theoretical studies of convectively forced mesoscale flows in three dimensions part ii shear flow with a critical level convectively forced mesoscale flows in a shear flow with a critical level are theoretically investigated by obtaining analytic solutions for a hydrostatic nonrotating inviscid boussinesq airflow system the response to surface pulse heating shows that near the center of the moving mode the magnitude of the vertical velocity becomes constant after some time whereas the magnitudes of the vertical displacement and perturbation horizontal velocity increase linearly with time it is confirmed from the solutions obtained in present and previous studies that this result is valid regardless of the basic state wind profile and dimension the response to 3d finite depth steady heating representing latent heating due to cumulus convection shows that unlike in two dimensions a low level updraft that is necessary to sustain deep convection always occurs at the heating center regardless of the intensity of vertical wind shear and the heating depth for deep heating across a critical level little change occurs in the perturbation field below the critical level although the heating top height increases this is because downward propagating gravity waves induced by the heating above but not near the critical level can hardly affect the flow response field below the critical level when the basic state wind backs with height the vertex of v shaped perturbations above the heating top points to a direction rotated a little clockwise from the basic state wind direction this is because the v shaped perturbations above the heating top is induced by upward propagating gravity waves that have passed through the layer below where the basic state wind direction is clockwise relative to that above

ground motion to intensity conversion equations gmices a global relationship and evaluation of regional dependency we analyzed the regional dependence of ground motion to intensity conversion equations and derived a new global relationship to improve ground motion and intensity estimates for earthquake hazard applications including those related to the shakemap system for this purpose we merged several databases collected by other authors in different geographical regions to highlight any systematic regional effects in the relationship between macroseismic intensities and both peak ground velocity and peak ground acceleration our database contains macroseismic intensities derived from expert assignments or from the did you feel it database paired with peak ground motions pgm from seismic stations we constrain our intensity ground motion pairs to those with a maximum 2 km separation for each region we derived invertible relationships between intensities and ground motion using an orthogonal regression we also derived a global relationship to quantify the regional differences we investigated the dependence of intensity on predictor variables such as pgm magnitude and hypocentral distance our analyses indicate that pgm is the most robust predictor variable of intensity within one standard deviation our regional and global results are in agreement with the relations of worden et al 2012 for california faenza and michelini 2010 for italy tselentis and danciu 2008 for greece and atkinson and kaka 2007 for central eastern united states the earthquakes in the study ranged in magnitude from 2 5 to 7 3 and the distances ranged from less than a kilometer to about 200 km from the epicenter online material table summarizing published relationships and figures showing the relationship between peak ground acceleration and intensity

seismic hazard assessment 2003 2009 for the italian building code this paper describes the probabilistic assessment of seismic hazard psha of italy in view of the building codes from 2003 to 2009 a code was issued in 2003 as a prime minister ordinance requiring that a psha for updating the seismic zoning would be performed in one year in terms of horizontal peak ground acceleration pga with 10 probability of exceedance in 50 years on hard ground for the first time in italy a working group established by the istituto nazionale di geofisica e vulcanologia adopted a logic tree approach to model the epistemic uncertainty in the completeness of the earthquake catalog the assessment of the seismicity rates and m max and the ground motion prediction equations the seismic hazard has been computed over a grid of more than 16 000 points for the median value fiftieth percentile and the eighty fourth and sixteenth percentiles of the 16 branches of the logic tree using the same input model pga values and spectral accelerations for 10 spectral periods were computed for nine different probabilities of exceedance in 50 years this wealth of data made it possible to base the design spectra of a new building code on point hazard data instead of being related to just four zones the 2009 m w 6 3 l aquila earthquake has led many to attempt to test the reliability of this study in this paper we analyze suggestions coming from that event and conclude that significant changes to the design spectra are not to be recommended based just on evidence from the l aquila earthquake

a review and technical summary of the aapg associacion mexicana de geologos petroleros hedberg research conference on heavy oil origin prediction and production in deep waters a joint aapg associacion mexicana de geologos petroleros amgp hedberg research conference was held to examine issues associated with heavy oil in deep water this article reports on the meeting highlights deep water exploration has become increasingly important over the last three decades for the deep water environment to be economically viable these accumulations need to be both volumetrically significant and capable of maintaining high production rates largely independent of the rise in crude oil price there has been an increasing number of economically viable deep water discoveries where the resource base now exceeds 100 billion bbl oil equivalent a significant percentage of this resource is heavy oil with heavy oil dominating the resource base in such settings as offshore mexico and brazil economic success in both exploration and commercialization requires integration across disciplines as well as across the value chain integrating the upstream midstream and downstream operations basin models were commonly used as the integration tool for exploration programs the exploration risks associated with the deep water environment tend to be higher in part as a result of oil quality risk reduction can be partially accomplished through a better understanding of the factors that control oil quality including source rock facies thermal maturity and the alteration and migration histories although several factors may impact crude quality the consensus was that biodegradation was the dominant factor controlling quality in most deep water regions mexico being an exception where source rock character has an important function biodegradation is controlled by such factors as charge and thermal history and the geometry of the oil water contact where source facies is a key factor in establishing the presence of heavy oil migration distances tend to be more limited mixing of oils also appears to be an important factor in determining oil quality often improving or maintaining oil quality with the introduction of light oils into biodegraded oil the production of these heavy oils introduces several challenges above and beyond those associated with similar accumulations onshore and in shallow waters lessons learned from these settings can however be very useful when working in the deep water setting the value of continuous data collection and updating reservoir models was made clear in case studies from both angola and brazil where phased development or reservoir model recycling permitted the more efficient use of capital also of importance is the need for long term planning because of the long lives of heavy oil accumulations

intensity versus ground motion a new approach using italian data abstract the correlations between macroseismic intensity and peak ground acceleration and between macroseismic intensity and arias intensity are compared the data base consists of 56 records 168 time histories related to ns ew and z components derived from nine italian earthquakes that occurred between 1980 and 1990 the intensity data have been determined using two approaches 1 the standard approach which is a general description of the effects on a certain village town general intensity and 2 a localized approach based on a description of effects in the immediate vicinity and in the same lithological morphological and hydrogeological conditions as the recording instrument itself local intensity this second approach to determining intensity could more closely approximate the ground motion parameters obtained from the accelerograms indeed the results of the regressions that were performed show a clear improvement in the correlation when using the local instead of the general intensity in a comparison with peak ground acceleration arias intensity

gravitational slope deformation of a resurgent caldera new insights from the mechanical behaviour of mt nuovo tuffs ischia island italy abstract ischia island italy is an impressive example of the rare phenomenon of caldera resurgence the emplacement and replenishment of magmas at shallow depth resulted in a vertical uplift of about 900 m concentrated in the western portion of mt epomeo 789 m a s l as a consequence of this uplift the island has experienced several slope instabilities at different scales since the holocene from shallow mass movements to large rock and debris avalanches these mass wasting events which mobilised large volumes of greenish alkali trachytic tuff the mt epomeo green tuff megt were strictly related to volcano tectonic activity and the interaction between the volcanic slopes and the hydrothermal system beneath the island deep seated gravitational slope deformation dsgsd at mt nuovo located adjacent to densely populated coastal villages is an ongoing process that covers an area of 1 6 km 2 the mt nuovo dsgsd involves a rock mass volume of 190 mm 3 and is accommodated by a main shear zone and a series of sub vertical fault zones associated with high angle joint sets to improve our understanding of this gravity induced process we performed a physical porosity and permeability and mechanical uniaxial and triaxial deformation experiments characterisation of two ignimbrite deposits both from the megt that form a significant component of the nw sector of mt epomeo the main conclusions drawn from our experiments are twofold first the presence of water dramatically reduces the strength of the tuffs suggesting that the movement of fluids within the hydrothermal system could greatly impact slope stability second the transition from brittle dilatant to ductile compactant behaviour in the tuffs of the megt occurs at a very low effective pressure analogous to a depth of a couple of hundred metres and that this transition is likely moved closer to the surface in the presence of water we hypothesise that compactant porosity decreasing behaviour at the base of the layer could therefore facilitate slope instability although our results show that transient exposure to 300 c does not influence the short term strength of the tuff we speculate that the high in situ temperature could increase the efficiency of brittle and compactant creep and therefore increase the rate of slope deformation taken together our experimental data highlight a potentially important role for the hydrothermal system that reaches a minimum depth of 1 km in dictating the dsgsd at mt nuovo an understanding of this deformation process is not only important for the proximal coastal villages at risk of engulfment by a large debris avalanche but also for the towns and cities along the coast of the gulf of naples that are at risk to a secondary consequence of such an avalanche a tsunami wave

