Acoustic Doppler Measurement of Atmospheric Boundary Layer Velocity Structure Functions and Energy Dissipation Rates

Abstract

Acoustic echo sounder (echosonde) and meteorological tower measurements of the turbulent velocity structure parameters D(r) and Cv2 and the rate of dissipation of turbulent energy ε are compared. The two acoustic Doppler methods attempted, utilizing pulse differencing and Taylor hypothesis approaches, show good agreement. The small discrepancy in these parameters between the tower and echosonde is explained by the wind noise and ambient noise characteristics of the echosonde and by the effects of pulse volume averaging. Time-averaged, acoustically derived Cv2 values are compared with acoustic facsimile records in both stable and unstable atmospheric conditions. The temporal and (implicitly) the spatial variations of Cv2 were observed to be large, and correlated well with echosonde-detected waves, turbulent layers and thermal plumes. The hour-average vertical ε profiles for the two stability cases show reasonable comparison with those calculated by other investigators.