a momentum budget analysis of westerly wind events associated with the madden julian oscillation during dynamo abstractthe dynamics of the madden julian oscillation dynamo field campaign was conducted over the indian ocean io from october 2011 to february 2012 to investigate the initiation of the madden julian oscillation mjo three mjos accompanying westerly wind events wwes occurred in late october late november and late december 2011 momentum budget analysis is conducted to understand the contributions of the dynamical processes involved in the wind evolution associated with the mjo over the io during dynamo using european centre for medium range weather forecasts analysis this analysis shows that westerly acceleration at lower levels associated with the mjo active phase generally appears to be maintained by the pressure gradient force pgf which could be partly canceled by meridional advection of the zonal wind westerly acceleration in the midtroposphere tends to be mostly attributable to vertical advection the results herein imply that there is no simple linear dynamic model that can capture t

impacts of convectively coupled kelvin waves on environmental conditions for atlantic tropical cyclogenesis abstracthigh amplitude convectively coupled equatorial atmospheric kelvin waves cckws are explored over the tropical atlantic during the boreal summer 1989 2009 focus is given to the atmospheric environmental conditions that are important for tropical cyclogenesis cckws are characterized by deep westerly vertical wind shear to the east of its convectively active phase and easterly vertical wind shear to the west of it this dynamical signature increases vertical wind shear over the western tropical atlantic ahead of the convectively active phase and reduces vertical wind shear after its passage the opposite is true over the eastern tropical atlantic where the climatological vertical wind shear is easterly positive total column water vapor tcwv anomalies progress eastward with the convectively active phase of the cckw whereas negative tcwv anomalies progress eastward with the convectively suppressed phase during the passage of the convectively active phase of the cckw a zonally oriented strip o

double ramp on the main himalayan thrust revealed by broadband waveform modeling of the 2015 gorkha earthquake sequence abstract the 2015 m w 7 8 gorkha earthquake sequence that unzipped the lower edge of the main himalayan thrust mht in central nepal provides an exceptional opportunity to understand the fault geometry in this region however the limited number of focal mechanisms and the poor horizontal locations and depths of earthquakes in the global catalog impede us from clearly imaging the ruptured mht in this study we generalized the amplitude amplification factor aaf method to teleseismic distance that allows us to model the teleseismic p waves up to 1 5 hz we used well constrained medium sized earthquakes to establish aaf corrections for teleseismic stations that were later used to invert the high frequency waveforms of other nearby events this new approach enables us to invert the focal mechanisms of some early aftershocks which is challenging by using other long period methods with this method we obtained 12 focal mechanisms more than that in the gcmt catalog we also modeled the high frequency teleseismic p waves and the surface reflection phases pp and sp to precisely constrain the depths of the earthquakes our results indicate that the uncertainty of the depth estimation is as small as 1 2 km finally we refined the horizontal locations of these aftershocks using carefully hand picked arrivals the refined aftershock mechanisms and locations delineate a clear double ramp geometry of the mht with an almost flat decollement sandwiched in between the flat dip 7 degrees portion of the mht is consistent with the coseismic rupture of the mainshock which has a well constrained slip distribution the fault morphology suggests that the ramps both along the up dip and down dip directions play a significant role in stopping the rupture of the 2015 gorkha earthquake our method can be applied to general subduction zone earthquakes and fault geometry studies

dynamical aspects of twin tropical cyclones associated with the madden julian oscillation abstract a nonlinear shallow water model on the sphere is used to study barotropic aspects of the formation of twin tropical disturbances by madden julian oscillation mjo convection in the model the effect of mjo convection upon the lower tropospheric tropical circulation was simulated by an eastward moving meridionally elongated mass sink straddling the equator the intensity and propagation speed of the mass sink were chosen to simulate observations that mjo convection intensifies while nearly stationary in the eastern equatorial indian ocean weakens while moving eastward over the maritime continent again intensifies once it reaches the west pacific ocean and finally becomes stationary and dies off near the date line this mass sink produced twin cyclones in the two regions where it was stationary namely where it was initially turned on and where it was turned off in addition the mass sink produced two zonally elongated cyclonic potential vorticity anomalies straddling the equator in the reg

the structure and annual variation of antisymmetric fluctuations of tropical convection and their association with rossby gravity waves abstract the signature of 4 5 day period rossby gravity waves is searched for in the tropical convection field across the indian pacific oceans the convergence divergence field of these waves in the lower troposphere is anticipated to produce an antisymmetric fluctuation in tropical convection antisymmetric fluctuations of tropical convection are shown to exhibit a pronounced spectral peak at a 4 5 day period only during boreal fall and only within about 30 longitude of the date line the peak amplitude occurs around 7 5 latitude these fluctuations propagate westward at 15 20 m s 1 with zonal wavelength of about 7000 9000 km the fluctuations of convection are coherent and out of phase with the equatorial meridional wind which also exhibits a pronounced spectral peak at a 4 5 day period in the lower troposphere near the date line the antisymmetric zonal wind also is strongly coherent with the antisymmetric convective fluctuations in this region the horizontal distributions of the 4 5 day power an

seismicity change revealed by etas pi and z value methods a case study of the 2013 nantou taiwan earthquake abstract on mar 27 2013 a ml6 2 earthquake occurred in the nantou area of central taiwan which caused one death and nearly 90 injured two months later another ml6 3 earthquake struck the same region on june 2 2013 the epicenter of which is close to the march ml6 2 earthquake seismicity is a sensitive indicator of stress rate and inelastic deformation process in crust therefore examination of temporal changes in seismicity is important to understand the preparatory processes of damaging inland earthquakes in this study we applied the epidemic type aftershock sequences model etas model to the earthquake data covering broader taiwan region which is maintained by the central weather bureau cwb of taiwan to investigate precursory temporal changes in seismicity for the ml6 2 nantou earthquake we regard the march ml6 2 and june ml6 3 earthquakes as an event sequence and especially focus on temporal changes in seismicity prior to the ml6 2 event application of more than one model to an earthquake catalog would be informative in elucidating the relationships between seismicity precursors and the preparatory processes of large earthquakes based on this motivation we further applied two different approaches the pattern informatics pi method and the zmap method which is a gridding technique based on the standard deviate z value test to the same earthquake data of cwb as a result we found that the epicenter of the 2013 ml6 2 nantou earthquake was surrounded by three main seismic quiescence regions prior to its occurrence the assumption that this is due to precursory slip stress drop on fault plane or its deeper extent of the ml6 2 nantou earthquake is supported by previous researches based on seismicity data geodedic data and numerical simulations using rate and state dependent friction laws

the madden julian oscillation barotropic dynamics and north pacific tropical cyclone formation part i observations low level barotropic dynamics may help to explain the modulation of eastern and western north pacific tropical cyclones by the madden julian oscillation mjo during northern hemisphere summer the mjo is characterized by alternating periods of westerly and easterly 850 mb zonal wind anomalies across the tropical pacific ocean when mjo 850 mb wind anomalies are westerly small scale slow moving eddies grow through barotropic eddy kinetic energy eke conversion from the mean flow these growing eddies together with strong surface convergence 850 mb cyclonic shear and high mean sea surface temperatures create a favorable environment for tropical cyclone formation periods of strong mjo easterlies over the pacific are characterized by lesser eke and negligible eddy growth by barotropic conversion the term 2 x is a leading contributor to low level barotropic eke conversion during mjo westerly 2 u9 u periods across the pacific indicating the importance of zonal variations in the westerly jet for producing concentrations of eddy energy this mechanism can be described as wave accumulation associated with variations of the low level zonal flow the conversion term 2 y contributes a smaller portion of the total conversion u9y9 u over the eastern pacific but is of comparable importance to 2 x during westerly mjo events in the 2 u9 u western pacific

