hydrothermal alteration of tertiary igneous rocks from the isle of skye northwest scotland hydrothermal alteration of tertiary granites from skye involed the reaction of igneous amphibole biotite ferroaugite fayalite alkali feldspar plagioclase feldspar magnetite and ilmenite with aqueous fluid primarily to combinations of secondary alkali feldspar chlorite and montmorillonite lesser amounts of muscovite calcite epidote prehnite zeolite and pyrite also developed during mineralogical alteration of the granites there was a net addition to rock of h and a net loss of ca fe and probably na there is no positive evidence for a significant change in their al si mg or k contents hydrothermal alteration of skye granite involved not only large scale migration of 18o 16o d and h but also of ca fe and probably na mineral thermometry combined with textural observations suggests that chemical isotopic and most mineralogical alteration were synchronous and occurred at 350 450 c textural observations further suggest that the mechanism of isotopic exchange between granite and hydrothermal fluid primarily was solution reprecipitation

evaluation of planetary boundary layer parameterizations in tropical cyclones by comparison of in situ observations and high resolution simulations of hurricane isabel 2003 part ii inner core boundary layer and eyewall structure this is the second of a two part study of the representation of the planetary boundary layer pbl in highresolutionweatherresearchandforecastmodel wrf simulationsofhurricaneisabel 2003 theyonsei university ysu pbl parameterization and the mellor yamada janjic myj pbl parameterization are evaluated by direct comparison to in situ data obtained by research aircraft the numerical model simulation design details of the pbl schemes and the representation of the boundary layer in the outer core were presented in part i this part presents a detailed study of the inner core pbl including its axisymmetric and asymmetric structures and comparisons to analyses of dropsonde data from previous studies although neither pbl scheme was designed specifically for hurricane conditions their simulated boundary layers are reasonably good representations of the observed boundary layer both schemes reproduce certain unique features of the hurricane boundary layer such as the separate depths of the well mixed layer and the inflow layer and the pronounced wind speed maxima near the top of the inflow layer modification of the original ysu and myj schemes to have ocean roughness lengths more in agreement with recent studies considerably improves the results of both schemes even with these improvements the myj consistently produces larger frictional tendencies in the boundary layer than the ysu scheme leading to a stronger lowlevel inflow and a stronger azimuthal wind maximum at the top of the boundary layer for both schemes differences in the low level asymmetries between the simulated and observed wind fields appear to be related to eyewall asymmetries forced by environmental wind shear the effects of varying horizontal and vertical resolutions are also considered increasing the vertical resolution in the pbl results in minor improvements in the inner core structures increasing the horizontal resolution around the eyewall also leads to improved boundary layers as well as an improvement of the vertical structure of the inner core wind field a summary and discussion of the results of both parts i and ii is provided

dependence of tropical cyclone intensification on the boundary layer representation in a numerical model we present idealized numerical model experiments to investigate the dependence of tropical cyclone intensification and in particular the kinematic structure of the tropical cyclone boundary layer on the boundary layer parametrization in the model the study is motivated by recent findings highlighting the important dynamical role of the boundary layer in tropical cyclone intensification the calculations are carried out using the pennsylvania state university national center for atmospheric research fifth generation mesoscale model mm5 predictions using one of five available schemes are compared not only between themselves but where possible with recent observational analyses of boundary layer structure at this stage the study falls short of being able to advocate the use of a particular scheme although certain shortcomings of individual schemes are identified the current inability to determine the optimum scheme has implications for the predictability of tropical cyclone intensification copyright 2010 royal meteorological society

evolution of the oceanic lithosphere in the equatorial atlantic from rayleigh wave tomography evidence for small scale convection from the pi lab experiment

on the characteristic height scales of the hurricane boundary layer in this study data from 794 gps dropsondes deployed by research aircraft in 13 hurricanes are analyzed to studythecharacteristicheightscalesofthehurricaneboundarylayer theheightscalesaredefinedinavariety of ways the height of the maximum total wind speed the inflow layer depth and the mixed layer depth the height of the maximumwind speed and the inflow layerdepth are referred to asthe dynamical boundarylayer heights while the mixed layer depth is referred to as the thermodynamical boundary layer height the data analyses show that there is a clear separation of the thermodynamical and dynamical boundary layer heights consistent with previous studies on the boundary layer structure in individual storms the dynamical boundary layer height is found to decrease with decreasing radius to the storm center the thermodynamic boundary layer height which is much shallower than the dynamical boundary layer height is also found to decrease with decreasing radius to the storm center the results also suggest that using the traditional critical richardson number method to determine the boundary layer height may not accurately reproduce the height scale of the hurricane boundary layer these different height scales reveal the complexity of the hurricane boundary layer structure that should be captured in hurricane model simulations

