Top PDF The Madden-Julian Oscillation: Observation, Modeling, and Theory

The Madden-Julian Oscillation: Observation, Modeling, and Theory

The Madden-Julian Oscillation: Observation, Modeling, and Theory

Matsuno (1966) theory applies to small-amplitude surface waves in two dimensions on the equator of a rotating planet. The assumption of a basic state of rest is implicit. The theory can be applied to small-amplitude waves in three dimensions by treating each vertical normal mode separately. There are two parameters in the Matsuno theory, the planetary vorticity gradient β and the gravity wave c. Each normal mode has a different value of c. The value of c depends on the mode number, the scale height of the atmosphere, whether it is weakly or strongly stratified, and whether it is moist or dry. There are theories on how to relate the dry dynamics to the moist dynamics, although exactly why moist waves have the same dispersion pattern as the dry waves, but with different values of c, remains a mystery (Kiladis et al. 2009). WK99 have shown that there is a particular range of c values for which a close correspondence exists between wavenumber-frequency spectral peaks of the OLR data and the dispersion relations of the linear equatorial waves. The c values are usually expressed in terms of equivalent depth h = c 2 /g, where g is the gravitational acceleration.
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Pham, Nguyen Dinh
  

(2009):


	Rotational Motions in Seismology: Theory, Observation, Modeling.


Dissertation, LMU München: Fakultät für Geowissenschaften

Pham, Nguyen Dinh (2009): Rotational Motions in Seismology: Theory, Observation, Modeling. Dissertation, LMU München: Fakultät für Geowissenschaften

In seismology, observations are traditionally based on measurements of inertial seismometers that record three components (vertical, north-south, and east-west) of earthquake induced ground translations (displacement, velocity, or acceleration). There are theoretical studies suggesting that in addition to translations, rotational ground motions should be measured (e.g., Aki and Richards, 2002). This type of observation might be relevant for: (1) correcting translation signals recorded by classical seismometers for contamination by ground rotation (Graizer, 2005; Graizer, 2006; Pillet and Virieux, 2007); (2) extracting additional information on earthquake source properties (e.g., Takeo and Ito, 1997; Takeo, 1998), soil - structure – interactions (Trifunac and Todorovska, 2001), and properties of the subsurface (Igel et al., 2007; Fichtner and Igel, 2008); (3) providing additional ground motion information to earthquake engineers for seismic design (e.g., Li et al., 2001, 2002). However, the lack of instrumental resolution did not allow seismologists to record this kind of motions in a consistent way until recently (Pancha et al., 2000; Schreiber et al., 2005; Cochard et al., 2006; Igel et al., 2005, 2007).
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Observation, characterization and modeling of memristor current spikes

Observation, characterization and modeling of memristor current spikes

The mem-con model of memristance [16] is a recently announced theoretical model that relates real world q and ϕ to Chua’s constitutive equations and has been suc- cessful in modeling our memristors [17]. The mem-con theory has the concept of a memory property, the physical or chemical attribute of the device that holds the memory of the device. In titanium dioxide (and many others) it is related to the number of the oxygen vacancies. The presence of oxygen vacancies allows the creation of a doped form of titanium dioxide TiO 2 − x which is more conducting

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Mediation Analysis via Observation Oriented Modeling

Mediation Analysis via Observation Oriented Modeling

Observation Oriented Modeling (OOM) is one alternative that does not require the assumption of continuous quantity. While not as mathematically complex as structural equation modeling, multilevel modeling, or item response theory, it nonetheless provides a flexible and compelling framework for conceptualizing and analyzing data. In a general sense, it prompts investigators to expend more “shoe leather” (Freedman, 1991) in order to think more deeply what they are investigating and to make the observations necessary to corroborate their theories. More specifically, it challenges investigators to develop integrated models (see Grice, 2011; Grice et al., 2012) that explicate how the observations are to be made in accord with how things or qualities in nature (e.g., attributes, behaviors, etc.) are ordered. Examples of integrated models are Bohr’s early model of the atom and biological models like the Kreb’s cycle or the biochemical pathways of a Eukaryotic cell. Ideally, Donnellan et al. (2005) and Kaczynski et al. (2006) would have developed integrated models which could then have been used to guide the analyses above. Even without such models in hand, however, a number of advantages to OOM over traditional methods can be gleaned from the analyses.
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Dynamics of the Jovian atmosphere from observation and theory

