observational analysis of a gust front to bore to solitary wave transition within an evolving nocturnal boundary layer abstract the evolution of a gust front to bore to solitary wave transition and comprehensive information on the evolving nocturnal boundary layer nbl associated with this change are described with analysis of radar and profiler measurements the observations were obtained on 21 june 2002 in the oklahoma panhandle during the international h2o project the evolution of this system from a strong bore initiated by a vigorous gust front to a solitary wave was observed over a 4 h period with doppler radar and surface measurements detailed information on the mature bore structure was obtained by a cluster of profiling instruments including two boundary layer wind profilers a lidar ceilometer and a microwave profiling radiometer a strong bore was initiated by an extensive gust front that perturbed an incipient nbl whose development prior to sunset was enhanced by shading from the parent mesoscale convective system at the time of bore formation the nbl was about 300 m deep and exhibited a surface t

the morning glory an extraordinary atmospheric undular bore summary observations made during an expedition in october 1980 to study morning glory wind squalfs in the gulf of carpentaria region of northern australia are described during a ten day period in burketown north queensland six squalls were documented on consecutive mornings 8 1 3 october including two moving from the south an apparently unusual direction the unique data gathered from the latter confirm that these have the same character as their north easterly counterparts that is they are undular bores the origin of southerly glories remains uncertain but at least in some cases appears to be linked with the northeast advance of a frontal trough across central australia while the data are equivocal it seems possible that the motion of the front into the developing nqcturnal inversion could generate waves or hydraulic type disturbances which run along the inversion layer ahead of the front as proposed by tepper 1950 the efficacy of such a mechanism is demonstrated by a simple laboratory experiment evidence is presented which suggests that morning glory type events occur elsewhere in the world sometimes as precursors to cold fronts observations in the gulf of carpentaria region show that they are effective triggers of deep convection when they advance into air with a sufficient degree of conditional instability

analysis of a lower tropospheric gravity wave train using direct and remote sensing measurement systems abstracton 10 august 2014 a gravity wave complex generated by convective outflow propagated across much of oklahoma the four dimensional evolution of the wave complex was analyzed using a synthesis of near surface and vertical observations from the oklahoma mesonet and atmospheric radiation measurement arm southern great plains networks two atmospheric emitted radiance interferometers aeri one located at the arm sgp central facility in lamont oklahoma and the other in norman oklahoma were used in concert with a doppler wind lidar dwl in norman to determine the vertical characteristics of the wave complex hydraulic theory was applied to the aeri derived observations to corroborate the observationally derived wave characteristics it was determined that a bore soliton wave packet initially formed when a density current interacted with a nocturnal surface based inversion and eventually propagated independently as the density current became diffuse the soliton propagated within an elevated invers

turbulent mixing processes in atmospheric bores and solitary waves deduced from profiling systems and numerical simulation abstract families of solitary waves solitons associated with two atmospheric bores on the same day were observed by an unprecedented number of ground based and airborne profiling systems during the international h2o project ihop in addition a very high resolution numerical weather prediction model initialized with real data was used with success to simulate one of the bores and the evolving soliton the predicted wave amplitude phase speed wavelength and structure compared well to these extraordinarily detailed observations the observations suggest that during the active phase when turbulent mixing was active which was prior to bore collapse the bores and waves vigorously mixed dry air from above a nocturnal boundary layer down to the surface refractivity computed from near surface radar observations showed pronounced decreases due to sudden drying during the passage of the bores in this phase but refractivity increases appeared during the period of bore collapse during both phases the

a new look at the super outbreak of tornadoes on 3 4 april 1974 abstract the outbreak of tornadoes from the mississippi river to just east of the appalachian mountains on 2 5 april 1974 is analyzed using conventional techniques and the pennsylvania state university national center for atmospheric research fifth generation mesoscale model mm5 the mm5 was run for 48 h using the ncep ncar reanalysis dataset for initial conditions it is suggested that the first damaging squall line within the storm of 2 5 april 1974 herein referred to as the super outbreak storm was initiated by updrafts associated with an undular bore the bore resulted from the forward advance of a pacific cold front into a stable air mass the second major squall line within the super outbreak storm which produced the strongest and most numerous tornadoes was directly connected with the lifting associated with a cold front aloft this second squall line was located along the farthest forward protrusion of a pacific cold front as it occluded with a lee trough dryline an important factor in the

