An observational study of turbulence inside a close basin

Turbulence inside the Meteor Crater, a small, close basin in Northern Arizona, is examined using data from 3D sonic anemometers mounted at multiple levels on a flux tower on the center floor of the crater. The results are compared to simultaneous turbulence observations on the plain outside the crater. The comparisons indicate that the bowl-shaped crater amplifies the diurnal oscillations of temperature and heat fluxes, with the amplification most pronounced under quiescent synoptic conditions. The crater's rim shelters the crater atmosphere from mean background flows with wind speeds inside the crater usually less than half the speeds on the outside plain. However, the flows in the crater are much more turbulent, with turbulence generated by the conversion of mean flow into turbulent motion. On days with near-surface winds outside the crater greater than 10 m s-1, turbulent kinetic energy can reach extremely large values (~15 m2 s-2) inside the crater. Compared to the velocity and temperature spectra outside, spectral peaks occur at lower frequencies inside the crater, especially for the cross-stream wind component. A constant flux layer, if exists, is very shallow (less than 2 m) on the crater floor, suggesting that the similarity theory-based empirical formulas may not be proper for describing properties of the surface-layer within the crater.