respective influences of iod and enso on the tibetan snow cover in early winter using reanalysis data and snow cover data derived from satellite observations respective influences of indian ocean dipole iod and el nino southern oscillation enso on the tibetan snow cover in early winter are investigated it is found that the snow cover shows a significant positive partial correlation with iod in the pure positive iod years with no co occurrences of el nino negative geopotential height anomalies north of india are associated with warm and humid southwesterlies to enter the plateau from the bay of bengal after rounding cyclonically and supply more moisture this leads to more precipitation more snow cover and resultant lower surface temperature over the plateau these negative geopotential height anomalies north of india are related to the equivalent barotropic stationary rossby waves in the south asian wave guide the waves can be generated by the iod related convection anomalies over the western central indian ocean in contrast in the pure el nino years with no co occurrences of the positive iod the anomalies of moisture supply and surface temperature over the plateau are insignificant suggesting negligible influences of enso on the early winter tibetan snow cover further analyses show that enso is irrelevant to the spring early summer tibetan snow cover either whereas the iod induced snow cover anomalies can persist long from the early winter to the subsequent early summer

can the southern hemisphere annular mode affect china winter monsoon 1 many previous studies suggested that the anomalous northern hemisphere annular mode nam and associated low boundary forcing e g snow cover greatly influence the china winter monsoon cwm variability on interannual to inter decadal timescales in this article it is found that the southern hemisphere annular mode sam also well correlates with the two observed cwm major modes which has not been revealed before note that the two cwm major modes are obtained by performing empirical orthogonal function eof analysis on winter surface air temperature at 160 gauge stations across china for the 1951 2006 period they explain around 70 of the total cwm variances thefirsteofmodeexhibitsahomogeneousspatialpatternwiththecorrespondingprincipal component displaying a significant inter decadal variation which reflects the warming trend in china during the past 56 years the second eof mode shows a meridional seesaw patternandisbasicallyassociatedwithsignificantinterannualvariations bothoftheleading modes are intimately associated with the simultaneous sam like hemispheric circulation anomalies moreover thesam likeanomaliessignalprecursoryconditionsforthefirstcwm mode in boreal autumn the relevant physical mechanisms by which anomalous autumn sam may affect the cwm are investigated with ncar community atmospheric model version 3 cam3 when sam is in a strong phase during boreal autumn the circumantarctic upper level jet stream displaces poleward and the corresponding surface wind speeds reduce in the region between 45s and 30s inducing a hemispheric scale warm sea surface temperature sst belt beneath such an anomalously warm sst belt persists through boreal winter and weakens the hadley cell the weakened hadley cell in boreal wintercorrespondstoanomaloussoutherliesprevailinginthelowertroposphereoverchina which favor a weak cwm the intimate linkage between the autumn sam and cwm may be instrumental for understanding interactions between the northern and southern hemisphere and can provide a way to predict the cwm variations

zonally asymmetric response of the southern ocean mixed layer depth to the southern annular mode interactions between the atmosphere and ocean are mediated by the mixed layer at the ocean surface the depth of this layer is determined by wind forcing and heating from the atmosphere variations in mixed layer depth affect the rate of exchange between the atmosphere and deeper ocean the capacity of the ocean to store heat and carbon and the availability of light and nutrients to support the growth of phytoplankton however the response of the southern ocean mixed layer to changes in the atmosphere is not well known here we analyse temperature and salinity data from argo profiling floats to show that the southern annular mode sam the dominant mode of atmospheric variability in the southern hemisphere leads to large scale anomalies in mixed layer depth that are zonally asymmetric from a simple heat budget of the mixed layer we conclude that meridional winds associated with departures of the sam from zonal symmetry cause anomalies in heat flux that can in turn explain the observed changes of mixed layer depth and sea surface temperature our results suggest that changes in the sam including recent and projected trends attributed to human activity drive variations in southern ocean mixed layer depth with consequences for air sea exchange ocean sequestration of heat and carbon and biological productivity

