observations of vertical wind shear heterogeneity in convective boundary layers abstract dual doppler wind syntheses from mobile radar observations obtained during the international h2o project document some of the spatial variability of vertical wind profiles in convective boundary layers much of the variability of popular forecasting parameters such as vertical wind shear magnitude and storm relative helicity is thought to result from pressure and temperature gradients associated with mesoscale boundaries e g drylines outflow boundaries fronts these analyses also reveal substantial heterogeneity even in the absence of obvious mesoscale wind shifts in regions many might have classified as horizontally homogeneous with respect to these parameters in the past this heterogeneity is closely linked to kinematic perturbations associated with boundary layer convection when a mean wind is present the large spatial variability implies significant temporal variability in the vertical wind profiles observed at fixed locations with the temporal variability increasing with mean win

analysis of a nontornadic storm during vortex 95 abstract analysis of a supercell storm that did not produce a tornado near hays kansas is presented a well defined midlevel mesocyclone was apparent throughout most of the storm s life cycle numerous shallow circulations were observed along the rear flank gust front during the data collection period six of these circulations strengthened into intense low level mesocyclones each of these mesocyclones failed to produce a tornado the strongest low level mesocyclone referred to as vortex 4 underwent a life cycle that was consistent with other tornadic mesocyclones documented in the literature these results illustrate that the presence of a long lived mesocyclone at low levels is not sufficient for tornadogenesis to occur the kinematic structure of the low level mesocyclone that did not produce a tornado is compared with a tornadic mesocyclone from another storm in order to understand the characteristic differences between these circulations the results lead to the conclusion that the presence of

field evidence for flank instability basal spreading and volcano tectonic interactions at mt cameroon west africa the mt cameroon volcano is the highest and most active volcano of the cameroon volcanic line little geological information is available for improving the understanding of the structure of this large volcanic system and its relationship to regional tectonics after reviewing the tectonic evolution of the region the analysis of a digital elevation model and results from a field campaign dedicated to mapping geological structures in the summit area and at the se base of mt cameroon are presented mt cameroon is a lava dominated volcano with long steep over 30 flanks it is elongate parallel to its well defined rift zone the summit plateau is bordered by 10 m high cliffs formed by summit subsidence along normal faults geological profiles were measured along rivers cutting through a topographic step at the se base of mt cameroon this step is associated with deformed miocene sediments from the douala basin that are overlain by volcanic products weak sediments of this area are deformed by 050 060 and 020 030 trending asymmetrical folds verging toward the se and thrusts faults related to the spreading of the volcano over its mechanically weak substratum combined remote sensing and field observations suggest that spreading is accommodated by summit subsidence and flanks sliding both slow spreading movements and catastrophic collapses of the steep flanks are interpreted to result from complex interactions between the growing edifice repeated dyke intrusions the weak sedimentary substratum and tectonic structures

analysing the topographic form of stratovolcanoes abstract the goal of this study is to explore ideal analytic functional forms that best fit the topographic shape of n 190 isolated stratovolcanoes from around the world using a stochastic model for the piling of lava flows to demonstrate one set of physical processes that give rise to a stratovolcano s topography we find that although the ideal form fits well for many stratovolcanoes there exist deviations from this shape particularly where the edifice is more protuberant than expected we explore sub surface factors such as the emplacement of magma beneath a volcano edifice that may be responsible for these deviations and estimate the relative contribution of dyke intrusions on the height and shape of a volcanic edifice versus the constructional piling of lava from this comparison we are able to gain more insight into the role of important subsurface physical factors such as chamber depth and total intruded volume we find that low basal ellipticity is a characteristic of nearly all volcanoes that fit the ideal stratovolcano form by fitting along each quadrant bisected by either a semi major or semi minor ellipse axis we find that the volcanoes chosen in this study fall into four groups 1 volcanoes that are axisymmetric and fit the ideal form well 2 volcanoes that are not axisymmetric but may be fit to the ideal form using different fitting parameters in each quadrant 3 volcanoes that have axisymmetric protuberant deviations in all quadrants and 4 volcanoes that have non axisymmetric protuberant deviations that are only present in a couple of quadrants we show that in some cases the non axisymmetry of volcanoes in category 2 may be understood as the result of the piling of eruptive products along a regional planar trend for edifices in categories 3 and 4 we model protuberant deviations as the result of a statistical distribution of elastic tensile dislocations representing dykes which emanate from a magma reservoir and cause uplift at the surface we support this interpretation of the excess topography in a few case studies where independent geologic and geophysical data corroborate our model results

observed and numerically simulated structure of a mature supercell thunderstorm abstract through the interactive use of doppler radar analyses and a three dimensional numerical storm simulation the detailed structure of a supercell tornadic storm is analyzed this storm named the del city storm occurred in central oklahoma on 20 may 1977 the storm exhibits certain important features which are essential to maintaining its longevity and which promote the storm s transition to its tornadic phase these features are strongly influenced by the rotational character of the storm separates the precipitation from the updraft and which orients the resulting downdrafts to which reinforce low level convergence along the gust front and sustain the storm analyses of air parcel and rain trajectories within the storm provide a detailed visualization of this internal structure these trajectories reveal that air parcels rising through the cyclonically rotating updraft actually turn anticyclonically with height owing to the influence of the storm relative environmental wind field downdraft traj

radar research on thunderstorms and lightning weather radars can resolve many phenomena related to thunderstorms echoes from clear air water and ice condensate and ionized lightning channels can all be identified radial velocity data from two doppler radars are synthesized to show a storm mesocyclone with updraft speeds as large as 40 m s 1 moist boundary layer air flowing into the storm and outflow into the upper troposphere maximum wind speeds in tornadoes can be remotely measured using doppler spectra obtained with a high prf radar doppler radars can detect thunderstorm gusts even when they are in the clear air many tens of kilometres away from the storm and radar detection of the ionized channels caused by lightning opens new avenues into thunderstorm research

