climatology of upper tropospheric lower stratospheric utls jets and tropopauses in merra abstracta global climatology 1979 2012 from the modern era retrospective analysis for research and applications merra shows distributions and seasonal evolution of upper tropospheric jets and their relationships to the stratospheric subvortex and multiple tropopauses the overall climatological patterns of upper tropospheric jets confirm those seen in previous studies indicating accurate representation of jet stream dynamics in merra the analysis shows a northern hemisphere nh upper tropospheric jet stretching nearly zonally from the mid atlantic across africa and asia in winter spring this jet splits over the eastern pacific merges again over eastern north america and then shifts poleward over the north atlantic the jets associated with tropical circulations are also captured with upper tropospheric westerlies demarking cyclonic flow downstream from the australian and asian monsoon anticyclones and associated easterly jets multiple tropopauses associated with the thermal tropopause break

tropopause inversion layer seasonal and latitudinal variations and representation in standard radiosonde data and global models 1 previous publications have given information on the seasonal and latitudinal variations of the tropopause inversion layer til as seen in high resolution radiosonde data sets when soundings are averaged using the tropopause as a reference level this paper presents a more quantitative analysis of the latitudinal and seasonal structure of the til than has been given previously to do this we define the region over which the static stability relaxes from its overshoot value at the tropopause to its local minimum in the stratosphere this region is seen to increase monotonically in thickness from about 1 km at low latitudes to about 4 to 5 km at high latitudes when the seasons are defined as winter djf spring mam summer jja and fall son the transition from tropical behavior occurs a little poleward of 20 n in both djf and mam and moves to a little poleward of 30 n in jja and son somewhat surprisingly it is also shown that almost identical information about the til can be derived from standard radiosonde data for our period of analysis because of their reporting of the tropopause and other significant levels but caution needs to be used in doing this since the number of reported significant levels has varied significantly over the long term and with some distinct discontinuities finally we discuss what sort of information on the til can be obtained from global models given their relatively coarse vertical resolution

double tropopause formation in idealized baroclinic life cycles the key role of an initial tropopause inversion layer 1 recent studies have shown that double tropopauses exist in all seasons and at all longitudes in the midlatitudes as of yet the key mechanism responsible for their formation is not known in this study we explore the connection between double tropopauses and midlatitude baroclinic eddies this is investigated in the context of idealized life cycle experiments the key finding of this study is that large areas of double tropopauses form spontaneously at the nonlinear stage of the life cycle evolution provided an extratropical tropopause inversion layer is present in the balanced initial temperature profile we also show that the areas covered with double tropopauses grow as the strength of the initial tropopause inversion layer is increased without such a layer as in canonical examples of baroclinic life cycles much studied in the literature no double tropopause formation occurs in agreement with observations double tropopauses in our life cycle experiments form predominantly in areas of cyclonic flow at upper levels however the air masses that end up between the two tropopauses are found to originate from high latitudes this appears to differ from a recently published case study where the air between double tropopauses was shown to originate partly from low latitudes such a discrepancy suggests that more than one pathway may exist to advect air masses between the two tropopauses

climatological features of global multiple tropopause events 1 this study examines various climatological features related to multiple tropopause events mt events the analysis is based on the lapse rate definition of the tropopause and is performed on a radiosonde data subset taken from the integrated global radiosonde archive database the global statistics of mt events are analyzed taking into consideration both their seasonal and geographical variations our results are in moderate qualitative agreement with those of earlier studies they reinforce the analytical findings of other researchers but at the same time highlight important differences in both the number and position of the maximum occurrence of mt events we found a latitudinal band of multiple tropopause occurrence in the northern hemisphere and three centers in the southern hemisphere which coincided with identified zones of maximum cyclogenesis the climatological features of pressure temperature and vertical separation of mt events revealed the complexity of these phenomena which behave very differently according to latitude and season

