cross equatorial influence of winter hemisphere subtropical cold surges abstract two case studies are presented of winter hemisphere cold surges affecting the summer hemisphere tropics one case has been chosen from each of the northern and southern hemispheres in both instances the subtropical rise in pressure is tracked equatorward this leads to a pressure rise at the equator and the establishment of a west east pressure gradient at low latitudes in the opposite hemisphere these effects lead in turn to an enhanced cross equatorial component of flow and enhanced monsoon westerly flow in the summer hemisphere both enhanced wind flow effects are observed through a deep layer from the surface up to at least 500 mb in both cases the sequence of events also includes the development of a tropical cyclone in the summer hemisphere monsoon trough the generality of the above sequence of events is investigated with time series data for several seasons it is shown that day to day changes in equatorial pressure are significantly correlated to pressure changes in the winter hemis

the structure and annual variation of antisymmetric fluctuations of tropical convection and their association with rossby gravity waves abstract the signature of 4 5 day period rossby gravity waves is searched for in the tropical convection field across the indian pacific oceans the convergence divergence field of these waves in the lower troposphere is anticipated to produce an antisymmetric fluctuation in tropical convection antisymmetric fluctuations of tropical convection are shown to exhibit a pronounced spectral peak at a 4 5 day period only during boreal fall and only within about 30 longitude of the date line the peak amplitude occurs around 7 5 latitude these fluctuations propagate westward at 15 20 m s 1 with zonal wavelength of about 7000 9000 km the fluctuations of convection are coherent and out of phase with the equatorial meridional wind which also exhibits a pronounced spectral peak at a 4 5 day period in the lower troposphere near the date line the antisymmetric zonal wind also is strongly coherent with the antisymmetric convective fluctuations in this region the horizontal distributions of the 4 5 day power an

circulation anomalies associated with tropical convection during northern winter abstract lagged cross correlations between outgoing longwave radiation olr and national meteorological center global analyses are utilized to isolate the preferred upper level and surface circulation anomalies associated with tropical convection during northern winter three intraseasonal time scales are studied 30 70 14 30 and 6 14 days in the 30 70 day band the upper level circulation signals are zonally elongated with zonal wavenumbers 0 2 dominant higher frequency signals are dominated by zonal wavenumbers 5 and 6 in the 14 30 day band convection over the eastern hemisphere is associated with upper level anticyclones in the subtropics and appears to be linked in some cases to midlatitude wave trains the strongest signals are for convection over africa australia and the eastern indian ocean only weak signals are seen for convection over indonesia in these regions of upper level easterlies olr anomalies peak prior to the maximum anomalies in wind suggesting forcing of the circulation b

evolution of the cloud pattern during the formation of tropical cyclone twins symmetrical with respect to the equator abstract the evolution of the pattern of the deep convective cloud is presented for three selected cases of tropical cyclone twins symmetrical with respect to the equator in each case the pattern evolution is similar and can be separated into four distinct stages

seasonal variations of tropical intraseasonal oscillations a 20 25 day oscillation in the western pacific abstract spectral analysis within a movable time window is used to investigate the frequency and intensity of tropical oscillations with intraseasonal time scales surface and rawinsonde time series from several locations in the western pacific and indian oceans are used evidence is provided that the madden julian oscillation mjo in the indian ocean region shows a seasonal variation in its preferred period from 50 days during northern hemisphere winter to about 35 days during summer though this evidence is weak and stretches the limits of our ability to define a precise period for the oscillation in the western tropical pacific during the september december season a pronounced spectral peak with a central frequency between 20 and 25 days is observed this spectral peak appears to reveal an oscillation that is distinct from the mjo but may also result from coupling between the large scale motion and latent heat release on much smaller scales a relationship between the oscillation and the occurrence

synoptic scale disturbances near the equator abstract a spectral analysis of winds analyzed and initialized at the european centre for medium range weather forecasts reveals an abundance of power in the 850 mb meridional wind along the equator with periods near four days the power is mostly in the westward propagating component using high pass filtered data it is shown that the waves have westward phase and eastward group propagation relative to the mean wind the longest wavelengths are found over the pacific ocean while the shortest are found over the convectively variable regions of indonesia south america and africa mean phase speeds at 850 mb are positively correlated with the mean wind on the equator at 500 mb and below and negatively correlated with the mean wind above that level the effective advecting zonal wind of the disturbances seems to be the density weighted average of the lower troposphere the structure of the disturbances bears resemblance to the expected structure of an equatorially trapped mixed rossby gravity wave over t

