Three tethersondes were operated in a 1-km-diameter limestone sinkhole at 2500 m MSL in Utah’s Bear Mountains in September 1999 to investigate the physical processes leading to the development of strong nocturnal temperature inversions and the extreme minimum temperatures found there. The surprising development of a persistent, elevated, 20-m deep superadiabatic sub-layer at the top of the cold pool and just below an intense capping inversion layer has led to the formulation and testing of hypotheses concerning the origin of such a layer. An investigation of the energetics of the basin atmosphere suggests that it is produced by cooling associated with the radiative flux divergence profile within the basin. Cold air generated by this cooling convects downwards into the basin atmosphere, distributing the cooling throughout the cold pool and causing the capping inversion layer to develop a stronger and stronger temperature jump as the night progresses. The talk will focus on basin energetics and the evidence for interactions between turbulent and radiative processes.