a new type of volcano flank failure the resurgent caldera sector collapse ischia italy 1 this study is the first description of recurrent and rapid lateral failure of the resurgent portion of a caldera complex the sliding planes and the characteristics of debris avalanche deposits resemble those of cone sector collapses but the main triggering mechanism proposed at ischia caldera italy is related to intermittent resurgence during the last 33 ka the increase in resurgence rate produced major collapses southward due to three main mechanisms that contributed to an increase in shear stress i magma driven uplift which produced increase in static loading ii faulting and associated deformation which induced tilting and steepening of the original layering and iii earthquake shaking due to coseismic faulting the largest episodes of flank failure occurred in the interval 8 6 5 7 ka bp these were followed by magma eruption and a decrease in the resurgence rate recognition of this phenomenon is particularly important in recent active calderas located near the coast as it can trigger tsunamis

sensitivity of mesospheric mean flow planetary waves and tides to strength of gravity wave drag a global circulation model which extends from the surface to 125 km is used to study how the strength of gravity wave drag affects the dynamics of the mesosphere the strength of gravity wave drag has a strong influence on the zonal mean state of the mesosphere in particular the magnitude and variability of the summer mesopause temperature and the shear on the top of the mesospheric jets this change in the zonal mean state strongly affects the susceptibility of the mesosphere to baroclinic and or barotropic instability and hence the formation of the 2 day wave the 2 day wave in turn interacts nonlinearly with the diurnal tide producing secondary waves and a reduction in amplitude of the diurnal tide previous studies with quasi linear mechanistic tidal models have captured some semiannual variation in tidal amplitude through direct interactions between tides and gravity waves our fully nonlinear global circulation model results support an alternative explanation in terms of interactions between planetary waves and tides

simple shearing block resurgence in caldera depressions a model from pantelleria and ischia abstract similar resurgent blocks occur in caldera depressions at the islands of pantelleria and ischia the two blocks which are tilted show similar deformation patterns and similar distributions of volcanic vents related to resurgence the remaining parts of the floors of the two calderas are not deformed similarities between the two features are so striking that the resurgence mechanism must have been alike a dynamic model for resurgence is presented and called simple shearing block resurgence the triggering mechanism is an increase of the magmatic pressure in the upper part of a shallow magma chamber which results in a vertical direction of the maximum stress applied on the roof rocks the block is first defined by high angle inland dipping marginal detachments and then deformed through a simple shearing mechanism reverse faults on its mostly uplifted side determine an horizontal shortening of the block which is balanced on the opposite side by normal faults oblique movements take place along the other two sides due to this distribution of the stress around the block magmas can reach the surface only through the extensional faults on the less uplifted side

observed temperature two day wave and its relatives near the stratopause the two day wave is observed in the upper atmosphere research satellitemicrowave limb sounder temperature data around 40 58 km between december 1991 and september 1994 the two day wave temperature signature is most significant after each solstice when the derived easterly winds near the stratopause extend across the equator to at least 208 latitude in the winter hemisphere and the zonal mean winds near the equator are inertially unstable with observed inertial instability disturbances the observed two day wave consists of a 2 0 day period zonal wavenumber 3 and a 1 8 day period zonal wavenumber 4 component named 3 2 0 and 4 1 8 respectively the 3 2 0 component is dominant during two of the three available austral summers but its amplitude is much weaker than the 4 1 8 component during the two observed boreal summers during the austral summers correspondence between amplification of the two day wave temperature signatures regions of reversed potential vorticity gradient due to meridional curvature of the zonal mean flow and the critical lines for the 3 2 0 and 4 1 8 modes suggest barotropic instability as a source of both wave components momentum redistribution by observed inertial instability appears to barotropically destabilize the equatorward flank of the easterly jet where the wave components subsequently grow during the boreal summers the 4 1 8 component appears to be excited by instability that is associated with vertical shear and curvature of the flow seated above the observational domain the boreal 3 2 0 mode appears unrelated to the zonal flow instability within the observational domain and may reflect a normal mode like response during these periods

a three dimensional mountain wave imaged in satellite radiance throughout the stratosphere evidence of the effects of directional wind shear swath scanned thermal radiances from the advanced microwave sounding units amsu a on the noaa and aqua satellites are used to image the horizontal temperature structure of a long wavelength mountain wave that formed over southern scandinavia on 14 january 2003 data from all six stratospheric channels show this wave propagating through the full depth of the stratosphere in channels 9 11 altitudes 20 90 hpa the imaged wave has a phase structure broadly consistent with a stationary wave radiated by the southeastward flow over and above the quasi elliptical terrain of southern norway channel 12 radiances at 10 hpa however show a remarkable abrupt change in imaged wave structure the horizontal wavelength contracts phase lines rotate anticlockwise by 30 40 and peak activity migrates to the south to lie over denmark and northern germany similar structure persists in channels 13 and 14 at 2 5 hpa with progessively increasing radiance amplitudes these features are stable over the 10 hours of amsu a measurements from five separate overpasses and are validated against independent radiances acquired by the atmospheric infrared sounder airs and retrieved airs amsu a temperature profiles from the aqua overpass this change at the channel 11 12 interface coincides with an onset of anticlockwise rotation backing and intensification of background stratospheric winds with height fourier ray and spatial ray modelling incorporating these directionally sheared winds and simplified orographic forcing reproduce the salient features of the observations but only after wave induced temperature perturbations have been converted to channel radiances using a forward model the differential visibility of various components of this three dimensional mountain wave to the amsu a channel weighting functions has a first order impact on the observations at heights above 10 hpa once that is factored in the combined observations and modelling provide direct experimental support for the shutts model s predictions of how backing wind vectors affect the vertical evolution of three dimensional mountain waves implications of these observations for orographic gravity wave drag parametrization are briefly discussed copyright 2007 royal meteorological society

forecasting giant catastrophic slope collapse lessons from vajont northern italy rapid giant landslides or sturzstroms are among the most powerful natural hazards on earth they have minimum volumes of similar to10 6 10 7 m 3 and normally preceded by prolonged intervals of accelerating creep are produced by catastrophic and deep seated slope collapse loads similar to1 10 mpa conventional analyses attribute rapid collapse to unusual mechanisms such as the vaporization of ground water during sliding here catastrophic collapse is related to self accelerating rock fracture common in crustal rocks at loads similar to1 10 mpa and readily catalysed by circulating fluids fracturing produces an abrupt drop in resisting stress measured stress drops in crustal rock account for minimum sturzstrom volumes and rapid collapse accelerations fracturing also provides a physical basis for quantitatively forecasting catastrophic slope failure c 2003 elsevier science b v all rights reserved

the potential failure of monte nuovo at ischia island southern italy numerical assessment of a likely induced tsunami and its effects on a densely inhabited area ischia is the emergent top of a large volcanic complex that rises more than 1 000 m above the sea floor at the north western end of the gulf of naples caldera resurgence in the central part of the island has resulted in the formation of differentially displaced blocks among which mt epomeo 787 m a s l is the most uplifted deformation and slope instability have been recognised as common features induced by a block resurgence mechanism that causes uplift and favours gravitational loading and flank failure the monte nuovo block a topographic high on the north western flank of mt epomeo has recently been interpreted as a block affected by deep seated gravitational slope deformation this block may undergo a catastrophic failure in the case of renewal of magmatic activity this paper investigates the potential failure of the monte nuovo block as a rockslide debris avalanche the consequent tsunami generation and wave propagation and discusses the catastrophic effects of such an event mobilization prone volume has been estimated at about 160 106 m3 and would move from a maximum elevation of 400 m a s l the landslide itself would sweep away a densely populated territory as large as 3 5 km2 the highest waves generated by the tsunami on which this paper is mainly focussed would hit the northern and western shores of ischia however the high coast would prevent inundation and limit devastation to beaches harbours and surrounding areas most of the tsunami energy would head towards the north east hitting the campania coast severe inundation would affect an area of up to 20 km2 around the mouth of the volturno river including the urban area of castel volturno in contrast less energy would travel towards the south and the gulf of naples would be perturbed by long persisting waves of limited damaging potential

