extrusion tectonics of the okhotsk plate northeast asia based on focal mechanism geologic and lineament data faulting in the chersky range northeast asia changes from right lateral transpression between north america and eurasia to left lateral strike slip between north america and the okhotsk plate the location of the okhotsk eurasia boundary is poorly constrained available data suggest this boundary is right lateral the okhotsk plate is being compressed and extruded from between north america and eurasia resulting in high levels of microseismic activity along the southern flanks of the chersky range

imprint of the north american plate in siberia revealed by gps 1 gps observations in east siberia combined with global observations collected 1995 2002 place constraints on the geometry and motions of the eurasian north american and pacific plates in east asia by comparing velocities relative to eurasia and to north america we conclude that east siberia to the east of the cherskiy range belongs to the north american plate hypothesized for three decades but not proven because of uncertainties with the plate boundary arising from the ambiguous seismicity smaller plates in east asia such as okhotsk and amurian can neither be resolved nor excluded by the gps velocities

changes in occurrence of cold surges over east asia in association with arctic oscillation 1 it has been newly found that the occurrence of cold surges in east asia is significantly influenced by the arctic oscillation ao in the present study the events of cold surge are objectively determined based on several synoptic criteria and the phase dependency of its occurrences in association with the ao has been revealed during the negative ao phase the frequency of cold surge occurrence is relatively increased than that of neutral and positive ao phases the variation of upper level trough and jet stream over east asia and the siberian high in association of ao are suggested to explain the change of cold surge occurrences

impacts of mjo convection over the maritime continent on eastern china cold temperatures abstractthe present study shows that winter cold events over eastern china can be induced by madden julian oscillation mjo associated anomalous convection over the maritime continent we conduct

genesis pathways and terminations of intense global water vapor transport in association with large scale climate patterns author s sellars sl kawzenuk b nguyen p ralph fm sorooshian s abstract 2017 the authors the connected object connect algorithm is applied to global integrated water vapor transport data from the nasa s modern era retrospective analysis for research and applications version 2 reanalysis product for the period of 1980 to 2016 the algorithm generates life cycle records in time and space evolving strong vapor transport events we show five regions located in the midlatitudes where events typically exist off the coast of the southeast united states eastern china eastern south america off the southern tip of south africa and in the southeastern pacific ocean global statistics show distinct genesis and termination regions and global seasonal peak frequency during northern hemisphere late fall winter and southern hemisphere winter in addition the event frequency and geographical location are shown to be modulated by the arctic oscillation pacific north american pattern and the quasi biennial oscillation moreover a positive linear trend in the annual number of objects is reported increasing by 3 58 objects year over year

precursory signals of east asian winter cold anomalies in stratospheric planetary wave pattern the impacts of the stratospheric polar vortex changes on the tropospheric climate variability have been emphasized in previous studies the present study presents evidence for precursory signals of cold anomalies over east asia in the stratospheric wave pattern during november through march the leading two empirical orthogonal function eof modes of daily 50 hpa geopotential height anomalies along 65 n correspond to changes in the amplitude and phase of the stratospheric planetary wavenumber 1 respectively composite analysis is performed to unravel the temporal evolution of anomalies during 8 phases of 34 events identified based on the second eof mode with a complete life cycle for the period 1979 2016 the surface cold anomalies over eastern china emerge in phase 3 corresponding to negative and positive 50 hpa height anomalies on the north atlantic and russian far east sector respectively and peak in phase 5 corresponding to positive 50 hpa height anomalies over eurasia when the siberian high extends southeastward and the east asian trough deepens with anomalous surface northerly winds downward propagation of stratospheric signal is detected over western europe and western siberia the former is a source region of the tropospheric rossby wave trains propagating along the polar front jet and subtropical jet the downward propagation of stratospheric signal is related to the reflection of stratospheric planetary wavenumber 1 pattern and contributes to the development of the tropospheric rossby wave train that in turn leads to the strengthening of the siberian high and the deepening of the east asian trough

interseismic coupling and asperity distribution along the kamchatka subduction zone 1 gps measurements of interseismic horizontal surface velocities reveal the degree of kinematic coupling of the plate boundary thrust along the kamchatka subduction zone from about 51 degrees to 57 degrees n latitude inversions for the distribution of aseismic slip rate along the similar to 15 degrees nw dipping underthrust suggest a nonslipping plate interface in southern kamchatka above similar to 50 km depth along the segment that ruptured in the m w 9 1952 earthquake north of similar to 53 degrees n the subduction interface experiences significant aseismic slip consistent with the lower seismic moment release in m 8 5 earthquakes along this portion of the subduction zone the gps velocities are consistent with a boundary element forward model in which historic earthquake rupture zones are represented as locked asperities surrounded by a zero shear stress subduction interface loaded by plate convergence models in which the complete rupture zones of historic earthquakes are considered locked greatly overpredict the degree of kinematic coupling reducing the area of the locked model asperities to the central 25 area of historic rupture zones fits the data well suggesting that large earthquakes involve small fully locked core asperities surrounded by conditionally stable portions of the plate interface areas of low aseismic slip rate appear to be roughly correlated with areas of low isostatic gravity anomalies over offshore forearc basins while less coupled portions of the kamchatka subduction zone coincide with high gravity anomalies offshore of two peninsulas possibly related to the subduction of the emperor meji seamount chain and the kruzenstern fracture zone

relative contributions of synoptic and intraseasonal variations to strong cold events over eastern china the present study investigates the relative roles of intraseasonal oscillations isos and synoptic variations in strong cold events over eastern china during the boreal winter the isos and synoptic variations explain about 55 and 20 of the total area mean temperature anomaly in eastern china respectively the advection of synoptic winds on synoptic temperature gradients has a leading contribution to the temperature decrease before the cold events and thus the synoptic variations are important in determining the time of peak cold anomalies the isos have a larger role in sustaining the cold events the height anomalies associated with isos and synoptic variations are manifested as rossby wave trains propagating along the polar front jet over the eurasian continent before the cold events they both contribute to the deepening of the east asian trough and the development of cold events compared to the iso wave train the synoptic wave train has a smaller spatial scale and moves faster there are obvious intraseasonal signals in the stratosphere about 1 week before the cold events over eastern china large negative height anomalies associated with the weakening of the polar vortex are observed over the north atlantic these anomalies move eastwards and propagate downwards after reaching the west coast of europe the downward moving stratospheric signal triggers height anomalies in the troposphere over the entrance region of the polar front jet then the anomalies propagate towards east asia along the wave train contributing to the intensification of the siberian high and the east asian trough and the occurrence of cold events over eastern china

