convective momentum transport by rainbands within a madden julian oscillation in a global nonhydrostatic model with explicit deep convective processes part i methodology and general results abstractthe convective momentum transport cmt properties of 13 215 rainbands within a madden julian oscillation mjo event simulated by a global nonhydrostatic model are examined cmt vectors which represent horizontal accelerations to the mean winds due to momentum flux convergences of deviation winds are derived for each rainband the cmt vectors are composited according to their locations relative to the mjo center while a similar number of rainbands are detected in the eastern and western halves of the mjo convective envelope cmt vectors with large zonal components are most plentiful between 0 and 20 to the west of the mjo center the zonal components of the cmt vectors exhibit a coherent directionality and have a well organized three layer structure positive near the surface negative in the low to midtroposphere and positive in the upper troposphere in the low to midtroposphere where the longitudinal difference in the mean zonal wind across the mjo is 10 m s 1 on average the net acceler

acceleration source spectra anticipated for large earthquakes in northeastern north america a set of 16 large intraplate earthquakes are considered on the basis of their tectonic settings compressive focal mechanisms and shallow focal depths as possible analogs for large earthquakes that may be anticipated to occur in northeastern north america the earthquakes range in seismic moment from 5 1023 to 3 1026 dyne cm and include the mainshocks and largest aftershocks of the 1982 miramichi canada the 1985 to 1988 nahanni canada and the 1988 tennant creek australia earthquake sequences the teleseismic recordings of these earthquakes are spectrally analyzed by correcting the logarithmically averaged acceleration spectra for the frequency dependent effects of attenuation and interference of the depth and direct phases the resulting acceleration source spectra are generally flat at high frequencies the mainshock spectra exhibit intermediate spectral falloffs that is u where 1 over frequencies that characteristically extend from 0 1 to 0 5 hz in contrast the largest aftershocks of the three sequences named above exhibit 2 spectral shapes the high frequency source spectral levels increase with seismic moment approximately as ru m 1 3 the 1988 saguenay canada earthquake which occurred significantly deeper than the other earthquakes exhibits an anomalous spectral shape combining the teleseismic data with strong motion recordings indicates that the intermediate spectral falloff for this earthquake extends from 0 2 to 3 hz the spectral amplitude at 3 hz is a factor of 3 higher than the amplitude anticipated for an earthquake of this size from the other 15 earthquakes

stress drops for intermediate depth intraslab earthquakes beneath hokkaido northern japan differences between the subducting oceanic crust and mantle events spatial variations in the stress drop for 1726 intermediate depth intraslab earthquakes were examined in the subducting pacific plate beneath hokkaido using precisely relocated hypocenters the corner frequencies of events and detailed determined geometry of the upper interface of the pacific plate the results show that median stress drop for intraslab earthquakes generally increases with an increase in depth from 10 to 157 mpa at depths of 70 300 km more specifically median stress drops for events in the oceanic crust decrease 9 9 6 8 mpa at depths of 70 120 km and increase 6 8 17 mpa at depths of 120 170 km whereas median stress drop for events in the oceanic mantle decrease 21 6 14 0 mpa at depths of 70 170 km where the geometry of the pacific plate is well determined the increase in stress drop with depth in the oceanic crust at depths of 120 170 km for which several studies have shown an increase in velocity can be explained by an increase in the velocity and a decrease in the water content due to the phase boundary with dehydration in the oceanic crust stress drops for events in the oceanic mantle were larger than those for events in the oceanic crust at depths of 70 120 km differences in both the rigidity of the rock types and in the rupture mechanisms for events between the oceanic crust and mantle could be causes for the stress drop differences within a slab

convective momentum transport associated with the madden julian oscillation based on a reanalysis dataset abstracta better understanding of multiscale interactions within the madden julian oscillation mjo including momentum exchanges is critical for improved mjo prediction skill in this study convective momentum transport cmt associated with the mjo is analyzed based on the noaa climate forecast system reanalysis cfsr a three layer vertical structure associated with the mjo as previously suggested in the mesoscale momentum tendency profile based on global cloud resolving model simulations is evident in the subgrid scale momentum tendency from the cfsr positive negative subgrid scale momentum tendency anomalies are found near the surface negative positive anomalies are found in the low to midtroposphere and positive negative anomalies in the upper troposphere are found within and to the west east of the mjo convection this tends to damp the mjo circulation in the free atmosphere while enhancing mjo winds near the surface in addition it could also reduce the mjo eastward propagation

ground motion relations for eastern north america predictive relations are developed for ground motions from eastern north american earthquakes of 4 0 m 7 25 at distances of 10 r 500 km the predicted parameters are response spectra at frequencies of 0 5 to 20 hz and peak ground acceleration and velocity the predictions are derived from an empirically based stochastic ground motion model the relations differ from previous work in the improved empirical definition of input parameters and em pirical validation of results the relations are in demonstrable agreement with ground motions from earthquakes of m 4 to 5 there are insufficient data to adequately judge the relations at larger magnitudes although they are consistent with data from the saguenay m 5 8 and nahanni m 6 8 earthquakes the underlying model parameters are constrained by empirical data for events as large as m 6 8

smooth and rapid slip near the japan trench during the 2011 tohoku oki earthquake revealed by a hybrid back projection method abstract we developed a new back projection method that uses teleseismic p waveforms to integrate the direct p phase with reflected phases from structural discontinuities near the source and used it to estimate the spatiotemporal distribution of the seismic energy release of the 2011 tohoku oki earthquake we projected a normalized cross correlation of observed waveforms with corresponding green s functions onto the seismic source region to obtain a high resolution image of the seismic energy release applying this method to teleseismic p waveform data of the 2011 tohoku oki earthquake we obtained spatiotemporal distributions of seismic energy release for two frequency bands a low frequency dataset and a high frequency dataset we showed that the energy radiated in the dip direction was strongly frequency dependent the area of major high frequency seismic radiation extended only downdip from the hypocenter whereas the area of major low frequency seismic radiation propagated both downdip and updip from the hypocenter we detected a large release of seismic energy near the japan trench in the area of maximum slip which was also the source area of the gigantic tsunami when we used only the low frequency dataset the timing of this large seismic energy release corresponded to an episode of smooth and rapid slip near the japan trench and reflects the strong dependence of the seismic energy distribution obtained on the frequency band of the input waveform dataset the episode of smooth and rapid slip may have been the trigger for a release of roughly all of the accumulated elastic strain in the seismic source region of the 2011 tohoku oki earthquake

the oceanic mesoscale convective system and associated mesovortex observed 12 december 1992 during toga coare this study documents the precipitation and kinematic structure of a mature mature to decaying westward propagating near equatorial oceanic mesoscale convective system mcs observed by airborne doppler radars during toga coare the tropical ocean global atmosphere coupled ocean atmosphere response experiment this system occurred on 12 december 1992 during the convectively active phase of an intraseasonal oscillation and was followed at its dissipating stage by a redevelopment of convection that led to the mcs observed on 13 december 1992 these two successive mcss were associated with a two day atmospheric disturbance radar deduced airflows at two time periods reveal many similarities with other tropical oceanic cloud clusters in particular a marked rear inflow jet associated with a midlevel cyclonic mesovortex was observed within the rear of the stratiform region the mesovortex was better defined both in size and depth during the mature to decaying stage and was located more inside the system within a region of convergence due to the westward propagation of the rear inflow countergradient transports of momentum normal to the mean orientation of the system at midlevels and downgradient transports at lower and higher levels helped to intensify this rear inflow these transports were mostly accomplished by eddy structures cyclonic vorticity was concentrated at the rear of the mcs and peaked at the centre of the observed closed wind circulation as previously observed stretching of the pre existing vertical vorticity was the dominant dynamical mechanism which helped to amplify the mesovortex at mid to upper levels while tilting of the horizontal vorticity into the vertical was a lesser mechanism and had an opposite effect in most respects advective processes were negatively correlated with the stretching and tilting mechanisms but not sufficiently to be balanced the resulting tendency was an increase of cyclonic vorticity at low to mid levels and a net decrease above

