a measurement of lunar tides in the mesosphere at adelaide south australia wind measurements at adelaide 35 s at heights from 76 to 98 km are analyzed for semidiurnal or semimonthly lunar tides two data sets are used one of about 2 years 1984 1985 and one of 1 year 1986 the lunar tide amplitude generally has its largest values at the equinoxes though this pattern changes in 1984 1985 at the greatest heights to solstice maxima especially in winter july diurnal average amplitudes reach 4 m s 1 while the largest value obtained was 8 m s 1 inferred vertical wavelengths of the propagating tides were rather variable and there was evidence of possible mode coupling and interference in summer wavelengths of 25 km occurred below 92 km and were evanescent above while in winter long wavelengths were found in the 78 to 90 km range with shorter 38 km wavelengths above that height comparisons of phases with results from saskatoon and kyoto suggest that around 95 km antisymmetric modes may be dominant in june and december and symmetric modes in february diurnal variations in the lunar tide were evident and year to year changes were seen in some aspects comparison with currently available models shows several points of disagreement

propagating diurnal disturbances embedded in the madden julian oscillation 1 fine structure of large scale intraseasonal disturbance associated with the madden julian oscillation mjo was analyzed using the 3 hourly 3b42 trmm rainfall data over the maritime continent diurnal cycle becomes pronounced during the passage of mjo and the eastward propagating diurnal disturbances pdds dominate as an internal structure of large scale convection system of mjo importantly fast pdds that penetrate through the islands are observed within the slowly propagating mjo system this eastward penetration of pdds through the islands result in a sudden shift of the convection center from the western part of the islands to the east causing an overall propagation of the mjo from the indian ocean to the pacific our results demonstrate that the diurnal cycle of convection over and around the major islands thus plays an active role in the propagation of the mjo over the maritime continent

a global view of the atmospheric lunar semidiurnal tide 1 atmospheric lunar semidiurnal tides are studied using 10 years of temperature data collected by the thermosphere ionosphere mesosphere energetics and dynamics sounding of the atmosphere using broadband emission radiometry satellite the amplitudes and phases in the temperature field are calculated by performing least mean square fit in a data set of about 60 day interval combining ascending and descending data together the mean tidal structures are studied for the height range from 20 to 120 km between 50 latitude and centered on each month from february 2002 to january 2012 a clear signature of the 12 42 h lunar semidiurnal tide is observed in the data characteristic of propagating waves is observed in the vertical amplitude and phase profiles in almost all heights the best conditions of propagation for the lunar semidiurnal tide are reached in the lower thermosphere region asymmetry between the hemispheres and seasonal variability is observed in the amplitudes of the tide longitudinal variations are also observed which reveals the existence of nonmigrating components in addition to the dominant migrating lunar tide

ichthyornis aves from the early turonian late cretaceous of alberta an isolated left humerus from the cretaceous toothed bird ichthyornis is described the fossil comes from the vimy member of the kaskapau formation at watino alberta and is early turonian in age the watino specimen is the oldest well authenticated record of ichthyornis and the oldest cretaceous skeletal fossil of a bird from the western hemisphere the wide geographic distribution of ichthyornis within the western interior of north america is in keeping with nomadic habits as inferred from strongly flying modern marine birds

the madden julian oscillation recorded in early observations from the tropical rainfall measuring mission trmm a satellite data analysis is performed to explore the madden julian oscillation mjo focusing on the potential roles of the equatorial rossby er and kelvin waves measurements from the tropical rainfall measuring mission trmm precipitation radar pr and visible infrared scanner virs are analyzed in the frequency wavenumber domain to identify and ultimately filter primary low frequency modes in the tropics the space time spectrum of deep storm fraction estimated by pr and virs exhibits notable kelvin wave signals at wavenumbers 5 8 a distinct mjo peak at wavenumbers 1 7 and periods of about 40 days and a signal corresponding to the er wave these modes are separately filtered to study the individual modes and possible relationship among them in the time longitude space in 10 cases analyzed here an mjo event is often collocated with a group of consecutive kelvin waves as well as an intruding er wave accompanied with the occasional onset of a stationary convective phase the spatial and temporal relationship between the mjo and kelvin wave is clearly visible in a lag composite diagram while the ubiquity of the er wave leads to a less pronounced relation between the mjo and er wave a case study based on the geostationary meteorological satellite gms imagery together with associated dynamic field captures the substructure of the planetary scale waves a cross correlation analysis confirms the mjo related cycle that involves surface and atmospheric parameters such as sea surface temperature water vapor low clouds shallow convection and near surface wind as proposed in past studies the findings suggest the possibility that a sequence of convective events coupled with the linear waves may play a critical role in mjo propagation an intraseasonal radiative hydrological cycle inherent in the local thermodynamic conditions could be also a potential factor responsible for the mjo by loosely modulating the envelope of the entire propagation system

