The goal of the International Best Track Archive for Climate Stewardship (IBTrACS) project is to collect the historical tropical cyclone best-track data from all available Regional Specialized Meteorological Centers (RSMCs) and other agencies, combine the disparate datasets into one product, and disseminate in formats used by the tropical cyclone community Each RSMC forecasts and monitors storms for a specific region and annually archives best-track data, which consist of information on a storm's position, intensity, and other related parameters IBTrACS is a new dataset based on the best-track data from numerous sources Moreover, rather than preferentially selecting one track and intensity for each storm, the mean position, the original intensities from the agencies, and summary statistics are provided This article discusses the dataset construction, explores the tropical cyclone climatology from IBTrACS, and concludes with an analysis of uncertainty in the tropical cyclone intensity record

The International Best Track Archive for Climate Stewardship (IBTrACS)Unifying Tropical Cyclone Data

An analytical theory is presented to describe the combined motion of waves and currents in the vicinity of a rough bottom and the associated boundary shear stress. Characteristic shear velocities are defined for the respective wave and current boundary layer regions by using a combined wave-current friction factor, and turbulent closure is accomplished by employing a time invariant turbulent eddy viscosity model which increases linearly with height above the seabed. The resulting linearized governing equations are solved for the wave and current kinematics both inside and outside the wave boundary layer region. For the current velocity profile above the wave boundary layer, the concept of an apparent bottom roughness is introduced, which depends on the physical bottom roughness as well as the wave characteristics. The net result is that the current above the wave boundary layer feels a larger resistance due to the presence of the wave. The wave-current friction factor and the apparent roughness are found as a function of the velocity of the current relative to the wave orbital velocity, the relative bottom roughness, and the angle between the currents and the waves. In the limiting case of a pure wave motion the predictions of the velocity profile and wave friction factor from the theory have been shown to give good agreement with experimental results. The reasonable nature of the concept of the apparent bottom roughness is demonstrated by comparison with field observations of very large bottom roughnesses by previous investigators. The implications of the behavior predicted by the model on sediment transport and shelf circulation models are discussed.

Combined wave and current interaction with a rough bottom

1. Introduction 2. Observation techniques 3. Description of ocean waves 4. Statistics 5. Linear wave theory (oceanic waters) 6. Waves in oceanic waters 7. Linear wave theory (coastal waters) 8. Waves in coastal waters 9. The SWAN wave model Appendices References Index.

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Waves in Oceanic and Coastal Waters

Recent measurements of wave spectra and observations by remote sensing of the sea surface indicate that the author's (1958) conception of an upper-limit asymptote to the spectrum, independent of wind stress, is no longer tenable. The nature of the equilibrium range is reexamined, using the dynamical insights into wave–wave interactions, energy input from the wind and wave-breaking that have been developed since 1960. With the assumption that all three of these processes are important in the equilibrium range, the wavenumber spectrum is found to be of the form , where p ∼ ½ and the frequency spectrum is proportional to u*gσ−4. These forms have been found by Kitaigorodskii (1983) on a quite different dynamical basis; the latter is consistent with the form found empirically by Toba (1973) and later workers. Various derived spectra, such as those of the sea-surface slope and of an instantaneous line traverse of the surface, are also given, as well as directional frequency spectra and frequency spectra of slope.The theory also provides expressions for the spectral rates of action, energy and momentum loss from the equilibrium range by wave-breaking and for the spectrally integrated rates across the whole range. These indicate that, as a wave field develops with increasing fetch or duration, the momentum flux to the underlying water by wave-breaking increases asymptotically to a large fraction of the total wind stress and that the energy flux to turbulence in the water, occurring over a wide range of scales, increases logarithmically as the extent of the equilibrium range increases. Interrelationships are pointed out among different sets of measurements such as the various spectral levels, the directional distributions, the total mean-square slope and the ratio of downwind to crosswind mean-square slopes.Finally, some statistical characteristics of the breaking events are deduced, including the expected length of breaking fronts (per unit surface area) with speeds of advance between c and c+dc and the number of such breaking events passing a given point per unit time. These then lead to simple expressions for the density of whitecapping, those breaking events that produce bubbles and trails of foam, the total number of whitecaps passing a given point per unit time and, more tenuously, the whitecap coverage.

