microphysical structure of the marine boundary layer under strong wind and sea spray formation as seen from a 2d explicit microphysical model part iii parameterization of height dependent droplet size distribution abstractthis paper completes a series of studies using a 2d hybrid lagrangian eulerian model to investigate the effect of sea spray on the thermodynamics and microphysics of the hurricane mixed layer the evolution of the mixed layer was simulated by mimicking the motion of an air volume in a lagrangian sense toward a tropical cyclone eyewall along a background airflow during the radial motion sea surface temperature pressure background wind speed sea spray production rate and turbulence intensity were altered according to the available observations analysis of the interaction between the hurricane mixed layer and the upper layers in terms of entrainment heat and moisture fluxes gives a new insight into the role of sea spray in the thermodynamics and microphysics of the mixed layer the evaporation of sea spray leads to an increase in the relative humidity by 10 15 and to a decrease in temperature by about 1 1 5 k as compared to cases where sea spray is excluded sea spray leads to formation o

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

40ar 39ar and rbsr analyses from ductile shear zones from the atacama fault zone northern chile the age of deformation abstract the influence of deformation on the k ar and the rb sr isotope system is investigated it is assumed that due to the diffusion processes involved deformation has a similar effect on isotopic equilibrium as has temperature in order to examine the influence of deformation on the k ar and the rb sr isotope systems two shear zones from the atacama fault zone afz situated in the north chilean coastal cordillera have been investigated the afz which was active as a sinistral strike slip fault during the mesozoic has two sets of shear zones one formed under amphibolite sz1 one under greenschist facies conditions sz2 rb sr and 40ar 39ar age determinations were conducted on samples from cross sections of each set in sz1 the hornblendes and bioties from a weakly deformed sample reveal cooling ages of 153 152 and 150 1 ma respectively biotite from the center of the shear zone of sz1 gave an isochron of 143 9 0 3 ma mswd 0 04 which is interpreted as the age of deformation which produced resetting of the mineral system in sz2 hornblendes yielded 40ar 39ar plateau cooling ages of 138 ma biotites from undeformed samples gave rb sr and 40ar 39ar total degassing ages of 130 1 ma whereas biotite from the mylonitic rocks yielded 126 125 ma which dates the time of deformation sr isotope homogenization occurred in the mylonitic rocks and is most likely a result of deformation the formation of sz1 can be correlated to the araucanian nevadan phase the deformation in sz2 is related to the onset of uplift and cooling of the coastal cordilleran magmatic arc

an estimation of turbulent characteristics in the low level region of intense hurricanes allen 1980 and hugo 1989 this study analyzes the flight level data collected by research aircraft that penetrated the eyewalls of category 5 hurricane hugo 1989 and category 4 hurricane allen 1980 between 1 km and the sea surface estimates of turbulent momentum flux turbulent kinetic energy tke and vertical eddy diffusivity are obtained before and during the eyewall penetrations spatial scales of turbulent eddies are determined through a spectral analysis the turbulence parameters estimated for the eyewall penetration leg are found to be nearly an order of magnitude larger than those for the leg outside the eyewall at similar altitudes in the low level intense eyewall region the horizontal length scale of the dominant turbulent eddies is found to be between 500 and 3000 m and the corresponding vertical length scale is approximately 100 m the results suggest also that it is unwise to include eyewall vorticity maxima evm in the turbulence parameter estimation because the evms are likely to be quasi two dimensional vortex structures that are embedded within the three dimensional turbulence on the inside edge of the eyewall this studyis afirstattempt at estimatingthe characteristics of turbulent flow in the low leveltroposphereof an intense eyewall using in situ aircraft observations the authors believe that the results can offer useful guidance in numerical weather prediction efforts aimed at improving the forecast of hurricane intensity because of the small sample size analyzed in this study further analyses of the turbulent characteristics in the high wind region of hurricanes are imperative

