detection of potential fields source boundaries by enhanced horizontal derivative method a high resolution method to image the horizontal boundaries of gravity and magnetic sources is presented the enhanced horizontal derivative ehd method the ehd is formed by taking the horizontal derivative of a sum of vertical derivatives of increasing order the location of ehd maxima is used to outline the source boundaries while for gravity anomalies the method can be applied immediately magnetic anomalies should be previously reduced to the pole we found that working on reduced to the pole magnetic anomalies leads to better results than those obtainable by working on magnetic anomalies in dipolar form even when the magnetization direction parameters are not well estimated this is confirmed also for other popular methods used to estimate the horizontal location of potential fields source boundaries the ehd method is highly flexible and different conditions of signal to noise ratios and depths to source can be treated by an appropriate selection of the terms of the summation a strategy to perform high order vertical derivatives is also suggested this involves both frequency and space domain transformations and gives more stable results than the usual fourier method the high resolution of the ehd method is demonstrated on a number of synthetic gravity and magnetic fields due to isolated as well as to interfering deep seated prismatic sources the resolving power of this method was tested also by comparing the results with those obtained by another high resolution method based on the analytic signal the success of the ehd method in the definition of the source boundary is due to the fact that it conveys efficiently all the different boundary information contained in any single term of the sum application to a magnetic data set of a volcanic area in southern italy helped to define the probable boundaries of a calderic collapse marked by a number of magmatic intrusions previous interpretations of gravity and magnetic fields suggested a subcircular shape for this caldera the boundaries of which are imaged with better detail using the ehd method

the effect of relative flow on the asymmetric structure in the interior of hurricanes abstract asymmetric structure of tropical cyclones simulated by the geophysical fluid dynamics laboratory high resolution triply nested movable mesh hurricane model was analyzed emphasis was placed on the quasi steady component of the asymmetric structure in the region of the eyewall it was found that the asymmetry was primarily caused by the relative wind that is the flow entering and leaving the storm region relative to the moving storm a set of idealized numerical experiments was first performed both with a constant and a variable coriolis parameter f and the addition of basic flows that were either constant or sheared with height analysis was then made for one case of hurricane gilbert 1988 to demonstrate that the quasi steady asymmetric structure analyzed in the idealized studies could be identified in this real data case vorticity analysis in the variable f experiment indicated that quasi steady asymmetries resulted in the eyewall region through the effect of vorticity advection due to

hurricane vortex dynamics during atlantic extratropical transition abstract simulations of six atlantic hurricanes are diagnosed to understand the behavior of realistic vortices in varying environments during the process of extratropical transition et the simulations were performed in real time using the advanced research weather research and forecasting wrf model arw using a moving storm centered nest of either 4 or 1 33 km grid spacing the six simulations ranging from 45 to 96 h in length provide realistic evolution of asymmetric precipitation structures implying control by the synoptic scale primarily through the vertical wind shear the authors find that as expected the magnitude of the vortex tilt increases with increasing shear but it is not until the shear approaches 20 m s 1 that the total vortex circulation decreases furthermore the total vertical mass flux is proportional to the shear for shears less than about 20 25 m s 1 and therefore maximizes not in the tropical phase but rather during et this has important implications for predictin

effects of parameterized boundary layer structure on hurricane rapid intensification in shear abstractthis study investigates the role of the parameterized boundary layer structure in hurricane intensity change using two retrospective hwrf forecasts of hurricane earl 2010 in which the ver

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

isentropic analysis on the intensification of hurricane edouard 2014 abstractan isentropic analysis technique is adopted in this study to investigate the intensification of hurricane edouard 2014 predicted by an experimental real time convection permitting hurricane analysis and forecast system this technique separates the vertical mass transport in terms of equivalent potential temperature e for the rising air parcels at high entropy from the subsiding air at low entropy it is found that as edouard intensifies the vertical circulation becomes wider via the expansion of upward downward mass flux to higher lower e in the early developing stages the asymmetric convection dominates the vertical circulation and leads to a remarkable upward mass flux maximum center in the upper troposphere when edouard becomes intense the axisymmetric convection becomes important to the upper level vertical mass transport while the asymmetric convection still dominates the low level vertical mass transport development of the warm core in the eye leads to double maxima along the

