Method of making an apertured casting

An apertured casting is made by first forming a duplicate in the shape of the finished casting, positioning refractory metal bodies such as wires in the duplicate at points corresponding to apertures or passageways in finished products, forming a ceramic coating on the duplicate, removing the duplicate material, firing the ceramic in a vacuum or inert atmosphere, vacuum casting the metal in the ceramic form, removing the ceramic form, heating the cast object in an atmospheric furnace to oxidize the refractory metal bodies and then leaching the oxidized refractory bodies from the casting with a molten caustic agent or acid solution

Evaluation of a laboratory test model annular momentum control device

A 4068 Nm Sec laboratory test model annular momentum control device (AMCD) was described and static and dynamic test results were presented. An AMCD is a spinning annular rim suspended by noncontacting magnetic bearings and powered by a noncontacting linear electromagnetic motor. Test results include spin motor torque characteristics and spin motor and magnetic bearing drag losses. Limitations of some of the design approaches taken was also discussed

Humanitarian Action and Military Intervention: Temptations and Possibilities.

Although the war in Liberia in July 2003 claimed hundreds of lives, the international community was reluctant to intervene. In this article, the author debates the question: does international military intervention equal protection of populations? The role of humanitarian organisations in military intervention is considered. Aid organisations cannot call for deployment of a protection force without renouncing their autonomy or appealing to references outside their own practices. Such organisations provide victims with vital assistance and contribute to ensuring that their fate becomes a stake in political debate by exposing the violence that engulfs them, without substituting their own voices for those of the victims. The political content of humanitarian action is also outlined and military intervention in the context of genocide is discussed. The author concludes that the latter is one of the rare situations in which humanitarian actors can consider calling for an armed intervention without renouncing their own logic

Réponse du cycle hydrologique aux forçages anthropiques : Que nous disent les dernières simulations du GIEC ?

International audienceThe aim of this article is to make an inventory of the main results published since the IPCC 3rd Assessment report and to the french communitycontribution on the response of the hydrological cycle to the anthropic forcings taken into account in the climatic scenarios of the 21st century.L’objectif de cet article est de dresser un bref inventaire des principaux résultats publiés depuis le 3e rapport d’évaluation du Giec et de situer lacontribution de la communauté française sur le thème de la réponse du cycle hydrologique aux forçages anthropiques pris en compte dans lesscénarios climatiques du XXIe siècle

Indian Ocean Sea Surface Temperature and El Niño-Southern Oscillation: A New Perspective

International audienceHere we show that the 1976-1977 climate regime shift was accompanied by aremarkable change in the lead-lag relationships between Indian Ocean Sea SurfaceTemperature (SST) and El Niño evolution. After the 1976-1977 regime shift, acorrelation analysis suggests that southern Indian Ocean SSTs observed during lateboreal winter are a key precursor in predicting El Niño evolution as the traditionaloceanic heat content anomalies in the equatorial Pacific or zonal wind anomalies overthe equatorial western Pacific. The possible physical mechanisms underlying this highlysignificant statistical relationship are discussed. After the 1976-1977 regime shift,southern Indian Ocean SST anomalies produced by Mascarene High pulses duringboreal winter trigger coupled air-sea processes in the tropical eastern Indian Oceanduring the following seasons. This produces a persistent remote forcing on the Pacificclimate system, promoting wind anomalies over the western equatorial Pacific andmodulating the regional Hadley cell in the southwest Pacific. These modulations, inturn, excite Rossby waves, which produce quasi-stationary circulation anomalies in theextratropical South Pacific, responsible for the development of the southern branch ofthe “horseshoe” El Niño pattern.The change of the background SST state that occured in the late 1970s over the IndianOcean may also explain why ENSO evolution is different before and after the 1976-1977 regime shift. These results shed some light on the possible influence of globalwarming or decadal fluctuations on El Niño evolution through changes inteleconnection patterns between the Indian and Pacific Oceans

Turbulent transport in the outer region of rough-wall open-channel flows: the contribution of large coherent shear stress structures (LC3S)

Acoustic Doppler velocity profiler (ADVP) measurements of instantaneous three-dimensional velocity profiles over the entire turbulent boundary layer height, δ, of rough-bed open-channel flows at moderate Reynolds numbers show the presence of large scale coherent shear stress structures (called LC3S herein) in the zones of uniformly retarded streamwise momentum. LC3S events over streamwise distances of several boundary layer thicknesses dominate the mean shear dynamics. Polymodal histograms of short streamwise velocity samples confirm the subdivision of uniform streamwise momentum into three zones also observed by Adrian et al. (J. Fluid Mech., vol. 422, 2000, p. 1). The mean streamwise dimension of the zones varies between 1δ and 2.5δ. In the intermediate region (0.2<z/δ<0.75), the contribution of conditionally sampled u'w' events to the mean vertical turbulent kinetic energy (TKE) flux as a function of threshold level H is found to be generated by LC3S events above a critical threshold level Hmax for which the ascendant net momentum flux between LC3S of ejection and sweep types is maximal. The vertical profile of Hmax is nearly constant over the intermediate region, with a value of 5 independent of the flow conditions. Very good agreement is found for all flow conditions including the free-stream shear flows studied in Adrian et al. (2000). If normalized by the squared bed friction velocity, the ascendant net momentum flux containing 90% of the mean TKE flux is equal to 20% of the shear stress due to bed friction. In the intermediate region this value is nearly constant for all flow conditions investigated herein. It can be deduced that free-surface turbulence in open-channel flows originates from processes driven by LC3S, associated with the zonal organization of streamwise momentum. The good agreement with mean quadrant distribution results in the literature implies that LC3S identified in this study are common features in the outer region of shear flow