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

tropical tropopause transition layer cirrus as represented by calipso lidar observations the spatial and temporal variability of cirrus cloud fraction within the tropical tropopause transition layer ttl is investigated based on three years of data from the cloud aerosol lidar and infrared pathfinder satellite observations calipso mission analyzed in conjunction with fields from the european centre for medium range weather forecasts re analysis era interim and temperature profiles from radiosondes launched at manus island papua new guinea 28s 1478e ttl cirrus is found to be mainly confined to the rising branch of the hadley cell within 158 of the equator with maximum cloud fraction between 14 and 15 km the time varying spatial pattern ofcloud fraction within this beltdoesnot resemble the pattern of cloud fractionin the layer below aswould be expected ifthe ttl cirruswere formed bythe spreading ofthe anvils of convective clouds on the contrary within the stably stratified layer above 13 km cirrus cloud fraction and temperaturebothappear tobemodulatedbytheplanetary scalevertical velocityfield thetime varyingspatial patterns arereminiscentofthevertical propagatingkelvinwaveresponsetoanequatorialheatsource withthe coldest cloudiest air in the ttl centered approximately 308 of longitude to the east of the strongest heating

zonal and vertical structure of the madden julian oscillation abstract a statistical study of the three dimensional structure of the madden julian oscillation mjo is carried out by projecting dynamical fields from reanalysis and radiosonde data onto space time filtered outgoing longwave radiation olr data mjo convection is generally preceded by low level convergence and upward motion in the lower troposphere while subsidence cooling and drying prevail aloft this leads to moistening of the boundary layer and the development of shallow convection followed by a gradual and then more rapid lofting of moisture into the middle troposphere at the onset of deep convection after the passage of the heaviest rainfall a westerly wind burst region is accompanied by stratiform precipitation where lower tropospheric subsidence and drying coincide with continuing upper tropospheric upward motion the evolution of the heating field leads to a temperature structure that favors the growth of the mjo the analysis also reveals distinct differences in the vertical structure

spatial and temporal variation of b values in southwest china in our study we used an improved bayesian method based on a basis spline b spline function to estimate the spatial and temporal variations of b values in southwest china we propose that b values combined with seismicity and tectonic background can provide a fairly clear stress condition and can be used in earthquake hazard analysis very low b values in southwest china appear to be related to the 2008 m s 8 0 wenchuan earthquake we also suggest that the decreasing b value trend in the longmen shan area from 2000 to 2008 may be an indicator of the 2008 m s 8 0 wenchuan earthquake

precise relative earthquake depth determination using array processing techniques precise determination of hypocentral depth remains one of the most relevant problems in earthquake seismology it is well known that using depth phases allows for significant improvement in event depth determination however routinely and systematically picking such phases for teleseismic or regional arrivals is problematic due to poor signal to noise ratios around the pp and sp phases to overcome this limitation we have taken advantage of the additional information carried by seismic arrays we use velocity spectral analysis to precisely measure pp p times the individual estimates obtained at different subarrays for all pairs of earthquakes are combined using a double difference algorithm in order to precisely map seismicity in regions where it is tightly clustered we illustrate this method by relocating intermediate depth earthquakes in the nazca subducting plate beneath northern chile where we confirm the existence of a narrowly spaced double seismic zone previously imaged using a local dedicated deployment as a second example we relocate the aftershock sequence of the 2014 mw 7 9 intermediate depth rat islands earthquake and provide evidence of a subvertical fault plane for the mainshock finally we show that the resulting relative depth errors are typically smaller than 2 km

seismicity analysis of the 2016 ms5 0 yunlong earthquake yunnan china and its tectonic implications we relocate earthquakes occurring 1 week before and 1 month after the 2016 yunlong ms5 0 earthquake by simultaneously using p and s travel times and waveform cross correlation data in the double difference relocation algorithm we then use the well relocated earthquakes as template events and scan through the continuous waveforms to search for and locate weak events by using the match and locate method a total of 4602 events are detected by using 660 templates which is 3 times the number of events listed in the yunnan seismic networks catalogue our refined catalogue reveals three stages of seismic activity and energy release processes during the 2016 yunlong ms5 0 earthquake sequence we also refine the focal depths and mechanisms of 12m 3 0 earthquakes using the broadband waveform modeling method both the relocated hypocenters and focal mechanisms of the 12m 3 0 earthquakes delineate fault strike and dip angles of 200 and 75 respectively indicating that the seismogenic fault could be a nne striking blind or subfault located between the weixi qiaohou fault and lancangjiang fault our results could contribute to better understanding of local seismic hazard evaluations in the vicinity of yunlong area of yunnan china

a shallow fault zone structure illuminated by trapped waves in the karadere duzce branch of the north anatolian fault western turkey summary we discuss the subsurface structure of the karadere duzce branch of the north anatolian fault based on analysis of a large seismic data set recorded by a local passcal network in the 6 months following the mw 7 4 1999 izmit earthquake seismograms observed at stations located in the immediate vicinity of the rupture zone show motion amplification and long period oscillations in both p and s wave trains that do not exist in nearby off fault stations examination of thousands of waveforms reveals that these characteristics are commonly generated by events that are well outside the fault zone the anomalous features in fault zone seismograms produced by events not necessarily in the fault may be referred to generally as fault zone related site effects the oscillatory shear wave trains after the direct s arrival in these seismograms are analysed as trapped waves propagating in a low velocity fault zone layer the time difference between the s arrival and trapped waves group does not grow systematically with increasing source receiver separation along the fault these observations imply that the trapping of seismic energy in the karadere duzce rupture zone is generated by a shallow fault zone layer traveltime analysis and synthetic waveform modelling indicate that the depth of the trapping structure is approximately 3 4 km the synthetic waveform modelling indicates further that the shallow trapping structure has effective waveguide properties consisting of thickness of the order of 100 m a velocity decrease relative to the surrounding rock of approximately 50 per cent and an s wave quality factor of 10 15 the results are supported by large 2 d and 3 d parameter space studies and are compatible with recent analyses of trapped waves in a number of other faults and rupture zones the inferred shallow trapping structure is likely to be a common structural element of fault zones and may correspond to the top part of a flower type structure the motion amplification associated with fault zone related site effects increases the seismic shaking hazard near fault zone structures the effect may be significant since the volume of sources capable of generating motion amplification in shallow trapping structures is large

a model for convectively coupled tropical waves nonlinearity rotation and comparison with observations abstract recent observational analysis of both individual realizations and statistical ensembles identifies moist convectively coupled kelvin waves in the tropics with supercluster envelopes of convection this observational analysis elucidates several key features of these waves including their propagation speed of roughly 15 m s 1 and many aspects of their dynamical structure this structure includes anomalously cold temperatures in the lower troposphere and warm temperatures in the upper troposphere below 250 hpa within and sometimes leading the heating region and strong updrafts in the wave and an upward and westward tilting structure with height below roughly 250 hpa other key features in the wave are that anomalous increases in convective available potential energy cape and surface precipitation lead the wave while the trailing part of the supercluster is dominated by stratiform precipitation the main result in this paper is the development of a simple model convective parameterization with n

equatorial dry air intrusion and related synoptic variability in mjo initiation during dynamo abstractdynamics of the madden julian oscillation dynamo was conducted over the equatorial indian ocean io from october 2011 to march 2012 during mid to late november a strong madden julian oscillation mjo event denoted mjo 2 initiated in the western io and passed through the dynamo observation array dry air intrusions associated with synoptic variability in the equatorial region played a key role in the evolution of mjo 2 first a sharp dry air intrusion surging from the subtropics into the equatorial region suppresses convection in the itcz south of the equator this diminishes subsidence on the equator associated with the itcz convection which leads to an equatorward shift of convection it is viewed as a contributing factor for the onset of equatorial convection in mjo 2 once the mjo convection is established a second type of dry air intrusion is related to synoptic gyres within the mjo convective envelope the westward propagating gyres draw drier air from the subtropics into the equa

characteristics of 3 4 and 6 8 day period disturbances observed over the tropical indian ocean abstract a field observational campaign i e the mirai indian ocean cruise for the study of the mjo convection onset mismo was conducted over the central equatorial indian ocean in october december 2006 during mismo large scale organized convection associated with a weak madden julian oscillation mjo broke out and some other notable variations were observed water vapor and precipitation data show a prominent 3 4 day period cycle associated with meridional wind variations filtered anomalies at midlevels in reanalysis data i e the japan meteorological agency jma climate data assimilation system jcdas show westward phase velocities and the structure is consistent with mixed rossby gravity waves estimated equivalent depths are a few tens of meters typical of convectively coupled waves in the more rainy part of mismo 16 26 november the 3 4 day waves were coherent through the lower and midtroposphere while in the less active early november period midlevel fluctuations appear le

