polarimetric and dual doppler radar observations of the lipscomb county texas supercell thunderstorm on 23 may 2002 abstract polarimetric and dual doppler observations of a supercell observed by the national center for atmospheric research ncar s band polarimetric spol radar two doppler on wheels dow radars and the greek xpol radar on 23 may 2002 during the international h2o project ihop are presented the polarimetric radar observations began as the storm organized into a supercell and continued for over an hour while the storm was in its mature phase the hydrometeor distribution within the mature storm was retrieved using a fuzzy logic hydrometeor classification algorithm the dual doppler radar observations began around the time that the polarimetric radar observations concluded and they covered the end of the mature phase and much of the dissipation phase of the storm the dual doppler wind syntheses are used to evaluate the importance of the forward flank outflow in augmenting the horizontal vorticity field near the storm above 400 m in this case having a relatively weak low level mesocyclone the pa

petrology and mineralogy of wollastonite and melilite bearing paralavas from the central apennines italy small outcrops of wollastonite and melilite bearing pyrometamorphic rocks paralavas are found along the apennine chain in central italy at the localities of colle fabbri and ricetto these rocks have coarse to fine grained crystalline spotted and glassy textures the colle fabbri rocks have abundant and ubiquitous wollastonite with plagioclase clinopyroxene melilite is found only in the most ca rich and silica poor samples garnet perovskite quartz leucite silica rich glassy mesostasis and ocelli filled by calcite are present locally the ricetto rock is made up of wollastonite and melilite with minor clinopyroxene set in a glassy matrix with a few crystals of restitic quartz these rocks have variable contents of sio2 43 to 64 wt and cao 37 to 3 7 wt the latter decreases with increasing mgo al2o3 fe2o3 tot tio2 k2o sio2 and most trace elements excluding sr peculiar parageneses e g coexisting melilite and anorthite in the most silica poor samples abundance of wollastonite mineral compositions gehlenite rich melilite al ti and fe3 rich clinopyroxene al ti rich but fe poor garnet and major and trace element geochemistry suggest that the colle fabbri and ricetto rocks are not ultimately mantle derived but are the result of melting devolatilization and recrystallization of marly sediments 50 60 to 5 10 calcite with clay minerals quartz likely due to coal fires the 87sr 86sr and 143nd 144nd range from 0 70772 to 0 71190 and from 0 51223 to 0 51219 respectively again suggesting sedimentary protoliths of a mixed nature substantial chemical and isotopic differences between these samples and those from the roman magmatic province are highlighted

vortex2 observations of a low level mesocyclone with multiple internal rear flank downdraft momentum surges in the 18 may 2010 dumas texas supercell abstractobservations collected in the second verification of the origins of rotation in tornadoes experiment during a 15 min period of a supercell occurring on 18 may 2010 near dumas texas are presented the primary data collection platforms include two ka band mobile doppler radars which collected a near surface short baseline dual doppler dataset within the rear flank outflow of the dumas supercell an x band phased array mobile doppler radar which collected volumetric single doppler data with high temporal resolution and in situ thermodynamic and wind observations of a six probe mobile mesonet rapid evolution of the dumas supercell was observed including the development and decay of a low level mesocyclone and four internal rear flank downdraft rfd momentum surges intensification and upward growth of the low level mesocyclone were observed during periods when the midlevel mesocyclone was minimally displaced from the low level circulation suggesting an upward directed perturbation pressure g

the system mg2sio4 ca2sio4 caal2o4 naalsio4 sio2 one atmosphere liquidus equilibria of analogs of alkaline mafic lavas one atmosphere liquidus relationships in the system mg2sio4 fo ca2sio4 la naalsio4 ne caal2o4 ca sio2 sil are presented as analogs for alkaline mafic lavas liquidus diagrams are constructed from electron microprobe analyses of quenched liquids and coexisting mineral phases produced in melting experiments and they are depicted in terms of sub projections within the pseudo quaternary system fo la ne ca sil the ne and ca components are combined to create a normative feldspathoid component defined as ne ne ne ca liquidus relations at ne 0 5 from this study are compared to relations at ne 0 0 and 1 0 from previous studies in general liquidus temperatures decrease and positions of liquidus boundaries involving feldspathic phases shift toward the ne ca component as ne increases the pseudoinvariant points fo di pl mel l and fo pl mel sp l exist at ne 0 5 these equilibria between forsterite plagioclase melilite liquid are not present in the system when ne 1 0 because a boundary curve fo di ne l separates the plagioclase and melilite liquidus fields the liquidus diagrams provide useful analogs for the crystallization sequences of natural primary alkali olivine basalts basanitoids basanites olivine nephelinites olivine melilite nephelinites and olivine melilitites

rapid scan polarimetric doppler radar observations of tornadogenesis and tornado dissipation in a tornadic supercell the el reno oklahoma storm of 24 may 2011 abstracton 24 may 2011 a mobile rapid scan x band polarimetric doppler radar raxpol collected data on a supercell as it produced two tornadoes near el reno oklahoma the first tornado rated an ef 3 was documented from intensification to decay and the genesis and intensification of a second tornado that was rated an ef 5 was subsequently also documented the objective of this study is to examine the spatiotemporal evolution of the rotation associated with the tornadoes i as the first tornado weakened to subtornadic intensity and ii as the second tornado formed and intensified it is found that weakening did not occur monotonically the transition from tornadic to subtornadic intensity over the depth of the radar volume 4 km occurred in less than 30 s but this behavior is contingent upon the threshold for doppler shear used to define the tornado similarly the onset of a tornadic strength doppler velocity couplet occurred within a 30 s period over all elevations additionally the evolutio

the lagrange tornado during vortex2 part i photogrammetric analysis of the tornado combined with single doppler radar data abstractthis study presents a single doppler radar analysis combined with cloud photography of the lagrange wyoming tornado on 5 june 2009 in an attempt to relate the radar observed hook echo weak echo hole weh and rotational couplet to the visual characteristics of the tornado the tornado was rated ef2 the circulation at low levels went through two intensification periods based on azimuthal shear measurements the first intensification was followed by the appearance of a brief funnel cloud the second intensification was coincident with the appearance of a second funnel cloud that remained in contact with the ground until the tornado dissipated a deep weh rapidly formed within the hook echo after damaging wind was identified at the ground and before the appearance of a funnel cloud the echo pattern through the hook echo on 5 june undergoes a dramatic evolution initially the minimum radar reflectivities are near the surface 15 dbz and the weh does not suggest a tapered structure near the gro

the 8 june 1995 mclean texas storm part i observations of cyclic tornadogenesis abstract on 8 june 1995 scientists participating in the verification of the origins of rotation in tornadoes experiment vortex collected airborne doppler radar data in a storm that produced a family of tornadoes near mclean texas the electra doppler radar eldora scanned three significant tornadoes during their formative and mature stages one of the tornadoes was of f4 f5 intensity evidence from pseudo dual doppler analyses of the eldora data reveals a process of cyclic tornado formation qualitatively similar to that depicted in previous conceptual models in particular the rear flank gust front appears to play a major role in determining the location of the next vortex in the series when a tornado forms a small region 3 5 km wide of outflow surges ahead of the tornado producing a local bulge in the gust front a new vorticity maximum may form near the leading edge of the outflow in contrast to what is suggested by earlier conceptual models intersection of the rear flank gust front with a w