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

analysis of long period seismic waves excited by the may 18 1980 eruption of mount st helens a terrestrial monopole long period 100 to 260 s love and rayleigh waves excited by the eruption of mount st helens on may 18 1980 and recorded by ida sro and asro stations were analyzed to determine the mechanism of the eruption the amplitude radiation patterns of both rayleigh and love waves are two lobed with a nodal direction in e5 s for rayleigh waves and in n5 e for love waves these radiation patterns preclude any double couple mechanism the radiation pattern the initial phase the relatively large amplitude ratio of love to rayleigh waves and the existence of clear nodes in the radiation patterns of fundamental mode and higher mode rayleigh waves suggest that the source is represented by an almost horizontal less than 15 from the horizontal single force pointed toward s5 w the surface wave spectra fall off very rapidly at periods shorter than 75 s suggesting a very slow source process although the details of the source time history could not be determined a smooth bell shaped time function f o s t 1 2 f o l cos t for 0 t 2 and f o s t 0 for t 2 with 75 s is considered appropriate on the basis of comparison between synthetic and observed seismograms and of the shape of the source spectrum the peak value of the force f 0 is about 10 18 dynes the tailing end of the source time function could not be resolved and some overshoot may be added the magnitude and the time history of the force can be explained by a northward landslide followed by a lateral blast observed at the time of the eruption two distinct events about 110 s apart can be identified on body wave and short period surface wave records the first event may correspond to the earthquake which triggered the landslide and the lateral blast the second event appears to correspond to a second large earthquake and explosion which took place about 2 minutes after the first earthquake

limitation of one dimensional ocean models for coupled hurricane ocean model forecasts abstract wind stress imposed on the upper ocean by a hurricane can limit the hurricane s intensity primarily through shear induced mixing of the upper ocean and subsequent cooling of the sea surface since shear induced mixing is a one dimensional process some recent studies suggest that coupling a one dimensional ocean model to a hurricane model may be sufficient for capturing the storm induced sea surface temperature cooling in the region providing heat energy to the hurricane using both a one dimensional and a three dimensional version of the same ocean model it is shown here that the neglect of upwelling which can only be captured by a three dimensional ocean model underestimates the storm core sea surface cooling for hurricanes translating at 5 m s 1 for hurricanes translating at 2 m s 1 more than half of the storm core sea surface cooling is neglected by the one dimensional ocean model since the majority of hurricanes in the western tropical north atlantic ocean translate at 5 m s 1 the

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

effects of large eddies on the structure of the marine boundary layer under strong wind conditions abstract a model of the atmospheric boundary layer bl is presented that explicitly calculates a two way interaction of the background flow and convective motions the model is utilized for investigation of the formation of large eddies roll vortices and their effects on the structure of the marine boundary layer under conditions resembling those of tropical cyclones it is shown that two main factors controlling the formation of large eddies are the magnitude of the background wind speed and air humidity determining the cloud formation and latent heat release when the wind speed is high enough a strong vertical wind shear develops in the lower part of the bl which triggers turbulent mixing and the formation of a mixed layer as a result the vertical profiles of velocity potential temperature and mixing ratio in the background flow are modified to allow for the development of large eddies via dynamic instability latent heat release in clouds was found to be the major energy source of large eddi

the characteristics of seismic signals produced by lahars and pyroclastic flows volcan de colima mexico abstract the general characteristics of seismic signals produced by pyroclastic flows generated by either the collapse of a lava dome or an eruptive column and lahars at volcan de colima mexico are discussed the paper concentrates on the 2004 2006 activity associated with and following the extrusion of andesitic block lava in october november 2004 it is shown that the duration of the broad band seismic records of pyroclastic flows lasts a few minutes while the duration of seismic records of lahars continues for tens of minutes or hours the spectra of seismic records produced by pyroclastic flows are characterized by lower peak frequencies around 3 4 hz than for lahars around 6 8 hz this difference in the frequency content together with the difference in the duration of seismic signals allows early diagnostic of the events in real time

why rolls are prevalent in the hurricane boundary layer recent remote sensing observations show that the hurricane boundary layer flow although energetic is not a region of homogeneous turbulence in fact the observations convincingly demonstrate that a large fraction of the turbulent flow in the regions away from the deep convective rainbands is highly organized into intense horizontal roll vortices that are approximately aligned with the mean wind and span the depth of the boundary layer these observations show that rolls strongly increase the flux of momentum between the underlying surface and the main body of the storm compared to an equivalent hurricane boundary layer flow without rolls the linear and nonlinear dynamics of hurricane boundary layer roll formation are outlined and it is shown why rolls are in fact the expected basic hurricane boundary layer state the model presented here explains the hurricane roll features currently documented in field programs and makes predictions that can be tested in future experiments the primary effects of rolls on the boundary layer fluxes are inherently nonlocal and nongradient and hence cannot be captured by standard downgradient turbulence parameterizations used in hurricane simulations however the nonlinear theory is the proper starting point for developing boundary layer parameterizations that include roll modification of the turbulent fluxes