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

on the interpretation of eof analysis of enso atmospheric kelvin waves and the mjo abstractempirical orthogonal function eof analysis is frequently applied to derive patterns and indexes used to identify and track weather and climate modes as expressed in state variables or proxies of convection individual eofs or pairs of eofs are often taken to be a complete description of the phenomenon they are intended to index at the same time in the absence of projection of the phenomenon onto multiple eofs yielding multiple similar eigenvalues each eof is often assumed to represent a physically independent phenomenon this project analyzed the leading eofs of the earth s skin temperature on the equator and outgoing longwave radiation olr anomalies filtered for atmospheric equatorial kelvin waves results show that the leading two eofs of the skin temperature data including east pacific el nino and el nino modoki frequently evolve as a quadrature pair during el nino events even though the first eof explains roughly 6 times as much variance as the second they together diagnose the longit

a simple multicloud parameterization for convectively coupled tropical waves part ii nonlinear simulations observations in the tropics point to the important role of three cloud types congestus stratiform and deep convective clouds besides ubiquitous shallow boundary layer clouds for both the climatology and large scale organized anomalies such as convectively coupled kelvin waves two day waves and the madden julian oscillation recently the authors have developed a systematic model convective parameterization highlighting the dynamic role of the three cloud types through two baroclinic modes of vertical structure a deep convective heating mode and a second mode with lower troposphere heating and cooling corresponding respectively to congestus and stratiform clouds the model includes both a systematic moisture equation where the lower troposphere moisture increases through detrainment of shallow cumulus clouds evaporation of stratiform rain and moisture convergence and decreases through deep convective precipitation and also a nonlinear switch that favors either deep or congestus convection depending on whether the lower middle troposphere is moist or dry here these model convective parameterizations are applied to a 40 000 km periodic equatorial ring without rotation with a background sea surface temperature sst gradient and realistic radiative cooling mimicking a tropical warm pool both the emerging walker cell climatology and the convectively coupled wave fluctuations are analyzed here while various parameters in the model are varied the model exhibits weak congestus moisture coupled waves outside the warm pool in a turbulent bath that intermittently amplify in the warm pool generating convectively coupled moist gravity wave trains propagating at speeds ranging from 15 to 20 m s 1 over the warm pool while retaining a classical walker cell in the mean climatology the envelope of the deep convective events in these convectively coupled wave trains often exhibits large scale organization with a slower propagation speed of 3 5 m s 1 over the warm pool and adjacent region occasional much rarer intermittent deep convection also occurs outside the warm pool the realistic parameter regimes in the multicloud model are identified as those with linearized growth rates for large scale instabilities roughly in the range of 0 5 k day 1

the association of the evolution of intraseasonal oscillations to enso phase abstract the pacific ocean intraseasonal kelvin wave is a leading oceanic mode that links intraseasonal tropical atmospheric variations with interannual variations in the coupled ocean atmosphere system this study considers the premise that these waves may evolve differently with their associated weather patterns during different phases of el nino southern oscillation enso if atmospheric and oceanic intraseasonal modes interact and evolve differently during various stages of enso this result may provide useful information with regard to the role of these intraseasonal processes in enso evolution this work utilizes signals of the oceanic kelvin wave as a statistical basis for a simple composite averaging technique that is applied during different phases of enso to objectively analyze the evolution of oceanic and the associated portions of atmospheric intraseasonal oscillations results confirm the above premise and suggest that coupling between kelvin waves and atmospheric convection evolves differen

advancement in source estimation techniques using broadband regional seismograms one important constraint on source retrieval from regional seismograms comes from the amplitude difference between various phases such as pnl surface wave sv sh because the misfit errors used in some waveform inversions are normalized by the data and synthetics the amplitude information in the data has not been fully utilized in this article we modify the cut and paste source estimation technique zhao and helmberger 1994 by removing this type of normalization it is shown that the modified method increases the stability and resolution of inversion when multiple stations at different distance ranges are used a distance scaling factor is introduced to compensate for the amplitude decay with distance by applying the technique to the terrascope data we have determined source mechanisms and depths of 335 southern californian events with m l 3 5 the amplitude decays with distance are r 1 13 for pnl r 0 55 for love waves and r 0 74 for rayleigh waves in contrast to generally shallow source depths reported by the southern california short period network the depth distribution from waveform inversion shows a strong peak around 12 km with few earthquakes occurring above 5 km and below 20 km

horizontal and vertical structure of observed tropospheric equatorial rossby waves equatorial rossby er waves are identified in an 8 year data set of national meteorological center operational analyses the westward moving waves have symmetric circulations about the equator and eastward energy dispersion with maximum zonal wind perturbations along the equator and meridional wind maxima roughly 10 15 off the equator they have maximum amplitude in the lower troposphere and are associated with convective signals at roughly the mean latitude of the tropical convergence zones the circulations thus possess many of the features of the equatorially trapped n 1 rossby modes derived by matsuno 1966 they are generally around zonal planetary wavenumber 6 scale and have a deep nearly equivalent barotropic structure up to 100 mbar this is in contrast with the madden julian oscillation and mixed rossby gravity waves which generally have a first baroclinic mode vertical structure during the intensive observing period iop of the tropical ocean global atmosphere toga coupled ocean atmosphere response experiment coare and in other years westward propagating er disturbances along the equator are observed by using 6 to 30 day filtered circulation data at 850 mbar zonal wind anomalies at 850 mbar are preferentially associated with like signed anomalies in a deep layer at this frequency as was observed during coare the er waves are most common during northern winter in the central pacific although they can be detected sporadically over the other ocean basins and in other seasons as well one source for the equatorial rossby waves appears to be upper level extratropical rossby wave activity propagating into the eastern pacific although the equatorial waves are sometimes present during the northern summer when the extratropical source is absent we cite evidence that propagation of er wave activity from the central into the western pacific is related to occurrences of westerly wind bursts

the role of topographically induced vortices in tropical cyclone formation over the indian ocean abstractthe role of sumatra and adjacent topographic features in tropical cyclone tc formation over the indian ocean io is investigated sumatra as well as the malay peninsula and java have mountainous terrain that partially blocks low level flow under typical environmental stratification for easterly low level flow these terrain features often produce lee vortices some of which subsequently shed and move westward from the northern and southern tips of sumatra and thence downstream over the io since sumatra straddles the equator extending in a northwest southeast direction from approximately 6 n to 6 s the lee vortices while counter rotating are both cyclonic hence they can serve as initial disturbances that eventually contribute to tc formation over the io in addition low level equatorial westerly flow impinging on sumatra is also typically blocked and diverges at times contributing to cyclonic circulations over the io primarily near the southern end of the island data from two recen

earthquakes induced by water injection at 3 km depth within the rongchang gas field chongqing china 1 unwanted water amounting more than 1 million m 3 has been injected intermittently at a pumping pressure of 2 1 2 9 mpa over hydrostatic at 2 6 2 9 km depth within the rongchang gas field western chongqing china since july 1988 the injections have induced more than 32 000 surface recorded earthquakes including 2 of m l 5 14 of m l 4 and more than 100 of m l 3 up until the end of 2006 we examined the epidemic type aftershock sequence etas model and the temporal evolution of several statistics of the earthquake sequence the random component in the etas model can be considered as an indicator of fluid driven activity while the rate of omori law type aftershocks indicates stress triggering of the preceding earthquakes we observed three distinct seismic activity phases that were coincident with different injection periods phase i corresponds to initial injections with low injection rate long time interval and shows a vast majority of omori type events and only 8 externally forced activity phase ii corresponds to a period of high injection rates and shows intense earthquake activity characterized by a high percentage 45 of fluid driven earthquakes phase iii demonstrates decreasing seismicity as a result of a lowering in the injection rate more than 70 of earthquakes occurred randomly over time indicating the dominance of external triggering the physical mechanism that induced the rongchang earthquake sequence was a change in coulomb s failure stress caused by pore pressure diffusion and transformed from seismic slip of preceding earthquakes a pressure increase of 2 1 2 9 mpa at the injection well is more than sufficient to induce failure within the local formations