momentum and mass transport by convective bands comparisons of highly idealized dynamical models to observations the importance of the vertical transport of horizontal momentum by convective clouds has been documented in studies of momentum budgets e g shapiro and stevens 1980 sui and yanai 1986 furthermore it is obvious that the boundary layer wind itself and hence surface heat moisture and momentum transports is affected by deep convection most of the airsea transfer in tropics is concentrated in regions with deep convection

evolution and dynamics of a late stage squall line that occurred on 20 february 1993 during toga coare abstract airborne doppler and flight level data are used to document the structure and evolution of portions of a late stage horseshoe shaped squall line system and its effect on vertical momentum and mass transports this system which occurred on 20 february 1993 during the tropical ocean global atmosphere coupled ocean atmosphere response experiment was similar to many previously studied but had some unique features first a slow moving transverse band which formed the southern leg of the horseshoe drew most of its low level updraft air from the squall line stratiform region on its north side rather than the environment to the south second a long lived cell with many properties similar to a midlatitude supercell formed 150 km to the rear of the squall line this cell was tracked for 4 h as it propagated into and then through the cold pool and finally dissipated as it encountered the convection forming the northern edge of the horseshoe finally as the squall line was dissipating a new con

the oceanic mesoscale convective system observed with airborne doppler radars on 9 february 1993 during toga coare structure evolution and budgets data collected on 9 february 1993 during the tropical ocean and global atmosphere programme coupled ocean atmosphere response experiment toga coare with the doppler radars on board the two national oceanic and atmospheric administration wp 3d and the national center for atmospheric research electra aircraft are analysed to study the structure and evolution of an equatorial oceanic mesoscale convective system mcs observations lasted more than five hours a period during which the cloud cluster characteristics changed from convective to stratiform this mesoscale system was approximately aligned along the tropospheric wind shear but it was nearly perpendicular to the low level shear series of three dimensional fields of reflectivity air velocity components retrieved pressure and temperature perturbations show similarities with previously observed convective systems over the tropical oceans in particular although the cloud top reached 18 km altitude relatively weak vertical motions and temperature perturbations resulted from a moderate convective instability in the low levels a cold front to rear flow intensified and deepened as the overall structure evolved from convective to stratiform the vertical profiles of mean horizontal divergence evolved from low level convergence in the cross line direction for the earliest analyses to mid level convergence from all directions during the later stratiform phase vertical momentum fluxes were important and led to an increase in the cross line wind shear and a decrease in the along line one analysis of radiosounding data from the nearest stations of the toga coare array shows that the period during which airborne doppler observations were conducted was characterized by relatively strong large scale ascent and apparent sources of heat moisture and momentum these diagnosed values and the mean radarderived ones agree fairly well this shows that the early convective and late stratiform phases of the mcs are equally important for the apparent sources of heat and momentum

simulated convective lines with parallel stratiform precipitation part i an archetype for convection in along line shear abstract this article the first of two describing convective lines with parallel stratiform ps precipitation addresses the basic kinematic and precipitation features of these systems the ps mode appears to be the preferred organizational structure in environments with line parallel vertical wind shear this archetype for long lived convective systems has received relatively little attention to date and yet it is frequently implicated in flash flooding because it entails both the along line movement of hydrometeors and back building convective development as a reality check this paper presents conventional observations of the wind and reflectivity fields associated with an archetypal ps system from 2 may 1997 thereafter analyses of idealized numerical simulations serve as the basis for a more detailed investigation of ps systems internal structures and processes the observations and simulations suggest several unique aspects of the ps structure the environment s vertically sheared 3d wind prof

convective momentum transport in a simple multicloud model for organized convection abstractconvective momentum transport cmt is the process of vertical transport of horizontal momentum by convection onto the environmental flow the significance of cmt from mesoscale to synoptic and planetary scale organized cumulus convection has been established by various theoretical and observational studies a new strategy mimicking the effect of unresolved mesoscale circulation based on the weak temperature gradient wtg approximation with a gaussian profile to redistribute the heating due to parameterized cumulus convection at the subgrid scale is adopted here to construct a cmt parameterization for general circulation models gcms two main regimes of cmt are considered an upscale squall line regime and a downscale non squall line regime an exponential probability distribution is used to select which of these two effects is active conditional on the state of the large scale shear the shear itself is used as a measure of the persistence of mesoscale organized circulation due to the presen

notes and correspondence convective eddy momentum tendencies in long cloud resolving model simulations abstract domain average momentum budgets are examined in several multiday cloud resolving model simulations of deep tropical convection in realistic shears the convective eddy momentum tendency f neglected in many global circulation models looks broadly similar in two and three dimensional simulations it has a large component in quadrature with the mean wind profile tending to cause momentum profile features to descend this component opposes and exceeds in magnitude the corresponding large scale vertical advective tendency which would tend to make features ascend in convecting regions the portion of f in phase with the mean wind is isolated by vertically integrating f u yielding a kinetic energy tendency that is overwhelmingly negative the variation of this energy damping with shear flow kinetic energy and convection intensity measured by rain rate gives a cumulus friction coefficient around 40 to 80 per centimeter of rain in 3d runs large scatter reflects the effects of varying co

towards optimal observational array for dealing with challenges of el nino southern oscillation predictions due to diversities of el nino this paper investigates the optimal observational array for improving the initialization of el nino southern oscillation predictions by exploring the sensitive areas for target observations of two types of el nino predictions the sensitive areas are identified by calculating the optimally growing errors oges of the zebiak cane model as corrected by the optimal forcing vector that is determined by assimilating the observed sea surface temperature anomalies sstas it is found that although the oges have similar structures for different start months of predictions the regions covered by much large errors for the ssta component tend to locate at different zonal positions and depends on the start months furthermore these regions are also in difference between two types of el nino events the regions covered by large errors of oges represent the sensitive areas for target observations considering the dependence of the sensitive areas on related el nino types and the start months of predictions the present study propose a quantitative frequency method to determine the sensitive areas for target observations associated with two types of el nino predictions which is expected to be applicable for both types of el nino predictions with different start months as a result the sensitive areas that describe the array of target observations are presented with a reversal triangle like shape locating in the eastern pacific specifically the area of 120 w 85 w 0 s 11 s and an extension to the west along the equator and then gathering at the 180 longitude and the western boundary hindcast experiments demonstrated that such observational array is very useful in distinguishing two types of el nino and superior to the tao triton array it is therefore suggested that the observational array provided in the present study is towards the optimal one and the original tao triton array should be further optimized when applied to predictions of the diversities of el nino events

spatiotemporal variation of stress drop during the 2008 mogul nevada earthquake swarm we estimate stress drops for 148 shallow 6 km earthquakes in the complex 2008 mogul nevada swarm using empirical green s function derived spectral ratios near source temporary broadband seismometers deployed before the mw4 9 main shock provide high quality records of many foreshocks and aftershocks and an ideal opportunity to investigate uncertainties in corner frequency measurement as well as stress drop variation related to space time depth mechanism and magnitude we explore uncertainties related to source model measurement approach cross correlation limit and frequency bandwidth p s wave results range from 0 2 0 15 0 3 0 15 to 36 20 58 7 mpa a variation greater than the error range of each individual estimate although this variation is not explained simply by any one parameter spatiotemporal variation along the main shock fault plane is distinct coherent clusters of high and low earthquakes are seen and high foreshocks correlate with an area of reduced aftershock productivity these observations are best explained by a difference in rheology along the fault plane average s of 3 9 1 1 4 0 1 1 mpa using p s are similar to those found for earthquakes in a variety of settings implying that these shallow potentially fluid driven earthquakes do not have systematically lower than average tectonic earthquakes 4 mpa and therefore have similar or higher due to proximity to the surface expected ground motions compared to typical earthquakes the unprecedented detail achieved for these shallow small magnitude earthquakes confirms that when measured precisely is a valuable observation of physically meaningful fault zone properties and earthquake behavior

