The Oklahoma Mesonet (Brock et al., 1995), a system of 115 automated measurement stations across Oklahoma, is serving as the foundation for the Oklahoma Atmospheric Surface-layer Instrumentation System (OASIS) Project. OASIS (Brotzge et al. 1999a; Richardson et al., 1999) is a 3-year project (October 1997 to October 2000) designed to enhance the Mesonet's capability to measure boundary layer fluxes of sensible, latent, and ground heat, as well as the radiation balance. Approximately 90 Mesonet sites will directly measure the net radiation and ground heat flux and indirectly estimate the sensible heat flux using similarity theory; latent heat flux will be calculated as a residual from the conservation of energy equation. In addition, nine of the 90 sites also will use eddy correlation techniques to determine the sensible and latent heat fluxes and measure net radiation using a four-way net radiometer.

The OASIS98 field project was conducted during the first year of the OASIS Project with a focus of determining the accuracy with which OASIS instrumentation could measure surface fluxes. In order to accomplish this, the tower-based components of the National Center for Atmospheric Research's (NCAR) Integrated Surface Flux Facility (ISFF, previously the Atmosphere-Surface Turbulent Exchange Research, ASTER, facility) was used (Businger et al, 1990). The ISFF measures surface fluxes by eddy-correlation and measures atmospheric profiles of temperature, moisture, and wind speed and direction. The ISFF- measured surface fluxes served as the reference for OASIS measurements and provided an estimate of the uncertainty associated with OASIS measurements. This paper will examine and discuss initial results from the OASIS98 field project and provide an initial assessment of the accuracy of OASIS measurements.