Winds at the 75–110 km level at college, ALaska

Abstract

Neutral atmospheric winds at College, Alaska have been derived from radar measurements of the drift of meteor trails. The wind values in the height interval of 75–110 km were obtained for the period from December 1966 to August 1968. It was found that the semi-diurnal variation at College does not display a well defined tidal pattern that is observed at mid-latitudes. The diurnal variation is usually the largest periodic component, but its maximum amplitude is usually less than 30 m/sec. Both the zonal and meridional prevailing wind velocities frequently exceed 20 m/sec and these components exhibit seasonal trends that are similar to lower latitude observations. The height variations in the wind were generally greater in the summer than in the winter and spring, but the ±6 km height resolution of the measurements prevented a detailed examination of vertical wind shear. During the winter of 1967–1968, a reversal of the apparent normal winter flow occurred during the time of a major stratospheric warming. There is evidence indicating that a southward flow occurs on the nightside of the auroral zone during times of auroral substorms.