Simulating ENSO Ssta from TAO/Triton Winds: The Impacts of 20 Years of Buoy Observations in the Waveguide and Comparison with Reanalysis Products

The fundamental importance of near-equatorial zonal wind stress in the evolution of the tropical Pacific Ocean’s seasonal cycle and El Niño-Southern Oscillation (ENSO) events is well known.  It has been two decades since the TAO/Triton buoy array was deployed, in part to provide accurate surface wind observations across the Pacific waveguide. It is timely to revisit the impact of TAO/Triton winds on our ability to understand the evolution of SST in this region. This work shows that forced ocean model simulations of SST anomalies (SSTAs) during the periods with a reasonably high buoy data return rate can reproduce the major elements of SSTA variability during ENSO events, using a wind stress field computed from TAO/Triton observations only. Forcing with reanalysis wind fields does not give similarly satisfactory results. Comparison of several reanalysis wind fields with TAO/Triton observations reveals substantial differences in variability and trends. In particular, the negative trend in the ERA-Interim reanalysis is much larger than, and the NCEP reanalysis variability much less than seen in the TAO/Triton observations. There are also mean biases. Thus, even with the TAO/Triton observations available for assimilation into these wind products, there remain oceanically important differences. The direct wind observations from the TAO/Triton array remain critical to understanding the evolution of the coupled ocean atmosphere system in the equatorial Pacific.  The reanalyses we examine would be more useful for these purposes if their equatorial Pacific wind products were more strongly constrained by the available TAO/Triton observations than they are currently.