Revisiting the possible links between the Quasi-Biennial Oscillation and the Indian summer monsoon using NCEP R-2 and CMAP fields

International audienceIn the past the stratospheric Quasi-Biennial Oscillation (QBO) has sometimes been proposed toexplain the tendency for the Indian Summer Monsoon (ISM) to alternate between strong andweak years. In this study, NCEP Reanalysis-2 and CMAP fields are statistically analyzed toassess the relationship between equatorial zonal winds in the stratosphere and ISM. In a firststep, it is shown that zonal winds at 15hPa during the preceding winter (January-February) arethe best stratospheric predictor of the summer rainfall over the Indian subcontinent as a whole.This relationship mainly holds for August and September, or the late ISM. Surprisingly, theQBO pattern is not significantly associated with the rainfall variability during June-July or theearly ISM. CMAP and NCEP R-2 fields corroborate these findings and show that westerlyQBO years are associated with a deepening of the monsoon trough over the Gangetic plainsand decreased convective activity in the eastern equatorial Indian region. However, furtherstatistical analysis shows that the QBO-ISM link is complex since a westerly QBO phase at 15hPa in boreal winter leads to a weaker monsoon surface circulation with, in particular, aweakening of the Somali Jet at the beginning of the monsoon, but a much stronger circulationin September. At that time, the Tibetan High is reinforced, the tropical easterly jet at 200 hPa isstronger over India and the local reversed Hadley circulation is also strengthened north of theequator. The mechanisms by which the QBO may affect ISM have been explored through inparticular correlations between stratospheric winds and tropopause temperature and pressurefields. Our results provide support for an out of phase behavior of convective activity betweenthe Indian sub-continent and the equatorial Indian Ocean induced by the QBO phase, especiallyduring the late ISM. During a westerly QBO phase, convective activity is, in September,enhanced over India, which brings higher precipitation, compared to the east phase. This work also suggests that the winter QBO at 15 hPa could have some skill in foreshadowing the late ISM

Oceanic factors controlling the Indian summer monsoon onset in a coupled model

International audienceDespite huge socio-economical impacts, the predictability of the Indian summer monsoon (ISM) onset remains drastically limited by the inability of both current forced and coupled models to reproduce a realistic monsoon seasonal cycle. In the SINTEX-F2 coupled model, the mean ISM onset estimated with rainfall or thermo-dynamical indices is delayed by approximately 13 days, but it occurs 6 days early in the atmosphere-only component of the coupled model. This 19 days lag between atmospheric-only and coupled runs, which is well above the observed standard-deviation of the ISM onset (10 days in the observations), suggests a crucial role of the coupling, including Sea Surface Temperatures (SST) biases, on the delayed mean onset in the coupled model. On the other hand, the key-factors governing the interannual variability of the ISM onset date are also fundamentally different in the atmospheric and coupled experiments and highlight the importance of El Niño–Southern Oscillation (ENSO) and ocean–atmosphere coupling for a realistic simulation of the variability of the ISM onset date. At both interannual and seasonal timescales, we demonstrate the importance of the meridional gradients of tropospheric temperature, moisture and vertical shear of zonal wind in the Indian Ocean for a realistic ISM onset simulation. Taking into account that the tropical tropospheric temperature and the vertical shear are not only controlled by local processes, but also by large-scale processes, we need to examine not only the Indian Ocean SST biases, but also those in others tropical basins in order to understand the delay of the mean onset date in the coupled model. During April and May, the main tropical SST biases in the coupled model are a strong warm bias in the Indian, Pacific and Atlantic Oceans, associated with an important excess of equatorial precipitations, and thus a warmer equatorial free troposphere. In order to identify the keys tropical SST regions influencing the mean ISM onset date, sensitivity coupled experiments have been performed. In these experiments, the SST is corrected separately in each tropical basin. The correction of SST biases in the tropical Indian and Atlantic oceans only slightly improves the onset date in the coupled model and produces “El Niño-like” changes in the tropical Pacific. Conversely, the correction of the Pacific SST biases advances the onset date by 9 days compared to the control coupled run. These results suggest that, while the correction of Indian SST biases improves the rainfall spatial distribution, the delayed mean ISM onset date is mainly control by the tropical Pacific Ocean SST biases

The Curious Case of Indian Ocean Warming

Supplemental information related to this paper is available at the Journals Online website: http://dx.doi.org/10.1175/JCLI-D-14-00471.s1International audienceRecent studies have pointed out an increased warming over the IndianOcean warmpool (the central-eastern Indian Ocean characterized by sea surface temperatures greater than 28.08C) during the past half-century, although the reasons behind this monotonous warming are still debated. The results here reveal a larger picture—namely, that the western tropical Indian Ocean has been warming for more than a century, at a rate faster than any other region of the tropical oceans, and turns out to be the largest contributor to the overall trend in the global mean sea surface temperature (SST). During 1901–2012, while the Indian Ocean warm pool went through an increase of 0.78C, the western Indian Ocean experienced anomalous warming of 1.28C in summer SSTs. The warming of the generally cool western Indian Ocean against the rest of the tropical warmpool region alters the zonal SST gradients, and has the potential to change the Asian monsoon circulation and rainfall, as well as alter the marine food webs in this biologically productive region. The current study using observations and global coupled ocean–atmosphere model simulations gives compelling evidence that, besides direct contribution from greenhouse warming, the long-term warming trend over the western Indian Ocean during summer is highly dependent on the asymmetry in the El Niño–Southern Oscillation (ENSO) teleconnection, and the positive SST skewness associated with ENSO during recent decades