Numerical experiments using mesonh/forefire coupled Atmospheric-fire model

International audienceIn this study we attempt to couple the MesoNH atmospheric model in its large eddy simulation configuration with a fire contour model, ForeFire. Coupling is performed at each atmospheric time step, with the fire propagation model inputting the wind fields and outputting heat and vapour fluxes to the atmospheric model. ForeFire model is a Lagrangian front tracking model that runs at a typical front resolution of 1 meter. If the approach is similar to other successful attempts of fire-atmosphere coupled models, the use of MesoNH and ForeFire implied the development of an original coupling method. Fluxes outputted to the atmospheric models are integrated using polygon clipping method between the fire front position and the atmospheric mesh. Another originality of the approach is the fire rate of spread model that integrates wind effect by calculating the flame tilt. This reduced physical model is based on the radiating panel hypothesis. A set of idealized simulation are presented to illustrate the coupled effects between fire and the atmosphere. Preliminary results show that the coupled model is able to reproduce results that are comparable to other existing numerical experiments with a relatively small computational cost (one hour for a typical idealized case on a 200 GFlops capable computer). MesoNH serves as a research model for the meteorological systems in France and Europe, and is well integrated within the operational tool chain. Future validation scenarios will be performed on nested simulations of real large wildfires

Transport and scavenging of soluble gases in a deep convective cloud

A one-dimensional entraining/detraining plume model is used to examine the transport and scavenging of soluble gases in tropical deep convection. The model is applied to a continental system observed over Brazil during the Trace and Atmospheric Chemistry Near the Equator-Atlantic (TRACE-A) TRACE-A aircraft campaign with outflows extending from 7 to 16 km altitude. Six gases are simulated: CO (inert tracer), CH3OOH, CH2O, H2O2, HNO3, and SO2. Observed (simulated) convective enhancement factors (CEF) at 7–12 km altitude, representing the ratios of postconvective to preconvective mixing ratios, are 2.4 (1.9) for CO, 11 (9.5) for CH3OOH, 2.9 (3.1) for CH2O, 1.9 (1.2) for H2O2, and 0.8 (0.4) for HNO3. Simulated scavenging efficiencies in the convective column are 5% for CH3OOH, 23% for CH2O, 66% for H2O2, 77% for HNO3, and 28% for SO2. The large CEF for CH3OOH reflects its low solubility and its boundary layer enrichment relative to the upper troposphere. The Henry's law constant for CH2O puts it at the threshold for efficient scavenging. Scavenging of SO2 is limited by the rate of aqueous phase reaction with H2O2, as H2O2 is itself efficiently scavenged by Henry's law equilibrium; efficient scavenging of SO2 requires unusually high cloud water pH (pH>6) to enable fast aqueous phase oxidation by O3. Both HNO3 and H2O2 are efficiently scavenged in the lower (warm) part of the cloud, but H2O2 is released as the cloud freezes due to low retention efficiency during riming. Significant scavenging of H2O2 still takes place by cocondensation with ice in the glaciated cloud but is less efficient than in the warm cloud. Inefficient scavenging of H2O2 in glaciated clouds may explain the observation, in TRACE-A and elsewhere, that H2O2 is enhanced in deep convective outflows while HNO3 is depleted. Model results indicate little direct transfer of air from the boundary layer to the cloud anvil in the convective plume, because of low-level detrainment in the warm cloud and high-level entrainment in the glaciated cloud. We find instead a convective ladder effect where midlevel outflow during the growing phase of the storm is reentrained into the convective plume as the storm matures.Engineering and Applied Science

Spin-Exchange optical pumping in a van

International audienceThe advent of spin-hyperpolarization techniques designed to overcome the sensitivity issue of nuclear magnetic resonance owing to polarization transfer from more ordered systems has recently raised great enthusiasm. However, the out-of-equilibrium character of the polarization requires a close proximity between the area of production and the site of use. We present here a mobile spin-exchange optical pumping setup that enables production of laser-polarized noble gases in a standalone mode, in close proximity to hospitals or research laboratories. Only compressed air and mains power need to be supplied by the host laborator

Thank you Earth's Future reviewers in 2019

AGU's open‐access transdisciplinary science journal Earth's Future continued to grow in size and stature in 2019, with ~40% acceptance rate for ~280 new submissions that were evaluated by a similar number of external reviewers; their names are listed here

Dynamiques des systèmes de culture du bassin de la Seine : mise en évidence d'une intensification des pratiques culturales au cours des trois dernières décennies

