sensitivity of the initiation of an isolated thunderstorm over the beijing metropolitan region to urbanization terrain morphology and cold outflows to gain insight into the processes leading to the convective initiation ci of an isolated thunderstorm near the central urban area cua of the beijing metropolitan region bmr on 9 august 2011 a series of numerical sensitivity experiments by removing or modifying the cua terrain morphology and convectively generated cold outflows is performed results show that the cua accounts for the formation of cloud condensation near the top of the mixed layer at the ci site as a result of the growing boundary layer depth through its urban heat island effects and urban induced convergence between a warm and moist southerly flow and an easterly flow on the downstream side the northerly approaching cold outflows from the mesoscale convective system mcs facilitate the generation of northerly flows through a northwestward concaved valley such that the enhanced low level convergence with the southerly and easterly flows near the cua could determine the timing of the outbreak of shallow clouds near the mixed layer top into an intense thunderstorm when the concaved valley on the northwest of the cua is eliminated little northerly flows ahead of the cold outflow boundaries into the ci site would be present the results obtained herein appear to have significant implications to understanding and forecasting the development of afternoon thunderstorms in the bmr under weak gradient environments

seismic reflection borehole and outcrop geometry of late wisconsin tills at a proposed landfill near toronto ontario the search for new landfill sites in the greater toronto area of southern ontario canada is producing a wealth of data regarding the subsurface stratigraphy and geometry of late wisconsin 25 ka

drumlins carved by deforming till streams below the laurentide ice sheet the peterborough drumlin field 5000 km 2 is the largest in central canada and was formed during readvance of the laurentide ice sheet shortly after 13 000 b p morphometric analysis of 998 drumlins combined with study of 6921 borehole logs and downhole geophysical data has established the distribution of drumlin types and their stratigraphy along a 70 km flow line through the drumlin field in the north drumlins are spindle shaped composed of till resting directly on bedrock and were formed by deformation of till into low pressure zones in the lee of bedrock scarps eskers record subglacial drainage by channeled meltwaters flowing on bedrock to the south drift thickness increases and eskers are absent drumlins are larger and more ovoid and are composed of overridden proglacial and glaciolacustrine sediments overlain erosively by deformation till till is thin over drumlin crests and thick in interdrumlin swales and records subglacial cannibalization and mixing of overridden sediments the drumlin form is the product of erosion by streams of deforming till flowing in swales separating cores composed of older sediments systematic down field changes in drumlin shape and size can be related to decreased duration of subglacial deformation toward the limit of the readvance and increased thickness of preexisting sediments available for dissection by subglacial till streams absence of eskers in the central and southern parts of the drumlin field suggests that the ice base was drained by mass flow of the deforming substrate the substantial subsurface data available from the peterborough area indicate that drumlins are predominantly erosional in origin and are the geomorphological expression of a deforming subglacial bed below the margin of the laurentide ice sheet

the use of vertical wind shear versus helicity in interpreting supercell dynamics a series of idealized simulations of supercell storms are presented for environments representing straight through circular hodographs to clarify the character of the storm dynamics over the large spectrum of hodograph shapes commonly observed the primary emphasis is on comparing and contrasting recent theories of supercell dynamics based on updraft shear interactions storm relative environmental helicity sreh and beltrami flow solutions to help clarify the degree to which each theory can represent the essential storm dynamics one of the particular questions being addressed is whether storm dynamics are significantly different for straight versus curved hodographs which has become a point of some controversy over recent years in agreement with previous studies the authors find that the physical processes that promote storm maintenance rotation and propagation are similar for all hodograph shapes employed and are due primarily to nonlinear interactions between the updraft and the ambient shear associated with the localized development of rotation on the storm s flank significant correlations between the updraft and vertical vorticity are also observed across the shear spectrum and in agreement with predictions of linear theories associated with sreh this correlation increases for increasing hodograph curvature however storm steadiness and propagation must already be known or inferred for such concepts to be applied thus limiting the applicability of this theory as a true predictor of storm properties tests of the applicability of beltrami solutions also confirm reasonable agreement for purely circular hodographs for which the analytical solutions are specifically designed however analysis of the model results indicates that the terms ignored for such solutions representing the nonlinear effects associated with storm rotation are more significant than those retained over most of the hodograph spectrum which severely limits the general applicability of such analyses

radar observed characteristics of precipitating systems during name 2004 abstract a multiradar network operated in the southern gulf of california goc region during the 2004 north american monsoon experiment is used to analyze the spatial and temporal variabilities of local precipitation based on the initial findings of this analysis it is found that terrain played a key role in this variability as the diurnal cycle was dominated by convective triggering during the afternoon over the peaks and foothills of the sierra madre occidental smo precipitating systems grew upscale and moved wnw toward the gulf distinct precipitation regimes within the monsoon are identified the first regime a corresponded to enhanced precipitation over the southern portions of the coast and goc typically during the overnight and early morning hours this was due to precipitating systems surviving the westward trip 7 m s 1 3 4 m s 1 in excess of steering winds from the smo after sunset likely because of enhanced environmental wind shear as diagnosed from local soundings the second

strontium isotopic evidence for the origin of siderite ankerite and magnesite mineralizations in the eastern alps metasomatic magnesite siderite and ankerite mineralizations within paleozoic sediments of the northern greywacke zone and its metamorphic counterpart in the crystalline basement upper austroalpine unit were investigated with respect to their strontium isotopic composition the results support a sedimentary s l model for the magnesites within visean platform carbonates of the veitsch nappe and an epigenetic hydrothermal model for the siderites and ankerites in devonian platform carbonates of the noric nappe and from huttenberg the fe transporting fluids can be characterized either as magmatogene or more probably as metamorphogene by increasing the stage of recrystallization and or remobilization due to at least two later metamorphic overprints sr in the various ore minerals beame enriched in radiogenic 87sr

results of 2 and 3 d high resolution seismic reflection surveying of surficial sediments to investigate the potential of seismic reflection methods for studying surficial sediments 2 and 3 d high resolution surveys have been conducted across a plot of land adjacent to a landfill in northern switzerland results of the reflection profiling demonstrated that closely spaced common reflection points 2 5 m and high fold 12 data were prerequisites for producing clear images at this site for the 3 d survey an area of 115 160 m was covered with common reflection points every 2 5 2 5 m three dimensional migration of the resultant 18 to 70 fold data proved to be a critical step in correctly locating out of plane reflections and collapsing diffractions that were prominent features in the 2 d profile data within the 3 d data volume a conspicuous reflective zone and a marked decrease in reflection amplitudes at 200 m depth delineates the bedrock surface immediately above this level are continuous reflections from flat lying lacustrine sediments these are in turn overlain by regions of strong reflected energy interpreted as either large erratic blocks anomalous compaction zones or gravel channels lenses