extension in compressional orogenic belts the eastern alps extension in the eastern alps encompasses the following 1 extension accompanying simple shear crustal stacking subhorizontal stretching occurs along flat lying foliations and regionally consistent stretching lineations with associated high strains on a local scale stretching results from extrusion of ductile sediments squeezed between rigid basement blocks basement blocks during thrust sheet imbrication the overall geometric effect is crustal thickening 2 classical extensional tectonics extension first occurs as a consequence of accretion and underthrusting of continental and oceanic material and represents gravitational adjustment of an unstable orogenic wedge extension then occurs as a consequence of terminal continental collision and is accommodated by lateral extrusion of crustal of crustal blocks the overall geometric effect is crustal thinning extension is generally oriented subparallel to the strike of the orogen

multiscale aspects of thunderstorm gust fronts and their effects on subsequent storm development abstract an investigation of severe storms that occurred on 23 may 1974 in central oklahoma reveals interesting information on the multifaceted role of thunderstorm produced gust fronts the data reveal that the interaction of outflow boundaries with a cold front initiate the storms studied in this report then the gust fronts produced by these storms have important effects on their own structure and life histories detailed doppler analysis show that these storms propagate discretely along their outflow boundaries despite their supercell structure additionally one storm is affected by its interaction with the boundary produced by a previous storm this interaction appears responsible for tornadogenesis

vortex lines within low level mesocyclones obtained from pseudo dual doppler radar observations abstract vortex lines passing through the low level mesocyclone regions of six supercell thunderstorms three nontornadic three tornadic are computed from pseudo dual doppler airborne radar observations obtained during the verification of the origins of rotation in tornadoes experiment vortex in every case at least some of the vortex lines emanating from the low level mesocyclones form arches that is they extend vertically from the cyclonic vorticity maximum then turn horizontally usually toward the south or southwest and descend into a broad region of anticyclonic vertical vorticity this region of anticyclonic vorticity is the same one that has been observed almost invariably to accompany the cyclonic vorticity maximum associated with the low level mesocyclone the vorticity couplet straddles the hook echo of the supercell thunderstorm the arching of the vortex lines and the orientation of the vorticity vector along the vortex line arches compared to the orientation of the ambient barotrop

observations of low level baroclinity generated by anvil shadows abstract low level cooling beneath the cirrus anvil canopies of supercell thunderstorms is documented in two verification of the origins of rotation in tornadoes experiment cases and in the 17 may 1981 arcadia oklahoma supercell surface temperature decreases of 3 c or more occurred beneath the anvils within 45 min of the onset of overcast conditions cooling was confined to the lowest few hundred meters of the boundary layer and believed to be due mainly to a deficit in the energy budget following a reduction of incoming shortwave radiation in the three cases studied the vertical wind shear was strong thus mixing prevented the formation of an inversion layer strong insolation at the ground outside of the anvil shadows coupled with the cooling beneath the cirrus canopies led to corridors of baroclinity along the shadow edges it is shown that residence times in these baroclinic zones may be long enough for parcels to acquire considerable horizontal vorticity e g 10 2 s 1 en route to a storm u

reply to capitanio 2005 mineralogic and bulk rock composition of italian wollastonite and melilite bearing paralava and clinker further evidence of their pyrometamorphic nature two small outcrops of wollastonite and melilite bearing paralavas with a pyrometamorphic genesis have been found along the apennine chain in central italy at the localities of colle fabbri and ricetto recent papers added new data strengthening the hypothesis that the ricetto wollastonite and melilite bearing rocks were produced by pyrometamorphism of carbonate rich siliciclastic sedimentary rocks in addition these new papers depicted the ricetto paralavas as having wide mineralogical and compositional variations due to liquid immiscibility and or carbonate devolatilization paralleling the trend observed for other paralavas e g colle fabbri italy british columbia canada wyoming u s a etc the source of heat for inducing pyrometamorphism was not investigated in the original paper which was the subject of the comment capitanio et al 2004 on the basis of 14c age determination and of a mineralogical study argued convincingly that heat was supplied to the ricetto rocks by wood combustion for charcoal production

the structure and classification of numerically simulated convective storms in directionally varying wind shears abstract using a three dimensional numerical cloud model we investigate the effects of directionally varying wind shear on convective storm structure and evolution over a wide range of shear magnitudes as with a previous series of experiments using unidirectional wind shear profiles weisman and klemp the current results evince a spectrum of storm types ranging from short lived single cells at low shears multicells at intermediate shears to supercells at high shears with a clockwise curved hodograph the supercellular growth is confined to the right flank of the storm system while multicellular growth is favored on the left flank an analysis of the dynamic structure of the various cells reveals that the quasi steady supercell updrafts are strongly enhanced by dynamically induced pressure gradients on the right flank of the storm system we use this feature along with other related storm characteristics such as updraft rotation to propose a dynamically based storm classification scheme following

observations related to the rotational dynamics of the 20 may 1977 tornadic storms abstract observations of the 20 may 1977 tornadic storms are used to evaluate recent theories on the initiation of rotation at mid and low levels and to verify recent thermodynamic retrieval results using the lengthy data record from a variety of sensors available for this day it appears that the mechanism that initiates low level rotation is different from that at midlevels attempts to identify the source of the low level rotation as vertical tilting baroclinically generated horizontal vorticity were inconclusive the recent thermodynamic retrieval results of hane and ray and of brandes for these storms are in good agreement with independent measurements where available however verification is hindered by the sparseness of these measurements noticeable differences in the region of the rear flank downdraft suggest that there is room for improvement in the retrieval methods investigation of the cyclic generation of rotation along gust fronts indicates that the source of low level rotation is not der

airborne doppler radar analysis of supercells during cops 91 abstract on 26 may 1991 noaa p 3 airborne doppler radar data were collected near two tornadic supercells in the southern plains during the cooperative oklahoma profiler studies cops 91 field program the 3 cm radar mounted in the tail of the aircraft was operated using the fore aft scanning technique fast both storms were sampled just minutes after each had produced a tornado the cops 91 storms are the first tornadic supercells to be sampled extensively by airborne doppler radar using the fast methodology pseudo dual doppler analyses of a dissipating storm in southwest kansas show no remaining low level circulation even though the storm had just produced a tornado the analyses of a storm in northwest oklahoma reveal better defined features in the wind field near the surface in contrast to what has been previously observed in post tornadic supercells the cyclonic vorticity in both storms was greater aloft than at low levels the 26 may 1991 storms provide further evidence that supercells often

finescale single and dual doppler analysis of tornado intensification maintenance and dissipation in the orleans nebraska supercell abstract finescale single and dual doppler observations are used to diagnose the three dimensional structure of the wind field surrounding a tornado that occurred near the town of orleans nebraska on 22 may 2004 the evolution of the vorticity and divergence fields and other structures near the tornado are documented in the lowest kilometer changes in tornado intensity are compared to the position of the tornado relative to primary and secondary gust fronts circulation on scales of a few kilometers surrounding the tornado remains relatively constant during the analysis period which spans the intensifying and mature periods of the tornado s life cycle stretching of vertical vorticity and tilting of horizontal vorticity are diagnosed but the latter is near or below the threshold of detectability in this analysis during the observation period in the analyzed domain low level circulation within 500 m of the tornado increased several minutes before vortex relative and ground relative near surface wind

