the role of tropical atlantic sst anomalies in modulating western north pacific tropical cyclone genesis the connection between north tropical atlantic nta sea surface temperature sst anomalies and tropical cyclone tc genesis over the western north pacific wnp and associated physical mechanisms are investigated in this study we demonstrate a remarkable negative correlation of wnp tc genesis frequency with the preceding boreal spring nta sst anomalies our analysis suggests that major factors for tc genesis including distributions of large scale vorticity and midtropospheric humidity are rendered unfavorable by remote teleconnections while barotropic energy conversion from the large scale flow is suppressed as shown in recent studies the remote teleconnection from the atlantic is sustained and enhanced throughout the typhoon season through local air sea interactions these results suggest that boreal spring nta sst anomaly could be a new predictor for the seasonal wnp tc activity

the pacific meridional mode and the occurrence of tropical cyclones in the western north pacific abstractthis study investigates the association between the pacific meridional mode pmm and tropical cyclone tc activity in the western north pacific wnp it is found that the positive pmm phase favors the occurrence of tcs in the wnp while the negative pmm phase inhibits the occurrence of tcs there observed relationships are consistent with those from a long term preindustrial control experiment 1000 yr of a high resolution tc resolving geophysical fluid dynamics laboratory gfdl forecast oriented low ocean resolution flor coupled climate model the diagnostic relationship between the pmm and tcs in observations and the model is further supported by sensitivity experiments with flor the modulation of tc genesis by the pmm is primarily through the anomalous zonal vertical wind shear zvws changes in the wnp especially in the southeastern wnp the anomalous zvws can be attributed to the responses of the atmosphere to the anomalous warming in the northwestern part of the pmm pattern during th

persistent upwelling and front over the sulu ridge and their variations the persistent upwelling and front isolated over the sulu ridge are newly detected by a suite of satellite measurements and confirmed by historical cruise observations a three dimensional tide circulation coupled model is employed to investigate the dynamic mechanisms the intense vertical velocity shear induced by the vigorous internal tidal mixing is identified as the vital dynamic factor to trigger the upwelling and nutrient pumping through the strong tide topography interactions satellite observations indicate that the pronounced surface cooling and phytoplankton bloom are isolated over the sulu ridge throughout the year the steady front characterizes 10 20 km width and strength over 0 3 degrees c km near the southern edge the feature is further confirmed by the numerical simulation and in situ hydrological observation modeling experiment suggests that a quasi symmetrical vertical circulation bifurcation across the sulu ridge due to the asymmetry of tidal currents is the main mechanism to maintain the persistent upwelling and front moreover the local wind forcing plays an important regulating role in the seasonal and interannual variations the surface cooling and thermal front intensity reach the maximum in winter under the forcing of strong northeasterly monsoons due to prolonged el nino southern oscillation enso effects the surface cooling was significantly weakened during 1998 and 2010 summer further analysis indicates the fact that the southwesterly monsoon is weakened dramatically as part of the anticyclonic atmospheric circulation anomalies over the northwest pacific the latter results from the significant influence of tropical indian ocean capacitor effect associated with el nino southern oscillation

intensified interannual relationship between tropical cyclone genesis frequency over the northwest pacific and the sst gradient between the southwest pacific and the western pacific warm pool since the mid 1970s abstractthe sea surface temperature gradient sstg between the southwest pacific swp 40 20 s 160 e 170 w and the western pacific warm pool wwp 0 16 n 125 165 e in boreal spring was revealed to contribute significantly to the interannual variability of tropical cyclone tc genesis frequency over the western north pacific wnp since 1980 the present study extends the analysis back to 1951 results show that the interannual relationship between the sstg and wnp tc genesis frequency is statistically significant only after the mid 1970s while insignificant prior to 1974 further analyses show that the sstg is strongly negatively correlated with the sst anomaly ssta in the central pacific cp in the recent period while with the ssta in the equatorial eastern pacific ep in the prior period in the prior period the spring positive negative ep ssta induces an anticyclonic cyclonic circulation over the wnp this partly offsets the impact of the sstg anomaly on the atmospheric circulation ov

decadal changes in tropical cyclone activity over the western north pacific in the late 1990s a pronounced decadal change in tropical cyclone tc activity over the western north pacific wnp in the late 1990s was identified based on a comparison of the two epochs that occurred before and after the late 1990s the tc genesis number exhibited an evident decrease over the southern wnp s wnp 5 20 n 105 170 e and an increase over the northern wnp n wnp 20 25 n 115 155 e which partly corresponded to a significant northward migration in the seasonal mean latitudinal location of tc genesis i e from 17 2 n to 18 7 n after the late 1990s the northwestward moving track became the most dominant track mode accompanied by the weakening of both the westward moving track and the northeastward recurving track meanwhile the tc occurrence frequency tcf experienced evident increases over southeastern china and the okinawa islands while prominent decreases occurred over the south china sea the philippine sea japan and east of japan changes in the tcf were determined by tc genesis changes tc track shifts and variations in regional tc durations which were all ascribed to the decadal change in tropical indo pacific sea surface temperature the full picture on the decadal changes in the wnp tc activity revealed in this study may provide useful guidance for regional tc seasonal forecasts and future projections

glacial induced closure of the panamanian gateway during marine isotope stages mis 95 100 2 5 ma the final phase of the closure of the panamanian gateway and the intensification of northern hemisphere glaciation nhg both occurred during the late pliocene glacial interglacial g ig variations in sea level might therefore have had a significant impact on the remaining connections between the east pacific and the caribbean here we present combined foraminiferal mg ca and 18o measurements from ocean drilling program odp site 1241 from the east pacific and odp site 999 from the caribbean the studied time interval covers the first three major g ig marine isotope stages mis 95 100 2 5 ma 2 5 ma after the intensification of nhg analyses were performed on the planktonic foraminifera neogloboquadrina dutertrei and globigerinoides sacculifer representing water mass properties in the thermocline and the mixed layer respectively changes in sea water temperature relative salinity and water column stratification strongly suggest that the panamanian gateway temporarily closed during glacial mis 98 and 100 as a result of changes in ice volume equivalent to a drop in sea level of 60 90 m reconstructed sea surface temperatures sst from g sacculifer show a glacial decrease of 2 5 c at site 1241 but increases of up to 3 c at site 999 during glacial mis 98 and 100 suggesting that the panamanian gateway closed during these glacial periods the mg ca temperatures of n dutertrei remain relatively stable in the east pacific but do show a 3 c warming in the caribbean at the onset of these glacial periods suggesting that the closing of the gateway also changed the water column stratification we infer that the glacial closure of the gateway allowed the western atlantic warm pool to extend into the southern caribbean increasing sst g sacculifer and deepening the thermocline n dutertrei additionally ice volume appears to have become large enough during mis 100 to survive the relatively short lasting interglacial mis 99 so that the gateway remained closed towards the end of mis 98 during mis 97 and into mis 96 temperatures on both sides are mostly similar suggesting water masses exchanged again additionally caribbean variations in sst and 18owater follow a precession like cyclicity rather than the obliquity controlled variations characteristic of the east pacific and many other tropical areas suggesting that regional atmospheric processes related to the trade winds and the intertropical convergence zone itcz had a dominant impact in the caribbean

