origin of the catalina eddy abstract during late springs through early fall the normal regime of low level westerly and northwesterly flow within the bight of southern california is occasionally interrupted by periods of southerly flow elevated marine layers and increased low level cloudiness this transition often termed the catalina eddy is limited to narrow zone of 100 km from the coastal mountains and brings cooler temperatures and improved air quality this paper describes the initiation and evolution of catalina eddy events using both composite and case study approaches it is found that this phenomenon is produced by the interaction between the synoptic scale flow and the formidable topography of the region as a result of synoptic scale pressure falls along the central california coast and or mesoscale lee troughing southeast of point conception an alongshore pressure gradient with lower pressure to the north becomes established the result of such a pressure gradient in a coastal zone with an adjacent topographic barr

atmospheric vortex streets on a radarsat sar image we analyze the sea surface imprint of two atmospheric vortex streets avs s observed on a radarsat a canadian earth observation satellite synthetic aperture radar sar image of the aleutian islands in the western gulf of alaska acquired on may 5 1999 the radarsat sar instrument is operated in c band with hh polarization these avs s are interpreted as the atmosphere analog of classic von karman vortex streets the sar image along with radiosonde data and surface weather charts reveal that the avs lengths are 196 km and 111 km for avs 1 and avs 2 respectively there are five and two pairs of vortices within each avs the vortex shedding period is estimated to be between 35 and 48 minutes the vortex shedding started approximately 4 6 and 2 6 hours prior to the sar imaging time for avs 1 and avs 2 respectively there are seven and three pairs of vortices within the respective avs s the vortex tangential velocity is estimated to be between 1 7 and 2 3 m s and the energy dissipated during the vortex lifetime is estimated to be between 24 9 and 23 6 j m

factors influencing cavity detection in karst terrain on two dimensional 2 d direct current dc resistivity survey a case study from the western part of thailand to create a three dimensional 3 d cave and cavity network model in karst terrain from two dimensional 2 d direct current resistivity dcr profiles we first need to recognize their effects on the inversion results from a number of special cases 2 d and 3 d cavity models are created to demonstrate effects from 1 depth of the cavity 2 size and shape 3 distance to the edge of the cavity 4 orientations inclination and declination of the cavity and 5 several smaller cavities lying in an array for other complicated models combinations of these factors can be used to infer the results two parallel dcr profiles from the western part of thailand were first inverted with the 2 d inversion for interpretation knowledge gained from the numerical modeling on these special cases is helpful to constrain the interpretation and also to extend the interpretation to 3 d this gives us a picture of the 3 d cave and cavity networks beneath the area of study two main connected cavities between these two profiles can be inferred from the data along with several local cavities near the surface

numerical simulation of topographically forced mesoscale variability in a well mixed marine layer abstract a simple nonlinear numerical model of a well mixed marine layer is used to study topographically forced mesoscale variability off coastal california the model is used to simulate a persistent wind maximum observed near point conception during northwesterly winds the model also demonstrates the development of a coastally trapped kelvin wave and a marine layer eddy when the large scale forcing is suddenly reduced the model is a one layer two dimensional gridpoint model with idealized coastal topography the model assumes that potential temperature and wind are constant with height in the layer and that the layer is capped by an inversion effects of diabatic heating water vapor entrainment and spatial variations of potential temperature are neglected in order to focus on topographic effects the model solves for the two horizontal components of the marine layer wind and the marine layer height a comparison of the model results with observations taken near point conception during the 1983 o

analysis of a california catalina eddy event abstract during the period 26 29 may 1968 a shallow cyclonic circulation known 1ocally as a catalina eddy developed in the offshore waters of southern california a synoptic and mesoscale analysis of the event establishes the following 1 the incipient circulation forms on the coast near santa barbara downwind of the coastal mountains 2 cyclonic shear vorticity appears offshore in response to lee troughing downstream of the coastal mountains between vandenberg and pt mugu california 3 mountain wave activity may be aiding incipient eddy formation in association with synoptic scale subsidence and the generation of a stable layer new the crest of the coastal mountains 4 a southeastward displacement and offshore expansion of the circulation occurs following the passage of the synoptic scale ridge line and 5 dissipation of the eddy occurs with the onset of a broad onshore flow