a three dimensional trajectory model with advection correction for tropical cyclones algorithm description and tests for accuracy abstractwhen computing trajectories from model output gridded winds are often temporally interpolated to a time step shorter than model output intervals to satisfy computational stability constrai

a numerical simulation of cyclic mesocyclogenesis abstract a three dimensional nonhydrostatic numerical model the advanced regional prediction system is used to study the process of cyclic mesocyclogenesis in a classic supercell thunderstorm during the 4 h simulation the storm s mesocyclone undergoes two distinct occlusions with the beginning of a third indicated at the end of the simulation the occlusion process exhibits a period of approximately 60 min and is qualitatively similar in each case initial midlevel 3 7 km mesocyclogenesis proceeds according to the classic picture that is via tilting of streamwise environmental vorticity the development of an evaporatively driven rear flank downdraft rfd signals the beginning of the occlusion process the developing rfd wraps cyclonically around the mesocyclone causing the gust front to surge outward simultaneously the occluding mesocyclone rapidly intensifies near the surface trajectory analyses demonstrate that this intensification follows from the tilting and stretching of near ground

mobile x band polarimetric doppler radar observations of the 4 may 2007 greensburg kansas tornadic supercell abstracton 4 may 2007 a supercell produced an ef 5 tornado that severely damaged the town of greensburg kansas volumetric data were collected in the greensburg storm by the university of massachusetts x band mobile polarimetric doppler radar umass x pol for 70 min 10 tornadoes were detected this mobile doppler radar dataset is one of only a few documenting an ef 5 tornado and the supercell s transition from short track cyclic tornado production mode 1 to long track tornado production mode 2 using bootstrap confidence intervals it is determined that the mode 2 tornadoes moved in the same direction as the supercell vault in contrast the mode 1 tornadoes moved to the left with respect to the vault from polarimetric data collected in this storm the authors infer the presence of large oblate drops high zdr high hv in the forward flank and surrounding some of the tornadoes the authors speculate that the weak echo column wec in the greensburg tornado which extended above 10 km agl

the san angelo texas supercell of 31 may 1995 visual observations and tornadogenesis abstract airborne radar analysis combined with cloud photogrammetry of a supercell that formed on 31 may 1995 near san angelo texas is presented the superposition of the doppler wind syntheses with the cloud pictures provides a unique view of the relationship between the low level mesocyclone and the developing lowered cloud base the mesocyclone accompanying the storm went through two periods of intensification the end of the first period of intensification did not lead to the formation of a tornado an occlusion downdraft formed but was primarily driven by negative buoyancy rather than a downward directed perturbation pressure gradient recent studies have suggested that cold downdrafts inhibit the formation of tornadoes the present study supports this hypothesis and provides the first quantitative view of the vertical structure of this downdraft the mesocyclone evolved through a second period of intensification that produced a weak tornado that was visually apparent from the aircraft no occlusio

the kellerville tornado during vortex damage survey and doppler radar analyses abstract a detailed aerial and ground survey of a long track 50 km f5 tornado is presented the survey revealed that the tornado exhibited unusual nonlinear movements at two different locations one portion of the track was associated with a pronounced sinusoidal pattern while another location was characterized by a cusplike pattern for the first time high resolution dual doppler wind measurements can be used to evaluate mechanisms for such deviations from a linear tornado path the analyses of data collected with electra doppler radar eldora suggest that these departures are trochoidal marks produced as the tornado was revolving within the larger scale mesocyclone retrieved perturbation pressures indicate that the mesocyclone departed significantly from a cyclostrophically balanced state during these deviations the maximum vorticity associated with the mesocyclone at low levels was shown to be an unreliable indicator of the tornado s intensity vertical cross sections of wind vertical vorticity

an assessment of low level baroclinity and vorticity within a simulated supercell abstractidealized supercell modeling has provided a wealth of information regarding the evolution and dynamics within supercell thunderstorms however discrepancies in conceptual models exist including uncertainty regarding the existence placement and forcing of low level boundaries in these storms as well as their importance in low level vorticity development this study offers analysis of the origins of low level boundaries and vertical vorticity within the low level mesocyclone of a simulated supercell low level boundary location shares similarities with previous modeling studies however the development and evolution of these boundaries differ from previous conceptual models the rear flank gust front develops first whereas the formation of a boundary extending north of the mesocyclone undergoes numerous iterations caused by competing outflow and inflow before a steady state boundary is produced a third boundary extending northeast of the mesocyclone is produced through evaporative cooling of

apparent western termination of the north pyrenean fault and tectonostratigraphic units of the western north pyrenees france and spain the surface geology of the north pyrenees southern france is markedly different east and west of longitude 0 25 w a line just west of lourdes east of this longitude the north pyrenean fault npf the major structure in the north pyrenees is clearly identifiable and this fault and other faults in the north pyrenean zone are subvertical west of longitude 0 25 w the npf is not identifiable at the earth s surface suggesting to some that the npf is not continuous and is not a regionally significant feature and that low angle as well as high angle faults are present in the fault zone while east of lourdes there is both a relatively continuous belt of mesozoic metamorphic rock and a geophysically detected 15 km step in depth to the moho neither is clearly recognized west of lourdes again bringing into question the continuity of the npf however in order to accommodate opening of the bay of biscay as much as 400 km of translation along a continuous npf or north pyrenean fault zone npfz is required we have compiled a map covering a 100 km long area in the western pyrenees the compilaation is based on our mapping and published maps by others the compilation and our field work provide the data to delineate four new tectonostratigraphic units these units are coherent stratigraphic sequences characterized by marked differences in stratigraphic thickness and depositional history each unit is bounded by regional faults that delineate four tectonic sheets the principal stratigraphic differences between the four tectonostratigraphic units were produced during deposition in cretaceous basins along the northern pyrenees the regional bounding faults are reverse and were formed during the main phase of the pyrenean orogeny that is during late cretaceous and tertiary times some are reactivated basin boundary faults and some of these are reactivated faults of cretaceous or older age in the western pyrenees the npf which was an active left slip fault during the late jurassic and early cretaceous is cut by these faults and is covered by tectonic sheets these sheets formed during the paleogene account for the apparent termination of the npf near longitude 0 25 w and obscure the step in the moho

centrifuging of hydrometeors and debris in tornadoes radar reflectivity patterns and wind measurement errors high resolution doppler radar observations of tornadoes reveal a distinctive tornado scale signature with the following properties a reflectivity minimum aloft inside the tornado core described previously as an eye a high reflectivity tube aloft that is slightly wider than the tornado core and a tapering of this high reflectivity tube near the ground the results of simple one dimensional and two dimensional models demonstrate how these characteristics develop important processes in the models include centrifugal ejection of hydrometeors and or debris by the rotating flow and recycling of some objects by the nearsurface inflow and updraft doppler radars sample the motion of objects within the tornado rather than the actual airflow since objects move at different speeds and along different trajectories than the air error is introduced into kinematic analyses of tornadoes based on radar observations in a steady axisymmetric tornado objects move outward relative to the air and move more slowly than the air in the tangential direction in addition the vertical air relative speed of an object is less than it is in still air the differences between air motion and object motion are greater for objects with greater characteristic fall speeds i e larger denser objects and can have magnitudes of tens of meters per second estimates of these differences for specified object and tornado characteristics can be obtained from an approximation of the one dimensional model doppler on wheels observations of the 30 may 1998 spencer south dakota tornado demonstrate how the apparent tornado structure can change when the radar scatterer type changes when the spencer tornado entered the town and started lofting debris changes occurred in the doppler velocity and reflectivity fields that are consistent with an increase in mean scatterer size

