly reversed condition occurs during the warm phase of the amo yielding drier conditions in north america this new understandingprovides a foundation for further studyand better prediction of the variations of north american summer precipitation especially when modulated by other multidecadal variations for example the pacific decadal oscillation and interannual variations associated with the enso and the arctic oscillation

present day lithospheric strength of the eastern alps and its relationship to neotectonics 1 we calculate the present day lithospheric strength of the eastern alps along the new reflection seismic profile transalp to examine vertical and lateral strength variations and their implications on neotectonic activity of the eastern alps the large scale geometry of the eastern alps and the spatial distribution of upper and lower crustal layers and the lithospheric mantle is constrained by the deep seismic line two rheological models coupled to a kinematic thermal model that accounts for the thermal evolution of the eastern alps for the last 30 myr are investigated for the present day lithospheric configuration in the eastern alps models with strong model a and weak model b crustal rheologies predict the european and the adriatic plates to be stronger than the central zone of the orogen comprising the region between the inntal fault and the periadriatic fault model a is characterized by a brittle ductile boundary between 14 and 9 km depth and strong coupling of the mechanically strong lower crust to the upper mantle whereas model b suggests the presence of a thick decoupling zone between the upper crust and the upper mantle and a shallower brittle ductile boundary 7 10 km of these end member scenarios model a is in better agreement with neotectonic data including seismicity down to the upper lower crust boundary within the adriatic plate uplift of the central zone of the eastern alps and the southern alps and eastward escape of fault bound blocks such deformation pattern is best explained by lateral extrusion upon north south compression supporting a strong weak strong configuration of tectonic units along the transalp line

the regional forcing of northern hemisphere drought during recent warm tropical west pacific ocean la nina events northern hemisphere circulations differ considerably between individual el nino southern oscillation events due to internal atmospheric variability and variation in the zonal location of sea surface temperature forcing over the tropical pacific ocean this study examines the similarities between recent northern hemisphere droughts associated with la nina events and anomalously warm tropical west pacific sea surface temperatures during 1988 1989 1998 2000 2007 2008 and 2010 2011 in terms of the hemispheric scale circulations and the regional forcing of precipitation over north america and asia during the cold season of november through april the continental precipitation reductions associated with recent central pacific la nina events were most severe over north america eastern africa the middle east and southwest asia high pressure dominated the entire northern hemisphere mid latitudes and weakened and displaced storm tracks northward over north america into central canada regionally over north america and asia the position of anomalous circulations within the zonal band of mid latitude high pressure varied between each la nina event over the northwestern and southeastern united states and southern asia the interactions of anomalous circulations resulted in consistent regional temperature advection which was subsequently balanced by similar precipitation modifying vertical motions over the central and northeastern united states the spatial variation of anomalous circulations resulted in modest inter seasonal temperature advection variations which were balanced by varying vertical motion and precipitation patterns over the middle east and eastern africa the divergence of moisture and the advection of dry air due to anomalous circulations enhanced each of the droughts

warm season subseasonal variability and climate extremes in the northern hemisphere the role of stationary rossby waves abstractthis study examines the nature of boreal summer subseasonal atmospheric variability based on the new nasa modern era retrospective analysis for research and applications merra for the period 1979 2010 an analysis of the june july and august subseasonal 250 hpa meridional wind anomalies shows distinct rossby wave like structures that appear to be guided by the mean jets on monthly subseasonal time scales the leading waves the first 10 rotated empirical orthogonal functions reofs of the 250 hpa wind explain about 50 of the northern hemisphere wind variability and account for more than 30 60 of the precipitation surface temperature variability over a number of regions of the northern middle and high latitudes including the u s northern great plains parts of canada europe and russia the first reof in particular consists of a rossby wave that extends across northern eurasia where it is a dominant contributor to monthly surface temperature and precipitation variability and