geometry and controls on fracturing in a natural fault bend fold rosario field maracaibo basin venezuela the rosario oil field lies between the perija mountain front and lake maracaibo and produces from fractured cretaceous carbonates and tertiary clastics we interpret the structure as a detached fault bend fold which ramps through cretaceous cogollo and la luna carbonates and flattens into an upper detachment at the base of the upper cretaceous colon shale the structural relief formed primarily during the mid miocene and younger seismic and well control on the three dimensional geometry illustrates the effects of 1 lithology and displacement variation on fold geometry 2 an oblique footwall ramp on hangingwall faulting and 3 fold curvature on fracturing and hydrocarbon production fold geometry at different structural levels is strongly controlled by lithology stiff cogollo and la luna carbonates exhibit kink style folding above the upper fault bend the weak colon shale decouples the faulted carbonates from the concentrically folded tertiary clastics regions of enhanced faulting and fracturing of cretaceous carbonates are a function of structural position we observe normal faults in the hangingwall where the strike of the footwall ramp changes from n20 degrees e to n65 degrees e fold curvature highlights fold hinges yet distributed faulting is seismically imaged in the forelimb suggesting that rocks fracture as they migrate through the ramp upper flatmore fault bend production rates are higher near the forelimb relative to the flat crestal region less

the double tropopause and its dynamical relationship to the tropopause inversion layer in storm track regions using high resolution dynamic limb sounder observations and era interim reanalysis this study demonstrates that the warm conveyor belt wcb is a mechanism responsible for the relationship between the double tropopause dt and the tropopause inversion layer til a relationship recently suggested in the literature based on idealized model simulations of baroclinic disturbances using these data sets spatial and temporal characteristics of the dt til relationship are examined over a 3 year period 2005 2008 in the extratropics results from satellite data show that as the til increases in strength so does the frequency of the dt regardless of season or hemisphere the inverse relationship is found in the tropics using only dt profiles zonal composites of wind relative vorticity and temperature from reanalysis data show that as the til increases in strength the upper tropospheric circulation switches from cyclonic to anticyclonic and the upward vertical motion increases this result suggests the wcb as a mechanism since it is on the anticyclonic side of the jet and is characterized by the movement of tropical air poleward and upward from the surface to verify this relationship the vertical and horizontal development of a synoptic scale baroclinic system is analyzed over a 4 day period results show the equatorward extension of the polar tropopause and thus the formation of the dt due to the strengthening of the til in the region of vertical motion associated with the wcb moreover this result suggests that air movement within the dt could originate from high latitudes when associated with a baroclinic disturbance

contribution of nonlinear mechanisms in the persistence of multiple tidal inlet systems abstract multiple tidal inlet stability has been modeled following either a single inlet stability approach or a simple linear analytical approach and the results suggest that these systems are not stable however there is evidence that shallow multiple tidal inlet systems are strongly nonlinear and that they can be stable on a historical time scale based on numerical simulations of the hydrodynamics of ria formosa a shallow lagoon in the south of portugal in which multiple tidal inlets have persisted in a historical time scale the effects of tidal distortion and residual circulation on the persistence of multiple inlets in the system were analyzed numerical simulations using a 2 d vertically averaged finite element model served 1 to identify the existence of three hydrodynamically independent sub embayments in the system 2 to create realistic physical disturbances change in inlet cross sectional area and analyze the hydrodynamic response of the system to such disturbances 3 to identify and quantify the existing nonlinear hydrodynamic processes tidal distortion ebb flood dominance residual flow patterns and 4 to analyze the overall stability of the western sub embayment using the closure curve approach the results show the importance of the nonlinear processes in the hydrodynamics of multiple inlet systems and the need to consider them when analyzing inlet stability in such systems and suggest that specifically for ria formosa if the existing jetties at one of the inlets in the western sub embayment were removed this area of the system would reach natural stability and equilibrium with three inlets

extratropical tropopause transition layer characteristics from high resolution sounding data 1 accurate determination of the tropopause is important for applications such as dynamical analysis and forecasting radiative transfer calculations and the diagnosis of chemical transport in the atmosphere in this paper we examine how well the extratropical tropopause is determined in the national centers for environmental prediction high resolution global forecast system gfs model analysis over the continental united states using high resolution aircraft and radiosonde data the gfs analyses and sounding data compare well with rms differences of approximately 600 m which is comparable to the vertical resolution of the model the gfs tropopause is a good proxy in areas without in situ observations but near the subtropical jet the gfs analysis often mistakenly identifies the secondary rather than the primary tropopause we also explore an alternative method to identify the tropopause by fitting a smoothed step function to the static stability profile this new approach provides a measure of the depth of the troposphere stratosphere transition and facilitates the study of the dynamical behavior of the tropopause region in particular using the transition depth we are able to identify the statistical behavior of temperature in profiles with deep or shallow tropopause transition layers

