MEASUREMENTS OF THE DIURNAL TIDES IN THE 80- TO 100-km ALTITUDE RANGE AT ARECIBO.

The incoherent scatter radar at Arecibo has been used to measure the 80- to 100-km wind system on two November and two April days. The wind system is shown to correspond most closely to the S//1//,//1 mode diurnal tide. Dissipation effects were always important, and in the April data the tide was seen to 'break' at an altitude of 92 km and an amplitude of 60 m/s. The observed vertical wavelength was lambda //z equals 19. 5 km; a Richardson number of 0. 2, a 40 degree K temperature oscillation, and an upward energy flux of 4. 2 multiplied by 10** minus **4 W/m**2 were inferred.