recent intensified impact of december arctic oscillation on subsequent january temperature in eurasia and north africa this study reveals an intensified influence of december arctic oscillation ao on the subsequent january surface air temperature sat over eurasia and north africa in recent decades the connection is statistically insignificant during 1957 58 1979 80 p1 which becomes statistically significant during 1989 90 2011 12 p2 the possible causes are further investigated associated with positive december ao during p2 significant anomalous anticyclone emerges over the central north atlantic which is accompanied with significant westerly and easterly anomalies along 45 65 n and 20 40 n respectively this favors the significant influence of december ao on the subsequent january sat and atmospheric circulation over eurasia and north africa via triggering the north atlantic tripole sea surface temperature sst anomaly that persists into the subsequent january by contrast the december ao related anomalous anticyclone during p1 is weak and is characterized by two separate centers located in the eastern and western north atlantic correspondingly the westerly and easterly anomalies over the north atlantic ocean are weak and the related tripole sst anomaly is not well formed unfavorable for the persistent impact of the december ao into the subsequent january further analyses indicate that the different anomalous anticyclone associated with the december ao over the north atlantic may be induced by the strengthened synoptic scale eddy feedbacks over the north atlantic which may be related to the interdecadal intensification of the storm track activity additionally the planetary stationary wave related to the december ao propagates from surface into upper stratosphere at mid latitudes during p2 which further propagates downward to the troposphere and causes anomalous atmospheric circulation in the subsequent january

a new dynamical index for classification of cold surge types over east asia the cold surges over east asia can be classified into wave train type and blocking type according to their dynamic origins in the present study two dynamic indices are proposed to objectively identify cold surge types using potential temperature on the dynamic tropopause at 2 potential vorticity units 2 pvu surface the two indices are designed to represent primary characteristics of the two types of cold surge the wave train index wi is defined as a difference of anomalous on the 2 pvu surface between the western north pacific and northeast china which captures a southward northward intrusion of cold warm air mass related to the trough ridge pattern the blocking index bi is defined as a difference of anomalous between the subarctic region and northeast china which indicates air mass overturning related to a reversal of the usual meridional gradient commonly observed in the occurrence of blocking type cold surge composite analyses based on the distribution of the wi and bi clearly demonstrate the dynamic evolutions of corresponding cold surge types the wave train cold surge is associated with a southeastward expansion of the siberian high and northerly wind near surface which is caused by growing baroclinic waves during the blocking cold surge a geopotential height dipole indicating the subarctic blocking and deepening of east asian coastal trough induces a southward expansion of the siberian high and northeasterly wind compared to the wave train type the blocking cold surge exhibits a longer duration and stronger intensity in the new framework of these dynamic indices we can detect a third type of cold surge when both the wave train and the blocking occur together in addition we can exclude the events that do not have the essential features of the upper tropospheric disturbances or the subarctic anticyclonic circulation which are responsible for cold surge occurrence using the new indices

processes for occurrence of strong cold events over eastern china abstracta strong cold event hit eastern china around 24 january 2016 with surface air temperature reaching more than 10 c below the climatological mean in most regions of eastern china south of 40 n a total of 37 strong cold events similar to the january 2016 event with temperature anomalies over eastern china exceeding 5 c have been identified during the winters from 1979 80 to 2015 16 a comparative analysis of events with surface temperature anomalies of the same intensity but limited to north of 40 n indicates that the southward invasion of cold air to eastern china south of 40 n is related to two factors one is the latitudinal location of the upper level wave train the surface siberian high and the midtropospheric east asian trough over the mid to high latitude eurasian continent the other is a subtropical upper level wave train emanating from the midlatitude north atlantic the emergence of the subtropical wave train is related to the positive phase of the north atlantic oscillation nao wh

relationship between stationary planetary wave activity and the east asian winter monsoon 1 the variability of both the stationary planetary wave activity and the east asian winter monsoon is strongly associated with the thermal contrast between oceans and landmasses in this study we explore the interannual relationship between the monsoon and the wave activity defined by an index of the difference in the divergence of eliassenpalm flux between 50 n at 500 hpa and 40 n at 300 hpa it is found that compared to the winters of low wave activity the equatorward propagation of planetary waves in the middle and upper troposphere is stronger in the high wave activity winters during these high activity winters the upward wave propagation from the troposphere into the stratosphere becomes weaker this is accompanied by a smaller perturbation in the polar vortex which tends to be colder and stronger in the meantime the east asian westerly jet stream the east asian trough the siberian high and the aleutian low all become weaker apparently in particular the weakening of the siberian high and the aleutian low decreases the northeasterly wind over east asia leading to a warming condition in the region especially in northeastern asia a further analysis reveals that the zonal wavenumber 2 pattern of planetary waves contributes dominantly to the variability of the east asian winter monsoon

performance of the cmip5 models in simulating the arctic oscillation during boreal spring this study evaluates the performance of thirty coupled models from the coupled model intercomparison project phase 5 cmip5 in capturing the arctic oscillation ao during boreal spring we focus on model s ability in simulating spring ao s spatial structure dominant temporal frequencies and climatic impacts the anomalous anticyclone over the north pacific and the north atlantic in the positive spring ao phase is much stronger in most of the models than in the observations this may be due to that most models simulate a stronger interannual variability of atmospheric anomalies over the north pacific and north atlantic in addition the center of the anomalous anticyclone over the north pacific in the mme shifts obviously southeastward and that over the north atlantic shift northeastward compared to the observations inter model longitudinal spread is larger than the latitudinal spread in the anomalous anticyclone center over both the north pacific and north atlantic most of the models produce periods longer than the observed 4 year spectral peak in spring ao index in addition the model s ability in reproducing the vertical structure of zonal wind tends to have a close relation with the model s performance in capturing the vertical structure of air temperature related to the spring ao furthermore there exist larger spreads among the models in simulating the spring ao related surface air temperature over the russian far east and the west coast of north america these spreads were partly related to the biases of the models in capturing the atmospheric circulation anomalies related to the pacific center of the spring ao

annular modes in the extratropical circulation part i month to month variability the leading modes of variability of the extratropical circulation in both hemispheres are characterized by deep zonally symmetric or annular structures with geopotential height perturbations of opposing signs in the polar cap region and in the surrounding zonal ring centered near 458 latitude the structure and dynamics of the southern hemisphere sh annular mode have been extensively documented whereas the existence of a northern hemisphere nh mode herein referred to as the arctic oscillation ao has only recently been recognized like the sh mode the ao can be defined as the leading empirical orthogonal function of the sea level pressure field or of the zonally symmetric geopotential height or zonal wind fields in this paper the structure and seasonality of the nh and sh modes are compared based on data from the national centers for environmental prediction national center for atmospheric research reanalysis and supplementary datasets the structures of the nh and sh annular modes are shown to be remarkably similar not only in the zonally averaged geopotential height and zonal wind fields but in the mean meridional circulations as well both exist year round in the troposphere but they amplify with height upward into the stratosphere during those seasons in which the strength of the zonal flow is conducive to strong planetary wave mean flow interaction midwinter in the nh and late spring in the sh during these active seasons the annular modes modulate the strength of the lagrangian mean circulation in the lower stratosphere total column ozone and tropopause height over mid and high latitudes and the strength of the trade winds of their respective hemispheres the nh mode also contains an embedded planetary wave signature with expressions in surface air temperature precipitation total column ozone and tropopause height it is argued that the horizontal temperature advection by the perturbed zonal mean zonal wind field in the lower troposphere is instrumental in forcing this pattern a companion paper documents the striking resemblance between the structure of the annular modes and observed climate trends over the past few decades

