dryline on 19 june 2002 during ihop part i airborne doppler and leandre ii analyses of the thin line structure and convection initiation the evolution and finescale structure of a dryline that initiated a line of thunderstorms is presented both the along line variability and mean vertical structure were examined using data collected by an airborne doppler radar and a water vapor differential absorption lidar dial the initiation of convection appeared to result from the diurnally induced easterly flow in the maritime air east of the dryline that typically develops late in the day this flow increased the low level convergence and allowed rising parcels of air to reach the level of free convection the along line variability was largely attributed to numerous misocyclones distorting the thin line of radar reflectivity by advecting dry moist air across the dryline south north of the misocyclone the misocyclones also influenced the location of the updrafts with most of the peak values positioned north of the circulations as a result these updrafts were fortuitously positioned in regions of high mixing ratio where the first convective cells initiated

the origin of a severe thunderstorm in kansas on 10 may 1985 abstract this study of the oklahoma kansas area on 10 may 1985 undertakes to explain why severe convection developed in only a small portion of northwestern kansas despite large potential instability for surface air over the entire region and despite the approach of a mobile upper level trough from the southwest special soundings from the o k prf storm program showed that a persistent thermodynamic lid above the warm moist surface boundary layer separated this layer from the middle and upper troposphere in which the instability could be realized and was almost completely effective in suppressing deep convection only one of the soundings with these characteristics showed temporary removal of this lid and the only convective storm developed near the place and time of this removal this coincidence points to removal as the likely although not certain cause isentropic trajectories showed that adiabatic lifting was the cause and that this lift was part of a series of mesoscale waves with wavelengths of

a dryline in southeast wyoming part i multiscale analysis using observations and modeling on 22 june 2010 abstracta first observational and modeling study of a dryline and associated initiation of deep convection over the high plains of southeastern wyoming is presented radar and station measurements show that the dryline is a well defined convergent humidity boundary with a modest density i e buoyancy gradient its development intensity and movement are regulated by the terrain diurnal land surface and boundary layer processes and synoptic scale evolution at least one of the thunderstorms that emerged from the dryline became severe weather research and forecasting model wrf simulations accurately reproduce measured aspects of this dryline as well as the timing and location of convection initiation the wrf output is used further to characterize the dryline vertical and horizontal structures and to examine convection initiation processes a dryline bulge over a local terrain ridge appears to be an essential ingredient in convection initiation on this day just north of this bulge the surface con

finescale vertical structure and dynamics of some dryline boundaries observed in ihop abstract several radar fine lines all with a humidity contrast were sampled in the central great plains during the 2002 international h2o project ihop this study primarily uses aircraft and airborne millimeter wave radar observations to dynamically interpret the presence and vertical structure of these fine lines as they formed within the well developed convective boundary layer in all cases the fine line represents a boundary layer convergence zone this convergence sustains a sharp contrast in humidity and usually in potential temperature across the fine line the key question addressed herein is whether at the scale examined here 10 km the airmass contrast itself in particular the horizontal density virtual potential temperature difference and resulting solenoidal circulation is responsible for the sustained convergence and the radar fine line for the 10 cases examined herein the answer is affirmative

the evolution of an oklahoma dryline part i a meso and subsynoptic scale analysis abstract a study is made of the 8 june 1974 oklahoma dryline and tornado outbreak case using data synthesis 1 to fit existing concepts on dryline structure and behavior to this case and 2 to identify processes contributing to moisture convergence along the dryline the dryline undergoes a major transformation in structure from sloped to slopeless during the day as implied from mesoscale 10 100 km and subsynoptic scale 100 1000 km analysis of virtual potential temperature fields mesoscale examination of dryline movement reveals the presence of wavelike perturbations which propagate along the dryline irregardless of its slope and contribute more to its eastward progression than does the downward slope of the terrain all but one of 22 tornadoes reported in oklahoma on this date were associated with thunderstorms that formed within a subsynoptic moisture convergence region at the dryline in central oklahoma results indicate a downward transport of southwesterly momentum through a well develope

the triple point on 24 may 2002 during ihop part i airborne doppler and lase analyses of the frontal boundaries and convection initiation an analysis of the initiation of deep convection near the triple point between a cold front and dryline is presented high spatial resolution doppler wind syntheses combined with vertical cross sections of mixing ratio q and aerosol scattering ratio retrieved from a lidar flying over the triple point provide an unprecedented view of the initiation process the doppler wind synthesis revealed variability along the dryline similar to the precipitation core gap structure documented for oceanic cold fronts vertical cross sections through the dryline suggest a density current like structure with the hot and dry air being forced up and over the moist air double thin lines associated with moisture gradients were also resolved the vertical profile of retrieved q approximately perpendicular to the dryline showed a pronounced jump in the depth of the moisture layer across the triple point analyses of dropsonde data show the existence of virtual potential temperature v gradients across the cold front and the dryline although the vertical velocity was strong at the triple point deep convection initiated 50 km to the east the location where convection first developed was characterized by a prominent aerosol and moisture plume reduced static stability and the largest potential instability an internal gravity wave may have provided the lift to initiate convection

