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Gravity wave activity in vertical winds observed by the Poker Flat MST Radar

1981; American Geophysical Union; Volume: 8; Issue: 3 Linguagem: Inglês

10.1029/gl008i003p00285

1944-8007

W. L. Ecklund, K. S. Gage, A. C. Riddle,

Tropical and Extratropical Cyclones Research

Over 30 days of nearly continuous observations of the vertical wind up to 20 km obtained using part of the MST radar at Poker Flat, Alaska, are presented in this report. These observations are typical of a longer 6‐month set of observations and demonstrate several new features. The most obvious feature is the extent to which the magnitude of the vertical wind fluctuations is controlled by propagating planetary scale waves, which modulate the large‐scale wind field. Enhanced wind and wind shear in intense baroclinic zones greatly increase gravity wave activity as seen in the vertical winds. Although shorter period fluctuations in vertical velocity on occasion show very regular sinusoidal oscillations with periods from 5 to 30 minutes, typically the vertical velocity fluctuations are irregular with no well‐defined oscillation period. Steady vertical winds of up to 1 m/s lasting for several hours are observed at certain low altitudes when background winds and wind shear are enhanced. The occurrences are not unusual and are probably due to mountain lee wave activity.