influence of upper tropospheric inertial stability on the convective transport of momentum this study verifies the apparent high positive correlation between environmental and convection relative inertial stability and the transport of momentum by deep convection we evaluate the hypothesis that convection structurally aligns itself to best access the region of lowest upper tropospheric inertial stability while forming the lowest convective updraught relative inertial stability a numerical experiment evaluates variations in the structure behaviour and momentum transport characteristics of deep convection across the tropical plume genesis region in the eastern pacific this unique region forms as a precursor to tropical plume genesis and possesses spatially varying very low upper tropospheric inertial stability the potential vorticity locally reaches zero or becomes slightly negative in the northern hemisphere our results show that the vertical transport of horizontal momentum is predictable given knowledge of the inertial stability fields immediately surrounding the convection it is conjectured that the preferred mode of convective organization squall line dominated versus more three dimensional near the intertropical convergence zone is a function of the ambient inertial stability therefore as the convection organizes itself it selects the most efficient access to regions of lowest inertial stability to enable its upper tropospheric outflow copyright 2003 royal meteorological society

exploring the initial errors that cause a significant spring predictability barrier for el nino events 1 within the zebiak cane model we identify two types of initial errors that have significant season dependent evolutions related to the spring predictability barrier spb for el nino events one type includes the sea surface temperature anomaly ssta errors that have a zonal dipolar pattern with positive anomalies in the central equatorial pacific and negative ones in the eastern equatorial pacific the other type consists of the ssta errors with a spatial structure opposite to that of the former type the zonal dipolar pattern shows negative anomalies in the central equatorial pacific and positive anomalies in the eastern equatorial pacific the patterns of these two types of errors are nearly opposite of each other the former causes the el nino event to be underpredicted and the latter causes the el nino event to be overpredicted for strong el nino events the former tends to have a larger effect on the predictions than the latter but for weak el nino events it is very difficult to determine which type of initial errors results in worse predictions it is thought that strong weak el nino events could be affected by strong weak nonlinearities there are also other initial errors however they do not yield considerable season dependent evolutions nor can a common characteristic be extracted from their patterns the two types of initial errors suggest two dynamical behaviors of error growth related to the spb in one case the initial errors grow in a manner similar to the el nino events in the other case the initial errors develop with a tendency opposite to the el nino events the two types of initial errors may capture the errors that exhibit significant season dependent evolutions related to the spb in addition they may provide information regarding the sensitive area of enso predictions because of their localized regions therefore if these types of initial errors exist in the realistic el nino southern oscillation enso predictions and if a data assimilation or a target method can filter them the enso forecast skill may be improved for ensemble forecast studies different signs of prediction errors caused by the two types of initial errors could illustrate why the ensemble mean offers a better forecast than a single prediction

scale interactions involved in the initiation structure and evolution of the 15 december 1992 mcs observed during toga coare part ii mesoscale and convective scale processes abstract this paper the second of a series documents the precipitation and kinematic and thermodynamic structure of a tropical mesoscale convective system observed by instrumented aircraft on 15 december 1992 during toga coare radar derived precipitation fields indicate that the studied system consists of two subsystems s1 and s2 characterized by distinct internal dynamics and morphological structures the retrieved kinematic and thermodynamic structures are compared in detail with the synoptic scale characteristics described in part i of this paper so as to evaluate the scale interactions involved in the internal organization of this convective system it is shown essentially that the synoptic scale circulation governs the mesoscale and convective scale motions and therefore determines the internal organization of the selected system in particular this study highlights the major role played by the synoptic scale vertical wind shear in the internal structure of this tropical mesoscale system m

organizational modes of midlatitude mesoscale convective systems this paper discusses common modes of mesoscale convective organization using 2 km national composite reflectivity data the authors investigated linear mesoscale convective systems mcss that occurred in the central united states during may 1996 and may 1997 based upon the radar observed characteristics of 88 linear mcss the authors propose a new taxonomy comprising convective lines with trailing ts leading ls and parallel ps stratiform precipitation while the ts archetype was found to be the dominant mode of linear mcs organization the ls and ps archetypes composed nearly 40 of the studied population in this paper the authors document the characteristics of each linear mcs class and use operational surface and upper air data to describe their different environments in particular wind profiler data reveal that the stratiform precipitation arrangement associated with each class was roughly consistent with the advection of hydrometeors implied by the mean middle and upper tropospheric storm relative winds which were significantly different among the three mcs modes case study examples are presented for both the ls and ps classes which have received relatively little attention to this point as well the authors give a general overview of the synoptic scale meteorology accompanying linear mcss in this study which was generally similar to that observed by previous investigators

the role of environmental shear and thermodynamic conditions in determining the structure and evolution of mesoscale convective systems during toga coare abstract a collection of case studies is used to elucidate the influence of environmental soundings on the structure and evolution of the convection in the mesoscale convective systems sampled by the turboprop aircraft in the tropical ocean global atmosphere toga coupled ocean atmosphere response experiment coare the soundings were constructed primarily from aircraft data below 5 6 km and primarily from radiosonde data at higher altitudes the well documented role of the vertical shear of the horizontal wind in determining the mesoscale structure of tropical convection is confirmed and extended as noted by earlier investigators nearly all convective bands occurring in environments with appreciable shear below a low level wind maximum are oriented nearly normal to the shear beneath the wind maximum and propagate in the direction of the low level shear at a speed close to the wind maximum when there is appreciable shear at middle levels 800 400 mb convective bands form parallel to the shear with

earthquake source scaling relationships from 1 to 5 ml using seismograms recorded at 2 5 km depth the scaling relationships of earthquake sources less than about magnitude 3 have been the subject of considerable controversy over the last two decades studies of such events have shown a tendency for the constant stress drop self similarity of larger earthquakes to breakdown at small magnitudes and an apparent minimum source dimension of about 100 m has been observed other studies showed that this apparent breakdown in scaling could be an artifact of severe near surface attenuation limiting the spatial resolution of surface data in this study source parameters are determined for over 100 nearby tectonic earthquakes from recordings at a depth of 2 5 km in granite in the cajon pass scientific drill hole southern california comparison of the seismograms recorded at this depth with those at the wellhead clearly demonstrates the effect of the severe attenuation in the upper kilometers of the earth s crust source parameters are calculated by spectral modeling of three component p and s waves assuming four source models based on the brune 2 n 2 model in model l n 2 is fixed and q of p and s waves is determined to be 912 581 1433 and 1078 879 1323 respectively the numbers in parentheses are 1 standard deviation in model 2 qp qs 1000 is assumed and n is allowed to vary the 2 model is a good average for the data set but there is some real scatter supported by the data in model 3 qp qs 1000 is also assumed and 2 is constrained and in model 4 attenuation is ignored and n is allowed to vary source dimensions of less than 10m are observed for all four models 10 times smaller than the proposed minimum no breakdown in constant stress drop scaling is seen in the downhole data approximately ml 1 to 5 5 m0 109 1016 nm the ratio between radiated seismic energy estimated by integrating the velocity squared spectra with adequate signal bandwidth and seismic moment appears to decrease gradually with decreasing moment in the magnitude range 1 to 7 this is not incompatible with a constant stress drop but could result from errors in calculating energy the ratio of the s wave energy to that radiated by the p waves is about 14 after correction for attenuation this low value is consistent with the corner frequency shift of about 1 3 this corner frequency shift is observed for all four source models and therefore is interpreted as being source controlled