rate of sediment yield following small scale volcanic eruptions a quantitative assessment at the merapi and semeru stratovolcanoes java indonesia sediment yields were calculated on the anks of merapi and semeru volcanoes in java indonesia using two different methods during the rst year following the 22 november 1994 eruption of merapi a sediment yield in excess of 1 5 105 m3 km 2 yr 1 was calculated in the boyong river drainage basin based on the volumes of sediment that were trapped by ve check dams at semeru sediment discharges were assessed in the curah lengkong river from direct measurements on the lahars in motion and on the most signi cant stream ows the calculated rate of sediment yield during one year of data in 2000 was 2 7 105 m3 km 2 yr 1 sediment yields are dominated by rain triggered lahars which occur every rainy season in several drainage basins of merapi and semeru volcanoes mostly during the rainy season extending from october to april the return period of lahars carrying sediment in excess of 5 105 m3 is about one year in the curah lengkong river at semeru at merapi the volume of sediments transported by a lahar did not exceed 2 8 105 m3 in the boyong river during the rainy season 1994 95 on both volcanoes the sediments are derived from similar sources pyroclastic ow surges deposits rockfalls from the lava domes and old material from the riverbed and banks however daily explosions of vulcanian type at semeru provide a more continuous sediment supply than at merapi therefore sediment yields are larger at semeru copyright 2004 john wiley sons ltd

creating a more realistic idealized supercell thunderstorm evolution via incorporation of base state environmental variability abstractconvective environments are known to be heterogeneous in both time and space yet idealized models use fixed base state environments to simulate storm evolution recently the base state su

surface fitting in geomorphology examples for regular shaped volcanic landforms abstract in nature several types of landforms have simple shapes as they evolve they tend to take on an ideal simple geometric form such as a cone an ellipsoid or a paraboloid volcanic landforms are possibly the best examples of this ideal geometry since they develop as regular surface features due to the point like circular or fissure like linear manifestation of volcanic activity in this paper we present a geomorphometric method of fitting the ideal surface onto the real surface of regular shaped volcanoes through a number of case studies mt mayon mt somma mt semeru and mt cameroon volcanoes with circular as well as elliptical symmetry are addressed for the best surface fit we use the minimization library minuit which is made freely available by the cern european organization for nuclear research this library enables us to handle all the available surface data every point of the digital elevation model in a one step half automated way regardless of the size of the dataset and to consider simultaneously all the relevant parameters of the selected problem such as the position of the center of the edifice apex height and cone slope thanks to the highly performing adopted procedure fitting the geometric surface along with calculating the related error demonstrates the twofold advantage of the method firstly we can determine quantitatively to what extent a given volcanic landform is regular i e how much it follows an expected regular shape deviations from the ideal shape due to degradation e g sector collapse and normal erosion can be used in erosion rate calculations secondly if we have a degraded volcanic landform whose geometry is not clear this method of surface fitting reconstructs the original shape with the maximum precision obviously in addition to volcanic landforms this method is also capable of constraining the shapes of other regular surface features such as aeolian glacial or periglacial landforms

an analysis of cold season supercell storms using the synthetic dual doppler technique abstractcold season tornadic outbreaks occur with regularity in the southeastern united states however detailed analyses of parent supercell storms in the cold season environment often low cape high shear are scarce this is often because storms do not always move close enough to radars for a comprehensive single doppler analysis and significant topography or trees in the southeast make it difficult for mobile radars to operate thus limiting dual doppler coverage however during the super tuesday tornado outbreak of 5 6 february 2008 two tornadic supercell storms passed within 30 40 km of the weather surveillance radar 1988 doppler wsr 88d sites in memphis and nashville tennessee knqa and kohx respectively the relative steadiness of these storms during passage along with the large motion vector from the southwest at 20 25 m s 1 allowed the application of a synthetic dual doppler sdd analysis as such a detailed analysis of these storms was completed including examinations of low lev

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

finestructure of the del city edmond tornadic mesocirculation abstract interrelationships among severe thunderstorm wind flow tornado parent circulation and tornado are examined with dense single and dual doppler radar observations from the del city edmond oklahoma storm of 20 may 1977 beginning with tornadogenesis rising inflow air from right hand quadrants and subsiding air from a developing downdraft on the storm s rear are wrapped in a large spiral pattern about the tornado the updraft appears to drive the tornado while the downdraft appears to form as entrained environmental air concentrated by the intensifying parent circulation is cooled evaporatively

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

impacts of lapse rates on low level rotation in idealized storms abstractadiabatic lapse rates appear to be a common feature in the lower troposphere on tornado days this article reviews physical reasons why lapse rates may influence surface vortex intensification and reports on numerical simulations designed to study the key processes in the idealized numerical model an initial mesocyclone like vortex and nonvarying convection like heat source are used in different environmental stability profiles the scales of interest in these simulations typify those of a parent supercell and the developing circulations constitute direct responses to the imposed heating downward parcel displacements are needed for surface vortex development in environments with no preexisting surface vorticity in the simulations under neutral stratification there is strong heating induced subsidence anchored near the storm edge whereas under stable stratification there are instead gravity waves that propagate away to the far field in addition under weak or neutral low level stratification

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

active versus passive continental rifting evidence from the west african rift system fitton j g 1983 active versus passive continental rifting evidence from the west african rift system in p morgan and b h baker processes of continental rifting tectonophysics 94 473 481 the west african rift system comprises the cretaceous benue trough and the tertiary to recent volcanic cameroon line the two features are remarkably similar in shape and size and may be superimposed perfectly by rotating one with respect to the other by 7 about a pole in sudan three stages in the geological history of the system are postulated 1 the benue trough was produced by lithosphere stretching as one arm of an rrr triple junction during the early stages of the opening of the south atlantic 2 at about 80 ma santonian a short lived period of clockwise rotation interrupted the otherwise anticlockwise rotation of africa and decoupled the lithosphere from the asthenosphere the hot zone in the asthenosphere beneath the benue trough thus became displaced relative to the lithosphere and moved to a new position beneath cameroon and the gulf of guinea 3 anticlockwise rotation and asthenosphere lithosphere coupling were restored allowing the hot zone to manifest itself as the cameroon line the cameroon line is possibly a unique example of what a rift system produced actively by a thermal anomaly in the asthenosphere would look like it is significant that despite a long history of volcanism and uplift the cameroon line has not developed a graben structure the implication is that rift systems with graben structures are produced passively by lithosphere stretching

