Hybrid EnKF-OI filter

A hybrid ensemble and optimal interpolation filter, combining flow-dependent ensemble covariances with time-invariant climatological backgrounds. The combination is done linearly and adaptively both in space and time.

For detail see El Gharamti, et al. (2024): Leveraging a Novel Hybrid Ensemble and Optimal Interpolation Approach for Enhanced Streamflow and Flood Prediction.

Note: This release is supported for WRF-Hydro only and is based on DART version v9.11.7