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

numerical simulation of cyclone sidr using a cloud resolving model characteristics and formation process of an outer rainband abstractcyclone sidr one of the most devastating tropical cyclones that resulted in several thousand deaths and substantial damages developed in the north indian ocean and made landfall over the bangladesh coast on 15 november 2007 observation and simulation results show that sidr was embedded in a nonuniform environment and contained an intense outer rainband to the east of its center and a significant frontal band to the northwest a detailed study of the outer rainband is performed by numerical simulation the eastern band was a long quasi straight shape in the meridional direction that remained stationary relative to the cyclone center this band was composed of convective cells that developed southeast of the center within a synoptic scale convergence zone and propagated along the band toward the northeast quadrant the speed of the downwind propagating cells was greater than that of the cyclone which resulted in a convective cluster northeast of the center only the downwind portion of the band

rapidly intensifying hurricane guillermo 1997 part i low wavenumber structure and evolution abstract the structure and evolution of rapidly intensifying hurricane guillermo 1997 is examined using airborne doppler radar observations in this first part the low azimuthal wavenumber component of the vortex is presented guillermo s intensification occurred in an environmental flow with 7 8 m s 1 of deep layer vertical shear as a consequence of the persistent vertical shear forcing of the vortex convection was observed primarily in the downshear left quadrant of the storm the greatest intensification during the 6 h doppler observation period coincided with the formation and cyclonic rotation of several particularly strong convective bursts through the left of shear semicircle of the eyewall some of the strongest convective bursts were triggered by azimuthally propagating low wavenumber vorticity asymmetries mesoscale budget analyses of axisymmetric angular momentum and relative vorticity within the eyewall are presented to elucidate the mechanisms contributing to guillermo s structural evol

branching of the tsushima current in 1981 83 abstract satellite derived sea surface temperatures illustrate the variability of the path of the tsushima current in the sea of japan in the spring of 1981 the tsushima current did not split as it left the korea strait and flowed into the sea of japan which is contrary to the historical concept of branching warm water remained along honshu the main island of japan making a strong front oriented in an east west direction hydrographic data confirm that this spring condition lasted through to the fall of 1981 on the other hand during the springs of 1982 and 1983 the branching is evident from satellite images one branch flowed northward along the east coast of korea and the other flowed eastward along honshu of japan

eastern pacific hurricanes jimena of 1991 and olivia of 1994 the effect of vertical shear on structure and intensity abstract shear is a key inhibitor of tropical cyclone intensification although its signature is readily recognized in satellite imagery and theoretical or modeling studies provide some insight detailed observations have been limited airborne radar and in situ observations in hurricanes jimena of 1991 and olivia of 1994 are a step toward better understanding each storm was observed on two consecutive days initially both had small eyes 16 18 km radius and maximum winds of 57 m s 1 over sea surface temperatures sst 28 c in easterly environmental shear jimena maintained constant intensity or weakened gradually for 2 days in 13 20 m s 1 easterly shear olivia intensified in 8 m s 1 shear on the first day overnight the shear diminished to reverse and became westerly on the second day olivia weakened as the shear increased to 15 m s 1 from the west the storm moved over cooler sst and became surrounded by dryer air as convection weakened and the outer rainbands ceased to be effective barriers

downdrafts and the evolution of boundary layer thermodynamics in hurricane earl 2010 before and during rapid intensification abstractusing a combination of noaa p 3 aircraft tail doppler radar noaa and nasa dropsondes and buoy and drifter based sea surface temperature data different types of downdrafts and their infl

interannual variability of the korea strait bottom cold water and its relationship with the upper water temperatures and atmospheric forcing in the sea of japan east sea 1 a 35 yearlong temperature data set is analyzed to investigate the long term temperature variability in the korea strait and its relationship with the temperature variability in the upper layer of the sea of japan east sea the second cyclostationary empirical orthogonal function mode of the vertical temperature section in the korea strait describes the interannual variability of the korea strait bottom cold water ksbcw according to the corresponding principal component time series the strength of the ksbcw fluctuates yearly with a major spectral peak around 3 years multiple regression analysis shows that the interannual ksbcw variability is closely linked with the temperature variability in the southwestern region of the sea of japan east sea at about 50 100 m depth along 40 n the source of the ksbcw is traced at about 50 m extending eastward from the east coast of korea to about 135 e at 37 n the source is traced at a deeper level about 50 100 m confined more toward the east coast of korea with a hint of double core characteristics the interannual ksbcw variability is also related to the southward wind stress along the east coast of korea it appears that strong cooling warming of upper water temperature induced by the basin scale wind stress results in the interannual ksbcw variability this connection is verified by showing a reasonable interannual covariability between the ksbcw and the basin scale wind stress

a convective cell in a hurricane rainband abstract on 10 october 1983 the two noaa wp 3d aircraft completed a mission designed to provide airborne doppler radar data for a convective cell embedded in a weak rainband on the trailing side of hurricane raymond comparisons of the wind field produced from the pseudo dual doppler radar technique with in situ wind measurements suggest that the larger convective scale feature may be resolved if the sampling time is kept to a minimum the convective cell was found to move downband faster than any environmental winds but slightly slower than the winds found in the reflectivity core that delineates the cell in the core of the cell the tangential wind is increased and the radial inflow turns to outflow with respect to the circulation center the flow field demonstrates that the downband stratiform portion of a rainband is not from cells currently active since the updraft detrains upwind relative to the cell but rather it is due to the fallout from ice particles placed into the upper troposphere by clouds t

