typhoon induced highly nonlinear internal solitary waves off the east coast of korea 1 highly nonlinear internal solitary waves isws propagating both onshore and offshore were detected in a sar image taken approximately 19 hours after typhoon maemi s passage across the east coast of korea analysis of ocean buoy data suggests that the isws were generated by near inertial waves in response to typhoon wind the near inertial waves can propagate seaward due to a downwelling coastal jet positive relative vorticity offshore of the jet and interact with sharply varying topography producing the isws the area of sharply varying topography approximately 28 km off the coast is suggested as a source region for the isws simple calculations of wave speed based on the two layered korteweg devries kdv equation with upper layer thickness and densities at both layers fixed indicate that the isws were generated 6 hours prior to the time of the acquisition of the sar image approximately 13 hours after the typhoon passage consistent with simultaneous buoy measurements

semidiurnal internal tides off the east coast of korea inferred from synthetic aperture radar images 1 semidiurnal internal tides propagating toward and along the east coast of korea are elucidated from the surface manifestation of non linear internal wave nliw packets in synthetic aperture radar sar images taken on september 2 1996 the sar images reveal two pairs of nliw packets one on the northern side of the southwestern east japan sea and the other on the western side the nliw packets appear to be generated by the semidiurnal internal tide and influenced by a temperature front and bottom topography during their propagation a geometric optics model simulates westward refraction of semidiurnal internal tides under the influence of a mesoscale circulation pattern during august 1996 and bottom shoaling this westward refraction contrasts with the eastward refraction of two year mean vertical displacements and is consistent with the distribution of nliws seen in the sar images

linking emergence of the central pacific el nino to the atlantic multidecadal oscillation abstractthe ocean atmosphere coupling in the northeastern subtropical pacific is dominated by a pacific meridional mode pmm which spans between the extratropical and tropical pacific and plays an important role in connecting extratropical climate variability to the occurrence of el nino analyses of observational data and numerical model experiments were conducted to demonstrate that the pmm and the subtropical pacific coupling experienced a rapid strengthening in the early 1990s and that this strengthening is related to an intensification of the subtropical pacific high caused by a phase change of the atlantic multidecadal oscillation amo this pmm strengthening favored the development of more central pacific cp type el nino events the recent shift from more conventional eastern pacific ep to more cp type el nino events can thus be at least partly understood as a pacific ocean response to a phase change in the amo

theory of radar imaging of internal waves radar images taken over ocean areas in particular those obtained by the synthetic aperture radar sar onboard the american seasat satellite in 19781 2 sometimes show features that seem to be surface manifestations of oceanic internal waves3 11 here i present a theory explaining the large radar signatures of internal waves in which the imaging is attributed to variations in the short scale surface roughness induced by current variations associated with internal waves

the generation of internal waves on the continental shelf by hurricane andrew observed currents temperature and salinity from moored instruments on the louisiana continental slope and shelf reveal multiple baroclinic oscillations during hurricane andrew in august 1992 these measurements are supplemented by numerical models in order to identify possible internal wave generation mechanisms the princeton ocean model is run with realistic topography stratification and wind forcing to extend the observations to mississippi canyon and other areas on the shelf a two layer isopycnal model is used with idealized topography and spatially uniform winds to isolate internal waves generated in and around the canyon the combination of the observations and the results from the numerical models indicates several possible mechanisms for generating long internal waves 1 near inertial internal waves were generated across the slope and shelf by dislocation of the thermocline by the wind stress 2 interaction of inertial flow with topography generated internal waves along the shelf break which bifurcated into landward and seaward propagating phases 3 downwelling along the coast depressed the thermocline after downwelling relaxes an internal wave front propagates as a kelvin wave and 4 poincare waves generated within mississippi canyon propagate seaward while being advected westward over the continental slope these processes interact to produce a three dimensional internal wave field which was only partly captured by the observations

