Goto, Y. (2008).
Improved Vegetation Characterization and Freeze Statistics in a Regional Spectral Model for the Florida Citrus Farming Region. Ph.D. thesis, Florida State University, Tallahassee, FL.
Abstract: This study focused on the effective use of a numerical climate model for agriculture in Florida, especially in the citrus farming region of the Florida peninsula, because of the impact of agriculture to Florida's economy. For the analyses of the ensemble, the climate models used in this study were the FSU/COAPS Global Spectral Model and FSU/COAPS Regional Spectral Model (FSU/COAPS RSM) coupled with a land-surface model. The multi-convective scheme method and variable initial conditions were used for the ensembles. Severe freezes impacting agriculture in Florida were associated with some major climate patterns, such as El Niño and Southern Oscillation (ENSO) and North Atlantic Oscillation (NAO). In the first part of this study, seasonal ensemble integrations of the regional model were examined for the tendencies of freezes in the Florida peninsula during each ENSO or NAO phase is examined. Mean excess values of minimum temperatures from thresholds on the basis of the Generalized Pareto Distribution (GPD), which represents the extreme data in a dataset, were used to analyze the freezes in the regional model. According to some previous studies, El Niño winters obtain fewer freezes than the other ENSO phases. Although the ensemble comprised only 19 winters, the ensemble found variability patterns in minimum temperatures in each climate phase similar to the findings in the previous studies which were based on the observed data. The FSU/COAPS RSM was coupled with Community Land Model 2.0 (CLM2), to represent the land-surface conditions. Although the coupling improved the temperature forecast of the RSM, it still has a cold bias and simulates smaller diurnal temperature changes than actually occur in southern Florida. Among the prescribed surface data, Leaf Area Index (LAI) for southern Florida in the CLM2 is lower than those observed by MODIS (Moderate Resolution Imaging Spectroradiometer). In the first experiment of this part, the sensitivity of the temperature forecast to the LAI in the climate models was investigated, by modifying the LAI data in the CLM2 based on the monthly MODIS observations. In the second experiment, newly created prescribed datasets of LAI and plant functional types for the CLM2 based on the MODIS observations were applied to the RSM. The substitution increased the diurnal temperature change in southern Florida slightly but almost consistently.
Goto, Y., Shin, D. W., & O'Brien, J. J. (2006).
Sensitivity of leaf area index in Florida to temperature simulation by FSURSM. Research Activities in Atmospheric and Ocean Modeling, CAS/JSC Working Group on Numerical Experimentation.
Goto-Maeda, Y., Shin, D. W., & O'Brien, J. J. (2008). Freeze probability of Florida in a regional climate model and climate indices.
Geophys. Res. Lett., 35(11).
Gouillon, F. (2010).
Internal Wave Propagation and Numerically Induced Diapycnal Mixing in Oceanic General Circulation Models. Ph.D. thesis, Florida State University, Tallahassee, FL.
Abstract: Numerical ocean models have become powerful tools for providing a realistic view of the ocean state and for describing ocean processes that are difficult to observe. Recent improvements in model performance focus on simulating realistic ocean interior mixing rates, as ocean mixing is the main physical process that creates water masses and maintains their properties. Below the mixed layer, diapycnal mixing primarily arises from the breaking of internal waves, whose energy is largely supplied by winds and tides. This is particularly true in abyssal regions, where the barotropic tide interacts with rough topography and where high levels of diapycnal mixing have been recorded (e.g., the Hawaiian Archipelago). Many studies have discussed the representation of internal wave generation, propagation, and evolution in ocean numerical models. Expanding on these studies, this work seeks to better understand the representation of internal wave dynamics, energetics, and their associated mixing in several different classes of widely used ocean models (e.g., the HYbrid Coordinate Ocean Model, HYCOM; the Regional Ocean Modeling System, ROMS; and the MIT general circulation model, MITgcm). First, a multi-model study investigates the representation of internal waves for a wide spectrum of numerical choices, such as the horizontal and vertical resolution, the vertical coordinate, and the choice of the numerical advection scheme. Idealized configurations are compared to their corresponding analytical solutions. Some preliminary results of realistic baroclinic tidal simulations are shown for the Gulf of Mexico. Second, the spurious diapycnal mixing that exists in models with fixed vertical coordinates (i.e., geopotential and terrain following) is documented and quantified. This purely numerical error arises because, in fixed-coordinate models, the numerical framework cannot properly maintain the adiabatic properties of an advected water parcel. This unrealistic mixing of water masses can be a source of major error in both regional and global ocean models. We use the tracer flux method to compute the spurious diapycnal diffusivities for both a lockexchange scenario and a propagating internal wave field using all three models. Results for the lock exchange experiments are compared to the results of a recent study. Our results, obtained by using three different model classes, provide a comprehensive analysis of the impact of model resolution choice and numerical framework on the magnitude of the spurious diapycnal mixing and the representation of internal waves.
Gouillon, F. (2008). Internal wave generation over a ridge using the HYbrid Coordinate Ocean Model (HYCOM). In
AGU, Orlando, FL.
Gouillon, F., Dukhovskoy, D. D., Morey, S. L., & O'Brien, J. J. (2006).
Modeling tides in a semi-enclosed basin: A case study of the Gulf of Mexico (J. Cote, Ed.). Research Activities in Atmospheric and Ocean Modeling, Report No. 36. Geneva, Switzerland,: World Meteorological Organization.
Gouillon, F., Morey, S. L., Dukhovskoy, D. S., & O'Brien, J. J. (2010). Forced tidal response in the Gulf of Mexico.
J. Geophys. Res., 115(C10).
Gould, W. J., & Smith, S. R. (2006). Research vessels: Underutilized assets for climate observations.
Eos Trans. AGU, 87(22), 214.
Grant, J., Erlebacher, G., & O'Brien, J. (2002). Case study: Visualizing ocean flow vertical motions using Lagrangian-Eulerian time surfaces. In
IEEE Visualization 2002 Conference (pp. 529–532).
Green, P. M. (1996).
Regional analysis of Canadian, Alaskan, and Mexican precipitation and temperature for ENSO impact. Master's thesis, Florida State University, Tallahassee, FL.