Evidence of a downward-propagating, annual wind reversal in the equatorial stratosphere


  • Richard J. Reed,

  • William J. Campbell,

  • Lowell A. Rasmussen,

  • Dale G. Rogers


Stratospheric wind data for Canton Island (3°S) and Nairobi, Kenya (2°S), reveal that during the period July 1955–February 1960 alternate bands of easterly and westerly winds progressed downward from the highest level of observation (30 km) at intervals of approximately 1 year, suggesting the presence of a 2-year zonal wind oscillation in the equatorial stratosphere. The bands circle the entire globe, reach their greatest strength near 25 km, are about 10 km deep at intermediate levels, move downward at about 1 km per month, and weaken and become erratic near the tropopause. On the basis of ozone measurements it is argued that the downward propagation represents a wave motion, not a mass transport. The periodic appearance of westerly momentum at the equator suggests the presence of disturbances in the tropical stratosphere which transport momentum in a preferred manner.