Historical Reanalysis: What, How, and Why?

Abstract

Historical reanalyses combine observations of past weather with simulations from modern numerical weather prediction models to provide a consistent, global history of the weather. Recently, a new reanalysis was released that allows observations of the ocean to impact the atmosphere and vice versa. “CERA-20C: A Coupled Reanalysis of the Twentieth Century” by P. Laloyaux et al. (2018, https://doi.org/10.1029/2018MS001273) describes the first coupled centennial reanalysis, thereby providing more balanced estimates of the ocean-atmosphere system and allowing for a broader range of studies of the entire Earth system. Results suggest that similar methods could also be leveraged to improve modern weather forecasts.