numerical simulations of radiative cooling beneath the anvils of supercell thunderstorms abstract numerical simulations of supercell thunderstorms that include parameterized radiative transfer and surface fluxes are performed using the advanced regional prediction system arps to investigate the effects of anvil shadows on the near storm environment if the simulated storm is nearly stationary the maximum low level air temperature deficits within the shadows are about 2 k which is roughly half the cooling found in some previous observations it is shown that the extinction of downwelling shortwave radiation by the anvil cloud creates a differential in the flux of downwelling shortwave radiation between the sun and the shade that is at least an order of magnitude greater than the differential of any other term in either the surface radiation or the surface energy budgets the loss of strong solar heating of the model surface within the shaded regions leads to a reduction of surface temperatures and stabilization of the model surface layer beneath the anvil the reduction in vertical mixing

on the development of above anvil cirrus plumes in extratropical convection abstractexpansive cirrus clouds present above the anvils of extratropical convection have been observed in satellite and aircraft based imagery for several decades despite knowledge of their occurrence the precise mechanisms and atmospheric conditions leading to their formation and maintenance are not entirely known here the formation of these cirrus plumes is examined using a combination of satellite imagery four dimensional ground based radar observations assimilated atmospheric states from a state of the art reanalysis and idealized numerical simulations with explicitly resolved convection using data from 20 recent events 2013 present it is found that convective cores of storms with above anvil cirrus plumes reach altitudes 1 6 km above the tropopause thus it is likely that these clouds represent the injection of cloud material into the lower stratosphere comparison of storms with above anvil cirrus plumes and observed tropopause penetrating convection without plumes reveals an associat

initiation of deep convection over an idealized mesoscale convergence line abstractthis study performs cloud resolving simulations of cumulus convection over an idealized surface based convergence zone to investigate the mechanisms and sensitivities of deep convection initiation forced by mesoscale ascent the surface convergence forms in response to a localized diurnal heating anomaly over an otherwise homogeneous and unheated surface producing a strong boundary layer updraft over the center of the heat source this updraft gives rise to a line of cumuli that gradually deepen and in some cases transition into deep convection to statistically investigate the factors controlling this transition a new thermal tracking algorithm is developed to follow incipient cumulus cores as they ascend through the troposphere this tool is used to isolate the impacts of key environmental parameters cloud layer lapse rate midlevel humidity etc and initial core parameters near cloud base horizontal area vertical velocity etc on the ultimate cloud top height in general the initial

the ayers rock australia earthquake of 28 may 1989 a temporally isolated mb 5 8 intraplate event abstract at 0255 utc on 28 may 1989 an m b 5 8 earthquake shook the yulara resort and uluru national park in the northern territory of australia the epicenter lay 40 km west of ayers rock in an area where moderate size earthquakes had not previously been recorded within 215 km although many people at yulara and uluru were alarmed damage to buildings was minimal the australian national university anu installed an array of 11 seismographs in the epicentral area 6 days after the m b 5 8 event no aftershocks were detected by the anu network during 2 weeks of recording with an estimated detection threshold of magnitude 1 to 0 another group of seismologists who operated a single recorder near uluru beginning 59 hours after the main shock and continuing through july and 6 other recorders for 6 days in early june also failed to observe any aftershocks within the sensitivity of the arrays the ayers rock event was a temporally isolated earthquake the absence of aftershock activity is in sharp contrast to the seismicity pattern following two magnitude 5 2 earthquakes near tennant creek in january 1987 and to other earthquakes of magnitude 4 2 to 6 3 observed in continental intraplate settings worldwide

orogenic convection in subtropical south america as seen by the trmm satellite abstractextreme orogenic convective storms in southeastern south america are divided into three categories storms with deep convective cores storms with wide convective cores and storms containing broad stratiform regions data from the tropical rainfall measuring mission satellite s precipitation radar show that storms with wide convective cores are the most frequent tending to originate near the sierra de cordoba range downslope flow at upper levels caps a nocturnally enhanced low level jet thus preventing convection from breaking out until the jet hits a steep slope of terrain such as the sierra de cordoba mountains or andean foothills so that the moist low level air is lifted enough to release the instability and overcome the cap this capping and triggering is similar to the way intense convection is released near the northwestern himalayas however the intense storms with wide convective cores over southeastern south america are unlike their himalayan counterparts in that they exhibit leadi

the role of vertical wind shear in modulating maximum supercell updraft velocities abstractobserved supercell updrafts consistently produce the fastest mid to upper tropospheric vertical velocities among all modes of convection two hypotheses for this feature are investigated

the influence of upper tropospheric potential vorticity on convective morphology abstract extensive research has illuminated the roles that buoyancy and vertical wind shear have in determining convective mode the goal of this study is to examine synoptic forcing as measured by the form of the waves on the dynamic tropopause and the strength of the resultant temperature advection together with the environmental variables that are currently used to differentiate storm type logistic regression is used to make this discrimination and provides the preliminary results first multicellular lines and isolated rotating cells are associated with weaker synoptic forcing second where an upper level feature is present multicellular convection lines and clusters combined is favored relative to isolated storms when there is stronger synoptic forcing the shape of the upper level potential vorticity pv feature is elongated and there is a more southerly component in the deep layer 0 6 km mean wind third when an upper level feature is present and the convection is multicellular cluste

constraining fault friction by re examining earthquake nodal plane dips we have assembled a catalogue of well constrained focal mechanisms for earthquakes that occurred on continental dip slip faults that have experienced only small displacements during their current phase of activity nodal planes for both reverse and normal faulting events are seen to vary between 30 and 60 and are concentrated towards the centre of this range the observed distributions suggest the reactivation of structures with a low coefficient of friction less than 0 3 and possibly as low as 0 1 we propose that this low coefficient of friction corresponds to the presence of weak materials in pre existing fault zones