the catalina eddy and its effect on pollution over southern california abstract a case study of a catalina eddy during project basin is presented there appears to he a topographic influence in the generation of this eddy detailed surface and upper air data over los angeles illustrate the effect of the eddy on the boundary layer and on the transport of ozone out of the basin isentropic analyses are consistent with visual satellite images of the phenomena the catalina eddy was shown to extend throughout the entire depth of the strong temperature inversion that exist over los angeles with maximum wind speeds within the inversion surface ozone levels downwind of the eddy are shown to vary depending on the local circulations

low froude number flow past three dimensional obstacles part i baroclinically generated lee vortices abstract we study the flow of a density stratified fluid past a three dimensional obstacle using a numerical model our special concern is the response of the fluid when the froude number is near or less than unity linear theory is inapplicable in this range of froude number and the present numerical solutions show the rich variety of phenomena that emerge in this essentially nonlinear flow regime two such phenomena which occupy parts i and ii of this study are the formation of a pair of vertically oriented vortices on the lee side and a zone of flow reversal on the windward side of the obstacle the ice vortices have been explained as a consequence of the separation of the viscous boundary layer from the obstacle however this boundary layer is absent by design in the present experiments and lee vortices still occur we argue that a vertical component of vorticity develops on the lee side owing to the tilting of horizontally oriented vorticity produced baroclinically as the isentropes deform in r

geostatistical integration using 2 d electrical resistivity and 3 d gravity methods for detecting cavities in a karst area two dimensional 2 d electrical resistivity and three dimensional 3 d gravity explorations were undertaken to estimate the 3 d distribution of karst cavities at the area of yongweol ri in korea where ground subsidence has occurred although the gravity method is a low cost way of analyzing a 3 d continuous structure its vertical resolving power is poor in contrast the electrical resistivity method can provide a 2 d and or 3 d subsurface structure with a much higher lateral and vertical resolution than the gravity method accordingly geostatistical methods and density information were used to enhance the 2 d resistivity structure revealed by the electrical resistivity method into a 3 d structure the assumptions are first that each data set senses the same underlying geological structure in terms of different material properties and secondly that two different material properties are correlated locally or globally throughout the entire target area as a result the distribution of limestone cavities can be estimated under the assumption that they are mostly filled with groundwater and clayey soils and have abnormally low levels of resistivity and density the estimated distribution corresponds with the grouting borehole imaging and monitoring data in this example it can be seen that the integration analysis of 2 d electrical resistivity and 3 d gravity methods is a very powerful tool for 3 d subsurface imaging and that the method can provide enhanced imaging capabilities for 3 d cavities

geoelectrical model calculations for two dimensional resistivity distributions for the calculation of geoelectrical model curves for a two dimensional resistivity distribution the potential equation is transformed by means of a fourier cosine transform into a two dimensional helmholtz equation containing the separation parameter the numerical solution of this equation for different values of for an irregular grid is obtained using the method of finite differences combined with the method of overrelaxation the method by which derivatives are replaced by finite differences turned out to be very important especially for high resistivity contrasts after testing several methods designed to deal with any type of resistivity distribution a method of discretization similar to that used by brewitt taylor and weaver 1976 for magnetotelluric modeling for h polarization was found the best examples are given of model curves for schlumberger soundings over a vertical fault covered by overburden the incorrect use of horizontal layer models leads to erroneous interpretations that are more complex than the real subsurface situations

application of the pole dipole resistivity technique to the detection of solution cavities beneath highways using a multiconductor electrode cable and a 30 post switching system pole dipole electrical resistivity measurements with a linear electrode array demonstrated a strong correlation between resistivity anomalies and subsurface voids at four sites in florida solution cavities below the water table are filled with a groundwater solute mixture which is characterized by a lower electrical resistivity than the enclosing country rock eocene and younger limestone air filled cavities above the water table exhibit markedly high resistivity anomalies confirmation drilling of postulated cavities and other anomalies suggests the method can be used with confidence for identification and location of highway threatening solution cavities with diameters as small as 3 to 5 m to a depth of 25 to 30 m

