Cross-Spectral Analysis of the SST/10-m Wind Speed Coupling Resolved by Satellite Products and Climate Model Simulations

TitleCross-Spectral Analysis of the SST/10-m Wind Speed Coupling Resolved by Satellite Products and Climate Model Simulations
Publication TypeJournal Article
Year of Publication2019
AuthorsLaurindo, Lucas C., Siqueira Leo, Mariano Arthur J., and Kirtman Benjamin P.
JournalClimate Dynamics
Volume52
Number9-10
Pages5071-5098
Date Published09/2018
Abstract / Summary

This study aims to determine the spatial-temporal scales where the SST forcing of the near-surface winds takes places and its relationship with the action of coherent ocean eddies. Here, cross-spectral statistics are used to examine the relationship between satellite-based SST and 10-m wind speed (w) fields at scales between 10² –10⁴ km and 10¹ –10³ days. It is shown that the transition from negative SST/w correlations at large-scales to positive at oceanic mesoscales occurs at wavelengths coinciding with the atmospheric first baroclinic Rossby radius of deformation; and that the dispersion of positively-correlated signals resembles tropical instability waves near the equator, and Rossby waves in the extratropics. Transfer functions are used to estimate the SST-driven w response in physical space (wc), a signal that explains 5–40% of the mesoscale w variance in the equatorial cold tongues, and 2–15% at extratropical SST fronts. The signature of ocean eddies is clearly visible in wc, accounting for 20–60% of its variability in eddy-rich regions. To provide further insight on the role of ocean eddies in the SST-driven coupling, the analysis is repeated for two climate model (CCSM) simulations using ocean grid resolutions of 1° (eddy-parameterized, LR) and 0.1° (eddy-resolving, HR). The lack of resolved eddies in LR leads to a significantly underestimated mesoscale w variance relative to HR. Conversely, the wc variability in HR can exceed the satellite estimates by a factor of two at extratropical SST fronts and underestimate it by a factor of almost six near the equator, reflecting shortcomings of the CCSM to be addressed in its future developments.

URLhttp://doi.org/10.1007/s00382-018-4434-6
DOI10.1007/s00382-018-4434-6
Journal: Climate Dynamics
Year of Publication: 2019
Volume: 52
Number: 9-10
Pages: 5071-5098
Date Published: 09/2018

This study aims to determine the spatial-temporal scales where the SST forcing of the near-surface winds takes places and its relationship with the action of coherent ocean eddies. Here, cross-spectral statistics are used to examine the relationship between satellite-based SST and 10-m wind speed (w) fields at scales between 10² –10⁴ km and 10¹ –10³ days. It is shown that the transition from negative SST/w correlations at large-scales to positive at oceanic mesoscales occurs at wavelengths coinciding with the atmospheric first baroclinic Rossby radius of deformation; and that the dispersion of positively-correlated signals resembles tropical instability waves near the equator, and Rossby waves in the extratropics. Transfer functions are used to estimate the SST-driven w response in physical space (wc), a signal that explains 5–40% of the mesoscale w variance in the equatorial cold tongues, and 2–15% at extratropical SST fronts. The signature of ocean eddies is clearly visible in wc, accounting for 20–60% of its variability in eddy-rich regions. To provide further insight on the role of ocean eddies in the SST-driven coupling, the analysis is repeated for two climate model (CCSM) simulations using ocean grid resolutions of 1° (eddy-parameterized, LR) and 0.1° (eddy-resolving, HR). The lack of resolved eddies in LR leads to a significantly underestimated mesoscale w variance relative to HR. Conversely, the wc variability in HR can exceed the satellite estimates by a factor of two at extratropical SST fronts and underestimate it by a factor of almost six near the equator, reflecting shortcomings of the CCSM to be addressed in its future developments.

DOI: 10.1007/s00382-018-4434-6
Citation:
Laurindo, LC, L Siqueira, AJ Mariano, and BP Kirtman.  2019.  "Cross-Spectral Analysis of the SST/10-m Wind Speed Coupling Resolved by Satellite Products and Climate Model Simulations."  Climate Dynamics 52(9-10): 5071-5098.  https://doi.org/10.1007/s00382-018-4434-6.