“…The deterministic methods , such as direct method, FSAP (Forward Sensitivity Analysis Procedure) and ASAP (Adjoint Sensitivity Analysis Procedure), involve differentiation of the system under investigation 65 and exactly computing the sensitivities; while the statistical methods, such as sampling based methods, variance based methods, and FAST (Fourier Amplitude Sensitivity Test), rely on multiple simulations to obtain statistically reliable results . By operating backward in time to describe the propagation of information, adjoint models can be used for sensitivity 70 analysis and adaptive observations (Errico, 1997;Palmer et al, 1998;Baker and Daley, 2000;Daescu and Navon, 2004;Alekseev and Navon, 2010;Godinez and Daescu, 2011). In our previous study, we presented an ensemble method to study the sensitivity (Che et al, 2013), which is simple to implement, and can be used for different target functions for various purposes.…”