Between stomata and clouds: Unveiling vegetation-atmospheric boundary layer interactions with high resolution observations and modeling

Vegetation and atmosphere interact by exchanging energy, water and carbon. Yet, uncertainties remain in how these exchanges are represented in Earth system models, particularly regarding their diurnal evolution, vertical variability within canopies, and sensitivity to clouds. This dissertation addresses these gaps by integrating observations and modeling, linking leaf-scale processes to canopy and atmospheric dynamics. Modeling approaches range from a conceptual atmospheric model to canopy-resolving Large Eddy Simulations. Study cases represent three contrasting ecosystems: an agricultural field, a tropical rainforest, and a temperate forest. Results show that diurnal variations in ecosystem water and CO₂ exchange are governed by radiation, temperature, and vapor pressure deficit. Within-canopy stratification can decouple lower canopy layers from the overlying atmosphere, affecting residence times. A multi-spectral canopy radiative transfer scheme is also developed, enabling analysis of spectral influences on microclimate and photosynthesis. Overall, the findings highlight the need to better represent diurnal, vertical, and cloud-related processes in land-atmosphere models and demonstrate the value of canopy-resolving approaches.