cyclical slope instability and volcanism related to volcano tectonism in resurgent calderas the ischia island italy case study abstract the results of a detailed stratigraphic study carried out in the areas located to the east and south west of mt epomeo at ischia are presented and compared with those of previous geological archaeological and historical investigations to show the relationships among caldera resurgence volcanism and slope instability in the past 5 5 ka resurgence at ischia began at about 30 ka b p and occurred through intermittent uplifting and tectonic quietness phases during the past 5 5 ka reactivation of faults and related volcanic activity was accompanied by emplacement of deposits generated by surface gravitational movements these deposits were generated in four main phases dated between 5 5 and 2 9 ka around 2 9 ka between 2 6 and 2 3 ka and between 2 3 and 1 9 ka respectively deposits formed by gravitational movements preceded and followed the emplacement of volcanic rocks testifying that slope instability was induced by vertical movements which also activated and or reactivated faults and fractures that fed volcanism the results of this study therefore suggest that although slope failure can occur as a consequence of a variety of factors resurgence has to be considered a factor inducing a particularly intense slope instability resurgence is accompanied by activation of faults and renewal of volcanism causing oversteepening of the slopes and generating seismicity that could trigger surface gravitational movements furthermore the availability of large amount of loose material rapidly accumulated along the slopes during eruptions favors landslide generation

mountain waves and wakes generated by south georgia implications for drag parametrization high resolution simulations of flows over south georgia south atlantic are used to increase understanding of the likely influence of small isolated mountainous islands on the large scale flow and to ascertain the extent to which parametrization schemes can account for the missing drag in models where such islands are only partially resolved long duration 1 month austral winter forecasts with a horizontal grid spacing of 1 5 km are used to quantify the mountain wave momentum fluxes generated by the island and the low level drag associated with flow blocking dynamics the characteristics of the drag such as the occurrence of high and low drag states its dependence on wind direction and the spectral contributions to the mountain wave momentum flux are considered flow splitting and low level wave breaking are shown to be responsible for wake regions that extend for hundreds of kilometres from the island regions of deceleration are also evident in the stratosphere due to mountain wave dissipation the extent to which an orographic drag parametrization scheme can reproduce the drag is investigated by comparison with coarse resolution 15 km grid spacing simulations in which the orography is poorly resolved and a large proportion of the drag is parametrized it is demonstrated that the total of the resolved plus parametrized drag in these simulations closely resembles that at high resolution although it is underpredicted during instances of high drag simple modifications to the scheme which enhance the drag when the low level flow is approximately normal to the major axis of the subgrid orography are shown to rectify this the study demonstrates that at least for relatively simple isolated mountain ranges the drag and mountain wave momentum fluxes can be predicted in a deterministic sense by a well tuned parametrization scheme of suitable complexity although inclusion of stochastic effects might lead to yet further improvements

structural constraints on deep seated slope deformation kinematics abstract a significant sackung type deep seated slope gravitational deformation dsgsd was recognised for the first time by the authors in the middle part of valfurva east of bormio rhaetian alps italy the reconstruction of its kinematics age and state of activity is presented through a detailed description of its morphological geomechanical and structural features an integrated multi disciplinary approach was performed to achieve a clear comprehension of the phenomenon field surveys and aero photo interpretation were carried out in order to clarify the structural geological and geomorphological setting in which the dsgsd developed a kinematic conceptual model of the slope deformation was developed through the analysis of morpho structures of their significance and relationships with lithological markers and quaternary deposits after a geomechanical characterisation of the rock mass involved in the slope deformation numerical modelling was performed to verify the hypotheses made on kinematics and driving factors of the phenomenon the sackung affects pre permian metapelites metabasites and marbles belonging to the upper austroalpine basement of the campo nappe as well as late pleistocene and holocene glacial and rock glacier deposits the deformation started after the late wurmian age 15 000 11 000 years b p and continued until few centuries ago not excluding a present day low rate activity deformation consists in a large oblique sagging along a deep confined sliding surface associated with gravitational reactivation of pre existing late alpine and recent tectonic brittle structures leading to the formation of n s and wnw ese trending gravitational morpho structures the evolution of the wnw ese trending system resulting in asymmetric trenches led to progressive failure of the lower part of the slope during the last 10 000 years as testified by large paleo landslide accumulations and it is still in progress numerical modelling indicates post glacial unloading as the main triggering factor of the slope deformation the importance of this deep seated slope deformation is enhanced by the occurrence of the 30 mm 3 active ruinon landslide in the lower part of the slope such landslide is subjected to rapid evolution and threatens the valley floor establishing an important risk factor connected to human lives and socio economic activities

oil quality in deep water settings concerns perceptions observations and reality as exploration migrates into deeper water crude oil quality becomes increasingly important variations in oil quality which are reflected in such properties as api gravity viscosity sulfur content and acid number impact both value and producibility in fact issues of oil quality in deep water may in some cases be more critical than issues of hydrocarbon volume problems associated with deep water are commonly thought to be amplified largely as a result of the expansion of the biodegradation window the expanded window is a result of lower temperatures at the mud line a review of data from the gulf of mexico and the gulf of guinea reveals that other factors may have a greater influence on oil quality for example in the gulf of mexico strong evidence exists that the nature of the source rock is a major factor in establishing sulfur content and api gravity oils derived from an upper jurassic oxfordian calcareous source rock generate oils with higher sulfur contents than those derived from cretaceous argillaceous source rocks in the gulf of guinea although many of the newly discovered pools are shallowly buried and evidence for biodegradation exists crude oil quality is mitigated by multiple charging events in both regions evidence also exists for phase segregation which introduces light oils and condensates into the shallow part of the sedimentary sequence both phase segregation and multiple charging events appear to be largely a result of an individual trap s structural evolution the available data therefore suggest that some of the risks associated with oil quality may be reduced through a more detailed assessment of a prospect s filling history and structural evolution and an understanding of the nature of the source facies however there clearly are such situations as offshore brazil where the risks associated with oil quality appear more difficult to mitigate

influences of gravity waves on convectively induced turbulence cit a review thunderstorms are known to produce turbulence such turbulence is commonly referred to as convectively induced turbulence or cit and can be hazardous to aviation although this turbulence can occur both within and outside the convection out of cloud cit is particularly hazardous since it occurs in clear air and cannot be seen by eye or onboard radar furthermore due to its small scale and its ties to the underlying convection it is very difficult to forecast guidelines for out of cloud cit avoidance are available but they are oversimplified and can be misleading in the search for more appropriate and physically based avoidance guidelines considerable research has been conducted in recent years on the nature of the phenomenon and in particular its connection to gravity waves generated by the convection this paper reviews the advances in our understanding of out of cloud cit and its relation to convective gravity waves and provides several detailed examples of observed cases to elucidate some of the underlying dynamics

stationary gravity wave structure in flows with directional wind shear most theoretical studies of flow over mountains assume that the wind direction is constant for two dimensional orographic ridges this is not an issue since only the component of the wind across the ridge forces internal gravity waves a special case of rectilinear flow is when the wind component changes sign i e the wind direction changes discontinuously through 180 degrees such a point is a critical level for all stationary gravity waves for isolated three dimensional mountains the gravity wave response comprises waves of all azimuthal orientations and each of these may have a different critical level height depending on whether the wind backs or veers with height using a combination of ray tracing methods and stationary phase solutions the structure of the stationary hydrostatic gravity wave field generated by an isolated mountain is studied for a simple wind field which backs with height in contrast to the behaviour for unidirectional flow wave action does not accumulate indefinitely beneath the critical level but is continuously advected downwind by the component of the wind parallel to the phase lines instead of the wave energy becoming unbounded following a ray as in the 2d case the wave energy decays to zero along a trailing wake zone downwind of the mountain along phase lines this is just an extension of the asymptotic wake found in the linear solutions of smith for constant flow over an isolated mountain the work described here underlines the desirability of including the effects of selective critical level absorption in the gravity wave drag parametrization schemes of numerical weather prediction models

mapping and characterization of the api gravity of offshore hydrocarbon seepages using multispectral aster data abstract the objective of this work is the qualitative remote characterization api gravity degree of oil seepages on the ocean surface in order to achieve this goal multispectral data acquired by the advanced spaceborne thermal emission and reflection aster sensor are employed aster registered tracts of oil along oceanic sectors of the campos basin brazil and the bay of campeche gulf of mexico in several occasions numerous evidences indicate that these oil patches bear a straight link to oceanic seepages the delimitation and segmentation of these seepages in the aster imagery are accomplished making use of an unsupervised neural network fuzzy clustering algorithm spectra representative of the seepages are extracted from atmospherically corrected aster data pixels 9 bands spanning from visible to shortwave infrared wavelengths contained in the classified segments the aster spectra are checked against a predictive api partial least square regression model this model is established on the basis of oil spectra of known oapi varying from 13 to 47 yielded by laboratory measurements considering this model api gravity degrees of 19 6 1 37 and 15 9 2 9 are remotely estimated for the seepage in the campos basin and the bay of campeche respectively oils produced from campos and campeche fields typically show api varying from 17 24 and 12 16 5 correspondingly these results indicate the potential of the methodology proposed and of aster data and alike to remotely infer physical chemical properties of hydrocarbons since a close match was verified between predicted and true api gravity degrees for both study areas the data methods and experience gained in this research can be operationally tested in offshore oil exploration and likewise be adapted to environmental monitoring of oil spills in coastal regions

