On model validation for meso/submesoscale currents: Metrics and application to ROMS off Central California
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Authors
Ivanov, L.M.
Collins, C.A.
Marchesiello, P.
Margolina, T.M.
Subjects
Models
ROMS
Submesoscale features
Mesoscale features
Subsurface drifters
Satellite altimetry
ROMS
Submesoscale features
Mesoscale features
Subsurface drifters
Satellite altimetry
Advisors
Date of Issue
2009
Date
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Language
Abstract
ROMS with horizontal grid spacing of 3.5 km for the region off Central California was compared to RAFOS
float observations and satellite altimetry on meso/submesoscales. The approach introduced and used two
new metrics for model-data comparison, as well as suggested how to calculate these metrics for different
spatio-temporal scales. The first metric consisted of the first two moments of exit time and was used to
compare ROMS against RAFOS float observations at mid-depths (between 300 m and 350 m). Exit time is
the time a float launched at a point takes to leave a domain for the first time. The second metric was spectral
entropy and was used to estimate how well ROMS reproduced variability of the sea surface height
(SSH) anomaly field extracted from an AVISO data set (1992–2007) for specified temporal and spatial
scales. Calculations showed that ROMS reproduced the mid-depth mesoscale/submesoscale currents next
to the coast in a very accurate manner (low-order exit time statistics of floats were reproduced by ROMS
with an accuracy better than 95%); but ROMS overestimated the speed of westward drift of floats by as
much as 20–30% at distances greater than 350 km from the coastline. ROMS predicted the variability of
the mesoscale (100–400 km) SSH anomaly field for temporal scales of 1–12 months with a reasonable
accuracy. A wavelet transform modulus maxima technique applied to the spectral entropy of SSH anomaly
also demonstrated good agreement between ROMS and satellite altimetry for mesoscales characterized
by singular exponents and multi-fractal spectra for 1–12 month time scales.
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Article
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The article of record as published may be located at http://dx.doi.org/10.1016/j.ocemod.2009.02.003
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Ocean Modelling, Volume 28, (2009), pp. 209–225
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This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.