the tropopause in the polar regions abstract the polar and subpolar tropopause in both hemispheres is investigated using the ecmwf reanalysis era data from 1979 to 1993 and radiosonde data from 1989 to 1993 both the thermal and the dynamical criteria are applied to each dataset the tropopauses derived from the radiosonde data are used to validate the era derived tropopauses and to investigate the sharpness of the tropopause the validation reveals that the era data are well suited for the determination of the tropopause a comparison between the thermal and the dynamical tropopause shows a very good agreement except for polar winter and there is clear evidence that the dynamical criterion is more appropriate in winter the results show that the annual cycle of the polar tropopause can be classified into three different patterns a single wave with a tropopause pressure maximum in winter and a minimum in summer is typical for the subpolar parts of eastern siberia and north america a double wave with pressure maxima in spring and autumn

a climatology of multiple tropopauses derived from gps radio occultations with champ and sac c 1 a global climatology of multiple tropopauses mt is discussed based on global positioning system gps radio occultation ro data from the german champ challenging minisatellite payload and the us argentinian sac c satelite de aplicaciones cientificas c satellite mission for the period may 2001 april 2005 in this study we present first detailed investigations about the geographical and temporal distribution of mt during different seasons the thickness of the layer between the lowest first and highest last tropopause has a strong annual cycle in the vicinity of the subtropical jet stj stream region values vary between 4 5 km during winter and 2 3 km during summer respectively whereas higher differences were found on the northern hemisphere it is shown that the occurrence distribution of mt is in good agreement with the mean climatological location of the stj 30 40 on both hemispheres in particular during winter time

stratigraphic controls on eformation patterns in fault related folds a detachment fold example from the sierra madre oriental northeast mexico abstract deformation patterns are described by the style intensity and distribution of structures throughout a volume of rock in fault related folds presently observed deformation patterns are controlled by structural factors like kinematic history environmental factors like burial history and stratigraphic factors like layer thickness and competence to demonstrate the role of stratigraphy in controlling fold related deformation patterns we document the stratigraphic variability of mesostructures at one structural position on a map scale detachment fold unique assemblages of faults fractures and cleavages in certain stratigraphic intervals define a mechanical stratigraphy comprised of several units each exhibiting a characteristic deformation response to the folding process the varying response of each mechanical unit suggests that folding mechanisms such as orthogonal flexure flexural slip or flexural flow were sequentially or coevally operative in each of the units using the simple theoretical strain distributions associated with each folding mechanism and the fact that each mechanical unit accommodates fold related strain by developing a characteristic set of mesostructures we are able to predict general deformation patterns elsewhere in the fold the significance of this approach is that it recognizes that even in a single structure fold kinematics and deformation response may be dramatically different in various parts of a stratigraphic section because of this the quality and character of reservoir rocks in anticlinal traps may change markedly over short stratigraphic distances predictions of fold related deformation based solely on fold kinematics are unlikely to resolve these variations

3 d deformation pattern analysis and evolution of the anisclo anticline southern pyrenees understanding the genetic relationships of folding related deformation structures is of importance for both academic and industrial purposes we analysed the three dimensional deformation pattern of the anisclo anticline in the southern pyrenees the specifically designed statistical method includes sequential steps of statistical and spatial data analysis and classification our results indicate that pressure solution cleavage frequency exhibits a spatial distribution that depends on the position within the fold conversely such a dependence does not occur in joints and veins consequently our data suggest that pressure solution cleavage is the most appropriate deformation structure for unravelling fault fold kinematics in carbonate multilayer in particular we found that the spacing of solution cleavages s is related to the corresponding bed thickness h this supports the use of h s value for deformation intensity quantification instead of spacing in the anisclo anticline analysis of h s indicates the occurrence of three main deformation panels whose restoration suggests that fold evolution progressed from layer parallel shortening to decollement folding up to thrust breakthrough and fault propagation folding comparison of h s values with finite strain data indicates that line length was not preserved during fold evolution this evidence has important implications for the kinematic interpretation of layer parallel shortening and cross section balancing