uncertainties in trajectory calculations within near surface mesocyclones of simulated supercells abstractthis study addresses the sensitivity of backward trajectories within simulated near surface mesocyclones to the spatiotemporal resolution of the velocity field these backward trajectories are compared to forward trajectories computed during run time within the numerical model it is found that the population of backward trajectories becomes increasingly contaminated with inflow trajectories that owe their existence to spatiotemporal interpolation errors in time varying and strongly curved confluent flow these erroneous inflow parcels may mistakenly be interpreted as a possible source of air for the near surface vortex it is hypothesized that unlike forward trajectories backward trajectories are especially susceptible to errors near the strongly confluent intensifying vortex although the results are based on model output dual doppler analysis fields may be equally affected by such errors

are supercells resistant to entrainment because of their rotation abstractthis research investigates a hypothesis posed by previous authors which argues that the helical nature of the flow in supercell updrafts makes them more resistant to entrainment than nonsu

morphometry of scoria cones and their relation to geodynamic setting a dem based analysis abstract the morphometry of a great number of scoria cones belonging to volcanic fields of various geodynamic settings has been measured and analyzed addressing the question whether there is a relation between the prevalent cone shape in a given field and the geodynamic setting of the field itself morphometric analysis was carried out on freely downloadable digital elevation models dems the accuracy of the used dems and the associated error in scoria cone morphometry were determined by cross comparing high resolution lidar derived dems usgs ned tinitaly dem and aster gdem the 10 m tinitaly 01 and usgs ned dems are proven to be suitable for scoria cone morphometry whereas aster gdem can be used reliably for cones with volume greater than 30 10 6 m 3 according to a detailed morphometry of all scoria cones we propose that the cones related to subductional setting show relatively higher values of h c o w co and lower values of w cr w co than the cones related to extensional setting the detected differences can be imputable to peculiar eruption dynamics resulting in slight but systematic changes in shape and differences in lithological and sedimentological characteristics that govern post eruptive erosion to constrain the pathway of scoria cone erosion the detected morphometric changes were also interpreted using a simple linear degradation model utilizing the obtained simulation results the inferred initial cone base and the age of scoria cones we calculated a diffusion coefficient k for several dated cones which are related to the prevalent climate our results despite the high error associated allow to assess the median k for all volcanic fields due to the complexity of the factors behind it is not easy to understand if the prevalent shape characterizing a certain volcanic field is due mainly to sin eruptive or post eruptive mechanisms however our distinction between the two main geodynamic settings may be the first step to decipher these factors

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

construction and degradation of a broad volcanic massif the vicuna pampa volcanic complex southern central andes nw argentina the vicuna pampa volcanic complex at the se edge of the arid puna plateau of the central andes records the interplay between volcanic construction and degradational processes the low sloping vicuna pampa volcanic complex with a 1200 m deep southeastward opening depression was previously interpreted as a collapse caldera based on morphological considerations however characteristic features associated with collapse calderas do not exist and close inspection instead suggests that the vicuna pampa volcanic complex is a strongly eroded broad massif type composite volcano of mainly basaltic to trachyandesitic composition construction of the vicuna pampa volcanic complex occurred during two distinct cycles separated by the development of the depression the first and main cycle took place at ca 12 ma and was dominated by lava flows and subordinate scoria cones and domes the second cycle possibly late miocene in age affected the sw portion of the depression with the emplacement of domes we interpret the central depression as the result of a possible sector collapse and subsequent intense fluvial erosion during middle to late miocene time facilitated by faulting steepened topography and wetter climate conditions compared to today we estimate that 65 of the initial edifice of 240 km 3 was degraded the efficiency of degradation processes for removing mass from the vicuna pampa volcanic complex is surprising considering that today the region is arid and the stream channels within the complex are predominantly transport limited forming a series of coalesced aggraded alluvial fans and eolian infill hence the vicuna pampa volcanic complex records the effects of past degradation efficiency that differs substantially from that of today

particle aggregation in volcanic eruption columns we develop a model to describe the formation of aggregates in a volcanic eruption column the model combines a description of the rate of collision and sticking of particles with a model of the vertical transport in the eruption column we thereby determine the evolution of the grain size distribution as a function of height in the eruption column we consider aggregates in which liquid water provides the binding agent for sufficiently large eruption columns we find that this limits the vertical extent of the zone where aggregates may form since near the source all water is in the vapor form while in the upper part of the column the mixture becomes very cold and freezes however in many cases we find that the particles spend sufficient time in the central region where the water is in the liquid form that a substantial amount of aggregation occurs furthermore we predict that owing to the reduction in the binding efficiency of water as particle size increases gilbert and lane 1994 there is a relatively narrow size distribution of aggregates at the plume top we also model the airfall deposits associated with this aggregate rich distribution of particles which is injected to the top of the eruption column we show that the relatively narrow size distribution of particles at the top of the column coupled with the gravitational settling and transport by ambient winds may lead to enhanced deposition close to the source and in some cases secondary thickening of the deposit the relatively near source deposition of fine ash in these deposits is associated with the fallout of aggregates as a simple application we show that the present dynamical aggregation model is consistent with the secondary thickening of the deposit from the may 18 1980 eruption of mount st helens

