This shows both the receiver Power and corresponding signal to noise (SNR) ratio for the period in question. The layer which can be seen in the last 2/3 of the period at around 1.0 to 1.5 km is a layer of higher refractivity suggesting an inversion. Upper atmospheric sounding conducted at Adelaide Airport 40km south on 10/11/97 at 22:00 UTC showed an inversion layer at around 1.3 to 1.5 km agreeing with the height of the above layer.