longitudinal variation of the lunar tide in the equatorial electrojet the atmospheric lunar tide is one known source of ionospheric variability the subject received renewed attention as recent studies found a link between stratospheric sudden warmings and amplified lunar tidal perturbations in the equatorial ionosphere there is increasing evidence from ground observations that the lunar tidal influence on the ionosphere depends on longitude we use magnetic field measurements from the champ satellite during july 2000 september 2010 and from the two swarm satellites during november 2013 february 2017 to determine for the first time the complete seasonal longitudinal climatology of the semidiurnal lunar tidal variation in the equatorial electrojet intensity significant longitudinal variability is found in the amplitude of the lunar tidal variation while the longitudinal variability in the phase is small the amplitude peaks in the peruvian sector 285 e during the northern hemisphere winter and equinoxes and in the brazilian sector 325 e during the northern hemisphere summer there are also local amplitude maxima at 55 e and 120 e the longitudinal variation is partly due to the modulation of ionospheric conductivities by the inhomogeneous geomagnetic field another possible cause of the longitudinal variability is neutral wind forcing by nonmigrating lunar tides a tidal spectrum analysis of the semidiurnal lunar tidal variation in the equatorial electrojet reveals the dominance of the westward propagating mode with zonal wavenumber 2 sw2 with secondary contributions by westward propagating modes with zonal wavenumber 3 sw3 and 4 sw4 eastward propagating waves are largely absent from the tidal spectrum further study will be required for the relative importance of ionopsheric conductivities and nonmigrating lunar tides

mesosphere thermosphere tidal coupling during the september 21 25 1987 ltcs 1 campaign the thermosphere ge 90 km is dynamically coupled to the mesophere and lower atmospheric regions by gravity waves tides and planetary waves which propagate upward from below and often undergo dissipation in the 80 to 150 km region this paper focuses on the mesosphere thermosphere coupling due to the solar semidiurnal atmospheric tide during the first lower thermosphere coupling study ltcs campaign interval of september 21 25 1987 during this period determinations of semidiurnal eastward u and northward v velocity components and temperature delta t are available within the 80 to 150 km region from a total of 13 incoherent scatter meteor and spaced antenna radars a new method is developed and reported here for assimilating such data sets into a self consistent global empirical description of the tidal dynamics between 80 and 150 km using a set of numerically generated hough mode extension hme functions for u v and delta t corresponding to the 2 2 2 3 2 4 and 2 5 semidiurnal tidal modes a least squares fit to the radar data is performed the fit results in a single complex normalizing factor for each hme from which globally continuous and internally consistent semidiurnal oscillations in u v and delta t as well as vertical velocity and density canmore be derived the quality of fit to these data from various height regions including both northern and southern hemispheres establishes the internal consistency between these measurements as well as the applicability of the method to future data sets the resulting empirical model reproduces the data significantly better than recent theoretical models suggesting use of the method for deriving tidal boundary conditions for thermospheric general circulation models less

a diurnal modulation of the lunar tide in the upper atmosphere analysis of geomagnetic data from several stations in the equatorial region shows that the amplitude of the lunar semimonthly tide frequently does not have the expected symmetry about noon in its diurnal variation there is a distinct tendency for larger amplitudes in the morning at many stations this effect is largest in equinoctial months though there are regional differences analysis of data from different years confirms its presence the interaction between solar and lunar tides in the middle atmosphere may be responsible for the observed modulation

lunar tidal winds measured in the upper atmosphere 78 105 km at saskatoon canada abstract six years of winds data measured by the partial reflection drifts technique have been analyzed for lunar tides data are available at 3 km intervals of height and are separately analyzed in two year datasets to cheek consistency a month by month seasonal variation is derived largest amplitudes of the lunar tide occur in january february with a smaller maximum in summer the vertical wavelength is longest in summer and the tide then resembles that predicted for a pure 2 2 mode in winter vertical wavelengths range from 25 to 81 km in different years several of these results do not agree with the model of forbes an o1 component of the lunar tide could not be detected

