geographic variability in the export of moist static energy and vertical motion profiles in the tropical pacific 1 column integrated moist static energy mse budgets were calculated using daily data from three reanalyses 1998 2001 and isccp radiative cooling the mse export by the circulation was separated into vertical and horizontal mse advection components in order to examine how observationally derived vertical motion profiles affect gross moist stability calculations in a 2000 km wide region in the central eastern pacific itcz vertical motions import mse implying a negative gross moist stability horizontal mse advection is negative and of similar magnitude to vertical mse advection in rainy regions geographic differences in export of mse by the vertical circulation are primarily due to differences in the shape of the vertical motion profile in the west pacific warm pool rainy regions mean horizontal convergence extends up to 300 mb while in parts of the pacific itcz where meridional sst gradients are strong the vertical motion profile is bottom heavy with convergence below 800 mb and divergence above on daily timescales the mode of vertical motion variability has little dependence on precipitation rate and is consistent with observed regional differences in the vertical structure of trmm pr reflectivities

estimation of entrainment rate in simple models of convective clouds a method for estimating lateral entrainment rate in clouds is suggested linking its magnitude to buoyant production of vertical kinetic energy within a cloud updraught in single column model studies the formulation captures the high values of entrainment seen in shallow convection and the values an order of magnitude lower in cases of deep convection as suggested by observational studies and large eddy model simulations together with a realistic vertical variation comparison is made with other recent attempts to parametrize entrainment

role of maritime continent land convection on the mean state and mjo propagation abstractthe maritime continent mc region is known as a barrier in the life cycle of the madden julian oscillation mjo during boreal winter the mjo detours the equatorial mc land region sout

eastward propagating intraseasonal oscillation represented by chikira sugiyama cumulus parameterization part ii understanding moisture variation under weak temperature gradient balance abstractthe eastward propagating intraseasonal oscillation represented by the chikira sugiyama cumulus scheme in a general circulation model was investigated focusing on the variation of the free tropospheric humidity the net effect of the vertical advection and cloud process amplifies the positive moisture anomaly in the mature phase supporting the moisture mode theory the horizontal advection causes the eastward propagation of the field the variation of the moisture profile is accurately understood by using environmental vertical velocity outside cumuli the velocity is regulated by a thermodynamic balance under a weak temperature gradient a nondimensional parameter plays an important role in the moisture variation which characterizes the efficiency of moistening drying induced by external heating cooling in the middle and lower troposphere the major moistening factor is the radiative warming anomaly which induces the upward environmental vertical velocity anomaly the reevaporation of th

seasonality of the structure and propagation characteristics of the mjo the seasonality of the madden julian oscillation mjo is documented in observational data and a nonlinear shallow water model is used to help interpret some of the contrasts in mjo structure between the boreal winter season november march ndjfm and the asian summer monsoon period june september jjas at upper tropospheric levels the flanking rossby waves remain centered around 28 degrees n s year round but they tend to be stronger in the winter hemisphere where the climatological mean jet stream is stronger rendering the subtropical circulation more sensitive to forcing by a near equatorial heat source amplitudes of the mjo related deep convection and lower tropospheric zonal wind are stronger in the summer hemisphere where the column integrated water vapor is larger during ndjfm the equatorial asymmetry is subtle as in the annual mean moisture convergence into swallowtail shaped regions of enhanced deep convection is an integral part of the equatorial rossby wave signature and the eastward propagation is due to moistening of the air to the east of the enhanced convection by poleward moisture advection during the asian summer monsoon in jjas the convection assumes the form of northward propagating west northwest east southeast oriented rainbands embedded within cyclonic shear lines these features are maintained by frictional convergence of moisture and their northward propagation is mainly due to the presence of features in the climatological mean fields that is the west east moisture gradient over india and the arabian sea and the southwesterly low level monsoon flow over the northwest pacific