airborne pseudo dual doppler analysis of a dryline outflow boundary intersection abstract on 3 june 1995 as part of the verification of the origins of rotation in tornadoes experiment vortex the electra doppler radar eldora onboard the national center for atmospheric research ncar electra aircraft made possible a high resolution examination of clear air motions in the texas panhandle in and around the intersection of the dryline and a surface baroclinic boundary a location commonly referred to as the triple point the eldora observations as well as conclusions drawn from analyses of these data are presented and discussed a transverse secondary circulation associated with the dryline is visualized through analyses of the eldora data typical values of rising and sinking air are found to be 2 m s 1 and 2 3 m s 1 respectively these vertical velocities are approximately the same as those indicated by in situ data collected onboard the electra because the maximum in rising motion is found at the western edge of the dewpoint gradient and because the low level relative airfl

a magnitude attenuation function derived for the 2014 pisagua chile sequence using strong motion data in this note we derive an attenuation function for computing magnitude values equivalent to m w using strong motion data we analyze 106 earthquakes of the 1 april 2014 m w 8 1 pisagua sequence which occurred along the 1877 seismic gap in northern chile we considered both foreshocks and aftershocks with moment magnitude available from moment tensor inversion in the geofon bulletin and recorded by the integrated plate boundary observatory chile strong motion network the maximum peak displacement measured over the double integrated traces is used to construct the magnitude scale following a nonparametric approach a bootstrap analysis is performed to assess the uncertainty of the model parameters and cross validation tests are performed to proof the suitability of the derived model in predicting the m w in the analyzed area with an uncertainty of 0 2 magnitude units the derived scale is applied to an early aftershock which occurred about 155 s after the mainshock initially missed in bulletins published by rapid global earthquake monitoring agencies e g national earthquake information center and geofon because its phase arrivals at regional teleseismic distances mix with those of the mainshock and its later arrivals the estimated magnitude equivalent to m w is 6 6 0 3 which rank this event as the second largest aftershock of the sequence after the m w 7 6 earthquake that occurred on 3 april 2014

airborne doppler radar analysis of supercells during cops 91 abstract on 26 may 1991 noaa p 3 airborne doppler radar data were collected near two tornadic supercells in the southern plains during the cooperative oklahoma profiler studies cops 91 field program the 3 cm radar mounted in the tail of the aircraft was operated using the fore aft scanning technique fast both storms were sampled just minutes after each had produced a tornado the cops 91 storms are the first tornadic supercells to be sampled extensively by airborne doppler radar using the fast methodology pseudo dual doppler analyses of a dissipating storm in southwest kansas show no remaining low level circulation even though the storm had just produced a tornado the analyses of a storm in northwest oklahoma reveal better defined features in the wind field near the surface in contrast to what has been previously observed in post tornadic supercells the cyclonic vorticity in both storms was greater aloft than at low levels the 26 may 1991 storms provide further evidence that supercells often

a dryline in southeast wyoming part ii airborne in situ and raman lidar observations part i of this study describes the mesoscale structure of a dryline over southeastern wyoming this dryline formed just east of the western rim of the high plains on 22 june 2010 and became more defined as it progressedeastwardduringtheafternoon partialsodescribesthenumericallysimulatedstructureandevolution of this dryline and the observed initiation of deep convection in the vicinity of the dryline an instrumented aircraft the university of wyoming king air repeatedly flew across this dryline mostly low enough to penetrate the moist air wedge east of the dryline flight level in situ data along these low level penetrations indicate relatively high values of convective available potential energy cape 1500jkg 21 yet low convective inhibition within a few kilometers of the dryline water vapor transects obtained from a compact nadir pointing raman lidar aboard the aircraft reveal an extremely sharp humidity gradient below flight level along the dryline coinciding with the fineline seen in operational weather radar base reflectivity imagery theyalsorevealseveralplumesofhigher specifichumiditywithinthedryelevatedmixedlayerabovethemoistair wedge possibly precursors of cumulus clouds the vertical structure of the dryline revealed by raman lidar and the flight level data correspond well to that in the high resolution numerical simulation

kinematic and moisture characteristics of a nonprecipitating cold front observed during ihop part i across front structures abstract a wide array of ground based and airborne instrumentation is used to examine the kinematic and moisture characteristics of a nonprecipitating cold front observed in west central kansas on 10 june 2002 during the international h2o project ihop this study the first of two parts is focused on describing structures in the across front dimension coarsely resolved observations from the operational network and dropsondes deployed over a 200 km distance centered on the front are combined with higher resolution observations from in situ sensors doppler radars a microwave radiometer and a differential absorption lidar that were collected across a 40 km swath that straddled a 100 km segment of the front the northeast southwest oriented cold front moved toward the southeast at 8 10 m s 1 during the morning hours but its motion slowed to less than 1 m s 1 in the afternoon in the early afternoon the cold front separated cool air with a northerly component flow of 2 4 m s 1 from a 10 km wide ban