predictability of a coupled model of enso using singular vector analysis part i optimal growth in seasonal background and enso cycles the fastest initial error growth optimal growth in the zebiak and cane zc forecast model for the el nino southern oscillation enso is analyzed by singular value decomposition of a forward tangent model along a trajectory in a reduced eof space in this paper part i of ii optimal growth about the seasonally varying background and enso cycles from a long model run are discussed among the many forms of nonlinearity in zc the discontinuity of the slope in subsurface temperature at zero thermocline depth and the nonlinear advection of sst are the most significant that positive perturbations grow much faster than negative perturbations around the seasonally varying background is first attributable to the discontinuity and second attributable to nonlinear advection about the seasonally varying background 6 month optimal growth is largest for early boreal spring starts which is related to the enhanced atmospheric heating due to equatorward movement of the itcz one dominant growing structure is found characterized by north south and east west sst dipoles convergent winds on the equator in the eastern pacific and a deepened thermocline in the whole equatorial belt this structure is insensitive to start month and optimization time optimal growth about enso cycles in a long model run is generally much smaller than that about the seasonally varying background as before one dominant growing structure insensitive to start time and optimization time is found during the warm phase of enso optimal growth is modulated by season as is that about the seasonal varying background during the onset and mature phases of enso the final pattern of the optimal structure in 6 months is confined to the eastern pacific during the decay phase of enso it spreads to the western pacific as well during the cold phase of enso optimal growth has two maxima in a year early spring and fall the optimal perturbation propagates westward associated with surface layer wind interaction the authors also compare the singular vector analysis in eof space and the standard one in physical space the importance of norm definition to optimal growth and optimal structure is discussed

variability of seismic source spectra estimated stress drop and radiated energy derived from cohesive zone models of symmetrical and asymmetrical circular and elliptical ruptures large variability of earthquake stress drops and scaled energy has been commonly reported in the literature but it is difficult to assess how much of this variability is caused by underlying physical source processes rather than simply observational uncertainties here we examine a variety of dynamically realistic rupture scenarios for circular and elliptical faults and investigate to what extent the variability in seismically estimated stress drops and scaled energy comes from differences in source geometry rupture directivity and rupture speeds we numerically simulate earthquake source scenarios using a cohesive zone model with the small scale yielding limit where the solution approaches a singular crack model with spontaneous healing of slip compared to symmetrical circular source models asymmetrical models result in larger variability of estimated corner frequencies and scaled energy over the focal sphere the general behavior of the spherical averages of corner frequencies and scaled energy in the subshear regime extends to the supershear regime although shear mach waves generated by the propagation of supershear rupture lead to much higher corner frequency and scaled energy estimates locally our results suggest that at least a factor of 2 difference in the spherical average of corner frequencies is expected in observational studies simply from variability in source characteristics almost independent of the actual stress drops translating into a factor of 8 difference in estimated stress drops furthermore radiation efficiency estimates derived from observed seismic spectra should not be directly interpreted as describing rupture properties unless there are independent constraints on rupture speed and geometry

on the characteristics of earthquake stress release variations in japan abstract the amount of stress released during earthquakes is a fundamental characteristic of the earthquake rupture process as such it represents a key parameter for improving our understanding of earthquake source physics and for reliable ground motion prediction large earthquake populations usually show variations in stress release as large as three orders of magnitude but the underlying mechanisms have remained largely elusive and particularly the dependence of stress release on earthquake size is still a matter of debate here i use a unique dataset from japan encompassing earthquakes of a wide magnitude range and spatial coverage to show that stress release variations of crustal earthquakes are strongly correlated with heat flow variations indicating that they are thermally controlled in contrast subcrustal events depict highest stress release in regions of strong subduction interface coupling and overall less pronounced variability as compared with crustal earthquakes stress release is overall only weakly dependent on earthquake size but at local scales i e within individual earthquake sequences the dependence can be very strong and apparently varies with stress regime accounting for these systematic variations reduces the stress release variability on local scale by a factor of two to three as compared with the full earthquake population a finding that is of key significance in the endeavor to reduce the uncertainties in future ground motion predictions

earthquake stress drops and inferred fault strength on the hayward fault east san francisco bay california we study variations in earthquake stress drop with respect to depth faulting regime creeping versus locked fault behavior and wall rock geology we use the p wave displacement spectra from borehole seismic recordings of m 1 0 4 2 earthquakes in the east san francisco bay to estimate stress drop using a stack and invert empirical green s function method the median stress drop is 8 7 mpa and most stress drops are in the range between 0 4 and 130 mpa an apparent correlation between stress drop and magnitude is entirely an artifact of the limited frequency band of 4 55 hz there is a trend of increasing stress drop with depth with a median stress drop of 5 mpa for 1 7 km depth 10 mpa for 7 13 km depth and 50 mpa deeper than 13 km we use s p amplitude ratios measured from the borehole records to better constrain the first motion focal mechanisms high stress drops are observed for a deep cluster of thrust faulting earthquakes the correlation of stress drops with depth and faulting regime implies that stress drop is related to the applied shear stress we compare the spatial distribution of stress drops on the hayward fault to a model of creeping versus locked behavior of the fault and find that high stress drops are concentrated around the major locked patch near oakland this also suggests a connection between stress drop and applied shear stress as the locked patch may experience higher applied shear stress as a result of the difference in cumulative slip or the presence of higher strength material the stress drops do not directly correlate with the strength of the proposed wall rock geology at depth suggesting that the relationship between fault strength and the strength of the wall rock is complex

contribution of the location and spatial pattern of initial error to uncertainties in el nino predictions with the zebiak cane model the contribution of the location and spatial pattern of initial error in sea surface temperature anomalies ssta to uncertainty in el nino predictions is investigated using an approach based on conditional nonlinear optimal perturbation cnop which seeks to find the initial error i e the cnop error that satisfies a given constraint and that causes the largest prediction error at the prediction time the computed cnop error of ssta has a dipole pattern in the equatorial central and eastern pacific the initial error from the equatorial central and eastern pacific tends to grow more significantly than those from other locations because of the contribution of annual mean states the location of the initial error plays an important role in the error evolution e g the shallow annual mean thermocline in the eastern pacific favors feedback between the thermocline and sea surface temperature meanwhile the specific dipole structure of the initial error is also crucial for optimal error growth even with the same magnitude as the cnop error random initial error in the equatorial central and eastern pacific does not evolve significantly over time initial errors of ssta with a similar spatial pattern to the cnop error i e the dipole pattern of ssta error give rise to larger prediction errors than those without similar spatial pattern do consequently the magnitude of the prediction error at the prediction time depends on the combined effects of the location and spatial pattern of the initial error if additional observation instruments are deployed to observe sea surface temperature with limited coverage they should preferentially be deployed in the equatorial central and eastern pacific

estimating mass and momentum fluxes in a line of cumulonimbus using a single high resolution doppler radar we present a method to derive the vertical wind field at a scale of 1 2 km from a high resolution doppler radar by performing vertical scans in the plane of the mean wind and tracking turbulent features on a scale of several hundred metres in the radial velocity field between consecutive scans the method is applied to a line of cumulonimbus clouds observed by the high resolution chilbolton radar in southern england the storm was not a squall line since it was propagating parallel rather than perpendicular to its length a sequence of scans was taken over an hour long period from these scans we derive the u and w components of the wind updraughts of up to 15 m s 1 are found from these observations the mass flux of a typical storm cell was estimated over the 50 min lifetime of the cell the total mass of air transported from the boundary layer to the upper troposphere was found to be around 50 megatonnes the profile of hour averaged momentum flux against height was then calculated and compared to the vertical shear of the mean horizontal wind it was found that above 4 5 km the momentum flux was down gradient with an equivalent eddy diffusivity of around 103 m2s 1 below this height however the flux was counter gradient with an equivalent eddy diffusivity of around 103m2s 1 we propose a mechanism to explain this behaviour involving the prevalence of precipitation cooling and descent on the downshear side of convergence lines a synthesis of the major wind flows in the storm reveals that despite superficial appearance the storm did not fit the usual multi cell paradigm in which gust fronts play a key roll in triggering new cells downwind rather the convergence lines associated with the convection were more akin to warm frontal surfaces that remain tied to the base of each cell new cells tending to form upwind of older cells copyright 2008 royal meteorological society

