Multi-model evaluation of the sensitivity of the global energy budget and hydrological cycle to resolution

This study undertakes a multi-model comparison with the aim to describe and quantify systematic changes of the global energy and water budgets when the horizontal resolution of atmospheric models is increased and to identify common factors of these changes among models. To do so, we analyse an ensemble of twelve atmosphere-only and six coupled GCMs, with different model formulations and with resolutions spanning those of state-of-the-art coupled GCMs, i.e. from resolutions coarser than 100 km to resolutions finer than 25 km. The main changes in the global energy budget with resolution are a systematic increase in outgoing longwave radiation and decrease in outgoing shortwave radiation due to changes in cloud properties, and a systematic increase in surface latent heat flux; when resolution is increased from 100 to 25 km, the magnitude of the change of those fluxes can be as large as 5 W m−2. Moreover, all but one atmosphere-only model simulate a decrease of the poleward energy transport at higher resolution, mainly explained by a reduction of the equator-to-pole tropospheric temperature gradient. Regarding hydrological processes, our results are the following: (1) there is an increase of global precipitation with increasing resolution in all models (up to 40 × 103 km3 year−1) but the partitioning between land and ocean varies among models; (2) the fraction of total precipitation that falls on land is on average 10% larger at higher resolution in grid point models, but it is smaller at higher resolution in spectral models; (3) grid points models simulate an increase of the fraction of land precipitation due to moisture convergence twice as large as in spectral models; (4) grid point models, which have a better resolved orography, show an increase of orographic precipitation of up to 13 × 103 km3 year−1 which explains most of the change in land precipitation; (5) at the regional scale, precipitation pattern and amplitude are improved with increased resolution due to a better simulated seasonal mean circulation. We discuss our results against several observational estimates of the Earth's energy budget and hydrological cycle and show that they support recent high estimates of global precipitation

Deposition by Glow Discharge Sputtering of Thin Epitaxial Films of I Alloys (AgPd, CuPd, CuRh)

Thin films of CuRh, CuPd, and AgPd were deposited by glow discharge sputtering onto (100) magnesium oxide single crystals. The rhodium and palladium content ranged from 0% to 100% of precious metal and the film thickness was usually between 10 and 100 nm. The composition, epitaxial relationship, crystallinity, and phase diagram were investigated as a function of substrate temperature and target composition. A comparison of the three systems was realized. Conditions of epitaxy were determined for the pure metals and their alloys. The temperature of epitaxy of the alloys, even at very low precious metal concentrations, is close to that of the group VIII elements. The parallel epitaxial relationship between the deposit and the substrate is identical for the three systems, namely (001)[110]dSCOPUS: cp.jinfo:eu-repo/semantics/publishe

What IASI can tell us in the aftermath of the Hunga Tonga exceptional eruption

info:eu-repo/semantics/nonPublishe

Surface segregation study of Ib-VIII single-crystal alloys

info:eu-repo/semantics/publishe

Satellite Observations of Gravity Waves at the Stratospheric Speed Limit from the Hunga-Tonga Hunga Ha'apai Volcanic Eruption

International audienceOn 15th January 2022, a major volcanic eruption occurred between the islands of Hunga Tonga and Hunga Ha’apai (175.4W, 20.5S). Located under only a shallow depth of water, this submarine volcano launched an explosive plume of ash and flash-boiled water up through the ocean upwards into the atmosphere, with an explosive energy comparable to Krakatau in 1883. The explosion generated global-scale atmospheric waves that were detectable from the surface to the edge of space. This single event also sent shockwaves through the global research community, triggering upwards of several thousands of scientific studies. In this presentation, we focus on ultra-fast stratospheric gravity waves generated by the initial explosion that propagated over the entire Pacific region detected by satellite. We analyse brightness temperature perturbations in the 4.3 and 15 micron bands of the AIRS/Aqua, CrIS/Suomi-NPP, CrIS/JPSS-1, IASI/MetOp-B and IASI/MetOp-C instruments, supported by GOES radiance observations. An atmospheric "explosion time" of 04:28:48 UTC is calculated using surface pressure station anomalies and allows us to measure lower-bound propagation speeds of the leading atmospheric waves. Strikingly, we find not only a clear signal of the surface Lamb wave throughout the stratosphere travelling near the sound speed at 318 m/s, but also a leading gravity wave packet travelling at up to 275 m/s, with an apparent vertical depth greater than the depth of the atmosphere. This is, to our knowledge, one of the fastest gravity wave packets ever observed. These results are combined with airglow observations over Hawaii in the lower thermosphere to provide an independent estimate of phase speeds. Finally, analysis of small-scale gravity waves propagating in the ash plume reveal wave periods close to fastest possible oscillation speed near 5 mins. This event triggered gravity waves with speeds, scales and extents that are unprecedented in nearly 20 years of satellite observations, and will likely keep scientists busy for many years to come as we seek to understand the atmospheric response to this unique eruption

Satellite Observations of Gravity Waves at the Stratospheric Speed Limit from the Hunga-Tonga Hunga Ha'apai Volcanic Eruption

