Complex terrains feature significant land-atmosphere interactions that modulate local to regional hydroclimate systems, with elevated vulnerabilities to the hydroclimate variability and intensified extremes. There is an ongoing need to better understand and assess the coupled earth system processes over these regions. Such integrated investigations require a synergy of new insights from observations and advanced dynamical and statistical modeling. This session welcomes the submissions on the theories, simulations, and applications of such knowledge, including but not limited to: 1) investigations of climate variability that highlight the connections and interactions within multiple processes of the earth system from global to local scales; 2) understanding of sequential or compound hydroclimate extremes (storm, flooding, snow, drought, heatwave, wildfires, etc.) from the view of land-atmosphere interactions; 3) modeling and projections of climate variability and extremes with numerical or statistical tools, such as high-resolution climate models and physics-informed machine learning approaches.