regional moment tensor inversion for strong aftershocks of the august 17 1999 izmit earthquake mw 7 4 we analyzed the source mechanisms of the thirty largest aftershocks 4 0 ml 6 2 of the august 17 1999 izmit earthquake mw 7 4 by applying the regional moment tensor inversion method using data from near regional broadband stations the inversion solutions were compared to 17 well constrained first motion solutions and were seen to be in good agreement we found that the dominance of strike slip motion is the main characteristic of the izmit earthquake sequence significant aftershock activity was recorded to the west and east of the un ruptured extremities in the east the aftershocks located near the town of duzce represent an early replica of the november 12 1999 duzce earthquake mw 7 2 in terms of locations and source mechanisms in the marmara sea where the fault geometry is still very poorly resolved most aftershocks have right lateral strike slip solutions with strike direction parallel to the submerged branches of the north anatolian fault

variations associated with cores and gaps of a pacific narrow cold frontal rainband abstract a noaa p 3 instrumented aircraft observed an intense fast moving narrow cold frontal rainband ncfr as it approached the california coast on 19 february 2001 during the pacific coastal jets experiment airborne doppler radar data obtained while the frontal system was well offshore indicated that a narrow ribbon of very high radar reflectivity convective cores characterized the rainband at low levels with echo tops to 4 5 km and pseudo dual doppler analyses showed the low level convergence of the prefrontal air the ncfr consisted of gaps of weaker reflectivity and cores of stronger reflectivity along its length perhaps as a result of hydrodynamic instability along its advancing leading edge in contrast to some earlier studies of cold frontal rainbands density current theory described well the motion of the overall front the character of the updraft structure along the ncfr varied systematically along the length of the precipitation cores and in the gap regions the vertical shear of the c

structure and evolution of the 22 february 1993 toga coare squall line organization mechanisms inferred from numerical simulation abstract mechanisms responsible for meso and convective scale organization within a large tropical squall line that occurred on 22 february 1993 during the tropical ocean global atmosphere coupled ocean atmosphere response experiment are investigated using a three dimensional numerical cloud model the squall line occurred in an environment typical of fast moving tropical squall lines characterized by moderate convective available potential energy and moderate to strong vertical shear beneath a low level jet with weak reverse vertical shear above a well simulated aspect of the observed squall line is the evolution of a portion of its leading convective zone from a quasi linear to a three dimensional bow shaped structure over a 2 h period this transition is accompanied by the development of both a prominent mesoscale vortex along the northern edge of the 40 60 km long bow shaped feature and elongated bands of weaker reflectivity situated rearward and oriented transverse to the leading edge within enha

the genesis of severe long lived bow echoes abstract a series of idealized simulations using a nonhydrostatic cloud model is used to investigate the genesis of bow echoes a bow shaped system of convective cells that is especially noted for producing long swaths of damaging surface winds it is hypothesized that severe long lived bow echoes represent a dynamically unique form of mesoconvective organization being produced for a restricted range of environmental conditions including a convective available potential energy cape of at least 2000 m2 s2 and vertical wind shears of at least 20 m s 1 over the lowest 2 5 5 km agl the key structural features include a 40 100 km long bow shaped segment of convective cells with a strong rear inflow jet extending to the leading edge of the bow at 2 3 km agl and cyclonic and anticyclonic eddies referred to as bookend vortices on the northern and southern flanks of the bowed segment respectively this structure characteristically develops three to four hours into the lifetime of a convective system a

structure of a midlatitude squall line formed in strong unidirectional shear abstract data from five doppler radars the surface mesonet aircraft and rawinsondes from the cooperative convective precipitation experiment ccope are used to document the structure and evolution of a squall line with unusually persistent cells and an anvil that spreads downwind in strong upper level westerlies the environmental sounding showed linear shear of 4 m s 1 km 1 through the troposphere a convective available potential energy of 600 m2 s 2 and a convective richardson number of 10 based on the wind in the lowest 6 km the orientation of the squall line comprised of high reflectivity centers spaced 20 40 km apart changed with time initially the squall line axis was normal to the environmental shear but with time it became parallel to the shear vector as the northeastern portion of the subcloud cold dome merged with cold air generated by individual storms that had formed ahead of the line the intensity of the cells within the squads line diminished as its axis became more parallel