how does the eye warm part ii sensitivity to vertical wind shear and a trajectory analysis abstractin part ii of this study idealized simulations of tropical cyclones are used to investigate the influence of vertical wind shear on the structure of warming and descent in the eye results are compared with the no shear simulation that was analyzed in part i during intensification of a tropical cyclone in a quiescent environment time averaged eye descent is maximized at 12 13 km height warming is not generally maximized at these levels however because the static stability is at a minimum consequently the perturbation temperature is maximized at midlevels each of the above results remains valid for sheared tropical cyclones and therefore shear does not systematically alter the height of the warm core an analysis of over 90 000 parcel trajectories yields further insight into the mechanisms of eye warming and addresses several outstanding questions regarding the character of eye descent the rate at which parcels are stirred from the eye into the eyewall is a strong function of intensity w

demonstration of two pulses of paleogene deformation in the andes of peru abstract new radiometric ages of about 25 m y on volcanic materials in a marine intercalation within clastic continental strata of the upper moquegua formation near caraveli southern peru together with an age of 25 3 0 4 m y obtained by tosdal et al from a locality about 300 km to the ese show that the formation contains strata of late oligocene as well as miocene age and demonstrate that the coastal region was at a low elevation during latest oligocene time because the unconformities between the upper moquegua formation and the underlying lower moquegua formation and between the lower moquegua formation and underlying paleocene rocks cannot both represent the same tectonic event two discrete paleogene events must be present in the andes of peru although the exact timing of these events is uncertain the unconformities are likely to be of paleocene and middle eocene age or possibly of middle eocene and oligocene age

thermodynamic and kinematic influences on precipitation symmetry in sheared tropical cyclones bertha and cristobal 2014 abstractprior studies have shown an association between symmetrically distributed precipitation and tropical cyclone tc intensification although environmental vertical wind shear typically forces an asymmetric precipitation distribution in tcs the magnitude of this asymmetry can exhibit considerable variability even among tcs that experience similar shear magnitudes this observational study examines the thermodynamic and kinematic influences on precipitation symmetry in two such cases bertha and cristobal 2014 consistent with the impact of the shear both tcs exhibited a tilted vortex as well as a pronounced azimuthal asymmetry with the maximum precipitation occurring in the downshear left quadrant however bertha was characterized by more symmetrically distributed precipitation and relatively modest vertical motions while cristobal was characterized by more azimuthally confined precipitation and much more vigorous vertical motions observations showed three potential hindrances to precipitat

an idealized numerical study of shear relative low level mean flow on tropical cyclone intensity and size abstractgiven comparable background vertical wind shear vws magnitudes the initially imposed shear relative low level mean flow lmf is hypothesized to modify the structure and convective featu

secondary circulation of tropical cyclones in vertical wind shear lagrangian diagnostic and pathways of environmental interaction abstractthis study introduces a lagrangian diagnostic of the secondary circulation of tropical cyclones tcs here defined by those trajectories that contribute to latent heat release in the region of high inertial stability of the tc core this definition accounts for prominent asymmetries and transient flow features trajectories are mapped from the three dimensional physical space to the two dimensional entropy temperature space the mass flux vector in this space subsumes the thermodynamic characteristics of the secondary circulation the lagrangian diagnostic is then employed to further analyze the impact of vertical wind shear on tcs in previously published idealized numerical experiments one focus of this analysis is the classification and quantitative depiction of different pathways of environmental interaction based on thermodynamic properties of trajectories at initial and end times confirming results from previous work vertical shear significantly increases the intrusion of low equivalent