a wave number frequency wavelet analysis of convectively coupled equatorial waves and the mjo over the indian ocean convectively coupled equatorial waves and the madden julian oscillation mjo constitute the dominant coherent modes of planetary to synoptic scale organized convection in the tropics this work presents a space time wavelet analysis of outgoing longwave radiation olr data globally at wavenumbers 0 1 and isolated more closely about the indian ocean at higher wavenumbers the mean power spectrum shows broad similarity to fourier power spectra in previous works after normalization by a red background the seasonal cycle of the power spectrum is analyzed along with its association with the phases of an index of the mjo and background state zonal winds at a variety of pressure levels over the indian ocean results show substantial variability across the seasonal cycle and the mjo in the distribution of power above the background results also show that the spectral peaks associated with the mjo and kelvin and equatorial rossby waves lose 20 50 of their normal variance during periods of strong easterly wind in the upper troposphere over the indian ocean while at the same time fast westward moving waves increase between wavenumbers 7 and 14 and periods of 2 6 days

the influences of convectively coupled kelvin waves on multiscale rainfall variability over the south china sea and maritime continent in december 2016 abstractwe studied the scale interactions of the convectively coupled kelvin waves kws over the south china sea scs and maritime continent mc during december 2016 three kws were observed nea

a detailed view of the injection induced seismicity in a natural gas reservoir in zigong southwestern sichuan basin china 1 seismicity at a gas reservoir located in the relatively stable sichuan basin china mirrors the injection pressure of unwanted water suggesting that the seismicity is injection induced injection under high pressure on a routine basis began on 9 january 2009 and continued to july 2011 during the injection period over 120 000 m3 of water was pumped under a wellhead pressure of up to 6 2 mpa into the limestone formation of permian 2 45 to 2 55 km beneath the surface the injection induced more than 7000 surface recorded earthquakes including 2 m4 the largest one was ml4 4 20 m3 and more than 100 m2 events data observed by a nearby local seismic network and five temporal stations provide a detailed view of the spatiotemporal distribution of the induced earthquakes most events were limited to depths ranging from 2 5 to 4 km which is consistent with the limestone formation of permian in a map view hypocenters are concentrated in a nnw extended ellipsoidal zone approximately 6 km long and approximately 2 km wide centered approximately at the injection well multisources of evidence such as the shear mechanism pattern of hypocenter distribution and small elevated pore pressure as compared with the least principal stress in the region show that the induced earthquakes occurred as a result of lowering of the effective normal stress on known or unknown preexisting blind faults which are critically loaded under the regional stress field epidemic type aftershock sequence modeling results indicate that injection inducing and earthquake triggering are both important during earlier periods of injection while later periods are dominated by forced injection induced seismicity

tectonic and volcanic evolution of dark terrain and its implications for the internal structure and evolution of ganymede furrows in ancient dark terrain on ganymede form three systems that are each hemispheric or greater in scale the oldest of the systems designated system iii is dominated by approximately concentric troughs centered on about 60 n 50 w system i in the anti jovian hemisphere contains concentric and subradial furrows arrayed around a large degraded palimpsest centered at 15 s 165 w furrows in each system formed on and locally are buried by dark volcanic materials that embay and infill preexisting topographic features they crosscut extremely few well preserved older craters and they occur on surfaces having significantly different relative crater ages system ii also in the anti jovian hemisphere contains widely spaced radially arrayed furrows commonly 500 2000 km in length which are organized around a large area of dark smooth resurfacing material intense dark terrain fracturing and some of the globally oldest light material the total thickness of dark terrain resurfacing estimated using the stratigraphy of different dark material deposits and the rim heights of the largest crater size class whose density was depleted by each deposit is probably in the range of 3 8 km multiple models of the origin of each furrow system were tested using observed geologic features and patterns systems i and iii were found to be most consistent with reactivation of impact generated multiringed structures by endogenic global extension during a period of widespread dark material volcanism that obliterated a dense ancient crater population system ii was found to be most consistent with fracturing of a single circular isostatic uplift covering an entire hemisphere on the basis of geologic observations and interpretations and theoretical models of convection in spheres it is hypothesized that the uplift developed by long term warming of the upwelling current of a single axisymmetric convection cell in an initially cooler undifferentiated interior such wanning would also have created global expansion and supplied the tensional stress inferred to have formed systems i and iii this hypothesis is supported by the concentration around the center of system ii of intense fracturing and relatively young dark volcanic deposits suggestive of high lithospheric heat flow lithospheric thinning and stress concentration an observed long term decrease in the width of extensional tectonic features interpreted to be of endogenic origin is also consistent with lithospheric thinning due to warming of a cool interior

observations of a convectively coupled kelvin wave in the eastern pacific itcz abstract a case study of a convectively coupled kelvin wave in the eastern pacific intertropical convergence zone itcz is presented as observed during the 1997 pan american climate studies pacs tropical eastern pacific process study tepps the large scale convective envelope associated with this disturbance with a zonal scale of approximately 1000 2000 km propagates eastward at 15 m s 1 along the mean convective axis of the itcz this envelope consists of many smaller scale westward moving convective elements with zonal scales on the order of 100 500 km as the convectively coupled kelvin wave disturbance propagates eastward it exerts a strong control on local convection radar and vertical profiler data collected aboard the noaa r v ronald h brown during the wave passage show that convection deepens rapidly as the kelvin wave approaches from the west progressing from isolated shallow cumuli to organized deep convective features within just 12 h initially rainfall in the vicinity of the s

tropical cyclogenesis associated with kelvin waves and the madden julian oscillation abstractthe madden julian oscillation mjo influences tropical cyclone formation around the globe convectively coupled kelvin waves are often embedded within the mjo but their role in tropical cyclogenesis remains uncertain this case study identifies the influences of the mjo and a series of kelvin waves on the formation of two tropical cyclones typhoons rammasun and chataan developed in the western north pacific on 28 june 2002 two weeks earlier conditions had been unfavorable for tropical cyclogenesis because of uniform trade easterlies and a lack of organized convection the easterlies gave way to equatorial westerlies as the convective envelope of the madden julian oscillation moved into the region a series of three kelvin waves modulated the development of the westerlies cyclonic potential vorticity pv developed in a strip between the growing equatorial westerlies and the persistent trade easterlies farther poleward rammasun and chataan emerged from the apparent breakdown of this strip the

estimating the etas model from an early aftershock sequence forecasting aftershock probabilities as early as possible after a main shock is required to mitigate seismic risks in the disaster area in general aftershock activity can be complex including secondary aftershocks or even triggering larger earthquakes however this early forecasting implementation has been difficult because numerous aftershocks are unobserved immediately after the main shock due to dense overlapping of seismic waves here we propose a method for estimating parameters of the epidemic type aftershock sequence etas model from incompletely observed aftershocks shortly after the main shock by modeling an empirical feature of data deficiency such an etas model can effectively forecast the following aftershock occurrences for example the etas model estimated from the first 24 h data after the main shock can well forecast secondary aftershocks after strong aftershocks this method can be useful in early and unbiased assessment of the aftershock hazard

