Stream Core Research Articles

Exploration of initiation and stabilization properties of oblique detonation in a combustor with hydrogen fuel pre-injection

This study delves into the innovative aspects of hydrogen fuel injection and mixing within the duct of an oblique detonation engine (ODE) from both theoretical and numerical perspectives. By solving the multi-species reactive Reynolds-Averaged Navier-Stokes (RANS) equations alongside a hydrogen combustion model, the fluid dynamics and combustion processes in the combustor are thoroughly examined. The analysis shows that employing ramp-cantilever injectors for fuel delivery leads to fuel accumulation in the gas stream core, leaving a deficiency near the wall area. By supplementing ramp-cantilever injectors with wall injectors, fuel distribution adjacent to the wall is significantly enhanced, enabling the successful establishment of a detonation mode. However, the confined space and geometric constraints generate complex flow patterns, particularly due to boundary layer separation. The combustor operates in a stable configuration featuring an oblique shock-oblique detonation-separation shock (OSW-ODW-SSW) structure. Conversely, an oblique shock-oblique detonation-normal detonation-separation shock (OSW-ODW-NDW-SSW) arrangement is found to be unstable. Adjusting the position of the expansion corner on the upper wall forward stabilizes the unstable configuration, maintaining the ODW. Spatial flow inhomogeneities, especially equivalence ratio variations, are identified as crucial factors that can hinder ODW initiation and stability. These findings emphasize the pivotal role of optimizing fuel distribution, refining geometrical design, and ensuring flow uniformity in guaranteeing the efficiency and stability of oblique detonation engines. The outcomes provide valuable insights for future improvements in ODE design and operation.

Analysis of the Relationship between Upper-Level Aircraft Turbulence and the East Asian Westerly Jet Stream

The jet stream is a primary factor contributing to turbulence, especially for upper-level aircraft. This study utilized pilot reports and ERA5 data from 2023 to investigate the relationship between upper-level turbulence and the East Asian westerly jet (EAJ). The results indicate that approximately 45.9% of upper-level aircraft turbulence occurs within the jet stream, with the lowest proportion in August and the highest in January. Additionally, the strongest vertical wind shear (VMS) is found concentrated in the lower part of the jet stream core, particularly in the South–Down part of the jet stream, where upper-level aircraft turbulence occurs most frequently (27.1%). The most turbulent area is located between 30–40° N and 110–120° E, with the main air routes experiencing turbulence being the Henan sections of G212 and B208. From a seasonal perspective, there is less frequent occurrence of upper-level aircraft turbulence in summer and autumn but more in winter and spring. The EAJ volume increases with the strengthening of the jet core wind speed, with the jet core regions being most distinct at altitudes of 200~300 hPa. Meanwhile, the jet stream intensity index peaks at 70.6 m/s in January and reaches its lowest value of 7.1 m/s in August. The jet stream axis shifts southward in winter and northward in summer, reaching the southernmost position in December at 32.2° N and the northernmost position in August at 43.5° N. Furthermore, the VMS at turbulence points within the jet stream is higher than that at the turbulence points outside the jet stream, and the Richardson number (RI) is lower. Moreover, the temporal distribution of upper-level aircraft turbulence is primarily determined by the location and intensity of the jet stream, of which the jet stream intensity index provides guidance and thus serves as a reliable indicator.

Roles of eddy generation and jet characteristics in setting the annual cycle of Siberian storm track

AbstractThe Siberian storm track is one of the drivers of the East Asian extreme weather events. Using the daily JRA‐55 reanalysis data from 1980 to 2021, this study examines roles of eddy generation and jet characteristics in setting the annual cycle of Siberian storm track. It is found that there are two peaks of Siberian storm track intensity in boreal spring and autumn. The possible reason for such an annual cycle is explored by analyzing the maximum Eady growth rate over the Siberian region and jet characteristics. The stronger Siberian Eady growth rate in boreal spring and autumn, favoring a stronger baroclinic eddy generation, could contribute to the stronger intensity of Siberian storm tracks in these two seasons. Furthermore, the Siberian jet stream cores during boreal spring and autumn are located north of 50° N and resembles more an eddy‐driven jet. While in winter, the subtropical jet stream enhanced and the eddy‐driven jet becomes relatively weaker, which is less efficient to generate midlatitude baroclinic eddies. Besides, the eddy‐driven jet can modulate the horizontal wave propagations from upstream, which also plays a role in amplifying the spring and autumn Siberian storm tracks.