Spectral and statistical properties of the equilibrium range in wind-generated gravity waves

http://personalpages.to.infn.it/~onorato/publications_files/2013_Onorato_etal_PhysRep.pdf

Rogue waves and their generating mechanisms in different physical contexts

The upper ocean's response to three hurricanes [Norbert (1984), Josephine (1984) and Gloria (1985)] is examined using field observations and a numerical ocean model. Our goal is to describe the physical processes that determine the structure and amplitude of hurricane-driven upper-ocean currents. All three of these Northern Hemisphere hurricanes produced a rightward-biased response of the mixed-layer current and transport. This asymmetry arises because the wind stress vector rotates clockwise on the right side of the track and remains nearly parallel with the inertially rotating mixed-layer current during most of the hurricane passage. The maximum observed mixed-layer current varied from 0.8 m s−1 in response to Josephine, which was a large but comparatively weak hurricane, to 1.7 m s−1 in response to Gloria, which was very large and also intense. These cases have been simulated with a three-dimensional numerical model that includes a treatment of wind-driven vertical mixing within the primitive ...

Forced Stage Response to a Moving Hurricane

Many empirical and heuristic distribution functions for wave crest heights have been proposed, but their predictions differ considerably. Part of the lack of agreement is due to the difficulty of making measurements that accurately record the true height of the wave crests. Surface following buoys effectively cancel out the second-order nonlinearity by making a Lagrangian measurement. Pressure transducers filter the nonlinear components of the signal in complicated ways. Wave staffs have varying degrees of sensitivity to spray. The location of the instruments also plays an important role. There is clear evidence from measurements in the North Sea that spurious crests due to spray are a problem downwind even from mounting supports that appear transparent. Much of the theoretical nonlinearity can be captured by calculations correct to second order. Explicit calculation of the interactions of each pair of components in a directional spectrum is straightforward although computationally intensive. This technique has the advantage that the effects of wave steepness, water depth, and directional spreading are included with no approximation other than the truncation of the expansion at second order. Comparisons with measurements that are believed to be of the best quality show good agreement with these second-order calculations. Simulations for a set of JONSWAP spectra then lead to parametric crest distributions, which can be used easily in applications.

https://journals.ametsoc.org/doi/pdf/10.1175/1520-0485%282000%29030%3C1931%3AWCDOAS%3E2.0.CO%3B2

Wave Crest Distributions: Observations and Second-Order Theory

Wavestaff measurements made in the Gulf of Mexico and Waverider measurements from the Baltimore Canyon area have been used to study the form of ocean wave spectra at high frequencies. The observations are statistically consistent with the idea that the tail of the spectrum is in equilibrium with the local wind. Analysis showed that the spectral range between the mean wave frequency and about two and one half times that frequency is consistently proportional to the inverse of the fourth power of the frequency. At higher frequencies, the classical inverse fifth power law seems to hold. In the inverse fourth power range, the amplitude of the spectrum is also proportional to the wind friction velocity. These relationships should permit a reliable specification of this saturated range when only local wind observations are available. If the significant wave height and mean period are known, the amplitude of the tail of the spectrum can be predicted with somewhat greater accuracy. However, this relationship should be used with caution when the height and period statistics are influenced by swell.

Measurements of a saturated range in ocean wave spectra

The response of the ocean to hurricanes was investigated using aircraft-deployable expendable current profilers (AXCP). The goals were to observe and separate the surface wave and surface mixed layer (SML) velocities under the storms and to map the across-track and along-track velocity and temperature response in the mixed layer and thermocline. Custom instrumentation was prepared, including slower failing AXCPs, and the AXCP equipment was installed on NOAA WP-3D aircraft. Research flights were made into two 1984 hurricanes: Norbert, in the eastern Pacific off Baja California (19°N, 109°W), and Josephine, off the east coast of the United States (29°N, 72°W). Thirty-one probes were deployed in each hurricane, and about half the AXCPs provided temperature and velocity profiles. Most velocity profiles exhibited strong surface wave contributions, slablike velocities in the SML, strong shears beneath the SML, and only weak flows in the upper thermocline. Separation of the surface gravity wave velociti...

Ocean Response to a Hurricane. Part I: Observations

Previous studies of wind-driven currents have naturally concentrated on the prediction of destructive storm surges. However, the present and planned construction of large facilities in offshore waters makes study of the currents themselves equally important. Here we show that it is possible to model three-dimensional time-dependent currents by numerical integration over a two-dimensional grid followed by an evaluation of convolution integrals over the sea slope and wind stress. Solutions for idealized cases are compared with analytical results, and a study of a hurricane in the Gulf of Mexico is presented.

George Z. Forristall

Papers

Forced Stage Response to a Moving Hurricane

Wave Crest Distributions: Observations and Second-Order Theory

Measurements of a saturated range in ocean wave spectra

Ocean Response to a Hurricane. Part I: Observations

Three‐dimensional structure of storm‐generated currents