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Ta-Tm

Tahiti Shuttle Experiment
See Hawaii-Tahiti Shuttle Experiment.

TAMEX
Acronym for Taiwan Area Mesoscale Experiment. The planning phase of this took place from 1985-86 and the field operations phase during 1987.

TAO
Acronym for Tropical Atmosphere Ocean array, a TOGA experiment, an array of approximately 70 moorings in the tropical Pacific Ocean that telemeter oceanographic and meteorological data to shore in real-time via the Argos satellite system. The development of TAO was motivated by the 1982-1983 El Nino event, the strongest of the century up to that time. It was neither predicted nor detected until it nearly reached its peak, prompting the need for real-time data from the tropical Pacific for monitoring, prediction, and improved understanding of El Nino.

PMEL began the development of the ATLAS mooring in 1983 with support from the NOAA EPOCS program. Prototype ATLAS moorings were field tested in early 1984, with a modest array deployed along 110W in late 1984. Additional ATLAS deployments were made beginning in 1985 at the start of the 10-year TOGA program. The array, now named TAO, grew slowly during the first half of TOGA, and then rapidly during the second half as the ATLAS moorings proved a great success. The full array was not completed until the final month of TOGA (Dec. 1994). During the 10 years TAO was under development, over 400 buoys were deployed on 83 cruises using 17 ships from 6 countries.

After TOGA ended, TAO continued under the sponsorship of CLIVAR, GOOS and GCOS. NOAA was comissioned to service the array east of 165E in 1996, and in 1997 the U.S. Congress authorized long term sustained support of the array as part of an operational ENSO observing system. On Jan. 1, 2000, it was officially renamed the TAO/TRITON array, with sites west of 165E occupied by TRITON buoys maintained by Japan's JAMSTEC.

The current operationally supported measurements of the array consist of winds, SST, relative humidity, air temperature, and subsurface temperature at 10 depths in the upper 500 m. Five moorings along the equator also measure water velocity. Additional moorings or enhancements to existing moorings are occasionally added in support of specific research objectives. See Hayes et al. (1990) and McPhaden (1995).

[http://www.pmel.noaa.gov/tao/]

TAO
Acronym for Transport Processes in the Atmosphere and the Oceans, a program to study transport processes in geophysical fluids mainly from a theoretical point of view. See the TAO Web site.

TAO/TRITON
The new name of the TAO mooring array as of Jan. 1, 2000. See TAO.

TAP
Acronym for Transarctic Acoustic Propagation experiment, carried out in April 1994 at an ice camp north of Svalbard. A joint US/Russian scientific party deployed an experimental 20 MHz source and transmitted various signals to listening stations in the Beaufort and Lincoln Seas for 5 days. TAP was a feasibility test to see if acoustic signals could be used to study the Arctic and monitor it on a long term basis. See Pawlowicz et al. (1995) and the TAP Web site.

TAPS
Acronym for Tracor Acoustic Profiling System, a family of instruments developed by TRACOR to study the size and extent of populations of very small marine life by measuring the acoustic signals backscattered from them at frequencies in the MHz range. The TAPS sensors can be lowered through the water column in cast mode, attached to net systems such as the MOCNESS, or deployed on a SeaSoar unit.

[http://www.aard.tracor.com/home/eco/MarEco.html]

TAS
Abbreviation for Tropical Atlantic Study, a part of the TTO program.

TASC
Acronym for Trans-Atlantic Study of Calanas finmarchicus, an EU-funded program to understand the physical and biological processes which control the population dynamics of the copepod Calanus finmarchicus, a key zooplankton species in the northeast Atlantic. A key goal is to establish the relationship between the physical and biological factors affecting annual recruitment and reproduction of the species as a step towards predicting the consequences of future climate change. See the TASC Web site.

Tasman Front
See Stanton (1981).

