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Computed response of tetrahedral constant-density balloons to vertical sinusoidal and helical air motions
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1971
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Description:The quantitative response of some particular examples of constant density balloons to vertical sinusoidal and helical atmospheric oscillations has been estimated by using a digital computer to solve the equation of motion for the balloon. Results were obtained for wave periods of 4 to 48 minutes, velocity amplitudes of 0.3 to 3.5 meters per second, and wave amplitudes of 10 to 1600 meters. For vertical air motions, phase lead angle decreases and amplitude response increases as atmospheric stability, balloon radius, and air period decrease, and as vertical air speed and drag coefficient increase. For a typical wave of 15 minutes period and 300 meters amplitude, the phase lead is only 5% of the wave length and amplitude response is 94%. A rearrangement of the equation allows an estimation of the trajectory of the air parcel, initially associated with the balloon, from the radar-tracked balloon movements. For helical air motions that are characterized entirely as solid rotation, or are irrotational with a solid rotation core, the balloon eventually spirals into the center of the helix provided the helix is sufficiently long and persists for sufficient time. For helical motions in which the air speed is dependent only on time, the balloon track becomes elliptical. It is clear from these studies that care must be exercised in interpreting constant level balloon data. Statistics involving the vertical fluctuations of the balloon may not be related to similar statistics for the air. However, it is suggested that the air motions can be estimated from the balloon motions through the solution of the equation of motion.
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Rights Information:CC0 Public Domain
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