Dynamics of the Jovian atmosphere from observation and theory

observations. Numerical modeling is a powerful tool to validate theories and augment classical means of validation from laboratory experiments and observations. Observation and numerical modeling are becoming more active in the planetary sciences due to the advance of spacecraft observing time and computer time. From the first encounter with Jupiter by the Pioneer 10 and 11 in 1973 and 1974, to the grand tours of the twin Voyagers in 1979, to the 8-year (1995-2003) orbiting by the Galileo, to the Cassini’s flyby in 2000, observations from spacecrafts continue to progress our understanding of the jovian atmosphere. Specifically, the lengthy 6-month observations with numerous instruments and high transmission rate, a large data storage capacity, and a wide spectral range enabled Cassini to acquire high-quality time-lapse data during its Jupiter flyby. These data have enriched our knowledge of the jovian atmosphere, and more studies associated with the new Cassini observation are still being conducted. On the other hand, many numerical models have been applied to study the jovian atmospheric dynamics including convective storms, vortices, and multiple jets since the Voyager time. These models range from deep convection models (Busse, 1976; Aurnou and Olson, 2001; Christensen, 2001; Heimpel et al., 2005), to quasi-geostrophic (QG) models (singular layer or multi-lyaer) (Williams, 1979; Panetta, 1993; Marcus et al., 2000), to shallow water models (Dowling and Ingersoll, 1989; Cho and Polvani, 1996), to general circulation models (GCMs) (Dowling et al., 1998, 2006). The great success of these models suggests that numerical modeling plays an ever important role in the study of planetary sciences.
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On observation-driven time series modeling

On observation-driven time series modeling

ibility conditions often impose restrictions on the parameter space that are unfeasible to be checked in practice. This occurs because these invertibility conditions depend on the properties of the Data Generating Process (DGP) that are unknown. Wintenberger (2013) noted this problem for the EGARCH model of Nelson (1991) and proposed to replace the unfeasible conditions with a feasible empirical invertibility condition. This method deliv- ers a consistent QML estimator for the EGARCH model. We note that this problem is not a peculiarity of the EGARCH model but a general problem for observation-driven models with nonlinearities in the filtered parameter recursion. Therefore, often, the asymptotic theory can be ensured only for either degenerate or very small parameter regions that are unrealistic in empirical applications. As examples, we consider the Beta-t-GARCH model of Harvey (2013) and Creal et al. (2013), the location model of Harvey and Luati (2014) and the autoregressive model of Blasques et al. (2014b) and Delle Monache and Petrella (2016). We build on the work of Wintenberger (2013) and deliver a general the- ory for observation-driven models that ensures the consistency of the ML estimator under feasible invertibility conditions. The resulting theory is shown to cover applications of practical interest such as modeling of financial stock returns and macroeconomic vari- ables. An appealing feature of our theoretical results is that they hold also in the case of model misspecification. In this situation, the consistency is proved with respect to a pseudo-true parameter.
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Theory of planet formation and comparison with observation

Theory of planet formation and comparison with observation

As one can see, we do not include any mechanism which could lead to the so called “radius anomaly” observed for many transiting Hot Jupiter which have radii clearly larger than expected from standard internal structure modeling as done here. The physical mechanisms leading to this bloating are not yet understood, and discussed in dedicated studies (e.g. Leconte et al., this volume).

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A trio-interaction theory for Madden–Julian oscillation

A trio-interaction theory for Madden–Julian oscillation

numerical models’ problems, we suggest focusing on the zonal structural asymmetry in the lower troposphere generated by the BL moisture feedback, including the phase leading of the BL moisture convergence to major convection (by about 4–5 days) and the associated lower troposphere moistening (increase in equivalent potential temperature), destabilization (increase of the convective instability), the 700  hPa diabatic heating and the gen- eration of MJO available potential energy. In the mod- els with good MJO simulation, the BL convergence can enhance congestus cloud heating and upward transport of moisture that further feeds back to BL moisture con- vergence. This positive feedback could amplify the effects of frictional convergence feedback. In the models with poor MJO simulation, the BL convergence is very weak to the east of MJO convective center, while the associated shallow convective heating as well as the vertically tilted structure disappears (Jiang and al 2015). This implies that MJO simulation may be sensitive to shallow and conges- tus cumulus parameterization schemes and the BL turbu- lence parameterization in GCMs. While the BL frictional convergence always exists in GCMs to various degrees, the ways by which BL convergence interacts with shallow and congestus clouds in different GCMs may differ and this interaction could significantly affect the frictional convergence feedback and thus the MJO behavior. This interactive process should be represented correctly in the numerical modeling of MJO with GCMs, including the lower tropospheric convective mixing and low cloud feedback.
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Land-sea surface air temperature contrast on the western coast of Sumatra Island during an active phase of the Madden-Julian Oscillation

