impact of tropical pacific precipitation anomaly on the east asian upper tropospheric westerly jet during the boreal winter abstractthe leading mode of boreal winter precipitation variability over the tropical pacific for the period 1980 2010 shows a west east dipole pattern with one center over the western north pacific wnp and maritime continent and the other center over the equatorial central pacific cp observational evidence shows that the variability of the east asian upper tropospheric subtropical westerly jet eaj has a significant correlation with precipitation anomalies over the wnp and cp and that tropical precipitation anomalies over wnp and cp have a distinct influence on the variation of the eaj a series of numerical experiments based on a linear baroclinic model are performed to confirm the influence of the heating anomalies associated with precipitation perturbations over the wnp and cp on the eaj the results of numerical experiments indicate that a heat source over the wnp can excite a northward propagating rossby wave train in the upper troposphere over east asia and facilitate a poleward eddy momentum

nonlinearity of the extratropical response to tropical forcing abstract a primitive equations dry atmospheric model is used to investigate the atmospheric response to a tropical diabatic forcing pattern and explore how the atmospheric response changes as a function of the amplitude of the forcing the forcing anomaly represents a linear fit of the model forcing to a tropical sst pattern of an el nino la nina type the time averaged 500 hpa geopotential height anomaly responses of two long integrations with forcing anomalies of equal amplitudes but opposite signs show an asymmetric feature that is similar to observations and to previous modeling results related to el nino and la nina ensemble experiments with 61 different amplitudes of this forcing pattern are conducted an eof analysis of the ensemble mean of the 90 day averaged 500 hpa height for different amplitudes of forcings shows that the leading mode of the forced variability resembles the pacific north american pna pattern while the second mode is a wave train across the north atlantic to eurasia the r

interdecadal change in the principal mode of winter spring precipitation anomaly over tropical pacific around the late 1990s evidence show that the dominant mode of winter spring precipitation anomaly over the tropical pacific experienced a pronounced interdecadal change around 1998 based on the extended empirical orthogonal function eeof technique a zonal dipole pattern of precipitation anomaly is dominant during the pre 1998 period corresponding to a positive principle component pc1 positive precipitation anomaly over the equatorial eastern pacific ep decays eastward from winter to spring which is identified as an eastward decaying ep mode during the post 1999 period there is a zonal triple pattern with enhanced precipitation over the equatorial central pacific cp and reduced precipitation over the western north pacific and equatorial southeastern pacific with a positive pc1 this triple pattern of precipitation anomaly maintains with decreasing amplitude from winter to spring which is called the fixedly decaying cp mode for short such interdecadal shift is controlled by differing sea surface temperature sst anomaly pattern the interdecadal differences of winter spring wind stress and thermocline over tropical pacific might result in the interdecadal change in the sst anomaly and then precipitation mode via modulating physical oceanic feedback processes in addition the effect of two distinct precipitation modes on the north pacific teleconnection and north american surface temperature anomaly was strikingly different before 1998 the eastward decaying ep mode might induce a significant tropical northern hemisphere tnh like teleconnection only in winter leading to a north to south pattern of north american temperature anomaly which is greatly limited in spring after 1999 a northwest to southeast response of north american temperature sustains from winter to spring resulting from the maintenance of the pacific north america pna like pattern simulated by the fixedly decaying cp mode

recent estuarine sedimentation rates from shallow inter tidal environments in western scotland implications for future sea level trends and coastal wetland development during the mid late holocene large sections of the scottish coastline have been characterized by falling relative sea levels resulting from differential glacio isostatic uplift of this region of northern britain the complex interplay between crustal and sea level movements continues to influence the morphological development of the scottish coast a number of geophysical models predict ongoing uplift of the scottish landmass however a number of recent studies based upon the analysis of satellite altimetry data indicate a late 20th century acceleration in the rate of eustatic sea level rise detailed geochemistry radiometric dating and diatom analysis on selected sediment cores from four mature coastal marsh environments in argyll western scotland provides an opportunity to investigate the linkages between twentieth century crustal movements eustatic sea level rise and recent rates of sedimentation recorded within marsh sediments across the proposed scottish glacio isostatic uplift dome solid phase major and trace element geochemistry has been used to examine the extent to which post depositional physical disturbance and or chemical reactions may have influenced the reliability of the radiometric dating methods geochemical data indicate that the evolution of these marsh environments has not been significantly influenced by physical disturbance and overall the supply of minerogenic material to the marshes has been quite uniform vertical distributions of 210pbexcess and 137cs activity have been measured and used to develop models of recent marsh vertical accretion dating of the cores reveals subtle variations in the rates of sediment accumulation over the last c 70 years between sites for much of the last hundred years or so sedimentation rates have been in good overall agreement with various estimations for sea level rise although at the more easterly sites these estimates are generally exceeded however quasi equilibrium between marsh sedimentation and sea level rise for much of the twentieth century is indicated from the diatom analysis over the most recent period of marsh development 10 years a significant increase in the rate of surface sedimentation is recorded at all sites across the study area diatom analysis of these surface layers reveals an increase in the relative abundance of marine polyhalobous taxa in the near surface sediments this signifies a very recent increase in the rate of regional relative sea level rise indicating that a regional threshold in coastal forcing has now been exceeded these findings provide clear evidence that recent relative sea level rise is now outpacing estimated rates of glacio isostatic adjustment gia across the proposed scottish uplift dome