processes controlling vertical coupling and decoupling between the upper and lower crust of orogens results from fiordland new zealand the pre cenozoic configuration of western new zealand allows determination of the effects of magmatism and a changing lower crustal rheology on the evolution of a cretaceous orogen from upper to lower crustal levels 10 50 km beginning at 126 ma a composite batholith dominated by diorite was emplaced into the lower crust during emplacement deformation was partitioned into zones weakened by magma and heat leading to the development of two layer parallel shear zones at the upper and lower contacts of the batholith transient vertical decoupling of the crust above and below the batholith occurred from 126 ma until 120 ma as magma was emplaced into and moved through a weak thick lower crust by 116 ma however much of the batholith had crystallized and the lowermost crust had cooled from 750 c t 850 c to t 650 700 c cooling was aided by the juxtaposition of pre existing crust against hot new crust and by the efficient extraction of partial melts out of the lower crust cooling together with dehydration of the lower crust and mafic compositions led to the development of a strong dry lower crustal root by 116 ma a strong lower crust resulted in high degrees of vertical coupling between the upper and lower crust during contraction from 116 to 105 ma even as magma continued to be emplaced into the mid upper crust a narrow focused orogenic style in the upper crust at this time reflected a highly viscous lower crust through which compressional stresses were transferred vertically the results imply that changes in plate boundary dynamics rather than the thermal weakening of thick lower crust during convergence controlled the onset of regional extension at 108 105 ma

cross seasonal influence of the december february southern hemisphere annular mode on march may meridional circulation and precipitation abstractnew evidence suggests that interannual variability in zonal mean meridional circulation and precipitation can be partially attributed to the southern hemisphere annular mode sam the dominant mode of climate variability in the southern hemisphere sh extratropics a cross seasonal correlation exists between the december february djf sam and march may mam zonal mean meridional circulation and precipitation this correlation is not confined to the sh it also extends to the northern hemisphere nh subtropics when the preceding djf sam is positive counterclockwise and clockwise meridional cells accompanied by less and more precipitation occur alternately between the sh middle latitudes and nh subtropics in mam in particular less precipitation occurs in the sh middle latitudes the sh tropics and the nh subtropics but more precipitation occurs in the sh subtropics and the nh tropics a framework is built to explain the cross seasonal impact of sam related sst anomalies evidence indic

southern hemisphere circulation features associated with el nino southern oscillation events abstract composite seasonal mean and anomaly fields prepared from operational numerical analyses have been used to describe the southern hemisphere sh circulation features associated with el nino southern oscillation enso events the period of analyses available 1972 83 has limited the composites to include only three enso events the reliability and stability of the composites has been tested using multiple permutation methods and by comparison with the results obtained using a longer period 1950 79 of sh rawinsonde station data in the sh winter a weak equivalent barotropic wavetrain pattern of anomalies extends over australia and the south pacific ocean to south america this wavetrain pattern is quite variable in amplitude and location between enso events although it is more stable over the subtropical pacific in the sh summer the circulation anomalies are more zonally symmetric with increased height at low and high latitudes and decreased height in middle latitudes the circulation anoma

modulation of the tibetan plateau snow cover on the enso teleconnections from the east asian summer monsoon perspective theeastasiansummermonsoon easm mayexhibitratherlargevariabilitybetweenyearscharacterized by the same enso phase such inconsistency reduces the easm predictability based on enso results in this study show that the tibetan plateau snow cover tpsc exerts a modulating effect on enso teleconnections and enso significantly correlates with the easm only during the reduced tpsc summers three dimensional circulation structures are examined to manifest that the typical enso signals in reduced tpsc summers tend to be stronger than in excessive tpsc summers numerical and theoretical evidences indicate that the anomalously reduced tpsc can force positive geopotential height anomalies at the upper troposphereandweakenthejetstreamsacrosseasternasiaandnorthwesternpacific governedbysuchbasic state zonal flows the extratropical rossby wave response to the enso forcing usually has a larger amplitude and pronounced westward development in such case enso extends its influences to eastern asia and enhances its connection with the easm