small earthquakes deviate from the omega square model as revealed by multiple spectral ratio analysis we examine the omega square model by estimating the source spectra of 196 m w 3 2 4 0 shallow earthquakes in the northern ibaraki prefecture and the fukushima prefecture hamadori area of japan using multiple spectral ratio analysis spectral ratios of the seismograms of target events to those of multiple nearby small events empirical green s function egf events allow for negation of path and site effects and are fitted by the omega square model the residual spectra for different egf events exhibit similar curves indicating how the source spectra of the target events deviate from the omega square model many earthquakes deviate remarkably whereas other events fit well the possible implications of these findings are incoherencies in the rupture process the double corner frequency model and a high frequency falloff exponent value slightly higher than 2 although this is still an open question this study will help to improve the source spectrum model enhancing not only source studies but strong motion assessments and other seismological studies online material figures showing results of spectral analysis of the events with the largest and smallest peak to peak amplitudes

temperature moisture dependence of the deep convective transition as a constraint on entrainment in climate models abstractproperties of the transition to strong deep convection as previously observed in satellite precipitation statistics are analyzed using parcel stability computations and a convective plume velocity equation a set of alternative entrainment assumptions yields very different characteristics of the deep convection onset boundary here measured by conditional instability and plume vertical velocity in a bulk temperature water vapor thermodynamic plane in observations the threshold value of column water vapor above which there is a rapid increase in precipitation referred to as the critical value increases with temperature but not as quickly as column saturation and this can be matched only for cases with sufficiently strong entrainment this corroborates the earlier hypothesis that entraining plumes can explain this feature seen in observations and it places bounds on the lower tropospheric entrainment examination of a simple interactive entrainment scheme in which a minimum turbulent entrai

analysis of cloud resolving model simulations for scale dependence of convective momentum transport abstractwe use 3d cloud resolving model crm simulations of two mesoscale convective systems at midlatitudes and a simple statistical ensemble method to diagnose the scale dependency of convective

asperity model of an earthquake dynamic problem a previous study that presented the static solution for an asperity model of an earthquake is extended to solve the dynamic problem that develops when failure occurs on the boundary of an asperity patch and then spreads over the surrounding displacement shadow region the boundary integral equation method is coupled with basic constitutive equations for failure and friction to solve the dynamic problem with different parameters used for the strong asperity patch and weak shadow region no friction displacement weakening friction and velocity strengthening friction are all investigated depending on the type and amount of friction that is present the dynamic solutions for slip on the fault exhibit a range of different features including overshoot of the static solution and oscillation rupture front velocities that may be greater than or less than the s velocity and change with position and either total or partial release of the static moment common characteristics of the solutions are that failure on the asperity patch is almost independent of failure on the shadow region and that the displacement deficit on the shadow region is released by propagating slip pulses the stress concentrations of the asperity model are sufficient to produce nonlinear elastic effects in a region extending outward from the fault to distances comparable with the dimensions of the shadow region beginning with the solutions for slip on the fault waveforms are simulated for an earthquake of magnitude m w 1 44 and compared with data recorded at a distance of 8 65 km simulations that contain both source and propagation effects are capable of explaining most of the basic features of the observational data including general agreement with the shape of the waveforms in the time domain the levels and slopes of the spectra at low frequencies less than 10 hz and at high frequencies greater than 100 hz and some of the interference effects present in both the time and frequency domains

midtropospheric anticyclonic vortex street associated with a cloud band near a cold front abstract the characteristics and formation mechanism of an anticyclonic vortex street of meso scale which appeared near a cold front around the ryukyu islands japan on 11 april 1995 were examined by an analysis of observational data a numerical simulation and a linear stability theory the vortex street was generated near the midtroposphere on the north edge of a cloud band along the cold front the diameter of individual vortices was 70 km and the interval between vortices was 100 200 km the phase speed of the vortices was nearly equal to the wind speed at the 400 hpa level the cloud band was accompanied by a weak wind region in which the along front wind was about 15 m s 1 weaker than that in the environment a region of large anticyclonic horizontal shear 10 4 s 1 existed on the north side of this weak wind region to examine a detailed structure and formation mechanism of the weak wind region a numerical simulation was performed regions of active convection and convective cloud bands

representing convective organization in prediction models by a hybrid strategy the mesoscale organization of precipitating convection is highly relevant to next generation global numerical weather prediction models which will have an intermediate horizontal resolution grid spacing about 10 km a primary issue is how to represent dynamical mechanisms that are conspicuously absent from contemporary convective parameterizations a hybrid parameterization of mesoscale convection is developed consisting of convective parameterization and explicit convectively driven circulations this kind of problem is addressed for warm season convection over the continental united states although it is argued to have more general application a hierarchical strategy is adopted cloud systemresolving model simulations represent the mesoscale dynamics of convective organization explicitly and intermediate resolution simulations involve the hybrid approach numerically simulated systems are physically interpreted by a mechanistic dynamical model of organized propagating convection this model is a formal basis for approximating mesoscale convective organization stratiform heating and mesoscale downdraft by a first baroclinic heating couplet the hybrid strategy is implemented using a predictor corrector strategy explicit dynamics is the predictor and the first baroclinic heating couplet the corrector the corrector strengthens the systematically weak mesoscale downdrafts that occur at intermediate resolution when introduced to the betts miller janjic convective parameterization this new hybrid approach represents the propagation and dynamical structure of organized precipitating systems therefore the predictor corrector hybrid approach is an elementary practical framework for representing organized convection in models of intermediate resolution

interaction of an upper tropospheric jet with a squall line originating along a cold frontal boundary abstracton 8 june 2003 an expansive squall line along a surface cold frontal boundary was sampled during the bow echo and mesoscale convective vortex experiment the naval research laboratory p 3 aircraft and the national oceanic and atmospheric administration p 3 aircraft simultaneously sampled the leading and trailing edge of this squall line respectively with x band doppler radars data from these two airborne radar systems have been synthesized to produce a pseudo quad doppler analysis of the squall line yielding a detailed three dimensional kinematic analysis of its structure a simulation of the squall line was carried out using the weather research and forecasting model to complement the pseudo quad doppler analysis the simulation employed a 3 km convection allowing nested domain centered over the pseudo quad doppler domain along with a 9 km parent domain to capture the larger synoptic scale cyclone the pseudo quad doppler analysis reveals that the convective line was embedded within the up

characterization of momentum transport associated with organized moist convection and gravity waves abstract tropical convection is inherently multiscalar involving complex fields of clouds and various regimes of convective organization ranging from small disorganized cumulus up to large organized convective clusters in addition to being a crucial component of the atmospheric water cycle and the global heat budget tropical convection induces vertical fluxes of horizontal momentum there are two main contributions to the momentum transport the first resides entirely in the troposphere and is due to ascent descent and organized circulations associated with precipitating convective systems the second resides in the troposphere stratosphere and farther aloft and is caused by vertically propagating gravity waves both the convective momentum transport and the gravity wave momentum flux must be parameterized in general circulation models yet in existing parameterizations these two processes are treated independently this paper examines the relationship between the convective momentum transport and

convective momentum transport and perturbation pressure field from a cloud resolving model simulation this study uses a 2d cloud resolving model to investigate the vertical transport of horizontal momentum and to understand the role of a convection generated perturbation pressure field in the momentum transport by convective systems during part of the tropical ocean and global atmosphere coupled ocean atmosphere response experiment toga coare intensive observation period it shows that convective updrafts transport a significant amount of momentum vertically this transport is downgradient in the easterly wind regime but upgradient during a westerly wind burst the differences in convective momentum transport between easterly and westerly wind regimes are examined the perturbation pressure gradient accounts for an important part of the apparent momentum source in general it is opposite in sign to the product of cloud mass flux and the vertical wind shear with smaller magnitude examination of the dynamic forcing to the pressure field demonstrates that the linear forcing representing the interaction between the convective updrafts and the large scale wind shear is the dominant term while the nonlinear forcing is of secondary importance thus parameterization schemes taking into account the linear interaction between the convective updrafts and the large scale wind shear can capture the essential features of the perturbation pressure field the parameterization scheme for momentum transport by zhang and cho is evaluated using the model simulation data the parameterized pressure gradient force using the scheme is in excellent agreement with the simulated one the parameterized apparent momentum source is also in good agreement with the model simulation other parameterization methods for the pressure gradient are also discussed