is midlatitude convection an active or a passive player in producing global circulation patterns abstract the ability of persistent midlatitude convective regions to influence hemispheric circulation patterns during the northern hemisphere summer is investigated global rainfall data over a 15 yr period indicate anomalously large july total rainfalls occurred over mesoscale sized midlatitude regions of north america and or southeast asia during the years of 1987 1991 1992 and 1993 the anomalous 200 hpa vorticity patterns for these same years are suggestive of rossby wave trains emanating from the regions of anomalous rainfall in the midlatitudes results from an analysis of an 11 yr mean monthly 200 hpa july wind field indicate that in the climatological mean rossby waveguides are present that could assist in developing a large scale response from mesoscale sized regions of persistent convection in the midlatitudes this hypothesis is tested using a barotropic model linearized about the 200 hpa july time mean flow and forced by the observed divergence anomalies the model results are in qualit

impact of the mechanical characteristics of weak rocks and trona ore beds on the main drift deformation at the beypazari mine turkey abstract in northern turkey the main drift t 2000 and a roadway t 3000 were excavated for beypazari trona natural soda underground mine project between the years 1999 and 2001 this work was one of the most important mining projects in turkey in the last decade t 2000 was designed as a main drift with a length of 965 m 14 inclined and excavated with a cross sectional area of 18 m 2 the t 3000 roadway was driven in the trona beds for the first production panel in this study in situ and laboratory studies have been made to define the formations through which the drift has been driven in situ engineering geology measurements were carried out consisting of field observation mapping boreholes and laboratory tests on samples collected from the trona field and the boreholes after drift excavation and support installation the deformations and the loads on the supports were measured as a result of this study the deformational characteristics of the trona ore beds and weak rocks and their effect on the main drift t 2000 deformation have been determined the importance of this study lies in the fact that most natural soda mines in the world apply room and pillar mining methods this study is probably the first investigation on underground openings with steel set support systems and rock deformations in natural soda beds

maintenance of circulation anomalies during the 1988 drought and 1993 floods over the united states the large scale circulation anomalies associated with the 1988 drought and the 1993 floods are investigated with the national centers for environmental prediction reanalysis data and a linear stationary wave model the transient vorticity and thermal forcings are explicitly calculated and the diabatic heating is derived as a residual in the thermodynamic energy equation using the april june amj data for 1988 and june august jja data for 1993 the linear stationary wave model is able to reproduce the main features of the geopotential height anomaly for the two seasons when all forcings are included this provides a basis for further investigation of stationary wave response to different forcing mechanisms using the linear model within the linear model framework the linear model responses to different forcings are examined separately the results indicate that the 1988 anomaly over the united states is a result of both the diabatic heating and the transient vorticity and thermal forcings the large anticyclonic anomalies over the north pacific and canada are forced mainly by the diabatic heating the 1993 anomaly however is dominated by the response to transient vorticity forcing by further separating the linear model responses to regional diabatic heating anomalies in 1988 the results indicate that the western north pacific heating is entirely responsible for the anticyclonic center over the north pacific which causes the northward shift and intensification of the pacific jet stream the eastern north pacific heating cooling couplet is the most important for maintaining the north american circulation

amplified contiguous united states summer rainfall variability induced by east asian monsoon interdecadal change the strength of the dominant variability of contiguous united states conus summer rainfall during 1960 2013 experiences an interdecadal change in the early 1990s before the early 1990s the variation in conus summer rainfall is relatively small in amplitude standard deviation 0 64 mm day 1 whereas after it amplifies remarkably with its standard deviation 1 31 mm day 1 roughly doubling observational diagnoses and simulation results show that enhanced east asian subtropical monsoon variability plays a direct role in strengthening the conus summer rainfall dipole variability besides a northward shift of the east asian summer monsoon is also responsible for the amplification of the conus summer rainfall variability this northward shift of the east asian rain belt pushes the rainfall perturbation farther to the north much closer to the subtropical east asian upper level westerly jet stream as a result the east asian subtropical monsoon heating induces the upper level asia north america teleconnection pattern more effectively leading to the larger amplitude of conus summer rainfall variability