preliminary study on the effects of permian volcanism on the tahe ordovician oil pools in tarim basin abstract crude oil densities change remarkably among the various oil pools of tahe field multi stage generation and recharge of light oil and gas from source rocks during pool formation have been assumed to account for this phenomenon the hypothesis of multi stage recharging and pool formation however is in conflict with the assumptions deducted from paleo structure evolution and stratigraphic pressure of the pools variations in salinity of stratigraphic water indicate that heavy oil cannot possibly be connected to fresh water oxidization associated with the unconformities over the oil pools utilizing research on the distribution of permian volcanic craters conduits and rocks interpreted from well and 3 d seismic data the present study shows that the closer the pools are to the volcanic conduits the denser the oil is volcanic activity does not occur at the eastern tahe pool which shows normal oil and condensate gas the findings illustrate the impact of permian volcanic activity on ordovician oil pools

global measurements of stratospheric mountain waves from space temperatures acquired by the cryogenic infrared spectrometers and telescopes for the atmosphere crista during shuttle mission sts 66 have provided measurements of stratospheric mountain waves from space large amplitude long wavelength mountain waves at heights of 15 to 30 kilometers above the southern andes mountains were observed and characterized with vigorous wave breaking inferred above 30 kilometers mountain waves also occurred throughout the stratosphere 15 to 45 kilometers over a broad mountainous region of central eurasia the global distribution of mountain wave activity accords well with predictions from a mountain wave model the findings demonstrate that satellites can provide the global data needed to improve mountain wave parameterizations and hence global climate and forecast models

large variations in balloon ascent rate over hawaii 1 a sequence of nine weather balloons were launched recently over the island of hawaii during the nights of 12 13 and 17 december 2002 providing measurements of ascent rate horizontal wind speed and direction temperature and other quantities the measurements show short intervals of altitude with a large increase in ascent rate occurring only near the tropopause indicating regions of strong upward air velocity at this location the large ascent rates correlate well to the strength of a jet stream and with the presence of a local critical level indicating mountain waves as the primary cause no corresponding decreases in ascent rate were measured suggesting strong three dimensional effects

observations of the quasi 2 day wave from the high resolution doppler imager on uars a strong westward traveling oscillation with a period of 2 days and zonal wave number 3 is observed in the mesospheric and lower thermospheric winds from the high resolution doppler imager on the upper atmosphere research satellite the important events happen in january july and september october of which the occurrence in january is the strongest with an amplitude over 60ms 1 detailed analyses for the periods of january 1992 and january 1993 reveal a cause and effect relationship in the wave developing process at 95km the global structures of the wave amplitude and phase are also presented

a new gravity wave drag scheme incorporating anisotropic orography and low level wave breaking impact upon the climate of the uk meteorological office unified model a new anisotropic gravity wave drag parametrization scheme which represents high drag states modelled on hydraulic jump flow blocking and internal wave reflection theory including trapped lee waves is presented the scheme is shown to represent the breaking of waves over mountains better than previous schemes by comparison with mesoscale simulations of pyrex case studies extended simulations of the meteorological office unified model at climate resolution are presented showing the impact of the new scheme and a combination of the scheme with a new orographic roughness parametrization results show a changed distribution of surface gravity wave surface stress mostly due to mountain anisotropy and a greater tendency for lower troposphere wavc drag inclusion of the orographic roughness parametrization halves the gravity wave stress the combined effect of these schemes for climate integrations being a slight improvement to the tropospheric flow

observations and numerical simulations of mountain waves in the presence of directional wind shear three research aircraft observed small amplitude gravity waves over the south western french alps on 13 november 1999 during the mesoscale alpine programme map radiosonde ascents and global positioning system dropsondes deployed by map research aircraft indicate that the upstream flow was characterized by topographic blocking below 2 km and low level directional wind shear associated with a synoptic scale depression that extended above the alpine crest the in situ vertical velocity data from the three research aircraft and backscatter from lidar onboard the low level and upper level aircraft exhibit gravity wave signatures in the lower troposphere that are characterized by relatively short horizontal wavelengths on a scale of 5 km or less the in situ flight level and backscatter data also suggest a rapid decrease in the wave amplitude with height due to a directional critical layer that partially absorbs wave energy in the lower to middle troposphere in concert with a decrease in the scorer parameter with height that traps the wave energy numerical simulation results obtained from the non hydrostatic coupled ocean atmosphere mesoscale prediction system model using a horizontal resolution of 556 m indicate the presence of low level wave breaking above the highest peaks and confirm the presence of trapped waves and a directional critical level results based on linear theory and nonlinear model simulations suggest that the absorption of wave energy associated with the directional critical layer has an important impact on the wave characteristics including the momentum flux copyright 2006 royal meteorological society

alleviation of a systematic westerly bias in general circulation and numerical weather prediction models through an orographic gravity wave drag parametrization systematic westerly biases in the northern hemisphere wintertime flow of the meteorological office 15 layer operational model and 11 layer general circulation model are described evidence that the failure to parametrize subgrid scale orographic gravity wave drag may account for such biases is presented this evidence is taken from aircraft studies surface pressure drag measurements and studies of the zonally averaged momentum budget a parametrization scheme is described in which the surface stress is proportional to the near surface wind speed and static stability and to the variance of subgrid scale orography the stress is absorbed in the vertical by considering the influence of such gravity wave activity on static stability and vertical wind shear a richardson number dependent wave breaking formulation is devised and the vertical stress profile determined by a saturation hypothesis whereby the breaking waves are maintained at marginal stability it is shown that wave breaking preferentially occurs in the boundary layer and in the lower stratosphere results from a simple zonally symmetric model show how the adjustment to thermal wind balance with a wave drag in the stratosphere warms polar regions by adiabatic descent and decelerates the mean westerlies in the troposphere the influence of the parametrization scheme on integrations of the 11 layer model is described and found to be generally beneficial in a discussion of the reasons why this problem has only recently emerged it is suggested that the satisfactory northern hemisphere winter circulations of previous coarser general circulation models were due to a compensation implied by underestimating both the surface drag and the horizontal flux of momentum by explicitly resolved large scale eddies

review of wave turbulence interactions in the stable atmospheric boundary layer flow in a stably stratified environment is characterized by anisotropic and intermittent turbulence and wavelike motions of varying amplitudes and periods understanding turbulence intermittency and wave turbulence interactions in a stably stratified flow remains a challenging issue in geosciences including planetary atmospheres and oceans the stable atmospheric boundary layer sabl commonly occurs when the ground surface is cooled by longwave radiation emission such as at night over land surfaces or even daytime over snow and ice surfaces and when warm air is advected over cold surfaces intermittent turbulence intensification in the sabl impacts human activities and weather variability yet it cannot be generated in state of the art numerical forecast models this failure is mainly due to a lack of understanding of the physical mechanisms for seemingly random turbulence generation in a stably stratified flow in which wave turbulence interaction is a potential mechanism for turbulence intermittency a workshop on wave turbulence interactions in the sabl addressed the current understanding and challenges of wave turbulence interactions and the role of wavelike motions in contributing to anisotropic and intermittent turbulence from the perspectives of theory observations and numerical parameterization there have been a number of reviews on waves and a few on turbulence in stably stratified flows but not much on wave turbulence interactions this review focuses on the nocturnal sabl however the discussions here on intermittent turbulence and wave turbulence interactions in stably stratified flows underscore important issues in stably stratified geophysical dynamics in general

analysis of seismic driven instability of mt nuovo in the ischia island italy abstract ischia is a volcanic island located at the margin of the gulf of naples in the southeastern tyrrhenian sea italy in this article we investigate the stability of the deep seated block known as mt nuovo in the northwestern flank of the mt epomeo volcano under a combined gravitational and seismic load mt nuovo is bounded by a number of active seismic faults and is placed close to the epicentral area of the 1883 casamicciola earthquake i mcs x m w 5 8 that is the largest shock occurring in the island in historical times we explore the hypothesis that a casamicciola like earthquake might occur with an epicenter in the mt nuovo block area using relationships between maximum seismic intensity and peak ground acceleration found in the literature as well as a new relationship derived specifically for this study we apply the minimum lithostatic deviation method which is a variant of the limit equilibrium method to assess the stability of the block the main finding is that mt nuovo would be mobilized if such an earthquake took place on a fault very close to the block which would give rise to a catastrophic mass failure and to a disastrous tsunami this calls for the need of continuous monitoring of the volcano seismicity and deformation pattern

