Author/Authors :
Jacobs، نويسنده , , Gregg A. and Bartels، نويسنده , , Brent P. and Bogucki، نويسنده , , Darek J. and Beron-Vera، نويسنده , , Francisco J. and Chen، نويسنده , , Shuyi S. and Coelho، نويسنده , , Emanuel F. and Curcic، نويسنده , , Milan and Griffa، نويسنده , , Annalisa and Gough، نويسنده , , Matthew and Haus، نويسنده , , Brian K. and Haza، نويسنده , , Angelique C. and Helber، نويسنده , , Robert W. and Hogan، نويسنده , , Patrick J. and Huntley، نويسنده , , Helga S. and Iskandarani، نويسنده , , Mohamed and Judt، نويسنده , , Falko and Kirwan Jr.، نويسنده , , A.D. and Laxague، نويسنده , , Nathan and Valle-Levinson، نويسنده , , Arnoldo and Lipphardt Jr.، نويسنده , , Bruce L. and J. Mariano، نويسنده , , Arthur and Ngodock، نويسنده , , Hans E. and Novelli، نويسنده , , Guillaume and Olascoaga، نويسنده , , M. Josefina and ضzgِkmen، نويسنده , , Tamay M. and Poje، نويسنده , , Andrew C. and Reniers، نويسنده , , Ad J.H.M. and Rowley، نويسنده , , Clark D. and Ryan، نويسنده , , Edward H. and Smith، نويسنده , , Scott R. and Spence، نويسنده , , Peter L. and Thoppil، نويسنده , , Prasad G. and Wei، نويسنده , , MOZHENG WEI، نويسنده ,
Abstract :
Ocean prediction systems rely on an array of assumptions to optimize their data assimilation schemes. Many of these remain untested, especially at smaller scales, because sufficiently dense observations are very rare. A set of 295 drifters deployed in July 2012 in the north-eastern Gulf of Mexico provides a unique opportunity to test these systems down to scales previously unobtainable. In this study, background error covariance assumptions in the 3DVar assimilation process are perturbed to understand the effect on the solution relative to the withheld dense drifter data. Results show that the amplitude of the background error covariance is an important factor as expected, and a proposed new formulation provides added skill. In addition, the background error covariance time correlation is important to allow satellite observations to affect the results over a period longer than one daily assimilation cycle. The results show the new background error covariance formulations provide more accurate placement of frontal positions, directions of currents and velocity magnitudes. These conclusions have implications for the implementation of 3DVar systems as well as the analysis interval of 4DVar systems.