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

a contribution to the ore genesis of the magnesite deposit of eugui navarra spain in the area of the magnesite deposits of eugui navarra spain studies on illite crystallinity the degree of graphitization of carbonaceous material measurements of vitrinite reflectivity and fluid inclusions have been carried out on dolomites magnesites schists and carbonaceous matter these rocks have suffered metamorphism of very low to low grade the magnesite appears generally concordant with the namurian dolomitic rocks showing a typically banded structure the genetic model proposed involves an early mg concentration during sedimentation syndiagenetic dolomitization lateral circulation of saline solutions and formation of diagenetically crystallized rhythmites dcr and final compaction the formation of magnesite took place under the conditions of low pressure and temperatures close to 150 c very similar to all strata bound ore deposits deformation and regional metamorphism only caused minor removal recrystallization and transformation of the clay minerals and carbonaceous matter

the spatial and temporal variability of convective storms over the northeast united states during the warm season abstract a spatial and temporal climatology of convective storms over the northeast united states during the warm season april september is presented using composite national operational weather radar nowrad data at 2 km grid spacing from 1996 to 2007 as well as cloud to ground lightning from the national lightning data network nldn on a 10 km grid from 2001 to 2007 there are preferred regions for convective storms within new york s hudson river valley western and southeastern pennsylvania central new jersey and across the delmarva peninsula a favored initiation area during the early afternoon is the immediate lee of the appalachians with a tendency for these convective systems to move eastward to the coast by late evening there is a sharp gradient in convective frequency within 20 km of the coast on average as a result of the relatively stable marine boundary layer but as the sea surface warms by midsummer this convective activity increases near the coast with a nocturnal 0600 1200 utc c

magnesite deposits and occurrences in the west carpathians of czecho slovakia abstract magnesite occurrences in the west carpathians a part of the alpine orogenic system have been known since the second half of the 19th century they are hosted by cambrian silurian devonian carboniferous permian lower and upper triassic sedimentary units economically most important are crystalline magnesite veitsch type and locally associated talc in the devonian sequence of the veporides and in the caboniferous of the gemerides yearly production 2 3 million tonnes traditionally the slovak magnesite deposits had been interpreted as hydrothermal metasomatic related to magmatically derived fluids more recently a sedimentary diagenetic origin of the magnesite with mg derived in full or in part from the contemporaneous submarine basaltic volcanism is considered more probable after deposition and diagenesis the magnesites and their host rocks were metamorphosed in greenschist carboniferous of the gemerides to amphibolite devonian of the veporides facies

a new genetic model for the north african metasomatic siderite deposits based on published accounts of the diagenetic evolution of evaporite diapirs and geological preliminary geochemical and fluid inclusion data a new genetic model is presented for the north african metasomatic siderite deposits

investigation of microphysical processes occurring in isolated convection during name abstracta major objective of the north american monsoon experiment name was to quantify microphysical processes within convection occurring near the steep topography of northwestern mexico a previous study compared examples of isolated convection using polarimetric radar data and noted a dependence on mixed phase processes via drop freezing and subsequent riming growth along the coastal plain and western slopes with an even greater role of melting ice in rainfall production over the highest terrain despite the higher frequency of these isolated cells compared to organized convective systems the latter were responsible for 75 of rainfall therefore this study seeks to evaluate the role of mesoscale organization on microphysical processes and describes the evolution of these systems as a function of topography similar to isolated convection both warm rain and ice based processes played important roles in producing intense rainfall in organized convection although similarities existed between cell

flow over heated terrain part ii generation of convective precipitation previous studies have shown that thunderstorms in the rocky mountain region have preferred areas in which to form there has been some indication that these areas depend on the midtropospheric wind direction a nonhydrostatic model with a terrain following horizontal grid is employed to investigate the initiation of precipitating convection over heated topography horizontally homogeneous meteorological conditions with no directional shear in the vertical wind profile are used the numerical simulations indicate that precipitating convection was more likely to be generated downwind of ridges than upwind of them initiation of these storms was more likely downwind of ridges with their long axis parallel to the wind direction than downwind of ridges with their long axis perpendicular to the wind direction in part i of this study it was shown that heating induced convergence is larger downwind of a ridge with its longer axis parallel to the wind direction for the orographic configuration of the rocky mountains total precipitation is maximized for southerly and northwesterly winds slower wind speeds are more likely and faster wind speeds are less likely to produce convective storms soundings with larger instability are more likely to produce convection the soundings with a greater temperature lapse rate produce more initiation locations and soundings with greater moisture produce greater amounts of precipitation even though a number of assumptions were made for this study the authors believe the results explain a significant amount of the observed variability in the initiation locations of precipitating convection in the rocky mountains during the summer because of the theoretical basis for this work detailed in part i of this study the authors believe it should explain convective initiation in other mountainous areas that are subject to strong solar heating