warm core vortex amplification over land abstract a convectively generated mesoscale vortex that was instrumental in initiating and organizing five successive mesoscale convective systems over a period of three days is documented two of these convective systems were especially intense and resulted in widespread heavy rain with localized flooding based upon radar and satellite data the detectable size of the vortex became much larger following the strong convective developments nearly tripling its initial diameter over its three day life cycle during nighttime when convection typically intensified within the vortex movement of the system tended to slow following dissipation of the convection in the morning the daytime movement accelerated cross sections of potential vorticity taken through the vortex center clearly show a maximum at midlevels and a well defined minimum directly above the vortex and the potential vorticity maximum were essentially colocated and the system was nearly axisymmetric in the vertical over the three day life

a theory for strong long lived squall lines abstract we study herein the mechanics of long lived line oriented precipitating cumulus convection squall lines using two and three dimensional numerical models of moist convection these models used in juxtaposition enable us to address the important theoretical issue of whether a squall line is a system of special long lived cells or whether it is a long lived system of ordinary short lived cells our review of the observational literature indicates that the latter is the most consistent paradigm for the vast majority of cases but on occasion a squall line may be composed of essentially steady supercell thunderstorms the numerical experiments presented herein show that either type of squall line may develop from an initial line like disturbance depending on the magnitude and orientation of the environmental shear with respect to the line with shallow shear oriented perpendicular to the line a long lived line evolves containing individually short lived cells our analysis of this type o

the initiation and organization of convective cells atop a cold air outflow boundary abstract on 13 july 1986 a cold air outflow from thunderstorms over illinois and missouri propagated through the mist microburst and severe thunderstorm network over northern alabama the study of this outflow is important since the gust front was solely responsible for the initiation of numerous convective cells previous studies have documented the initiation of convection due to colliding gust fronts in addition there was a pronounced mesoscale organization of the cells atop the outflow boundary this was most likely due to a combination of kelvin helmholtz k h and internal gravity ig wave activity in contrast to previous cases the k h wave crests were oriented nearly perpendicular to the gust front within the analysis area the resulting intersections between the circulations associated with the k h waves and the gust front produced favorable locations for the initiation of convection subsequently the convective cells remained along the updraft side of the k h wave circulations as they pro

simulated convective lines with parallel stratiform precipitation part i an archetype for convection in along line shear abstract this article the first of two describing convective lines with parallel stratiform ps precipitation addresses the basic kinematic and precipitation features of these systems the ps mode appears to be the preferred organizational structure in environments with line parallel vertical wind shear this archetype for long lived convective systems has received relatively little attention to date and yet it is frequently implicated in flash flooding because it entails both the along line movement of hydrometeors and back building convective development as a reality check this paper presents conventional observations of the wind and reflectivity fields associated with an archetypal ps system from 2 may 1997 thereafter analyses of idealized numerical simulations serve as the basis for a more detailed investigation of ps systems internal structures and processes the observations and simulations suggest several unique aspects of the ps structure the environment s vertically sheared 3d wind prof

the johnstown flood of july 1977 a long lived convective system abstract the heavy rains responsible for the disastrous flash floods new johnstown pennsylvania on the night of 19 20 july 1977 are shown to be part of a large quasi circular mesoscale convective complex this complex can be traced back to an origin in south dakota nearly 96 h earlier the complex tends to become more compact and intense during the night with a radius of 150 km and to expand in response to new and peripheral convection during the day on the small synoptic scale the system is characterized by a pool of cool air at the surface and throughout the lower troposphere just north of the centroid of the rainstorm by a cyclonic circulation of substantial intensity in the lower and middle troposphere and by anticyclonic circulation in the upper troposphere airflow relative to the moving storm is southeasterly at the surface veering rapidly to southwesterly in the boundary layer and then to westerly in the upper troposphere substantial convective instability is present throughout the env

kinematic and precipitation structure of the 10 11 june 1985 squall line abstract high frequency 90 min rawinsonde data from a special mesoscale network 26 sites have been combined with wind profiler dense automated surface network data 80 stations spaced 50 km apart and a series of high resolution dual doppler radar analyses in a common framework attached to a moving squall line system to form a comprehensive dataset describing the mature phase of the 10 11 june 1985 squall line observed during pre storm the dual doppler radar analyses covered a 200 300 km2 area from the leading edge of the convective line to the back edge of the trailing stratiform precipitation region thus providing high resolution wind information over a very broad portion of the storm system the comprehensive analysis is used to resolve several aspects of the trailing stratiform region that had remained unclear from previous studies first a difference in the horizontal scale was found between the mesoscale updraft which at upper levels was on the scale of the trailing stratiform cloud a

