rectification of the madden julian oscillation into the enso cycle an ocean general circulation model forced with idealized purely oscillating wind stresses over the western equatorial pacific similar to those observed during the madden julian oscillation mjo developed rectified low frequency anomalies in sst and zonal currents compared to a run in which the forcing was climatological the rectification in sst resulted from increased evaporation under stronger than normal winds of either sign from correlated intraseasonal oscillations in both vertical temperature gradient and upwelling speed forced by the winds and from zonal advection due to nonlinearly generated equatorial currents the net rectified signature produced by the mjo like wind stresses was sst cooling about 0 48c in the west pacific and warming about 0 18c in the central pacific tending to flatten the background zonal sst gradient it is hypothesized that in a coupled system such a pattern of sst anomalies would spawn additional westerly wind anomalies as a result of sst induced changes in the low level zonal pressure gradient this was tested in an intermediate coupled

synoptic settings of westerly wind bursts the morphology of westerly wind bursts wwbs during the 1980s is investigated using 1000 mbar winds analyzed by the european center for medium range weather forecasts ecmwf the variety of synoptic situations in which wwbs occur are explored so that the dynamics of wwb generation and maintenance can be studied and so that those interested in short and long term forecasts of conditions over the equatorial pacific will have an increased knowledge of those elements associated with wwbs wwbs are identified by searching for episodes in which the zonal wind was at least 5 m s 1 over at least 10 longitude for two or more days this definition based on surface winds rather than elevated winds or wind anomalies reflects the impact wwbs have on air sea interaction processes the spatial and temporal criteria provide a synoptic scale envelope for such interactions and mitigate against erroneous analyses according to these criteria 131 distinct wwbs occurred during the 1980s a new two dimensional classification scheme has been developed the nine patterns in it describe the near surface flow during 90 of these wwbs a single cyclone or a series of cyclones in one or both hemispheres and several different types of cross equatorial flow are the major components of the patterns only 8 of the bursts were associated with concurrent cyclones in both the northern and southern hemispheres four bursts involving cross equatorial flow are subjected to further study the flow is decomposed into barotropic and baroclinic parts and into rotational and divergent baroclinic components one of the bursts was predominantly barotropic and another predominantly baroclinic the cross equatorial flow in all four cases was predominantly divergent in nature the information from these cases coupled with the typical vertical structures and small meridional length scales associated with the various synoptic patterns suggests that simple baroclinic models of circulations driven by near equatorial heating are not adequate to describe the dynamics during wwbs

variability of intraseasonal kelvin waves in the equatorial pacific ocean abstract previous observational work has demonstrated that the phase speed of oceanic equatorial kelvin waves forced by the madden julian oscillation mjo appears to vary substantially processes that are responsible for systematic changes in the phase speed of these waves are examined using an ocean general circulation model the model was integrated for 26 yr with daily wind stress derived from the ncep ncar reanalysis the model is able to reproduce observed systematic changes of kelvin wave phase speed reasonably well providing a tool for the analysis of their dynamics the relative importance of the upper ocean background state and atmospheric forcing for phase speed changes is determined based on a series of model experiments with various surface forcings systematic changes in phase speed are evident in all model experiments that have different slowly varying basic states showing that variations of the upper ocean background state are not the primary cause of the changes the model experiments t

zonal and vertical structure of the madden julian oscillation abstract a statistical study of the three dimensional structure of the madden julian oscillation mjo is carried out by projecting dynamical fields from reanalysis and radiosonde data onto space time filtered outgoing longwave radiation olr data mjo convection is generally preceded by low level convergence and upward motion in the lower troposphere while subsidence cooling and drying prevail aloft this leads to moistening of the boundary layer and the development of shallow convection followed by a gradual and then more rapid lofting of moisture into the middle troposphere at the onset of deep convection after the passage of the heaviest rainfall a westerly wind burst region is accompanied by stratiform precipitation where lower tropospheric subsidence and drying coincide with continuing upper tropospheric upward motion the evolution of the heating field leads to a temperature structure that favors the growth of the mjo the analysis also reveals distinct differences in the vertical structure