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 univariant curve liquid forsterite anorthite diopside in the system cmas at 1 bar solid solutions and melt structure one atmosphere liquid present experiments were carried out in the cmas system using an ordinary quench furnace apparatus the runs including reversal and duplicate experiments describe the univariant curve l fo an di between the invariant points q l fo an di sp and f l fo an di oen located respectively at 1245 1 c and 1244 1 c the thermal divide on this curve m3 l fo an di is located at 1275 1 c and plots well within the silica saturated field in agreement with longhi s 1987 experiments along the univariant curve l fo an di liquid composition evolves away from the thermal divide either toward invariant points q or f and pierces the silica saturation plane i e the join di an en in the silica saturated field in this compositional range the al solubility in clinopyroxene changes drastically from one side of the thermal divide to the other with great increase of al solubility in the silica undersaturated field four endmembers must be used to describe the complex solid solution of anorthite caal2si2o8 camgsi3o8 mgal2si2o8 and si4o8 the last two of these are present only within the silica saturated field unlike clinopyroxene the mg content of anorthite is insensitive to the thermal barrier but is only sensitive to silica saturation plane olivine composition can be described by a binary solid solution of forsterite and monticellite with no ca in the m2 site as with anorthite olivine compositions exhibit a marked change with crossing of the silica saturation plane the above features imply that the solubility of minor elements in crystalline phases al in clinopyroxene ca in olivine and mg in anorthite selectively respond to only one or another of these particular plane results have many important consequences one is the likelihood of changes in melt speciation depending on position with respect to the thermal divide and the silica saturation plane

diagnosed three dimensional axisymmetric structure of the mulhall tornado on 3 may 1999 on 3 may 1999 an unusually large tornado that caused f4 level damage and killed several people was intercepted by the doppler on wheels dow mobile radar near mulhall oklahoma from a range of 4 to 9 km resulting in high resolution volumetric data every 55 s up to 1 5 km altitude over a period of 14 min for the first time the evolution and three dimensional structure of a tornado were deduced using the ground based velocity track display gbvtd technique after the circulation center was determined the tangential wind and radial wind were derived from the gbvtd technique at each radius and height in addition the axisymmetric vertical velocity angular momentum vorticity and perturbation pressure were deduced from the tangential and radial wind fields this study focuses on the axisymmetric aspects of this tornado the primary circulation of the mulhall tornado consisted of an 84 m s 1 peak axisymmetric tangential wind with the radius of maximum wind rmw ranging from 500 to 1000 m the secondary circulation exhibited a two cell structure characterized by a central downdraft surrounded by an annular updraft near the rmw the calculated maximum pressure deficit from a 3 km radius to the tornado center at 50 m altitude was 80 hpa the maximum vorticity during the first 8 min of observation was located inside the rmw away from the tornado center this vorticity profile satisfied the necessary condition of barotropic instability as the tornado weakened afterward the vorticity monotonically increased toward the center the computed swirl ratios were between 2 and 6 consistent with the observed multiple vortex radar signatures and the vorticity pattern swirl ratios were generally smaller during the weakening phase

dynamic multi scale modes of severe storm structure detected in mobile doppler radar data by entropy field decomposition abstractthe detection of complex spatially and temporally varying coherent structures in data from highly nonlinear and non gaussian systems is a challenging problem in a wide range of scientific d

high temporal resolution polarimetric x band doppler radar observations of the 20 may 2013 moore oklahoma tornado abstract on 20 may 2013 the cities of newcastle oklahoma city and moore oklahoma were impacted by a long track violent tornado that was rated as an ef5 on the enhanced fujita scale by the national weather service despite a relatively sustained long track damage surveys revealed a number of small scale damage indicators that hinted at storm scale processes that occurred over short time periods the university of oklahoma ou advanced radar research center s px 1000 transportable polarimetric x band weather radar was operating in a single elevation ppi scanning strategy at the ou westheimer airport throughout the duration of the tornado collecting high spatial and temporal resolution polarimetric data every 20 s at ranges as close as 10 km and heights below 500 m agl this dataset contains the only known polarimetric radar observations of the moore tornado at such high temporal resolution providing the opportunity to analyze and study finescale phenomena occurring on rapid time scales analysis

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

evolution of a turbiditic foreland basin and analogy with an accretionary prism example of the eocene south pyrenean basin the south pyrenean tertiary basin was an east west trending foreland trough which developed from early eocene to miocene times in a north south trending compressive regime a turbiditic series of lower and middle eocene age hecho group enables us to define the typical features of the tectono sedimentary evolution of the basin 1 slope and shelf derived carbonate turbidites and megaturbidites bear witness to the seismic activity of the basin borders 2 the southern basin border evidenced by the onlap of the turbidites onto slope and shelf deposits migrated progressively southwards in time and 3 the deformation pattern is characterized in the meso cenozoic sediments by a complex thrust fold system of thin skinned tectonics style its specific geometry and kinematics were influenced by the pre deformation geometry onlap this thrust fold system is related to south directed basement nappes and its front advanced progressively southwards in time from this data we infer an evolutionary model for this highly mobile basin it was a flexural basin linked to the northward bending of the lithosphere in the foreland of a south directed crustal accretionary prism as the nappes advanced the basin migrated progressively southwards in the foreland direction as for the actual basin evolution many analogies with accretionary prism trench systems of active margins exist

wollastonite anorthite gehlenite and fassaite bearing rocks igneous petrological oddity or paralavas we briefly review the petrological and geochemical features and physical characteristics of the colle fabbri and ricetto rocks to discuss their possible paramagmatic origin i e derived from complete melting after devolatilization of marly protoliths without any orthomagmatic ultimately mantle derived chemical or thermal input contrary to the various comments that have been made the overall mineralogical petrological and geochemical data provided in the literature well agree with this finding

fine scale doppler radar observations of tornadoes observations obtained with a mobile pencil beam doppler radar revealed many previously unresolved structures within tornadic storms and tornadoes and helped verify various aspects of conceptual models radar data from the parent circulations indicate the existence of spiral reflectivity bands intense radial wind shear zones and multiple larger scale velocity maxima tornado structures observed include debris shields clear axial eye regions multiple reflectivity bands surrounding the center of the eye and occasional reflectivity protrusions into the eye velocity and reflectivity data from tornado scale circulations show evidence of axial downdrafts