organization of tropical convection in low vertical wind shears the role of water vapor abstract a modeling study is conducted to gain insight into the factors that control the intensity and organization of tropical convection and in particular to examine if organization occurs in the absence of factors such as vertical wind shear or underlying sea surface temperature sst gradient the control experiment integrates a cloud resolving model for 15 days using a 3d domain exceeding 1000 km in length with no imposed winds and horizontally uniform sst and forcing for convection after 2 days of random activity the convection organizes into clusters with dimensions of approximately 200 km convective systems propagate through the clusters at speeds of 2 3 m s 1 while the clusters themselves propagate at minimal speeds of around 0 5 m s 1 examining the thermodynamic structure of the model domain it is found that the convective free bands separating the clusters are very dry throughout the troposphere and due to virtual temperature effects are correspondingly warmer in the lower tropospher

archaea in black sea water column particulate matter and sediments evidence from ether lipid derivatives abstract phytane and long chain c40 head to head acyclic c40 0cy and cyclic isoprenoids with 1 3 cyclopentyl rings c40 1cy c40 2cy and c40 3cy derived from archaeal core lipids are present in black sea particulate matter from both the oxic and anoxic zones and in sediment cores from the central basin and the western continental margin the occurrence of these ether linked isoprenoids throughout the water column and sediments suggests that archaea are widely distributed in the black sea methanogens are the probable source of ether linked phytane and some of the acyclic c40 compounds while psychrophilic archaea related to hyperthermophiles are the likely sources of the cyclic isoprenoids

evolution of the madden julian oscillation in two types of el nino abstractevolution characteristics of the madden julian oscillation mjo during the eastern pacific ep and central pacific cp types of el nino have been investigated mjo activities are strengthened over the western pacific during the predeveloping and developing phases of ep el nino but suppressed during the mature and decaying phases in contrast mjo activities do not show a clear relationship with cp el nino before their occurrence over the western pacific but they increase over the central pacific during the mature and decaying phases of cp el nino lag correlation analyses further confirm that mjo activities over the western pacific in boreal spring and early summer are closely related to ep el nino up to 2 11 months later but not for cp el nino ep el nino tends to weaken the mjo and lead to a much shorter range of its eastward propagation anomalous descending motions over the maritime continent and western pacific related to el nino can suppress convection and moisture flux convergence the

an idealized semi empirical framework for modeling the madden julian oscillation abstractthe authors present a simple semi empirical model to explore the hypothesis that the madden julian oscillation can be represented as a moisture mode destabilized by surface flux and cloud radiative feedbacks the model is one dimensional in longitude the vertical and meridional structure is entirely implicit the only prognostic variable is column water vapor w the zonal wind field is an instantaneous diagnostic function of the precipitation field the linearized version of the model has only westward propagating relative to the mean flow unstable modes because wind induced surface latent heat flux anomalies occur to the west of precipitation anomalies the maximum growth rate occurs at the wavelength at which the correlation between precipitation and surface latent heat flux is maximized this wavelength lies in the synoptic to planetary scale range and is proportional to the horizontal scale associated with the assumed diagnostic wind response to precipitation anomalies the nonlinear version

a unified moisture mode framework for seasonality of the madden julian oscillation abstractthe madden julian oscillation mjo exhibits pronounced seasonality while it is largely characterized by equatorially eastward propagation during the boreal winter mjo convection undergoes marked poleward movement over the asian monsoon region during summer producing a significant modulation of monsoon rainfall in classical mjo theories that seek to interpret the distinct seasonality in mjo propagation features the role of equatorial wave dynamics has been emphasized for its eastward propagation whereas coupling between mjo convection and the mean monsoon flow is considered essential for its northward propagation in this study a unified physical framework based on the moisture mode theory is offered to explain the seasonality in mjo propagation moistening and drying caused by horizontal advection of the lower tropospheric mean moisture by mjo winds which was recently found to be critical for the eastward propagation of the winter mjo is also shown to play a dominant role in operating t

modeling tropical convergence based on the moist static energy budget abstract the vertically integrated moist static energy equation provides a convenient starting point for the construction of simple models of the time mean low level convergence in the tropics a vertically integrated measure of the moist static stability the gross moist stability proves to be of central importance minima in this quantity mark the positions of the tropical convergence zones we argue that the positions of these minima are determined by the time mean moisture field which is in turn closely tied to the time mean surface temperature

