| Section T | T index | 321-329 of 589 terms |
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tofan—(Also spelled tufon, tufan.) A violent spring storm common in the mountains of Indonesia.
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tongue—In oceanography, a three-dimensional, tonguelike intrusion of finite extent in the along- front direction. See interleaving.
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top-down/bottom-up diffusion—An atmospheric boundary layer theory that splits turbulent transport into two components, one that is entrained into the boundary layer top and then diffused downward, and one that is injected from the earth's surface and brought upward into the boundary layer. These two linearly decomposed components of a passive scalar assume that the top-down component has zero flux at the surface while the bottom-up component has zero flux at the top. This theory allows some aspects of vertical transport across a mixed layer to be modeled, even though the actual vertical gradient of the passive scalar is zero, which is often the case for vigorous buoyant convection.
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topographic amplification factor—A ratio, calculated solely from topographic (terrain elevation) data, of the diurnal temperature amplitude or range in a valley to that at the same altitude over the adjacent plain. The diurnal amplitude is larger (or “amplified”) over the valley than over the plain because the volume of air is less in the valley, but the amount of heating or cooling is approximately the same in both locations. The significance of the temperature differential caused by this amplification is that it produces a horizontal pressure gradient between the valley and the surrounding plains, or along the axis of the valley itself, that reverses twice per day, driving the diurnally varying along- valley wind system, upvalley during the day and downvalley at night. See upvalley wind, downvalley wind.
McKee, T. B., and R. D. O'Neal, 1989: The role of valley geometry and energy budget in the formation of nocturnal valley winds. J. Appl. Meteor., 28, 445–456.
Steinacker, R., 1984: Area-height distribution of a valley and its relation to the valley wind. Contrib. Atmos. Phys., 57, 64–71.
Whiteman, C. D., 1990: Observations of thermally developed wind systems in mountainous terrain. Meteor. Monogr., No. 45, 9–13.
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topographic waves—Waves with a restoring force arising from variations in depth. The stretching or compression of displaced columns of water generates anomalous vorticity tending to drive them back to their original position.
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