aftershocks and surface faulting associated with the intraplate guinea west africa earthquake of 22 december 1983 abstract this study reports on the results of geological and seismological field studies conducted following the rare occurrence of a moderate sized west african earthquake m b 6 4 with associated ground breakage the epicentral area of the northwestern guinea earthquake of 22 december 1983 is a coastal margin intraplate locale with a very low level of historical seismicity the principal results include the observation that seismic faulting occurred on a preexisting fault system and that there is good agreement among the surface faulting the spatial distribution of the aftershock hypocenters and the composite focal mechanism solutions we are not able however to shed any light on the reason s for the unexpected occurrence of this intraplate earthquake thus the significance of this study is its contribution to the observational datum for such earthquakes and for the seismicity of west africa the main shock was associated with at least 9 km of surface fault rupture trending east southeast to east west measured fault displacements up to 13 cm were predominantly right lateral strike slip and were accompanied by an additional component 5 to 7 cm of vertical movement southwest side down the surface faulting occurred on a preexisting fault whose field characteristics suggest a low slip rate with very infrequent earthquakes there were extensive rockfalls and minor liquefaction effects at distances less than 10 km from the surface faulting and main shock epicenter main shock focal mechanism solutions derived from teleseismic data by other workers show a strong component of normal faulting motion that was not observed in the ground ruptures a 15 day period of aftershock monitoring commencing 22 days after the main shock was conducted eleven portable analog short period vertical seismographs were deployed in a network with an aperture of 25 km and an average station spacing of 7 km ninety five aftershocks were located from the more than 200 recorded events with duration magnitudes of about 1 5 or greater analysis of a selected subset 91 of those events define a tabular aftershock volume 26 km long by 14 km wide by 4 km thick trending east southeast and dipping steeply 60 to the south southwest composite focal mechanisms for groups of events distributed throughout the aftershock volume exhibit right lateral strike slip motion on subvertical planes that strike almost due east although the general agreement between the field geologic and seismologic results is good our preferred interpretation is for three en echelon faults striking almost due east west

influence of upper tropospheric inertial stability on the convective transport of momentum this study verifies the apparent high positive correlation between environmental and convection relative inertial stability and the transport of momentum by deep convection we evaluate the hypothesis that convection structurally aligns itself to best access the region of lowest upper tropospheric inertial stability while forming the lowest convective updraught relative inertial stability a numerical experiment evaluates variations in the structure behaviour and momentum transport characteristics of deep convection across the tropical plume genesis region in the eastern pacific this unique region forms as a precursor to tropical plume genesis and possesses spatially varying very low upper tropospheric inertial stability the potential vorticity locally reaches zero or becomes slightly negative in the northern hemisphere our results show that the vertical transport of horizontal momentum is predictable given knowledge of the inertial stability fields immediately surrounding the convection it is conjectured that the preferred mode of convective organization squall line dominated versus more three dimensional near the intertropical convergence zone is a function of the ambient inertial stability therefore as the convection organizes itself it selects the most efficient access to regions of lowest inertial stability to enable its upper tropospheric outflow copyright 2003 royal meteorological society

oceanic intraplate seismicity the occurrence of seismicity at the surface of the globe largely along preferential lines now recognized as mid oceanic ridges and subduction zones was key evidence for the development of the theory of plate tectonics in the 1960s indeed many plate boundaries especially some of the southern less accessible ridges were drawn at least initially on the basis of this evidence alone the mere concept of intraplate seismicity may then appear as somewhat of a paradox if not as a failure of the whole theory however and as shown later in this paper the relatively low level of this seismicity warrants its consideration as a perturbation in the general framework of nearly rigid plates additionally intraplate earthquakes are of great value since in the oceanic environment they are our only clue to the state of stress of the lithosphere thereby providing us with critical insight into the forces responsible for its motion understanding para meters that control these earthquakes is made easier with respect to a continental situation by the generally younger age of the ocean floor and the much simplified tectonic history of any given oceanic province on the other hand seismic detection capabilities are greatly reduced at sea because of both logistics and generally higher seismic attenuation thus our knowledge of many aspects of oceanic intraplate seismicity is still rudimentary it is in this general framework that the present paper reviews the following points

linear and nonlinear propagation of supercell storms abstract a nonlinear formula for updraft motion in supercell storms is derived from petterssen s formula for the motion of systems and the vertical equation of motion and tested on form preserving disturbances at each level continuous propagation of an updraft maximum is determined largely by the horizontal gradient of the nonhydrostatic vertical pressure gradient force nhvpgf at the updraft center the nhvpgf is deduced from the formal solution of the poisson equation for nonhydrostatic pressure in anelastic flow subject to homogeneous neumann boundary conditions at the ground and top boundary recourse also is made to published fields of partitioned vertical pressure gradient force updraft motion is partitioned into parts forced by horizontal gradients of hydrostatic pressure linear interaction between the environmental shear and updraft and nonlinear dynamical effects the dynamics of supercell storms for nearly straight and highly curved hodographs are found to be different nonlinear rotation

low level mesovortices within squall lines and bow echoes part i overview and dependence on environmental shear this two part study proposes fundamental explanations of the genesis structure and implications of lowlevel meso g scale vortices within quasi linear convective systems qlcss such as squall lines and bow echoes such mesovortices are observed frequently at times in association with tornadoes idealized simulations are used herein to study the structure and evolution of meso g scale surface vortices within qlcss and their dependence on the environmental vertical wind shear within such simulations significant cyclonic surface vortices are readily produced when the unidirectional shear magnitude is 20 m s 21 or greater over a 0 2 5 or 0 5 km agl layer as similarly found in observations of qlcss these surface vortices form primarily north of the apex of the individual embedded bowing segments as well as north of the apex of the larger scale bow shaped system they generally develop first near the surface but can build upward to 6 8 km agl vortex longevity can be several hours far longer than individual convective cells within the qlcs during this time vortex merger and upscale growth is common it is also noted that such mesoscale vortices may be responsible for the production of extensive areas of extreme straight line wind damage as has also been observed with some qlcss surface vortices are also produced for weaker shears but remain shallow weak and short lived although similar in size and strength to mesocyclones associated with supercell storms and also sometimes producing similar hooklike structures in the rain field it is also shown that the present vortices are quite distinct structurally and dynamically most critically such vortices are not associated with long lived rotating updrafts at midlevels and the associated strong dynamically forced vertical accelerations as occur within supercell mesocyclones