the relationship of coal optical fabrics to alleghanian tectonic deformation in the central appalachian fold and thrust belt pennsylvania vitrinite in coal is optically anisotropic in reflected light owing to a preferred orientation of its component molecular structure such reflectance fabrics can under some circumstances provide a record of stress and strain events occurring during coal metamorphism based upon observed differences in the orientation and shape of vitrinite reflectance indicatrices vris differing tectonic histories are suggested for three regions within the bituminous and anthracite coal fields of the northern appalachian coal basin pennsylvania vris of coals from the north central fields on the allegheny plateau have oblate geometries similar to those of most coals worldwide indicative of only mild tectonic deformation maximum reflectance orientations for north central field coals are polymodal and aligned with polymodal alleghanian fold axes low volatile bituminous coals from the broad top field south central pennsylvania exhibit much stronger tectonic reflectance fabrics and bear evidence that low volatile bituminous rank was attained only after folding was completed in this part of the fold and thrust belt vris of coals from the western middle anthracite field reflect a more complex tectonic history and indicate that most coalification here preceded the final phase of alleghanian folding vrls of coals from an underground mine in the western middle anthracite field provide additional details on strain directions and timing of coalification coal rank increases very slightly down section but r min decreases down section opposite to the expected trend these coals probably attained anthracite rank prior to the principal phase of alleghanian folding but at least some coalification continued after folding as suggested by reconstructed coalification pathways on the axial ratio diagram during this final coalification phase the stratigraphically upper beds caught up in rank with the stratigraphically lower beds through elongation of r max parallel to the fold axes and elongation of r min in a subvertical direction vris of the stratigraphically upper beds were transformed to a prolate geometry whereas those of the lower beds retained their original oblate form

gradual unlocking of plate boundary controlled initiation of the 2014 iquique earthquake a long foreshock series unlocked the south american plate boundary until eventually initiating the m 8 1 iquique chile earthquake two groups publishing in this issue of nature analyse the seismic context of the iquique earthquake that occurred off the coast of northern chile on 1 april 2014 in a seismic zone that had been quiescent since a significant event in 1877 gavin hayes et al identify areas of remaining or elevated earthquake hazard along the megathrust fault in the region and conclude that the 2014 iquique event was not the earthquake that had been anticipated given that significant sections of the northern chile subduction zone have not ruptured in almost 150 years they suggest that it is likely that future megathrust earthquakes will occur south and potentially north of the 2014 iquique sequence bernd schurr et al show that the april 2014 earthquake broke a central fraction of the northern chile seismic gap the last major segment of the south american plate boundary that had yet to rupture in the past century from july 2013 up to the april earthquake they identify three seismic clusters along this part of the plate boundary each lasting a few weeks with earthquakes of increasing peak magnitudes they conclude that these seismic clusters and their slip transients reflect a gradual weakening of the central part of the seismic gap that was instrumental in initiating the final failure on 1 april 2014 northern chile was struck by a magnitude 8 1 earthquake following a protracted series of foreshocks the integrated plate boundary observatory chile monitored the entire sequence of events providing unprecedented resolution of the build up to the main event and its rupture evolution here we show that the iquique earthquake broke a central fraction of the so called northern chile seismic gap the last major segment of the south american plate boundary that had not ruptured in the past century1 2 since july 2013 three seismic clusters each lasting a few weeks hit this part of the plate boundary with earthquakes of increasing peak magnitudes starting with the second cluster geodetic observations show surface displacements that can be associated with slip on the plate interface these seismic clusters and their slip transients occupied a part of the plate interface that was transitional between a fully locked and a creeping portion leading up to this earthquake the b value of the foreshocks gradually decreased during the years before the earthquake reversing its trend a few days before the iquique earthquake the mainshock finally nucleated at the northern end of the foreshock area which skirted a locked patch and ruptured mainly downdip towards higher locking peak slip was attained immediately downdip of the foreshock region and at the margin of the locked patch we conclude that gradual weakening of the central part of the seismic gap accentuated by the foreshock activity in a zone of intermediate seismic coupling was instrumental in causing final failure distinguishing the iquique earthquake from most great earthquakes finally only one third of the gap was broken and the remaining locked segments now pose a significant increased seismic hazard with the potential to host an earthquake with a magnitude of 8 5