a preliminary morphology of precipitation systems in tropical northern australia a preliminary morphology of convective systems observed in the vicinity of darwin australia is presented several types of tropical convection during monsoonal and break season flow are identified using specific examples and compared with a range of systems observed worldwide in the general context of the bulk richardson number a significant spectrum of convective activity ranging from low shear and low convective available potential energy cape to high shear and moderate to high cape typical of mid latitude severe storms is identified significant differences between monsoonal flow and break season systems are apparent the formation of convective lines perpendicular to the low level shear and the apparent balance between advancing shallow cold pools and the shear are ubiquitous features convective scale downdraughts and mesoscale descent appear to be responsible for redistribution of 700 mb momentum to the planetary boundary layer pel the motion of the break season squall lines appears to result from an equilibrium between the cold pool and the undisturbed environmental pel flow deviations from this balance are hypothesized to result in the observed propagating and non propagating or slow moving modes examples of these modes are given showing the classical continuous development of new cells in a balanced state along the leading edge of long lived squalls and in the propagating case the discontinuous development of new cells on the cold pool ahead of the squall

formation of mesoscale lines of pirecipitation severe squall lines in oklahoma during the spring abstract four distinct kinds of severe mesoscale convective line development are identified in oklahoma during the spring based on the analysis of an 11 year period of reflectivity data from the national severe storms laboratory s 10 cm radar in norman oklahoma the primary classes of fine formation are broken line back building broken areal and embedded areal each is described in detail along with illustrative examples comparisons are made with other observations and with numerical model simulations the former two classes of line formation have been previously documented while the latter two have not only the broken areal squall line has been realistically simulated numerically the environment for each of the types of line development was determined from data from the standard national weather service surface and upper air networks and from special rawinsonde launches it was found that broken line formation tends to occur along cold fronts in a multicell environment while back building occur

structure and evolution of numerically simulated squall lines abstract using a three dimensional numerical cloud model we investigate the effects of vertical wind shear on squall line structure and evolution over a wide range of shear magnitudes depths and orientations relative to the line we find that the simulated squall lines are most sensitive to the magnitude of the component of shear perpendicular to the line and that we may reproduce much of the range of observed structures by varying this single parameter for weak shear a line of initially upright to downshear tilted short lived cells quickly tilts upshear producing a wide band of weaker cells extending behind the surface outflow boundary for moderate to strong shear the circulation remains upright to downshear tilted for longer periods of time with vigorous short lived cells confined to a relatively narrow band along the system s leading edge at later times however these systems may also weaken as the circulation tilts upshear for strong deep shears oriented obliquely to the line the squal

organizational modes of midlatitude mesoscale convective systems this paper discusses common modes of mesoscale convective organization using 2 km national composite reflectivity data the authors investigated linear mesoscale convective systems mcss that occurred in the central united states during may 1996 and may 1997 based upon the radar observed characteristics of 88 linear mcss the authors propose a new taxonomy comprising convective lines with trailing ts leading ls and parallel ps stratiform precipitation while the ts archetype was found to be the dominant mode of linear mcs organization the ls and ps archetypes composed nearly 40 of the studied population in this paper the authors document the characteristics of each linear mcs class and use operational surface and upper air data to describe their different environments in particular wind profiler data reveal that the stratiform precipitation arrangement associated with each class was roughly consistent with the advection of hydrometeors implied by the mean middle and upper tropospheric storm relative winds which were significantly different among the three mcs modes case study examples are presented for both the ls and ps classes which have received relatively little attention to this point as well the authors give a general overview of the synoptic scale meteorology accompanying linear mcss in this study which was generally similar to that observed by previous investigators

seismic hazard in the marmara sea region following the 17 august 1999 izmit earthquake on 17 august 1999 a destructive magnitude 7 4 earthquake occurred 100 km east of istanbul near the city of izmit on the north anatolian fault this 1 600 km long plate boundary 1 2 slips at an average rate of 2 3 cm yr 1 refs 3 5 and historically has been the site of many devastating earthquakes 6 7 this century alone it has ruptured over 900 km of its length 6 models of earthquake induced stress change 8 combined with active fault maps 9 had been used to forecast that the epicentral area of the 1999 izmit event was indeed a likely location for the occurrence of a large earthquake 9 10 here we show that the 1999 event itself significantly modifies the stress distribution resulting from previous fault interactions 9 10 our new stress models take into account all events in the region with magnitudes greater than 6 having occurred since 1700 ref 7 as well as secular interseismic stress change constrained by gps data 11 these models provide a consistent picture of the long term spatio temporal behaviour of the north anatolian fault and indicate that two events of magnitude equal to or greater than the izmit earthquake are likely to occur within the next decades beneath the marmara sea south of istanbul

