Troposphere – Stratosphere

Transient Luminous Events

Red sprites, blue jets, and elves
NASA and adapted from Carlos Moralles (AeroVironment and Tom Nelson (FMA)

As part of the TARANIS mission, we are interested in the production of chemical species related to electrical discharges. The study carried out allows the development of a model of electrical discharge propagation in the stratosphere, coupled with the MIPLASMO chemistry model of LPC2E extended to plasma chemistry of excited species (including about 700 chemistry-plasma reactions). The first results made it possible to evaluate the NOx production associated with a Blue Jet or Gigantic Jet landfill. Thus the results of the MIPLASMO electric discharge model were used as input for a feasibility study of the HALESIS instrument (High Altitudes Luminous Events Studied) in collaboration with LATMOS

Biomass Burning

The objective is to study the physico-chemical characteristics of biomass fires, from their emission sources and during their transport at high altitude, as well as their impacts on air quality and climate.

Chemistry at the heart of the plume

The objective is to better characterize and quantify fire emissions and plume chemistry. These poorly known data are a major source of uncertainty in chemistry-climate models for fire impacts. These studies are carried out with the help of measurements from SPECIES and electrochemical mini-sensors coupled with modelisation.

Impact of biomass fires on aerosol content

The study of the role of biomass fires from Africa and South-East Asia on the aerosol content of UTLS over the Indian Ocean and in the Asian monsoon high pressure system is conducted respectively via balloon measurements with LOAC from St-Denis-de-la-Réunion (as part of projects of LEFE-CHAT SATORI, Université de la Réunion and Labex VOLTAIRE) and from India (BATAL and Labex VOLTAIRE projects). Sporadic episodes of intense fires at mid-latitudes (especially in North America) are also likely to impact the stratospheric aerosol content at the hemispheric scale with a magnitude comparable to that of moderate volcanic eruptions and quantifiable by LOAC in situ observations and spatial measurements (CALIOP/Calipso, OMPS, SAGEIII). The contribution of these different sources and the mechanisms of transport of aerosols and precursors on a global scale are also investigated using the WACCM Chemistry-Climate model.

– Study of the transport of a plume

The exploitation of the results related to the DACCIWA-APSOWA and SHIVA airborne campaigns (FP7) with regard to the chemistry and transport of biomass fire plumes in the equatorial region is carried out using the regional FLEXPART and WRF-CHEM models. The main objective is to understand the evolution of the chemical composition of the plume over time and atmospheric transport, and its regional impact on air quality and climate.

 

  • Chimie au cœur du panache 
    L’objectif est de mieux caractériser et quantifier les émissions des feux et la chimie du panache. Ces données mal connues sont une grande source d’incertitude dans les modèles chimie-climat d’impacts des feux. Ces études sont menées avec l’aide de mesure provenant du SPIRIT puis du SPECIES ou des mini-capteur électrochimique couplées à la modalisation.

 

  • Impact des feux de biomasse sur le contenu en aérosols
    Feux de biomasse en région équatoriale pendant SHIVA par le hublot du falcon-20 et par le satellite de la NOAA

    L’étude du rôle des feux de biomasse issus d’Afrique et de l’Asie du sud-est, sur le contenu en aérosols de l’UTLS respectivement au-dessus de l’Océan Indien et dans l’anticyclone de la mousson asiatique, est conduite via des mesures sous ballons avec LOAC depuis St-Denis-de-la-Réunion (cadre de projets du LEFE-CHAT SATORI, de l’Université de la Réunion et du Labex VOLTAIRE) et depuis l’Inde (projet BATAL, Labex VOLTAIRE). La contribution de ces différentes sources et les mécanismes de transport des aérosols et précurseurs à l’échelle globale sont également investigués au moyen du modèle de Chimie-Climat WACCM.

Volcanoes

The objective is to better characterize and quantify volcanic emissions (gases and aerosols) and their contribution to the chemical and particulate composition of the troposphere and stratosphere. The research program is a continuum of studies of mechanisms from subsurface processes, reactivity within the volcanic plume, characterization of emission fluxes and the impact of these emissions on the chemical and particulate composition of the troposphere and stratosphere. This continuum is based on laboratory measurements, in situ measurements, remote measurements, as well as modelling tools at different scales, ranging from process models to Chemistry-Climate models.

– Volcanoes degassing mechanism and high temperature chemistry

The objective is to be able to predict the evolution of volcanic activity from emission monitoring and conversely to predict emissions from information on the type of volcanic activity. Within the frame of the Equipex PLANEX (2012-2019) led by ISTO (our OSUC partner), measurements of gases emitted by magma subjected to high temperatures (> 1000°C) and pressures (> 1000 bar), are likely to give information on sub-surface processes and high temperature chemistry during the initial mixing between volcanic gases and ambient air. These processes are poorly understood, particularly how they modulate halogen emissions.

– Reactivity and chemistry of processes within the volcanic plume

Our goal is to understand volcanic emissions and their rapid chemical evolution in the volcanic plume, first at high temperatures near-to-the-source, and then at low-temperatures as the plume disperses into the troposphere. We are interested in particular in multiphase plume atmospheric chemistry involving halogens, that causes ozone destruction in the downwind plume and may lead to mercury deposition. The fate of halogenated compounds and aerosols in plumes is characterized by in-situ measurements made using small sensors on the ground, and on moving platforms such as drone or balloon. The instruments developed and deployed in volcanic plumes include electrochemical mini-sensors for SO2, HCl, H2S and other gases and optical particle counters e.g. LOAC.

 

Colonnes de SO2 observées par OMI et simulées par CCATT-BRAMS (01/2005) lors du dégazage intense de l’Ambrym (Vanuatu) .

Impact of volcanic emissions on the climate system

 

Numerical modelling is an essential tool to quantify the regional and global impacts of the highly reactive halogen-aerosols-SO2 emissions from volcanoes. Our suite of models includes: high temperature chemistry (HSC, ChemKin in collaboration with OSUC partner ICARE), 0D and 1D plume chemistry (PlumeChem), tropospheric regional-scale (WRF-CHEM) and global chemistry-climate (WACCM-CARMA with microphysics) models.  These process models will make it possible to interpret campaign measurements and identify key processes in order to fill in the gaps from local scales to the regional and global scales, and assess impacts of the volcanic emissions.

– IMAGETNA: Volcano Flux

Diminution de l’ozone (en %) due aux émissions de l’Ambrym en janvier 2005 calculée par le modèle CCATT-BRAMS.

Knowledge of the emission fluxes of chemical species emitted by volcanoes and their variability is necessary to assess the contribution of volcanoes to the chemical composition of the atmosphere. The objective is to be able to study the emission fluxes of several typical species such as SO2, CO2, HNO3, using innovative hyperspectral infrared imaging technology.

For more information: Excerpt from the film “Scanning the ETNA, in great depth, an unprecedented expedition”. For the OSUC produced by 4scienceprod http://dai.ly/x50bjo8 – IMAGETNA or Volcanoes-Flow