Characteristics of Atmospheric Turbulence in Stable Stratification at Syowa Station in Antarctica

Abstract

An atmospheric turbulence in stable stratification was observed at Syowa Station in Antarctica during the period from February to December in 1970. Its characteristics are analyzed in relation to the stability (Richardson number, Ri) in the surface air layer.
The vertical mean wind speed at the height of 20m is observed to be about one-third of the longitudinal mean wind speed at the same height above the slope with an inclination of about 10 degrees. The standard deviations of the longitudinal, lateral and vertical wind speed fluctuations decrease exponentially with the increase of Ri. The ratios of the standard deviations of the longitudinal, lateral and vertical wind speed fluctuations to the friction velocity are independent of Ri. The energy dissipation rate increases roughly in proportion to the 0.5 power of Ri. The scale of the atmospheric turbulence seems to be a solid body of a long and narrow cubic vortex, i.e., length:breadth:height=6.3:1.9:1. The characteristic scale of the atmospheric turbulence which is the largest turbulon is independent of the stability of Ri. Furthermore the scale of the smallest turbulon increases exponentially with the value of Ri. The nondimensional frequency at the maximum spectral density of the longitudinal wind speed increases with the value of Ri. On the other hand, however, the peak frequency of the lateral wind speed is independent of Ri, and that of the vertical wind speed decreases with the increase of Ri.