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

transient environmental sensitivities of explicitly simulated tropical convection abstract a three dimensional cloud resolving model maintained in a statistically steady convecting state by tropics like forcing is subjected to sudden 10 min stimuli consisting of horizontally homogeneous temperature and or moisture sources with various profiles ensembles of simulations are used to increase the statistical robustness of the results and to assess the deterministic nature of the model response for domain sizes near contemporary global model resolution the response to middle and upper tropospheric perturbations is predominantly local in the vertical convection damps the imposed stimulus over a few hours low level perturbations are similarly damped but also produce a vertically nonlocal response enhancement or suppression of new deep convective clouds extending above the perturbed level experiments show that the effective inhibition layer for deep convection is about 4 km deep far deeper than traditional convective inhibition defined for undilute lifted parcels both the local

eastward propagating intraseasonal oscillation represented by chikira sugiyama cumulus parameterization part i comparison with observation and reanalysis abstractthe eastward propagating intraseasonal oscillation represented by the chikira sugiyama cumulus parameterization in an atmospheric general circulation model is compared with observations and reanalyses the scheme is characterized by state dependent entrainment rates that vertically vary affected by the environment the zonal wavenumber frequency power spectrum shows a strong signal corresponding to the madden julian oscillation the eastward propagating feature of the convective region and accompanying anomalous zonal wind structure is well extracted by the first and second modes of the combined empirical orthogonal function ceof with a reasonable explained variance for the first mode though the second mode is not sufficiently reproduced the basic features of the composited anomalous fields including moisture temperature and vertical and zonal winds resemble those of the reanalysis in both the free troposphere and surface air the anomalous free tropospheric moisture exhibits its westward ti

simulation of the madden julian oscillation in the ncar ccm3 using a revised zhang mcfarlane convection parameterization scheme abstract this study presents the simulation of the madden julian oscillation mjo in the ncar ccm3 using a modified zhang mcfarlane convection parameterization scheme it is shown that with the modified scheme the intraseasonal 20 80 day variability in precipitation zonal wind and outgoing longwave radiation olr is enhanced substantially compared to the standard ccm3 simulation using a composite technique based on the empirical orthogonal function eof analysis the paper demonstrates that the simulated mjos are in better agreement with the observations than the standard model in many important aspects the amplitudes of the mjos in 850 mb zonal wind precipitation and olr are comparable to those of the observations and the mjos show clearly eastward propagation from the indian ocean to the pacific in contrast the simulated mjos in the standard ccm3 simulation are weak and have a tendency to propagate westward in the indian ocean nevertheless there remain several deficiencies that are yet

northward propagation initiation and termination of boreal summer intraseasonal oscillations in a zonally symmetric model abstracta simple multilayer zonally symmetric model using a multicloud convective parameterization and coupled to a dynamical bulk atmospheric boundary layer is used here to simulate boreal summe

barrier effect of the indo pacific maritime continent on the mjo perspectives from tracking mjo precipitation abstractexplanations for the barrier effect of the indo pacific maritime continent mc on the mjo should satisfy two criteria first they should include specific features of the mc namely its intricate land sea distributions and elevated terrains second they should include mechanisms for both the barrier effect and its overcoming by some mjo events guided by these two criteria a precipitation tracking method is applied to identify mjo events that propagate across the mc mjo c and those that are blocked by the mc mjo b about a half of mjo events that form over the indian ocean propagate through the mc most of them 75 become weakened over the mc the barrier effect cannot be explained in terms of the strength horizontal scale or spatial distribution of mjo convection when it approaches the mc from the west a distinction between mjo b and mjo c is their precipitation over the sea versus land in the mc region mjo c events rain much more over the sea than over land whereas rainfall over

