Cloud-based solutions for distributed climate modeling

ECCO in the cloud - overviewA new, cloud-based framework for climate modeling is introduced allowing to run climate models at the “click of a button”. The framework aims to simplify dissemination of climate models, increase transparency of modeling activities, expand their user base, and facilitate broader research collaboration.NASA Physical Oceanograph

Above-ground biomass and productivity in a rain forest of eastern South America

Abstract: The dynamics of tropical forest woody plants was studied at the Nouragues Field Station, central French Guiana. Stem density, basal area, above-ground biomass and above-ground net primary productivity, including the contribution of litterfall, were estimated from two large permanent census plots of 12 and 10 ha, established on contrasting soil types, and censused twice, first in 1992¿1994, then again in 2000¿2002. Mean stem density was 512 stems ha¿1 and basal area, 30m2 ha¿1. Stem mortality rate ranged between 1.51% and 2.06% y¿1. In both plots, stem density decreased over the study period. Using a correlation between wood density and wood hardness directly measured by a Pilodyn wood tester,we found that the mean wood densitywas 0.63 g cm¿3, 12% smaller than the mean of wood density estimated from the literature values for the species occurring in our plot. Above-ground biomass ranged from 356 to 398Mgha¿1 (oven-dry mass), and it increased over the census period. Leaf biomass was 6.47Mg ha¿1. Our total estimate of aboveground net primary productivity was 8.81 MgC ha¿1 y¿1 (in carbon units), not accounting for loss to herbivory, branchfalls, or biogenic volatile organic compounds, whichmay altogether account for an additional 1MgC ha¿1 y¿1. Coarse wood productivity (stem growth plus recruitment) contributed to 4.16 MgC ha¿1 y¿1. Litterfall contributed to 4.65MgC ha¿1 y¿1 with 3.16 MgC ha¿1 y¿1 due to leaves, 1.10 MgC ha¿1 y¿1 to twigs, and 0.39MgC ha¿1 y¿1 to fruits and flowers. The increase in above-ground biomass for both trees and lianas is consistentwith the hypothesis of a shift in the functioning of Amazonian rain forests driven by environmental changes, although alternative hypotheses such as a recovery from past disturbances cannot be ruled out at our site, as suggested by the observed decrease in stem density. Key Words: above-ground biomass, carbon, French Guiana, net primary productivity, tropical fores

Involvement of a single periplasmic hydrogenase for both hydrogen uptake and production in some Desulfovibrio species

Au cours de cette étude, nous avons montré que plusieurs bactéries sulfato-réductrices possédant un nombre différent de gènes codant pour des hydrogénases, oxydent le lactate en absence de sulfate lorsqu'elles sont en coculture avec #Methanospirillum hungatei. L'efficacité du transfert d'hydrogène avec la bactérie méthanogène n'est pas corrélée avec le nombre de gènes codant pour l'hydrogénase chez ces bactéries sulfato-réductrices. #Desulfovibrio vulgaris Groningen, qui possède uniquement le gène de l'hydrogénase à nickel-fer (hydrogénase [NiFe]), oxyde l'hydrogène en présence de sulfate et produit de l'hydrogène au cours de la fermentation du pyruvate. L'hydrogénase de #D. vulgaris Groningen a été purifiée et caractérisée. Son poids moléculaire est de 87 kDA et elle est constituée de deux sous-unités différentes (60 et 28 kDa). L'hydrogénase de cette bactérie contient 10,6 atomes de fer, 0,9 atome de nickel et 12 atomes de soufre par molécule et son spectre d'absorption est caractéristique d'une protéine à centre fer-soufre. Les activités catalytiques de consommation et production d'hydrogène sont de 332 et 230 unités/mg de protéine, respectivement. Les cellules de #D. vulgarie Groningen contiennent exclusivement l'hydrogénase [NiFe] quelles que soient les conditions de croissance, ainsi que l'ont montré des études biochimiques et immunologiques. L'immunocytolocalisation de cryosections ultrafines de cellules ayant poussé sur différents milieux indique que l'hydrogénase [NiFe] est localisée dans l'espace périplasmique, le marquage étant plus important sur les cellules cultivées sur H2 et sulfate ou pyruvate seul que sur celles cultivées sur lactate et sulfate. Les résultats nous permettent de conclure que #D. vulgaris Groningen contient une seule hydrogénase de type [NiFe] située dans l'espace périplasmique tel que cela a été décrit chez #D. gigas. (Résumé d'auteur

Timescales and regions of the sensitivity of Atlantic meridional volume and heat transport: Toward observing system design