variations in earthquake size distribution across different stress regimes the earthquake size distribution follows in most instances a power law1 2 with the slope of this power law the b value commonly used to describe the relative occurrence of large and small events a high b value indicates a larger proportion of small earthquakes and vice versa statistically significant variations of b values have been measured in laboratory experiments mines and various tectonic regimes such as subducting slabs near magma chambers along fault zones and in aftershock zones3 however it has remained uncertain whether these differences are due to differing stress regimes as it was questionable that samples in small volumes such as in laboratory specimens mines and the shallow earth s crust are representative of earthquakes in general given the lack of physical understanding of these differences the observation that b values approach the constant 1 if large volumes are sampled4 was interpreted to indicate that b 1 is a universal constant for earthquakes in general5 here we show that the b value varies systematically for different styles of faulting we find that normal faulting events have the highest b values thrust events the lowest and strike slip events intermediate values given that thrust faults tend to be under higher stress than normal faults we infer that the b value acts as a stress meter that depends inversely on differential stress

origin of convectively coupled kelvin waves over south america convectively coupled kelvin waves over the south american continent are examined through the use of temporal and spatial filtering of reanalysis satellite and gridded rainfall data they are most prominent from november to april the season analyzed herein the following two types of events are isolated those that result from preexisting kelvin waves over the eastern pacific ocean propagating into the continent and those that apparently originate over amazonia forced by disturbances propagating equatorward from central and southern south america the events with precursors in the pacific are mainly upper level disturbances with almost no signal at the surface those events with precursors over south america on the other hand originate as upper level synoptic wave trains that pass over the continent and resemble the cold surges documented by garreaud and wallace as the wave train propagates over the andes it induces a southerly low level wind that advects cold air to the north precipitation associated with a cold front reaches the equator a few days later and subsequently propagates eastward with the characteristics of a kelvin wave the structures of those waves originating over the pacific are quite similar to those originating over south america as they propagate to eastern south america and into the atlantic south america kelvin waves that originate over neither the pacific nor the midlatitudes of south america can also be identified in a composite sense these form over the eastern slope of the andes mountains close to the equator there are also cases of cold surges that reach the equator yet do not form kelvin waves the interannual variability of the pacific originating events is related to sea surface temperatures in the central eastern pacific ocean when equatorial oceanic conditions are warm there tends to be an increase in the number of disturbances that reach south america from the pacific

convectively coupled kelvin waves in cmip5 coupled climate models this study provided a quantitative evaluation of convectively coupled kelvin waves cckws over the indian ocean and the pacific ocean simulated by 20 coupled climate models that participated in coupled model intercomparison project phase 5 the two leading empirical orthogonal function eof modes of filtered daily precipitation anomalies are used to represent the eastward propagating cckws in both observations and simulations the eigenvectors and eigenvalues of the eof modes represent the spatial patterns and intensity of cckws respectively and the lead lag relationship between the two eof principle components describe the phase propagation of cckws a non dimensional metric was designed in consideration of all the three factors i e pattern amplitude and phase propagation for evaluation the relative rankings of the models based on the skill scores calculated by the metric are conducted for the indian ocean and the pacific ocean respectively two models noresm1 m and mpi esm lr are ranked among the best 20 for both the regions three models inmcm4 mri cgcm3 and hadgem2 es are ranked among the worst 20 for both the regions while the observed cckw amplitude is greater north of the equator in the pacific some models overestimate the cckw ampliutde in the southern hemisphere this bias is related to the mean state precipitation bias along the south pacific convergence zone

mixed rossby gravity waves and western pacific tropical cyclogenesis part i synoptic evolution abstract a large amplitude mixed rossby gravity wave packet is identified in the western pacific using 6 10 day bandpass filtered winds individual disturbances of 2300 3000 km wavelength propagated westward as the packet moved slowly eastward the packet first appeared and subsequently amplified within a region of active convection associated with the madden julian oscillation mjo which was isolated by low pass filtered outgoing longwave radiation the packet lasted about 5 weeks then rapidly dispersed as the active mjo moved away from it to the east west of 150 e individual disturbances within the packet turned northwestward away from the equator indicating an apparent transition from mixed rossby gravity waves to off equatorial tropical depression td type disturbances cyclones filled with cloud and anticyclones cleared during the transition nevertheless convective structure consistent with mixed rossby gravity waves remained outside the circulation centers and three tropical cyclones for

analysis of convectively coupled kelvin waves in the indian ocean mjo abstract the active convective phase of the madden julian oscillation hereafter active mjo comprises enhanced moist deep convection on its own temporal and spatial scales as well as increased variance in convection associated with higher frequency modes synoptic scale cloud superclusters apparently associated with convectively coupled kelvin waves occur within the active convective envelopes of most mjo events these convectively coupled kelvin waves also occur during the suppressed convective phase of the mjo hereafter suppressed mjo this observational study presents an analysis of outgoing longwave radiation and reanalysis data to determine how these waves behave differently as they propagate through the active and suppressed mjo time indices of the mjo and kelvin waves are derived for over the equatorial indian ocean dates of local extrema in these indices are used to composite data to discern how the waves and associated circulations behave on average then further composites are made based o

a climatology of waves in the equatorial region abstract propagating anomalies of moisture and moist deep convection in the tropics are organized into a variety of large scale modes these include but are not limited to the so called intraseasonal oscillations convectively coupled waves similar to those predicted by shallow water theory on the equatorial beta plane and tropical depression type disturbances along with the annual and diurnal cycles these modes act and interact to control much of the variance of tropical convection analyses of 10 yr of outgoing longwave radiation olr and precipitable water pw data are carried out to develop comparative climatologies of these wavelike modes the analysis relaxes the commonly used cross equatorial symmetry constraints which allows study of the portions of the wavelike processes that are asymmetric across the equator mean background states are found for olr and for pw as functions of day of the year examination of anomalies together with the background reveals much about how the waves are affec

some aspects of western hemisphere circulation and the madden julian oscillation abstractalthough the greatest variance in convection associated with the madden julian oscillation mjo occurs over the indo pacific warm pool the mjo is associated with substantial circulation patterns in the tropics and the extratropics of the western hemisphere reanalysis data suggest that upper tropospheric easterly wind anomalies on the equator between 40 and 140 w precede 86 of active convective phases of mjo events greater than one standard deviation in amplitude over the indian ocean basin during the northern hemisphere winter composites of those mjo events that are preceded by westerly wind anomalies and those events preceded by easterly wind anomalies are compared results show that those events that are preceded by westerly wind anomalies fail to thrive and do not yield the amplitude in convection or the canonical atmospheric circulation response that is associated with those preceded by easterly wind the composite of events preceded by easterly winds reveals that these winds amplify coi

an analysis of convectively coupled kelvin waves in 20 wcrp cmip3 global coupled climate models abstract output from 20 coupled global climate models is analyzed to determine whether convectively coupled kelvin waves exist in the models and if so how their horizontal and vertical structures compare to observations model data are obtained from the world climate research program s wcrp s coupled model intercomparison project phase 3 cmip3 multimodel dataset ten of the 20 models contain spectral peaks in precipitation in the kelvin wave band and of these 10 only 5 contain wave activity distributions and three dimensional wave structures that resemble the observations thus the majority 75 of the global climate models surveyed do not accurately represent convectively coupled kelvin waves one of the primary sources of submonthly zonally propagating variability in the tropics the primary feature common to the five successful models is the convective parameterization three of the five models use the tiedtke nordeng convective scheme while the other two utilize the pan and randall scheme

observed relationships between oceanic kelvin waves and atmospheric forcing abstract the madden julian oscillation mjo has been implicated as a major source of the wind stress variability that generates basin scale kelvin waves in the equatorial pacific one source of debate concerning this relationship is the apparent difference in the frequencies of the two processes this work utilizes data from the tropical atmosphere ocean tao array of moored buoys along with outgoing longwave radiation data to show by means of a multiple linear regression model and case studies that the frequency discrepancy is due to a systematic decrease in the phase speeds of the kelvin waves and an increase in the period of the waves toward the east as conditions adjust toward el nino among the potential contributing factors to this phase speed decrease is an apparent air sea interaction that enhances the wind forcing of some of the kelvin waves allowing them to continue to amplify because the propagating wind stress anomaly decelerates to the speed of the developing kelvin wave instead of the sig