the structure and evolution of seasonal wind anomalies over the near equatorial eastern indian and western pacific oceans abstract the longitude height time evolution of seasonally averaged wind anomalies over the near equatorial eastern indian and western pacific oceans is examined using multiyear time series derived from a network of eight rawinsonde stations data at six pressure levels between 850 and 150 mb are considered the first two modes of an empirical orthogonal function analysis of zonal wind fluctuations are cross correlated at lag with spatial structures suggesting that the dominant pattern of variability on seasonal time scales is best described as a propagating oscillation this space time structure is confirmed using a complex empirical orthogonal function analysis which indicates that over half of the interseasonal zonal wind variance at these stations is associated with an eastward propagating mode denoted e1 wind anomalies described by e1 are negatively correlated in the upper and lower troposphere at each station and are out of phase between the southern tip of india and the central pacific so

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

winter monsoon convection in the vicinity of north borneo part ii effects on large scale fields abstract an observational study of the thermodynamic and kinematic structure and properties of monsoon convective systems and their large scale environment over the southern south china sea during the field phase december 1978 of the winter monsoon experiment wmonex has been carried out the primary observations used are from three soviet research vessels positioned in a triangular array off the north coast of borneo during the period 6 28 december computations of thermodynamic fields divergence and vertical motion have been made for the duration of the field phase based on six hourly rawinsonde releases at the ship sites analysis of the data indicates that the degree of convective activity over the southern south china sea is modulated by long period synoptic forcing monsoon surges easterly waves and also significantly by diurnal forcing land sea breeze circulations a diurnal cycle of convection persists in the region whether the synoptic scale forcing is weak or strong convection over wate

horizontal and vertical structure of observed tropospheric equatorial rossby waves equatorial rossby er waves are identified in an 8 year data set of national meteorological center operational analyses the westward moving waves have symmetric circulations about the equator and eastward energy dispersion with maximum zonal wind perturbations along the equator and meridional wind maxima roughly 10 15 off the equator they have maximum amplitude in the lower troposphere and are associated with convective signals at roughly the mean latitude of the tropical convergence zones the circulations thus possess many of the features of the equatorially trapped n 1 rossby modes derived by matsuno 1966 they are generally around zonal planetary wavenumber 6 scale and have a deep nearly equivalent barotropic structure up to 100 mbar this is in contrast with the madden julian oscillation and mixed rossby gravity waves which generally have a first baroclinic mode vertical structure during the intensive observing period iop of the tropical ocean global atmosphere toga coupled ocean atmosphere response experiment coare and in other years westward propagating er disturbances along the equator are observed by using 6 to 30 day filtered circulation data at 850 mbar zonal wind anomalies at 850 mbar are preferentially associated with like signed anomalies in a deep layer at this frequency as was observed during coare the er waves are most common during northern winter in the central pacific although they can be detected sporadically over the other ocean basins and in other seasons as well one source for the equatorial rossby waves appears to be upper level extratropical rossby wave activity propagating into the eastern pacific although the equatorial waves are sometimes present during the northern summer when the extratropical source is absent we cite evidence that propagation of er wave activity from the central into the western pacific is related to occurrences of westerly wind bursts

organization of convection within the madden julian oscillation convection associated with the madden julian oscillation mjo is organized over a broad range of time and space scales within a large scale envelope of activity the large scale envelope of convection is characterized as an eastward propagating disturbance predominantly of zonal wavenumber 2 which is confined over the warmest waters of the indian and western pacific oceans large scale convection is shifted toward the disturbance s temperature anomaly which appears to result from frictional effects in the boundary layer synoptic and mesoscale convective activity is enhanced within the wet phase of the large scale envelope the increase at synoptic scales occurs uniformly over all scales but little difference in the character of the variability is observed between dry and wet phases the enhanced mesoscale activity within the wet phases exhibits a marked tendency to be organized into westward propagating clusters with periods near 2 days and half wavelengths of about 1000 km the role of these modes for the evolution of the mjo is discussed

