Nino-Ruiz, Elias D.Sandu, AdrianCheng, Haiyan2018-07-252018-07-252018-07-06Nino-Ruiz, E.D.; Sandu, A.; Cheng, H. Efficient Formulation and Implementation of Data Assimilation Methods. Atmosphere 2018, 9, 254.http://hdl.handle.net/10919/84387This Special Issue presents efficient formulations and implementations of sequential and variational data assimilation methods. The methods address three important issues in the context of operational data assimilation: efficient implementation of localization methods, sampling methods for approaching posterior ensembles under non-linear model errors, and adjoint-free formulations of four dimensional variational methods.application/pdfenCreative Commons Attribution 4.0 Internationalensemble Kalman filterposterior ensemblemodified Cholesky decompositionsampling methodsempirical orthogonal functionsGaussian mixture modelsEditorial2018-07-25https://doi.org/10.3390/atmos9070254