interdecadal change of the structure of the enso mode and its impact on the enso frequency in the late 1970s the enso cycle exhibited frequency change the oscillation period increased from 2 4 yr high frequency during 1962 75 to 4 6 yr low frequency during 1980 93 observations suggest that this frequency change was accompanied by a significant change in the structure of the coupled enso mode in comparison with the high frequency regime the structure of the coupled mode in the low frequency regime shows three distinctive features during the warm phase of enso the eastward shift of the westerly anomalies the meridional expansion of the westerly anomalies and the weaker intensity of the easterly anomalies in the eastern pacific to test the robustness of the relationship between the oscillation period and the structure of the coupled mode the authors designed empirical atmospheric models based on observations and coupled them with the ocean model of zebiak and cane numerical experiments demonstrate that the enso period is sensitive to changes in the wind anomaly pattern in a way much like the observed enso frequency structure relation the increase of the enso period after 1980 is mainly due to the eastward shift of the zonal wind stress with respect to the sst anomalies physical explanations of the dependence of enso frequency on the structure of the coupled mode are provided by diagnosing the relative contributions of the thermocline feedback and zonal advection feedback on enso evolution

sedimentary response of arctic coastal wetlands to sea level rise abstract arctic coastal wetlands are of international importance providing a range of ecosystem services they differ markedly from atlantic saltmarshes in the limited development of the creek network associated plant species and the influence of the rapid influx of sediment during the spring thaw this study presents the findings of research conducted in five arctic coastal wetlands in northern norway utilising 210pb and 137cs radionuclide dating techniques to investigate the recent sedimentary responses of these wetlands to alterations in sea level rise historically coastal wetland evolution has been driven by glacio isostatic adjustment gia with rates between 0 5 and 1 mm yr similar to sites in scotland and the northern and eastern baltic resulting in wetland progradation dating of the sedimentary horizons suggests broad agreement between sediment accretion rates derived from both the 210pb methods and 137cs impulse dating methods with average rates of sediment accretion being between 0 3 and 1 9 mm yr dependent on site and zonation sea level rise in the region is between 2 2 and 2 8 mm yr accounting for gia meaning that at present sea level rise appears to be outpacing sediment accretion resulting in negative elevation capital the results of this study indicate that recent increases in sea level as a result of climate change are likely to have reversed the historical trend of progradation driven by isostatic uplift coupled with sediment accretion suggesting that there may be losses of arctic coastal wetland extent and associated ecosystem services in some areas

quasi stationary extratropical wave trains associated with distinct tropical pacific seasonal mean convection patterns observational and amip model results in this paper mechanisms for the formation of quasi stationary extratropical wave trains associated with four distinct winter patterns of seasonal mean tropical pacific convection anomalies including the western cp w cp pattern la nina ln pattern cp el nino cpen pattern and ep el nino epen pattern are investigated by utilizing observational and six atmospheric model intercomparison project phase 5 amip5 high skilled models access1 0 canam4 ccsm4 cmcc cm hadgem2 a mpi esm lr datasets the observational results show that tropical pacific forcing induces upper level anomalous rossby wave source that force vorticity over the central north pacific through modulating the local hadley circulation then excite eastward propagation of quasi stationary planetary waves penetrating into the north atlantic and finally establish the associated teleconnections in mid and high latitudes by local synoptic eddy mean flow interaction different structures of wave trains may be explained by evident differences in intensity and scale of the extratropical vorticity forcing originating from distinct convection anomalies over the tropical pacific the mme results further confirm the possible physical processes obtained from observations but there still exist some significant differences these cover the north pacific and north america and can possibly be attributed to the models simulation ability of extratropical vorticity forcing and local storm track intensity in addition the stratosphere troposphere interaction plays an important role for extratropical atmospheric circulation anomalies the stratospheric polar vortex not only modulates the underlying wave train especially for the north atlantic europe sector but is also affected by the upper tropospheric disturbance in high latitudes through the upward wave activity flux

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

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

atmosphere ocean thermal coupling in the north atlantic a positive feedback in this article it is examined whether a positive atmosphere ocean feedback is found over the north atlantic through a series of general circulation model gcm experiments a 60 year integration of an atmospheric gcm agcm coupled with a 50 m deep motionless ocean was conducted the coupled run was compared with two uncoupled runs one with prescribed mid latitude climato logical sea surface temperatures ssts and the other with daily ssts derived from the coupled experiment the uncoupled atmosphere forces the slab ocean to obtain sst responses in these runs consistent with previous studies the coupled atmosphere ocean fields show interannual variances larger than those in the uncoupled runs due to reduction in the local thermal damping patterns of maximum atmosphere ocean covariability show the north atlantic oscillation nao and tripole sst anomalies both in the coupled and uncoupled fields indicating a dominant role of the atmosphere in generating the sst anomalies on the other hand analyses of the temporal variability in the three runs suggest an active role of sst anomalies in determining the polarity of the air sea coupled variability longer than the interannual time scale a combined analysis of forcing sst upper air height and the response sst anomalies in the uncoupled run identified that a patch of positive sst anomalies in the mid latitude band around 40 n effectively excite the positive phase of the nao which in turn reinforces the tripole sst anomalies this relationship was further confirmed by a nine member ensemble agcm experiment forced by the relevant sst anomalies since the forcing and response sst anomaly patterns bear some resemblance these results manifest positive feedback at work in the coupled atmosphere ocean patterns the processes responsible for this positive feedback were elaborated by a series of linear model experiments the local thermal adjustment of the atmosphere to the sst anomalies results in increased precipitation over the gulf stream region associated diabatic heating applied to a linear baroclinic model yields a positive height response to the east which highly influences the southern part of the nao this stationary response in turn induces a northward deflection in the storm track activity leading to an eddy vorticity feedback that tends to force the positive phase of the nao

