| Abbreviation | Definition |
|---|---|
| AA | Academic Alliance |
| AAWO | Association of American Weather Observers |
| AAWS | Average Annual Wind Speed |
| AB | Aurora Borealis |
| ACARS | ARINC Communication Addressing and Reporting System |
| ACCA | Automatic Cloud Cover Assessment |
| ACES | Altus Cumulus Electrification Study |
| ACFP | Advanced Computer Flight Plan |
| ACIA | Arctic Climate Impact Assessment |
| ACON | Atlantic Coast Observer Network |
| ACP | Aluminium Composite Panel |
| ACP | Atmospheric Chemistry Program |
| ACRF | ARM Climate Research Facility |
| ACRID | Advanced Climate Research Infrastructure for Data |
| ACRIM | Active Cavity Radiometer Irradiance Monitor |
| ACRP | Atmospheric Composition Research Program |
| ACRS | Astrographic Catalog Reference Stars |
| ACSG | Atmospheric Chemistry SubGroup |
| ACTIF | Achieving Technological Innovation in Flood Forecasting |
| ACU | Acquisition Control Unit |