asymmetric hurricane boundary layer structure from dropsonde composites in relation to the environmental vertical wind shear this study investigates the asymmetric structure of the hurricane boundary layer in relation to the environmentalverticalwind shearin theinner core region data from1878 gps dropsondesdeployed by research aircraft in 19 hurricanes are analyzed in a composite framework kinematic structure analyses based on doppler radar data from 75 flights are compared with the dropsonde composites shear relative quadrantmeancomposite analysesshow that boththekinematicandthermodynamic boundarylayerheight scalestend to decrease with decreasing radius consistent with previous axisymmetric analyses there is still a clear separation between the kinematic and thermodynamic boundary layer heights both the thermodynamic mixed layer and height of maximum tangential wind speed are within the inflow layer the inflow layer depth is found to be deeper in quadrants downshear with the downshear right dr quadrant being the deepest the mixed layer depth and height of maximum tangential wind speed are alike at the eyewall but are deeper outside in quadrants left of the shear the results also suggest that air parcels acquire equivalent potential temperature ue from surface fluxes as they rotate through the upshear right ur quadrant from the upshear left ul quadrant convection is triggered in the dr quadrant in the presence of asymmetric mesoscale lifting coincident with a maximum in ue energy is then released by latent heating in the downshear left dl quadrant convective downdrafts bring down cool and dry air to the surface and lower ue again in the dl and ul quadrants this cycling process may be directly tied to shear induced asymmetry of convection in hurricanes

turbulence structure of the hurricane boundary layer between the outer rainbands abstract as part of the coupled boundary layers air sea transfer cblast hurricane program flights were conducted to directly measure turbulent fluxes and turbulence properties in the high wind boundary layer of hurricanes between the outer rainbands for the first time vertical profiles of normalized momentum fluxes sensible heat and humidity fluxes and variances of three dimensional wind velocities and specific humidity are presented for the hurricane boundary layer with surface wind speeds ranging from 20 to 30 m s 1 the turbulent kinetic energy budget is estimated indicating that the shear production and dissipation are the major source and sink terms respectively the imbalance in the turbulent kinetic energy budget indicates that the unmeasured terms such as horizontal advection may be important in hurricane boundary layer structure and dynamics finally the thermodynamic boundary layer height estimated based on the virtual potential temperature profiles is roughly half of the boundary

development of microporosity diffusion channels and deuteric coarsening in perthitic alkali feldspars turbidity is an almost universal feature of alkali feldspars in plutonic rocks and has been investigated by us in alkali feldspars from the klokken syenite using sem and tem it is caused by the presence of myriads of tubular micro inclusions either fluid filled micropores or sites of previous fluid inclusions and is associated with coarsening of microperthite and development of sub grains micropores are abundant in coarsened areas in which porosities may reach 4 5 but are almost absent from uncoarsened pristine braind microperthite areas the coarsening is patchy and involves a scale increase of up to 103 without change in the composition of the phases low albite and low microcline or in the bulk composition of the crystal it occurs abruptly along an irregular front within individual crystals which retain their original shapes the coherent braid microperthite gives way across the front to an irregular semi coherent film perthite over a few m and then to a highly coarsened irregular patch perthite containing numerous small sub grains on scales of a few hundred nm in both phases the coarsening and micropore formation occured at a t 400 450 c and it is inferred to have been driven by the release of coherent strain energy low angle grain boundary migration being favoured by a fluid the patchy nature of the coarsening and the absence of a relationship with initial grain boundaries suggest that the fluid was of local origin possibly arising in part through exsolution of water from the feldspar the sub grain texture and microporosity modify profoundly the permeability of the rock and greatly enhance the subsequent reactivity of the feldspars