a madden julian oscillation event realistically simulated by a global cloud resolving model a madden julian oscillation mjo is a massive weather event consisting of deep convection coupled with atmospheric circulation moving slowly eastward over the indian and pacific oceans despite its enormous influence on many weather and climate systems worldwide it has proven very difficult to simulate an mjo because of assumptions about cumulus clouds in global meteorological models using a model that allows direct coupling of the atmospheric circulation and clouds we successfully simulated the slow eastward migration of an mjo event topography the zonal sea surface temperature gradient and interplay between eastward and westward propagating signals controlled the timing of the eastward transition of the convective center our results demonstrate the potential making of month long mjo predictions when global cloud resolving models with realistic initial conditions are used

lunar and solar tidal variabilities in mesospheric winds and eej strength over tirunelveli 8 7 n 77 8 e during the 2009 major stratospheric warming 1 mesospheric wind observations by the medium frequency radar and geomagnetic field observations at tirunelveli 8 7 n 77 8 e 1 75 n dip angle are used to study the relative importance of solar and lunar influences in the variabilities of mesospheric tides and equatorial electrojet eej strength during the unprecedented major stratospheric sudden warming ssw of 2009 it is observed that the afternoon reversal in the eej popularly known as counter electrojet occurs consecutively for several days during the ssw event when there is an enhancement of solar semidiurnal tide in both zonal wind at 90 km and eej strength over tirunelveli although the amplitude of lunar tides also shows enhancement it is much less than that of solar the diurnal tidal amplitude in zonal wind and eej strength also shows large enhancement just before the onset of ssw however solar semidiurnal tide dominates diurnal tide during the ssw the diurnal tidal phase in zonal wind shifts to a few hours earlier during the ssw the lunar semidiurnal tidal phase shifts to later hours in both zonal wind and eej strength the main observation of the present study is that the large semidiurnal tide observed during the ssw 2009 is mostly solar driven and only partly lunar driven although tidal planetary wave interaction also may play a vital role although a similar behavior is noticed during the ssw 2006 also the large lunar semidiurnal tide observed in the eej strength without having large lunar semidiurnal tide in the underlying mesospheric winds needs further investigation

tropical oceanic rainfall and sea surface temperature structure parsing causation from correlation in the mjo abstractbased upon on the findings of y li and r e carbone the association of tropical rainfall with sst structure is further explored with emphasis on the mjo passband analyses include the tropical indian ocean maritime continent and tropical western pacific regions the authors examine the anomalies of and correlations between sst structure the frequency of rainfall events and rainfall amount based on detailed examination of a 49 month time series all findings are statistical inferences and interpretations consistent with established theory the statistical inferences are broadly consistent with a pivotal role played by the convergent laplacian of sst together with an expected but somewhat indirect role of sst itself the main role of sst in the mjo passband appears limited to production of moist static energy which is highly correlated with cumulative precipitation yet bears a decidedly conditional relationship to the occurrence of rainfall if rain occurs then more rain is likely over

the madden julian oscillation observed during the toga coare iop global view abstract during the toga coare intensive observing period november 1992 february 1993 two pronounced madden julian oscillation mjo events associated with super cloud clusters and westerly wind bursts were observed this paper presents a global view of the mjos including the origin of the super clusters in the indian ocean their migration into the maritime continent and the toga coare large scale soundings array lsa in the western equatorial pacific and their rapid decay over cold water of the eastern pacific the structure and evolution of the mjo are examined with emphasis on the coupling between large scale motion and convection because of differences in propagation speeds the positions of maximum zonal wind perturbations relative to deep convection undergo systematic changes during the travel of the mjo however the centers of deep convection always coincide with those of large scale ascent the super cloud cluster accompanies a wide area of warm air in the upper troposphere over the warm