thrust tectonics in the south central pyrenees abstract surface structural data and published stratigraphies are combined to construct two balanced and restored sections through the nogueras zone of the south central pyrenees the allochthonous nogueras zone units are interpreted as the foreland dipping margin of a major antiformal stack in the palaeozoic rocks of the pyrenean axial zone their structural evolution is summarized in a hangingwall sequence diagram this reinterpretation of the nogueras zone is incorporated into a new n s balanced and restored section from the centre of the pyrenean axial zone to the ebro basin a classical rocky mountains piggy back thrust model is employed and the resulting section is a significant departure from those previously published it is argued that gravity gliding has never been an important mechanism in the alpine pyrenees section restoration casts doubt on the correlation of the surface expression of the north pyrenean fault and the seismically detected moho step beneath it

high resolution dual doppler analyses of the 29 may 2001 kress texas cyclic supercell abstract on 29 may 2001 doppler on wheels radars collected data on a supercell near kress texas the supercellular storm cyclic in nature produced multiple mesocyclones throughout its lifetime dual doppler syntheses were conducted using a grid spacing of 100 m resulting in the highest resolution observational analysis of a cyclic supercell to date in addition collection of data from ground based radar allowed for the analysis of near ground features irresolvable with airborne radar providing another advantage over previous studies the syntheses revealed a number of evolving low level mesocyclones over the observation period of 900 s while nontornadic during the synthesis period the supercell exhibited evidence of strong vertical vorticity greater than 10 2 s 1 low level circulation with classic cyclic structure and multiple tornadoes beginning 3600 s later a comparison between the current results conceptual models and previous lower resolution analyses is presented a striking similarity

comparison between the galicia and aquitaine margins abstract there is a great similarity between the galicia margin and the aquitaine margin i e the aquitaine basin and the north pyrenean zone in particular the timing of the rifting as well as the resulting structures exposure of perodotite tilted fault blocks normal and transverse faults half grabens are practically the same this comparison leads to the interpretation that the northern side of the pyrenean fold belt is inherited from the mesozoic deep passive margin of europe the cenozoic thrust sheets and reverse faults of the northern pyrenees zone are tentatively interpreted as former rift structures tilted blocks and listric faults which were removed during the convergence of the iberian and european plates during the paleocene and eocene

genesis of the goshen county wyoming tornado on 5 june 2009 during vortex2 abstractthe genesis of a strong and long lived tornado observed during the second verification of the origins of rotation in tornadoes experiment vortex2 in goshen county wyoming on 5 june 2009 is studied mobile radar mobile mesonet rawinsonde and photographic data are used to produce an integrated analysis of the evolution of the wind precipitation and thermodynamic fields in the parent supercell to deduce the processes that resulted in tornadogenesis several minutes prior to tornadogenesis the rear flank downdraft intensifies and a secondary rear flank downdraft forms and cyclonically wraps around the developing tornado kinematic and thermodynamic analyses suggest that horizontal vorticity created in the forward flank and hook echo is tilted and then stretched near the developing tornado tilting and stretching are enhanced in the developing low level circulation as the secondary rear flank downdraft develops intensifies and wraps around the circulation center shortly thereafter the to

a comparison of near surface buoyancy and baroclinity across three vortex2 supercell intercepts abstractobservations obtained during the second verification of the origin of rotation in tornadoes experiment vortex2 are analyzed for three supercell intercepts these intercepts used a fleet of deployable sticknet probes complemented by mobile radars and a mobile mesonet to map state quantities over the expanse of target storms two of the deployments occurred for different stages of a supercell storm near and east of dumas texas on 18 may 2010 a comparison of the thermodynamic and kinematic characteristics of the storm provides a possible explanation for why one phase was weakly tornadic and the other nontornadic the weakly tornadic phase features a stronger horizontal virtual temperature gradient antiparallel to the forward flank reflectivity gradient and perpendicular to the near surface flow direction suggesting that air parcels could acquire more significant baroclinic vorticity as they approach the low level mesocyclone the strongly tornadic 10 may 2010 case near seminole oklahoma fea

thick and thin skinned tectonics in the pyrenees abstract a comparison is made between the gavarnie thrust and the merens fault in the axial zone of the pyrenees the former has a gentle dip and quite a large displacement at least 12 km but does not cut through either hercynian or alpine isograds the latter has a smaller displacement 5 km but dips steeply and cuts through both hercynian and alpine isograds at a high angle on this basis and on the basis of shear zone geometries immediately north of it it is proposed that the merens fault nucleated as a steeply 65 80 dipping structure while the gavarnie thrust nucleated with a shallow attitude the merens fault is not a backward rotated thrust fault nor is it the root zone for any major nappe structure similar steep ductile structures occur within the gavarnie nappe and may reflect considerable internal strain in basement lithologies the relationship between steep and shallow structures is not yet clear the shear zones may pre date the thrusting in which case they may be thick skinned structures affecting the whole lithosphere or they may be contemporary with thrusting reflecting only local thickening above a decollement rheological models can be used to test proposed geometrical and kinematic models for the lithosphere scale evolution of the pyrenees suggested models are dominated by a cool rigid high level mantle wedge beneath the north pyrenean zone which probably controlled the location of north dipping thrust faults thick skinned shortening is possible in thick crust in the axial zone but is very unlikely in the north pyrenean zone where steeply rooted structures would have to cut through the strongest part of the lithosphere

post emplacement extension within a thrust sheet from the central pyrenees secondary faults and related veins in a small thrust sheet the pic de port vieux thrust sheet in the footwall of the gavarnie thrust in the central pyrenees are used to infer the deformation sequence that accompanied its emplacement initial deformation was characterized by distributed bedding parallel simple shear this was superseded by localized deformation involving arrays of extensional faults the first faults to form were x shears and were succeeded first by conjugate faults x x9 shears and then arrays of r shears that locally cut the thrust i e developed subsequent to its emplacement extension veins are used to infer the orientation of the ambient stress system during the deformation sequence a forward rotation of the stress sytem towards the vertical was associated with the x and x x9 shears and is considered to reflect loading of the 4 km thick overlying gavarnie thrust sheet a later backward rotation of the stress system then occurred returning 1 to 45 obliquity to the pic de port vieux thrust and was associated with the r shear development this later event produced extensional shearing of the thrust sheet and is equated with a proposed episode of spreading gliding within the overlying thrust pile a model for this spreading gliding relates it to the active tectonics of the developing south pyrenean thrust belt

syntectonic vein development in a thrust sheet from the external french alps abstract the geometry and age relations of syntectonic veins within calcareous rocks of one imbricate sheet within a thrust belt in the external french alps are described the earliest veins developed during the main ductile deformation by cleavage parallel extension the majority of the syntectonic veins developed towards the end of the deformation and after the formation of second folds they include a conjugate set of normal shears an abundant set of upright extension veins and en echelon sets the dominantly simple shear strain making up the main ductile phase of deformation occurred by a mechanism of grain to grain pressure solution the stretching lineation records the overall direction of thrust sheet movement a change in the microchemical mechanism of pressure solution is thought to have caused the change from first to second phase deformation as recorded by slaty cleavage and crenulation folds in the field from the shear and vein geometries directions of principal stress have been inferred the directions rotated throughout the deformation the maximum principal stress being inclined to bedding during simple shear strain becoming normal to bedding during the phase of abundant vein growth and becoming vertical at the very end of the deformation