morning glory wave clouds in oklahoma a case study abstract early in the morning on 9 june 1982 a system of traveling wave cloud lines passed over 0klahoma and in particular over the relatively dense mesonetwork of surface stations including the instrumented 444 m ktvy television tower operated by the u s national severe storms laboratory an analysis of the network and other data presented herein shows that in structure the associated disturbance was an internal undular bore propagating on a low level stable layer similar to morning glory type disturbances which are common at certain times of the year in parts of northern australia moreover the speed of propagation of the component bore waves is in broad agreement with theoretical calculations there is evidence that the disturbance emanated late the previous evening from an area of rapidly growing intense thunderstorms located more than 400 km north northwest of the surface mesonetwork possible mechanisms for generation are discussed but the data pertaining to genesis are insufficient to

structure of an atmospheric undular bore generated from colliding boundaries during cape abstract a case study of a sea breeze front originating from the east coast of florida colliding with a gust front moving toward the southeast is presented single and multi doppler radar analyses combined with serial balloon ascents suggest that the denser sea breeze flow undercut the cold pool behind the gust front and may have generated a westward propagating undular bore in addition another undular bore was generated by the collision and propagated eastward through the cape network the latter bore propagated upstream against the southeasterly flow behind the sea breeze front and was apparent as a narrow band 5 6 km wide of near zero radial velocities embedded within an overall flow that was positive as seen by the cp 4 doppler radar as the eastern bore propagated through the dual doppler lobe defined by the ncar cp 3 and cp 4 radars a detailed and unique wind synthesis revealed its three dimensional kinematic structure significant along bore variability was shown in the convergence and verti

an observational study of atmospheric bore formation from colliding density currents abstract observations from east central florida during the convection and precipitation electrification cape experiment are used to investigate the factors that influence atmospheric bore formation from colliding density currents ten cases involving the collision of a gust front with a sea breeze front are analyzed with doppler radar and sounding and surface mesonet data the gust fronts in these collisions were generally deeper denser and faster propagating than their sea breeze front counterparts seven of the 10 cases produced dual boundaries that moved away from each other in a relative sense after the collision post collision boundaries moving in the same direction and oriented similarly to the pre collision gust front occurred in all 10 cases they transported mass in the manner of a density current in six cases while the others behaved more like bores or bore density current hybrids as they were characterized by little or no mass transport similarity of gust front and sea breeze front prop

numerical simulation of thunderstorm outflow dynamics part i outflow sensitivity experiments and turbulence dynamics abstract in this first paper of a two part series a two dimensional numerical model is developed and used to investigate the dynamics of thunderstorm outflows by focusing only on the outflow and using essentially inviscid equations and high spatial resolution we are able to explicitly represent important physical processes such as turbulent mixing to simplify interpretation of the results the model atmosphere used in all experiments is calm and dry adiabatic this approach allows us to establish basic characteristics of modeled outflows in simple physical settings and provides a foundation for future studies using more realistic environments all simulated outflows are initialized by prescribing a controlled horizontal flux of cold air into the model domain through a lateral boundary in a series of sensitivity tests we examine three parameters of the cold air source region 1 the vertical temperature deficit profile 2 the magnitude of the temperature deficit and 3 the cold air depth by hol

3d scattering image of mt vesuvius in this article we apply a passive scattering imaging method derived from the method developed by nishigami 1991 to data from the coda of the local volcano tectonic vt earthquakes of mt vesuvius this method provides the space distribution of the strong scatterers together with a rough estimate of their strength in the development of our method we use a realistic raytracing calculated with a ray bending approach in the 3d velocity model of mt vesuvius structure obtained with travel time inversion the inversion procedure adopted for the scattering imaging in the present study is based on the conjugate gradient method cgm the volume under study is divided into cubic cells with different dimensions in a multiscale approach we obtain the best resolution 900 m cubic cell size in the central part of the volume under study roughly in a radius of 4 km centered in the crater within a depth of 5 km we analyzed the coda signals after filtering in two frequency bands the first centered at 12 hz and the second at 18 hz where most of the seismic energy is concentrated results show that most of the strong scatterers are located in the depth range between the surface and 3000 m below the sea level in correspondence with the crater axis where most of the seismicity occurs part of the scatterers are located in the zones characterized by the maximum velocity contrasts

the spectacular undular bore in iowa on 2 october 2007 a visually impressive undular bore moved across much of iowa on 2 october 2007 and video animations were captured by numerous webcams the bore was sampled very well by doppler radar at close range and also by the high density mesoscale network of surface stations in place over iowa and 1 min automated surface observing system asos surface data at des moines iowa radar and surface observations are presented along with a brief analysis of the structure of the bore

