surface microseismic in an extreme environment a surface microseismic survey was conducted in a noisy suburban active oil field environment unconventional patch acquisition survey design and careful processing allowed the extraction of more than 8000 events from the noisy data patch acquisition and multichannel noise attenuation were critical components of the success of the project the computation of microseismic source mechanisms from the surface depended on solving for accurate velocities and statics in the preprocessing stage

diurnally modulated cumulus moistening in the preonset stage of the madden julian oscillation during dynamo abstractatmospheric soundings radar and air sea flux measurements collected during dynamics of the madden julian oscillation dynamo are employed to study mjo convective onset i e the transition from shallow to deep convection in the tropical indian ocean the findings indicate that moistening of the low midtroposphere during the preonset stage of the mjo is achieved by simultaneous changes in the convective cloud population and large scale circulation namely cumuliform clouds deepen and grow in areal coverage as the drying by large scale subsidence and horizontal westerly advection wane the reduction of large scale subsidence is tied to the reduction of column radiative cooling during the preonset stage which ultimately links back to the evolving cloud population while net column moistening in the preonset stage is tied to large scale circulation changes a new finding of this study is the high degree to which the locally driven diurnal cycle invigorates convective clouds and cumulus moiste

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

first observations of turbulence parameters in the troposphere over the bay of bengal and the arabian sea using radiosonde 1 this paper discusses the turbulence characteristics of the free atmosphere over the bay of bengal and the arabian sea during the premonsoon season of 2006 the turbulence scaling concepts developed over the past decades for application to oceanic mixing are used for retrieving turbulence properties in the free atmosphere from high resolution soundings as described by clayson and kantha 2008 the variability in the vertical turbulence structure over a large spatial region is studied using this novel method for the first time investigations revealed the presence of a highly turbulent band at upper troposphere below the cold point tropopause cpt with significant enhancements in thorpe length and eddy diffusion coefficient this increased turbulence is studied in conjunction with the observations of the tropical tropopause layer ttl it is seen that the lower and upper boundaries of this turbulence band nearly coincide with the height where the potential temperature lapse rate begins to show a decrease lrhmin and cold point tropopause respectively the ttl is the transition regime from convectively dominated troposphere to radiatively dominated stratosphere and is characterized by a decrease in the static stability the enhanced zonal and meridional wind shear observed in this region shows that the stability in this region is further weakened because of the breaking of kelvin helmholtz waves which results in the enhancement of turbulence the study reveals the potential of high resolution soundings to be used in the investigations of turbulence in the free atmosphere

evidence of gravity wave saturation and local turbulence production in the summer mesosphere and lower thermosphere during the state experiment this study utilizes the unique data set obtained during the structure and atmospheric turbulence environment state experiment conducted during june 1983 at poker flat alaska to examine the structure and characteristics of the wave field near the summer mesopause it is shown that the rocket and radar data together permit a much more detailed specification of wave parameters than would be possible using either data set alone the results of this analysis suggest that the wave field near the summer mesopause is composed in general of a superposition of wave motions which act collectively to produce regions in which the wave field is convectively or dynamically unstable these regions are found to correlate well with zones of enhanced turbulence and small scale wave activity suggesting the processes and effects of wave field saturation

radiosonde observations of partially trapped lee waves over tasmania australia a well defined family of lee waves over southern tasmania australia is analyzed using a routine radiosonde sounding released from hobart at 1100 utc june 18 1991 pronounced fluctuations in the ascent rate of the radiosonde are analyzed using a new technique called the horizontal projection method the dominant horizontal wavelength is found to be 8249 m an advanced very high resolution radiometer avhrr infrared satellite image at 1554 utc is used to check this calculation and gives a horizontal wavelength of 8 9 1 4 km the horizontal projection method takes account of the vertical variation of background flow and the trajectory of the radiosonde when the scorer parameter is a strong function of height as is the case with the 1100 utc sounding it is inappropriate to assume that the vertical wavenumber is constant with height in particular the vertical wavelength at low levels is about 4 5 km the waves become evanescent between the heights of 2 5 km and 9 km and above that the vertical wavelength is typically 10 15 km as a consistency check linear wave theory is used to calculate the resonant wave modes supported by the background profiles of wind and potential temperature these are the wave modes that are most likely responsible for the lee wave clouds seen in the avhrr satellite image the horizontal wavelength for the resonant wave mode is 8188 m in agreement with the estimates based on the avhrr satellite image and from the horizontal projection method the paper highlights the dangers of interpreting radiosonde soundings as vertical snapshots of the atmosphere and assuming that the vertical wavenumber can be characterized by a single value it is shown that treating the radiosonde sounding as a vertical profile and analysing wave like structures in the ascent rate using standard spectral methods gives an incorrect vertical wavelength of 1906 238 m the paper concludes that operational radiosonde soundings can be used to make accurate quantitative measurements of orographically generated waves provided that the vertical variation in the background flow and the motion of the radiosonde through the wave field are taken into account

