density log of a 181 m long ice core from berkner island antarctica a 181 m long ice core was drilled at 79 36 51 s 45 43 28 w near the summit of berkner island antarctica 886 m a s l berkner island is located between the filchner and ronne ice shelves and the ice near the summit shows little lateral flow the density of the ice core was measured every 3 mm along its length using attenuation of a gamma ray beam which gave an absolute accuracy of 2 as expected there is a general density increase with depth the maximum densities of 900 kg m 3 being reached just above 100 m depth comparison with the electrical conductivity method ecm shows density variations with the same wavelength as the annual signals which can be seen in the ecm log higher acidity during summer in the shallowest part of the core the density of winter layers is higher than that of summer layers a relationship which is reversed at greater depth we assume that the densification rates for the two types of firn are different similar density phenomena were observed on ice cores from greenland showing that such phenomena are not a local effect

the madden julian oscillation barotropic dynamics and north pacific tropical cyclone formation part i observations low level barotropic dynamics may help to explain the modulation of eastern and western north pacific tropical cyclones by the madden julian oscillation mjo during northern hemisphere summer the mjo is characterized by alternating periods of westerly and easterly 850 mb zonal wind anomalies across the tropical pacific ocean when mjo 850 mb wind anomalies are westerly small scale slow moving eddies grow through barotropic eddy kinetic energy eke conversion from the mean flow these growing eddies together with strong surface convergence 850 mb cyclonic shear and high mean sea surface temperatures create a favorable environment for tropical cyclone formation periods of strong mjo easterlies over the pacific are characterized by lesser eke and negligible eddy growth by barotropic conversion the term 2 x is a leading contributor to low level barotropic eke conversion during mjo westerly 2 u9 u periods across the pacific indicating the importance of zonal variations in the westerly jet for producing concentrations of eddy energy this mechanism can be described as wave accumulation associated with variations of the low level zonal flow the conversion term 2 y contributes a smaller portion of the total conversion u9y9 u over the eastern pacific but is of comparable importance to 2 x during westerly mjo events in the 2 u9 u western pacific

temporal and spatial variability of surface mass balance at dome fuji east antarctica by the stake method from 1995 to 2006 the surface mass balance smb at dome fuji east antarctica was estimated using 36 bamboo stakes grid of 6 6 placed at 20 m intervals from 1995 to 2006 the heights of the stake tops from the snow surface were measured at 0 5 cm resolution twice monthly in 1995 1996 1997 and 2003 and once a year for the rest of the study period to account for snow settling the average snow density at the stake base during the measurements was used for converting the stake height data to smb the annual smb from 1995 to 2006 at dome fuji was 27 3 1 5 kg m 2 a 1 this result agrees well with the annual smb from ad 1260 to 1993 26 4 kg m 2 a 1 estimated from volcanic signals in the dome fuji ice core over the period 1995 2006 there were 37 8 6 of the measurements negative or zero annual smb results variation in the multi year averages of annual smb decreased with the square root of the number of observation years and 10 years of observations of a single stake allowed the estimation of annual smb at 10 accuracy the frequency distributions of annual and monthly smb were examined the findings clarify the complex behavior of the annual and monthly smb at dome fuji which will be common phenomena in areas of low snow accumulation of the interior of the antarctic ice sheet

tropical indian ocean influence on northwest pacific tropical cyclones in summer following strong el nino abstract in the summer following a strong el nino tropical cyclone tc number decreases over the northwest nw pacific despite little change in local sea surface temperature the authors analysis suggests el nino induced tropical indian ocean tio warming as the cause the tio warming forces a warm tropospheric kelvin wave that propagates into the western pacific inducing surface divergence off the equator the tropospheric kelvin wave suppresses convection and induces an anomalous anticyclone over the nw pacific both anomalies unfavorable for tcs the westerly vertical shear associated with the warm kelvin wave reduces the magnitude of vertical shear in the south china sea and strengthens it in the nw pacific an east west variation that causes tc activity to increase and decrease in respective regions these results help improve seasonal tc prediction

na2so4 and mgso4 salts during the holocene period derived by high resolution depth analysis of a dome fuji ice core we analyzed the profiles of ionic chemical species in three 500 mm sections of an ice core from dome fuji antarctica dated 3 0 8 9 and 13 3 kyr bp before present and compared the profiles to those in the surface snow the 3 0 and 8 9 kyr sections are from the holocene and the 13 3 kyr section slightly predates the holocene the analyses were done on 2 mm thick slices within each section at each depth the primary ionic species were na h cl and so 4 2 a the so 4 2 na and mg 2 levels varied with depth in each section over distances ranging from several millimeters to several centimeters also the correlation coefficients between na and so 4 and between mg 2 and so 4 2 for each depth were 0 90 or greater in contrast to the value of 0 59 or less in the surface snow defined here as 0 3 4 m from the surface these results suggest that almost all na and mg 2 in the holocene ice exists as na 2 so 4 and mgso 4 salts and the formation of these salts occurs not only in the atmosphere during transport but also in the firn layer

snow and firn permeability at siple dome antarctica the nature of air snow exchange processes depends upon both the physical characteristics of the snow and forcing from the atmosphere an understanding of snow air transport processes and models of these processes are important for interpreting ice cores and for predicting remotely sensed snow surface characteristics accurate modeling requires knowledge of the physical characteristics of the snow and firn in this paper measurements of snow and firn permeability from the surface down to 12 m depth at siple dome antarctica are presented the permeability varies greatly as a function of layer and depth generally increasing to approximately 3 m and generally decreasing below that the maximum permeability 280 10 10 1 0 m2 occurs at approximately 3 m depth the lowest permeability in the top 12 m of snow and firn 10 10 10w m2 was measured in the surface wind pack the measurements show that layering and microstructure have large effects on permeability a mathematical expression for the overall variation of permeability with depth is presented it is shown that snow density is a poor indicator of permeability quantitative microscopy may be helpful in relating observed snow characteristics to permeability and useful in modeling firnification and chemical species transport

