Evaluation of the Tropical Pacific Observing System from the ocean data assimilation perspective

Abstract

The drastic reduction in the number of observation data from the Tropical Atmospheric Ocean (TAO)/Triangle Trans-Ocean Buoy Network (TRITON) array since 2012 has given rise to a need to assess the impact of those data in ocean data assimilation (DA) systems. This article provides a review of existing studies evaluating the impacts of data from the TAO/TRITON array and other components of the Tropical Pacific Observing System (TPOS) on current ocean DA systems used for a variety of operational and research applications. It can be considered as background information that can guide the evaluation exercise of TPOS. Temperature data from TAO/TRITON array are assimilated in most ocean DA systems which cover the tropical Pacific in order to constrain the ocean heat content, stratification, and circulation. It is shown that the impacts of observation data depend considerably on the system and application. The presence of model error often makes the results difficult to interpret. Nevertheless there is consensus that the data from TAO/TRITON generally have positive impacts complementary to Argo floats. In the equatorial Pacific, the impacts are generally around the same level or larger than those of Argo. We therefore conclude that, with the current configuration of TPOS, the loss of the TAO/TRITON data is having a significant detrimental impact on many applications based on ocean DA systems. This conclusion needs to be kept under review because the equatorial coverage by Argo is expected to improve in the future.

Ocean Observations to Improve Our Understanding, Modeling, and Forecasting of Subseasonal-to-Seasonal Variability

“…Hence, accurate observations of the evolution of Tropical Pacific WWV can help improve ENSO process understanding and predictions on seasonal timescales. Accurate analysis and initialization of ocean sub-surface states in the equatorial Pacific is of great importance for S2S prediction (Fujii et al, 2015).…”

“…Ocean observing system experiments are conducted at ECMWF and other global forecasting centers to evaluate the use of ocean observations in ocean reanalyses Fujii et al, 2015;Xue et al, 2017). In these ocean reanalyses produced at ECMWF, specific observing systems are withdrawn in a controlled manner.…”

Evaluation of tropical Pacific observing systems using NCEP and GFDL ocean data assimilation systems

“…To assess and to develop pathways to ameliorate degradation in TAO/TRITON, the TPOS 2020 workshop was held in January 2014 (http://www.ioc-goos.org/tpos2020). One major focus of the workshop was to provide an assessment of the impact of the decline in the TAO/TRITON array on the ocean state estimation, particularly in the context of ENSO monitoring and ocean initializations for seasonal forecast models (Fujii et al 2015;Hu and Kumar 2015).…”

The impact of Argo observations in a global weakly coupled ocean–atmosphere data assimilation and short‐range prediction system

“…In particular, Fujii et al . () address the impact of Argo observations in an operational seasonal forecasting system. There has also been recent work looking at the impact of atmospheric observations in a coupled prediction system (Laloyaux et al .…”

“…There has been much work on observation impact in ocean-only analyses and short-range forecasts (e.g., Lea et al 2014;Oke et al 2015a;2015b;Fujii et al 2019), and on the importance of sub-surface observations for seasonal to decadal coupled prediction (e.g., Kleeman et al 1995;Vidard et al 2007;Dunstone and Smith, 2010). In particular, Fujii et al (2015) address the impact of Argo observations in an operational seasonal forecasting system. There has also been recent work looking at the impact of atmospheric observations in a coupled prediction system (Laloyaux et al 2016), but relatively little on the importance of ocean observations, beyond sea surface temperatures, on short-range weather forecasts.…”