Located in the lower foothills of the Sierra Nevada Mountains on privately owned land, the Vaira Ranch site is classified as a grassland dominated by C3 annual grasses. Managed by local rancher, Fran Vaira, brush has been periodically removed for cattle grazing. Species include a variety of grasses and herbs, including purple false brome, smooth cat's ear, and rose clover. Growing season is confined to the wet season only, typically from October to early May.

The research approach of the University of California, Berkeley Biometeorology Laboratory involves the coordinated use of experimental measurements and theoretical models to understand the physical, biological, and chemical processes that control trace gas fluxes between the biosphere and atmosphere and to quantify their temporal and spatial variations. The research objectives of the Vaira Ranch site span from overall project goals to publication-specific topics. They are as follows: 1) Comparing radiative, convective and latent energy flux densities of an annual grassland over the course of multiple growing seasons; 2) The relative contributions of vegetation and the soil on CO2 and water vapor exchange; 3) Spatial variability of understory fluxes; 4) The impact of sloping terrain on the interpretation of flux covariances; 5) Characterize evapotranspiration, energy fluxes and related bulk parameters in monthly and annual timescales; 6) Investigate which abiotic and biotic factors control the interannual variability of water and energy fluxes; 7) The influence of growing season length on annual evapotranspiration amount; 8) Transition timing of energy-limited to water-limited modulate annual amount of evapotranspiration; 9) The controlling factors of evapotranspiration and atmospheric demand or stomatal regulation; 10) The response of evapotranspiration to changes in solar radiation amounts in water-limited and energy-limited periods.