monthly mean island surface winds in the central tropical pacific and el nino events abstract the monthly mean surface wind changes during recent enso events as observed from 11 islands in the tropical pacific are described two different composite enso wind fields are evaluated and compared the month to month wind changes during each event are also discussed the wind changes for each event between 1953 and 1980 except 1969 show several common features i westerly anomalies appear first west of the date line and then at the date line sometime in summer 0 to fall 0 then intensify over the following several months the anomalies are confined to within 3 of the equator during this stage ii in either november 0 december 0 or january 1 there is an abrupt southward shift of the narrow band of westerly anomalies so that the maximum anomaly is then at 5 s latitude at the date line and nearly normal conditions prevail north of the equator iii westerly anomalies are gone or greatly reduced one to two months after the southward shift the event to event variations are

a theory for midlatitude forcing of tropical motions during winter monsoons abstract in order to understand the northeasterly monsoon surges and associated tropical motions over southeast asia during northern winter the dynamic response of the tropical atmosphere to midlatitude pressure surges is studied using the linearized shallow water equations on an equatorial plane the forcing is specified to have a gaussian spatial distribution with a zonal scale corresponding to approximately wavenumber 7 and a meridional scale of approximately 11 it rises rapidly from zero to maximum within one day or less and then decays slowly over 2 4 days the main results are as follows 1 after an initial period of gravity wave type motions with strong northerly winds the main tropical response takes the form of a rossby wave group 2 a pronounced northeast southwest tilt in this rossby wave group develops due to the faster westward group velocity of the lower meridional modes relative to the higher meridional modes 3 several conspicuous features of the rossby response closely resemble t

dynamics of the itcz boundary layer abstractthis paper presents high resolution numerical solutions of a nonlinear zonally symmetric slab model of the intertropical convergence zone itcz boundary layer the boundary layer zonal and meridional flows are forced by a specified pressure field which can also be interpreted as a specified geostrophically balanced zonal wind field ug y one narrow on equatorial peak in boundary layer pumping is produced when the forcing is easterly geostrophic flow along the equator and two narrow peaks in boundary layer pumping are produced on opposite sides of the equator a double itcz when the forcing is westerly geostrophic flow along the equator in the case when easterlies are surrounding a westerly wind burst once again a double itcz is produced but the itczs have significantly more intense boundary layer pumping than the case of only westerly geostrophic flow a comparison of the numerical solutions to those of classical ekman theory suggests that the meridional advection term y plays a vita

cross equatorial interactions during tropical cyclogenesis abstract this paper presents evidence that winter hemisphere events influence the genesis of tropical cyclones in the summer hemisphere equatorial trough a rawinsonde composite technique is used to study the large scale flow prior to cyclone development this is compared with a composite of the flow during quiet or nontropical cyclone periods the composites span the equator so that changes can be monitored in the winter hemisphere flow and in cross equatorial effects the composite analyses correspond well to the results of case study and time series analyses presented in a companion paper on the basis of these results an idealized scenario of the important synoptic events leading to cyclogenesis in the equatorial trough is described

modulation of equatorial subseasonal convective episodes by tropical extratropical interaction in the indian and pacific ocean regions composite relationships among outgoing longwave radiation sea level pressure surface winds and upper tropospheric circulation are examined for northern winter during subseasonal episodes of eastward progression of convection from the indian ocean to the western pacific this evolution often culminates with westerly wind burst events and strong air sea interaction associated with regional scale convective blowups in the western equatorial pacific we first document some of these interactions in the composites for two timescales the submonthly 6 30 days and that of the madden julian oscillation mjo timescale 30 70 days we then analyze the december 1992 period during the tropical ocean global atmosphere coupled ocean atmosphere response experiment toga coare to illustrate how these composite relationships are manifested in a case study convection in the indian ocean for the composites is shown to be associated with a northern hemisphere wave train at 200 mbar arcing through the midlatitudes that can contribute to convective blowups farther east on the submonthly 6 30 days timescale in the intertropical convergence zone itcz in the eastern pacific the eastern asian trough that is part of this wave train is associated with pressure surges from the northern hemisphere and subsequent convection over southeast asia as the mjo convective envelope moves east to australasia midlatitude wave trains in either hemisphere include upper level troughs east of asia and australia and pressure surges from either hemisphere that contribute to pressure rises over the indonesian region and a subsequent shift of the convective envelope to the western pacific the vertical wind structure for the december 1992 case study is consistent with the composite surface and upper level winds and also shows strong vertical wind shear in the boundary layer a sharply defined westerly maximum near 700 mbar and an intensification of the upper level easterlies near 100 mbar very deep westerlies to 200 mbar are confined to shorter timescales the case study illustrates the various time and space scale interactions noted in the composites reciprocal interactions between the tropics and the midlatitudes on the submonthly and mjo timescales in both the composites and the case study involve pressure surges and wave interaction that influence subsequent convection as the convective envelope migrates eastward from the tropical indian to pacific ocean region