dual doppler analysis of winds and vorticity budget terms near a tornado abstract three dimensional dual doppler observations with unprecedented finescale spatial and temporal resolution are used to characterize the vector wind field and vorticity generation terms in and near a weak short lived tornado the beam widths of the two doppler on wheels dow mobile radars at the range of the tornado are 250 m with gate lengths of 75 m resulting in a resolution of less than 107 m3 one of the dows collected data during the 240 s prior to the formation of the tornado enabling examination of the genesis process a single set of volumetric scans suitable for dual doppler analyses were completed by both dows permitting the calculation of vertical and horizontal vorticity divergence and stretching and tilting terms in the vorticity budget of the large but weak tornado and its surroundings but no local tendency terms analyses of the dual doppler vector wind fields document for the first time in a supercellular tornado revealed several structures expected to be associated with

documenting a rare tornado merger observed in the 24 may 2011 el reno piedmont oklahoma supercell abstractunique observations of the interaction and likely merger of two cyclonic tornadoes are documented one of the tornadoes involved in the interaction was the enhanced fujita scale ef5 el reno piedmont oklahoma tornado from 24 may 2011 and the other was a previously undocumented tornado data from three s band radars twin lakes oklahoma ktlx norman oklahoma koun and the multifunction phased array radar mpar are used to detail the formation of the second tornado which occurred to the northwest of the original tornado in an area of strong radial convergence radar data and isosurfaces of azimuthal shear provide evidence that both tornadoes formed within an elongated area of mesocyclone scale cyclonic rotation the path taken by the primary tornado and the formation location of the second tornado are different from previous observations of simultaneous cyclonic tornadoes which have been most often observed in the cyclic tornadogenesis process the merger of the two tornadoes occurred d

pseudotachylyte bearing strike slip duplex structures in the fort foster brittle zone s maine abstract detailed 1 60 scale mapping of the fort foster brittle zone in the mylonitic rye formation of southernmost maine has revealed the intricate internal duplex structure of a system of probable paleozoic age dextral strike slip faults that have produced abundant pseudotachylyte and minor breccia the internal configuration of this brittle zone consists of a mosaic of individual pseudotachylyte generation zones as slab duplex structures individual duplex zones are up to 100 m in length and 1 m or less in width and are defined by pairs of layer parallel slip surfaces along which frictional melts were produced these slab duplex structures are interpreted as zones of displacement transfer between long overlapping layer parallel en echelon strike slip fault surfaces contractional duplexes develop layer parallel compressional structures that tend to shorten and thicken the fault bounded slabs by the formation of lateral ramps and conjugate faults kinks and asymmetric folds extensional duplexes develop layer parallel stretching and thinning by the formation of oblique dextral shears high angle conjugate pairs and localized fault breccias the production of pseudotachylyte by friction melting along layer parallel fault surfaces in these exposures is attributed to rapid slip during paleoseismic events the rupture structures developed during these events may be characteristic of fault structure and mechanics at near focal depths in a strike slip seismogenic zone

comment on melluso et al 2003 the ricetto and colle fabbri wollastonite and melilite bearing rocks of the central apennines italy the bimodal rock of ricetto consists of a felsic glassy component which prevails volumetrically at the top of the rock and mafic spherules of acicular diopside anorthite wollastonite pseudomorph after melilite which are concentrated at the bottom of the rock this texture clearly indicates liquid immiscibility which can be modeled in the compositional space sio 2 al 2 o 3 mgo cao and al 2 o 3 cao feo t mgo the spinifex and dendritic forms are due to quenching from a melt at temperature of 1000 1100 c melilite was the first phase to crystallize and the subsequent rapid cooling caused its breakdown to a more stable assemblage the strict chemical similarity between the rock under study and the surrounding siliciclastic sandstones together with the results of 1 4 c radiometric analysis on coal fragments found at bottom of the convex central part of the body demonstrate that the rock of ricetto is a man made pyrometamorphic product the genetic attribution of the colle fabbri occurrence to pyrometamorphic phenomena somewhat similar to ricetto is difficult to be asserted as the crystallization history at colle fabbri has been much more complicated than at ricetto the common presence of melilite and wollastonite cannot account for a direct comparison between the ricetto and colic fabbri rocks as conspicuous mineralogic petrologic and geologic differences exist between these two occurrences

partitioning of deformation within several external thrust zones of the appalachian orogen mesoscopic contractional and extensional faults dominate many external thrust zones the fault arrays occur in the hanging walls of some thrusts and in the footwalls of others in a thrust zone from the little mountains fold thrust belt of new york state mesoscopic faults cut and offset a major thrust contact and involved rocks from the thrust s hanging wall and its footwall simultaneously the little mountains exposure indicates that minor faults were active during thrust slip and are not early formed features which were passively translated with the remainder of a sheet when both contractional and extensional mesoscopic faults occur in thrust zones foreland dipping extensional faults overprint contractional faults contractional and extensional microfaults with r 1 and r 2 riedel shear geometries are common in external thrust zone cataclasites and resemble the mesoscopic fault patterns though the evolution of cataclasite layers differs from that of mesoscopic fault arrays contraction and ext

paleostresses associated with faults of large offset abstract in order to test empirically the limitations of paleostress analysis we used etchecopar s computer program to compute the orientations and relative magnitudes of paleostress principal values in two southern appalachian u s a thrust zones from minor fault and slickenside attitudes in both thrust zones faults are closely spaced many faults have offsets whose magnitudes exceed the distance to adjacent faults of comparable size and deformation was strongly non coaxial while even in the less deformed thrust zone bulk strains due to fault movement have axial ratios as high as 10 1 nearly 75 of the fault slickenside pairs in each thrust zone conform with paleostress tensors that indicate 1 sequential transport parallel compression transport parallel extension and extension oblique to transport and 2 low resolved shear stresses on the thrusts finite strains measured in one thrust zone share a principal plane with the first two tensors and the inclinations of the paleostress and finite strain principal directions in that plane are consistent with thrust parallel shearing relative magnitudes of paleostress and strain principal values do not correlate well moreover the locations and inferred origins of fault slickenside pairs inconsistent with paleostress tensors suggest that stresses in rocks between faults were not as is assumed in paleostress analyses uniform this complexity may also occur in faulted rocks where bulk strains are small paleostress tensors from rocks with large bulk strains may be viable but they must be interpreted cautiously

mobile sounding observations of a tornadic storm near the dryline the canadian texas storm of 7 may 1986 abstract on 7 may 1986 thunderstorms formed during the afternoon near a dryline in the texas panhandle under weak synoptic scale forcing five tornadoes and large hail were produced by one storm near canadian texas the focus of the paper is the analysis of soundings obtained by a storm intercept crew a sounding launched into the wall cloud of the storm just after the fourth tornado indicated a nearly pseudomoist adiabatic lapse rate a temperature excess of 10 c over the environment at 500 mb and an updraft speed of almost 50 m s 1 near 6 km agl in reasonable agreement with parcel theory

