Ta-Tm

 

2050 Project

A joint project among the World Resources Institute, the Brookings Institution, and the Santa Fe Institute to explore the question of how a sustainable existence on this planet can be achieved by the middle of the next century. More information can be found at the 2050 Project Web site.

 

TAGB

Abbreviation for total aboveground biomass.

 

Tahiti Shuttle Experiment

See Hawaii-Tahiti Shuttle Experiment.

 

taiga

A biome consisting of swampy coniferous forests in high northern latitudes.

 

TAMEX

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

 

TAMU

Abbreviation for Texas A&M University. There is a graduate school of oceanography at this institution, more about which can be obtained at the TAMU Oceanography Web site.

 

TAO

1. Acronym for Tropical Atmosphere Ocean array, a TOGA experiment. See the TAO data site and also Hayes et al. (1990) and McPhaden (1995). 2. 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.

 

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.

 

taphonomy

The branch of paleontology that deals with the processes by which animal and plant remains become preserved as fossils, i.e. the changes undergone by an organism from its death until its discovery as a fossil. See Briggs and Crowther (1990), Ch. 3.

 

TARFOX

Acronym for Tropospheric Aerosol Radiative Forcing Observational Experiment, a field project of IGAC to measure the direct effects of tropospheric aerosols on regional radiation budgets of the cloud-free atmosphere, while simultaneously measuring the chemical, physical, and optical properties of the responsible aerosols. Other goals are to perform a radiative column closure study in one of the most polluted regions of the globe, i.e. the U.S. eastern seaboard, and the extend these measurements and analyses to other regions of the globe using validated satellite measurements. See the TARFOX Web site.

 

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 E and 37 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.

 

taxon

A taxonomic group of any rank, e.g. species, family, class, etc.; an organism contained in such a group. The plural is taxa.

 

taxonomy

The theory and practice of classifying organisms. Its components include classification, nomenclature, circumspection or description, and identification aids. In the strict biological sense it refers to all information science aspects of handling the different sets of organisms. Taxonomy should be distinguished from the broader topic of biosystematics. See Heywood (1995).

 

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).

 

TBM

Abbreviation for Terrestrial Biogeochemical Model.

 

TDRSS

Abbreviation for Tracking and Data Relay Satellite System, a constellation of NASA satellites and ground stations that track and relay data to and from low-altitude, Earth-orbiting satellites.

 

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. Teleconnections are typically found by searching for correlations in the anomalies of fields such as the sea surface temperature, with the idea being that correlations suggest the communications of perturbations from one region to another.

 

temperate

Descriptive of a climate in which the temperatures are moderate or mild, or of any climate in middle latitudes.

 

temperature inversion

In meteorology, a region of negative lapse rate.

 

temperature lapse rate

The rate of decrease of temperature with height.

 

temporale

A cyclonic tropical weather system that affects the Pacific side of Central America and originates in the Pacific Intertropical Convergence Zone. These systems are characterized by very heavy rainfalls over several days. Unlike hurricanes, similarly wet systems, their winds are usually weak and they possess a cold mid-tropospheric core. They are typically move slowly, last several days, and cause damaging floods and landslides in the mountainous regions of Central America.

 

tephra

Airborne pyroclastic material ejected during volcanic eruptions. Explosive eruptions can produce a tephra blanket that covers a very large area simultaneously.

 

tephrochronology

The use of tephra layers to provide dating information. The tephra blankets ejected by explosive volcanic eruptions form isochronous stratigraphic layers or markers that can be dated either directly via potassium-argon dating or fission-track dating, or indirectly by using carbon-14 dating to date organic material above and/or below a tephra layer. The use of this method requires that each tephra layer be precisely identified using such characteristics as stratigraphic position, thickness, color, weathering, grain size, and chemical analyses.

Tephrochronology has proved to be a valuable paleoclimate tool in the volcanic regions of the world. For example, it has been used extensively in western North America where explosive volcanic eruptions over the last million years have produced dozens of distinct and widespread tephra layers. It has also been useful in glacial history investigations as well as in studies of marine sediments containing ash layers. Tephra layers, correctly identified and dated, can provide a minimum date for an underlying layer, a maximum date for an overlying layer, or a pair of bracketing dates for a layer sandwiched between two tephra layers. See Bradley (1985).

 

TERRA

Acronym for Terrestrial Ecosystems Regional Research and Analysis Laboratory, whose mission is to incorporate realistic consideration of land and natural resource management understanding into terrestrial ecosystem components of earth system modeling. See the TERRA Web site.

 

TerrainBase

An ongoing project to develop a research quality collection of digital terrain models. See the TerrainBase Web site.

 

TERRA Nova

A fast publication research, review and news journal covering the full range of the Earth sciences. It is the official journal of the European Union of Geosciences, and selected articles can be found online at the TERRA Nova Web site.

 

Tertiary

The first of two periods of the Cenozoic era, lasting from 66.4 to 1.6 Ma. It precedes the Quaternary period and follows the Cretaceous period of the Mesozoic era, and is comprised of the Paleocene, Eocene, Oligocene, Miocene, and Pliocene epochs. Originally designated an era, it had the five periods rather than epochs listed above or, alternatively, the Paleogene and Neogene periods where the boundary coincided with that of the Oligocene and Miocene.