reflectance anisotropy of upper carboniferous coals in the appalachian foreland basin pennsylvania u s a abstract patterns of vitrinite reflectance anisotropy in coal are represented by a three dimensional graphical form resembling an ellipsoid termed the vitrinite reflectance indicating surface vri naturally occurring vris from the northern appalachian basin pennsylvania range in shape from biaxial negative to biaxial positive depending on their coalification history and tectonic setting vri shapes are measured by estimating the magnitudes of the three principal reflectances rmax rint and rmin either on oriented blocks or non oriented grain mounts spatial orientations of the principal axes are determined by reflectance measurements on oriented polished cores the various vri shapes are portrayed on axial ratio diagrams i e plots of r max r int on the vertical axis and r int r min on the horizontal axis axial ratio diagrams are also used to depict the progressive change in vri shape with coalification standard deviations of the principal reflectance axes as measured on oriented cores average around 0 09 in magnitude and 5 in orientation measurements are highly reproducible between pairs of oriented cores estimates of the principal reflectance magnitudes as measured on oriented vs non oriented samples agree on average to within 0 04 for rmax 0 08 for rint and 0 20 for rint coal bearing strata in the north central coal fields medium volatile bituminous coal to semianthracite in northern pennsylvania were diagenetically altered in a predominantly burial strain environment and exhibit structural evidence of only mild tectonic deformation vris from this suite of coals are biaxial negative with rmin axes roughly perpendicular to bedding with increasing rank toward the southeast these vris plot along a straight line pathway on the axial ratio diagram emanating from near the origin and extending through the biaxial negative deformation field vris of coals from the western middle anthracite field exhibit a wide range of shapes and orientations which is indicative of a more complex tectonic history in their present day orientation rmin axes are scattered about a great circle distribution the pole to which is precisely coincident with regional fold axes when beds are unfolded to a flat lying orientation they become significantly less scattered indicating that most coalification here preceded the final phase of alleghanian folding rmax axes of sporinite grains are alwayas aligned parallel to bedding which suggests that the strata were still flat lying and not subject to tectonic forces when the coals passed through the 1st and 2nd coalification jumps

mesoscale dynamics of the near dryline environment analysis of data from cops 91 abstract a technique is introduced using surface data from triangular networks of adjacent mesonet stations to estimate the terms in the horizontal equation of motion at anemometer level 10 m on either side of the dryline in the southern plains of the united states data from an instrumented surface mesonetwork in the texas panhandle and western and central oklahoma during the cooperative oklahoma profiler studies cops 91 field program were employed for this purpose east of the dryline and surface pressure trough the vertical mixing term had a component normal and to the right of the surface wind in accord with ekman theory west of the dryline and surface pressure trough the vertical mixing term had a component normal and to the left of the surface wind in disagreement with ekman theory it is suggested that disagreements with ekman theory may be due to baroclinic effects in the boundary layer it is also shown that during the day both the westward component of the pressure gradient force and the ea

the evolution of an oklahoma dryline part ii boundary layer forcing of mesoconvective systems abstract data from the national severe storms laboratory surface mesonetwork are objectively analyzed to give insight into processes that contributed to the development of three tornadic mesoconvective systems near the 8 june 1974 oklahoma dryline storm cells constituting each of the systems form over recurring zones of convergence within 20 km of the dryline different mechanisms appear to force the individual convergence zones storms of the first system appear simultaneously only after the establishment of a pressure trough just cast of a zone of convergence 15 km east of the dryline the convergence zone intensifies and progresses eastward with the storms meanwhile a second convergence zone appears at the dryline in response to apparent storm induced pressure systems trailing the storms the fact that deep convection did not occur over the second zone is attributed to static stabilization caused by mesoscale unsaturated downdrafts in the upper troposphere storms of the second system develop in a c

review and update of the applications of organic petrology part 1 geological applications abstract organic petrology developed as coal petrology at the beginning of the 20th century dedicated mainly to the study of coals because of their utilization in industry coal petrology was then considered a branch of coal science later with the development of specialized nomenclature classification of coal components and the standardization and improvement of analytical microscopical methods this discipline expanded in interests and name becoming organic petrology organic petrology carries a broader context being as well a tool applied in the study of dispersed organic matter in sedimentary rocks due to its importance in exploration for fossil fuel resources at present organic petrology is a discipline widely recognized for its role in fundamental and applied research with respect to both coal utilization and in geosciences throughout the 20th century several important monographs have been published on the discipline of organic petrology including stach s textbook of coal petrology 1st edition 1935 2nd 1975 3rd 1982 updated as the more general organic petrology by taylor et al 1998 more recently the text applied coal petrology the role of petrology in coal utilization was published by suarez ruiz and crelling 2008 this review is the first in a two part review series that describes and updates the role of organic petrology in geosciences a second part complementing this one and focused on the applications of organic petrology to other scientific fields will follow

boundary layer moisture regimes data from fifty two aircraft flight legs 100 150m above ground from hapex and fife are analysed to estimate characteristics of boundary layer moisture fluctuations in boundary layers with different bulk stability and surface energy regimes in hapex considerable effort was devoted to the quality of measurement of moisture fluctuations the data include repeated 120km flight legs flown at 150m over the same relatively homogeneous terrain allowing statistical examination of motion characteristics on horizontal scales up to 10km this study finds two prototype boundary layer regimes with significant boundary layer instability relatively weak surface evaporation and drier air aloft the entrainment drying boundary layer may develop this boundary layer is characterized by vertical divergence of the moisture flux and significant diffusion of dry air from the top downwards top down in this type of boundary layer dry air occasionally reaches the lower boundary layer leading to negative moisture skewness in spite of positive temperature and vertical velocity skewness associated with warm moist updraughts in contrast the moistening boundary layer associated with greater surface evaporation is characterized by positive moisture skewness near the surface in addition to the above turbulent moisture fluctuations some of the above data are characterized by 10km moisture variations with horizontal gradients often concentrated in narrow zones of horizontal convergence since corresponding signatures of vertical velocity and temperature are weaker these zones are referred to as mesoscale moisture fronts as a more general feature moisture variations on scales of 5km and greater are negatively correlated with temperature variations associated with cool moist regions and warm dry regions on scales of tens of kilometres and greater such negative correlation may be due to inhomogeneity of the surface energy budget the negative moisture temperature correlation leads to large mesoscale variations of relative humidity and the lifted condensation level

