surface and borehole seismic methods to delineate kimberlite pipes in australia gravity magnetic and electromagnetic methods are primary exploration techniques used in kimberlite exploration to define a kimberlite pipe s location and shape sometimes these methods produce nonunique results because of weathering of the upper part of a kimberlite pipe and its considerable inhomogeneity complex pipe geometries and associated faulting and fracturing may be very difficult to assess by potential field methods application of seismic methods in kimberlite exploration has been limited in sedimentary basins however kimberlite pipes are likely to be a suitable target for the application of seismic reflection methods because of the difference in elastic properties between the pipe material and the host rock the drawback of surface seismic methods is that they are not designed for direct detection of vertical bodies such as a pipe however a kimberlite pipe may be inferred from seismic data indirectly by observing the termination of reflections against its flanks such an approach can produce good results if the sedimentary sequence is of moderate to high reflectivity unfortunately mcarthur basin sediments of the northern territory in australia are quite poor reflectors figure 1 the only reflecting horizon would probably be the sandstone black shale interface at 140 m near surface conditions are also unfavorable for surface seismic because of a thick layer of bull dust which causes poor geophone coupling hence very poor seismic data quality is typical for this area in this study instead of attempting a conventional surface seismic reflection approach we used modes generated by a kimberlite pipe to precisely determine its location the single borehole imaging sbi method also was used for delineation of the kimberlite pipe shape at depth by a combined analysis of p and s wave data recorded on the surface and in downhole experiments the pipe s location shape

sea land breeze development during a summer bora event along the north eastern adriatic coast the interaction of a summer frontal bora and the sea land breeze along the north eastern adriatic coast was investigated by means of numerical simulations and available observations available measurements in situ radiosonde satellite images provided model validation the modelled wind field revealed several regions where the summer bora weaker than 6 m s 1 allowed sea breeze development in the western parts of the istrian peninsula and rijeka bay and along the north western coast of the island of rab along the western istrian coast the position of the narrow convergence zone that formed depended greatly on the balance between the bora jets northward and southward of istria in the case of a strong northern trieste bora jet the westerly istrian onshore flow presented the superposition of the dominant swirled bora flow and local weak thermal flow it collided then with the easterly bora flow within the zone with weakening of the trieste bora jet the convergence zone was a result of the pure westerly sea breeze and the easterly bora wind in general during a bora event sea breezes were somewhat later and shorter with limited horizontal extent the spatial position of the convergence zone caused by the bora and sea breeze collision was strongly curved the orientation of the head of the thermally induced flow was more in the vertical causing larger horizontal pressure gradients and stronger daytime maximum wind speed than in undisturbed conditions except for the island of rab other lee side islands in the area investigated did not provide favourable conditions for the sea breeze formation within a bora wake near the island of krk onshore flow occurred as well although not as a sea breeze flow but as the bottom branch of the lee rotor that was associated with the hydraulic jump like feature in the lee of the velika kapela mountain copyright 2010 royal meteorological society

ekman transport along the galician coast northwest spain calculated from forecasted winds 1 ekman transport is studied close to the galician coast by means of forecasted winds provided by meteogalicia from november 2001 to october 2004 three different coastal zones are identified western coast from mino river to cape finisterre middle coast from cape finisterre to cape ortegal and northern coast from cape ortegal to cape penas in addition to existence of long term variations the periodicity of the transport signal is characterized by an annual component 365 days a seasonal fluctuation 50 to 80 days and a timescale related to passing storms 15 20 days although the periodicity of the signal is similar at the three zones owing to external meteorological forcing the ekman transport is modulated by the presence of the coast in such a way that seasonal patterns vary in intensity and direction along the coast thus the autumn winter pattern is characterized by high transport at the northern and middle coast pointing landward perpendicular to the shoreline and moderate values at the western coast pointing landward and oblique to the shoreline on the other hand the spring summer pattern is characterized by high transport at the western coast pointing seaward perpendicular to the shoreline the same orientation is observed at the middle coast although with a lower magnitude finally ekman transport at the northern coast points landward and oblique to the shoreline the different transport orientations are shown to be responsible for the upwelling probability variation along the coast

effects of wind stress and wind stress curl variability on coastal upwelling abstract aircraft measurements during the winter 1989 shelf mixed layer experiment smile and summer 1982 coastal ocean dynamics experiment code were used to characterize the spatial variation of the low level wind and wind stress over the northern california shelf the curl of the wind stress was calculated from directly measured turbulent stress components the accuracy of the computed curl was estimated to be adequate to map the spatial structure wintertime measurements showed a concentration of large positive curl over 1 pa 100 km 1 west of point arena regardless of wind direction due to the effects of the coastal topography on the wind fields results from summertime measurements showed a similar local maximum of positive curl west of point arena larger curl values over 3 5 pa 100 km 1 however were observed across a hydraulic jump propagating from stewarts point for highly supercritical marine boundary layer flow a two layer vertically integrated numerical model of coastal upwellin

landstreamer seismics and physical property measurements in the siilinjarvi open pit apatite phosphate mine central finland abstractwe tested the applicability of a newly developed broadband 0 800 hz digital based seismic landstreamer for open pit mine planning in the apatite bearing siilinjarvi mine in central finland four seismic profiles in total approximately 2 5 km long 2 4 m source and landstreamer receiver spacing two inside the pit and two on its margins were acquired in combination with wireless recorders connected to 10 hz geophones and fixed at every 10 m spacing along the seismic profiles while the streamer data were being acquired downhole logging and laboratory physical property measurements on core and rock samples were carried out to not only support the seismic interpretations but also to provide information about the possible geophysical signature of these unique types of deposits in spite of a highly noisy mining environment seismic data of high quality were acquired however reflection processing and interpretations were challenged by the geologic complexities of several generations of basic and

sea breezes shallow and deep on the california coast abstract analyses of doppler lidar data reveal sea breezes occurring on two different depth and time scales at monterey bay california on a day with offshore gradient flow indicated before sunrise and after sunset the lidar data used in this study consist of vertical cross sections and profiles of the westerly onshore wind component u in the morning after 0900 pst a shallow sea breeze formed which reached a depth of 300 m by noon starting in early afternoon a deeper sea breeze layer formed in the lowest kilometer and by late afternoon the shallow sea breeze blended into the deeper sea breeze and was no longer evident maximum speeds of 6 m s 1 in the shallow sea breeze occurred at the surface whereas those in the deep sea breeze also 6 m s 1 were about 300 m above the surface it is hypothesized that the shallow sea breeze is a local phenomenon responding to a more local temperature contrast between the sea and the region between the ocean and the mountain ranges the deeper sea breeze on the