the onset of convection in the madden julian oscillation abstract an observational study of the onset of convection in the madden julian oscillation mjo was performed composites of radiosonde data from the comprehensive aerological reference data set were constructed for an ensemble of tropical stations located in the indian ocean maritime continent and western pacific ocean the composites suggest that for the off equatorial stations used in this study the mjo period may be set by the buildup and discharge of the low level moist static energy this result supports the discharge recharge hypothesis of blade and hartmann mjo events appear to begin when the off equatorial atmosphere has been destabilized through a combination of low level moist static energy buildup and concurrent drying of the middle troposphere by subsidence in the wake of the previous cycle of mjo convection the low level moist static energy buildup is controlled by a corresponding increase in low level moisture the increase in low level moisture is not caused by the 1000 mb convergen

mjo like coherent structures sensitivity simulations using the cloud resolving convection parameterization crcp abstract interaction between equatorially trapped disturbances and tropical convection is investigated using a nonhydrostatic global model that applies the cloud resolving convection parameterization crcp the crcp represents subgrid scales of the global model by embedding a 2d cloud resolving model in each column of the global model the modeling setup is a constant sst aquaplanet with the size and rotation of earth in radiative convective quasi equilibrium the global atmosphere is assumed to be initially at rest no large scale organization of convection is present outside the equatorial waveguide inside the waveguide on the other hand the model simulates spontaneous formation of coherent structures with deep convection on the leading edge and strong surface westerly winds to the west the westerly wind bursts these coherent structures resemble the madden julian oscillation mjo observed in the terrestrial tropics and are present in simulations applying prescribed and interactive radiation an

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

on large scale circulations in convecting atmospheres the dominant thinking about the interaction between large scale atmospheric circulations and moist convection holds that convection acts as a heat source for the large scale circulations while the latter supply water vapour to the convection we show that this idea has led to fundamental misconceptions about this interaction and offer an alternative paradigm based on the idea that convection is nearly in statistical equilibrium with its environment according to the alternative paradigm the vertical temperature profile itself rather than the heating is controlled by the convection which ties the temperature directly to the subcloud layer entropy the understanding of large scale circulations in convecting atmospheres can therefore be regarded as a problem of understanding the distribution in space and time of the subcloud layer entropy we show that the subcloud layer entropy is controlled by the sea surface temperature the surface wind speed and the large scale vertical velocity in the convecting layer and demonstrate how the recognition of this control leads to a simple physically consistent view of large scale flows ranging from the hadley and walker circulations to the 30 50 day oscillation in particular we argue that the direct effect of convection on large scale circulations is to reduce by roughly an order of magnitude the effective static stability felt by such circulations and to damp all of them

characteristics of precipitation cloud and latent heating associated with the madden julian oscillation abstract this study investigates the evolution of cloud and rainfall structures associated with madden julian oscillation mjo using tropical rainfall measuring mission trmm data two complementary indices are used to define mjo phases joint probability distribution functions pdfs of cloud top temperature and radar echo top height are constructed for each of the eight mjo phases the genesis stage of mjo convection over the western pacific phases 1 and 2 features a bottom heavy pdf characterized by abundant warm rain low clouds suppressed deep convection and higher sea surface temperature sst as mjo convection develops phases 3 and 4 a transition from the bottom heavy to top heavy pdf occurs the latter is associated with the development of mixed phase rain and middle to high clouds coupled with rapid sst cooling at the mjo convection peak phase 5 a top heavy pdf contributed by deep convection with mixed phase and ice phase rain and high echo top heights 5 km dominates the decay

lunar tidal winds at adelaide and saskatoon at 80 to 100 km heights 1985 1990 winds data from the two sites were analyzed for lunar tides in 2 year groups the variation with height of the phase and amplitude of the tide showed considerable variability from year to year yet in general seasonal variations at particular heights were similar to those determined previously phases of the tide at the two sites were compared in order to estimate whether the tide was symmetric or antisymmetric for this purpose it was found necessary to use only 1 year data sets the predominance of symmetric tides during solstice months and antisymmetric tides at the equinox came as a surprise yet the result is in broad agreement with phase relations of the lunar geomagnetic tide