the 1997 98 el nino evolution relative to previous el nino events abstract the evolution of the 1997 98 el nino is described using ncep sst and olr data ncep ncar reanalysis sea level pressure slp fields and the florida state university surface wind data from november 1996 to january 1997 the eastern pacific is characterized by equatorial cold sst and high slp anomalies while the western pacific is marked by off equatorial warm sst anomalies and off equatorial anomalous cyclones corresponding to this distribution are high olr anomalies in the equatorial central pacific and low olr anomalies in the off equatorial far western pacific the off equatorial anomalous cyclones in the western pacific are associated with a switch in the equatorial wind anomalies over the western pacific from easterly to westerly these equatorial westerly anomalies then appear to initiate early sst warmings around the date line in january february 1997 and around the far eastern pacific in march 1997 subsequently both the westerly wind and warm sst anomalies along with the low olr ano

evolution properties and spatial variability of mjo convection near and off the equator during dynamo abstractthis study investigates the evolution structure and spatial variability of madden julian oscillation mjo convection observed during the 2011 12 dynamics of the mjo dynamo field campaign generally the c band radars located in the near equatorial indian ocean shared mobile atmospheric research and teaching radar smart r on addu atoll gan and nasa toga on the r v roger revelle revelle observed similar trends in echo top heights stratiform rain fraction and precipitation feature size across the mjo life cycle these trends are closely related to changes in mid to upper tropospheric moisture sea surface temperature sst zonal wind and diagnosed vertical air motions however the evolution of convection moisture and vertical air motion at the r v mirai mirai located in the intertropical convergence zone itcz at 8 s exhibited a pattern nearly opposite to gan and revelle when the mjo was active over the equator convection was suppressed around mirai owing to induced subsiden

the role of shallow cloud moistening in mjo and non mjo convective events over the arm manus site abstractobservations from the atmospheric radiation measurement program arm site at manus island in the western pacific and re analysis products are used to investigate moistening by shallow cumulus clouds and by the circulation in large scale convective events large scale convective events are defined as rainfall anomalies larger than one standard deviation for a minimum of three consecutive days over a 10 10 domain centered at manus these events are categorized into two groups madden julian oscillation mjo events with eastward propagation and non mjo events without propagation shallow cumulus clouds are identified as continuous time height echoes from 1 min cloud radar observations with their tops below the freezing level and their bases within the boundary layer daily moistening tendencies of shallow clouds estimated from differences between their mean liquid water content and precipitation over their presumed life spans and those of physical processes and advection from re analysis

turbulence characteristics over tropical station gadanki 13 5 n 79 2 e estimated using high resolution gps radiosonde data 1 seasonal variation of the turbulence parameters refractivity structure constant cn2 eddy dissipation rate and eddy diffusivity k is presented using 3 years april 2006 to march 2009 of high vertical resolution gps radiosonde measurements over the tropical station gadanki 13 5 n 79 2 e first a correlation analysis was done in order to study the relative contributions of temperature t and relative humidity rh to the refractive index gradient m a strong positive negative correlation between m and rh t gradients is noticed up to 10 km above 10 km a strong positive correlation between m and t gradients is seen except at altitudes near the tropopause in the present study we flag the turbulent layers using the thorpe sorting method and estimate the structure constant cn2 for the turbulent layers the probability of occurrence of cn2 is derived from the cumulative distribution at each height and is found to decrease from 10 7 to 10 17 m 2 3 with height the probability of the occurrence of cn2 conditioned to the occurrence of turbulence as a function of height is derived and it is found that only the mean and the 90th percentile profile reach an altitude of 27 km the demarcation between the boundary layer and the free atmosphere as well as between the troposphere and the stratosphere are quite clear from the turbulence profile which allows us to identify the boundary layer and tropopause heights from turbulence profiles thus the present analysis introduces an alternative approach to identify the height of the boundary layer as well as the tropopause and also to characterize the probability of turbulence and thickness of turbulent eddies in the atmosphere with a finer scale size down to 5 m for the first time from a tropical latitude