petrogenesis of the late cretaceous northern alberta kimberlite province abstract at present 48 late cretaceous ca 70 88 ma kimberlitic pipes have been discovered in three separate areas of the northern alberta the mountain lake cluster the buffalo head hills field and the birch mountains field the regions can be distinguished from one another by their non archetypal kimberlite signature mountain lake or in the case of kimberlite fields primitive buffalo head hills to evolved birch mountains magmatic signatures the dominant process of magmatic differentiation is crystal fractionation and accumulation of olivine which acts as the main criteria to distinguish between primitive and evolved group i type kimberlite fields in the northern alberta this is important from the viewpoint of diamond exploration because the majority about 80 of the more primitive buffalo head hills kimberlites are diamondiferous whereas the more evolved birch mountains pipes are barren of diamonds for the most part petrographically the buffalo head hills samples are distinct from the birch mountains samples in that they contain less carbonate have a smaller modal abundance of late stage minerals such as phlogopite and ilmenite and have a higher amount of fresh coarse macrocrystal 0 5 mm olivine consequently samples from the buffalo head hills have the highest values of mgo cr and ni and have chemistries similar to those of primitive hypabyssal kimberlite in the northwest territories based on whole rock isotopic data the buffalo head hills k6 kimberlite has 87sr 86sr and end values similar to those of south african group i kimberlites whereas the birch mountains legend and phoenix kimberlites have similar end values between 0 and 1 9 but distinctly higher 87sr 86sr values 0 7051 0 7063 the lack of whole rock geochemical overlap between kimberlite and the freshest least contaminated mountain lake south pipe rocks reflects significant mineralogical differences and mountain lake is similar geochemically to olivine alkali basalt and or basanite intra field geochemical variations are also evident the k4 pipe buffalo head hills and xena and kendu pipes birch mountains are characterized by anomalous concentrations of incompatible elements relative to other northern alberta kimberlite pipes including chondrite normalized rare earth element distribution patterns that are less fractionated than the other kimberlite samples from the buffalo head hills and birch mountains the xena pipe has similar major element chemical signatures and high al clinopyroxene similar to or trending towards the mountain lake pipes in addition k4 and kendu have higher 87sr 86sr and lower end than bulk earth and plot in the bottom right quadrant of the nd sr diagram we suggest therefore that the k4 and kendu pipes contain a contribution from old lree enriched low sm nd lithosphere that is absent from the other kimberlites are affected by crustal contamination or both based on xenocryst populations the northern alberta kimberlite province mantle is dominated by carbonate saturated lherzolitic mantle higher levels of melt depletion characterize the buffalo head hills mantle sample despite high diamondiferous to barren pipe ratios in the buffalo head hills pipes mineral indicators of high diamond potential such as g10 garnet diamond inclusion composition chrome spinels and high sodium eclogitic garnet are rare

observed dynamics of coastal flow at cape mendocino during coastal waves 1996 abstract airborne in situ and remote meteorological measurements from around cape mendocino california sampled during the coastal waves 1996 field program are analyzed for three different days 7 12 and 26 june 1996 two days conformed to typical summertime conditions with a strong northerly downcoast flow while the wind on the third day was weaker on the first 2 days the flow was supercritical in the sense that the froude number was larger than unity and these 2 days feature expansion fans in the lee of the cape on the third day no such phenomenon was observed all 3 days had a strong thermal wind caused by the marine inversion sloping down toward the coast on the first 2 days the flow aloft was westerly or northerly so that the thermal wind added to the background flow results in a strong jet on the third day the flow aloft was southerly and consequently even with the added thermal wind the northerly flow in the marine layer was too weak to be supercritical the main difference between t

observations of large wind shear above the marine boundary layer near point buchon california abstractparticularly strong winds along the coast of southern california on 24 may 2012 were measured by the wyoming king air research aircraft during the precision atmospheric marine boundary layer experiment preamble the fast flow is bounded laterally by the coastal topography and vertically by a pronounced temperature inversion separating the cool moist air in the marine boundary layer mbl from the warm dry air aloft many studies have investigated the response of this two layer flow to changes in the coastline by invoking hydraulic theory which explains the essential characteristics including changes in mbl depth and the attendant wind processes occurring just above the mbl are important to the low level thermodynamic and kinematic structure observations on this day demonstrate how the large shear above the mbl can impact the lower atmosphere a typical two layer system was observed north of point buchon which was supercritical around point buchon the depth of the mbl decreased and wind i

physical modeling of an outflow event in howe sound british columbia outflow winds occur when differing air masses are separated by a coastal mountain barrier in extreme cases the cross barrier pressure gradient and the high degree of stratification often approaching a distinct layered structure result in channel winds which exhibit hydraulic features we present a study of outflow winds in howe sound british columbia a field investigation aimed specifically at locating and quantifying hydraulic effects was undertaken during the winter months of 1992 1993 microbarographs positioned in the region recorded pressure changes at discrete locations in the streamwise direction the pressures obtained during a severe outflow wind event which occurred from december 27 1992 to january 1 1993 show a highly variable lower layer depth suggestive of hydraulic control experiments were conducted with a three dimensional physical model that is geometrically and kinematically similar to howe sound synoptic conditions recorded during the outflow wind event in howe sound in december 1992 were used to determine appropriate model flow forcing the expanse of supercritical flow area was observed to be relatively sensitive to changes in along channel pressure gradient and downstream depth when compared to changes in discharge channel sinuosity and local topography appeared to force critical conditions at specific locations for example a channel bend combined with headlands was observed to force a situation where subcritical and supercritical streams flow side by side flow separation resulting in lateral shear discontinuities produced similar conditions these effects are discussed and put into context with field observations field and model results show good agreement

seismic delineation of the orion south kimberlite fort a la corne canada abstractthe orion south 140 141 kimberlite is a diamondiferous multiphase volcano sedimentary complex within the cretaceous fort a la corne kimberlite field of saskatchewan canada a network of seven high resolution 2d seismic reflection profiles were acquired to test the utility of using seismic methods in defining the subsurface architecture of the kimberlite complex and to provide auxiliary constraints on interborehole geologic correlations the seismic data were interpreted in conjunction with a set of drillhole geologic logs and associated geologic sections and models and physical rock properties from core measurements and geophysical logs core determined average density values for the kimberlite suite are low 2240 16 kg m3 but with some kimberlite facies having significantly higher values 2330 to 2540 kg m3 sonic velocities for the kimberlites are 2500 3500 m s as compared with 2000 m s and 3800 4500 m s for the enveloping shale and sandstone units respectively the kimberlite is

the horizontal momentum balance in the marine atmospheric boundary layer during code 2 abstract the horizontal momentum balance in the marine atmospheric boundary layer during the coastal ocean dynamics experiment code is analyzed using meteorological data from an array of surface moorings previous studies have indicated the presence of orographically generated mesoscale features that are induced by strong southward flow around point arena the present analysis demonstrates that during periods of strong southward flow the cross shore momentum equation is dominated by a balance between the ageostrophic acceleration associated with the flow curvature around point arena and the cross shore pressure gradient while the along shore momentum equation is dominated by a balance between vertical stress divergence and alongshore pressure gradient these balances are consistent with results from a shallow water model of the marine layer the calculations provide evidence for orographic modification of the horizontal structure of the boundary layer under a broader range of southward flow conditio