plate boundary forces are not enough second and third order stress patterns highlighted in the world stress map database 1 the world stress map project compiles a global database of contemporary tectonic stress information of the earth s crust early releases of the world stress map project demonstrated the existence of first order plate scale stress fields controlled by plate boundary forces and second order regional stress fields controlled by major intraplate stress sources such as mountain belts and zones of widespread glacial rebound the 2005 release of the world stress map project database provides for some areas high data density that enables us to investigate third order local stress field variations and the forces controlling them such as active faults local inclusions detachment horizons and density contrasts these forces act as major controls on the stress field orientations when the magnitudes of the horizontal stresses are close to isotropic we present and discuss examples for venezuela australia romania brunei western europe and southern italy where a substantial increase of data records demonstrates some of the additional factors controlling regional and local stress patterns

the effect of vertical wind shear on radiative convective equilibrium states abstract using a three dimensional cloud ensemble model a systematic exploration is undertaken of radiative convective equilibrium states as a function of the structure and magnitude of an imposed background flow with vertical shear in such simulations mesoscale organization appears naturally independent of the particulars of the initial condition as the magnitude of an imposed low level shear increases the convection becomes increasingly organized in lines or arcs propagating broadly downshear as predicted by earlier work when the shear is very strong the convection tends to organize into lines at an angle to the shear such that the line normal component is not far from its theoretical optimal value midlevel shear favors shear parallel lines but if it occurs in conjunction with sufficiently strong low level shear the convection can become very strongly organized into lines or arcs generally orthogonal to the low level shear optimal organization occurs when the depth of the shear layer is c

development and forcing of the rear inflow jet in a rapidly developing and decaying squall line during bamex abstract this study examines the development structure and forcing of the rear inflow jet rij through the life cycle of a small short lived squall line over north central kansas on 29 june 2003 the analyses were developed from airborne quad doppler tail radar data from the noaa and nrl p 3 aircraft obtained over a 2 h period encompassing the formation development and decay of the squall line during the bow echo and mesoscale convective vortex experiment bamex the strengthening of the system relative rear inflow to 17 m s 1 was concurrent with the formation of a bow echo an increased dynamic pressure gradient beneath the rearward tilted updraft and two counterrotating vortices at either end of the bow the later weakening of the rij to 8 m s 1 was concurrent with the weakening of the bow a decreased dynamic pressure gradient at midlevels behind the bow and the weakening and spreading of the vortices in a modeling study weisman quantified the forcing mechanisms responsible for the developm

asymmetric slip partitioning in the sea of marmara pull apart a clue to propagation processes of the north anatolian fault between 1939 and 1999 the north anatolian fault naf experienced a westward progression of eight large earthquakes over 800 km of its morphological trace the 2000 km long north anatolian transform fault has also grown by westward propagation through continental lithosphere over a much longer timescale 10 myr the sea of marmara is a large pull apart that appears to have been a geometrical mechanical obstacle encountered by the naf during its propagation the present paper focuses on new high resolution data on the submarine fault system that forms a smaller pull apart beneath the northern sea of marmara between two well known strike slip faults on land izmit and ganos faults the outstandingly clear submarine morphology reveals a segmented fault system including pull apart features at a range of scales which indicate a dominant transtensional tectonic regime there is no evidence for a single continuous purely strike slip fault this result is critical to understanding of the seismic behaviour of this region of the naf close to istanbul additionally morphological and geological evidence is found for a stable kinematics consistent both with the long term displacement field determined for the past 5 myr and with present day anatolia eurasia motion determined with gps however within the sea of marmara region the fault kinematics involves asymmetric slip partitioning that appears to have extended throughout the evolution of the pull apart the loading associated with the westward propagation process of the naf may have provided a favourable initial geometry for such a slip separation

interaction of an upper tropospheric jet with a squall line originating along a cold frontal boundary abstracton 8 june 2003 an expansive squall line along a surface cold frontal boundary was sampled during the bow echo and mesoscale convective vortex experiment the naval research laboratory p 3 aircraft and the national oceanic and atmospheric administration p 3 aircraft simultaneously sampled the leading and trailing edge of this squall line respectively with x band doppler radars data from these two airborne radar systems have been synthesized to produce a pseudo quad doppler analysis of the squall line yielding a detailed three dimensional kinematic analysis of its structure a simulation of the squall line was carried out using the weather research and forecasting model to complement the pseudo quad doppler analysis the simulation employed a 3 km convection allowing nested domain centered over the pseudo quad doppler domain along with a 9 km parent domain to capture the larger synoptic scale cyclone the pseudo quad doppler analysis reveals that the convective line was embedded within the up

