Tectonic plates

Theory of geology that explains the observed evidence for large scale motions within the Earth´s crust. Tectonic plates are the broken portions of the lithosphere. In the case of our planet, there are ten major ones and many minor plates. Phenomena like earthquakes, volcanic eruptions and mountain-building occur along boundaries between plates.


Physical quantity characterizing the mean random molecular motions in a physical body. Quantity measured by a thermometer.

Tephra / Pyroclast

Is the fragmental material produced by a volcanic eruption regardless of composition, fragment size or emplacement mechanism.


Instrument for measuring temperature, by virtue of the variation of the physical properties of a substance according to their thermal states, such as mercury.


Top of the thermosphere, at about 250 miles (400 km) from the surface.


Layer of the atmosphere, located above the mesopause, in which temperature generally increases with height. The thermosphere includes most of the ionosphere.


Sound characterized by being sharp and rumbling, emitted by rapidly expanding gases along the channel of a lightning discharge.

Thunderbolt / Ground discharge / Cloud-to-ground discharge

Lightning discharge occurring from cloud to ground. It follows a tortuous course and is usually branched downward from a distinct main channel (forked lightning).


In general, a local storm, invariably generated by a cumulonimbus cloud, characterized by sudden electrical discharges manifested as lightning and thunders. They are often accompanied by precipitation, in the form of rain showers or hail, occasionally snow or ice pellets. Usually, it has a short duration, seldom over two hours.

Tidal wave

Wave motion of tides. Popularly, it refers to an unusually high water level, along the shore.


Angle at which the Earth´s axis is leaning with respect to the sun. Inclination to the vertical of a significant feature of the circulation or pressure pattern or of the field of temperature or moisture.


First successful weather satellite, launched on April 1, 1960, from Cape Canaveral, Florida, USA.

TOMS (Total Ozone Mapping Spectrometer)

Satellite instrument that measures backscattered ultraviolet radiation to infer total ozone. The analysis of TOMS data allowed to discover the Antarctic ozone hole.

TOPEX/Poseidon satellite

Satellite altimeter designed to measure the ocean surface topography, with an almost global coverage from 66°N to 66°S, from late 1992 to the end of 2005. Its accuracy allowed estimating the global average sea level every 10 days, with a millimetrical precision. It was turned off on January 18, 2006.


Violently cyclonically rotating column of air of small diameter, in contact with the ground, extending from a severe thunderstorm. It can be pending from a cumuliform cloud or be underneath it. Not always, but often, it can be seen as a funnel cloud.

Trade Winds

Global-scale band of northeast (in the Northern Hemisphere) and southeast (in the Southern Hemisphere) winds in low latitudes, blowing from the subtropical highs toward the equatorial trough. They start blowing at about latitude 30° equatorward and their southern limit situates around 5° of latitude, that is very close to the Equator. They are basically surface winds, presenting great constancy of direction, and to a lesser degree, of speed. Trades are the most consistent wind system on earth.

Transport wind

It is the average wind speed in the mixing depth above the surface, and it is a good indication of the horizontal dispersion of suspended particles. The transport wind is the forecasted wind at the time of maximum mixing of the atmosphere, normally during the mid afternoon.

Tree rings

Variable width of rings produced by seasonal growth that can be observed in a cross section cut of a tree trunk. Their number corresponds to the age of the tree. Paleoclimatology and dendrochronology are scientific fields involved in the study of trees which, because of being very sensitive to weather changes and especially long-lived, provide information about climatic fluctuations that is not otherwise available.

Tropical cyclone

Generic term for a non-frontal synoptic scale cyclone that refers to any of them that is originated over tropical oceans, that is tropical depressions, tropical storms, hurricanes and typhoons.

Tropical depression

Tropical cyclone with maximum sustained winds up to 33 knots.

Tropical disturbance

Migratory, organized region of convective showers and thunderstorms, located in the Tropics that lack of a closed wind circulation.

Tropical Oceans Global Atmosphere (TOGA)

Program aimed specifically at the prediction of climatic phenomena on long time scales, that is, months to years. The TOGA program focuses on tropical oceans and their relationship to the global atmosphere.

Tropical storm

Tropical cyclone with maximum sustained winds between 34 and 64 knots.


Boundary between the troposphere and the stratosphere, usually characterized by an abrupt change of lapse rate.


Layer of the atmosphere extending from the Earth´s surface to the tropopause, that is a varying height of approximately 6 to 12 miles (10 to 20 km) -lower at the poles and highest at the equator- in which temperature decreases with height.


Elongated area of relatively low atmospheric pressure; the opposite of a ridge.


Waves generated by seismic activity, when a body of water is rapidly displaced on a massive scale, which generates a violent onrushing tide. They can range from unnoticeable to devastating. Historically, they have been referred as tidal waves, which is a mistake.


Colloquial name given in the USA to tornadoes.


Name given in the western North Pacific to tropical cyclones with maximum sustained winds of 64 knots or more (hurricane).