organized convective systems in the tropical western pacific as a process in general circulation models a toga coare case study we examine the large scale effects of organized convective systems in the tropical western pacific observed during the tropical ocean global atmosphere coupled ocean atmosphere response experiment toga coare in a case study approach we examine realizations of a supercluster associated with the onset of the december 1992 westerly wind burst in the t213 operational medium range weather forecasting model of the european centre for medium range weather forecasts ecmwf we idealize a supercluster as a hierarchy of three interacting scales namely organized cumulonimbus c 1 mesoscale convective systems c 2 and the supercluster component c 3 it is shown that the ecmwf model represents this hierarchy as a c 3 like surrogate whose influence dominates the effect of parametrized convection this causes over prediction of the model tendencies which in the case of zonal momentum is explained in elementary terms the structure of the resolved scale momentum flux is explained by moncrieff s 1992 archetypal theory of organized convection which has been verified against observations and cloud resolving model data sets the parametrization of subgrid scale convective momentum flux in the ecmwf model based on a momentum mixing concept produces subgrid scale tendencies that are physically different from transports associated with cumulonimbus convection in a shear flow we outline a strategy for parametrizing the momentum flux by the c 1 component based on the archetypal model the c 2 component which is part resolved and part parametrized is at odds with the assumptions of scale separation underpinning parametrization it is argued that this component should be represented as part of the prognostic treatment of convectively generated cirrus finally we suggest cloud resolving modelling studies to further quantify the structure and large scale impact of superclusters in a westerly wind burst environment ranging from idealized models to models having data assimilation capability

modulation of westerly wind bursts by sea surface temperature a semistochastic feedback for enso abstract westerly wind bursts wwbs in the equatorial pacific are known to play a significant role in the development of el nino events they have typically been treated as a purely stochastic external forcing of enso recent observations however show that wwb characteristics depend upon the large scale sst field the consequences of such a wwb modulation by sst are examined using an ocean general circulation model coupled to a statistical atmosphere model i e a hybrid coupled model an explicit wwb component is added to the model with guidance from a 23 yr observational record the wwb parameterization scheme is constructed such that the likelihood of wwb occurrence increases as the western pacific warm pool extends a semistochastic formulation which has both deterministic and stochastic elements the location of the wwbs is parameterized to migrate with the edge of the warm pool it is found that modulation of wwbs by sst strongly affects the characteristics of enso in particular coupled fe

radiated seismic energy from coda measurements and no scaling in apparent stress with seismic moment 1 the seismic coda consists of scattered waves that leave the earthquake source in a variety of directions the averaging of source radiation that results leads to stable ground motion spectra that we use as the basis for a robust measurement of radiated wave energy we apply an empirical green s function egf method to the seismic coda in order to investigate scaling of the radiated seismic energy we correct for path effects in the spectra of earthquakes by using a stack of closely located small earthquakes as an egf we apply this approach to four earthquake sequences in western north america that span a magnitude range from mw 3 0 mw 7 1 our estimates of scaled energy are consistent with independent measurements where available we find no dependence in individual seismic energy estimates on source station distance which validates the egf approximation we find that a constant scaled energy of 3 5 10 5 provides a reasonable fit to the data with no dependence of the scaled energy on seismic moment

multiscale waves in an mjo background and convective momentum transport feedback abstractthe authors use linear analysis for a simple model to study the evolution of convectively coupled waves ccws in a background shear and background moisture mimicking the observed structure of the madden julian oscillation mjo this is motivated by the observation in an idealized setting of intraseasonal two way interactions between ccws and a background wind it is found here that profiles with a bottom heavy moisture content are more favorable to the development of mesoscale squall line like waves whereas synoptic scale ccws are typically more sensitive to the shear strength the mjo envelope is thus divided into three regions in terms of the types of ccws that are favored an onset region in front that is favorable to kelvin waves a mature or active region in the middle in which squall lines are prominent and the stratiform and decay phase region in the back that is favorable to westward inertia gravity wig waves a plausible convective momentum transport cmt feedback is then provide

investigating uncertainties in empirical green s function analysis of earthquake source parameters i use a well recorded earthquake sequence to investigate the uncertainties of earthquake stress drops calculated using an empirical green s function egf approach the earthquakes in the largest m 2 1 repeating sequence targeted by the san andreas observatory at depth safod parkfield california are recorded by multiple borehole stations and have simple sources well constrained stress drops and abundant smaller earthquakes to use as egfs i perform three tests to estimate quantitatively the likely uncertainties to arise in less optimal settings i use egf earthquakes with a range of cross correlation values and separation distances from the main earthquakes the stress drop measurements decrease by a factor of 3 as the quality of the egf assumption decreases a good egf must be located within approximately one source dimension of the large earthquake with high cross correlation i subsample the large number of measurements for the main earthquakes to investigate the expected stress drop uncertainties in studies where fewer stations or egfs are available if only one measurement is available the uncertainties are likely to be at least 50 the uncertainties decrease to 20 with five or more measurements using multiple egfs is a good alternative to multiple stations to investigate the effects of limited frequency bandwidth i recalculate the corner frequencies after progressively decimating the sample rate decreasing the high frequency limit of the bandwidth decreases the estimate of the corner frequency and stress drop the corner frequency may be underestimated if it is within a factor of 3 of the maximum frequency of the signal

kīholo bay hawai i earthquake sequence of 2006 relationship of the main shock slip with locations and source parameters of aftershocks 1 we study the source process of the k holo bay earthquake mw 6 7 which occurred beneath the northwest part of the island of hawai i on 15 october 2006 and static stress drops of small earthquakes that occurred in 2006 and 2007 around the main shock including aftershocks we relocate the aftershocks to determine the fault plane from the two nodal planes the relocated aftershocks define an e w trending plane that dips to the south in good agreement with one of the nodal planes given by the global centroid moment tensor solution waveform inversion is performed with multiple time windows to investigate the rupture speed and the slip distribution of the main shock waveforms of an aftershock with mw 5 2 are used to calculate empirical green s functions our results indicate that the rupture propagated unilaterally to the west with a rupture speed greater than 3 0 km s 63 of the shear wave velocity this westward rupture is consistent with the fact that aftershocks are distributed predominantly to the west of the main shock epicenter most aftershocks are located on the edge of patches with a large slip or asperities and some also occur inside the patches we also estimate static stress drops of 39 earthquakes 2 5 ml 3 5 that occurred in 2006 and 2007 near the source region of the k holo bay earthquake static stress drops range from 0 12 to 8 6 mpa and aftershocks around large slip patches of the main shock likely to have larger stress drops

comprehensive analysis of earthquake source spectra in southern california we compute and analyze p wave spectra from earthquakes in southern california between 1989 and 2001 using a method that isolates source receiver and path dependent terms we correct observed source spectra for attenuation using both fixed and spatially varying empirical green s function methods estimated brune type stress drops for over 60 000 m l 1 5 to 3 1 earthquakes range from 0 2 to 20 mpa with no dependence on moment or local b value median computed stress drop increases with depth in the upper crust from about 0 6 mpa at the surface to about 2 2 mpa at 8 km where it levels off and remains nearly constant in the midcrust down to about 20 km however the results at shallow depths could also be explained as reduced rupture velocities near the surface rather than a change in stress drop spatially coherent variations in median stress drop are observed with generally low values for the imperial valley and northridge aftershocks and higher values for the eastern transverse ranges and the north end of the san jacinto fault we find no correlation between observed stress drop and distance from the san andreas and other major faults significant along strike variations in stress drop exist for aftershocks of the 1992 landers earthquake which may correlate with differences in main shock slip

measurements of spectral similarity for microearthquakes in western nagano japan 1 we use p wave spectral ratios to estimate the seismic energy of 23 microearthquakes mw 0 9 2 7 recorded on a dense network of surface and borehole stations in western nagano japan these events were recorded at 45 surface stations and 2 borehole stations the data set is unique in that most events have high signal to noise ratio at several surface stations and at the two borehole stations the redundancy provided by the large number of stations recording these events allows us to assess the uncertainty of our results we find that the seismic energy to moment er m0 ratios from p waves for the events in our data set are reliable that they vary between 1 10 6 and 1 10 4 and that smaller events tend to have smaller values of er m0 because they are relatively deficient in radiated energy above the corner frequency we observe two spectral effects a variation in corner frequency which accounts for most of the variation in er m0 and steeper spectral falloff rates which contribute to the small values of er m0 for some of the smaller events our estimates of moment and corner frequency suggest that m0 fc 3 e 0 and this implies that either the static stress drop or rupture velocity or both change with earthquake size