the madden julian oscillation observed during the toga coare iop global view abstract during the toga coare intensive observing period november 1992 february 1993 two pronounced madden julian oscillation mjo events associated with super cloud clusters and westerly wind bursts were observed this paper presents a global view of the mjos including the origin of the super clusters in the indian ocean their migration into the maritime continent and the toga coare large scale soundings array lsa in the western equatorial pacific and their rapid decay over cold water of the eastern pacific the structure and evolution of the mjo are examined with emphasis on the coupling between large scale motion and convection because of differences in propagation speeds the positions of maximum zonal wind perturbations relative to deep convection undergo systematic changes during the travel of the mjo however the centers of deep convection always coincide with those of large scale ascent the super cloud cluster accompanies a wide area of warm air in the upper troposphere over the warm

structure and characteristics of submonthly scale waves along the indian ocean itcz this study examines wave disturbances on submonthly 6 30 day timescales over the tropical indian ocean during southern hemisphere summer using japanese reanalysis jra25 jcdas products and national oceanic and atmospheric administration outgoing longwave radiation data the analysis period is december february for the 29 years from 1979 1980 through 2007 2008 an extended empirical orthogonal function eeof analysis of daily 850 hpa meridional wind anomalies reveals a well organized wave train pattern as a dominant mode of variability over the tropical indian ocean daily lagged composite analyses for various atmospheric variables based on the eeof result show the structure and evolution of a wave train consisting of meridionally elongated troughs and ridges along the indian ocean intertropical convergence zone itcz the wave train is oriented in a northeast southwest direction from sumatra toward madagascar the waves have zonal wavelengths of about 3 000 5 000 km and exhibit westward and southwestward phase propagation individual troughs and ridges as part of the wave train sequentially travel westward and southwestward from the west of sumatra into madagascar meanwhile eastward and northeastward amplification of the wave train occurs associated with the successive growth of new troughs and ridges over the equatorial eastern indian ocean this could be induced by eastward and northeastward wave energy dispersion from the southwestern to eastern indian ocean along the mean monsoon westerly flow in addition the waves modulate the itcz convection correlation statistics show the average behavior of the wave disturbances over the tropical indian ocean these statistics and other diagnostic measures are used to characterize the waves obtained from the composite analysis the waves appear to be connected to the monsoon westerly flow the waves tend to propagate through a band of the large meridional gradient of absolute vorticity produced by the mean monsoon westerly flow this suggests that the monsoon westerly flow provides favorable background conditions for the propagation and maintenance of the waves and acts as a waveguide over the tropical indian ocean the horizontal structure of the wave train may be interpreted as that of a mixture of equatorial rossby waves and mixed rossby gravity wavelike gyres

multiscale phenomena in the tropical atmosphere over the western pacific abstract multiscale variabilities in the atmosphere over the tropical western pacific during the 1979 northern hemisphere winter are studied with an aim at identifying possible interactions between phenomena of different spatial and temporal scales based on the convection index information derived from satellite measurements two intra seasonal oscillations isos are identified within the equatorial belt between 0 and 10 s in the analyzed period the two isos accompanied by both rotational and divergent circulations propagate eastward from the indian ocean to the western pacific over the warm pool in the western pacific the isos develop into quasi stationary systems with an enhanced rotational circulation characterized by a strong westerly jet in the lower troposphere the isos appear to interact with a number of regional and synoptic scale phenomena in the maritime continent and western pacific region for example the onset of the monsoon coincides with the arrival of the first iso at northern a