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

metallogenetic evolution of the east alpine paleozoic basement paleo metallogenetic sketch maps of the east alpine area are presented for the ordovician silurian the devonian lower carboniferous and the upper carboniferous permian mineralization and tectonic evolution are then discussed in the frame of a plate tectonic model compatible with recent results in western europe

gangue mineral 87 sr 86 sr ratios and the origin of mississippi valley type mineralization the 87 sr 86 sr ratio measurements in mississippi valley type gangue minerals and host marine carbonates ranging in age from upper cambrian to mississippian show that in northwestern ohio where the mineralization is sparse the minerals precipitated from fluids in local isotopic equilibrium with the host carbonates in which the minerals were emplaced in contrast most gangue minerals from districts of major mineralization in illinois kentucky virginia and tennessee contain strontium with higher 87 sr 86 sr ratios than the carbonate hosts and appear to have crystallized from fluids containing strontium from silicate minerals in the sedimentary succession no evidence has been found for a magmatie component in the ore fluid strontium data from elmwood tennessee show that the early ore fluids like those of northwestern ohio were in isotopic equilibrium with the host carbonates but that they were mixed with and displaced by introduced fluids containing more radiogenic strontium these findings are consistent with the two fluid mixing model for the mississippi valley mineralization where a fluid indigenous to the host carbonates and containing reduced sulfur was mixed with introduced fluids analogous to metal bearing and low sulfide oil field brines with an extensive history of chemical exchange with clays and other silicate minerals in the sedimentary succession

the statistical characteristics of convective cells in a monsoon regime darwin northern australia abstract a season of operational cell and track data from darwin australia has been analyzed to explore the statistical characteristics of the convective cell heights the statistics for the monsoon and break regimes are significantly different with the break season cells being higher for a given reflectivity threshold the monsoon cells produce more rain but there are fewer intense cells and there is a much larger contribution from stratiform rain the monsoon cells are also slightly larger but shorter lived than the breaks the shorter lifetime may reflect a more rapid transition to a longer lived stratiform character the monsoon regime is shown to be associated with large scale ascent and higher humidity that may lead to more frequent but weaker cells within regimes the subset of intense cells generally reach near the tropopause or overshoot however there is little evidence in the data for a multimodal distribution of cell heights except perhaps for the intense monsoon cases instead the pi

synoptic conditions associated with propagating and nonpropagating cloud rainfall episodes during the warm season over the east asian continent abstractusing european centre for medium range weather forecasts ecmwf analyses this study identifies common synoptic flow patterns associated with propagating long lived and nonpropagating short lived precipitation cloud episodes in the warm season over east asia 25 40 n 95 125 e among 123 initial cases during may july 1997 2003 86 were classified into three categories propagating cases with strong and weak forcing and nonpropagating ones with strong inhibition consisting of 10 types based on their 500 hpa flow patterns for each type composites at various levels when episodes moved across 100 105 110 115 and 120 e were made and discussed to elucidate the influence of synoptic conditions for propagating episodes with strong 500 hpa forcing 46 cases four types were identified in their composites favorable positive vorticity advection forcing from an approaching trough short wave exists aloft and concurrent development of southwest vortex and front wind shift line at low lev

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

statistical characteristics of convective clouds over the western ghats derived from weather radar observations x band radar observations at mandhardev 18 04 n 73 85 e are used to investigate statistics of convective clouds over the western ghats during monsoon season june september 2014 convective storms cells are identified using an objective tracking method to examine their spatio temporal variability thus quantifying the time continuous aspects of convective cloud population over the region for the first time an increased frequency of storm location and initiation along the windward mountains compared to coastal and lee side highlights orographic response to southwesterly flow with superimposed diurnal cycle an eastward progression of convective activity from upstream the barrier through windward slopes of mountains over to the lee side is observed storm area height and duration follow lognormal distributions wherein small sized storms contribute more to total population and unimodal distribution of 35 dbz top heights peaking at 5 5 km depicts the dominance of shallow convection storms exhibit a pronounced diurnal cycle with a peak in afternoon hours while the convective area maximum is delayed by several hours to that of precipitation flux cell lifetime and propagation show that cells move with slow speeds and have mean duration of 46 minutes they align east west nearly parallel to mountain ridges and their direction of movement is steered mostly by large scale winds at lower levels based on top heights convective cells are further classified into cumulus congestus and deep clouds in general congestus deep cells are most abundant in the windward leeward side a lead lag relationship between congestus and deep cells indicates midtroposphere moistening by congestus cells prior to deep convection

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

the role of environmental shear and thermodynamic conditions in determining the structure and evolution of mesoscale convective systems during toga coare abstract a collection of case studies is used to elucidate the influence of environmental soundings on the structure and evolution of the convection in the mesoscale convective systems sampled by the turboprop aircraft in the tropical ocean global atmosphere toga coupled ocean atmosphere response experiment coare the soundings were constructed primarily from aircraft data below 5 6 km and primarily from radiosonde data at higher altitudes the well documented role of the vertical shear of the horizontal wind in determining the mesoscale structure of tropical convection is confirmed and extended as noted by earlier investigators nearly all convective bands occurring in environments with appreciable shear below a low level wind maximum are oriented nearly normal to the shear beneath the wind maximum and propagate in the direction of the low level shear at a speed close to the wind maximum when there is appreciable shear at middle levels 800 400 mb convective bands form parallel to the shear with

radar observed diurnal cycle and propagation of convection over the pearl river delta during mei yu season using operational doppler radar and regional reanalysis data from 2007 2009 the climatology and physical mechanisms of the diurnal cycle and propagation of convection over the pearl river delta prd region of china during the mei yu seasons are investigated analyses reveal two hot spots for convection one along the south coastline of prd and the other on the windward slope of mountains in the northeastern part of prd overall convection occurs most frequently during the afternoon over prd due to solar heating on the windward slope of the mountains convection occurrence frequency exhibits two daily peaks with the primary peak in the afternoon and the secondary peak from midnight to early morning the nighttime peak is shown to be closely related to the nocturnal acceleration and enhanced lifting on the windward slope of southwesterly boundary layer flow in the form of boundary layer low level jet along the coastline nighttime convection is induced by the convergence between the prevailing onshore wind and the thermally induced land breeze in the early morning convection on the windward slope of the mountainous area is more or less stationary convection initiated near the coastline along the land breeze front tends to propagate inland from early morning to early afternoon when land breeze cedes to sea breeze and the prevailing onshore flow

