- Acronym for Wave Direction Measurement Calibration Project, a
program held in the vicinity of the Edda platform in the
Ekofisk field in the North Sea during winter 1985-1986.
Several wave buoys, platforms and wave staffs were
intercalibrated in this project.
See Allender et al. (1989).
- Walker circulation
- A name coined by Bjerknes for two circulation cells in the
equatorial atmosphere, one over the Pacific and one over the
Indian Ocean. Schematically these are longitudinal cells
where, on one side of the ocean, convection and the associated
release of latent heat in the air above lifts
isobaric surfaces upward in the
upper troposphere and creates a high pressure region there.
The lack or lesser degree of the same process on the other
side of the ocean results in lower pressure there, and a longitudinal
pressure gradient is established which, being on the equator,
cannot be balanced by the Coriolis force.
Thus a direct zonal circulation is driven in the equatorial plane
with countervailing winds at the surface and in the upper troposphere,
with concomitant rising and sinking branches on the appropriate sides
of the ocean.
The normal Walker circulation in the Pacific consists of air rising
over Indonesia, west winds in the upper troposphere, sinking air off
the west coast of South America, and east winds near the surface.
A reversed but weaker Walker circulation (and an enhanced
occurs during ENSO years.
In the Indian ocean the circulation cell proceeds in the opposite
sense (to the normal Pacific Walker cell), with sinking air over
cold waters off the Somali coast and a low-level acceleration
from west to east along the equator in the lower atmosphere.
See Henderson-Sellers and Robinson (1986) and
Kraus and Businger (1994).
- Walvis Basin
- See Cape Basin.
- Acronym for Wave Model Development and Implementation group,
an organization created to advanced sea surface state models.
See Group (1988).
- Acronym for the West African Monsoon Experiment, a component of
FGGE designed to study monsoonal
See WAMEX (1990).
- Warm Deep Water
Antarctic Circumpolar Water.
- Acronym for Waves And Storms in the North Atlantic, a project whose goal
is to verify or falsify the hypothesis of a worsening storm and wave
climate in the Northeast Atlantic and its adjacent seas in the 20th century.
The main conclusion of the project is that the storm- and wave-climate
in most of the Northeast Atlantic and in the North Sea has undergone significant
variations on times scales of decades, that is has indeed roughened in
the past decades, but that the present intensity seems to cmopare with
the intensity at the beginning of the century. Part of the variability
was found to be related to the
North Atlantic Oscillation.
See WASA (1998).
- Acronym for WOCE/Atlantic/Tropical-Boundary
- water mass
- In physical oceanography, a body of water with a common formation
history. A water mass is identified through relationships on a
T-S diagram, although additional
information about the degree of spatial and temporal variability
during its formation as expressed by a standard deviation is
almost always needed as well. A single T-S point, i.e. a
water type, along with its standard
deviation, may be sufficient for identification (especially
with deep water masses), although generally a set of T-S combinations,
i.e. a function in T-S space, is needed along with a standard
deviation envelope. Generally the standard deviation decreases
with depth. In practice not enough data is usually
available to calculate a standard deviation, so a point or line
in T-S space is specified around which the water mass properties
are presumed to vary.
See Emery and Meincke (1986a).
Examples include AAIW, AASW,
SAMW, SAUW, AACW,
WDW, AABW, ABW,
GSDW, ASW, PDW,
SIW, WSPCW, ESPCW,
WNPCW, ENPCW, NPEW,
SPEW, JSMW, JSPW,
IDW, PGW, ICW,
AAMW, BBW, LSW,
EMW, AIW, SACW,
NACW, MMW, MDW,
AW, and LIW.
See Emery and Meincke (1986b) and
Wright and Worthington (1970).
- water mass analysis
- A technique introduced by Jacobsen (1927) as a graphical method
for determining mixing coefficients in a
It was extended by Wüst in 1935
who developed his core layer method.
This was further extended by Tomczak (1981) who developed
a multi-parameter analysis technique by adding oxygen and nutrients
as additional quasi-conservative parameters. This idea was further
developed into what is currently known as
Optimum Multiparameter Analysis (OMP).
See Rees and Aiken (1995).
- water mass characteristics
- A property value or, more often, range of property values by
which a water mass can be identified
and tracked through the ocean.
The most commonly used are
potential density or
the density referenced to a particular depth or pressure.
Less often used by still quite valuable for certain applications
carbon 14 and
tritium. See also the entry on
- water type
- In physical oceanography, a point on a T-S diagram.