exploration for a cave by magnetic and electrical resistivity surveys ayvacik sinkhole example bozdag izmir western turkey abstractgeophysical survey techniques have been successfully applied to near surface cave detection in karstic terrains we used magnetic and electrical resistivity surveys to delineate the karstic structure of the ayvacik sinkhole which may be considered to be a vertical cave the magnetic total field anomaly map helped reveal the metamorphic and sedimentary units in the study area the total horizontal gradient map which was based on a calculated pseudogravity anomaly successfully identified the contact between the limestone unit and the cave system using these results we positioned and carried out a vertical electrical sounding ves survey with a schlumberger array along a line that consisted of 11 stations the ves data were then processed using a 1d global optimization technique which used a genetic algorithm and a 2d linearized least squares algorithm the results were generally in good agreement with each other and together they pointed out three geologic layers 1 an overburden layer 3

atmospheric karman vortex shedding from jeju island east china sea a numerical study abstracta mesoscale atmospheric numerical model is used to simulate two cases of karman vortex shedding in the lee of jeju island south korea in the winter of 2013 observed cloud patterns associated with the karman vortex shedding are successfully reproduced when the winter monsoon flows out from the eurasian continent a convective mixed layer develops through the supply of heat and moisture from the relatively warm yellow sea and encounters jeju island and dynamical conditions favorable for the formation of lee vortices are realized vortices that form behind the island induce updrafts to trigger cloud formation at the top of the convective boundary layer a sensitivity experiment in which surface drag on the island is eliminated demonstrates that the formation mechanism of the atmospheric karman vortex shedding is different from that behind a bluff body in classical fluid mechanics

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

lee vortex formation in free slip stratified flow over ridges part ii mechanisms of vorticity and pv production in nonlinear viscous wakes abstract the formation of orographic wakes and vortices is studied within the context of numerically simulated viscous flow with uniform basic state wind and stability past elongated free slip ridges the viscosity and thermal diffusivity are sufficiently large that the onset of small scale turbulence is suppressed it is found in part i of this study that wake formation in the viscous flow is closely tied to the dynamics of a low level hydraulic jump like feature in the lee of the obstacle here the role of the hydraulic jump in producing the vorticity and potential vorticity pv of the viscous wake is considered a method for diagnosing vorticity production is developed based on a propagator analysis of the lagrangian vorticity equation that generalizes cauchy s formula for the evolution of vorticity in a lagrangian framework application of the method reveals that the vertical vorticity of the wake originates through baroclinic generation and tilting in the mountain wave upstream of the jump however

devonian alkaline magmatic belt along the northern margin of the north china block petrogenesis and tectonic implications abstract some devonian magmatic rocks have been identified from the northern margin of the north china block ncb in recent years however their petrogenesis and tectonic setting are still highly controversial here we present new geochronological sr nd hf isotopic and whole rock chemical data on several newly identified and previously reported devonian alkaline complexes including mafic ultramafic rocks pyroxenites and gabbros alkaline rocks syenites monzonites and alkaline granites in the northern ncb we firstly identified some mafic ultramafic rocks coeval with monzonite and quartz monzonite in the sandaogou and wulanhada alkaline intrusions new zircon u pb dating of 16 samples from the baicaigou gaojiacun sandaogou wulanhada and chifeng alkaline intrusions combined with previous geochronological results indicate that the devonian alkaline rocks emplaced during the early middle devonian at around 400 380 ma and constitute an e w trending alkaline magmatic belt that extend ca 900 km long along the northern margin of the ncb whole rock geochemical and sr nd hf isotopic data reveal that the devonian alkaline rocks were mainly originated from partial melting of a variably enriched lithospheric mantle with different involvement of ancient lower crustal component and fractional crystallization the devonian alkaline magmatic belt rocks in the northern ncb are characterized by very weak or no deformations and were most likely related to post collision extension after arc continent collision between the bainaimiao island arc and the northern margin of north china craton during the latest silurian partial melting of subcontinental lithospheric mantle to produce the devonian alkaline magmatic rocks suggests that the northern north china craton has an inhomogeneous variably enriched subcontinental lithospheric mantle and was characterized by significant vertical crustal growth during the devonian period

