These files contain monthly observational data that have been quality-controlled using semi-automated computer programs as well as oversight by our staff. The filenames are prefixed with a label identifying one of three different observation intervals - ten minute (10min), one hour (1hr), and three hour (3hr). The rest of the filename consists of a standardized string composed of (in order) a three-letter code to indicate the station, the year, the month, and the frequency of the data (e.g. 3hr-[III][YYYY][MM]q3h.txt for three-hourly data).

Each set of daily observations begins at 0000 UTC. The hourly data are recorded at the top of every hourly interval: i.e. at 0000 UTC, 0100 UTC, 0200 UTC, 0300 UTC, etc. for the one-hour data; and at 0000 UTC, 0300 UTC, 0600, etc. for the three-hour data. Missing data are represented as 444.0.

The data files contain a two-line header that gives the year, month, 3 letter ID, Argos ID, and station name in the first line; and latitude, longitude, and elevation in the second line. The columns are organized in the following order:

• Year
• Julian day
• Month
• Day
• Observation time (UTC)
• Temperature (C)
• Pressure (hPa)
• Wind Speed (m/s)
• Wind Direction (deg)
• Relative Humidity (%)
• Delta-T (C)