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

seismic facies and regional architecture of the oak ridges moraine area southern ontario analysis of over 50 line kilometres of land based shallow seismic reflection profiles has provided a means of investigating the subsurface architecture and stratigraphic relationships of the glac

the characteristics of weakly forced mountain to plain precipitation systems based on radar observations and high resolution reanalysis the metropolis of beijing in china is located on a plain adjacent to high mountains to its northwest and the gulf of the bohai sea to its southeast one of the most challenging forecast problems for beijing is to predict whether thunderstorms initiating over the mountains will propagate to the adjacent plains and intensify in this study 18 warm season convective cases between 2008 and 2013 initiating on the mountains and intensifing on the plains under weak synoptic forcing were analyzed to gain an understanding of their characteristics the statistical analysis was based on mosaic reflectivity data from six operational doppler radars and reanalysis data produced by the four dimensional variational doppler radar analysis system vdras the analysis of the radar reflectivity data shows that convective precipitation strengthened on the plains at certain preferred locations to investigate the environmental conditions favoring the strengthening of the mountain to plain convective systems statistical diagnoses of the rapid update 12 min 3 km reanalyses from vdras for the 18 cases were performed by computing the horizontal and temporal means of cape convective available potential energy cin convective inhibition vertical wind shear and low level wind for the plain and mountain regions separately the results were compared with those from a baseline representing the warm season average and from a set of null cases and found considerable differences in these fields between the three datasets the mean distributions of vdras reanalysis fields were also examined the results suggest that the convergence between the low level outflows associated with cold pools and the south southeasterly environmental flows correspond well with the preferred locations of convective intensification on the plains

seismic facies of glacial deposits from marine and lacustrine environments seismic facies analysis is the interpretation of sedimentary processes and depositional environments from seismic reflection data the technique was primarily developed by the hydrocarbon industry as a predictive indicator of lithology it involves the description and geological interpretation of a number of seismic reflection parameters of which configuration character and external form are the most commonly analysed parameters in recent years the concept of seismic facies analysis has been increasingly used in high resolution seismic reflection studies of late cenozoic marineand lacustrine glacigenic sequences in support of non antarctic resource and development studies e g minerals hydrocarbons fish pipelines etc and high latitude environmental surveys such studies are key to the proper oversight and utilisation of the offshore environments and to understanding the processes associated with the growth and decay of ice sheets as examples the petroleum industry has long had problems drilling on northern glaciated shelves due in part to sub seabed boulder horizons and gas hydrates but also with icebergs furrowing the seabed and impacting on sea floor installations artificial islands constructed as ice protected drilling plat

rainfall occurrence in the u s warm season the diurnal cycle the diurnal occurrence of warm season rainfall over the u s mainland is examined particularly in light of forcings at multiple scales the analysis is based on a radar dataset of 12 seasons duration covering the u s mainland from the continental divide eastward the dataset resolves 2 km features at 15 min intervals thus providing a detailed view of both large and regional scale diurnal patterns as well as the statistics of events underlying these patterns the results confirm recent findings with respect to the role of propagating rainfall systems and the high frequency at which these are excited by sensible heating over elevated terrain between the rockies and the appalachians 60 of midsummer rainfall occurs in this manner most rainfall in the central united states is nocturnal and may be attributed to the following three main forcings 1 the passage of eastward propagating rainfall systems with origins near the continental divide at 105 w 2 a nocturnal reversal of the mountain plains solenoid which is associated with widespread ascent over the plains and 3 the transport of energetic air and moisture convergence by the great plains low level jet other features of interest include effects of the appalachians semidiurnal signals of regional significance and the impact of breezes along the gulf of mexico a modest effort was put forth to discern signals associated with el nino and the southern oscillation while tendencies in precipitation patterns are observed the record is too short to draw conclusions of general significance

generation processes of mesoscale convective systems following midlatitude troughs around the sichuan basin 1 the generation processes of mesoscale convective systems mcss that occurred over the sichuan basin in china were revealed in the early 2008 monsoon season mcs occurrences detected in meteosat geostational satellite images are associated with the traveling of midlatitude troughs after the onset of the indian monsoon three episodes of large scale mcss were generated under synoptic conditions of merging southwesterly low level monsoon flows with a northerly midlatitude air mass following the trough in the leeward of the tibetan plateau without direct migration of the vortex generated from the plateau surface numerical simulations using a weather research and forecast wrf model showed that the mcs was triggered in the evening by strengthening of the low level wind convergences with horizontal shear between the southerly monsoon flow with large convective available potential energy and the northerly dry intrusion a sudden increase in the northerly winds was confirmed by sonde observation data in the western basin and the winds were simulated as intrusions passing over the qinling mountains when the daytime clouds over the mountain were diminished sensitivity experiments by a wrf simulation revealed that the topography of the sichuan basin was able to capture the dry intrusion at the bottom to prevent the propagation of disturbances from the plateau and to cause the sudden onset of mcss apart from the plateau with a heavy precipitation zone

on the origin of the oak ridges moraine landscape analysis mapping sedimentology shallow geophysics and borehole data are integrated to better understand the complex landform sediment geometries and event sequences of the oak ridges moraine southern ontario a model for the origin of the oak ridges moraine is based on the recognition that the moraine is built on a high relief erosional surface unconformity consisting of drumlin uplands and a network of deep steep walled interconnected valleys tunnel channels the development of the moraine is thought to have occurred in four stages i subglacial sedimentation ii subaqueous fan sedimentation iii fan to delta sedimentation iv ice marginal sedimentation the model traces the transition from subglacial to proglacial conditions during moraine formation and examines the order and timing of sedimentation it is thought that the early stages of moraine construction are better exposed in the east in the west these stages are buried by later stages resume les etudes de paysage cartographie sedimentologie geophysique de subsurface et des carottes de trous des sondages ont ete menees conjointement pour chercher a mieux comprendre les configurations complexes des formes de relief sediments et les sequences des evenements qui ont affecte la moraine d oak ridges dans le sud de l ontario un modele interpretant l origine de la moraine d oak ridges est fonde sur le fait que cette moraine fut edifiee sur une surface d erosion discordance en terrain a topographie accentuee comprenant des drumlins sur terres elevees et des vallees a parois subverticales interconnectees chenaux tunnels le modele propose un developpement de la moraine en quatre phases i sedimentation sous glaciaire ii sedimentation d un eventail sous aquatique iii sedimentation de l eventail evoluant vers un depot deltaique iv sedimentation en bordure d un glacier le modele retrace la transition de conditions sous glaciaires a proglaciaires durant la formation de la moraine et traite de l ordre et de la chronologie du sediment il apparait que c est dans le secteur oriental que les premieres phases de l edification de la moraine sont le mieux exposees tandis que dans le secteur partie occidental elles sont enfouies sous le sediment des phases plus tardives