evaluation of planetary boundary layer parameterizations in tropical cyclones by comparison of in situ observations and high resolution simulations of hurricane isabel 2003 part i initialization maximum winds and the outer core boundary layer in this study thefirst of two parts the planetary boundarylayer pbl depicted in high resolution weather research and forecast model wrf simulations of hurricane isabel 2003 is studied and evaluated by direct comparisons with in situ data obtained during the coupled boundary layer and air sea transfer experiment cblast in particular two boundary layer schemes are evaluated the yonsei university ysu parameterization and the mellor yamada janjic myj parameterization investigation of these schemes is useful since they are available for use with wrf are both widely used and are based on entirely different methods for simulating the pbl in this first part the model domains and initialization are described for additional realism of the low level thermodynamic environment a simple mixed layer ocean model is used to simulate ocean cooling the ysu and myj schemes are discussed along with some modifications standard measures of the accuracy of the hurricane simulations such as track maximum surface wind speed and minimum surface pressure are describedforavarietyofparameterchoicesandforthetwoparameterizations theeffectsontrackandintensity of increased horizontal and vertical resolutions are also shown a modification of the original ysu and myj schemes to have ocean roughness lengths more in agreement with recent studies considerably improves the results of both schemes instantaneous wind maximaon the innermost grid with 1 33 kmresolutionare shown to be an accurate representation of the simulated 1 min sustained winds thesimulatedboundarylayersareevaluatedby directcomparison ofthepblassimulatedandasobserved by in situ data from the cblast experiment in the outer core region of the storm the two pbl schemes and their modifiedcounterparts reproduce the observed pbl remarkably well comparisonsare also made to the observed vertical fluxes of momentum heat and moisture in part ii the detailed comparisons of the intensities and structures of the simulated and observed innercore boundary layers are presented and the reasons for the differences are discussed

cryptoperthites and cooling rate in a layered syenite pluton a chemical and tem study alkali feldspars in the klokken layered syenite south greenland are optically either coarse turbid deuteric patch perthites or clear unaltered fine braid microor cryptoperthites irregular clear volumes can be found in most turbid grains electron microscopy shows that all clear crystals or volumes are cryptoperthites in which the periodicity of the exsolution lamellae increases systematically with distance from the roof of the intrusion from 40 nm to 300nm they are composed of low albite and diagonally associated maximum microcline a secondary coarsening is responsible for optically visible braid microperthites the layered series consists of interleaved granular syenites and coarser grained laminated syenites with mineral layering microprobe analyses show a downward decrease in ca and ba in the granular syenite feldspars consistent with chilling from the roof inwards most laminated syenite feldspars contain 1 an increasing to 5 in mafic layers the periodicity of the exsolution lamellae in the laminated syenite feldspars is consistently up to twice that in adjacent granular syenites periodicity is not influenced by ab or or an content but high an feldspars have continuous zig zag intergrowths while others are more lozengeshaped lamellar periodicities largely reflect cooling rate in the pluton cooling times in the exsolution interval were probably about 103 104 years at the top of the series whereas existing experimental data suggest that the periodicities would be reached in a few days or years the periodicities at the top of the granular series are only slightly greater than experimentally determined initial wavelengths for spinodal decomposition suggesting that little or no coarsening occurred despite the long cooling times coarsening did occur lower in the pile framework ordering and twinning must slow or stop coarsening the difference in periodicity between the granular and laminated syenite series may be caused by differences in amount of water incorporated in the feldspar structure from the magma the exsolution of this water at low temperatures could be the cause of the deuteric unmixed patch perthites small volumes of cryptoperthite which have escaped deuteric unmixing may be common in igneous rocks in general and may be useful relative indicators of cooling rate

symmetric and asymmetric structures of hurricane boundary layer in coupled atmosphere wave ocean models and observations abstractit is widely accepted that air sea interaction is one of the key factors in controlling tropical cyclone tc intensity however the physical mechanisms for connecting the upper ocean and air sea interface with storm structure through the atmospheric boundary layer in tcs are not well understood this study investigates the air sea coupling processes using a fully coupled atmosphere wave ocean model especially the coupling induced asymmetry in surface winds sea surface temperature air sea fluxes and their impacts on the structure of the hurricane boundary layer hbl numerical experiments of hurricane frances 2004 with and without coupling to an ocean model and or a surface wave model are used to examine the impacts of the ocean and wave coupling respectively model results are compared with the airborne dropsonde and surface wind measurements on board the noaa wp 3d aircraft the atmosphere ocean coupling reduces the mixed layer depth in the rear right quadrant due to storm induced ocean