a connection between the tropical pacific ocean and the winter climate in the asian pacific region the impact of the tropical pacific sea surface temperature sst anomaly on the winter mean surface air temperature sat in the asian pacific region is investigated during the period from 1948 to 2008 using both observations and a linear baroclinic model lbm a singular value decomposition svd analysis is conducted between the 500 hpa geopotential height z500 over the northern hemisphere and the sst over the tropical pacific ocean to obtain the large scale atmospheric patterns related to tropical pacific sst focus is given to the second pair of svd mode svd2 which bears some similarities in the z500 field to the arctic oscillation over the north atlantic sector and can impact the sat over a larger area of asian pacific in the winter of a positive svd2 the sat over the midlatitude to high latitude asian continent the arctic ocean the indian ocean and the western subtropical pacific ocean tends to be warmer than normal while the north pacific ocean around the bering strait is abnormally cold and vice versa examination of the associated surface general circulation shows that a positive svd2 tends to shift the siberian high southward and the aleutian low eastward resulting in anomalous weak pressure gradient between the asian continent the north pacific anomalous positive sea level pressure anomalies around japan and southerly wind along the east coast of the asian continent are observed at the same time the east asian trough at midtroposphere becomes weaker than normal and the east asian westerly jet stream is increased in magnitudes and shifted northward the analysis of the wave activity flux and result of idealized numerical experiments show a possible influence of the western tropical pacific sst forcing on the svd2

postglacial uplift and relative sea level changes in finnmark northern norway abstract the outer coast of finnmark in northern norway is where the former fennoscandian and barents sea ice sheets coalesced this key area for isostatic modelling and deglaciation history of the ice sheets has abundant raised shorelines but only a few existing radiocarbon dates constrain their chronology here we present three holocene sea level curves based on radiocarbon dated deposits from isolation basins at the outermost coast of finnmark located at the islands soroya and rolvsoya and at the nordkinn peninsula we analysed animal and plant remains in the basin deposits to identify the transitions between marine and lacustrine sediments terrestrial plant fragments from these transitions were then radiocarbon dated radiocarbon dated mollusk shells and marine macroalgae from the lowermost deposits in several basins suggest that the first land at the outer coast became ice free around 14 600 cal yr bp we find that the gradients of the shorelines are much lower than elsewhere along the norwegian coast because of substantial uplift of the barents sea also the anomalously high elevation of the marine limit in the region can be attributed to uplift of the adjacent seafloor after the younger dryas the coast emerged 1 6 1 0 cm per year until about 9500 9000 cal yr bp between 9000 and 7000 cal yr bp relative sea level rose 2 4 m and several of the studied lakes became submerged at the outermost locality rolvsoya relative sea level was stable at the transgression highstand for more than 3000 years between ca 8000 and 5000 cal yr bp deposits in five of the studied lakes were disturbed by the storegga tsunami ca 8200 8100 cal yr bp

seasonality in the local and remote atmospheric response to sea surface temperature anomalies abstract two apparently contradictory situations are provided by observations of the atmospheric response to sea surface temperature anomalies these are i the extratropical regions of the winter hemisphere appear to possess strong teleconnections with equatorial forcing but weak or non existent connections with local extratropical heating anomalies ii the extratropical regions of the summer hemisphere are quite sensitive to local thermal forcing but apparently unaffected by the remote forcing from equatorial regions an attempt is made to provide a consistent physical picture which simultaneously embraces these two situations with the aid of a simple linear model it is shown that the summer hemisphere is more sensitive to local forcing than the winter hemisphere because it is closer to the diabatic limit of webster 1981 thus allowing an efficient energy generation the winter hemisphere is much closer to the adjective limit the sensitivity of the midlatitudes to remote equatorial forcing

two distinct modes of tropical indian ocean precipitation in boreal winter and their impacts on equatorial western pacific abstractthe observational analysis reveals two distinct precipitation modes the zonal dipole dp mode and the monopole mp mode in the tropical indian ocean tio during the el nino mature winter even though sea surface temperature anomalies sstas have a similar basinwide warming pattern referred to as the indian ocean basin mode iobm the formation of the two precipitation modes depends on the distinct evolutions of the ssta in the tropical pacific and indian ocean both of the precipitation modes are preceded by an indian ocean dipole iod the iod associated with the dp mode developed in late summer and was triggered by pacific el nino through a sumatra philippine pattern the iod associated with the mp mode developed in early summer when the pacific sstas were still normal the different iod onset time leads to salient differences in subsequent evolution including the transfer of a dipole sst pattern to a basinwide pattern as a result in the boreal winter the zonal ssta gradient assoc

