Unusual Formaldehyde (HCHO) Vertical Profile Shapes During A Sea Breeze Event: Implications for Geostationary Satellite Trace Gas Retrievals
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Dynamics of the Remarkable Southern Hemisphere Winter of 2024
Typical Southern Hemisphere (SH) stratospheric winters are characterized by relatively weak planetary wave dynamics when compared to the Northern Hemisphere winter, especially in early and mid-winter. However, the SH stratospheric winter 2024 saw the development of two large wave events in July. These wave events were associated with the slowing of the polar vortex winds and positive polar temperature anomalies. The second of these two events saw the development of a zonal wavenumber two that was larger in amplitude than seen in the 1980-present record from the Modern Era Retrospective Analysis for Research and Applications – version 2 (MERRA-2). Here we present diagnostics characterizing the wave and mean circulation such as EP (Eliassen-Palm Flux) and residual mean meridional circulation during these events and trace the origin of these stratospheric disturbances to the troposphere. Results show the increase in wave activity associated with the slowing of the zonal wind and the increase in the strength of the poleward and downward circulation associated with the warm anomaly. Analysis of the wave and circulation anomalies will continue through September 2024.
Lawrence Coy↗
Ravel
Ravel is a tool for analyzing and visualizing parallel execution traces. It deduces a logical structure of parallel program events from the trace records and calculates comparative metrics. It displays the results of this analysis using multiple views at varying levels of detail to allow interactive exploration of the trace.
Source record↗
Ravel
Ravel is a tool for analyzing and visualizing parallel execution traces. It deduces a logical structure of parallel program events from the trace records and calculates comparative metrics. It displays the results of this analysis using multiple views at varying levels of detail to allow interactive exploration of the trace.
Source record↗
Observations of ionospheric electric fields above atmospheric weather systems
We report on the observations of a number of quasi-dc electric field events associated with large-scale atmospheric weather formations. The observations were made by the electric field experiment onboard the San Marco D satellite, operational in an equatorial orbit from May to December 1988. Several theoretical studies suggest that electric fields generated by thunderstorms are present at high altitudes in the ionosphere. In spite of such favorable predictions, weather-related events are not often observed since they are relatively weak. We shall report here on a set of likely E field candidates for atmospheric-ionospheric causality, these being observed over the Indonesian Basin, northern South America, and the west coast of Africa; all known sites of atmospheric activity. As we shall demonstrate, individual events often be traced to specific active weather features. For example, a number of events were associated with spacecraft passages near Hurricane Joan in mid-October 1988. As a statistical set, the events appear to coincide with the most active regions of atmospheric weather.
Farrell, W. M.↗
Benchmark Generation and Simulation at Extreme Scale
The path to extreme scale high-performance computing (HPC) poses several challenges related to power, performance, resilience, productivity, programmability, data movement, and data management. Investigating the performance of parallel applications at scale on future architectures and the performance impact of different architectural choices is an important component of HPC hardware/software co-design. Simulations using models of future HPC systems and communication traces from applications running on existing HPC systems can offer an insight into the performance of future architectures. This work targets technology developed for scalable application tracing of communication events. It focuses on extreme-scale simulation of HPC applications and their communication behavior via lightweight parallel discrete event simulation for performance estimation and evaluation. Instead of simply replaying a trace within a simulator, this work promotes the generation of a benchmark from traces. This benchmark is subsequently exposed to simulation using models to reflect the performance characteristics of future-generation HPC systems. This technique provides a number of benefits, such as eliminating the data intensive trace replay and enabling simulations at different scales. The presented work features novel software co-design aspects, combining the ScalaTrace tool to generate scalable trace files, the ScalaBenchGen tool to generate the benchmark, and the xSim tool to assess the benchmark characteristics within a simulator.
Lagadapati, Mahesh↗
Tools for Simulation and Benchmark Generation at Exascale
The path to exascale high-performance computing (HPC) poses several challenges related to power, performance, resilience, productivity, programmability, data movement, and data management. Investigating the performance of parallel applications at scale on future architectures and the performance impact of different architecture choices is an important component of HPC hardware/software co-design. Simulations using models of future HPC systems and communication traces from applications running on existing HPC systems can offer an insight into the performance of future architectures. This work targets technology developed for scalable application tracing of communication events and memory profiles, but can be extended to other areas, such as I/O, control flow, and data flow. It further focuses on extreme-scale simulation of millions of Message Passing Interface (MPI) ranks using a lightweight parallel discrete event simulation (PDES) toolkit for performance evaluation. Instead of simply replaying a trace within a simulation, the approach is to generate a benchmark from it and to run this benchmark within a simulation using models to reflect the performance characteristics of future-generation HPC systems. This provides a number of benefits, such as eliminating the data intensive trace replay and enabling simulations at different scales. The presented work utilizes the ScalaTrace tool to generate scalable trace files, the ScalaBenchGen tool to generate the benchmark, and the xSim tool to run the benchmark within a simulation.
