Reanalyses refer to the process of systematically reprocessing historical weather and climate data using the most up-to-date numerical models and quality control methods. This involves synthesizing both observational data (such as surface weather station measurements, satellite data, and weather balloon soundings) and model data to create a consistent and continuous record of past weather conditions. Reanalyses are used to study climate variability and change, assess model performance, and validate observational data. They are also valuable for understanding extreme weather events and their impacts on society and the environment.