potential vorticity diagnosis of a simulated hurricane part ii quasi balanced contributions to forced secondary circulations although the forced secondary circulations fscs associated with hurricane like vortices have been previously examined understanding is still limited to idealized axisymmetric flows and forcing functions in this study the individual contributions of latent heating frictional and dry dynamical processes to the fscs of a hurricane vortex are separated in order to examine how a hurricane can intensify against the destructive action of vertical shear and how a warm cored eye forms this is achieved by applying a potential vorticity pv inversion and quasi balanced omega equations system to a cloud resolving simulation of hurricane andrew 1992 during its mature stage with the finest grid size of 6 km it is shown that the latent heating fsc tilting outward with height acts to oppose the shear forced vertical tilt of the storm and part of the upward mass fluxes near the top of the eyewall is detrained inward causing the convergence aloft and subsidence warming in the hurricane eye the friction fsc is similar to that of the ekman pumping with its peak upward motion occurring near the top of the planetary boundary layer pbl in the eye about 40 of the pbl convergence is related to surface friction and the rest to latent heating in the eyewall in contrast the dry dynamical forcing is determined by vertical shear and system relative flow when an axisymmetric balanced vortex is subjected to westerly shear a deep countershear fsc appears across the inner core region with the rising sinking motion downshear upshear and easterly sheared horizontal flows in the vertical the shear fsc is shown to reduce the destructive roles of the large scale shear imposed as much as 40 including its forced vertical tilt moreover the shear fsc intensity is near linearly proportional to the shear magnitude and the wavenumber 1 vertical motion asymmetry can be considered as the integrated effects of the shear fscs from all the tropospheric layers the shear fsc can be attributed to the laplacian of thermal advection and the temporal and spatial variations of centrifugal force in the quasi balanced omega equation and confirms the previous finding of the development of wavenumber 1 cloud asymmetries in hurricanes hurricane eye dynamics are presented by synthesizing the latent heating fsc with previous studies the authors propose to separate the eye formation from maintenance processes the upper level inward mass detrainment forces the subsidence warming and the formation of an eye the surface pressure fall and increased rotation in the eyewall this increased rotation will induce an additional vertical pressure gradient force to balance the net buoyancy generated by the subsidence warming for the maintenance of the hurricane eye in this sense the negative vertical shear in tangential wind in the eyewall should be considered as being forced by the subsidence warming and maintained by the rotation in the eyewall

symmetric instability in the outflow layer of a major hurricane abstracta set of 327 dropsondes from the noaa g iv aircraft was used to create a composite analysis of the azimuthally averaged absolute angular momentum in the outflow layer of major hurricane ivan 2004 inertial instability existed over a narrow layer in the upper troposphere between the 350 and 450 km radii isolines of potential and equivalent potential temperature showed that the conditions for both dry and moist symmetric instability were satisfied in the same region but over a deeper layer from 9 to 12 km the radial flow maximized at the outer edge of the unstable region the symmetrically unstable state existed above a region of outward decrease of temperature between the cirrus overcast of the storm and clear air outside it is hypothesized that the temperature gradient was created as a result of longwave heating within the cirrus overcast and longwave cooling outside the cloudy region this produced isentropes that sloped upward with radius in the same region that absolute momentum surfaces

a statistical perspective on wind profiles and vertical wind shear in tropical cyclone environments of the northern hemisphere abstracta statistical analysis of tropical cyclone tc environmental wind profiles is conducted in order to better understand how vertical wind shear influences tc intensity change the wind profiles are computed from global atmospheric reanalyses around the best track locations of 7554 tc cases in the northern hemisphere tropics mean wind profiles within each basin exhibit significant differences in the magnitude and direction of vertical wind shear comparisons between tc environments and randomly selected non tc environments highlight the synoptic regimes that support tcs in each basin which are often characterized by weaker deep layer shear because weaker deep layer shear may not be the only aspect of the environmental flow that makes a tc environment more favorable for tcs two new parameters are developed to describe the height and depth of vertical shear distributions of these parameters indicate that in both tc and non tc environments vertical shear most frequently occurs in shallow layer

