Monitoring impacts and array-design implications of wind observations from the tropical Pacific moored buoys

Andrew M Chiodi, University of Washington/CICOES and NOAA/Pacific Marine Environmental Laboratory, Seattle, United States and Don Harrison, Pacific Marine Environmental Laboratory, Seattle, WA, United States
The tropical Pacific moored-buoy array spacing was based on the observed coherence length scales of surface winds from low-lying islands in the western-central tropical Pacific. In the years since its full deployment across the basin, winds from the moored-buoy array have proven critical to monitoring for decadal-scale changes in tropical Pacifi­c windstress and wind-driven changes in surface temperature as well as regional air-sea CO2 flux. The mooring winds have also been critical to identifying spurious trends and statistics in gridded wind analysis products that have been used to monitor the anomaly state of the tropical Pacific and its long-term change.

Recent forced ocean model experiment results confirm that the wind measuring component of the array works (to an often adequate degree) as designed for providing winds necessary to simulate (signal-to-noise ~2) ENSO-associated central Pacific sea surface temperature anomaly development, so long as most buoys are in service. Eastern equatorial Pacific surface temperature anomalies, however, are not hindcast accurately and questions remain about how to further improve hindcast accuracy across the basin.

The original assumption that the statistics calculated from western-central tropical Pacific island wind records are representative of open ocean conditions and other regions of the tropical Pacific has not been thoroughly reexamined. We revisit the original moored-buoy array design calculations using the wind observations provided by the array. We find that the character of key wind statistics changes across the tropical Pacific basin in ways that could not be determined from the original island wind study. In particular, the islands results provided a best-case answer for optimal mooring zonal spacing between adjacent buoys (minimally redundant coherence). Buoy zonal coherence scales shorten away from the islands. Buoy meridional coherence scales are longer than from the islands. Process studies are needed to determine the optimal array spacing away from the islands.