the ischia volcanic island southern italy inferences from potential field data interpretation abstract in this paper we present a study of the structural setting of the volcanic island of ischia by the analysis and interpretation of high resolution aeromagnetic and self potential data recently acquired over the island the magnetic data allowed us to locate the main anomaly sources and lineaments of the island and its offshore surroundings while the self potential sp data provided information on both the structural pattern of the resurgent caldera and the high temperature fluid circulation an inversion of the acquired magnetic and sp data and a joint modelling of the magnetic data and of a previous gravity data set along a sw ne profile allowed us to build a model of the island the model is characterized by the presence of an igneous very likely trachytic structure whose top is located at 1200 1750 m b s l such a body possibly formed by several neighbouring intrusions has a density contrast with the pyroclastic cover of about 0 4 gr cm 3 and its central western part below mt epomeo seems to be demagnetized the demagnetization should be connected to the high geothermal gradient measured in this portion of the island and may be due to hydro chemical alteration processes and or to the possible presence of partially melted spots within the intrusion our outcome is consistent with the results of previous geophysical geo volcanological and geothermal studies

high gravity wave activity observed in patagonia southern america generation by a cyclone passage over the andes mountain range fil pulido manuel arturo consejo nacional de investigaciones cientificas y tecnicas centro cientifico tecnologico conicet nordeste instituto de modelado e innovacion tecnologica universidad nacional del nordeste facultad de ciencias exactas naturales y agrimensura instituto de modelado e innovacion tecnologica argentina

fourier ray modeling of short wavelength trapped lee waves observed in infrared satellite imagery near jan mayen abstract a time dependent generalization of a fourier ray method is presented and tested for fast numerical computation of high resolution nonhydrostatic mountain wave fields the method is used to model mountain waves from jan mayen on 25 january 2000 a period when wavelike cloud banding was observed long distances downstream of the island by the advanced very high resolution radiometer version 3 avhrr 3 surface weather patterns show intensifying surface geostrophic winds over the island at 1200 utc caused by rapid eastward passage of a compact low pressure system the 1200 utc wind profiles over the island increase with height to a jet maximum of 60 70 m s 1 yielding scorer parameters that indicate vertical trapping of any short wavelength mountain waves separate fourier ray solutions were computed using high resolution jan mayen orography and 1200 utc vertical profiles of winds and temperatures over the island from a radiosonde sounding and an analysis system the radiosonde based simulations pr

seasonal variations of the diurnal tide induced by gravity wave filtering wind measurements with the uars spacecraft show that between 90 and 100 km altitude the fundamental diurnal tide is modulated semi annually with peak amplitudes of almost 100 m s near equinox more than a factor of two larger than during solstice applying hines doppler spread parameterization dsp for small scale gravity waves gw we present results from a numerical spectral model nsm to describe the seasonal variations in the mean zonal circulation interacting self consistently with the diurnal tide with the dsp the gw momentum source increases the amplitude of the tide at altitudes above 70 km in contrast to the rayleigh friction parameterization that causes damping since the tide absorbs gw momentum it reduces the wave generated semi annual oscillations sao in the mean zonal winds at equatorial latitudes outside the tropics gw momentum is absorbed by the mean zonal winds that peak near the summer and winter solstices as a result the gw reach the upper mesosphere with more momentum during equinox periods and thus cause a seasonal modulation of the tide that is predominately semi annual

nondissipative and dissipative momentum deposition by mountain wave events in sheared environments abstractmountain waves mws are generated during episodic cross barrier flow over broad spectrum terrain however most mw drag parameterizations neglect transient broad spectrum dynamics here

non hydrostatic effects on mountain wave breaking in directional shear flows mountain waves excited by narrow 3d orography are investigated using idealized numerical simulations of atmospheric flows with directional wind shear the stability of these waves is compared with the stability of hydrostatic mountain waves the focus is on understanding how wave breaking is modified via gravity wave critical level interaction when non hydrostatic dispersive effects arise the influence of non hydrostatic effects on wave breaking appears to be a function of the intensity of the background shear increasing the stability of the flow inhibiting wave breaking for weak wind shear but decreasing it instead enhancing wave breaking for stronger wind shear

mountain waves over the hohe tauern influence of upstream diabatic effects the structure and intensity of large amplitude trapped lee waves over the hohe tauern range of the alps on 20 september 1999 are investigated through the analysis of in situ aircraft observations airborne lidar global positioning system dropsondes rapid scan satellite imagery and a suite of linear and nonlinear model simulations observations indicate that the lee waves attained a maximum vertical velocity of more than 9 m s 1 potential temperature perturbations greater than 10 k and a horizontal wavelength of approximately 12 15 km high resolution nonlinear simulations accurately capture the trapped wave evolution and characteristics blocking of the southerly flow upstream of the hohe tauern decreases the depth of the layer that ascends the mountain crest and modulates the wave response vertically propagating waves are partially ducted into a train of lee waves as a result of weak stability aloft which forms due to diabatic processes associated with precipitation upstream of the hohe tauern crest linear analytic solutions confirm the importance of the weak stability layer in the upper troposphere for the development of the non hydrostatic evanescent waves results from idealized two dimensional nonlinear simulations suggest that the vertical depth of diabatic heating associated with the upstream precipitation is important in this case latent heating over a relatively shallow depth tunes the atmosphere for a nonlinear resonance that leads to strong descent in the lee and reinforcement of the lee waves copyright 2003 royal meteorological society

the summer wind field between 80 and 93 km observed by the mst radar at poker flat alaska 65 n abstract results of an analysis of the summertime wind field between 80 93 km over poker flat alaska are presented the data were obtained using the large but as yet incomplete mst radar at poker flat and cover the periods 17 june 13 july 1979 and 22 june 22 july 1980 zonal and meridional mean wind profiles and tidal components during these periods are examined and are compared with other observations at comparable latitudes as well as with current theoretical profiles while our results agree reasonably closely with other observations and theory some discrepancies exist and are discussed in addition to the expected 8 12 and 24 h components of atmospheric motions we find strong evidence for a 16 h component particularly during the 1979 data period in addition we show examples of the average power spectrum of wind fluctuations from 3 min to 8 days these spectra not only show the expected tidal peaks but show also that the spectral energy density is continuous between the shortest 8 h t

impacts of horizontal propagation of orographic gravity waves on the wave drag in the stratosphere and lower mesosphere the impact of horizontal propagation of mountain waves on the orographic gravity wave drag ogwd in the stratosphere and lower mesosphere of the northern hemisphere is evaluated for the first time using a fine resolution 1 arc min terrain and 2 5 2 5 european centre for medium range weather forecasts era interim reanalysis data during 2011 2016 two sets of ogwd are calculated offline according to a traditional parameterization scheme without horizontal propagation and a newly proposed scheme with horizontal propagation in both cases the zonal mean ogwds show similar spatial patterns and undergo a notable seasonal variation in winter the ogwd is mainly distributed in the upper stratosphere and lower mesosphere of middle to high latitudes whereas the summertime ogwd is confined in the lower stratosphere comparison between the two sets of ogwd reveal that the horizontal propagation of mountain waves tends to decrease increase the ogwd in the lower stratosphere middle to upper stratosphere and lower mesosphere consequently including the horizontal propagation of mountain waves in the parameterization of ogwd can reduce the excessive ogwd in the lower stratosphere and strengthen the insufficient gravity wave forcing in the mesosphere which are the known problems of traditional ogwd schemes the impact of horizontal propagation is more prominent in winter than in summer with the ogwd in western tibetan plateau rocky mountains and greenland notably affected

wave breaking and critical levels for propagating inertio gravity waves in the lower stratosphere this paper analyses and interprets the formation of mixed layers due to propagating inertio gravity waves observed during the fronts and atlantic storm track experiment the data used are high vertical resolution soundings launched from different sites located in the north atlantic sector in agreement with other studies attributing the origin of the inertio gravity waves to the adjustment of the jet stream near fronts the largest waves observed are often located in the vicinity of and above frontal bands the amplitude of these waves is large enough that they give rise to narrow mixed layers by a detailed analysis of the waves characteristics we can distinguish whether such a mixing is favoured by the presence of an inertia critical level where f or results from wave induced convective instability occurring far from critical levels here is the wave intrinsic frequency and f is the coriolis parameter these observations highlight the importance of inertio gravity waves in the vertical exchanges that occur in the stratosphere copyright 2002 royal meteorological society