an east asian cold surge case study abstract since a cold surge is a hazardous weather phenomenon in east asia the rapid population increase and economic growth over the past two decades require improvement in forecasting cold surges and their related weather events over this region however without a better understanding of these events this task cannot be accomplished a cold surge with a well defined cold front passing through taiwan was selected to illustrate its impact on the east asian weather system this case is typical of a large portion of surges occurring in the region major findings of this study are as follows coupling with the upper ridge trough structures of the wave train straddling the eastern seaboard of northeast asia cold surges occur sequentially a cold front with a prefront high pressure zone is formed by the new surge outflow interacting with the anticyclone of the aging surge the warm moist air advected northeastward along the cold front assists the development of the new surge s low center while the prefron

a strengthened impact of november arctic oscillation on subsequent tropical pacific sea surface temperature variation since the late 1970s the connection between november arctic oscillation ao and the following spring summer tropical pacific sea surface temperature sst experienced a pronounced enhancement around the late 1970s the connection was weak before but strong after the late 1970s the present study investigates the plausible reasons for the connection change after the late 1970s significant anomalous cyclone appears over subtropical north pacific and pronounced anomalous westerly winds occur over tropical western pacific in the positive phase of november ao as such november ao could exert a significant influence on the subsequent spring summer tropical pacific sst variation by contrast before the late 1970s anomalous cyclone and associated anomalous westerly winds to its south are weak and shift northward thereby the connection between november ao and tropical pacific sst is weak further analyses suggest that the interdecadal change in the anomalous cyclone over the subtropical north pacific may be related to the change in the november ao s pacific component and the strength of feedback of synoptic scale eddy to mean flow specifically after the late 1970s november ao s pacific component displays a zonally elongated structure which is favorable for the formation of easterly wind anomalies over the mid latitude north pacific and related wave mean flow interaction in addition feedback of synoptic eddy to mean flow is enhanced after the late 1970s which is partly related to the intensification of the north pacific storm track this may also contribute to enhancement of the anomalous cyclone over the subtropical pacific

earthquake recurrence and magnitude and seismic deformation of the northwestern okhotsk plate northeast russia 1 recorded seismicity from the northwestern okhotsk plate northeast asia is currently insufficient to account for the predicted slip rates along its boundaries due to plate tectonics however the magnitude frequency relationship for earthquakes from the region suggests that larger earthquakes are possible in the future and that events of mw 7 5 which should occur every 100 350 years would account for almost all the slip of the plate along its boundaries due to eurasia north america convergence we use models for seismic slip distribution along the bounding faults of okhotsk to conclude that relatively little aseismic strain release is occurring and that larger future earthquakes are likely in the region our models broadly support the idea of a single okhotsk plate with the large majority of tectonic strain released along its boundaries

dominant modes of interannual variability in eurasian surface air temperature during boreal spring abstractthis study investigates interannual variations of surface air temperature sat over mid and high latitudes of eurasia during boreal spring and their association with snow atmospheric circulation and sea surface temperature sst changes the leading mode of spring sat variations is featured by same sign anomalies over most regions the second mode features a tripole anomaly pattern with anomalies over the central part opposite to those over the eastern and western parts of eurasia a diagnosis of surface heat flux anomalies suggests that snow change contributes partly to sat anomalies in several regions mainly by modulating surface shortwave radiation but cannot explain sat changes in other regions atmospheric circulation anomalies play an important role in spring sat variability via wind induced heat advection and cloud induced surface radiation changes positive sat anomalies are associated with anomalous westerly winds from the north atlantic ocean or with anomalous anticyclone and souther

observed interannual oscillations of planetary wave forcing in the northern hemisphere winter 1 using ncep ncar reanalysis data from 1958 to 1998 two interannual oscillations in the eddy forcing due to planetary waves wavenumbers 1 3 are found in the northern hemisphere winter called as the stratospheric interannual oscillation sio and the tropospheric interannual oscillation tio the temporal evolutions are different between the sio and the tio suggesting different dynamic mechanisms the planetary waves tend to be bent equatorward in the troposphere during a positive tio phase and in the mid and upper stratosphere during a positive sio phase the result also suggests that upward propagation of planetary waves into the polar waveguide across the tropopause is closely associated with the tio further regression and correlation analyses suggest that the tio is closely linked to the northern annular mode nam whereas the sio is closely associated with the el nino southern oscillation enso

phase asymmetric downstream development of the north atlantic oscillation and its impact on the east asian winter monsoon 1 the phase asymmetry in a downstream pattern of the north atlantic oscillation nao is examined during boreal winter time we compared the downstream anomaly patterns associated with the positive and negative persistent nao events over several days both phases of the persistent nao events accompany quasi stationary wave trains in downstream upper levels however a distinct low level anomaly appears only for the negative persistent nao events the low level anomaly migrates eastward as a surface anticyclone that is confined to the low troposphere a few days later the surface anticyclone reaches central siberia and induces cold advection over east asia therefore the phase dependent downstream development of the nao expands the impact of the nao to the east asian region we also discuss the possible interaction between the upper and lower level anomalies a necessary condition for the amplification of the siberian high

can the okhotsk plate be discriminated from the north american plate the plate geometry in northeast asia has been a long standing question with a major issue being whether the sea of okhotsk and northern japanese islands are better regarded as part of the north american plate or as a separate okhotsk plate this question has been difficult to resolve because earthquake slip vectors along the kuril and japan trenches are consistent with either pacific north america or pacific okhotsk plate motion to circumvent this difficulty we also use slip vectors of earthquakes along sakhalin island and the eastern margin of the japan sea and compare them to the predicted eurasia okhotsk and eurasia north america motions for a model with a separate okhotsk plate we invert 10 eurasia okhotsk and 255 pacific okhotsk slip vectors with pacific north america and eurasia north america nuvel 1 data alternatively for a model without an okhotsk plate those eurasia okhotsk and pacific okhotsk data are regarded as eurasia north america and pacific north america data respectively the model with an okhotsk plate fits the data better than one in which this region is treated as part of the north american plate because the improved fit exceeds that expected purely from the additional plate the data indicate that the okhotsk plate can be resolved from the north american plate the motions on the okhotsk plate s boundaries predicted by the best fitting euler vectors are generally consistent with the recent tectonics the eurasia okhotsk pole is located at northernmost sakhalin island and predicts right lateral strike slip motion on the nne striking fault plane of the may 27 1995 neftegorsk earthquake consistent with the centroid moment tensor focal mechanism and the surface faulting along the northern boundary of the okhotsk plate the north america okhotsk euler vector predicts left lateral strike slip consistent with the observed focal mechanisms on the nw boundary of the okhotsk plate the eurasia okhotsk euler vector predicts e w extension discordant with the limited focal mechanisms and geological data this misfit may imply that another plate is necessary west of the magadan region in southeast siberia but this possibility is hard to confirm without further data such as might be obtained from space based geodesy

