Three heavily instrumented fixed-location atmospheric observatories that represent a broad range of conditions are operated by the Atmospheric Radiation Measurement (ARM) user facility to gather massive amounts of atmospheric data. These are:
- Southern Great Plains (SGP) – centered near Lamont, Oklahoma, United States
- North Slope of Alaska (NSA) – centered at Utqiaġvik (formerly Barrow), Alaska, United States
- Eastern North Atlantic (ENA) – located on Graciosa Island, Azores, Portugal.