indian ocean capacitor effect on indo western pacific climate during the summer following el nino significant climate anomalies persist through the summer june august after el nino dissipates in spring over the equatorial pacific they include the tropical indian ocean tio sea surface temperature sst warming increased tropical tropospheric temperature an anomalous anticyclone over the subtropical northwest pacific and increased mei yu baiu rainfall over east asia the cause of these lingering el nino effects during summer is investigated using observations and an atmospheric general circulation model gcm the results herein indicate that the tio warming acts like a capacitor anchoring atmospheric anomalies over the indo western pacific oceans it causes tropospheric temperature to increase by a moist adiabatic adjustment in deep convection emanating a baroclinic kelvin wave into the pacific in the northwest pacific this equatorial kelvin wave induces northeasterly surface wind anomalies and the resultant divergence in the subtropics triggers suppressed convection and the anomalous anticyclone the gcm results support this kelvin wave induced ekman divergence mechanism in response to a prescribed sst increase over the tio the model simulates the kelvin wave with low pressure on the equator as well as suppressed convection and the anomalous anticyclone over the subtropical northwest pacific an additional experiment further indicates that the north indian ocean warming is most important for the kelvin wave and northwest pacific anticyclone a result corroborated by observations these results have important implications for the predictability of indo western pacific summer climate the spatial distribution and magnitude of the tio warming rather than simply whether there is an el nino in the preceding winter affect summer climate anomalies over the indo western pacific and east asia

temperature gradient and initial snow density as controlling factors in the formation and structure of hard depth hoar we investigate how temperature gradient and initial density influence depth hoar growth in snow and seek to better define the range of conditions under which cohesive or hard depth hoar forms samples of 400 kg m 3 sieved snow were exposed to temperature gradients of 20 80 c m 1 and samples of four different densities were exposed to a 40 c m temperature gradient following exposure to temperature gradients penetrometer tests were made on samples to determine the presence of solid and or hard depth hoar grain bond orientation was analyzed in section planes by two dimensional stereological techniques where hard depth hoar developed results indicate that hard cohesive depth hoar forms from rounded grain snow having a density of 400 kg m 3 or greater following exposure to a temperature gradient of 20 c m 1 or greater hard depth hoar appears to consist of solid type depth hoar grains connected by necks with vertically preferred directions of grain elongation and organization of grain to grain chains this work corroborates atikaya s 1974 results but extends his observation of formation of hard depth hoar to weaker temperature gradients for high density snow our results also indicate that hard depth hoar is composed of faceted solid type anhedral grains

asymmetry in the duration of el nino and la nina abstract el nino and la nina are not a simple mirror image but exhibit significant differences in their spatial structure and seasonal evolution in particular sea surface temperature sst anomalies over the equatorial pacific cold tongue are larger in magnitude during el nino compared to la nina resulting in positive skewness of interannual sst variations the associated atmospheric deep convection anomalies are displaced eastward during el nino compared to la nina because of the nonlinear atmospheric response to sst in addition to these well known features an analysis of observational data for the past century shows that there is a robust asymmetry in the duration of el nino and la nina most el ninos and la ninas develop in late boreal spring summer when the climatological cold tongue is intensifying and they peak near the end of the calendar year after the mature phase el ninos tend to decay rapidly by next summer but many la ninas persist through the following year and often reintensify in

westerly wind bursts and their relationship with intraseasonal variations and enso part ii energetics over the western and central pacific abstract the mechanism of synoptic scale eddy development in the generation of westerly wind bursts wwbs over the western central pacific and their relationship with the el nino southern oscillation enso and the madden julian oscillation mjo were examined in the wwb occurrences barotropic structures of equatorial eddy westerlies with cyclonic disturbances were found from the surface to the upper troposphere the dominant contributions to substantial eddy kinetic energy eke were the barotropic energy conversion kmke in the lower and middle tropospheres and the conversion from eddy available potential energy peke in the upper troposphere low frequency environmental westerlies centered near the equator preceded strong zonal convergence and meridional shear resulting in the substantial kmke the activation of synoptic convection also contributed to an increase in eke through peke these energies were redistributed to the lower equatorial troposphere through energy flux convergence gke the

modulation of north pacific tropical cyclone activity by three phases of enso abstract tropical pacific ocean warming has been separated into two modes based on the spatial distribution of the maximum sea surface temperature sst anomaly an east pacific warming epw and a central pacific warming cpw when combined with east pacific cooling epc these three regimes are shown to have different impacts on tropical cyclone tc activity over the north pacific by differential modulation of both local thermodynamic factors and large scale circulation patterns in epw years the genesis and the track density of tcs tend to be enhanced over the southeastern part and suppressed in the northwestern part of the western pacific by strong westerly wind shear the extension of the monsoon trough and the weak wind shear over the central pacific increases the likelihood of tc activity to the east of the climatological mean tc genesis location in cpw years the tc activity is shifted to the west and is extended through the northwestern part of the western pacific the westward shifting of c

the local insolation signature of air content in antarctic ice a new step toward an absolute dating of ice records an accurate chronology of ice cores is still needed for interpreting the paleoclimatic record and to understand the relation between insolation and climate a new domain of research in this area has been stimulated by the work of m bender linking the record of n2 o2 ratio in the air trapped in the ice with the local insolation here we investigate the potential of the air content of polar ice v as another and complementary ice proxy of local insolation we propose that the long term changes in air content recorded in ice from the high antarctic plateau is dominantly imprinted by the local summer insolation the v measurements covering the last 440 000 yr and obtained along the epica dc edc ice core are presented 86 of the variance observed in the v record can be explained neither by air pressure nor by temperature changes and then should reflect properties influencing the porosity at close off other than temperature a wavelet analysis indicates a dominant obliquity period around 41 ka over the last 440 ka we propose a mechanism which can account for the observed anti correlation between local insolation and v and explain how the local insolation via the integrated summer insolation can affect the near surface snow structure and consequently the porosity at close off the v and the integrated summer insolation changes show high coherency over all the record and a variable phase relationship with a maximum phase difference of about 4000 yr around 200 ka ago the phase difference may reflect the difference between the edc2 chronology based on an inverse dating method and an accurately dated insolation curve our work by proposing a new and complementary ice proxy for local insolation should eventually contribute to the establishment of an absolute dating of the ice paleo record