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

in situ la icp ms trace elements analysis of magnetite the fenghuangshan cu fe au deposit tongling eastern china abstract the fenghuangshan deposit is a typical cu fe au skarn deposit in the tongling area anhui province eastern china the deposit has a paragenetic sequence of a prograde skarn stage followed by a retrograde skarn stage and a final quartz sulfide and carbonate stages magnetite in the fenghuangshan deposit mainly formed in the retrograde and carbonate stages according to the morphology of magnetite and mineral assemblage of ores we divided magnetite bearing ores into three groups group 1 early retrograde skarn stage is represented by a mineral assemblage of magnetite and chalcopyrite group 2 late retrograde skarn stage has a mineral assemblage of magnetite chalcopyrite and wollastonite with characteristic ring like magnetite group 3 carbonate stage is characterized by large amounts of calcite veins crosscut or associated with magnetite and intensive hematization of magnetite crosscut by the veins laser ablation la icp ms was used to determine trace element concentrations of magnetite from the three mineralization stages positive correlations among mg al ca and si in magnetite indicate that these lithophile elements have similar behavior during the skarn formation process calcium is an important discriminant element for magnetite in skarn deposits positive correlations are also evident for pb sn and w in magnetite which also indicates their similar behavior in general magnetite grains of different stages have similar normalized trace element patterns indicating that they share a common source however some elements such as co and mn in magnetite decrease from early retrograde skarn stage late retrograde skarn stage to carbonate stage which may be attributed to the precipitation of coexisting minerals sulfides and carbonates or the decreasing temperature magnetite grains of the retrograde stage have higher mg mn and si al contents than those of the carbonate stage indicating a decreasing degree of fluid rock interaction during the skarn formation process trace element data of skarn magnetite indicate a more widely compositional variation than previously suggested magnetite from the fenghuangshan cu fe au deposit has similar composition to those from other cu cu fe or cu polymetallic skarn deposits but different from those from fe skarn deposits such that magnetite composition is very powerful in establishing the origin of skarn deposits

decadal change of the spring snow depth over the tibetan plateau the associated circulation and influence on the east asian summer monsoon abstract the decadal change in the spring snow depth over the tibetan plateau and impact on the east asian summer monsoon are investigated using station observations of snow depth data and the ncep ncar reanalysis for 1962 93 during spring march april both the domain averaged snow depth index sdi and the first principal component of the empirical orthogonal function eof analysis exhibit a sharp increase in snow depth after the late 1970s which is accompanied by excessive precipitation and land surface cooling the correlation between sdi and precipitation shows a coherent remote teleconnection from the tibetan plateau northern india to western asia it is found that the increased snow depth over the plateau after the mid 1970s is concurrent with a deeper india burma trough an intensified subtropical westerly jet as well as enhanced ascending motion over the tibetan plateau additional factors for the excessive snowfall include more moisture supply associated with the intensification of the south

relation between eurasian snow cover snow depth and the indian summer monsoon an observational study abstract satellite derived snow cover data for 22 yr and snow depth data for 9 yr over eurasia have been analyzed to reexamine the possible relation of snow with the indian summer monsoon in contrast to the previous studies that use snow cover averaged over all of eurasia as a single number the frequency of occurrence of snow at each grid point over eurasia is correlated with the indian summer monsoon rainfall thus specific geographical regions over eurasia that are responsible for the well known inverse relationship between eurasian snow cover and indian monsoon rainfall are delineated it is found somewhat surprisingly that western eurasia is the only geographical region for which a significant inverse correlation exists between winter snow cover and subsequent summer monsoon rainfall however composites for high and low snow cover over eurasia show spatially homogeneous large scale patterns of snow cover and surface temperature anomalies winters of high and low snow cover for eurasia are found t

southern hemisphere origins for interannual variations of snow cover over the western tibetan plateau in boreal summer abstractthe climate response to the tibetan plateau tp snow cover tpsc has been receiving extensive concern however relatively few studies have been devoted to revealing the potential factors

modis terra observed seasonal variations of snow cover over the tibetan plateau 1 seasonal variations of snow cover fraction sfc over the tibet plateau tp are examined using the data acquired from the moderate resolution imaging spectroradiometer modis on the terra spacecraft in this study we first evaluate the accuracy of the modis high resolution snow cover data by comparing the data with in situ chinese snow observations results show that overall accuracy of modis snow data is about 90 over the tp area statistical analysis is then performed over the modis snow data during 2000 2006 it is found that the most persistent snow cover is located in the southern and western edges of the tp within large mountain ridges and western part of yarlung zangbo valley the higher scfs are mostly concentrated in the regions where the elevation is higher than 6000 m the duration for snow persistence varies in different elevation ranges and generally becomes longer with increases in the terrain elevation