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

coupling between mesosphere and ionosphere over beijing through semidiurnal tides during the 2009 sudden stratospheric warming 1 sudden stratospheric warming ssw in the winter of 2008 2009 is the strongest recorded ssw event the enhancement in semidiurnal variation of ionospheric tec total electron content with phase shift forward is shown during 22 to 27 january 2009 based on the tec observations in beijing 40 30 n 116 19 e geographic 39 73 n dip latitude we focus on finding the reason for the tec variation winds observed by an all sky meteor radar in the same observatory are used to study mesospheric variation the semidiurnal solar tide in the mesosphere starts to increase before the ssw and maintains oscillation with period 16 20 days during the ssw the semidiurnal lunar tides in tec and wind start to increase on 17 and 15 january respectively although the semidiurnal lunar tide in tec over beijing almost dies out on 1 february that over equatorial ionospheric anomaly crest does not vanish until 15 february when lunar tide in wind tends to be very weak the maximum of lunar tide in wind appears on 2 february at 96 km with amplitudes of 15 m s and 21 m s for zonal and meridional winds the phase comparison shows that lunar tides in tec and zonal wind reach their maxima at almost the same time which is 2 4 h lag behind the meridional wind the coupling between the mesosphere and ionosphere contributes to the semidiurnal variation of tec through both solar and semidiurnal lunar tides the enhancement in semidiurnal lunar tide is responsible for the tec peak shift forward during the ssw

attributing tropical cyclogenesis to equatorial waves in the western north pacific abstract tropical cyclogenesis is attributed to an equatorial wave when the filtered rainfall anomaly exceeds a threshold value at the genesis location it is argued that 0 mm day 1 simply requiring a positive anomaly is too small a threshold because unrelated noise can produce a positive anomaly a threshold of 6 mm day 1 is too large because two thirds of storms would have no precursor disturbance between these extremes consistent results are found for a range of thresholds from 2 to 4 mm day 1 roughly twice as many tropical cyclones are attributed to tropical depression td type disturbances as to equatorial rossby waves mixed rossby gravity waves or kelvin waves the influence of the madden julian oscillation mjo is even smaller the use of variables such as vorticity and vertical wind shear in other studies gives a larger contribution for the mjo it is suggested that its direct influence on the rainfall in forming tropical cyclones is less than for other variables the impacts of tropical

observed evolution of northward propagating intraseasonal variation over the western pacific a case study in boreal early summer abstractthis report describes the in situ observed evolution of the atmospheric profile during an event of the boreal summer intraseasonal variation bsisv in the tropical western pacific ocean the convectively active region of the bsisv proceeded northward over the sounding and radar network over the array the situation changed from a convectively inactive period to an active period inspection of the sounding data revealed the gradual moistening of the lower troposphere during the convectively inactive period the sounding derived heat and moisture budget analyses indicated that both the convective and large scale processes caused moistening of the lower and middle troposphere where the radar echo tops were observed most frequently this study is the first to identify such a preconditioning process for the bsisv in the western pacific using detailed in situ observational data during the preconditioning an increase in cape was observed as in previous studies of the mjo an increase of moisture

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

atmospheric tide 2 the solar and lunar semidiurnal components solar and lunar semidiurnal wind and temperature oscillations from the surface to 400 km are simulated for average solar activity conditions utilizing the numerical tidal model described in part 1 hough mode decomposition of the solstitial solar semidiurnal tide excited by h2o and o3 insolation absorption below 80 km indicates that it is characterized by a predominance of 2 2 below 60 km about equal contributions of 2 2 2 3 and 2 4 between 70 and 90 km mostly 2 4 with some 2 5 and 2 2 between 90 and 120 km and a predominance of 2 2 above 140 km with secondary contributions from 2 3 and 2 5 the solstitial lunar semidiurnal tide is characterized by a predominance of 2 2 below 70 km 2 4 with secondary contributions from 2 2 2 3 and 2 5 between 80 and 110 km and by 2 2 with a fairly strong secondary contribution from 2 3 above 120 km similar descriptions for both the solar and lunar oscillations apply at equinox except that the asymmetric 2 3 and 2 5 modes are absent relative to the solar component lunar temperature and wind amplitudes are sufficiently large 20 in the lower and upper thermosphere to account for some of the observed variability previously attributed to the solar tide amplitudes of the 2 4 and 2 5 modes above 100 km are significantly affected by mesospheric eddy diffusion coefficients in excess of 2 106 cm s 1 the total solar semidiurnal exospheric temperature oscillation for average solar conditions ranges from 10 20 k poleward of 40 n to 40 60 k equatorward of 30 n and has its origin in three sources of excitation all of comparable importance 1 euv solar radiation absorption in the lower thermosphere 100 200 km 2 in situ momentum coupling due to the interaction of diurnal winds and diurnally varying ion drag and 3 tides propagating upwards from below 100 km in addition the calculations are compared with rocket meteor radar partial reflection thomson scatter and satellite data to evaluate the consistency of the model with observations