Land-sea surface air temperature contrast on the western coast of Sumatra Island during an active phase of the Madden-Julian Oscillation

From Fig. 5, it can be seen that a sudden drop in air temperature occurred from the late afternoon to nighttime prior to the local active phase of the MJO, accompanied by the occurrence of precipitation at the observation site. After the rain stopped, air temperatures increased gradually. Then, the air temperatures dropped again when the next rainfall event occurred. If the drop in air temperatures was caused by radiative cooling of the sea surface, the decrease in air temperatures should have continued until the following morning, because radiative cooling would continue throughout the night- time. The increase in air temperature was due to the air being heated by the warm water, because during the nighttime, there was no solar irradiance to heat the sea surface. On 13 December 2015 when the active phase of the MJO passed over the Maritime Continent, a drop in surface air temperature occurred during the daytime, corresponding to the occurrence of precipitation. There- fore, it is reasonable to conclude that the variations of surface air temperature over the sea were caused by a drop in temperature associated with precipitation, and the subsequent increase in temperature resulted from heating by the warm water.
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Drastic thickening of the barrier layer off the western coast of Sumatra due to the Madden-Julian oscillation passage during the Pre-Years of the Maritime Continent campaign

Drastic thickening of the barrier layer off the western coast of Sumatra due to the Madden-Julian oscillation passage during the Pre-Years of the Maritime Continent campaign

where ρ cp is the volumetric heat capacity, Qrad is the penetrative solar radiation, and ω0T 0 at z = 0 is propor- tional to the net surface heat flux reduced by the solar radiation at the surface. Although it was difficult to dir- ectly estimate terms 5 and 6, the net surface heat flux was confirmed to become negative (~− 1 °C/day for 50 m depth: negative means losing heat to the atmos- phere) during the MJO wind burst forcing from the sur- face meteorological observation (not shown) and daily averaged temperature near the surface was decreased, as shown in Fig. 6. This result suggests that terms 5 and 6 contribute to the vertical potential temperature gradient tendency and is consistent with the development of the temperature inversion in the layer of 40–80 m depth. As shown in the profiles of Fig. 6a, b, the decreased temperature stratification near the surface led drastic IL deepening. Additionally, the temperature in the 20–50 m depth layer on 12 December (Fig. 6a) was mixed at approximately 29.6 °C, and such conditions were potentially favorable for drastic IL deepening. That is, before the IL deepening, there was a poten- tial condition of the mixed temperature just below the surface halocline, and the temperature stratifica- tion existed only near the surface above 20 m depth. After losing heat to the atmosphere near the surface, the temperature stratification near the surface disap- peared, and the ILD value drastically increased. How- ever, because the salinity stratification in the IL remained, the ML deepening showed a 1-day lag with the IL deepening.
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Effects of El-Niño, Indian Ocean Dipole and Madden-Julian Oscillation on Sea Surface Temperature and Rainfall Anomalies in Southeast Asia. Case Study: Biomass Burning Episode of 2015

Effects of El-Niño, Indian Ocean Dipole and Madden-Julian Oscillation on Sea Surface Temperature and Rainfall Anomalies in Southeast Asia. Case Study: Biomass Burning Episode of 2015

In climate research, the maritime continent (MC) is one of the most crucial regions to study [1]. MC can play a key role as heat and moisture source and can impact global atmospheric circulations and contribute to climate change [2]. MC is known to be the most active convective region where convection is influenced by local, regional and global atmospheric conditions such as monsoon, tropical convection, intra-seasonal oscillations and complex structure of the topography of land and sea around it [3,4]. The intertropical convergence zone (ITCZ) and its correlations with sea surface temperature (SST) and active precipitation are mostly responsible for convection in the MC region [5]. Despite its importance, inter-scale interactions of intra-seasonal and mesoscale variability forced by diurnal affects (e.g. oceanic circulation, wind, temperature and precipitation) errors are often found in the climate models of MC [6]. The MC has a signature seasonal cycle in its rainfall characterizing a typical monsoon climate [7]. Due to intricate topography of the region and vast unpopulated land areas dense rain gauge network is absent in most of the places of MC and gauge observation in the oceanic areas are also not became possible to obtain so far [8]. Satellite observation is the best available solution in such case to attain adequate temporal and spatial coverage of rainfall data [9]. Therefore, in this study computer model is used using the satellite data to investigate SST and rainfall. In the southern equator principally, rainy season peaks in DJF (December-February) and the drier season peaks in July-August [10].
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Madden Julian Oscillations in Total Column Ozone, Air Temperature and Surface Pressure Measured over Cochin during Summer Monsoon 2015