effects of low frequency wave interactions on intraseasonal oscillations abstract intraseasonal oscillations isos control much of the large scale variability of convection in the tropics on time scales of about 15 100 days these disturbances are often thought to be dominated by eastward propagating modes especially during austral summer but disturbances that propagate westward are also important this work demonstrates by means of a multiple linear regression model and a brief case study that eastward and westward moving intraseasonal modes often cooperatively interact with one another to produce many of the characteristics of the observed southern hemisphere summer iso these interactions appear to be facilitated by topography and or by the convective anomalies that are cooperatively induced by the eastward and the westward moving components of the oscillations these interactions do not occur during every period of intraseasonal convective activity but they do commonly occur during periods of high amplitude convective anomalies this analysis shows that eastward and

annual interannual and intraseasonal variability of tropical tropopause transition layer cirrus cloud fields based on the first three years of data from the cloud aerosol lidar and infrared pathfinder satellite observations calipso mission are used to investigate the relationship between cirrus within the tropical tropopause transition layer ttl and the madden julian oscillation mjo the annual cycle and el nino southern oscillation enso the ttl cirrus signature observed in association with the mjo resembles convectively induced mixed kelvin rossbywavesolutionsabovethepacificwarmpoolregion thissignatureiscenteredtotheeastofthe peak convection and propagates eastward more rapidly than the convection it exhibits a pronounced east ward tilt with height suggestive of downward phase propagation and upward energy dispersion a cirrus maximumisobservedoverequatorialafricaandsouthamericawhentheenhancedmjo relatedconvection enters the western pacific tropical mean ttl cirrus is modulatedby the mjo with more than twice as much ttl cirrus fractional coverage equatorward of 108 latitude when the enhanced convection enters the pacific than a few weeks earlier when the convection is over the indian ocean the annual cycle in cirrus clouds around the base of the ttl is equatorially asymmetric with more cirrus observed in the summer hemisphere higher in the ttl the annual cycle in cirrus clouds is more equatorially symmetric with a maximum in the boreal winter throughout most of the tropics the enso signature in ttl cirrus is marked by a zonal shift of the peak cloudiness toward the central pacific during el nino and toward the maritime continent during la nina

low velocity zones along the san jacinto fault southern california from body waves recorded in dense linear arrays we derive high resolution information on low velocity fault zone fz structures along the san jacinto fault zone sjfz southern california using waveforms of local earthquakes that are recorded at multiple linear cross fault arrays we observe clear across fault delays of direct p and s waves indicating damage zones at different segments of the sjfz we then compute synthetic traveltimes and waveforms using generalized ray theory and perform forward modeling to constrain the fz parameters at the southern section near the trifurcation area the low velocity zone lvz of the clark branch has a width of 200 m 30 45 reduction in vp and 50 reduction in vs from array data across the anza seismic gap we find a lvz with 200 m width and 50 reduction in both vp and vs nearly as prominent as that on the southern section we only find prominent lvzs beneath three out of the five arrays indicating along strike variations of the fault damage fz reflected phases are considerably less clear than those observed above the rupture zone of the 1992 landers earthquake shortly after the event this may reflect partially healed lvzs with less sharp boundaries at the sjfz given the relatively long lapse time from the last large surface rupturing event alternatively the lack of observed fz reflected phases could be partially due to the relatively small aperture of the arrays nevertheless the clear signatures of damage zones at anza and other locations indicate very slow healing process at least in the top few kilometers of the crust

convectively coupled equatorial waves 1 convectively coupled equatorial waves ccews control a substantial fraction of tropical rainfall variability their horizontal structures and dispersion characteristics correspond to matsuno s 1966 solutions of the shallow water equations on an equatorial beta plane namely kelvin equatorial rossby mixed rossby gravity and inertio gravity waves because of moist processes the tilted vertical structures of ccews are complex and their scales do not correspond to that expected from the linear theory of dry waves the dynamical structures and cloud morphology of ccews display a large degree of self similarity over a surprisingly wide range of scales with shallow convection at their leading edge followed by deep convection and then stratiform precipitation mirroring that of individual mesoscale convective complexes ccews have broad impacts within the tropics and their simulation in general circulation models is still problematic although progress has been made using simpler models a complete understanding of ccews remains a challenge in tropical meteorology

a combined wave number frequency and time extended eof approach for tracking the progress of modes of large scale organized tropical convection an algorithm combining filtering in the wave number frequency domain with time extended empirical orthogonal function eeof analysis is developed and applied to diagnose and track signals associated with modes of organized moist deep convection in the tropics the wave number frequency spectrum of outgoing long wave radiation olr is broken down into five broad filter bands in order to concentrate signals associated with the madden julian oscillation convectively coupled equatorial rossby kelvin and mixed rossby gravity waves easterly waves and low frequency variations such as the el nino southern oscillation enso the eeof patterns are obtained from analysis of the filtered data and principal component pc time series are generated by projection of temporally smoothed but otherwise unfiltered data onto the eeof patterns filtered data are reconstructed by taking the product of the eeof patterns and the corresponding pcs these reconstructed data compare well with unfiltered olr anomalies and with olr anomalies filtered in the wave number frequency domain for the same modes the method is easily applied in real time since results are not influenced by the proximity to the end of the dataset copyright 2009 royal meteorological society

a systematic relationship between the representations of convectively coupled equatorial wave activity and the madden julian oscillation in climate model simulations abstractthe relationship between a model s performance in simulating the madden julian oscillation mjo and convectively coupled equatorial wave ccew activity during wintertime is examined by analyzing precipitation from 26 general circulation models gcms participating in the mjo task force global energy and water cycle experiment gewex atmospheric system study gass mjo model intercomparison project as well as observations based on the tropical rainfall measuring mission trmm a model s performance in simulating the mjo is determined by how faithfully it reproduces the eastward propagation of the large scale intraseasonal variability isv compared to trmm observations results suggest that models that simulate a better mjo tend to 1 have higher fractional variances for various high frequency wave modes kelvin mixed rossby gravity and westward and eastward inertio gravity waves which are defined by the ratios of wave variances of specific wave modes to the total variance and 2 exhibit

focal depths for small to moderate earthquakes mn 2 8 in western quebec southern ontario and northern new york regional depth phase modeling is a useful technique to constrain earthquake focal depths for events within sparse networks we demonstrate how regional depth phases can be used to obtain focal depths for hundreds of earthquakes with m n 2 8 that occurred from 1980 to 2004 in southern ontario western quebec and northern new york state we discuss the development of regional depth phases with distance their use in focal depth determinations by matching waveforms to synthetics and possible sources of error in general focal depths can be determined to within about 3 km when there is at least one record at regional distances with clearly identifiable depth phases such as spmp or spg in southwestern ontario and northern new york focal depths range from 2 to 15 km in areas of western quebec and along the ottawa river valley in ontario focal depths range from 2 to 25 km more than half of the earthquakes in a cluster of activity near maniwaki in western quebec are deeper than 20 km all earthquakes deeper than 20 km occurred north of about 45 3 n there is an intriguing tendency for earthquake depths to cluster near 8 km 12 km 15 km and 22 km another interesting observation is that there are several earthquake pairs or small groups with very similar epicenters but quite different depths the most active regions in western quebec and along the ottawa river valley tend to exhibit a relatively wide range of focal depths along broad zones that trend roughly northwest suggesting that seismicity is occurring along diffuse northwest trending faults throughout the crust the wide range of focal depths may indicate the potential for a larger maximum scale of fault rupture and serve as a contemporary marker of locations where large events have occurred in the recent geologic past