Tasman Sea
A marginal sea located in the southwest Pacific centered at about 160$ ^\circ$ E and 37$ ^\circ$ S off the southwest coast of Australia. It is also surrounded by New Zealand to the east, Tasmania to the southwest, and the Coral Sea to the north. The maximum depth is 5943 m. The bathymetry is essentially composed of the east Australian Basin in the westerly part and the depression of New Caledonia to the east, with the two separated by the Lord Howe Sill. See Rotschi and Lemasson (1967).

Tatarskyi Strait
See Okhotsk Sea.

Taylor column
If relative motion is created in a rotating container by heating or by stirring and if an obstacle is placed on the bottom of the tank so that the moving fluid must flow around it, then the streamlines of the flow will form a column, going around the obstacle as if it extended to the top of the water. This is called a Taylor column. The same sort of phenomena can occur in real world analogues of this experimental example. This is a consequence of what is known as the Taylor-Proudman theorem. See Dutton (1986).

Taylor-Proudman theorem
A two-dimensional fluid flow theorem that states that geostrophic motion of a homogeneous fluid will be the same in all planes perpendicular to the axis of rotation. This has also been known as the Proudman-Taylor, Proudman or Taylor theorem. See Hide (1978).

TCIPO
Abbreviation for TOGA COARE International Project Office.

teleconnections
The ability of a phenomenon in one part of the world to influence phenomena in another part of the world. Examples include the influence of the ENSO phenomena on the Indian monsoon and the droughts in the Sahel region of Africa. Teleconnection pataterns are recurring and persistent large-scale patterns of pressure and circulation anomalies spanning vast geographical areas. They are also referred to as preferred modes of low-frequency or long time-scale variability. The patterns typically last for weeks to several months, although they can occasionally be prominent for several years and thus influence both the interannual and interdecadacal atmospheric and oceanic variability.

Teleconnection patterns are a naturally occurring part of the chaotic atmosphere, and arise primarily from internal atmospheric dynamics, although some are forced by changes in tropical SSTs and convection associated with the ENSO cycle and the Madden-Julian Oscillation. The patterns reflect large-scale changes in the wave and jet stream patterns in the atmosphere, and influence temperature, rainfall, storm tracks and jet stream location and intensity over large areas. For example, they can be responsible for abnormal weather patterns occurring simultaneously at widely separated locations.

A technique called Rotated Principle Coordinate Analysis (RPCA) has been used to determine the most prominent teleconnection patterns in the northern hemisphere extratropics. They are:

See Barnston and Livezey (1987) and Trenberth et al. (1998).

[http://www.cpc.ncep.noaa.gov/data/teledoc/telecontents.html]

temperature inversion
In meteorology, a region of negative lapse rate.

temperature lapse rate
The rate of decrease of temperature with height.

temperature ramp
A coherent structure found in the upper ocean that has been observed in both stable and unstable conditions. These are found in the upper few meters, are aligned with the wind, and marked by horizontal temperature changes of 0.1 K over 0.1 m. They indicate the upward transport of cool/warm fluid during stable/unstable conditions, and are driven by an instability triggered by the wind thought to be similar to the Kelvin-Helmholtzinstability. These are as yet not well understood.

TEP
Abbreviation for Transparent Exopolymer Particles, an organic ocean particle that is not normally detectable because it is transparent. These gel-like polysaccharide particles form the matrix of marine snow and play an important role in the coagulation of some algal blooms. See Alldredge and Jackson (1995).

TEPPS
Acronym for Tropical Eastern Pacific Process Study cruise, a 1997 PACS study whose purpose was to document the clouds and precipitation of the tropical eastern Pacific from the surface. The timing and location of the cruise were designed to permit the ship's instruments to sample storm structure when and where there is the greatest difference between the different satellite precipitation estimates. The scientific objectives were:

[http://www.atmos.washington.edu/gcg/MG/tepps/]

Tethys Sea
A paleogeographic term for a sea that partly intersected Pangaea in the Permian and later separated the two Mesozoic supercontinents of Laurasia and Gondwana.