metamorphism of stratified firn at dome fuji antarctica a mechanism for local insolation modulation of gas transport conditions during bubble close off 1 the evolution of the structure of a 112 59 m long firn core recovered at dome fuji east antarctica was investigated in order to improve understanding of firn densification and bubble formation processes which are important for interpreting local insolation proxies used for astronomical dating of deep ice cores using selected samples we measured physical properties including 1 the relative dielectric permittivities in both the vertical and horizontal planes 2 the bulk density at a resolution of millimeters 3 the three dimensional geometric structure of pore space and 4 crystal orientation fabrics we found that the firn at dome fuji contains horizontal strata with thicknesses of several centimeters near the surface of the ice sheet these strata are characterized by contrasting bulk density earlier field studies suggest that summer insolation causes densification of surface firn down to 30 m density maxima exhibited a clear positive correlation with the strength of structural anisotropy and c axis clustering around the vertical in contrast the correlation is negative in deeper firn confirming previous findings that initially less dense firn became denser than initially dense firn in addition numerous examples of textures indicating that deformation preferentially occurred in weaker layers were found moreover the initially dense firn layers were more permeable for air near the bottom of firn we propose a model linking firn properties with conditions for the gas transport processes near the bottom of firn the model explains how stronger insolation can lead to bulk ice with a lower o2 n2 ratio and smaller total gas content

connection between the decadal variability in the southern ocean circulation and the southern annular mode previous studies demonstrated the remarkable upward trend of the southern annular mode sam and southern ocean wind stress in association with anthropogenic forcing an oceanic reanalysis data set is used to investigate the response of the circulation in the southern ocean to the decadal variability of sam our results indicate the strengthening and the poleward shift of the northward ekman velocity as well as the ekman pumping rate which led to a corresponding strengthening trend in the deacon cell this strengthening in turn intensified the meridional density gradient and the tilting of the isopycnal surfaces on the interannual time scale the antarctic circumpolar currents acc transport exhibits a positive correlation with sam index as seen separately in observations however there is no significant trend in the total transport of acc possible reasons are discussed

orbital tuning chronology for the vostok climate record supported by trapped gas composition abstract we present data on the o2 n2 ratios of trapped gas samples for the entire length of the vostok climate record as in other cores o2 n2 ratios in these samples are less than the atmospheric ratio by a small and variable amount because o2 is selectively excluded during the gas trapping process and because o2 is also preferentially lost in poorly preserved core samples samples younger than 150 ka have large and variable o2 depletions samples older than 200 ka have o2 n2 ratios that replicate well and vary smoothly with depth we plot o2 n2 ratios of well replicated samples older than 160 ka using a chronology derived by matching the 18o of paleoatmospheric o2 18oatm to northern hemisphere june insolation on this timescale o2 n2 varies coherently with local 78 s summertime insolation based on time series analysis of the o2 n2 record and the dynamics of snow metamorphism at the surface we conclude that summertime insolation influences physical properties of ice grains that control the degree of o2 exclusion during bubble closeoff o2 n2 in vostok is thus arguably a property that records local summertime insolation and can be used to test independent chronologies for the core we show that the 18oatm chronology supported by the coincidence of o2 n2 ratios with insolation is also compatible with recent radiometric dating of corals from high sea stands we further successfully test the 18oatm tuning chronology by showing that it predicts a chronology for the gisp2 core which is essentially indistinguishable from the standard gisp2 chronology and therefore in excellent agreement with the radiometric chronology of hulu cave china an accurate chronology for the vostok ice core is now in place

contrasting eastern pacific and central pacific types of enso abstract surface observations and subsurface ocean assimilation datasets are examined to contrast two distinct types of el nino southern oscillation enso in the tropical pacific an eastern pacific ep type and a central pacific cp type an analysis method combining empirical orthogonal function eof analysis and linear regression is used to separate these two types correlation and composite analyses based on the principal components of the eof were performed to examine the structure evolution and teleconnection of these two enso types the ep type of enso is found to have its sst anomaly center located in the eastern equatorial pacific attached to the coast of south america this type of enso is associated with basinwide thermocline and surface wind variations and shows a strong teleconnection with the tropical indian ocean in contrast the cp type of enso has most of its surface wind sst and subsurface anomalies confined in the central pacific and tends to onset develop and decay in situ

the age of the air in the firn and the ice at summit greenland in the framework of the eurocore drilling project 1989 at summit central greenland air samples were collected from a drill hole in the firn at several depth levels the samples have been analyzed for 85kr co2 ch4 cfc s f 11 and f 12 contents and for the isotopic composition of nitrogen and oxygen the measured data are compared with the results of a diffusion model co2 for example takes 12 years with a standard deviation of 7 5 years to diffuse from the surface to the firn ice transition under the present climatic conditions at summit the difference between the age of the ice and the mean age of the occluded air is approximately 210 years an enrichment of the heavier isotopes due to separation by gravity has been observed molecular diffusion alone suffices to explain the observed concentration trends in the firn column we can however not exclude the existence of a convective zone below the surface we have also measured the density and closed porosity along the firn core that has been retrieved when drilling the hole the porosity data reveal that the air is occluded into bubbles mainly between 65 and 80 m corresponding to densities of 790 and 830 kg m3 respectively

strong modulation of the pacific meridional mode on the occurrence of intense tropical cyclones over the western north pacific abstractthis study finds a significant positive correlation between the pacific meridional mode pmm index and the frequency of intense tropical cyclones tcs over the western north pacific wnp

a flow law for anisotropic ice and its application to ice sheets a new formulation of the flow law of polycrystalline ice was derived for an rbitrary c axis orientation fabric pattern the rate factor of the flow law is given by a geometrical factor that can be calculated with c axis fabric data and stress condition a theoretical calculation combining this flow law with a lattice rotation model by intracrystalline slip in the constituent grains predicts the development of characteristic fabric patterns observed in many laboratory experiments and in the field according to this flow model of polycrystalline ice if significant recrystallization does not occur uniaxial compression makes the ice body harder with increasing strain whereas simple shear makes the ice body softer with strain this may significantly affect ice sheet dynamics