tropopause folds in era interim global climatology and relation to extreme weather events tropopause folds are intimately linked to upper level frontogenesis and jet stream dynamics they play an important role for stratosphere troposphere exchange the dynamical coupling of upper and lower tropospheric levels and for generating severe weather events this study presents a global climatology of tropopause folds using era interim reanalysis data from 1979 to 2012 and a refined version of a previously developed 3 d labeling and fold identification algorithm this algorithm objectively separates stratospheric and tropospheric air in complex situations e g in regions with strong low level inversions and in extratropical cyclones where diabatically generated potential vorticity anomalies typically occur three classes of tropopause folds are defined shallow medium and deep and their geographical distribution vertical extent and seasonal cycle are investigated most shallow folds occur along the subtropical jet stream in agreement with previous studies hot spots of medium and deep tropopause folds are found west of australia and along the coast of antarctica in the southern hemisphere and around the east coast of north america in the northern hemisphere seasonal cycles show maxima in winter for all fold classes medium and deep folds are frequently associated with surface wind gust and precipitation extremes as quantified for folds over the southern indian ocean wind gust extremes occur mainly in an elongated band upstream and equatorward of folds whereas precipitation extremes occur mainly east and poleward of folds overall in the considered region about 20 of medium folds and 33 of deep folds are associated with surface wind or precipitation extremes in the vicinity of the fold

climatological features of cutoff low systems in the northern hemisphere this study presents the first multidecadal climatology of cutoff low systems in the northern hemisphere the climatology was constructed by using 41 yr 1958 98 of ncep ncar reanalysis data and identifying cutoff lows by means of an objective method based on imposing the three main physical characteristics of the conceptual model of cutoff low the 200 hpa geopotential minimum cutoff circulation and the specific structure of both equivalent thickness and thermal front parameter fields several results were confirmed and climatologically validated 1 the existence of three preferred areas of cutoff low occurrence the first one extends through southern europe and the eastern atlantic coast the second one is the eastern north pacific and the third one is the northern china siberian region extending to the northwestern pacific coast the european area is the most favored region 2 the known seasonal cycle with cutoff lows forming much more frequently in summer than in winter 3 the short lifetime of cutoff lows most cutoff lows lasted 2 3 days and very few lasted more than 5 days and 4 the mobility of the system with few cutoff lows being stationary furthermore the long study period has made it possible i to find a bimodal distribution in the geographical density of cutoff lows for the european sector in all the seasons with the exception of winter a summer displacement to the ocean in the american region and a summer extension to the continent in the asian region and ii to detect northward and westward motion especially in the transitions from the second to third day of occurrence and from the third to fourth day of occurrence the long term cutoff low database built in this study is appropriate to study the interannual variability of cutoff low occurrence and the links between cutoff lows and jet stream systems blocking or major modes of climate variability as well as the global importance of cutoff low in the stratosphere troposphere exchange mechanism which will be the focus of a subsequent paper

hydrodynamics and equilibrium of a multiple inlet system although it is generally acknowledged that most multiple inlets are unstable and cannot coexist there is evidence to suggest that such inlets can indeed be stable over decadal time scales multiple inlet systems servicing a single embayment in contrast to single inlet systems confer particular hydrodynamic characteristics such as the potential existence of residual discharges and currents between the inlets this paper presents detailed measurements of hydrodynamic variables obtained over complete spring and neap tidal cycles in a multiple inlet system in southern portugal ria formosa the results indicate that the two main interconnected inlets servicing an embayment can coexist at least over a time scale of several decades however their coexistence cannot be explained simply using empirical equilibrium relations or inlet hydraulics although residual flow between the inlets appears to play an important role enhancing their stability it is the availability of sediment stored in the ebb tidal deltas and its capacity to be carried into the inlets during storm events that ultimately dictates the overall equilibrium independently of the flushing capability provided by the hydraulics such movement of sediment leads to the obstruction of the inlet channels thereby affecting the hydraulic efficiency and eventually leading to inlet closure in the long term the results augment existing knowledge concerning multiple inlet systems and improve understanding of their short to medium term stability