- water vapor feedback
- A positive feedback loop in the atmosphere wherein
an increase in temperature increases the water holding
capacity. This will lead to an increase in the amount
of atmospheric water vapor which, being a
greenhouse gas, will in
turn lead to another temperature increase. This process
is better understood in the lower troposphere where there
is reasonable certainty as to the feedback process. The
upper atmosphere, while not as well understood in this
regard, has a preponderance of evidence pointing to this.
The temperature change is not uniform with height and
the resulting changes in the vertical temperature gradient
can partially compensate for the water vapor feedback.
- water vapor mixing ratio
- The ratio of the mass of water vapor to the mass of dry air
in a specified volume as expressed in grams per kilogram.
- water vapor pressure
- The part of atmospheric pressure due to the water vapor in
- Acronym for Western Atlantic Ocean Experiment.
See Ray et al. (1990).
- Acronym for Western Atlantic Thermohaline Transport Study.
- wave action
- See Andrews and McIntyre (1978).
- wave climate
- The general condition of sea state
at a particular location, the principal elements of which
are the wave height, period parameters, and the wave direction.
The significant wave height
is usually used as the heighter parameter with the period
parameter either the significant wave period as determined from
time-series analysis, the period corresponding to the spectral
peak frequency, or the mean wave period from time-series or
spectral analysis. The wave direction is usually expressed
with the 16-point bearing system (i.e. NNE, WSW, etc.).
The wave climate is described in terms of months, seasons
See Goda (1990).
- wave-current interaction
- See Peregrine (1976) and
- wave forecasting
- Predicting the development and characteristics of ocean
surface gravity waves via semiempirical methods. These
methods use some theory in their foundation but require
basic data for the evaluation of various constants and
coefficients. Advances in the state-of-the-art are usually
a matter of collecting a larger database of winds and the
wave they generate. The two main approaches to wave forecasting
significant wave method
wave spectrum method.
See Komar (1976) and
- wave model
- A general term for numerical models designed to simulate the generation,
propagation, shoaling, interaction, refraction, reflection, etc. of
wind waves. These are used to predict wave fields for complicated
wave fields and bathymetry.
First generation wave models include:
Second generation models include:
Third generation models include:
- wave set-down
- See wave set-up.
- wave set-up
- A phenomenon local to the
surf zone wherein wave breaking
causes a stress or a landward push of the water which causes
it to pile up against the shore until the seaward slope
of this set-up is sufficient to oppose the wave stresses.
This is called wave set-up to distinguish it from storm
set-up or storm surge and from wind set-up, both of which
occur over a larger scale.
Wave set-up can range from 17-50% of the incident wave height
on natural beaches which can give values of up to 1 m during
large storms, which can result in a shoreward indundation of
50 m on a beach with a 1:50 slope. A related wave set-down
is found in the vicinity of the wave breaking point in the surf
zone, while the set-up occurs shoreward of this.
of the wave breaking point on the beach profile, with a small
set-down also found at
The mechanism by which waves can exert a stress on the fluid
in which they propagate is via a phenomenon called
See Holman (1990).
- wave spectrum
- A method for describing the characteristics of irregular waves in which
parameterized formulae are developed by spectral analysis of measured
Several wave spectra have been developed including:
- wave spectrum method
- A method of wave forecasting
that describes the waves generated by storms in terms of a
complete spectrum of periods and energies rather than in terms
of a single significant wave height or period. An example of a wave
spectrum method is the
P-N-J method, while a significant
wave method is the
See Komar (1976).
- A series of wavemodels, i.e.
WAVEWATCH III is a third-generation
that solves the spectral
action density balance equation for wavenumber-direction spectra.
It is implicitly assumed that the medium (i.e. depth and current)
as well as the wave field vary on time and space scales much larger
than the corresponding scales of a single wave.
The source code and complete documentation are available for
- WAVEWATCH I, developed at Delft University (Tolman (1991)),
- WAVEWATCH II, developed at NASA GSFC (Tolman (1992)), and
- WAVEWATCH III, developed at NOAA/NCEP.
- Abbreviation for
western boundary current.
- Abbreviation for World Data Center, a system of facilities established within
the framework of the IOC IODE
program to receive oceanographic data and inventories from
NODCs, RNODCs, marine
science organizations, and individual scientists. The data are collected
and submitted voluntarily from national programs or arise from
international cooperative ventures.
The WDCs are also responsbile for monitoring the performance of the
international data exchange system.