Madden Julian Oscillations in Total Column Ozone, Air Temperature and Surface Pressure Measured over Cochin during Summer Monsoon 2015

The Madden-Julian Oscillation (MJO) is the dominant mode of tropical intra-seasonal variability in the Asiatic monsoon region. The MJO is an eastward moving disturbance of clouds, rainfall, winds, and pressure that tra- verses the planet in the tropics and returns to its initial starting point in 30 to 60 days, on average. It connects weather and climate and influences high-impact events around the globe including monsoons, tropical cyclones, tornados, cold surges, flood and wildfires. Basic research in modeling, analysis and real time monitoring of MJO will lead to the improvement of intra-seasonal prediction of probabilities of extreme events like drought and floods. The Madden Julian Oscillation (MJO) represents the connection between the weather and seasonal-to- interannual climate variations. It significantly affects the tropical weather, climate and global atmospheric cir- culations. Many studies have demonstrated that MJO modulates the characteristics and strength of higher- frequency tropical variability, including tropical cyclogenesis and extreme precipitation events. The important timescales of different intraseasonal variations have been identified in the past three decades as the 10 - 20 and the 30 - 50 day scales, in addition to the synoptic scales [1]-[5]. Previous studies suggest that the intraseasonal and interannual variabilities are governed by a common spatial mode of variability [6]-[9]. Indian summer monsoon, which is a part of the Asian monsoon system, exhibits a wide spectrum of variability on daily, sub- seasonal, interannual, decadal and centennial time scales. The dominant time scales of intraseasonal variations of monsoon circulations and convections are 10 - 20 days and 30 - 60 days with comparable contributions to the total intraseasonal variability in the Indian region [9]. The Madden & Julian [10] 30 - 50-day mode is believed to be associated with northward propagation of clouds, rainfall and winds from
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The Madden Julian Oscillation: a literature review

The Madden Julian Oscillation: a literature review

Contrary to other interpretations of the MJO and ocean interaction, the United Kingdom Universities Global Atmospheric Modelling Project (UKUGAMP) (no date provided) regarded the MJO as a coupled ocean atmosphere process. For this to be correct, they state that the MJO must impact on the ocean dynamics and intraseasonal SST variations must organise convection. They suggest that convection associated with the MJO can generate SST anomalies by modulation of shortwave and latent heat fluxes at the ocean surface. This would result in a convection pattern with a positive SST anomaly before and to the east of it, and negative anomaly to the west and following it. Their MJO model SST did organise convection with a structure similar to that observed in the MJO, and the longer SST were high, the greater the magnitude of the precipitation anomaly. They proposed that the MJO is a coupled ocean atmosphere mechanism, with the periodicity determined by the strength of convection, surface fluxes and the heat capacity of the mixed layer. Work by other researchers does not support this theory at present.
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Relative oscillation theory for matrix Sturm Liouville difference equations extended

Relative oscillation theory for matrix Sturm Liouville difference equations extended

nonlinear dependence on the spectral parameter λ . This nonlinear dependence on λ is allowed both in the leading coefficients and in the potentials. Relative oscillation theory rather than measuring the spectrum of one single problem measures the difference between the spectra of two different problems. This is done by replacing focal points of conjoined bases of one problem by matrix analogs of weighted zeros of Wronskians of conjoined bases of two different problems.