the influence of topography and lower tropospheric winds on dryline morphology abstract the effects of topography wind shear and zonal wind speed on dryline formation and evolution are investigated using a three dimensional nonhydrostatic mesoscale model rather than conduct a case study a parameter study was performed to examine factors that control the depth and strength of the dryline circulation this study reveals that the potential for convective storm formation is greatest in those environments in which the cross dryline flow is weak above the dryline location this results in boundary layer flow nearly parallel to the north south oriented dryline boundary under these conditions the subsiding westerly flow and elevated residual layer formation do not strengthen the capping inversion above the eastern convective boundary layer in addition moist air parcels from near the surface are able to reside within the dryline updraft resulting in higher midtropospheric relative humidity subsequently increasing the likelihood of convective storm initiation as downslope westerly flo

formation and diurnal variation of the dryline abstract the formation and diurnal evolution of the dryline during fair weather have been investigated through the use of a two dimensional mesoscale model that includes condensation evaporation budget equations of surface energy and moisture field as well as turbulence and radiation parameterizations a moderately strong vertical wind shear was introduced on a sloping terrain where the soil is very dry on the west side but moist on the east initially a weak easterly geostrophic wind exists to the east but a weak westerly geostrophic wind to the west of the dryline during daytime deepening of the mixed layer due to vertical mixing especially on the west side forces the dryline to advance eastward the westerly wind on the west side is maintained by downward transport of westerly momentum due to strong vertical mixing the easterly wind on the east side is strengthened due to the inland sea breeze circulation therefore the resulting low level convergence sustains a strong moisture gradient along

observations of the finescale structure of a dryline during vortex 95 abstract the three dimensional finescale structure of a dryline observed over the texas panhandle during the verification of the origins in tornadoes experiment vortex on 6 may 1995 is presented high resolution observations documenting dryline evolution were collected from midafternoon while it moved slowly eastward until late afternoon as it retrogressed back to the west dryline variability in the horizontal along line direction was revealed by airborne doppler radar observations from the national center for atmospheric research electra doppler radar and ground based measurements from the nearby wsr 88d at amarillo texas this variability was created as the dryline interacted with horizontal convective rolls forming west of the dryline the rolls intersected the dryline at periodic locations creating radar reflectivity and vertical velocity maxima more importantly clouds initiated at these intersection points additional dryline variability was generated through the interaction of the low level fl

characteristics of dryline passage during cops 91 abstract the characteristics of dryline passage are documented through an analysis of data from an instrumented surface mesonetwork in the texas panhandle and western and central oklahoma during the cooperative oklahoma profiler studies field program some eastward moving drylines at the surface during the day were characterized by monotonic drops in dewpoint after dryline passage others were marked by a series of rapid drops punctuated by periods of no change after dryline passage which suggests that the dryline often progresses in discrete steps rather than continuously the dryline during the daytime was not always collocated with a pressure trough although the strongest dryline observed was analyses of surface pressure traces indicated that westward moving drylines during the evening did not display behavior characteristic of strong intense density currents as had been found in other studies evidence is presented in one case of 90 min oscillations in water vapor and wind behind the dryline

a modeling study of the dryline abstract results of a modeling study of the 24 may 1989 dryline are presented a nonhydrostatic two dimensional version of the colorado state university regional atmospheric modeling system csu rams is used to deduce the impact of east west variability of soil moisture and vegetation on convective boundary layer evolution and dryline formation the effects of the initial moisture and wind fields and the impact of the coriolis force on the model results are also examined model output is compared with special airborne and sounding observations of the 24 may dryline several findings of an earlier observational study of the 24 may dryline are supported in the present study the modeled drylines are broadly comparable to the observed dryline with respect to the following properties 1 width 10 km 2 strong horizontal moisture and virtual potential temperature gradients 4 g kg 1 10 km and 2 k 10 km 3 strong horizontal convergence updraft w e shear of n s wind component 8 10 4 s 1 1 m s 1 10 m

the evolution of low level rotation in the 29 may 1994 newcastle graham texas storm complex during vortex abstract this paper reports the results of an analysis of airflow evolution in the tornadic newcastle graham texas storm complex of 29 may 1994 a series of seven pseudo dual doppler analyses from 2242 to 2315 are performed from tail radar observations by the national oceanic and atmospheric administration p 3 aircraft subjective analyses of quasi horizontal single doppler radar observations provide a detailed look at structure and evolution of the hook echo and the low level newcastle mesocyclone special emphasis is placed on the evolution of low level i e below 1 km above ground level agl rotation of the parent mesoscale circulation of the newcastle tornado and the origins of mesoscale rotation preceding tornadogenesis the structure and evolution of the newcastle and graham mesocyclones are compared and contrasted the airborne doppler analyses reveal that the tornadic newcastle cell had supercell characteristics and that the newcastle storm circulation could be classified as a mesocyclone ba