why is the tropical cyclone boundary layer not well mixed abstractplausible diagnostics for the top of the tropical cyclone boundary layer include i the top of the layer of strong frictional inflow and ii the top of the well mixed layer that is the layer over which potential temperature is approximately constant observations show that these two candidate definitions give markedly different results in practice with the inflow layer being roughly twice the depth of the layer of nearly constant here the authors will present an analysis of the thermodynamics of the tropical cyclone boundary layer derived from an axisymmetric model the authors show that the marked dry static stability in the upper part of the inflow layer is due largely to diabatic effects the radial wind varies strongly with height and therefore so does radial advection of this process also stabilizes the boundary layer but to a lesser degree than diabatic effects the authors also show that this differential radial advection contributes to the observed superadiabatic layer ad

simulation and parameterization of the turbulent transport in the hurricane boundary layer by large eddies 1 hurricane boundary layer hbl processes especially the structure of the coherent large eddy circulations lecs and their induced vertical transport are not well understood this paper introduces a large eddy simulation les framework in a weather hindcasting mode developed from a multiple scale nested weather research and forecasting wrf model using the wrf les this study investigated the structure of the hbl lecs and the associated vertical transport during the landfall of hurricane ivan 2004 the simulation shows that the hbl lecs exist in a mean stable environment and consist of well defined updraft and downdraft statistically the hbl lecs are only slightly skewed with the updrafts and downdrafts relatively evenly distributed spatially the inversion base basically envelopes the upper boundary of lecs the trough in between two adjacent lecs is where most entrainment takes place whereas the crest of the lecs is where boundary layer air detrains out of the hbl in such a way lecs directly connect the surface the hbl and the main body of a hurricane vortex and enhance the exchange of energy moisture and momentum between them it is found that the current boundary layer schemes significantly underestimate the resolved turbulent fluxes due to the fact that the effects of lecs have not been included in the parameterizations on the basis of the statistical structure of lecs simulated by the wrf les this paper proposes a conceptual updraft downdraft model that can potentially be implemented in weather forecasting models to parameterize the fluxes induced by the hbl lec transport

helical circulations in the typhoon boundary layer 1 low level wind data from the wsr 88d in guam obtained in typhoon dale 1996 and typhoon keith 1997 are analyzed for coherent structures consistent with the results of previous studies of atlantic hurricanes velocity anomalies associated with coherent structures were found in the boundary layer of both storms a total of 99 cases of coherent structures also known as roll vortices were documented during a 6 h evaluation period for each storm storm relative roll location roll vorticity asymmetries in the upward and downward momentum fluxes and signatures of circulations transverse to the mean flow associated with roll circulations were explored the effects of terrain and convective precipitation systems such as rainbands on the occurrence of rolls were investigated the results support and extend prior findings of roll observations and can be used to help validate theoretical and numerical models of coherent structures within tropical cyclones moreover the wind variations documented in this study may have application for wave runup and wind damage potential in tropical cyclones

the source of explosive eruptions of sakurajima volcano japan to understand the nature of explosive eruptions in particular the role played by exsolution of magmatic gases we studied the seismic waveforms produced by two such eruptions of sakurajima volcano on october 30 and november 14 1986 an explosion begins when a mixture of magmatic gases and fragmented magma flows upward through a narrow vertical channel to the surface the source region is a reservoir of gas rich magma where the pressure drops as gases flow out the form of low frequency seismic waves can be explained by a source that consists of two components one component is a single force directed downward that represents the reaction to ejection of gas and magma the other more important component is a moment tensor that represents expansion or contraction of rock around a source the first motion of seismic waves produced by an explosion is directed away from the volcano tilt and strain measurements show that the initial motion directed outward is soon followed by subsidence around the volcano the eigenvectors of the seismic moment tensor are either nearly horizontal or vertical the ratio of horizontal to vertical eigenvalues was 1 8 1 for the october 30 explosion this suggests the geometry of the explosive source can be approximated as a buried vertical cylinder the volume of contraction 2 l03 m3 can be produced by a pressure change of 0 3 mpa over a cylinder with a radius of 160 m and a height of 300 m we propose that an explosive eruption occurs after a small shallow source of high pressure forms within a vertical conduit possibly exsolution of magmatic gases eventually the small source bursts and pushes open a pathway to the surface providing an upward escape for trapped gases it is this burst that causes the initial outwardly directed motion at the surface a deeper reservoir of gas rich magma is then subjected to a lower confining pressure and also bursts causing the explosion