distinct winter patterns of tropical pacific convection anomaly and the associated extratropical wave trains in the northern hemisphere in this paper distinct patterns of boreal winter convection anomalies over the tropical pacific and associated wave trains in the extratropics are addressed the first leading mode eof1 of convection anomalies as measured by outgoing longwave radiation demonstrates an east west oscillation of deep convection with centers over the equatorial central pacific cp and over the tropical western north pacific and the maritime continent the second leading mode eof2 is also a dipole pattern with opposite centers straddling 170 w possibly modifying eof1 to some extent combining the first two leading modes five major categories of tropical convection anomalies can be identified for the period 1979 80 2012 13 the comparison between these five categories and the corresponding sst anomaly patterns indicates a nonlinear relationship between convection and sst the combination of eof1 and eof2 with in phase pcs exhibits an east west dipole pattern with opposite signs over west of the dateline and the maritime continent the negative phase of the two pcs named la nina pattern induces a negative pacific north american positive north atlantic oscillation teleconnection in the extratropics approximately opposite responses can be detected in its positive phase named cp el nino pattern the negative pc2 superposing positive pc1 named ep el nino pattern shows the strongest convection anomalies with enhanced depressed convection over the eastern western pacific and leads to a tropical northern hemisphere like teleconnection pattern and an anomalous anticyclone extending from the north pacific to the north atlantic the positive pc2 with neutral pc1 named western cp pattern shows weakly enhanced convection to the west of the dateline as a response to local sst warming around the dateline this convection anomaly pattern although weak is important and excites a northeastward wave train from the tropics to greenland resulting in surface air temperature cooling covering the northeastern north america and warmer and wetter conditions over western europe

sediment accretion and recent sea level rise in the solent southern england inferences from radiometric and geochemical studies abstract a detailed radionuclide and geochemical study has been carried out on recent sediments from the solent estuarine system southern england the vertical distributions of a series of radionuclides 210 pb 137 cs 238 pu 239 240 pu 241 am and 60 co have been examined which provide a measure of the rate of sediment accumulation in southern england estuaries the reliable use of radionuclides as indicators of sediment accumulation depends in part on their chemical immobility lack of redox migration 60 co in particular shows evidence for redox mobilization hence it is essential to use a number of chemically different or inert radionuclides to eliminate possible bias in calculated sediment accumulation rates while local intra estuary effects influence rates of sediment accumulation the main control of vertical saltmarsh growth over the solent area is a rise in mean sea level dating of saltmarsh cores indicates a 4 5 mm year 1 rise in relative sea level over the last 100 years in good agreement with tide gauge data comparison with data from the literature implies that a recent acceleration in sea level rise has occurred from 1 2 mmyear 1 to 4 5 5 mm year 1 possibly due to changes in tidal regime or an acceleration in crustal subsidence

pacific east asian teleconnection how does enso affect east asian climate observational evidence is presented to show a teleconnection between the central pacific and east asia during the extreme phases of enso cycles this pacific east asian teleconnection is confined to the lower troposphere the key system that bridges the warm cold events in the eastern pacific and the weak strong east asian winter monsoons is an anomalous lower tropospheric anticyclone cyclone located in the western north pacific the western north pacific wind anomalies develop rapidly in late fall of the year when a strong warm or cold event matures the anomalies persist until the following spring or early summer causing anomalously wet dry conditions along the east asian polar front stretching from southern china northeastward to the east of japan kuroshio extension using atmospheric general circulation and intermediate models the authors show that the anomalous philippine sea anticyclone results from a rossby wave response to suppressed convective heating which is induced by both the in situ ocean surface cooling and the subsidence forced remotely by the central pacific warming the development of the anticyclone is nearly concurrent with the enhancement of the local sea surface cooling both the anticyclone and the cooling region propagate slowly eastward the development and persistence of the teleconnection is primarily attributed to a positive thermodynamic feedback between the anticyclone and the sea surface cooling in the presence of mean northeasterly trades the rapid establishment of the philippine sea wind and sst anomalies implies the occurrence of extratropical tropical interactions through cold surge induced exchanges of surface buoyancy flux the central pacific warming plays an essential role in the development of the western pacific cooling and the wind anomalies by setting up a favorable environment for the anticyclone sst interaction and midlatitude tropical interaction in the western north pacific

pacific east asian teleconnection part ii how the philippine sea anomalous anticyclone is established during el nino development the anomalous philippine sea anticyclone psac conveys impacts of el nino to east asian climate during the mature and decay of an el nino from the winter to ensuing summer it is shown that the anomalous psac forms in fall about one season prior to the peak el nino its strength increases with the el nino intensity and its sign reverses during a la nina the psac formation concurs with abnormal deepening of the east asian trough and with increasing number of northward recurvature of tropical storms in the western pacific the psac establishment is abrupt coupling with a swing from a wet to dry phase of an intraseasonal oscillation iso and often concurrent with early retreat of the east asian summer monsoon the iso becomes inactive after psac establishment the development of the psac is attributed to combined effects of the remote el nino forcing tropical extratropical interaction and monsoon ocean interaction the developing el nino induces off equatorial as cending rossby wave responses and land surface cooling in northeast asia both deepen the east asian trough in fall and induces vigorous tropical extratropical exchange of air mass and heat which enhances the cold air outbreak and initiation of the psac through exciting descending rossby waves the el nino induced indonesian subsidence generates low level anticyclonic vorticity over south asia which is advected by mean monsoon westerly instigating the anomalous psac the iso interacting with the underlying ocean plays a critical role in the abrupt establishment of psac the wind evaporation entrainment feedback tends to amplify suppress iso before after winter northeasterly monsoon commences suggesting the roles of atmosphere ocean inter action and the seasonal march of background winds in changing the philippine sea iso intensity and maintaining psac

