| Acronym | Meaning |
 | UICP | Uniform Inventory Control Program |
 | UID | User Identification |
 | UIL | Upper Interval Limit |
 | UIP | UCAR Intellectual Property |
 | UIPPA | See IUPAP |
 | UK AEA | United Kingdom Atmomic Energy Authority |
 | UKAERE | United Kingdom Atomic Energy Research Establishment |
 | UKMO | United Kingdom Meteorological Office |
 | ULAFOS | UCAR And Lower Atmospheric Facilities Oversight Section |
 | ULTRIX | UNIX-based Operating System For Digital Equipment Corporation Computers |
 | UM | University Of Michigan |
 | UMASS | University Of Massachusetts |
 | UMC | UCAR Managment Committee |
 | UMF | User Master File |
 | UMIST | University Of Manchester Institute Of Science And Technology |
 | UMP | Upper Mantle Project |
 | UN | United Nations |
 | UNAM | Universidad Autonoma De Mexico |
 | UNAVCO | University NAVSTAR [not An Acronym] Consortium |
 | UNCED | United Nations Conference On Environment And Development |
 | UNCHE OR UNCHE | United Nations Conference On The Human Environment |
 | UNCOQ | Unaccompanied NonCommissioned Officers' Quarters |
 | UND | University Of North Dakota |
 | UNEP | United Nations Environment Programme |
 | UNESCO | United Nations Educational |
 | UNICOS | Unix Cray Operating System |
 | UNIDATA | UNIDATA Program Center |
 | UNIDATA | University Data Interactive Computing And Communications Systems |
 | UNIX | A Computer Operating System Developed By AT&T And Modified Extensively By The University Of California At Berkeley |
 | UNOLS | University-National Oceanographic Laboratory System |
 | UNU | United Nations University |
 | UOM | Upper-ocean Model |
 | UOP | UCAR Office Of Programs |
 | UOQ | Unaccompanied Officers' Quarters |
 | UPC | Unidata Program Center |
 | UPO | UCAR Projects Office |
 | UPS | Uninterruptible Power Supply |
 | UQAM | Universite De Quebec A Montreal |
 | URC | University Relations Committee |
 | URIP | University Research Initiative Program |
 | URL | Universal Resource Locter |
 | URSI | International Union Of Radio Science |
 | USA | United States Army |
 | USACE | United State Army Corps Of Engineers |
 | USAF | United States Air Force |
 | USAFGL | United States Air Force Geophysical Laboratory |
 | USAN | University Satellite Accessed Network |
 | USAP | United States Antarctic Program |
 | USARP | United States Antarctic Research Program |
 | USC-GARP | United States Committee For GARP |