the occurrence of cirrus clouds associated with eastward propagating equatorial n 0 inertio gravity and kelvin waves in november 2011 during the cindy2011 dynamo campaign 1 cirrus cloud variability associated with n 0 eastward inertio gravity equatorial waves and equatorial kelvin waves both with the period of 4 days and equatorial kelvin wave with another periodicity 16 days were observed in the tropical indian ocean 8 0 s 80 5 e in november of 2011 during the cooperative indian ocean experiment on intraseasonal variability in the year 2011 cindy2011 dynamics of the madden julian oscillation dynamo field campaign using balloon borne cryogenic frostpoint hygrometers vaisala radiosondes and a shipborne high spectral resolution lidar system during early to mid november the cirrus cloud appearance corresponded primarily with high supersaturation and high relative humidity caused by the temperature disturbances associated with the 4 day waves between 12 km altitude and the cold point tropopause the cirrus clouds disappeared under the unfavorable downward wind and dry conditions that were caused by the 4 day waves although the 16 day wave was generating favorable conditions our multi instrument cirrus measurements revealed that we must consider the phases of various overlapping waves when estimating dehydration efficiency caused by cirrus clouds around the cold point tropopause

gravity wave activity associated with tropical convection detected in toga coare sounding data upper air sounding data collected at santa cruz 10 s 165 e in the western tropical pacific ocean during november 1992 february 1993 have been used to estimate the gravity wave activity in the upper troposphere and lower stratosphere large amplitude gravity waves with vertical wavelengths of 2 5 km were found in almost all the soundings time series describing the wave activity in two height ranges 10 17 km the upper troposphere and 17 24 km the lower stratosphere are presented and compared to simple measures of the convective cloud activity there is enhanced gravity wave activity associated with increased convection on intraseasonal timescales

vertical fluctuation energy in united states high vertical resolution radiosonde data as an indicator of convective gravity wave sources 1 convectively generated internal gravity waves at extratropical latitudes are difficult to identify by climatological analysis of the temperature and horizontal wind fields from radiosonde profiles using traditional analysis methods here we show that by analyzing ascent rate profiles we define a new variable vertical fluctuation energy ve we can identify convection sources in climatological analyses analysis of a 9 year time series 1998 2006 of united states high vertical resolution radiosonde data shows that ve maximizes in summer in midlatitudes within the troposphere 2 8 9 km and peaks at local afternoon early evening during the summer over most of the contiguous united states furthermore the apparent dominant vertical wavelength based on fourier analysis of the low pass filtered ascent rate fluctuations also increase and decrease with ve both on diurnal and seasonal timescales ve in the lower stratosphere however does not show this same relationship to convection but analysis of the vertical wavelength does show some of the features seen in tropospheric ve unlike midlatitude stations ve within both the troposphere and the lower stratosphere over tropical western pacific island stations is highly correlated with convective precipitation and inversely correlated with outgoing longwave radiation we interpret this difference by using the 4 d gravity wave regional or global ray tracer ray tracing model with a source spectrum representative of a convection source

tropospheric turbulence over the tropical open ocean role of gravity waves a large set of soundings obtained in the indian ocean during 3 field campaigns is used to provide statistical characteristics of tropospheric turbulence and its link with gravity wave gw activity the thorpe method is used to diagnose turbulent regions of a few hundred meters depth above the mixed layer turbulence frequency varies from 10 in the lower troposphere up to 30 around 12km heights gw are captured by their signature in horizontal wind normalized temperature and balloon vertical ascent rate these parameters emphasize different parts of the wave spectrum from longer to shorter vertical wavelengths respectively composites are constructed in order to reveal the vertical structure of the waves and their link with turbulence the relatively longer wavelength gw described by their signature in temperature gwt are more active in the lower troposphere where they are associated with clear variations in moisture turbulence is then associated with minimum static stability and vertical shear stressing the importance of the former and the possibility of convective instability conversely the short waves described by their signature in balloon ascent rate gww are detected primarily in the upper troposphere and their turbulence is associated with a vertical shear maximum suggesting the importance of dynamic instability furthermore gww appear to be linked with local convection whereas gwt are more active in suppressed and dry phases in particular of the madden julian oscillation these waves maybe associated with remote sources such as organized convection or local fronts such as those associated with dry air intrusions