the vertical vorticity structure within a squall line observed during bamex banded vorticity features and the evolution of a bowing segment abstracta quasi linear convective line with a trailing stratiform region developed during the bow echo and mesoscale convective vortex experiment bamex while being sampled by two airborne doppler radars the finescale reflectivity and doppler velocities recorded by the radars documented the evolution of the convective line bands of positive and negative vertical vorticity oriented parallel to the convective line were resolved in the analysis this type of structure has rarely been reported in the literature and appears to be a result of the tilting and subsequent stretching of ambient horizontal vorticity produced by the low level wind shear vector with a significant along line component the radar analysis also documented the evolution of an embedded bow echo within the convective line embedded bow echoes have been documented for a number of years however a detailed analysis of their kinematic structure has not been previously reported in the literature the counterrotating circulation patterns tha

the role of convectively generated rear inflow jets in the evolution of long lived mesoconvective systems abstract in this study the structure of convectively generated rear inflow jets and their role in the evolution of long lived mesoconvective systems are investigated through an analysis of idealized three dimensional simulations using a nonhydrostatic cloud model rear inflow jets are generated within these systems in response to the upshear tilting of the convective circulation as the horizontal buoyancy gradients along the back edge of the expanding system create a circulation that draws midlevel air in from the rear within this framework a wide range of rear inflow strengths and structures are produced depending on the magnitude of the ambient convective available potential energy cape and the vertical wind shear in general for environments characterized by weak to moderate vertical wind shear and weak to moderate cape the rear inflow jet descends and spreads along the surface well behind the leading edge of the gust front and the subsequent convective activity becomes weaker however for e

midlevel cyclonic vortices generated by mesoseale convective systems abstract despite the large number of convective systems that occur over the central united states every year there are typically only a few well defined midlevel vortices apparent in satellite imagery after the overlying anvil debris from some convective complexes has dissipated or advected away a climatology of mesoscale convectively generated vortex mcv events for 1981 1988 is presented and the synoptic setting in which the circulation becomes apparent is discussed proximity sounding data from numerous cases are used to examine features of the kinematic and thermodynamic setting of mcvs at various lifelycle stages defined by satellite imagery features ofthe large scale environment that appear conducive to the formation and longevity of mcvs include weak flow weak vertical shear weak background relative vorticity and intense horizontal and vertical moisture gradients the rapid mesovortex generation observed can be explained by the stretching term of the vorticity equation most mcvs emerge fro

structure and evolution of the 22 february 1993 toga coare squall line aircraft observations of precipitation circulation and surface energy fluxes abstract this study documents the precipitation and kinematic structure of a mature eastward propagating oceanic squall line system observed by instrumented aircraft during the tropical ocean global atmosphere coupled ocean atmosphere response experiment toga coare doppler radar and low level in situ observations are used to show the evolution of the convection from an initially linear nnw sse oriented convective line to a highly bow shaped structure with an embedded low to midlevel counterclockwise rotating vortex on its northern flank in addition to previously documented features of squall lines such as highly upshear tilted convection on its leading edge a channel of strong front to rear flow that ascended with height over a rear inflow that descended toward the convective line and a pronounced low level cold pool apparently fed from convective and mesoscale downdrafts from the convective line rearward the observations of this system showed distinct multiple maxima in updraft strength with

moment tensor inversion of recent small to moderate sized earthquakes implications for seismic hazard and active tectonics beneath the sea of marmara summary we retrieve the moment tensors of 64 small to moderate sized events that occurred mostly beneath the sea of marmara using near field data recorded at strong motion and broad band seismic stations the near field displacement records are inverted to their sources utilizing kuge s method where the best fit between the synthetic and observed seismograms is achieved through searching a centroid moment tensor cmt point in a grid scheme we also analyse the stress fields acting in the eastern and western parts of the sea of marmara by inverting the p and t axes of the focal mechanisms obtained significant biases in the stress tensors are obtained the nearly horizontal maximum compressive axis 1 in the western part is rotated 16 counter clockwise compared with 1 in the eastern part the 2 axis is close to vertical shear tectonic regime in the east and the plunge of 2 axis in the west is 36 transpressive tectonic regime changes in the 3 axis are also observed that is it is close to horizontal in the east and dips 49 in the west the spatial distribution of the focal mechanisms suggests that the stress field in the eastern part of the sea of marmara is homogenous compared with the western part and we identify five distinct subsidiary faults 1 a wnw ese striking right lateral strike slip fault located a few kilometres sw of the princes islands 2 a wsw ene striking right lateral strike slip fault named the yalova hersek fault 3 an e w striking normal fault located onshore between