simulations of supercritical flow around points and capes in a coastal atmosphere fully 3d nonlinear model simulations for supercritical flow along locations at the california coast at cape mendocino and point sur are presented the model results are objectively and subjectively verified against measurements from the coastal waves 1996 experiment with good results they are then analyzed in terms of the flow structure the impact of the local terrain the atmospheric forcing on the ocean surface and the momentum budgets it is verified that the flow is supercritical fr 1 within a rossby radius of deformation from the coast and that it can be treated as a reduced gravity shallow water flow bounded by a sidewall the coastal mountain barrier as the supercritical flow impinges on irregularities in the coastline orientation expansion fans and hydraulic jumps appear the modeled froude number summarizes well the current understanding of the dynamics of these events in contrast to inviscid irrotational hydraulic flow the expansion fans appear as curved lines of equal pbl depth and lens shaped maxima in wind speed residing at the pbl slope this is a consequence of the realistic treatment of turbulent friction modeled mean pbl vertical winds in the hydraulic features range 6 1 2 cm s21 while larger vertical winds 6 5 10 cm s21 are due to the flow impinging directly on the mountain barrier local terrain features at points or capes perturb the local flow significantly from the idealized case by emitting buoyancy waves the momentum budget along straight portions of the coast reveals a semigeostrophic balance modified by surface friction while being geostrophic in the across coast direction the along coast momentum shows a balance between the pressure gradient force and the turbulent friction in the expansion fans the flow is ageostrophic and the imbalance is distributed between turbulent friction and ageostrophic acceleration according to the magnitude of the former there is also a good correspondence between the magnitude of the local curl of the surface stress vector and the measured depression in sea surface temperature sst in areas where the latter is large and the along coast flow is relatively weak implying that a substantial portion of the upwelling is driven locally supplying the measured sst in the numerical simulations with a considerable depression along the coast had only marginal feedback effects on the character of the flow

deep electrical structure of northern alberta canada implications for diamond exploration geophysical studies of upper mantle structure can provide constraints on diamond formation teleseismic and magnetotelluric data can be used in diamond exploration by mapping the depth of the lithosphere asthenosphere boundary studies in the central slave craton and at fort a la corne have detected conductors in the lithospheric mantle close to or beneath diamondiferous kimberlites graphite can potentially explain the enhanced conductivity and may imply the presence of diamonds at greater depth petrologic arguments suggest that the shallow lithospheric mantle may be too oxidized to contain graphite other diamond bearing regions show no upper mantle conductor suggesting that the correlation with diamondiferous kimberlites is not universal the buffalo head hills in alberta host diamondiferous kimberlites in a proterozoic terrane and may have formed in a subduction zone setting long period magnetotelluric data were used to investigate the upper mantle resistivity structure of this region magnetotell

upwelling response to atmospheric coastal jets off central chile a modeling study of the october 2000 event the spatial and temporal variability of nearshore winds in eastern boundary current systems affect the oceanic heat balance that drives sea surface temperature changes in this study regional atmospheric and oceanic simulations are used to document such processes during an atmospheric coastal jet event off central chile the event is well reproduced by the atmospheric model and is associated with the migration of an anomalous anticyclone in the southeastern pacific region during october 2000 a robust feature of the simulation is a sharp coastal wind dropoff which is insensitive to model resolution as expected the simulated oceanic response is a significant sea surface cooling a surface heat budget analysis shows that vertical mixing is a major contributor to the cooling tendency both in the jet core area and in the nearshore zone where the magnitude of this term is comparable to the magnitude of vertical advection sensitivity experiments show that the oceanic response in the coastal area is sensitive to wind dropoff representation this is because total upwelling i e the sum of coastal upwelling and ekman pumping depends on the scale of wind dropoff because the latter is much larger than the upwelling scale coastal wind dropoff has only a weak positive effect on vertical velocities driven by ekman pumping but has a strong negative effect on coastal upwelling interestingly though the weakening of coastal winds in the dropoff zone has a larger effect on vertical mixing than on vertical advection with both effects contributing to a reduction of cooling

oxygen isotope systematics of the precambrian basement of alberta implications for paleoproterozoic and phanerozoic tectonics in northwestern alberta we have conducted a regional survey of the oxygen isotope compositions of drill core samples from the precambrian basement of the alberta sedimentary basin the majority of samples have whole rock 18o smow values between 7 and 11 as is typical of crustal rocks however there are also a significant number of samples with 18o values less than 5 in these samples high grade minerals such as pyroxene amphibole and biotite commonly show retrograde alteration to chlorite and or epidote the majority of low 18o samples are from a 250 x 50 km zone in northwestern alberta which we refer to as the kimiwan isotope anomaly the anomaly is significant in that the most reasonable explanation for generating such a laterally extensive zone of rocks with 18o values below 5 is through high temperature interaction with surface derived fluids in an extensional tectonic setting we propose therefore that the low 18o samples define a hitherto unrecognized extensional zone in the alberta basement avai

transcritical flows in the coastal marine atmospheric boundary layer abstract numerical solutions of shallow water flow in a variable width channel are computed to model the summertime marine atmospheric boundary layer off the u s west coast using an idealization of the coastline in the vicinity of point arena california as an example several steady state base flows are presented that are hydraulically transcritical these flows are strongly nonlinear weakly rotational and are forced by constant pressure gradients and damped by nonlinear bottom drag at the sea surface the transcritical base flows are supercritical in the vicinity of bends in the coastline but are subcritical to the north upstream and to the south downstream where the coastline is straight within the supercritical region orographic bends in the coastline produce expansion fans and compression jumps the same structures found in globally supercritical flows when the imposed pressure gradient forcing is increased the resulting base flow has a supercritical to subcritical transitional jump that

diurnal cycle of supercritical along coast flows abstract in this study a three dimensional hydrostatic mesoscale model is used to address the transient behavior of supercritical along coast flow a control experiment and several sensitivity tests are performed in order to investigate the diurnal cycle of flow characteristics an idealized representation of the northern california terrain is used and the model results are interpreted within the reduced gravity shallow water concept in two preceding studies by the authors this theory appeared to be violated since the flow accelerated along the coastline upstream of the change in coastline orientation even though the flow was supercritical here it is shown that the criticality of the flow for typical summertime conditions along the california coast actually varies diurnally the gradual acceleration of the flow along the upstream coastline is established during a subcritical phase of the simulation thus the shallow water concept is not violated because the along coast jet is primarily driven by

canadian kimberlites geological characteristics relevant to emplacement in canada more than 770 kimberlites have erupted in diverse tectonic settings over a period of 1000 ma and over an area at least 5000 km across the kimberlites represent at least 30 comagmatic fields one pipe type dominates each of the different kimberlite fields even with the discovery of a significant number of new kimberlite fields this review of recent data substantiates the previous proposal that there are at least three distinct classes of kimberlite pipes which show a correlation with the nature of the country rocks into which they were emplaced new data show that a variation on the prairies pipe type occurs when kimberlites were emplaced into competent paleozoic sediments resulting in steeper sided pipes infilled with similar pyroclastic kimberlite new data for each pipe type are summarised and the contrasting characteristics of the three pipe types are considered to reflect fundamentally different styles of eruption and deposition apparently uniform near surface olivine and volatile rich kimberlite magmas were modified differently during the contrasting emplacement processes resulting in distinct textural rock types pyroclastic kimberlite pk tuffisitic kimberlite tk and associated hypabyssal kimberlite hk or resedimented kimberlite rvk dominating each type of pipe the substantiated correlation of pipe type with country rock geology could indicate variable constraints on volatile exsolution which affected the nature of the magmatic eruptions in different settings

