Markku J. Santala, ExxonMobil Upstream Research Co.
Results of a 16 year long HYCOM simulation of the Atlantic Ocean north of 20 deg S at a nominal spatial resolution of 1/3deg performed by the the Naval Research Lab are compared versus observationally derived eddy statistics. The model was run on a frequent time step but since only 193 monthly snapshots were archived over the period of January 18, 1980 to December 31, 1995 there are some limitations on the validation. The validation presented only focuses on the climatology of the Loop Current and its associated eddies within the Gulf of Mexico.
From previous modeling studies we know that a resolution of 1/3deg is not high enough to capture all of the eddy dynamics. Hence, it is not surprising that this evaluation identifies a number of deficiencies in the model results. The model does produce a Loop Current and sheds eddies in a somewhat random pattern. Looking at the percent occurrence of eddies the general pattern produced by HYCOM mimics observationally-based results but with a notable difference; the Loop Current and eddies do not penetrate far enough north in the central Gulf. There is less randomness in the paths of eddies than has been observed in nature and peak speeds produced in the model are low compared to historical observations (with the coarse resolution of the model the low modeled speeds are not at all unexpected). We also have a limited amount (18 months) of results from a 1/12deg HYCOM run. We also examine the differing tendencies in the higher resolution run.