dynamics and thermodynamics of a warming event in a coupled tropical atmosphere ocean model abstract a simple coupled ocean atmosphere model similar to that of zebiak and cane is used to examine the dynamic and thermodynamic processes associated with el nino southern oscillation enso the model is run for 300 years the interannual variability which results is regular with a period of either 3 or 4 years quantized by the annual cycle the amplitude 1 5 m s 1 wind and 2 c sst anomalies period and structure of the interannual variability compare well with observations the model warm event is initiated in the spring prior to the event peak and is well described as an instability of the coupled system during instability growth the sea surface temperature sst anomaly is primarily generated by vertical upwelling processes the sst anomaly can be approximately described by the expression t t kth t where t is the sst anomaly t time h the upper layer thickness pycnocline perturbation and an effective damping time which includes heat loss to the atmosphere kt parameterizes

is enso a cycle or a series of events 1 after early ideas that saw el ninos as isolated events the advent of coupled models brought the conception of enso as a cycle in which each phase led to the next in a self sustained oscillation twenty two years of observations that represent the el nino and la nina peaks east pacific sst and the memory of the system zonal mean warm water volume suggest a distinct break in the cycle in which the coupled system is able to remain in a weak la nina state for up to two years so that memory of previous influences would be lost similarly while the amplitude of anomalies persists from the onset of a warm event through its termination there is no such persistence across the la nina break these observations suggest that el ninos are in fact event like disturbances to a stable basic state requiring an initiating impulse not contained in the dynamics of the cycle itself

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

the association of the evolution of intraseasonal oscillations to enso phase abstract the pacific ocean intraseasonal kelvin wave is a leading oceanic mode that links intraseasonal tropical atmospheric variations with interannual variations in the coupled ocean atmosphere system this study considers the premise that these waves may evolve differently with their associated weather patterns during different phases of el nino southern oscillation enso if atmospheric and oceanic intraseasonal modes interact and evolve differently during various stages of enso this result may provide useful information with regard to the role of these intraseasonal processes in enso evolution this work utilizes signals of the oceanic kelvin wave as a statistical basis for a simple composite averaging technique that is applied during different phases of enso to objectively analyze the evolution of oceanic and the associated portions of atmospheric intraseasonal oscillations results confirm the above premise and suggest that coupling between kelvin waves and atmospheric convection evolves differen

episodes of surface westerly winds as observed from islands in the western tropical pacific we describe the characteristics of surface westerly wind episodes in the tropical pacific between mid 1957 and 1980 as they can be determined from a collection of daily average wind records from islands several types of frequency of occurrence and duration statistics are presented events in which the maximum westerly anomalies exceed 7 m s 1 are not common but are prominent in the records there is strong seasonal and geographical variation in frequency of occurrence four types of westerly episodes are found we call them types n c s or fs according to whether the maximum westerly wind is found north of centered on south of or far south of the equator near the international date line sixteen 45 47 and 47 events of type n c s and fs are identified respectively the strongest westerly winds are associated with type c and s events maximum daily average values can exceed 20 m s 1 only type c and s events are found to have substantial equatorial zonal wind anomalies several examples of type c and s events are presented composite events of each type have been computed and their characteristics are described in order to explore relationships between equatorial westerly events and cyclones all of the named tropical cyclones within a region encompassing the near date line islands have been identified various statistics are presented but no absolute relationships have been identified the similarity between the composite type c and s anomaly patterns and patterns of the el nino southern oscillation monthly mean zonal wind anomaly previously documented in the literature is striking evidently the westerly events often dominate in the monthly average anomaly

the intraseasonal oscillation in eastern pacific sea levels how is it forced abstract daily sea level and surface winds at eastern pacific shore locations and equatorial islands together with gridded five day averages of 850 mb winds have been analyzed for the 1979 84 period to determine how the 40 60 day intraseasonal oscillation of eastern pacific sea levels is forced as described by spillane et al for 1971 75 the oscillation was also present in 1980 84 from callao peru to san francisco with maximum energy near 52 57 days and band limits of 43 and 65 days during 1980 84 there was no evidence for forcing of the large scale oscillation in the eastern pacific although a local contribution of forcing was superimposed on the remote signal at the california stations interannual fluctuations in amplitude were evident in the sea level time series consistent with those of the corresponding wind oscillation in the western equatorial pacific the oscillation was best developed in both variables in 1980 82 and became weak or nonexistent during the recovery phase of the 1982 83 e

analysis of convectively coupled kelvin waves in the indian ocean mjo abstract the active convective phase of the madden julian oscillation hereafter active mjo comprises enhanced moist deep convection on its own temporal and spatial scales as well as increased variance in convection associated with higher frequency modes synoptic scale cloud superclusters apparently associated with convectively coupled kelvin waves occur within the active convective envelopes of most mjo events these convectively coupled kelvin waves also occur during the suppressed convective phase of the mjo hereafter suppressed mjo this observational study presents an analysis of outgoing longwave radiation and reanalysis data to determine how these waves behave differently as they propagate through the active and suppressed mjo time indices of the mjo and kelvin waves are derived for over the equatorial indian ocean dates of local extrema in these indices are used to composite data to discern how the waves and associated circulations behave on average then further composites are made based o