the evolution of hurricane humberto 2001 abstractin 2001 the national oceanic and atmospheric administration and the national aeronautical and space administration marshaled their resources to sample hurricane humberto for 3 successive days during the fourth convection and moisture experiment camex 4 humberto developed from a tropical storm into a category 2 hurricane despite the deep layer vertical shear of the environmental horizontal wind vws increasing markedly on the second and third days of sampling as exhibited in earlier studies the eyewall convection developed an azimuthal wavenumber 1 n 1 asymmetry as the vws increased horizontal divergence and vertical stability within 100 km of the eye exhibited persistent relationships to the vws vector the warm core evolved in an unexpected way the warm anomaly was initially located in the lower troposphere and built upward as the storm intensified the maximum temperature anomaly remained in the lower troposphere on all 3 days while the development of the upper tropospheric warm anom

polygonal eyewalls asymmetric eye contraction and potential vorticity mixing in hurricanes hurricane eyewalls are often observed to be nearly circular structures but they are occasionally observed to take on distinctly polygonal shapes the shapes range from triangles to hexagons and while they are often incomplete straight line segments can be identified other observations implicate the existence of intense mesovortices within or near the eye region is there a relation between polygonal eyewalls and hurricane mesovortices are these phenomena just curiosities of the hurricane s inner core circulation or are they snapshots of an intrinsic mixing process within or near the eye that serves to determine the circulation and thermal structure of the eye as a first step toward understanding the asymmetric vorticity dynamics of the hurricane s eye and eyewall region these issues are examined within the framework of an unforced barotropic nondivergent model polygonal eyewalls are shown to form as a result of barotropic instability near the radius of maximum winds after reviewing linear theory simulations with a high resolution pseudospectral numerical model are presented to follow the instabilities into their nonlinear regime when the instabilities grow to finite amplitude the vorticity of the eyewall region pools into discrete areas creating the appearance of polygonal eyewalls the circulations associated with these pools of vorticity suggest a connection to hurricane mesovortices at later times the vorticity is ultimately rearranged into a nearly monopolar circular vortex while the evolution of the finescale vorticity field is sensitive to the initial condition the macroscopic end states are found to be similar in fact the gross characteristics of the numerically simulated end states are predicted analytically using a generalization of the minimum enstrophy hypothesis in an effort to remove some of the weaknesses of the minimum enstrophy approach a maximum entropy argument developed previously for rectilinear shear flows is extended to the vortex problem and end state solutions in the limiting case of tertiary mixing are obtained implications of these ideas for real hurricanes are discussed

objective determination of hurricane tracks from aircraft observations abstract an algorithm for location of hurricane centers by least squares using aircraft data has been developed as the aircraft traverses the eye lines of position normal to the wind are constructed each 100 m along its track an additional line of position is constructed normal to the track at the closest point of approach to the center the center coordinates are then chosen such that the sum of the squares of the normal distances from the center to the lines of position is minimized a cubic spline storm track is first constructed using centers based on winds in a coordinate system fixed to the earth a track based upon winds in moving storm centered coordinates may be obtained by transformation of the winds into such a coordinate system and iterative redetermination of the centers for intense hurricanes the centers can be located with an accuracy of 3 km and the mean motion over a period of four to six hours determined to within 4 of direction and 0 5 m s 1 of speed the details of the track osc

an organic geochemical profile of the toarcian anoxic event in northern italy abstract a suite of black shales calcareous shales and limestones representing the toarcian anoxic event jurassic 192 ma was collected from a 14 m length of core taken from the belluno trough northern italy and examined in detail to assess variations in depositional environment during this interval geochemical and optical data indicate organic matter of algal and bacterial origin with only trace contribution from terrestrial sources detailed biological marker data interpreted with the aid of multivariate statistics demonstrate fluctuations in primary producers and bacterial populations during black shale deposition the onset of the anoxic event was not abrupt but characterized by an apparent gradual development of anoxia and consequent enhanced organic matter preservation different hopane biomarkers proved especially useful in recognizing preservation potential in the section and correlate well with other preservation indicators increased oxygenation at the end of the event may have been associated with changes in primary productivity

an extreme event in the eyewall of hurricane felix on 2 september 2007 abstractduring a routine penetration into hurricane felix late on 2 september 2007 noaa42 encountered extreme turbulence and graupel flight level horizontal wind gusts of over 83 m s 1 and vertical wind speeds varying from 10 m s 1 downward to 31 m s 1 upward and back to nearly 7 m s 1 downward within 1 min this led the plane to rise nearly 300 m and then return to its original level within that time though a dropwindsonde was released during this event the radars and data systems on board the aircraft were rendered inoperable limiting the amount of data obtained the feature observed during the flight is shown to be similar to that encountered during flights into hurricanes hugo 1989 and patricia 2015 and by a dropwindsonde released into a misovortex in hurricane isabel 2003 this paper describes a unique dataset of a small scale feature that appears to be prevalent in very intense tropical cyclones providing new evidence for eye eyewall mixing processes that may be related to intensity change

