LaCasce, J. H., Escartin, J., Chassignet, E. P., & Xu, X. (2018). Jet instability over smooth, corrugated and realistic bathymetry. J. Phys. Oceanogr. , .
Abstract: The stability of a horizontally- and vertically-sheared surface jet is examined, with a focus on the vertical structure of the resultant eddies. Over a flat bottom, the instability is mixed baroclinic/barotropic, producing strong eddies at depth which are characteristically shifted downstream relative to the surface eddies. Baroclinic instability is suppressed over a large slope for retrograde jets (with a flow anti-parallel to topographic wave propagation), and to a lesser extent for prograde jets (with flow parallel to topographic wave propagation), as seen previously. In such cases, barotropic (lateral) instability dominates if the jet is sufficiently narrow. This yields surface eddies whose size is independent of the slope but proportional to the jet width. Deep eddies still form, forced by interfacial motion associated with the surface eddies, but they are weaker than under baroclinic instability and are vertically aligned with the surface eddies. A sinusoidal ridge acts similarly, suppressing baroclinic instability and favoring lateral instability in the upper layer.
A ridge with a 1 km wavelength and an amplitude of roughly 10 m is sufficient to suppress baroclinic instability. Surveys of bottom roughness from bathymetry acquired with shipboard multibeam echosounding reveal that such heights are common, beneath the Kuroshio, the Antarctic Circumpolar Current and, to a lesser extent, the Gulf Stream. Consistent with this, vorticity and velocity cross sections from a 1/50° HYCOM simulation suggest that Gulf Stream eddies are vertically aligned, as in the linear stability calculations with strong topography. Thus lateral instability may be more common than previously thought, due to topography hindering vertical energy transfer.
Langland, R. H., Maue, R. N., & Bishop, C. H. (2008). Uncertainty in atmospheric temperature analyses. Tellus A , 60 (4), 598–603.
LaRow, T. E., Y.-K. Lim, D. W. Shin, S. D. Cocke, and E. Chassignet. (2007). High resolution ensemble west Atlantic basin seasonal hurricane simulations . CAS/JSC Working Group on Numerical Experimentation.
LaRow, T. E., & Cocke, S. (2004, Spring). Methods for Multi¬Model Proxies for Climate Studies. CLIVAR Exchanges Newsletter .
LaRow, T. E., & Cocke, S. D. (1999). Simulation of the 1997/98 and 1991/92 ENSO event using a Coupled Ocean-Atmosphere Regional Spectral Model (H. Ritchie, Ed.). Research Activities in Atmospheric and Oceanic Modelling.
LaRow, T. E., Cocke, S., & Shin, D. W. (2003). Multi-convection as a multi-model proxy for seasonal climate studies. CLIVAR Exchanges , 28 .
Latif, M., Anderson, D., Barnett, T., Cane, M., Kleeman, R., Leetmaa, A., et al. (1998). A review of the predictability and prediction of ENSO. J. Geophys. Res. , 103 (C7), 14375–14393.
Laurencin, C., & Misra, V. (2018). Characterizing the Variations of the motion of the North Atlantic tropical cyclones. Meteorol Atmos Phys , 130 (303), 1–12.
Abstract: In this study, we examine the seasonal and interannual variability of the North Atlantic (NATL) tropical cyclone (TC) motion from the historical Hurricane Database (HURDAT2) over the period 1988-2014. We characterize these motions based on their position, lifecycle, and seasonal cycle. The main findings of this study include: (1) of the 11,469 NATL TC fixes examined between 1988 and 2014, 81% of them had a translation speed of < 20 mph; (2) TCs in the deep tropics of the NATL are invariably slow-moving in comparison with TCs in higher latitudes. Although fast-moving TCs (> 40 mph) are exclusively found north of 30 N, the slow-moving TCs have a wide range of latitude. This is largely a consequence of the background steering flow being weaker (stronger) in the tropical (higher) latitudes with a minimum around the subtropical latitudes of NATL; (3) there is an overall decrease in the frequency of all categories of translation speed of TCs in warm relative to cold El Niño Southern Oscillation (ENSO) years. However, in terms of the percentage change, TCs with a translation speed in the range of 10-20 mph display the most change (42%) in warm relative to cold ENSO years; and (4) there is an overall decrease in frequency across all categories of TC translation speed in small relative to large Atlantic Warm Pool years, but in terms of percentage change in the frequency of TCs, there is a significant and comparable change in the frequency over a wider range of translation speeds than the ENSO composites. This last finding suggests that Atlantic Warm Pool variations have a more profound impact on the translation speed of Atlantic TCs than ENSO.
Laxenaire, R., Speich, S., & Alexandre S. (2019). Evolution of the thermohaline structure of one Agulhas Ring reconstructed from satellite altimetry and Argo floats. Journal of Geophysical Research. Oceans , 124 (12), 8969–9003.
Le Sommer, J., Chassignet, E. P., & Wallcraft, A. J. (2018). Ocean Circulation Modeling for Operational Oceanography: Current Status and Future Challenges. In and J. Verron J. Tintoré A. Pascual E. P. Chassignet (Ed.), New Frontiers in Operational Oceanography (pp. 289–305). Tallahassee, FL: GODAE OceanView.
Abstract: This chapter focuses on ocean circulation models used in operational oceanography, physical oceanography and climate science. Ocean circulation models area particular branch of ocean numerical modeling that focuses on the representation of ocean physical properties over spatial scales ranging from the global scale to less than a kilometer and time scales ranging from hours to decades. As such, they are an essential build-ing block for operational oceanography systems and their design receives a lot of attention from operational and research centers.