ml scale in northwestern turkey from 1999 izmit aftershocks updates we present an update of the local magnitude scale previously calibrated for northwestern turkey by baumbach et al 2003 the path coverage in the westernmost part of the analyzed area has been increased as well as the number of amplitudes for distance greater than 110 km furthermore a set of recordings from accelerometric stations operated by the kandilli observatory and earthquake research institute koeri has been merged with the recordings by the sapanca bolu and german task force seismological networks in all 4047 recordings from 528 earthquakes recorded by 31 seismometers and 23 accelerometers are considered to calibrate the local magnitude scale over a hypocentral distance range from 10 to 190 km by analyzing the unit covariance matrix and the resolution matrix we show how the source to station geometries of the seismic and strong motion networks affect the uncertainties of the computed station corrections attenuation coefficients and magnitudes the assumptions made concerning the reference station correction and the change in the amplification for the wood anderson torsion seismograph from 2800 to 2080 uhrhammer and collins 1990 introduced an offset of about 0 34 in the magnitudes with respect to baumbach et al 2003 with the updated local magnitude scale ranges from 0 50 to 5 91 the distribution of the residuals with distance confirms that the extension of both the magnitude and distance ranges and the improved path coverage have preserved the high quality that characterized the data set analyzed by baumbach et al 2003

a case study of severe storm development along a dryline within a synoptically active environment part i dryline motion and an eta model forecast through a case study approach the motion of a dryline on 16 may 1991 within a synoptically active environment in the southern plains along which severe storms ultimately developed is examined in detail observations from research aircraft surface mesonetwork stations mobile ballooning vehicles radar wind profilers and operational surface and upper air networks are examined and combined additionally output from the operational mesoscale eta model is examined to compare predictions of dryline motion with observations and to aid in interpretation of observations the dryline on this day advanced rapidly eastward and included formation of a bulge additionally in at least two instances it exhibited redevelopment loss of definition at one location and gain at another aircraft observations revealed that an eastward redevelopment occurred in the early afternoon and was characterized by a series of four steps along the western edge of the boundary layer moisture the westernmost and easternmost steps coincide with the locations of the dryline before and after redevelopment respectively the retreat of the dryline in the central and southern portion of the analysis domain in the late afternoon included both continuous motion and redevelopment toward the west northwest this dual mode retreat of the dryline was accompanied by gradual backing of the winds and moistening in low levels the eta model forecast initialized at 1200 utc produced dryline features that were qualitatively similar to observed fields the eastward motion of a broad area of enhanced moisture gradient agreed well with observations following an initial spinup period a north south moisture convergence axis preceded the rapid eastward motion of the dryline by several hours lack of subsidence in the air behind the modeled dryline leads to the conclusion that processes other than downward transfer of horizontal momentum by larger scale motions that would support eastward advection produced the rapid dryline motion and observed eastward dryline bulge results of diagnosing physical processes affecting model dryline motion point toward boundary layer vertical mixing coupled with advection of dry air aloft as vital components in rapid advance of the dryline eastward in this synoptically active case

the dryline on 22 may 2002 during ihop ground radar and in situ data analyses of the dryline and boundary layer evolution abstract on the afternoon and evening of 22 may 2002 high resolution observations of the boundary layer bl and a dryline were obtained in the eastern oklahoma and texas panhandles during the international h2o project using overdetermined multiple doppler radar syntheses in concert with a lagrangian analysis of water vapor and temperature fields the 3d kinematic and thermodynamic structure of the dryline and surrounding bl have been analyzed over a nearly 2 h period the dryline is resolved as a strong 2 4 g kg 1 km 1 gradient of water vapor mixing ratio that resides in a nearly north south oriented zone of convergence maintained through frontogenesis the dryline is also located within a gradient of virtual potential temperature which induces a persistent solenoidally forced secondary circulation initially quasi stationary the dryline retrogrades to the west during early evening and displays complicated substructures including small wavelike perturbations that travel from south to north at nea

