This paper reports the first power spectra of ozone (O3) in the surface layer for which the data quality approaches that of high-quality spectra of meteorological properties. These results are employed in a surface layer scalar similarity study involving temperature, moisture, and O3 measurements over cotton. All data were obtained during the California Ozone Deposition Experiment, in the San Joaquin Valley of California, during July and August, 1991. A detailed comparison of nondimensional scalar power spectra during unstable conditions showed that the three scalars behaved similarly, thereby providing the first completely general test of scalar similarity theory. ¿ 1998 American Geophysical Union