relationship between the arctic oscillation and cold surges over east asia abstract the present study reveals the changes in the characteristics of cold surges over east asia associated with the arctic oscillation ao based on circulation features cold surges are grouped into two general types wave train and blocking types the blocking type of cold surge tends to occur during negative ao periods that is the ao related polarity of the blocking type however the wave train type is observed during both positive and negative ao periods although the wave train features associated with negative ao are relatively weaker the cold surges during negative ao are stronger than those during positive ao in terms of both amplitude and duration the cold surges during positive ao in which the extent of effect is confined to inland china passes through east asia quickly because of weaker siberian high and aleutian low leading to short duration of these cold surges in contrast the cold surge during negative ao characterized by a well organized anticyclone cyclone couplet with high p

influence of the madden julian oscillation on wintertime surface air temperature and cold surges in east asia 1 the variations of wintertime surface air temperature sat and the occurrences of cold surges over east asia in association with the madden and julian oscillation mjo are examined the mjo is defined as a combination of the two leading empirical orthogonal function modes of 850 and 200 hpa zonal winds and outgoing longwave radiation in the tropics the spatial pattern and magnitude of sat anomalies over east asia significantly change with respect to mjo phases composite analysis reveals that the mjo sat relationship is mainly affected by strong temperature advection in the lower troposphere in addition occurrences of cold surges are identified using objectively determined synoptic criteria and their relation to the mjo is analyzed most extreme cold surges occur when the mjo convection center is located over the indian ocean and it is suggested that mjo induced circulation anomalies may reinforce the amplification of normal cold surges to extreme cold surges

propagation of the arctic oscillation from the stratosphere to the troposphere geopotential anomalies ranging from the earth s surface to the middle stratosphere in the northern hemisphere are dominated by a mode of variability known as the arctic oscillation ao the ao is represented herein by the leading mode the first empirical orthogonal function of low frequency variability of wintertime geopotential between 1000 and 10 hpa in the middle stratosphere the signature of the ao is a nearly zonally symmetric pattern representing a strong or weak polar vortex at 1000 hpa the ao is similar to the north atlantic oscillation but with more zonal symmetry especially at high latitudes in zonal mean zonal wind the ao is seen as a north south dipole centered on 40 45 n in zonal mean temperature it is seen as a deep warm or cold polar anomaly from the upper troposphere to 10 hpa the association of the ao pattern in the troposphere with modulation of the strength of the stratospheric polar vortex provides perhaps the best measure of coupling between the stratosphere and the troposphere by examining separately time series of ao signatures at tropospheric and stratospheric levels it is shown that ao anomalies typically appear first in the stratosphere and propagate downward the midwinter correlation between the 90 day low pass filtered 10 hpa anomaly and the 1000 hpa anomaly exceeds 0 65 when the surface anomaly time series is lagged by about three weeks the tropospheric signature of the ao anomaly is characterized by substantial changes to the storm tracks and strength of the midtropospheric flow especially over the north atlantic and europe the implications of large stratospheric anomalies as precursors to changes in tropospheric weather patterns are discussed

interannual variations of the dominant modes of east asian winter monsoon and possible links to arctic sea ice two dominant modes of the winter temperature over east asia a northern mode and a southern mode and their links with arctic climate conditions are analyzed the relationships of the two modes with arctic sea ice are different the northern mode is closely linked to variations in sea ice of the arctic barents laptev sea in previous autumn and most of the arctic in concurrent winter the southern mode seems independent from the arctic sea ice variations but is associated with sea surface temperature sst anomalies in the equatorial central eastern pacific results suggest an effect of arctic sea ice variation on the northern mode and an influence of tropical sst anomalies on the southern mode reduced sea ice over the arctic increases 1000 500 hpa thickness over the high latitudes of eurasian continent which reduces the meridional thickness gradient between the middle and high latitudes and thus weakens the extratropical upper level zonal wind the weakened zonal wind provides a favorable dynamic condition for the development of a high latitude ridge around the ural mountain reduced arctic sea ice also tends to enhance the siberian high through both thermodynamic and dynamic processes the above atmospheric circulation patterns provide a favorable condition for the intrusion of cold air to northern east asia

impacts of early autumn arctic sea ice concentration on subsequent spring eurasian surface air temperature variations this study reveals a close relation between autumn arctic sea ice change sic in the laptev sea eastern siberian sea beaufort sea and subsequent spring eurasian surface air temperature sat variation specifically more less sic over the above regions in early autumn generally correspond to sat warming cooling over the mid high latitudes of eurasia during subsequent spring early autumn arctic sic affects spring eurasian sat via modulating spring arctic oscillation ao associated atmospheric changes the meridional temperature gradient over the mid high latitudes decreases following the arctic sea ice loss this results in deceleration of prevailing westerly winds over the mid latitudes of the troposphere which leads to increase in the upward propagation of planetary waves and associated eliassen palm flux convergence in the stratosphere over the mid high latitudes thereby westerly winds in the stratosphere are reduced and the polar vortex is weakened through the wave mean flow interaction and downward propagation of zonal wind anomalies a negative spring ao pattern is formed in the troposphere which favors sat cooling over eurasia the observed autumn arctic sic spring eurasian sat connection is reproduced in the historical simulation 1850 2005 of the flexible global ocean atmosphere land system model spectral version 2 fgoals s2 the fgoals s2 also simulates the close connection between autumn sic and subsequent spring ao further analysis suggests that the prediction skill of the spring eurasian sat was enhanced when taking the autumn arctic sic signal into account

combined effects of the mjo and the arctic oscillation on the intraseasonal eastern china winter temperature variations abstractthe present study reveals that the madden julian oscillation mjo related temperature anomalies over east asia have notable differences among positive neutral and negative arctic oscilla

independent active microplate tectonics of northeast asia from gps velocities and block modeling 1 independent okhotsk and amurian microplate motions are tested using velocities from 123 gps sites 80 from within the proposed okh and amu plate boundaries used to constrain the plate kinematics of northeast asia a block modeling approach is used to incorporate both rigid block rotation and near boundary elastic strain accumulation effects in a formal inversion of the gps velocities models include scenarios with and without independent okh and amu plate motion our modeling favors scenarios with independent okh and amu motion based on the application of f test statistics the independent okh plate rotates 0 231 deg myr clockwise with respect to north america about a pole located north of sakhalin the modeled amu plate rotates 0 298 deg myr counterclockwise with respect to nam about a pole located west of the magadan region the plate motion parameters of the independent plates are consistent with the kinematics inferred from earthquake focal mechanism solutions along their boundaries

the association between stratospheric weak polar vortex events and cold air outbreaks in the northern hemisphere previous studies have identified an association between temperature anomalies in the northern hemisphere and the strength of stratospheric polar westerlies large regions in northern asia europe and north america have been found to cool during the mature and late stages of weak vortex events in the stratosphere a substantial part of the temperature changes are associated with changes in the northern annular mode nam and north atlantic oscillation nao pressure patterns in the troposphere the apparent coupling between the stratosphere and the troposphere may be of relevance for weather forecasting but only if the temporal and spatial nature of the coupling is known using 51 winters of re analysis data we show that the development of the lower tropospheric temperature relative to stratospheric weak polar vortex events goes through a series of well defined stages including the formation of geographically distinct cold air outbreaks at the inception of weak vortex events a precursor signal in the form of a strong high pressure anomaly over northwest eurasia is associated with long lived and robust cold anomalies over asia and europe a few weeks later near the mature stage of the weak vortex events a shorter lived cold anomaly emerges off the east coast of north america the probability of cold air outbreaks increases by more than 50 in one or more of these regions during all phases of the weak vortex events this shows that the stratospheric polar vortex contains information that can be used to enhance forecasts of cold air outbreaks as large changes in the frequency of extremes are involved this process is important for the medium range and seasonal prediction of extreme cold winter days three hundred year pre industrial control simulations by 13 coupled climate models corroborate our results copyright 2010 royal meteorological society and crown copyright