hurricane boundary layer theory in the light of the plethora of definitions for the hurricane boundary layer we advocate a dynamical definition based on the distribution of agradient flow we seek also to clarify the fundamental role of the boundary layer in the hurricane intensification process in particular we contrast the differences between unsteady boundary layers that are able to facilitate the spin up of the vortex above and steady boundary layers that cannot if slaved to the time dependent vortex aloft the latter can spin up the interior vortex only indirectly by changing its thermodynamic properties through vertical advection of these from below and adjustment to thermal wind balance these differences are highlighted by an analytical demonstration that the application of a zero vertical gradient condition on velocity above a steady boundary layer does not provide a direct means of allowing the boundary layer to determine the flow in the interior vortex this result assumes that frictional forces are negligible at this boundary finally echoing a few previous insights we question the applicability of conventional boundary layer theory at radii of strong ascent into the eyewall where the flow is akin to that of separation in aerodynamic boundary layers copyright c 2010 royal meteorological society

reply to comments on symmetric and asymmetric structures of hurricane boundary layer in coupled atmosphere wave ocean models and observations in our original paper lee and chen 2012 hereafter lc12 we documented the three dimensional 3d structure in hurricane frances s 2004 boundary layer using both observations and a coupled atmosphere wave ocean model namely the university of miami coupled model umcm zhang et al 2014 hereafter z14 raised a few questions mainly on some perceived differences between lc12 and a previous study by zhang et al 2011 hereafter z11 we stand by our original results and conclusions and provide some specific responses to z14 the following numbers are corresponding to the sections in z14

atypical thermodynamic profiles in hurricanes the global positioning system dropwindsondes deployed in hurricane bonnie on 26 august 1998 with supporting deployments in hurricanes mitch 1998 and humberto 2001 are used to identify three unusual thermodynamic structures in the lower cloud and subcloud layers two of these structures impact the energy content of the inflow and therefore the intensity of the hurricane first positive lapse rates of equivalent potential temperature are found near the top of the inflow these layers insulate the inflow from the negative impacts of entrainment mixing and promote rapid energy increases especially near the eyewall the second structure is a rapid decrease of equivalent potential temperature adjacent to the sea surface this is essentially a prominent surface layer that owes its existence to both higher moisture content and a superadiabatic lapse rate the steep lapse rate most often occurs under and near the eyewall where wind speeds at the surface exceed hurricane force the author speculates that water loading from spray increases the residence time of air parcels in the surface layer contributing to the creation of this structure the third feature is a moist absolutely unstable layer previously identified by bryan and fritsch for the midlatitudes these layers are found adjacent to the eyewall in rainbands and in the hub cloud within the eye and are evidence of mesoscale or vortex scale convergence and the very modest instabilities often found in the core of a hurricane

rapakivi granites south greenland hydrothermal alteration of igneous layering igneous layering is developed in the proterozoic rapakivi granite suite of south greenland in an area on the south easternmost coast of the island of angnikitsoq the layering at this locality is unusual in that it is defined by interstitial phases we suggest that large scale hydrothermal alteration has converted a fine grained pyroxene cumulate in which original cumulate pyroxenes occurred in the interstices between larger feldspars to interstitial biotite and green amphibole

the dynamics of boundary layer jets within the tropical cyclone core part ii nonlinear enhancement abstract observations of wind profiles within the tropical cyclone boundary layer until recently have been quite rare however the recent spate of observations from the gps dropsonde have confirmed that a low level wind speed maximum is a common feature of the tropical cyclone boundary layer in part i a mechanism for producing such a maximum was proposed whereby strong inward advection of angular momentum generates the supergradient flow the processes that maintain the necessary inflow against the outward acceleration due to gradient wind imbalance were identified as being i vertical diffusion ii vertical advection and iii horizontal advection and a linear analytical model of the boundary layer flow in a translating tropical cyclone was presented and used to diagnose the properties of the jet and the near surface flow a significant shortcoming was that the jet was too weak which was argued to be due to the neglect of vertical advection here a high resolution dry hydrostatic numerical

comments on symmetric and asymmetric structures of hurricane boundary layer in coupled atmosphere wave ocean models and observations abstract in a recent paper lee and chen 2012 hereafter lc12 presented numerical simulations of symmetric and asymmetric hurricane boundary layer structures in a fully coupled atmosphere wave ocean model and used these simulations to compare aspects of the boundary layer structure against an analysis of observations one of their main conclusions was that the azimuthally averaged inflow layer tends to misrepresent the overall inflow structure in tropical cyclones especially the asymmetric structure p 3593 another main conclusion was that the complicated asymmetric three dimensional boundary layer structures attributed by them to be due in part to the air sea and wind wave coupling make it difficult to parameterize the atmosphere wave ocean coupling effects without a fully coupled model p 3593 after careful examination of their study we have a number of questions regarding their methodology their interpretations including their interpretations of previous literature and their conclusions specifically we inquire about aspects of the methodology for defining the dynamical boundary layer depth the selection of the boundary layer scheme and we question the conclusions inferred in addition to the foregoing concerns inaccuracies in their literature review are noted and inconsistencies between their conclusions and reported results are identified for many decades physical processes across the air sea interface and within the atmospheric boundary layer have been known to be essential for the development and maintenance of a tropical cyclone ooyama 1969 emanuel 1986 1995 smith et al 2009 smith and montgomery 2010 bryan and rotunno 2009 bryan 2012 however the boundary layer is the least observed part of a storm in particular its turbulence structure with the advent of the global positioning system gps dropsonde hock and franklin 1999 the mean boundary layer structure has been progressively studied