modulation of the convectively coupled kelvin waves over south america and the tropical atlantic ocean in association with the madden julian oscillation abstractin this study evidence of the strong modulation of the convectively coupled kelvin wave cckw activity by the madden julian oscillation mjo is presented with a particular focus over the south america and tropical atlantic region the mjo impacts on cckws over this region as noted in anomalous fields of rainfall as well as vertical profiles of wind moisture and temperature are primarily through the modulation of kelvin wave amplitude with secondary effects on vertical structure and little impact on wavenumber cckw activity is enhanced during mjo phases 8 1 and 2 and damped during mjo phases 4 5 and 6 further analyses reveal that the strong modulation of the mjo on the cckw activity could be largely through two factors namely the vertical zonal wind shear and the lower to middle tropospheric specific humidity the cckw activity tends to be enhanced during mjo phases when the easterly vertical wind shear and positive low to midtroposphere moisture anomalies are present and vice ve

extratropical forcing of convectively coupled kelvin waves during austral winter abstract observations are presented that link extratropical rossby wave disturbances excited in the southern hemisphere subtropical jet to the initiation of convectively coupled kelvin waves in the pacific intertropical convergence zone itcz during austral winter a baroclinic zonal wavenumber 6 eastward propagating rossby wave train in the subtropical jet turns northeastward in the vicinity of australia inducing upper tropospheric divergence and vertical motion fields that spread equatorward and induce cloudiness anomalies in the tropics lower tropospheric pressure surges excited from the extratropics also induce kelvin wave like geopotential height and temperature anomalies at the surface providing additional lower tropospheric convergence and vertical motion forcing the tropical outgoing longwave radiation olr and circulation fields propagate eastward in tandem with the extratropical rossby wave train at approximately 17 m s 1 kelvin wave activity in the central pacific itcz thus appears to

how systematic is organized tropical convection within the mjo 1 recent theories of the dynamics of the madden julian oscillation mjo have been building on its multiscale structure while it is observed that much of the convection within the mjo envelope is related to higher frequency equatorial waves it is not known to what extent this organization is systematic from one mjo event to another for instance it is of interest to know whether mjo favors waves of particular types and propagation direction and how this variability changes seasonally this work presents a wavenumber frequency spectral analysis of the mjo convective envelope which indicates that there is no strong preferred scale of high frequency organization that is ubiquitous to the mjo this null finding supports the use of convective parametrizations in modeling the mjo since while moist convection is likely critical to its initiation and maintenance the particular details of that organization may not be critical for its prediction and simulation

remotely triggered seismicity in yunnan southwestern china following the 2004 mw9 3 sumatra earthquake 1 following the 2004 mw9 3 sumatra earthquake seismicity rate increased sharply over a wide area of up to 2700 km away in yunnan province southwestern china raised seismicity lasts for 14 days during this period more than 800 earthquakes with magnitude between 1 5 and 5 1 occurred this is perhaps the most impressive example of remotely triggered seismicity yet observed major events were clustered at several sites that exhibit complex fault geometries such as step overs and junctures we use statistic approaches including the statistics to examine the statistical significance of the seismic rate increases associated with the sumatra main shock and conclude that there is a reasonable probability that the raised seismicity was remotely triggered by the sumatra earthquake both rapid onset of dynamic triggering the very first event is a m4 6 earthquake occurred during the passage of the rayleigh wave from the sumatra earthquake and delayed response activated a few hours to a few days after the sumatra earthquake are well established the triggered activities show more earthquake swarm like characteristics as indicated by the epidemic type aftershock sequence modeling results large percentage of random components and less magnitude dependence in omori law type self triggering multiple sources of evidence including intensive hydrothermal activities and low velocity and high vp vs zones in the lower to middle crust suggests that magma mantle generated fluids have a role in the region high fluid pressure in branched fault zones weakened the faults making them sensitive to external disturbances and leading to fluid driven seismicity

convectively coupled equatorial waves within the mjo during cindy dynamo slow kelvin waves as building blocks this study examines the relationship between the mjo and convectively coupled equatorial waves ccews during the cindy2011 dynamo field campaign using satellite borne infrared radiation data in order to better understand the interaction between convection and the large scale circulation the spatio temporal wavelet transform stwt enables us to document the convective signals within the mjo envelope in terms of ccews in great detail through localization of space time spectra at any given location and time three mjo events that occurred in october november and december 2011 are examined it is in general difficult to find universal relationships between the mjo and ccews implying that mjos are diverse in terms of the types of disturbances that make up its convective envelope however it is found in all mjo events that the major convective body of the mjo is made up mainly by slow convectively coupled kelvin waves these kelvin waves have relatively fast phase speeds of 10 13 m s 1 outside of and slow phase speeds of 8 9 m s 1 within the mjo sometimes even slower eastward propagating signals with 3 5 m s 1 phase speed show up within the mjo which as well as the slow kelvin waves appear to comprise major building blocks of the mjo it is also suggested that these eastward propagating waves often occur coincident with n 1 wig waves which is consistent with the schematic model from nakazawa in 1988 some practical aspects that facilitate use of the stwt are also elaborated upon and discussed

influence of the basic state zonal flow on convectively coupled equatorial waves observational data are used to test the hypothesis that the basic state modulates the dispersion properties of convectively coupled equatorial waves ccews this hypothesis is based on shallow water theory which predicts that the zonal speed of propagation of such tropospheric equatorial modes is altered by the equivalent depth and the basic zonal flow localized space time spectra are calculated to investigate how ccew spectral peaks vary across the tropics and how they are affected by the variations in zonal wind observed geographically and by season doppler shifting by the basic state barotropic zonal flow is readily identified once this doppler shifting is taken into account the equivalent depths of ccews inferred from global power spectra are surprisingly uniform both geographically and temporally however there are also detectable modulations that appear consistent with changes in vertical shear of the zonal flow along with other shifts that are not as easily explained

atlantic tropical cyclogenesis a three way interaction between an african easterly wave diurnally varying convection and a convectively coupled atmospheric kelvin wave abstractthis paper explores a three way interaction between an african easterly wave aew the diurnal cycle of convection over the guinea highlands ghs and a convectively coupled atmospheric equatorial kelvin wave cckw these interactions resulted in the genesis of tropical storm debby over the eastern tropical atlantic during late august 2006 the diurnal cycle of convection downstream of the ghs during the month of august is explored convection associated with the coherent diurnal cycle is observed off the coast of west africa during the morning later convection initiates over and downstream of the ghs during the afternoon these convective features were pronounced during the passage of the pre debby aew the superposition between the convectively active phase of a strong cckw and the pre debby aew occurred shortly after merging with the diurnally varying convection downstream of the ghs the cckw aew interaction preceded tropical cyclogenesis by 18 h the cckw provided a favorable environment

eastward propagating 2 to 15 day equatorial convection and its relation to the tropical intraseasonal oscillation anomalies of outgoing longwave radiation olr in 1980 1989 were examined in a narrow latitude band about the equator to elucidate the propagation and interaction of tropical intraseasonal oscillations tios and synoptic scale convective activity hovmoller diagrams of olr data reconstructed from two frequency bands corresponding to periods of 30 60 days and 2 15 days respectively revealed a clear distinction between the phase speed of eastward moving tios 3 7 m s 1 and that of eastward synoptic scale convection 10 13 m s 1 coherent propagation of tios from the indian to the western pacific oceans was often observed with temporary diminution of amplitude over the maritime continent propagation of high frequency anomalies was generally confined to an individual basin dominance of eastward propagating synoptic scale convection in the equatorial zone contrasts sharply with the westward propagation of off equatorial convergence zones interaction between the tio and high frequency activity resolved by daily olr was visible as a modest enhancement of eastward synoptic scale events and of high frequency activity in general during the convectively active phase of the tio

kelvin waves and tropical cyclogenesis a global survey abstractconvectively coupled atmospheric kelvin waves are among the most prominent sources of synoptic scale rainfall variability in the tropics but large uncertainties surround their role in tropical cyclogenesis this study identifies the modulation of tropical cyclones relative to the passage of a kelvin wave s peak rainfall i e its crest in each basin tropical cyclogenesis is generally inhibited for 3 days before the crest and enhanced for 3 days afterward composites of storms forming in the most favorable lags illustrate the dynamical impacts of the waves in most basins the tropical cyclone actually forms during the convectively suppressed phase of the wave the 850 hpa equatorial westerly anomalies provide the cyclonic vorticity for the nascent storm and 200 hpa easterly anomalies enhance the outflow the wind anomalies persist at both levels longer than the kelvin wave s period and are often related to the madden julian oscillation mjo the onset of these wind anomalies occurs with the