mesoscale simulation of supercritical subcritical and transcritical flow along coastal topography abstract a mesoscale atmospheric model is used to address the characteristics of stratified flow bounded by a side wall along a varying coastline initial froude number values are varied through alteration of marine inversion strength permitting examination of supercritical subcritical and transcritical flow regimes encountering several coastal configurations consistent with shallow water models sharp drops in boundary layer depth and flow acceleration occur in flow rounding convex bends however significant flow response occurs in the stratified layer aloft which is unexplained by conventional shallow water theory the strongest flow acceleration occurs in the transcritical case while regardless of inversion strength the deformation of the isentropes aloft shows general structural similarity advection of horizontal momentum is an important component of the horizontal force balance a simulation having several coastline bends exhibits a detached oblique hydraulic jump upwind of a concave bend t

deep rifts as sources for alkaline intraplate magmatism in eastern north america intracontinental magmatism in eastern north america does not exhibit the regular time progression associated with mantle plume activity instead the magmatism is sporadic but locally persistent suggesting that the magmas rise from a mantle source that drifts with the continental plate a spatial association with ancient rifts further suggests that this source is fertile9 melt generating material emplaced in the mantle lithosphere during the early stages of rifting

linear theory of the sea breeze in a thermal wind this article investigates the linear dynamics of the sea breeze in an along shore thermal wind shear the present analysis shows that the sea breeze circulation is tilted towards the slanted isentropes associated with the thermal wind at a critical value of the thermal wind shear the tilt of the sea breeze circulation becomes equal to the slope of the background isentropes the present analysis also shows a spatial shift between the heating pattern and the sea breeze circulation the present linear theory is then applied to interpret measurements made in the vicinity of new york city where there is a warm season synoptic southwesterly jet it is compared with observations and past numerical simulations agreement is found with respect to the enhanced along coast wind that follows the tilted isentropes the order of magnitude of the isentrope tilt and the clockwise rotating wind hodograph showing the jet maximum peaking at 1800 solar time there is a disagreement between theory and observations on the phase lag between the jet maximum and the cross shore pressure gradient maximum however this disagreement can reasonably be attributed to either the angle made by the synoptic jet to the coastline and or the presence of friction the inland spatial shift of the breeze indicated by the theory might also be indirectly confirmed by the coastal inlan dw ind observations of al arger diurnal amplitude for a stronger synoptic jet copyright c 2011 royal meteorological society

adjustment of the marine atmospheric boundary layer to a coastal cape abstract during summer significant changes in marine atmospheric boundary layer mabl speed and depth occur over small spatial scales 100 km downstream from topographic features along the california coast in june and july 1996 the coastal waves 96 project collected observations of such changes at capes with an instrumented aircraft this paper presents observations from the 7 june flight when the layer averaged speed increased 9 m s 1 and depth decreased by 500 m over a 75 km downwind from cape mendocino accompanied by enhanced surface fluxes and local cloud clearing the acceleration and thinning are reproduced when the flow is modeled as a shallow transcritical layer of fluid impinging the bends of a coastal wall leading to the interpretation that they are produced by an expansion fan model runs were produced with different coastlines and imposed pressure gradients with the best match provided by a coastline in which the cape protruded into the flow and forced a response in the subcritical r

coastal jet adjustment near point conception california with opposing wind in the bight abstracttypical spring and summer conditions offshore of california consist of strong northerly low level wind contained within the cool well mixed marine boundary layer mbl that is separated from the warm and dry free troposphere by a sharp temperature inversion this system is often represented by two layers constrained by a lateral boundary aircraft measurements near point conception california on 3 june 2012 during the precision atmospheric mbl experiment preamble captured small scale features associated with northerly flow approaching the point with the added complexity of encountering opposing wind in the santa barbara channel an extremely sharp cloud edge extends south southwest of point conception and the flight strategy consisted of a spoke pattern to map the features across the cloud edge lidar and in situ measurements reveal a nearly vertical jump in the mbl from 500 to 100 m close to the coast and a sharp edge at least 70 km away from the coast in this case it is hypothesized that

the marine atmospheric boundary layer jet in the coastal ocean dynamics experiment the vertical and horizontal structure of the atmospheric boundary layer near the northern california coast was investigated during spring upwelling conditions as part of the 1981 coastal ocean dynamics experiment two daytime aircraft flights were devised to measure mean and turbulent quantities for 25 km tracks along and across the continental shelf from 30 to 1200 m altitude the pacific high offshore and an inland thermal low characterized the synoptic situations and equatorward winds resulted which produced intense ocean upwelling the wind profile was found to be jet shaped maximum wind speeds were 25 m s 1 and 16 m s 1 at 400 and 100 m respectively in the two flights above and below the heights of the jet speed maxima the wind speed decreased rapidly sharp density inversions existed at the levels of the peak wind speeds in one flight the inversion also sloped down toward the coast turbulence was effectively confined below the inversions strong zonal temperature gradients above the inversion between the hot land and cool marine air caused a thermal wind for which the wind speed decreased with height below the inversion turbulent stress divergence was large and effective in transferring the horizontal momentum of the wind to the sea slowing the wind there was also a small thermal wind below the inversion but opposite to the one above owing to the well mixed air temperature following the sea surface temperature which was cold at the coast and relatively warmer offshore owing to the upwelling these effects explain the jet shaped wind profile the mean momentum equations show that an acceleration toward the coast can balance the pressure gradient coriolis and turbulent stress divergence forces and there were some observations to support this complete balance was not obtained for the turbulent kinetic energy budget inferred dissipation rates were too large

potential field signatures of buried precambrian basement in the western canada sedimentary basin an internally consistent levelled compilation of magnetic data is derived for alberta and northeastern british columbia with bouguer gravity data this compilation is used to refine the definition of precambrian basement domains within the western canada sedimentary basin magnetic data are draped at a constant distance above the mapped basement surface to reduce the effects of varying magnetic source depths automated interpretation methods that effectively map outlines of magnetic sources are used to characterize the internal structure of the domains and to aid in their delineation the basement domain map thus derived differs from previous interpretations in the extension of domains further to the southwest due mainly to the availability of new public domain magnetic data and the more precise definition of domain boundaries based on the magnetic source location maps the nahanni hottah chinchaga thorsby vulcan and kiskatinaw domains are weakly magnetic and characterized by magnetic sources tha

on the surface wind speed probability density function over complex terrain 1 the physical mechanisms determining the shape of the surface wind speed probability density function over complex terrain are investigated using observations from a dense mesoscale network and a high spatial resolution mesoscale simulation for the 1992 to 2005 period results indicate that the atmospheric stability plays a major role in controlling the shape of the wind speed distribution but its effects are strongly modulated by the contribution of different atmospheric scales of motion such as the mesoscale or synoptic scale the local topographic features further modulate the relative contribution of each mechanism as a consequence of the complicated interaction of these atmospheric processes the surface wind speed distribution can present a complicated shape that is not always expected to fit a unimodal weibull type distribution over complex terrain regions

the subglacial geomorphology of southeast alberta evidence for subglacial meltwater erosion a coherent pattern of landforms in southeast alberta forms a subglacial landform continuum scoured bedrock tracts flutes transverse bed forms and tunnel channels in this continuum are inferred to be products of erosion by turbulent subglacial meltwater flows beneath the laurentide ice sheet bedrock and glacigenic sediment are truncated by an erosional surface flutes and extensive boulder lags across the truncation surface strongly suggest erosion by high velocity turbulent flows tunnel channels dissect the erosion surface and record channelization of earlier sheet flows convex longitudinal profiles of channels indicate subglacial meltwater flow northeast southwest trending transverse bed forms are superimposed on the preglacial divide and may be either glaciotectonic ridges or fluvial bed forms landforms reflect the dominance of erosion in the subglacial environment likely by catastrophic meltwater flows of the livingstone lake megaflood event the subglacial meltwater hypothesis accounts for e

