From these daily values the monthly mean zonal wind components were calculated for the levels 70, 50, 40, 30, 20, 15, and 10 hPa and a data set from 1953 to the present was produced by
combining the
observations of the three radiosonde stations Canton Island (
closed 1967), Gan / Maledive Islands (
closed 1975), and Singapore (data file: qbo.dat).