the rapakivi granites of south greenland stable isotope characteristics of their black and white facies and the nature of their protolith abstract the rapakivi granites of south greenland were emplaced into the ketilidian orogenic belt at about 1 74 ga during an episode of extensional tectonics petrographically they can be subdivided into a roughly subequal black facies and white facies distinguished by the colour turbidity of the alkali feldspars and by the associated mineralogy which is more hydrous i e amphibole and biotite compared to olivine and pyroxene in the white facies the oxygen isotope composition of these rocks is notably homogeneous from thirteen outcrops sampled over an area extending some 200 km 100 km all alkali feldspars have an average 18 o of 10 2 0 4 this lack of variation is consistent with the consensus petrogenetic model which invokes a very well mixed two component protolith the high abundance of 18 o mean whole rock 18 o 9 4 argues that the major contribution perhaps 90 although originally mantle derived had undergone 18 o enrichment in a low temperature sedimentary cycle there is no oxygen isotopic distinction between alkali feldspars in the black and white facies which is argued to be a consequence of the relatively anhydrous nature of the melt hydrogen isotope compositions vary widely by 30 but are coherent on a hand specimen scale as demonstrated by approximately equal d of biotite and alkali feldspar it is not clear at which stage the d h heterogeneity was introduced

observed boundary layer wind structure and balance in the hurricane core part i hurricane georges abstract the gps dropsonde allows observations at unprecedentedly high horizontal and vertical resolution and of very high accuracy within the tropical cyclone boundary layer these data are used to document the boundary layer wind field of the core of hurricane georges 1998 when it was close to its maximum intensity the spatial variability of the boundary layer wind structure is found to agree very well with the theoretical predictions in the works of kepert and wang in particular the ratio of the near surface wind speed to that above the boundary layer is found to increase inward toward the radius of maximum winds and to be larger to the left of the track than to the right while the low level wind maximum is both more marked and at lower altitude on the left of the storm track than on the right however the expected supergradient flow in the upper boundary layer is not found with the winds being diagnosed as close to gradient balance the tropical cyclone boundary layer model of kepert and wan

oxygen isotope fractionation in quartz albite anorthite and calcite laboratory measurements of equilibrium oxygen isotope fractionation in quartz albite anorthite and calcite have been carried out by anhydrous exchange between silicates and calcite at temperatures of 600 c and above exchange in these systems is as rapid as exchange between silicates and water fractionation factors can be summarized in the following equations qc 0 38 106t 2 abc 0 57 106t 2 anc 1 59 106t 2 from which the silicate pair fractionations are readily obtained these results are compared with published theoretical estimates as well as data derived from hydrothermal experiments some significant differences are found in particular it is difficult to reconcile all of the hydrothermal data either with theoretical calculations or with the present experimental data the new experiments provide an internally consistent set of fractionation factors suitable for isotopic thermometry and for test of disequilibrium in natural systems

a new mechanism of granite emplacement intrusion in active extensional shear zones one of the principal ways in which continental crust grows is by the incorporation from deeper within the earth of large volumes of granitic magma a space problem exists1 as to how these magmas are accommodated in the crust traditionally two main emplacement mechanisms have been emphasized forceful intrusion whereby buoyancy driven magmas physically push the crust aside creating granitic diapirs and balloons and passive emplacement characterized by replacive mechanisms such as cauldron subsidence and stoping although more recent work2 3 has demonstrated that space for granites may be created within bends and offsets of large transcurrent faults the simple view of either forceful or passive still fails to account for the intrusive mechanisms of many granites here we report the discovery of a new igneous intrusion mechanism in the superbly exposed proterozoic continental crust of south greenland we have observed that rapakivi granite was intruded as large scale sheets along ductile extensional shear zones that were active during emplacement in such a process the space problem seems to be simply resolved