response of the summer marine layer flow to an extreme california coastal bend abstract a summer wind speed maximum extending more than 200 km occurs over water around point conception california the most extreme bend along the u s west coast the following several causes were investigated for this wind speed maximum 1 synoptic conditions 2 marine layer hydraulic flow effects 3 diurnal variations 4 mountain leeside downslope flow 5 sea surface temperature structure and 6 island influence synoptic conditions set the general wind speed around point conception and these winds are classified as strong moderate or weak the strong wind condition extends about point conception reaching well offshore toward the southwest and the highest speeds are within 20 km to the south moderate wind cases do not extend as far offshore and they have a moderate maximum wind speed that occurs over a smaller area in the western mouth of the santa barbara channel the weak wind speed case consists of light and variable winds about point conception each category occurs about one third

large scale structure of the june july 1996 marine boundary layer along california and oregon abstract data from surface stations profilers long range aircraft surveys and satellites were used to characterize the large scale structure of the marine boundary layer off of california and oregon during june and july 1996 to supplement these observations june july 1996 averages of meteorological fields from the u s navy s operational coupled ocean atmospheric mesoscale prediction system coamps model were generated for the region model calculations show a broad band of fast northerly surface winds exceeding 7 m s 1 extending along the california oregon coast buoy measured peaks of 7 1 m s 1 off bodega bay 7 2 m s 1 off point piedras blancas and 8 8 m s 1 near point conception were reported mean winds at the buoys located 15 25 km offshore are generally faster than those at coastal stations and all station winds are faster in the afternoon the aircraft and station observations confirm that an air temperature inversion typically marks the top of the marine boundary layer which deepens offs

kimberlite sourced bentonite its paleoenvironment and implications for the late cretaceous k14 kimberlite cluster northern albertathis article is one of a selection of papers published in this special issue on the theme geology of northeastern british columbia and northwestern alberta diamonds shallow gas gravel and glaciers kimberlite sourced bentonite layers have been discovered in late cretaceous sedimentary drill cores located within the buffalo head hills kimberlite field north central alberta two bentonites are unambiguously differentiated from common intermediate to felsic volcanic derived alberta bentonite by having similar whole rock geochemical composition to ultramafic rocks from the buffalo head hills kimberlite field and worldwide crater facies kimberlite the results demonstrate that the geochemical analysis of bentonite can provide a quick cost effective means of testing for low volume kimberlite volcanism the kimberlite sourced bentonite is associated with a cluster of buffalo head hills kimberlites known as the k14 complex the k14a kimberlite occurrence has a previously reported 206pb 238u perovskite emplacement age of 86 8 2 1 ma this age is compatible with early or mid cenomanian 99 96 ma and mid coniacian to santonian 88 84 ma palynological results for mudstone underlying and bracketing the

the summertime low level jet and marine boundary layer structure along the california coast abstract this paper examines the strong summertime northerly low level jet llj that frequently exists along the california coast the persistent synoptic scale pressure distribution north pacific high to the west thermal low to the east and baroclinity created by the juxtaposition of the heated continent and the cool marine layer produce the mean structure of this llj strong diurnal thermal forcing coupled with topographic influences on the flow modulate the jet structure position and intensity a mesoscale model is used to examine many of the complex facets of the llj flow dynamics several sensitivity studies in addition to a control experiment aid in this investigation principal findings of this study include the following the pronounced east west slope of the marine planetary boundary layer mpbl is not due primarily to colder sst values along the coast dynamically forced low level coastal divergence coupled with synoptic scale divergence appears to be dominant in determining mpbl i

a numerical study of the convection triggering and propagation associated with sea breeze circulation over hainan island based on high resolution numerical simulations the effects of sea breeze circulation sbc on associated convective initiation and propagation over hainan island are investigated the results show that the blocking of synoptic wind on the windward side of the mountains inhibits the occurrence of windward side valley breeze and sea breeze in the context of low mountains weak synoptic wind not only favors the combination of the sbc with the valley breeze circulation on the leeward side of the mountains but also makes the convergence zone between the synoptic wind and the leeward side combined circulation stay near the tops of the mountains leading to the accumulation of large quantities of water vapor taking place over the mountaintops the combined effect of enhanced water vapor and high temperatures over the mountaintops can result in the generation of much larger convective available potential energy cape than the surrounding areas the coupling of the large cape with the considerable converging ascending motion and abundant water vapor near the tops of the mountains promotes the occurrence of a strong convection band cb over the mountaintops during the cb propagation under the steering of synoptic wind the flow across the cb continuously and strongly opposes the sbc front and the fronts of the kelvin helmholtz billows behind resulting in successive and strong lifting motion as well as large quantities of water vapor and high cape near these fronts these lead to an apparent downstream wave like propagation of the cb

adjustment of the marine atmospheric boundary layer to the large scale bend in the california coast 1 observations of the surface wind field off the u s west coast were made from satellite by the sea surface microwave imager ssm i during june 1994 and june 1996 the coast bends inward 28 at 40 n latitude northerly wind speeds are high within a region that extends far south and offshore of this bend bounded on the east by the california coast on average the high speed wind zone extends 250 km from shore and 800 km alongcoast long coast perpendicular aircraft transects show that moving onshore the depth of the mabl decreases the northerly wind speed increases and the froude number increases a network of oceanographic buoys records the surface wind speed direction and pressure from six buoy pressure measurements the geostrophic wind vector was computed to represent the synoptic flow over the oregon northern california coastal waters the satellite surface wind fields were composited by the direction of the buoy geostrophic background wind the predominant direction is 210 180 a high speed region extends south of the bend for directions in the 0 180 range moving counterclockwise which corresponds to a downcoast component of the pressure gradient for directions between 180 and 0 flow splits at the bend and the region of highest winds is found to its north and offshore a high speed region south of the bend was present in 65 of the satellite wind maps as well as in the june averages the flow s response to coastal promontories such as point arena is nested within this broad zone of fast thin likely supercritical flow

paleomagnetic dating of the northern alberta kimberlites due to the vast amount of economic interest diamonds have created in northern alberta there is a need to pro duce an accurate geological model for the northern alberta kimberlite province to aid in the development of such a model the emplacement ages of two kimberlite occurrences k5 and k6 from the buffalo head hills region of north central alberta and the ultramafic mountain lake body from northwestern alberta were estimated using paleomagnetic methods paleomagnetic poles obtained in our study do not differ statistically from the reference poles for late mesozoic cenozoic for north america besse and courtillot 2002 with the aid of polarity determinations palynology and radio genic dating the paleomagnetic results allow for new constraints on the emplacement age of the selected ultramafic occurrences the paleomagnetic emplacement ages established for the k5 k6 and mountain lake bodies are 90 83 ma 83 0 79 1 ma and not older than 79 1 ma respectively resume en raison du grand intereteconomique que les diamants ont creedans le nord de l alberta il est necessaire de developper un modele geologique precis de la province kimberlitique du nord de l alberta afin d aider au developpement d un tel modele les ages de la mise en place de deux occurrences de kimberlite k5 et k6 de la region des collines buffalo head du centre nord de l alberta et de l amas ultrabasique mountain head du nord ouest de l alberta ont eteestimes par une methode paleomagnetique les poles paleomagnetiques obtenus dans notre etude ne different statistiquement pas des poles de reference pour l amerique du nord au mesozoo que tardif cenozoo que besse and courtillot 2002 grace aux determinations de polarite ala palynologie et ala datation radiogenique les resultats paleomagnetiques limitent l age de la mise en place des occurrences ultramafiques selectionnees les ages paleomagnetiques de la mise en place etablis pour les amas k5 k6 et mountain lake sont respectivement de 90 83 ma 83 0 79 1 ma et pas plus vieux que 79 1 ma traduit par la redaction