can multiple tidal inlets be stable abstract the gorge stability of inlets connecting the same bay to the ocean is analysed the basic premise is that when the tidal maximum of the bottom shear stress in an inlet is larger than the equilibrium shear the inlet is in a scouring mode and when smaller than the equilibrium shear stress the inlet is in a shoaling mode the tidal maximum of the bottom shear stress equals the equilibrium shear stress when the inlet is in equilibrium with the hydraulic environment an inlet is called stable when after a small change the cross sectional area returns to its equilibrium value using a linearized lumped parameter model for the flow in the inlets it is shown that for a two inlet bay system neither of the two inlets can be stable this implies that when assuming the inlets to be in equilibrium with the hydraulic environment a small change in the cross sectional area of one or both of the inlets will result in the closure of one or both of the inlets starting with the results for the two inlet bay system arguments are presented that suggest a similar conclusion holds for multiple inlets i e ultimately all inlets will close or at best one will remain open

a study of multiple tropopause structures caused by inertia gravity waves in the antarctic abstractmultiple tropopauses mts defined by the world meteorological organization are frequently detected from autumn to spring at syowa station 69 0 s 39 6 e the dynamical mechanism of mt events was examined by observations of the first mesosphere stratosphere troposphere mst radar in the antarctic the program of the antarctic syowa mst incoherent scatter is radar pansy and of radiosondes on 8 11 april 2013 the mt structure above the first tropopause is composed of strong temperature fluctuations by a detailed analysis of observed three dimensional wind and temperature fluctuation components it is shown that the phase and amplitude relations between these components are consistent with the theoretical characteristics of linear inertia gravity waves igws numerical simulations were performed by using a nonhydrostatic model the simulated mt structures and igw parameters agree well with the observation in the analysis using the numerical simulation data it is seen that igws were generate

cyclone anticyclone asymmetry concerning the height of the thermal and the dynamical tropopause abstract the differences between upper tropospheric cyclones and anticyclones are investigated regarding the height of the thermal and the dynamical tropopause the problem is addressed in an idealized framework by analyzing axisymmetric balanced flows which are characterized by a radial scale r and a tropopause potential temperature anomaly where cyclones and anticyclones differ only by the sign of the height of the thermal tropopause significantly differs from the height of the dynamical tropopause unless the anomaly is shallow there is a pronounced asymmetry in that the differences are much larger and more likely to occur in the case of cyclones two factors contribute to this asymmetry first for a given amplitude cyclones and anticyclones have different aspect ratios in geometric space second for a high latitude winter scenario the critical lapse rate of the wmo thermal tropopause is asymmetric with respect to typical tropospheric and stratospheric lapse rates simulated station s

surface cyclones in the era 40 dataset 1958 2001 part i novel identification method and global climatology abstract a novel method is introduced to generate climatological frequency distributions of meteorological features from gridded datasets the method is used here to derive a climatology of extratropical cyclones from sea level pressure slp fields a simple and classical conception of cyclones is adopted where a cyclone is identified as the finite area that surrounds a local slp minimum and is enclosed by the outermost closed slp contour this cyclone identification procedure can be applied to individual time instants and climatologies of cyclone frequency fc are obtained by simple time averaging therefore unlike most other climatologies the method is not based on the application of a tracking algorithm and considers the size of cyclones in combination with a conventional cyclone center tracking algorithm that allows the determination of cyclone life times and the location of cyclogenesis and cyclolysis additional frequency fields can be obtained for special categories of cyclones that are gener

propagation of the arctic oscillation from the stratosphere to the troposphere geopotential anomalies ranging from the earth s surface to the middle stratosphere in the northern hemisphere are dominated by a mode of variability known as the arctic oscillation ao the ao is represented herein by the leading mode the first empirical orthogonal function of low frequency variability of wintertime geopotential between 1000 and 10 hpa in the middle stratosphere the signature of the ao is a nearly zonally symmetric pattern representing a strong or weak polar vortex at 1000 hpa the ao is similar to the north atlantic oscillation but with more zonal symmetry especially at high latitudes in zonal mean zonal wind the ao is seen as a north south dipole centered on 40 45 n in zonal mean temperature it is seen as a deep warm or cold polar anomaly from the upper troposphere to 10 hpa the association of the ao pattern in the troposphere with modulation of the strength of the stratospheric polar vortex provides perhaps the best measure of coupling between the stratosphere and the troposphere by examining separately time series of ao signatures at tropospheric and stratospheric levels it is shown that ao anomalies typically appear first in the stratosphere and propagate downward the midwinter correlation between the 90 day low pass filtered 10 hpa anomaly and the 1000 hpa anomaly exceeds 0 65 when the surface anomaly time series is lagged by about three weeks the tropospheric signature of the ao anomaly is characterized by substantial changes to the storm tracks and strength of the midtropospheric flow especially over the north atlantic and europe the implications of large stratospheric anomalies as precursors to changes in tropospheric weather patterns are discussed

