U.S. Global Surface Airways Hourly Observations

Observations are made by trained personnel, or by automated equipment that has been tested by the controlling agency. Stations are usually fully instrumented and therefore record a complete range of meteorological parameters. Observations are generally recorded for the 24-hour period midnight to midnight.

The major parameters are clouds, visibility, winds, air temperature, sky cover, relative humidity, air pressure, and present weather. However, there have been several historical changes in the way observations have been recorded, including the advent of the Automated Surface Observing System (ASOS) in 1992. The detailed parameters, allowing for such changes, are: sky condition in tenths and height per layer; sky condition in eighths and height per layer; altimeter setting; sky condition in tenths and cloud coverage by layer; sky condition in eighths and cloud coverage by layer; ceiling height; cloud type and height by layer; total amount of sky cover by the first two cloud layers and by the first three cloud layers; dew point temperature in tenths Celsius; dew point temperature in Fahrenheit; horizontal visibility; station pressure; present weather code; present weather between 5 and 10 statute miles in vicinity; relative humidity; sea level pressure; air temperature in tenths Celsius; air temperature in Fahrenheit; wet bulb temperature in tenths Fahrenheit; total sky cover in eighths; total sky cover and total opaque sky cover measured in tenths; wind direction and speed to 16 points; wind direction and speed; and wind direction and speed from ASOS.

All parameters are not reported by all stations. The oldest data was orginally in manuscript form. Older manuscript data is keyed and added to the archived digital data set from time to time; the earliest digital data is currently from 1936.

Users should be aware that DSI-3280 and DSI-3283 (C00365) are similar. The only difference is that DSI-3280 contains quality controlled data that has been hand checked by personnel at the archive. DSI-3283 only contains data that is automatically quality controlled, therefore, it is considered to be raw data.