role of subtropical precipitation anomalies in maintaining the summertime meridional teleconnection over the western north pacific and east asia abstract the meridional teleconnection patterns over the western north pacific and east asia wnp ea during summer have a predominant role in affecting east asian climate on the interannual time scale a well known seesaw pattern of tropical subtropical precipitation is associated with the meridional teleconnection and the subtropical precipitation anomaly has been previously viewed as a result of anomalous circulations associated with the teleconnection in this study however the authors suggest that subtropical precipitation anomalies in turn can significantly affect large scale circulations and may be crucial for maintenance of the meridional teleconnection diagnosis by using observational and reanalysis data indicates that the meridional teleconnection patterns are clearer in summers when the subtropical rainfall anomalies are greater the simulated results by a linear baroclinic model indicate that a subtropical heat source which is equivalent to the diagnosed positive subtropical precipitati

impact of heating anomalies associated with rainfall variations over the indo western pacific on asian atmospheric circulation in winter observational data show that the dominant mode of the boreal winter rainfall anomalies in the tropical indo western pacific iwp is a west east dipolar pattern which is called the indo western pacific dipole iwpd mode and is related to el nino southern oscillation it is found that corresponded to the iwpd mode is a new atmospheric teleconnection pattern a wave train pattern emitted from the iwp toward asia and the northwest pacific in winter during the positive negative phase of the iwpd the teleconnection pattern features the negative positive anomalies of 200 hpa geopotential height h200 centered at 30 n 110 e and the positive negative anomalies of h200 centered at 45 n 140 e the teleconnection pattern represents the dominant mode of the boreal winter h200 anomaly over asia a series of simple atmospheric model experiments are performed to confirm that this winter teleconnection pattern is induced by the heating anomalies associated with the iwpd and the heating anomalies over the equatorial central pacific are not important to this teleconnection pattern from the iwp toward asia and the northeast pacific the iwpd is strengthened after the climate regime shift of the 1970s which leads to a stronger teleconnection pattern

forced planetary waves in the northern hemisphere winter wave coupled orographic and thermal forcings abstract a more complete and new formulation of the orographic forcing and new thermal forcings are included in a steady state model of the northern hemisphere planetary waves when both forcings are included the simulation produces excellent results which are compared in detail with observations in particular the siberian high the tropospheric east asian trough and subtropical tropospheric east asian jet stream maxima are well reproduced even though the forcing is primarily extratropical in origin the modes uses a lower boundary condition in which the orographic forcing is determined by the effects of the total flow not just the zonal mean basic state consequently the net orographic forcing changes when thermal forcing is added and the tow solution is not equal to the linear sum of the solutions with orographic and thermal forcings separately the thermally induced orographic forcing is found to be very significant and in the troposphere there is strong interaction between the two forcings with

interdecadal change in the tropical pacific precipitation anomaly pattern around the late 1990s during boreal spring abstractthe leading mode of boreal spring precipitation variability over the tropical pacific experienced a pronounced interdecadal change around the late 1990s the pattern before 1998 features positive precipitation anomalies over the equatorial eastern pacific ep with positive principle component years the counterpart after 1998 exhibits a westward shift of the positive center to the equatorial central pacific cp observational evidence shows that this interdecadal change in the leading mode of precipitation variability is closely associated with a distinctive sea surface temperature sst anomaly pattern the westward shift of the anomalous precipitation center after 1998 is in tandem with a similar shift of maximum warming from the ep to cp diagnostic analyses based on a linear equation of the mixed layer temperature anomaly exhibit that an interdecadal enhancement of zonal advection za feedback process plays a vital role in the shift in the leading mode of both the tropical pacific sst and t

atmospheric circulation cells associated with the el nino southern oscillation abstract atmospheric circulation cells associated with the el nino southern oscillation enso are described and examined using the ncep ncar reanalysis field and the ncep sea surface temperature sst from january 1950 to december 1999 the divergent wind and pressure vertical velocity are employed for the identification of atmospheric circulation cells the warm phase of enso shows positive sst anomalies in the equatorial eastern pacific and along the east coast of asia and the west coast of north america and negative sst anomalies in the off equatorial western pacific and in the central north pacific associated with this sst anomaly distribution are variations of atmospheric zonal and meridional circulation cells over the pacific the equatorial zonal walker circulation cell is weakened consistent with previous schematic diagrams the anomalous meridional hadley circulation cell in the eastern pacific shows the air rising in the tropics flowing poleward in the upper troposphere sinking in the subt