Lagadapati, Mahesh↗
Jeagle: a JAVA Runtime Verification Tool
We introduce the temporal logic Jeagle and its supporting tool for runtime verification of Java programs. A monitor for an Jeagle formula checks if a finite trace of program events satisfies the formula. Jeagle is a programming oriented extension of the rule-based powerful Eagle logic that has been shown to be capable of defining and implementing a range of finite trace monitoring logics, including future and past time temporal logic, real-time and metric temporal logics, interval logics, forms of quantified temporal logics, and so on. Monitoring is achieved on a state-by-state basis avoiding any need to store the input trace. Jeagle extends Eagle with constructs for capturing parameterized program events such as method calls and method returns. Parameters can be the objects that methods are called upon, arguments to methods, and return values. Jeagle allows one to refer to these in formulas. The tool performs automated program instrumentation using AspectJ. We show the transformational semantics of Jeagle.
DAmorim, Marcelo↗
FIRE: A Failure-Adaptive RL Framework for Edge Computing Migrations
In edge computing, users' service profiles are migrated between edge servers due to user mobility. Reinforcement Learning (RL) frameworks have been proposed to do so, often trained on simulated data. However, existing RL frameworks overlook occasional server failures, which although rare, impact latency-sensitive applications like AR/VR and real- time obstacle detection. These rare failures, being not adequately represented in historical training data, pose a challenge for data-driven RL algorithms. We introduce FIRE, a framework that adapts to rare events by training a RL policy in an edge computing digital twin environment. We propose FIRE-ImRE, an importance sampling-based Q-learning algorithm, which samples rare events proportionally to their impact on the value function. FIRE considers delay, migration, failure, and backup placement costs across individual and shared service profiles. We prove FIRE-ImRE's boundedness and convergence to optimality. Next, we introduce novel deep Q-learning (FIRE-ImDQL) and actor critic (FIRE-ImACRE) versions of our algorithm to enhance scalability. Here, we extend our framework to accommodate users with varying risk tolerances of rare failure events. Through trace-driven experiments, we show that FIRE reduces edge computing costs compared to vanilla RL and the greedy baseline in the event of failures.
Edge computing↗
Analysis of WRF extreme daily precipitation over Alaska using self‐organizing maps
Abstract We analyze daily precipitation extremes from simulations of a polar‐optimized version of the Weather Research and Forecasting (WRF) model. Simulations cover 19 years and use the Regional Arctic System Model (RASM) domain. We focus on Alaska because of its proximity to the Pacific and Arctic oceans; both provide large moisture fetch inland. Alaska's topography also has important impacts on orographically forced precipitation. We use self‐organizing maps (SOMs) to understand circulation characteristics conducive for extreme precipitation events. The SOM algorithm employs an artificial neural network that uses an unsupervised training process, which results in finding general patterns of circulation behavior. The SOM is trained with mean sea level pressure (MSLP) anomalies. Widespread extreme events, defined as at least 25 grid points experiencing 99th percentile precipitation, are examined using SOMs. Widespread extreme days are mapped onto the SOM of MSLP anomalies, indicating circulation patterns. SOMs aid in determining high‐frequency nodes, and hence, circulations are conducive to extremes. Multiple circulation patterns are responsible for extreme days, which are differentiated by where extreme events occur in Alaska. Additionally, several meteorological fields are composited for nodes accessed by extreme and nonextreme events to determine specific conditions necessary for a widespread extreme event. Individual and adjacent node composites produce more physically reasonable circulations as opposed to composites of all extremes, which include multiple synoptic regimes. Temporal evolution of extreme events is also traced through SOM space. Thus, this analysis lays the groundwork for diagnosing differences in atmospheric circulations and their associated widespread, extreme precipitation events.