A dual (adjoint) model is used to explore elements of the oceanic state influencing the meridional volume and heat transports (MVT and MHT) in the sub-tropical North Atlantic so as to understand their variability and to provide the elements of useful observational program design. Focus is on the effect of temperature (and salinity) perturbations. On short timescales (months), as expected, the greatest sensitivities are to local disturbances, but as the timescales extend back to a decade and longer, the region of influence expands to occupy much of the Atlantic basin and significant areas of the global ocean, although the influence of any specific point or small area tends to be quite weak. The propagation of information in the dual solution is a clear manifestation of oceanic teleconnections. It takes place through identifiable “dual” Kelvin, Rossby, and continental shelf-waves with an interpretable physics, in particular in terms of dual expressions of barotropic and baroclinic adjustment processes. Among the notable features are the relatively fast timescales of influence (albeit weak in amplitude) between 26°N and the tropical Pacific and Indian Ocean, the absence of dominance of the sub-polar North Atlantic, significant connections to the Agulhas leakage region in the southeast Atlantic on timescales of 5–10 years, and the marked sensitivity propagation of Doppler-shifted Rossby waves in the Southern Ocean on timescales of a decade and beyond. Regional, as well as time-dependent, differences between MVT and MHT sensitivities highlight the lack of a simple correspondence between their variability. Some implications for observing systems for the purpose of climate science are discussed.National Oceanographic Partnership Program (U.S.) (‘‘Estimating the Circulation and Climate of the Ocean’’ (ECCO) and the ‘‘Atlantic MOC Observing System Studies Using Adjoint Models’’ projects)National Science Foundation (U.S.) (NSF Collaboration in Mathematics and Geoscience (CMG) project ‘‘Uncertainty Quanti- fication in Geophysical State Estimation’’

Gain properties of dye-doped polymer thin films

Hybrid pumping appears as a promising compromise in order to reach the much coveted goal of an electrically pumped organic laser. In such configuration the organic material is optically pumped by an electrically pumped inorganic device on chip. This engineering solution requires therefore an optimization of the organic gain medium under optical pumping. Here, we report a detailed study of the gain features of dye-doped polymer thin films. In particular we introduce the gain efficiency $K$, in order to facilitate comparison between different materials and experimental conditions. The gain efficiency was measured with various setups (pump-probe amplification, variable stripe length method, laser thresholds) in order to study several factors which modify the actual gain of a layer, namely the confinement factor, the pump polarization, the molecular anisotropy, and the re-absorption. For instance, for a 600 nm thick 5 wt\% DCM doped PMMA layer, the different experimental approaches give a consistent value $K\simeq$ 80 cm.MW$^{-1}$. On the contrary, the usual model predicting the gain from the characteristics of the material leads to an overestimation by two orders of magnitude, which raises a serious problem in the design of actual devices. In this context, we demonstrate the feasibility to infer the gain efficiency from the laser threshold of well-calibrated devices. Besides, temporal measurements at the picosecond scale were carried out to support the analysis.Comment: 15 pages, 17 figure

ESR study of the single-ion anisotropy in the pyrochlore antiferromagnet Gd2Sn2O7

Single-ion anisotropy is of importance for the magnetic ordering of the frustrated pyrochlore antiferromagnets Gd2Ti2O7 and Gd2Sn2O7. The anisotropy parameters for the Gd2Sn2O7 were measured using the electron spin resonance (ESR) technique. The anisotropy was found to be of the easy plane type, with the main constant D=140mK. This value is 35% smaller than the value of the corresponding anisotropy constant in the related compound Gd2Ti2O7.Comment: 8 pages, 3 figure

Air-Sea Interactions in a High-Resolution Ocean-Atmosphere Simulation

During the past few years the Goddard Earth Observing System (GEOS) and Massachusetts Institute of Technology (MIT) modeling groups have produced, respectively, global atmosphere-only and ocean-only simulations with km-scale grid spacing. These simulations have proved invaluable for process studies and for the development of satellite and in-situ sampling strategies. Nevertheless, a key limitation of these "nature" simulations is the lack of interaction between the ocean and the atmosphere, which limits their usefulness for studying air-sea interactions and for designing observing missions to study these interactions. We present here results from a coupled GEOS-MIT "nature run" simulation, wherein we have coupled a cubed-sphere-720 (~ 1/8) configuration of the GEOS atmosphere to a lat-lon-cap-1080 (~ 1/12) configuration of the MIT ocean. We compare near-surface diagnostics of this fully coupled ocean-atmosphere simulation to equivalent atmosphere-only and ocean-only simulations. A particular focus of the comparisons is the coupled versus uncoupled differences in interactions between Sea Surface Temperature (SST) and ocean surface wind. We discuss, in particular, a several-day mode of temporal variability in the SST-wind cycle and how it is represented in the different model simulations and in observationally-based products. A mechanism for the cycle, which is driven by SST-wind feedback, is proposed