Impact of latitude dependent background error covariance

摘要

1 Introduction The spatial and multivariate structure of the analysis increments in variational analysis is driven by the formulation of the background error covariance matrix B.The matrix B plays a crucial role in variational data assimilation (Fisher 2003).The NMC method provides an estimate of matrix B including the regression coefficients,which is used in defining "balance" part of different control variables.The control variable is the "unbalanced" part of the field,which is obtained by removing "balanced" part form the respective "full" field (Bannister 2008).