Williams, M. (2010). Characterizing Multi-Decadal Temperature Variability in the Southeastern United States. Master's thesis, Florida State University, Tallahassee, FL.
Abstract: Prior studies of the long-term temperature record in the Southeastern United States (SE US) mostly discuss the long-term cooling trend, and the inter-annual variability produced by the region's strong ties to El Niño Southern Oscillation (ENSO). An examination of long-term temperature records in the SE US show clear multi-decadal variations in temperature, with relative warm periods in the 1920's through the mid 1950's and a cool period in the late 1950's through the late 1990's. This substantial shift in multi-decadal variability is not well understood and has not been fully investigated. It appears to account for the long-term downward trend in temperatures. An accurate characterization of this variability could lead to improved interannual and long-term forecasts, which would be useful for agricultural planning, drought mitigation, water management, and preparation for extreme temperature events. Statistical methods are employed to determine the spatial coherence of the observed variability on seasonal time scales. The goal of this study is to characterize the nature of this variability through the analysis of National Weather Service Cooperative Observer Program (COOP) station data in Florida, Georgia, Alabama, North Carolina, and South Carolina. One finding is a shift in the temperature Probability Distribution Function (PDF) between warm regimes and cool regimes.
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Williford, C. E., Krishnamurti, T. N., Torres, R. C., Cocke, S., Christidis, Z., & Vijaya Kumar, T. S. (2003). Real-Time Multimodel Superensemble Forecasts of Atlantic Tropical Systems of 1999. Mon. Wea. Rev., 131(8), 1878–1894.
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Winsberg, M. D., O'Brien, J. J., Zierden, D., & Griffin, M. (2003). Florida Weather. Gainesville, FL: University Press of Florida.
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Winterbottom, H. (2010). The Development of a High-Resolution Coupled Atmosphere-Ocean Model and Applications Toward Understanding the Limiting Factors for Tropical Cyclone Intensity Prediction. Ph.D. thesis, Florida State University, Tallahassee, FL.
Abstract: The prediction of tropical cyclone (TC) motion has improved greatly in recent decades. However, similar trends remain absent with respect to TC intensity prediction. Several hypotheses have been proposed attempting to explain why dynamical NWP models struggle to predict TC intensity. The leading candidates are as follows: (1) the lack of an evolving ocean (i.e., sea-surface temperature) boundary condition which responds as a function of the atmosphere (e.g., TC) forcing, (2) inappropriate initial conditions for the TC vortex (e.g., lack of data assimilation methods), (3) NWP model grid-length resolutions which are unable to resolve the temporal and length scale for the features believed responsible for TC vortex intensity. modulations (i.e., eye-wall dynamics, momentum transport, vortex Rossby wave interactions, etc.), and (4) physical parametrization which do not adequately represent the air-sea interactions observed during TC passage. In this study, a coupling algorithm for two independent, high-resolution, and state-of-the-art atmosphere and ocean models is developed. The atmosphere model -- the Advanced Weather Research and Forecasting (WRF-ARW) model is coupled to the HYbrid Coordinate Ocean Model (HYCOM) using a (UNIX) platform independent and innovative coupling methodology. Further, within the WRF-ARW framework, a dynamic initialization algorithm is developed to specify the TC vortex initial condition while preserving the synoptic-scale environment. Each of the tools developed in this study is implemented for a selected case-study: TC Bertha (2008) and TC Gustav (2008) for the coupled-model and TC vortex initialization, respectively. The experiment results suggest that the successful prediction (with respect to the observations) for both the ocean response and the TC intensity cannot be achieved by simply incorporating (i.e., coupling) an ocean model and/or by improving the initial structure for the TC. Rather the physical parametrization governing the air-sea interactions is suggested as the one of the weaknesses for the NWP model. This hypothesis is (indirectly) supported through a diagnostic evaluation of the synoptic-scale features (e.g., sea-level pressure and the deep-layer mean wind beyond the influence of the TC) while the assimilated TC vortex is nudged toward the observed intensity value. It is found -- in the case of TC Gustav (2008) using WRF-ARW, that as the assimilated TC vortex intensity approaches that of the observed, the balance between the mass and momentum states for WRF-ARW is compromised leading to unrealistic features for the environmental sea-level pressure and deep-layer (800- to 200-hPa) mean wind surrounding the TC. Forcing WRF-ARW to assimilate a TC vortex of the observed maximum wind-speed intensity may ultimately compromise the prediction for the TC's motion and subsequently mitigate any gains for the corresponding intensity prediction.Suggestions for additions to the coupled atmosphere-ocean model include a wave-model (WAVEWATCH3), the assimilation of troposphere thermodynamic observations, and modifications to the existing atmospheric boundary-layer parametrization. The current suite of atmosphere model parametrizations do not accurately simulate the observed azimuthal and radial variations for the exchange coefficients (e.g., drag and enthalpy) that have been indicated as potentialpredictor variables for TC intensity modulation. However, these modifications should be implemented only after the limitations for the current coupled-model and TC vortex initialization methods are fully evaluated.
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WOCE Data Products Committee. (2000). WOCE Global Data, Version 2.0, Surface Meteorology. WOCE Report No. 171/00, World Ocean Circulation Experiment International Project Office, Southampton, UK.
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WOCE Data Products Committee. (2000). WOCE Global Data, Version 2.0, Surface Fluxes. WOCE Report No. 171/00, World Ocean Circulation Experiment International Project Office, Southampton, UK [cdrom].
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WOCE Data Products Committee. (1998). WOCE Global Data, Version 1.0, Surface Fluxes. WOCE Report No. 158/98, World Ocean Circulation Experiment International Project Office, Southampton, UK.
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WOCE Data Products Committee. (1998). WOCE Global Data, Version 1.0, Surface Meteorology Atlantic and Southern Oceans. WOCE Report No. 158/98, World Ocean Circulation Experiment International Project Office, Southampton, UK.
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WOCE Data Products Committee. (1998). WOCE Global Data, Version 1.0, Surface Meteorology Pacific and Indian Oceans. WOCE Report No. 158/98, World Ocean Circulation Experiment International Project Office, Southampton, UK.
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Woodruff, S. D., N. Scott, D. I. Berry, M. A. Bourassa, E. Charpentier, S. Gulev, H. Haar, E. C. Kent, R. W. Reynolds, G. Rosenhagen, M. Rutherfor, V. Swail, S. J. Worley, H.-M. Zhang, R. Zollner. (2010). Surface In situ Datasets for Marine Climatological Applications. In D. D.E. and Stammer Harrison J. Hall (Ed.), Proceedings of OceanObs'09: Sustained Ocean Observations and Information for Society (Vol. 2).
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