The special intensive observation period that we present here took place when Szeged was at the edge of a high pressure system over central Europe, but affected by shallow mid and high clouds corresponding to the northern part of a low pressure system in the southern Adriatic sea. The surface winds were very weak, and past midnight the cloud cover diminished progressively, vanishing at sunrise. During the partially cloudy part of the night a temperature inversion developed in the lowest 100 m with an unstable layer of 30 m touching the surface, since the latter stayed warmer than the air during this period. When the skies cleared up at the sunrise, a very stable narrow layer developed, generating an early morning surface inversion that was not wiped up by the solar heating until nearly 3 hours after sunrise. This anomalous nighttime behaviour is explored in detail, also looking at the behaviour of the numerical models for that episode.
This campaign is a part of a more general action for the understanding of the dynamics of the ABL in the Pannonian basin, which includes analysis of the already available data and numerical studies at various scales (from microscale to the whole Pannonian basin), with special interest on air quality issues. Further campaigns are planned in the future.