SPREADS: From Research to Operational Open-Source Data Assimilation System

Abstract. The Scalable PaRallelised EArth Data Assimilation System (SPREADS) is a next-generation data assimilation system developed at CMCC-Foundation (Euro-Mediterranean Center on Climate Change) to support operational global forecasts. Built upon the Data Assimilation Research Testbed (DART), SPREADS incorporates key advancements such as First Guess at Appropriate Time (FGAT), enhanced observation handling via D4O (Database for Observations), and high-performance parallelisation to significantly improve computational efficiency and scalability. A major focus of SPREADS is the assimilation of a vastly increased number of asynchronous satellite-based radiances, which have been shown to substantially enhance analysis quality. Designed for coupled atmosphere-land-ocean-ice assimilation, SPREADS forms the core of the CMCC Earth SYstem Modelling and Data Assimilation (ESYDA division) operational forecast system. This paper presents the modifications made to DART, evaluates preliminary results, and outlines future developments toward fully coupled data assimilation.