dipole structure of interannual variations in summertime tropical cyclone activity over east asia the present study examines variations in summertime july september tropical cyclone tc activity over east asia during the period 1951 2003 to represent tc activity a total of 853 tc best tracks for the period were converted to tc passage frequencies tpfs within 5 5 latitude longitude grids tpfs are defined as the percentage values obtained by dividing the number of tc appearances in each grid box by the total number of tcs each year empirical orthogonal function analysis of the tpf showed three leading modes two tropical modes that represent the long term trend and the relationship with enso and one midlatitude mode that oscillates between south of korea and southeast of japan with an interannual time scale the latter proved to be the most remarkable climatic fluctuation of summertime tc activity in the midlatitudes and is referred to as the east asian dipole pattern eadp in this paper anomalous atmospheric flows directly connected to the eadp are an enhanced anticyclonic cyclonic circulation centering around japan when the tpf is high south of korea southeast of japan thereby showing an equivalent barotropic structure in the entire troposphere this regional circulation anomaly varies in conjunction with the zonally oriented quasi stationary rossby wave train in the upper troposphere this wave train is meridionally trapped in the vicinity of the summer mean jet stream therefore the mean jet stream alters its internal meandering structure according to the phase of the wave train

identification of cyclone track regimes in the north atlantic a langrangian type climatology of north atlantic cyclones is established based on the high resolution european centre for medium range weather forecasts data set of the 1000 hpa height field first an algorithm is introduced to identify mid latitude cyclones and cyclone paths with as few constraints as possible cluster analysis of relative cyclone displacements yields three types of cyclone tracks characterizing stationary north eastward and zonally travelling storms the internal lagrangian statistics of these cyclone track types reveal representative life cycles for central pressure and geopotential height gradients and a power law scaling behaviour of cyclone displacements finally a basic climatology of north atlantic cyclone track regimes is deduced in terms of a time series and circulation statistics

pattern classification of typhoon tracks using the fuzzyc means clustering method abstract a fuzzy c means clustering method fcm is applied to cluster tropical cyclone tc tracks fcm is suitable for the data where cluster boundaries are ambiguous such as a group of tc tracks this study introduces the feasibility of a straightforward metric to incorporate the entire shapes of all tracks into the fcm that is the interpolation of all tracks into equal number of segments four validity measures e g partition coefficient partition index separation index and dunn index are used objectively to determine the optimum number of clusters this results in seven clusters from 855 tcs over the western north pacific wnp from june through october during 1965 2006 the seven clusters are characterized by 1 tcs striking the korean peninsula and japan with north oriented tracks 2 tcs affecting japan with long trajectories 3 tcs hitting taiwan and eastern china with west oriented tracks 4 tcs passing the east of japan with early recurving tracks 5 tcs traveling the easternmost re

interdecadal changes in summertime typhoon tracks abstract the present work examines interdecadal variations of typhoon tracks in the western north pacific wnp during the boreal summer june september for the period 1951 2001 typhoon tracks are expressed as percentage values of the total number of typhoon passages into a 5 5 latitude longitude grid box with respect to the total number of typhoons formed in the wnp the analysis period is divided into two interdecadal periods id1 1951 79 and id2 1980 2001 from id1 to id2 typhoon passage frequency decreased significantly in the east china sea and philippine sea but increased slightly in the south china sea the time series of typhoon passage frequency over the east china sea and south china sea further reveal a regime shift in the late 1970s while those over the philippine sea indicate a continuous downward trend of 9 decade 1 the interdecadal changes in typhoon tracks are associated with the westward expansion of the subtropical northwestern pacific high snph in the late 1970s the e

classifying north atlantic tropical cyclone tracks by mass moments a new method for classifying tropical cyclones or similar features is introduced the cyclone track is considered as an open spatial curve with the wind speed or power information along the curve considered to be a mass attribute the first and second moments of the resulting object are computed and then used to classify the historical tracks using standard clustering algorithms mass moments allow the whole track shape length and location to be incorporated into the clustering methodology tropical cyclones in the north atlantic basin are clustered with k means by mass moments producing an optimum of six clusters with differing genesis locations track shapes intensities life spans landfalls seasonal patterns and trends even variables that are not directly clustered show distinct separation between clusters a trend analysis confirms recent conclusions of increasing tropical cyclones in the basin over the past two decades however the trends vary across clusters

contrasting eastern pacific and central pacific types of enso abstract surface observations and subsurface ocean assimilation datasets are examined to contrast two distinct types of el nino southern oscillation enso in the tropical pacific an eastern pacific ep type and a central pacific cp type an analysis method combining empirical orthogonal function eof analysis and linear regression is used to separate these two types correlation and composite analyses based on the principal components of the eof were performed to examine the structure evolution and teleconnection of these two enso types the ep type of enso is found to have its sst anomaly center located in the eastern equatorial pacific attached to the coast of south america this type of enso is associated with basinwide thermocline and surface wind variations and shows a strong teleconnection with the tropical indian ocean in contrast the cp type of enso has most of its surface wind sst and subsurface anomalies confined in the central pacific and tends to onset develop and decay in situ