erosion of bedrock by subglacial meltwater georgian bay ontario a regional view a spectacular series of sculpted erosional forms s forms is mapped and described from a 70 km wide area along the shore of georgian bay ontario which except for a scattered boulder lag has been swept clean of sediment a great variety of sculpted forms is described and illustrated and grouped into three classes transverse longitudinal and nondirectional forms transverse forms comprise transverse troughs muschelbruche sichelwannen and comma forms longitudinal forms comprise spindle flutes cavettos and furrows and nondirectional forms consist of undulating surfaces and potholes transverse forms are preferentially located on stoss slopes and longitudinal forms on lee slopes of rock rises undulating nondirectional forms are found on distal slopes and potholes at major breaks in slope this correlation of form and bed topography suggests that relief exerts considerable control on both form and location form geometry is also inferred to be related to coherent flow structures and their int

diurnal evolution and distribution of warm season convective storms in different prevailing wind regimes over contiguous north china the diurnal evolution and distribution of warm season convective storms in different prevailing wind regimes at the 925 hpa and 500 hpa levels over contiguous north china have been studied using a climatology based on radar reflectivity mosaics soundings and reanalysis data from 15 may to 15 september in 2008 2011 in the wind regimes at the 925 hpa level the frequency of occurrence of convection is highest for south southwesterly flows followed by that for south southeasterly flows the low level southerly warm and moist flow over the foothills and plains favors initiation and intensification of convection resulting from topographic forcing among the wind regimes at the 500 hpa level the frequency of occurrence of convection shows a pronounced maximum for west southwesterly flows and most of these storms initiate and develop over the foothills and plains convection in the wind regime shows the morphology and slowly east southeastward moving characteristics of well organized longer lived systems with environmental conditions conducive to vertical wind shear and instability at the 500 hpa level the high frequency of occurrence of convection for west southwesterly flows is followed by that for west northwesterly flows under west northwesterly flows convective storms initiated over mountains located to the northwest in the early afternoon move rapidly to the plains in the southeast of the study region these storms show the primary formation characteristics of shorter lived convection and intensify noticeably as they move from the mountains to the foothills and plains

the propagation and diurnal cycles of deep convection in northern tropical africa the propagation and diurnal cycle of organized convection in northern tropical africa are examined using five years 1999 2003 of digital infrared imagery for may august reduced dimension techniques are used to document the properties of cold clouds proxies for deep convection and precipitation large scale environments are diagnosed from global analyses organized convection in africa consists of coherent sequences or episodes which span an average distance of about 1000 km and last about 25 h a substantial fraction of events exhibits systematic propagation at regional to continental scales while undergoing decay and regeneration episodes with 36 h duration and 1472 km span recur at a one per day interval most episodes have phase speed of 10 20 m s 1 which is faster than most african easterly waves convective episodes tend to initiate in the lee of high terrain consistent with thermal forcing from elevated heat sources average diurnal frequency maxima result from the superposition of local diurnal maximum with the delayed phase arrival of systems propagating from the east propagation occurs with moderate low to mid tropospheric shear which varies with the african easterly jet migration and west african monsoon phases frequent deep convection occurs with local shear maxima near high terrain for the peak monsoon period and for 10 w 10 e where easterly waves and convective systems are frequent 35 of cold cloud episodes occur east of the wave trough compared with about 24 to the west based on the coherent behaviour of organized propagating convection inferences may be made regarding the prediction of precipitation beyond one or two days copyright 2008 royal meteorological society

isotopic fronts in hydrothermally mineralized carbonate rocks advective dispersive fluid flow through permeable and porous rock causes systematic alteration of the infiltrated rock o and sr isotopes can be used as tracers to monitor exchange processes between mineralizing hydrothermal solutions and carbonate host rocks fluid infiltration into rock of initially uniform isotopic composition leads to characteristic changes in 18o and 87sr in the rock that depend on infiltration distance fluid velocity diffusivity and reaction kinetics for fast fluid solid equilibrium during advective flow the shape of such alteration profiles can be described by the dimensionless peclet number p e which expresses the fluid flux infiltration distance and diffusivity in the case of mineralization from low to moderate temperature solutions isotope exchange is not instantaneous but kinetically controlled and a similar parameter the damkohler number n d expressing fluid flux isotope exchange rate and infiltration distance becomes more useful n d and p e values have been estimated for various examples of carbonatehosted hydrothermal mineralization in the eastern alps austria and the benue trough nigeria by modelling o and sr isotope data from ore or gangue minerals and host rock the values obtained enable a rough differentiation between pervasive and channelled fluid flow as the prevailing transport mechanism to be made results indicate that both highly channelled fluid flow through fractures without significant interaction with the wall rock and pervasive fluid flow with infiltration distances into the percolated host rock of the order of 100 m occur near mineral deposits in the latter case the extent of o and sr isotopic alteration of the host rock can be used as an effective exploration tool