normal faulting in the upper continental crust observations from regions of active extension abstract observations of present day normal faulting in regions of active continental extension may be helpful when interpreting the geological record in older extensional basins the most obvious manifestation of active extension is normal faulting in earthquakes earthquake foci are mostly confined to the upper seismogenic continental crust whose thickness imposes a scale on the observed deformation large earthquakes move faults with lengths similar or large compared with the thickness of the seismogenic layer large seismogenic normal faults on the continents appear to be restricted to a dip range of around 30 60 dips significantly gentler than 20 have not been observed in fault plane solutions of large earthquakes large seismographic normal faults are approximately planar in cross section and cut through the base of the upper seismogenic layer rotating about a horizontal axis as they move a reasonable estimate of the regional extension can often be made from the dip of the large normal faults and the tilt of the blocks they bound the domino model such faults are rarely continuous for more than 15 20 km but commonly change strike or step in an en echelon fashion this segmentation may occur on a scale controlled by the thickness of the seismogenic layer and is an important influence on sedimentation and drainage these observations are common to large seismogenic normal faults from a variety of tectonic settings and suggest that the kinematics of normal faulting may not be strongly influenced by the forces responsible for the extension which can vary widely in nature and magnitude small earthquakes which move faults that are small compared with the seismogenic layer thickness show no simple pattern and often can be interpreted as internal deformation of blocks bounded by large faults in some places the seismogenic basement faults do not reach the surface but are decoupled from the sedimentary cover by layers of weak lithology faults in the sedimentary cover may be strongly curved in cross section requiring their hangingwalls to deform internally estimating extension from such faults is not straightforward and requires a knowledge of the hangingwall deformation estimates made in this way are often very non unique and prone to large errors we postulate that the thickness of the seismogenic upper crust controls both the maximum length of large normal fault segments along strike and the maximum size of blocks that can rotate coherently about a horizontal axis

the dependence of numerically simulated convective storms on vertical wind shear and buoyancy abstract the effects of vertical wind shear and buoyancy on convective storm structure and evolution are investigated with the use of a three dimensional numerical cloud model by varying the magnitude of buoyant energy and one directional vertical shear over a wide range of environmental conditions associated with severe storms the model is able to produce a spectrum of storm types qualitatively similar to those observed in nature these include short lived single cells certain types of multicells and rotating supercells the relationship between wind shear and buoyancy is expressed in terms of a nondimensional convective parameter which delineates various regimes of storm structure and in particular suggests optimal conditions for the development of supercell type storms applications of this parameter to well documented severe storm cases agree favorably with the model results suggesting both the value of the model in studying these modes of convection as well as the value of this representation i

the 8 june 1995 mclean texas storm part ii cyclic tornado formation maintenance and dissipation abstract on 8 june 1995 scientists participating in the verification of the origins of rotation in tornadoes experiment vortex collected a unique dataset with the electra doppler radar eldora the eldora observations document the sequential life cycles of storm scale circulations associated with three large tornadoes in a supercell thunderstorm near mclean texas a qualitative description of the evolution of the storm was provided in part i of this paper during the first stage of development of each storm scale circulation interaction of the updraft with the environmental low level horizontal vorticity produced a vorticity column that increased in intensity with height as the vortex matured vorticity increased greatly at low levels i e below 2 km agl and exceeded that aloft each tornadic vortex was located near the rear side of the updraft where the surrounding low level horizontal vorticity was modified locally most likely by weak baroclinity within the storm tilting of low level horizo

the evolution of convective storms initiated by an isolated mountain ridge abstractthe evolution of convective storms over the black hills an isolated mountain ridge in south dakota and wyoming and a regional convection hotspot is investigated using a 10 yr observational climatology and quasi idealized numerical simulations radar observed diurnally forced mountain convection events are classified according to their maximum cell track length and duration which are quantified using an automated cell tracking algorithm environmental conditions during these events are obtained from operational radiosonde and model analysis data these data suggest that mountain forced convective cells generally struggle to survive in the convectively inhibited flow downwind of the black hills those cells that do survive downwind prefer environments with strong bulk vertical shear over the 0 6 km layer which favors organized multicellular or supercellular convection under slightly weaker shear the cells tend to dissipate rapidly as they propagate downwind relatively weak winds aloft when c

numerical simulation of tornadogenesis in a high precipitation supercell part i storm evolution and transition into a bow echo abstract a nested grid primitive equation model rams version 3b was used to simulate a high precipitation hp supercell which produced two weak tornadoes six telescoping nested grids allowed atmospheric flows ranging from the synoptic scale down to the tornadic scale to be represented in the simulation all convection in the simulation was initiated with resolved vertical motion and subsequent condensation latent heating from the model microphysics no warm bubbles or cumulus parameterizations were used part i of this study focuses on the simulated storm evolution and its transition into a bow echo the simulation initially produced a classic supercell that developed at the intersection between a stationary front and an outflow boundary as the simulation progressed additional storms developed and interacted with the main storm to produce a single supercell this storm had many characteristics of an hp supercell and eventually evolved into a bow echo with a rotating comma head structure an analysi

source parameters of earthquakes along the coastal margin of west africa and comparisons with earthquakes in other coastal margin settings abstract the coastal margins of western africa and most of the eastern americas are considered to be stable continental interiors where large earthquakes occur infrequently since these regions have similar geologic and tectonic histories it might seem reasonable to expect similarities between their large earthquakes on the other hand current plate forces acting on these regions differ and may lead to regional differences in earthquakes to examine the similarities of coastal margin earthquakes we first determined the source parameters for six earthquakes of m 5 5 occurring along the coastal margin of west africa a region that has not previously been studied in detail results of this analysis indicate that the earthquakes are shallow 8 15 km strike slip events along high angle faults dips generally 80 with nodal planes having orientations similar to those of faults mapped in the exposed precambrian basement five out of seven events show complexities in their source time functions east of the cameroon line most p axes trend northeast southwest to east west earthquakes west of the cameroon line show less coherency of stress field with p axes for onshore events trending northwest southeast and for offshore events north south to northeast southwest in contrast m 5 5 earthquakes of the eastern coastal margin of north and south america have reverse mechanisms with more moderate dips on nodal planes 45 70 and over 50 have east west oriented p axes which reflect stresses caused by the motion of north and south america relative to europe and africa in north america earthquakes appear to occur on faults that cannot be associated with surficial geology occur shallower or deeper than west african events and have shorter rupture lengths for the equivalent moment these differences suggest that west african events may not serve as useful analogs for events expected along the american coastal margin

a simple model of convective drafts accounting for the perturbation pressure term abstracta simple anelastic two column model of convective updraft accounting explicitly for the perturbation pressure term is developed there is no vertical wind shear in the environment and two