a method for simulating effects of quasi stationary wave anomalies on regional climate abstract a combined observational and numerical modeling methodology was employed to examine the interaction of large scale quasi stationary waves with regional forcing in the drought of 1988 and flood of 1993 in the north central united states the study implements and tests a new lateral boundary condition closure approach enabling regional climate modeling sensitivity studies to account for anomalies external to the simulated domain thirty day regional simulations of the continental united states using the mm5 regional model successfully reproduced the anomalous drought and flood conditions in an additional set of simulations the observed large scale quasi stationary wave anomalies in the dynamic and thermodynamic fields were filtered out through adjustment of the observationally based lateral boundary conditions in these filtered simulations the simulated meteorological fields over the drought flood areas for both years tended toward those for normal years suggesting that the proposed filtering te

la nina diversity and northwest indian ocean rim teleconnections the differences in tropical pacific sea surface temperature sst expressions of el nino southern oscillation enso events of the same phase have been linked with different global atmospheric circulation patterns this study examines the dynamical forcing of precipitation during october december ond and march may mam over east africa and during december march djfm over central southwest asia for 1950 2010 associated with four tropical pacific sst patterns characteristic of la nina events the cold phase of enso the self organizing map method along with a statistical distinguishability test was used to isolate la nina events and seasonal precipitation forcing was investigated in terms of the tropical overturning circulation and thermodynamic and moisture budgets recent la nina events with strong opposing sst anomalies between the central and western pacific ocean phases 3 and 4 force the strongest global circulation modifications and drought over the northwest indian ocean rim over east africa during mam and ond subsidence is forced by an enhanced tropical overturning circulation and precipitation reductions are exacerbated by increases in moisture flux divergence over central southwest asia during djfm the thermodynamic forcing of subsidence is primarily responsible for precipitation reductions with moisture flux divergence acting as a secondary mechanism to reduce precipitation eastern pacific la nina events in the absence of west pacific sst anomalies phases 1 and 2 are associated with weaker global teleconnections particularly over the indian ocean rim the weak regional teleconnections result in statistically insignificant precipitation modifications over east africa and central southwest asia

effects of quasi stationary large scale anomalies on some mesoscale features associated with the 1993 flood a regional model simulation we investigate the effect of quasi stationary large scale anomalies on mesoscale factors contributing to the 1993 u s midwest flood by performing 30 day simulations with a mesoscale model the contributions of anomalous mesoscale features to the flood were quantified by contrasting model integrations forced by initial and lateral boundary conditions with and without large scale anomalous stationary waves that are believed to have been responsible for the flood supplementing previous investigations the present study finds the following 1 the large scale anomalies produced environmental conditions that favored a generation of mcc like systems rather than individual convective cells or squall lines that would have produced less precipitation over large areas ambient conditions favoring mesoscale convective complex mcc include an intensified east west orientation of quasistationary fronts weaker upper tropospheric inertial stability and a strong low level jet llj 2 the anomalous ageostrophic wind component to the far south of the flood region texas area and geostrophic wind component over the flood region bridged together to form an extended moisture conveyer that sustained the long lasting 1993 flood

connection between sea surface anomalies and atmospheric quasi stationary waves abstractlarge scale quasi stationary atmospheric waves qsws are known to be strongly connected with extreme events and general weather conditions yet despite their importance there is still a