regional seasonal and diurnal variations of extreme convection in the south asian region abstract temporal and spatial variations of convection in south asia are analyzed using eight years of tropical rainfall measuring mission trmm precipitation radar pr data and ncep reanalysis fields to identify the most extreme convective features three types of radar echo structures are defined deep convective cores contiguous 3d convective echo 40 dbz extending 10 km in height represent the most vertically penetrative convection wide convective cores contiguous convective 40 dbz echo over a horizontal area 1000 km2 indicate wide regions of intense multicellular convection and broad stratiform regions stratiform echo contiguous over an area 50 000 km2 mark the mesoscale convective systems that have developed the most robust stratiform regions the preferred locations of deep convective cores change markedly from india s east coast in the premonsoon to the western himalayan foothills in the monsoon they form preferentially in the evening and over land as near surface moist flow is cap

convective episodes in the east central united states nine years of composited radar data are investigated to assess the presence of organized convective episodes in the east central united states in the eastern united states the afternoon maximum in thunderstorms is ubiquitous over land however after removing this principal diurnal peak from the radar data the presence and motion of organized convective systems becomes apparent in both temporally averaged fields and in the statistics of convective episodes identified by an objective algorithm convective echoes are diurnally maximized over the appalachian chain and are repeatedly observed to move toward the east partly as a result of this the daily maximum in storms is delayed over the piedmont and coastal plain relative to the appalachian mountains and the atlantic coast during the 9 yr studied the objective algorithm identified 2128 total convective episodes 236 yr 1 with several recurring behaviors many systems developed over the elevated terrain during the afternoon and moved eastward often to the coastline and even offshore in addition numerous systems formed to the west of the appalachian mountains and moved into and across the eastern u s study domain in particular many nocturnal convective systems from the central united states entered the western side of the study domain frequently arriving at the eastern mountains around the next day s afternoon maximum in storm frequency a fraction of such well timed systems succeeded in crossing the appalachians and continuing across the piedmont and coastal plain convective episodes were most frequent during the high instability low shear months of summer which dominate the year round statistics even so an important result is that the episodes still occurred almost exclusively in above average vertical wind shear despite the overall dominance of the diurnal cycle the data show that adequate shear in the region frequently leads to long lived convective episodes with mesoscale organization

diurnal variations of summer precipitation over contiguous china 1 diurnal variations of summer precipitation over contiguous china are studied using hourly rain gauge data from 588 stations during 1991 2004 it is found that summer precipitation over contiguous china has large diurnal variations with considerable regional features over southern inland china and northeastern china summer precipitation peaks in the late afternoon while over most of the tibetan plateau and its east periphery it peaks around midnight the diurnal phase changes eastward along the yangtze river valley with a midnight maximum in the upper valley an early morning peak in the middle valley and a late afternoon maximum in the lower valley summer precipitation over the region between the yangtze and yellow rivers has two diurnal peaks one in the early morning and another in the late afternoon

cold pools in shear gravity currents exist in many forms and develop within many types of flow the dynamics of long lived cumulonimbus are thought to be strongly influenced by the interaction of a spreading pool of cold low level air which may act as a gravity current and the ambient sheared flow in the boundary layer in interpreting two and three dimensional numerical models of such phenomena the behaviour of the vorticity dynamics in the ambient flow and the spreading cold air is commonly discussed in order to investigate these vorticity ideas from a gravitycurrent perspective three dimensional numerical simulations have been performed in which a cold pool spreads from an isolated source in the presence of a horizontal flow that is sheared with height it has been found that the shear of the incoming ambient flow does not qualitatively alter the horizontal spread of the cold pool and that the location of the region of maximum horizontal convergence remains on the along wind axis the actual strength of the ambient wind which is shown analytically to be measured by the wind strength at the head height has a greater bearing on the cold pool shape than the shear consequently it must be the details of the moist convection which play a crucial role in determining the cold pool s development in sheared flows as such this model is a general indication of the robustness of gravity current theory even in the presence of mean shear the vortex structure on the flanks of the spreading cold air is found to be significantly modified with a reversal in the dominant sign of vorticity and an increase in its intensity when such mean shear exists

diurnal variations of warm season precipitation over northern china abstract this study examines the diurnal variations of the warm season precipitation over northern china using the high resolution precipitation products obtained from the climate prediction center s morphing technique cmorph during may august of 2003 09 the areas of focus are the yanshan taihangshan mountain ranges along the east peripheries of the loess and inner mongolian plateaus and the adjacent north china plains it is found that the averaged peak in local precipitation begins early in the afternoon near the top of the mountain ranges and propagates downslope and southeastward at a speed of 13 m s 1 the peak reaches the central north china plains around midnight and the early morning hours resulting in a broad area of nocturnal precipitation maxima over the plains the diurnal precipitation peak minimum is closely collocated with the upward downward branch of a mountain plains solenoid mps circulation both the mps and a low level southwesterly nocturnal jet are likely to be jointly resp

origin of siderite mineralization in western guizhou sw china constrains from rees c o sr and s isotopes abstract numerous siderite deposits in western guizhou of sw china are mainly hosted in the middle devonian dolostones the larger caiyuanzi cyz and xiongxiongjia xxj deposits have an ore reserve in excess of 300 mt with an average ore grade of 35 total iron there are banded and massive siderite ores and sulfide siderite ores the major ore mineral is magnesian siderite and gangue minerals are ankerite dolomite kaolinite quartz and carbon there are also metallic minerals including pyrite chalcopyrite and minor galena tetrahedrite and enargite rare earth elements rees and carbon oxygen and strontium isotope data indicate a marine origin of the host dolostones and a hydrothermal metasomatic origin of the siderite mineralization the variations of rees and carbon and oxygen isotopic compositions of siderite from the cyz and xxj deposits reflect the variable mineralization processes and different fluid rock ratios the lree depletion of siderite from the cyz deposit could be due to crystallographic control whereas the lree depletion along with mree enrichment and positive eu anomalies of siderite from the xxj deposit was possibly controlled by both crystallography and fluid composition siderite and calcite have 13 c pdb and 18 o smow values ranging from 8 to 4 01 and from 13 42 to 20 07 respectively the variations in c and o isotopic compositions of siderite and calcite may reflect metasomatic replacement of marine carbonates by hydrothermal fluids at different fluid rock ratios dolostones have 87 sr 86 sr initial values of 0 70844 0 70920 whereas siderite and calcite have values ranging from 0 71396 to 0 71708 negative correlations of initial sr isotope ratios versus carbon and oxygen isotopes of the host dolostones siderite and calcite indicated that carbonate minerals were metasomatic products of marine carbonates by hydrothermal fluids leaching from the proterozoic basement rocks iron was possibly derived from the basement leaching rather than from the continental weathering the 34 s cdt values 19 9 to 13 6 of sulfides associated with siderite indicated that the sulfur was probably derived from the marine sulfates through either bacterial sulfate reduction or organic mediated thermochemical reduction