observational estimates of the horizontal eddy diffusivity and mixing length in the low level region of intense hurricanes this study examines further the characteristics of turbulent flow in the low level region of intense hurricanes using in situ aircraft observations the data analyzed here are the flight level data collected by research aircraft that penetrated the eyewalls of category 5 hurricane hugo 1989 category 4 hurricane allen 1980 and category 5 hurricane david 1979 between 1 km and the sea surface estimates of horizontal eddy momentum flux horizontal eddy diffusivity and horizontal mixing length are obtained it is found that the horizontal momentum flux and horizontal diffusivity increase with increasing wind speed the horizontal mixing length increases slightly with wind speed also but the mixing length is not significantly dependent on the wind speed the magnitude of the horizontal momentum flux is found to be comparable to that of the vertical momentum flux indicating that horizontal mixing by turbulence becomes nonnegligible in the hurricane boundary layer especially in the eyewall region within the context of simple k theory the results suggest that the average horizontal eddy diffusivity and mixing length are approximately 1500 m 2 s 21 and 750 m respectively at about 500 m in the eyewall region corresponding to the mean wind speed of approximately 52 m s 21 it is recalled also that the mixing length is a virtual scale in numerical models and is quantitatively smaller than the energy containing scale of turbulent eddies the distinction between these two scales is a useful reminder for the modeling community on the representation of small scale turbulence in hurricanes

a user friendly one dimensional model for wet volcanic plumes 1 this paper presents a user friendly graphically based numerical model of one dimensional steady state homogeneous volcanic plumes that calculates and plots profiles of upward velocity plume density radius temperature and other parameters as a function of height the model considers effects of water condensation and ice formation on plume dynamics as well as the effect of water added to the plume at the vent atmospheric conditions may be specified through input parameters of constant lapse rates and relative humidity or by loading profiles of actual atmospheric soundings to illustrate the utility of the model we compare calculations with field based estimates of plume height 9 km and eruption rate 4 105 kg s during a brief tephra eruption at mount st helens on 8 march 2005 results show that the atmospheric conditions on that day boosted plume height by 1 3 km over that in a standard dry atmosphere although the eruption temperature was unknown model calculations most closely match the observations for a temperature that is below magmatic but above 100 c

infrasonic jet noise from volcanic eruptions 1 the lowermost section of a vulcanian or plinian volcanic eruption column may be thought of as a momentum driven turbulent free shear jet flow we propose that large amplitude and long duration infrasonic 20 hz signals recorded at ranges of tens of kilometers during powerful eruptions at mount st helens usa and tungurahua ecuador represent a low frequency form of jet noise a preliminary test of this hypothesis is made by comparing the observed infrasonic spectra to the empirically derived similarity spectra for pure air jets although the spectral shapes are in approximate agreement the observed volcanic signals have additional complexities not present in the pure air laboratory data these features may result from multiphase flow containing solid particles and liquid droplets very high temperatures and perhaps complex crater morphology however the overall similarity between the volcanic signals and jet noise indicates that broadband infrasound measurements at volcanoes may provide a quantitative link to eruption jet dynamics and would aid substantially in the remote assessment of volcanic hazard