mu radar and lidar observations of clear air turbulence underneath cirrus abstract turbulence generation mechanisms prevalent in the atmosphere are mainly shear instabilities breaking of internal buoyancy waves and convective instabilities such as thermal convection due to heating of the ground in the present work clear air turbulence underneath a cirrus cloud base is described owing to coincident observations from the vhf 46 5 mhz middle and upper atmosphere mu radar a rayleigh mie raman rmr lidar and a balloon radiosonde on 7 8 june 2006 at shigaraki japan 34 85 n 136 10 e time height cross section of lidar backscatter ratio obtained at 2206 lt 7 june 2006 showed the presence of a cirrus layer between 8 0 and 12 5 km msl downward penetrating structures of ice crystals with horizontal and vertical extents of 1 0 4 0 km and 200 800 m respectively have been detected at the cirrus cloud base for about 35 min at the same time the mu radar data revealed clear air turbulence layers developing downward from the cloud base in the environment of the protuberances

microphysical characteristics of mjo convection over the indian ocean during dynamo the microphysical characteristics of precipitating convection occurring in various stages of the madden julian oscillation mjo over the indian ocean are determined from data obtained from the national center for atmospheric research dual polarimetric doppler s band radar s polka deployed as part of the dynamics of the mjo dynamo field experiment active mjo events with increased rainfall occurred in october november and december 2011 during each of these active mjo phases in addition to enhanced rainfall convection became deeper and ice phase microphysics played a greater role s polka consistently showed nonoriented small ice particles dominating the radar echoes at altitudes of 9 10 km dry aggregates concentrated between 7 and 9 km and wet aggregates and graupel near the melting level 5 km graupel occurred mainly in actively convective towers while the wet aggregates occurred almost exclusively in the stratiform regions of mesoscale convective systems mcss during each of the three multiweek mjo active phases the maximum rainfall occurred in short bursts lasting a few days each multiday rainy period began with deepening convective elements and a concurrent increase in occurrence of dry aggregates which maximized just prior to organization into mcss the peak rainfall occurrence coincided with the maximum coverage of the radar domain by mcss reflecting large stratiform regions that exhibited the most frequent occurrence of wet aggregates during the december active mjo phase however the mcss were shallower and had a slightly lower tendency for wet aggregates in the stratiform regions and therefore generally weaker brightbands

gravity waves generated by convection during twp ice 2 high frequency gravity waves high frequency gravity waves are analyzed using radiosonde soundings taken during the tropical warm pool international cloud experiment twp ice the intrinsic periods of these waves are estimated to be between 10 and 50 min the high frequency wave activity in the stratosphere defined by mass weighted variance of the vertical motion of the sonde has a maximum following the afternoon local convection indicating that these waves are generated by local convection the wave activity is the strongest in the lower stratosphere below 22 km and during the suppressed monsoon period is modulated with a 3 4 day period the concentration of the wave activity in the lower stratosphere is consistent with the properties of the environment in which these waves propagate whereas its 3 4 day modulation is explained by the variation of the convection activity in the twp ice domain for shallow convection the wave activity has a weak tendency to increase as the rainfall intensity increases the wave activity associated with deep convection which typically occurs at high rainfall intensities is larger and has more spread than that associated with shallow convection