characteristics of mesoscale convective systems over china and its vicinity using geostationary satellite fy2 abstractthis study investigates mesoscale convective systems mcss over china and its vicinity during the boreal warm season may august from 2005 to 2012 based on data from the geostationary satellite fengyun 2 fy2 series the authors classified and analyzed the quasi circular and elongated mcss on both large and small scales including mesoscale convective complexes mccs persistent elongated convective systems pecss meso circular convective systems m ccss meso elongated convective system m ecss and two additional types named small meso circular convective systems sm ccss and small meso elongated convective systems sm ecss results show that nearly 80 of the 8696 mcss identified in this study fall into the elongated categories overall mcss occur mainly at three zonal bands with average latitudes around 20 30 and 50 n the frequency of mcss occurrences is maximized at the zonal band around 20 n and decreases with increase in latitude during the eight warm seasons the p

variation in n2 o2 ratio of occluded air in dome fuji antarctic ice ancient atmospheric gases are trapped in polar ice sheets the gas molecules are stored in air bubbles at shallow depth and are incorporated into clathrate hydrates below a depth at which the hydrostatic pressure becomes greater than the formation pressure of the air clathrate hydrate significant gas fractionation has been found from measurements of the depth profile of the n2 o2 composition ratios in clathrate hydrates and air bubbles of vostok antarctic ice to investigate the effect of the ice condition on the fractionation process we measured the n2 o2 ratios in clathrate hydrates and air bubbles from dome fuji antarctic ice using raman spectroscopy the results showed that the n2 o2 ratios in the clathrate hydrates of the dome fuji ice are slightly lower than those of the vostok ice although the tendency of the variation of the n2 o2 ratio with depth is similar the difference in the n2 o2 ratio between the dome fuji ice and the vostok ice for the transition zone is attributed to the difference of the ice temperature and the snow accumulation rate on the other hand it is concluded that the difference in the bubble free ice zone was caused by gas loss from the ice core after coring the n2 o2 ratio of clathrate hydrate increases after coring because of higher diffusion rate and lower dissociation pressure of o2 than of n2 our data suggest that the effect of gas loss in the dome fuji ice is relatively small and so the gas composition in the dome fuji ice can be a precise paleoenvironmental indicator

asymmetry in zonal phase propagation of enso sea surface temperature anomalies 1 it is often emphasized in the literature that the phase propagation of el nino sea surface temperature sst anomalies along the equator changed from westward to eastward after a mid to late 1970s climate regime shift in the pacific theories have been developed to explain this change of phase propagation in terms of changes in background state on which el nino events develop those theories also suggest that the direction of la nina anomaly phase propagation should have changed from westward to eastward as well however the direction of la nina sst anomaly phase propagation did not change after the mid to late 1970s instead la nina ssts continued to exhibit westward phase propagation along the equator a feature overlooked in both observational analyses and theories this paper highlights the asymmetry in zonal phase propagation between el nino and la nina sea surface temperature anomalies since 1980 and discusses the implications of that asymmetry for understanding el nino southern oscillation enso dynamics

microstructure dependent densification of polar firn derived from x ray microtomography the densification of dry polar snow and firn results in a continuous increase of density with depth accompanied by significant density fluctuations within seasonal layers density measurements of high spatial resolution reveal a persistent minimum of density fluctuations in the vicinity of the snow firn transition 0 55 0 65 g cm 3 in firn core records in this study we give an explanation for the fluctuation minimum by applying a new method of x ray microtomography to obtain three dimensional 3 d structural data of a greenland firn core at 13 different depths between 10 and 78 m a set of 16 samples of 40 cm total length for each depth interval was measured a reconstructed firn segment of 40 cm covers 1 2 years of snow accumulation using digital image analysis techniques different structural parameters are estimated including 3 d pore and particle sizes and specific surface areas it is shown that the densification rates of snow and firn layers consisting of coarse particles are much higher than those consisting of fine particles within the same depth interval this causes a density crossing of fine and coarse grained layers with a minimum of density variations at the crossover point this crossing over implies that formerly dense layers in the seasonal density signal are not of the same origin as dense layers in the deeper part of the firn column and that the seasonal density signal will totally change shape with depth it is speculated that in coarse and fine grained firn the dominant mechanism of densification acts over different regimes of density

snow crystal growth with varying surface temperatures and radiation penetration the temperature field is derived for a sinusoidally varying surface temperature with varying solar radiation penetration the growth rates of snow crystals are calculated to explain the rapidly growing layers of faceted crystals i e depth hoar that form just below the surface at high altitudes and in polar snow the solutions also show that a layer of wet snow can exist just below the surface even on days when the surface temperature remains sub freezing

age difference between polar ice and the air trapped in its bubbles air entrapped in bubbles formed in cold ice has essentially the same composition as that of the atmosphere at the time of bubble formation the analysis of dated ice samples therefore enables the history of atmospheric composition to be investigated 1 3 the age of the entrapped air is however not the same as that of the surrounding ice because air bubbles only become isolated from the atmosphere during the transition from firn to ice typically the age of the ice at this transition is between 100 and 3 000 yr depending mainly on firn temperature and snow accumulation rate the mean age difference between ice and enclosed air as well as the age distribution width for a given sample are especially important for the investigation of the anthropogenic increase of co2 and trace gases in the atmosphere over the last centuries and for the comparison of climatic parameters recorded in the ice with parameters recorded in the bubbles for siple station antarctica this age difference and age distribution width were deduced from the bubble volume measured as a function of depth the values are 95 yr and 22 yr respectively

homogeneous climate variability across east antarctica over the past three glacial cycles recent ice core studies have raised the disturbing possibility that glacial interglacial climate changes may be non uniform across antarctica1 2 these findings have been confined to records from the ross sea sector of the continent but significant deviations in other areas would call into question the widely assumed validity of the climate record obtained from vostok east antarctica on large spatial scales3 here we present an isotopic profile from a core drilled at dome fuji4 5 situated 1 500 km from vostok in a different sector of east antarctica the two records show remarkable similarities over the past three glacial cycles the extent of the dome fuji record in both large amplitude changes such as terminations interglacials and interstadials and more subtle glacial events even when the origin of precipitation is accounted for our results indicate that antarctic climate is essentially homogeneous at the scale of the east antarctic plateau possibly as a consequence of the symmetry of the plateau and the adjacent ocean

