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- Title
Assessing the Impact of Nontraditional Ocean Observations for Prediction of the East Australian Current.
- Authors
Siripatana, Adil; Kerry, Colette; Roughan, Moninya; Souza, João Marcos A. C.; Keating, Shane
- Abstract
Accurate forecasting of ocean currents in dynamic regions remains a critical challenge due to the sparsity of observations in global ocean observing networks and the limited resolution of present‐day regional ocean models. Lately, traditional observing platforms have been complemented by newly available data streams capable of sampling at higher spatial and/or temporal resolutions in dynamically significant regions in near‐real time. However, the relative merits and trade‐offs of incorporating these "nontraditional" observations into ocean state estimates have not been thoroughly investigated. Here, we perform a detailed statistical and dynamical comparison of two high‐resolution reanalysis products assimilating different combinations of traditional and nontraditional observations in the East Australian Current (EAC) system, a vigorous western boundary current. We show that sea‐surface height and temperature are well‐constrained by satellite measurements; however, below the surface, a reanalysis incorporating fully available observations better represents the ocean state. The core of the EAC jet is effectively constrained by subsurface observations from deep water moorings upstream of jet separation, while radar‐derived nearshore surface velocities in the separation zone are found to resolve the submesoscale cyclonic band inshore of the EAC. Cost function sensitivity analysis of both products reveals excessive model adjustment at depth causing the reanalyzes to overestimate alongshore transport relative to a 22‐year freely evolving simulation. Overall, the assimilation of nontraditional observations delivers marked improvement in representing dynamical features of the EAC. However, this improvement is not as pronounced in the model forecast due to the introduction of nonphysical dynamics or forcing, suggesting that other improvements such as increased model resolution are required. Plain Language Summary: Estimating and forecasting the ocean state is challenging in a highly dynamic region such as a western boundary current. Integrating ocean observations with numerical models through data assimilation improves the quality of ocean prediction. This study investigates the improvement made by assimilating a range of less traditional observations (TRAD) (such as glider and high frequency coastal radar) when combined with more TRAD (such as satellite derived observations of sea surface temperature and height and deep profiles) in the East Australian Current (EAC). Overall, marked improvement in estimating the EAC dynamics has been observed when the more targeted observations are included. Key Points: The relative merits and trade‐offs of diverse observational data streams on ocean state estimation and forecasting are assessed using two high‐resolution reanalysis products of the East Australian Current (EAC) systemA reanalysis product that assimilates all available observations better represents the ocean state compared to one that assimilates traditionally available observations only. In particular, submesoscale surface vorticity and mesoscale eddies are effectively constrained through assimilation of radar‐derived nearshore surface velocities and subsurface glider observationsIn the forecast, the system that assimilates only traditionally available observations displays similar surface and subsurface predictive skill to the system assimilating all available observations
- Subjects
EAST Australian Current; PACIFIC Ocean currents; OCEANOGRAPHIC research; OCEAN temperature; MESOSCALE eddies
- Publication
Journal of Geophysical Research. Oceans, 2020, Vol 125, Issue 12, p1
- ISSN
2169-9275
- Publication type
Article
- DOI
10.1029/2020JC016580