oxidatively and thermally altered high volatile bituminous coals in high temperature coal fire zone no 8 of the wuda coalfield north china abstract coal fires have received increasing attention due to their environmental economic and social impacts their significant influence on coal properties is widely documented by geophysical and geochemical methods the present paper demonstrates by means of coal petrological methods significant changes of microstructure optical appearance and optical properties of medium rank bituminous coals affected by an underground coal fire the studied changes are suggested to result from distinct oxidative and thermal alterations induced by a high temperature regime temperatures over 800 c encountered in the coal fire zone no 8 wuda coalfield the investigated coal seam no 9 represents a high volatile a bituminous coal and is dominated by vitrinite followed by inertinite with minor amounts of liptinite the microstructure of the coal fire affected coals facilitate a broad spectrum of characteristic features the microscopic analyses revealed development of 1 non tectonic fissures and non tectonic fractures 2 distinct micropores 3 dark oxidations rims and 4 bright spots interpreted as incipient mesophases optical properties were characterised for megasporinite and vitrinite in the examined megasporinite a noticeable anisotropy and distinct granular appearance was observed in the investigated coals both a dominant increase as well as a minor decrease in both random and maximum vitrinite reflectances were documented for 1 coal grains and 2 dark rimmed vitrinite at non tectonic fissures and non tectonic fractures in addition also a characteristic bimodal vitrinite population was measured the increase in bireflectance was clearly documented for two sub zones within the coal fire zone no 8 the applied kilby s cross plots suggested a large overlapping of the data sets of r max and r min indicating marked changes in vitrinite structure the applied coal petrological approach revealed distinct changes to the coal s microstructure appearance as well as to optical properties induced by the underground coal fire the presented coal petrographic approach may help determine the extent of coal fires in coal mines and the direction of propagation of coal fire front

a shallow water model of the diurnal dryline this study explores the diurnal variation in the movement and structure of the dryline using a one dimensional shallow water model the model is adapted to test some common theories of dryline motion including the diurnal variation in surface friction static stability inversion erosion and momentum mixing aloft these mechanisms of diurnal variation are first studied individually and then in unison a diurnal variation in the surface friction produces a model dryline that moves westward during the day in disagreement with observations and has a southerly wind maximum near midnight a diurnal variation in the static stability produces a model dryline that steepens in slope and moves eastward during the day and then surges westward at night with a southerly wind maximum 6 to 9 h after the minimum stability inversion erosion during the day produces a nearly vertical model dry front that moves eastward during the day with surface southwesterlies at sunset the model dryline surges westward with a southerly wind maximum before midnight a diurnal variation of the momentum mixing aloft has no significant effect on the model dryline results show that the combined case with a diurnal variation of surface friction inversion erosion and static stability with terrain most accurately describes the observed dryline system the westward surge depicted in the model is compared to the flow evolution of the corresponding dam break problem for a rotating fluid

mobile sounding observations of a tornadic storm near the dryline the canadian texas storm of 7 may 1986 abstract on 7 may 1986 thunderstorms formed during the afternoon near a dryline in the texas panhandle under weak synoptic scale forcing five tornadoes and large hail were produced by one storm near canadian texas the focus of the paper is the analysis of soundings obtained by a storm intercept crew a sounding launched into the wall cloud of the storm just after the fourth tornado indicated a nearly pseudomoist adiabatic lapse rate a temperature excess of 10 c over the environment at 500 mb and an updraft speed of almost 50 m s 1 near 6 km agl in reasonable agreement with parcel theory

an observational study of the dryline abstract this study presents analyses of data collected in the vicinity of a cloud free dryline that occurred in western oklahoma on 24 may 1989 observations reveal sharp contrasts across the quasi stationary north south dryline during midafternoon of greatest significance is a pronounced gradient of virtual potential temperature although horizontal convergence and vorticity also maximize at the dryline the environment of the 24 may dryline is dominated by vertical mixing that maintains a convective boundary layer cbl on both sides of the dryline the dryline resembles a mixing zone containing varying proportions of hot dry air to the west side and warm moist air from the lowest 200 m within 10 km to the east of the dryline the mixing zone slopes eastward from the surface dryline location then becomes a quasi horizontal elevated moist layer above the cbl east of the dryline saturation point analysis indicates that the mixing zone is characterized by a single mixing line structure defined by

analysis of a dryline during ihop implications for convection initiation abstract a detailed analysis of a dryline that formed on 22 may 2002 during the international h2o project ihop is presented the dryline was classified as a null case since air parcels lifted over the convergence boundary were unable to reach the level of free convection preventing thunderstorms from forming a secondary dryline associated with a distinct moisture discontinuity developed to the west of the primary dryline the primary dryline exhibited substantial along frontal variability owing to the presence of misocyclones this nonlinear pattern resembled the precipitation core gap structure associated with cold fronts during one of the analysis times although the misocyclones were positioned within the gap regions radar refractivity has been recently shown to accurately retrieve the low level moisture fields within the convective boundary layer however its use in forecasting the initiation of convection has been restricted to qualitative interpretations this study introduces the total derivati

finescale radar observations of the 22 may 2002 dryline during the international h2o project ihop abstract the dryline has long been associated with the development of severe thunderstorms in the southern plains during the spring and early summer months the propagation and structure of the dryline are closely tied to surface processes that are neither well understood nor well resolved with current observational capabilities as a result there are often large errors in forecasts of dryline position and structure improvements in radar technology have allowed for better observations of the dryline in recent years here very finescale radar observations taken with the university of massachusetts amherst umass mobile w band radar during an international h2o project ihop double dryline event on 22 may 2002 in the oklahoma panhandle are presented the observations are placed in the context of the dryline secondary circulation which describes flow in a plane normal to the dryline the narrow half power beamwidth of the antenna on the w band 0 18 permitted the measurements of channels of upward 8