See the IODE Web site.
- See Warm Deep Water.
- Weber number
- A dimensionless number
that relates the inertial force to the
surface tension force. It is given by
where is the kinematic viscosity, a characteristic
length scale, the fluid density and
the surface tension.
It is generally used in momentum transfer calculations such as
bubble/droplet formation and breakage of liquid jets.
- See Barber (1992) and other papers therein.
- Weddell Gyre
- See Deacon (1979),
Orsi et al. (1993) and
Schröder and Fahrbach (1999).
- Weddell Gyre Boundary
- See Continental Water Boundary.
- Weddell Sea
- More about which later.
- Weddell-Scotia Confluence
- The zone separating the waters of the
Weddell Sea from those of the
Scotia Sea in the
This is a line extending from the South Shetland Islands near
the Antarctic Peninsula in a northeastward direction across the
southern Scotia Sea to as far as 30 E. The deep
waters on either side of the boundary are distinguishable
on the basis of their temperature and salinity properties, with
those to the north of the line (from the southeast Pacific) being
warmer and slightly saltier.
The water column in the western WSC itself is nearly homogenuous
due to vertical mixing that is active to one degree or another
throughout the year. As one proceeds eastward lateral mixing processes
gradually mix this homogenous water with the stratified waters to
the north and south until such stratification is restored on
the WSC is no longer in evidence. The complex bathymetry in the
region is thought to play a major part in inducing the lateral
See Patterson and Sievers (1980).
- Weddell Sea Bottom Water (WSBW)
- A type of water found in the seas surrounding Antarctica with
temperatures ranging from -1.4 to 0.8 C and salinities
of 34.65 ppt. It underlies
Antarctic Bottom Water (AABW) and is
found on the slopes and southern and western ages of the Weddell
- Weddell Deep Water (WDW)
- In physical oceanography, a water mass type
formed in the Weddell Sea by surface cooling
and subsequent convection in the polyna. This water has stable
properties with a potential temperature between 0.4-0.7 C.
WDW mixes with water above the continental slope in the Weddell Sea
to serve as one source for
Antarctic Bottom Water.
See Gordon (1982) and Tomczak and Godfrey (1994).
- Wedderburn number
- A dimensionless number
expressing a balance between surface wind stress and the pressure
gradient resulting from the slope of the interface.
It is given by:
where is the depth of the thermocline, is the fetch length (the
length of the reservoir at the thermocline in the direction of the wind),
is the surface friction velocity, and g' is the
is given by:
where is the wind velocity at 10 meters, is the
density of the air, and is the drag coefficient.
Meanings for various values of the Wedderburn number have been
- the buoyancy force is greater than the applied wind stress,
i.e. there is strong vertical stratification with very little horizontal
- wind stress and buoyancy forcing are nearly equal,
and therefore horizontal mixing is important;
- the time scale for vertical mixing is small compared
to horizontal advection.
- well mixed estuary
- One of four principal types of estuaries
as distinguished by prevailing flow conditions.
In this type the water column is (as you might have guessed)
well mixed with essentially no variation in salinity in a vertical
column. The Thames estuary is an example of this type.
- Acronym for Western North Pacific Experiment, a Japanese program
taking place on the Hakuho Maru from Jan. 11-Feb. 5, 1991.
See Fujiyoshi et al. (1995).
- Acronym for Western Equatorial Pacific Ocean Circulation Study,
a program taking place from 1985-1988 to examine the complex
current structures in a relatively poorly explored part of
See Lindstrom et al. (1987) and
Lukas et al. (1991).
- Acronym for the U.S.-U.S.S.R. Weddell Polynya Expedition
of 1981 aboard the Soviet icebreaker SOMOV.
See Chen (1982).
- West African Trough
- See Guinea Basin.
- West Europe Basin
- An ocean basin located in the eastern North Atlantic Ocean
off the west coast of Europe (and also called the
Northeastern Atlantic Basin). This includes the
Porcupine Abyssal Plain west of Britain, the Biscay
Abyssal Plain, and is connected to the
Iberia Basin to the south
by the Theta Gap.
See Fairbridge (1966).
- West Spitsbergen Current
- A current flowing offshore of West Spitsbergen Island in the eastern
part of Fram Strait.
This current carries comparatively warm water from the Atlantic into
the Arctic Ocean.