parameterization of directional absorption of orographic gravity waves and its impact on the atmospheric general circulation simulated by the weather research and forecasting model abstractin this work a new parameterization scheme is developed to account for the directional absorption of orographic gravity waves ogws using elliptical mountain wave theory the vertical mom

the ischia debris avalanche first clear submarine evidence in the mediterranean of a volcanic island prehistorical collapse sector or flank collapse with related debris avalanches is increasingly recognized as a relatively common volcanic behaviour in particular for large hot spot related oceanic islands here we report the case of a catastrophic collapse that occurred at ischia volcanic island in prehistorical times and was driven by the volcano tectonic uplift of mt epomeo the major relief of the island the collapse left a subaerial to submarine horseshoe scar on the southern flank of the island and generated a debris avalanche incorporating thousands of giant blocks dispersed as far as 50 km from the island during the emplacement part of the debris avalanche evolved into a debris flow covering an area of 250 300 km2 this constitutes the first clear evidence of a submarine debris avalanche in the mediterranean sea the major collapse was followed and probably also preceded by recurrent less catastrophic terrestrial and underwater failures two other undersea hummocky deposits are found north and west of the island and might tentatively be correlated to the major southern collapse such volcanic behaviour previously unknown for ischia volcano has likely triggered tsunami waves over the entire bay of naples raising the question of their impact on prehistorical historical communities

slope instability induced by volcano tectonics as an additional source of hazard in active volcanic areas the case of ischia island italy ischia is an active volcanic island in the gulf of naples whose history has been dominated by a caldera forming eruption ca 55 ka and resurgence phenomena that have affected the caldera floor and generated a net uplift of about 900 m since 33 ka the results of new geomorphological stratigraphical and textural investigations of the products of gravitational movements triggered by volcano tectonic events have been combined with the information arising from a reinterpretation of historical chronicles on natural phenomena such as earthquakes ground deformation gravitational movements and volcanic eruptions the combined interpretation of all these data shows that gravitational movements coeval to volcanic activity and uplift events related to the long lasting resurgence have affected the highly fractured marginal portions of the most uplifted mt epomeo blocks such movements mostly occurring since 3 ka include debris avalanches large debris flows lahars smaller mass movements rock falls slumps debris and rock slides and small debris flows and deep seated gravitational slope deformation the occurrence of submarine deposits linked with subaerial deposits of the most voluminous mass movements clearly shows that the debris avalanches impacted on the sea the obtained results corroborate the hypothesis that the behaviour of the ischia volcano is based on an intimate interplay among magmatism resurgence dynamics fault generation seismicity slope oversteepening and instability and eruptions they also highlight that volcano tectonically triggered mass movements are a potentially hazardous phenomena that have to be taken into account in any attempt to assess volcanic and related hazards at ischia furthermore the largest mass movements could also flow into the sea generating tsunami waves that could impact on the island s coast as well as on the neighbouring and densely inhabited coast of the neapolitan area

vhf radar measurements and model simulations of mountain waves over wales very high frequency vhf radar measurements of mountain waves over aberystwyth wales during 29 november 1997 are presented and compared with the predictions made by a three dimensional numerical model which is based on the linearized equations of motion the radar height time plot of vertical velocity reveals a wave field in the troposphere and lower stratosphere which changes significantly throughout the day four separate radiosonde soundings taken during the day are used to represent the steady background flow in the numerical model in this case the steady state model wave fields are shown to compare qualitatively well with the radar measurements and the three dimensional information provided by the model is used to help explain the changes in the wave field observed by the radar throughout the day the radiosonde profiles are interpolated in time to provide approximate basic state data at two hour intervals model steady state vertical velocity fields based on each of these 13 approximate basic state profiles are used to generate a model time height vertical velocity plot which is qualitatively similar to that obtained from the radar measurements indicating that to a reasonable approximation the evolving wave field can be regarded as a sequence of independent steady states this is generally true if the basic state flow remains steady over the time taken for wave packets to propagate over several wavelengths group velocity arguments are used to show that for typical mountain waves in the troposphere such time scales are generally less than one hour model simulations in which the basic state flow is allowed to vary in time continually based on either the interpolated radiosonde soundings or the radar horizontal wind measurements are conducted in this case the simulated wave fields are always unsteady the waves show a tendency to drift in response to changes in the basic state wind field for example during instances when the wind speed at a given level decreases whilst the wind direction remains the same the waves show an upwind phase propagation with a typical phase speed of the order of 1 m s 1 the consequence of this unsteadiness for the propagation of the waves is discussed copyright 2002 royal meteorological society

the uppermost crust structure of ischia southern italy from ambient noise rayleigh waves abstract ambient noise measurements were performed at the island of ischia southern italy along alignments of 2 4 7 km by using two three component seismic stations synchronous noise recordings of 2 20 h were cross correlated over 20 30 s windows stacked and iteratively band pass filtered to enhance the dispersive wave trains frequency time analysis was performed on the vertical and radial components of cross correlations and the fundamental mode rayleigh wave group velocity was obtained validation of the dispersion data was possible with those obtained from an earthquake recording along a close path the non linear inversion of average rayleigh wave group velocity dispersion curves along 13 paths receiver inter distances allowed the definition of shear wave velocity models in the uppermost 1 2 km of the crust the correlation of vs profiles vs depth and drilling stratigraphy allowed to attribute vs lower than 1 km s to tuffs and vs of 1 41 km s to very fractured lavas higher vs are found in the central area of the island in correspondence of the resurgent area the top of the trachytic lava basement with vs of 2 2 2 4 km s and density of 2 3 g cm3 is about 0 6 0 7 km deep b s l in the centre of ischia below altered very fractured lava or thermally altered tuff

the 2009 april 6 mw 6 3 l aquila central italy earthquake finite fault effects on intensity data summary we analyse the spatial distribution of the intensity data points surveyed after the mw 6 3 2009 l aquila central italy earthquake with the aim to recognize and quantify finite fault and directivity effects the study is based on the analysis of the residuals evaluated with respect to attenuation with distance models calibrated for l aquila earthquake we apply a non parametric approach considering both the epicentral and the rupture distance which accounts for the finite extension of the source then starting from a simplified kinematic rupture model of the l aquila fault we compute four directivity predictors proposed in literature and assess their correlation with intensity residuals we derive a so called intensity directivity factor by the correlation between theoretical predictors and observed residuals that allows us to identify and quantify the intensity data points affected by forward and backward directivity during l aquila earthquake we find that the effects are more pronounced in the forward directivity direction and increments up to 1 mcs intensity unit are expected moreover the directivity predictor that accounts for radiation pattern poorly correlates with residuals these results show that the spatial distribution of the l aquila macroseismic field is affected by source effects and in particular that directivity induced amplification effects can be recognized we show that the quasi unilateral rupture propagation along the fault can explain the high intensity patterns observed along specific direction at relatively large distance from the instrumental epicentre in accordance with the seismological source models derived from the analysis of instrumental observations

space time structure of mesoscale motions in the stable boundary layer in this article we examine the stochastic characteristics of non turbulent motions in the stable boundary layer the behaviour of mesoscale motions in the atmospheric stable boundary layer is poorly understood beyond case studies of unusually well defined events or monotonic waves eight networks of wind observations are analysed in order to examine stochastically the space time characteristics of such motions in the stable boundary layer the networks include a variety of surface conditions and network configurations although none of the networks is optimal for our studies collectively the networks allow examination of scales from tens of metres to tens of kilometres a variety of analysis tools reveal the complexity of mesoscale motions near the surface in stratified flow for the data as a whole the horizontal scale of coherence increases systematically with time scale albeit with large scatter between records the relationship between spatial coherence and time scale is posed in terms of a velocity scale which is found to be unrelated to the wind speed the time variability of the flow decreases systematically with increasing spatial averaging suggesting that comparison of model winds with implied spatial averaging over the grid area with observations requires suitable spatial averaging of the observations additional characteristics are discussed in terms of non dimensional ratios of velocity scales necessary improvements of network measurements are also noted copyright 2008 royal meteorological society

aircraft measurements and numerical simulations of mountain waves over the central alps a pre map test case in preparation for the field phase of the mesoscale alpine project map in situ research aircraft observations from the dlr falcon and three dimensional high resolution numerical simulations are used to investigate mountain waves generated during a south fohn event on 10 october 1987 the model simulation qualitatively compares favourably with the aircraft observations in terms of identifying the horizontal and vertical locations of maximum gravity wave amplitude and rapid decay of wave amplitudes in the lower stratosphere however even with reasonably specified large scale conditions the vertical velocity and temperature perturbations are not in quantitative agreement with the aircraft measurements the results highlight some deficiencies that still exist in our predictive capability to simulate gravity wave generation and propagation explicitly over three dimensional topography for non steady conditions the complexity of the gravity wave response points toward the necessity of a straightforward aircraft observing strategy that features linear flight segments oriented along the cross mountain wind direction a rapid repetition of these segments in order to assess the significance of transients and a combination of in situ measurements with remote sensing data e g from lidar systems and dropsondes an approach that was successfully applied during the map

