Search results for "Boundary"
showing 10 items of 1626 documents
The Asian tropopause aerosol layer within the 2017 monsoon anticyclone: microphysical properties derived from aircraft-borne in situ measurements
2021
The Asian summer monsoon is an effective pathway for aerosol particles and precursors from the planetary boundary layer over Central, South, and East Asia into the upper troposphere and lower stratosphere. An enhancement of aerosol particles within the Asian monsoon anticyclone (AMA), called the Asian tropopause aerosol layer (ATAL), has been observed by satellites. We discuss airborne in situ and remote sensing observations of aerosol microphysical properties conducted during the 2017 StratoClim field campaign within the AMA region. The aerosol particle measurements aboard the high-altitude research aircraft M55 Geophysica (maximum altitude reached of ∼20.5 km) were conducted with a modifi…
New particle formation events measured on board the ATR-42 aircraft during the EUCAARI campaign
2010
Aerosol properties were studied during an intensive airborne measurement campaign that took place at Rotterdam in Netherlands in May 2008 within the framework of the European Aerosol Cloud Climate and Air Quality Interactions project (EUCAARI). The objective of this study is to illustrate seven events of new particle formation (NPF) observed with two Condensation Particle Counters (CPCs) operated on board the ATR-42 research aircraft in airsectors around Rotterdam, and to provide information on the spatial extent of the new particle formation phenomenon based on 1-s resolution measurements of ultra-fine particle (in the size range 3–10 nm diameter, denoted N<sub>3-10</sub> herea…
Aerosol closure study by lidar, sun photometry, and airborne optical counters during DAMOCLES field campaign at El Arenosillo sounding station, Spain
2011
We present a comparison of aerosol properties derived from in situ and remote sensing instruments during DAMOCLES campaign, aimed at investigating the equivalence between the instrumentation and methodologies employed by several Spanish groups to study atmospheric aerosols at a regional background site. The complete set of instruments available during this closure experiment allowed collecting a valuable high-resolution aerosol measurement data set. The data set was augmented with airborne in situ measurements carried out in order to characterize aerosol particles during the midday of 29 June 2006. This work is focused on aerosol measurements using different techniques of high-quality instr…
The impact of a mesoscale convective system cold pool on the northward propagation of the intertropical discontinuity over West Africa
2009
The interaction between a mesoscale convection system cold pool and the intertropical discontinuity (ITD) is investigated on two consecutive days (5 and 6 June 2006), in the framework of the African Monsoon Multidisciplinary Analysis Special Observing Period (SOP 1a). Satellite imagery and surface meteorological observations are used to track the movement of the ITD prior to and after its interaction with the cold pool. The impact of the northward propagating cold pool on the Sahelo-Saharan planetary boundary layer (PBL) thermodynamics and aerosol vertical distribution is analyzed by means of airborne and ground-based measurements over the two-day period. Complementary European Centre for M…
Northward bursts of the West African monsoon leading to rainfall over the Hoggar Massif, Algeria
2009
The Hoggar Massif is a comparatively populated region in the Sahara, where water supply is a critical problem due to the lack of nearby sources and unaffordable water pumping. In the present paper, we analyse the influence of the West African monsoon (WAM) on precipitation over the Hoggar during summer. We investigate (1) two rainfall events during 23-27 July 2006, accounting for almost half of the precipitation of this year, and (2) the representativity of this period with regard to ERA-40 ECMWF re-analyses (1979 to 2001). By the end of July 2006, two consecutive northward bursts of the WAM flow reached the Hoggar and caused an increase in low-level humidity. In the afternoon of these days…
Ship emissions measurement in the Arctic by plume intercepts of the Canadian Coast Guard icebreaker &lt;i&gt;Amundsen&lt;/i&gt; from …
2016
Abstract. Decreasing sea ice and increasing marine navigability in northern latitudes have changed Arctic ship traffic patterns in recent years and are predicted to increase annual ship traffic in the Arctic in the future. Development of effective regulations to manage environmental impacts of shipping requires an understanding of ship emissions and atmospheric processing in the Arctic environment. As part of the summer 2014 NETCARE (Network on Climate and Aerosols) campaign, the plume dispersion and gas and particle emission factors of effluents originating from the Canadian Coast Guard icebreaker Amundsen operating near Resolute Bay, NU, Canada, were investigated. The Amundsen burned dist…
Initial chemical transport of reducing elements and chemical reactions in oxide cathode base metal
2002
Abstract In the present work, the formation of compounds associated to the diffusion of reducing elements (Mg and Al) to the nickel surface of a one-piece oxide cathode has been studied. Those compounds have been evidenced after the annealing steps at high temperature performed on cathode base metal prior to the emitting coating deposition. Therefore, they form the “initial” interface between the nickel and the coating, in other words, the interface existing at the beginning of cathode life. Extensive analysis to characterize the nickel base prior to coating deposition has been performed by means of scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX), …
Understanding sigma-phase precipitation in a stabilized austenitic stainless steel (316Nb) through complementary CALPHAD-based and experimental inves…
2014
Abstract Sigma-phase precipitation in a 316Nb “stabilized” austenitic stainless steel was studied through complementary CALPHAD-based and dedicated experimental investigations. Thermokinetic calculations performed using Thermo-Calc (with the DICTRA module) and MatCalc software showed that the sigma phase (σ) precipitated directly at γ-austenite grain boundaries (GB) via a common solid-state reaction when carbon and nitrogen contents fell below a critical threshold. Residual δ ferrite was found to be more susceptible to σ-phase precipitation; this type of precipitation occurred via two mechanisms that depended on the concentration profiles of δ-ferrite stabilizing elements induced by previou…
The Calabrian Stage redefined
2008
The name Calabrian was introduced in the geological literature by the French stratigrapher Maurice Gignoux in 1910, and later described in his important monograph (633 pages) "Les formations marines pliocènes et quaternaires de l'Italie du sud et de la Sicile" published in 1913. Detailed data were provided on several sections (Santa Maria di Catanzaro, Caraffa, Monasterace, Palermo) and on their fossil content. The Calabrian Stage has commonly been used for over fifty years as the oldest subdivision of the Quaternary, notably in the time scales of Berggren & van Couvering (1974) and Haq & Eysinga (1987). However, after the GSSP for the Pliocene/Pleistocene boundary (P/P) was approved by INQ…
Dasymetric distribution of votes in a dense city
2017
[EN] A large proportion of electoral analyses using geography are performed on a small area basis, such as polling units. Unfortunately, polling units are frequently redrawn, provoking breaks in their data series. Previous electoral results play a key role in many analyses. They are used by political party workers and journalists to present quick assessments of outcomes, by political scientists and electoral geographers to perform detailed scrutinizes and by pollsters and forecasters to anticipate electoral results. In this paper, we study to what extent more complex geographical approaches (based on a proper location of electors on the territory using dasymetric techniques) are of value in…