the appearance of sustained equatorial surface westerlies during the 1982 pacific warm event in june 1982 a band of anomalous southerly surface wind extending from the equator as far south as the tasman sea formed east of australia 150 e to 160 e this flow crossed the equator just before the appearance of sustained westerly winds on the equator somewhat west of the date line because these westerly winds induced the initial strong equatorial warming of the ocean east of the date line during the 1982 el nino southern oscillation enso event the southerly jet appears to be an important atmospheric component leading to the onset of the vigorous phase of this event some historical evidence suggests that anomalous southerly winds in the same region occurred prior to the appearance of sustained equatorial westerly winds in the major enso events of 1957 1965 and 1972

global teleconnections in the 250 mb streamfunction field during the northern hemisphere winter abstract teleconnections of the streamfunction in the global domain based on ecmwf 250 mb winds for the 11 northern winters from 1978 79 through 1988 89 are documented in this study a zonal structure with a node near the equator indicating an out of phase relationship between the streamfunctions in the northern and southern hemisphere appears to mask the fluctuations of the asymmetric components of streamfunction after removing zonal means a global pattern emerges as the dominant structure in the low frequency band this pattern consists of several dipoles straddling either the exit region of midlatitude jets or the equator indicating the existence of teleconnections not only between the midlatitudes and the tropics but also between the northern and southern hemispheres teleconnection patterns in the intermediate frequency band are predominantly wavelike seven waveguides are identified based on the one point lag correlation maps for base points near the maximum teleconnectivity among them are thr

large scale circulation associated with westerly wind bursts and deep convection over the western equatorial pacific the relationship between deep equatorial convection over the western pacific and atmospheric circulation during november to february 1986 1992 is studied using cross correlations between outgoing longwave radiation olr and national meteorological center global analyses we focus on intraseasonal convective events on the 6 to 30 day timescale over two regions just east of borneo and over the tropical ocean and global atmosphere toga coupled ocean atmosphere response experiment coare domain to the northeast of new guinea although comparatively little work has been done on this timescale we show that the bulk of the intraseasonal variability in both convection and low level circulation over the tropical western pacific occurs in this period range as a comparison with these higher frequency events the evolution of coare convection on the 30 to 70 day timescale is also considered the results of the historical data analysis are compared to a case study of deep convection associated with strong surface westerly winds during november 1989 this analysis is meant to serve as a benchmark for future case studies from the tropical ocean global atmosphere coare experiment and other periods in general 6 to 30 day equatorial convection in the regions studied occurs in conjunction with low level equatorial westerly wind anomalies paired anomalous cyclonic circulations straddling the equator and a strengthening of the sea level pressure gradient along the equator the increase in the pressure gradient appears most often tied to the simultaneous equatorward movement of high pressure systems originating over southeastern asia and australia a surge of trades over the central pacific also accompanies the development of convection over both study regions following the convective peak the low level westerlies slowly decay as the northern cyclone moves northwestward away from the equator in a track characteristic of a tropical depression it is also observed that low level westerly anomalies occur frequently without deep convection the vertical structure during convective events along the equator on the 30 to 70 day timescale and over indonesia in the 6 to 30 day band is baroclinic with easterly anomalies at upper levels overlying low level westerlies at 200 mbar a strengthened meridional outflow from the olr signal into a wave train on the equatorward side of the asian jet is observed to develop following the convective peak suggesting forcing of this circulation by the convection over the coare domain there is evidence that 6 to 30 day convection often occurs in conjunction with deep westerly flow it is suggested that these types of events are frequently characterized by vertical propagation of westerlies from the surface to the upper troposphere as is shown for a case study from november 1989 this westerly burst episode is shown to have many features in common with the typical case as defined from historical data

the role of cross equatorial tropical cyclone pairs in the southern oscillation abstract the locations and frequencies of cross equatorial tropical cyclone pairs over the pacific ocean are compared between years of contrasting equatorial pacific sea surface temperature sst and atmospheric circulation anomalies i e high versus low southern oscillation so indices during the period 1971 79 weak southeast trade winds associated with low so indices allow warm 29 c surface water in the equatorial 0 5 s zone to extend eastward across the dateline encouraging formation of cyclone pairs near the dateline the cyclone pairs in turn provide the linkage between warm water and equatorial convection as indicated by canton island rainfall during southern summer in general the occurrences of cyclone pairs vary in longitude with the eastward excursions of warm equatorial water furthermore cyclone pairs appear to provide a positive feedback by advancing the eastward warm water extent in 1974 75 when no cyclone pairs developed near the dateline in spite of sufficiently high sst