frictional moisture convergence in a composite life cycle of the madden julian oscillation abstract a composite life cycle of the madden julian oscillation mjo is constructed using an index based on the first two eofs of the bandpass filtered 20 80 days 850 mb zonal wind averaged from 5 n to 5 s every 2 5 around the equator precipitation 1000 mb convergence 850 mb wind and 200 mb wind are composited for the period 1979 95 water vapor integrated from the surface to 300 mb is composited for the period 1988 92 frictional moisture convergence at the equator is shown to play an important role in the life cycle of the madden julian oscillation mjo regions of boundary layer convergence foster growth of positive water vapor anomalies to the east of convection this convergence coincides with 850 mb easterly wind anomalies as is consistent with kelvin wave dynamics drying of the atmosphere occurs rapidly after the passage of convection with the onset of 850 mb westerly perturbations possible mechanisms for this drying include boundary layer divergence and subsidence or horizontal advect

effects of convective processes on gcm simulations of the madden julian oscillation abstract weak temporal variability in tropical climates such as the madden julian oscillation mjo is one of major deficiencies in general circulation models gcms the uncertainties in the representation of convection and cloud processes are responsible for these deficiencies with the improvement made to the convection scheme the iowa state university isu gcm which is based on a version of the ncar community climate model is able to simulate many features of mjo as revealed by observations in this study four 10 yr 1979 88 isu gcm simulations with observed sea surface temperatures are analyzed and compared to examine the effects of the revised convection closure convection trigger condition and convective momentum transport cmt on the mjo simulations the modifications made in the convection scheme improve the simulations of amplitude spatial distribution eastward propagation and horizontal and vertical structures especially for the coherent feature of eastward propagating convection a

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

causal evidence that rotational moisture advection is critical to the superparameterized madden julian oscillation abstractthe authors investigate the hypothesis that horizontal moisture advection is critical to the eastward propagation of the madden julian oscillation mjo consistent diagnostic evidence has been found in recent mjo permitting global models viewed from the moisture mode dynamical paradigm to test this idea in a causal sense tropical moisture advection by vorticity anomalies is artificially modulated in a superparameterized global model known to produce a realistic mjo signal boosting horizontal moisture advection by tropical vorticity anomalies accelerates and amplifies the simulated mjo in tandem with reduced environmental gross moist stability limiting rotational horizontal moisture advection shuts the mjo down these sensitivities are robust in that they are nearly monotonic with respect to the control parameter and emerge despite basic state sensitivities favoring the opposite response speedup confirms what several diagnostic lines of evidence already suggest that anomalous moisture advecti

numerical study of ground motion differences between buried rupturing and surface rupturing earthquakes recent ground motion observations suggest that surface rupturing earth quakes generate weaker near fault ground motion than buried earthquakes this dif ference is significant in the period range of 0 3 3 sec contributing factors to this phenomenon may include the effect of fault zone weakness at shallow depth on rup ture dynamics and rupture directivity during earthquakes we present results from numerical experiments of spontaneous dynamic rupture and near source ground motion simulations of surface rupturing and buried earth quakes and discuss mechanisms for the observed ground motion differences the surface rupturing earthquake is modeled with a shallow zone of 5 km thickness con taining areas of negative stress drop within the framework of the slip weakening fric tion model and lower rigidity surface rupturing models with this weak zone generate lower amplitude ground velocity than do models without this modification observed ground motion differences between surface and buried events are qual itatively reproduced by imposing higher stress drop in the buried earthquakes than in the surface earthquakes combined with introducing a deeper rupture initiation for buried rupture enhancing upward rupture directivity effects for the latter events in the context of our simplified model parameterization then the observed differences in ground motion could arise from combined effects of relative weakness of the shal low layer of faults the relatively larger stress drops of buried ruptures and a tendency of near fault sites to record strong upward directivity from buried ruptures