the impact of a changing southern hemisphere annular mode on antarctic peninsula summer temperatures since the mid 1960s rapid regional summer warming has occurred on the east coast of the northern antarctic peninsula with near surface temperatures increasing by more than 2 degrees c this warming has contributed significantly to the collapse of the northern sections of the larsen ice shelf coincident with this warming the summer southern hemisphere annular mode sam has exhibited a marked trend suggested by modeling studies to be predominantly a response to anthropogenic forcing resulting in increased westerlies across the northern peninsula observations and reanalysis data are utilized to demonstrate that the changing sam has played a key role in driving this local summer warming it is proposed that the stronger summer westerly winds reduce the blocking effect of the antarctic peninsula and lead to a higher frequency of air masses being advected eastward over the orographic barrier of the northern antarctic peninsula when this occurs a combination of a climatological temperature gradient across the barrier and the formation of a fohn wind on the lee side typically results in a summer near surface temperature sensitivity to the sam that is 3 times greater on the eastern side of the peninsula than on the west sam variability is also shown to play a less important role in determining summer temperatures at stations west of the barrier in the northern peninsula similar to 62 degrees s both at the surface and throughout the troposphere this is in contrast to a station farther south similar to 65 degrees s where the sam exerts little influence

coupled ocean atmosphere ice response to variations in the southern annular mode abstract the coupled ocean atmosphere ice response to variations in the southern annular mode sam is examined in the national center for atmospheric research ncar community coupled climate model version 2 the model shows considerable skill in capturing the predominantly zonally symmetric sam while regional deviations between model and observation sam winds go a long way in explaining the generally small differences between simulated and observed sam responses in the ocean and sea ice systems vacillations in the position and strength of the circumpolar winds and the ensuing variations in advection of heat and moisture result in a dynamic and thermodynamic forcing of the ocean and sea ice both meridional and zonal components of ocean circulation are modified through ekman transport which in turn leads to anomalous surface convergences and divergences that strongly affect the meridional overturning circulation and potentially the pathways of intermediate water ventilation a heat budget analysis de

spatial variability of sea level pressure and 500 mb height anomalies over the southern hemisphere abstract the spatial variability of mean sea level pressure slp and 500 mb height anomalies over the southern hemisphere during summer djf and winter jja is determined using eigenvector analysis based on daily synoptic maps from 1972 to 1979 the patterns of spatial distribution of pressure and height anomalies are further verified and examined by means of station data and the eigenvectors are compared between the seasons and to those found for the northern hemisphere the first eigenvector shows that midlatitude anomalies of slp and 500 mb height are of an opposite sign to those found over and around antarctica the pattern is highly barotropic and suggests strengthening and weakening of the zonal wind in alternating latitude belts the 500 mb height differences are calculated for five midlatitude to antarctic station pairs using data from the late 1950 s onward these latitudinal height differences are also used to describe the association between the hemispheric westerlies and the southern oscil

cretaceous high p granulites at milford sound new zealand metamorphic history and emplacement in a convergent margin setting granulite facies orthogneiss of the arthur river complex arc at milford sound western fiordland records a complex early cretaceous magmatic and orogenic history for the pacific gondwana margin that culminated in the emplacement and burial of a dioritic batholith the western fiordland orthogneiss wfo enstatite bearing mafic to intermediate protoliths of the arc and wfo intruded the middle to upper crust the early deformation history of the arc is preserved in the pembroke granulite where two pyroxene s1 assemblages that reflect p 750 c were only patchily recrystallized during later deformation s1 is cut by garnet bearing leucogabbroic to dioritic veins which are cut by distinctive d2 fractures involving anorthositic veins and garnet diopside plagioclase bearing reaction zones these zones are widespread in the arc and wfo and record conditions of p 14 kbar and t 750 c garnet clinopyroxene bearing corona reaction textures that mantle enstatite in both the arc and wfo reflect early cretaceous burial by approximately 25 km of continental crust most of the arc is formed from the milford and harrison gneisses which contain steeply dipping s4 assemblages that envelop the pembroke granulite and involve garnet hornblende diopside clinozoisite rutile and plagio clase with or without kyanite the p t history of rocks in western fiordland reflects pronounced early cretaceous convergence related tectonism and burial possibly related to the collision and accretion of island arc material onto the pacific gondwana margin

interpretation of recent southern hemisphere climate change climate variability in the high latitude southern hemisphere sh is dominated by the sh annular mode a large scale pattern of variability characterized by fluctuations in the strength of the circumpolar vortex we present evidence that recent trends in the sh tropospheric circulation can be interpreted as a bias toward the high index polarity of this pattern with stronger westerly flow encircling the polar cap it is argued that the largest and most significant tropospheric trends can be traced to recent trends in the lower stratospheric polar vortex which are due largely to photochemical ozone losses during the summer fall season the trend toward stronger circumpolar flow has contributed substantially to the observed warming over the antarctic peninsula and patagonia and to the cooling over eastern antarctica and the antarctic plateau