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

equatorial waves including the madden julian oscillation in trmm rainfall and olr data four years of outgoing longwave radiation olr and rainfall data from the tropical rainfall measuring mission trmm are investigated to find the dominant large scale wave modes in the tropics by using space time cross section analysis and spectral analysis the longitudinal and latitudinal behaviors of the overall waves and the dominant waves are observed despite the noisy nature of precipitation data and the limited sampling by the trmm satellite pronounced peaks are found for kelvin waves n 5 1 equatorial rossby waves er and mixed rossby gravity waves mrg madden julian oscillation mjo and tropical depression td type disturbances are also detected the seasonal evolution of these waves is investigated an appendix includes a study of sampling and aliasing errors due to the peculiar space time sampling pattern of trmm it is shown that the waves detected in this study are not artifacts of these sampling features the results presented here are compared with previous studies consistency with their results gives confidence in the trmm data for wave studies the results from this study can be utilized for modeling and testing theories also it may be useful for the future users of the trmm data to understand the nature of the trmm satellite sampling

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

abrupt termination of the 1997 98 el nino in response to a madden julian oscillation the role of the madden julian oscillation a global atmospheric wave in the tropics that is associated with convective activity and propagates eastwards with a period of about 30 60 days refs 1 2 in triggering el nino events has been discussed before3 4 5 6 7 8 but its possible connection with a termination of el nino has yet to be investigated despite the difficulty in explaining the timing of el nino terminations by the basic wind induced oceanic wave processes9 10 for the extreme 1997 98 event the mechanism of both onset and termination have been investigated3 but the reason for the abruptness of the termination has yet to be resolved here we present global data of precipitation sea surface temperatures and wind speeds that show a precipitation system associated with an exceptionally strong madden julian oscillation travelling around the equator in may 1998 the propagation of this atmospheric system was associated with an abrupt intensification of the easterly trade winds over the eastern equatorial pacific ocean combined with the already shallow equatorial thermocline in the central and eastern pacific ocean at that time3 these strong winds provided the triggering mechanism for the observed accelerated ending of the 1997 98 el nino event

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

high resolution simulation of mean convection and its intraseasonal variability over the tropics in the mri jma 20 km mesh agcm abstract tropical mean convection and its organization on different spatiotemporal scales in a simulation using the meteorological research institute japan meteorological agency mri jma global atmospheric general circulation model agcm at 20 km resolution tl959l60 has been investigated comparison with two lower resolution simulations of 120 km tl159l40 and 180 km tl95l40 shows that convection climatological fields and moist stability over the indian ocean and south pacific convergence zone are better represented in tl959l60 than in lower resolution simulations however the simulated three dimensional structure of the walker and hadley cells and the vertical structure of convective heating do not show marked improvement relative to lower resolution simulations the amplitude and phase speed of convectively coupled equatorial waves show that although the kelvin waves the observed hierarchical structure of cloud clusters associated with the madden julian oscillation mjo convection and th

variability in the characteristics of precipitation systems in the tropical pacific part i spatial structure regional and temporal variability in the vertical and horizontal characteristics of tropical precipitating clouds are investigated using the precipitation radar pr and the visible and infrared scanner virs on board the tropical rainfall measuring mission trmm satellite the present study focuses on the three oceanic regions west central and east pacific together with two continental regions for comparison and the two separate time periods february 1998 and february 2000 under different phases of the el nino southern oscillation enso in order to examine regional and enso related variations the height spectrums of storms are investigated in terms of radar echo top height and infrared brightness temperature the variability in the spectrum clearly correlates with the large scale circulation and its enso related change on the basis of the height spectrum storm systems are classified into the four categories of shallow cumulus congestus deep stratiform and deep convective the deep stratiform and deep convective categories both of which have very cold cloud tops are differentiated by radar echo top heights so that deep convective systems are accompanied with an appreciable amount of large frozen particles aloft while shallow events are dominant in the probability of occurrence over relatively cold oceans deep convective systems take their place for warmer sea surface temperatures ssts the turnover occurs at the sst threshold of 28 29 c for all the oceanic regions and years investigated except the west pacific in 2000 for which deep convective systems prevail over the entire range of sst rain correlation scale length rcsl and cloud correlation scale length ccsl are introduced as statistical indicators of the horizontal scale of storms while the rcsl is 8 18 km for shallow and cumulus congestus type clouds without significant regional and temporal variations the rcsl and ccsl associated with deep stratiform and deep convective systems consistently exceed 100 km and exhibit a systematic variability the rcsl and ccsl in the central and east pacific particularly increase significantly in the el nino year