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

firn air δ15n in modern polar sites and glacial interglacial ice a model data mismatch during glacial periods in antarctica the phase lag between atmospheric composition air bubbles and temperature water isotopes can be quantified from ice cores provided that the age difference between entrapped air and the surrounding air can be correctly estimated this difference depends on the lock in depth lid when air no longer mixes with the atmosphere the lid can be estimated from firnification models or from the air isotopic composition 15n and 40ar both methods give consistent results for greenland and one coastal site in antarctica byrd new firn measurements in greenland northgrip and antarctica berkner island bas depot dome c confirm that firnification models correctly reproduce the present lid over a large range of surface conditions however a systematic mismatch is observed for the last glacial maximum lgm in east antarctic sites vostok dome c dome f questioning the model s validity here we use new 15n measurements from two coastal antarctic sites kohnen station and law dome providing depth estimates again distinct from firnification model calculations we show that this discrepancy can be resolved by revising the estimate of past accumulation rates 15n measurements can therefore help to constrain past accumulation rate and improve ice core dating

seasonal modulations of different impacts of two types of enso events on tropical cyclone activity in the western north pacific the paper examines different impacts of eastern pacific warm cold epw epc and central pacific warm cold cpw cpc events on tropical cyclones tcs in the western north pacific wnp by considering the early season of april june amj the peak season of july september jas and the late season of october december ond during amj epw epc is associated with a significant increase of the tc genesis number in the southeastern southwestern sub region of the wnp but no class of el nino southern oscillation enso events shows a significant change in the tc lifetime and intensity during jas epw corresponds to an increase decrease of the tc genesis number in the southeastern northwestern sub region but cpw shows no significant change epc increases the tc genesis in the northwestern and northeastern sub regions and decreases the genesis in the southwestern sub region whereas cpc suppresses the genesis in the southeastern sub region both the lifetime and intensity of tcs are increased in epw but only a shortened lifetime is seen for cpc during ond epw reduces the tc genesis in the southwestern and northwestern sub regions whereas cpw enhances the genesis in the southeastern sub region over the south china sea cpw and cpc show a significant decrease and increase of the tc genesis respectively the tc lifetime is significantly longer in both epw and cpw and shorter in epc and tcs tend to be more less intense in epw cpc all of these variations are consistent with the development of enso related sst anomalies during different seasons and are supported by distributions of the genesis potential index a combination of large scale oceanic and atmospheric factors that affect tc activity tcs in the wnp mainly take the straight westward northwestward and recurving tracks during amj of epw years the tc steering flow patterns favor the recurving track and suppress the straight westward and northwestward tracks during jas epw is associated with the steering flows that are unfavorable for tcs to move northwestward or westward whereas cpw favors the northwestward track and suppresses the straight westward track the steering flow patterns during ond are similar to those during jas except that epc may increase the possibility of the northwestward track

modeling the densification of polar firn including heat diffusion application to close off characteristics and gas isotopic fractionation for antarctica and greenland sites 1 modeling the densification of polar firn is essential to estimate variations of close off characteristics density close off depth delta age in relation with past climate parameters temperature and accumulation rates furthermore the air composition in the firn is modified by gravitational and thermal fractionation and stable isotope measurements of permanent gases like nitrogen or argon can provide information on the amplitude of these fractionations in this work we propose a new model coupling firn densification and heat diffusion in addition to the determination of the firn thickness and gas ice age differences the model allows a reconstruction of the time evolution of the temperature for different sites in antarctica vostok and greenland gisp2 and therefore the evolution of gravitational and thermal isotopic fractionations in firn under present day conditions the modeled profiles are in good agreement with the available temperature measurements in firn for sites with low accumulation rates such as vostok the results show the existence of temperature gradients in the firn column even when no rapid climatic changes occur the comparison of the modeled 15n results to measurements allows to better constrain the 18o temperature relationship used to infer the surface temperature history and for gisp2 the model validates the long term borehole based temperature

tropical cyclone track characteristics as a function of large scale circulation anomalies abstract factors that contribute to intraseasonal variability in western north pacific tropical cyclone track types are investigated it is hypothesized that the 700 mb large scale circulation can affect tropical cyclone track characteristics by enhancing or excluding genesis in certain regions and concurrently prohibiting or favoring recurving versus straight tracks a track type climatology indicates that genesis location alone may explain some of the variability in track type although some genesis regions have no preference for straight moving or recurving tracks a formation north of 20 n or east of 150 e and north of 10 n favors a recurvature track these recurving storms are classified as recurving north and recurving storms that form in regions with nearly equal probability of straight or recurving tracks are classified as recurving south a compositing technique is used to define anomalous 700 mb large scale circulations that exist during the formation of tropical cyclones that subsequently fol

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

age scale of the air in the summit ice implication for glacial interglacial temperature change the air occluded in ice sheets and glaciers has in general a younger age defined as the time after its isolation from the atmosphere than the surrounding ice matrix because snow is first transformed into open porous firn in which the air can exchange with the atmosphere only at a certain depth firn ice transition the pores are pinched off and the air is definitely isolated from the atmosphere the firn ice transition depth is at around 70 m under present climatic conditions at summit central greenland the air at this depth is roughly 10 years old due to diffusive mixing whereas the ice is about 220 years old this results in an age difference between the air and the ice of 210 years this difference depends on temperature and accumulation rate and did thus not remain constant during the past we used a dynamic firn densification model to calculate the firn ice transition depth and the age of the ice at this depth and an air diffusion model to determine the age of the air at the transition past temperatures and accumulation rates have been deduced from the 18o record using time independent functions we present the results of model calculations of two paleotemperature scenarios yielding a record of the age difference between the air and the ice for the greenland ice core project grip and the greenland ice sheet project two gisp2 ice cores for the last 100 000 years during the holocene the age difference stayed rather stable around 200 years while it reached values up to 1400 years during the last glaciation for the colder scenario the model results are compared with age differences obtained independently by matching corresponding climate events in the methane and 18o records assuming a very small phase lag between variations in the greenland surface temperature and the atmospheric methane the past firn ice transition depths are compared with diffusive column heights obtained from 15n of n2 measurements the results of this study corroborate the large temperature change of 20 to 25 k from the coldest glacial to holocene climate found by evaluating borehole temperature profiles