low level kinematic thermodynamic and reflectivity fields associated with hurricane bonnie 1998 at landfall during 11 h on 26 august 1998 two noaa wp 3d aircraft deployed 85 global positioning system gps dropwindsondes within 2 of latitude of the circulation center of hurricane bonnie as it made landfall in north carolina about 75 of the sondes successfully collected data which were used to create a series of storm relative horizontal maps of kinematic and thermodynamic variables from 10 m to 2 km reflectivity fields were analyzed from the weather surveillance radar 1988 dopplers wsr 88ds located at wilmington and morehead city north carolina and the tail and lower fuselage radars aboard the wp 3ds gps sonde performance and deployment spacing is adequate to identify several aspects of the vortex these include 1 warm dry stable air in the offshore flow that results in reduced equivalent potential temperatures entering the southern portion of the eyewall 2 cooler air collocated with the upwelled water in the right rear quadrant and under the eyewall and 3 an atypical radial wind pattern with strong inflow southwest of the circulation center and outflow northeast of the center the strongly asymmetric structure found at 10 m becomes much more homogeneous by 2 km altitude no intense rainbands developed over land in the onshore flow nor did the bands in the onshore flow undergo any significant changes once they made landfall beyond the eyewall the offshore flow contained much less precipitation than the onshore portion of the storm characteristics beyond the eyewall appear to have been modulated by the proximity to land but hurricane intensity did not vary the authors infer that the lower energy content of the inflow was offset by the contraction of the eyewall

a new perspective on origin of the east sea intermediate water observations of argo floats abstract the east sea intermediate water esiw defined as the salinity minimum in the east sea hereafter es sea of japan is examined with respect to its overall characteristics and its low salinity origin using historical argo float data from 1999 to 2015 our findings suggest that the esiw is formed in the western japan basin 40 42 n 130 133 e especially west of the north korean front in north korean waters where strong negative surface wind stress curl resides in wintertime the core esiw near the formation site has temperatures of 3 4 c and less than 33 98 psu salinity warmer and fresher than that in the southern part of the es in order to trace the origin of the warmer and fresher water at the sea surface in winter we analyzed the data in three different ways 1 spatial distribution of surface water properties using monthly climatology from the argo float data 2 seasonal variation of heat and salt contents at the formation site and 3 backtracking of surface drifter trajectories based on these analyses it is likely that the warmer and fresher surface water properties found in the esiw formation site are attributed to the low salinity surface water advected from the southern part of the es in autumn

low frequency current observations in the korea tsushima strait abstract high resolution continuous current measurements made in the korea tsushima strait between may 1999 and march 2000 are used to examine current variations having time periods longer than 2 days twelve bottom mounted acoustic doppler current profilers provide velocity profiles along two sections one section at the strait entrance southwest of tsushima island and the second section at the strait exit northeast of tsushima island additional measurements are provided by single moorings located between korea and tsushima island and just north of cheju island in cheju strait the two sections contain markedly different mean flow regimes a high velocity current core exists at the southwestern section along the western slope of the strait for the entire recording period the flow directly downstream of tsushima island contains large variability and the flow is disrupted to such an extent by the island that a countercurrent commonly exists in the lee of the island the northeastern section is marked b

importance of the upper level warm core in the rapid intensification of a tropical cyclone 1 in this study the rapid intensification ri of tropical cyclone is examined using a 72 h cloud permitting prediction of hurricane wilma 2005 with a record breaking intensity of 882 hpa results show the formation of an upper level warm core from the descending air of stratospheric origin in the eye which coincides with the onset of ri it reaches the peak amplitude of more than 18 c from its initial conditions at the time of peak intensity the descending air is associated with the detrainment of convective bursts in the eyewall and it appears as perturbation cyclonic radial inflows above the upper outflow layer and causes the subsidence warming below we hypothesize that the upper divergent outflow layer favors the generation of a warm core by protecting it from ventilation by environmental flows use of the hydrostatic equation shows that the warm core of stratospheric origin contributes more than twice as much as the lower level warm column to the pressure change at the peak intensity of wilma results suggest that more attention be paid to the magnitude of storm relative flows and vertical wind shear in the upper troposphere rather than just vertical shear in the typical 850 200 hpa layer in order to reasonably predict the ri of tropical cyclones

mesoscale motion fields associated with a slowly moving gate convective band abstract the structure of the convective band of 14 september in the dense gate observing array is determined using wind and thermodynamic data primarily from multiple aircraft penetrations which are well distributed in the vertical and in time the well defined mesoscale features in the line which are 10 40 km in scale quasi two dimensional and persist for several hours determine the distribution of the convective scale features which are 5 km or less in size three dimensional not generally detectable for more than one flight leg at the leading edge a 30 km zone of strong ascent is computed from two dimensional continuity here lifting of the ambient air creates a favorable environment not found elsewhere for deep cumulonimbus clouds to develop their updrafts are weak 2 4 m s 1 on the average behind the updraft zone below 3 4 km is a broad descent zone it corresponds to the stratiform rain area and has little convection and some drying at lower levels on the average the mass flux by