a climatology of waves in the equatorial region abstract propagating anomalies of moisture and moist deep convection in the tropics are organized into a variety of large scale modes these include but are not limited to the so called intraseasonal oscillations convectively coupled waves similar to those predicted by shallow water theory on the equatorial beta plane and tropical depression type disturbances along with the annual and diurnal cycles these modes act and interact to control much of the variance of tropical convection analyses of 10 yr of outgoing longwave radiation olr and precipitable water pw data are carried out to develop comparative climatologies of these wavelike modes the analysis relaxes the commonly used cross equatorial symmetry constraints which allows study of the portions of the wavelike processes that are asymmetric across the equator mean background states are found for olr and for pw as functions of day of the year examination of anomalies together with the background reveals much about how the waves are affec

permafrost response to surface temperature change and its implications for the 40 000 year surface temperature history at prudhoe bay alaska the geothermal data of lachenbruch et al 1982 in ice bearing permafrost at prudhoe bay are interpreted in terms of the temperature history on a time scale of 40 000 years or longer to this end two theories are developed a forward theory to calculate the response of ice bearing permafrost to a surface temperature disturbance and an inverse theory to calculate parameters characterizing the surface temperature history from suitable measurements in this permafrost the inverse theory shows that two pieces of information characterizing the surface temperature history on a long time scale and the equilibrium geothermal heat flux can usually be determined but the results depend upon the quality of the data the structure of the surface temperature disturbance and the timing of the measurements the memory of the permafrost may range from near zero to hundreds of thousands of years the geothermal data indicate that the prudhoe bay ground surface temperature has a 40 000 year average of minus 10 9 plus minus 3 0c and a value at glacial maximum of minus 10 9 plus minus 4 6c the limits correspond to the estimated uncertainties in the data and they depend somewhat on the structure of the surface temperature disturbance over the last 40 000 years or so the minus 10 9c temperaturemore is the same as that which prevailed before the 1 8 k warming of the past century the limits placed on the variation of the ground surface temperature by this interpretation are not in accord with limits placed by some existing interpretations of other paleoclimatic indicators it is concluded that a consistent understanding of climate history and geothermal regime in northern alaska does not yet exist less

observed relationships between oceanic kelvin waves and atmospheric forcing abstract the madden julian oscillation mjo has been implicated as a major source of the wind stress variability that generates basin scale kelvin waves in the equatorial pacific one source of debate concerning this relationship is the apparent difference in the frequencies of the two processes this work utilizes data from the tropical atmosphere ocean tao array of moored buoys along with outgoing longwave radiation data to show by means of a multiple linear regression model and case studies that the frequency discrepancy is due to a systematic decrease in the phase speeds of the kelvin waves and an increase in the period of the waves toward the east as conditions adjust toward el nino among the potential contributing factors to this phase speed decrease is an apparent air sea interaction that enhances the wind forcing of some of the kelvin waves allowing them to continue to amplify because the propagating wind stress anomaly decelerates to the speed of the developing kelvin wave instead of the sig

effects of low frequency wave interactions on intraseasonal oscillations abstract intraseasonal oscillations isos control much of the large scale variability of convection in the tropics on time scales of about 15 100 days these disturbances are often thought to be dominated by eastward propagating modes especially during austral summer but disturbances that propagate westward are also important this work demonstrates by means of a multiple linear regression model and a brief case study that eastward and westward moving intraseasonal modes often cooperatively interact with one another to produce many of the characteristics of the observed southern hemisphere summer iso these interactions appear to be facilitated by topography and or by the convective anomalies that are cooperatively induced by the eastward and the westward moving components of the oscillations these interactions do not occur during every period of intraseasonal convective activity but they do commonly occur during periods of high amplitude convective anomalies this analysis shows that eastward and