complex ruptures of the 11 april 2011 mw 6 6 iwaki earthquake triggered by the 11 march 2011 mw 9 0 tohoku earthquake japan abstract after the 11 march 2011 m w 9 0 tohoku earthquake japan a swarm of shallow normal faulting earthquakes was triggered in a localized region beneath the border between fukushima and ibaraki prefectures in eastern honshu here we examine the coseismic displacement field and a fault model of the largest event of the swarm the 11 april 2011 m w 6 6 iwaki earthquake radar interferometry applied to data of the japanese alos satellite reveals complex ruptures associated with the iwaki earthquake in particular the interferogram clearly shows multiple surface ruptures along each of the subparallel yunodake and itozawa faults the slip distributions on these faults as estimated by inverting the interferogram suggest that the faults dip 60 70 westward and that slip on the itozawa fault extended to a splay fault at depths shallower than about 5 km our results indicate that the highland area west of the itozawa fault was downthrown by up to 2 4 m during the iwaki earthquake online material original and de trended interferograms over a wider area

analytic representation of the large scale organization of tropical convection the pivotal role of mesoscale organization on the large scale coherence of tropical convection is represented by a nonlinear dynamical model the general model consists of two interlocked systems a mesoscale parameterization of organized convection and a two layer model of large scale equatorial dynamics the lower layer dynamics is rossby gyre like whereas outflow from organized convection maintains the upper layer circulation the transports of zonal momentum in the vertical and meridional directions are key processes an archetype of the general model in spite of being brutally simplified represents the convective organization momentum transport and equatorial superrotation realized by the cloud resolving convection parameterization or superparameterization explicit approach developed by grabowski the mesoscale parameterization is an analytic equivalent of the cloud system resolving models used in this computational approach finally issues in parameterizing convective organization are discussed

global variations of stress drop for moderate to large earthquakes 1 we investigate the global variation of earthquake stress drops using spectra of about 2000 events of mb 5 5 between 1990 and 2007 we use an iterative least squares method to isolate source displacement spectra from travel path and receiver contributions based on a convolutional model the observed p wave source spectra are corrected with a globally averaged empirical correction spectrum and estimates of near source attenuation assuming a brune type source model we estimate corner frequencies and compute stress drops stress drop estimates for individual earthquakes range from about 0 3 to 50 mpa but the median stress drop of about 4 mpa does not vary with moment implying earthquake self similarity over the mw 5 2 to 8 3 range of our data a comparison of our results with previous studies confirms this observation over most of the instrumentally observable magnitude range while the absolute values of our estimated stress drops depend upon the assumed source model we identify relative regional variations of stress drop that are robust with respect to the processing parameters and modeling assumptions which includes an inherent assumption of constant rupture velocity we find a dependence of median stress drop on focal mechanism with a factor of 3 5 times higher stress drops for strike slip earthquakes and also find a factor of 2 times higher stress drops for intraplate earthquakes compared to interplate earthquakes

stress drops of repeating earthquakes on the san andreas fault at parkfield i calculate well resolved corner frequencies and stress drops for 25 earthquakes 1989 2006 in the three repeating sequences targeted by the san andreas fault observatory at depth using borehole data and multiple highly correlated empirical green s functions egfs the earthquakes in the largest magnitude m 2 1 cluster exhibit source spectra well fit by a circular source model the corner frequencies correlate with those from the regional study by allmann and shearer 2007 suggesting that the interevent variability is resolvable the earthquakes have stress drops between 25 and 65 mpa with a gradual increase before the 2004 m6 earthquake followed by an immediate decrease then a rapid return to previous levels the spectra of the cluster of m 1 9 earthquakes include high frequency energy not fit by simple source models and so stress drops are unreliable and probably underestimated 1 20 mpa there is no correlation with previous studies and interevent variation is not resolvable the earthquakes in the smallest magnitude cluster m 1 8 have the highest corner frequencies but similar stress drops 4 120 mpa the stress drops exhibit the same temporal variation as the first cluster but there is poor correlation with allmann and shearer 2007 probably because their frequency bandwidth is too limited

organized convection parameterization for the itcz abstractmesoscale convective systems mcss are of fundamental importance in the dynamics of the atmospheric circulation and the climate system they are often observed to develop over significant terrain in ambient shear flows in midlatitudes and embedded within the madden julian oscillation mjo and convectively coupled equatorial wave ccew envelopes as well as in the intertropical convergence zone itcz yet general circulation models gcms fail to resolve these systems and their underlying convective parameterizations are not directed to represent organized circulations shear parallel mcss which are common in the itcz have a three dimensional structure and as such present a serious modeling challenge here a previously developed multicloud model mcm is modified to parameterize mcss one of the main modifications is the parameterization of stratiform condensation to capture extended stratiform outflows which characterize mcss resulting from strong upper level jets linear analysis show

kinematic characteristics of air flowing into and out of precipitating convection over the west pacific warm pool an airborne doppler radar survey air flowing into and out of 25 cloud systems over the west pacific warm pool was sampled by doppler radars on board two noaa wp 3d aircraft and the ncar electra aircraft during the tropical ocean global atmosphere coupled ocean atmosphere response experiment toga coare in convective cells updraught inflows and downdraught outflows tended to be positioned adjacent to each other at sharp updraught downdraught interfaces sloping at various angles and directions the updraught inflows were sometimes shallow and sometimes deep often extending well above the boundary layer downdraught outflow magnitudes were usually stronger than updraught inflows and the horizontal directions of the inflow and outflow were frequently offset from each other at angles of 90 in stratiform precipitation regions the dominant airflow features were descending mid level inflows located at the bases of anvils and often extending into the interior of the precipitation system these stratiform inflows originated at levels between 5 and 10 km and descended to about 3 km a few extended down to the surface stratiform inflows were typically strong and sandwiched between weaker stratiform outflows at upper and lower altitudes the stratiform region inflow and outflow directions were frequently offset by 90 in the horizontal the mid level inflow currents entered the stratiform regions horizontally from a direction similar to that of the large scale ambient wind the mid level stratiform inflow tended to occur in the same vertical plane as the convective downdraught outflow although the mid level stratiform inflow appeared to be slowed by horizontal pressure gradients before connecting with the convective downdraught outflow in other respects the mesoscale systems differed from a simplified two dimensional model of airflow the systems moved primarily by discrete propagation and updraughts and downdraughts tended to have orthogonal horizontal relative airflow

the seismic radiation from composite models of faulting abstract the failure of an asperity i e the dynamic rupture of a small fault area with finite stress drop surrounded by a broken or weak fault area which has no stress drop but which slips after the asperity fails is proposed as a model for the rupture process of a subevent in a composite earthquake the rupture area of the composite earthquake surrounding the subevent is modeled by the weak fault area surrounding the asperity in the subevent model the resulting seismic moment of the subevent is proportional to the stress drop and the rupture area of the subevent as well as the radius of the composite earthaquake by setting the stress drops of the asperity models equal to the dynamic stress drops of the subevents the composite earthquake can be modeled as the sum of a set of subevents which cover the rupture area of the composite earthquake the scaling of the high and low frequency radiation from composite earthquakes composed of asperities is commensurate with generally observed spectral scaling laws in contrast to composite earthquakes composed of cracks or smaller earthquakes a simple filtering strategy is proposed for filtering the waveforms radiated by cracks to approximate the waveforms radiated by asperities the p and s waves radiated by an m l 5 2 earthquake which occurred on 9 may 1983 at coalinga california are simulated using the p and s waves radiated by an m l 3 6 aftershock the aftershock waveforms are first filtered to approximate the radiation from asperities with the appropriate rupture areas and then the waveforms of 12 asperity subevents are summed together to simulate the waveforms and spectra of the composite earthquake