finescale radar observations of the 22 may 2002 dryline during the international h2o project ihop abstract the dryline has long been associated with the development of severe thunderstorms in the southern plains during the spring and early summer months the propagation and structure of the dryline are closely tied to surface processes that are neither well understood nor well resolved with current observational capabilities as a result there are often large errors in forecasts of dryline position and structure improvements in radar technology have allowed for better observations of the dryline in recent years here very finescale radar observations taken with the university of massachusetts amherst umass mobile w band radar during an international h2o project ihop double dryline event on 22 may 2002 in the oklahoma panhandle are presented the observations are placed in the context of the dryline secondary circulation which describes flow in a plane normal to the dryline the narrow half power beamwidth of the antenna on the w band 0 18 permitted the measurements of channels of upward 8

crystallization sequences of ca al rich inclusions from allende an experimental study the equilibrium crystallization sequence at 1 atmosphere in air of a melt corresponding in composition to the average composition of type b ca al rich inclusions from the allende meteorite is spinel 1550 c melilite 1400 c ak22 anorthite 1260 c ti al rich clinopyroxene 1230 c ti fassaite the melilite becomes increasingly akermanitic with decreasing temperature the pyroxene is similar in composition to fassaites from type b inclusions preliminary results suggest that the crystallization sequence is similar at oxygen fugacities near the iron wustite buffer the results of these experiments have been integrated with available phase equilibrium data in the system cao mgo al 2o 3 sio 2tio 2 and a phase diagram for predicting the crystallization sequences of liquids with compositions of coarse grained ca al rich inclusions has been developed available bulk compositions of coarse grained inclusions form a well defined trend in terms of major elements extending from type a and bl inclusions near the spinel melilite join to more pyroxene rich type b2 inclusions the trend deviates from the expected sequence of solid condensates from a nebular gas at p 10 3 atm if pure diopside is assumed to be the clinopyroxene that condenses the type a b1 end of the trend is similar in composition to calculated equilibrium condensates at 1202 1227 c and the trend as a whole parallels the sequence of condensates expected from diopside condensation at 1170 c the trend is consistent to first order with the condensation of solid ti rich fassaite in place of pure diopside at higher temperatures than those at which pure diopside is predicted to condense partially molten condensates may be likely in this case or if the nebular pressure is higher than 10 3 atm

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

phase equilibrium constraints on angrite petrogenesis parameterizations of liquidus boundaries and solid solution in the cmas fe system shi 1992 have been employed to depict the liquidus equilibria relevant to the petrogenesis of angrites angrites are basaltic achondrites characterized by highly aluminous augite fassaite intermediate mg fe olivine and late stage cafe olivine kirschsteinite two important features of the equilibria on the olivine liquidus surface relevant to angrite petrogenesis are 1 the presence of a thermal divide on the ol aug plag liq boundary curve which separates the compositions of source materials that produce low silica angritic melts that crystallize highly aluminous augite from those that produce higher silica melts with tholeiitic to eucritic crystallization patterns and 2 the change in the pseudo invariant point on the low silica side of the thermal divide from a plagioclase peritectic involving spinel ol aug plag sp liq at high to intermediate mg mg mg fe to two pseudo eutectics involving kirschsteinite ol aug plag kir liq and ol kir plag sp liq at low mg the fassaitic aluminous augite pyroxene composition in angra dos reis ador the presence of minor green spinel and the absence of primary kirschsteinite prinz et al 1977 indicate that crystallization of the ador parental liquid was governed by the intermediate mg set of equilibria such that following crystallization of ol aug plag the plagioclase reacted completely at the plagioclase peritectic with the interstitial liquid which subsequently crystallized beyond the plagioclase peritectic onto the ol aug sp liquidus boundary curve the ador bulk composition is consistent with trapping 10 of the parental liquid in a cumulate with cotectic proportions of fassaite and olivine lewis cliff lew 86010 crystallized from a liquid with mg similar to that of ador but on the ol plag cotectic closer to the thermal divide such that the first pyroxene to crystallize had much lower al content than that of ador in the late stages of crystallization the 86010 residual liquid and that of lew87051 encountered the low mg set of equilibria involving kirschsteinite these relationships require either a higher degree of melting for the 86010 parent magma or source region different than ador s these relationships are also consistent with compositionally dependent ree partition coefficients between fassaite and the ador liquid being as much as 1 5 2 times higher than those for the 86010 liquid at the onset of pyroxene crystallization the combination of a trapped liquid component higher partition coefficients and smaller degrees of melting help to explain the observation that ador an apparent cumulate has ree concentrations twice as high as those in 86010 mittlefehdlt and lindstrom 1990 an apparent chilled liquid the absence of a strong negative eu anomaly in the ador parent liquid however requires relatively high degrees of partial melting to eliminate plagioclase in the source region resorption of plagioclase at the peritectic eliminates the eu anomaly that develops during crystallization so ultimately different source regions are required progressive iron loss from devolatilized primitive chondrites allende murchison produces source regions capable of producing a wide range of melt compositions with angritic to eucritic crystallization behavior the compositions of carbonaceous and ordinary chondrite provide a similar range of potential source region compositions however primitive chondrite fe source regions that produce angrite like melts have mg that is too low whereas chondrite fe sources that have mg sufficiently high to yield the mg in angrite minerals have too much silica or orthopyroxene component to yield angrite like liquids no single group of meteorites fe simultaneously satisfies the constraints of mg and silica component however mixtures of fe depleted chondrite plus a low silica component similar to ca al rich inclusions cais can satisfy the constraints the absence in angrites of 48ca and 50ti anomalies typical of cais lugmair and galer 1992 suggests that the low silica component was not simply an enrichment of cais but was the result of direct accretion of high temperature condensate grossman 1972 into sizable thermally shielded planetesimals thus angrites cryptically record mixing of planetesimal sized heterogeneities in the early solar system

strain models within spreading nappes abstract internal strain within nappes and thrust sheets is especially important in the understanding of emplacement mechanisms in this paper strain patterns within spreading nappes are investigated theoretically and experimentally three types of spreading nappe are distinguished using various boundary conditions spreading gliding spreading and extruding spreading nappes each type is placed in its proper natural environment strain components and strain gradients are summarized from the use of scale models performed with analogue materials mathematical computations from experimental modelling allow the calculation of 1 1 the schistosity trajectories in vertical flow planes 2 2 the relationship between stretch and transport direction and 3 3 the spatial distribution of different types of strain ellipsoid these provide some tests which make it possible to demonstrate in the field whether nappes are or are not gravity induced finally some field examples from the central alps and the pyrenees are briefly discussed they provide good support to the strain models presented in the present paper

the arcadia oklahoma storm of 17 may 1981 analysis of a supercell during tornadogenesis abstract on 17 may 1981 an extensive dataset was collected for a supercell thunderstorm that produced an f2 tornado near arcadia in central oklahoma coordinated dual doppler scans of the storm by 10 cm research radars were collected at approximately 5 min intervals from 30 min before the tornado touched down until 15 min after the tornado had dissipated the arcadia storm was also well sampled by a 444 m tall instrumented tower the low level inflow updraft mesocyclone and rear precipitation core of the supercell all passed across the tower a comparison of the instrumented tower measurements with a dual doppler synthesis reveals that the latter qualitatively resolved the low level flow however the magnitudes of the low level horizontal winds and updraft speed were underestimated in addition the vertical shear of the horizontal wind in the lowest kilometer was unresolved in the doppler winds in the storm environment horizontal vorticity was strong 1 5 10 2 s 1 and approximately streamwise