low level inversions over the tropical pacific thermodynamic structure of the boundary layer and the above inversion moisture structure abstract the structure of the boundary layer over a broad region of the equatorial pacific is studied using dropwinsonde measurements made in january february may and june of 1979 low level inversions of sufficient strength to inhibit deep convection are found to be present in more than 50 of the soundings these inversions appear to play a critical role in regulating convective activity over the central and eastern pacific the tops of the inversions have an average pressure level of approximately 300 mb and show little latitudinal or longitudinal variation the majority of the inversion soundings approximately 70 have a reversal in the mixing ratio profile qreversal above the inversion that appears as a dry layer at the top of the inversion layer capped by a relatively moist layer this moist layer is on the average 2 g kg 1 more moist than the corresponding soundings that have no qreversal no systematic regional or temporal variations in the frequency of occurrence of the qreversal or the str

summertime coastal current reversal opposing offshore forcing and local wind near the middle east coast of korea observation and dynamics a 6 year long current measurement at a buoy station off the middle east coast of korea reveals an equatorward reversal of coastal current in summer opposing poleward local wind stress and offshore boundary current the current reversal extends about 40 km offshore from the coast and is concurrent with warming and freshening of water column estimates of the depth averaged alongshore momentum balance suggest a major balance between the alongshore pressure gradient and the lateral friction sources of the pressure gradient for the summertime current reversal are identified as the alongshore buoyancy gradient driven by the wind curl gradient and the prevalence of warmer and lower salinity water in the north alongshore pressure gradient and velocity induced by the wind curl gradient are quantified which yields the observed seasonal current reversal

enso teleconnection to the isopycnal depth fluctuations of the east japan sea intermediate water in the ulleung basin during 1968 2002 abstractthis study first detects the decadal variability in the depths of the east japan sea ejs intermediate water esiw using in situ observations and relates it to strong el nino southern oscillations ensos using multitaper cross spectrum and cyclostationary empirical orthogonal function analysis this study found significant coherences at the 99 confidence level and opposite phases between nino 3 and the esiw isopycnal depths in the ulleung basin ub at a period of 14 1 yr during 1968 2002 this suggests a teleconnection between strong ensos and the esiw the cause of which is explored when a strong el nino en develops the pacific north american pattern is intensified by the en related rossby wave interfering constructively with the climatological stationary wave the amplified wave propagates upward into the stratosphere and breaks weakening the polar vortex the en related geopotential height increases over the pole with poleward converging air and decreases over the yakutsk basin yb

the cenomanian turonian oceanic anoxic event ii palaeoceanographic controls on organic matter production and preservation correlation of the 13c spike with the well dated occurrences of strata rich in organic carbon detailed in schlanger et al this volume indicates that a global episode of intense organic carbon orgc burial took place during the latest cenomanian earliest turonian oceanic anoxic event oae a plenus through i labiatus macrofossil zones and upper r cushmani trz through w archecretacea prz foraminiferal zones over a period of no more than 1 million years m y the shape of the 13c curve indicates that rates of orgc burial gradually increased in the early part of the late cenomanian increased more rapidly in the later cenomanian and levelled off at peak values in latest cenomanian early turonian time during the maximum rate of orgc burial the 13c values decreased nearly to pre late cenomanian levels in the early to middle turonian the decrease in 13c reflects decreasing rates of orgc burial following the cenomanian turonian oceanic anoxic event as well as the probable oxidation and return of significant amounts of orgc to the oceans following regression and re oxygenation of much of the deeper water masses in contact with the seafloor

spatial and temporal variability of the north korean cold water leading to the near bottom cold water intrusion in korea strait abstract in the deepest region of korea strait the surface temperature is highest in august lowest in march while the near bottom temperature is lowest in september highest in may cross spectral analysis of the monthly temperature data between the two layers shows high coherence at the annual frequency with phase of 154 why and how does such a nearly opposite phasing occur between the surface and the near bottom temperatures there this study aims at answering these questions using historical and recently observed data cold and relatively fresh subsurface water flowing southward along the east coast of korea and known as the north korean cold water nkcw becomes noticeable in april near the sokcho coast the zonal temperature gradient there is largest around june the width of the nkcw becomes larger from april to august after october the nkcw retreats back toward the coast the southward movement of the nkcw is thus strong over a period of six to seven months and weak in winter especially in february the nkcw flows southward relatively quickly along the coast in april to october and arrives at the ulleung basin within one to two months because of the sill between the ulleung basin and korea strait this water cannot continue to flow to south but piles up for about two to three months before it moves over the sill the convergence of the subsurface cold water in the ulleung basin displaces the isopycnals upward and this water then intrudes over the sill along the isopycnals this explains why in april or may when this water appears noticeably at the sokcho coast the near bottom water in korea strait is warmest and in august or september when the nkcw which is piled up enough at the southern end of the ulleung basin intrudes to korea strait the near bottom temperatures there are at their lowest the origin of the nkcw seems to be the water of salinity less han 34 1 psu and surface density of 27 or higher which sinks in the northwestern east sea in january march the sinking of the water results from surface cooling in winter and is intensified due to the strong negative windstress curl the cold and relatively fresh water formed in the northwestern east sea is hypothesized to flow to the ulleung basin along three major paths along the east coast of korea through the channel north of ulleung do island and through the channel between ulleung do and dok do islands

