Energy Dependence of the Nernst-Ettingshausen Effect Induced By Pulsed Laser Light in Bismuth Films

The behavior with the irradiation energy and with the magnetic field of the thermomagnetic response induced by laser pulses in 5.5-μm Bi films at room temperature is reported in this paper. The Nernst-Ettingshausen coefficient at an applied magnetic field of 1 T is estimated: QNE≃1.0×10-5 V/T K. A good agreement is found when these results are compared with those reported earlier in polycrystalline bulk samples obtained by a conventional method. This supports the reliability of the pulsed laser technique in the measurement of weak transport effects and indicates that the optically pumped carriers hardly influence the transport properties of bismuth

Impact of the sea surface temperature forcing on hindcasts of Madden-Julian Oscillation events using the ECMWF model

This paper explores the sensitivity of hindcasts of the Madden Julian Oscillation (MJO) to the use of different sea surface temperture (SST) products as lower boundary conditions in the European Centre for Medium-range Weather Forecasts (ECMWF) atmospheric model. Three sets of monthly hindcast experiments are conducted, starting from initial conditions from the ERA interim reanalysis. First, as a reference, the atmosphere is forced by the SST used to produce ERA interim. In the second and third experiments, the SST is switched to the OSTIA (Operational Sea Surface Temperature and Sea-Ice Analysis) and the AVHRR-only (Advanced Very High Resolution Radiometer) reanalyses, respectively. Tests on the temporal resolution of the SST show that monthly fields are not optimal, while weekly and daily resolutions provide similar MJO scores. When using either OSTIA or AVHRR, the propagation of the MJO is degraded and the resulting scores are lower than in the reference experiment. Further experiments show that this loss of skill cannot be attributed to either the difference in mean state or temporal variability between the SST products. Additional diagnostics show that the phase relationship between either OSTIA or AVHRR SST and the MJO convection is distorted with respect to satellite observations and the ERA interim reanalysis. This distortion is expected to impact the MJO hindcasts, leading to a relative loss of forecast skill. A realistic representation of ocean–atmosphere interactions is thus needed for MJO hindcasts, but not all SST products – though accurate for other purposes – fulfill this requirement

Monte Carlo simulation of a liquid scintillation counter using geant4 code

This paper presents a first approach to the use of the GEANT4 Monte Carlo (MC) technique in liquid scintil-lation counting (LSC) applied to measurements in radiological laboratories. The GEANT4 software was developed by RD44,a worldwide collaboration of national institutes, laboratories, and large high-energy physics experiments. GEANT4 is a pub-lic software package composed of tools that can be used to accurately simulate the passage of particles through matter. TheGEANT4 catalog of processes at optical wavelengths includes refraction and reflection at medium boundaries, bulk absorp-tion, and Rayleigh scattering. Processes that produce optical photons include the Cherenkov effect, transition radiation, andscintillation.The simulated setup includes a vial containing the scintillation cocktail in between 2 opposite photomultipliers tubes (PMTs)working in sum-coincidence mode. The decay of several beta emitters (such as 14C and 3H) can be simulated, as well as alphaor EC emitters. Additionally, significant information could be obtained, such as the energy deposited by decay into the scin-tillation cocktail or the light output generated into the scintillation cocktail. GEANT4 is a useful tool for efficiency calibra-tion, stopping power calculations, or wall effect studies for different scintillation cocktails and geometries.Junta de Andalucia Excellence Project RNM-0256

Measurement of Pu and U isotopes on the 1 MV AMS system at the Centro Nacional de Aceleradores

In the last decade, compact AMS systems have demonstrated their potential to measure actinides (236U, 239,240,244Pu, 237Np). With an appropriate detection system, kinematic filters with enough mass resolution, and a simple chemical procedure, the determination of plutonium isotopes and 237Np at environmental levels is currently possible with this new generation of facilities with even better performance than with conventional AMS systems. However, the measurement of 236U (T1/2=23.4 My), produced by neutron capture on 235U, is still a challenge, due to the interference caused by 235U and 238U. In this work, we will explore the possibilities that the 1 MV AMS system at the CNA offers for the measurement of uranium isotopes at environmental levels, in terms of detection limit, efficiency, and precision. Considering the very promising 239Pu/238U mass suppression factor achieved with our system, of about 10-9, a limiting 236U/238U atomic ratio of about 10-11 was expected, approaching the levels expected in natural uranium. However, to date, only the 10-9 level has been obtained, possibly due to the lack of an appropriate uranium material. Currently, different natural uranium materials are being studied, in order to elucidate the origin of the interference. On the other hand, we will discuss the status of the plutonium measurements at our facility, based on the experience we have accumulated in recent years from the analysis of different matrixes over a wide range of plutonium concentrations

Fourth clivar workshop on the evaluation of ENSO processes in climate models: ENSO in a changing climate

n/aThe organizers acknowledge the generous support of the World Climate Research Programme/CLIVAR, the Centre National de la Recherche Scientifique–Institut National des Sciences de l’Univers (CNRS-INSU), the LabEx L-IPSL, and Sorbonne Universités and wish to thank Lei Han, from the International CLIVAR Global Project Office in Qingdao, China, for his invaluable help in organizing this workshop

ENSEMBLES: a new multi-model ensemble for seasonal-to-annual predictions: Skill and progress beyond DEMETER in forecasting tropical Pacific SSTs

A new 46-year hindcast dataset for seasonal-to-annual ensemble predictions has been created using a multi-model ensemble of 5 state-of-the-art coupled atmosphere-ocean circulation models. The multi-model outperforms any of the single-models in forecasting tropical Pacific SSTs because of reduced RMS errors and enhanced ensemble dispersion at all lead-times. Systematic errors are considerably reduced over the previous generation (DEMETER). Probabilistic skill scores show higher skill for the new multi-model ensemble than for DEMETER in the 4–6 month forecast range. However, substantially improved models would be required to achieve strongly statistical significant skill increases. The combination of ENSEMBLES and DEMETER into a grand multi-model ensemble does not improve the forecast skill further. Annual-range hindcasts show anomaly correlation skill of ∼0.5 up to 14 months ahead. A wide range of output from the multi-model simulations is becoming publicly available and the international community is invited to explore the full scientific potential of these data

Everything Hits at Once: How Remote Rainfall Matters for the Prediction of the 2021 North American Heat Wave

In June 2021, Western North America experienced an intense heat wave with unprecedented temperatures and far-reaching socio-economic consequences. Anomalous rainfall in the West Pacific triggers a cascade of weather events across the Pacific, which build up a high-amplitude ridge over Canada and ultimately lead to the heat wave. We show that the response of the jet stream to diabatically enhanced ascending motion in extratropical cyclones represents a predictability barrier with regard to the heat wave magnitude. Therefore, probabilistic weather forecasts are only able to predict the extremity of the heat wave once the complex cascade of weather events is captured. Our results highlight the key role of the sequence of individual weather events in limiting the predictability of this extreme event. We therefore conclude that it is not sufficient to consider such rare events in isolation but it is essential to account for the whole cascade over different spatiotemporal scales