internal waves in the strait of messina studied by a numerical model and synthetic aperture radar images from the ers 1 2 satellites a new numerical two layer model is presented which describes the generation of internal tidal bores and their disintegration into internal solitary waves in the strait of messina this model is used to explain observations made by the synthetic aperture radar sar from the european remote sensing satellites ers 1 and ers 2 the analysis of available ers 1 2 sar data of the strait of messina and adjacent sea areas show that 1 northward as well as southward propagating internal waves are generated in the strait of messina 2 southward propagating internal waves are observed more frequently than northward propagating internal waves 3 sea surface manifestations of southward as well as northward propagating internal waves are stronger during periods where a strong seasonal thermocline is known to be present 4 southward propagating internal bores are released from the sill between 1 and 5 hours after maximum northward tidal flow and northward propagating internal bores are released between 2 and 6 hours after maximum southward tidal flow and 5 the spatial separation between the first two internal solitary waves of southward propagating wave trains is smaller in the period from july to september than in the period from october to june the numerical two layer model is a composite of two models consisting of 1 a hydrostatic generation model which describes the dynamics of the water masses in the region close to the strait s sill where internal bores are generated and 2 a weakly nonhydrostatic propagation model which describes the dynamics of the water masses outside of the sill region where internal bores may disintegrate into internal solitary waves due to a technique for movable lateral boundaries the generation model is capable of simulating the dynamics of a lower layer that may intersect the bottom topography the proposed generation propagation model depends on one space variable only but it retains several features of a fully three dimensional model by including a realistic channel depth and a realistic channel width it is driven by semidiurnal tidal oscillations of the sea level at the two open boundaries of the model domain numerical simulations elucidate several observed characteristics of the internal wave field in the strait of messina such as north south asymmetry times of release of the internal bores from the strait s sill propagation speeds and spatial separations between the first two solitary waves of internal wave trains

influence of coastal fronts on near inertial internal waves 1 a numerical model with a coastal boundary and near shore surface or bottom front is used to examine the role of the coast and front upon the generation and propagation of wind induced near inertial internal waves when stratification extends to the coast near inertial internal waves are produced at the coastal boundary however when the near shore region is well mixed the source of near inertial internal wave production is the front near inertial internal waves generated on the positive vorticity side of the front propagate away in the horizontal those generated on the negative vorticity side are trapped although some vertical propagation occurs when a coastal boundary is included significant inertial currents are found at depth phase shifted by 180 from the surface this goes some way to explain the recent observed distributions of inertial energy found in near coastal measurements

quasigeostrophic forcing of ascent in the occluded sector of cyclones and the trowal airstream a numerical model based analysis of the quasigeostrophic forcing for ascent in the occluded quadrant of three cyclones is presented based upon a natural coordinate partitioning of the q vector into its along and acrossisentrope components qs and qn respectively the qn component describes the geostrophic contribution to the rate of change of the magnitude of pu traditional frontogenesis whereas the qs component describes the geostrophic contribution to the rate of change of direction of pu rotational frontogenesis it is shown that convergence of qs simultaneously creates the isobaric thermal ridge characteristic of the thermal structure of occluded cyclones and provides the predominant dynamical support for ascent within the occluded quadrant the absence of significant qn convergence there suggests that quasigeostrophic q g frontogenesis plays a subordinate role both in forcing vertical motions and in affecting three dimensional structural changes in the occluded sector of post mature phase midlatitude cyclones a cyclonically ascending cloud and precipitation producing airstream that originates in the warm sector boundary layer and flows through the trowal portion of the occluded structure is supported by the upward vertical motions implied by the identified q g forcing this airstream is referred to as the trowal airstream and it is shown to be responsible for the production of the wrap around cloud and precipitation commonly associated with occluded systems the relationship of the trowal airstream to previously identified cloud and precipitation producing airflows in cyclones is discussed