characterization of aftershock fault plane orientations of the 1999 izmit turkey earthquake using high resolution aftershock locations 1 joint inversion for hypocentral parameters and the velocity field is nowadays a state of the art tool to obtain high resolution images of seismically active regions in this study we focus on the location accuracy of aftershocks of the 1999 mw 7 4 izmit nw turkey earthquake we obtained a new velocity model for the region and depicted its improvement on absolute locations in terms of uncertainty and misfit two well developed aftershock clusters located in the akyazi area and karadere duzce region were analyzed in detail based on a waveform cross correlation approach that allowed improving the location accuracy by a factor of 6 relocation results reveal that hypocenters form narrow planes of activity that can be correlated with focal mechanisms of the larger aftershocks as well as nearby clouds of activity with no internal structure down to the resolved scale of 300 m

midlevel vorticity structure of the 10 11 june 1985 squall line abstract the comprehensive analysis of the kinematic structure of the mature phase of the 10 11 june 1985 squall line system was used to examine the midlevel vertical vorticity structure of the storm to show that relative vertical vorticity in the stratiform region at midlevels was organized into bands both cyclonic and anticyclonic oriented parallel to the convective line with anticyclonic vorticity between the rear of the convective line and the heaviest stratiform precipitation and cyclonic vorticity farther back since previous studies have not found anticyclonic vorticity over such a large portion of the stratiform region at midlevels and since the concentration of anticyclonic vorticity may have been detrimental to the longevity of the storm by limiting the development of an inertially stable cyclonic circulation the tilting and stretching terms of the vertical vorticity equation were computed to determine how the observed vertical vorticity pattern was maintained tilting of horizontal vorticit

a first deep seismic survey in the sea of marmara deep basins and whole crust architecture and evolution abstract increased source strength streamer length and dense spatial coverage of seismic reflection profiles of the seismarmara leg 1 allow to image the deep structure of the marine north marmara trough nmt on the strike slip north anatolian fault naf west of the destructive izmit 1999 earthquake a reflective lower crust and the moho boundary are detected they appear upwarped on an e w profile from the southern central basin eastwards towards more internal parts of the deformed region thinning of the upper crust could use a detachment suggested from an imaged dipping intracrustal reflector that would allow upper crustal material to be dragged from beneath it and above the lower crust accounting for the extensional component but also southwest motion of the southern margin of the nmt sections across the eastern half of the nmt crossing the cinarcik and imrali basins reveal several faults that are active reaching into the basement and have varying strike and proportions of normal and strike slip displacement they might be viewed as petals of a large scale negative flower structure that spreads over a width of 30 km at surface and is rooted deeper in the lithosphere under the central basin a very thick sediment infill is revealed and its extensional bounding faults are active and imaged as much as 8 km apart down to 6 km depth we interpret them as two deep rooted faults encompassing a foundering basement block rather than being merely pulled apart from a jog in a strike slip above a decollement the deep basin lengthening would account for only a modest part of the proposed 60 km finite motion since 4 myr along the same direction oblique to the nmt that sidesteps the shear motion from its two ends thus differential motion occurred much beyond the deep basins like subsidence involving the nmt bounding faults and the intracrustal detachments the complex partitioned motion localized on active faults with diverse natures and orientations is suggested to represent the overburden deformation induced from horizontal plane simple shear occurring in depth at lithospheric scale and in front of the north anatolian fault when it propagated through the region

tornadoes and downbursts in the context of generalized planetary scales abstract in order to cover a wide range of horizontal dimensions of airflow the author proposes a series of five scales maso meso miso to be read as my so moso and muso arranged in the order of the vowels a e 1 o u the dimensions decrease by two orders of magnitude per scale beginning with the planet s equator length chosen to be the maximum dimension of masoscale for each planet mesoscale highs and lows were described on the basis of mesoanalyses while sub mesoscale disturbances were depicted by cataloging over 20 000 photographs of wind effects taken from low flying aircraft during the past 15 years various motion thus classified into these scales led to a conclusion that extreme winds induced by thunderstorms are associated with misoscale and mososcale airflow spawned by the parent mesoscale disturbances