estimating mass and momentum fluxes in a line of cumulonimbus using a single high resolution doppler radar we present a method to derive the vertical wind field at a scale of 1 2 km from a high resolution doppler radar by performing vertical scans in the plane of the mean wind and tracking turbulent features on a scale of several hundred metres in the radial velocity field between consecutive scans the method is applied to a line of cumulonimbus clouds observed by the high resolution chilbolton radar in southern england the storm was not a squall line since it was propagating parallel rather than perpendicular to its length a sequence of scans was taken over an hour long period from these scans we derive the u and w components of the wind updraughts of up to 15 m s 1 are found from these observations the mass flux of a typical storm cell was estimated over the 50 min lifetime of the cell the total mass of air transported from the boundary layer to the upper troposphere was found to be around 50 megatonnes the profile of hour averaged momentum flux against height was then calculated and compared to the vertical shear of the mean horizontal wind it was found that above 4 5 km the momentum flux was down gradient with an equivalent eddy diffusivity of around 103 m2s 1 below this height however the flux was counter gradient with an equivalent eddy diffusivity of around 103m2s 1 we propose a mechanism to explain this behaviour involving the prevalence of precipitation cooling and descent on the downshear side of convergence lines a synthesis of the major wind flows in the storm reveals that despite superficial appearance the storm did not fit the usual multi cell paradigm in which gust fronts play a key roll in triggering new cells downwind rather the convergence lines associated with the convection were more akin to warm frontal surfaces that remain tied to the base of each cell new cells tending to form upwind of older cells copyright 2008 royal meteorological society

towards a new hybrid cumulus parametrization scheme for use in non hydrostatic weather prediction models classical mass flux parametrization schemes for cumulus convection generally transport heat and moisture only but do not include a net mass transport this is well justified for large grid spacings comprising the whole convective circulation in the local grid column such that all convective mass fluxes locally cancel out a conceptual problem arises for finer grid spacings as used in contemporary numerical weather prediction nwp models when convection becomes partially resolvable this problem can be overcome by the hybrid approach presented here only updraft and downdraft are parametrized with a net mass transport the environmental subsidence is treated by the grid scale equations the total mass flux in the continuity equation is split into a grid scale and a subgrid scale contribution this parametrization scheme is designed for use in any nonlinear non hydrostatic and fully compressible nwp model we here have chosen the lokal modell lm of deutscher wetterdienst idealized dry mass lifting experiments without convective heat transport demonstrate the feasibility of the hybrid approach entrainment causes grid scale convergence and the detrained air if set to the environmental temperature spreads mainly horizontally on the grid gravity waves are generated when convection starts and ends whereas their amplitude depends on the details of the switching on and off of convection the stationary state after about 30 minutes does not four model runs with different grid spacings 3 5 km to 28 km confirm that the mass exchange between the model grid and the parametrization scheme is independent of the chosen grid spacing total mass in a convective circulation cell is conserved to better than 0 1 but only if the damping layer at the upper boundary of the lm is shifted to above 20 km for moist convection with convective heat transport a simple cloud model for an updraft has been set up as the detrained air at the cloud top is colder than the environment it moves down by about 1 km but then mainly spreads horizontally again over several tens of kilometres as in the dry case without convective heat transport the hybrid mass flux approach with both a grid scale and a subgrid scale contribution may fill the gap between coarse grid models grid spacing 50 km with classical parametrization schemes and very highly resolved explicit convection modelling with a grid spacing of the order of 100 m copyright 2007 royal meteorological society

an example of the relationship between rift and dome recent geodynamic evolution of the hoggar swell and of its nearby regions central sahara southern algeria and eastern niger abstract from essential gravimetrical and petrological data we propose a new model of geodynamic evolution for the volcanic hoggar swell and its nearby regions the eastern hoggar the tenere troughs and the north hoggar troughs correspond to a single distensive structure which developed during the late mesozoic by reactivation of n s and nw se trending pan african faults in response to the stress field probably associated with the central atlantic opening contemporaneously as suggested by the xenoliths entrained by the cenozoic alkali basaltic eruptions of the eastern hoggar an extensive lower crustal basic magmatism of tholeiitic affinity and probably associated with crustal stretching may have developed beneath the hoggarian part of this distensive structure on the other hand at the hoggar level a transverse lineament oriented ne sw oued amded cross cuts the distensive structure this lineament subsequently controlled the localization of the mio plio quaternary volcanic districts and possibly upper mantle modifications through reheating partial melting metasomatism and magmatic veining produced by astenospheric material transfer gas fluid kimberlitic to carbonatitic magmas resulting in a density reduction on the other hand the high deformation of the peridotitic inclusions of the cenozoic alkali basalts emplaced along the oued amded lineament may indicate that this lineament has also controlled the emplacement of small sized asthenospheric diapirs into the upper mantle thus in the hoggar it appears that doming was probably preceded by a rifting phase and that doming and cenozoic volcanism were possibly controlled by the intersection of this rift by a transverse wrench fault

some seismological and geometric features of intraplate earthquakes to understand the nature and cause of intraplate earthquakes we carried out a systematic search for common features associated with them various geological geophysical and seismic data were analyzed and geometric and seismic parameters were compared for 29 intraplate events m 4 5 occurring worldwide the results suggest that intraplate earthquakes occur by the reactivation of pre existing zones of weakness in a compressional stress regime which is generally oriented parallel to the absolute direction of plate motion two styles of faulting were observed for type a earthquakes observed in the eastern united states eastern china western europe and west africa deformation occurs by strike slip motion on steeply dipping faults type b events are usually associated with thrust or normal faulting and were observed in eastern canada fennoscandia australia and peninsular india focal depths did not explain the differences between type a and type b earthquakes rather the differences are due to the perturbation of a regional stress field by a local stress field the regional stress field for type a events is primarily due to ridge push forces the method of stress perturbation varied from region to region the earthquakes in the type b category were further divided into three subcategories type b1 occurring in eastern canada and fennoscandia type b2 occurring in australia peninsular india and central brazil and type b3 occurring in the gulf coast of the u s the inferred causes of the perturbing stresses are deglaciation intracontinental resistive forces resulting from the collision of plates and the deposition of a large thickness of sediments respectively type a events were found to be associated with intersecting faults and generally supported the intersection model of talwani 1988 and had analogs in plate boundary events

some characteristics of thunderstorms over bathurst and melville islands near darwin australia a study defining the occurrence structure and evolution of maritime continent island thunderstorms over bathurst and melville islands near darwin australia is presented satellite data for the november december pre monsoon transition season show unambiguous records of island thunderstorms on at least 65 of days over the period 1978 1986 storms develop most commonly between 1230lst and 1530lst and radar data indicate a mean lifetime of 2 5 h non occurrence was found on only 7 of the days examined and was associated with a return to dry flow typical of the early transition season with middle level subsidence or suppressed conditions in the wake of previous convective activity environmental sounding data indicated that these maritime continent thunderstorms develop in a regime with moderate cape low to moderate shear and high moisture the dynamic regime is characteristic of multicellular storms examination of the evolution of the storms indicates the existence of a typical lifecycle but with considerable variability in detail initially the lifecycle is consistent with the multicellular storm concept but the developing storms tend to aggregate to form one or more mesoscale systems which in turn may develop into propagating squall lines in the mature stage the developing storms have preferred geographic regions of genesis and intensification over the islands and while motion of the storms is variable it is generally consistent with the mean surface to 700mb pressure weighted flow

