Meteorological Events Affecting Cold-Air Pools in a Small Basin

Meteorological events affecting the evolution of temperature inversions or cold-air pools in the 1-km-diameter, high-altitude (similar to 1300 m MSL) Grunloch basin in the eastern Alps are investigated using data from lines of temperature dataloggers running up the basin sidewalls, nearby weather stations, and weather charts. Nighttime cold-air-pool events observed from October 2001 to June 2002 are categorized into undisturbed inversion evolution, late buildups, early breakups, mixing events, layered erosion at the inversion top, temperature disturbances occurring in the lower or upper elevations of the pool, and inversion buildup caused by the temporary clearing of clouds. In addition, persistent multiday cold-air pools are sometimes seen. Analyses show that strong winds and cloud cover are the governing meteorological parameters that cause the inversion behavior to deviate from its undisturbed state, but wind direction can also play an important role in the life cycle of the cold-air pools, because it governs the interaction with steep or gentle slopes of the underlying topography. Undisturbed cold-air pools are unusual in the Grunloch basin. A schematic diagram illustrates the different types of cold-air-pool events.