buoyancy of convective vertical motions in the inner core of intense hurricanes part ii case studies abstract this is the second of two papers on the buoyancy of convective vertical motions in the inner core of intense hurricanes this paper uses extensive airborne radar dropwindsonde and flight level observations in hurricanes guillermo 1997 and georges 1998 to illustrate typical azimuthal distribution of buoyant convection and demonstrate that the low level eye can be an important source region for buoyant eyewall convection in both hurricanes eyewall vertical velocity and radar reflectivity are asymmetric and exhibit persistent relationships with the direction of the environmental vertical wind shear mesoscale vertical motions exhibit a wavenumber 1 structure with maximum ascent downshear and weak descent upshear the mesoscale reflectivity maxima are located left of shear buoyant eyewall updraft cores and transient convective scale reflectivity cells are predominantly downshear and left of shear most eyewall downdraft cores that transport significant mass downward are located upshear nega

miniature supercells in an offshore outer rainband of hurricane ivan 2004 abstract airborne doppler radar observations are used to document the structure of three miniature supercells embedded in an outer rainband of hurricane ivan on 15 september 2004 the cells were located more than 100 km offshore beyond the doppler range of coastal radars the combination of large cape large vertical wind shear and moderate cell relative helicity with an apparent midlevel dry air intrusion provided an offshore environment supporting rotating storms each shallow cell contained a 5 7 km diameter mesocyclonic updraft with midlevel updraft and vorticity maxima that exceeded 6 m s 1 and 0 008 s 1 respectively such offshore structures are consistent with miniature supercells observed onshore in association with tropical cyclone tornado outbreaks the strong updrafts resulted from a combination of kinematic convergence thermal instability and shear induced vertical perturbation pressure gradients mesocyclone production largely resulted from the tilting and subsequent stretching of low l

analyzing simulated convective bursts in two atlantic hurricanes part i burst formation and development abstractunderstanding the structure and evolution of the tropical cyclone tc inner core remains an elusive challenge in tropical meteorology especially the role of transient asymmetric features such as localized strong updrafts known as convective bursts cbs this study investigates the formation of cbs and their role in tc structure and evolution using high resolution simulations of two atlantic hurricanes dean in 2007 and bill in 2009 with the weather research and forecasting wrf model several different aspects of the dynamics and thermodynamics of the tc inner core region are investigated with respect to their influence on tc convective burst development composites with cbs show stronger radial inflow in the lowest 2 km and stronger radial outflow from the eye to the eyewall around z 2 4 km than composites without cbs asymmetric vorticity associated with eyewall mesovortices appears to be a major factor in some of the radial flow anomalies that lead to cb development the anomalous outfl

a multiscale numerical study of hurricane andrew 1992 part ii kinematics and inner core structures despite considerable research understanding of the temporal evolution of the inner core structures of hurricanes is very limited owing to the lack of continuous high resolution observational data of a storm in this study the results of a 72 h explicit simulation of hurricane andrew 1992 with a grid size of 6 km are examined to explore the inner core axisymmetric and asymmetric structures of the storm during its rapid deepening stage based on the simulation a conceptual model of the axisymmetric structures of the storm is proposed most of the proposed structures confirm previous observations the main ingredients include a main inflow outflow in the boundary layer upper troposphere with little radial flow in between a divergent slantwise ascent in the eyewall a penetrative dry downdraft at the inner edge of the eyewall and a general weak subsiding motion in the eye with typical warming drying above an inversion located near an altitude of about 2 3 km the storm deepens as the axes of these features contract it is found that the inversion divides the eye of the hurricane vertically into two parts with a deep layer of warm dry air above and a shallow pool of warm moist air below the air aloft descends at an average rate of 5c m s 21 and has a residency time of several days in contrast the warm moist pool consists of air from the main inflow and penetrative downdrafts offset somewhat by the air streaming in a returning outflow into the eyewall in the lowest 2 km it is subject to the influence of the upward heat and moisture fluxes over the underlying warm ocean the warm moist pool appears to play an important role in supplying high ue air for deep convective development in the eyewall the penetrative downdraft is dry and originates from the return inflow in the upper troposphere and it is driven by sublimative evaporative cooling under the influence of the asymmetric radial inflow of dry cold air in the midtroposphere it penetrates to the bottom of the eye azimuthally downshear with a width often greater than 100 km in a radially narrow zone along the slantwise inner edge of the eyewall it is further shown that all the meteorological fields are highly asymmetric whereas the storm scale flow features a source sink couplet in the boundary layer and dual gyres aloft the inner core structures exhibit alternative radial inflow and outflow and a series of inhomogeneous updrafts and downdrafts all the fields tilt more or less with height radially outward and azimuthally downshear furthermore pronounced fluctuations of air motion are found in both the eye and the eyewall sometimes a deep layer of upward motion appears at the center of the eye all these features contribute to the trochoidal oscillation of the storm track and movement the main steering appears to be located at the midtroposphere 4 5 km and the deep layer mean winds represent well the movement of the hurricane