electrical and multiparameter radar observations of a severe hailstorm using data from the 11 cm csu chill multiparameter radar the simultaneous evolution of the radar inferred precipitation structure and electrical characteristics of a severe hailstorm is investigated we compare the substorm point discharge current intracloud ic lightning flash rate cloud to ground cg lightning flash rate ground strike location and flash polarity to the progression of precipitation types and amounts this study is unique in that it presents multiparameter radar observations of a thunderstorm complex which exhibited an extremely high ic to cg ratio ic cg 20 70 and predominantly positive cg lightning over 74 after it became severe producing large hail and weak tornadoes in particular we investigate the reported relationship between large hail and positive cg lightning although a direct correlation is found between a rapid increase in ic cg the first positive cg lightning flashes and the initial production of hail aloft the temporal and spatial behavior of large hail and positive cg lightning appear to be anticorrelated as broad peaks in the positive cg flash rate lag relative maxima in the fallout of large hail by up to 30 min the majority of positive ground strikes were adjacent to the main precipitation core in a region of light rain and little or no hail at the surface aloft radar data indicated that ice crystals were aligned vertically in a strong electric field corona point observations at the surface indicate that these regions adjacent to the convective core were characterized by net positive charge aloft possible mechanisms to explain these observations are discussed

is buoyancy a relative quantity basic concepts of buoyancy are reviewed and considered first in light of simple parcel theory and then in a more complete form it is shown that parcel theory is generally developed in terms of the density temperature difference between an ascending parcel and an environment surrounding that parcel that is buoyancy is often understood as a relative quantity that apparently depends on the choice of a base state environmental profile however parcel theory is most appropriately understood as a probe of the static stability of a sounding to finite vertical displacements of hypothetical parcels within the sounding rather than as a useful model of deep convection the thermal buoyancy force as measured by the temperature difference between a parcel and the base state and vertical perturbation pressure gradient force together must remain independent of the base state the vertical perturbation pressure gradient force can be decomposed to include a term due to thermal buoyancy and another due to the properties of motion in the flow some thought experiments are presented to illustrate the ambiguous relevance of the base state it is concluded that buoyancy is not a relative quantity in that it cannot be dependent on the choice of an essentially arbitrary reference state buoyancy is the static part of an unbalanced vertical pressure gradient force and as such is determined locally not relative to some arbitrary base state outside of a parcel this has direct application to the diagnosis of buoyancy from numerical simulations done properly such a diagnosis must include not only the thermal buoyancy term but also the perturbation pressure gradient force due to buoyancy

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

the dependence of storm longevity on the pattern of deep convection initiation in a low shear environment the sensitivity of storm longevity to the pattern of deep convection initiation e g multiple quasi linearly arranged initial deep convective cells versus an isolated deep convective cell is examined using idealized cloud resolving simulations conducted with a low shear initial environment when multiple deep convective cells are initialized in close proximity to one another using either a line of thermals or a shallow airmass boundary long lived storms are produced however when isolated deep convection is initiated the resultant storm steadily decays following initiation these results illustrate that a quasi linear mechanism such as a preexisting airmass boundary that initiates multiple deep convective cells in close proximity can lead to longer lived storms than a mechanism that initiates isolated deep convection the essential difference between the experiments conducted is that an isolated initial storm produces a shallower cold pool than when a quasi linear initiation is used it is argued that the deep cold pools promote deep forced ascent systematic convective cell redevelopment and thus long lived storms even in environments with small values of vertical shear the difference in cold pool depth between the simulations is attributed to differences in the horizontal flux of cold air to the gust front with a single initial storm the few convective cells that subsequently form provide only a limited source of cold air leading to a cold pool that is shallow and incapable of fostering continued updraft redevelopment

damaging surface wind mechanisms within the 10 june 2003 saint louis bow echo during bamex abstract detailed radar and damage survey analyses of a severe bow echo event that occurred on 10 june 2003 during the bow echo and mesoscale convective vortex mcv experiment are presented a bow echo formed just east of saint louis missouri and produced a continuous straight line wind damage swath approximately 8 km in width and 50 km in length along with five f0 f1 tornadoes careful superposition of the damage survey analysis and weather surveillance radar 1988 doppler wsr 88d data from saint charles missouri klsx showed that the primary straight line wind damage swath was not collocated with the bow echo apex as has been suggested in previous studies rather the primary damage swath was found north of the bow apex collocated with a low level vortex that formed on the leading edge of the bow echo much of the primary damage swath appeared to have been created by the low level vortex moreover most of the surface straight line wind damage was generated during the early stages of bow echo mo

burial history and thermal evolution of the northern and eastern saharan basins the numerical one dimensional reconstruction of the burial history and thermal evolution of the sedimentary section and basement was conducted for 32 wells in the east algerian basins with the help of the galo basin modeling system these reconstructions allowed the performance of a quasi two dimensional analysis of the burial history of the basins changes in rock temperatures the lithosphere thickness and maturation conditions of organic matter during basin development along the four profiles crossing the study region the modeling assumed that the highest thermal activation in the history of the saharan basins with the heat flow more than 100 mw m2 and the thinnest lithosphere on the order of 25 35 km took place during the late carboniferous to permian in the dahar and oued el mya basins the uplift responsible for this activation caused erosion of 2000 3000 m of ordovician to lower carboniferous strata the ghadames and illizi basins were subjected at the same time to more moderate erosion and thermal activation with heat flow less than 75 mw m2 in the triassic cretaceous interval maximum subsidence occurred in the northern areas which were characterized by maximal thermal activation and the thinnest lithosphere in the permian at present the situation is opposite to that in the permian the highest thermal regime occurs in the southern areas of the study region and especially in the illizi basin where heat flow reaches and even exceeds 100 mw m2 and the thickness of the lithosphere decreases as much as 30 km the modeling also assumes stretching of the lithosphere in the northeastern and central parts of the illizi basin with maximal amplitude of about 1 16 during the cenozoic the analysis shows that the hercynian erosion could account for only a few of the abrupt changes in vitrinite profiles in the saharan basins and that triassic and later intrusive activity and associated hydrothermal heat transfer accurately explain the steplike character of maturation profiles