the history and economics of gold mining in china abstract as the largest producer of gold in the world china s gold reserves are spread across a number of orogenic belts that were constructed around ancient craton margins during various subduction collision cycles as well as within the cratonic interior along reactivated paleo sutures among the major gold deposits in china is the unique class of world s richest gold mines in the jiaodong peninsula in the eastern part of the north china craton with an overall endowment of 3000 tons following the dawn of metal in the third millennium bc in western china placer gold mining was soon in practice particularly during the xia shang and zhou dynasties during 1096 ad mining techniques were developed to dig underground tunnels and the earliest mineral processing technology was in place to pan gold from crushed rock ores however ancient china did not witness any major breakthrough in gold exploitation and production and the growth in the gold ownership was partly due to the silk road that enabled the sale of silk products and exquisite artifacts to the west in exchange of gold products in the modern times the proven reserves of gold resources in china have steadily increased from 4614 7 tons in 2005 up to 6864 79 tons in 2010 with a growth rate of 48 76 in the past ten years the rate of production increased by 70 launching china as the top producer of gold in the world in 2008 when the production reached 300 tons per year the gross industrial output of gold industry in china increased sharply from 20 82 billion yuan up to 229 29 billion yuan between 2000 and 2010 registering 9 times growth and breaking the world record a simultaneous hike in the proportion of gross value in gdp from 0 21 in 2003 up to 0 58 in 2010 is also recorded

an observational and modeling study of an atmospheric internal bore during name 2004 abstract observations from the 2004 north american monsoon experiment name have been used to identify an atmospheric internal bore that occurred over the gulf of california goc on 31 july 2004 this bore disturbance was identified at bahia kino along the northwest coast of mexico during the late evening of 31 july it was hypothesized to have originated from the interaction of a gravity current from a large mesoscale convective system mcs which formed along the western slopes of the sierra madre occidental during the afternoon and a surface stable layer that developed from a sea breeze circulation it is suggested that the bore s energy was trapped at low levels by an elevated stable layer the vertical structure and undular nature of the bore was initially identified from 915 mhz wind profiler data at bahia kino results show a series of waves along the bore s leading edge and turbulent mixing of air from above the stable layer to the surface on the downstream face of the leading undulation the

the influence of the rocky mountains on the 13 14 april 1986 severe weather outbreak part ii evolution of a prefrontal bore and its role in triggering a squall line abstract in this paper part ii of a series the evolution of a prefrontal bore on the leeside of the rockies and its subsequent propagation and initiation of convection farther downstream over eastern colorado and western nebraska are investigated the observational evidence for this sequence of events was obtained from combined analyses of high resolution goes satellite imagery and program for regional observing and forecasting services mesonetwork data over the colorado region for the severe weather event that occurred during 13 14 april 1986 a 2d nonhydrostatic numerical model is used to further understand the initiation of the bore and its ability to propagate farther downstream and trigger convection analysis of satellite imagery and mesonet data indicated that an internal bore ahead of a cold front a moderate downslope windstorm and a quasi stationary hydraulic jump were generated within a few hours along the iceslope as a pacific cold front and its attendant upper level jet streak advanced o

radiometer and profiler analysis of the effects of a bore and a solitary wave on the stability of the nocturnal boundary layer abstract this study uses data from a microwave profiling radiometer mpr along with 915 mhz wind profiler doppler radar and surface data to quantify the kinematic and thermodynamic effects of two wave features an undular bore and a soliton on the nocturnal boundary layer nbl at high temporal resolution both wave features passed directly over the mpr and the wind profiler allowing for detailed analyses the effects of the wave features on the convective environment are examined and convective initiation ci associated with the wave features is discussed the undular bore was illustrated well in doppler velocity data and profiler measurements indicated that it produced four wavelengths of upward and downward motion mpr derived time height sections of potential temperature and mixing ratio showed an increase in the depth of the stable boundary layer along with a decrease in stability partially associated with mixing of the nbl the soliton produced a temporary decrease in the depth of the nbl

the life cycle of an undular bore and its interaction with a shallow intense cold front abstract the evolution of an undular bore and its associated wind shift spawned by the passage of a shallow surface cold front over the southern great plains of the united states is examined using surface and remote sensing observations along with output from a high resolution numerical model simulation observations show that a separation between the wind shift and thermodynamic properties of the front was induced by the formation of a bore over south central kansas around 0200 utc 29 november 2006 by the time the front bore complex passed through lamont oklahoma approximately 4 h later the bore had reached its maximum intensity and its associated wind shift preceded the trailing baroclinic zone by 20 min within several hours the bore decayed and a cold frontal passage characterized by a wind shift coincident with thermodynamic properties was observed at okmulgee oklahoma thus a substantial transformation in both the structural and dynamical characteristics of the bore as well as its relations