contrasting impacts of the arctic oscillation on surface air temperature anomalies in southern china between early and middle to late winter abstractin the boreal winter the arctic oscillation ao evidently acts to influence surface air temperature sat anomalies in china this study reveals a large intraseasonal variation in the relationship between the winter ao and southern china sat anomalies specifically a weak in phase relationship occurs in december but a significant out of phase relationship occurs in january and february the authors show that the linkage between the ao and southern china sat anomalies strongly depends on the ao associated changes in the middle east jet stream mejs and that such an ao mejs relationship is characterized by a significant difference between early and middle to late winter in middle to late winter the azores center of high pressure anomalies in the positive ao phase usually extends eastward and yields a significantly anomalous upper level convergence over the mediterranean sea which can excite a rossby wave train spanning the arabian sea and intensify the mejs in early winter however the azo

the relationship between the north atlantic jet and tropical convection over the indian and western pacific oceans abstractboreal winter jet variability over the north atlantic is investigated using 40 yr european centre for medium range weather forecasts re analysis era 40 data where the variability is defined by the first eof of the zonal wind on seven vertical levels the principal component time series of this eof is referred to as the jet index a pattern correlation analysis indicates that the jet index more accurately describes intraseasonal north atlantic zonal wind variability than does the north atlantic oscillation nao a series of composite calculations of the jet index based on events of intraseasonal convective precipitation over the tropical indian and western pacific oceans reveals the following statistically significant relationships 1 negative jet events lead enhanced indian ocean precipitation 2 positive jet events lag enhanced indian ocean precipitation 3 positive jet events lead enhanced western pacific ocean precipitation and 4 negative jet events lag enhanced western pacific ocean p

the melting arctic and midlatitude weather patterns are they connected abstractthe potential of recent arctic changes to influence hemispheric weather is a complex and controversial topic with considerable uncertainty as time series of potential linkages are short 10 yr and understanding involves the relative contribution of direct forcing by arctic changes on a chaotic climatic system a way forward is through further investigation of atmospheric dynamic mechanisms during several exceptionally warm arctic winters since 2007 sea ice loss in the barents and kara seas initiated eastward propagating wave trains of high and low pressure anomalous high pressure east of the ural mountains advected arctic air over central and eastern asia resulting in persistent cold spells blocking near greenland related to low level temperature anomalies led to northerly flow into eastern north america inducing persistent cold periods potential arctic connections in europe are less clear variability in the north pacific can reinforce downstream arctic changes and arctic amplification

the influence of boreal spring arctic oscillation on the subsequent winter enso in cmip5 models this study examines the influence of boreal spring arctic oscillation ao on the subsequent winter el nino southern oscillation enso using 15 climate model outputs from the coupled model intercomparison project phase 5 cmip5 results show that out of the 15 cmip5 models ccsm4 and cnrm cm5 can well reproduce the significant ao enso connection these two models capture the observed spring ao related anomalous cyclone anticyclone over the subtropical western central north pacific and westerly easterly winds over the tropical western central pacific in contrast the spring ao related anomalous circulation over the subtropical north pacific is insignificant in the other 13 models and the simulations in these models cannot capture the significant influence of the spring ao on enso further analyses indicate that the performance of the cmip5 simulations in reproducing the ao enso connection is related to the ability in simulating the spring north pacific synoptic eddy intensity and the spring ao s pacific component strong synoptic scale eddy intensity results in a strong synoptic eddy feedback on the mean flow leading to strong cyclonic circulation anomalies over the subtropical north pacific which contributes to a significant ao enso connection in addition a strong spring ao s pacific component and associated easterly wind anomalies to its south may provide more favorable conditions for the development of spring ao related cyclonic circulation anomalies over the subtropical north pacific

an integrated global model of present day plate motions and plate boundary deformation summary in this paper we present a global model gsrm 1 of both horizontal velocities on the earth s surface and horizontal strain rates for almost all deforming plate boundary zones a model strain rate field is obtained jointly with a global velocity field in the process of solving for a global velocity gradient tensor field in our model we perform a least squares fit between model velocities and observed geodetic velocities as well as between model strain rates and observed geological strain rates model velocities and strain rates are interpolated over a spherical earth using bi cubic bessel splines we include 3000 geodetic velocities from 50 different mostly published studies geological strain rates are obtained for central asia only and they are inferred from quaternary fault slip rates for all areas where no geological information is included a priori constraints are placed on the style and direction but not magnitude of the model strain rate field these constraints are taken from a seismic strain rate field inferred from normalized focal mechanisms of shallow earthquakes we present a global solution of the second invariant of the model strain rate field as well as strain rate solutions for a few selected plate boundary zones generally the strain rate tensor field is consistent with geological and seismological data with the assumption of plate rigidity for all areas other than the plate boundary zones we also present relative angular velocities for most plate pairs we find that in general there is a good agreement between the present day plate motions we obtain and longterm plate motions but a few significant differences exist the rotation rates for the indian arabian and nubian plates relative to eurasia are 30 13 and 50 per cent slower than the nuvel1a estimate respectively and the rotation rate for the nazca plate relative to south america is 17 per cent slower on the other hand caribbean north america motion is 76 per cent faster than the nuvel 1a estimate while crustal blocks in the india eurasia collision zone move significantly and self consistently with respect to bounding plates only a very small motion is predicted between the nubian and somalian plates by integrating plate boundary zone deformation with the traditional modelling of angular velocities of rigid plates we have obtained a model that has already been proven valuable in for instance redefining a no net rotation model of surface motions and by confirming a global correlation between seismicity rates and tectonic moment rates along subduction zones and within zones of continental deformation

relationship between ural siberian blocking and the east asian winter monsoon in relation to the arctic oscillation and the el nino southern oscillation this study attempts to assess the possible linkage between ural siberian blocking and the east asian winter monsoon eawm during the boreal winter the dominance of blocking thermally enhances cold advection downstream the frequent occurrence of ural siberian blocking potentially promotes a cold eawm and vice versa the seasonal blocking activity can be regarded as the combined effect of the arctic oscillation ao and the el nino southern oscillation enso weakened strengthened meridional flow in the positive negative phase of the ao is unfavorable favorable for the formation of blocking highs because the ao shows a close relationship with the north atlantic oscillation nao its teleconnection with ural siberian blocking may exist in the form of an eastward propagating wave train be that as it may the wave train signal across east asia may be disturbed by the external effect of a strong enso event which probably enhances weakens the westerlies near siberia in its warm cold phase consequently the blocking eawm relationship is stronger weaker when the ao and enso are in phase out of phase if both ao and enso attain the positive negative phase the siberian high tends to be weaker stronger and the temperature tends to be higher lower in east asia with less more ural siberian blocking on the other hand if they are out of phase they are not strongly linked to the intensity of the siberian high and the blocking activity over ural siberia is unclear