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

global eastward propagation signals associated with the 4 5 year enso cycle longitude time evolution of sea surface temperature anomalies ssta reveals a slow southeastward propagation from the western north pacific wnp around 20 n to the nino 3 4 region in the equatorial central pacific the propagation is manifested as a narrow southwest northeast oriented ssta band across the subtropical north pacific and its journey takes about 2 3 years the propagating ssta appears to engage the initiation of the el nino southern oscillation enso the anomalies of surface winds sea level pressure outgoing longwave radiation and velocity potential all exhibit a concurrent and distinct eastward propagation one that appears to be circumglobal and is coupled with the predominant 4 5 year frequency of the enso cycle it is suggested that the previously found warming cooling in the indian ocean induced by el nino la nina the progressive ssta and wind anomalies across the indian ocean towards the wnp and the predominant 4 5 year frequency of the north pacific oscillation collectively contribute to the reported ssta propagation the findings implicate that monitoring the ssta propagation from the wnp towards the tropical central pacific could be useful in tracking the enso development

roles of tropical sst anomalies in modulating the western north pacific anomalous cyclone during strong la nina decaying years this study re explores the roles of tropical sst anomalies in modulating the anomalous cyclone over the indo western pacific during strong la nina decaying years via a series of numerical experiments the results suggest that central to eastern equatorial pacific cooling western north pacific wnp warming and indian ocean cooling all contribute to the indo western pacific cyclonic wind anomalies the wnp sst anomalies play a role via a rossby wave type response as the positive sst anomalies in the wnp decay the local forcing effect decays as well the indian ocean remote forcing seems to play an important role during boreal summer via cold kelvin wave induced cyclonic shear and boundary layer convergence during strong la nina decaying years the negative sst anomalies in the equatorial central to eastern pacific can maintain and persist into summer such cooling could induce anomalous walker circulation with ascending branch over the maritime continent to philippines and descending branch over central to eastern pacific which links the wnp climate to the equatorial central and eastern pacific sst anomalies the convective heating over the wnp induced remotely by central to eastern pacific cooling in turn forces atmospheric rossby wave to its west which may amplify the anomalous cyclone over the indo western pacific

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

contributions of the north pacific meridional mode to ensemble spread of enso prediction abstractseasonal prediction of el nino southern oscillation enso employs the ensemble method which samples the uncertainty in initial conditions while much attention has been given to the ensemble mean the ensemble spread limits the reliability of the forecast spatiotemporal coevolution of intermember anomalies of sea surface temperature sst and low level winds over the pacific is examined in ensemble hindcasts two types of evolution of intermember sst anomalies in the equatorial pacific are identified the first features an apparent southwestward propagation of the sst spread from the subtropical northeastern pacific southeast of hawaii to the central equatorial pacific in boreal winter spring indicative of the precursor effect of the north pacific meridional mode npmm on enso variability extratropical atmospheric variability generates ensemble spread in enso through wind evaporation sst wes in the subtropical northeastern pacific and then bjerknes feedback on the equator in the second ty

geomagnetic secular variation impulses the secular variation of the earth s internal magnetic field changes on time scales of the order of a year such impulses occurred in 1969 and probably in 1913 they provide constraints on deep mantle conductivity which appears to be rather low and on the motions of the top of the fluid core which are probably dominated by westward drift present data favour the existence of upwelling of core material at the core mantle boundary the impulses can be correlated with extrema in the earth s rotation rate and interpreted in terms of electromagnetic core mantle coupling

interannual to decadal variability and trends of sea level in the south china sea interannual to decadal variability and trends of sea level in the south china sea scs are studied using altimetric data during 1993 2012 and reconstructed sea level data from 1950 2009 the interannual variability shows a strong seasonality surface wind anomalies associated with el nino southern oscillation explain the sea level anomaly pattern in the interior scs while rossby waves radiated from the eastern boundary dominate the sea level variability in the eastern scs decadal variability of sea level in the scs follows that in the western tropical pacific with large variance found west of luzon island local atmospheric forcing makes a negative contribution to decadal variability in the central scs and rossby waves radiated from the eastern boundary appear to be important during 1993 2012 decadal sea level averaged in the scs is significantly correlated with the pacific decadal oscillation pdo r 0 96 the decadal variability associated with the pdo accounts for most part of sea level trends in the scs in the last two decades

interdecadal variability in tropical cyclone frequency over the south china sea and its association with the indian ocean sea surface temperature 1 during the period 1958 2001 the frequency of tropical cyclone tc genesis over the south china sea scs experienced an obvious interdecadal change around the mid 1970s compared to the period from late 1950s to early 1970s the number of tcs is significantly reduced during mid 1970s through late 1990s this interdecadal change in the tc frequency appears to relate to the increase in sea surface temperature sst of the tropical indian ocean the difference of the circulation between the warm phase and the cold phase of the tropical indian ocean sst provides support for the influence of the tropical indian ocean warming on the variability of the tc frequency over the scs in the warm phase lower level convergent and ascending flows over the tropical indian ocean are accompanied by upper level divergent flows part of which go toward the scs leading to upper level convergence and descent there consequently two lower level anticyclones develop and the tc genesis is suppressed over the scs

interannual variation in the tropical cyclone formation over the western north pacific abstract the interannual variation in tropical cyclone genesis frequency over the western north pacific was examined for the active tropical cyclone including summer and fall during 1979 94 an emphasis was put on the possible effect of the interannual variation of atmospheric circulation and monsoon trough on tropical cyclone occurrence the major findings of this study are the following a distinct increase decrease of tropical cyclone genesis frequency occurs north of the climatological location of the monsoon trough in the philippine sea during summers june august with anomalous cold warm sea surface temperature sst over the nino3 region the interannual variation of tropical cyclone genesis in this region results from the appearance of an anomalous cyclonic anticyclonic cell situated in a summer teleconnection wave train emanating from the western tropical pacific and progressing along the rim of the north pacific in addition to the north south interannual variation there is also a long

