Scaling field-based crop model to regional scale using assimilation of Earth Observation data and high spatial resolution meteorological forcing data.

Improving assimilation methods of Earth Observation descriptors into crop models :*Build a framework for scaling field-based crop models to regional scale using assimilation of Earth Observation data and high spatial resolution meteorological forcing data * Pilot models on corn and soybean crops in Ontario and Quebec* Aggregate models to regional scale to predict crop yield and biomass response to climate variation

Estimation des besoins en eau pour l’irrigation à différentes échelles spatiales, de la parcelle cultivée au périmètre irrigué.

The central question of my PhD thesis is the control of agrometeorological models by satellite data from optical and thermal sensors to monitor the crop water budget in semi-arid environments. The general objective of this work, entitled “Spatial estimation of actual evapotranspiration and irrigation volumes using water and energy balance models forced by optical remote sensing data (VIS/ NIR/TIR)”, is to develop and test methods for estimating the hydrological variables related to crop water budget, i.e. evapotranspiration, crop water requirements and irrigation volumes, at scales ranging from plot to regional level and for relatively long time periods (up to the agricultural season). The operational perspective is to provide tools for irrigation and watershed management. Our study area is the Kairouan semi-arid plain located in central Tunisia, occupied by irrigated agriculture and where most of the water is extracted from an overexploited aquifer. The adopted approach combines field experimentation, modeling and the use of multi-sensor / multi-resolution remote sensing data. Both types of tools used to estimate hydrological variables (ET and irrigation volumes) are: i) a daily water balance model, SAMIR (Simonneaux et al., 2009), simulating water fluxes at a daily time step and ii) an instantaneous energy balance model, SPARSE (Boulet et al., 2015), which characterizes the water status at the satellite overpass time.

In the context of a changing climate, the agricultural sector faces the challenge to produce more food with less water by increasing crop water productivity. This work aims to assess potential impacts of climate change on winter wheat and tomato water productivity as well as on crop water requirement, net irrigation requirement and relative yield loss under different irrigation scenarios, taking into consideration the foreseen climate change in the Mediterranean for the period 2000-2050. The study is based on a GISapproach that permits spatial elaboration, presentation and analysis of climate change impacts on both country and regional scale. A particular attention is given to the possible changes in the length of growing cycle and the starting date of growing season due to expected air temperature increase in the future.