growth and erosion rates of the east carpathians volcanoes constrained by numerical models tectonic and climatic implications abstract the east carpathian volcanic range experienced an along arc late miocene to quaternary migration of eruptive activity during its 11 ma long activity here a novel and complex methodology is presented that yields new geochronological and geomorphological constraints on the evolution of the 20 volcanic edifices new unspiked k ar ages either constrain their lifespan 6 79 0 10 6 47 0 09 ma for seaca t tarca 5 47 0 08 4 61 0 07 ma for v rghis or date the youngest volcanic activity central c limani in parallel numerical reconstructions of volcanic paleo topographies were performed to quantify their shape at the end of their construction stage the inferred initial volcano size shows a wide range 3 to 592 km3 making up the four main successive volcanic segments 910 880 279 and 165 km3 for c limani gurghiu north harghita and south harghita segment respectively totalizing 2200 km3 and an average growth rate of 200 km3 ma at range scale at the volcano scale with only consideration to their respective time spans i e avoiding repose periods growth rate is characterized by two major trends a moderate growth rate 137 km3 ma for the older volcanoes 11 3 6 ma followed by a lower growth rate 28 km3 ma obtained for the plio quaternary volcanoes comparing reconstructed and current topographies yielded a total eroded volume of 524 125 km3 defining averaged denudation of 22 and a 20 m ma erosion rate erosion rates for major climatic periods were computed which highlight the contrasting climatic contexts since 11 ma the highest erosion rate 38 m ma occurred during transitional moderate subtropical continental climate period 9 5 8 2 ma an intermediate erosion rate 14 m ma characterized a moderate continental climate period 8 2 6 8 ma when conditions became less humid the lowest erosion rate 7 m ma reflects the prevailing continental but occasionally semi arid climate 6 8 5 8 ma the highest erosion rate 28 m ma was obtained for plio quaternary times during the interglacial glacial cycles such a quantitative morphometric and geochronological approach demonstrates its efficiency to study volcanic dynamism including both constructional and erosional processes through time

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

morphometry and evolution of arc volcanoes volcanoes change shape as they grow through eruption intrusion erosion and deforma tion to study volcano shape evolution we apply a comprehensive morphometric analysis to two contrasting arcs central america and the southern central andes using shuttle radar topography mission srtm digital elevation models we compute and defi ne parameters for plan ellipticity irregularity and profi le height width summit basal width slope shape as well as size height width volume we classify volcanoes as cones sub cones and massifs and recognize several evolutionary trends many cones grow to a critical height 1200 m and volume 10 km 3 after which most widen into sub cones or massifs but some grow into large cones large cones undergo sector collapse and or gravitational spreading without sig nifi cant morphometry change other smaller cones evolve by vent migration to elliptical sub cones and massifs before reaching the critical height the evolutionary trends can be related to magma fl ux edifi ce strength structure and tectonics in particular trends may be controlled by two balancing factors magma pressure versus lithostatic pressure and conduit resistance versus edifi ce resistance morphometric analysis allows for the long term state of individual or volcano groups to be assessed morphological trends can be integrated with geological geophysical and geochemical data to better defi ne volcano evolution models

barrier effect of underground structures on aquifers abstract impervious structures below the water table modify the natural groundwater flow in aquifers they act as barriers causing heads to rise upgradient and to fall downgradient we define the barrier effect as the increase in head loss across the barrier with respect to the natural conditions prior to construction we distinguish between regional the minimum head loss observed at long distances and local the maximum head loss observed close to the structure barrier effects we use numerical and analytical methods to derive semi empirical equations to quantify the two barrier effects for semi permeable partially penetrating or fully penetrating but finite in length and barriers with a by pass in confined aquifers the resulting equations depend on the barrier geometry and on the natural head gradient in the aquifer and they are easy to apply we test their validity at two construction sites obtaining excellent agreement between the computed and observed barrier effects

the 6 may 2010 elevated supercell during vortex2 abstractan elevated supercell from the second verification of the origins of rotation in tornadoes experiment vortex2 on 6 may 2010 is investigated observations show that the supercell formed over a stable inversion and was likely decoupled from the surface quintessential features of a supercell were present including a hook echo albeit bent anticyclonically and midlevel mesocyclone and the storm was quasi steady during the observing period a weak surface cold pool formed but it was apparently devoid of air originating from midlevels idealized modeling using near storm soundings is employed to clarify the structure and maintenance of this supercell the simulated storm is decoupled from the surface by the stable layer additionally the reflectivity structure of the simulated supercell is strikingly similar to the observed storm including its peculiar anticyclonic curving hook echo air parcels above 1 km reached their lfcs as a result of the simulated supercell s own dynamic lifting which li

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

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

tornadogenesis in a high resolution simulation of the 8 may 2003 oklahoma city supercell abstracta 50 m grid spacing advanced regional prediction system arps simulation of the 8 may 2003 oklahoma city tornadic supercell is examined a 40 min forecast run on the 50 m grid produces two f3 intensity tornadoes that track within 10 km of the location of the observed long track f4 intensity tornado the development of both simulated tornadoes is analyzed to determine the processes responsible for tornadogenesis trajectory based analyses of vorticity components and their time evolution reveal that tilting of low level frictionally generated horizontal vorticity plays a dominant role in the development of vertical vorticity near the ground this result represents the first time that such a mechanism has been shown to be important for generating near surface vertical vorticity leading to tornadogenesis a sensitivity simulation run with surface drag turned off was found to be considerably different from the simulation with drag included a tornado still developed in the no drag simulation but it was

reconstructing eroded paleovolcanoes on gran canaria canary islands using advanced geomorphometry abstract original volcanic edifices of two successive stages of gran canaria are reconstructed using a geomorphometric analysis of existent or restored paleosurfaces in the reconstruction surface fitting was applied preferably to planezes i e triangular facets of original volcano flanks and quasi planar surfaces qps those occurring on planezes or scattered slightly eroded portions derived from original cone surfaces with the help of red relief image map rrim analysis out of the long lasting mid miocene to holocene subaerial evolution of the island the late miocene fataga volcano and the subsequent pliocene roque nublo volcanoes were the largest and highest the eruptive center of fataga a composite edifice 12 2 8 8 ma that may have grown up excentrically with respect to the previous tejeda caldera is well defined by both two planezes named veneguera mogan and fataga tirajana and qps remnants its calculated original volume 1000 km3 is close to the largest stratovolcanoes on earth however its 3300 m elevation obtained by exponential fit may have been significantly lower due to the complex architecture of the summit region e g a caldera responsible for ignimbrite eruptions roque nublo a 3 7 2 9 ma stratovolcanic cone which was superimposed upon the fataga rocks 3 km west of the fataga center has left no considerable paleosurfaces behind due to heavy postvolcanic erosion yet its remnant formations preserved in a radial pattern unambiguously define its center moreover surface fitting of the outcropping rocks can be corrected taking the erosion rate for the past 3 ma into account such a corrected surface fit points to a regular shaped 3000 m high cone with a 25 km radius and ca 940 km3 original volume also comparable with the dimensions of the largest terrestrial stratovolcanoes

