OASIS98

The two main objectives of the OASIS surface-layer Intercomparison of Fluxes (SIF) Project were to:

1. Examine theuncertainties associated with the measurement of surface fluxes made in the OASIS Project
2. Validate the reference sensorsused at the OASISintercomparison facility.

NCAR's ASTER facilities were requested to provide a reference for intercomparison with OASIS-measured fluxes. This was done by carefully comparing the estimated surface fluxes obtained using OASIS instrumentation with those directly measured by ASTER. Measurement of the following parameters by ASTER were required: momentum, sensible heat, and water vapor fluxes by eddy-correlation; vertical profiles of wind, temperature, and humidity; net radiation, soil heat flux, soil temperature, and soil moisture.

The OASIS intercomparion facility was developed for the OASIS Project in which high quality reference sensors are being used to verify the accuracy of potential OASIS instrumentation (e.g., high quality 4-way net radiation measurements are being compared with measurements from lower quality, less expensive net radiation sensors). ASTER measurements were compared with the OASIS reference sensors. In addition, ASTER's ability to measure profiles of temperature, water vapor, humidity, and wind at multiple levels made it possible to assess the quality of the fetch at the OASIS intercomparison facility. Finally, ASTER's mechanically-aspirated temperature and relative humidity measurements were compared with naturally-ventilated measurements made by OASIS.