Structure and local parameters of self-compressed plasma streams in external magnetic field

Abstract The influence of the external axial magnetic field on pinching plasma flows generated by a magnetoplasma compressor (MPC) has been studied using magnetic and electric probes. In the presence of an external magnetic field, temperature measurements show two groups of electrons with different temperatures near the plasma stream core. The external magnetic field leads to a noticeable increase in the electric current in the plasma stream, electron temperature, and the formation of the current-sheet-like structure observed in the MPC for the first time.

Identification of Patterns and Relationships of Jet Stream Position with Flood-Prone Precipitation in Iran during 2006–2019

Jet streams are atmospheric phenomena that operate on a synoptic scale and can intensify the descending/ascending conditions of the air at the lower levels of the atmosphere. This study aimed to identify the patterns and location of the jet stream in southwest Asia during the days of widespread rainfall in Iran based on two criteria: “highest frequency of stations involved” and “maximum cumulative amount on the day of peak rainfall”. For this purpose, the daily precipitation data for 42 synoptic stations in Iran during the period 2006–2019 from the Meteorological Organization of Iran, the daily data at 500 hPa Geopotential Height (HGT), and U and V wind components at 500 and 300 hPa from NCEP/NCAR were gathered. Synoptic patterns were obtained based on daily precipitation data, daily maps at HGT 500 hPa, and U and V wind components at 500 and 300 hPa. The analysis of patterns showed that the position of precipitation cores is associated with the position and extension of jet stream centers at 300 hPa in winter, spring, and autumn. The main position of jet stream cores during flood-causing rainfall at 300 hPa was over the northern part of Saudi Arabia, the Mesopotamia basin, and southern Iran. This position seems to have provided the conditions for the convergence of the earth’s surface and the divergence of the atmosphere for the easy passage of moisture from the Red Sea, Aden Sea, and the Persian Gulf, and in the second rank, the Mediterranean Sea and the Arabian Sea.

Integration-based extraction and visualization of jet stream cores

Abstract. Jet streams are fast three-dimensional coherent air flows that interact with other atmospheric structures such as warm conveyor belts (WCBs) and the tropopause. Individually, these structures have a significant impact on the midlatitude weather evolution, and the impact of their interaction is still a subject of research in the atmospheric sciences. A first step towards a deeper understanding of the meteorological processes is to extract the geometry of jet streams, for which we develop an integration-based feature extraction algorithm. Thus, rather than characterizing jet core line purely as extremal line structure of wind magnitude, our core-line definition includes a regularization to favor jet core lines that align with the wind vector field. Based on the line geometry, proximity-based filtering can automatically detect potential interactions between WCBs and jets, and results of an automatic detection of split and merge events of jets can be visualized in relation to the tropopause. Taking ERA5 reanalysis data as input, we first extract jet stream core lines using an integration-based predictor–corrector approach that admits momentarily weak air streams. Using WCB trajectories and the tropopause geometry as context, we visualize individual cases, showing how WCBs influence the acceleration and displacement of jet streams, and how the tropopause behaves near split and merge locations of jets. Multiple geographical projections, slicing, as well as direct and indirect volume rendering further support the interactive analysis. Using our tool, we obtained a new perspective on the three-dimensional jet movement, which can stimulate follow-up research.