Glisan, Justin M.↗
The Foggy EUV Corona and Coronal Heating by MHD Waves from Explosive Reconnection Events
In 0.5 arcsec/pixel TRACE coronal EUV images, the corona rooted in active regions that are at the limb and are not flaring is seen to consist of (1) a complex array of discrete loops and plumes embedded in (2) a diffuse ambient component that shows no fine structure and gradually fades with height. For each of two not-flaring active regions, found that the diffuse component is (1) approximately isothermal and hydrostatic and (2) emits well over half of the total EUV luminosity of the active-region corona. Here, from a TRACE Fe XII coronal image of another not-flaring active region, the large sunspot active region AR 10652 when it was at the west limb on 30 July 2004, we separate the diffuse component from the discrete loop component by spatial filtering, and find that the diffuse component has about 60% of the total luminosity. If under much higher spatial resolution than that of TRACE (e. g., the 0.1 arcsec/pixel resolution of the Hi-C sounding-rocket experiment proposed by J. W. Cirtain et al), most of the diffuse component remains diffuse rather being resolved into very narrow loops and plumes, this will raise the possibility that the EUV corona in active regions consists of two basically different but comparably luminous components: one being the set of discrete bright loops and plumes and the other being a truly diffuse component filling the space between the discrete loops and plumes. This dichotomy would imply that there are two different but comparably powerful coronal heating mechanisms operating in active regions, one for the distinct loops and plumes and another for the diffuse component. We present a scenario in which (1) each discrete bright loop or plume is a flux tube that was recently reconnected in a burst of reconnection, and (2) the diffuse component is heated by MHD waves that are generated by these reconnection events and by other fine-scale explosive reconnection events, most of which occur in and below the base of the corona where they are seen as UV explosive events, EUV blinkers, and type II spicules. These MHD waves propagate across field lines and dissipate, heating the plasma in the field between the bright loops and plumes.
Moore, Ron L.↗
An Overview of the Runtime Verification Tool Java PathExplorer
We present an overview of the Java PathExplorer runtime verification tool, in short referred to as JPAX. JPAX can monitor the execution of a Java program and check that it conforms with a set of user provided properties formulated in temporal logic. JPAX can in addition analyze the program for concurrency errors such as deadlocks and data races. The concurrency analysis requires no user provided specification. The tool facilitates automated instrumentation of a program's bytecode, which when executed will emit an event stream, the execution trace, to an observer. The observer dispatches the incoming event stream to a set of observer processes, each performing a specialized analysis, such as the temporal logic verification, the deadlock analysis and the data race analysis. Temporal logic specifications can be formulated by the user in the Maude rewriting logic, where Maude is a high-speed rewriting system for equational logic, but here extended with executable temporal logic. The Maude rewriting engine is then activated as an event driven monitoring process. Alternatively, temporal specifications can be translated into efficient automata, which check the event stream. JPAX can be used during program testing to gain increased information about program executions, and can potentially furthermore be applied during operation to survey safety critical systems.
Havelund, Klaus↗
TraceContract
TraceContract is an API (Application Programming Interface) for trace analysis. A trace is a sequence of events, and can, for example, be generated by a running program, instrumented appropriately to generate events. An event can be any data object. An example of a trace is a log file containing events that a programmer has found important to record during a program execution. Trace - Contract takes as input such a trace together with a specification formulated using the API and reports on any violations of the specification, potentially calling code (reactions) to be executed when violations are detected. The software is developed as an internal DSL (Domain Specific Language) in the Scala programming language. Scala is a relatively new programming language that is specifically convenient for defining such internal DSLs due to a number of language characteristics. This includes Scala s elegant combination of object-oriented and functional programming, a succinct notation, and an advanced type system. The DSL offers a combination of data-parameterized state machines and temporal logic, which is novel. As an extension of Scala, it is a very expressive and convenient log file analysis framework.
Kavelund, Klaus↗
Small-Scale Gravity Waves in ER-2 MMS/MTP Wind and Temperature Measurements during CRYSTAL-FACE
Lower stratospheric wind and temperature measurements made from NASA's high-altitude ER-2 research aircraft during the CRYSTAL-FACE campaign in July 2002 were analyzed to retrieve information on small scale gravity waves (GWs) at the aircraft's flight level (typically approximately 20 km altitude). For a given flight segment, the S-transform (a Gaussian wavelet transform) was used to search for and identify small horizontal scale GW events, and to estimate their apparent horizontal wavelengths. The horizontal propagation directions of the events were determined using the Stokes parameter method combined with the cross S-transform analysis. The vertical temperature gradient was used to determine the vertical wavelengths of the events. GW momentum fluxes were calculated from the cross S-transform. Other wave parameters such as intrinsic frequencies were calculated using the GW dispersion relation. More than 100GW events were identified. They were generally high frequency waves with vertical wavelength of approximately 5 km and horizontal wavelength generally shorter than 20 km. Their intrinsic propagation directions were predominantly toward the east, whereas their ground-based propagation directions were primarily toward the west. Among the events, approximately 20% of them had very short horizontal wavelength, very high intrinsic frequency, and relatively small momentum fluxes, and thus they were likely trapped in the lower stratosphere. Using the estimated GW parameters and the background winds and stabilities from the NCAR/NCEP reanalysis data, we were able to trace the sources of the events using a simple reverse ray-tracing. More than 70% of the events were traced back to convective sources in the troposphere, and the sources were generally located upstream of the locations of the events observed at the aircraft level. Finally, a probability density function of the reversible cooling rate due to GWs was obtained in this study, which may be useful for cirrus cloud models.