intraseasonal behavior of clouds temperature and motion in the tropics abstract the spectral character of tropical convection is investigated in an 11 yr record of outgoing longwave radiation from the advanced very high resolution radiometer to identify interaction with the tropical circulation along the equator in the eastern hemisphere the space time spectrum of convection possesses a broad peak at wave numbers 1 3 and eastward periods of 35 95 days significantly broader than the dynamical signal of the madden julian oscillation mjo this quasi discrete convective signal is associated with a large scale anomaly that propagates across and modulates time mean or climatological convection over the equatorial indian ocean and western pacific outside that region the convective signal is small even though under amplified conditions coherence can be found east of the date line and in the subtropics having a zonal scale of approximately wavenumber 2 anomalous convection propagates eastward at some 5 m s 1 and suppresses as well as reinforces climatological convection

kinematic and thermodynamic characteristics of the flow over the western pacific warm pool during toga coare abstract rawinsonde and satellite infrared radiation ir data from the tropical ocean global atmosphere toga coupled ocean atmosphere response experiment coare are used to investigate mean and transient behavior and horizontal variability of the atmosphere over the western pacific warm pool infrared data for the 4 mo intensive observing period iop and vertical motion fields indicate that the intensity of convection height of maximum upward motion and sst all increased from west 140 e to east across the coare domain iop mean ir data show a double itcz intertropical convergence zone structure north and south of the intensive flux array ifa centered at 2 s 156 e although marked variability in the patterns occurred on a month to month basis three prominent westerly wind bursts occurred over the ifa during the 4 mo iop in association with the intraseasonal oscillations isos strong upward motion usually occurred 1 3 weeks prior to the peak low level westerlies subsidence dominated when

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

a joint satellite and global cloud resolving model analysis of a madden julian oscillation event model diagnosis 1 in this study a methodology to diagnose a global cloud resolving model gcrm is explored on the basis of a joint analysis with satellite measurements the madden julian oscillation experiment carried out with the nonhydrostatic icosahedral atmospheric model nicam is used as the test bed the nicam output is compared with tropical rainfall measuring mission trmm and cloudsat measurements in terms of composite analysis contoured frequency by altitude diagrams cfads and the joint histogram of cloud top and precipitation top heights it is found in the composite diagram that the gcrm reproduces a slow eastward migration of a convective envelope well comparable to the satellite measurement the gcrm cfad qualitatively reproduces trmm and cloudsat cfads except that the gcrm tends to overly produce snow in deep convection the joint histograms reveal that while the overproduction of snow is evident nicam simulated snow is incapable of producing 94 ghz radar echoes higher than 5 dbz this deficiency can be mitigated by a modification to microphysical parameterization in the way that a proportion of small particles is enhanced in the snow mass spectrum

a moist static energy budget analysis of quasi 2 day waves using satellite and reanalysis data a moist static energy mse budget analysis is applied to quasi 2 day waves to examine the effects of thermodynamic processes on the wave propagation mechanism the 2 day waves are defined as westward inertia gravity wig modes identified with filtered geostationary infrared measurements and the thermodynamic parameters and mse budget variables computed from reanalysis data are composited with respect to the wig peaks the composite horizontal and vertical mse structures are overall as theoretically expected from wig wave dynamics a prominent horizontal mse advection is found to exist although the wave dynamics is mainly regulated by vertical advection the vertical advection decreases mse around the times of the convective peak plausibly resulting from the first baroclinic mode associated with deep convection normalized gross moist stability ngms is used to examine the thermodynamic processes involving the large scale dynamics and convective heating ngms gradually decreases to zero before deep convection and reaches a maximum after the convection peak where low high ngms leads lags deep convection the decrease in ngms toward zero before the occurrence of active convection suggests an increasingly efficient conversion from convective heating to large scale dynamics as the wave comes in while the increase afterward signifies that this linkage swiftly dies out after the peak