the inverse problem in microtectonics and the separation of tectonic phases abstract the algorithm of inverse problems is applied to three cases in microtectonics a collection of striations measured on pre existing faults may be processed automatically and interpreted in terms of tectonic stress a comparison is made between two different methods formerly proposed by the authors both methods are tested with field data the theoretical results agree with independent field criteria for a separation of tectonic phases

properties of a simulated convective boundary layer in an idealized supercell thunderstorm environment abstractnearly all previous numerical simulations of supercell thunderstorms have neglected surface fluxes of heat moisture and momentum this choice precludes horizontal inhomogeneities associated with dry boundary layer convection in the near storm environment as part of a broader study on how mature supercell thunderstorms are affected by a convective boundary layer cbl with quasi two dimensional features i e boundary layer rolls this paper documents the methods used to develop a realistic cbl in an idealized environment supportive of supercells the evolution and characteristics of the modeled cbl including the horizontal variability of thermodynamic and kinematic quantities known to affect supercell evolution are presented the simulated rolls result in periodic bands of perturbations in temperature moisture convective available potential energy cape vertical wind shear and storm relative helicity srh vertical vorticity is shown to arise within the boundary layer through the tilt

self consistent earthquake fault scaling relations update and extension to stable continental strike slip faults using seismic moment m length l data for stable continental region scr faults augmented by data not included in previous studies this article reassesses and confirms the bilinear scaling relation for the dip slip faults of leonard 2010 furthermore using the new data i propose a separate bilinear relation for estimating magnitude from surface rupture length there are now a small number of scr strike slip earthquakes for which the fault dimensions have been estimated i use these to constrain a trilinear scaling relation for this class of fault for the four fault types interplate dip slip interplate strike slip scr intraplate dip slip and scr intraplate strike slip the scaling relations for the 10 permutations of m d l w and a are given

mesoscale dynamics in the palm sunday tornado outbreak abstract radar and satellite imagery suggest that strong mesoscale forcing occurred in the palm sunday tornado outbreak on 27 march 1994 parallel lines of severe thunderstorms within each of three mesoscale convective systems developed just ahead of a cold front in mississippi and alabama on this date analyses of routine meteorological observations barograph data and forecasts from the eta and ngm models and a mesoscale research model mass are used to examine the relative roles of large scale dynamics and mesoscale processes in triggering and organizing the mesoscale convection quasigeostrophic forcing was absent in the outbreak region likewise a thermally direct circulation system transverse to the upper level jet that was present to the northwest of the outbreak region was decoupled from the strong low level ascent occurring in northern alabama and mississippi at the time of the outbreak strong ageostrophic frontogenesis in the presence of conditional symmetric instability csi was the chief

tropical convection the effects of ambient vertical and horizontal vorticity we present a series of idealized numerical model experiments to investigate aspects of deep convection in tropical depressions including the effects of boundary layer wind structure on storm structure especially on vertical vorticity production and updraught splitting and the combined effects of horizontal and vertical shear on vertical vorticity production with and without background rotation in warm cored disturbances such as tropical depressions the vertical shear and horizontal vorticity change sign at some level near the top of the boundary layer so that unlike in the typical middle latitude supercell storm the tilting of horizontal vorticity by a convective updraught leads not only to dipole patterns of vertical vorticity but to a reversal also in sign of the updraught rotation with height this finding has implications for understanding the merger of convectively induced vorticity anomalies during vortex evolution ambient cyclonic horizontal shear and or cyclonic vertical vorticity favour amplification of the cyclonically rotating gyre of the dipole consistent with an earlier study storm splitting occurs in environments with pure horizontal shear as well as pure vertical shear but the morphology of splitting is different in both situations splitting is found to require a relatively unstable sounding and relatively strong wind shear

dynamical influences of anvil shading on simulated supercell thunderstorms abstractnumerical simulations of supercell thunderstorms including parameterized radiative transfer and surface fluxes are performed using the advanced regional prediction system arps model to investigate how low level air temperature deficits within anvil shadows affect the simulated storms the maximum temperature deficits within the modeled cloud shadows are 1 5 2 0 k which is only about half that previously observed within the shadows the loss of strong solar heating cools and stabilizes the near surface layer which suppresses vertical mixing and modifies the near surface vertical wind shear in a case of a stationary storm the enhanced easterly shear present beneath the anvil leads to a thinning of the outflow layer and corresponding acceleration of the rear flank gust front far ahead of the overlying updraft weakening the low level mesocyclone it is further shown that the direct absorption and emission of radiation by clouds does not significantly affect the simulated supercells varying th

experimental evidence for the formation of liquid saline water on mars evidence for deliquescence of perchlorate salts has been discovered in the martian polar region while possible brine flows have been observed in the equatorial region this appears to contradict the idea that bulk deliquescence is too slow to occur during the short periods of the martian diurnal cycle during which conditions are favorable for it we conduct laboratory experiments to study the formation of liquid brines at mars environmental conditions we find that when water vapor is the only source of water bulk deliquescence of perchlorates is not rapid enough to occur during the short periods of the day during which the temperature is above the salts eutectic value and the humidity is above the salts deliquescence value however when the salts are in contact with water ice liquid brine forms in minutes indicating that aqueous solutions could form temporarily where salts and ice coexist on the martian surface and in the shallow subsurface

comparison of source scaling relations of eastern and western north american earthquakes source scaling relations have been obtained for earthquakes in eastern north america and other continental interiors and compared with a relation obtained for earthquakes in western north america the scaling relation for eastern north american earthquakes was constructed from measurements of seismic moment and source duration obtained by the waveform modeling of seismic body waves the events used include nine events of m blg magnitude 4 7 to 5 8 that occurred after 1960 and four earlier events with magnitudes between 5 5 and 6 6 the scaling relation for events in other continental interiors was used for comparative purposes and to provide constraints for large magnitudes detailed analysis of the uncertainties in the scaling relations has allowed the resolution of two important issues concerning the source scaling of earthquakes in eastern north america first the source characteristics of earthquakes in eastern north america and other continental interiors are consistent with constant stress drop scaling and are inconsistent with nonconstant scaling models such as that of nuttli 1983 second the stress drops of earthquakes in eastern north america and other continental interiors are not significantly different from those of earthquakes in western north america and have median values of approximately 100 bars the source parameters of earthquakes in eastern north america are consistent with a single constant stress drop scaling relation whereas the source parameters of earthquakes in western north america are much more variable and show significant departures from an average scaling relation in which stress drop decreases slightly with seismic moment