See Perkin and Lewis (1984),
Pfirman et al. (1994) and
- western boundary current (WBC)
- The intensification of the western limb of an oceanic circulation
gyre. This is inevitable given a rotating earth, a meridional
boundary, and a zonal wind stress pattern that reverses direction
at some latitude as was shown using a simple dynamical model in
the classic paper of Stommel (1948). Common features
of such currents include their flowing as swift narrow streams along
the western continental rise of ocean basins, their extension to
great depth well below the thermocline, and their separation from
the coast at some point and continuation into the open ocean as
narrow jets that develop instabilities along their paths. The most
well-known western boundary currents are the
Gulf Stream and the
See Hogg and Johns (1995).
- Western Mediterranean Circulation Experiment (WMCE)
- A program to study the circulation of the western Mediterranean
Sea from the Strait of Sicily to the Strait of Gibraltar using
scales ranging from basin size to 1 km and depths from the
surface to the deepest layers. The specific goals were to
study the major features of the circulation and their variation
in space and time, the physical forcing mechanisms, the affects
of the circulation on the chemical, biological and optical
properties of the western Mediterranean, and to implement the
knowledge gained into numerical models.
The field study began in November 1985 and ended in March 1987,
and consisted of the placement of long-term current meter
moorings as well as campaigns for procuring measurements
from aircraft. The field campaigns ran concurrently with
those of two other experiments: POEM
and the Gibraltar Experiment,
with some effort being expended to make the three campaigns
complementary to each other.
See La Violette (1990).
- Western Mediterranean Deep Water (WMDW)
- See Perkins and Pistek (1990).
- Western North Atlantic Central Water (WNACW)
- See Poole and Tomczak (1999).
- Western North Atlantic Water (WNAW)
- A water mass defined by Iselin (1936) and
() to define water found in the
North Atlantic Current.
The WNAW definition can be subsumed into the broader definition of
North Atlantic Subpolar Mode Water,
and thus can be seen as a variety of the latter.
Se Read (2001).
- Western North Pacific Central Water (WNPCW)
- In physical oceanography, the dominant water mass
in the northern subtropical gyre,
formed and subducted in the northern
STC. This is fresher than
NPEW at all temperatures and saltier than
ENPCW except at temperatures above about
17 C (the upper thermocline). It is separated to the east from
ENPCW at around 170 W and to the south from NPEW at around
See Tomczak and Godfrey (1994), p. 165.
- Western Pacific Warm Pool (WPWP)
- An ENSO-related phenomenon conventionally defined as
SSTs greater than or equal to
28 C. It is a large area of heat accumulation in the
global ocean and related to the development of El Nino.
See Ho et al. (1995).
- Western South Atlantic Central Water (WSACW)
- See Poole and Tomczak (1999).
- Western South Pacific Central Water (WSPCW)
- In physical oceanography, a water mass which
is one of six distinguishable
Central Water masses in the Pacific Ocean.
Its T-S properties are almost indistinguishable from those of
ICW and SACW, indicative
of similar atmospheric conditions during formation. It is formed
and subducted in the
STC between Tasmania and New Zealand, and is
geographically restricted by that and Australia at 150 W.
It is separated to the east from the fresher
ESPCW in a broad transition zone between
145 and 100 W, and to the north from
SPEW, fresher above 8 C and saltier
below, at around 15 S.
See Tomczak and Godfrey (1994), p. 164.
- Western Tropical Atlantic Experiment (WESTRAX)
- An international field program conducted during 1989-1991 in the
western boundary region of the tropical Atlantic between
0 and 10 N.
Moored current meter observations were collected in the
North Brazil Current (NBC) near the
equator, near 4 N, and near 6 N to investigate
the structure and variability of the NBC.
See Brown et al. (1992).
- Acronym for
Western Tropical Atlantic Experiment.
- A 1982 cruise in the western tropical South Pacific Ocean whose
goal was to reassess the regional distribution of the water masses
in the area, to identify possible fronts in the region, and to get some
idea of the frequency of occurrence of water mass layering, intrusions
WESTROPAC was performed using the R. V. Sprightly of the CSIRO.
It consisted of three individual cruises identified as Sprightly
cruises Sp9/82 (from Sydney to Honiara), Sp10/82 (from Honiara to
Nouméa), and Sp11/82 (from Nouméa to Sydney).
See Tomczak and Gu (1987).
- wet-bulb temperature
- The temperature obtained by covering the bulb of a
with a silk or cotton wick saturated with distilled water
and drawing air over it at a velocity not less than
1000 ft/min. This is often accomplished by swinging the
covered thermometer on the end of a string or rope.
