MESOSPHERIC TEMPERATURE INVERSIONS WITH OVERLYING NEARLY ADIABATIC LAPSE-RATE - AN INDICATION OF A WELL-MIXED TURBULENT LAYER

The Rayleigh lidar technique was applied to study the thermal structur e of the middle atmosphere. Observations were carried out on a routine basis for one year (130 clear nights) at the main campus of York Univ ersity near Toronto (44 degrees N,80 degrees W). Mesospheric temperatu re inversions were generally found to occur below a height of 70 ion d uring winter and above during summer. The most interesting aspect of o ur observations was that the inversions were often associated with an overlying nearly adiabatic lapse rate which extended for several kilom etres. We interpret this as being an indication (or signature) of a we ll-mixed turbulent layer. A one-dimensional numerical model was applie d to demonstrate that a well-defined turbulent layer within the mesosp here can bring about a thermal structure quite similar to that which w as commonly observed - an inversion with overlying nearly adiabatic la pse.