Improving NCEP model winds by including more offshore observations

What is it about?

Wind fields on the West Florida Continental Shelf are investigated using observations from five University of South Florida Coastal Ocean Monitoring and Prediction System buoys and seven of NOAA’s National Ocean Service and National Weather Service, National Data Buoy Center stations or buoys spanning the 10 year period, 2004–2013. These observations are compared with NOAA’s National Center for Environmental Prediction (NCEP) reanalysis wind fields (NCEP winds). The analyses consist of vector correlations in both the time and frequency domains. The primary findings are that winds observed on and near the coastline underestimate those observed offshore and that NCEP winds derived from assimilating mostly land-based observations also underestimate winds observed offshore. With regard to wind stress, and depending upon location, wind stress derived from NCEP winds are 6%–49% lower than what is computed from observations over open water. A corollary is that wind forcing fields that are underestimated may result in coastal ocean model circulation fields that are also underestimated. These analyses stress the importance of having offshore wind observations, and suggest that adding more offshore wind observations will lead to improved coastal ocean wind fields and hence to improved model renditions of coastal ocean model circulation and related water property fields.

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Why is it important?

Being that coastal ocean ecosystem functionality begins with water property distributions that are largely determined by the coastal ocean circulation (e.g., see WFS examples in Weisberg and He [2003], Walsh et al. [2003], Weisberg et al. [2015, 2016a], and Liu et al. [2016]), our results are particularly germane to ecosystems-based management of the coastal ocean. Adding more in situ offshore wind observations will likely be a means for improving coastal ocean wind forcing fields and hence coastal ocean model fields of circulation and attendant water properties.

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