remote sensing evidence for baroclinic tide origin of internal solitary waves in the northeastern south china sea 1 evidence for baroclinic tide origin of internal solitary waves isws in the northeastern south china sea is presented based on 116 internal wave packets observed in satellite images from 1995 to 2001 these wave packets can be divided into two types a single wave isw packet containing only one isw with without an oscillating tail and a multiple wave isw packet composed of a group of rank ordered isws all of the 22 single wave isw packets occur in the deep water zone it is suggested that the isws instead of being generated by the lee wave mechanism are developed by nonlinear steepening of the baroclinic tides which are produced by the strong tidal currents flowing over a ridge in luzon strait this suggestion is verified by an ers 2 sar image which records such an evolution process from a baroclinic tide to a single isw in its spatial domain

the linkage between the warm and the cold conveyor belts in an idealized extratropical cyclone abstractthis study continues the investigation of airstreams in idealized moist baroclinic waves and addresses the formation of the cold conveyor belt ccb its linkage to the warm conveyor belt wcb and their impact on the development of a midlatitude cyclone the ccb is identified as a coherent bundle of trajectories characterized by weak ascent and a strong increase of potential vorticity pv along the flow in contrast to the wcb defined as the trajectories with maximum ascent the authors illuminate the role of the two conveyor belts in the formation of two strong pv anomalies that form in the upper wcb negative pv anomaly and lower troposphere ccb positive pv anomaly respectively and thereby establish a link between these airstreams and relevant aspects of the dynamics of extratropical cyclones the ccb moves close to the surface along the colder side of the bent back front and experiences a pv increase as it passes below a region of maximum latent heat release at midtropospheric level

near inertial current oscillations off the mid east coast of korea abstract near inertial current oscillations were observed at depths of 620 and 790 m at a current meter mooring station in water 840 m deep off the mid east coast of korea the oscillatory inertial motions with an amplitude of up to 8 cm s existed during 73 days between august 27 and november 7 of 1986 with a large temporal variation in speed spectral analysis of the data was conducted and the result showed that the most dominant signal in the records was clockwise rotation whose frequency was close to the inertial frequency the peak frequency of the near inertial oscillations was slightly greater than the local inertial frequency f 0 0511 cph by 2 5 these clockwise oscillations had the mean amplitude of about 2 5 cm s reaching an instantaneous maximum of 7 5 cm s the mean ratio of the semi major axis to the semi minor one was found to be about 1 2 and the mean direction of the major axis was nearly parallel to the isobaths around the mooring station high near inertial energy parallel continuously during the first 15 days and then appeared in the form of group wave packets lasting several days during the remaining period three prominent events of wave packets were more energetic at the deeper depth the phase difference between the two horizontal near inertial current vectors changed largely with time but it remained relatively constant during each of the three energetic events changing its sign from one event to another the horizontal near inertial current vector rotated clockwise with increasing depth during one event but counterclockwise during the other two events the corresponding phase propagation was upward with a phase speed of 2 5 cm s for the clockwise polarization with depth but downward with 1 8 and 1 1 cm s for the counterclockwise rotating events

conceptual models of upper level frontogenesis in south westerly and north westerly flow the conceptual model proposed by shapiro as it is applied to the evolution of an upper level frontal zone within a baroclinic wave is reviewed and its limitations are investigated through previous literature and two casestudies presented in this paper the early stages in the evolutions of these two cases are used to examine specific limitations of this conceptual model 1 upper level frontogenesis in south westerly flow that evolves from a state of equivalent barotropy to a state of cold advection along the front and 2 upper level frontogenesis in northwesterly flow with along front variation in the sign of the thermal advection such that warm advection occurs upstream of cold advection in the thermal trough vector frontogenesis diagnostics for the lagrangian rate of change of the magnitude and direction of the horizontal potential temperature gradient including tilting due to vertical motion are derived these diagnostics are applied to the two cases to examine the maintenance of the potential temperature gradient and the development of cold advection along each upper level front the upper level front in south westerly north westerly flow was maintained primarily by deformation tilting frontogenesis in agreement with previous research the increasing cold advection along the upper level front in both cases was related to an upstream vorticity maximum for the case in south westerly flow the pre existing vorticity maximum approached a downstream equivalent barotropic upper level front in a manner similar to an instant occlusion resulting in cold advection along the length of the upper level front for the case in north westerly flow an intensifying vorticity maximum concentrated the cold advection in the base of the thermal trough as warm advection developed upstream these two cases are compared to upper level fronts in previous literature and a climatology of upper level fronts associated with landfalling cyclones over the eastern north pacific ocean the results indicate that these two cases are typical of early evolutions of upper level fronts that can occur in south westerly and north westerly flow therefore a revised version of the shapiro conceptual model is presented that represents more accurately the early evolutions exhibited in the present and previous studies