effect of boreal spring precipitation anomaly pattern change in the late 1990s over tropical pacific on the atmospheric teleconnection observational evidence showed that the leading mode of precipitation variability over the tropical pacific during boreal spring experienced a pronounced interdecadal change around the late 1990s characterized by a precipitation pattern shift from an eastern pacific ep type to a central pacific cp type the distinct impacts of such a precipitation pattern shift on the extratropical atmospheric teleconnection were examined an apparent poleward teleconnection extending from the tropics to the north atlantic region was observed after 1998 while there was no significant teleconnection before 1998 to understand why only the cp type precipitation mode is associated with a striking atmospheric teleconnection after 1998 diagnostic analyses with the eliassen palm flux and rossby wave source rws based on the barotropic vorticity equation were performed the results show that for the ep type precipitation mode no significant rws anomalies appeared over the subtropical pacific due to the opposite effect of the vortex stretching and absolute vorticity advection processes for the cp type precipitation mode however there are both significant vorticity forcing source over the subtropical cp and clear poleward propagation of rossby wave the spatial distribution of the cp type precipitation pattern tends to excite a conspicuous anomalous southerly and a well organized negative vorticity center over the subtropical cp where both the mean absolute vorticity gradient and mean divergence flow are large hence the interaction between the heating induced anomalous circulation and the basic state made the generation of rossby waves conceivable and effective such corresponding teleconnection responses to the prescribed heating were also examined by using a linear baroclinic model lbm it turned out that significant poleward teleconnection pattern is only caused by the cp type precipitation mode rather than by the ep type precipitation mode further sensitive experiments demonstrated that the change in spring basic state before and after 1998 played a relatively minor role in exciting such a teleconnection pattern when compared with the tropical precipitation anomaly pattern change

210pb and 137cs in margin sediments of the arctic ocean controls on boundary scavenging 1 210pb and 137cs were measured in 25 sediment cores collected during the international polar year from a transect spanning the north american arctic margin from the north bering sea to baffin bay davis strait profiles and inventories of the radioisotopes were used to determine sediment mixing and accumulation at each site and to assess the intensity of scavenging and burial sediment accumulation rates derived from 210pb and validated using 137cs are between 0 04 and 0 23 g cm 2 yr 1 210pb cannot be used to derive sedimentation rates for vigorously biomixed sediments from the north bering chukchi shelf elevated 137cs activities and inventories in recently deposited sediments imply delayed inputs of particle associated 137cs to the sediments likely transported from the watershed to the coast and subsequently redistributed to shelf slope sediments inventories of 210pbex in all cores meet or exceed the estimated supply of 210pbex from atmospheric deposition and decay of 226ra in the water column this implies that in contrast to the deep arctic ocean basin there is a sufficient supply of suspended particulates along the north american arctic margin to scavenge the supply of 210pbex 210pbex inventories in sediments are up to 21 fold greater than the in situ supply at some sites large inventories of 210pbex in sediments along the north bering chukchi shelf result primarily from focusing while those along the north chukchi slope barrow canyon and in baffin bay davis strait reflect strong boundary scavenging likely supported by lateral exchanges with deep interior atlantic origin waters

the impact of tropical western pacific convection on the north pacific atmospheric circulation during the boreal winter in this study we investigate the impact of atmospheric convection over the western tropical pacific 100 145 e 0 20 n on the boreal winter north pacific atmosphere flow by analyzing national center for environmental prediction reanalysis 1 extended reconstructed sea surface temperature and global precipitation climatology project data the western tropical pacific convection is not only the main energy source driving the local hadley and walker circulations but it also significantly influences north pacific circulation by modifying a mid latitude jet stream through the connection with the local hadley circulation on the one hand this strong convection leads to a northward expansion of local hadley cells simultaneous with a northward movement of the western north pacific jet because of the close correlation between the jet and hadley circulation boundaries on the other hand this strong convection also intensifies tropical pacific walker circulation which reduces the eastern pacific sea surface temperature resembling a la nina state through the enhanced equatorial upwelling the cooling of the eastern tropical pacific has an inter tropical convergence zone located further north thus the local hadley circulation moves northward as a result the jet axis over the eastern north pacific which also corresponds to the boundary of the local hadley circulation moves to higher latitude consequently this northward movement of the jet axis over the north pacific is reflected as a northwest southeast dipole sea level pressure slp pattern the composite analysis of slp over the north pacific against the omega pa s at 500 hpa over the western tropical pacific actually reveals that this northwest southeast dipole structure is attributed to the intensified tropical western pacific convection which pushes the pacific jet to the north finally we also analyzed south pacific for the austral winter as did previously to north pacific and found that the results were consistent

dynamical and boundary forcing characteristics of regional components of the asian summer monsoon abstract in this paper the authors present a description of the internal dynamics and boundary forcing characteristics of two major subcomponents of the asian summer monsoon asm that is the south asian monsoon sam and the east southeast asian monsoon eam the description is based on a new monsoon climate paradigm in which the variability of asm is considered as the outcome of the interplay of a fast and an intermediate monsoon subsystem under the influence of slow external forcings two sets of regional monsoon indices derived from dynamically consistent rainfall and wind data are used in this study results show that the internal dynamics of sam are representative of a classical monsoon system in which the anomalous circulation is governed by rossby wave dynamics where anomalous vorticity induced by an off equatorial heat source is balanced by the advection of planetary vorticity on the other hand the internal dynamics of eam are characterized by a hybrid monsoon system featuring m