Development of a hardware configuration and a calculating program for a membrane plant equipped with polarization layer separation units

Various types of membrane units, including standard units for permeate separating, which are currently used for various liquids processing, are considered. Their advantages and disadvantages, working conditions and operating features are assessed. The principle of operation of membrane units with the bleed of the polarization layer is analyzed. A distinctive feature of such devices is the separation of the feed stream into three parts: adjacent to the membrane, including a polarization layer, with an increased concentration of high molecular substances (HMS) – concentrate, a spent stream core to be re-processed – retentate, and permeate, that practically contains no HMS. The unit scheme and the principle of operation of the plant completed with this equipment are given. A feature of this plant is the parallel arrangement of the membrane devices. In this configuration of the plant, there are two flow circulation loops and two tanks, in one of which there will be a depleted solution, in the other the retentate. During operation, the circulation of the depleted flow is provided. In this case, the resulting polarization layer (concentrate) will be discharged into the second tank. The working process continues until the complete depletion of the solution in the first tank. In the event that the solution in this tank is exhausted, and the required concentration of the product has not been reached, the second tank with the concentrate activates and the process continues. The principle of operation in this case is similar. The rotation of tanks continues until the required degree of concentration of the product is obtained. A calculation algorithm, a block diagram and a program for calculating the operating time of a membrane installation are proposed, for which a certificate of state registration of a computer program has been obtained. The calculation algorithm and program interface are presented. This program makes it possible to predict the operation of such installations and provides for the possibility of optimizing their operation.т.п.)

Observations of the variability of the New England shelf break by shipboard echosounders

The New England Shelf Break is a dynamic region where warm salty slope water meets with colder less saline shelf water to form a distinct front. The position and shape of the front is modified by a range of processes on differing temporal and spatial scales. While seasonal changes are well documented, the influence of shorter time scale processes throughout the water column are less well understood. Of interest is the influence of meso-scale physical oceanographic processes such as meanders in the Gulf Stream and warm core rings and eddies. From March to June 2021 five cruises to the New England Shelf Break were conducted as part of the ONR Task Force Oceans New England Shelf Break Acoustics Experiments. The shipboard broadband echo sounders on the R/V Neil Armstrong were used to ensonify the front during each of these five cruises. Significant changes were observed, especially during the transit of a warm core eddy through the study area. Groups of scatterers in the study area were targeted by Deep-See (a broadband tow sled) and a broadband echo sounder equipped REMUS 600 to enable ensonification of individual targets to aide in acoustic identification of biology at the shelf break front.

Francis 99 CFD through RapidCFD accelerated GPU code

Francis turbines research and development (R&D) requires performance assessment through hydraulic laboratory model testing which can be assisted by auxiliary tools like computational fluid dynamics (CFD), widely used recently. CFD has a history of seeking and requiring ever higher computational performance (HPC) because of the parallelism where Graphics Processor Units (GPUs) have emerged as a major paradigm for solving complex computational problems. However, their implementation to CFD solvers is still a challenge and the tremendous computational power of the GPUs has been wasted. This work presents how the open source RapidCFD code, based on OpenFOAM and ported to Nvidia CUDA, enabled GPUs to be able of running almost entire simulations in thousands of parallel stream cores packed in small form factor hardware in order to solve the incompressible Reynolds-Average-Navier-Stokes (RANS) equations. The simulations were based on a full 3D Francis turbine case which consisted of a grid domain of 23 million cells, including spiral case with stay vanes, distributor, runner and draft tube. CFD results of shaft torque, static pressure and velocity components in steady state deploying a multiple reference frame (MRF) motion approach were compared with available experimental data for main operation conditions at different distributor opening angles: best efficiency operation point (BEP), part load operation point (PL) and full load operation point (HL). The obtained data showed that by transferring directly all the computations to the GPUs, it is possible to make CFD simulations faster compared with central processing units (CPUs). Thus, it is expected to obtain an affordable low computational cost in optimization processes or full range performance evaluations.