generation and trapping of gravity waves from convection with comparison to parameterization some parameterizations of gravity wave mean flow forcing in global circulation models gcms add realism by describing wave generation by tropospheric convection because the convection in gcms is itself a parameterized process these convectively generated wave parameterizations necessarily use many simplifying assumptions in this work the authors use a realistic simulation of wave generation by convection described in previous work which was validated by observations from the darwin area wave experiment dawex to test these assumptions and to suggest some possible improvements to the parameterizations in particular the authors find that wave trapping in the troposphere significantly modifies the spectrum of vertically propagating waves entering the stratosphere above convective wave sources and offer a linear method for computing wave transmission and reflection effects on the spectrum suitable for inclusion in the parameterizations the wave fluxes originate from both a time varying heating mechanism and an obstacle effect mechanism acting in the simulation methods for including both mechanisms in the parameterizations are described waves emanating from the obstacle effect remain very sensitive to the depth of penetration of latent heating cells into an overlying shear zone which will continue to make it difficult to accurately parameterize in a gcm where the convective cells are not resolved

the correlation of peak ground horizontal acceleration with magnitude distance and seismic intensity for friuli and ancona italy and the alpide belt a new sample of strong motion data has been analyzed in this paper namely 120 records from the 1976 friuli earthquake 40 from the 1972 ancona swarm and 64 from different alpide belt shocks the sample is the result of the selection of peak recorded horizontal acceleration of every three component record greater than 0 015 g linear regressions were applied to the data with the purpose of understanding the geography and the site dependence separate analyses have been carried out firstly taking into account acceleration a magnitude ml and distance d then computing a imm relationships and comparing the respective standard errors of the estimates finally a ml d imm regressions for the total sample from friuli ancona and the alpide belt have been computed the main result are 1 1 the friuli data are 70 per cent lower than those of the alpide belt and ancona 2 2 the ancona set of data is closely related to the alpidic set at a magnitude level of 4 0 3 3 the expected accelerations in friuli are close to the average values recorded in the circumpacific belt region intermediate earthquakes excluded while the alpide belt accelerations are close to the circumpacific maxima 4 4 site dependence between data recorded in friuli on thick consolidated alluvium tha and on rock like ri is not statistically significative 5 5 friuli sites with thin alluvium tha exhibit stronger average accelerations and a significant difference in the ml coefficient which is 0 47 with a standard error of 0 05 as regards the ri tha category which has a value of 0 35 with a standard error of 0 04 6 6 the standard errors of the estimates of the regressions a imm in the case of friuli and the alpide belt are close to the corresponding standard errors of the regressions a ml d it may be concluded that a imm correlations are in some cases a valuable tool for seismic risk estimations especially for being able to use the historical information

the interaction between regional and local tectonics during resurgent doming the case of the island of ischia italy abstract the volcanic island of ischia is located on the tyrrhenian margin of central italy characterized by plio quaternary nw se and ne sw trending extensional fractures ischia displays a resurgent dome uplifted by at least 800 m in the last 33 ka remote sensing and field data have been collected to study the structural setting of the island the deformation pattern associated with resurgence and the superimposition of the regional and the resurgence induced stress fields nw se and ne sw extensional fracture systems predominate throughout the island and around the resurgent block suggesting a relationship with the regional extensional structures these systems were formed before resurgence and were partly reactivated during resurgence the reactivation of pre existing regional systems during resurgence confined the extent of the uplifted area n s and e w trending systems have been found exclusively at the borders of the dome and are interpreted as being induced by resurgence the topmost resurgent block shows an octagonal shape in map view and is tilted at an angle of 15 around a ne sw trending horizontal axis the block is partly bordered by high angle inward dipping regional faults more than 90 in volume of the volcanic products coeval with resurgence on ischia have been erupted outside the resurgent block area suggesting that the resurgence process locally replaced volcanic activity in the last 33 ka

large amplitude mountain wave breaking over greenland abstract a large amplitude mountain wave generated by strong southwesterly flow over southern greenland was observed during the fronts and atlantic storm track experiment fastex on 29 january 1997 by the noaa g iv research aircraft dropwindsondes deployed every 50 km and flight level data depict a vertically propagating large amplitude wave with deep convectively unstable layers potential temperature perturbations of 25 k that deformed the tropopause and lower stratosphere and a vertical velocity maximum of nearly 10 m s 1 in the stratosphere the wave breaking was associated with a large vertical flux of horizontal momentum and dominated by quasi isotropic turbulence the coupled ocean atmosphere mesoscale prediction system coamps nonhydrostatic model with four nested grid meshes with a minimum resolution of 1 7 km accurately simulates the amplitude location and timing of the mountain wave and turbulent breakdown finescale low velocity plumes that resemble wakelike structures emanate from highl

mountain wave turbulence in the presence of directional wind shear over the rocky mountains abstractmountain wave turbulence in the presence of directional wind shear over the rocky mountains in colorado is investigated pilot reports pireps are used to select cases in which moderate or severe turbulence encounters were reported in combination with significant directional wind shear in the upstream sounding from grand junction colorado gjt for a selected case semi idealized numerical simulations are carried out using the wrf arw atmospheric model initialized with the gjt atmospheric sounding and a realistic but truncated orography profile to isolate the role of directional wind shear in causing wave breaking sensitivity tests are performed to exclude the variation of the atmospheric stability with height the speed shear and the mountain amplitude as dominant wave breaking mechanisms significant downwind transport of instabilities is detected in horizontal flow cross sections resulting in mountain wave induced turbulence occurring at large horizontal distances from the first wave br

the parametrization of drag induced by stratified flow over anisotropic orography a new parametrization of drag arising from the flow over unresolved topography ut in a general circulation model gcm is presented it is comprised of three principle components a parametrization of the source spectrum and drag associated with freely propagating hydrostatic gravity waves in the absence of rotation a parametrization of the drag associated with low level wave breaking and a parametrization of low level drag associated with upstream blocking and lee vortex dynamics novel features of the scheme include a new procedure for defining the ut in each gcm grid cell which takes account of the gcm resolution and includes only the scales represented by the parametrization scheme a new method of representing the azimuthal distribution of vertical momentum flux by two waves whose direction and magnitude systematically vary with the flow direction and with the anisotropy of the ut in each gcm grid cell and a new application of form drag in the lowest levels which can change the direction of the low level flow so that it is more parallel to unresolved two dimensional topographic ridges the new scheme is tested in the canadian centre for climate modelling and analysis third generation atmospheric gcm at horizontal resolutions of t47 and t63 five year seasonal means of present day climate show that the new scheme improves mean sea level pressures or mass distribution and improves the tropospheric circulation when compared with the gravity wave drag scheme used currently in the gcm the benefits are most pronounced during northern hemisphere winter it is also found that representing the azimuthal distribution of the momentum flux of the freely propagating gravity wave field with two waves rather than just one allows 30 50 more gravity wave momentum flux up into the middle atmosphere depending on the season the additional momentum flux into the middle atmosphere is expected to have a beneficial impact on gcms that employ a more realistic representation of the stratosphere

dynamics of orographic gravity waves observed in the mesosphere over the auckland islands during the deep propagating gravity wave experiment deepwave abstracton 14 july 2014 during the deep propagating gravity wave experiment deepwave aircraft remote sensing instruments detected large amplitude gravity wave oscillations within mesospheric airglow and sodium layers at altitudes z 78 83 km downstream of the auckland islands located 1000 km south of christchurch new zealand a high altitude reanalysis and a three dimensional fourier gravity wave model are used to investigate the dynamics of this event at 0700 utc when the first observations were made surface flow across the islands terrain generated linear three dimensional wave fields that propagated rapidly to z 78 km where intense breaking occurred in a narrow layer beneath a zero wind region at z 83 km in the following hours the altitude of weak winds descended under the influence of a large amplitude migrating semidiurnal tide leading to intense breaking of these wave fields in subsequent observations starting at 1000 utc the linear fourier model constrained by upstream reanalysis