patterns of tropical pacific convection anomalies and associated extratropical wave trains in amip5 in this paper the performance of 18 coupled model intercomparison project phase 5 cmip5 models forced by observational ssts in simulating the tropical pacific convective variation and the atmospheric responses in the extratropics are assessed the multi model ensemble mean results of 18 cmip5 models show that five major patterns of tropical pacific convection anomaly in winter can indeed be well reproduced however the simulation of the corresponding extratropical responses for each pattern exists some deficiency except for the la nina pattern compared with observations we defined an optimized subset of well performing models access1 0 canam4 ccsm4 cmcc cm hadgem2 a mpi esm mr in tropical pacific deep convection according to the ranking of model skill score these models exhibit approximately identical convection anomaly patterns in both amplitude and spatial structure to the observation which potentially might improve the representation of extratropical teleconnections with the tropical pacific especially for the cp el nino cpen ep el nino epen and western cp w cp patterns both evident atmospheric anomalies of cpen and epen patterns over the na e sector and the northeastward propagating wave trains of w cp pattern can be quite well simulated in the high skilled models

interdecadal changes in the major modes of asian australian monsoon variability strengthening relationship with enso since the late 1970s abstract the present paper develops an integral view of the year to year variability across the entire asian australian monsoon a am system which covers one third of the global tropics between 40 and 160 e using season reliant empirical orthogonal function s eof analysis the authors identified two major modes of variability for the period 1956 2004 the first exhibits a prominent biennial tendency and concurs with the turnabout of el nino southern oscillation enso providing a new perspective of the seasonally evolving spatiotemporal structure for tropospheric biennial oscillation the second mode leads enso by one year the remote el nino forcing the monsoon warm pool ocean interaction and the influence of the annual cycle are three fundamental factors for understanding the behavior of the first mode the monsoon ocean interaction is characterized by a positive feedback between the off equatorial convectively coupled rossby waves and the underlying sea surface temperature sst dipole anoma

recent rates of sedimentation on irregularly flooded boreal baltic coastal wetlands responses to recent changes in sea level abstract boreal baltic coastal wetlands differ markedly from temperate salt marshes by their generally low maximum elevation between 0 and 1 m above m s l low seaward gradients and the irregular nature of flooding that is characteristic of the ne baltic sea coastal region as a result of these factors these wetlands have been considered to be threatened by future sea level rise this study presents results for two boreal baltic coastal wetland sites in estonia using the 210 pb and 137 cs radiometric dating methods to investigate the sedimentary development of these coastal systems recent coastal evolution has been largely driven by continuing glacio isostatic adjustment gia with maximum rates of 2 8 mm yr 1 around the nw estonian coast and the inherited geomorphological setting of generally flat lying coastal topography resulting in coastal emergence broad agreement exists between calculated rates of sedimentation identified within the core sequences average rates of sedimentation using the 210 pb excess cf cs or simple model range between 0 2 and 1 3 mm yr 1 these rates are corroborated using 137 cs which also suggests an increase in sedimentation rates during recent decades approaching maximum values for current land uplift additionally the 210 pb excess crs model reveals periods of sedimentation greatly in excess of these values in response to coastal flooding from known storm activity this study indicates that changes in sea level caused by variations in atmospheric pressure and storm surges can contribute a significant sedimentary component which coupled with gia processes has driven coastal wetland development emergence and the historical progradation of these wetland systems the recent acceleration in the rate of global sea level rise may subtly alter this relationship however current rates of gia and sedimentation will continue to maintain the progradation of boreal baltic coastal wetlands in the coming decades

el nino la nina and the nonlinearity of their teleconnections the paradigm of an atmospheric system varying linearly with respect to extreme phases of the el nino southern oscillation is questioned it is argued that the global response to tropical pacific sea surface temperature forcing will be inherently nonlinear a physical basis for this intrinsic nonlinearity is the thermodynamic control on deep convection climate statistics for warm and cold events of the tropical pacific are analyzed separately for the northern winter periods during 1950 96 composite analysis of 500 mb heights reveal planetary scale teleconnection patterns as noted in earlier studies a new result is the evidence for an appreciable 358 longitude phase shift between the warm and cold event circulation composites and the two wave trains appear to have different tropical origins a large nonlinear component in north american surface climate anomalies is also found which is consistent with such a phase shift in teleconnections in the tropics rainfall anomalies also show evidence of nonlinear behavior the maximum rain anomalies along the equator are located east of the date line during warm events but west of the date line during cold events the interpretation of this behavior is complicated however by the fact that composite warm event sst anomalies are not the exact inverse of their cold event counterparts idealized atmospheric general circulation model agcm experiments are performed in order to test the question of whether the observed nonlinearity is an intrinsic property of the atmospheric system the model is forced with a composite sst anomaly that undergoes a realistic seasonally varying enso life cycle as described by e rasmusson and t carpenter both positive and negative phases of the sst anomaly are used and a 40 member ensemble of warm and cold event model simulations is conducted a nonlinear climate response in the agcm is found that closely resembles the observed composites including a shift in the equatorial positions of the maxmium rain responses and a phase shift of teleconnection patterns in the upper troposphere barotropic model experiments indicate that the inherent nonlinearity in the tropical rain response may itself be responsible for the phase shift in the extratropical teleconnection patterns