microearthquake spectra from the anza california seismic network site response and source scaling abstract we analyzed spectra of local microearthquakes recorded by the anza california seismic network to isolate the effects of site response and to investigate the scaling of source parameters for small earthquakes spectra of microearthquakes m m o 19 dyne cm at anza have shapes characteristic of the receiver sites and are generally independent of the source region thus the site response is a major conditioner of the observed spectral shape to remove the effects of site response from the spectra of a m 3 event and isolate its source spectrum we divided by the spectra of an adjacent aftershock used as an empirical green9s function event the spectral ratios indicate that the apparent corner frequencies of small earthquakes m o 19 dyne cm observed at even the high f max stations on hard rock are much lower than the source corner frequencies the spectral ratios are consistent with stress drop remaining constant with decreasing seismic moment for events with moments as small as 10 18 dyne cm the spectral ratios display remarkable agreement between sites which showed vast differences in their original spectra indicating that the spectral division effectively removed the site response the source spectrum of the m 3 event has a high frequency spectral fall off of about 2 an apparent dependence of high frequency fall off with seismic moment in the original spectra can also be explained by the effects of site response the difference between the p and s wave corner frequencies and high frequency roll offs in the observed spectra for these events is the result of the site response and is not a source property the shapes of the spectra of microearthquakes at anza can largely be explained by attenuation at shallow depth with a frequency independent q for some sites near surface resonances are also apparent in the spectra of microearthquakes it is indicated by t values determined for each site that q p q s for the shallow low q layer further evidence of low near surface q is observed in the anomalous spectra of an unusually shallow earthquake source depth 1 km in the network the spectra from this shallow event are depleted in high frequency energy at most stations relative to those of deeper events this observation can be explained by a low q surficial zone for stations of the network situated on alluvium this low q layer has a maximum thickness of about 3 km and maximum p and s wave q values of 30 to 50

analysis of the african easterly jet using aircraft observations from the jet2000 experiment analyses of the african easterly jet aej are presented which are based on meridional transects of high resolution dropsonde observations made during jet2000 an aircraft campaign conducted in the last week of august 2000 the observations have confirmed that the aej is closely defined by geostrophic balance the baroclinicity between the extreme northern and southern profiles accurately determines the altitude of the jet core while the location and morphology of the jet core correspond to a locally defined geostrophic wind measure the potential vorticity pv structure has also been found to accord with theoretical expectations with distinctive positive and negative pv anomalies equatorward and poleward of the jet core respectively the thermodynamic structure of the aej environment can be categorized into coherent layers the monsoon layer is a humid zone connected to the land surface extending northwards into the sahel and increasing in depth towards the south this layer is affected by the land surface on diurnal time scales through the growing convective mixed layer and through shallow cumulus clouds above the monsoon layer is the saharan air layer sal which can be identified as a layer of low static stability and low pv the sal is deep where it merges with the saharan boundary layer in the north and becomes thinner toward the south it has been shown that the boundaries of the sal can be approximated to good accuracy as adiabatic surfaces meaning that the sal comprises air which is adiabatically connected to the land surface via the saharan boundary layer the upper region of the sal is identified as a layer of high relative humidity where altocumulus and stratocumulus layers are observed finally the troposphere above the sal is again almost pseudoadiabatic with small baroclinicity which determines the closure of the aej core aloft through inspection of thermodynamic tracers evidence of convective and lateral transport and exchange between these layers is also presented copyright 2005 royal meteorological society

comparison of the initial errors most likely to cause a spring predictability barrier for two types of el nino events in this paper the spring predictability barrier spb problem for two types of el nino events is investigated this is enabled by tracing the evolution of a conditional nonlinear optimal perturbation cnop that acts as the initial error with the biggest negative effect on the el nino predictions we show that the cnop type errors for central pacific el nino cp el nino events can be classified into two types the first are cp type 1 errors possessing a sea surface temperature anomaly ssta pattern with negative anomalies in the equatorial central western pacific positive anomalies in the equatorial eastern pacific and accompanied by a thermocline depth anomaly pattern with positive anomalies along the equator the second are cp type 2 errors presenting an ssta pattern in the central eastern equatorial pacific with a dipole structure of negative anomalies in the east and positive anomalies in the west and a thermocline depth anomaly pattern with a slight deepening along the equator cp type 1 errors grow in a manner similar to an eastern pacific el nino ep el nino event and grow significantly during boreal spring leading to a significant spb for the cp el nino cp type 2 errors initially present as a process similar to a la nina like decay prior to transitioning into a growth phase of an ep el nino like event but they fail to cause a spb for the ep el nino events the cnop type errors are also classified into two types ep type 1 errors and 2 errors the former is similar to a cp type 1 error while the latter presents with an almost opposite pattern both ep type 1 and 2 errors yield a significant spb for ep el nino events for both cp and ep el nino their cnop type errors that cause a prominent spb are concentrated in the central and eastern tropical pacific this may indicate that the prediction uncertainties of both types of el nino events are sensitive to the initial errors in this region the region may represent a common sensitive area for the targeted observation of the two types of el nino events

upscale impact of mesoscale convective systems and its parameterization in an idealized gcm for an mjo analog above the equator abstractthe madden julian oscillation mjo typically contains several superclusters and numerous embedded mesoscale convective systems mcss it is hypothesized here that the poorly simulated mjo

evidence for non constant energy moment scaling from coda derived source spectra 1 we present two lines of evidence showing the ratio of seismically radiated energy er to seismic moment mo increases with increasing moment for crustal events spanning 5 orders in seismic moment this ratio often referred to as the scaled energy er m0 has been elusive and the subject of recent debate within the seismological community because significant frequency dependent corrections must be made to account for source and path heterogeneity it is not uncommon that energy estimates of the same event by different researchers have significantly different values to minimize some of the potential problems we used the regional coda methodology outlined by mayeda et al 2003 on 4 large earthquake sequences mw 7 4 and 7 2 izmit duzce mw 7 2 gulf of aqaba mw 7 3 landers and mw 7 2 hector mine this methodology has been shown to provide the lowest variance estimate of the source spectrum when compared against traditional direct wave estimates in our first approach we made energy estimates from coda derived spectra and observed that increases with increasing moment for 3 7 mw 7 4 in our second approach we used the simple idea outlined by prieto et al 2004 to directly test for self similarity under self similarity earthquake source spectra scaled by 3 should have the same shape to test this one needs very stable spectra either through spectral stacking of direct wave spectra or by the use of stable coda derived spectra for all sequences we found that the mainshocks and larger aftershocks had significantly different spectral shapes than the smaller events the scaled 3 spectra of the larger events represented an upper bound having larger amplitudes near the corner frequency in fact an 3 5 scaling moved the larger events closer to the mean of the spectral population though the spectral shape differences persisted these results strongly suggest that earthquakes are not scaling self similarly and that complexities in the rupture process such as variable slip velocity exist between small and large events

widespread seismicity excitation throughout central japan following the 2011 m 9 0 tohoku earthquake and its interpretation by coulomb stress transfer 1 we report on a broad and unprecedented increase in seismicity rate following the m 9 0 tohoku mainshock for m 2 earthquakes over inland japan parts of the japan sea and izu islands at distances of up to 425 km from the locus of high 15 m seismic slip on the megathrust such an increase was not seen for the 2004 m 9 1 sumatra or 2010 m 8 8 chile earthquakes but they lacked the seismic networks necessary to detect such small events here we explore the possibility that the rate changes are the product of static coulomb stress transfer to small faults we use the nodal planes of m 3 5 earthquakes as proxies for such small active faults and find that of fifteen regions averaging 80 by 80 km in size 11 show a positive association between calculated stress changes and the observed seismicity rate change 3 show a negative correlation and for one the changes are too small to assess this work demonstrates that seismicity can turn on in the nominal stress shadow of a mainshock as long as small geometrically diverse active faults exist there which is likely quite common