Concernant plus particulièrement les intérêts de la communauté Francaise impliquée dans le volet régional (INRA – Bordeaux, LSCE, CNRM, CESBIO), les points de recherche concernent :

La compréhension des échanges de CO2 entre la Couche Limite Atmosphérique et la surface de l’échelle locale jusqu’à l’échelle régionale.
Actuellement cette voie de recherche a été peu approfondie et est absolument nécessaire pour établir un lien entre les observations locales des flux de CO2 (réseau de surface Euroflux, dont 2 sites de mesures sur la forêt des Landes tenus par l’INRA) et les inversions des flux de surface à partir des modèles atmosphériques globaux (LSCE avec LMD-Z) portant sur de grandes mailles (quelques centaines de km) et sur des échelles de temps mensuelles. Comprendre la variabilité des concentrations de CO2 à fine échelle d’espace (2 km) et de temps (l’heure) est de première importance pour une quantification précise des échanges aux interfaces (surface et entraînement au sommet de la CLA) et par advection.

Le développement d’une modélisation à mésoéchelle du cycle du carbone dans le modèle de recherche communautaire MésoNH en liaison avec la modélisation grande échelle développée au LSCE devant permettre une meilleure initialisation et la prise en compte de l’advection à grande échelle dans le domaine régional. Il s’agit d’un point capital pour analyser le poids relatifs des facteurs régionaux et d’échelle synoptique. Par ailleurs, ce projet bénéficiera du développement en cours d’une assimilation à mésoéchelle (projet Arome du CNRM) qui permettra de ré analyser les situations de CarboEurope, en particulier d’assimiler les observations thermodynamiques in-situ (radio sondages, mesures aéroportées) ainsi que le développements d’une assimilation des concentration du CO/CO2 atmosphérique en liaison avec l’Université d’Amsterdam.

Le développement d’un dispositif expérimental basé sur des flux de surface pour les types de végétation représentatifs du Sud Ouest avec le ciblage de 2 zones particulières :

  • la forêt Landaise caractérisée par un vaste écosystème régulièrement soumis aux advections océaniques
  • la zone Toulousaine plus continentale et caractérisée par un parcellaire agricole.

Le dispositif expérimental est organisés autour d’une dizaine de sites de flux (forêt des Landes, vigne, prairie, grande cultures de maïs et blé), 2 tours élevées de mesure du CO2, un site de radiosondage (CNRM), 2 profileurs (CNRM, Uni. Amsterdam), et 4 avions (le Piper Aztec de Météo-France et 3 Sky Arrow de IBIMET-Italie- Franco Miglietta) permettant d’estimer le bilan régional du CO2 dans la CLA. Du point de vue des opérations aéroportées, le projet consiste à utiliser le Piper Aztec pour des vols d’encadrement de la zone, dans et au-dessus de la CLA pour estimer le transport du CO2 et 3 Sky Arrow spécialement équipés pour les mesures turbulentes pour estimer les flux à différents niveaux (possibilité de voler à très basse altitude) suivant différentes stratégies (vols lagrangiens en particulier suivant les enseignements de l’expérience COCA qui s’est déroulé dans les Landes en juillet 2002, Schmitgen et al. 2004 et de l’expérience RECAB – Hollande 2002).

Workpackage

Activity 3.1 Experiment planning, data consolidation and data management

Objectives (5 yr plan)

  • 3.1.1 To collect existing main driving climate, weather, soil and land use characteristics of the area.
  • 3.1.2 To produce a 2 km resolution database of fossil fuel emission for the area.
  • 3.1.3 To produce a geo-referenced set of forest growth and land use data since 1980.
  • 3.1.4 To optimise flight and deployment patterns for the experimental aircraft and ground based systems using a high-resolution modelling framework.
  • 3.1.5 To develop and maintain an easily accessible system for data entry, storage and retrieval for all regional modelling efforts.
  • 3.1.6 To compile, check, store and make available the data of the Regional Experiment Component.

Outline of work plan

Tasks 3.1.1 : The main purpose of this task is to provide estimates of the carbon balance of the region using all available data and atmospheric model information. It will involve inventories of existing data (Obj 3.1.1), a new assessment at high resolution (2 km) of fossil fuel emissions of the area of the experiment.

Task 3.1.2 : For the slow cycle, we will use the 8 km resolution downscaled weather information that is available at CNRM and will be extended for use in biogeochemical models. These models will be calibrated with flux data for the main land use types and then run for a 20-year period. The required input data on land use history and management is obtained in WP1. We intend to use the MesoNH model, which will be extended to carry CO 2 in the simulation.

Task 3.1.3 : For the fast cycle we will use a data assimilation system at mesoscale that mirrors the system developed for the large scale (Camels and Continental Integration Component). We will mainly use the French Arome system developed at CNRM for this purpose and extend it to carry CO 2 in the assimilation procedure.

