Measurements of r0 and θ0: two decades and 18 sites

Abstract

We present a statistical analysis of r0 and u0 measurements collected over the last 2 decades at 18 different sites. Although the site altitudes varied from sea level to 3 km, the major distinguishing feature between average r0 values was the presence or absence of a turbulent, atmospheric boundary layer above the surface. For locations without a strong boundary-layer inversion, the mean coherence length, r0, was 93 6 6 mm and the mean isoplanatic angle, u0, was 9.4 6 0.5 mrad. Where a boundarylayer inversion was present, the corresponding values for r0 and u0 were 53 6 2 mm and 6.5 6 0.5 mrad, respectively.