TEW
Acronym for Transport of Equatorial Waters, a research project.

Texas Current
See Vastano et al. (1995).

THEP
Acronym for TOGA Heat Exchange Program.

thermal diffusivity
A number that characterizes the rate of molecular diffusion of heat in a liquid. In the temperature range from 0 to 30$ ^\circ$C, this varies from 0.1809 to 0.284 cm$ ^2$/s for air and from 0.0013 to 0.0015 cm$ ^2$/s for water.

thermal equator
An imaginary line connecting those points around the globe with the highest mean temperature for the given period. As such, the position of the thermal equator varies with the season. Due to the thermal inertia of the ocean, the position of this moves north and south with the Sun but is always between the Sun and the geographic equator. The mean position is north of the geographic equator due mainly to the majority of land masses being in the northern hemisphere.

thermal expansion coefficient
A quantity arising from taking derivatives of the density in the $ (p, \theta , S)$ representation of the equation of state. This is defined in seawater as:

$\displaystyle \alpha\,=\,-{1\over\rho}\, {{\left.{{\partial\rho}\over{\partial\... ...left.{{\partial\theta}\over{\partial T}}\right\vert}_{S,\rho}} \right] }^{-1} }$

where $ \rho$ is the in situ density, $ \theta$ is the potential temperature, $ S$ is the salinity, and $ T$ is the temperature. In practice, $ {{\partial\rho}\over{\partial T}}$ can be obtained from the International Equation of State of seawater, and $ {{\partial\theta}\over{\partial T}}$ from Bryden (1973). In general, a $ <$ 0, and -a increase with increasing temperature and pressure.

McDougall (1987b) gives a polynomial expression for $ \alpha / \beta$ (with a similar expression for $ \beta$ found in the saline contraction coefficient entry used to find just $ \alpha$):

$\displaystyle \alpha /\beta\,$ $\displaystyle =$ $\displaystyle \, +0.665157 \times {10^{-1}}\,+\, 0.170907 \times {10^{-1}}\theta\,-\, 0.203814 \times {10^{-3}}{\theta^2}$  
  $\displaystyle +$ $\displaystyle \,0.298357 \times {10^{-5}}{\theta^3}\,-\, 0.255019 \times {10^{-7}}{\theta^4}\,+\, (S\,-\,35.0)[+0.378110 \times {10^{-2}}$  
  $\displaystyle -$ $\displaystyle \,0.846960 \times {10^{-4}}\theta\,-\, 0.164759 \times {10^{-6}}p \,-\, 0.251520 \times {10^{-11}}{p^2} ]$  
  $\displaystyle +$ $\displaystyle \,{{(S\,-\,35.0)}^2}[-0.678662 \times {10^{-5}}]\,+\, p[0.380374 \times {10^{-4}}\,-\, 0.933746 \times {10^{-6}}\theta$  
  $\displaystyle +$ $\displaystyle \,0.791325 \times {10^{-8}}{\theta^2}]\,+\, 0.512857 \times {10^{-12}}{p^2}{\theta^2}\,-\, 0.302285 \times {10^{-13}}{p^3}$  

where the rms error of the fit is 0.000894 psu $ {^\circ}C{^{-1}}$ and a check value is 0.34763 psu $ {^\circ}C{^{-1}}$ at $ S$ = 40 psu, $ \theta$ = 10.0$ ^\circ$C and $ p$ = 4000 db. See McDougall et al. (1987) and the related saline contraction coefficient and adiabatic compressibility.

thermal wind equations
These allow the calculation of the vertical variation of velocity from the density field. The name thermal is an artifact from the original meteorological use where the temperature field was used as a proxy for the density field. In oceanography, the fact that salinity can also significantly contribute to variations in the density field leads to the use of density rather than temperature. The thermal wind equations are derived from the horizontal equations of motion and the hydrostatic equation, beginning with the equations of motion reduced to the geostrophic equations, i.e.