morphodynamics of the barrier inlet system west central florida the barrier inlet system along the gulf coast of peninsular florida has one of the most diverse morphologies of any barrier system in the world the delicate balance between tidal and wave generated processes on this low energy coast permits only slight changes in either of these processes to result in significant and rapidly developing morphologic responses some of these responses are the result of natural phenomena such as hurricanes opening tidal inlets closure of inlets due to longshore transport of sediment and changes in the availability of sediment tidal prism is the primary factor in controlling inlet morphology and is greatly influenced by anthropogenic activities in the backbarrier area human activity has also modified the coast in many ways over the past several decades beginning with the construction of the first causeways in the 1920s the various modifications by development have resulted in important morphodynamic changes in the barrier inlet system these include hardening the coast on the beach and at inlets dredging and filling in backbarrier environments and construction of fill type causeways connecting the islands to the mainland construction of seawalls and jetties has inhibited normal coastal processes examples include the downdrift erosion at blind pass and big sarasota pass construction of fill type causeways between the barriers and the mainland has created artificial tidal divides that reduce the tidal prism at some inlets thereby resulting in instability or closure such as blind pass and dunedin pass this is further exacerbated by dredge and fill construction that reduces tidal prism by reducing the area of open water in the backbarrier dredging of the intracoastal waterway also results in a negative impact on selected inlets by channeling tidal flux away from some inlets impacts of these changes inhibit the barrier inlet environments from responding to open coast processes

predicting the orientation of joints from fold shape results of pseudo three dimensional modeling and curvature analysis we treat layers of sedimentary rock as elastic plates and predict the orientations of joints by assuming that they open parallel to the maximum instantaneous stretch of a layer because the direction of maximum instantaneous stretch is parallel to the maximum curvature of a surface we hypothesize that joints will trend parallel to the minimum curvature of an elastically deformed layer after constructing pseudo three dimensional trishear models of laramide style uplifts that grow self similarly we calculated the direction of minimum curvature axes during the evolution of the fold our analysis of minimum curvature axes in evolving folds suggests several important characteristics for fold related joint sets 1 joints that are neither parallel nor perpendicular to the fold axis may be induced by local fold related strains 2 at any time during folding joint orientations may vary according to the structural position on a fold 3 at any location on a fold joint orientation may depend on when a joint forms during the evolution of the fold and 4 joint patterns in trishear folds may vary with stratigraphic position natural folds that evolve along simple geometric pathways may develop fold related joint sets the orientation dominance abutting relationships spacing and continuity of which will vary systematically throughout the structure this variation in joint system architecture may reflect the history of fold growth

investigation of double tropopause spatial and temporal global variability utilizing high resolution dynamics limb sounder temperature observations 1 this study examines the seasonal variation of the double tropopause dt using data from the high resolution dynamics limb sounder the combination of high data density and high vertical resolution available with this satellite instrument allows for the detailed analysis of fine scale structures such as the dt the spatial distribution of dt frequency is examined for all seasons from 2005 to 2007 global analysis of this distribution reveals that dts have a strong tendency to follow the zonal wind pattern and are present all year over the andes moreover during northern hemisphere winter spring there is a 15 decrease in the dt frequency over the eastern pacific and western atlantic two regions of wave breaking produced from a weakening of the zonal flow significant dt thickness values are also present over these regions but are found to extend further poleward than the corresponding frequency pattern a time series of dt frequencies is analyzed and shows an increase in daily frequencies during 2006 that highlights the interannual variability of this thermal structure for the first time dt duration is investigated in the extratropics utilizing a hovmoller diagram of dt frequency this representation highlights two preferred regions of formation the pacific and atlantic the slope of the feature gives it a speed of 18 m s in the northern hemisphere and a slightly faster speed for the southern hemisphere these speeds and the corresponding structures highlight a potential connection between upper tropospheric waves and dts