If the atmosphere is saturated with water vapor, the
water in the wick will not evaporate and the dry and wet
bulb temperatures will be the same. If the atmosphere is
not completely saturated, the water will evaporate from the
wick at a rate depedent upon the degree of saturation. The
evaporation will cool the bulb and lower the temperature
reading over that of the dry-bulb temperature to that of the
- white noise
- Noise that results in a spectrum where all frequency components
have the same amount of energy. This can also refer the the resulting
spectrum as well as the process. Compare to
- White Sea
- One of the seas found on the Siberian shelf in the
Arctic Mediterranean Sea.
It is located to the west of the
Barents Sea and is otherwise
See Zenkevitch (1963).
- Abbreviation for Woods Hole Oceanographic Institution.
- Abbreviation for WOCE Hydrographic Program Office.
See the WOCE entry.
- Acronym for World Hydrological Cycle Observing System.
- Wilkes, Charles (1798-1877)
- See Peterson et al. (1996), p. 72.
- A violent squall in the Straits of Magellan.
This is a region
where the winds are almost constantly strong and westerly.
- wind chill temperature
- The hypothetical air temperature in calm conditions that would
cause the same heat flux from the skin as occurs for the true winds
and the true air temperature.
- wind scatterometry
- A method wherein a specialized radar called a scatterometer is
used to measure the near-surface wind speed and direction.
The technique is indirect, i.e. the instrument tranasmits microwave
pulses and receives backscattered power from the ocean surface.
Changes in wind velocity cause changes in ocean surface roughness, modifying
the radar cross-section of the ocean and the magnitude of backscattered
power. This backscattered power is measured by scatterometers to
obtain an estimate of the normalized radar cross-section of the
sea surface. The cross-section varies with both wind speed and direction
when measured at moderate incidence angles, allowing the development of a
transfer function called a
geophysical model function
relating the former to the latter.
Multiple, collocated, nearly simultaneous cross-section measurements
acquired from several directions can be used to simultaneously solve
for wind speed and direction.
See Naderi et al. (1991).
- wind stress
- The dominant driving source for the surface layer of the world's oceans.
The wind stress represents a complex interfacial momentum
exchange process between the wind and the underlying wind waves and
Historically, the measurement of the wind stress has been a problematic
task. It is usually measured above the sea surface from fixed towers,
ships or low-flying aircraft. The most direct approach is a technique
called the eddy correlation method
wherein the directional components
of the near-surface turbulent stress covariance in the atmospheric
boundary layer are measured.
A popular alternative technique for measuring the magnitude of the
wind stress is based on equilibrium turbulent boundary layer modeling.
The vertical wind profile is taken to have the form:
where is the wind speed at height meters above the surface,
is the surface wind friction velocity given by
is the density of air,
is the aerodynamic roughness length,
= 4 is the von Kármán constant,
is a thermal stratification function given for unstable
, and for stable conditions
is the Monin-Obukhov stability length scale defined by:
where is the virtual temperature and the gravitational
acceleration. The associated drag coefficient is:
where is the wind speed 10 meters above the sea surface.
The roughness length varies according to conditions. At low wind
speeds with aerodynamically smooth flow over the surface it is given by:
where is the kinematic viscosity of the air. As the winds
grow stronger, the roughness length is given by:
where is known as the Charnock coefficient, which ranges
from 0.011 for well-developed ocean conditions to 0.0145-0.018
for coastal sites with less mature waves.
High variability among various measurements led to a proposed extension
of the Charnock relation in which the roughness length is a function of
the wave age, i.e.
where is the phase speed of the spectral peak waves.
Several forms for this function have been proposed.
Another technique for estimating the wind stress is the
inertial dissipation method,
which depends on an assumed dependent on the friction velocity
in the spectral level of the inertial subrange of the turbulence
See Banner et al. (1999).
- Winter Intermediate Water (WIW)
- A water mass ...
See Perkins and Pistek (1990).
- Winter Water
- See Antarctic Surface Water (AASW).
- Winter Weddell Sea Experiment
- An experiment taking place in 1986.
- Abbreviation for
Winter Intermediate Water.
- WKB approximation
- More later.
- Abbreviation for
Western Mediterranean Circulation Experiment.
- Abbreviation for
Western Mediterranean Deep Water.
- Acronym for Winter Monsoon Experiment, a program taking place from
Dec. 1, 1978 to Mar. 5, 1979 in
the Indian Ocean, the western part of the Pacific Ocean, and
in adjacent continental areas.