numerical simulations of orographic gravity waves in flows which back with height numerical simulations are carried out to determine the steady state gravity wave structure above a circularly symmetric bell shaped hill when the wind backs with height two types of idealized basic state flow are considered one representing the advection of a uniform baroclinic shear flow and the other being a flow of constant speed but with a wind vector that rotates uniformly in height of particular interest is the nature of the critical level processes that must appear at all heights due to the three dimensionality of the wave field and the rotation of the wind vector as suggested by linear theory a critical level or asymptotic wake is found downwind of the hill at any height where downwind refers to the wind at that level only for small hills where the nondimensional mountain height unity the simulated vertical momentum flux profiles are in very good agreement with linear hydrostatic wave theory if it is assumed that wave component critical level absorption is total i e no wave transmission or reflections are permitted the vertical momentum fluxes generated by a 1 km high hill show nonlinear enhancement by a factor of about 1 5 an interesting feature of the gravity wave field generated by this 1 km mountain is an asymptotic wake that is dominated by a single intense shear layer in which the richardson number is order unity

effects of horizontal geometrical spreading on the parameterization of orographic gravity wave drag part i numerical transform solutions abstractnumerical transform solutions for hydrostatic gravity waves generated by both uniform and sheared flow over elliptical obstacles are used to quantify effects of horizontal geometrical spreading on amplitude evolution with height both vertical displacement and steepness amplitudes are considered because of their close connections to drag parameterizations in weather and climate models novel diagnostics quantify the location and value of the largest wavefield amplitudes most likely to break at each altitude these horizontal locations do not stray far from the obstacle peak even at high altitudes resulting vertical profiles of wave amplitude are normalized to remove density and refraction effects thereby quantifying the horizontal geometrical spreading contribution currently absent from parameterizations horizontal geometrical spreading produces monotonic amplitude decreases with height through wave action conservation as waves propagate into progressively larger horizontal areas accumulated

a new subgrid scale orographic drag parametrization its formulation and testing a scheme for the representation of subgrid scale orography sso in numerical weather prediction and climate models is presented the new scheme arose in part from a desire to represent nonlinear low level mountain drag effects not currently parametrized an important feature of the scheme is that it deals explicitly with a low level flow which is blocked when the effective height of the subgrid scale orography is sufficiently high in this new scheme it is assumed that for this blocked flow separation occurs at the mountain flanks resulting in a form drag this drag is parametrized on model levels which are intersected by the sso and provides a dynamically based replacement for envelope orography the upper part of the low level flow goes over the orography and generates gravity waves at the model resolutions considered t106 and t213 it is assumed that the length scales characteristic of the sso are sufficiently small for the coriolis force to be neglected the various parameters of the scheme are adjusted using an off line procedure in which the scheme is used to estimate the mountain drag and the momentum profiles above the pyrenees and these estimates are validated with the pyrex data forecasts using t106 and t213 resolutions with this new scheme and with mean orography show that the forecast mountain drag consistently reproduces the drag measured during pyrex whenever the flow component normal to the ridge is large isentropic flow diagnostics further show that the new scheme has a realistic impact on the flow dynamics reinforcing the low level wake observed in mesoscale analyses of the flow with this new scheme and a mean orography the ecmwf model outperformed in forecast skill a version of the model which had an envelope orography and the old gravity wave drag scheme while no longer suffering any disadvantages of envelope orography the proposed low level drag parametrization should also be relevant at model horizontal resolutions much higher than t213

seismically induced landslide susceptibility evaluation application of a new procedure to the island of ischia campania region southern italy in this paper we present an approach for evaluating landslide susceptibility in seismic areas it is known that earthquake induced landslide susceptibility is related to several often interplaying factors nevertheless an effective grade 2 zonation should be characterized by a good balance between simplicity quickness and reliability the gis based procedure we present employs only three factors that we believe are the most significant in this susceptibility assessment the type of outcropping rocks soils the slope angle and the mcs intensity the local annual precipitation certainly an essential factor is considered here as a parameter whose seasonal pattern is constant in time and space each of the three parameters is expressed as a significance percentage and the resulting seismic landslide susceptibility level of an area is given by the average of the significances of the first two factors multiplied by the significance of the third factor the procedure was set and tested on the volcanic island of ischia southern italy which was affected by several historical earthquake induced landslides the results of this susceptibility zonation test at ischia show a very good match between the distribution of the sources of historical landslides and the areas we identified as the most susceptible ones

potential mass movements on the palinuro volcanic chain southern tyrrhenian sea italy and consequent tsunami generation abstract the palinuro volcanic chain pvc is located about 80 km offshore the campania region italy in the southern sector of the tyrrhenian sea the chain consists of 15 volcanic edifices aligned in an e w direction with two distinct major seamounts palinuro and glabro they cover a 90 km long and 20 km wide area with a present day volume of 2700 km3 palinuro volcanism emplaced between 0 8 and 0 3 ma although shallow seismicity and hydrothermalism indicate an ongoing volcanic activity a geomorphological analysis of the volcanic chain and data from a multichannel seismic profile reveal large volumes of buried chaotic material suggesting gravity mass sliding from the volcano flanks and slide scars a stability analysis of the palinuro flanks has been carried out to determine the sectors potentially prone to sliding in case of shallow volcanic earthquakes landslides are simulated by adopting a scenario based approach tsunamis induced by these mass movements and their propagation across the tyrrhenian sea are modeled results suggest that shallow earthquakes m 4 6 4 8 are able to destabilize the flanks of the volcanic chain generating slope failures sliding volumes in the order of 1 5 km3 and 2 4 km3 may induce waves as high as 1 5 and 6 m respectively along the peri tyrrhenian coast our results underline the need for further investigations on the stability of the submarine volcanoes of the tyrrhenian basin these volcanoes are still poorly known although their instability could trigger large tsunamis along the southern italy coastal sectors our recommendation is that multiparamertic monitoring networks on pvc and periodic oceanic cruises should be put into action and further that a systematic evaluation of the tsunami hazard related to possible sliding phenomena on the flanks of the tyrrhenian seamounts should be performed

the climatology of small scale orographic precipitation over the olympic mountains patterns and processes the climatology of small scale patterns of mountain precipitation is poorly constrained yet important for applications ranging from natural hazard assessment to understanding the geologic evolution of mountain ranges synthesizing four rainy seasons of high resolution precipitation observations and mesoscale model output from the penn state ncar mm5 reveals a persistent small scale pattern of precipitation over the 10 km wide 800 m high ridges and valleys of the western olympic mountains washington state usa this pattern is characterized by a 50 70 excess accumulation over the ridge crests relative to the adjacent valleys in the annual mean while the model shows excellent skill in simulating these patterns at seasonal time scales major errors exist for individual storms investigation of a range of storm events has revealed the following mechanism for the climatological pattern regions of enhanced condensation of cloud water are produced by ascent in stable flow over the windward slopes of major ridges synoptically generated precipitation grows by collection within these clouds leading to enhanced precipitation which is advected by the prevailing winds instances of atypical patterns of precipitation suggest that under certain conditions during periods with a low freezing level or convective cells fundamental changes in small scale patterns may occur however case studies and composite analysis suggest that departures from the pattern of ridge top enhancement are rare the basic patterns and processes appear robust to changes in temperature winds and background rainfall rates copyright 2008 royal meteorological society

pressure drag and momentum fluxes due to the alps ii representation in large scale atmospheric models a three dimensional numerical model with interactive grid nesting is used to study the pressure drag and associated momentum fluxes due to the alpine complex for a specified upstream wind and static stability profile four basic questions are addressed which are relevant to the problems of flow description in the vicinity of mountains and the impact of orography in the context of mesoscale numerical weather prediction and general circulation models i what is the dependence of basic quantities such as the pressure drag on the model s horizontal resolution ii is there a need for non hydrostatic dynamics to account properly for the flow characteristics near steep mountains iii is there an effective role for enhanced orography such as an envelope formulation iv might a gravity wave drag parametrization scheme be able to represent adequately the highest resolution fluxes and surface drag in a much coarser resolution model a series of experiments with both hydrostatic and non hydrostatic models at resolutions of 80 40 20 10 and 5 km is analysed and two of these experiments are repeated with an envelope orography it is concluded that hydrostatic simulations are sufficient to describe the basic dynamics even at 5 km resolution however there is a strong dependence of the drag and momentum fluxes on resolution with the drag at 80 km resolution being almost half that at the highest resolution it is also shown that the use of an envelope orography at coarser resolutions can compensate significantly for the drag under estimation but is less effective in representing the vertical stress profiles or the direction of the stress vectors which are systematically in error at the coarsest resolution the potential role of gravity wave drag is confirmed and possible improvements considered it is suggested that both envelope orography and gravity wave drag may make a significant contribution until resolutions are as high as 10 to 20 km