systematic variation of summertime tropical cyclone activity in the western north pacific in relation to the madden julian oscillation abstract the variability of observed tropical cyclone tc activity i e genesis track and landfall in the western north pacific wnp is examined in relation to the various categories of the madden julian oscillation mjo during summer june september for the period 1979 2004 the mjo categories are defined based on the empirical orthogonal function analysis of outgoing longwave radiation data the number of tcs increases when the mjo related convection center is located in the wnp the axis of a preferable genesis region systematically shifts like a seesaw in response to changes in the large scale environments associated with both the eastward and northward propagation of the mjo and the intraseasonal variability of the wnp subtropical high furthermore the authors show that the density of tc tracks in each mjo category depends on the systematic shift in the main genesis regions at first order also the shift is affected by the prevailing large scale steering flows in each mjo category when th

tropical cyclone movement and surrounding flow relationships abstract this paper presents results of a comprehensive study of the relationship between the movement of tropical cyclones and the large scale circulation which surrounds them cyclones have been stratified by direction and speed of movement latitude intensity change and size as determined by the radius of the outermost closed surface isobar in three ocean basins the northwest pacific the west atlantic and the australian south pacific region twenty one different stratifications are available in the northwest pacific 13 in the west atlantic and 6 in the australian south pacific area cyclone movement and surrounding flow relationships were studied at different pressure levels and a variety of radii pressure weighted layer averages were also analyzed in search of such relationships results show an important relationship between surrounding large scale flow and tropical cyclone movement for all stratifications the winds in the mid troposphere 500 700 mb at 5 7 latitude radius from the cyclone

sources and paleoclimatic significance of holocene bignell loess central great plains usa abstract this paper reexamines the stratigraphy sources and paleoclimatic significance of holocene bignell loess in the central great plains a broadly similar sequence of loess depositional units and paleosols was observed in thick bignell loess sections up to 300 km apart suggesting that these sections record major regional changes in the balance between dust deposition and pedogenesis new optical ages together with previously reported radiocarbon ages indicate bignell loess deposition began 9000 11 000 yr ago and continued into the late holocene some bignell loess is

tropical cyclone track characteristics as a function of large scale circulation anomalies abstract factors that contribute to intraseasonal variability in western north pacific tropical cyclone track types are investigated it is hypothesized that the 700 mb large scale circulation can affect tropical cyclone track characteristics by enhancing or excluding genesis in certain regions and concurrently prohibiting or favoring recurving versus straight tracks a track type climatology indicates that genesis location alone may explain some of the variability in track type although some genesis regions have no preference for straight moving or recurving tracks a formation north of 20 n or east of 150 e and north of 10 n favors a recurvature track these recurving storms are classified as recurving north and recurving storms that form in regions with nearly equal probability of straight or recurving tracks are classified as recurving south a compositing technique is used to define anomalous 700 mb large scale circulations that exist during the formation of tropical cyclones that subsequently fol

influence of stratospheric quasi biennial oscillation on tropical cyclone tracks in the western north pacific 1 the possible influence of the stratospheric quasibiennial oscillation qbo on tropical cyclone tc passages in the western north pacific wnp is examined using tc data recorded by the tokyo typhoon center and the qbo index derived from reanalysis data the influence is observed to be significant the number of tcs approaching the east china sea is large during the westerly phase of the qbo however during the easterly phase the number of tcs approaching the eastern offshore of japan is large this difference in the tc tracks is found to be related to the background flow change associated with the qbo however the total number of tc events over the wnp and the sum of the number of tcs approaching the aforementioned two regions appear to be unrelated to the qbo phases citation ho c h h s kim j h jeong and s w son 2009 influence of stratospheric quasi biennial oscillation on tropical cyclone tracks in the western north pacific geophys res lett 36 l06702 doi 10 1029 2009gl037163

two types of el nino events cold tongue el nino and warm pool el nino abstract in this study two types of el nino events are classified based on spatial patterns of the sea surface temperature sst anomaly one is the cold tongue ct el nino which can be regarded as the conventional el nino and the other the warm pool wp el nino the ct el nino is characterized by relatively large sst anomalies in the nino 3 region 5 s 5 n 150 90 w while the wp el nino is associated with sst anomalies mostly confined to the nino 4 region 5 s 5 n 160 e 150 w in addition spatial patterns of many atmospheric and oceanic variables are also distinctively different for the two types of el nino events furthermore the difference in the transition mechanism between the two types of el nino is clearly identified that is the discharge process of the equatorial heat content associated with the wp el nino is not efficient owing to the spatial structure of sst anomaly as a result it cannot trigger a cold event it is also demonstrated that zonal advective feedback i e zonal adve