Task 3.1.4 Operation of data centre for atmosphere data :

The data base of the regional experiment will primarily be based at CNRM. The Data Centre of the regional component receives, checks and stores the data of the component, delivers meta-data to the Central Database and creates links for data access with the Central Database. The regioanl component has assigned Dr. Noilhan of CNRM as Data Centre manager. It will contain links to the RECAB database and consolidated datasets of the RECAB campaigns. It will contain in an easily accessible form all the data the reanalysis of the RECAB campaigns, main driving climate, weather, soil and land use characteristics of the area of the Regional experiment, the 2 km resolution data of fossil fuel emission for the area and a geo-referenced set of forest growth and land use data since 1980. It will contain all the experimental data collected during the experiment (aircraft data, meteorological data and surface observations and remote sensing).

Activity 3.2 Surface flux and aircraft flux measurement

Objectives (5 yr plan)

  • 3.2.1 To take measurements of CO 2 fluxes and energy balance above the main vegetation types in the region during the five year period and during the intensive observation period.
  • 3.2.2 To perform regular measurements of the fluxes of heat, water vapour, CO 2 and momentum with a low flying research aircraft (Sky Arrow).
  • 3.2.3 To measure the city emissions of Bordeaux and Toulouse at selected periods.

Outline of work plan

Task 3.2.1 : Continuous tower-based measurements. Measurements are taken along the most dominant land cover types in the experimental domain (see detailed 18 month plan) by INRA and CNRM and Alterra additional during the intensive period.

Task 3.2.2 : During the test campaign IBIMET and ISAFOM will fly their Sky arrow in the domain to test the feasibility and produce test data for modelling development as well as producing high resolution visible RS images of the area around tower location and selected transects.

Task 3.2.3 : Durind the intensive campaigns Alterra will bring in an additional Sky Arrow for flux measurements.

Activity 3.3 Scalar concentration measurements from tall towers and aircraft

Objectives (5 yr plan)

  • 3.3.1 To take high precision measurements of CO 2 concentrations and 14C at one to two tall towers at the in- and outflow of the domain.
  • 3.3.2 To perform regular flights with small aircraft to sample the boundary evolution of CO 2 concentrations and 13C.
  • 3.3.3 To perform at fixed locations continuous measurements of windspeed and temperature in the boundary layer with a profiling system.
  • 3.3.4 To perform twice daily radio soundings at a regular radio sounding site in Bordeaux , augmented with an intensive campaign in the summer of 2005 where bi-hourly releases will track the evolution of the boundary layer.

Outline of work plan

Task 3.3.1 : Tall tower-based scalar concentration measurements. The installation of the two towers is detailed in the 18 month workplan. At the inflow and outflow positions of the domain (near Toulouse and Bordeaux ) one to two towers equipped with high precision gas chromatographs will measure the concentrations of CO 2, and 14C (depending on national resources). CMDL NDIR-CO 2 sensors are built for this purpose. Implementation will start in 2005.

Task 3.3.2 : Airborne flask sampling. A small commercial plane will sample the boundary layer structure for CO 2, 13C and CO for 3 to 5 days. Flask samples will be analysed at MPI-BGC. During the intensive campaign, flights are planned on 1 day every week to take 3 profiles at 5 levels in the boundary layer.

Task 3.3.3 : Radio soundings. We will extend the routine WMO observations at Bordeaux during the test campaign and later during the full campaigns. We will also install UHF profile systems and RASS_Sodar systems at a location where they contribute most to our understanding of the heterogeneity of the area.

Activity 3.4 Modelling and integration

Objectives (5 yr plan)

  • 3.4.1 To reanalyse the RECAB campaigns with a set of regional models and to apply downscaling techniques with a view to better planning the experiment and guiding the model development.
  • 3.4.2 To develop and apply a multiple constraint data assimilation system that produces the best possible estimates of the regional carbon balance at the grid of the atmospheric model (2 km) for the year 2005.
  • 3.4.3 To produce a long term (20 years) bottom up estimate at 2 km resolution of the carbon balance of the region.
  • 3.4.4 To separate the biospheric sink in the region from the contribution of anthropogenic sources.

Outline of work plan

Task 3.4.1 : We will reanalyse the RECAB campaigns with mesoscale models (RAMS, Meso-NH) and apply down scaling techniques (inverse models), to guide both the development of the data assimilation system and the planning of the experiments. This will lead to a “proof of concept”.

Task 3.4.2 : In the first 18 months we will initiate the development of this regional CDAS in parallel with effort in CAMELS. For the slow cycle, we will use the 8 km resolution downscaled weather information that is available at CNRM, which will be extended for use in biogeochemical models. These models will be calibrated with flux data for the main land use types and then run for a 20-year period. The required input data on land use history and management is obtained in WP1. The models we intend to use, comprise Orchid, LPJ, ISBA-A-g s. We will concentrate on setting up uniform calibration and model procedures in the first 18 months, 20 year runs will be ready towards month 48.

Task 3.4.3 : For the fast cycle we will use a data assimilation system at mesoscale that mirrors the system developed for the large scale (Camels and Continental Integration Component). We will mainly use the French Arome system and Meso-NH developed at CNRM for this purpose and extend it to carry CO 2 in the assimilation procedure. This will be used finally to separate biospheric from anthropogenic sources.