abnormal upwelling and chlorophyll a concentration off south vietnam in summer 2007 the present study investigates a strong upwelling and concurrent phytoplankton bloom off the south vietnam coast in august 2007 analysis of the alongshore wind offshore ekman transport wind stress curl and other parameters indicates the southwesterly summer monsoon plays an important role in this peculiar case the change of monsoonal wind involves variations of atmospheric circulation on multiple time scales on the interannual time scale a positive indian ocean dipole iod in 2007 accompanying with a la nina event acts to enhance the southwesterly monsoon over the south china sea scs the enhanced southwesterly wind is regarded as a major factor in promoting the upwelling and the phytoplankton bloom off the south vietnam coast on the intraseasonal time scale variations of the sea surface temperature sst and sea surface wind at 30 60 day periods reveal that the sst cooling develops with the evolution of the southwesterly wind anomalies with nearly one week delay implying the great significance of the madden julian oscillation mjo moreover a tropical storm formed in the western scs in early august reinforces the westerly wind and sst cooling among multiple factors on different time scales the mjo event is considered as the major cause since it induces the maximum velocity 4 m s of the southwesterly wind anomalies as a result the high chlorophyll a concentration 0 56 mg m 3 and low sst center 27 degrees c develops in the region off the south vietnam coast and advects to the central scs riding on the northern rim of the southern anticyclonic gyre

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

upwelling in the continental shelf of northern south china sea associated with 1997 1998 el nino 1 a strong upwelling off the continental shelf of the northern south china sea scs in 1998 summer is reinvestigated using a suite of new satellite measurements and numerical modeling previous studies indicate that the upwelling in the western scs especially off the vietnam coast almost disappears during 1998 summer following the el nino because of the weakened southwest monsoon this study identifies that the coastal upwelling in the adjacent northern scs nscs is significantly strengthened during 1998 summer and the alongshore wind stress is dramatically enhanced over the region as a result the offshore ekman transport in 1998 summer is the strongest almost twice the average of the other 17 years during 1997 2007 the chl a concentrations in the representative upwelling regions are much higher than any in other years further analysis suggests that two adjacent basin scale upwellings in the scs have different responses and maintaining mechanisms because of the anticyclonic atmospheric circulation anomaly over the scs and northwest pacific the northern flank of the atmospheric circulation anomaly intensifies the monsoonal winds off the nscs coast while the southern flank suppresses the southwesterly winds along the vietnam coast

role of scale interactions in the abrupt change of tropical cyclone in autumn over the western north pacific tropical cyclone tc activity in autumn september november over the western north pacific experienced an abrupt change in 1998 which can be detected by the bayesian change point analysis during the decade before the regime shift 1988 1997 the occurrence frequency of tc genesis increased significantly over the tropical western pacific where the seasonal cyclonic flow intraseasonal oscillation iso and synoptic scale eddy sse were all strengthened compared to those observed in the decade after 1998 1998 2007 the tc trajectories also exhibited spatial differences during the active decade the tcs had a higher probability to move westward into the philippine sea and the south china sea and recurved northeastward toward the east of japan meanwhile the northwestward propagating tcs approaching taiwan and southeastern coast of china were reduced to understand the role of mean flow iso sse interaction in the decadal changes of sse and associated tc activity we diagnosed a newly proposed sse kinetic energy ke equation that separates the contributions of seasonal mean circulation and iso to the sse the results show that during the active tc decade the sse obtained higher ke from both mean flow and iso through eddy barotropic energy conversion when the enhanced sse momentum flux interacted with the strengthened monsoon trough and vigorous iso cyclonic anomaly over the western tropical pacific the increased sse ke contributed positively to the increased tc genesis over the main genesis region 7 5 20 n 130 170 e it also benefited the growth of tcs over the philippine sea and the south china sea during the active decade the decadal change in tc frequency over the extratropics was related to the eddy baroclinic energy conversion instead of the barotropic conversion associated with scale interaction during the active tc decade sse gained more less ke from the sse available potential energy over the east of japan the east china sea favoring disfavoring the succeeding development of tcs in this region

effect of excessive equatorial pacific cold tongue bias on the el nino northwest pacific summer monsoon relationship in cmip5 multi model ensemble el nino induces an anomalous lower tropospheric anticyclone over the tropical northwest pacific nwp accompanied by suppressed local convection and rainfall the tropical nwp anomalies persist until the following summer with major effects on the asian summer monsoons based on the phase 5 of the coupled model intercomparison project cmip5 multi model ensemble this study finds that climate models commonly underestimate this el nino nwp teleconnection with too weak tropical nwp anticyclone and rainfall anomalies in post el nino summers potentially limiting the models skill in seasonal prediction of the asian summer monsoons the analyses show that such underestimated nwp anomalies in post el nino summers in cmip5 models can be traced back to the well known excessive equatorial pacific cold tongue error in the mean models with an excessive westward extension of pacific cold tongue tend to displace westward the simulated pattern of el nino related warm sst anomalies along the equator the warm sst biases over the western pacific in cmip5 models would enhance the local atmospheric convection rainfall and induce low level cyclonic circulation anomalies over the tropical nwp with a gill type rossby wave response resulting in the commonly underestimated nwp anticyclone and rainfall anomalies during post el nino summers the present results along with our previous finding that the equatorial cold tongue bias would distort the projections of tropical pacific warming pattern under increased greenhouse gas scenario imply that reducing equatorial cold tongue bias in models can substantially improve climate simulation and prediction projection for the tropical pacific and asian monsoons

on the geomagnetic jerk of 1969 french and british scientists have published reports describing a sudden change in the geomagnetic secular acceleration which took place around 1969 they claimed that this change called an impulse or jerk took place in a period of a year or two and that the sources for the jerk were internal a recent paper by alldredge questioned their method of analysis and concluded that abrupt changes in the observed field which occur in a year or two do not originate in the core of the earth this paper questions alldredge s conclusion and provides further evidence in support of the reports of the french and british investigators the average centroid of the jerk is found to be 1969 5 evidence is presented that indicates that the centroid of the jerk differs for the various spherical harmonics so that the centroid of the degree one spherical harmonic is significantly later than the centroids for the next three harmonics new estimates for the spherical harmonic coefficients for the jerk and the prejerk and postjerk secular acceleration are given some possible further investigations are suggested