a lagrangian trajectory view on transport and mixing processes between the eye eyewall and environment using a high resolution simulation of hurricane bonnie 1998 the transport and mixing characteristics of a large sample of air parcels within a mature and vertically sheared hurricane vortex are examined data from a high resolution 2 km horizontal grid spacing numerical simulation of real case hurricane bonnie 1998 are used to calculate lagrangian trajectories of air parcels in various subdomains of the hurricane namely the eye eyewall and near environment to study the degree of interaction transport and mixing between these subdomains it is found that 1 there is transport and mixing from the low level eye to the eyewall that carries air possessing relatively high values of equivalent potential temperature e which can enhance the efficiency of the hurricane heat engine 2 a portion of the low level inflow of the hurricane bypasses the eyewall to enter the eye and this air both replaces the mass of the low level eye and lingers for a sufficient time order 1 h to acquire enhanced entropy characteristics through interaction with the ocean beneath the eye 3 air in the mid to upper level eye is exchanged with the eyewall such that more than half the air of the eye is exchanged i n5hi nthis case of a sheared hurricane and 4 that one fifth of the mass in the eyewall at a height of 5 km has an origin in the mid to upper level environment where e is much less than in the eyewall which ventilates the ensemble average eyewall e by about 1 k implications of these findings for the problem of hurricane intensity forecasting are briefly discussed

concentric eye walls secondary wind maxima and the evolution of the hurricane vortex abstract research aircraft observations in recent hurricanes support the model of shapiro and willoughby 1982 for the tropical cyclone s response to circularly symmetric convective heat sources convective rings in both nature and the numerical model the tangential wind commonly increases rapidly just inside the radius of maximum wind and decreases inside the eye near the central axis of the vortex thus both secondary outer wind maxima and eyewall wind maxima often contract as they intensify this response is independent of the horizontal spatial scale of the maximum an outer maximum is frequently observed to constrict about a pre existing eye and replace it this chain of events often coincides with a weakening or at least a pause in intensification of the vortex as a whole the concentric eye phenomenon is a common but by no means universal feature of tropical cyclones it is most frequently observed in intense highly symmetric systems

atypical thermodynamic profiles in hurricanes the global positioning system dropwindsondes deployed in hurricane bonnie on 26 august 1998 with supporting deployments in hurricanes mitch 1998 and humberto 2001 are used to identify three unusual thermodynamic structures in the lower cloud and subcloud layers two of these structures impact the energy content of the inflow and therefore the intensity of the hurricane first positive lapse rates of equivalent potential temperature are found near the top of the inflow these layers insulate the inflow from the negative impacts of entrainment mixing and promote rapid energy increases especially near the eyewall the second structure is a rapid decrease of equivalent potential temperature adjacent to the sea surface this is essentially a prominent surface layer that owes its existence to both higher moisture content and a superadiabatic lapse rate the steep lapse rate most often occurs under and near the eyewall where wind speeds at the surface exceed hurricane force the author speculates that water loading from spray increases the residence time of air parcels in the surface layer contributing to the creation of this structure the third feature is a moist absolutely unstable layer previously identified by bryan and fritsch for the midlatitudes these layers are found adjacent to the eyewall in rainbands and in the hub cloud within the eye and are evidence of mesoscale or vortex scale convergence and the very modest instabilities often found in the core of a hurricane

tropical cyclone eye thermodynamics in intense tropical cyclones sea level pressures at the center are 50 100 hpa lower than outside the vortex but only 10 30 hpa of the total pressure fall occurs inside the eye between the eyewall and the center warming by dry subsidence accounts for this fraction of the total hydrostatic pressure fall convection in the eyewall causes the warming by doing work on the eye to force the thermally indirect subsidence soundings inside hurricane eyes show warm and dry air aloft separated by an inversion from cloudy air below dewpoint depressions at the inversion level typically 850 500 hpa are 10 30 k rather than the 100 k that would occur if the air descended from tropopause level without dilution by the surrounding cloud the observed temperature and dewpoint distribution above the inversion can however be derived by 100 hpa of undilute dry subsidence from an initial sounding that is somewhat more stable than a moist adiabat it is hypothesized that the air above the inversion has remained in the eye since it was enclosed when the eyewall formed and that it has subsided at most a few kilometers the cause of the subsidence is the enclosed air s being drawn downward toward the inversion level as the air below it flows outward into the eyewall shrinkage of the eye s volume is more than adequate to supply the volume lost as dry air is incorporated into the eyewall or converted to moist air by turbulent mixing across the eye boundary the moist air below the inversion is in thermodynamic contact with the sea surface its moisture derives from evaporation of seawater inside the eye frictional inflow of moist air under the eyewall and from moist downdrafts induced as condensate mixes into the eye the moist air s residence time in the eye is much shorter than that of the dry air above the inversion the height of the inversion is determined by the balance between evaporation inflow and inward mixing on one hand and loss to the eyewall updrafts on the other