seismic moment assessment of earthquakes in stable continental regions ii historical seismicity summary this part i study in conjunction with part 11 develops a method to determine within specified uncertainty bounds the seismic moment and thus moment magnitude of all earthquakes of stable continental regions scr for which instrumental or intensity data exist its basis is polynomial regression analysis using a database of scr earthquakes with direct seismic moment determination the independent variables include modern teleseismic magnitudes and regional magnitudes part i and isoseismal areas or number of recording stations part 11 part i11 is an application of the methodology of parts i and i1 to several major historical earthquakes all data used in the regressions are assigned individual uncertainties estimated from the literature or from experience formal confidence limits 68 per cent or 95 per cent on both the regression formulas and the predicted seismic moment values are then possible via error propagation analysis the most complete development is for the teleseismic magnitudes m and mb for both the final regression for log m is a quadratic formula that closely emulates the relationship between amplitude magnitudes and log m expected from dislocation theory and source scaling arguments regressions are also derived for the regional magnitudes mlg and m because there are many scr events mainly pre 1964 that have no teleseismic magnitudes prediction uncertainties from teleseismic magnitudes in moment magnitude units are in the ao 18 0 28 range and from regional magnitudes in the ko 23 0 38 range over a wide magnitude band finally the methodology developed here is generic even though the database is specific application to plate boundary oceanic intraplate or active continental intraplate regions should be straightforward

enregistrement sedimentaire d un episode d approfondissement brutal de la marge sud guineenne au quaternaire recent abstract during the equamarge ii cruise 1988 along the guinean continental margin central equatorial atlantic a 2 17 m long core has been sampled at 840 m water depth on the top of one of the volcanic seamounts cropping out in this area planktonic foraminiferal assemblages observed within the 2 13 m unconsolidated sediments indicate an age of 0 20 to 0 15 ma corresponding to the transition from interglacial to glacial events depth of deposition of the calcareous sand ranges between 150 200 m and progressively decreased during the glacial stage onset detailed sedimentological and micropaleontological studies carried out on the 4 cm thick indurated core cap indicate a deposition depth of 50 100 m or even less taking into account the pleistocene sea level fluctuations these data suggest a rapid subsidence of the magmatic seamount since the upper most pleistocene

a possible mechanism of tornadogenesis associated with the interaction between a supercell and an outflow boundary without horizontal shear abstractusing the insert restart method developed in this study tornadogenesis processes associated with the interaction between a supercell and an outflow boundary were investigated a highly idealized outflow boundary promoted surface vortex intensification in a preconditioned supercell having a strong surface vortex in particular a tornado like vortex was observed in an experiment with a moderate outflow boundary this intensification was associated with the enhancement of the near surface horizontal convergence by the outflow boundary the optimal coldness of the outflow boundary was explained by the balance between the enhancement of the near surface horizontal convergence and the buoyancy reduction by the outflow boundary sensitivity experiments demonstrated that despite a less favorable environment a storm with a boundary interaction might reach a similar maximum near surface vorticity as a storm without a boundary in a more favorable environment

seismotectonics of the guinean earthquake of december 22 1983 field geological and seismological investigations conducted after the guinean earth quake on december 22 1983 show a shallow dextral strike slip fault with a large normal component the nw se horizontal compressive stress deduced from this event is consistent with measurements made at other places in this region old fissures some of them reactivated during this earthquake show that this intraplate area cons titutes a localized weakness zone in the crust

paleoseismicity of two historically quiescent faults in australia implications for fault behavior in stable continental regions paleoseismic studies of two historically aseismic quaternary faults in australia confirm that cratonic faults in stable continental regions scr typically have a long term behavior characterized by episodes of activity separated by quiescent intervals of at least 10 000 and commonly 100 000 years or more studies of the approximately 30 km long roopena fault in south australia and the approximately 30 km long hyden fault in western australia document multiple quaternary surface faulting events that are unevenly spaced in time the episodic clustering of events on cratonic scr faults may be related to temporal fluctuations of fault zone fluid pore pressures in a volume of strained crust the long term slip rate on cratonic scr faults is extremely low so the geomorphic expression of many cratonic scr faults is subtle and scarps may be difficult to detect because they are poorly preserved both the roopena and hyden faults are in areas of limited or no significant seismicity these and other faults that we have studied indicate that many potentially hazardous scr faults cannot be recognized solely on the basis of instrumental data or historical earthquakes although cratonic scr faults may appear to be nonhazardous because they have been historically aseismic those that are favorably oriented for movement in the current stress field can and have produced unexpected damaging earthquakes paleoseismic studies of modern and prehistoric scr faulting events provide the basis for understanding of the long term behavior of these faults and ultimately contribute to better seismic hazard assessments

dual doppler and single doppler analysis of a tornadic storm undergoing mergers and repeated tornadogenesis abstract dual doppler observations with unprecedented finescale spatial and temporal resolution are used to characterize the vector wind field in and near a tornado occurring near kiefer oklahoma on 26 may 1997 analyses of the dual doppler vector wind fields document in detail for the first time several structures associated with the tornado a proximate updraft region a rear flank downdraft wrapping around the tornado a double gust front structure occluding near the tornado and a region of enhanced vorticity separated from the tornado that may have been associated with cyclic tornadogenesis the analyses are compared to conceptual and computer models of tornadic storms a subsequent tornadogenesis was observed with radar every 18 s providing a finescale temporal view of the genesis process the genesis process was complex and the evolution of tornado intensity parameters was not monotonic in time low level rotation contracted and intensified then broadened then contracted and intensified a se

structures and dynamics of quasi 2d mesoscale convective systems abstract recently three distinct archetypes for midlatitude linear mesoscale convective systems mcss have been identified this article focuses on the fundamentals of two of these archetypes convective lines with trailing stratiform ts precipitation and convective lines with leading stratiform ls precipitation both the ts and ls modes typically exhibit quasi 2d reflectivity patterns and quasi 2d environmental storm relative wind fields ongoing work has revealed that there are three common flow structures for these quasi 2d mcss front fed ts systems which are sustained by front to rear storm relative inflow as well as front fed ls and rear fed ls systems which are sustained by rear to front storm relative inflow this paper summarizes the observed structures of the front fed ts front fed ls and rear fed ls modes and then outlines an idealized numerical experiment in which these modes were simulated the authors analyze the basic simulated kinematic and microphysical structures and provid

