Inversionslager

Inversionslager, or inversion layer, is a meteorological phenomenon characterized by a layer of the atmosphere in which temperature increases with altitude, rather than decreasing as in the standard lapse rate. This creates a statically stable stratification that suppresses vertical air motion.

Inversions can form by radiative cooling of the Earth's surface during clear and calm nights (radiation inversion), by the advection of warmer air over cooler air near the surface (advection inversion), or by subsidence of sinking air that warms as it compresses (subsidence inversion). They commonly occur in the lower troposphere and may extend from a few tens of meters to several kilometers above the ground; inversion strength is measured by the temperature difference across the layer.

Consequences: The stable conditions trap moisture, aerosols, and pollutants, leading to fog and smog in valleys and urban basins; suppress cloud formation and convection; can affect aviation, as low-level wind shear and reduced visibility complicate takeoffs and landings.

Observation and study: Inversions are diagnosed using radiosondes, weather balloons, ground-based lidars and radars, and satellite data. They are a common feature in many climates, notably during winter in mid-latitudes and in coastal or valley regions where cold air pools.