effects of vertical wind shear on the intensity and structure of numerically simulated hurricanes a series of numerical simulations of tropical cyclones in idealized large scale environments is performed to examine the effects of vertical wind shear on the structure and intensity of hurricanes the simulations are performed using the nonhydrostatic pennsylvania state university national center for atmospheric research fifth generation mesoscale model using a 5 km fine mesh and fully explicit representation of moist processes when large scale vertical shears are applied to mature tropical cyclones the storms quickly develop wavenumber one asymmetries with upward motion and rainfall concentrated on the left side of the shear vector looking downshear in agreement with earlier studies the asymmetries develop due to the storm s response to imbalances caused by the shear the storms in shear weaken with time and eventually reach an approximate steady state intensity that is well below their theoretical maximum potential intensity as expected the magnitude of the weakening increases with increasing shear all of the storms experience time lags between the imposition of the large scale shear and the resulting rise in the minimum central pressure while the lag is at most a few hours when the storm is placed in very strong 15 m s21 shear storms in weaker shears experience much longer lag times with th e5ms 21 shear case showing no signs of weakening until more than 36 h after the shear is applied these lags suggest that the storm intensity is to some degree predictable from observations of largescale shear changes in all cases both the development of the asymmetries in core structure and the subsequent weakening of the storm occur before any resolvable tilt of the storm s vertical axis occurs it is hypothesized that the weakening of the storm occurs via the following sequence of events first the shear causes the structure of the eyewall region to become highly asymmetric throughout the depth of the storm second the asymmetries in the upper troposphere where the storm circulation is weaker become sufficiently strong that air with high values of potential vorticity and equivalent potential temperature are mixed outward rather than into the eye this allows the shear to ventilate the eye resulting in a loss of the warm core at upper levels which causes the central pressure to rise weakening the entire storm the maximum potential vorticity becomes concentrated in saturated portions of the eyewall cloud aloft rather than in the eye third the asymmetric features at upper levels are advected by the shear causing the upper portions of the vortex to tilt approximately downshear the storm weakens from the top down reaching an approximate steady state intensity when the ventilated layer can descend no farther due to the increasing strength and stability of the vortex at lower levels

a lagrangian trajectory view on transport and mixing processes between the eye eyewall and environment using a high resolution simulation of hurricane bonnie 1998 the transport and mixing characteristics of a large sample of air parcels within a mature and vertically sheared hurricane vortex are examined data from a high resolution 2 km horizontal grid spacing numerical simulation of real case hurricane bonnie 1998 are used to calculate lagrangian trajectories of air parcels in various subdomains of the hurricane namely the eye eyewall and near environment to study the degree of interaction transport and mixing between these subdomains it is found that 1 there is transport and mixing from the low level eye to the eyewall that carries air possessing relatively high values of equivalent potential temperature e which can enhance the efficiency of the hurricane heat engine 2 a portion of the low level inflow of the hurricane bypasses the eyewall to enter the eye and this air both replaces the mass of the low level eye and lingers for a sufficient time order 1 h to acquire enhanced entropy characteristics through interaction with the ocean beneath the eye 3 air in the mid to upper level eye is exchanged with the eyewall such that more than half the air of the eye is exchanged i n5hi nthis case of a sheared hurricane and 4 that one fifth of the mass in the eyewall at a height of 5 km has an origin in the mid to upper level environment where e is much less than in the eyewall which ventilates the ensemble average eyewall e by about 1 k implications of these findings for the problem of hurricane intensity forecasting are briefly discussed

the effects of vertical wind shear on the distribution of convection in tropical cyclones abstract the influence of vertical wind shear on the azimuthal distribution of cloud to ground lightning in tropical cyclones was examined using flash locations from the national lightning detection network the study covers 35 atlantic basin tropical cyclones from 1985 99 while they were over land and within 400 km of the coast over water a strong correlation was found between the azimuthal distribution of flashes and the direction of the vertical wind shear in the environment when the magnitude of the vertical shear exceeded 5 m s 1 more than 90 of flashes occurred downshear in both the storm core defined as the inner 100 km and the outer band region r 100 300 km a slight preference for downshear left occurred in the storm core and a strong preference for downshear right in the outer rainbands the results were valid both over land and water and for depression storm and hurricane stages it is argued that in convectively active tropical cyclones deep divergent circulations oppose the ver

low wavenumber structure and evolution of the hurricane inner core observed by airborne dual doppler radar abstract the asymmetric dynamics of the hurricane inner core region is examined through a novel analysis of high temporal resolution three dimensional wind fields derived from airborne dual doppler radar seven consecutive composites of hurricane olivia s 1994 wind field with 30 min time resolution depict a weakening storm undergoing substantial structural changes the symmetric and asymmetric mechanisms involved in this transformation are considered separately to zeroth order the weakening of the primary circulation is consistent with the axisymmetric vortex spindown theory of eliassen and lystad for a neutrally stratified atmosphere vertical shear however increased dramatically during the observation period leading to a strong projection of the convection onto an azimuthal wavenumber 1 pattern oriented along the maximum vertical shear vector recent theoretical ideas elucidating the dynamics of vortices in vertical shear are used to help explain this asymmetry the role of asymmetric vorticity d