strontium isotopes in magnesites from permian and triassic strata eastern alps abstract the sr isotopic composition of sediment hosted magnesites in permian and scythian series of upper austroalpine units eastern alps has been determined the results suggest diagenetic metasomatic magnesite formation by mg rich pore solutions the depositional environment of the magnesite bearing rocks is reflected by different isotopic compositions with initial 87 sr 86 sr ratios close to contemporaneous sea water in marine sediments 0 7071 0 7083 and higher ratios being typical for lacustrine and coastal environments influenced from the hinterland 0 7133 0 7139 coarser grained recrystallized magnesite and magnesite veins show a distinct increase in their sr isotopic ratios 0 7202 0 7220 which can be attributed to metamorphic fluids of eoalpine age the findings of these magnesite occurrences which have been affected only by very low grade metamorphism are compared with similar results from spar magnesites associated with metamorphosed paleozoic sedimentary rocks a similar genetic model is proposed for the first magnesite mineralization in those paleozoic strata but with variably intense later recrystallisation during metamorphism

evidence for recent groundwater flow through late wisconsinan till near toronto ontario the northern till is a thick 50 m late winsconsinan diamict unit that occurs throughout south central ontario the till has generally been regarded as massive and uniform with a very low vertical hydraulic conductivity it is similar to many other till units of mid continental north american glaciated terrain in that it is believed to inhibit recharge to underlying aquifers and afford a high degree of protection to these aquifers from surface and near surface sources of contamination standard methods of estimating hydraulic conductivity k for the northern till such as laboratory testing of core samples other studies and rising falling head field piezometer tests this study and other studies characteristically yield values on the order of 10 11 to 10 9 m s typically these values indicate advective traveltimes through the till on the order of hundreds to thousands of years in contrast isotopic evidence 2h 18o and 3h from till pore waters indicates the presence of modern post 1952 wate

siderite mineralization of the gemericum superunit western carpathians slovakia review and a revised genetic model ore geology reviews 24 267 298 a reply

organic and inorganic geochemistry of ljubija siderite deposits nw bosnia and herzegovina the ljubija siderite deposits hosted by a carboniferous sedimentary complex within the inner dinarides occur as stratabound replacement type ore bodies in limestone blocks and as siderite sulfides veins in shale three principal types of ore textures have been recognized including massive dark siderite and ankerite siderite with zebra texture and siderite veins the ore and host rocks have been investigated by a combination of inorganic major trace and rare earth element concen trations organic characterization of hydrocarbons includ ing biomarkers and stable isotope geochemical methods isotope ratios of carbonates sulfides sulfates kerogen and individual hydrocarbons new results indicate a marine origin of the host carbonates and a hydrothermal metasomatic origin of the fe mineralization the differ ences in ore textures e g massive siderite zebra siderite are attributed to physicochemical variations e g changes in acidity temperature and or salinity of the mineralizing fluids and to the succession and intensity of replacement of host limestone vein siderite was formed by precipitation from hydrothermal fluids in the late stage of mineralization the equilibrium fractionation of stable isotopes reveals higher formation temperatures for zebra siderites around 245 c then for siderite vein around 185 c sulfur isotope ratios suggest permian seawater or permian evaporites as the main sulfur source fluid inclusion composition confirms a contribution of the permian seawater to the mineralizing fluids and accord with a permian mineralization age organic geochemistry data reflect mixing of hydrocarbons at the ore site and support the hydrothermal metasomatic origin of the ljubija iron deposits

3 d seismic imaging of complex structures in glacial deposits a small scale shallow penetration 3 d reflection seismic survey has been carried out over stratified glacial formations to test the method s potential for delineating fine structural details with a reasonable field effort and cost recording was carried out with a 96 channel engineering seismograph blank shotgun shells were used as the energy source field records were obtained with usable reflection energy up to 500 hz exploring approximately a 220 m cubical volume although special processing was required to attenuate strongly dispersed and scattered surface waves a stacked data volume of good quality has been assembled more than 15 reflecting horizons with vertical resolution of about 1 5 m were clearly delineated within the wisconsin sediments results are in good agreement with local outcrops and core information the identified reflectors interbeds within the late wisconsin tills are extremely important these reflectors may provide potential hydraulic channels for the movement of surface c

siderite mineralization of the gemericum superunit western carpathians slovakia review and a revised genetic model ore geology reviews 24 267 298 a discussion radvanec et al 2004 provided a revised version of their metamorphic hydrothermal model for siderite and associated mineral deposits of the western carpathians compared to the previous version grecula 1995 grecula et al 1996 the upgraded model emphasizes the dominant role of retrograde variscan metamorphic processes and admits remobilization of the variscan siderite and other ore components during the alpine orogenic cycle similar to the previous versions the variscan ore forming processes genetically related to metamorphism are believed to dominate not only in the siderite vein and metasomatic deposits but also in the superimposed vein sulphides p 292 the revised model is unsustainable in light of recent knowledge the major pitfalls are summarized and commented as follows