cross equatorial influences of submonthly scale southerly surges over the eastern indian ocean during southern hemisphere winter 1 lower tropospheric southerly surges occurring at submonthly timescales over the eastern indian ocean eio during southern hemisphere sh winter are extratropical tropical interaction phenomena involving various processes this study examined the physical mechanism driving equatorial wave disturbances associated with surge induced cross equatorial flow over the eio japanese 25 year reanalysis jra25 and tropical rainfall measuring mission satellite trmm 3b42 data products from june to august for the 7 years from 1998 to 2004 were analyzed composite analyses of low level wind and vorticity fields reveal that an equatorial clockwise gyre develops just after cross equatorial penetration of southerly surge winds this gyre is interpreted as an equatorially trapped rossby wave that develops asymmetrically around the equator in response to surge induced cross equatorial flow eddy vorticity budget analysis demonstrates the dynamic role of the southerly surge in the genesis of the equatorial clockwise gyre the result indicates that an injection of negative absolute vorticity into the equatorial tropics due to both advective and convergent processes associated with the surge winds is primarily responsible for the gyre genesis cross equatorial advection of basic state absolute vorticity by the surge eddy winds and vortex stretching by surge wind convergence are most effective in spinning up the equatorial clockwise gyre wave activity flux analysis further emphasizes that rossby wave energy propagation from the sh extratropics into the equatorial eio region is caused by the southerly surge these dynamic diagnostics suggest that the southerly surge plays a lateral forcing role in exciting the equatorial wave disturbance over the eio composite analyses of moisture flux and precipitation anomalies characterize the equatorial clockwise gyre as a convectively coupled equatorial rossby wave enhanced cross equatorial moisture transport due to the southerly surge appears to be linked to precipitation along the west coast of the southern indo china peninsula a case study of the southerly surge event during august 2000 illustrates the formation of the equatorial clockwise gyre and its convectively coupled equatorial rossby wave signature

the first appearance of troodon in the upper cretaceous site of danek bonebed and a reevaluation of troodontid quantitative tooth morphotypes the systematic position of the small theropod dinosaur troodon has had a confusing history and has been identified at different times as a lizard a pachycephalosaurid and a coelurosaurid troodon

an evaluation of ship data in the equatorial western pacific abstract theoretical and observational studies suggest that the equatorial western pacific plays an important role in the origin and maintenance of the el nino southern oscillation phenomenon historical data within this critical region are sparse except for a scattering of island stations and a merchant shipping lane along 155 e the usefulness of ship data along this track is assessed utilizing exploratory data analysis and analysis of variance systematic biases are revealed in the surface wind pressure and sea surface temperature measurements the noise level in the data is quantified using standard error estimates and signal to noise ratios associated with various time averages it is shown that zonal wind is capable of detailing synoptic scale variations however meridional wind surface pressure and sea surface temperature are better suited for estimating lower frequency variations

fluid pressures and fluid flows from boreholes spanning the nantroseize transect through the nankai trough sw japan abstract iodp expedition 314 acquired annular pressure while drilling measurements in six holes extending from the outer forearc basin to the base of the trench slope these data provide pressures inside the borehole near the bit during drilling the pressures reflect the cuttings load in the borehole and the viscous resistance to flow of fluids up the borehole due to pumping from the rig floor and due to fluid exchange with the formation the forearc basin site provides a reference locality that extends to 1402 m and whose pressure curve is apparently controlled dominantly by the cuttings load and the rig floor pumping rate all other holes show at least initial pressure curves that are very similar to that at the forearc basin site despite pumping rates varying by about 20 30 some small variations in pressure curves can be positively correlated to the penetration rate that controls cutting load two holes crossing a fracture zone show pressure anomalies extending to above lithostatic conditions and modeled fluid influx rates of 3000 l m or 150 of the rig floor pumping rate a third hole probably in the same highly overpressured zone shows a near lithostatic pressure value just prior to losing the bottom hole assembly due to stuck pipe the extraordinarily high pressures occur in the upper portion of the hanging wall of the megasplay fault zone and may reflect residual conditions from the 1944 m 8 1 earthquake a penetration of the lower boundary of the megasplay fault zone shows only minor fluid pressure anomalies around the fault surface a hole through the frontal thrust records fluid pressure anomalies in sandy sediments of the footwall apparently due to expulsion of fluids from loading by the hanging wall