a synoptic and dynamical characterization of wave train and blocking cold surge over east asia through an agglomerative hierarchical clustering method cold surges over east asia are classified into two distinct types based on the spatial pattern of the geopotential height anomalies at 300 hpa one is the wave train type that is associated with developing large scale waves across the eurasian continent the other is the blocking type whose occurrence accompanies subarctic blocking during the wave train cold surge growing baroclinic waves induce a southeastward expansion of the siberian high and strong northerly winds over east asia blocking cold surge on the other hand is associated with a southward expansion of the siberian high and northeasterly winds inherent to a height dipole consisting of the subarctic blocking and the east asian coastal trough the blocking cold surge tends to be more intense and last longer compared to the wave train type the wave train cold surge is associated with the formation of a negative upper tropospheric height anomaly southeast of greenland approximately 12 days before the surge occurrence further analysis of isentropic potential vorticity reveals that this height anomaly could originate from the lower stratosphere over the north atlantic cold surge of the blocking type occurs with an amplifying positive geopotential and a negative potential vorticity anomaly over the arctic and the northern eurasia in stratosphere these anomalies resemble the stratospheric signature of a negative phase of the arctic oscillation this stratospheric feature is further demonstrated by the observation that the blocking type cold surge occurs more often when the arctic oscillation is in its negative phase

decadal relationship between the north atlantic oscillation and cold surge frequency in taiwan 1 the close decadal relationship between the north atlantic oscillation nao and the cold surge frequency in northern taiwan is identified the cold surge frequency was higher lower in 1957 1977 1981 2001 which corresponded to the negative positive phase of the nao the teleconnection pattern associated with the nao suggests that the siberian high the ridge upstream of lake baikal and the east asian trough which are well known circulation characteristics favorable for cold surge occurrences were enhanced in the negative nao phase a weakened upper level convergence over the mediterranean sahara occurring in the negative nao phase was associated with a wave like pattern spreading toward east asia along the subtropical jet stream barotropic modeling results suggest that the suppressed upper level convergence in the mediterranean sahara region may force a wave train emanating toward east asia along the subtropical jet stream which acts as a rossby waveguide the barotropic wave pattern may result in a stronger low level northerly over subtropical east asia and create a favorable background for the further southward penetration of cold air and therefore more frequent cold surge occurrence the same process may be applied to the period when the nao is in the positive phase

tethyan collision forces and the stress field of the eurasian plate resistive forces along convergent plate boundaries have a major impact on surface deformation most visibly at collisional plate boundaries although quantification of these forces is key to understanding the evolution and present state of mountain belts they remain highly uncertain due to the complexity of plate boundary structures and rheologies in previous studies of the eurasian plate we have analysed the balance of plate boundary forces tractions resulting from lithosphere mantle coupling and intraplate variations in topography and density structure this yielded a range of acceptable force distributions in this study we investigate to which extent the observed present day stress field provides further constraints on the distribution of forces we address the dynamics of the eurasian plate as a whole this enables us to base our analysis on mechanical equilibrium of a tectonic plate and to evaluate all forces as part of an internally consistent set of forces driving and deforming eurasia we incorporate tractions from convective mantle flow modelling in a lithospheric model in which edge and lithospheric body forces are modelled explicitly and compute resulting stresses in a homogeneous elastic thin shell intraplate stress observations used are from the world stress map project eurasia s stress field turns out to be particularly sensitive to the distribution of collision forces on the plate s southern margin and to a much lesser extent to lithospheric density structure and tractions from mantle flow stress observations require collision forces on the india eurasia boundary of 7 0 10 5 tn m 1 and on the arabia eurasia boundary of 1 3 2 7 tn m 1 implication of mechanical equilibrium of the plate is that forces on the contacts with the african and australian plates amount to 1 0 2 5 and 0 1 3 tn m 1 respectively we use our results to assess the validity of the classical view that the mean elevation of an orogenic plateau can be taken as a measure of the magnitude of the compressive in this case collision related forces involved for both the tibetan and the iranian plateaus two plateaus with significantly different average elevations we find that the horizontal force derived from the excess gravitational potential energy collapse force is in balance with the collision force

interannual variation of the east asian cold surge activity abstract the occurrence frequency of the east asian cold surge exhibits an interannual variation in concert with the el nino southern oscillation enso cycle that is the cold surge occurs more less frequently during warm cold enso winters because the cold surge high low dipoles are coupled with the upper level synoptic short waves any mechanism modulating the activity of these waves would affect the cold surge activity the streamfunction budget analysis in the short wave regime indicates that the development of the cold surge short wave train over east asia and the northwest pacific is modulated by the north pacific enso short wave train due to the coupling between the upper level cold surge short wave train and the surface cold surge dipole it is inferred from this streamfunction budget analysis that the interannual variation of the cold surge occurrence frequency is a result of this modulation

the signature of the annular modes in the tropical troposphere the extratropical annular modes are coupled with a distinct pattern of climate anomalies that spans the circulation of the tropical troposphere the signature of the annular modes in the tropical troposphere exhibits a high degree of equatorial symmetry it is associated with upper tropospheric zonal wind anomalies centered about the equator midtropospheric temperature anomalies located 208n and 208s and opposing mean meridional circulation anomalies that span the subtropics of both hemispheres the linkages between the annular modes and the tropical circulation are only evident during the cold season months and are most robust in association with the northern hemisphere annular mode nam the coupling between the annular modes and the circulation of the tropical troposphere is consistent with forcing by waves originating at extratropical latitudes both annular modes are characterized by anomalies in the eddy momentum flux convergence at tropical latitudes that act to reinforce the changes in the tropical wind and temperature fields the most pronounced tropical anomalies lag indices of the annular modes by 2 weeks and are found over the eastern tropical pacific where climatological westerlies permit extratropical waves to propagate into the deep tropics the linkages between the nam and the tropical tropospheric circulation are

an analysis of the large scale climate anomalies associated with the snowstorms affecting china in january 2008 abstract extraordinarily frequent and long lasting snowstorms affected china in january 2008 causing above normal precipitation below normal temperature and severe icing conditions over central southern china these snowstorms were closely linked to the change in the middle east jet stream mejs which intensified and shifted southeastward the change in mejs was accompanied by southeastward shifts of the ridge and the trough over europe and western asia the intensified mejs also strengthened the trough embedded in the southern branch of the subtropical westerlies over the southern tibetan plateau enhancing the water vapor transport from western asia and the bay of bengal to china in the meantime the subtropical western pacific high swph was stronger and its ridgeline was farther north than normal the anomalous high slowed down the eastward propagation of weather systems to the pacific and favored convergence of water vapor over central southern china the mejs is usually strong when the arctic

hydrothermal rare earth element xenotime mineralization at maw zone athabasca basin canada and its relationship to unconformity related uranium deposits a discussion