coupled ocean atmosphere feedback in the southern annular mode abstract previous studies have demonstrated that while the southern annular mode sam is an intrinsic feature of the atmosphere it projects strongly onto the ocean and sea ice properties and circulation this study investigates the extent of back interaction whereby these oceanic sam anomalies feed back to the atmosphere a comparison between atmosphere only and full coupled climate models demonstrates that air sea interactions in the coupled system act to increase the persistence of the sam in the atmosphere to identify the nature of feedback from the ocean to the atmosphere ensemble experiments are carried out in both atmosphere only and full coupled models whereby a continuous sam like sea surface temperature sst anomaly is imposed both coupled and uncoupled experiments show a direct thermal response that affects the lower tropospheric temperature and surface meridional winds an indirect upper troposphere wide response is also seen whose characteristics are sensitive to the coupling for the

autochthonous inheritance of zircon through cretaceous partial melting of carboniferous plutons the arthur river complex fiordland new zealand tims and shrimp u pb analyses of zircons from milford orthogneiss metadiorite p 1 1 4 gpa t 750 c of the arthur river complex of northern fiordland reveal a bimodal age pattern zircons are predominantly either paleozoic 357 0 4 2 ma and prismatic with oscillatory zoning or cretaceous 133 9 1 8 ma and ovoid with sector or patchy zoning the younger age component is not observed overgrowing older grains most grains of both ages are overgrown by younger cretaceous 120 ma metamorphic zircon with very low u and th u 0 01 we interpret the bimodal ages as indicating initial igneous emplacement and crystallisation of a dioritic protolith pluton at 357 ma followed by early cretaceous granulite facies metamorphism at 134 ma during which a significant fraction 60 of the zircon grains dissolved and subsequently reprecipitated effectively in situ in partial melt pockets the remaining 40 of original paleozoic grains were apparently not in contact with the partial melt remained intact and show only slight degrees of pb loss sector zoning of the cretaceous grains discounts their origin by solid state recrystallisation of paleozoic grains the alternative explanation that the paleozoic component represents a 40 inherited component in an early cretaceous transgressive dioritic magma is considered less likely given the relatively high solubility of zircon in magma of this composition the absence of 134 ma overgrowths the single discrete age of the older component equivalent time integrated 177hf 176hf compositions of both age groups and the absence of the cambrian proterozoic detrital zircon that dominates regional cambro ordovician metasedimentary populations similar bimodal carboniferous early cretaceous age distributions are characteristic of the wider arthur river complex 8 of 12 previously dated dioritic samples have a paleozoic component averaging 51 furthermore the age and chemical suite affinity of these and several more felsic rocks can be matched with those of the relatively unmetamorphosed carboniferous plutonic terrane along the strike of the mesozoic margin in southern fiordland also supporting the in situ derivation of the carboniferous inherited component

boreal spring southern hemisphere annular mode indian ocean sea surface temperature and east asian summer monsoon 1 the relationships among the boreal spring southern hemisphere annular mode sam the indian ocean io sea surface temperature sst and east asian summer monsoon easm are examined statistically in this paper the variability of boreal spring sam is closely related to the io sst when the sam is in its strong positive phase in boreal spring with low pressure anomalies over the south pole and high pressure anomalies over middle latitudes sstover the subtropics and middle latitudes of the south indian ocean sio increases which persists into the summer following the positive sst anomalies over the subtropics and midlatitudes of the sio sst in the equatorial indian ocean and bay of bengal increases in summer moreover the variability of sst in the equatorial indian ocean and bay of bengal is closely related to easm when sst in the equatorial indian ocean and bay of bengal increases easm tends to be weak therefore the io sst may play an important role bridging boreal spring sam and easm the atmospheric circulations and surface heat exchanges contribute to the sst anomalies in the sio when the spring sam is in its strong positive phases the regional ferrel cell weakens and the anomalous upward motions at 20s 30s cause an increase of low cloud cover and downward longwave radiation flux the surface atmospheric circulations also transport more less warmer cooler air from middle latitudes north of 50s high latitudes south of 60s into 50s 60s and warm the air which reduces the temperature difference between the ocean and atmosphere and consequently reduces sensible heat flux from the ocean to atmosphere the increased downward longwave radiation and decreased sensible heat are responsible for the sst increase in the sio the atmospheric circulation and surface heat flux anomalies are of opposite signs following the strong negative phases of sam