the garden city kansas storm during vortex 95 part i overview of the storm s life cycle and mesocyclogenesis abstract analysis of a supercell storm that produced an f1 tornado near garden city kansas is presented this event provided one of the first opportunities to synthesize data collected by a new airborne radar platform called eldora electra doppler radar developed by the national center for atmospheric research the early stages of development of the midlevel mesocyclone and the entire evolution of the low level mesocyclone are captured over a 70 min period the low level mesocyclone began as an incipient shallow circulation along a synoptic scale trough the circulation intensified and grew in depth via vortex stretching under the influence of a strong updraft as this rotation built up from the boundary layer it initially remained separate and distinct from the midlevel mesocyclone subsequently the two mesocyclones merge to produce a single column of rotation 4 5 km in diameter an occlusion downdraft develops within the mesocyclone circulation during the last passes by the storm signaling the beg

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

on the reliability of hook echoes as tornado indicators abstract a study of radar echoes associated with the tornadoes of the 3 april 1974 outbreak was performed to evaluate the usefulness of echo shape as an indicator of tornadic thunderstorms the hook shape was usually successful in characterizing an echo as tornadic with a false alarm rate of 169 because hook echoes were relatively rare however a less restrictive shape called distinctive was more successful at detecting tornadic thunderstorms identifying 65 of the tornadic echoes an echo had a distinctive shape if it possessed a marked appendage on its right rear flank or was in the shape of a spiral comma or line echo wave pattern lewp characteristics of the distinctive echo are given

observations of the surface boundary structure within the 23 may 2007 perryton texas supercell abstractin situ data collected within a weakly tornadic high precipitation supercell occurring on 23 may 2007 near perryton texas are presented data were collected using a recently developed fleet of 22 durable rapidly deployable probes dubbed sticknet as well as four mobile mesonet probes kinematic and thermodynamic observations of boundaries within the supercell are described in tandem with an analysis of data from the shared mobile atmospheric research and teaching radar observations within the rear flank downdraft of the storm exhibit large deficits of both virtual potential temperature and equivalent potential temperature with a secondary rear flank downdraft gust front trailing the mesocyclone a primarily thermodynamic boundary resided across the forward flank reflectivity gradient of the supercell this boundary is characterized by small deficits in virtual potential temperature coupled with positive perturbations of equivalent potential temperature the opposing thermodynamic perturbatio

high resolution mobile doppler radar observations of cyclic mesocyclogenesis in a supercell abstract on 15 may 2003 two ground based mobile doppler radars scanned a supercell that moved through the texas panhandle and cyclically produced mesocyclones the two radars collected data from the storm during a rapid cyclic mesocyclogenesis stage and a more slowly evolving tornadic period a 3 cm wavelength radar scanned the supercell continuously for a short time after it was cyclic but close to the time of tornadogenesis a 5 cm wavelength radar scanned the supercell the entire time it exhibited cyclic behavior and for an additional 30 min after that the volumetric data obtained with the 5 cm wavelength radar allowed for the individual circulations to be analyzed at multiple levels in the supercell most of the circulations that eventually dissipated moved rearward with respect to storm motion and were located at distances progressively farther away from the region of rear flank outflow the circulations associated with a tornado did not move nearly as far rearward relative to the storm the mean

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

mobile phased array doppler radar observations of tornadoes at x band abstracta mobile phased array doppler radar the mobile weather radar 2005 x band phased array mwr 05xp has been used since 2007 to obtain data in supercells and tornadoes rapidly updating volumetric data of tornadic vortex signatures tvss associated with four tornadoes are used to investigate the time height evolution of tvs intensity position and dissipation up through storm midlevels both tvs intensity and position were highly variable in time and height even during tornado mature phases in one case a tvs associated with a tornado dissipated aloft and a second tvs formed shortly thereafter while there was one continuous tvs near the ground in a second case the tvs associated with a long lived violent tornado merged with a second tvs likely a second cyclonic tornado causing the original tvs to strengthen tvs dissipation occurred first at a height of 1 5 km agl and then at progressively higher levels in two cases tvs dissipation occurred last in the lowest 1 km in three cases exami

the influence of environmental low level shear and cold pools on tornadogenesis insights from idealized simulations abstractidealized dry simulations are used to investigate the roles of environmental vertical wind shear and baroclinic vorticity generation in the development of near surface vortices in supercell like pseudostorms a cyclonically rotating updraft is produced by a stationary cylindrical heat source imposed within a horizontally homogeneous environment containing streamwise vorticity once a nearly steady state is achieved a heat sink which emulates the effects of latent cooling associated with precipitation is activated on the northeastern flank of the updraft at low levels cool outflow emanating from the heat sink spreads beneath the updraft and leads to the development of near surface vertical vorticity via the baroclinic mechanism as has been diagnosed or inferred in actual supercells that have been simulated and observed an intense cyclonic vortex forms in the simulations in which the environmental low level wind shear is strong and the heat sink is of intermediate strength relative to the

rapid scan super resolution observations of a cyclic supercell with a dual polarization wsr 88d abstract in recent years there has been widespread interest in collecting and analyzing rapid updates of radar data in severe convective storms to this end conventional single polarization rapid scan radars and phased array radar systems have been employed in numerous studies however rapid updates of dual polarization radar data in storms are not widely available for this study a rapid scanning strategy is developed for the polarimetric prototype research weather surveillance radar 1988 doppler wsr 88d radar in norman oklahoma koun which emulates the future capabilities of a polarimetric multifunction phased array radar mpar with this strategy data are collected over an 80 sector with 0 5 azimuthal spacing and 250 m radial resolution super resolution with 12 elevation angles thus full volume scans over a limited area are collected every 71 73 s the scanning strategy was employed on a cyclic nontornadic supercell storm in western oklahoma on 1 june 2008 the evolution of the pola

episodic discrete and distributed deformation consequences and controls in a thrust culmination from the central pyrenees abstract the pic de port vieux culmination is a 0 5 km long thrust culmination in the footwall of the gavarnie thrust in the central pyrenees the culmination comprises a set of blind thrusts that imbricate a 50 m thick mesozoic cover sequence comprising triassic red beds and upper cretaceous limestone sandwiched between underlying hercynian basement and the overlying palaeozoic strata of the gavarnie thrust sheet an intense cleavage developed within the culmination associated with the oblique tip lines of the thrusts as they climbed from the basement into the cover strata detailed mapping shows that the distributed strain associated with the fault tips locally re activated earlier folded thrusts creating upper detachments to the system and produced a set of new overstepping isolated faults the main detachment occurred along the roof of the culmination using the back limbs of folds in the roof thrust the movement on these detachments can be demonstrated to have been episodic with periods of fault slip producing splays that were then folded during periods when distributed deformation was dominant the main control on this episodic deformation is modelled as the result of feedback between increase in fluid pressure associated with inelastic porosity reduction during cleavage development and fluid pressure bleed off associated with fault zone dilatancy in the culmination