$\displaystyle fv\,=\,{1\over\rho}\, {{\partial p}\over{\partial x}}$

$\displaystyle fu\,=\,-{1\over\rho}\, {{\partial p}\over{\partial y}},$

where $ f\,=\,2\Omega\sin\phi$ is the Coriolis parameter, $ u$ and $ v$ the horizontal velocity components, $ p$ the pressure, and $ \rho$ the density. The vertical derivative of each equation is taken, the order of differentiation switched for the pressure, and the hydrostatic equation ( $ dp/dt\,=\,\rho\,g$) substituted to obtain

$\displaystyle {{\partial (\rho f u)}\over{\partial z}}\,=\, -g\,{{\partial\rho}\over{\partial x}}$

$\displaystyle {{\partial (\rho f v)}\over{\partial z}}\,=\, g\,{{\partial\rho}\over{\partial y}}.$

These equations only give the variation of the velocity with depth. Further information must be supplied to obtain absolute velocities.

thermobaric coefficient
A quantity defined as:

$\displaystyle b\,=\,{1\over 2} \left({1\over \beta}{ {\partial\beta} \over {\partial p} }\,-\, {1\over \alpha}{ {\partial\alpha} \over {\partial p} }\right)$

where $ \beta$ is the saline contraction coefficient, $ \alpha$ is the thermal expansion coefficient, and $ p$ is the pressure. It can also be defined in terms of the adiabatic compressibility $ \kappa$ as

$\displaystyle b\,=\,{1\over 2} \left({1\over \beta}{ {\partial\kappa} \over {\partial S} }\,-\, {1\over \alpha}{ {\partial\kappa} \over {\partial\theta} }\right)$

where $ S$ is the salinity and $ \theta$ is the potential temperature. See McDougall (1987b).

thermobaricity
A phenomena related to the pressure dependence of the thermal expansion coefficient for the density of seawater. The dependence of the compressibility of seawater on both potential temperature and salinity means that water parcels displaced laterally without doing any work against gravity will not follow neutral surfaces defined in terms of spatially averaged (rather than instantaneous or local) potential temperature and salinity. They will move off this surface in a process called thermobaricity. For example, stirring by mesoscale eddies leads to a net motion of fluid across neutral surfaces. The process called cabbeling leads to the same result of moving fluid across neutral surface, although by mixing at the molecular level rather than by stirring. See McDougall (1987b).

thermocline
Specifically the depth at which the temperature gradient is a maximum. Generally a layer of water with a more intensive vertical gradient in temperature than in the layers either above or below it. When measurements do not allow a specific depth to be pinpointed as a thermocline a depth range is specified and referred to as the thermocline zone. The depth and thickness of these layers vary with season, latitude and longitude, and local environmental conditions. In the midlatitude ocean there is a permanent thermocline residing between 150-900 meters below the surface, a seasonal thermocline that varies with the seasons (developing in spring, becoming stronger in summer, and disappearing in fall and winter), and a diurnal thermocline that forms very near the surface during the day and disappears at night. There is no permanent thermocline present in polar waters, although a seasonal thermocline can usually be identified.

The basic dynamic balance that maintains the permanent thermocline is thought to be one between the downward diffusive transport of heat and the upward convective transport of cold water from great depths. A review of the governing dynamics of the permanent thermocline can be found in Pedlosky (1987).

thermocline zone
See thermocline.

thermoelectric Schlierenmeter
An instrument used in the mid-20th century to record rapid temperature changes in the ocean. It consisted of a constantin wire soldered to copper wires in two places. One junction was exposed to the sea water, and the other embedded in compact insulation material. The thermoelectric current induced depended on the temperature difference between the two junctions, and was indicated by means of a remote galvanometer. This instrument therefore measured the temperature difference between the sea water and the insulated junction rather than the temperature itself. See Dietrich (1963).

thermogram
See thermograph.