synchronous variability in the southern hemisphere atmosphere sea ice and ocean resulting from the annular mode zonally symmetric fluctuations of the midlatitude westerly winds characterize the primary mode of atmospheric variability in the southern hemisphere during all seasons this is true not only in observations but also in an unforced 15 000 yr integration of a coarse resolution r15 coupled ocean atmosphere model here it is documented how this mode of atmospheric variability known as the southern annular mode sam generates ocean circulation and sea ice variations in the model integration on interannual to centennial timescales that are tightly in phase with the sam the positive phase of the sam is associated with an intensification of the surface westerlies over the circumpolar ocean around 608s and a weakening of the surface westerlies farther north this induces ekman drift to the north at all longitudes of the circumpolar ocean and ekman drift to the south at around 308s through mass continuity the ekman drift generates anomalous upwelling along the margins of the antarctic continent and downwelling around 458s the anomalous flow diverging from the antarctic continent also increases the vertical tilt of the isopycnals in the southern ocean so that a more intense circumpolar current is also closely associated with positive sam in addition the anomalous divergent flow advects sea ice farther north resulting in an increase in sea ice coverage finally positive sam drives increases in poleward heat transport at about 308s while decreases occur in the circumpolar region ocean and sea ice anomalies of the opposite sign occur when the sam is negative the ocean and sea ice fluctuations associated with the sam constitute a significant fraction of simulated ocean variability poleward of 308s year round the robustness of the mechanisms relating the sam to oceanic variability suggests that the sam is likely an important source of large scale variability in the real southern hemisphere ocean

definition of antarctic oscillation index following walker s work about his thmous three oscillations published during the 1920 30s many papers were written about atmospheric oscillations a iburth atmospheric oscillation in the middle and high southern latitudes was lbund and nanted the grotarctic oscillation ao a refiers to a large scale alternation of atmospheric mass between the mid latitudes and high latitudes surthce pressure in order to understand the spatial structure of sea level pressure variation in detail empirical orthogonal fitnction analysis is applied an objective index of the antarctic oscillation index aoi is defined as the diffierence of zonal mean sea level pressure between 40os and 65os the aoi has the potential tbr clarifying climate regimes in the southern hemisphere similar to how the na and the npo has been used in the northern hemisphere were there other oscillation s besides nao npo and s especially in the southern hemisphere it had been supposed that there might be other atmospheric oscillation s in the high southern latitudes although as early as in the first quarter of this century walker 1928 had stated that just as in the north atlantic there is a pressure opposition between the azores and iceland there is an opposition between the high pressure belt across chile and the argentine on the one hand and the low pressure area of weddell sea and the bellingshausen sea on the other the scarcity of data in the southern hemisphere hindered the search tbr new oscillation s during the last two decades more comprehensive data over the southern hemisphere became available and more analyses were carried out see kidson 1975 rogers and van loon 1982 mo and l 7 ite 1985 2 4o 1986 connolley 1997 gong and wang 1998 a tburth atmospheric oscillation in the middle and high southern latitudes was tbund and nanted as the antarctic oscillation a wang 1992 gong and wang 1998 the term ao relrs to a large scale alternation of atmospheric mass between the mid latitude sur hce pressure

the effect of enso on tibetan plateau snow depth a stationary wave teleconnection mechanism and implications for the south asian monsoons abstract an atmospheric stationary wave teleconnection mechanism is proposed to explain how enso may affect the tibetan plateau snow depth and thereby the south asian monsoons using statistical analysis the short available record of satellite estimates of snow depth and ray tracing it is shown that wintertime enso conditions in the central pacific may produce stationary barotropic rossby waves in the troposphere with a northeastward group velocity these waves reflect off the north american jet turning equatorward and enter the north african asian jet over the eastern atlantic ocean once there the waves move with the jet across north africa south asia the himalayas and china anomalous increases in upper tropospheric potential vorticity and increased wintertime snowfall over the tibetan plateau are speculated to be associated with these rossby waves the increased snowfall produces a larger tibetan plateau snowpack which persists through the spring and summer and weakens the intensity of the

links between the antarctic oscillation and winter rainfall over western south africa 1 relationships between the antarctic oscillation aao and winter rainfall over western south africa are investigated this region receives most of its annual rainfall during austral winter and often experiences severe drought it is found that 6 6 of the 7 8 wettest driest winters jja during 1948 2004 occur during negative positive aao phase i e positive negative pressure anomalies over antarctica and negative positive anomalies over the midlatitudes the mechanisms by which the aao appears to influence winter rainfall involve shifts in the subtropical jet and changes in the low level moisture flux upstream over the south atlantic and in the mid level uplift low level convergence and relative vorticity over the region the anomalous circulation patterns extend into spring thus the springs following the identified winters also show similar rainfall anomalies

