Wind and waves in extreme hurricanes

Waves breaking at the ocean surface are important to the dynamical, chemical and biological processes at the air-sea interface. The traditional view is that the white capping and aero-dynamical surface roughness increase with wind speed up to a limiting value. This view is fundamental to hurricane forecasting and climate research but it has never been verified at extreme winds. Here we show with observations that at high wind speeds white caps remain constant and at still higher wind speeds are joined, and increasingly dominated, by streaks of foam and spray. At surface wind speeds of ?40 m/s the streaks merge into a white out, the roughness begins to decrease and a high-velocity surface jet begins to develop. The roughness reduces to virtually zero by ?80 m/s wind speed, rendering the surface aero-dynamically extremely smooth in the most intense part of extreme (or major) hurricanes (wind speed > 50 m/s). A preliminary assessment shows that cross swell, dominant in large regions of hurricanes, allows the roughness under high wind conditions to increase considerably before it reduces to the same low values.

[1]  Dongliang Zhao,et al.  Dependence of Whitecap Coverage on Wind and Wind-Wave Properties , 2001 .

[2]  James L. Franklin,et al.  The NCAR GPS Dropwindsonde , 1999 .

[3]  P. K. Taylor,et al.  The Dependence of Sea Surface Roughness on the Height and Steepness of the Waves , 2001 .

[4]  Qin Chen,et al.  Directional spectra of hurricane‐generated waves in the Gulf of Mexico , 2011 .

[5]  M. Longuet-Higgins.  The statistical analysis of a random, moving surface , 1957, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.

[6]  Leo H. Cohen,et al.  Relationship of oceanic whitecap coverage to wind speed and wind history , 2008 .

[7]  G. Burgers,et al.  A sea drag relation for hurricane wind speeds , 2010 .

[8]  J. Garratt.  Review of Drag Coefficients over Oceans and Continents , 1977 .

[9]  W. Oost,et al.  Wave Energy Dissipation by Whitecaps , 1996 .

[10]  W. Large,et al.  Open Ocean Momentum Flux Measurements in Moderate to Strong Winds , 1981 .

[11]  M. Donelan,et al.  Relative rates of sea‐air heat transfer and frictional drag in very high winds , 2010 .

[12]  Hendrik L. Tolman,et al.  Source Terms in a Third-Generation Wind Wave Model , 1996 .

[13]  J. C. Dietrich,et al.  Origin of the Hurricane Ike forerunner surge , 2011 .

[14]  John A. T. Bye,et al.  Charnock dynamics: a model for the velocity structure in the wave boundary layer of the air–sea interface , 2008 .

[15]  Jin Wu.  Wind‐stress coefficients over sea surface from breeze to hurricane , 1982 .

[16]  Edward J. Walsh,et al.  The Southern Ocean Waves Experiment. Part I: Overview and Mean Results , 1999 .

[17]  Leo H. Holthuijsen,et al.  A Method for the Routine Analysis of Pitch-and-Roll Buoy Wave Data , 1988 .

[18]  David W. Wang,et al.  Bottom-Up Determination of Air-Sea Momentum Exchange Under a Major Tropical Cyclone , 2007, Science.

[19]  N. Reul,et al.  Air Flow Structure Over Short-gravity Breaking Water Waves , 2008 .

[20]  Jun A. Zhang,et al.  Air-sea exchange in hurricanes : Synthesis of observations from the coupled boundary layer air-sea transfer experiment , 2007 .

[21]  P. Black,et al.  Turbulent Fluxes in the Hurricane Boundary Layer. Part I: Momentum Flux , 2007 .

[22]  M. D. Stokes,et al.  Observed physical and environmental causes of scatter in whitecap coverage values in a fetch‐limited coastal zone , 2008 .

[23]  M. Powell,et al.  A Hurricane Boundary Layer and Wind Field Model for Use in Engineering Applications , 2009 .

[24]  Edward C. Monahan,et al.  Optimal Power-Law Description of Oceanic Whitecap Coverage Dependence on Wind Speed , 1980 .

[25]  W. Nordberg,et al.  Measurements of Microwave Emission from a Foam-Covered, Wind-Driven Sea , 1971 .

[26]  S. Elgar.  Waves in Oceanic and Coastal Waters , 2007 .

[27]  Martin White,et al.  Automated Processing of Sea Surface Images for the Determination of Whitecap Coverage , 2009 .

[28]  Kerry A. Emanuel,et al.  A Similarity Hypothesis for Air–Sea Exchange at Extreme Wind Speeds , 2003 .

[29]  J. C. Dietrich,et al.  Hurricane Gustav (2008) Waves and Storm Surge: Hindcast, Synoptic Analysis, and Validation in Southern Louisiana , 2011 .

[30]  Mark A. Donelan,et al.  On momentum flux and velocity spectra over waves , 1999 .

[31]  B. I. Miller.  A STUDY OF THE FILLING OF HURRICANE DONNA (1960) OVER LAND , 1964 .