core top calibration of mg ca in tropical foraminifera refining paleotemperature estimation 1 optimal use of mg ca as a paleotemperature proxy requires establishing calibrations for different species of foraminifera and quantifying the influence of dissolution to achieve this goal we have measured mg ca and 18o in a series of tropical and subtropical core tops including four depth transects the ceara rise the sierra leone rise and the rio grande plateau in the atlantic and the ontong java plateau in the pacific focusing on spinose mixed layer dwelling species globigerinoides ruber and globigerinoides sacculifer and nonspinose thermocline dwelling neogloboquadrina dutertrei shell mg ca in g sacculifer is 5 15 lower than in g ruber while n dutertrei mg ca is 49 55 lower than in g ruber this statistically significant offset has allowed us to establish different calibrations for each species multilinear regression analysis was used to develop calibration equations that include a correction term for the dissolution effect on mg ca in foraminiferal calcite presented in this paper are two sets of calibrations one set using core depth as a dissolution correction and another using co32 as a dissolution parameter the calibrations suggest that g ruber is the most accurate recorder of surface temperature while g sacculifer records temperatures below the surface at 20 30 m the depth habitat of n dutertrei is more uncertain owing to the wide range in habitat depths depending on hydrographic conditions but on average mg ca and 18o data suggest it is at 50 m of the three species n dutertrei is the most sensitive to dissolution up to 23 decrease in shell mg ca per km while g sacculifer is the most resistant

time transgressive north atlantic productivity changes upon northern hemisphere glaciation 1 marine biological export productivity declined in high latitude regions in the north pacific and southern ocean 2 7 million years ago in parallel with the intensification of northern hemisphere glaciation here we present data from the north atlantic which show a similar but time transgressive pattern of high latitude productivity decline from 3 3 to 2 5 ma with productivity decreasing first at 69 n hundreds of thousands of years before it declined at 58 n we propose that the cumulative data are best explained by an equatorward migration of the westerly winds which caused a southward shift in the zone of ekman divergence and upwelling associated major nutrient supply over this time interval we suggest that a similar equatorward migration of the westerly winds may also help explain the productivity changes observed in other high latitude regions particularly the southern ocean at 2 7 ma equatorial and temperate atlantic sites began to show orbitally paced productivity pulses consistent with a shoaling and meridional contraction of the nutrient poor warm sphere that characterizes the low latitude upper ocean this timing coincides with observed productivity changes in southern ocean consistent with previous findings that the southern ocean exerts a strong influence on the fertility of the low latitude atlantic finally we propose that the unique basin geometry of the north atlantic caused deep water formation in this region to remain relatively stable despite equatorward migration of winds and ocean fronts

influence of the north pacific victoria mode on western north pacific tropical cyclone genesis the victoria mode vm is defined as the second empirical orthogonal function mode eof2 of sea surface temperature anomalies sstas in the north pacific north of 20 n this study examines the influence of the spring vm on the tropical cyclone tc genesis over the western north pacific wnp during summer may august for the period 1960 2016 our analysis demonstrates that the spring vm exhibits a good relationship with the following summer tropical cyclone frequency tcf over the wnp characterized by positive correlations over the eastern wnp ewnp and negative correlations over the western wnp wwnp during strongly positive vm cases the sstas in the north pacific 5 20 n associated with the spring vm persist until summer via the wind evaporation sst wes feedback the low level convergence divergence caused by the vm related sstas combined with a strengthened weakened wnp monsoon trough as well as a weakened strengthened west pacific subtropical high wpsh result in the enhanced suppressed tc genesis over the ewnp wwnp it appears that the spring vm may be a useful predictor for the wnp tcs in summer

indo pacific climate during the decaying phase of the 2015 16 el nino role of southeast tropical indian ocean warming this study investigates the influence of southeast tropical indian ocean setio sea surface temperature sst warming on indo pacific climate during the decaying phase of the 2015 16 el nino by using observations and model experiments the results show that the setio sst warming in spring 2016 enhanced local convection and forced a c shape wind anomaly pattern in the lower troposphere the c shape wind anomaly pattern over the eastern tropical indian ocean consists of anomalous westerly flow south of the equator and anomalous easterly flow north of the equator the anomalous easterly flow then extended eastward into the western north pacific wnp and facilitates the development or the maintenance of an anomalous anticyclone over the south china sea scs correspondingly the eastern part of the bay of bengal the scs and the wnp suffered less rainfall such precipitation features and the associated c shape wind anomaly pattern shifted northward about five latitudes in summer 2016 additionally the setio warming can induce local meridional circulation anomalies which directly affect indo pacific climate numerical model experiments further confirm that the setio sst warming plays an important role in modulating indo pacific climate

western caribbean sea surface temperatures during the late quaternary 1 mg ca ratios in the planktonic foraminifera globigerinoides ruber from colombian basin core odp 999a suggest that caribbean sea surface temperatures ssts were from 2 1 to 2 7 c colder than the present during the last three glacial maximums in comparison faunal derived ssts simmax method show that august ssts in the caribbean varied 2 c over the past 360 kyr whereas february ssts varied between 21 0 c and 26 5 c changes in the mg ca sst record contain a strong 23 kyr periodicity suggesting the mg ca sst record reflects a warm season weighted sst average rather than an annual mean sst combining several dissolution indices we identify brief periods of decreased carbonate preservation in our record and show that mis 11 stands out as the most intensive dissolution cycle in the caribbean over the last 460 kyr comparison of caribbean sst change with a similar estimate of tropical sst variability in the western pacific over the past 360 kyr reveals shifts in the east west tropical sst gradient that are coeval with glacial interglacial climate change and consistent both with a southward migration of the glacial itcz and with a glacial el nino like mode of tropical circulation

the seawater neodymium and lead isotope record of the final stages of central american seaway closure the shoaling and final closure of the central american seaway cas resulted in a major change of the global ocean circulation and has been suggested as an essential driver for strengthening of atlantic meridional overturning circulation amoc the exact timing of cas closure is key to interpreting its importance here we present a reconstruction of deep and intermediate water nd and pb isotope compositions obtained from fossil fish teeth and the authigenic coatings of planktonic foraminifera in the eastern equatorial pacific ocean drilling program odp site 1241 and the caribbean odp sites 998 999 and 1000 covering the final stages of cas closure between 5 6 and 2 2 ma the data for the pacific site indicate no significant atlantic caribbean influence over this entire period the caribbean sites show a continuous trend to less radiogenic nd isotope compositions during the pliocene consistent with an enhancement of upper north atlantic deep water unadw inflow and a strengthening of the amoc superimposed onto this long term trend shorter term changes of intermediate caribbean nd isotope signatures approached more unadw like values during intervals when published reconstructions of seawater salinity suggested complete closure of the cas the data imply that significant deep water exchange with the pacific essentially stopped by 7 ma and that shallow exchange which still occurred at least periodically until approximately 2 5 ma may have been linked to the strength of the amoc but did not have any direct effect on the intermediate and deep caribbean nd isotope signatures through mixing with pacific waters