el nino impacts on precipitation in the western north pacific east asian sector abstract in this study the western north pacific east asian wnp ea rainfall anomaly induced by the strong el nino in 1982 83 1991 92 and 1997 98 and its association with the mean state are examined over the northern part of the wnp ea region north of 20 n which is dominated by southwest northeast tilting frontal systems positive rainfall anomalies from the fall before the el nino peak phase year 0 to the first wet period after the peak phase year 1 are affected by low and midlevel horizontal moisture convergence anomalies induced by low level anticyclonic circulation anomalies over the wnp region that are associated with el nino over the southern part of the wnp ea region south of 20 n which is dominated by tropical convection positive precipitation anomalies in the first and second wet periods of year 0 and negative precipitation anomalies from the fall of year 0 to the second wet period of year 1 are associated with the variation of the net energy into the atmosphere which is main

seismo and neotectonics in finnmark kola peninsula and the southern barents sea part 1 geological and neotectonic framework abstract as a background for assessing the seismo and neotectonics of the finnmark kola peninsula region emphasis has been directed towards the lineament framework involving a careful examination of digital landsat tm imagery integrated with a variety of data sets ranging from geophysics and digital elevation models to microtectonics based on a detailed field structural control of many of the multiphase lineaments in this 70 000 km2 area of the northeastern part of the fennoscandian shield as well as microscopic investigation of the fault mylonites and breccias five principal lineament sets were distinguished of the nw se polyphasal megafractures the murmansk shear zone carries geological and isotopic evidence of an archaean tectonothermal history and demarcates an important terrane boundary lineaments irrespective of their trends were classified according to their significance in the regional geological framework some lineaments are clearly associated with gravity and aeromagnetic anomalies and probably extend to deep crustal levels quite a few of the prominent faults within lineament zones were reactivated in post glacial times in one area in finnmark core drilling through a se dipping post glacial reverse fault has confirmed its listric shape at depth earthquake focal mechanisms for this same fault are presented in the second part of this dual contribution

records of radionuclide deposition in two salt marshes in the united kingdom with contrasting redox and accumulation conditions single cores from two salt marshes in the united kingdom located near different nuclear facilities were investigated to compare chronostratigraphic estimates derived from the natural radionuclide 210pbexcess with estimates from the known times of introduction of artificial radionuclides to the environment both cores selected had clear visual indications of redox zonation and evidence for diagenetic redox perturbation of the radionuclide records was also sought in the core from beaulieu marsh on the south coast of england the redox zonation was revealed by the profiles of the redox sensitive elements mn i fe p as and s and the records of nuclear discharges were entirely contained within oxidized conditions in the upper 40 cm the constant flux constant sedimentation 210pbexcess accumulation estimate was 76 of that derived from the 1963 fallout 137cs level 0 35 vs 0 46 g cm 2 yr 1 dry mass but the constant flux 210pbexcess method indicated that accumulation rates were lower at beaulieu before 1950 on any timescale 137cs appears earlier in the sediment record than its introduction to the environment but although downward diffusion of 137cs relative to 241am has clearly occurred the 137cs peak still appeared in place and there was negligible penetration of 137cs into underlying reduced conditions this core also contained a peak of the 60co discharges from either or both the winfrith and la hague nuclear plants that peaked in 1980 and 1984 respectively the sediments in the core from wyre marsh on the eastern coast of the irish sea had accumulated more rapidly than those at beaulieu and in this case the redox zonation could be established only from mn and s profiles here the constant initial activity 210pbexcess accumulation rate estimate was 125 of that derived from the 137cs peak correlated with the 1975 sellafield discharge maximum 0 79 vs 0 64 g cm 2 yr 1 sellafield discharge 137cs swamps fallout or chernobyl 137cs signals in this core but the 137cs and 241am sediment records are well separated and remain consistent with the slightly different discharge patterns over time this is so despite the fact that the maximum activity levels of both isotopes are now located well into reducing conditions out of which mn must have migrated the 210pb profile appeared similarly unaffected by the oxidized reduced boundary in this case this core was too short to define the limits of any downward 137cs migration 210pbexcess accumulation rate estimates for salt marshes should be viewed with some caution because of the steady state assumptions inherent in all 210pbexcess methods and the potential for fluctuating accumulation conditions and open system behavior in salt marshes

stress induced brittle fragmentation of magmatic melts theory and experiments 1 the release of kinetic energy during explosive volcanic eruptions is a key parameter for hazard assessment and civil defense the explosive production of volcanic ash by intensive fragmentation of magma and host rocks represents a substantial part of this energy for cases of explosive eruption where predominantly host rock was fragmented phreatomagmatic eruptions to form the major part of volcanic ash rock mechanical parameters could be measured and fragmentation energies assigned in cases where most of the produced ash is of juvenile origin magmatic eruptions a general method for the determination of fragmentation energy is still lacking in this article we introduce a thermodynamic approach that relates grain size data of the produced ash deposits to shear rates acting during the deformation of magma with the use of a standardized fragmentation experiment the physical parameters needed to determine the specific fragmentation energy and deformation history were measured the experiment was calibrated and tested with two case histories of the campi flegrei volcanic field southern italy both eruptions are classified as most probable worst case scenarios during the next period of activity to be expected within the next 10 100 years using the experimentally determined specific fragmentation energies the total mass of produced ash of each eruption and assuming an energy dissipation as observed in the experiments the total kinetic energy release of the worst case campi flegrei eruptive events to come were calculated with 25 and 40 kt tnt equivalent