International audienceOn 15th January 2022, a major volcanic eruption occurred between the islands of Hunga Tonga and Hunga Ha’apai (175.4W, 20.5S). Located under only a shallow depth of water, this submarine volcano launched an explosive plume of ash and flash-boiled water up through the ocean upwards into the atmosphere, with an explosive energy comparable to Krakatau in 1883. The explosion generated global-scale atmospheric waves that were detectable from the surface to the edge of space. This single event also sent shockwaves through the global research community, triggering upwards of several thousands of scientific studies. In this presentation, we focus on ultra-fast stratospheric gravity waves generated by the initial explosion that propagated over the entire Pacific region detected by satellite. We analyse brightness temperature perturbations in the 4.3 and 15 micron bands of the AIRS/Aqua, CrIS/Suomi-NPP, CrIS/JPSS-1, IASI/MetOp-B and IASI/MetOp-C instruments, supported by GOES radiance observations. An atmospheric "explosion time" of 04:28:48 UTC is calculated using surface pressure station anomalies and allows us to measure lower-bound propagation speeds of the leading atmospheric waves. Strikingly, we find not only a clear signal of the surface Lamb wave throughout the stratosphere travelling near the sound speed at 318 m/s, but also a leading gravity wave packet travelling at up to 275 m/s, with an apparent vertical depth greater than the depth of the atmosphere. This is, to our knowledge, one of the fastest gravity wave packets ever observed. These results are combined with airglow observations over Hawaii in the lower thermosphere to provide an independent estimate of phase speeds. Finally, analysis of small-scale gravity waves propagating in the ash plume reveal wave periods close to fastest possible oscillation speed near 5 mins. This event triggered gravity waves with speeds, scales and extents that are unprecedented in nearly 20 years of satellite observations, and will likely keep scientists busy for many years to come as we seek to understand the atmospheric response to this unique eruption

What IASI can tell about the exceptional Hunga Tonga eruption

info:eu-repo/semantics/nonPublishe

Trends in spectrally resolved OLR from 10 years of IASI measurements

The Earth’s Outgoing Longwave Radiation (OLR) is a key component in the study of climate. As part of the Earth’s radiation budget, it reflects how the Earth-atmosphere system compensates the incoming solar radiation at the top of the atmosphere. At equilibrium, incoming and outgoing radiation compensate each other on average. Any perturbation of this balance through, for example, a variation of the climate drivers (e.g. rise in greenhouse gases concentration) causes a climate response (e.g. surface temperature increase) which brings the radiation budget back to equilibrium. OLR estimates from dedicated broadband instruments are available since the mid-1970s and have considerably improved our understanding of the Earth-atmosphere system and of its long-term changes. However, such instruments only provide an integrated OLR over a broad spectral range and are therefore not well suited for tracking separately the impact of the different parameters affecting the OLR, making it difficult to identify compensating biases and errors in climate models. Better constraints can be obtained from spectrally resolved OLR (i.e. the integrand of broadband OLR, in units of W m-2 (cm-1)-1) derived from infrared hyperspectral sounders. Recently, we developed an algorithm to derive clear-sky spectrally resolved OLR from measurements made by the IASI sounder on board the Metop satellites at the 0.25 cm-1 native spectral sampling of the L1C spectra (Whitburn et al. 2020). It is based on a set of spectrally resolved angular distribution models (ADMs) developed from synthetic spectral for a large selection of scene types associated with different states of the atmosphere and the surface. Here, we present the retrieval algorithm and evaluate how the derived-OLR compares with other known and widely used datasets such as the CERES and the AIRS integrated and spectral OLR. We then analyze the changes in 10 years (2008-2017) of the spectrally resolved OLR (at the 0.25 cm-1 spectral sampling) and we relate them to known changes in greenhouse gases concentrations (CO2, CH4, H2O, …) and climate phenomena activity such as El Niño-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO).info:eu-repo/semantics/nonPublishe

Time evolution of temperature profiles retrieved from 13 years of IASI data using an artificial neural network

info:eu-repo/semantics/nonPublishe

Passage des frontières

En choisissant de consacrer sa thèse à l'apport de la littérature francophone dans la formation des élèves issus d'autres espaces linguistiques et culturels, Luc Collès a opéré un double et spectaculaire passage des frontières : le professeur de langue maternelle devenait professeur de FLE, et l'amateur d'analyses structurales n'avait plus d'yeux désormais que pour la manière dont les différences culturelles modelaient non seulement le langage et la littérature, mais aussi toutes nos relations et toutes les dimensions de l'action humaine. Les cinq parties qui composent cet ouvrage résument bien la diversité du parcours foisonnant de ce jeteur de ponts en mettant en évidence les thèmes majeurs qui l'ont mobilisé au long de sa carrière et à propos desquels il a fait œuvre de fondateur : l'enseignement de la littérature, la didactique du FLE et de l'interculturel, la promotion de la francophonie, la littérature migrante et l'interrogation sur les enjeux de la transmission du fait religieux dans le contexte des sociétés multiculturelles