thermograph
A recording thermometer which measures a continuous trace of temperature called a thermogram. The classical version of this featured a bi-metallic strip attached to a lever holding a pen. As the strip expanded and contracted in response to temperature changes, the pen moved across a piece of paper on a drum rotating via some clockwork mechanim. Such things are done using solid state devices sending binary data to other solid state devices in these modern times.

thermohaline
In oceanography, descriptive of a combination of temperature and salinity effects.

thermohaline circulation
That part of the ocean circulation driven by temporal and spatial differences in both the salinity and temperature of the waters that comprise the world ocean. A simplified schematic model of this circulation is the conveyor belt model.

thermohaline convection
See double diffusive convection.

thermometric depth
A depth determination that actually represents a pressure determination and is used more for the determination of the position of bottle samplers and instruments on research vessels than for the determination of the depth of the water above the seafloor. This sort of depth control is needed because of the large wire angles that can frequently occur when a ship is at station and currents at depth move the wire away from the vertical position, causing the true depth of the instruments to not correspond to the length of the wire. The method uses two mercury thermometers, one pressure protected which measures the temperature in situ and the other unprotected and subject to elastic deformation by the pressure of the water column. The unprotected thermometer thus registers not only a rise in mercury corresponding to the in situ temperature but also a rise proportional to the hydrostatic pressure and, therefore, to the depth. The accuracy of this method, first determined and extensively discussed by Wüst during his work aboard the Meteor, is $ \pm$20 m at 5000 m depth. See Dietrich (1963).

thermosolutal convection
See double diffusive convection.

thermosphere
One of two regions into which the ocean depths are sometimes divided according to temperature, the other being the psychrosphere. The thermosphere is the upper regions of the ocean where the temperature is greater than 10$ ^\circ$ C. This coincides with the ocean troposphere.

thermostad
A layer where the vertical change of temperature is very small and displays a local minimum.

thermosteric anomaly
The portion of the specific volume anomaly that accounts for most of the effects of salinities and temperatures differing from the standard calculation levels of 35 ppt and 0$ ^\circ$ C, respectively. These three terms account for the individual effects of salinity and temperature perturbations as well as their combined effect.

THETIS
Abbreviation for Tomography System for Monitoring the Western Mediterranean Basin, a project that started in October 1993 and was completed in September 1995. The objective of the project was to use tomography to study the Western Mediterranean Sea. THETIS-I investigated changes on the 100 km scale, and THETIS-II was aimed at observing basin scale heat content changes at scales up to 600 km. The second experiment consisted of a network of seven moorings with tomographic transceivers, current meters, and temperature sensors deployed in January 1994 and recovered in October 1994. See the THETIS Web site.

Thompson, Benjamin (1753-1814)
See Peterson et al. (1996), p. 48.

Thomson, Charles Wyville (1830-1882)
See Peterson et al. (1996), p. 93.

Thorpe scale
In a stratified ocean, a vertical profile may contain regions of static instability. Vertical displacements can be created by reordering the profile to achieve static stability. An RMS value of these displacements within a specific depth range is a length scale called the Thorpe Scale. It can empirically be related to the Ozmidov scale. See McDougall et al. (1987).

Thracian Sea
The northern part of the Aegean Sea.

THRUST
Acronym for Tsunami Hazards Reduction Utilizing Systems Technology, a NOAA PMEL project to demonstrate the use of satellite technology with existing tsunami warning methods to create a low-cost, reliable, local tsunami warning system. See Bernard (1991).