detailed topography of the devonian grosmont formation surface from legacy high resolution seismic profiles northeast alberta abstractthe devonian grosmont formation in northeastern alberta canada is the world s largest accumulation of heavy oil in carbonate rock with estimated bitumen in place of 64 5 109 m3 much of the reservoir unconformably subcrops beneath cretaceous sediments this is an eroded surface modified by kartstification known as the sub mannville unconformity smu we studied the reanalysis and integration of legacy seismic data sets obtained in the mid 1980s to investigate the structure of this surface standard data processing was carried out supplemented by some more modern approaches to noise reduction the interpretation of these reprocessed data resulted in some key structural maps above and below the smu these seismic maps revealed substantially more detail than those constructed solely on the basis of well log data in fact the use of only well log information would likely result in erroneous interpretations although features smaller than about 40 m in radius cannot be easily discerned at the smu

impact of nearshore wind stress curl on coastal circulation and primary productivity in the peru upwelling system 1 coastal upwelling dynamics are strongly affected by alongshore wind stress and nearshore wind stress curl a coupled physical biogeochemical regional model and lagrangian diagnostics are used in the peru current system to determine how the upwelling of nutrients and the primary productivity are impacted by the spatial structure of the nearshore wind stress three wind stress products derived from the ers and quikscat scatterometers and a smoothed quikscat field mainly differing in nearshore wind stress curl patterns were used simulations are found to produce significantly different mean surface chlorophyll distributions and show that strong upwelling favorable nearshore wind stress curl may locally induce a wide coastal productive zone through upwelling of nutrient replete waters brought by a shoaling coastal undercurrent using wind stress products with realistic nearshore patterns is therefore crucial for the modeling of coupled physical biogeochemical coastal processes

the marine layer off northern california an example of supercritical channel flow abstract during the spring and summer northerly winds driven by the north pacific high pressure system are prevalent over the northern california continental shelf only interrupted for periods of a few days when weak or southerly winds occur in the course of the coastal ocean dynamics experiment code fixed station and observations were made to describe the temporal and spatial structure of the lower atmosphere and their relation to the strong upwelling of coastal waters in a region extending up to 40 km offshore and 100 km along the coast these observations suggest that atmospheric conditions during the spring and summer usually fall into one of three categories the surface wind can be everywhere weak pattern 1 it can blow at large speeds in a uniform pattern pattern 2 or finally the structure of the northerly surface wind can be complex with large changes in the wind speed and corresponding changes in the surface pressure over short spatial scales pattern 3 the latter pattern which o

coastal perturbations of marine layer winds wind stress and wind stress curl along california and baja california in june 1999 abstract month long simulations using the fifth generation pennsylvania state university national center for atmospheric research mesoscale model mm5 with a horizontal resolution of 9 km have been used to investigate perturbations of topographically forced wind stress and wind stress curl during upwelling favorable winds along the california and baja california coasts during june 1999 the dominant spatial inhomogeneity of the wind stress and wind stress curl is near the coast wind and wind stress maxima are found in the lees of major capes near the coastline positive wind stress curl occurs in a narrow band near the coast while the region farther offshore is characterized by a broad band of weak negative curl curvature of the coastline such as along the southern california bight forces the northerly flow toward the east and generates positive wind stress curl even if the magnitude of the stress is constant the largest wind stress curl is simulated in the lees of point conception and the santa ba

approximating edges of source bodies from magnetic or gravity anomalies cordell and grauch 1982 1985 discussed a technique to estimate the location of abrupt lateral changes in magnetization or mass density of upper crustal rocks the final step of their procedure is to identify maxima on a contoured map of horizontal gradient magnitudes we attempt to automate their final step our method begins with gridded magnetic or gravity anomaly data and produces a plan view of inferred boundaries of magnetic or gravity sources the method applies to both local surveys and to continent wide compilations of magnetic and gravity data e g zietz 1982 simpson et al 1983a kane et al 1982

adjustment of the summer marine boundary layer around point sur california an instrumented c 130 aircraft flew over water around point sur california on 17 june 1996 under strong northwest wind conditions and a strong marine inversion patterns were flown from 30 to 1200 m elevation and up to 120 km offshore nearshore marine air accelerated past point sur reaching a surface maximum of 17 ms 21 in the lee winds measured over water in and above the marine layer were alongshore with no significant cross shore flow sea level pressure 10 m air temperature and air temperature inversion base generally decreased toward the coast and were an absolute minimum just downcoast of the wind speed maximum the sea surface temperature also decreased toward the coast but was an absolute minimum directly off point sur the nearcoast air temperature inversion base height was 400 m north of point sur decreased to a minimum of 50 m in the lee of point sur then increased farther to the south wind speeds were at a maximum centered along the air temperature inversion base the fastest was 27 m s 21 in the lee of point sur using a froude number calculation that includes the lower half of the capping layer the marine layer in the area is determined to have been supercritical most of the marine layer had froude numbers between 1 0 and 2 0 with the extreme range of 0 8 2 8 temperatures in the air temperature inversion in the lee were substantially greater than elsewhere modifying the surface pressure gradient the overall structure was a hydraulic supercritical expansion fan in the lee of point sur under the influence of rotation and surface friction the naval research laboratory nonhydrostatic coupled ocean atmosphere mesoscale prediction system coamps indicated a broad supercritical marine boundary layer moving to the south along central california and point sur during the aircraft flight the marine boundary layer thinned and accelerated into the lee of point sur which was the site of the fastest sea level wind speed along central california isotherms dip and speeds decreased in the lee of point sur in the capping inversion well above the marine layer coamps forecasted a compression shock wave initiating off the upwind side of the topography behind point sur and other coastal points to the north evidence from the model and the aircraft supports the existence of an oblique hydraulic jump on the north side of point sur

a revised crustal stress orientation database for canada abstract the canadian database on contemporary crustal stress has not been revised systematically in the past two decades here we present the results of our new compilation that contains 514 new data records for the orientation data of maximum compressive horizontal stress and 188 data records that were re assessed in total the canadian stress database has now 1667 data records which is an increase of about 45 from these data a new canadian stress map as well as one for the province of alberta is presented to analyse the stress pattern we use the quasi median on the circle as a smoothing algorithm that generates a smoothed stress map of the maximum compressive horizontal stress orientation on a regular grid the newly introduced quasi interquartile range on the circle estimates the spreading of the data and is used as a measure for the wave length of the stress pattern the result of the hybrid wavelength analysis confirms that long spatial wavelength stress patterns 1000 km exist in large areas in canada the observed stress pattern is transmitted through the intra plate regions the results reveal that shorter spatial wave length variation of the maximum compressive horizontal stress orientation of less than 200 km prevails particularly in south eastern and western canada regional stress sources such as density contrasts active fault systems crustal structures etc might have a significant impact in these regions in contrast to these variations the observed stress pattern in the alberta basin is very homogeneous and mainly controlled by plate boundary forces and body forces the influence of curvature of the rocky mountains salient in southern alberta is minimal the present day horizontal stress orientations determined herein have important implications for the production of hydrocarbons and geothermal energy in the alberta basin

