"Multivariate localization functions for strongly coupled data assimilation"

The International Symposium on Data Assimilation Online (ISDA-Online) May 7, 2021
"Coupled Data Assimilation"
International Symposium on Data Assimilation - Online

Localization is widely used in data assimilation schemes to mitigate the impact of sampling errors on ensemble-derived background error covariance matrices. In strongly coupled data assimilation when different components have disparate dominant spatial scales, localization between model domains must properly account for the multiple length scales at play. In this talk we present a new multivariate localization function which extends the fifth-order piecewise rational Gaspari-Cohn localization function. The function produces non-negative definite localization matrices which are suitable for use in variational data assimilation schemes. We compare the performance of different multivariate localization functions in a simple experiment with the bivariate Lorenz '96 system.