| U MASS | University Of Massachusetts | - | Business and Finance |
| U.S./JC | United States/Japan Cooperation | - | Business and Finance |
| U.S./JC | United States/Japan Cooperation | - | Business and Finance |
| UAC | United Aircraft Corporation | - | Business and Finance |
| UAO | Upper Atmosphere Observatory | - | Business and Finance |
| UARC | Upper Atmosphere Research Corporation | - | Business and Finance |
| UARS | Upper Atmosphere Research Satellite | - | Business and Finance |
| UAV | Unmanned Aerial Vehicles | - | Business and Finance |
| UCAID | University Corporation For Advanced Internet Development | - | Business and Finance |
| UCAR | University Corporation For Atmospheric Research | - | Business and Finance |
| UCAR | Unmanned Combat Armed Rotorcraft | - | Business and Finance |
| UCARF | UCAR Foundation | - | Business and Finance |
| UCARIP | UCAR Intellectual Property | - | Business and Finance |
| UCARIPO | UCAR Intellectual Property Officer | - | Business and Finance |
| UCARNET | University Cooperation For Atmospheric Research Network | - | Business and Finance |
| UCARSOFT | UCAR Software | - | Business and Finance |
| UCARTS | UCAR Trade Secrets | - | Business and Finance |
| UCLA | University Of California At Los Angeles | - | Business and Finance |
| UCSB | University Of California At Santa Barbara | - | Business and Finance |
| UCSD | University Of California At San Diego | - | Business and Finance |
| UEDS | Unidata Experimental Data Service | - | Business and Finance |
| UF | Universal Format | - | Business and Finance |
| UGGI | See IUGG | - | Business and Finance |
| UGV | Unmanned Ground Vehicles | - | Business and Finance |
| UH | University Of Hawaii | - | Business and Finance |
| UHF | Ultra-high Frequency | - | Business and Finance |
| UHF | Ultra-high Frequency | - | Business and Finance |
| UHURU | N/A | - | Business and Finance |
| UHV | Use An Ultrahigh Vacuum | - | Business and Finance |
| UI | Unit Of Issue | - | Business and Finance |
| UI/UM PRICE | Unit Of Issue/Unit Of Measure Price | - | Business and Finance |
| UIC | Unit Identification Code | - | Business and Finance |
| UICP | Uniform Inventory Control Program | - | Business and Finance |
| UID | User Identification | - | Business and Finance |
| UIL | Upper Interval Limit | - | Business and Finance |
| UIP | UCAR Intellectual Property | - | Business and Finance |
| UIPPA | See IUPAP | - | Business and Finance |
| UK AEA | United Kingdom Atmomic Energy Authority | - | Business and Finance |
| UKAERE | United Kingdom Atomic Energy Research Establishment | - | Business and Finance |
| UKMO | United Kingdom Meteorological Office | - | Business and Finance |
| ULAFOS | UCAR And Lower Atmospheric Facilities Oversight Section | - | Business and Finance |
| ULTRIX | UNIX-based Operating System For Digital Equipment Corporation Computers | - | Business and Finance |
| UM | University Of Michigan | - | Business and Finance |
| UMASS | University Of Massachusetts | - | Business and Finance |
| UMC | UCAR Managment Committee | - | Business and Finance |
| UMF | User Master File | - | Business and Finance |
| UMIST | University Of Manchester Institute Of Science And Technology | - | Business and Finance |
| UMP | Upper Mantle Project | - | Business and Finance |
| UN | United Nations | - | Business and Finance |
| UNAM | Universidad Autonoma De Mexico | - | Business and Finance |
| UNAVCO | University NAVSTAR [not An Acronym] Consortium | - | Business and Finance |
| UNCED | United Nations Conference On Environment And Development | - | Business and Finance |
| UNCHE OR UNCHE | United Nations Conference On The Human Environment | - | Business and Finance |
| UNCOQ | Unaccompanied NonCommissioned Officers' Quarters | - | Business and Finance |
| UND | University Of North Dakota | - | Business and Finance |
| UNEP | United Nations Environment Programme | - | Business and Finance |
| UNESCO | United Nations Educational | - | Business and Finance |
| UNICOS | Unix Cray Operating System | - | Business and Finance |
| UNIDATA | UNIDATA Program Center | - | Business and Finance |
| UNIDATA | University Data Interactive Computing And Communications Systems | - | Business and Finance |
| UNIX | A Computer Operating System Developed By AT&T And Modified Extensively By The University Of California At Berkeley | - | Business and Finance |
| UNOLS | University-National Oceanographic Laboratory System | - | Business and Finance |
| UNU | United Nations University | - | Business and Finance |
| UOM | Upper-ocean Model | - | Business and Finance |
| UOP | UCAR Office Of Programs | - | Business and Finance |
| UOQ | Unaccompanied Officers' Quarters | - | Business and Finance |
| UPC | Unidata Program Center | - | Business and Finance |
| UPO | UCAR Projects Office | - | Business and Finance |
| UPS | Uninterruptible Power Supply | - | Business and Finance |
| UQAM | Universite De Quebec A Montreal | - | Business and Finance |
| URC | University Relations Committee | - | Business and Finance |
| URIP | University Research Initiative Program | - | Business and Finance |
| URL | Universal Resource Locter | - | Business and Finance |
| URSI | International Union Of Radio Science | - | Business and Finance |
| USA | United States Army | - | Business and Finance |
| USACE | United State Army Corps Of Engineers | - | Business and Finance |
| USAF | United States Air Force | - | Business and Finance |
| USAFGL | United States Air Force Geophysical Laboratory | - | Business and Finance |
| USAN | University Satellite Accessed Network | - | Business and Finance |
| USAP | United States Antarctic Program | - | Business and Finance |
| USARP | United States Antarctic Research Program | - | Business and Finance |
| USC-GARP | United States Committee For GARP | - | Business and Finance |
| USCG | United States Coast Guard | - | Business and Finance |
| USDA | United States Department Of Agriculture | - | Business and Finance |
| USDC | United States Department Of Commerce | - | Business and Finance |
| USDI | United States Department Of Interior | - | Business and Finance |
| USERC | United States Environmental And Resources Council | - | Business and Finance |
| USFS | United States Forest Service | - | Business and Finance |
| USGCRP | United States Global Change Research Program | - | Business and Finance |
| USGS | United States Geological Survey | - | Business and Finance |
| USIC | UCAR Space Implementation Committee | - | Business and Finance |
| USJGOFS | United States Joint Global Ocean Flux Study | - | Business and Finance |
| USN | United States Navy | - | Business and Finance |
| USPHS | United States Public Health Service | - | Business and Finance |
| USRA | Universities Space Research Association | - | Business and Finance |
| USSDM | Unidata System For Scientific Data Management | - | Business and Finance |
| USTAR | UCAR Scientist's Technical Areas Of Research | - | Business and Finance |
| USWRP | United States Weather Research Program | - | Business and Finance |
| UT | Universal Time | - | Business and Finance |
| UT / LS | Upper Troposphere/ Lower Stratosphere | - | Business and Finance |