cluster analysis of typhoon tracks part i general properties a new probabilistic clustering technique based on a regression mixture model is used to describe tropical cyclone trajectories in the western north pacific each component of the mixture model consists of a quadratic regression curve of cyclone position against time the best track 1950 2002 dataset is described by seven distinct clusters these clusters are then analyzed in terms of genesis location trajectory landfall intensity and seasonality both genesis location and trajectory play important roles in defining the clusters several distinct types of straight moving as well as recurving trajectories are identified thus enriching this main distinction found in previous studies intensity and seasonality of cyclones though not used by the clustering algorithm are both highly stratified from cluster to cluster three straight moving trajectory types have very small withincluster spread while the recurving types are more diffuse tropical cyclone landfalls over east and southeast asia are found to be strongly cluster dependent both in terms of frequency and region of impact the relationships of each cluster type with the large scale circulation sea surface temperatures and the phase of the el nino southern oscillation are studied in a companion paper

clustering of eastern north pacific tropical cyclone tracks enso and mjo effects 1 a probabilistic clustering technique is used to describe tropical cyclone tracks in the eastern north pacific on the basis of their shape and location the best track data set is decomposed in terms of three clusters these clusters are analyzed in terms of genesis location trajectory landfall intensity seasonality and their relationships with the el nino southern oscillation enso and madden julian oscillation mjo longitudinal track location plays a strong discriminating role in the regression mixture model s solution with the average track orientation becoming more zonal toward the west this progression encapsulates well the relationship between tropical cyclones over the eastern tropical pacific and the mjo or enso two of the clusters describe tropical cyclones tcs with tracks that lie near the coast of mexico and central america the most frequent cluster contains tracks that trend west northwestward while the second most frequent one has genesis locations that lie slightly to the southeast of those in the most frequent cluster and tracks that run typically parallel to the central american coast this second cluster is shown to be significantly associated with the westerly phase of the mjo the third least frequent cluster contains tcs with westward trajectories over the central and eastern equatorial pacific some of these tcs have an impact on hawaii and other islands as far as the central and western north pacific regions the least frequent cluster is strongly related to enso while the others are not it occurs significantly more frequently during el nino conditions examination of the large scale patterns of atmospheric circulation and sea surface temperature associated with each of our three clusters are consistent with previous studies anomalous low level westerly zonal winds from the monsoon trough and mjo meet anomalous easterlies near the region of genesis in each cluster

models of tropical cyclone wind distribution and beta effect propagation for application to tropical cyclone track forecasting abstract a model of the tangential wind speed in the outer regions of tropical cyclones is proposed based on approximate conservation of angular momentum the purpose is to derive an operationally useful model of the beta effect propagation bep which barotropic numerical models have shown to be primarily related to the outer wind structure the functional dependence of the predicted bep speeds over a range of latitudes and the radii ro at which the cyclonic winds are reduced to zero is determined from dimensional analysis given the empirical nature of the profile and imprecise estimates of ro only four tropical cyclone sizes or outer wind structures are defined based on the magnitude of the bep speeds and their relative contributions to the total motion a second aspect of bep from the barotropic model integrations is the development of a trailing anticyclone to the southeast of the tropical cyclone as a result of rossby wave dispersion the four tropical cyclone size categories or outer wind structu

tropical cyclone activity in the northwest pacific in relation to the el nino southern oscillation phenomenon abstract the interannual variations in tropical cyclone activity in the northwest pacific nwpac and their relationships with the el nino southern oscillation enso phenomenon were studied using the method of spectral analyses time series of a southern oscillation index soi defined as the sea level pressure difference between easter island and darwin and tropical cyclone activity in the entire nwpac ocean basin as well as in different regions of the nwpac were analyzed two spectral peaks are apparent in all these time series one corresponds to the generally accepted southern oscillation with a period of 3 to 3 5 years and another at the quasi biennial oscillation qbo frequency cross spectral analyses between the soi and tropical cyclone activity show significant coherence in these two spectral peaks the dominant peak is at the southern oscillation frequency with the soi leading typhoon activity by almost a year at the qbo frequency the two series are almost in phase cyclone activity in t