The relationship between the polar jet stream and extreme wildfire events in North America

AbstractNorthern hemisphere mid-latitudeweather is strongly influenced by the polar jet stream (PJS), which dictates the position of storm tracks; this influence also extends to weather patterns conducive to the ignition and growth of large wildfires. We examined the role of the PJS on extreme wildfire events in North America (NA) between 40° and 70°N latitude, using fire spread events (FSEs) for 2002—2016. Climatologies of the 300-hPa wind components and derived quantities show that the PJS weakens and moves northward in the Boreal summer coincident with the fire season. We use spatio-temporal compositing of 300-hPa winds and 500-hPa geopotential height anomalies to show that FSEs are associated with an upper-level ridge and high centered over events, except eastern Canada where patterns are displaced westward. Ridge patterns persist longer for FSEs in western NA compared with Eastern NA, as well as for May to August compared with April, September and October. These tropospheric patterns also occur concomitantly with surface weather drivers of fire spread including positive daily mean temperature and vapor pressure deficit anomalies and negative precipitation anomalies. Distributions of maximum and minimum latitudinal jet stream peak, ridge and trough positions, relative to FSEs, confirm that events occur predominantly southward of the jet stream core and near a ridge for low split flow configurations but not necessarily for high split flow configurations. These findings have wide-reaching implications for better understanding NA fire regimes and potential fire management strategies (eg. resource pre-positioning and tactical suppression) through improved forecasting of fire weather.

Mid-level convection in a warm conveyor belt accelerates the jet stream

Abstract. Jet streams and potential vorticity (PV) gradients along upper-level ridges, troughs and zonal flows form a waveguide that governs midlatitude dynamics. Warm conveyor belt (WCB) outflows often inject low-PV air into ridges, and the representation of WCBs is seen as a source of uncertainty for downstream forecasts. Recent studies have highlighted the presence of mesoscale structures with negative PV in WCBs, the impact of which, on large-scale dynamics, is still debated. Here, fine-scale observations of cloud and wind structures acquired with airborne Doppler radar and dropsondes provide rare information on the WCB outflow of the Stalactite cyclone and the associated upper-level ridge on 2 October 2016 during the North Atlantic Waveguide and Downstream Impact Experiment (NAWDEX). The observations show a complex tropopause structure associated with two jet stream cores along the northwestern edge of the ridge. A reference convection-permitting simulation with full physics reproduces the observed structures and reveals the presence of elongated negative PV bands along the eastern jet stream core. In contrast, a sensitivity experiment with heat exchanges due to cloud processes being cut off shows lower cloud tops, weaker jet stream cores, a ridge less extended westward and the absence of negative PV bands. A Lagrangian analysis based on online trajectories shows that the anticyclonic branch of the WCB outflow enters the eastern jet stream core in the reference simulation, while it is absent in the sensitivity experiment. The anticyclonic ascents and negative PV bands originate from the same region near the cyclone's bent-back front. The most rapid ascents coincide with mid-level convective cells identified by clustering analysis, which are located in a region of conditional instability below the jet stream core and above a low-level jet. Horizontal PV dipoles are found around these cells, with the negative poles reaching absolute negative values, and the convective cells thus appear as the source of the negative PV bands. The results show that mid-level convection within WCBs accelerates the jet stream and may influence the downstream large-scale circulation.

Climatic analysis of effective jet streams frequency on extreme precipitations in west of Iran

Abstract In this study, the frequency of effective jet streams was analyzed in extreme and widespread precipitations in the west of Iran. For this purpose, the daily precipitation of 69 synoptic and climatic stations over 18,624 days (1961–2010) were selected. Then, 119 days of extreme and widespread precipitation in the study area were chosen based on generalized distribution for conducting related reviews and analyses. The frequency of jet streams in the geographical location from 0° to 120°E and −10° to 80°N were reviewed at four levels (250, 300, 400 and 500 hPa). Due to the large volume of information, only the highest and lowest levels (250 and 500 hPa) in relation to the surface were considered. According to the results, the highest frequency of jet stream was observed at 250 hPa. The second quarter of the jet stream core lay over the west of Iran (which is associated with increasing positive vorticity as well as upper-level divergence and lower-level convergence of the atmosphere). In general, the extension of jet stream up to 500 hPa indicated an unstable layer thickness, which can cause extreme and widespread precipitation in the west of Iran. The results of selected days based on cluster analysis and Lund correlation revealed that in rainy days, the wind speed was more than 50 m/s and the subtropical jet stream speed was over 40 m/s, leading to extreme precipitation in the west of Iran.

