When the elevation angles are <10°, the GMD antenna is misdirected by indirect signals reflected from the ground and large spurious oscillations and steps appear in the elevation angle measurements. The mesoscale features which have vertical wavelengths from 1.5–3 km include oscillations in wind direction and speed.
With GMD measurements 10 times min−1 instead of the usual 1 min−1 and when elevation angles are > 10°, the computed winds and ascent rates reproduced both the macroscale and mesoscale features derived from the FPS-16 data. A direct comparison is possible because the measurements were made simultaneously by tracking the same effective target, which for the FPS-16 was metallic chaff in the balloon that carried the radiosonde transmitter. A machine method for computing winds from radiosonde and GMD-1 rawin tracking data is developed and the resulting winds are compared to those computed from precision FPS-16 radar tracking data.
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