analysis of a reconstructed oceanic kelvin wave dynamic height dataset for the period 1974 2005 abstract intraseasonal oceanic kelvin waves are the dominant mode of variability in the thermocline of the equatorial pacific dynamic height data from the tropical atmosphere ocean tao array of buoys moored in the tropical pacific offer a convenient grid on which to study the waves but can only be effectively applied to study basinwide wave activity since about 1988 because of insufficient data at earlier times kelvin wave signals are also present in sea level data from island and coastal sites from the university of hawaii sea level center some of which are available from before 1970 and up to 2003 this work describes a technique for reconstructing equatorial dynamic height data back to 1974 by utilizing regression relationships between the tao data and daily sea level time series from 11 stations in the tropical pacific the reconstructed data are analyzed for skill in approximating kelvin wave signals when tao data are available reconstructed kelvin wave signals prior to the tao period are then

u pb zircon geochronology of roxbury conglomerate boston basin massachusetts tectono stratigraphic implications for avalonia in and beyond se new england high precision ca tims 206pb 238u zircon dates from sandstone and brighton igneous rocks associated with roxbury conglomerate in the boston basin eastern massachusetts provide constraints on the age and tectonic significance of these deposits detrital zircon suites from roxbury related sandstones representing in ascending order the franklin park member proposed name the brookline member and the squantum member establish closely comparable maximum depositional ages of 595 14 0 90 598 87 0 71 and 596 39 0 79 ma respectively the youngest of these is the best maximum age estimate of the conglomerate brighton dacite near the base of the brookline member and amygdaloidal andesite near the top yield respective crystallization ages of 584 19 0 70 ma and 585 37 0 72 ma these virtually identical dates support previous interpretations of these particular units as shallow intrusions and thus represent minimum ages of associated conglomerate the roxbury brighton sequence is traditionally shown as inter fingering northward with 570 ma mudstone of the cambridge argillite but the age range of the conglomerate makes this impossible conglomerate lacking quartzite clasts typical of the roxbury proper and associated with 593 19 0 73 ma rhyolite on the south side of the basin is re assigned to the lynn mattapan volcanic complex which rests unconformably on dedham granite in basement exposed west and north of the basin as well calc alkaline geochemistry and ages of the 609 to 584 ma dedham lynn mattapan brighton assemblage link it with 630 to 580 ma arc sequences in other northern appalachian avalonian terranes roxbury conglomerate accumulated in fault bounded intra arc basins near the end of this magmatic cycle

oxygen strontium and neodymium isotope composition of fossil shark teeth as a proxy for the palaeoceanography and palaeoclimatology of the miocene northern alpine paratethys the upper marine molasse sediments of southern germany were deposited during the early to middle miocene a period of significant change for the global miocene palaeoceanography palaeoclimate and the regional palaeogeography because of the ongoing alpine himalayan orogeny to address the influence of the alpine uplift on climate and oceanography of the northern alpine molasse basin a combined o sr and nd isotope study was undertaken on fossil teeth from sharks synodontaspis sp galeocerdo cf aduncus chaenogaleus sp and button like teeth from the bony fish of the upper marine molasse chrysophrys molassica average 18o values for hydroxyapatite of teeth from two sites are 20 3 1 0 6 and 21 2 1 0 5 while their average 87sr 86sr and 143nd 144nd ratios are 0 70850 0 00001 2 and 0 70882 0 00003 2 and 0 51220 and 0 51223 both at 0 00001 2 respectively by comparison to the sr evolution curve for the global ocean the sr isotope compositions suggest ages of about 22 and 17 ma for the teeth these ages are in good agreement with the depositional ages which suggests open marine conditions open marine conditions are also compatible with 1 lower average 18o values and 87sr 86sr ratios for the one site compared to higher 18o values and higher 87sr 86sr ratios for the other site 2 estimates for seawater temperatures which are similar to other estimates from deposits of similar latitude and age 3 a comparison of seawater temperatures with average ambient air temperature estimates deduced from continental palaeoclimate indicators nd isotope compositions are compatible with an influence of the north atlantic on the paratethys assuming constant salinity and seawater oxygen isotope composition a 4 c cooling can be inferred from average 18o values of the teeth between 22 and 17 ma this is similar to trends observed for foraminiferal records from the mediterranean tethys but different from foraminiferal and molluscan records of the north atlantic and the north sea during this period and allows for the possibility that the alpine orogeny had an influence on the regional circum alpine climate