intensified impact of east indian ocean sst anomaly on tropical cyclone genesis frequency over the western north pacific abstracta recent finding is the significant impact of the sea surface temperature anomaly ssta over the east indian ocean eio on the genesis frequency of tropical cyclones tcs over the western north pacific wnp in this study it is shown that such an impact is significant only after the late 1970s the results based on both data analysis and numerical model experiments demonstrate that prior to the late 1970s the eio ssta is positively correlated with the equatorial central pacific ssta and the latter produces an opposite atmospheric circulation response over the wnp to the former as a result the impact of the eio ssta on the tc genesis over the wnp is largely suppressed by the latter after the late 1970s the area coverage of the eio ssta is expanding this considerably enhances the large scale circulation response over the wnp to the eio ssta and significantly intensifies the impact of the eio ssta on tc genesis frequency over the wnp the results from this study have great implications for s

impacts of the boreal spring indo pacific warm pool hadley circulation on tropical cyclone activity over the western north pacific abstractthis study investigated the impacts of the interannual variability in the boreal spring regional hadley circulation over the indo pacific warm pool ipwp on the tropical cyclone tc activity over the western north pacific wnp the principal modes of the interannual variability in the ipwp hadley circulation were calculated using empirical orthogonal function eof analysis the leading mode eof 1 features cross equatorial southerly wind anomalies over the indian ocean and maritime continent and has an evident impact on wnp tc activity during summer in the summer following a positive phase of the eof 1 a cyclonic circulation anomaly with upward motion positive relative vorticity anomalies and weak sea level pressure dominates the wnp and this favors increased tc genesis however large positive vertical wind shear anomalies over the south china sea and philippine sea inhibit the tc intensification a positive wind sea surface temperature sst precipitation feedback was found to facili

influences of enso induced indo western pacific sst anomalies on extratropical atmospheric variability during the boreal summer the causes for the observed occurrence of anomalous zonally symmetric upper level pressure ridges in the midlatitude belts of both hemispheres during the year after warm el nino southern oscillation enso events have been investigated sea surface temperature sst anomalies in the indo western pacific iwp sector were simulated by allowing an oceanic mixed layer model for that region to interact with local atmospheric changes forced remotely by observed enso episodes in the eastern central tropical pacific the spatiotemporal evolution of these sst conditions through a composite enso cycle was then inserted as lower boundary conditions within the iwp domain in an ensemble of atmospheric general circulation model gcm integrations this experimental setup is seen to reproduce zonally symmetric geopotential height anomalies with maximum amplitudes being attained over the extratropics in the boreal summer after the peak phase of enso the model evidence hence supports the notion that these globalscale atmospheric changes are primarily responses to sst perturbations in iwp which are in turn linked to enso variability in the equatorial pacific by the atmospheric bridge mechanism experimentation with a stationary wave model indicates that the eastern hemisphere portion of the aforementioned atmospheric signals are attributable to forcing by tropical heat sources and sinks associated with precipitation anomalies in the iwp region which are closely related to the underlying sst changes diagnosis of the output from the gcm integrations reveals that these circulation changes due to diabatic heating are accompanied by alterations of the propagation path and intensity of the high frequency eddies at locations farther downstream the geopotential tendencies associated with the latter disturbances bear some resemblance to the anomalous height pattern in the western hemisphere such local eddy mean flow feedbacks hence contribute to the zonal symmetry of the atmospheric response pattern to forcing in the iwp region analysis of zonally averaged circulation statistics indicates that the mean meridional circulation induced by divergence of anomalous transient eddy momentum fluxes in enso events could also generate zonally symmetric perturbations in midlatitudes the model simulated precipitation and surface temperature anomalies in the north american sector in response to sst changes in iwp suggest an increased frequency of droughts and heat waves in that region during the summer season after warm enso events

role of tropics in changing the response to milankovich forcing some three million years ago appeared in regions that today have intense oceanic upwelling the eastern equatorial pacific and the coastal zones of southwestern africa and california there was furthermore a significant change in the earth s response to milankovich forcing obliquity signals became large but those associated with precession and eccentricity remained the same the latter change in the earth s response can be explained by hypothesizing that the global cooling during the cenozoic affected the thermal structure of the ocean it caused a gradual shoaling of the thermocline around 3 ma the thermocline was sufficiently shallow for the winds to bring cold water from below the thermocline to the surface in certain upwelling regions this brought into play feedbacks involving

forced and internal variability of tropical cyclone track density in the western north pacific abstractforced interannual to decadal variability of annual tropical cyclone tc track density in the western north pacific between 1979 and 2008 is studied using tc tracks from observations and simulations by a 25 km resolution version of the gfdl high resolution atmospheric model hiram that is forced by observed sea surface temperatures ssts two modes dominate the decadal variability a nearly basinwide mode and a dipole mode between the subtropics and lower latitudes the former mode links to variations in tc number and is forced by sst variations over the off equatorial tropical central north pacific whereas the latter might be associated with the atlantic multidecadal oscillation the interannual variability is also controlled by two modes a basinwide mode driven by sst anomalies of opposite signs located in the tropical central pacific and eastern indian ocean and a southeast northwest dipole mode connected to the conventional eastern pacific enso the seasonal evolution of the enso effect

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

contributions of sst anomalies in the indo pacific ocean to the interannual variability of tropical cyclone genesis frequency over the western north pacific abstractthis study attempts to evaluate quantitatively the contributions of sea surface temperature sst anomalies in the indo pacific ocean to the interannual variability of tropical cyclone tc

late pliocene to early pleistocene changes in the north atlantic current and suborbital scale sea surface temperature variability the strength and latitudinal position of the north atlantic current nac determines the position of the arctic front and heat transport to the high northern latitudes with potentially important consequences for northern hemisphere glaciation a southward shift in the nac and reduced poleward heat transport is hypothesized to have triggered the last major climate transition in earth s history late pliocene intensification of northern hemisphere glaciation inhg in turn inhg is hypothesized to have led to the amplification of climate variability on suborbital time scales to date however only a handful of adequately resolved records are available to test these two hypotheses here we present a new late pliocene to earliest pleistocene record from integrated ocean drilling program site u1313 north atlantic 41 n 2 9 to 2 4 ma we use mg ca derived paleotemperature records in planktic foraminiferal calcite to investigate changes in summer sea surface temperatures sst on orbital and suborbital time scales our results call into question the suggestion that significant weakening and or southward shift of the nac served as a trigger for northern hemisphere cooling and intensified continental ice sheet growth across inhg in contrast to the late pleistocene during inhg we find that the position of the nac and arctic front probably lay well to the north of site u1313 and that the amplitude of suborbital sst variability did not change on glacial interglacial time scales conservative estimates of late pliocene to earliest pleistocene interglacial summer ssts in our record are up to 3 c warmer than present while glacial summer ssts are only 2 c to 3 c cooler in fact our interglacial summer ssts are remarkably similar to those of the mid pliocene our findings indicate that inhg must have involved amplifying feedback mechanisms that are tightly coupled to ice sheet growth but that these processes were insufficiently developed by the late pliocene earliest pleistocene to have triggered large amplitude changes in suborbital climate in the midlatitude north atlantic