high resolution proxy record of holocene climate from a loess section in southwestern nebraska usa abstract multi proxy analysis was used to produce a high resolution paleoclimatic record from an exceptionally thick section of the holocene bignell loess near wauneta southwestern nebraska in the central great plains the wauneta section has excellent age control based on optically stimulated luminescence osl and radiocarbon dating and records multiple episodes of rapid loess deposition alternating with slower deposition and soil formation the lowermost and uppermost osl ages obtained from the bignell loess are 10 250 610 years 5 9 m depth and 100 10 years 0 1 m depth respectively as a result the holocene has been temporally confined stratigraphically the bignell loess overlies the late pleistocene peoria loess deposited 21 14 ka and the two units are separated by the brady soil which is distinguished by its color and other pedogenic features l a b color parameters and organic carbon content of bignell loess are sensitive proxies to differentiate drought induced aeolian sediment layers from the intercalated soil horizons soil organic carbon derived 13 c data suggest that the c 3 dominated floral environment during peoria loess deposition shifted dramatically to a c 4 dominated environment during brady soil formation in response to a warming trend even greater c 4 abundance characterized the late holocene high resolution 13 c data support the contention that c 3 vs c 4 vegetation change in the holocene reflects ecosystem response to frequent vegetation disturbance under arid conditions time series analysis reveals that 13 c and color parameters display high frequency variation with periodicities of 103 118 years and 103 years respectively similar periodicities were also reported in studies of north dakota lakes though the physical mechanism responsible is uncertain comparison of bignell loess color and tropical pacific sea surface temperatures ssts allows evaluation of a proposed teleconnection between drought in the great plains and la nina like conditions in the tropical pacific the loess color index and eastern tropical pacific sst display broad similarities through the late pleistocene and holocene that are consistent with this teleconnection on the other hand drought centered at 3800 years ago is not consistent with the teleconnection and the end of early holocene aridity at the wauneta section around 6500 years ago is much earlier than the corresponding rise in sst and increase in el nino frequency in the eastern tropical pacific

present state of tectonic stress of the friuli area eastern southern alps stress orientations are determined for the friuli area from focal mechanisms using the inversion technique of gephart and forsyth 1984 the data consist of 244 fault plane solutions selected for the period 1988 1995 where the data coverage was poor this period was extended to 1978 1996 local magnitude ranges from 2 0 to 4 3 and the depths extend from 4 to 16 km the friuli area is subdivided into five seismotectonic zones on the basis of tectonic characteristics seismic activity and focal mechanisms and for each zone a stress tensor is determined the results show that the active tectonic stress in the friuli area is heterogeneous and conditioned by the complex structural pattern which is characterized by two indented tectonic wedges the western and central parts of the area are mainly affected by a compressional state of stress while in the eastern part a strike slip state of stress prevails the orientation of the principal stresses varies from the western to the eastern part of the area and differences are also noticeable with depth in the central part of the friuli area the maximum compressional stress is n s trending at shallow depths 10 km changing to nw se at deeper levels the maximum compressional stress is nw se oriented in the western part while in the eastern part it is n s oriented

u s summer precipitation and temperature patterns following the peak phase of el nino abstractevidence for spatially coherent but different u s summer precipitation and surface air temperature anomalies during the evolving phase and during the summers following the peak phase of the winter el nino is presented the spatial patterns during the decaying phase of el nino are distinctive from patterns in the preceding summer when el nino is in its evolving phase that is the traditional simultaneous composite patterns associated with el nino the analysis of a multimodel ensemble of global atmospheric models forced by observed sea surface temperature further confirms that the differences in the u s summer precipitation and surface temperature anomalies between the developing and decaying phases of el nino are a result of the atmospheric response to tropical warm sst anomalies that are shifted eastward and are confined east of 120 w during the decaying phase of el nino given the distinctive pattern and relatively large amplitude of these anomalies during the decaying phase of el nino

first deep seismic reflection images of the eastern alps reveal giant crustal wedges and transcrustal ramps 1 the alps are considered as a classical example for an orogen created by continental plate collision in this study we present new images obtained from deep seismic reflection profiling in the eastern alps between munich and venice which give rise to examine and revise existing concepts the seismic sections exhibit a prominent bi verging reflection pattern at crustal scale a major ramp like structure outcropping at the inn valley fault can be traced southward over 80 km into the mountain root where relics of the subducted penninic ocean are expected new models of the evolution of the eastern alps show an upper lower crustal decoupling along transcrustal thrust faults with opposite thrust directions of both the european and the adriatic african continents