By Abhirup Banerjee, University of Hamburg

Abstract 

Data assimilation combines observational data with model simulations to provide accurate and dynamically consistent representations of Earth’s systems. 4D-Var data assimilation leverages the adjoint model to integrate observations over time, producing optimal state estimates. Adjoint methods, widely used in parameter estimation and sensitivity analysis, are invaluable for understanding and optimizing Earth system processes.

In this talk, I will introduce the adjoint method using a toy model, followed by an overview of the Coupled Earth System Model (CESAM), highlighting its ability to capture complex Earth system interactions. I will then discuss our ongoing work on Indian heatwaves, where adjoint-derived sensitivity diagnostics and reanalysis datasets are employed to explore atmospheric and surface processes driving these events. This study provides critical insights into the dynamics and predictability of heatwaves, offering pathways to enhance future projections and preparedness strategies.