iod influence on the early winter tibetan plateau snow cover diagnostic analyses and an agcm simulation using diagnostic analyses and an agcm simulation the detailed mechanism of indian ocean dipole iod influence on the early winter tibetan plateau snow cover ewtpsc is clarified in early winter of pure positive iod years with no co occurrence of el nino the anomalous dipole diabatic heating over the tropical indian ocean excites the baroclinic response in the tropics since both baroclinic and barotropic components of the basic zonal wind over the arabian peninsula increase dramatically in early winter due to the equatorward retreat of the westerly jet the baroclinic mode excites the barotropic rossby wave that propagates northeastward and induces a barotropic cyclonic anomaly north of india this enables the moisture transport cyclonically from the northern indian ocean toward the tibetan plateau the convergence of moisture over the plateau explains the positive influence of iod on the ewtpsc in contrast the basic zonal wind over the arabian peninsula is weak in autumn this is not favorable for excitation of the barotropic rossby wave and teleconnection even though the iod related diabatic heating anomaly in autumn similar to that in early winter exists this result explains the insignificant significant positive partial correlation between iod and the autumn early winter tibetan plateau snow cover after excluding the influence of enso the sensitivity experiment forced by the iod related sst anomaly within the tropical indian ocean well reproduces the baroclinic response in the tropics the teleconnection from the arabian peninsula and the increased moisture supply to the tibetan plateau also the seasonality of the atmospheric response to the iod is simulated

the effects of the indo pacific warm pool on the stratosphere sea surface temperature sst in the indo pacific warm pool ipwp plays a key role in influencing east asian climate and even affects global scale climate change this study defines ipwp nino and ipwp nina events to represent the warm and cold phases of ipwp sst anomalies respectively and investigates the effects of these events on stratospheric circulation and temperature results from simulations forced by observed sst anomalies during ipwp nino and nina events show that the tropical lower stratosphere tends to cool during ipwp nino events and warm during ipwp nina events the responses of the northern and southern polar vortices to ipwp nino events are fairly symmetric as both vortices are significantly warmed and weakened however the responses of the two polar vortices to ipwp nina events are of opposite sign the northern polar vortex is warmed and weakened but the southern polar vortex is cooled and strengthened these features are further confirmed by composite analysis using reanalysis data a possible dynamical mechanism connecting ipwp sst to the stratosphere is suggested in which ipwp nino and nina events excite teleconnections one similar to the pacific north america pattern in the northern hemisphere and a rossby wave train in the southern hemisphere which project onto the climatological wave in the mid high latitudes intensifying the upward propagation of planetary waves into the stratosphere and in turn affecting the polar vortex

kyanite paragonite bearing assemblages northern fiordland new zealand rapid cooling of the lower crustal root to a cretaceous magmatic arc fiordland new zealand exposes the lower crustal root of an early cretaceous magmatic arc that now forms one of earth s most extensive high p granulite facies belts the arthur river complex a dioritic to gabbroic suite in northern fiordland is part of the root of the arc and records an early cretaceous history of emplacement tectonic burial and high p granulite facies metamorphism that accompanied partial melting of the crust late random intergrowths of kyanite quartz and plagioclase partially pseudomorph minerals in the earlier high t assemblages of the arthur river complex indicating high p cooling of an over thickened crustal root by c 200 c the kyanite intergrowths are themselves partially pseudomorphed by paragonite commonly in the presence of phengitic white mica biotite plagioclase intergrowths that partially pseudomorph phengitic white mica and diopside plagioclase intergrowths that partially pseudomorph jadeitic diopside combined with published thermochronology results are consistent with later rapid decompression a short duration anticlockwise p t path may be explained by the high p juxtaposition of comparatively cool upper crustal rocks following their tectonic burial and under thrusting during the waning stages of early cretaceous orogenesis this was then followed by the decompression giving the rapid exhumation within 20 myr of peak metamorphism as suggested by the isotopic data