extratropical forcing of tropical pacific convection during northern winter abstract statistical evidence is presented to support the notion that tropical convection in the eastern pacific and atlantic intertropical convergence zone itcz during northern winter can be forced by disturbances originating in the extratropics the synoptic scale transients in these regions are characterized at upper levels by strong positive tilts in the horizontal and appear to induce vertical motions ahead of troughs as in midlatitude baroclinic systems two case studies of such interactions are examined one for the eastern north pacific itcz and another somewhat different type of interaction for the south pacific convergence zone spcz over the western south pacific both cases are associated with upper level troughs strong cold advection deep into the tropics and the formation of a frontal boundary at low levels the itcz case is characterized by the advection of anomalously high isentropic potential vorticity air southward a strong poleward flux of heat and westerly momentum and the devel

variability in the south pacific deep western boundary current from current meter observations and a high resolution global model observations of the south pacific deep western boundary current from the world ocean circulation experiment pacific current meter array 9 woce pcm 9 current meter array are compared with the los alamos national laboratory high resolution global ocean model a simple integration of pcm 9 velocity yields a mean northward transport of water deeper than 3000 m that is some 5 times greater than the model mean transport of 3 35 106 m3 s 1 the low modeled abyssal transport suggests a poor simulation of the mean thermohaline circulation however model and observed transport variability correlate significantly space time spectral analysis shows planetary waves are responsible for most of the variability and are resolved well in the model the details of interaction of the long waves at the western boundary are different in model and data the model reflects these waves predominantly as planetary short waves which decay over the region 600 800 km east of the kermadec ridge pcm 9 has a higher proportion of energy as topographic waves along the kermadec ridge these two classes of waves are associated with the two observed zonal scales in the boundary current the model results can be separated into vertical modes baroclinic energy is found at all timescales including those too short for free baroclinic waves the baroclinic flow correlates with the barotropic so as to enhance surface and reduce abyssal kinetic energy this is the signature of planetary wave scattering at the submerged western boundary ridge and results in enhanced baroclinic wave energy in the tasman sea

observation of 3 6 day meridional wind oscillations over the tropical pacific 1973 1992 vertical structure and interannual variability abstract rawinsonde data from tropical pacific stations were examined for westward propagating 3 6 day meridional wind oscillations in the troposphere and lower stratosphere 1973 1992 four types were identified from cross spectrum and principal component analysis 1 the dominant oscillation near 250 mb had a period slightly greater than 5 days zonal wavenumber 4 6 and modified rossby gravity structure near the date line 2 in the western pacific lower troposphere there was broadband activity with short zonal scale coupled to upper tropospheric waves in nh summer 3 in the central pacific during nh autumn there was a well defined 4 day oscillation with maximum amplitude in the lower troposphere and baroclinic phase tilt above the vertical structure suggested coupling to deep tropical convection this interpretation was supported by correlation of meridional wind with antisymmetric outgoing longwave radiation 4 in the stratosphere rossby gravity waves had periods 4 days and zonal wavenu

moored surface wind observations at four sites along the pacific equator between 140 and 95 w abstract mooted surface wind measurements were recorded along the pacific equator at 140 124 110 and 95 w during portions of 1980 85 minimum record length is one year the annual mean and monthly mean westward speeds at 110 w were about 1 5 m s 1 higher during the year preceding the 1982 83 el nino than in the year following this event the annual cycle which moved westward at 0 8 m s 1 consisted of weak westward and northward speeds in february april and vice versa in september october the spectral slope between 5 day and 0 05 day periods was 1 5 the rms amplitude of the 95 statistically significant diurnal period oscillation was 0 3 m s 1 and the meridional component was nearly twice as large as the zonal component the diurnal period wave was coherent at the 95 confidence level between 95 and 124 w with westward phase propagation of about 138 m s 1 no statistically significant at the 95 confidence level spectral peak was found in the 40 to 50 day intraseasonal period band the s