the garden city kansas storm during vortex 95 part ii the wall cloud and tornado abstract on 16 may 1995 a supercell storm produced an f1 tornado near garden city kansas during vortex verification of the origins of rotation in tornadoes experiment this event provided the first opportunity to synthesize data collected by a new airborne radar platform called eldora electra doppler radar developed by the national center for atmospheric research the evolution of the low and midlevel mesocyclone was presented in a companion paper in this paper the sequence of events that triggered tornadogenesis within the mesocyclone circulation is shown the occlusion downdraft documented in part i appears to promote vortex breakdown resulting in the generation of multiple vorticity centers it is one of these centers that intensifies into the garden city tornado the structural relationship between the observed wall cloud and the radar reflectivity associated with the developing hook echo and the kinematic wind field is also presented although the wall cloud appears to be uniform there

volcanic geomorphology an overview abstract the review examines the role of geomorphology in analyzing the volcanoes on earth five objectives are stressed first classifications of volcanic landforms should be improved to take care of the complexity in volcanic landform generation as magmatic systems style of eruption and the erupted material all influence the morphology second geomorphology should contribute to the science of volcanology through its capability in reconstructing growth stages in complex volcanoes and also in analyzing the structural factors which contribute to the catastrophic collapse of volcanoes third geomorphology can contribute to physical volcanology by assessing the effects of topography on transport erosion and deposition of volcanogenic flows and identifying the sources and climatic tectonic conditions which govern the emplacement of volcaniclastic deposits fourth volcanic geomorphology a identifies sedimentary facies associations b constructs facies models for dynamic volcano delivery systems and c analyzes the characteristics of sediment gravity flows in order to determine relevant parameters for modelling their behaviour fifth process oriented geomorphology is critical in developing accurate methods for measuring rates of geomorphic processes that shape ephemeral volcanic constructs and for evaluating and comparing geomorphic impacts on disturbed catchments and the related hydrologic response before during and after eruptions this should help to refine parameters for the exponential decay model finally volcanic geomorphology is essential for risk assessment through geomorphic hazard zonation and composite risk zonation such treatments are necessary in order to face the enhanced challenge posed by the combination of natural hazards and the increasing number of people who are at risk around volcanoes

the 29 june 2000 supercell observed during steps part i kinematics and microphysics this is a two part study that addresses the kinematic microphysical and electrical aspects of a severe storm that occurred in western kansas on 29 june 2000 observed during the severe thunderstorm electrification and precipitation study steps field campaign in this first part polarimetric and doppler radar data are used along with a simple particle growth model to examine the evolution of the kinematic and microphysical properties of the storm from its earliest developing phase through its mature and dissipating phases during its severe stage the storm exhibited frequent positive cloud to ground lightning strikes very large 5 cm hail and a tornado doppler derived winds radar reflectivity and hydrometeor classifications from the polarimetric data over a nearly 4 h period are presented it is shown that updraft velocity and vertical vorticity had to reach magnitudes of at least 10 m s 1 and 10 2 s 1 and occupy major portions of the storm before it could produce most of the observed severe storm characteristics furthermore the establishment of cyclonic horizontal flow around the right flank of the updraft core was essential for hail production most of the largest hail grew from near millimeter sized particles that originated in the mid to upper level stagnation region that resulted from obstacle like flow of environmental air around the divergent outflow from the upper part of the updraft these recycling embryonic particles descended around the right flank of the updraft core and reentered the updraft intermingling with other smaller particles that had grown from cloud base along the main low level updraft stream

a numerical study of a nontornadic supercell over france abstract a case of a nontornadic supercell over france is simulated with a three dimensional nonhydrostatic cloud model the simulation starts from an operational data analysis without any superimposed perturbation the initial convective cell is triggered by a mesoscale convergence line associated with a preexisting thermal boundary the model succeeds in simulating right and left moving storms arising from a splitting process of the initial convective cell the right moving storm exhibits the characteristics of a supercell with a hooklike structure in the precipitation field a midlevel rotating updraft and a low level cyclonic vortex a vorticity budget analysis is performed along backward parcel trajectories for the initial storm and for the supercell phases with emphasis on the impacts of the preexisting thermal boundary and the associated low level variations of shear similar mechanisms as those found for the cases over homogeneous environment operate globally indeed the simulation exhibits a

retrieval of model initial fields from single doppler observations of a supercell thunderstorm part ii thermodynamic retrieval and numerical prediction in this two part study a single doppler parameter retrieval technique is developed and applied to a real data case to provide model initial conditions for a short range prediction of a supercell thunderstorm the technique consists of the sequential application of a single doppler velocity retrieval sdvr followed by a variational velocity adjustment a thermodynamic retrieval and a moisture specification step in part i the sdvr procedure is described and results from its application to a supercell thunderstorm are presented in part ii results from the thermodynamic retrieval and the numerical model prediction for this same case are presented for comparison results from parallel sets of experiments using dual doppler derived winds and winds obtained from the simplified velocity retrieval described in part i are also shown following the sdvr the retrieved wind fields available only within the storm volume are blended with a base state background field obtained from a proximity sounding the blended fields are then variationally adjusted to preserve anelastic mass conservation and the observed radial velocity a gal chen type thermodynamic retrieval procedure is then applied to the adjusted wind fields for all experiments full retrieval simplified retrieval and dual doppler the resultant perturbation pressure and potential temperature fields agree qualitatively with expectations for a deep convective storm an analysis of the magnitude of the various terms in the vertical momentum equation for both the full retrieval and dual doppler experiments indicates a reasonable agreement with predictions from linear theory in addition the perturbation pressure and vorticity fields for both the full retrieval and dual doppler experiments are in reasonable agreement with linear theory predictions for deep convection in sheared flow following a simple moisture specification step short range numerical predictions are initiated for both retrieval experiments and the dual doppler experiment in the full single doppler retrieval and dual doppler cases the general storm evolution and deviant storm motion are reasonably well predicted for a period of about 35 minutes in contrast the storm initialized using the simplified wind retrieval decays too rapidly indicating that the additional information obtained by the full wind retrieval primarily low level polar vorticity is vital to the success of the numerical prediction sensitivity experiments using the initial fields from the full retrieval indicate that the predicted storm evolution is strongly dependent on the initial moisture fields overall the numerical prediction results suggest at least some degree of short term predictability for this storm and provide an impetus for continued development of single doppler retrieval procedures