supercritical flow interaction within the cape blanco cape mendocino orographic complex abstract supercritical flow interaction occurring in the marine boundary layer between closely spaced coastal capes is investigated with a mesoscale numerical prediction model as an extension of previous work the u s navy s coupled ocean atmosphere mesoscale prediction system coamps is used to perform idealized model simulations with marine layers of varying upstream froude number to elucidate the different flow responses for a single convex bend the impact upon the supercritical flow of introducing a series of closely spaced coastal bends is then investigated the expansion fan is significantly reduced in magnitude and size by the formation of a compression wave at a blocking concave bend approximately 150 km downstream building upon the idealized marine layer response real data forecasts are then examined for several time periods of supercritical flow interaction between cape blanco oregon and cape mendocino california observations from the coastal waves 1996 cw96 field program were colle

the dynamics of orographic wake formation in flows with upstream blocking the development of orographic wakes and vortices is revisited from the dynamical perspective of a three dimensional 3d vorticity vector potential formulation particular emphasis is given to the role of upstream blocking in the formation of the wake scaling arguments are first presented to explore the limiting form of the 3d vorticity inversion for the case of flow at small dynamical aspect ratio it is shown that in the limit of small the inversion is determined completely by the two horizontal vorticity components that is the part of the velocity induced by the vertical component of vorticity vanishes in the small limit this result leads to an approximate formulation of small fluid mechanics in which the three governing prognostic variables are the two horizontal vorticity components and the potential temperature the remainder of the study then revisits the problem of orographic wake formation from the perspective of this small vorticity dynamics framework previous studies have suggested that one of the potential routes to stratified wake formation is through the blocking of flow on the upstream side of the barrier this apparent link between blocking and wake formation is shown to be relatively straightforward in the small vorticity context in particular it is shown that blocking of the flow inevitably leads to a horizontal vorticity distribution that favors deceleration of the leeside flow at the ground this process of leeside flow deceleration as well as the subsequent time evolution of the wake is illustrated through a series of numerical initial value problems involving flows past 2d and 3d barriers it is proposed that the initiation of the wake flow in these stratified problems resembles the flow produced by a retracting piston in shallow water theory

practical techniques for 3d resistivity surveys and data inversion1 techniques to reduce the time needed to carry out 3d resistivity surveys with a moderate number 25 to 100 of electrodes and the computing time required to interpret the data have been developed the electrodes in a 3d survey are normally arranged in a square grid and the pole pole array is used to make the potential measurements the number of measurements required can be reduced to about one third of the maximum possible number without seriously degrading the resolution of the resulting inversion model by making measurements along the horizontal vertical and 45 diagonal rows of electrodes passing through the current electrode the smoothness constrained least squares inversion method is used for the data interpretation the computing time required by this technique can be greatly reduced by using a homogeneous half space as the starting model so that the jacobian matrix of partial derivatives can be calculated analytically a quasi newton updating method is then used to estimate the partial derivatives for subsequent iterations this inversion technique has been tested on synthetic and field data where a satisfactory model is obtained using a modest amount of computer time on an 80486dx2 66 microcomputer it takes about 20 minutes to invert the data from a 7 by 7 electrode survey grid using the techniques described below 3d resistivity surveys and data inversion can be carried out using commercially available field equipment and an inexpensive microcomputer

actual extension of sinkholes considerations about geophysical geomorphological and field inspection techniques in urban planning projects in the ebro basin ne spain abstract aerial photographs historical cartographies and field inspection are useful tools in urban planning design on mantled karst because they permit a wide time interval to be analyzed in the case of zaragoza city several works have confirmed the interest of these approaches in configuring the urban planning code and therefore represent a promising technique nevertheless some caveats should be taken into account when using this kind of information a detailed analysis is presented comparing in a case study from the surroundings of zaragoza geomorphological historical analysis and field inspection with geophysical data field inspection in a noncultivated area permits the constraint of the presence of karst indicators below the geomorphological resolution of aerial photographs and shows results consistent with geophysical surveys the studied case shows an inner zone coinciding with the sinkhole mapped from aerial photographs that correlates with changes in the position of the substratum and changes in thickness of alluvial sediments the integrated analysis permits us to define an external subsidence ring around the geomorphological sinkhole whose surface is twice the size of the inner zone this outer ring is indicated by geometrical changes in gpr profiles increases of thickness of the conductive shallower unit toward the collapse and small collapses on marginal cracks these results support the higher extension of karst hazards linked to sinkholes with respect to their geomorphological expression and the needed detailed analysis to constrain the real sinkhole size or the use of security radii surrounding this surficial evidence when geomorphological data is used for the hazard analyses or the urban planning at karstic zones

