edu.ucar.opensky::articles:17233 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-26T14:34:10.331205 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.org/ark:/85065/d7zc845j An ensemble conditional nonlinear optimal perturbation approach: Formulation and applications to parameter calibration 2010-09-30T00:00:00Z publication https://n2t.org/ark:/85065/d7zc845j https://doi.org/10.1029/2009WR008508 Tian, X. author Xie, Z. author Dai, Aiguo author UCAR/NCAR - Library publisher The conditional nonlinear optimal perturbation (CNOP) method proposed by Mu et al. (2003) has been a useful tool for studying predictability dynamics. Its further applications are, however, hampered by the need of an adjoint model. Aiming to solve this problem, an ensemble conditional nonlinear optimal perturbation (EnCNOP) approach is proposed in this paper by merging the Monte Carlo method and the proper orthogonal decomposition (POD) technique into the CNOP to transform an implicit optimization problem into an explicit one. This approach is further formulated for parameter calibration. Numerical experiments with a 1-D model of the soil water equation show that the EnCNOP approach outperforms a dual-pass optimization framework on the basis of the ensemble Kalman filter (EnKF) and a shuffled complex evolution approach (SCE-UA) in terms of both increasing the calibration precision and reducing the computational costs. In particular, the EnCNOP approach outperforms the SCE-UA when only an approximate value range of the input parameters is known. Our EnCNOP method is further implemented within a complicated highly nonlinear land surface model (namely, NCAR CLM3) and evaluated through a case study which illustrates its applicability to complex, highly nonlinear problems. UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact PDF Text theme Resource Type 2016-01-01T00:00:00Z publication An edited version of this paper was published by AGU. Copyright 2010 American Geophysical Union. None eng geoscientificInformation