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HYCOM performance in the Gulf of Mexico During the DWH Oil Spill
George Halliwell, Nick Shay, Debra Willey, Ole Martin Smedstad, Patrick Hogan, Gustavo Goni, Robert Atlas
NOAA/AOML/PhOD
(Abstract received 01/06/2011 for session X)
ABSTRACT
During the Deepwater Horizon oil spill, nine synoptic aircraft surveys were conducted in the eastern Gulf of Mexico from a NOAA P3 aircraft using AXBTs, AXCTDs, and AXCPs between 8 May and 9 July. This unprecedented dataset provides an opportunity to evaluate the performance of ocean nowcast-forecast systems in a dynamically active region and to quantify the impact of such synoptic surveys on the accuracy of data-assimilative ocean analysis products. This presentation focuses on three topics: First, a large error reduction in HYCOM analyses was achieved by changing the vertical projection algorithm used in altimetry data assimilation from Cooper-Haines to MODAS synthetics. Second, the performance of HYCOM products (1/12-degree global and 1/25-degree GoM) are evaluated against several other ocean nowcast-forecast products, specifically NCEP RTOFS HYCOM, NRL IASNFC NCOM, SABGOM ROMS, and NOAA/NOS NGOM POM. Ocean analyses that did not assimilate the P3 aircraft profiles produced by all five of these models demonstrate that the HYCOM analysis is equal to or superior to the other model products. Finally, the impact of assimilating the P3 profiles is quantitatively assessed by performing an Observing System Experiment using the 1/25-degree GoM HYCOM, one that assimilated all observations and another that denied the P3 profile observations. Assimilation of P3 observations reduced bias and RMS errors in upper-ocean temperature by 20-40% at the P3 profile locations. Further evaluation of these OSE results is being conducted using observations (e.g. Nancy Foster DWH cruise) and analyses (e.g. tropical cyclone heat potential) available from AOML PhOD and other sources that were not assimilated by either experiment.
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2011 LOM Workshop, Miami, Florida February 7 - 9, 2011