an observational study of vortex spacing in island wake vortex streets abstract vortex streets are a frequent occurrence in stratocumulus topped flow downwind of mountainous islands theoretical studies dating back to von karman supported by laboratory and numerical studies have yielded similarity theories for the size and spacing of these vortices behind bluff bodies despite dynamical differences between such two dimensional flows and the three dimensional flow past isolated islands satellite case studies suggest these geometric similarities may also hold for the atmospheric case in this study two of the resulting dimensionless ratios are measured using satellite imagery one is the aspect ratio between cross street and along street spacing of the vortices the second is the ratio of the cross street spacing to the crosswind width of the island a 30 image sample from the aqua and terra moderate resolution imaging spectroradiometer satellites is analyzed to obtain these ratios the resulting set of values for the two dimensionless ratios is tested against the values f

the santa cruz eddy part i observations and statistics a shallow cyclonic circulation that occurs in the summertime over the monterey bay california is investigated since it is often centered offshore from the city of santa cruz and has never been studied in detail before it is named the santa cruz eddy sce in this study its horizontal size is 10 40 km and its vertical extent is 100 500 m the sce is important for local weather because it causes surface winds along the santa cruz coast to blow from the east instead of from the northwest the latter being the climatological summer pattern for this area as a consequence of the eddy cool and moist air is advected from the south and southeast into the santa cruz area bringing both relief from the heat and fog to the city the sce is unique in its high frequency of occurrence most vortices along the western american coast form only during unusual weather events whereas the sce forms 78 79 of the days during the summer the sce frequency was determined after analyzing two years of data with empirical orthogonal functions eofs from a limited observational network and satellite imagery an explanation of the formation mechanism of the sce will be provided in part ii of this study

detection and 2d modelling of cavities using pole dipole array the resistivity method is often used in cave prospecting in this paper the pole dipole array ability to detect cavities at different depths and with different water contents is investigated the research was performed using analogical and numerical modelling according to the results empty caves at a depth less than four times its diameter can be easily detected the ability of the pole dipole array to detect water filled caves reaches a minimum at filling percentages of 30 50 overburden effects research shows that low resistivity overburden reduces the resolution capability of the array this study shows that equivalent results can be obtained by modelling the empty caves as infinite resistivity bodies or alternatively as very high resistivity ones the analysis of field data acquired in the macico calcario estremenho portugal shows the practical importance of the pole dipole array in cavities prospecting

the structure and variability of the marine atmosphere around the santa barbara channel the santa barbara channel is a region characterized by coupled interaction between the lower level atmosphere the underlying ocean and the elevated topography of the coastline the nature of these interactions and the resulting weather patterns vary between summer and winter during summer synoptic winds are largely controlled by the combined effect of the north pacific anticyclone and the thermal low located over the southwestern united states resulting in persistent northwesterly winds a well defined marine atmospheric boundary layer mabl with properties distinct from the free atmosphere above is a conspicuous feature during the summer the wind has different characteristics in each of three zones maximum winds occur in the area extending south and east from pt conception zone 1 where they initially increase as they turn to follow the coast then decrease farther east winds are usually weak in zone 2 located in the easternmost part of the channel offshore from the oxnard plain winds are also weak in zone 3 sometimes reversing to easterly at night in a narrow band located along the mainland coast summer air temperature at the surface follows the sst closely and varies significantly with location summer sea level pressure gradients are large with the lowest pressure occurring on the northeast end of the santa barbara channel diurnal variations are strongest in summer although the modulation is weakest in zone 1 the diurnal variation is parallel to the coast in all of zone 3 but the oxnard plain where it is perpendicular to the coast the height of the marine layer varies between 300 m in late afternoon and 350 m in late morning in winter synoptic conditions are driven by traveling cyclones and sometimes accompanied by fronts these are usually preceded by strong southeast winds and followed by strong northwest winds atmospheric parameters are distributed more uniformly than in summer and diurnal variations are greatly reduced sea level air temperature and pressure are more spatially uniform than in the summer spatial variations in the observed fields in the summer are consistent with a hydraulic model of the mabl as a transcritical expansion fan the summertime situation is governed by a coupled interaction between the atmosphere and the underlying water the ocean influences the density of the mabl to the extent that it behaves distinctly from the free atmosphere above resulting in strong winds polarized in the direction parallel to the coast in turn these winds provoke an upwelling response in the coastal ocean which in part determines the surface properties of the water