characteristics and predictability of a supercell during hymex sop1 an analysis is presented here of intense convection affecting the friuli venezia giulia region fvg northeastern italy during the intensive observation period 2b iop2b in the first special observation period sop1 of hymex hydrological cycle in mediterranean experiment the present study focuses on the first of three severe convection episodes that affected fvg on the morning of 12 september 2012 in the first episode a supercell which produced hail and severe damage to trees and buildings was observed on the plain of fvg the available observations are analysed together with a high resolution mesoscale model in order to identify the relevant mechanisms for the formation and development of the cell six different simulations were performed starting at three different initial times using respectively two different analysis forecasts as initial boundary conditions a large spread in forecast precipitation is found among the six simulations only a few of the simulations were able to reproduce intense rainfall on the plain of fvg during the morning although with significant differences in the rainfall distribution among them one of the six simulations well reproduces the observed elongated distribution of the intense rainfall maximum the characteristics of the cell responsible for this distribution are consistent with those expected for a supercell and its simulated evolution near the adriatic coast agrees well with the other observations some instability parameters over the fvg plain and offshore over the northern adriatic sea are analysed every 5 min showing that during this event the potential instability varies significantly over small space and time intervals and among the simulations the best simulations have the best match to the observed potential instability calculated using the mean characteristics of the lowest 500 m layer

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

the impact of spatial variations of low level stability on the life cycle of a simulated supercell storm abstract this study reports on the dynamical evolution of simulated long lived right moving supercell storms in a high cape strongly sheared mesoscale environment which initiate in a weakly capped region and subsequently move into a cold boundary layer bl and inversion region before dissipating the storm simulations realistically approximate the main morphological features and evolution of the 22 may 1981 binger oklahoma supercell storm by employing time varying inflow lateral boundary conditions for the storm relative moving grid which in turn are prescribed from a parent fixed steady state mesoscale analysis to approximate the observed inversion region to the east of the dryline on that day a series of full life cycle storm simulations have been performed in which the magnitude of boundary layer coldness and the convective inhibition are varied to examine the ability of the storm to regenerate and sustain its main updraft as it moves into environments with increasing convective stability the

the owl horn radar signature in developing southern plains supercells abstract during spring 2001 in the southern plains a recurring hitherto undocumented reflectivity signature that the authors have called the owl horn signature because the radar reflectivity pattern resembles the profile of the great horned owl was observed on a mobile x band radar display the reflectivity signature was always located at the rear side of a developing supercell spanned the entire rear side of the storm and was always seen on low level plan position indicator ppi scans it lasted on the order of only 5 10 min and was not an artifact of the radar a study of the owl horn signature was undertaken using the tracking radar echoes by correlation technique trec to estimate the wind field trec has previously been applied to clear air and hurricane environments and to the internal motions of severe storms but not to their evolution the characteristics of the signature are presented and then through the application of trec to the radar reflectivity data doppler wind data were no

a tropical squall line observed during toga coare extended comparisons between simulations and doppler radar data and the role of midlevel wind shear abstract results from a three dimensional cloud model are extensively compared with airborne doppler radar data in the case of a tropical oceanic squall line observed during the tropical ocean global atmosphere coupled ocean atmosphere response experiment the comparison is based on the precipitation patterns the dynamical and thermodynamical distributions and the vertical transport of horizontal momentum the model simulates the evolution of the mesoscale convective system mcs frontal convective line from a quasi linear to a broken pattern the area located south of the break which designates the region where the mcs leading edge reorientates from the n s to the e w direction is composed of a pronounced bow shaped structure with two vortices located on both sides of a strong rear inflow the vertical circulation is characterized by a jump updraft and an overturning downdraft both structures exhibit a vertical intense updraft in the break zone whereas the jump updraft is more sloped and less in

a new volcanic province an inventory of subglacial volcanoes in west antarctica abstract the west antarctic ice sheet overlies the west antarctic rift system about which due to the comprehensive ice cover we have only limited and sporadic knowledge of volcanic activity and its extent improving our understanding of subglacial volcanic activity across the province is important both for helping to constrain how volcanism and rifting may have influenced ice sheet growth and decay over previous glacial cycles and in light of concerns over whether enhanced geothermal heat fluxes and subglacial melting may contribute to instability of the west antarctic ice sheet here we use ice sheet bed elevation data to locate individual conical edifices protruding upwards into the ice across west antarctica and we propose that these edifices represent subglacial volcanoes we used aeromagnetic aerogravity satellite imagery and databases of confirmed volcanoes to support this interpretation the overall result presented here constitutes a first inventory of west antarctica9s subglacial volcanism we identified 138 volcanoes 91 of which have not previously been identified and which are widely distributed throughout the deep basins of west antarctica but are especially concentrated and orientated along the 3000 km central axis of the west antarctic rift system