warm upwelling regions in the pliocene warm period 1 given the importance of upwelling processes to coastal productivity and regional climate it is critical to study the role of upwelling regions within the context of global climate change we generated sea surface temperature sst records for the last 5 million years in three important upwelling regions the eastern equatorial pacific the california margin and the peru margin prior to 3 0 ma ssts at all sites were significantly warmer than today by 3 9 c indicating that cold upwelling regions that characterize the modern pacific ocean did not exist in the early pliocene warm period 4 6 to 3 1 ma earth s most recent period of sustained global warmth alkenone phosphorus and organic carbon mass accumulation rate records indicate that changes in productivity and sst were decoupled and that upwelling of nutrient enriched water occurred even when ssts were warm during the early pliocene thus the long term trends in sst are likely explained by changes in the temperature of upwelled water rather than in the strength of upwelling favorable winds alone the fact that gradual cooling of upwelling regions began before the onset of significant northern hemisphere glaciation provides further evidence that the growth of ice sheets and their influence on atmospheric winds alone can not explain the cooling of upwelling regions our results suggest that the long term average ssts of upwelling regions are influenced by global changes in the depth and or temperature of the ventilated thermocline

el nino phases embedded in asian and north american drought reconstructions abstract the amplitude of el nino southern oscillation enso varies substantially at each phase of its evolution affecting the timing and patterns of atmospheric teleconnections around the globe instrumental records are too short to capture the full behavior of enso variability here we use the well validated monsoon asia drought atlas mada and north america drought atlas nada for the past 700 years and show that tree ring records from different regions represent tropical sea surface temperature sst conditions at various phases of enso three modes of tree ring based summer drought variability are found to be correlated with enso summer droughts over the maritime continent and southwest north america na and a dipole mode between central and south asia a lagged correlation analysis is performed to determine the time when precipitation and temperature anomaly imprints on summer droughts as recorded in tree rings drought anomalies in the maritime continent and southwest na represent enso at the developing and peak phases respectively while those over central south asia are associated with tropical wide sst anomalies including the indian ocean at the decay phase of enso thus proxy records from different regions can provide valuable information on long term behavior of enso at different phases

calibration of mg ca thermometry in planktonic foraminifera from a sediment trap time series 1 paired mg ca and 18o measurements on planktonic foraminiferal species g ruber white g ruber pink g sacculifer g conglobatus g aequilateralis o universa n dutertrei p obliquiloculata g inflata g truncatulinoides g hirsuta and g crassaformis from a 6 year sediment trap time series in the sargasso sea were used to define the sensitivity of foraminiferal mg ca to calcification temperature habitat depths and calcification temperatures were estimated from comparison of 18o of foraminifera with equilibrium calcite based on historical temperature and salinity data when considered together mg ca mmol mol of all species except two show a significant r 0 93 relationship with temperature t c of the form mg ca 0 38 0 02 exp 0 090 0 003 t equivalent to a 9 0 0 3 change in mg ca for a 1 c change in temperature small differences exist in calibrations between species and between different size fractions of the same species o universa and g aequilateralis have higher mg ca than other species and in general data can be best described with the same temperature sensitivity for all species and pre exponential constants in the sequence o universa g aequilateralis g bulloides g ruber g sacculifer other species this approach gives an accuracy of 1 2 c in the estimation of calcification temperature the 9 sensitivity to temperature is similar to published studies from culture and core top calibrations but differences exist from some literature values of pre exponential constants different cleaning methodologies and artefacts of core top dissolution are probably implicated and perhaps environmental factors yet understood planktonic foraminiferal mg ca temperature estimates can be used for reconstructing surface temperatures and mixed and thermocline temperatures using g ruber pink g ruber white g sacculifer n dutertrei p obliquiloculata etc the existence of a single mg thermometry equation is valuable for extinct species although use of species specific equations will where statistically significant provide more accurate evaluation of mg ca paleotemperature

high amplitude variations in north atlantic sea surface temperature during the early pliocene warm period 1 we provide the first continuous orbital resolution sea surface temperature sst record from the high latitude north atlantic a region critical to understanding the origin of the plio pleistocene ice ages and proximal to regions that became frequently glaciated after 2 7 ma we analyzed sediments from ocean drilling program site 982 over the last 4 ma for their alkenone unsaturation index and compared this surface water signal to a benthic 18o record obtained from the same section we find that while ocean surface temperatures were significantly warmer 6 c than modern temperatures during the early pliocene they were also as variable as those during the late pleistocene a surprising result in light of the subdued variance of oxygen isotopic time series during the interval of 3 5 ma we propose two possible explanations for the high orbital scale sst variability observed either that a strong high latitude feedback mechanism not involving large continental ice sheets alternately cooled and warmed a broad region of the northern high latitudes or that by virtue of its location near the northern margin of the north atlantic drift the site was unusually sensitive to obliquity driven climate shifts on supraorbital time scales a strong sustained cooling of north atlantic ssts 4 5 c occurred from 3 5 to 2 5 ma and was followed by an interval of more modest cooling an additional 1 5 c from 2 5 ma to the present evolutionary orbital scale phase relationships between north atlantic sst and benthic 18o show that sst began to lead 18o significantly coincident with the onset of strong cooling at site 982 3 5 ma we speculate that these changes were related to the growth and subsequent persistence of a greenland ice sheet of approximately modern size through interglacial states

was the 1970 geomagnetic jerk of internal or external origin annual mean data from worldwide magnetic observatories show that there was a jerk1 step change in the second time derivative in the geomagnetic field which took place over an interval of 2 yr around 1970 if such a short lived phenomenon originated in the earth s core and were still detectable after passing through the mantle to the surface this would imply a much lower conductivity for the lower mantle than had been believed previously here we show by an objective test that most of the jerk has an internal origin

