State estimates and analysis of the Tropical Pacific Ocean from 2010 to 2018

A state estimate assimilating data from the Tropical Pacific Observing System (TPOS) is used to compute budgets for heat, salt and mass in the Equatorial Pacific. For the period 2010 to 2018, overlapping 4-month hindcasts were produced using the 4-Dimensional Variational (4D-Var) method to adjust initial conditions and atmospheric forcing of a one-third degree regional model. Consistency within uncertainty with satellite SSH and Argo, XBT, and CTD profiles is achieved. Comparison to independent observations from Tropical Atmosphere Ocean (TAO) moorings shows that for timescales shorter than 100 days, the state estimate improves estimates of TAO temperature relative to an optimally-interpolated Argo product, especially at at timescales shorter than 20 days. The state estimate provide a dynamically-consistent, property-conserving, large-scale framework for investigating the mechanisms involved in events such as the 2015-16 El Niño, or the variability in the eastern edge of the warm pool. Heat budgets are used to quantify the contributions of lateral advection, vertical advection, mixing, and air-sea fluxes in controlling temperature variability. The state estimate is also evolving into new products: a higher-resolution (one-sixth degree) model run is forced with adjusted initial conditions and atmospheric forcing from the coarse-resolution hindcasts and is being coupled to a biogeochemical model.