Monthly Tropical Stratospheric Zonal Winds from Radiosondes Data Source and Processing: Monthly mean zonal wind data for the tropics are provided as a service for the global QBO and trend analysis communities. The original data source and processing chain were established by the Free University of Berlin (FUB). Currently, the data is processed at the Karlsruhe Institute of Technology (KIT, ROR:04t3en479), Institute of Meteorology and Climate Research (IMK), Germany with the tools developed at FUB. Data Description: The dataset includes monthly mean zonal wind values at pressure levels 100, 90, 80, 70, 60, 50, 45, 40, 35, 30, 25, 20, 15, 12, and 10 hPa, derived from radiosonde observations at four equatorial stations: Kiribati (Canton Island) - data from 1953 to 1967 (closed) Maldives (Gan Island) - data from 1967 to 1975 (closed) Singapore (Payalebar) - data from 1975 to 1989 Singapore (Changi) - data from 1989 onwards Important Notes: Values for 100 hPa from October 1967 are solely from Singapore (Changi). Values for 100 hPa before October 1967 are from Kiribati (Canton Island) when available. Detailed information about the radiosonde stations and their periods of operation is provided below. Additional Information: Access the data in other formats: https://www.atmohub.kit.edu/english/807.php Detailed List of Radiosonde Stations: Station Name Location (Lat, Lon) Data Period Pressure Levels (hPa) Kiribati (Canton Island) -2.7667, -171.7167 1953 - 1967 (closed) Above 100 (until August 1967) 100 (until September 1967) Maldives (Gan Island) -0.6933, 73.1556 1967 - 1975 (closed) Above 100 (September 1967 to December 1975) Singapore (Payalebar) 1.3667, 103.9167 1975 - 1989 Above 100 (January 1976 to May 1989) Singapore (Changi) 1.3678, 103.9825 1989 - present 100 (October 1967 to May 1989), All levels from June 1989