structural changes preceding rapid intensification in tropical cyclones as shown in a large ensemble of idealized simulations abstractstructural changes that precede rapid intensification ri of tropical cyclones tcs are examined in a full physics model by conducting a large ensemble 270 of idealized tc simulations the processes leading to ri in a representative case with moderate shear are consistent with previous studies for weakly sheared cases the most distinct changes are that the vortex tilt and the vortex size begin to decrease more rapidly 6 h before the onset of ri a vorticity budget analysis for the upper layer around the low level center reveals that the vertical vorticity is increased by vertical advection stretching and tilting terms before ri whereas the horizontal advection is small thus the upright vortex structure is not achieved through a vortex alignment process but rather is built upward by deep convection the ensemble simulations are generated by changing the intensity and size of the initial vortex the magnitude of vertical wind shear and the translation speed the ensemble members that show

the role of polygonal eyewalls in rapid intensification of typhoon megi 2010 abstracthigh resolution numerical experiments for typhoon megi 2010 in the western north pacific are conducted using the advanced research version of the weather research and forecasting wrf mo

decadal changes in meridional overturning circulation in the east sea sea of japan abstractmeridional overturning circulation moc is vital to distributing heat freshwater and dissolved matter in semi enclosed deep marginal seas such as the east sea es as our understanding

warm saline bottom water in the ancient ocean considerable isotopic evidence indicates that oceanic bottom water was much warmer in the geological past a simple convection model driven by multiple turbulent buoyant plumes and observations of present deep water formation have led to the development of a theory for the formation of warm saline bottom water it is suggested that changes in the size and configuration of marginal seas in net evaporation zones due to lithospheric plate motions and eustatic sea level change caused these seas to become sources of warm saline bottom water evidence from the palaeotemperature record and palaeogeography during the late cretaceous is used to reinforce the hypothesis climatic and chemical consequences of the formation of warm saline bottom water are discussed

intermediate level circulation of the southwestern part of the east japan sea estimated from autonomous isobaric profiling floats 1 with trajectory data from autonomous isobaric profiling floats palace apex and provor we obtained a detailed intermediate level circulation pattern over the southwestern part of the east japan sea the circulation pattern which is consistent with moored current meter data obtained at a few locations is largely controlled by the bottom topography the main features we have found are as follows 1 a cyclonic circulation along the korean coast and the continental break around the ulleung basin and the western side of oki spur to the yamato rise and 2 a cold current from the japan basin to the ulleung basin through the ulleung interplain gap which is a part of the anticyclonic flow over the korea plateau a taylor column

buoyancy of convective vertical motions in the inner core of intense hurricanes part i general statistics abstract the buoyancy of hurricane convective vertical motions is studied using aircraft data from 175 radial legs collected in 14 intense hurricanes at four altitudes ranging from 1 5 to 5 5 km the data of each leg are initially filtered to separate convective scale features from background mesoscale structure convective vertical motion events called cores are identified using the criteria that the convective scale vertical velocity must exceed 1 0 m s 1 for at least 0 5 km a total of 620 updraft cores and 570 downdraft cores are included in the dataset total buoyancy is calculated from convective scale virtual potential temperature pressure and liquid water content using the mesoscale structure as the reference state core properties are summarized for the eyewall and rainband regions at each altitude characteristics of core average convective vertical velocity maximum convective vertical velocity and diameter are consistent with previous studies of hurricane convection most cores are superi

low level thermodynamic kinematic and reflectivity fields of hurricane guillermo 1997 during rapid intensification abstract from 0600 utc 2 august to 1200 utc 3 august hurricane guillermo 1997 deepened by 54 hpa over the eastern north pacific ocean easily exceeding the thresholds that define rapid intensification ri the noaa wp 3ds observed a portion of this ri with similar two aircraft missions on consecutive days the aircraft jettisoned 70 successful global positioning system gps dropwindsondes or gps sondes which reveal how conditions in the lower troposphere on the octant to quadrant scale evolved within 250 km of the eye reflectivity fields demonstrate that the deepening is correlated with a spiraling in of the northern eyewall that reduces the eye diameter by 10 km this behavior contrasts the more uniform contraction witnessed during eyewall replacement cycles mixing between the lower eye and eyewall as detailed by other investigators appears to have triggered the reduction in the eye diameter after ri the eyewall remains asymmetrical with the tallest echo tops and heaviest rain rates located o

two distinct regimes in the kinematic and thermodynamic structure of the hurricane eye and eyewall abstract using aircraft flight level data the present work demonstrates that the kinematic and thermodynamic distributions within the eye and eyewall of strong hurricanes are observed to evolve between two distinct regimes in the first regime angular velocity is greatest within the eyewall and relatively depressed within the eye in the second regime radial profiles of angular velocity are nearly monotonic with maxima found at the eye center considering sequential profiles within individual hurricanes the authors find that the evolution of the kinematic distribution is often marked by a transition from the first regime to the second the transition can occur in less than 1 h also noted during the transition are dramatic changes in the thermodynamic structure of the hurricane prior to the transition regime 1 the eye is typically very warm and dry and the equivalent potential temperature is often elevated within the eyewall and relatively depressed within the eye after the transition regime 2