construction and destruction of mont pelee volcano volumes and rates constrained from a geomorphological model of evolution this study presents long term volumes and construction rates for the mont conil mont pelee volcano and rate estimates at which volcanic activity creates relief an algorithm shapevolc is used to numerically model topographic surfaces volcano morphology is analyzed using current digital elevation model in combination with mapped geology to produce 10 paleotopographies at the end of four constructional stages and three destructional events volumes of each constructional stage were estimated at about 35 2 km3 26 2 km3 8 3 km3 and 2 5 km3 for a total cumulative erupted volume of 72 2 km3 we estimate that mont pelee accounted for about 10 of the lesser antilles arc production in the last 100 kyr the volcano has been built at an average rate of 0 13 km3 kyr during the last 550 kyr during that time construction rates varied by a factor of 15 from 0 04 km3 kyr in early stages up to 0 52 km3 kyr after the second flank collapse volumes displaced by each flank collapse were estimated at 14 7 km3 8 8 km3 and 3 5 km3 thus about 37 of the total constructed volume integrated over the volcano s lifetime the rate at which flank collapses removed material off the island is 0 15 km3 kyr in contrast long term erosion rates outside collapsed areas are estimated at about 0 05 0 7 km3 kyr or 11 km3 of material removed this latter rate is not negligible which strengthens the importance of taking into account recurrent small erosional events on the geomorphological evolution of a volcanic island in a tropical context

the structure and evolution of a numerically simulated high precipitation supercell thunderstorm the structure and evolution of a high precipitation hp supercell thunderstorm is investigated using a threedimensional nonhydrostatic cloud scale numerical model tass the model is initialized with a sounding taken from a mesoscale modeling study of the environment that produced the 28 november 1988 raleigh tornadic thunderstorm tass produces a long lived convective system that compares favorably with the observed raleigh tornadic thunderstorm the simulated storm evolves from a multicell type storm to a multiple updraft supercell storm the storm complex resembles a hybrid multicell supercell thunderstorm and is consistent with the conceptual model of cool season strong dynamic hp supercells that are characterized by shallow mesocyclones the origin of rotation in this type of storm is often in the lowest levels interactions between various cells in the simulated convective system are responsible for the transition to a supercellular structure an intense low level updraft core forms on the southwest flank of the simulated storm and moves over a region that is rich in vertical vorticity the stretching of this preexisting vertical vorticity in the storm s lowest levels is the most important vertical vorticity production mechanism during the initial stages of the main updraft s development interactions with an extensive cold pool created by the storm complex are also important in producing vertical vorticity as the main updraft grows overall the development of vorticity associated with the main updraft appears similar to nonsupercellular tornadic storms however classic supercell signatures are seen early in the simulation associated with other updrafts e g formation of vortex couplet due to tilting of ambient horizontal vorticity storm splitting etc and are deemed important in the storm s supercell stage rotation is sustained in the lowest levels of the storm despite large amounts of precipitation located near and within the main mesocyclone pulsating downdrafts periodically invigorate the storm and the gust front never occludes thus allowing the main updraft to persist for a prolonged period of time the storm s intensity is also maintained by frequent updraft mergers

hook echoes and rear flank downdrafts a review abstract nearly 50 years of observations of hook echoes and their associated rear flank downdrafts rfds are reviewed relevant theoretical and numerical simulation results also are discussed for over 20 years the hook echo and rfd have been hypothesized to be critical in the tornadogenesis process yet direct observations within hook echoes and rfds have been relatively scarce furthermore the role of the hook echo and rfd in tornadogenesis remains poorly understood despite many strong similarities between simulated and observed storms some possibly important observations within hook echoes and rfds have not been reproduced in three dimensional numerical models

mantle echoes associated with deep convection observations and numerical simulations abstract finescale radar observations of intense thermals starting plumes during the early stages of precipitation formation were collected by an airborne doppler radar on two separate days the radar data were recorded as the aircraft flew underneath the developing echoes mantle echoes echoes that often appear as an inverted u shape were observed on both days striking in one of the scans was the resemblance of the echo to a mushroom cloud resulting from a nuclear explosion numerical simulations using a two dimensional cloud resolving model were run to augment the interpretation of the observations one of the important conclusions was the proposed modification to the default bulk microphysical scheme used in the model the default scheme yields a rush to precipitation leading to the early establishment of large precipitation contents which is not supported by the observations suggested modifications to the scheme are presented

numerical simulation of tornadogenesis in an outer rainband minisupercell of typhoon shanshan on 17 september 2006 abstract on 17 september 2006 three tornadoes occurred along the east coast of kyusyu island in western japan during the passage of an outer rainband in the right front quadrant of typhoon shanshan to clarify the structure of the tornado producing storms and the mechanism of tornadogenesis quadruply nested numerical simulations were performed using a nonhydrostatic model with an innermost horizontal grid spacing of 50 m several simulated convective storms in the outermost rainband exhibited characteristics of a minisupercell one storm had a strong rotating updraft of more than 30 m s 1 and a large vertical vorticity exceeding 0 06 s 1 this storm spawned a tornado when the low level mesocyclone intensified the tornado was generated on the rear flank gust front near the mesocyclone center when a secondary rear flank downdraft rfd surge advanced cyclonically around the low level mesocyclone and overtook the rear flank gust front at its left front edge backward trajectories and vorticity budget anal

direct surface thermodynamic observations within the rear flank downdrafts of nontornadic and tornadic supercells abstract despite the long surmised importance of the hook echo and rear flank downdraft rfd in tornadogenesis only a paucity of direct observations have been obtained at the surface within hook echoes and rfds in this paper in situ surface observations within hook echoes and rfds are analyzed these mobile mesonet data have unprecedented horizontal spatial resolution and were obtained from the verifications of the origins of rotation in tornadoes experiment vortex and additional field experiments conducted since the conclusion of vortex the surface thermodynamic characteristics of hook echoes and rfds associated with tornadic and nontornadic supercells are investigated to address whether certain types of hook echoes and rfds are favorable or unfavorable for tornadogenesis tornadogenesis is more likely and tornado intensity and longevity increase as the surface buoyancy potential buoyancy as measured by the convective available potential energy and equivalent potential temperature in the r

