Monitoring energy and mass transfers during the Alpilles-ReSeDA experiment

Abstract

The Alpilles-ReSeDA program was initiated to develop and test methods for interpreting remote sensing data that could lead to a better evaluation of soil and vegetation processes. This article presents the experiment that was setup in order to acquire the necessary data to achieve this goal. Intensive measurements were performed for almost one year over a small agricultural region in the South of France (20 kilometers square). To capture the main processes controlling land-atmosphere exchanges, the local climate was fully characterized, and surface energy fluxes, vegetation biomass, vegetation structure, soil moisture profiles, surface soil moisture, surface temperature and soil temperature were monitored. Additional plant physiological measurements and a full characterization of physical soil parameters were also carried out. After presenting the different types of measurements, examples are given in order to illustrate the variability of soils and plant processes in the area in response to the experienced climate. surface energy fluxes / evapotranspiration / soil moisture / soil physical properties / experiment / vegetation characterization Résumé-Suivi des échanges d'énergie et de masse au cours de l'expérimentation Alpilles-ReSeDA. Le programme Alpilles-ReSeDA a été mis en place pour développer et tester des méthodes permettant une meilleure utilisation des données de télédétection pour le suivi du fonctionnement des sols et des cultures. Cet article présente l'expérimentation qui a été réalisée pour acquérir un jeu de données permettant cette analyse. Des mesures intensives ont été réalisées pendant presque une année sur une petite région agricole du Sud de la France (20 kilomètres carrés). De façon à suivre l'ensemble des processus contrôlant les échanges surface-atmosphère, l'ensemble des paramètres climatiques locaux ont été mesurés, ainsi que les flux d'énergie de surface, les caractéristiques de structure de la végétation et du sol, l'humidité et les températures du sol, la température de surface. Des mesures des paramètres physiologiques des plantes et des caractéristiques physiques des sols ont également été entreprises. Après avoir présenté les différents types de mesures réalisées, des exemples présentant la variabilité des couverts végétaux et des sols dans la zone d'étude sont présentés.

Impact of surface heterogeneity on a buoyancy-driven convective boundary layer in light winds

“…In these conditions, the feedbacks between the surface and the atmosphere are not considered. Our simulations have been conducted with surface properties and patch size as close as possible to an actual agricultural landscape, with surface parameters extracted from the Reseda dataset (Olioso et al 2002;Courault et al 2003).…”

“…A reference configuration for the simulation is defined using a homogeneous terrain covered with vegetation such as a meadow with well-developed grass, similar to the configuration of the Reseda experiment conducted in 1997 over a small agricultural area in south-eastern France (Olioso et al 2002).…”

An improved SVAT model calibration strategy based on the optimisation of surface temperature temporal dynamics

“…Latent and sensible heat fluxes were continuously measured (20 0 time step) by means of both the Bowen ratio (over the whole period) and the Eddy correlation method (between 15th of March and 4th of April, DOY 74 -94). The Bowen ratio deduced fluxes were reprocessed [Olioso et al, 2002] because of over-estimations (bias of +15 W.m…”

“…All these processes were carried out in order to obtain a coherent and continuous set of data corresponding to a complete vegetation cycle, for the validation and/or calibration of SVAT models [Olioso et al, 2002].…”

Estimation of the Surface Energy Balance

“…Mecikalski et al (1999) have applied the Norman et al (1995) approach to continental scale with encouraging results. Efforts related to combined modeling and data assimilation using radiometric measurements have been reported by Castelli et al (1999), Olioso et al (2002), Boni et al (2001a, b), and Caparrini et al (2003Caparrini et al ( , 2004.…”