The Turbulence Characteristics of the Atmospheric Surface Layer on the North Slope of Mt. Everest Region in the Spring of 2005

Turbulence measurements at 3 m performed at the base camp of Mt. Everest during the spring of 2005 were used to study the atmospheric turbulent characteristics under conditions of down-slope ambient wind (katabatic wind). The cases where large-scale forcing resulted in a down-slope ambient wind were considered. Firstly, the normalized standard deviations of wind speed (u and v components) were larger than those reported in the literature. Then the (co)spectral characteristics of turbulence under near neutral stratification were described depending on the prevailing wind; case A-southerly with wind speed larger than 6 m s(-1) during daytime, case B-southerly with wind speed less than 6 in s(-1) and case C-northerly wind. The analysis of the averaged spectra and co-spectra revealed that low frequency perturbations had a large influence on the variance of u and w wind components, and also altered the co-spectra of momentum and sensible heat flux under near neutral stratification. The features of spectral shape and power were different from the previous ones under ideal flat and homogeneous conditions. The possible cause of these features is due to strong down-valley flow induced by (normal) glacier wind.