Dans le cadre du programme PIREN-Seine, la participation de l'Unité de Recherche INRA de Mirecourt à l'axe de recherche "Territoire, carbone, azote, changements globaux" consiste à comprendre les dynamiques des activités agricoles sur l'ensemble du bassin de la Seine, afin de mettre en évidence leurs impacts sur la dégradation de l'environnement. Pour analyser ces dynamiques et leur répartition spatiale au sein du bassin, nous développons une modélisation stochastique de descripteurs choisis à différents niveaux d'organisation des activités agricoles, qui sont le système de production, l'assolement, la succession de cultures

Thank you to Earth’s Future Reviewers in 2018

Peer review is one of the most important professional activities for scientists, because it ensures the quality of science that is shared with colleagues and with the world. Reviewers generously donate their time and effort with the knowledge that are key to sustaining scientific rigor. Earth’s Future is fortunate to engage excellent reviewers that support the growth and reputation of our young journal as it receives and publishes highâ quality, highâ impact articles. We recognize the time, effort, and dedication that each review requires and extend a heartfelt thank you to all of our reviewers. Last year, Earth’s Future received 395 peer reviews from 297 individuals that are listed below; reviewers who contributed three or more reviews are recognized in italics. Our acceptance rate remains steady at ~40%, while the number of submissions continue to increase at a healthy pace (269 in 2018).Thank you all for your important and valued contributions to our science in 2018.Key PointsLast year, Earth’s Future received 395 peer reviews from 297 individualsThank you all for your important and valued contributions to our science in 2018Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/150554/1/eft2549_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/150554/2/eft2549.pd

CarrotAge, a software for mining land-use data

Colloque avec actes et comité de lecture. internationale.International audienceWe have developed a knowledge discovery system based on high-order hidden Markov models for analysing spatio-temporal data bases. This system, named \carottage, takes as input an array of discrete data -- the rows represent the spatial sites and the columns the time slots -- and builds a partition together with its \aposteriori probability. \carottage has been developed for studying the cropping patterns of a territory. It uses therefore an agricultural french database, named \teruti, which records every year the land-use category of a set of sites regularly spaced. The results of \carottage are interpreted by agronomists and used in research works linking agricultural land use and water management. Moreover, \carottage can be used to find out and study crop sequencies in large territories, that is a main question for agricultural and environmental research

CarrotAge, un logiciel pour la fouille de données agricoles

Colloque avec actes et comité de lecture. nationale.National audienceCe texte présente le logiciel CarottAge qui a été développé pour aider à l'analyse de bases de données agricoles. CarottAge utilise les modèles de Markov cachés pour segmenter des séquences temporelles ou spatiales en zones homogènes et interprétables. Ce logiciel a été mis en oeuvre dans différents projets de recherche qui concernent des problématiques agro-environnementales. Nous présentons deux exemples, l'un en Midi-Pyrénées, l'autre dans le bassin de la Seine

On the relative role of convection, chemistry, and transport over the South Pacific Convergence Zone during PEM-Tropics B: A case study

A mesoscale 3D model (Meso‐NH) is used to assess the relative importance of convection (transport and scavenging), chemistry, and advection in the vertical redistribution of HOx and their precursors in the upper tropical troposphere. The study is focused on marine deep convection over the South Pacific Convergence Zone (SPCZ) during the PEM‐Tropics B Flight 10 aircraft mission. The model reproduces well the HOx mixing ratios. Vertical variations and the contrast between north and south of the SPCZ for O3 are captured. Convection uplifted O3‐poor air at higher altitude, creating a minimum in the 9–12 km region, in both modeled and observed profiles. The model captured 60% of the observed HCHO variance but fails to reproduce a peak of HCHO mixing ratio at 300 hPa sampled during the northern spirals. Simulated HCHO mixing ratios underestimate observations in the marine boundary layer. In the model, convection is not an efficient process to increase upper tropospheric HCHO, and HCHO is unlikely to serve as a primary source of HOx. Convection plays an important role in the vertical distribution of CH3OOH with efficient vertical transport from the boundary layer to the 10–15 km region where it can act as a primary source of HOx. The SPCZ region acts as a barrier to mixing of tropical and subtropical air at the surface and at high altitudes (above 250 hPa). The 400–270 hPa region over the convergence zone was more permeable, allowing subtropical air masses from the Southern Hemisphere to mix with tropical air from NE of the SPCZ and to be entrained in the SPCZ‐related convection. In this altitude range, exchange of subtropical and tropical air also occurs via airflow, bypassing the convective region SW and proceeding toward the north of the SPCZ