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Domain Modeling Theory and Practice

Domain Modeling Theory and Practice

Everyday huge amount of data is being captured and stored. This can either be due to several social initiatives, technological advancement or by smart devices. This involves the release of data which differs in format, language, schema and standards from various types of user communities and organizations. The main challenge in this scenario lies in the inte- gration of such diverse data and on the generator of knowledge from the existing sources. Various methodology for data modeling has been proposed by different research groups, under different approaches and based on the scenarios of the different domain of application. However, a few method- ology elaborates the proceeding steps. As a result, there is lack of clarifi- cation how to handle different issues which occurs in the different phases of domain modeling. The aim of this research is to presents a scalable, in- teroperable, effective framework and a methodology for data modeling. The backbone of the framework is composed of a two-layer, schema and lan- guage, to tackle diversity. An entity-centric approach has been followed as a main notion of the methodology. A few aspects which have especially been emphasized are: modeling a flexible data integration schema, dealing with the messy data source, alignment with an upper ontology and implementa- tion. We evaluated our methodology from the user perspective to check its practicability.
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Near-global impact of the Madden-Julian Oscillation on rainfall

Near-global impact of the Madden-Julian Oscillation on rainfall

The Madden-Julian Oscillation (MJO) is an atmospheric, large scale, eastward propagating circulation anomaly that originates over the Western Indian Ocean, is confined to the tropics, moves at around 5-10 ms -1 and has a recurrence interval of around 30 to 80 days (Madden and Julian, 1972, 1994) Evidence suggests that the MJO is responsible for much of the observed intraseasonal climate variance not only in the tropics , but also in higher latitudes (Bond and Vecchi, 2003, Chen and

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Spatial and temporal resolution of geographic information: an observation-based theory

Spatial and temporal resolution of geographic information: an observation-based theory

collection is spatially detailed. They rather tell that, within the current observation collection, the closest locations are within a distance equal to the minimum spacing, the farthest within a distance equal to the maximum spac- ing. Regarding the total spacing, one disadvantage is the need to specify a spatial ordering for the observation col- lection. As discussed in [53], this choice might involve some arbitrariness. The ultimate implication of the use of total spacing as criterion, is that a decision-maker will be provided with different values of spatial resolution for an observation collection, with no means to decide which one to choose for his or her purpose. In addition, there are cases such as the one from Fig. 4a where the total spacing fails to capture the fact that two observation collections have different amounts of spatial detail. It is indeed arguable that (under the assumption that the size of the points is negligible) the two observation collections from Fig. 4a have the same spacing S. The use of the mean spacing has the advantage that it is no longer necessary to define what observation is the first, and what is the next. However, a serious drawback of this criterion is that, when applied to the observation collections from Fig. 4b, it gives the same value. In other words, this criterion fails to cap- ture the fact, as far as Fig. 4b is concerned, the observation collection further right is spatially more detailed than the observation collection further left.
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Early-Stopping of Scattering Pattern Observation with Bayesian Modeling

Early-Stopping of Scattering Pattern Observation with Bayesian Modeling

Scientific data is one of the targets of study in the data en- gineering field. Compressed sensing(Donoho 2006)(Bour- guignon, Carfantan, and B¨ohm 2007)is a popular technology for reconstruction by sparse modeling of a few data. Com- pressed sensing assumes that the signal sources are sparsly distributed. Under the constraint of sparsity, a compressed sensing model can be accurately estimated without many sensing data. In such case, we can reduce the sensing data without loss of accuracy. Here, compressed sensing has been used to accelerate the measurements(Lustig et al. 2008). On the other hand, while smoothness is suitable for fast SANS, sparsity might be unsuitable for it.
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High frequency wave propagation in the earth: theory and observation

High frequency wave propagation in the earth: theory and observation

The wave -theoretical analysis of acoustic and elastic waves refracted by a spherical boundary across which both velocity and density increase abruptly and thence either increase or decr[r]

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Theory and Modeling in Nanoscience

Theory and Modeling in Nanoscience

Various computational issues were iden- tified as important for computational nano- science. In particular, an open source soft- ware development framework for multiscale modeling was identified as a real need. The OCTA project in Japan (http://octa.jp) may point the way towards development of such an open source software development framework, or may indeed be the appropri- ate framework on which to expand simula- tion capabilities. Visualization of nanoscale systems is challenging, since the spatio- temporal scales cover such large orders of magnitude. Truly effective parallelization of Monte Carlo was identified as an important issue. Specifically, efficient domain decom- position parallelization of Monte Carlo on very large systems with long range forces was seen as an unsolved problem with rami- fications for computational nanoscience. Finally, parallel codes for any TMS method that scales efficiently to tens of thousands of processors were targeted. This is because the highest-performance computers are headed towards this number of processors, yet it is not clear that any scalable codes exist at this point for such large machines.
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