observations of kelvin helmholtz instability at a cloud base with the middle and upper atmosphere mu and weather radars 1 using the very high frequency 46 5 mhz middle and upper atmosphere radar mur ka band 35 ghz and x band 9 8 ghz weather radars a kelvin helmholtz kh instability occurring at a cloud base and its impact on modulating cloud bottom altitudes are described by a case study on 8 october 2008 at the shigaraki mu observatory japan 34 85 n 136 10 e kh braids were monitored by the mur along the slope of a cloud base gradually rising with time around an altitude of 5 0 km the kh braids had a horizontal wavelength of about 3 6 km and maximum crest to trough amplitude of about 1 6 km nearly monochromatic and out of phase vertical air motion oscillations exceeding 3 m s 1 with a period of 3 min 20 s were measured by the mur above and below the cloud base the axes of the billows were at right angles of the wind and wind shear both oriented east north east at their altitude the isotropy of the radar echoes and the large variance of doppler velocity in the kh billows including the braids indicate the presence of strong turbulence at the bragg 3 2 m scale after the passage of the cloud system the kh waves rapidly damped and the vertical scale of the kh braids progressively decreased down to about 100 m before their disappearance the radar observations suggest that the interface between clear air and cloud was conducive to the presence of the dynamical shear instability by reducing static stability and then the richardson number near the cloud base downward cloudy protuberances detected by the ka band radar had vertical and horizontal scales of about 0 6 1 1 and 3 2 km respectively and were clearly associated with the downward air motions observed oscillations of the reflectivity weighted doppler velocity measured by the x band radar indicate that falling ice particles underwent the vertical wind motions generated by the kh instability to form the protuberances the protuberances at the cloud base might be either kh billow clouds or perhaps some sort of mamma reflectivity weighted particle fall velocity computed from doppler velocities measured by the x band radar and the mur showed an average value of 1 3 ms 1 within the cloud and in the protuberance environment

radiosonde observations of equatorial atmosphere dynamics over indonesia 2 characteristics of gravity waves this paper discusses the characteristics of gravity waves in the equatorial region revealed by analyzing radiosonde measurements of wind velocity and temperature fluctuations at 0 35 km with a height resolution of 150 m made every 5 7 hours between february 27 and march 22 1990 in east java indonesia we conducted hodograph analysis to delineate vertical and horizontal propagation characteristics and found that most gravity waves were generated in the middle of the troposphere and that they propagated upward into the stratosphere the amplitudes of wind velocity and temperature fluctuations due to gravity waves were larger in the stratosphere than in the troposphere the direction of horizontal propagation of gravity waves was rather uniformly distributed in the troposphere but it became eastward in the lower stratosphere being opposite to that of the mean winds because of quasi biennial oscillation the vertical wavenumber spectra of wind velocity were described fairly well by a saturated model spectrum although their amplitudes were smaller in the stratosphere a typical vertical wavelength was 2 2 5 km while the horizontal phase velocities were 5 7 and 12 m s in the troposphere and stratosphere respectively the amplitudes of small scale gravity waves were significantly larger in the equatorial stratosphere than at middle latitudes time height variation of the wind velocity variance due to gravity waves showed a clear correlation with that for high relative humidity which implies that cloud convection is an important mechanism of gravity wave generation in the equatorial region

the event to event variability of the boreal winter mjo 1 during boreal winters perturbations of the convection by the madden julian oscillation mjo peak over three basins distributed in longitude south of the equator the eastern indian ocean io the south of the maritime continent mc and the western pacific ocean po we use the observed outgoing longwave radiation olr and low level wind to identify and characterize all wintertime mjo events between 1979 and 2010 there is a large event to event variability with some mjo events organized at the planetary scale having their amplitude well distributed over the 3 basins and some showing only basin scale organization with a convective perturbation peaking over one or two basins the average of the mjo amplitude for the three basins shows an intriguing decadal variability consistent for both olr and low level wind the disparity between the 3 basins is dominated by an alternation between mjo amplitude peaking on either the indian or the pacific ocean this indo pacific alternation depicted by an indo pacific index ipi is partly related to enso in el nino conditions there is not only an extension of the mjo perturbation further east but also an increase of the mjo perturbation over the western pacific and a diminution of the mjo perturbation over the eastern indian ocean

intermittent mixing in strongly stratified fluids as a random walk in strongly stratified geophysical fluids such as the stratosphere and the ocean the vertical mixing of tracers is largely due to patches of turbulence that are intermittent in time and space heuristic models for this type of mixing are studied which extend that of dewan 1981 a the recognition that in these models fluid particles undergo continuous time random walks allows the derivation of closed form results for the particle position statistics the particle dispersion is shown generally to be diffusive in the long time limit however the early time non diffusive regime is also analysed since a time scale estimate indicates its practical importance in particular for stratospheric mixing because the restratification of fluid patches previously homogenized by turbulence takes a finite time the probability for a fluid region to become turbulent may depend on the time elapsed since it has last been turbulent this introduces a memory effect whose consequences for the tracer mixing are analysed in detail using a simple non markovian model the heuristic models studied allow the large scale dispersive effects of the turbulent patches to be inferred from the properties of individual patches this highlights those properties that might most usefully be determined from investigations of the dynamics of the turbulent patches themselves