evidence for major input of riverine organic matter into the ocean abstract the changes in the structure of xad 8 isolated dissolved organic matter dom samples along a river penobscot river to estuary penobscot bay to ocean across the gulf of maine transect and from the pacific ocean were investigated using selective and two dimensional 2d nuclear magnetic resonance nmr spectroscopy coupled with elemental and carbon isotope analysis the results provide important insights into the nature of relatively stable structures in the river to ocean continuum and the enigma of the fate of terrestrial dom in the marine system first lignin and carboxyl rich alicyclic molecules crams which are indistinguishable from mass spectrometry were clearly differentiated with nmr spectroscopy nmr unambiguously showed that crams persisted along the river to ocean transect and in the pacific ocean while lignin residues dramatically decreased in abundance from the river to the coastal ocean and the pacific ocean the results challenge a previous conclusion that lignin derived compounds are refractory and can accumulate in the coastal ocean the loss of terrestrial plant derived aromatic compounds such as lignin and tannin residues throughout the sequence of riverine coastal and open ocean dom extracts could also partially explain the decreasing organic carbon recovery by xad 8 isolation and the change in carbon stable isotope composition from riverine dom 13 c 27 6 to ocean dom 13 c 23 0 extracts the observation from advanced nmr of similar cram molecules in xad 8 isolated dom samples from the penobscot river to the penobscot bay and from the ocean refutes a previous conclusion that xad isolated dom samples from seawater and river are distinctly different the alicyclic structural features of crams and their presence as the major structural units in dom extracts from the penobscot river to gulf of maine transect together with the deduced old 14 c age of crams in the ocean imply that terrestrial crams may persist on timescales long enough to be transported into the ocean

cluster analysis of typhoon tracks part ii large scale circulation and enso abstract a new probabilistic clustering method based on a regression mixture model is used to describe tropical cyclone tc propagation in the western north pacific wnp seven clusters were obtained and described in part i of this two part study in part ii the present paper the large scale patterns of atmospheric circulation and sea surface temperature associated with each of the clusters are investigated as well as associations with the phase of the el nino southern oscillation enso composite wind field maps over the wnp provide a physically consistent picture of each tc type and of its seasonality anomalous vorticity and outgoing longwave radiation indicate changes in the monsoon trough associated with different types of tc genesis and trajectory the steering winds at 500 hpa are more zonal in the straight moving clusters with larger meridional components in the recurving ones higher values of vertical wind shear in the midlatitudes also accompany the straight moving tracks compared to

el nino modoki and its possible teleconnection 1 using observed data sets mainly for the period 1979 2005 we find that anomalous warming events different from conventional el nino events occur in the central equatorial pacific this unique warming in the central equatorial pacific associated with a horseshoe pattern is flanked by a colder sea surface temperature anomaly ssta on both sides along the equator empirical orthogonal function eof analysis of monthly tropical pacific ssta shows that these events are represented by the second mode that explains 12 of the variance since a majority of such events are not part of el nino evolution the phenomenon is named as el nino modoki pseudo el nino modoki is a classical japanese word which means a similar but different thing the el nino modoki involves ocean atmosphere coupled processes which include a unique tripolar sea level pressure pattern during the evolution analogous to the southern oscillation in the case of el nino hence the total entity is named as el nino southern oscillation enso modoki the enso modoki events significantly influence the temperature and precipitation over many parts of the globe depending on the season the impacts over regions such as the far east including japan new zealand western coast of united states etc are opposite to those of the conventional enso the difference maps between the two periods of 1979 2004 and 1958 1978 for various oceanic atmospheric variables suggest that the recent weakening of equatorial easterlies related to weakened zonal sea surface temperature gradient led to more flattening of the thermocline this appears to be a cause of more frequent and persistent occurrence of the enso modoki event during recent decades

cluster analysis of tropical cyclone tracks in the southern hemisphere a probabilistic clustering method is used to describe various aspects of tropical cyclone tc tracks in the southern hemisphere for the period 1969 2008 a total of 7 clusters are examined three in the south indian ocean three in the australian region and one in the south pacific ocean large scale environmental variables related to tc genesis in each cluster are explored including sea surface temperature low level relative vorticity deep layer vertical wind shear outgoing longwave radiation el nino southern oscillation enso and the madden julian oscillation mjo composite maps constructed 2 days prior to genesis show some of these to be significant precursors to tc formation most prominently westerly wind anomalies equatorward of the main development regions clusters are also evaluated with respect to their genesis location seasonality mean peak intensity track duration landfall location and intensity at landfall enso is found to play a significant role in modulating annual frequency and mean genesis location in three of the seven clusters two in the south indian ocean and one in the pacific the enso modulating effect on genesis frequency is caused primarily by changes in low level zonal flow between the equator and 10 s and associated relative vorticity changes in the main development regions enso also has a significant effect on mean genesis location in three clusters with tcs forming further equatorward poleward during el nino la nina in addition to large shifts in mean longitude the mjo has a strong influence on tc genesis in all clusters though the amount modulation is found to be sensitive to the definition of the mjo