a mesoscale vortex couplet observed in the trailing anvil of a multicellular convective complex abstract observations collected during the oklahoma kansas pre storm experiment are used to document the evolution and structure of a mesoscale vortex couplet that developed in the mesoscale convective system that occurred on 16 17 june 1985 the evolution of the circulations was captured by dual doppler radar observations for 1 4 hours this allowed an evaluation of the various terms of the vertical vorticity equation which give insight into the mechanisms that are important in the generation of the circulations the primary mechanism responsible for the formation of the observed vortices was the interaction of the larger scale flow with low level momentum transported to higher levels by multiple convective updrafts as a consequence vertical shear of the horizontal wind was important to initial vorticity production the vorticity generated in this manner was subsequently increased in strength due to middle level convergence when the convection weakened and dissipated the primary source of vorticity w

rear inflow in squall lines with trailing stratiform precipitation abstract the relative airflow and accompanying precipitation structure of squall lines trailed by mesoscale regions of stratiform rain are examined with emphasis on the occurrence of rear inflow i e the intrusion of environmental air into these storms across the trailing precipitation boundary three cases from kansas and oklahoma provide examples of strong rear inflow which crosses the back edge of the stratiform precipitation area at relative speeds exceeding 10 m s 1 the vertical profiles of relative flow at the trailing precipitation boundary of these three systems were remarkably similar with the rear inflow confined to a jet like layer centered at about 550 mb doppler radar data for two of these cases showed that the rear inflow jet occupied a continuous channel extending from middle levels at the back edge of the stratiform region to lower levels of the leading convective region where it merged with outflow from convective downdrafts to bolster the leading gust front strong front to rea

mesoscale organization of springtime rainstorms in oklahoma abstract radar reflectivity and raingage data obtained during six springtimes indicate the types of mesoscale organization that occur in association with major rain events in oklahoma at least 25 mm of rain in 24 h over an area exceeding 12 500 km2 in these storms the primary rain area is found to be a contiguous region of precipitation 10s to 100s of km in scale that consists partly of deep convection and partly of stratiform rain the patterns of rain formed by the convective and stratiform areas comprise a continuous spectrum of mesoscale structures about two thirds of the cases examined exhibited variations on the type of organization in which convective cells arranged in a moving line are followed by a region of stratiform rain storm organization was graded according to the degree to which it matched an idealized model of this leading line trailing stratiform structure the precipitation pattern was further graded according to whether its structure was relatively symmetric with respect to an a

high winds generated by bow echoes part ii the relationship between the mesovortices and damaging straight line winds airborne radar analysis of a mesovortex that developed near the apex of a bow echo is presented the mesovortex was shown to play a critical role in determining the location of intense straight line wind damage at the surface the perturbation pressure gradient force in natural coordinates along the parcel path accelerated the horizontal winds however intense mesovortices modified the low level outflow and largely determined the locations where the strongest winds occurred regions of maximum winds are accounted for as a superposition of the vortex and the flow in which it is embedded the strongest winds occur on the side of the vortex where translation and rotation effects are in the same direction this model explains the observed tongue of high wind speeds that were confined to the periphery of the mesovortex the origin of the mesovortex is also examined similarities and differences of this bow echo event with recent modeling studies are presented

three dimensional evolution of simulated long lived squall lines abstract simulations of squall lines using nonhydrostatic convection resolving models have been limited to two dimensions or three dimensions with the assumption of along line periodicity the authors present 3d nonhydrostatic convection resolving simulations produced using an adaptive grid model where the lines are finite in length and the restriction to along line periodicity is removed the base state for the simulations is characterized by weak shallow shear and high convective available potential energy cape an environment in which longlived midlatitude mesoscale convective systems mcss are observed the simulated systems bear strong resemblance to many observed systems suggesting that large scale forcing absent in the horizontally homogeneous environment is not needed to produce many of the distinguishing features of midlatitude mcss in simulations without coriolis forcing the presence of line ends leads to mature symmetric systems characterized by a central region of strong convectio

cloud resolving simulations of mesoscale vortex intensification and its effect on a serial mesoscale convective system abstract the authors performed numerical simulations of the 27 28 may 1998 mesoscale convective vortex mcv and mesoscale convective system mcs to understand how the mcv modulated the convection and how the convection intensified the vortex the fifth generation pennsylvania state university national center for atmospheric research psu ncar mesoscale model mm5 was used initialized with the analysis from the rapid update cycle version 2 ruc 2 and nested to achieve 1 5 km grid spacing covering the mcs the model successfully simulated a north south convective band that formed near the center of the mcv in the early evening the simulation then correctly reoriented the convection along a roughly east west line in response to northward transport of warm conditionally unstable air within the nocturnal low level jet balanced vertical motion was found to contribute substantially to mesoscale lifting and thermodynamic destabilization which localized the convection horizontal transport of moist uns