Wang, L.↗
Simulating and benchmarking neutron total scattering instrumentation from inception of events to reduced and fitted data
In the design and realization of modern neutron scattering instrumentation, particularly when designing beamline concepts from the ground up, it is desirable to fully benchmark against realistically simulated data. This is especially true for total scattering beamlines, where the future deliverable data is to be analysed in both reciprocal- and real-space representations, and needs must be carefully balanced to ensure sufficient range, resolution and flux of the instrument. An approach to optimize the design of neutron scattering instrumentation via a workflow including ray-tracing simulations, event-based data reduction, heuristic analysis and fitting against realistically simulated spectra is demonstrated here. The case of the DISCOVER beamline concept at the Spallation Neutron Source is used as an example. The results of the calculations are benchmarked through simulation of existing instrumentation and subsequent direct comparison with measured data. Finally, on the basis of the validated models, the ability to explore design characteristics for future beamline concepts or future instrument improvements is demonstrated through the examples of detector tube size and detector layout.
47 OTHER INSTRUMENTATION↗
CME Magnetic Structure and IMF Preconditioning Affecting SEP Transport
Coronal mass ejections (CMEs) and solar energetic particles (SEPs) are two manifestations of the various solar phenomena that are known to cause severe space weather effects throughout the heliosphere. The evolution of CMEs after eruption, especially in terms of their magnetic structure, and the configuration of the interplanetary magnetic field (IMF) that influences the transport of SEPs are currently areas of active research. These two aspects are not necessarily independent of each other, especially during solar maximum when multiple eruptive events can occur close in time. Accordingly, we present in this work theanalysis of a CME that erupted from the Sun on 2012 May 11 (SOL2012-05-11) and an SEP event following an eruption that took place on 2012 May 17 (SOL2012-05-17),∼20◦in both latitude and longitude away from the May 11 CME source region. After observing in detailthe eruption and early evolution of the May 11 CME using remote-sensing data from three viewpoints, we evaluate its propagation through interplanetary space using several models.Then, we analyse in-situ measurements from five predicted impact locations (Venus, Earth, the Spitzer Space Telescope, the Mars Science Laboratory en route to Mars, and Mars) in the inner heliosphere in order to search for CME signatures. We find that all five in-situlocations detect signatures of an impulsive SEP event, which we trace back to the May 17 eruption. These findings suggest that the May 11 CME, which was crossing the various locations around the time of the May 17 eruption, provided a direct magnetic connectivityfor the efficient transport of SEPs with an impulsive profile. We discuss the space weather implications of CME evolution, regarding in particular its magnetic structure, and CME-driven IMF preconditioning that facilitates SEP transport from a later event. Finally, this work remarks the importance of the availability of data from multiple spacecraft, even those that do not include space weather research as their primary objective.
Erika Palmerio↗
On the Information Content of Program Traces
Program traces are used for analysis of program performance, memory utilization, and communications as well as for program debugging. The trace contains records of execution events generated by monitoring units inserted into the program. The trace size limits the resolution of execution events and restricts the user's ability to analyze the program execution. We present a study of the information content of program traces and develop a coding scheme which reduces the trace size to the limit given by the trace entropy. We apply the coding to the traces of AIMS instrumented programs executed on the IBM SPA and the SCSI Power Challenge and compare it with other coding methods. Our technique shows size of the trace can be reduced by more than a factor of 5.
Frumkin, Michael↗
Quantifying fish otolith mineralogy for trace-element chemistry studies
Otoliths are frequently used to infer environmental conditions or fish life history events based on trace-element concentrations. However, otoliths can be comprised of any one or combination of the three most common polymorphs of calcium carbonate - aragonite, calcite, and vaterite - which can affect the ecological interpretation of otolith trace-element results. Previous studies have reported heterogeneous calcium carbonate compositions between left and right otoliths but did not provide quantitative assessments of polymorph abundances. In this study, neutron diffraction and Raman spectroscopy were used to identify and quantify mineralogical compositions of Chinook salmon Oncorhynchus tshawytscha otolith pairs. We found mineralogical compositions frequently differed between otoliths in a pair and accurate calcium carbonate polymorph identification was rarely possible by visual inspection alone. The prevalence of multiple polymorphs in otoliths is not well-understood, and future research should focus on identifying otolith compositions and investigate how variations in mineralogy affect trace-element incorporation and potentially bias environmental interpretations.
60 APPLIED LIFE SCIENCES↗