model studies of near inertial waves in flow over the oregon continental shelf abstract two dimensional primitive equation model studies of wind forced flow over a continental shelf show that under upwelling conditions high levels of near inertial wave energy are found in the interior over the shelf the regions of elevated wave energy with maximum wave amplitudes of around 0 2 m s 1 persist for up to two weeks and have spatial scales of 20 40 m vertically and 5 20 km horizontally relatively high dissipation levels are associated with these concentrations of wave energy when forced with downwelling favorable winds model results show very little subsurface inertial energy on the shelf a comparison of inertial wave propagation using the primitive equation model and a linearized version of the model demonstrates strong dependence on the background flow field the behavior of inertial waves using the linearized model is completely different very little subsurface inertial energy is seen on the shelf in either upwelling or downwelling conditions except where the bottom slope

the structure and evolution of a continental winter cyclone part i frontal structure and the occlusion process the frontal structure and occlusion process in a cyclone of moderate intensity that affected the central united states in january 1995 is examined the deep warm frontal zone associated with this cyclone had a lateral extension to the southwest of the sea level pressure minimum that although characterized by cold air advection near the surface had many of the characteristics of a warm front aloft in fact this feature had a structure similar to the so called bent back fronts previously documented only in association with explosively deepening maritime cyclones the development of a warm occluded structure was investigated with the aid of a numerical simulation of the event performed using the university of wisconsin nonhydrostatic modeling system the development of the warm occluded structure was asynchronous in the vertical occurring first at midtropospheric levels and later near the surface in contrast to the classical occlusion process near the surface the warm occluded front was formed as the warm front was overtaken by the frontogenetically inactive portion of the historical coldfrontal zone at midtropospheric levels the warm occluded structure formed as a result of the cold frontal zone approaching and subsequently ascending the warm frontal zone in accord with a component of the classical occlusion mechanism the observed asynchronous evolution of the occluded structure is proposed to result from the vertical variation in vortex strength associated with the upper level potential vorticity pv anomaly that controls the cyclogenesis it is suggested that the occlusion process begins aloft where the associated vortex strength is greatest and gradually penetrates downward toward the surface during the cyclone life cycle additionally a characteristic treble clef shape to the upper level pv anomaly is shown to be a sufficient condition for asserting the presence of a warm occluded structure in the underlying troposphere

reexamining the cold conveyor belt abstract despite the popularity of the conveyor belt model for portraying the airflow through midlatitude cyclones questions arise as to the path of the cold conveyor belt the lower tropospheric airflow poleward of and underneath the warm front some studies beginning with carlson s analysis of the eastern u s cyclone of 5 december 1977 depict the cold conveyor belt moving westward reaching the northwest quadrant of the storm turning abruptly anticyclonically rising to jet level and departing the cyclone downstream hereafter the anticyclonic path other studies depict the cold conveyor belt reaching the northwest quadrant turning cyclonically around the low center and remaining in the lower troposphere the cyclonic path to clarify the path of the cold conveyor belt the present study reexamines carlson s analysis of the cold conveyor belt using an observational and mesoscale numerical modeling study of the 5 december 1977 cyclone this reexamination raises several previously unappreciated

prototypical solitons in the south china sea 1 surface signatures associated with non linear internal waves are often seen in satellite images of the western south china sea scs slope and shelf observation in the deep sea to the east are rare here we report on the evolution of an energetic packet as it propagated through the deep central basin of the scs toward the western slope and shelf the waves have amplitudes estimated at 170 m half widths of 3 km and phase speeds of 2 9 0 1 m s faster than the mode 1 linear phase speed of 2 6 m s the shape and observed phase speed were consistent with the korteweg devries kdv model over the 65 km path that they were tracked the intrinsic velocity shear of the waves is small compared to pre existing shears and the waves exhibit weak turbulence the kdv fit and a satellite derived estimate of horizontal wave extent imply a westward energy flux of 4 5 gw for each crest