spectral characteristics of turbulence in the hurricane boundary layer over the ocean between the outer rain bands spectra and cospectra of wind velocity potential temperature and humidity have been analysed using data collected in the atmospheric boundary layer in hurricanes fabian 2003 and isabel 2003 during the coupled boundary layer air sea transfer cblast hurricane experiment the spectra and cospectra are normalized following the surface layer scaling methods according to similarity theory it is found that the cblast data gathered in the mixed layer between the outer rain bands below 400 m can be grouped into well defined curves for spectra of wind velocity potential temperature and humidity and for cospectra of momentum and humidity flux however the cospectra of sensible heat flux do not exhibit well defined universal shape the cblast universal shape spectra and cospectra generally resemble the shapes of those from previous studies but shift to higher frequencies that correspond to smaller wavelengths of turbulent eddies that contain most of the energy this work highlights the structural difference between the hurricane boundary layer and the standard atmospheric boundary layer over land and ocean copyright 2010 royal meteorological society

characterization of the 2008 kasatochi and okmok eruptions using remote infrasound arrays 1 the 2008 plinian eruptions of kasatochi and okmok volcanoes were recorded by six remote international monitoring system infrasound arrays high amplitude infrasound at these stations combined with remote sensing permits insight into important volcanic source parameters such as origin times durations and source characteristics infrasound from the 7 8 august kasatochi eruption consists of three well defined eruption pulses with the first two steam rich and the last ash rich pulse 2 is the most energetic and impulsive okmok produced over 9 h of continuous infrasound on 12 13 july acoustic propagation modeling for the okmok eruption and first kasatochi pulse predict thermospheric ducting and origin times consistent with seismic and satellite observations however theoretical acoustic origin times of pulses 2 3 are predicted to occur 15 min earlier than the seismic stratospheric ducting for these later pulses provides more consistent origin times although both volcanoes ejected ash into the stratosphere 15 km kasatochi produced higher amplitude infrasound than okmok previous studies have shown sustained infrasound with frequencies 2000 km and does not seem to be appreciably affected by changes in ash content between the eruption pulses

volcanic plume height measured by seismic waves based on a mechanical model journal of geophysical research vol 116 b01306 doi 10 1029 2010jb007620 2011 volcanic plume height measured by seismic waves based on a mechanical model stephanie g prejean 1 and emily e brodsky 2 received 4 april 2010 revised 3 november 2010 accepted 23 november 2010 published 26 january 2011 1 in august 2008 an unmonitored largely unstudied aleutian volcano kasatochi erupted catastrophically here we use seismic data to infer the height of large eruptive columns such as those of kasatochi based on a combination of existing fluid and solid mechanical models in so doing we propose a connection between a common observable short period seismic wave amplitude to the physics of an eruptive column to construct a combined model we estimate the mass ejection rate of material from the vent on the basis of the plume height assuming that the height is controlled by thermal buoyancy for a continuous plume using the estimated mass ejection rate we then derive the equivalent vertical force on the earth through a momentum balance finally we calculate the far field surface waves resulting from the vertical force the model performs well for recent eruptions of kasatochi and augustine volcanoes if v the velocity of material exiting the vent is 120 230 m s 1 the consistency between the seismically inferred and measured plume heights indicates that in these cases the far field 1 s seismic energy radiated by fluctuating flow in the volcanic jet during the eruption is a useful indicator of overall mass ejection rates thus use of the model holds promise for characterizing eruptions and evaluating ash hazards to aircraft in real time on the basis of far field short period seismic data this study emphasizes the need for better measurements of eruptive plume heights and a more detailed understanding of the full spectrum of seismic energy radiated coeruptively citation prejean s g and e e brodsky 2011 volcanic plume height measured by seismic waves based on a mechanical model j geophys res 116 b01306 doi 10 1029 2010jb007620 1 introduction and motivation 2 empirical studies have suggested that the amplitude of high frequency or broadband seismic waves radiated during large volcanic eruptions generally scales with the height of an eruption column mcnutt 1994a however a direct calculation of the expected seismic wave amplitude based on physical models has not yet been successful connecting commonly observable data such as seismic wave amplitudes to a model of the flow in the eruptive jet would provide a new tool to test and improve our understanding of eruptive physics for instance small scale turbulence is thought to play a major role in the entrainment of hot particles and gases and hence the buoyancy of eruptive columns yet there are few measurements of the strength or distribution of small scale features in real eruptive columns andrews and gardner 2009 using seismic data to provide observational constraints on eruption column flow processes is particularly attractive as seismic data are often available even in remote u s geological survey alaska volcano observatory anchorage alaska usa department of earth and planetary sciences university of california santa cruz california usa copyright 2011 by the american geophysical union 0148 0227 11 2010jb007620 settings thus use of the seismic database would greatly increase the number and type of eruptions amenable to study 3 pragmatically a physical model connecting plume height and seismic data would allow the use of seismology as a remote sensing technology to infer volcanic plume height it would be a particularly useful tool for exploring eruption dynamics in remote environments where direct observation is not possible such as the volcanoes of the northern pacific ocean although many volcano observa tories worldwide are gradually replacing short period seismometers with broadband seismometers we still largely rely on short period instruments for forecasting monitoring and analyzing eruptions these realities motivate the development of the model described below 4 in this study we build on previous work to develop a physical model for the expected amplitude of seismic waves from an eruption that generates a plume of a given height as a cautionary note we explore the potential errors in this formulation and describe situations where the model is not applicable such as small eruptions or eruptions where most mass ejected is not entrained in the plume after reviewing previous work on coeruptive seismology and the char acteristics of the 2008 kasatochi and 2006 augustine eruptions we use the connection between plume height and b01306 1 of 13

