Ali, A., Christensen, K. H., Breivik, Ø., Malila, M., Raj, R. P., Bertino, L., et al. (2019). A comparison of Langmuir turbulence parameterizations and key wave effects in a numerical model of the North Atlantic and Arctic Oceans.
Ocean Modelling, 137, 76–97.
Abstract: Five different parameterizations of Langmuir turbulence (LT) effect are investigated in a realistic model of the North Atlantic and Arctic using realistic wave forcing from a global wave hindcast. The parameterizations mainly apply an enhancement to the turbulence velocity scale, and/or to the entrainment buoyancy flux in the surface boundary layer. An additional run is also performed with other wave effects to assess the relative importance of Langmuir turbulence, namely the Coriolis-Stokes forcing, Stokes tracer advection and wave-modified momentum fluxes. The default model (without wave effects) underestimates the mixed layer depth in summer and overestimates it at high latitudes in the winter. The results show that adding LT mixing reduces shallow mixed layer depth (MLD) biases, particularly in the subtropics all year-around, and in the Nordic Seas in summer. There is overall a stronger relative impact on the MLD during winter than during summer. In particular, the parameterization with the most vigorous LT effect causes winter MLD increases by more than 50% relative to a control run without Langmuir mixing. On the contrary, the parameterization which assumes LT effects on the entrainment buoyancy flux and accounts for the Stokes penetration depth is able to enhance the mixing in summer more than in winter. This parametrization is also distinct from the others because it restrains the LT mixing in regions of deep MLD biases, so it is the preferred choice for our purpose. The different parameterizations do not change the amplitude or phase of the seasonal cycle of heat content but do influence its long-term trend, which means that the LT can influence the drift of ocean models. The combined impact on water mass properties from the Coriolis-Stokes force, the Stokes drift tracer advection, and the wave-dependent momentum fluxes is negligible compared to the effect from the parameterized Langmuir turbulence.
Griffin, J. (2009).
Characterization of Errors in Various Moisture Roughness Length Parameterizations. Master's thesis, Florida State University, Tallahassee, FL.
Abstract: Often the parameterization of the moisture roughness length is not seen as being important, as long as the parameterization seems reasonable; that is, it is within the rather considerable bounds of error for the data sets used to determine the parameterization. However, the choice of parameterization does influence height adjustments of humidity and calculations of turbulent heat fluxes. This paper focuses on the calculation of the turbulent heat fluxes using different parameterizations of roughness length. Five roughness length parameterizations are examined herein. These parameterizations include wall theory; the Clayson, Fairall, Curry parameterization; the Liu, Katsaros, Businger parameterization; Zilitinkevich et al. parameterization; and the COARE3.0 parameterization. Turbulent heat fluxes are calculated from each parameterization of the roughness length and are compared to observed turbulent heat flux values. The bulk latent heat flux estimates have a much better signal to noise ratio than the sensible heat fluxes, and are therefore the focus of the comparison to observations. This comparison indicates how to improve the proportionality in the above roughness length parameterizations, which are causing modeled turbulent heat flux magnitudes to be too large in four of the five parameterizations. The modeled turbulent heat fluxes are evaluated again after the modification of the parameterizations. Significant improvements in both the bias and the root mean square error (RMSE) are seen. Three parameterizations see roughly the same improvements of around 17Wm^-2 in the bias and roughly 10Wm^-2 in the RMSE. The largest improvements are in the Liu, Katsaros, Businger parameterization with bias improvements of over 45Wm^-2 and a RMSE reduction of nearly 32Wm^-2.
Hong, S. - Y., Park, H., Cheong, H. - B., Kim, J. - E. E., Koo, M. - S., Jang, J., et al. (2013). The Global/Regional Integrated Model system (GRIMs).
Asia-Pacific J Atmos Sci, 49(2), 219–243.
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.
Moroni, D. F. (2008).
Global and Regional Diagnostic Comparison of Air-Sea Flux Parameterizations during Episodic Events. Ph.D. thesis, Florida State University, Tallahassee, FL.
Abstract: Twenty turbulent flux parameterizations are compared globally and regionally with a focus on the differences associated with episodic events. The regional focus is primarily upon the Gulf Stream and Drake Passage, as these two regions contain vastly different physical characteristics related to storm and frontal passages, varieties of sea-states, and atmospheric stability conditions. These turbulent flux parameterizations are comprised of six stress-related parameterizations [i.e., Large and Pond (1981), Large et al. (1994), Smith (1988), HEXOS (Smith et al. 1992, 1996), Taylor and Yelland (2001), and Bourassa (2006)] which are paired with a choice of three atmospheric stability parameterizations ['Neutral' assumption, Businger-Dyer (Businger 1966, Dyer 1967, Businger et al. 1971, and Dyer 1974) relations, and Beljaars-Holtslag (1991) with Benoit (1977)]. Two remaining turbulent flux algorithms are COARE version 3 (Fairall et al. 2003) and Kara et al. (2005), where Kara et al. is a polynomial curve fit approximation to COARE; these have their own separate stability considerations. The following data sets were used as a common input for parameterization: Coordinated Ocean Reference Experiment version 1.0, Reynolds daily SST, and NOAA WaveWatch III. The overlapping time period for these data sets is an eight year period (1997 through 2004). Four turbulent flux diagnostics (latent heat flux, sensible heat flux, stress, curl of the stress) are computed using the above parameterizations and analyzed by way of probability distribution functions (PDFs) and RMS analyses. The differences in modeled flux consistency are shown to vary by region and season. Modeled flux consistency is determined both qualitatively (using PDF diagrams) and quantitatively (using RMS differences), where the best consistencies are found during near-neutral atmospheric stratification. Drake Passage shows the least sensitivity (in terms of the change in the tails of PDFs) to seasonal change. Specific flux diagnostics show varying degrees of consistency between stability parameterizations. For example, the Gulf Stream's latent heat flux estimates are the most inconsistent (compared to any other flux diagnostic) during episodic and non-neutral conditions. In all stability conditions, stress and the curl of stress are the most consistent modeled flux diagnostics. Sea-state is also a very important source of modeled flux inconsistencies during episodic events for both regions.
Keywords: Parameterizations, Parameterization, Algorithm, Probability Density, Probability Distribution, Pdf, Drake Passage, Kuroshio, Gulf Stream Ect, Cold Tongue, Indian Ocean, Pacific Ocean, Southern Oceans, Atlantic Ocean, Tropics, Sea-State
Shin, D. W., LaRow, T. E., & Cocke, S. (2003). Convective scheme and resolution impacts on seasonal precipitation forecasts.
Geophys. Res. Lett., 30(20).