observations of highly nonlinear internal solitons generated by near inertial internal waves off the east coast of korea solitary internal wave packets were observed in may 1999 propagating toward the east coast of korea with thermocline displacements up to twentysix meters downward from the initial depth of twenty meters high nonlinearity of these waves is represented by the second order kdv model better than kdv equations regular occurrence of solitary internal wave packets with the period of about nineteen hours suggests the generation by near inertial internal waves which has not been reported in the literature yet

structure and generation of turbulence at interfaces strained by internal solitary waves propagating shoreward over the continental shelf abstract detailed observations of the structure within internal solitary waves propagating shoreward over oregon s continental shelf reveal the evolving nature of interfaces as they become unstable and break creating turbulent flow a persistent feature is high acoustic backscatter beginning in the vicinity of the wave trough and continuing through its trailing edge and wake this is demonstrated to be due to enhanced density microstructure increased small scale strain ahead of the wave trough compresses select density interfaces thereby locally increasing stratification this is followed by a sequence of overturning high density microstructure and turbulence at the interface which is coincident with the high acoustic backscatter the richardson number estimated from observations is larger than 1 4 indicating that the interface is stable however density profiles reveal these preturbulent interfaces to be o 10 cm thick much thinner than can be resolved with shipboard velocity measurements by as

a cyclone phase space derived from thermal wind and thermal asymmetry abstract an objectively defined three dimensional cyclone phase space is proposed and explored cyclone phase is described using the parameters of storm motion relative thickness asymmetry symmetric nonfrontal versus asymmetric frontal and vertical derivative of horizontal height gradient cold versus warm core structure via the thermal wind relationship a cyclone s life cycle can be analyzed within this phase space providing substantial insight into the cyclone structural evolution an objective classification of cyclone phase is possible unifying the basic structural description of tropical extratropical and hybrid cyclones into a continuum stereotypical symmetric warm core tropical cyclone and asymmetric cold core extratropical cyclone life cycles are illustrated using 1 navy operational global atmospheric prediction system nogaps operational analyses and 2 5 ncep ncar reanalyses the transitions between cyclone phases are clearly illustrated within the phase space including extratro

the occlusion process in a midlatitude cyclone over land abstract a historical review highlights the lack of consensus regarding the structure and evolution of occluded fronts and cyclones in order to better understand the occlusion process this paper and its companion examine a model simulation of the 14 16 december 1987 cyclone over the eastern united states the structure of an occluded front was observed at low levels as the cold front caught up with the warm front while aloft an upperlevel frontal zone appeared to play a role in the occlusion process although the thermal structure of this storm suggested that a cold type occlusion should have formed the model simulation produced a warm type occlusion structure an extensive review of the literature on occluded fronts suggested that cold type occlusions are rare if they exist at al1 finally the occluded front simulated in this case is compared critically to the norwegian t bone and other conceptual models of cyclone evolution

can near inertial internal waves in the east sea be observed by synthetic aperture radar 1 near inertial 18 hours internal waves were observed in the mid western part of the east sea on may 18 and 19 2004 using c band synthetic aperture radar sar images current and temperature measurements obtained during the field experiment from 10 may to 9 june 2004 iwxes2004 internal wave experiment in the east sea were analyzed to investigate the processes by which near inertial internal waves can be seen in sar images and how they progress the spatial distributions of horizontal wavelength and phase speed estimated from two successively acquired sar images are consistent with those inferred from water temperature and current measurements carried out during the field experiment based on these two independent observations sar and iwxes2004 we report a strong possibility that the observed wave patterns in the sar images during iwxes2004 are near inertial internal waves propagating westward off the east coast of the korean peninsula with a phase speed of about 0 3 m s