airborne measurements of coastal jet transition around point conception california low level winds along the californian coast during spring and early summer are typically strong and contained within the cool well mixed marine boundary layer mbl a temperature inversion separates the mbl from the warmer free troposphere this setup is often represented by a two layer shallow water system with a lateral boundary near a prominent point such as point conception california the fast moving mbl flow is supercritical and can exhibit distinct features including a compression bulge and an expansion fan measurements from the university of wyoming king air research aircraft on 19 may 2012 during the precision atmospheric mbl experiment preamble captured wind in excess of 14ms 21 off of point conception under clear skies and wind 2ms 21 east of san miguel in the california bight a compression bulge was identified upwind of point conception when the flow rounds the point the mbl undergoes a near collapse and there is a spike in mbl height embedded in the general decrease of mbl height with greater turbulence just downwind that is associated with greater mixing through the inversion layer lidar and in situ measurements reveal that transport of continental aerosol is present near the pronounced mbl height change and that there is a complex vertical structure within the santa barbara channel horizontal pressure gradients are obtained by measuring the slope of an isobaric surface observations of wind and pressure perturbations are able to be linked through a simple bernoulli relationship variation of mbl depth explains most but not all of the variation of the isobaric surface

seismic methods in mineral exploration and mine planning a general overview of past and present case histories and a look into the future abstractdue to high metal prices and increased difficulties in finding shallower deposits the exploration for and exploitation of mineral resources is expected to move to greater depths consequently seismic methods will become a more important tool to help unravel structures hosting mineral deposits at great depth for mine planning and exploration these methods also can be used with varying degrees of success to directly target mineral deposits at depth we review important contributions that have been made in developing these techniques for the mining industry with focus on four main regions australia europe canada and south africa a wide range of case studies are covered including some that are published in the special issue accompanying this article from surface to borehole seismic methods as well as petrophysical data and seismic modeling of mineral deposits at present high resolution 2d surveys mostly are performed in mining areas but there is a general increasing trend in the use of 3

gap winds in a fjord part ii hydraulic analog abstract a simple shallow water model of gap wind in a channel that is based upon hydraulic theory is presented and compared with observations and output from a 3d mesoscale numerical model the model is found to be successful in simulating gap winds the speed and depth of gap wind flow is strongly controlled by topography horizontal or vertical channel contractions can act to force strong shallow supercritical flow downwind and light deep subcritical flow upwind force balance analysis of the hydraulic model output confirms mesoscale model results and indicates that the prime force balance in gap wind is between external pressure gradient and friction for supercritical flow and between external pressure gradient and height pressure gradient for subcritical flow this force balance changes near channel controls when the balance is between advection and height pressure gradient sensitivity analyses show positive sensitivity of gap wind speed to changes in discharge and external pressure gradient nega

the sea breeze and gravity current frontogenesis the development of a sea breeze circulation into a sea breeze front in often observed late in the afternoon measurements of horizontal temperature and humidity profiles in a number of sea breeze circulation made using an instrumented light aircraft are presented on each of the four days for which data are presented an initial weak horizontal temperature gradient extending over a distance of 5 to 10 kilometres developed later in the into a sharp front only a few hundred metres across the data are discussed in terms of simple gravity current frontogenesis models applied to the development of sharp sea breeze front from an initial diffuse transition between the air over the land sea examination of the equations for frontogenesis and the result of some previous laboratory experiments on gravity current frontogenesis lead to the proposal that given sufficient contrast between land and sea temperatures the formation of a sea breeze front depends on the balance between convergent horizontal winds which act to generate a front and turbulent convective mixing over the land which tends to prevent its formation the differences in driving force wind convergence and turbulent intensity are discussed for each day on which data are available and are shown to be consistent with the theory proposed

sst wind interaction in coastal upwelling oceanic simulation with empirical coupling observations primarilyfromsatellites haveshownastatisticalrelationshipbetweenthesurfacewindstress and underlying sea surface temperature sst on intermediate space and time scales in many regions inclusive of eastern boundary upwelling current systems in this paper this empirical sst wind stress relationship is utilized to provide a simple representation of mesoscale air sea coupling for an oceanic model forced by surface winds namely the regional oceanic modeling system roms this model formulation is applied to an idealized upwelling problem with prevailing equatorward winds to determine the coupling consequencesonflow sst stratification andwindevolutions theinitiallyuniformwindfieldadjuststhrough coupling to a cross shore profile with weaker nearshore winds similar to realistic ones the modified wind stress weakens the nearshore upwelling circulation and increases sst in the coastal zone the sst induced wind stress curl strengthens offshore upwelling through ekman suction the total curl driven upwelling exceeds the coastal upwelling the sst induced changes in the nearshore wind stress field also strengthen and broaden the poleward undercurrent the coupling also shows significant impact on the developing mesoscale eddies by damaging cyclonic eddies more than anticyclonic eddies which leads to dominance by the latter dynamically this is a consequence of cyclones with stronger sst gradients that induce stronger wind perturbations inthis particularupwellingproblemandthatarethereforegenerally moresusceptibletodisruption than anticyclones at finite rossby number the net effect is a weakening of eddy kinetic energy

seismic imaging through the volcanic rocks of the snake river plain insights from project hotspot hotspot the snake river geothermal drilling project was undertaken to better understand geothermal systems across the snake river plain volcanic province a series of surface and borehole seismic profiles were obtained to provide insights into volcanic stratigraphy and test the capabilities of engineering scale seismic imaging in such terranes the kimberly site drilled through 1 9 km of mostly rhyolite with thin sedimentary interbeds in the upper part of the section the kimama site drilled through 1 9 km of mostly basalt with sedimentary interbeds at 200 m depth and 1700 m depth the mountain home site contained numerous sediment and volcanic rock layers downhole and surface vibroseis seismic results suggest sedimentary interbeds at depth correspond with low velocity high temperature zones that relate to reflections on seismic profiles our results suggest that eruption flow volumes can be estimated and flow boundaries can be imaged with surface seismic methods using relatively high fold and wide angle coverage high frequency attenuation is observed at all sites and this deficit may be countered by acquisition design and a focus on signal processing steps separation of surface and body waves was obtained by muting and the potential for large static effects was identified and addressed in processing an accurate velocity model and lithology contacts derived from borehole information improved the confidence of our seismic interpretations