a theory for strong long lived squall lines revisited based on the analysis of idealized two and three dimensional cloud model simulations rotunno et al hereafter rkw and weisman et al hereafter wkr put forth a theory that squall line strength and longevity was most sensitive to the strength of the component of low level 0 3 km agl ambient vertical wind shear perpendicular to squall line orientation an optimal state was proposed by rkw based on the relative strength of the circulation associated with the storm generated cold pool and the circulation associated with the ambient shear whereby the deepest leading edge lifting and most effective convective retriggering occurred when these circulations were in near balance since this work subsequent studies have brought into question the basic validity of the proposed optimal state based on concerns as to the appropriate distribution of shear relative to the cold pool for optimal lifting as well as the relevance of such concepts to fully complex squall lines especially considering the potential role of deeper layer shears in promoting system strength and longevity in the following the basic interpretations of the rkw theory are reconfirmed and clarified through both the analysis of a simplified two dimensional vorticity streamfunction model that allows for a more direct interpretation of the role of the shear in controlling the circulation around the cold pool and through an analysis of an extensive set of 3d squall line simulations run at higher resolution and covering a larger range of environmental shear conditions than presented by wkr

siderite deposits in northern italy early permian to early triassic hydrothermalism in the southern alps abstract we present a minero petrographic geochemical and geochronological study of siderite orebodies from different localities of the southern alps northern italy siderite occurs as veins cutting the variscan basement and the overlying lower permian volcano sedimentary cover collio fm and as both veins and conformable stratabound orebodies in the upper permian verrucano lombardo and bellerophon fms and lower triassic servino and werfen fms sedimentary sequences of the lombardian and the venetian alps all types of deposits show similar major and rare earth ree element patterns suggesting a common iron mineralizing event the compositions of coexisting siderite fe rich dolomite and calcite suggest formation from hydrothermal fluids at relatively high temperature conditions 250 c geochemical modelling supported by ree analyses and by literature and new 1 3 c and 18 o isotopic data suggests that fluids responsible for the formation of siderite in the variscan basement and in the overlying lower permian cover were derived from dominant fresh water which leached fe and c from volcanic rocks mainly rhyolites rhyodacites and organic carbon bearing continental sediments on the basis of u th pb microchemical dating of uraninite associated with siderite in the val vedello and novazza deposits lombardian alps the onset of hydrothermalism is constrained to 275 13 ma early mid permian i e it was virtually contemporaneous to the plutonism and the volcanic sedimentary cycle reported in the same area orobic basin the youngest iron mineralizing event is represented by siderite veins and conformable orebodies hosted in lower triassic shallow marine carbonatic successions in this case the siderite forming fluids contained a seawater component interacted with the underlying permian successions and eventually replaced the marine carbonates at temperatures of 250 c the absence of siderite in younger rocks suggests an early triassic upper limit for the iron pulse in the southern alps which would thus predate the middle triassic magmatism based on the overlap between hydrothermalism extensional tectonics and in part magmatism the genesis of siderite in the southern alps may be related to plutonic activity and or magmatic underplating occurring since the permian in a geodynamic scenario preluding the opening of the neo tethys

a climatology of warm season cloud patterns over east asia based on gms infrared brightness temperature observations abstract in the present study hourly infrared ir brightness temperatures observed by the geostationary meteorological satellite gms over the region 20 40 n 95 145 e in may august 1998 2001 are used to compile a climatology of warm season cloud precipitation episodes over east asia with a goal to better understand the characteristics of warm season convection and the behavior of these episodes results are compared with those obtained in north america using radar derived data the convection in east asia similar to that in north america is shown to also exhibit coherent patterns and characteristics of propagating events in the longitude time hovmoller space with a preferred phase speed of 10 25 m s 1 considerably faster than warm season synoptic scale waves near the eastern edge of the tibetan plateau convection was most active with a strong diurnal signal peaking in late afternoon or early evening then propagating eastward the zonal span and duration of episodes could reach 3000 km and

diurnal variations of precipitation deep convection and lightning over and east of the eastern tibetan plateau abstract diurnal cycles of total rainfall precipitation features mesoscale convective systems mcss deep convection precipitation vertical structure and lightning over the eastern tibetan plateau tp and eastward through china are investigated using 11 yr of tropical rainfall measuring mission trmm measurements diurnal cycles of rainfall and precipitation features present apparent phase propagation eastward from the eastern tp for about 1000 km the phase propagation is most evident during the pre mei yu and mei yu seasons however it weakens with the northward progress of the east asian monsoon and ceases in midsummer during the pre mei yu season diurnal cycles of storm population total rainfall deep convection and lightning over the central and eastern tp foothills are in phase peaking during the early morning another striking feature of the pre mei yu season is that nocturnal rainfall and mcss prevail over the southeastern tp foothills following the deep convection and lightning maxim

tunnel channels and associated landforms south central ontario their implications for ice sheet hydrology the peterborough trenton drumlin field and associated meltwater erosion marks s forms were interpreted as the products of erosion by turbulent separated flows within a catastrophically released subglacial meltwater sheet the algonquin event recent theoretical modelling of ice sheet hydrology suggests progressive channelization of meltwater during the collapse of such a sheet inductive testing of this hypothesis using observations in south central ontario forms the crux of this paper a geometric model of the interaction of rough ice base and bed surfaces gives inferred meltwater flow patterns such a rough interactive geometry is suggested as the bed is drumlinized and flows responsible for drumlins may be expected to have eroded similar forms into the ice base three landforms in south central ontario namely tunnel channels megachannels and late stage sheet flow scours are described and interpreted as evidence of progressive channelization and flow diversion processes governed by the geometri

the sensitivity of simulated supercell structure and intensity to variations in the shapes of environmental buoyancy and shear profiles abstract convective storm simulations are conducted using varying thermal and wind profile shapes subject to the constraints of strict conservation of convective available potential energy cape and hodograph trace small and large cape regimes and straight and curved hodographs are studied each with a matrix of systematically varying thermal and wind profile shapes having identical levels of free convection and bulk richardson numbers favorable to supercell development differences in storm intensity and morphology resulting from changes in the profile shapes can be profound especially in the small cape regime where for the moderate shears studied here storms are generally weak except when the buoyancy is concentrated at low levels in stronger cape regimes less dramatic relative enhancements of storm updraft intensity are found when both the buoyancy and shear are concentrated at low levels peak midlevel vertical vorticity correlates roughly with peak updraft speed in the small cape regime but