A Study of Coupling Parameter Estimation Implemented by 4D-Var and EnKF with a Simple Coupled System

Figure 3

Time-averaged normalized absolute errors of (a) in EXP-2, (b) in EXP-4, (c) in EXP-3, and (d) in EXP-4 of the 4D-Var CPE. The absolute errors of and are normalized by their initial errors, that is, 0.1 and 0.01, respectively. The -axis is the atmospheric observational interval while the -axis denotes the minimization time window (MTW) in 4D-Var. The black solid circles stand for the scatter points used to create the contours. The dashed curve represents the 1.0 contour. Panels (a) and (b) use the upper shade scale while panels (c) and (d) use the lower shade scale. Note that 1 Time Unit = 100 time steps. EXP-1 only performs state estimation. EXP-2 instantaneously conducts state estimation and parameter estimation of . EXP-3 instantaneously conducts state estimation and parameter estimation of . EXP-4 instantaneously conducts state estimation and parameter estimations of and .

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