Dynamic stability of a jet near a transition in static stability

The vertical profile of the Earth's atmosphere in middle latitudes contains a sharp transition region between two roughly constant stability layers, termed the tropopause and also exhibits jet streams at nearly the same altitude, with the jet stream core possibly above or below the tropopause, depending on time and location. This proximity of the jet to the tropopause would be expected to greatly affect the dynamic stability of the jet, treated here with the jet modelled with the Bickley profile and the tropopause modelled as a smooth transition region with a tanh profile. Stability results are obtained numerically using a Chebyshev collocation spectral method. The results show that the jet becomes more unstable as it is moved further beneath the tropopause. Corresponding two- and three-dimensional nonlinear simulations of the flow confirm the initial growth, and indicate that when a jet is above the tropopause, the configuration is more stable and more likely to produce a strong single unstable mode. The simulations indicate that this instability will grow to form a solitary wave envelope pattern. Conversely, when a jet is below the tropopause, the jet is more likely to form a broad spectrum of motion.

Using the Polar Jet Stream Core Wind Speed to Estimate the Surface Low Pressure System value during winter

The work studied the relationship between polar jet stream core speed at 300 hPa level and the surface low pressure system on winter seasons during years from 2014 to 2016. Februaries were chosen from winter seasons which the polar jet stream passes with high frequencies over the area of study. The study presented that the structure of polar jet was almost continuous jet-type structure that the jet core was easy to recognize and it had indirect relationship with the low pressure systems at surface. the Pearson's (R) statistical test used to show the strength of that relationship which accessible values were between (0.6 - 1) that presented the core speed values as a good element to derive equation connecting between the low pressure system value in (hPa) at surface and core speed value in (kt) at 300 hPa level . The simple linear regression technique is used to drive the equation that connects between the low pressure system and the jet core speed value which was (Low pressure center value (hPa) =1042.57 ̶ (0.307 × core speed (kt) )) . The equation was tested against some jet stream cases at 300 hPa that were the highest value of the jet core speed, the lowest and middle selected value which presented the percentage errors were between (0.03-0.09). the chart analyzing presented the lowest low pressure system center corresponded the highest the jet core speed values as shown in 11 Feb., 2015 at 00 UTC which the core speed was 150 (kt) corresponding the surface low pressure system which was 993 (hPa)

Parametric Study of a Turbofan Engine with an Auxiliary High-Pressure Bypass

A parametric study of a novel turbofan engine with an auxiliary high-pressure bypass (AHPB) is presented. The underlying motivation for the study was to introduce and explore a configuration of a turbofan engine which could facilitate clean secondary burning of fuel at a higher temperature than conventionally realized. The study was also motivated by the developments in engineering materials for high-temperature applications and the potential utility of these developments. The parametric study is presented in two phases. Phase I presents a schematic of the turbofan engine with AHPB and the mathematics of the performance parameters at various stations. The proposed engine is hypothesized to consist of three streams—core stream, low-pressure bypass (LPB) stream, and the AHPB or, simply, the high-pressure bypass (HPB) stream. Phase II delves into the performance simulation and the analysis of the results in an ideal set-up. The simulation and results are presented for performance analysis when (i) maximizing engine thrust while varying the LPB and AHPB ratios, and (ii) varying the AHPB ratio while maintaining the LPB ratio constant. The results demonstrate the variations in performance of the engine and a basis for examining its potential utility for practical applications.