fine scale structure of the extratropical tropopause region 1 a vertically high resolved climatology of the thermal and wind structure of the extratropical tropopause region is presented the climatology is based on data from 80 u s radiosonde stations covering the period 1998 2002 time averages for each radiosonde station are computed using the tropopause as a common reference level for all vertical profiles within the mean a strong inversion at the tropopause in the mean vertical temperature gradient is uncovered that is temperature strongly increases with altitude within the lowermost stratosphere this tropopause inversion layer exists on average throughout the investigated extratropics about 30 n to 70 n accordingly the static stability parameter shows considerably enhanced values within the lowermost extratropical stratosphere compared to typical extratropical stratospheric values further aloft conventional averages are not able to capture the tropopause inversion layer mean profiles of the horizontal wind show behavior qualitatively corresponding to thermal wind balance winter and summer exhibit distinctly different climate states in the extratropical tropopause region an approximated potential vorticity is considered and found to be close to well mixed within the troposphere as well as within the tropopause inversion layer this suggests the view of the tropopause inversion layer as representing a dynamically active atmospheric layer some potential implications are discussed

tropopause folds and cross tropopause exchange a global investigation based upon ecmwf analyses for the time period march 2000 to february 2001 1 a new methodology is proposed to identify folds of the dynamical tropopause taken as the 2 potential vorticity pv units pvu isosurface from global analysis data sets from the european centre for medium range weather forecasts ecmwf it consists of a three dimensional subdivision of the atmosphere into stratospheric and tropospheric parts and a subsequent examination of multiple tropopause crossings in vertical profiles of the analyses the method is applied to a 1 year period starting in march 2000 seasonal mean fold frequency distributions show that folds occur preferentially in the subtropics with maximum frequencies of about 30 pronounced maxima are located in the subtropical bands that extend from 20 e to 120 e on both hemispheres during summer generally subtropical folds are comparatively shallow deep folds occur most frequently in midlatitudes during winter over eastern north america and the western north atlantic with maximum frequencies of about 1 detailed investigation of the relationship between individual folds and cross tropopause exchange events reveals that on the average individual folds in the extratropics are associated with larger exchange mass fluxes compared to the subtropics however due to the much higher frequency of subtropical folds the percentage of exchange events that are associated with tropopause folds is larger near 20 40 latitude 50 70 than further poleward 20 30 during winter and 10 20 during summer this indicates that tropopause folds are the key feature for cross tropopause exchange in the subtropics whereas in the extratropics other tropopause structures are at least of equal importance

morphodynamics of an anthropogenically altered dual inlet system john s pass and blind pass west central florida usa abstract the morphodynamics of the john s pass blind pass dual inlet system were investigated based on hydrodynamic and morphology measurements and numerical modeling the co existence of the dual inlets is realized by the dominance of mixed energy john s pass in terms of tidal prism and size of the ebb delta and the artificial maintenance of the wave dominated migratory blind pass due to the secondary role of blind pass the aggressive anthropogenic activities there do not seem to have a significant influence on the morphodynamics of john s pass on the other hand the opening in 1848 and subsequent evolution of john s pass had substantial influence on blind pass causing it to migrate rapidly to the south in addition anthropogenic activities had much more influence on the morphodynamics of the secondary blind pass than that of the dominating john s pass results from numerical modeling provide a semi quantitative understanding of the hydrodynamics and morphodynamics of john s pass and blind pass in association with cold front passages which have substantial influences on inlet morphology two large eddies are modeled from the interactions between the southward longshore current and john s pass ebb and flood flow respectively these eddies are closely related to the morphodynamics of the channel margin linear bar and longshore transport divergence at the downdrift side both are key features of a mixed energy inlet the shallow water and wave breaking induced longshore current and elevated sediment suspension along the ebb delta terminal lobe provide the pathway for sediment bypassing the morphodynamics of blind pass are dominated by wave forcing the weak ebb jet is not capable of forming a sizable ebb delta and tends to be deflected by the strong longshore current causing elevated longshore transport along the downdrift beach the 90 degree turn of the inlet which is common for wave dominated migratory inlets results in weak ebb flushing along the updrift north side of the inlet and is responsible for the alongshore migration of the inlet before the artificial stabilization and sedimentation along the northern side of the inlet following stabilization