active backstop faults in the mentawai region of sumatra indonesia revealed by teleseismic broadband waveform modeling abstract two earthquake sequences that affected the mentawai islands offshore of central sumatra in 2005 mw 6 9 and 2009 mw 6 7 have been highlighted as evidence for active backthrusting of the sumatran accretionary wedge however the geometry of the activated fault planes is not well resolved due to large uncertainties in the locations of the mainshocks and aftershocks we refine the locations and focal mechanisms of medium size events mw 4 5 of these two earthquake sequences through broadband waveform modeling in addition to modeling the depth phases for accurate centroid depths we use teleseismic surface wave cross correlation to precisely relocate the relative horizontal locations of the earthquakes the refined catalog shows that the 2005 and 2009 backthrust sequences in mentawai region actually occurred on steeply 60 degrees landward dipping faults masilo fault zone that intersect the sunda megathrust beneath the deepest part of the forearc basin contradicting previous studies that inferred slip on a shallowly seaward dipping backthrust static slip inversion on the newly proposed fault fits the coseismic gps offsets for the 2009 mainshock equally well as previous studies but with a slip distribution more consistent with the mainshock centroid depth 20 km constrained from teleseismic waveform inversion rupture of such steeply dipping reverse faults within the forearc crust is rare along the sumatra java margin we interpret these earthquakes as unsticking of the sumatran accretionary wedge along a backstop fault separating imbricated material from the stronger sunda lithosphere alternatively the reverse faults may have originated as pre miocene normal faults of the extended continental crust of the western sunda margin our waveform modeling approach can be used to further refine global earthquake catalogs in order to clarify the geometries of active faults

convectively coupled kelvin waves from linear theory to global models abstractthe authors analyze composite structures of tropical convectively coupled kelvin waves cckws in terms of the theory of raymond and fuchs using radiosonde data 3d analysis and reanalysis model output and annual integrations with the ecmwf model on the full planet and on an aquaplanet precipitation anomalies are estimated using the noaa interpolated olr and trmm 3b42 datasets as well as using model olr and rainfall diagnostics derived variables from these datasets are used to examine assumptions of the theory large scale characteristics of wave phenomena are robust in all datasets and models where kelvin wave variance is large indices from the theory representing column moisture and convective inhibition are also robust the results suggest that the cckw is highly dependent on convective inhibition while column moisture does not play an important role

migration of early aftershocks following the 2004 parkfield earthquake a significant number of the early aftershocks following large shallow earthquakes are missing in existing earthquake catalogues an analysis of the waveforms of 3 647 relocated earthquakes along the parkfield section of the san andreas fault reveals 11 times more aftershocks within three days of the 2004 parkfield earthquake than listed in a standard catalogue large shallow earthquakes are immediately followed by numerous aftershocks a significant portion of these events is missing in existing earthquake catalogues mainly because seismicity after the mainshock can be masked by overlapping arrivals of waves from the mainshock and aftershocks1 2 3 4 however recovery of the missing early aftershocks is important for understanding the physical mechanisms of earthquake triggering2 3 4 and for tracking postseismic deformation around the rupture zone associated with the mainshock5 6 7 here we use the waveforms of 3 647 relocated earthquakes8 along the parkfield section of the san andreas fault as templates9 10 to detect missing aftershocks within three days of the 2004 magnitude 6 0 parkfield earthquake we identify 11 times more aftershocks than listed in the standard catalogue of the northern california seismic network we find that the newly detected aftershocks migrate in both along strike and down dip directions with logarithmic time since the mainshock consistent with numerical simulations of the expansion of aftershocks caused by propagating afterslip11 12 the cumulative number of early aftershocks increases linearly with postseismic deformation in the first two days supporting the view that aftershocks are driven primarily by afterslip13 14

the spectrum of convectively coupled kelvin waves and the madden julian oscillation in regions of low level easterly and westerly background flow abstractthe zonal wavenumber frequency power spectrum of outgoing longwave radiation in the global tropics suggests that power in convectively coupled kelvin waves and the madden julian oscillation mjo is organized into two distinct spectral peaks with a minimum in power in between this work demonstrates that integration of wavelet power in the wavenumber frequency domain over geographical regions of moderate trade winds yields a similar pronounced spectral gap between these peaks in contrast integration over regions of background low level westerly wind yields a continuum of power with no gap between the mjo and kelvin bands results further show that signals in tropical convection are redder in frequency in these low level westerly wind zones confirming that kelvin waves tend to propagate more slowly eastward over the warm pool than other parts of the world results are consistent with the perspective that portions of disturbances labeled as kelvin waves and the mjo that are proximate to kelvin wa

fault plane determination of the 18 april 2008 mount carmel illinois earthquake by detecting and relocating aftershocks we developed a sliding window cross correlation scc detection technique and applied the technique to continuous waveforms recorded by the cooperative new madrid seismic network stations following the 18 april 2008 illinois earthquake the technique detected more than 120 aftershocks down to m l 1 0 in the 2 week time window following the mainshock which is three times more than the number of aftershocks reported by the seismic network most aftershocks happened within 24 hrs of the mainshock we then relocated all events by the double difference relocation algorithm accurate p and s wave differential arrival times between events were obtained by waveform cross correlation after relocation we used the l1 norm to fit all located events by a plane to determine the mainshock fault plane the best fit plane has a strike of 292 11 and dips 81 7 to the northeast this plane agrees well with the focal mechanism solutions of the mainshock and four largest aftershocks by combining the aftershock locations and focal mechanism solutions we conclude that the 18 april earthquake occurred on a nearly vertical left lateral strike slip fault orienting in the west northwest east southeast direction the fault coincides with the proposed left stepping divide accommodation zone in the la salle deformation belt and indicates reactivation of old deformation zone by contemporary stresses in the midcontinent

spatial temporal evolutions of early aftershocks following the 2013 mw 6 6 lushan earthquake in sichuan china we perform a comprehensive detection of early aftershocks following the 2013 mw 6 6 lushan earthquake which occurred in the southern longmenshan fault zone in sichuan province china about 5 years after the 2008 mw 7 9 wenchuan earthquake we use events in both standard and relocated catalogs as templates to scan through continuous waveforms 2 days before and 3 days after the main shock we successfully reduce the magnitude of completeness mc by more than 1 order and obtain up to 6 times more events than listed in both catalogs aftershocks in the first hour mostly occur around the main shock slip region and aftershocks at later times show systematic expansions in the along strike perpendicular strike and updip directions although postseismic deformation following the lushan main shock has not been clearly identified we suggest that early aftershock expansions are likely driven by afterslip of the lushan main shock this is consistent with the observations that most aftershocks were in the stress shadow of the lushan main shock and that there was significant slip deficit in the top 10 km of the crust we also find that seismicity on the back thrust fault was activated as soon as 20 min after the main shock earlier than previously reported we are unable to detect any clear foreshocks in the last 2 days before the lushan main shock

the role of tropical waves in tropical cyclogenesis abstract this paper analyzes relationships between tropical wave activity and tropical cyclogenesis in all of the earth s major tropical cyclone basins twenty nine years of outgoing longwave radiation data and global reanalysis winds are filtered and analyzed to determine statistical relationships between wave activity in each basin and the corresponding cyclogenesis composite analyses relative to the storm genesis locations show the structures of the waves and their preferred phase relationships with genesis five wave types are examined in this study including mixed rossby gravity waves tropical depression type or easterly waves equatorial rossby waves kelvin waves and the madden julian oscillation the latter is not one of the classical tropical wave types but is a wavelike phenomenon known to have a strong impact on tropical cyclogenesis tropical cyclone formation is strongly related to enhanced activity in all of the wave filter bands except for the kelvin band in each basin the structure o