sensitivity of high resolution idealized simulations of thunderstorms to horizontal resolution and turbulence parametrization idealized simulations of deep moist convection are performed with the meso nh model at kilometric scales to assess the impact of the horizontal grid spacing 4 km 2 km 1 km and 500 m and turbulence scheme one dimensional t1d versus three dimensional t3d turbulence the simulations generate one cell which splits into two convective systems a leftward moving multicellular system and a rightward moving supercell objective criteria based on statistical properties and bulk quantities are examined for both systems to characterize the convection they show that the accumulated rainfall and corresponding surface area increase with increasing resolution as does the area covered by the updraughts while the 90th quantile of the intensity of updraught cores decreases the 4 km horizontal grid spacing is set apart as it clearly under resolves the convective motions but the difference between 2 and 1 km horizontal resolutions is larger than between 1 km and 500 m suggesting the beginning of convergence at 500 m also 1 km appears to represent the deep convective structures more correctly than 2 km for a practical weather forecast of organized convective systems t3d induces more mixing and enhances the microphysical processes compared with t1d producing larger amounts of cloud cover and precipitation also the magnitude of the pressure anomaly on the southeastern flank of the supercell is stronger accentuating the path curvature the difference between t1d and t3d becomes perceptible at 2 km pointing out the necessity to deal with horizontal turbulent fluxes at kilometric resolutions although a stronger numerical diffusion added to t1d allows the necessary damping to be introduced at the spectral energy tail it removes a part of the physical mixing and still misses some variance at larger scales the ratio between resolved and total turbulent kinetic energy tke decreases with increasing resolution for both t1d and t3d which is unexpected the main explanation is insufficient turbulent mixing inside convective clouds more pronounced at coarser resolution which is also confirmed by the vertical velocity spectra at 500 m horizontal resolution the subgrid tke is mainly due to dynamical processes with maxima located at the upper level of the convective systems in areas of stronger potential temperatures associated with downdraughts however thermal production is mostly negative underlying the lack of entrainment at the cloud edges

determination of magnitudes of ancient earthquakes from dimensions of observed seismodislocations abstract equations to estimate the magnitude of ancient earthquakes where seismotectonic crustal deformations normal faults strike slip faults etc have been preserved in the epicentral region are presented the equations are based on the results of over one hundred earthquakes including 96 recent continental earthquakes in the magnitude range 5 2 8 7

variations in supercell morphology part i observations of the role of upper level storm relative flow abstract it is hypothesized that the precipitation intensity beneath a supercell updraft is strongly influenced by the amount of hydrometeors that are reingested into the updraft after being transported away in the divergent upper level flow of the anvil this paper presents the results of a climatological analysis of soundings associated with three types of isolated supercells having distinctive precipitation distributions the so called classic low precipitation lp and high precipitation hp storms it is shown that storm relative flow at 9 10 km above the ground is strongest in the environments of lp storms and relatively weak in the environments of hp storms with classic storms occurring in environments with intermediate magnitudes of upper storm relative flow it is plausible that comparatively strong flow in the anvil bearing levels of lp storms transports hydrometeors far enough from the updraft that they are relatively unlikely to be reingested into the updraft leading to greatly diminishe

mobile doppler radar observations of a tornado in a supercell near bassett nebraska on 5 june 1999 part i tornadogenesis abstract this two part paper details an analysis of high resolution wind and reflectivity data collected by a mobile w band doppler radar the dataset captures the near surface life history of a tornado in a supercell in north central nebraska on 5 june 1999 the formation of the tornado vortex near the ground is described from a sequence of sector scans ranging from 30 s intervals prior to tornadogenesis to 10 15 s intervals during much of the lifetime of the tornado cyclonic vortices of 100 200 m width were found along a bow shaped line of enhanced radar reflectivity at what appears to have been the leading edge of a rear flank gust front at the time of tornadogenesis one of these vortices was located just ahead of the nose of the bow shaped radar echo and a jet which were embedded within a larger scale cyclone at other times small scale cyclonic vortices coexisted with the tornado along an arc shaped line extending to its north and northeast but did not appear to interact with the tornado the

structural analysis of recent and active faults and regional state of stress in the epicentral area of the 1978 thessaloniki earthquakes northern greece during spring and summer 1978 macedonia greece suffered damaging seismic activity during the two main shocks which occurred on may 23 mb 5 7 and june 20 mb 6 1 seismic open cracks and faults were formed in the epicentral area 25 km nne from thessaloniki they have been mapped and their kinematics analyzed these studies have shown that they result from the reactivation of existing faults of pleistocene recent and historical age and that the crust is stretching along a n s to nne ssw direction in that part of the north aegean principal stress directions have been computed from the slip vectors measured on recent neotectonic faults and seismic cracks and faults this computation utilizing a simple mechanical model homogeneous deformation through the addition of small and independent displacements of rigid blocks in a highly fractured body a striking feature of this analysis is that the tensional directions 3 deduced from seismic faulting and from recent neotectonic faulting are nearly the same they are compatible with the regional tension axis deduced from focal mechanisms of north aegean and with the focal mechanisms of the 1978 thessaloniki main shocks they are also compatible with in situ stress measurements in this region studies of superficial seismic faulting strongly support previous assumptions proposed from aftershock distribution the 1978 thessaloniki earthquakes resulted from reactivation of several different faults situated within the same ne dipping fault zone of upper eocene lower oligocene age and older separating the serbo macedonian massif from the peonias east vardar zone

convergence behavior of idealized convection resolving simulations of summertime deep moist convection over land convection resolving models crms can explicitly simulate deep convection and resolve interactions between convective updrafts they are thus increasingly used in numerous weather and climate applications however the truncation of the continuous energy cascade at scales of mathcal o 1 km poses a serious challenge as in kilometer scale simulations the size and properties of the simulated convective cells are often determined by the horizontal grid spacing delta x in this study idealized simulations of deep moist convection over land are performed to assess the convergence behavior of a crm at delta x 8 4 2 1 km and 500 m two types of convergence estimates are investigated bulk convergence addressing domain averaged and integrated variables related to the water and energy budgets and structural convergence addressing the statistics and scales of individual clouds and updrafts results show that bulk convergence generally begins at delta x 4 km while structural convergence is not yet fully achieved at the kilometer scale despite some evidence that the resolution sensitivity of updraft velocities and convective mass fluxes decreases at finer resolution in particular at finer grid spacings the maximum updraft velocity generally increases and the size of the smallest clouds is mostly determined by delta x a number of different experiments are conducted and it is found that the presence of orography and environmental vertical wind shear yields more energetic structures at scales much larger than delta x sometimes reducing the resolution sensitivity overall the results lend support to the use of kilometer scale resolutions in crms despite the inability of these models to fully resolve the associated cloud field