tropical cyclone motion and evolution in vertical shear abstract the motion and the evolution of tropical cyclone like vortices in an environmental flow with vertical shear are investigated using a baroclinic primitive equation model the study focuses on the fundamental dynamics of a baroclinic vortex in vertical shear the influence of vortex structure and the role of diabatic heating the results show that the initial response of the vortex to the vertical shear is to tilt downshear as soon as the tilt develops the upper level anticyclonic and lower level cyclonic circulations begin to interact with each other as a result of these interactions the tilted axis of the vortex reaches a stable state after an initial adjustment which varies with the structure of the vortex its environmental flow shear and the cumulus convective heating the motion of an adiabatic vortex in vertical shear is controlled by both the steering of the environmental flow and vertical coupling mechanisms most of the vortices move with the environmental flow at about 650 hpa or

decadal changes of enso persistence barrier in sst and ocean heat content indices 1958 2001 decadal changes of el nino southern oscillation enso persistence barriers in various indices of sea surface temperature sst and ocean heat content ohc are examined in this study using observations and ocean data assimilation products for the period 1958 2001 it is found that the sst indices in the eastern and central equatorial pacific exhibit very different decadal barrier variability the variability is large for the eastern pacific sst indices nino1 2 and nino3 whose persistence barriers shifted abruptly in 1976 1977 and 1989 1990 in contrast the central pacific sst indices nino3 4 and nino4 experienced little decadal barrier variability and have had their persistence barriers fixed in spring in the past four decades the zonal mean ohc index averaged over the equatorial pacific shows decadal barrier changes similar to those in the eastern pacific sst indices and always leads the nino3 sst barrier by about one season it is noticed that the sst persistence barrier appeared first in the eastern pacific before 1976 1977 first in the central pacific between 1976 1977 and 1989 1990 and almost simultaneous in both the eastern and central pacific after 1989 1990 these timings coincide with the westward propagating eastward propagating and standing pattern of enso sst anomalies observed in these three periods these results suggest that enso sst anomalies in the equatorial pacific can be considered to consist of two different processes a central pacific process whose phase transition such as onset and barrier always happen in spring and an eastern pacific process whose phase transition and barrier change from decade to decade and are influenced by changes in the mean thermocline depth along the equatorial pacific

two types of el nino events cold tongue el nino and warm pool el nino abstract in this study two types of el nino events are classified based on spatial patterns of the sea surface temperature sst anomaly one is the cold tongue ct el nino which can be regarded as the conventional el nino and the other the warm pool wp el nino the ct el nino is characterized by relatively large sst anomalies in the nino 3 region 5 s 5 n 150 90 w while the wp el nino is associated with sst anomalies mostly confined to the nino 4 region 5 s 5 n 160 e 150 w in addition spatial patterns of many atmospheric and oceanic variables are also distinctively different for the two types of el nino events furthermore the difference in the transition mechanism between the two types of el nino is clearly identified that is the discharge process of the equatorial heat content associated with the wp el nino is not efficient owing to the spatial structure of sst anomaly as a result it cannot trigger a cold event it is also demonstrated that zonal advective feedback i e zonal adve

possible linkage between the monsoon trough variability and the tropical cyclone activity over the western north pacific abstractthe present study investigates the influence of the monsoon trough mt on the interannual variability of tropical cyclone tc activity over the western north pacific during july november for the period 1979 2007 it is shown that the tc activity is closely related to the mt location during the years when the mt extends eastward retreats westward more less tcs form within the southeastern quadrant of the western north pacific such a relationship can be explained by the changes in large scale environmental factors associated with the movement of the mt an eastward extension of the mt coincides with warmed ocean surface enhanced convection increased relative humidity in the lower and midtroposphere reduced vertical shear of zonal wind intensified upper level divergence and low level anomalous cyclonic vorticity over the southeast quadrant of the western north pacific these conditions associated with the eastern extension of the mt are favorable for tc genesis while those associated w

effects of molecular diffusion on trapped gas composition in polar ice cores abstract enrichment of nitrogen gas has been found from gas analyses of ice cores retrieved from deep parts of antarctica neither climate change nor gas loss through ice cracks explain the enrichment in order to investigate the mechanism of the gas composition change we develop a model of gas loss caused by molecular diffusion from clathrate hydrates toward the ice core surface through ice crystal we apply the model to interpret the data on the gas composition change in the dome fuji ice core during the storage for 3 years at 248 k the mass transfer coefficients determined using the model are 1 4 10 9 and 4 3 10 9 m s 1 at 248 k for n2 and o2 respectively the difference in the coefficient between n2 and o2 causes the change in the o2 n2 ratio of the trapped gas in the ice core during the storage during the storage period of 1000 days at 248 k the o2 n2 ratio changes from 9 9 to 20 5 the effect of the gas loss decreases as the storage temperature decreases the results have important implications for the accurate reconstructions of the paleo atmosphere from polar ice cores

tropical cyclone activity in the northwest pacific in relation to the el nino southern oscillation phenomenon abstract the interannual variations in tropical cyclone activity in the northwest pacific nwpac and their relationships with the el nino southern oscillation enso phenomenon were studied using the method of spectral analyses time series of a southern oscillation index soi defined as the sea level pressure difference between easter island and darwin and tropical cyclone activity in the entire nwpac ocean basin as well as in different regions of the nwpac were analyzed two spectral peaks are apparent in all these time series one corresponds to the generally accepted southern oscillation with a period of 3 to 3 5 years and another at the quasi biennial oscillation qbo frequency cross spectral analyses between the soi and tropical cyclone activity show significant coherence in these two spectral peaks the dominant peak is at the southern oscillation frequency with the soi leading typhoon activity by almost a year at the qbo frequency the two series are almost in phase cyclone activity in t