westerly wind bursts enso s tail rather than the dog westerly wind bursts wwbs in the equatorial pacific occur during the development of most el nino events and are believed to be a major factor in enso s dynamics because of their short time scale wwbs are normally considered part of a stochastic forcing of enso completely external to the interannual enso variability recent observational studies however suggest that the occurrence and characteristics of wwbs may depend to some extent on the state of enso components implying that wwbs which force enso are modulated by enso itself satellite and in situ observations are used here to show that wwbs are significantly more likely to occur when the warm pool is extended eastward based on these observations wwbs are added to an intermediate complexity coupled ocean atmosphere enso model the representation of wwbs is idealized such that their occurrence is modulated by the warm pool extent the resulting model run is compared with a run in which the wwbs are stochastically applied the modulation of wwbs by enso results in an enhancement of the slow frequency component of the wwbs this causes the amplitude of enso events forced by modulated wwbs to be twice as large as the amplitude of enso events forced by stochastic wwbs with the same amplitude and average frequency based on this result it is suggested that the modulation of wwbs by the equatorial pacific sst is a critical element of enso s dynamics and that wwbs should not be regarded as purely stochastic forcing in the paradigm proposed here wwbs are still an important aspect of enso s dynamics but they are treated as being partially stochastic and partially affected by the large scale enso dynamics rather than being completely external to enso it is further shown that wwb modulation by the large scale equatorial sst field is roughly equivalent to an increase in the ocean atmosphere coupling strength making the coupled equatorial pacific effectively self sustained

eastward propagating 2 to 15 day equatorial convection and its relation to the tropical intraseasonal oscillation anomalies of outgoing longwave radiation olr in 1980 1989 were examined in a narrow latitude band about the equator to elucidate the propagation and interaction of tropical intraseasonal oscillations tios and synoptic scale convective activity hovmoller diagrams of olr data reconstructed from two frequency bands corresponding to periods of 30 60 days and 2 15 days respectively revealed a clear distinction between the phase speed of eastward moving tios 3 7 m s 1 and that of eastward synoptic scale convection 10 13 m s 1 coherent propagation of tios from the indian to the western pacific oceans was often observed with temporary diminution of amplitude over the maritime continent propagation of high frequency anomalies was generally confined to an individual basin dominance of eastward propagating synoptic scale convection in the equatorial zone contrasts sharply with the westward propagation of off equatorial convergence zones interaction between the tio and high frequency activity resolved by daily olr was visible as a modest enhancement of eastward synoptic scale events and of high frequency activity in general during the convectively active phase of the tio

planetary scale circulations forced by intraseasonal variations of observed convection abstract interhemispheric differences of the madden julian oscillation mjo are investigated in a linearized primitive equation model heating is prescribed from the observed life cycle of the mjo in which anomalous convection is concentrated in the eastern hemisphere the dynamical response in the eastern hemisphere has the form of a forced disturbance that involves kelvin and rossby components these dynamical components propagate eastward along with the prescribed heating and have zonal wavenumber 2 structure in accord with observed behavior the behavior in the eastern hemisphere also resembles that emerging from frictional wave cisk in which heating follows autonomously from the circulation when the prescribed heating collapses near the date line the rossby component dissipates the kelvin component however continues to advance across the western hemisphere where it propagates at more than twice the speed of the disturbance in the eastern hemisphere the disturbance in the western hemisphere

a model for convectively coupled tropical waves nonlinearity rotation and comparison with observations abstract recent observational analysis of both individual realizations and statistical ensembles identifies moist convectively coupled kelvin waves in the tropics with supercluster envelopes of convection this observational analysis elucidates several key features of these waves including their propagation speed of roughly 15 m s 1 and many aspects of their dynamical structure this structure includes anomalously cold temperatures in the lower troposphere and warm temperatures in the upper troposphere below 250 hpa within and sometimes leading the heating region and strong updrafts in the wave and an upward and westward tilting structure with height below roughly 250 hpa other key features in the wave are that anomalous increases in convective available potential energy cape and surface precipitation lead the wave while the trailing part of the supercluster is dominated by stratiform precipitation the main result in this paper is the development of a simple model convective parameterization with n

the role of tropical waves in tropical cyclogenesis abstract this paper analyzes relationships between tropical wave activity and tropical cyclogenesis in all of the earth s major tropical cyclone basins twenty nine years of outgoing longwave radiation data and global reanalysis winds are filtered and analyzed to determine statistical relationships between wave activity in each basin and the corresponding cyclogenesis composite analyses relative to the storm genesis locations show the structures of the waves and their preferred phase relationships with genesis five wave types are examined in this study including mixed rossby gravity waves tropical depression type or easterly waves equatorial rossby waves kelvin waves and the madden julian oscillation the latter is not one of the classical tropical wave types but is a wavelike phenomenon known to have a strong impact on tropical cyclogenesis tropical cyclone formation is strongly related to enhanced activity in all of the wave filter bands except for the kelvin band in each basin the structure o