| Section T | T index | 581-589 of 589 terms |
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Tyndall flowers—Small water-filled cavities, often of basically hexagonal shape, that appear in the interior of ice masses upon which light is falling. Their formation results from the melting ice by radiative absorption at points of defect in the ice crystal lattice.
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type-α leader—A stepped leader that exhibits very little branching and with individual steps that are short and so weakly luminous as to be difficult to discern on high-speed streak photographs. Compare type-β leader.
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type-β leader—A stepped leader with the upper portion of the channel characterized by longer and brighter steps than those found in the lower portion of the channel. Many researchers report that a preliminary breakdown precedes the stepped leader in electric field records. The beta leader may be this preliminary stepped leader. Compare type-α leader.
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type—1. A specific classification of aircraft having the same basic design, including all modifications that result in a change in handling or flight characteristics. 2. See weather type.
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typhoon—(Also spelled typhon.) A severe tropical cyclone in the western North Pacific. The name is derived either from Cantonese t'ai fung (a “great wind”), from Arabic tufan (“smoke”), or from Greek typhon (a “monster”). Aristotle used typhon for a wind-containing cloud (Meteorologica, III, 1). For a more complete discussion, see tropical cyclone.
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typical year—The 12 months, January–December, selected from the entire period of record span for a given location as the most representative, or typical, for that month. Thus, for a given station, a typical year will be a composite year with, possibly, each month of data from a different calendar year. As applied to the building construction and energy management industries, a typical meteorological year (TMY) consists of a full set of 8760 hourly weather observations (365 days × 24 h) containing real weather sequences that represent the long-term climatic modal (i.e., most frequent) conditions for a particular location. The hourly data include extraterrestrial, global and direct solar radiation estimates and observed ceiling, sky cover, visibility, weather (type), sea level and station pressure, dry-bulb and dewpoint temperatures, cloud amounts, and total and opaque sky cover. TMY data have been utilized, for example, by engineers in the design and evaluation of energy systems.
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