Wind Pulse Effect on Coastal Current

Shallow water equations have been used to analyze the final stage of the response of a semi-infinite rotating basin to the wind impulse effect simulating the passage of a storm in the presence of a coastal current. It has been shown that the most significant effect upon a high storm intensity is that the coastal stream core shifts several kilometers toward the coast or from the coast, depending on the sign of the Ekman transport. The additional currents arising after the storm passage in the presence of an alongshore stream differ only quantitatively from the currents arising in its absence.

Improvement of temperature uniformity in microchannel with pin-fin based on endwall fillet structure

Energy and mass transfer process are involved in many industries, such as energy, transportation, aeronautics and astronautics, electronic, manufacturing, among which, the heat exchanger plays a very key role. With the development of science and technology and the increasing requirements for energy conservation and emission reduction, the efficiency of heat exchange system has to be promoted to meet the demand of higher heat intensity and thermal load. The high-efficient and energy-saving compact heat exchanger such as microchannel heat sink has gained more attractions in academic researches and engineering applications. Microchannel with pin-fin is widely used in engineering applications due to its high efficiency in heat and mass transfer, but the high temperature region formed in the rear of the cylinder and the non-uniformity temperature field increase the temperature gradient and generate extra thermal spreading resistance, which would, to a large extend, influence the regulation of the system and the economy and reliability of the equipments. Therefore, the endwall fillet structure is proposed in this work, based on researches about the performance of CDA (controlled diffusion airfoil) blade with fillet, to improve the temperature uniformity and heat transfer performance of microchannel with pin-fin. The periodical laminar flow and heat transfer performances are comparatively studied. The results show that the flow resistance coefficient f of the microchannel with filleted pin-fin does not increase significantly compared to traditional pin-fined microchannel, which means the introducing of the fillet will enhance the heat transfer while f of the microchannel is almost a constant. The maximum increase of f is only 2.03%. Moreover, two separate symmetrical secondary flows develop in microchannel with smooth cylinder, with one on the top of the other. After adding the proposed structures, at low Reynolds number, the lower span-wise secondary flow is enhanced as the radius increases and these two span-wise secondary flows gradually merge into one which develops along the normal direction. At high Reynolds number, the mainstream low-temperature core region is obvious asymmetry: it moves downwards gradually as Reynolds number increases. Besides, at low Reynolds number (0–120), the fillet improves the heat and mass transfer between the main stream core and areas near the wall, enhances the thermal uniformity of the pin-fin and heated walls, improves the heat transfer performance of the rear of the cylinder and eliminates the high temperature area in the pin-fin. And local high-temperature region on the top half of the microchannel decreases, which contributes to the extension of low-temperature region and the decrease of average temperature. As the radius of the fillet increases, the effects mentioned above are gradually enhanced. The heat transfer coefficient of the channel reaches a maximum augmentation of 16.93%, and the flow resistance coefficient of the microchannel with filleted pin-fin does not increase significantly. Comparing with the synthetical thermal performance coefficient of pin-fined microchannel heat sink, that of the proposed filleted pin-fin microchannel increases 16.22% at most. As the Reynolds number increases, the influence of the fillet structure decreases. The study motivation of combining separation flow researches of rotatory machines with heat transfer enhancement, as well as the resulting design are a beneficial attempt for scientific research and engineering application.