three evolution patterns of central pacific el nino 1 three evolution patterns are identified for the central pacific cp type of el nino based on events that occurred during 1958 2007 1 a symmetric decaying pattern whose sea surface temperature anomalies grow and decay symmetrically with respect to a peak phase 2 a prolonged decaying pattern that decays slowly and is followed by a warm event in the eastern pacific ep and 3 an abrupt decaying pattern that terminates rapidly after the peak and is followed by a cold event in the ep the depth of the equatorial thermocline is found to determine which evolution pattern occurs if the cp el nino occurs in a recharged thermocline state i e deeper than normal depth an ep warming may appear in the decaying phase of the cp event to slow down the decay giving rise to the prolonged decaying pattern if the thermocline is in a discharged state i e shallower than normal depth an ep cooling may occur to abruptly terminate the cp el nino if the thermocline is in a neutral state i e normal depth the cp event may have a symmetric pattern of growth and decay although a few exceptions exist these results indicate that the equatorial thermocline state at the peak phase of a cp el nino event can be a potential predictor of the way the event may decay

impact of shifting patterns of pacific ocean warming on north atlantic tropical cyclones two distinctly different forms of tropical pacific ocean warming are shown to have substantially different impacts on the frequency and tracks of north atlantic tropical cyclones the eastern pacific warming epw is identical to that of the conventional el nino whereas the central pacific warming cpw has maximum temperature anomalies located near the dateline in contrast to epw events cpw episodes are associated with a greater than average frequency and increasing landfall potential along the gulf of mexico coast and central america differences are shown to be associated with the modulation of vertical wind shear in the main development region forced by differential teleconnection patterns emanating from the pacific the cpw is more predictable than the epw potentially increasing the predictability of cyclones on seasonal time scales

el nino modoki and its possible teleconnection 1 using observed data sets mainly for the period 1979 2005 we find that anomalous warming events different from conventional el nino events occur in the central equatorial pacific this unique warming in the central equatorial pacific associated with a horseshoe pattern is flanked by a colder sea surface temperature anomaly ssta on both sides along the equator empirical orthogonal function eof analysis of monthly tropical pacific ssta shows that these events are represented by the second mode that explains 12 of the variance since a majority of such events are not part of el nino evolution the phenomenon is named as el nino modoki pseudo el nino modoki is a classical japanese word which means a similar but different thing the el nino modoki involves ocean atmosphere coupled processes which include a unique tripolar sea level pressure pattern during the evolution analogous to the southern oscillation in the case of el nino hence the total entity is named as el nino southern oscillation enso modoki the enso modoki events significantly influence the temperature and precipitation over many parts of the globe depending on the season the impacts over regions such as the far east including japan new zealand western coast of united states etc are opposite to those of the conventional enso the difference maps between the two periods of 1979 2004 and 1958 1978 for various oceanic atmospheric variables suggest that the recent weakening of equatorial easterlies related to weakened zonal sea surface temperature gradient led to more flattening of the thermocline this appears to be a cause of more frequent and persistent occurrence of the enso modoki event during recent decades

modelling of the densification of polar firn characterization of the snow firn transition the transformation of dry snow to firn is described by the transition between densification by deformationless restacking and densification by power law creep the observed decrease with temperature of the density at the snow firn transition seems to result from the competition between grain boundary sliding and power law creep these two densification processess occur concurrenlly in snow although there are probably micro regions in which sliding alone occurs validation ofa geometrical densifi cation model developed for ceramics has been obtained from densification data from several antarctic and greenland sites and from the characterization of the structure of polar firn

realistic models of anisotropic laminated lower crust the genesis of the laminated lower crust has been attributed to extensional processes leading to structural and textural ordering this implies that the lower crust might be anisotropic laboratory measurements of lower crustal rock samples and xenolithes show evidence of anisotropy in these rocks due to oriented structure in this paper we investigate the seismic shear wave response of realistic anisotropic lower crustal models using the anisotropic reflectivity method our models are based on representative petrophysical data obtained from exposed lower crustal sections in calabria south italy val strona and val sesia ivrea zone northern italy the models consist of stacks of anisotropic layers characterized by quantified elastic tensors derived from representative rock samples which provide alternating high and low velocity layers the seismic signature of the data is comparable to seismic observations of in situ lower crust for the models based on the calabria and val strona sequences shear wave splitting occurs for the moho reflection at offsets beyond 70 km with travel time delays up to 300 and 500 ms respectively the leading shear wave is predominantly horizontally polarized and followed by a predominantly vertically polarized shear wave contrastingly the val sesia model shows no clear evidence of birefringence isotropic versus anisotropic modelling demonstrates that the shear wave splitting is clearly related to the intrinsic anisotropy of the lower crustal rocks for the val strona sequence no evidence of birefringence caused by thin layering is found

impacts of an accumulation hiatus on the physical properties of firn at a low accumulation polar site 1 recent field investigations of a megadune region of east antarctica provide evidence that differences in grain size thermal conductivity and permeability across a megadune profile are due to spatial accumulation variability in the absence of significant microclimate variations the megadunes are low amplitude 2 8 m long wavelength 2 5 km bands with perceptible but low accumulation less than 40 mm water equivalent weq yr 1 and accumulation hiatus within several kilometers proximity as determined by remote sensing surface feature classification and ground penetrating radar profiling our hypothesis that accumulation rate impacts the extent of temperature gradient driven metamorphic growth in low accumulation rate sites is supported by measurements of various firn physical properties relatively small differences in accumulation rate less than 40 mm weq yr 1 result in large differences in physical properties including grain size thermal conductivity and permeability which are apparent in satellite based microwave data from both passive and active sensors the differences in physical snow structure between low accumulation areas and accumulation hiatus areas in the near surface are sufficiently distinct that evidence of past accumulation hiatus should be observable in the physical and chemical properties of an ice core record