 

TES

Acronym for Tropospheric Emission Spectrometer, an instrument used to obtain a long-term understanding of variations in the quantity, distribution and mixing of minor gases in the troposphere. This is a high-resolution, cooled Michelson interferometer developed to study a range of tropospheric minor constituents and hence to understand the chemistry of the polluted lower atmosphere.

 

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.

 

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 C, this varies from 0.1809 to 0.284 cm /s for air and from 0.0013 to 0.0015 cm /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 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.

where is the Coriolis parameter, u and v the horizontal velocity components, p the pressure, and the density. The vertical derivative of each equation is taken, the order of differentiation switched for the pressure, and the hydrostatic equation ( ) substituted to obtain

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

 

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.

 

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.

 

thermoluminescence dating

A radioisotope dating method based on the phenomenon wherein light is emitted from a mineral crystal when it is heated. The decay of radioisotopes in surrounding material produces free electrons in a crystal which are trapped in defects and dislodged when heated to produce thermoluminescence. The magnitude of the thermoluminescence of a sample is proportional to the length of time over which it has been exposed to radiation. The usefulness of this as a dating procedure is provided by the releasing of the electrons via thermoluminescence upon heating, allowing the determination of the length of time since a sample was last heated.

This method is widely used in archaeology to date pottery and flint samples. It is not yet in wide use in paleoclimatology, although it has been used to date sediment samples baked in contact with lava flows as well as inclusions within lava. A promising application area is dating certain types of marine and terrestrial sediments. Sunlight exposure during weathering and erosion tends to empty the electrons trapped in the crystal portion of the sediment, thus setting the clock to zero should it be subsequently buried beyond the reach of sunlight. The useful time scale of this type of dating is thought to be no greater than 1 million years, with an accuracy of about 10% of the sample age.

Problems with this method occur at both very low and very high radiation levels. A linear relationship between radiation dose and trapped electrons for a given material is generally determined in the laboratory and used to date other samples of the same material. At low radiation levels it has been found that this rate can be reduced or even disappear under a certain threshold level, and a sample can become saturated at high radiation levels and therefore cease trapping electrons. The latter effect is likely to occur with very old samples. Some materials are also known to lose electrons via a process called anomalous fading after very short periods of time. The water content of a sample's environment can also cause problems since water attenuates radiation, causing samples in water-filled environments to have fewer trapped electrons than those in dry environments. See Bradley (1985).

 

thermophoresis

Migration of aerosol down a temperature gradient. See Jaenicke (1993a).

 

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 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

In the determination of the specific volume of sea water, this refers to a subset of that group of factors known as the specific volume anomaly that account for most of the effects of salinities and temperatures that differ from the standard calculation levels of 35 ppt and 0 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.

 

THIR

Acronym for Temperature Humidity Infrared Radiometer, an instrument flown on Nimbus 7.

 

Thompson, Benjamin (1753-1814)

See Peterson et al. (1996), p. 48.

 

Thomson, Charles Wyville (1830-1882)

See Peterson et al. (1996), p. 93.

 

Thornthwaite scheme

A bioclimatic classification scheme that treats plants as physical mechanisms by which moisture is returned to the air. The variables APE and AAE are used in this scheme to distinguish between situations when the amount of moisture available to plants is limiting or nonlimiting. The APE in this case is calculated via a formula given in Thornthwaite (1948). See Prentice (1990).

 

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).

 

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 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 Wiegel (1964).

 

Tiempo

A quarterly electronic bulletin whose aim is to promote communication between the nations of the North and South on the issue of climate change, to promote the interests of developing nations in the climate debate, and to provide authoritative and timely information on relevant scientific, technical, and policy matters. The bulletin is published by the International Institute for Environment and Development in London and the University of East Anglia. See the Tiempo Cyberlibrary.

 

TIGER

Acronym for Thermal Infrared Ground Emission Radiometer.

 

tilt

See obliquity.

 

tilt modulation

A type of modulation of backscattered ripple waves measured by SAR that arises through variations in the local angle of incidence associated with variations in the facet normal. See Komen et al. (1996).

 

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 S and 127 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 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).

 

TIROS

Acronym for the Television Infrared Observation Satellite, the beginning of a long series of polar-orbiting meteorological satellites. TIROS was followed by the TOS (TIROS Operational System) series, the ITOS (Improved TIROS) series, and then the NOAA series. The TIROS spacecraft carried low resolution television and infrared cameras.

 

Tithonian

The last of three ages in the Late Jurassic epoch, lasting from 152 to 144 Ma. It is preceded by the Kimmeridgian age and followed by the Berriasian age of the Early Cretaceous epoch.

 

TIWE

Abbreviation for Tropical Instability Waves Experiment, a project of the APL of the University of Washington Department of Oceanography. See Qiao and Weisberg (1995).

 

Tizard Deep

See Brazil Basin.

 

TMAP

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

 

TMRP

Abbreviation for Tropical Meteorology Research Program, a WMO project.