A network-based detection scheme for the jet stream core

Abstract. The polar and subtropical jet streams are strong upper-level winds with a crucial influence on weather throughout the Northern Hemisphere midlatitudes. In particular, the polar jet is located between cold arctic air to the north and warmer subtropical air to the south. Strongly meandering states therefore often lead to extreme surface weather. Some algorithms exist which can detect the 2-D (latitude and longitude) jets' core around the hemisphere, but all of them use a minimal threshold to determine the subtropical and polar jet stream. This is particularly problematic for the polar jet stream, whose wind velocities can change rapidly from very weak to very high values and vice versa. We develop a network-based scheme using Dijkstra's shortest-path algorithm to detect the polar and subtropical jet stream core. This algorithm not only considers the commonly used wind strength for core detection but also takes wind direction and climatological latitudinal position into account. Furthermore, it distinguishes between polar and subtropical jet, and between separate and merged jet states. The parameter values of the detection scheme are optimized using simulated annealing and a skill function that accounts for the zonal-mean jet stream position (Rikus, 2015). After the successful optimization process, we apply our scheme to reanalysis data covering 1979–2015 and calculate seasonal-mean probabilistic maps and trends in wind strength and position of jet streams. We present longitudinally defined probability distributions of the positions for both jets for all on the Northern Hemisphere seasons. This shows that winter is characterized by two well-separated jets over Europe and Asia (ca. 20° W to 140° E). In contrast, summer normally has a single merged jet over the western hemisphere but can have both merged and separated jet states in the eastern hemisphere. With this algorithm it is possible to investigate the position of the jets' cores around the hemisphere and it is therefore very suitable to analyze jet stream patterns in observations and models, enabling more advanced model-validation.

The power of vertical geolocation of atmospheric profiles from GNSS radio occultation.

High‐resolution measurements from Global Navigation Satellite System (GNSS) radio occultation (RO) provide atmospheric profiles with independent information on altitude and pressure. This unique property is of crucial advantage when analyzing atmospheric characteristics that require joint knowledge of altitude and pressure or other thermodynamic atmospheric variables. Here we introduce and demonstrate the utility of this independent information from RO and discuss the computation, uncertainty, and use of RO atmospheric profiles on isohypsic coordinates—mean sea level altitude and geopotential height—as well as on thermodynamic coordinates (pressure and potential temperature). Using geopotential height as vertical grid, we give information on errors of RO‐derived temperature, pressure, and potential temperature profiles and provide an empirical error model which accounts for seasonal and latitudinal variations. The observational uncertainty of individual temperature/pressure/potential temperature profiles is about 0.7 K/0.15%/1.4 K in the tropopause region. It gradually increases into the stratosphere and decreases toward the lower troposphere. This decrease is due to the increasing influence of background information. The total climatological error of mean atmospheric fields is, in general, dominated by the systematic error component. We use sampling error‐corrected climatological fields to demonstrate the power of having different and accurate vertical coordinates available. As examples we analyze characteristics of the location of the tropopause for geopotential height, pressure, and potential temperature coordinates as well as seasonal variations of the midlatitude jet stream core. This highlights the broad applicability of RO and the utility of its versatile vertical geolocation for investigating the vertical structure of the troposphere and stratosphere.

Aging-Aware Compilation for GP-GPUs

General-purpose graphic processing units (GP-GPUs) offer high computational throughput using thousands of integrated processing elements (PEs). These PEs are stressed during workload execution, and negative bias temperature instability (NBTI) adversely affects their reliability by introducing new delay-induced faults. However, the effect of these delay variations is not uniformly spread across the PEs: some are affected more—hence less reliable—than others. This variation causes significant reduction in the lifetime of GP-GPU parts. In this article, we address the problem of “wear leveling” across processing units to mitigate lifetime uncertainty in GP-GPUs. We propose innovations in the static compiled code that can improve healing in PEs and stream cores (SCs) based on their degradation status. PE healing is a fine-grained very long instruction word (VLIW) slot assignment scheme that balances the stress of instructions across the PEs within an SC. SC healing is a coarse-grained workload allocation scheme that distributes workload across SCs in GP-GPUs. Both schemes share a common property: they adaptively shift workload from less reliable units to more reliable units, either spatially or temporally. These software schemes are based on online calibration with NBTI monitoring that equalizes the expected lifetime of PEs and SCs by regenerating adaptive compiled codes to respond to the specific health state of the GP-GPUs. We evaluate the effectiveness of the proposed schemes for various OpenCL kernels from the AMD APP SDK on Evergreen and Southern Island GPU architectures. The aging-aware healthy kernels generated by the PE (or SC) healing scheme reduce NBTI-induced voltage threshold shift by 30% (77% in the case of SCs), with no (moderate) performance penalty compared to the naive kernels.