anomalous winter climate conditions in the pacific rim during recent el nino modoki and el nino events present work compares impacts of el nino modoki and el nino on anomalous climate in the pacific rim during boreal winters of 1979 2005 el nino modoki el nino is associated with tripole dipole patterns in anomalies of sea surface temperature precipitation and upper level divergent wind in the tropical pacific which are related to multiple boomerangs of ocean atmosphere conditions in the pacific zonal and meridional extents of those boomerangs reflect their independent influences which are seen from lower latitudes in the west to higher latitudes in the east in the central pacific more moisture is transported from the tropics to higher latitudes during el nino modoki owing to displacement of the wet boomerang arms more poleward toward east discontinuities at outer boomerang arms manifest intense interactions between tropical and subtropical extratropical systems the pacific north american pattern and related climate anomalies in north america found in earlier studies are modified in very different ways by the two phenomena the seesaw with the dry north and the wet south in the western usa is more likely to occur during el nino modoki while much of the western usa is wet during el nino the moisture to the southwestern usa is transported from the northward shifted itcz during el nino modoki while it is carried by the storms traveling along the southerly shifted polar front jet during el nino the east asian winter monsoon related anticyclone is over the south china sea during el nino modoki as compared to its position over the philippine sea during el nino causing opposite precipitation anomalies in the southern east asia between the two phenomena

dipolar redistribution of summertime tropical cyclone genesis between the philippine sea and the northern south china sea and its possible mechanisms 1 recent observational records show that the dipole oscillation between the philippine sea ps and the northern south china sea nscs is a leading empirical orthogonal function eof of summertime tropical cyclone tc genesis in the western north pacific wnp this ps nscs oscillation is characterized by a distinguished decadal variability in addition to an interannual variability meanwhile the typical el nino southern oscillation enso related mode is found in the second eof mode which is predominantly interannual with regard to the ps nscs oscillation its interannual component appears to be linked with the previous wintertime enso event but the linkage is not so robust in the sense that about half of its significant events are classified as the enso related case whereas its decadal component is coupled to a sea surface temperature anomaly ssta in the central pacific with its equatorial core near the nino 4 region which is flanked by an opposite ssta on both sides along the latitudinal belt interestingly this ssta pattern resembles that related to the enso modoki and equivalently the transitional phase of enso the enso modoki is regionally manifested by the anomalous zonal sst gradient between the equatorial western and central pacific thus the decadal modulation of this anomalous zonal sst gradient can be regarded as an actual forcing that forms and modulates the decadal ps nscs oscillation in addition the decadal ps nscs oscillation is compared with the decadal basin wide tc genesis variation in terms of the pacific ssta pattern and the associated anomalous large scale environments

different pacific ocean warming decaying types and northwest pacific tropical cyclone activity abstractthis study focuses on statistical analysis of anomalous tropical cyclone tc activities and the physical mechanisms behind these anomalies different patterns of decaying of the warm sea surface temperature anomaly ssta over the equatorial central eastern pacific are categorized into three types eastern pacific warming decaying to la nina epwdl eastern pacific warming decaying to a neutral phase epwdn and a central pacific warming decaying year cpwd differences in tc activity over the western north pacific wnp corresponding to the above three types are discussed and possible mechanisms are proposed for epwdl tc genesis shows a significant positive negative anomaly over the northwestern southeastern wnp and more tcs move westward and make landfall over the southern east asian coast this is attributed primarily to the combined modulation of la nina and the warm equatorial east indian ocean ssta for epwdn enhanced tc genesis is observed over the northeastern wnp and suppress

so42 minimum in summer snow layer at dome fuji antarctica and the probable mechanism 1 by chemically analyzing snow samples at dome fuji antarctica we found that the snowdrift deposited just after snowfall and the snow layer down to 3 4 m have summer minima in the non sea salt nss so42 and na concentrations and summer maxima of cl na such a summer nss so42 minimum in either snowdrift or the snow layer has not been reported at any other site in antarctica and arises in spite of the known maximum in the nss so42 concentration in aerosol at dome fuji in summer we then did laboratory experiments to better understand the phenomenon the results supported the following mechanism for the summer nss so42 minimum in the snowdrift and snow layer in summer water vapor sublimates from within the snow in the daytime and condenses on the surface as frost in the nighttime resulting in a dilution of the nss so42 concentration this sublimation condensation process likely occurs at other cold inland regions in addition the results might be useful for obtaining a high resolution dating method for dome fuji deep ice cores by counting the number of layers with low nss so42 concentration

different evolutions of the philippine sea anticyclone between the eastern and central pacific el nino possible effects of indian ocean sst abstractthe authors examine different evolution features of the low level anticyclone over the tropical northwestern pacific between eastern pacific ep el nino events and central pacific cp el nino events during ep el nino the low level anticyclone shows an eastward movement from the northern indian ocean to the east of the philippines during cp el nino however the anticyclone is mostly confined to the west of the philippines it is weaker exhibits a shorter lifetime and lacks eastward movement compared to the philippine sea anticyclone psac during ep el nino investigation into the possible impact of indian ocean io sea surface temperature sst on the evolution of the low level anticyclone during ep and cp el nino indicates that both sst and low level atmospheric circulation over the io are related more strongly with ep el nino than with cp el nino the io sst tends to exert a more prominent influence on psac during ep el nino than during cp el nino during the developing summer and autum

impact of the indian ocean sst basin mode on the asian summer monsoon 1 following an el nino event a basin wide warming takes place over the tropical indian ocean peaks in late boreal winter and early spring and persists through boreal summer our observational analysis suggests that this indian ocean warming induces robust climatic anomalies in the summer indo west pacific region prolonging the el nino s influence after tropical east pacific sea surface temperature has returned to normal in response to the indian ocean warming precipitation increases over most of the basin forcing a matsuno gill pattern in the upper troposphere with a strengthened south asian high near the ground the southwest monsoon intensifies over the arabian sea and weakens over the south china and philippine seas an anomalous anticyclonic circulation forms over the subtropical northwest pacific collocated with negative precipitation anomalies all these anomaly patterns are reproduced in a coupled model simulation initialized with a warming in the tropical indian ocean mixed layer indicating that the indian ocean warming is not just a passive response to el nino but important for summer climate variability in the indo west pacific region the implications for seasonal prediction are discussed