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

an unusual aerial photograph of an eddy circulation in marine stratocumulus clouds abstractan aerial photograph of a cyclonic von karman like vortex in the marine stratocumulus clouds off the california coast taken by a commercial pilot near grover beach is presented it is believed that this is the first photograph of such an eddy taken from an airplane to appear in publication the eddy occurred with a strong inversion above a shallow marine boundary layer in the lee of high inversion penetrating terrain tower and surface wind measurements plotted on satellite imagery demonstrate that the grover beach eddy was not just a cloud level feature but extended through the marine atmospheric boundary layer mabl to the surface evolution of the flow during the formation of the eddy appears similar to idealized numerical simulations of blocked mabl flow from the literature the tower measurements sampled the northern part of the eddy circulation during its formation just offshore the 2 3 c temperature increases and then decreases during and after the eddy passage may be indicative o

numerical experiments of vortices in the wakes of large idealized mountains abstract the purdue mesoscale model pmm is applied to study the flow past large idealized mountains under a low froude number results show that for reynolds numbers in the range of 4 100 results also show that small perturbations in the oncoming wind the inclination of the oncoming wind and major axis of the mountain the mountain shape and the coriolis force all can contribute to atmospheric vortex shedding the reynolds number is not a good indicator of whether a vortex will stay or break away from the mountain in the atmosphere when the earth s rotation is included the simulated pressure field and wind increase considerably on the left hand side facing downstream of the mountain whic

the santa cruz eddy part ii mechanisms of formation the formation mechanism of the santa cruz eddy sce is investigated using the fifth generation pennsylvania state university national center for atmospheric research mesoscale model mm5 simulations of 25 26 august 2000 showed that two eddy instances formed on that night a finding supported by observations the two eddies had similar behavior they both formed in the sheltered santa cruz california area and then moved southeastward to finally dissipate after 7 11 h however the first eddy had greater vorticity wind speed horizontal and vertical extents and lifetime than the second eddy numerical simulations showed that the sces are formed by the interaction of the main northwesterly flow with the topographic barrier represented by the santa cruz mountains to the north of monterey bay additional numerical experiments were undertaken with no diurnal heating cycle no molecular or eddy viscosity and no horizontal thermal gradients at ground level in all cases vertical vorticity was still created by the tilting of horizontal vorticity generated by the solenoidal term in the vorticity equation this baroclinic process appeared to be the fundamental formation mechanism for both sces but more favorable conditions in the late afternoon including a south to north pressure gradient flow turning due to the sea breeze and an expansion fan coincided to intensify the first eddy

airborne observations of a catalina eddy summertime low level winds over the ocean adjacent to the california coast are typically from the north roughly parallel to the coastline past point conception the flow often turns eastward thereby generating cyclonic vorticity in the california bight clouds are frequently present when the cyclonic motion is well developed and at such times the circulation is referred to as a catalina eddy onshore flow south of the california bight associated with the eddy circulation can result in a thickening of the low level marine stratus adjacent to the coast during nighttime hours the marine stratus typically expands over a larger area and moves northward along the coast with the cyclonic circulation a catalina eddy was captured during the precisionatmosphericmarineboundarylayerexperimentinjuneof2012 measurementsweremadeofthe cloud structure in the marine layer and the horizontal pressure field associated with the cyclonic circulation using the university of wyoming king air research aircraft airborne measurements show that the coastal mountains to the south of los angeles block the flow resulting in enhanced marine stratus heights and a local pressure maximum near the coast the horizontal pressure field also supports a south north movement of marine stratus little evidence of leeside troughing south of santa barbara california was observed for this case implying that the horizontal pressure field is forced primarily through topographic blocking by the coastal terrain south of los angeles california and the ambient large scale circulation associated with the mean flow