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

frontal and radar refractivity analyses of the dryline on 11 june 2002 during ihop an analysis of a dryline that did not initiate convection during the observational period is presented the dryline was the weakest kinematic boundary observed during the international h2o project ihop but was associated with a large moisture gradient detailed dual doppler wind syntheses from an airborne doppler radar were combined with radar refractivity measurements providing a rare opportunity to examine both the kinematic and moisture characteristics of this boundary the radar thin line denotes the approximate kinematic position of the dryline and was quasi linear on this day in contrast the moisture pattern across the dryline was more complex than was suggested by the characteristics of the thin line prominent in the horizontal plots was the presence of narrow few kilometers wide channels of moisture extending 15 20 km into the dry air mass past studies have suggested that echo thin lines observed in the clear air can be used as a proxy for delineating the moisture contrast across the dryline in contrast the moisture extrusions were present even though the thin line was quasi linear and were located in weak echo regions along the thin line it is hypothesized that transverse rolls developed at an angle to the boundary layer winds and intersected the dryline the kinematic airflow associated with these rolls could have protected the moist tongues from the eroding effect of the dry flow west of the dryline the moisture extrusions appear to diminish with time as they mix with the surrounding dry air

a case study of severe storm development along a dryline within a synoptically active environment part ii multiple boundaries and convective initiation abstract a dryline that occurred on 16 may 1991 within a synoptically active environment is examined in detail using research aircraft radar surface satellite and upper air observations the work focuses on multiple boundaries in the dryline environment and initiation of tornadic storms in two along line areas aircraft measurements in the boundary layer reveal that both the east west extent of moisture gradients and the number of regions containing large moisture gradients vary in the along dryline direction aircraft penetrations of thinlines observed in clear air return from radar reveal that all thinlines are associated with convergence and a moisture gradient and that more distinct thinlines are associated with stronger convergence however significant moisture gradients are not always associated with either thinlines or convergent signatures convective clouds on this day formed at the dryline rather than significantly east of the dryline the three thunderstorm cells that occurred in east cen

finescale vertical structure and evolution of a preconvective dryline on 19 june 2002 abstract high resolution airborne cloud radar data and other international h2o project datasets are used to describe the vertical structure of an unusual prefrontal dryline this dryline observed in northwestern kansas on 19 june 2002 first progressed eastward and tilted toward the west and later became more stationary and reversed its tilt toward the moist side the convective boundary layer cbl depth difference also reversed only in the later phase did the dry side cbl become deeper than on the moist side echo and single dual doppler velocity data in a vertical transect across the dryline suggest a solenoidal circulation dynamically consistent with the observed horizontal buoyancy gradient both this gradient and the solenoidal circulation reversed in the later phase simultaneously confluence toward the dryline increased resulting in an increasing moisture gradient as well as a deepening cbl in the dryline convergence zone it is speculated that the baroclinically generated horizontal vortici

convective initiation on 19 june 2002 during ihop high resolution simulations and analysis of the mesoscale structures and convection initiation 1 the 19 june 2002 convective initiation ci case from the international h2o project ihop is simulated using the arps at 1 km grid spacing it involves three distinct ci groups ci a ci b and ci c associated with a cold front dryline system initial condition at 1800 utc 19 june 2002 was created using the arps 3dvar including standard as well as special observations the simulation captured the three groups of cis rather well with small timing and spatial errors ci a is most typical of dryline initiation vertical cross sections through the initiation locations show typical dryline structures with an upward moisture bulge forced by lifting along the dryline convergence for ci b the model predicted mesoscale structures agree with special ihop aircraft dropsonde observations closely strong low level convergence from opposing cold front and dryline circulations produces deep symmetric upwelling of moist air and the convection is initiated at the crest of the moisture bulge ci c is more typical of frontal convection where deep convection is first initiated at the front edge of the cold air for ci b and ci c north south moisture bands that have dryline characteristics and can be considered multiple drylines and contain enhanced vertical motion and upward moisture bulges intercept the dryline and cold front respectively providing the most favored locations on the dryline or cold front for initiation furthermore the air parcels feeding the initial cells at ci b and ci c have trajectories along the moisture bands and have already experienced uplifting when they reach the dryline and cold front locations

the finescale structure of a west texas dryline abstract during spring and early summer a surface confluence zone often referred to as the dryline forms in the midwestern united states between continental and maritime air masses the dewpoint temperature across the dryline can vary in excess of 18 c in a distance of less than 10 km the movement of the dryline varies diurnally with boundary layer growth over sloping terrain leading to an eastward apparent propagation of the dryline during the day and a westward advection or retrogression during the evening in this study we examine the finescale structure of a retrogressing dryline using data taken by a doppler lidar a dual channel radiometer and serial rawinsonde ascents while many previous studies were unable to accurately measure the vertical motions in the vicinity of the dryline our lidar measurements suggest that the convergence at the dryline is intense with maximum vertical motions of 5 m s 1 the winds obtained from the doppler lidar measurements were combined with the equations of m