EnOI-IAU Initialization Scheme Designed for Decadal Climate Prediction System IAP-DecPreS

A decadal climate prediction system named as IAP-DecPreS was constructed in the Institute of Atmospheric Physics (IAP), Chinese Academy of Sciences, based on a fully coupled model FGOALS-s2 and a newly developed initialization scheme, referred to as EnOI-IAU. In this paper, we introduce the design of the EnOI-IAU scheme, assess the accuracies of initialization integrations using the EnOI-IAU and preliminarily evaluate hindcast skill of the IAP-DecPreS. The EnOI-IAU scheme integrates two conventional assimilation approaches, ensemble optimal interpolation (EnOI) and incremental analysis update (IAU). The EnOI and IAU were applied to calculate analysis increments and incorporate them into the model, respectively. Three continuous initialization (INIT) runs were conducted for the period of 1950-2015, in which observational sea surface temperature (SST) from the HadISST1.1 and subsurface ocean temperature profiles from the EN4.1.1 data set were assimilated. Then nine-member 10 year long hindcast runs initiated from the INIT runs were conducted for each year in the period of 1960-2005. The accuracies of the INIT runs are evaluated from the following three aspects: upper 700 m ocean temperature, temporal evolution of SST anomalies, and dominant interdecadal variability modes, Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO). Finally, preliminary evaluation of the ensemble mean of the hindcast runs suggests that the IAP-DecPreS has skill in the prediction of the PDO-related SST anomalies in the midlatitude North Pacific and AMO-related SST anomalies in the tropical North Atlantic.