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Ensemble covariances adaptively localized with ECO-RAP. Part 2: a strategy for the atmosphere

Craig H Bishop, Daniel Hodyss

TELLUS SERIES A-DYNAMIC METEOROLOGY AND OCEANOGRAPHY | WILEY-BLACKWELL PUBLISHING, INC | Published : 2009

Abstract

Part 1's localization method, Ensemble COrrelations Raised to A Power (ECO-RAP), is incorporated into a Local Ensemble Transform Kalman Filter (LETKF). Because brute force incorporation would be too expensive, we demonstrate a factorization property for Part 1's Covariances Adaptively Localized with ECO-rap (CALECO) forecast error covariance matrix that, together with other simplifications, reduces the cost. The property inexpensively provides a large CALECO ensemble whose covariance is the CALECO matrix. Each member of the CALECO ensemble is an element-wise product between one raw ensemble member and one column of the square root of the ECO-RAP matrix. The LETKF is applied to the CALECO ens..

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University of Melbourne Researchers