an axisymmetric view of concentric eyewall evolution in hurricane rita 2005 abstractmultiplatform observations of hurricane rita 2005 were collected as part of the hurricane rainband and intensity change experiment rainex field campaign during a concentric eyewall stage of the storm s life cycle that occurred during 21 22 september satellite aircraft dropwindsonde and doppler radar data are used here to examine the symmetric evolution of the hurricane as it underwent eyewall replacement during the approximately 1 day observation period developing convection associated with the secondary eyewall became more symmetric and contracted inward latent heating in the emergent secondary eyewall led to the development of a distinct toroidal overturning circulation with inertially constrained radial inflow above the boundary layer and compensating subsidence in the moat region properties that are consistent broadly with the balanced vortex response to an imposed ring of diabatic heating outside the primary eyewall the primary eyewall s convection became more asymmetric during

reply to comments on nonlinear response of a tropical cyclone vortex to prescribed eyewall heating with and without surface friction in tcm4 implications for tropical cyclone intensification

the cenomanian turonian oceanic anoxic event i stratigraphy and distribution of organic carbon rich beds and the marine δ13c excursion marine strata deposited during late cenomanian and early turonian time display lithological faunal and geochemical characteristics which indicate that significant parts of the world ocean were periodically oxygen deficient at or very close to the cenomanian turonian boundary between 90 5 and 91 5ma ago oxygen deficiencies were particularly marked over a period of 1ma this short lived episode of oceanic oxygen deficiency has been termed the cenomanian turonian oceanic anoxic event oae the widespread distribution of anoxic sediments deposited synchronously during such a short lived event indicates that such sediments are not simply the product of coincidental local climatic or basinal water mass characteristics but are the result of a global expansion and intensification of the cenomanian turonian oxygen minimum zone related to feedback between sea level rise and regional palaeoceanography the palaeoceanography of the cenomanian turonian oae is discussed in detail in a companion paper by arthur et al 1987 from authors

mesoscale and convective scale characteristics of mature hurricanes part ii inner core structure of hurricane allen 1980 abstract the eyewall structure of hurricane alien is examined from analyses of multiple aircraft data on two days 5 and 8 august 1980 these data sets are unique in that for the first time three instrumented aircraft executed coordinated radial penetrations of the eyewall at multiple levels the data collected on 5 august illustrate the persistence of various features on horizontal scales 10 km over several hours composite cross sections constructed from the 8 august data show similar structure although the eye diameter had decreased to less than half that of 5 august the convergence of air in the eyewall was highly two dimensional this convergence supported organized ascent that was along the inner edge of the high reflectivity region and displaced inward several kilometers from the radius of maximum wind rmw a mean eyewall updraft of 5 6 m s 1 is computed from integration of the two dimensional continuity equation embedded within the two dimensional eyewall were cores of high reflectivity t

a numerical study of typhoon megi 2010 part i rapid intensification abstracttyphoon megi 15w was the most powerful and longest lived tropical cyclone tc over the western north pacific during 2010 while it shared many common features of tcs that crossed luzon island in the northern philippines megi experienced unique intensity and structural changes which were reproduced reasonably well in a simulation using the advanced research weather research and forecasting model arw wrf with both dynamical initialization and large scale spectral nudging in this paper processes responsible for the rapid intensification ri of the modeled megi before it made landfall over luzon island were analyzed the results show that megi experienced ri over the warm ocean with high ocean heat content and decreasing environmental vertical shear the onset of ri was triggered by convective bursts cbs which penetrate into the upper troposphere leading to the upper tropospheric warming and the formation of the upper level warm core in turn cbs with their roots inside of the eyewall in

an air sea interaction theory for tropical cyclones part ii evolutionary study using a nonhydrostatic axisymmetric numerical model abstract in part i of this study an analytical model for a steady state tropical cyclone is constructed on the assumption that boundary layer air parcels are conditionally neutral to displacements along the angular momentum surfaces of the hurricane vortex the reversible thermodynamics implied by this assumption allows the mature storm to be thought of as a simple carnot engine acquiring heat at the high temperature ocean surface and losing heat near the low temperature tropopause although the oceanic heat source is universally recognized as the sine qua non for the mature hurricane there is also wide acceptance of conditional instability of the second kind cisk which makes no specific reference to surface heat fluxes as the formative mechanism this ambivalence is seen in that all numerical simulation studies find it essential to have transfer from the ocean surface yet all start from a conditionally unstable atmosphere the hypothesis put forward in part i based on the steady state theory is t

eye excess energy and the rapid intensification of hurricane lili 2002 abstract over 4 5 days noaa and u s air force personnel in reconnaissance aircraft deployed 44 global positioning system dropwindsondes gps sondes in the eye of hurricane lili 2002 the vertical profiles derived from these gps sondes were used to determine the evolution of the height of the inversion presence and height of the hub cloud the height of the lifted condensation layer and the depth of the mixed layer as lili deepened underwent rapid intensification ri and eventually rapid decay the lower portion of the eye moistened and the lapse rate became moist adiabatic the inversion layer rose as lili intensified and then quickly fell over 1500 m at the beginning of ri comparison of the equivalent potential temperature e of the eye with that in the eyewall revealed that like many other hurricanes the eye was a reservoir for the warmest e the authors define a variable called eye excess energy that is a function of the difference in e between the eye and the eyewall and the depth over