[32]  Mingjing Tong,et al.  Hurricane Weather Research and Forecasting (HWRF) Model: 2015 Scientific Documentation , 2012 .

[33]  P. Black,et al.  Turbulent Fluxes in the Hurricane Boundary Layer. Part II: Latent Heat Flux , 2007 .

[34]  Radiation Stresses in Short-crested Waves ' J , 2022 .

[35]  Leo H. Holthuijsen,et al.  Statistics of Breaking Waves Observed as Whitecaps in the Open Sea , 1986 .

[36]  M. Donelan,et al.  On the Dependence of Sea Surface Roughness on Wave Development , 1993 .

[37]  N. Booij,et al.  A third-generation wave model for coastal regions-1 , 1999 .

[38]  P. Forget,et al.  Whitecap coverage in coastal environment for steady and unsteady wave field conditions , 2007 .

[39]  H. Tennekes,et al.  The Logarithmic Wind Profile , 1973 .

[40]  J. Kleiss,et al.  The Analysis of Sea Surface Imagery for Whitecap Kinematics , 2011 .

[41]  Shuyi S. Chen,et al.  The CBLAST-Hurricane program and the next-generation fully coupled atmosphere–wave–ocean models for hurricane research and prediction , 2007 .

[42]  A. M. Walker.  Statistical Analysis of a Random, Moving Surface , 1957, Nature.

[43]  Jeffrey L. Hanson,et al.  Automated Analysis of Ocean Surface Directional Wave Spectra , 2001 .

[44]  T. Marchok,et al.  The Operational GFDL Coupled Hurricane–Ocean Prediction System and a Summary of Its Performance , 2007 .

[45]  Nicolas Reul,et al.  On the limiting aerodynamic roughness of the ocean in very strong winds , 2004 .

[46]  O. Phillips.  Spectral and statistical properties of the equilibrium range in wind-generated gravity waves , 1985, Journal of Fluid Mechanics.

[47]  Hiroshi Yoshioka,et al.  Variation of whitecap coverage with wave-field conditions , 2007 .

[48]  A. Rutgersson,et al.  Evaluation of a Roughness Length Model and Sea Surface Properties with Data from the Baltic Sea , 2010 .

[49]  V. Kudryavtsev,et al.  Aerodynamic roughness of the sea surface at high winds , 2007 .

[50]  Peter G. Black,et al.  Hurricane Directional Wave Spectrum Spatial Variation in the Open Ocean , 2001 .

[51]  Mark D. Powell,et al.  Evaluations of Diagnostic Marine Boundary-Layer Models Applied to Hurricanes , 1980 .

[52]  Duncan B. Ross,et al.  Observations of oceanic whitecaps and their relation to remote measurements of surface wind Speed , 1974 .

[53]  Mark A. Donelan,et al.  The Air–Sea Momentum Flux in Conditions of Wind Sea and Swell , 1997 .

[54]  Clint Dawson,et al.  Performance of the Unstructured-Mesh, SWAN+ADCIRC Model in Computing Hurricane Waves and Surge , 2011, Journal of Scientific Computing.

[55]  M. Powell,et al.  Reduced drag coefficient for high wind speeds in tropical cyclones , 2003, Nature.

[56]  Marcel Zijlema,et al.  Modeling hurricane waves and storm surge using integrally-coupled, scalable computations , 2011 .

[57]  Ferris Webster,et al.  Whitecap coverage from satellite measurements: A first step toward modeling the variability of oceanic whitecaps , 2006 .

[58]  R. Lukas,et al.  Effects of Bubbles and Sea Spray on Air–Sea Exchange in Hurricane Conditions , 2010 .

[59]  P. Black,et al.  First direct measurements of enthalpy flux in the hurricane boundary layer: The CBLAST results , 2008 .

[60]  Jaak Monbaliu,et al.  Spectral Partitioning and Identification of Wind Sea and Swell , 2009 .

[61]  I. Renfrew,et al.  Aircraft‐based observations of air–sea fluxes over Denmark Strait and the Irminger Sea during high wind speed conditions , 2009 .

[62]  George H. Bryan,et al.  Evaluation of an Analytical Model for the Maximum Intensity of Tropical Cyclones , 2009 .

[63]  Lonneke Goddijn-Murphy,et al.  Parameterizations and Algorithms for Oceanic Whitecap Coverage , 2011 .

[64]  P. Dodge,et al.  Reconstruction of Hurricane Katrina's wind fields for storm surge and wave hindcasting , 2010 .

[65]  E. G. Banke,et al.  Variation of the sea surface drag coefficient with wind speed , 1975 .

[66]  K. Emanuel.  Sensitivity of Tropical Cyclones to Surface Exchange Coefficients and a Revised Steady-State Model incorporating Eye Dynamics , 1995 .

[67]  Isaac Ginis,et al.  A Physics-Based Parameterization of Air–Sea Momentum Flux at High Wind Speeds and Its Impact on Hurricane Intensity Predictions , 2007 .

[68]  P. Forget,et al.  Analysis of the Variations of the Whitecap Fraction as Measured in a Coastal Zone , 2004 .