Integrated Global Radiosonde Archive is a digital data set archived at the National Climatic Data Center (NCDC). This dataset contains monthly means of geopotential height, temperature, zonal wind, and meridional wind derived from the Integrated Global Radiosonde Archive (IGRA, DSI-6351). IGRA consists of radiosonde and pilot balloon observations at over 1500 globally distributed stations, and ... monthly means are available for the surface and mandatory levels at many of these stations. The period of record varies from station to station, with many extending from 1970 to present. Monthly means are computed separately for the nominal times of 0000 and 1200 UTC, considering data within two hours of each nominal time. A mean is provided, along with the number of values used to calculate it, whenever there are at least 10 values for a particular station, month, nominal time, and level. The monthly-mean files are updated on the fifth day of each month and are available online at no charge.