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

structure and formation mechanism on the 24 may 2000 supercell like storm developing in a moist environment over the kanto plain japan abstract the structure and formation mechanism of a supercell like storm in a moist environment below a melting layer were investigated using dual doppler radar analysis and a cloud resolving storm simulator cress the supercell like storm developed over the kanto plain japan on 24 may 2000 the environment of the supercell like storm possessed large convective available potential energy 1000 j kg 1 strong vertical wind shear 4 2 10 3 s 1 between the surface and 5 km above sea level and a moist layer the relative humidity was 60 90 below a melting layer at 3 km in height the dual doppler radar analysis with a variational method revealed that the supercell like storm had similar structures to those of a typical supercell in a dry environment below a melting layer such as that in the great plains in the united states the structures included a hook echo an overhanging echo structure and a strong updraft with strong vertical vorticity however some of the characteristics of the supercell

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

heat moisture and momentum budgets of isolated deep midlatitude and tropical convective clouds as diagnosed from three dimensional model output part ii sensitivity to ice phase and small changes in ambient shear strength and low level moisture supply abstract this project uses a three dimensional anelastic cloud model with a simple ice phase parameterization to evaluate the feedback of isolated deep convective clouds over a horizontal scale comparable to one grid cell in typical mesoscale numerical weather prediction models a more specific focus in this paper is the sensitivity of the feedback to modest changes in the initial vertical wind shear intensity and low level moisture supply as well as to the ice phase two parallel sets of comparative simulations are run for a quasi steady severe oklahoma supercell thunderstorm in strong vertical wind shear versus a weaker less persistent and narrower tropical atlantic cumulonimbus with a slowly decaying and pulsating updraft in much weaker shear the horizontal reynolds averaging approach of anthes is adopted to diagnose the budgets for heat moisture and horizontal momentum several similarities and differences between the midlatitude and tropical control experiments were delineated in part i the ma

erosion calderas origins processes structural and climatic control the origin and development of erosion modified erosion transformed and erosion induced depressions in volcanic terrains are reviewed and systematized a proposed classification addressing terminology issues considers structural geomorphic and climatic factors that contribute to the topographic modification of summit or flank depressions on volcanoes breaching of a closed crater or caldera generated by volcanic or non volcanic processes results in an outlet valley under climates with up to 2000 2500 mm annual rainfall craters and calderas are commonly drained by a single outlet the outlet valley can maintain its dominant downcutting position because it quickly enlarges its drainage basin by capturing the area of the primary depression multi drained volcanic depressions can form if special factors e g high rate geological processes such as faulting or glaciation suppress fluvial erosion normal fluvial erosion modified volcanic depressions the circular rim of which is derived from the original rim are termed erosion craters or erosion calderas depending on the pre existing depression the resulting landform should be classed as an erosion induced volcanic depression if the degradation of a cluster of craters produces a single drained irregular shaped basin or if flank erosion results in a quasi closed depression under humid climates craters and calderas degrade at a faster rate mostly at subtropical and tropical ocean island and island arc volcanoes their erosion results in so called amphitheater valleys that develop under heavy rainfall 2500 mm year rainstorms and high elevation differences structural and lithological control and groundwater in ocean islands may in turn preform and guide development of high energy valleys through rockfalls landsliding mudflows and mass wasting given the intense erosion amphitheater valleys are able to breach a primary depression from several directions and degrade the summit region at a high rate occasionally amphitheater valleys may create summit depressions without a pre existing crater or caldera the resulting negative landforms which may drain in several directions and the primary origin of which is commonly unrecognizable should be included in erosion transformed volcanic depressions

the regular shape of stratovolcanoes a dem based morphometrical approach abstract we studied the shape of the most regular shaped stratovolcanoes of the world to mathematically define the form of the ideal stratovolcano based on the shuttle radar topographic mission data we selected 19 of the most circular and symmetrical volcanoes which incidentally all belong to subduction related arcs surrounding the pacific the selection of volcanoes benefitted from the introduction of a new definition of circularity which is more robust than previous definitions being independent of the erosional dissection of the cone our study on the shape of stratovolcanoes was based on the analysis of the radial elevation profiles of each volcano the lower half section of the volcanoes is always well fitted by a logarithmic curve while the upper half section is not and falls into two groups it is fitted either by a line c type conical upper part or by a parabolic arc p type parabolic concave upper part a quantitative discrimination between these groups is obtained by fitting their upper slope with a linear function c type volcanoes show small whereas p type volcanoes show significant negative angular coefficient the proposed threshold between the two groups is 50 10 4 m chemical composition of eruptive products indicates higher sio 2 and or higher h 2 o content for c type volcanoes which could imply a higher incidence of mildly explosive e g strombolian eruptions we propose that this higher explosivity is responsible for forming the constant uppermost slopes by the deposition of ballistic tephra and its subsequent stabilisation at a constant angle by contrast p type volcanoes are characterized by a smaller sio 2 and h 2 o content which can be responsible for a higher incidence of effusive events and or a lower incidence of upper flank forming i e mild explosive eruptions therefore the concave upper flanks of these volcanoes may be shaped typically by lava flows based on this hypothesis we propose that the morphometric analysis of the elevation profile of stratovolcanoes can provide insights into their dominant eruptive style

using the translation speed and vertical structure of gust fronts to infer buoyancy deficits within thunderstorm outflow abstractthis study investigates whether the thermodynamics of supercell rear flank outflow can be inferred from the propagation speed and vertical structure of the rear flank gust front to quantif

erosion rates and erosion patterns of neogene to quaternary stratovolcanoes in the western cordillera of the central andes an srtm dem based analysis abstract erosion patterns and rates of 33 stratovolcanoes in the arid to hyperarid central andean volcanic zone 14 s to 27 s have been constrained by morphometric modelling all selected volcanoes belong to the short lived symmetrical circular andesitic stratocone type with ages spanning 14 ma to recent starting from the initial youthful volcano morphology of this type represented in our study by parinacota volcano and comparing reconstructed volumes of progressively eroded volcanoes such a time span allows us to infer long term erosion rates typical erosion rates of