association of double tropopause events with baroclinic waves 1 we herein propose a method for identifying breaks in the subtropical tropopause as found in the era interim reanalysis data the method uses the identification of double tropopauses and allows the quantification of the extension of the overlap between the tropical and extratropical tropopauses the correlations between the meridional extension of the superposition of tropopauses and the fields of geopotential potential vorticity or potential temperature reveal baroclinic wave patterns similar wave patterns were also identified in the potential temperature fields derived from gps radio occultation cosmic data the zonal propagation velocity of the anomalies in the meridional extension of the overlap was estimated using hovmoller diagrams the estimated zonal velocities suggest that the variability in the superposition of the tropopauses is associated with baroclinic rossby wave patterns in the subtropical upper troposphere and lower stratosphere

double tropopauses and the tropical belt connected to enso a detailed analysis of double tropopause dt occurrences requires vertically well resolved accurate and globally distributed information on the troposphere stratosphere transition zone here we use radio occultation observations from 2001 to 2018 with such properties we establish a connection between el nino southern oscillation enso phases and the distribution of dts by analyzing the global and seasonal dt characteristics the seasonal distribution of dts reveals several hotspot locations such as near the subtropical jet stream and over high mountain ranges where dts occur particularly often in this study we detect a higher number of dts during the cold la nina state while warmer el nino events result in lower dt rates affecting the structure of the tropopause region close to the nino 3 region this relates to a much lower first lapse rate tropopause altitude during la nina and corresponds to an apparent narrowing of the tropical belt there

the long term coupling between column ozone and tropopause properties abstract the observational data of the vertical temperature distribution and column ozone obtained from 10 main stations in the northern hemisphere are analyzed in order to explore the tropopause variations in conjunction with the dynamical variability in column ozone from the analysis presented it is evident that the summer distribution of the frequency of occurrence of the tropopause over greece apart from its main maximum around 12 km is also characterized by a secondary one around 16 km it is proposed that this elevated maximum possibly originates from the height variation of the tropopause from 12 to 16 km depending on whether the athens station is located below the cyclonic shear side or below the anticyclonic shear side of the subtropical jet stream it is also suggested that the transport in the upper troposphere and lower stratosphere that originated in the equatorial region forces the appearance of the multiple tropopauses above greece furthermore the observational analysis of the ver

recent widening of the tropical belt from global tropopause statistics sensitivities 1 several recent studies have shown evidence for a widening of the tropical belt over the past few decades one line of evidence uses statistics of the tropopause height to distinguish between tropics and extratropics and defines tropical edge latitudes as those latitudes at which the number of days per year with tropopause heights greater than 15 km exceeds a certain threshold typically 200 days yr this definition involves two somewhat arbitrary thresholds here the sensitivity of the resulting widening trend of the tropical belt to these thresholds is investigated using four different reanalysis data sets widening trends are found to be particularly sensitive to changes in the tropopause height threshold ways to objectively determine appropriate thresholds to define tropical edge latitudes based on tropopause statistics are presented trend estimates for the width of the tropical belt from different reanalysis data sets are found to be mostly inconsistent with each other despite consistent seasonal and interannual variations

the distribution of deformation in parallel fault related folds with migrating axial surfaces comparison between fault propagation and fault bend folding abstract in fault related folds that form by axial surface migration rocks undergo deformation as they pass through axial surfaces the distribution and intensity of deformation in these structures has been impacted by the history of axial surface migration upon fold initiation unique dip panels develop each with a characteristic deformation intensity depending on their history during fold growth rocks that pass through axial surfaces are transported between dip panels and accumulate additional deformation by tracking the pattern of axial surface migration in model folds we predict the distribution of relative deformation intensity in simple step parallel fault bend and fault propagation anticlines in both cases the deformation is partitioned into unique domains we call deformation panels for a given rheology of the folded multilayer deformation intensity will be homogeneously distributed in each deformation panel fold limbs are always deformed the flat crests of fault propagation anticlines are always undeformed two asymmetric deformation panels develop in fault propagation folds above ramp angles exceeding 29 for lower ramp angles an additional more intensely deformed panel develops at the transition between the crest and the forelimb deformation in the flat crests of fault bend anticlines occurs when fault displacement exceeds the length of the footwall ramp but is never found immediately hinterland of the crest to forelimb transition in environments dominated by brittle deformation our models may serve as a first order approximation of the distribution of fractures in fault related folds