current deformation rates and extrusion of the northwestern okhotsk plate northeast russia 1 northeast asia is a region of broad deformation resulting from the convergence of the eurasian eu and north american na plates part of this convergence has been suggested to be relieved by the extrusion and deformation of the okhotsk plate ok three models for the deformation of the seismically active northwestern corner of the okhotsk plate based on different modes of deformation partitioning are calculated and compared to observations from gps seismicity and geology the results suggest that this region is being extruded southeastward and deforming internally by a mixture of pure contraction smooth extrusion and rigid extrusion calculated extrusion rates are 3 5 5 mm yr comparable to estimates from geologic data and internal deformation rates are 3 0 10 9 yr 1 internal deformation may be only partially accommodated by seismicity but the short time span of seismic data leaves this subject to large uncertainty

spring arctic oscillation east asian summer monsoon connection through circulation changes over the western north pacific in the present study the links between spring arctic oscillation ao and east asian summer monsoon easm was investigated with focus on the importance of the north pacific atmospheric circulation and sea surface temperature sst to reduce the statistical uncertainty we analyzed high pass filtered data with the inter annual time scales and excluded the el nino southern oscillation signals in the climate fields using a linear fitting method the significant relationship between spring ao and easm are supported by the changes of multi monsoon components including monsoon indices precipitation and three dimensional atmospheric circulations following a stronger positive spring ao an anomalous cyclonic circulation at 850 hpa appears in southeastern asia and the western north pacific in summer with the easterly anomalies spanning from the pacific to asian continent along 25 n 30 n and the westerly anomalies south of 15 n at the same time the summer western north pacific subtropical high becomes weaker consistently the positive precipitation anomalies are developed over a broad region south of 30 n stretching from southern china to the western pacific and the negative precipitation anomalies appear in the lower valley of the yangtze river and southern japan the anomalous cyclone in the western north pacific persisting from spring to summer plays a key role in modulating easm and monsoon precipitation by a positive air sea feedback mechanism during spring the ao associated atmospheric circulation change produces warmer ssts between 150 e 180 near the equator the anomalous sensible and latent heating in turn intensifies the cyclone through a gill type response of the atmosphere through this positive feedback the tropical atmosphere and sst patterns sustain their strength from spring to summer that consequently modifies the monsoon trough and the western north pacific subtropical high and eventually the easm precipitation moreover the sst response to ao circulation is supported by the numerical simulations of an ocean model and the anomalous atmospheric circulation over the western north pacific is also reproduced by the dedicated numerical simulations using the coupled atmosphere ocean model the observation evidence and numerical simulations suggest the spring ao can impact the easm via triggering tropical air sea feedback over the western north pacific

the leading interannual variability modes of winter surface air temperature over southeast asia the present study analyzes the leading interannual variability modes of southeast asian surface air temperature sat during boreal winter the first empirical orthogonal function eof1 mode displays same sign sat anomalies over southeast asia with a center around the north indo china peninsula and south china the second eof eof2 shows a dipole sat anomaly pattern between the indo china peninsula and south china surface heat flux change may not be able to explain sat variation related to the eof1 but explain partly the sat change associated with the eof2 atmospheric anomalies play a crucial role in the sat variations via wind induced temperature advection specifically for the eof1 marked northerly anomalies appear over the southeast asia which bring colder air from higher latitude and contribute to negative sat anomalies change in the intensity of arctic oscillation siberian high and la nina like sea surface temperature sst anomalies over the tropical central eastern pacific play a key role in forming the northerly anomalies related to the eof1 for the eof2 at the lower troposphere a pair of anomalous cyclones appears over the tropical north and south indian ocean together with southwesterly wind anomalies extending from the indian ocean to the indo china peninsula which favor positive sat anomalies there formation of the twin cyclones is likely to be a gill type rossby wave response of the tropical indian ocean sst warming at the upper troposphere two wave trains one originated from the arctic region and another from the mediterranean sea contribute collectively to the atmospheric circulation anomalies over southeast asia related to the eof2

widespread fog over the indo gangetic plains and possible links to boreal winter teleconnections boreal wintertime planetary scale atmospheric circulations and their possible consequences to widespread fog occurrences over the indo gangetic plains igp region of the himalayan valley are investigated in this study among the different fog types radiation fog type seen at night or early morning hours favored by large scale subsidence aloft and strong near surface inversion is focused in this study a composite analysis reveals that upper air circulation associated with 105 fog days over the igp region show a trail linked to circulation anomalies over the eurasian continents and the arctic circle the findings suggest that there is a footprint of the arctic oscillation ao and conventional eurasian eu circulation patterns linked to anticyclonic circulation aloft over the igp region although widespread igp fog occurrences under the large scale subsidence environment are seen to occur during both phases of ao the negative ao phase high pressure environment over the arctic circle portends a greater likelihood for fog occurrences in the igp region a coupling of positive mid tropospheric height anomalies over western eurasia and the anticyclonic circulation anomalies over the igp region is evident during the igp fog periods concomitant with eu positive height excess over siberia phase further anomalous circulation over the igp region during the fog periods appears to rely more on the strength of the ao negative phase than the circulation strengths over eurasia on the contrary the eurasian circulation largely appears to influence the subsidence aloft over the igp region irrespective of the strength of the ao positive phase it is also noted that upper air circulation during non foggy periods over the igp region has conformity with positive ao phase and rapidly progressing eu pattern these planetary scale teleconnection pathways offer new dynamical insights into comprehending widespread igp fog scenario which have been hitherto perceived mostly from a regional context

clearing observed pgr in grace data aimed at global viscosity inversion weighted mass trends technique 1 the time variable gravity field shows the effects of large present day mass variations associated with hydrological phenomena and melting ice sheets resulting in a shaded post glacial rebound pgr signal a meaningful viscosity inversion based on a global scale comparison of grace data and pgr predictions is thus hard to obtain we derive a weighted surface mass distribution in water equivalent starting from an initial guess which portrays the secular effects of present day phenomena the gravity field it generates is then carefully removed from grace data resulting in a gravity pattern where the effects of pgr are clearer and ready to be compared with the predictions on the basis of viscoelastic stratified earth models and different pleistocene deglaciation models we show that the quality of a global preliminary viscosity inversion greatly improves

interannual variability of the east asian winter monsoon and related modulations of the planetary waves abstractinterannual variability of the east asian winter monsoon is investigated through composite analysis applied to observational data for 50 recent years although the monsoon activity itself is confined into the lower troposphere its midwinter variability tends to accompany upper tropospheric geopotential height anomalies similar to the eurasian eu and western pacific wp teleconnection patterns the eu like pattern is characterized by a wavy signature over the eurasian continent and the north atlantic with surface temperature anomalies over the far east and north america in the wp like pattern a meridional dipole of upper level height anomalies is evident over the far east these anomaly patterns related to the anomalous winter monsoon activity are found to accompany marked modulations of the climatological development of the upper tropospheric planetary waves from late autumn to midwinter enhanced monsoon activity in january associated with the wp like pattern involves anomalous seasonal

interdecadal variation of winter cold surge path in east asia and its relationship with arctic sea ice abstractthe paths of winter cold surge cs events in east asia ea from 1979 to 2017 are tracked by the flexible particle flexpart model using era interim daily datasets and the probability de

