A Brief Climatology of Vertical Wind Variability in the Troposphere and Stratosphere as Seen by the Poker Flat, Alaska, MST Radar

Abstract

A statistical analysis of vertical air motion has been performed for data taken in the 3-20 km altitude range by the Poker Flat MST radar during the period September 1979-January 1982. The variability of vertical velocities is analyzed as a function of season, time of day and synoptic weather conditions. The overall frequency distribution of vertical velocities can be approximated by the sum of two normal distributions: one with variance about 10 times larger than the other. The variability of vertical velocity at all levels is found to correlate most closely with horizontal wind speed at 700 mb on a day-to-day basis. The total variance is larger in summer than in winter at all hours of the day and especially during the afternoon hours. A statistically significant diurnal variation of vertical motions is found during summer with amplitude in the midtroposphere near 2 cm s⁻¹. Interpreting the vertical wind variability as a manifestation of vertically propagating waves, we compare the intensity here with earlier studies of turbulence variations. These comparisons show a plausible link between the intensity of turbulence at jet stream altitudes and the production of waves near the surface.