characteristics of the near surface currents in the indian ocean as deduced from satellite tracked surface drifters part i pseudo eulerian statistics using the 1985 2013 record of near surface currents from satellite tracked drifters the pseudo eulerian statistics of the near surface circulation in the indian ocean io are analyzed it is found that the distributions of the current velocities and mean kinetic energy mke in the io are extremely inhomogeneous in space and nonstationary in time the most energetic regions with climatologic mean velocity over 50cms 21 and mke over 500cm 2 s 22 are found off the eastern coast of somalia with maxima of over 100cms 21 and 1500cm 2 s 22 and the equatorial io associated with the strong annually reversing somalia current and the twice a year eastward equatorial jets high eddy kinetic energy eke is found in regions of the equatorial io western boundary currents and agulhas return current with a maximum of over 3000cm 2 s 22 off the eastern coast of somalia the lowest eke 500cm 2 s 22 occurs in the south subtropical gyre between 308 and 408s and the central eastern arabian sea annual and semiannual variability is a significant fraction of the total eke off the eastern coast of somalia and in the central eastern equatorial io in general both the mke and eke estimated in the present study are qualitatively in agreement with but quantitatively larger than estimates from previous studies these pseudo eulerian mke and eke fields based on the most extensivedrifterdatasettodate arethemostpreciseinsituestimatestodateandcanbeusedtovalidatesatellite and numerical results

signals of the south china sea summer rainfall variability in the indian ocean the present study investigates signals of the south china sea scs summer rainfall variability in the indian ocean it is found that the scs summer rainfall has a negative relationship with december january february djf western equatorial indian ocean wio sea surface temperature sst a positive relationship with an asymmetric mode of precipitation anomalies in the tropical indian ocean during march april may mam and a positive relationship with june july august jja south indian ocean sio sst the wio sst anomalies induce same sign southeast indian ocean sst anomalies through an anomalous zonal vertical circulation the southeast indian ocean sst anomalies last from late winter to early summer and induce opposite sign scs summer rainfall anomalies via an anomalous meridional vertical circulation the asymmetric mode influences the scs summer rainfall variation via the north indian ocean nio sst anomalies with significant cloud radiation and wind evaporation effect positive negative sio sst anomalies drive an anomalous direct circulation between the sio and the nio and an anomalous indirect circulation between the nio and the scs which facilitates the occurrence of cyclonic anti cyclonic wind anomalies over the scs western north pacific and results in positive negative scs summer rainfall anomalies partial correlation analysis indicates that the influence of djf wio sst anomalies and jja sio sst anomalies on the scs summer rainfall is partly enso independent while the mam asymmetric mode is mostly related to the preceding djf eastern pacific sst anomalies

impact of the cross tropopause wind shear on tropical cyclone genesis over the western north pacific in may the role of the 50 to 200 hpa zonal wind shear in modulating tropical cyclone tc genesis over the western north pacific wnp in may is investigated in this study concurrent with the strong cross tropopause shear over the key region 0 5 n 160 180 e suppressed convection was observed over the tropical wnp especially over the south china sea and the philippines the monsoon trough mt was confined westward however enhanced convection occurred in the weak shear years and the mt extended eastward this cross tropopause wind shear is negatively correlated with tc genesis in may with a decreased increased number of tcs corresponding to strong weak cross tropopause wind shear this cross tropopause wind shear can be treated as the combined impacts of the el nino southern oscillation enso events and the stratospheric quasi biennial oscillation qbo when decaying el nino events coupled with the easterly phase of the qbo were noted the cross tropopause wind shear was stronger with weakened convection and an enhanced western pacific subtropical high was observed tcs are rarely generated during these years in contrast the modulation of the qbo westerly phase on decaying la nina events is limited affected by the qbo westerly phase tc genesis in the may following la nina events is only slightly enhanced the energy analysis indicates that the combined impacts of the decaying el nino events and the qbo easterly phase might suppress the barotropic eddy kinetic energy conversion in may whereas the decaying la nina events and the qbo west phase act in an opposite manner

modulation of western north pacific tropical cyclone activity by the atlantic meridional mode this study examines the year to year modulation of the western north pacific wnp tropical cyclones tc activity by the atlantic meridional mode amm using both observations and the geophysical fluid dynamics laboratory forecast oriented low ocean resolution version of cm2 5 flor global coupled model 1 the positive negative amm phase suppresses enhances wnp tc activity in observations the anomalous occurrence of wnp tcs results mainly from changes in tc genesis in the southeastern part of the wnp 2 the observed responses of wnp tc activity to the amm are connected to the anomalous zonal vertical wind shear zvws caused by amm induced changes to the walker circulation during the positive amm phase the warming in the north atlantic induces strong descending flow in the tropical eastern and central pacific which intensifies the walker cell in the wnp the intensified walker cell is responsible for the suppressed enhanced tc genesis in the eastern western part of the wnp by strengthening weakening zvws 3 the observed wnptc amm linkage is examined by the long term control and idealized perturbations experiment with flor fa a suite of sensitivity experiments strongly corroborate the observed wnptc amm linkage and underlying physical mechanisms

effects of tropical north atlantic sst on tropical cyclone genesis in the western north pacific the tropical cyclone genesis number tcgn in july october jaso over the western north pacific wnp exhibits a robust interannual variation it shows a longitudinally tri pole pattern with a high in the eastern wnp and south china sea scs and a low in the western wnp which explain 42 2 and 23 4 of total tcgn variance in the eastern wnp and scs respectively the high low high pattern is similar to that derived from a tc genesis potential index gpi to understand the cause of the longitudinal distribution of the dominant interannual mode we examine the contributions of environmental parameters associated with gpi it is found that relative humidity and relative vorticity are important factors responsible for tc variability in the scs while vertical shear and relative vorticity are crucial in determining tc activity in eastern wnp a simultaneous correlation analysis shows that the wnp tcgn in jaso is significantly negatively correlated with a correlation coefficient of 0 5 with sea surface temperature anomalies ssta in the tropical north atlantic tna the longitudinal distribution of tc genesis frequency regressed onto tna ssta resembles that regressed upon the wnp tcgn series the spatial patterns of regressed environmental variables onto the ssta over the tna also resemble those onto tcgn in the wnp that is an increase of relative humidity in the scs and a weakening of vertical shear in the eastern wnp are all associated with cold ssta in the tna further analyses show that the cold ssta in the tna induce a negative heating in situ in response to this negative heating a low upper level anomalous aniti cyclonic cyclonic flows appear over the subtropical north atlantic and eastern north pacific and to east of the cold ssta anomalous low level westerlies appear in the tropical indian ocean given pronounced mean westerlies in northern indian ocean in boreal summer the anomalous westerly flows increase local surface wind speed and surface evaporation and cool the sst in situ cold ssta in northern indian ocean further suppress local convection inducing anomalous westerlies to its east leading to enhanced cyclonic vorticity and low surface pressure over the wnp monsoon trough region idealized numerical experiments further confirm this indian ocean relaying effect through which cold ssta in the tropical atlantic exert a remote impact to circulation in the wnp