comparison of the synoptic conditions in midlatitudes accompanying cold surges over eastern asia for the months of december 1974 and 1978 part i monthly mean fields and individual events abstract east asian cold surges during two periods of contrasting intensity december 1974 strong and december 1978 weak are studied it is shown that the midlatitude mechanisms initiating cold surges during both months are quite similar in nature synoptic scale short waves passing through the long wave trough position near the east asian coast act to release the cold air southward from the main reservoir over eastern siberia dynamic descent is initiated by these synoptic scale waves entering the northwesterly flow on the western side of the long wave trough anchored on the coast this is the descent center in the local direct circulation in the entrance region of the east asian jet maximum at 200 mb the frequency and intensity of the cold air surges for a given month depend on the large scale circulation pattern the average flow over asia for december 1974 and 1978 presents a contrast with respect to ridging over the midcontinent in december 1978 the flow was characterized by a low zonal inde

meridional displacement of the east asian trough and its response to the enso forcing this paper examined the underlying dynamic mechanisms associated with the meridional displacement of the east asian trough eat which is closely related to the temperature variability in the southern part of east asian winter monsoon eawm during the southward displacement of the eat the siberian high is stronger and the aleutian low is displaced southward this is due mainly to the anomalous cyclonic flow associated with seasonal eddies over the midlatitude central pacific which enhances the horizontal advection of cold warm air to the southern northern part of the eat in the lower troposphere the cold warm advection narrows thickens the height thickness and results in negative positive temperature anomalies in the southern northern part of the eat these anomalous circulation features can be reasonably explained by the phase of the el nino southern oscillation enso the results are also verified by the numerical experiments with prescribing enso like heat source anomalies over the tropical eastern and western pacific in an anomaly atmospheric general circulation model all of these results advance our understanding for the linkage between the enso and the eawm via its modulation of the eat

on the link between the subseasonal evolution of the north atlantic oscillation and east asian climate we analyse the impact of the north atlantic oscillation nao on the climate of east asia at subseasonal time scales during both winter and summer these teleconections have mainly been investigated at seasonal and longer time scales while higher frequency links are largely unexplored the nao is defined using extended empirical orthogonal functions on pentad mean observations which allows to elucidate the oscillation s spatial and temporal evolution and clearly separate the development and decay phases the downstream dynamical imprint and associated temperature and precipitation anomalies are quantified by means of a linear regression analysis it is shown that the nao generates a significant climate response over east asia during both the dry and wet seasons whose spatial pattern is highly dependent on the phase of the nao s life cycle temperature and precipitation anomalies develop concurrently with the nao mature phase and reach maximum amplitude 5 10 days later these are shown to be systematically related to mid and high latitude teleconnections across the eurasian continent via eastward propagating quasi stationary rossby waves instigated over the atlantic and terminating in the northeastern pacific these findings underscore the importance of rapidly evolving dynamical processes in governing the nao s downstream impacts and teleconnections with east asia

persistent severe drought in southern china during winter spring 2011 large scale circulation patterns and possible impacting factors 1 severe drought persisted in southern china from january to may in 2011 in this study a statistical analysis is carried out to discuss the multiple possible impacting factors including la nina the north atlantic oscillation nao and the thermal condition of the tibetan plateau tp the la nina event in 2010 11 excited a lower tropospheric anomalous cyclone over the northwestern pacific weakening the northwestern pacific subtropical high and caused an eastward shift of the high as a result transportation of wet and warm moisture from tropical oceans to southern china decreased the la nina event also strengthened the upper tropospheric east asian jet stream and deepened the east asian trough favoring a southward intrusion of dry northerly flow from the siberia the la nina condition in the previous two seasons also seemed to provide precursory signals for the drought moreover in january may 2011 the nao was in a positive phase and it tended to excite stationary rossby waves that were distributed along the sub polar and subtropical waveguides respectively the sub polar one induced an anomalous anticyclone over the siberia favoring a southward intrusion of high latitude northerly flow to southern china the subtropical one associated possibly with the enhanced convection over the broad region from the mediterranean to sahara was favorable for an influence of upper tropospheric flow on southern china the tp might also exert an influence on the drought by weakening the westerly flow to the southern flank of tp and reducing water vapor transport from the bay of bengal to southern china

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

hydrothermal rare earth element xenotime mineralization at maw zone athabasca basin canada and its relationship to unconformity related uranium deposits a reply

revel a model for recent plate velocities from space geodesy 1 we present a new global model for recent plate velocities revel describing the relative velocities of 19 plates and continental blocks the model is derived from publicly available space geodetic primarily gps data for the period 1993 2000 we include an independent and rigorous estimate for gps velocity uncertainties to assess plate rigidity and propagate these uncertainties to the velocity estimates the velocity fields for north america eurasia and antarctica clearly show the effects of glacial isostatic adjustment and australia appears to depart from rigid plate behavior in a manner consistent with the mapped intraplate stress field two thirds of tested plate pairs agree with the nuvel 1a geologic 3 myr average velocities within uncertainties three plate pairs caribbean north america caribbean south america and north america pacific exhibit significant differences between the geodetic and geologic model that may reflect systematic errors in nuvel 1a due to the use of seafloor magnetic rate data that do not reflect the full plate rate because of tectonic complexities most other differences probably reflect real velocity changes over the last few million years several plate pairs arabia eurasia arabia nubia eurasia india move more slowly than the 3 myr nuvel 1a average perhaps reflecting long term deceleration associated with continental collision several other plate pairs including nazca pacific nazca south america and nubia south america are experiencing slowing that began 25 ma the beginning of the current phase of andean crustal shortening

impact of subgrid scale orography on equatorial angular momentum budget and the cold surges in a general circulation model abstractthe dynamical relations between equatorial atmospheric angular momentum eaam equatorial mountain torques and cold surges are analyzed in a general circulation model gcm first the authors show that the global eaam budget is well closed in the gcm much better than in the ncep ncar reanalysis they then confirm that the equatorial torques due to the tibetan plateau the rockies and the andes are well related to the cold surges developing over east asia north america and south america respectively for all these mountains a peak in the equatorial mountain torque components precedes by few days the development of a cold surge confirming that the cold surge s preconditioning is dynamically driven by large scale mountains the authors also analyze the contribution of the subgrid scale orography sso parameterizations and find that they contribute substantially to the torques in experiments where these parameterizations are almost entirely reduced over a given massif the authors find th

global tectonics and space geodesy much of the success of plate tectonics can be attributed to the near rigidity of tectonic plates and the availability of data that describe the rates and directions of motion across narrow plate boundaries m 1 to 60 kilometers wide nonetheless many plate boundaries in both continental and oceanic lithosphere are not narrow but are hundreds to thousands of kilometers wide wide plate boundary zones cover m 15 percent of earth s surface area space geodesy which includes very long baseline radio interferometry satellite laser ranging and the global positioning system is providing the accurate long distance measurements needed to estimate the present motion across and within wide plate boundary zones space geodetic data show that plate velocities averaged over years are remarkably similar to velocities averaged over millions of years