an observational study of hurricane boundary layer small scale coherent structures abstract data with high temporal and spatial resolution from hurricanes isabel 2003 and frances 2004 were analyzed to provide a detailed study of near surface linear structures with subkilometer wavelengths of the hurricane boundary layer hbl the analysis showed that the features were omnipresent throughout the data collection displayed a horizontal and vertical coherency and maintained an average orientation of 7 left of the low level wind a unique objective wavelength analysis was conducted where wavelength was defined as the distance between two wind maxima or minima perpendicular to the features long axis and revealed that although wavelengths as large as 1400 m were observed the majority of the features had wavelengths between 200 and 650 m the assessed wavelengths differ from those documented in a recent observational study to evaluate the correlation between the features and the underlying near surface wind field time and spectral analyses were completed and ground relative freque

an observational case for the prevalence of roll vortices in the hurricane boundary layer abstract doppler velocity data from weather surveillance radar 1988 doppler wsr 88d radars during four hurricane landfalls are analyzed to investigate the presence of organized vortices in the hurricane boundary layer hbl the wavelength depth magnitude and track of velocity anomalies were compiled through analysis of doppler velocity data the analysis reveals alternating bands of enhanced and reduced azimuthal winds closely aligned with the mean wind direction resulting statistics provide compelling evidence for the presence of organized secondary circulations or boundary layer rolls across significant areas during four hurricane landfalls the results confirm previous observations of the presence of rolls in the hbl a potential limitation of the study presented here is the resolution of the wsr 88d data in particular analysis of higher resolution data e g from the doppler on wheels is needed to confirm that data aliasing has not unduly impacted the statistics reported here momentum flux

source parameters of the volcanic eruption earthquakes at mount tokachi hokkaido japan and a magma ascending model we estimate the source parameters of the eruption earthquakes observed at mount tokachi hokkaido japan in 1989 on the basis of the single force model by fitting the theoretical source spectra with the observed ones the peak amplitude of force and the source duration were estimated to be 10 7 10 10 n and 0 5 0 8 s respectively for the explosion earthquakes which have the largest magnitudes among the eruption earthquakes the peak amplitude of force is proportional to the square of source duration suggesting constant temperature inside the magma just beneath a crater for small eruption earthquakes which are small events accompanying weaker eruptions not explosive the source duration has a constant value independent of the peak amplitude of force this suggests that the temperature inside the magma is proportional to the square of radius of the magma body to give a physical explanation of the empirical relations of source parameters we present a magma ascending model as a source of eruption earthquakes a spherical batch of gas rich magma vertically migrates from a deep seated magma reservoir to the surface and is cooled by heat conduction when the magma reaches the ground surface it erupts and causes an eruption earthquake this model predicts that the ascending magma has a same temperature at the surface when the magma radius exceeds a critical magma radius cmr which is determined from the physical properties of the magma or volcano on the other hand when the magma radius is less than cmr the temperature increases with the radius the value of cmr for mount tokachi is estimated at about 10 m comparing the empirical relations derived from seismic analysis with the magma ascending model we conclude that the radius of an ascending batch of magma plays an important role in the generation of eruption earthquakes the magma batch whose radius is larger than cmr causes an explosion earthquake and the magma smaller than cmr causes a small eruption earthquake