the time varying geomagnetic field the scope of this review is limited to papers on the large scale geomagnetic field of deep internal origin and its secular variation published by u s authors and their colleagues during the 1983 1986 quadrennial the many fine papers on this broad topic by authors outside the u s are regretfully excluded fortunately most of them are cited by the u s authors listed in the reference section of this review labreque and mayhew this issue review papers treating the smaller scale fields usually attributed to visco inductively and remanently magnetized crustal geologic structures review articles dealing with external fields are surveyed by m schulz in the magnetosphere section of this u s national report booker and chave this issue review papers concerning the use of more rapidly fluctuating externally induced internal fields to probe the electrical properties of the crust and upper mantle lund and olson this issue review papers concerning paleo secular variation and core geodynamo theory

impact of the quasi biweekly oscillation on the super typhoon tracks in winter over the western north pacific this study investigates the tracks of category 4 and 5 typhoons tys in the western north pacific wnp in november december during 1979 2016 and their relationships with the intraseasonal oscillation iso including the 30 60 day and 12 25 day variations it is shown that the impact of iso on the ty tracks found in previous studies is mainly contributed by the quasi biweekly oscillation qbwo the impact on the ty tracks is through influence on the steering flows over the wnp accordingly tys are separated into two types moving westward tyw and northeastward tye qbwo in the wnp is associated with an active convection originated from the equatorial wnp which propagates northwestward and reaches the scs and middle high latitudes tyw mostly occurs in the decline stage of the qbwo life cycle while tye appears in the mature stage of qbwo for tyw qbwo hardly changes the background large scale circulation which features an anticyclonic circulation covering the entire wnp and scs thus tyw moves westward however tye appears in the mature phase of qbwo the strong convection induces an intense cyclonic circulation in western part of the wnp thus changes the steering flow the steering flow features an anticyclonic circulation over the mid eastern wnp which is favorable for tye to divert the direction and move northeastward

large scale environmental parameters associated with tropical cyclone formations in the western north pacific abstract the local environmental conditions associated with 405 tropical cyclone tc formations in the western north pacific during 1990 2001 are examined in this study six large scale parameters are obtained and computed from the ncep reanalyses with 2 5 latitude resolution these include the sea surface temperature 200 850 hpa vertical and meridional zonal shear 500 700 hpa average relative humidity convective available potential energy and 200 hpa divergence it is found that these parameters show quite consistent values in almost all the cases examined and near gaussian distributions are found for them the mean values of these distributions are 28 9 c 3 2 m s 1 2 3 m s 1 61 8 1184 1 j kg 1 and 5 2 10 6 s 1 for the above six domain averaged parameters respectively based on these distributions of values a formation potential area is defined as a location that possesses these environmental parameters all within the thresholds one standard deviation from the mean value found above

effect of the formation of the isthmus of panama on atlantic ocean thermohaline circulation the late cenozoic closure of the seaway between the north andsouth american continents is thought to have caused extensive changes in ocean circulation and northern hemisphere climate1 2 but the timing and consequences of the emergence of the isthmus of panama which closed the seaway remain controversial1 2 3 4 5 here we present stable isotope and carbonate sand fraction records from caribbean sediments which when compared to atlantic and pacific palaeoceanographic records indicate that the closure caused a marked reorganization of ocean circulation starting 4 6 million years ago shallowing of the seaway intensified the gulf stream and introduced warm and saline water masses to high northern latitudes these changes strengthened deep water formation in the labrador sea over the next million years as indicated by an increased deep water ventilation and carbonate preservation in the caribbean sea and favoured early pliocene warming of the northern hemisphere the evaporative cooling of surface waters during north atlantic deep water formation would have introduced moisture to the northern hemisphere although the pronounced intensification of northern hemisphere glaciation between 3 1 and 2 5 million years ago substantially lagged the full development of north atlantic deep water formation we propose that the increased atmospheric moisture content was a necessary precondition for ice sheet growth which was then triggered by the incremental changes in the earth s orbital obliquity

late pliocene millennial scale climate variability in the northern north atlantic prior to and after the onset of northern hemisphere glaciation 1 sediments recovered at ocean drilling program site 984 on the reykjanes ridge provided multicentennial scale records of late pliocene climate change over the onset of northern hemisphere glaciation nhg 2 95 2 82 ma short term climate variations prior to and after the onset of continent wide glaciation were compared to test the hypothesis of whether dansgaard oeschger do cycles may have been triggered by continental ice breakouts during two selected interglacial stages prior to and after nhg g15 and g1 climate variability resembled that found in the holocene and the mid pliocene warm period in contrast do like periodicities of 1470 2900 and 4400 years indeed only occurred in glacial stages after the onset of nhg g14 g6 and 104 but not in stage g20 prior to the onset these results suggest a causal link between do cycles and the late pliocene onset of major nhg and ice breakouts in the north atlantic

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

impact of intraseasonal oscillation on the tropical cyclone track in the south china sea this study investigates the impact of the intraseasonal oscillation iso on tropical cyclone tc tracks in the south china sea scs during 1970 2010 about one third of tcs in the scs move eastward while the other two thirds move westward in the tc genesis peak seasons of june october jjaso the westward moving tcs are controlled by the background tc steering flow of easterly and the eastward moving tcs by the tc steering flow induced by the iso the outgoing longwave radiation and wind fields show that the eastward moving tcs were mostly along the main axis of strong tc steering flow anomaly of westerly associated with the iso while the westward moving tcs were only weakly associated with the iso an experiment performed with a simple two level model further confirmed the result the interannual variation of tc tracks in the scs is also discussed it is found that the steering flow anomalies in the scs mostly favor eastward moving tcs in central pacific cp el nino and eastern pacific ep el nino years however the eastward flow anomalies are too weak to have strong influence on the majority of the tcs during la nina years tcs in the scs tend to move westward possibly related to the westward steering flow anomalies

reevaluation of mid pliocene north atlantic sea surface temperatures 1 multiproxy temperature estimation requires careful attention to biological chemical physical temporal and calibration differences of each proxy and paleothermometry method we evaluated mid pliocene sea surface temperature sst estimates from multiple proxies at deep sea drilling project holes 552a 609b 607 and 606 transecting the north atlantic drift sst estimates derived from faunal assemblages foraminifer mg ca and alkenone unsaturation indices showed strong agreement at holes 552a 607 and 606 once differences in calibration depth and seasonality were addressed abundant extinct species and or an unrecognized productivity signal in the faunal assemblage at hole 609b resulted in exaggerated faunal based sst estimates but did not affect alkenone derived or mg ca derived estimates multiproxy mid pliocene north atlantic sst estimates corroborate previous studies documenting high latitude mid pliocene warmth and refine previous faunal based estimates affected by environmental factors other than temperature multiproxy investigations will aid sst estimation in high latitude areas sensitive to climate change and currently underrepresented in sst reconstructions

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