numerical simulation of an intense squall line during 10 11 june 1985 pre storm part i model verification abstract a 24 h nested grid simulation of an intense squall line during the 1985 pre storm experiment is presented using an improved version of the pennsylvania state university national center for atmospheric research three dimensional mesoscale model although the model is initialized at 1200 utc 10 june 1985 with conventional meteorological observations it reproduces remarkably well many observed meso scale features that are analyzed from the high resolution network data these include 1 the generation of two areas of deep convection at the model initial time 2 the timing of the initiation of the squall line along a surface front 9 h into the model integration 3 the development of several convective bands at 2100 utc 4 the rapid intensification and rapid dissipation processes of the squall line as it entered and moved out of the network respectively 5 the generation of a presquall mesolow a squall induced mesohigh and a wake low as well as corresponding multiple surface convergence diverg

geomechanical model of the marmara sea region ii 3 d contemporary background stress field summary we present the contemporary 3 d background stress field of the marmara sea region derived from a geomechanical model the background stress field i e the component of the absolute stress state that is time independent over the seismic cycle primarily depends on the distribution of density and elastic parameters on the acting far field stresses from plate boundary forces and on fault geometries we take these into account to predict the 3 d background stress field including its spatial variations technically our model concept involves the definition of an appropriate initial stress state accounting for the gravitational reference stress state of the crust which is then changed by plate tectonics until the 3 d background stress field has evolved the modelled stress field agrees well with observations from earthquake focal mechanism solutions and their formal stress inversion with orientation of maximum horizontal stress and with the distribution of seismicity in the marmara sea in particular in the vicinity of fault bends the stress field deviates considerably from the regional nw se oriented maximum horizontal stress and exhibits variability of the stress regime our model results are consistent not only with dynamic observations but also with kinematic ones various kinematic observations are understandable from the stress field we show that a stress regime that indicates normal faulting in the basins is nonetheless reconcilable with almost pure strike slip motion on the main marmara fault the distribution of seismicity in the marmara sea can be explained in first order by the distribution of critical differential stress which is closely related to local fault geometries we refer the wide absence of seismicity between the bend of the main marmara fault near istanbul and the central basin to the relatively plane fault geometry of that segment normal stress on the main marmara fault is highly variable along strike which makes segment wise rupture more likely than a rupture of the seismic gap at once comparably low normal stress on the prince s islands segment indicates a shorter interevent time for this fault segment than for the central segment of the main marmara fault

izmit earthquake postseismic deformation and dynamics of the north anatolian fault zone 1 we have modeled postseismic deformation from 1999 to 2003 in the region surrounding the 1999 izmit and duzce earthquake ruptures using a three dimensional viscoelastic finite element method our models confirm earlier findings that surface deformation within the first few months of the izmit earthquake is principally due to stable frictional afterslip on and below the izmit earthquake rupture a second deformation process is required however to fit the surface deformation after several months viscoelastic relaxation of lower crust and or upper mantle with a viscosity of the order of 2 to 5 1019 pa s improves the models fit to later gps site velocities however for a linear viscous rheology this range of values is inconsistent with highly localized interseismic deformation around the north anatolian fault zone nafz that was well observed prior to the earthquake sequence the simplest solution to this problem is to assume that the effective viscosity of the relaxing material increases with time after large earthquakes that is that it has a power law or burger s body transient rheology a burger s body rheology with two characteristic viscosities 2 to 5 1019 pa s and at least 2 1020 pa s in the mantle is consistent with deformation around the nafz throughout the earthquake cycle

an assessment of the transport of atmospheric co2 into the arctic ocean data on concentration of total carbonate together with calcium total alkalinity salinity and temperature from the canadian expedition to study the alpha ridge cesar ice camp the ymer 80 expedition and the 1984 f s polarstern marginal ice zone experiment mizex 84 are used to assess the transport of co2 into the different water masses of the arctic ocean most of this co2 goes into the surface mixed layer and halocline waters a small flux to the atlantic layer is discernible no flux to the deep water could be observed it is possible to separate the carbon input to the arctic ocean into three components carbon from the atmosphere fixed in river drainage basins 40 20 1012 g c a 1 carbon from dissolved mineral calcium carbonate in river drainage basins 40 20 1012 g c a 1 and carbon from the atmosphere fixed over the continental shelves 129 65 1012 g c a 1 from these we estimate the transport of decayed organic carbon from the tundra to the arctic ocean and the new production of 45 20 g c m 2 a 1 for biogenic carbon over the continental shelves of the arctic ocean