antarctic oscillation signal on precipitation anomalies over southeastern south america 1 the relation between the antarctic oscillation aao and the precipitation in southeastern south america sesa is examined the aao influence is particularly strong during winter and late spring although of opposite sign in particular during spring aao positive negative phases are associated with the intensification of an upper level anticyclonic cyclonic anomaly weakened enhanced moisture convergence and decreased increased precipitation over sesa the combined influence of both enso and aao on sesa precipitation was also explored and significant correlation values between both oscillations are only observed during spring results show that during that particular season aao activity produces a strong modulation of the enso signal on sesa precipitation

potential influence of the november december southern hemisphere annular mode on the east asian winter precipitation a new mechanism as the leading mode of the global atmospheric mass inter annual variability the southern hemisphere annular mode sam may exert potential influences to the northern hemisphere nh climate but the related physical mechanism is not yet clear in this study it is found that the november december nd sam exhibits a significant inverse relationship with the winter precipitation over east asia particularly southern china observational and numerical evidences show that anomalous nd sam is usually associated with a south atlantic pacific dipole sea surface temperature anomaly ssta which persists into ensuring winter the dipole ssta can modulate the variability of the inter tropical convergence zone itcz in pacific subsequently a distinguished atmospheric tele connection pattern is induced and prevails over the nh mid latitude region as a response to the anomalous itcz large areas of high pressure anomalies are triggered at upper troposphere over east asia and centered over southern china which favors less precipitation over east asia particularly southern china and vice versa through such a physical mechanism the notable influence of the nd sam can sustain through the following season and impact on the nh winter climate

interhemispheric propagation of stationary rossby waves in a horizontally nonuniform background flow abstractsignificant interhemispheric teleconnections are identified that span the tropical easterlies in the boreal summer 300 hpa streamfunction such as the north africa antarctic naa and the north pacific south america npsa patterns these patterns are not supported by traditional wave theory since stationary waves in a basic state without meridional wind would be trapped in the easterlies to describe the interhemispheric responses more realistically two dimensional spherical rossby wave theory in a horizontally nonuniform basic state is considered conditions sufficient for the existence of one propagating wave are obtained and the meridional group velocity of the wave is shown to have the same direction as the meridional basic wind at the traditional critical latitude it is concluded that stationary waves with a specific wavelength can propagate across the easterlies from south north to north south via southerly northerly flows hence energy transport by stationary waves on a horizont

geochronology and geochemistry of high pressure granulites of the arthur river complex fiordland new zealand cretaceous magmatism and metamorphism on the palaeo pacific margin the arthur river complex is a suite of gabbroic to dioritic orthogneisses in northern fiordland new zealand the arthur river complex separates rocks of the median tectonic zone a mesozoic island arc complex from palaeozoic rocks of the palaeo pacific gondwana margin and is itself intruded by the western fiordland orthogneiss new shrimp u pb single zircon data are presented for magmatic metamorphic and deformation events in the arthur river complex and adjacent rocks from northern fiordland the arthur river complex orthogneisses and dykes are dominated by magmatic zircon dated at 136 129 ma a dioritic orthogneiss that occurs along the eastern margin of the complex is dated at 154 4 3 6 ma and predates adjacent plutons of the median tectonic zone rims on zircon cores from this sample record a thermal event at c 120 ma attributed to the emplacement of the western fiordland orthogneiss migmatitic palaeozoic orthogneiss from the arthur river complex 346 6 ma is interpreted as deformed wall rock very fine rims 5 20 lm also indicate a metamorphic age of c 120 110 ma a post tectonic pegmatite 81 8 1 8 ma may be related to phases of crustal extension associated with the opening of the tasman sea the arthur river complex is interpreted as a batholith emplaced at mid crustal levels and then buried to deep crustal levels due to convergence of the median tectonic zone arc and the continental margin

dynamics of an interhemispheric teleconnection across the critical latitude through a southerly duct during boreal winter abstractin this study an interhemispheric teleconnection pattern across the critical latitude from southern africa through south asia to the north pacific was revealed in boreal winter monthly averaged 250 hpa streamfunction fields obtained from both the 40 yr ecmwf re analysis era 40 and the ncep ncar reanalysis data from 1957 58 to 2001 02 classical rossby wave theory for zonally varying flow in which the effects of the basic state meridional wind are ignored predicts that stationary rossby waves cannot propagate across easterlies to elucidate the underlying mechanisms responsible for this interhemispheric teleconnection the theoretical basis for stationary wave propagation across the critical latitude is considered taking into account meridional ambient flow the theoretical results suggest that the southerly flow over east africa the western indian ocean and south asia creates a path for the northward propagation of stationary waves across the critical latitude stationary wavenumber and grou