supercritical channel flow in the coastal atmospheric boundary layer idealized numerical simulations numerical simulations of supercritical coastal flows were performed with a three dimensional nonlinear hydrostatic meso scale model with a higher order turbulence closure the purpose was to resolve questions from previous studies related to terrain forcing idealized terrain representing northern california was used this facilitated testing of hypotheses in a simple fashion it was found that the angle by which the coast turns away from the flow regulates the acceleration in the expansion fan and determines how far downstream the maximum in the wind speed is located simulations with curved coastlines confirmed that the gradual curvature of the coastal mountains north of cape mendocino is sufficient to excite an expansion fan a decreasing height of the terrain along the coast lead to an increased acceleration of the flow largest when the slope of the terrain was confined to the change in coastline orientation a cape perpendicular to the main coastal mountains significantly blocked the flow even when as low as half the upstream marine atmospheric boundary layer mbl depth moreover a realistic cape caused gravity wave breaking these simulations confirmed that the local terrain at cape mendocino is responsible for the collapse of the mbl in shelter cove one striking feature in this study was that the flow started to accelerate far upstream of the change in coastline orientation even in supercritical conditions this phenomenon was most pronounced in the cases with the highest wind speeds using normalized wind speed and the bernoulli function from calculated back trajectories it was concluded that this feature is not due to deviations from linearity or from the shallow water concept

multiscale and unsteady aspects of a deep fohn event during map a strong fohn event occurring during the mesoscale alpine programme intensive observing period 2b 19 20 september is simulated with the non hydrostatic model meso nh the grid nesting techniques and a suitable turbulence scheme allow a coherent downscaling from the analysed scales to the movements inside the rhine valley the flow regime around the alps changes from a flow around regime to a flow partly over regime when the wind increases ahead of the cold front simplified simulations allow us to estimate a non dimensional height for the alps which controls the flow regime the fohn characteristics and its temporal evolution are discussed using both measurements and simulation backward trajectories show that the fohn air comes from an altitude around 2 km above the po valley nonlinear phenomena such as wave breaking near 5 km above sea level just behind some secondary crests and hydraulic jumps in the foothills are found in the highest resolution simulation using a mesh of 625 m this mesh clearly improves the comparison of the numerical simulation with the observations collected in the rhine valley mass budgets detail the progressive building of the fohn jet in the rhine valley copyright 2003 royal meteorological society

on the interaction between sea breeze and summer mistral at the exit of the rhone valley the three dimensional structure and dynamics of the combination of the sea breeze and the mistral at the rhone valley exit in southeastern france have been investigated experimentally and numerically on 22 june 2001 the mistral refers to a severe northerly wind that develops along the rhone valley the exit of this valley is located near the mediterranean sea where sea breeze circulation often develops the sea breeze and the mistral coexist this day because of the weakness of this mistral event the event was documented in the framework of the experience sur site pour contraindre les modeles de pollution atmospherique et de transport d emissions escompte field experiment several important data sources are used airborne doppler lidar uhf wind profilers radiosoundings and surface stations as well as nonhydrostatic mesoscale simulations this paper examines the various mechanisms that drive the time and spatial variability of the mistral and the sea breeze in various regions of the rhone valley in the morning the sea breeze penetrates inland near the western side of the rhone valley then moves back because of the reinforcement of the mistral flow caused by the deepening of the leeward surface low due to convection at noon at midday the sea breeze penetrates inland in the middle of the rhone valley only in contrast to pure sea breeze episodes when the sea breeze can extend inland over a horizontal range of more than 150 km the presence of the mistral prevents the sea breeze from penetrating more than 40 km onshore in the late afternoon the sea breeze reaches the eastern side of the rhone valley but over a smaller horizontal range because of higher local topography and because the mistral is more intense in this part of the rhone valley the situations of sea breeze mistral interactions can have a severe impact on regional air quality indeed the southerly sea breeze which advects toward the countryside the pollutants emitted from the large coastal city of marseille france and its industrialized suburbs cannot penetrate far inland because of the mistral blowing in the opposite direction this leads to the stagnation of the pollutants near the area of emission that is also the most densely inhabited area of the region over one million inhabitants

coastal atmospheric circulation around an idealized cape during wind driven upwelling studied from a coupled ocean atmosphere model abstract the study analyzes atmospheric circulation around an idealized coastal cape during summertime upwelling favorable wind conditions simulated by a mesoscale coupled ocean atmosphere model the domain resembles an eastern ocean boundary with a single cape protruding into the ocean in the center of a coastline the model predicts the formation of an orographic wind intensification area on the lee side of the cape extending a few hundred kilometers downstream and seaward imposed initial conditions do not contain a low level temperature inversion which nevertheless forms on the lee side of the cape during the simulation and which is accompanied by high froude numbers diagnosed in that area suggesting the presence of the supercritical flow formation of such an inversion is likely caused by average easterly winds resulting on the lee side that bring warm air masses originating over land as well as by air warming during adiabatic descent on the lee side of the topographic obstacle mountain leeside

supercritical marine layer flow along a smoothly varying coastline abstract a model for hydraulically supercritical atmospheric marine layer flow along a smoothly varying coastline is formulated and solved numerically the model is motivated by a recent comparison of code observations to a simple hydraulic theory which suggested the presence of an expansion fan and a compression jump downstream of topographic features the marine layer is modeled as a homogeneous rotating fluid layer decelerated by surface friction and forced by imposed upper level pressure gradients the equations are solved by a characteristic based gridpoint scheme the results indicate that the expansion fan is a robust feature that persists under most conditions in the present more realistic model but is dramatically altered in structure by the presence of friction while the jump may weaken rapidly offshore due mainly to offshore variations of the layer height upstream of the jump the agreement between observations and model predictions is good enough to suggest that a first order description of

sea breeze induced mass transport over complex terrain in south eastern france a case study the structure and evolution of the sea breeze in southern france on 25 june 2001 is investigated experimentally and numerically this study shows how interactions between the sea breeze the synoptic flow and the complex terrain affect the sea breeze structure and quantifies and discusses the air mass transport associated with the sea breeze circulation the analysis of the front propagation and the associated turbulent kinetic energy budget allows four distinct stages of sea breeze front evolution to be identified quantification of the horizontal and vertical air mass fluxes is related to these four stages the horizontal advection is directly linked to the intensity of the sea breeze flow two main mechanisms contribute to the vertical export within the free troposphere anabatic upslope winds which are intensified by the sea breeze flow and frontogenesis at the sea breeze front which generates turbulence and mixing and upward motion copyright 2006 royal meteorological society

orographic shaping of us west coast wind profiles during the upwelling season spatial and temporal variability of nearshore winds in eastern boundary current systems is affected by orography coastline shape and air sea interaction these lead to a weakening of the wind close to the coast the so called wind drop off in this study regional atmospheric simulations over the us west coast are used to demonstrate monthly characteristics of the wind drop off and assess the mechanisms controlling it using a long term simulation we show the wind drop off has spatial and seasonal variability in both its offshore extent and intensity the offshore extent varies from around 10 to 80 km from the coast and the wind reduction from 10 to 80 we show that when the mountain orography is combined with the coastline shape of a cape it has the biggest influence on wind drop off the primary associated processes are the orographically induced vortex stretching and the surface drag related to turbulent momentum flux divergence that has an enhanced drag coefficient over land orographically induced tilting twisting can also be locally significant in the vicinity of capes the land sea drag difference acts as a barrier to encroachment of the wind onto the land through turbulent momentum flux divergence it turns the wind parallel to the shore and slightly reduces it close to the coast another minor factor is the sharp coastal sea surface temperature front associated with upwelling this can weaken the surface wind in the coastal strip by shallowing the marine boundary layer and decoupling it from the overlying troposphere