structure of an internal bore and dissipating gravity current as revealed by raman lidar abstract detailed moisture observations from a ground based raman lidar and special radiosonde data of two disturbances associated with a dissipating gust front are presented a synthesis of the lidar data with conventional meteorological data in conjunction with theoretical calculations and comparison to laboratory studies leads to the conclusion that the disturbances seen in both the lidar and accompanying barograph data represent a weak gravity current and an associated undular bore the disturbances display excellent coherence over hundreds of kilometers upstream of the lidar site bore formation occurs at the leading edge of the gust front coincidentally with the rapid weakening of the gravity current analysis suggests that the bore was generated by the collapse of the gravity current into a stable nocturnal inversion layer and subsequently propagated along this wave guide at nearly twice the speed of the gravity current the raman lidar provided detailed measurements of the vertical structure o

a nonclassical cold front observed during cops 91 frontal structure and the process of severe storm initiation abstract this case study addresses the issue of gravity current and bore development at surface cold fronts and the role of these phenomena in the generation of severe frontal convection the event investigated occurred on 27 april 1991 during the cooperative oklahoma profiler studies 1991 field project the development of a bore from a gravity current like structure along a cold front the subsequent propagation of the bore ahead of the front on a low level inversion and the process of severe thunderstorm development along the front are revealed by a dense network of remote sensing and other special observations evidence for the gravity current and bore is strengthened by comparisons made between the synthesized observations and theory the bore developed after a nocturnal inversion which acted as a waveguide had become established the bore and gravity current were both evident as fine lines in the radar reflectivity displays a microscale envelope of enhanced water vapor with an embedded roll cl

radar and profiler analysis of colliding boundaries a case study abstract the kinematics of a head on collision between two gust fronts followed by a secondary collision between a third gust front and a bore generated by the initial collision are described using analyses of weather surveillance radar 1988 doppler wsr 88d and mobile integrated profiling system mips data each gust front involved in the initial collision exhibited a nearly north south orientation and an east west movement the eastward moving boundary was 2 c colder and moved 7 m s 1 faster than the westward moving boundary two dimensional wind retrievals reveal contrasting flows within each gravity current one exhibited a typical gravity current flow structure while the other assumed the form of a gravity wave current hybrid with multiple vortices atop the outflow one of the after collision boundaries exhibited multiple radar finelines resembling a solitary wave shortly after the collision about 1 h after the initial collision a vigorous gust front intersected the eastward moving bore severa

the morning glory of the gulf of carpentaria an atmospheric undular bore abstract this paper presents the results of a field expedition mounted in late september early october 1979 to investigate the structure and origin of the morning glory of the gulf of carpentaria in northern australia the morning glory is a line wind squall accompanied by a pressure jump and often by a long roll cloud or series of such clouds it frequently occurs in the early morning especially in october in the gulf area a light aircraft fitted with a temperature and humidity probe was flown in two glories to determine their thermodynamic structure and wind fields wore obtained principally by tracking pilot balloons using the double theodolite method data also were obtained from a network of surface stations recording wind velocity and pressure installed at locations across cape york peninsula which is believed to be the area of genesis the morning glory is identified as an internal undular bore propagating on the nocturnal and or maritime inversion its origin appears to lie frequently

the generation of the morning glory abstract a high resolution cloud model is used to explore in detail the generation of the morning glory a low level nonlinear atmospheric internal wave observed on the southwestern side of cape york peninsula australia the model is two dimensional and nonhydrostatic and simulates an east west cross section of the southern part of cape york peninsula at a horizontal resolution of 200 m most of the numerical experiments are initialized at sunrise with a 5 m s 1 easterly flow and a sounding taken upstream from the peninsula the sea breezes that develop over cape york peninsula are highly asymmetric with the east coast sea breeze being both deeper and warmer than its western counterpart when the sea breezes meet the east coast sea breeze rides over that from the west coast and in the process produces a series of waves that propagate on the west coast sea breeze the model calculations show that when the phase speed of these waves matches the westward propagation speed of the east coast sea breeze the

the formation of internal bores in the atmosphere a laboratory model summary recently several atmospheric observations have been interpreted as internal undular bores or internal solitary waves evolving from internal bores that propagate along low level temperature inversions it has been speculated that such disturbances are generated by some type of gravity current such as cold fronts sea breeze fronts and thunderstorm outflows interacting with an existing temperature inversion in this paper we describe a systematic laboratory study in a water channel of internal bores and their generation by the movement of gravity currents through a two layer model of the atmosphere we compare the results of our laboratory experiments with previous theories and numerical simulations and with several detailed atmospheric observations of internal bores at different stages of development