Open Access Open Access  Restricted Access Subscription Access

ANOMALOUS VARIOMETER READINGS WHEN CIRCLING IN TILTED THERMALS

Julian West

Abstract


When one is correctly centered in a thermal it might be expected that the variometer reading would be constant. However, according to Brozel (1985) about 90% of thermals over flat terrain exhibit two maxima and two minima. When not correctly centered a variometer would be expected to indicate a purely sinusoidal variation of climb rate with one maximum and one minimum per circle. However, when not quite centered in a thermal, the author has often observed either two closely adjacent minima spaced by about 90-degrees and separated by a minor maximum, or a single minimum that is relatively flat in comparison with a much sharper maximum. In the former case the two minima are not of equal magnitude, the second one being less marked than the first. This implies the presence of higher order sinusoidal components, in particular a pronounced second harmonic. The purpose of this paper is to explain the origin of anomalous harmonics in variometer readings, and to suggest altemative centering methods when they are present.

Keywords


Meteorology, Atmospheric physics, Training, Coaching

Full Text:

PDF