Tiburon
A remote operated vehicle (ROV) developed at MBARI. See the Tiburon Web site.

tidal bore
To be completed.

tidal ellipse

tidal epoch
The phase lag of the maximum of a given constituent of an observed tide behind the corresponding maximum of the theoretical equilibrium tide.

tidal evolution
The changing of the Earth-Moon tidal characteristics over time. See Kagan (1997).

tidal friction
The first quantitative theory of the tidal evolution of the Earth-Moon system was presented in a series of papers by George Darwin (Darwin (1879), Darwin (1880b), and Darwin (1880a)) in the latter part of the 19th century where he showed that tidal friction can radically change the Moon's motion and the Earth's rotation on geologic time scales. One consequence of this theory is that paleotides had different periods. See Kagan and Sündermann (1996), Munk (1968), Munk and MacDonald (1960) and Munk (1997).

tidal wave
An egregious misnomer for a type of wave that has nothing to do with tides or tide-producing forces. See the more apt term seismic sea wave for a description.

tide
The periodic rising and falling of the water that results from the gravitational attraction of the moon and sun acting on the rotating earth. There are related phenomena that occur in the solid earth and the atmosphere called, strangely enough, earth tides and atmospheric tides. The forces that significantly effect the tides of the oceans are the gravitational forces of the sun and moon, the centrifugal force due to the movement of the earth in its orbit, the Coriolis force, and the frictional force due to the movement of the water with respect to its boundaries. See Cartwright (1999), Doodson and Warburg (1941), Douglas et al. (2000), Emery and Aubrey (1991), Open University (1989), Pirazzoli (1996), Pugh (1987), Rahman (1988) and Wiegel (1964).

Tide Chart
A map showing the water levels throughout a bay or estuary at a particular point in time. Tide Charts normally show the water levels on an hourly basis after high tide. They are available for a relatively few locations around the U.S. Contrast with Tide Table.

[http://co-ops.nos.noaa.gov/faq2.html]

Tide Table
A tidal prediction table showing the daily high and low tide predictions for a particular location. Contrast with Tide Chart.

[http://co-ops.nos.noaa.gov/faq2.html]

TIME
Acronym for Tsunami Inundation Modeling Exchange, an IOC project.

time series
Any series of observations of a physical variable that is sampled at changing time intervals. A regular sampling interval is usually presumed although not required.

time step
The basic unit of temporal resolution in a numerical model created by discretizing a continuum differential equation to create an analogous discrete algebraic equation. The model time advances by discrete steps as opposed to the (at least perceived) continuum nature of time in the real world.

Timor Sea
A regional sea located in the Australasian Mediterranean Sea and centered at about 12$ ^\circ$ S and 127$ ^\circ$ E. It consists of Timor Strait to the north and the Sahul Shelf to the south, with the former having a width of 80 km and a maximum depth of 3 km in the Timor Trench. Sills to the west (1860 m) and east (1400 m) control the allowable flow at depth. Overall, the flow is strongest in the strait and extends with decreasing velocities onto the shelf.

Current measurements show a transport from east to west on the order of 7 Sv through the strait and a seasonally varying 1-3 Sv on the shelf. The currents on the shelf flow northeastward along the shelf (to about 12.5$ ^\circ$ S where they turn more northward) from September until January. The onset of the monsoons in March turns the flow toward the southwest which continues until September, except near the coast where the southwestward flow reverses in May. See Cresswell et al. (1993).

TIWE
Abbreviation for Tropical Instability Waves Experiment, a project of the APL of the University of Washington Department of Oceanography. This study, taking place from 1990-1991, studied the life cycle and energy sources for tropical instability waves in the eastern Pacific. See Qiao and Weisberg (1995).

Tizard Deep
See Brazil Basin.

TMA spectrum
A wave spectrum developed to incorporate finite depth effects into the JONSWAP spectrum. See Bouws et al. (1984).

TMAP
Abbreviation for Thermal Modeling and Analysis Project. See the TMAP Web site.

TMR
Abbreviation for TOPEX microwave radiometer, an instrument on the TOPEX/POSEIDON mission. The TMR measures sea surface microwave emissivity at three frequencies (18, 21, and 37 GHz) to estimate to total water vapor content in the atmosphere. This estimate is used to correct to the water vapor-induced errors in the altimeter measurement. The 21 GHz channel is the primary channel for water vapor measurement, with the 18 GHz and 37 GHz channels used to remove the effects of wind speed and cloud cover, respectively. See Ruf et al. (1994).

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